PLATING BATH SOLUTIONS AND METHODS OF PLATING

Description

BACKGROUND

Numerous varieties of plating technologies are known in the art. These technologies include electrolytic plating which is also known as electro-plating and by other terms, and electroless plating also known as chemical, autocatalytic and by other terms.

Numerous varieties of plating technologies are known in the art. These technologies include electrolytic plating which is also known as electro-plating and by other terms, and electroless plating also known as chemical, autocatalytic and by other terms.

Electroless plating is a well-known and is an established commercial and industrial process for metal plating. The metal portion of the metal salt may be selected from suitable metals capable of being deposited through electroless plating. Such metals include, without limitation, nickel, cobalt, copper, gold, palladium, iron, other transition metals, and mixtures thereof, and metals deposited by an autocatalytic process. Generally, the electroless metal in the deposited coating is a metal, a metal alloy, a combination of metals, or a combination of metals and non-metals. Such coatings are often in the form of a metal, a metal and phosphorous, or a metal and boron. The metal or metal alloy is derived from the metal salt or metal salts used in the bath. Examples of the metal or metal alloy are nickel, nickel-phosphorous alloys, nickel-boron alloys, cobalt, cobalt-phosphorous alloys, and copper alloys. Other materials such as lead, cadmium, bismuth, antimony, thallium, copper, tin, and others can be deposited to form the bath and may be included in the coating.

The salt component of the metal salt may be any salt compound that aids and allows the dissolution of the metal portion in the bath solution. Such salts may include without limitation sulfates, chlorides, acetates, phosphates, carbonates, and sulfamates, among others.

Solutions often include reducing agents, which serve as electron donors. When reacting with the free-floating metal ions in the bath solution, the electroless reducing agents reduce the metal ions, which are electron acceptors, to metal for deposition onto the article. The use of a reducing agent avoids the need to employ a current, as required in conventional electroplating. Common reducing agents are sodium hypophosphite, sodium borohydride, n-dimethylamine borane (DMAB), n-diethylamine borane (DEAB), formaldehyde, and hydrazine.

Certain materials may be used in electroless plating baths where these materials serve two or more roles in the plating bath. For example, instead of using the typical combination of nickel sulfate as a metal salt and sodium hypophosphite as a reducing agent, it is possible to use nickel-hypophosphite in an electroless nickel plating bath. Nickel-hypophosphite, however, is very expensive and not widely used commercially due to its impractical cost.

Electroless nickel (EN) is one of the most commercialized varieties of electroless plating. The plating comprises an alloy of nominally 86-99% nickel and the balance with phosphorous, boron, or a few other possible elements. Electroless nickel is commonly produced in one of four alloy ranges: low (1-5% P), medium (6-9% P), or high (10-14% P) phosphorous, and electroless nickel-boron with 0.5-5% B. Certain manufacturers of the solutions used to produce these different versions of electroless nickel may use slightly different terms and/or specify a slightly different range of the percent phosphorous achievable from the plating baths using these solutions; but the terms and ranges above are consistent with typical industry practice. Each variety of electroless nickel provides properties with varying degrees of hardness, corrosion resistance, magnetism, solderability, brightness, internal stress, lubricity, and other properties. All varieties of electroless nickel can be applied to numerous articles, including metals, alloys, and nonconductors. In the electroless nickel plating industry, there are solutions for plating baths that are formulated, marketed, and used for different levels of phosphorous in the nickel alloy produced from these plating baths. For example, there are solutions with terms such as “medium-low phosphorous”, “medium-high phosphorous”, and others; but the vast majority of electroless nickel solutions made, sold, and used in the industry fall into the three main categories of low, medium, and high phosphorous.

Further, it is standard procedure in the industry to formulate a bath as either low, medium, or high phosphorous, and maintain the bath as such. It is never the case that during the course of a bath's line, it can be or is adjusted from one phosphorous type to another. That is, a low phosphorous bath is always a low phosphors bath, a medium is always an medium, and a high is always a high.

Electroless composite technology is a more recent development as compared to electrolytic composite technology.

The plating of articles with a composite coating bearing finely dispersed divided particulate matter is well documented. The inclusion of finely divided particulate matter within metallic matrices can significantly alter the properties of the coating with respect to properties such as wear resistance, lubricity, friction, thermal transfer, and appearance.

The co-deposition of particles in composite electroless plating can dramatically enhance existing characteristics and even add entirely new properties. These capabilities have made composite electroless coatings advantageous for a variety of reasons including, but not limited to, increased utility in conditions requiring less wear, lower friction, lubrication, indication, authentication, thermal transfer, insulation, higher friction, and others. Composite electroless coatings with nickel provide an additional environmental advantage over conventional electroless nickel coatings, which do not include particulate matter, in that the particles within composite electroless nickel coatings reduce the amount of nickel alloy used. Such nickel based composite coatings are also an alternative to chromium-based coatings which pose certain health and environmental challenges.

Particulate matter suitable for practical composite electroless plating may be from nanometers up to approximately 100 microns in size. The specific preferred size range depends on the application involved.

The particulate matter may be selected from a wide variety of distinct matter, such as but not limited to ceramics, glass, talcum, plastics, diamond (polycrystalline or monocrystalline types, natural or manmade by a variety of processes), graphite, oxides, silicides, carbonate, carbides, sulfides, phosphate, boride, silicates, oxylates, nitrides, fluorides of various metals, as well as metal or alloys of boron, tantalum, stainless steel, molybdenum, vanadium, zirconium, titanium, tungsten, as well as polytetrafluoroethylene (PTFE), silicon carbide, boron nitride (BN), aluminum oxide, graphite fluoride, tungsten carbide, talc, molybdenum disulfide (MoS), boron carbide and graphite. The boron nitride (BN), without limitation, may be hexagonal or cubic in orientation.

For increased friction on the surface of a resultant coating and/or increased wear resistance, hard particulates, such as but not limited to diamond, carbides, oxides, and ceramics, may be included in the plating bath. Application of an overcoat of a conventional plated layer on top of the composite plated layer is also done in the field in order to further embed the particulate matter within the coating.

For increased lubrication or reduction in friction in the resultant coating, “lubricating particles,” such as polytetrafluoroethylene (PTFE), boron nitride (BN), talc, molybdenum disulfide (MoS), graphite or graphite fluoride among others may be included in the plating bath. These lubricating particles may embody a low coefficient of friction, dry lubrication, improved release properties, and/or repellency of contaminants such as water and oil.

For light emitting properties in the resultant coating, particulates with phosphorescent properties such as, but not limited to, calcium tungstate may be included in the plating bath.

For identification, authentication, and tracking properties in the resultant coating, various particulate and solid materials may be included in the plating bath so they will be incorporated into the coating and detectable either visually, under magnified viewing, or detection with a suitable detector

The inclusion of insoluble particulate matter in composite electroless baths introduces additional instability. To overcome the extra instability due to the addition of insoluble particulate matter to the bath, such as described in U.S. Pat. No. 6,306,466, the general use of particulate matter stabilizers (PMSs) is believed to isolate the finely divided particulate matter, thereby maintaining the particular matter's “inertness”. Such PMSs are well-known, and include, without limitation, sodium salts of polymerized alkyl naphthalene sulfonic acids, disodium mono ester succinate (anionic and nonionic groups), fluorinated alkyl polyoxyethylene ethanols, tallow trimethyl ammonium chloride, and any of the PMS disclosed in U.S. Pat. No. 6,306,466, which is incorporated herein by reference.

The electroless metallizing bath may also contain one or more complexers, also known as complexing agents. A complexing agent acts as a buffer for reasons which may include pH control and maintaining control over the “free” metal salt ions in the solution, all of which aids in sustaining a proper balance in the bath solution.

The electroless metallizing bath may further contain a pH adjuster to also help control pH levels in the bath. Suitable pH adjusters may buffer the plating bath at a desired pH range.

Some materials may serve one or more functions within an electroless plating bath. For example, ammonium hydroxide is both a pH adjuster as well as a complexer; cadmium, aluminum, copper and others materials are both a stabilizer and a brightener, lactic acid is both a complexer and a brightener, some sulfur compounds like thiourea are both stabilizers and accelerators depending on concentration, and there are other multipurpose ingredients useful in electroless plating baths.

Ingredients typical in electroless plating and useful in the present invention include, but are not limited to the following materials in the following general categories:

Complexers

Acetic Acid, Alanine-beta, Aminoacetic Acid, Ammonium Bicarbonate, Ammonium Carbonate, Ammonium Chloride, Ammonium Hydroxide, Boric Acid, Citric Acid, Citrates, EDTA, Ethylenediamine, Fluoboric Acid, Glycerine, Glycine, Glycolic Acid, Glycolic Acid Salts, Hydroxyacetic Acid, Lactic Acid, Maleic Anhydride, Malic Acid, Malonic Acid, Orthoboric Acid, Oxalic Acid, Oxalic Acid Salts, Propionic Acid, Sodium Acetate, Sodium Glucoheptonate, Sodium Hydroxyacetate, Sodium Isethionate, Sodium or Potassium Pyrophosphate, Sodium Tetraborate, Succinic Acid, Succinate Salts, Sulfamic Acid, Tartaric Acid, Triethanolamine, Monocarboxylic Acids, Dicarboxylic Acids, Hydrocarboxylic Acids, Alkanolamines, and combinations and variations of such materials.

Stabilizers

2 Amino-Thiazole, Antimony, Arsenic, Bismuth Compounds, Cadmium Compounds, Lead Compounds, Heavy Metal Compounds, Iodobenzoic Acid, Manganese Compounds, Mercury Compounds, Molybdenum Compounds, Potassium Iodide, Sodium Isethionate, Sodium Thiocyanate, Sulfur Compounds, Sulfur Containing Aliphatic Carbonic Acids, Acetylenic Compounds, Aromatic Sulfides, Thiophenes, Thionaphthalenes, Thioarols, Thiodipropionic Acid, Thiodisuccinic Acid, Tin Compounds, Thallium Sulfate, Thiodiglycolic Acid, Thiosalicylic Acid, Thiourea, and combinations and variations of such materials.

Brighteners

Aluminum, Antimony Compounds, Cadmium Compounds, Copper, Lactic Acid, and combinations and variations of such materials.

pH Controllers

Ammonium Bicarbonate, Ammonium Carbonate, Ammonium Chloride, Ammonium Hydroxide, Potassium Carbonate, Potassium Hydroxide, Sodium Hydroxide, Sulfamic Acid, Sulfuric Acid, and combinations and variations of such materials.

Particulate Matter Stabilizers (Dispersants, Surfactants, Wetters)

Sodium salts of polymerized alkyl naphthalene, disodium mono ester succinate (anionic and nonionic groups), fluorinated alkyl polyoxyethylene ethanols, tallow trimethyl ammonium chloridesulfonic acids, disodium mono ester succinate (anionic and nonionic groups), fluorinated alkyl polyoxyethylene ethanols, tallow trimethyl ammonium chloride, and any of the PMS disclosed in U.S. Pat. No. 6,306,466, which is incorporated herein by reference, and combinations and variations of such materials.

Buffers

Borax, Boric Acid, Orthoboric Acid, Succinate Salts, and combinations and variations of such materials.

Reducing Agents

DMAB, DEAB, Hydrazine, Sodium Borohydride, Sodium Hypophosphite, and combinations and variations of such materials.

Accelerators

Fluoboric Acid, Lactic Acid, Sodium Fluoride, Anions of some mono and di carboxylic acids, fluorides, borates, sulfur compounds, and combinations and variations of such materials.

Metal Salts

Cobalt Sulfate, Copper Sulfate, Nickel Sulfate, Nickel Chloride, Nickel Sulfamate, Nickel Acetate, Nickel Citrate, and combinations and variations of such materials.

Historically electroless nickel and composite electroless plating processes have included heavy and/or toxic metals in the plating bath to overcome the inherent instability of the plating bath. Lead has been the most commonly used material to serve this purpose. Cadmium has also been used widely over the years as a brightener for electroless nickel coatings. But this incorporation of heavy metals into the plating baths presents multiple challenges. The heavy metals must be added in a sufficient amount to prevent the decomposition of the plating bath, but an increased concentration beyond the necessary level required to prevent the decomposition results in cessation or reduction of the plating rate. Increasingly stringent rules and regulations that restrict or prohibit the use of heavy metals, such as the Removal of Hazardous Substances (RoHS) and End-Of-Life Vehicle (ELV) Regulations. However, U.S. Pat. Nos. 7,744,685 and 8,147,601 disclose stable composite electroless nickel plating baths without the use of heavy and/or toxic metals. These patents are incorporated herein by reference.

Because the present invention is directed to various improvements over the prior art, the electroless nickel and composite electroless nickel solutions of the present invention may contain heavy metals or may be essentially free of heavy metals, which means that no such heavy metal is added to the plating bath and/or the heavy metal concentration should be no more than a level that would cause the coating on articles plated in said bath to have a heavy metal concentration in excess of any relevant regulations. The solutions of the present invention may also contain heavy metals less toxic and/or subject to fewer regulations than lead, cadmium and others.

In recent years, there has been a growing desire within the plating industry to avoid the use of ammonium hydroxide. Ammonium hydroxide is an effective non-heavy metal and very strong complexing agent and also a pH adjuster. Ammonium hydroxide, however, is objectionable to some plating shops due to environmental, health, and/or safety regulations, and also because of smell, and the difficulty it causes in the ability to remove the nickel from the plating bath at the end of the bath's life. Storage and handling of ammonium hydroxide is also problematic as it can cause storage drums and other containers to bloat, it emits a very noxious odor experienced when opening a container, pumping, and being transported, and causes a strong reaction when added to a hot plating bath unless the extra step of diluting the ammonium hydroxide by 50 percent by volume or more is performed in advance. Specially designed respirators are needed when handling ammonium hydroxide. It is therefore desirable to have a solution for an electroless nickel plating bath where this solution is free of ammonium hydroxide, and whereby the user or plater has the ability to use a chemical other than ammonium hydroxide as an auxiliary solution to maintaining the pH of the plating bath during usage.

In recent years, there has been a growing desire within the plating industry to use lower concentrations of metal salts in the plating baths. The primary justifications for this alternative to the conventional concentrations of metal salts in the plating baths are to 1) reduce the drag out of the metal salts from the plating baths to the subsequent rinse tanks and thereby reduce the amount of metal salts that need to be captured in subsequent waste treatment of the rinse water facilitating better environmental practices, 2) reduce the amount of metal salts that are essentially wasted when the plating bath comes to the end of its useful life and the bath is waste treated or otherwise disposed of, 3) improve the quality of the plating by lowering the amount of metal salts in the bath which have the potential to precipitate or react in the bath in ways other than the desired reduction and deposition onto articles immersed in the plating bath for the purpose of plating, especially effective in reducing shelf roughness, 4) lowering the cost to makeup a plating bath, 5) extend plating bath life, especially when plating onto aluminum substrates, 6) increase reducing agent efficiency, and 7) contain less metal and other substances in the mist emanating from the plating bath. An example of this practice is in the electroless nickel plating field where some platers are using plating baths with less than the traditional 6 grams per liter of nickel metal in the bath, for example, 3 grams per liter. The background and justification for using electroless nickel plating baths with reduced nickel content is well documented in: http://www.pfonline.com/articles/fifth-generation-reduced-ion-electroless-nickel-systems. When applied to electroless nickel plating systems, the present invention, which is directed to various improvements over the prior art, is able to operate effectively at any point in the range of 3 to 6 grams per liter of nickel metal in the plating bath, and other concentrations. Formulation of the solution useful for makeup and replenishment of an electroless nickel plating bath according to the present invention, but using less than the amount of a metal salt required to yield the traditional 6 grams per liter of nickel metal in the plating bath, has the benefit of reducing the quantity of ingredients in the solution and thereby making the solution easier to formulate and concentrate.

In addition, in recent years, health and environmental concerns have been raised about the inclusion of certain materials such as perfluorooctane sulfonate (PFOS) and perfluorooctanoic acid (PFOA) that may be used in plating systems, including composite plating systems, including those with PTFE. PFOS may be contained in certain particulate matter stabilizers (PMSs) useful for electroless plating. The present invention, directed toward improvements over the prior art, therefore includes compositions, baths, and methods for plating that may contain PFOA and/or PFOS, or may be free, or have only trace amounts of PFOA and/or PFOS.

While many elements of the EN plating chemistry, process, and industry have evolved, one essential methodology related to the technology has remained relatively unchanged since the early style baths were surpassed by formulations that were easier and more reliable to operate. This method includes initial makeup and to subsequently maintain the EN plating bath. Makeup of an EN bath involves combining the ingredients required to create a bath that is ready to be used for its intended purpose. Maintenance, also known as replenishment for this type of bath, of the EN bath involves replacing the chemical elements of the bath that have been depleted from the bath as plating occurs from the bath onto articles immersed in the bath or otherwise spent.

While it is possible to makeup and replenish a plating bath by adding the desired amount of each individual ingredient to form a solution, the established method to makeup and replenish a plating bath prior to U.S. Pat. No. 10,006,136, incorporated herein by reference, was to combine three or more separate pre-made solutions with water. Again, even when doing so, a low phosphorous bath is kept as low, a medium as a medium, and a high as a high.

When three solutions are used, it is common in the field to makeup an EN bath with an “A” solution, a “B” solution, and water. The A solution typically contains the metal salt (for example, nickel sulfate), and may contain other ingredients, and accounts for five to six percent of the volume of the plating bath. The B solution typically contains the reducing agent (for example, sodium hypophosphite), other functional ingredients like stabilizers, brighteners, pH buffers, chelators, complexing agents, accelerators, particulate matter stabilizers, etc., and accounts for fifteen to twenty percent of the volume of the plating bath. Keeping materials separated from one another-like separating the metal salt from the reducing agent-precludes the initiation of the chemical process whereby the metal separates and complexes or reduces. The balance, typically about eighty percent of the volume of the plating bath, is made up of water plus the possibility of an acid or base to adjust the pH of the EN bath before it is heated to the desired temperature and used for plating. The water is typically deionized water. That is, the initial bath is comprised of the A solution, the B solution, water, and potentially a pH adjuster, where the pH adjuster may be introduced into the water before being combined with A and B.

The use of one or multiple plating compositions for formulating a bath, as described herein, is referred to as a “plating bath system”.

As the bath is used, its contents need to be replenished. An EN bath is typically replenished with the A solution as well as a “C” solution. The C solution is typically similar to the B solution, containing the reducing agent (for example, sodium hypophosphite), other functional ingredients like stabilizers, brighteners, pH buffers, chelators, complexing agents, accelerators, particulate matter stabilizers, etc., but the specific combination and concentration of these chemicals are in different concentrations in the C solution than they are in the B solution. The reason for the difference of concentrations of these chemicals is the difference in the consumption or depletion rate of each material from the initial makeup concentration due to the plating reaction. C solutions are typically formulated to be used in a convenient ratio for replenishment relative to the A solutions, for example one part A solution plus two parts C solution; or for example one part A solution plus one part C solution.

The advantages of a single component EN system over EN systems using more than one component are well documented in U.S. Pat. Nos. 10,006,126, 10,731,257, and 10,731,258, which are incorporated herein by reference.

While the present invention is well suited to these types of single component EN systems, the present invention is also usable with multiple component EN systems as well.

When discussing the materials and solutions used in the makeup and replenishment of electroless plating baths, and if the system is a one, two, three, four or more solution system, it is customary in the field to count the number of solutions containing the primary functional ingredients such as metal salts, reducing agents like stabilizers, brighteners, pH buffers, chelators, complexing agents, accelerators, particulate matter stabilizers, etc., and mixtures thereof, as understood by practitioner in the field and other persons of ordinary skill in the art. The addition of any other ingredients to the plating bath is not considered an additional solution. For example, the addition of materials such as ammonium hydroxide, other hydroxides, carbonates and the like to adjust the pH of the plating bath is not considered a solution in the same way as a typical A, B, C, M, or R solution is counted in the system. These materials are considered auxiliary solutions. Solutions of additional stabilizers, brighteners, accelerators, PMSs, and other materials may also be used as auxiliary solutions to modify the plating bath for specific purposes, often for episodic purposes rather than consistent uses. If such materials were needed for consistent, routine purposes in the plating bath, they might be incorporated into one or more of the primary solutions such as the A, B, C, M, or R solutions. Similarly, the addition of particulate matter, in powder, liquid dispersion, or other form, is also considered an auxiliary material or solution, and is not considered a solution or component in the same way as a typical A, B, C, M, or R solution is considered as a solution in the system.

A single solution usable for both initial/makeup and replenishment purposes, such as One-Plate® solutions of Surface Technology, Inc. of Ewing, New Jersey have proven to be beneficial in the electroless nickel plating industry.

The typical operation of an electroless plating bath consists of the following steps. First, a plating bath is made up traditionally as already discussed in this disclosure. The plating bath is then heated by any of a number of mechanisms to reach a desired operating temperature. Articles for plating may be cleaned and otherwise pretreated according to their base metal(s) and condition, and immersed into the plating bath. While the articles are being plated for a time commensurate with the plating rate of the plating bath and the desired thickness of the plating onto the articles, the temperature and pH of the plating bath are typically monitored and maintained at desired levels. During or after the plating of the articles, the plating bath is analyzed to determine the composition of certain components in the plating bath. Typically, this analysis is intended to determine the metal content of the metal salt remaining in the plating bath, and this is accomplished by wet chemistry or by instrumental analysis. Knowing the present metal content allows one to determine how much additional metal salt and other chemicals are needed. Based on the concentration of this metal in the plating bath, the plating bath is traditionally replenished with two or more solutions containing the ingredients needed to replace what has been depleted through the plating process. This replenishment can be added to the plating bath by pouring, pumping, or other means. Analysis of other individual components, such as reducing agents and stabilizers, in the plating bath can be accomplished but is much less common, and therefore increases the potential for the ratio of ingredients to become imbalanced with the metal salt and other ingredients in the plating bath. This represents one further advantage of the single component systems whereby the ingredients will remain in the proper ratio as they are all contained in the single primary component used for makeup and replenishment of the plating bath.

BRIEF DESCRIPTION OF THE PRESENT INVENTION

The present invention is directed to a family of compositions (often referred to herein as “solutions”) for electroless plating baths, the baths themselves, their use, and the resultant plated articles.

Further, the present invention is directed to methods and solutions which individually and collectively produce plated layers of multiple types and purposes.

Further, the present invention is directed to methods and solutions which collectively are configured to extend the life of a bath by being convertible from one type of phosphorous bath to a different type of phosphorous bath.

The present invention is directed to plating solutions and processes which are commercially useful and viable.

Commercial viability means the performance of the solution and the plating bath resulting from the solution are consistent with or better than the state of the art before the present invention in plating based on factors including, but not limited to, economy of use, energy use, environmental considerations, lifetime, plating rate, coating quality, safety, and stability in storage, transport, and use.

The present invention is directed towards plating solutions and procedures that are capable of producing plating performance and coatings that are free of problems in the deposit being created consequential to the solution. Such problems include, but are not limited to skip plating, pitting, edge pull-back, step plating, dark or laminar deposit, roughness in deposits, streaks in deposit, dull or matte deposits, poor adhesion of the deposit to the substrate, poor corrosion and/or chemical resistance of the deposit.

In one embodiment the solution is free of fluorides and/or fluorocarbons. In one embodiment, the solution of the present invention avoids the use of heavy and/or toxic metals. In one embodiment, the solution is able to provide full functionality for plating even after being exposed to a variety of environmental conditions while in transport and/or storage, such as but not limited to temperature extremes. In one embodiment, the solution can be used as a concentrate for a bath. In one embodiment, the solution includes any of a variety of particulates and potentially stabilizers for particulates. In one embodiment, the solution is void of thiourea. In one embodiment, the solution includes metal at a low concentration. In one embodiment, the solution is at a pH consistent with the pH of the associated bath.

In this application, the terms “makeup” and “initial” are used interchangeably.

In this application, the term “coating” and the nouns “plating” and “layer” are used interchangeably.

The present invention is further directed towards solutions that are useful for the makeup and replenishment of a plating bath where the solutions are stable at high and low temperatures for increased stability and practicality in manufacture, transport, and storage. This stability can be derived from the selection of ingredients as disclosed herein.

The present invention is further directed to a low metal system of plating, where the operator of the plating process need not excessively monitor the concentration of metal in the bath. In addition, replenishment is much quicker using the one component solution of the present invention. In addition, because of the use of a single component instead of the traditional plurality of components, an operator can employ a small pump arranged for continuing replenishment and avoid manual replenishment completely. Such a pump may be automated or not. Such a low metal bath limits manual interaction with the bath and keeps concentration and performance at or near optimal levels, thereby assuring improved plating.

The present invention is further directed to an embodiment with coatings of up to 30% PTFE, and coatings which are RoHS (and comparable) compatible, coating with no PFOS, and/or no PFOA, and/or no fluorinated PMSs, and/or no intentionally added PFAS materials. In at least some embodiments, the coating includes both PTFE and nickel as a composite.

The present invention is further directed to extending bath life with limited interaction in monitoring a bath.

The present invention is further directed towards a single solution that is useful for the makeup and replenishment of a plating bath where the plating bath is stable for use for a multitude of metal turnovers and for a multitude of days in a plating tank with no maintenance or only a commercially acceptable amount of maintenance of the tank, heaters, pumps, filters, and/or other auxiliary equipment associated with the plating tank so as to achieve commercially adequate plating. The present invention is further directed towards a single solution that is useful for the makeup and replenishment of a plating bath where the plating bath is stable for composite plating, where particles in the plating bath may tend to destabilize the plating bath as particles embody surface area in the plating bath that can affect its stability.

Stable in solution means that the solution remains viable for plating while in solution and does not precipitate, disassociate, the nickel doesn't complex to the point of unusability, or have any reaction whereby plating would be impacted adversely.

The present invention is further directed towards a single solution that is useful for the makeup and replenishment of a plating bath where the solution can makeup a plating bath at a variety of metal concentrations such as but not limited to 3-6 g/l.

The present invention is further directed towards a single solution that is useful for the makeup and replenishment of a plating bath for plating electroless nickel with PTFE with a low metal concentration in the plating bath to reduce the cost and material waste of the plating bath.

The present invention is further directed towards solutions that are useful for the makeup and replenishment of a plating bath for plating electroless nickel with PTFE without fluorinated surfactants or, at least in some scenarios, no fluorine or fluorinated components at all.

The present invention is further directed toward concentrates useful to form the type of solutions disclosed herein, and thereby provide additional options and benefits for manufacture, storage, transportation, and use of said concentrates and solutions.

The present invention is further directed toward concentrates useful to make up and maintain plating baths concurrently with one or more other materials, and thereby provide additional options and benefits for manufacture, storage, transportation and use of said concentrates and solutions.

The present invention is further directed to processes and product related to a single solution for both the make-up and replenishment of an electroless plating bath at a particular defined phosphorous level and to an alternative single solution for both make-up and replenishment of the same electroless plating bath at a different phosphorous level.

The present invention is further directed to processes and products related to a single solution for both the make-up and replenishment of an electroless plating bath at a particular defined pH level and to an alternative single solution for both make-up and replenishment of the same electroless plating bath at a different pH level; such as from alkaline to acid and/or from acid to alkaline.

The present invention is further directed to processes and products related to a single solution for both the make-up and replenishment of an electroless plating bath without particulate material and to an alternative single solution for both make-up and replenishment of the same electroless plating bath including particulate material to produce a composite plated layer; and vice versa.

The present invention is able to operate effectively with or without ammonium hydroxide. The present invention is able to operate effectively with sodium hydroxide, potassium hydroxide, potassium carbonate, and the like as pH adjusters within the solution of the present invention or as auxiliary additives to affect the pH of the plating bath made with the solution of the present invention.

Though the present invention primarily focuses on some defined electroless plating systems, other plating systems also fall within the spirit and intent of this invention. Other examples include, but are not limited to: all electroless plating baths, all electroless nickel plating baths including any content of phosphorous and/or boron, poly alloy plating baths, electroless cobalt plating baths, EN systems with different levels of brightness, EN plating that is subsequently blackened, plating systems stabilized with heavy metals, toxic, non heavy metals, non toxic metals, or no metals, plating baths including nickel hypophosphite, composite plating systems, electroless cobalt, copper, palladium, gold, and/or silver plating baths, plating baths that are made up with or without ammonium hydroxide, plating baths that may be replenished and maintained with or without ammonium hydroxide, plating baths that are made up with or without ammonium hydroxide, and plating baths that may be replenished and maintained with or without ammonium hydroxide.

copper, palladium, gold, and/or silver plating baths, plating baths that are made up with or without ammonium hydroxide, plating baths that may be replenished and maintained with or without ammonium hydroxide, plating baths that are made up with or without ammonium hydroxide, and plating baths that may be replenished and maintained with or without ammonium hydroxide.

The present invention encompasses all varieties of baths used for electroless nickel coatings with varying concentrations or freedom from various materials such as, but not limited to, lead, cadmium, heavy metals, toxic metals, PFOA, PFOS and others that are subject of environmental and related regulations such as Restriction of Hazardous Substance Directive (RoHS), Directive on Waste Electrical and Electronic Equipment (WEEE), End of Life Vehicle Directive (ELV), Registration, Evaluation, Authorisation, and Restriction of Chemicals (REACH), and the like.

In describing the present invention's directions and preferred embodiments, specific terminology will be resorted to for the sake of clarity. However, the invention is not intended to be limited to the specific terms so selected, and is to be understood that each specific term includes all technical equivalence which operate in a similar manner to accomplish a similar purpose.

A functional benefit of the present invention includes cost and efficiency savings.

DETAILED DESCRIPTION

The present invention is directed to both economic and environmental improvements in the plating industry in that the present invention extends the life of a plating bath. The novel approach of the present invention involved extending a bath's life by repurposing the bath for a different type of plating, where the extension occurs after some period of usage, at the end of the plating bath's useful life, or before reaching that point.

In the present invention, a plating bath is formulated for plating at one level of phosphorous and the same bath, when replenished at or near the end of its useful life (or even before), said bath is replenished with one or more solutions for a second purpose, without the removal of any portion of the bath and without regenerating the bath in any way.

In one embodiment of the present invention, a first single solution useful for both the makeup and replenishment of a plating bath is used, where the bath is useful and economical on a commercial basis, as well as to the solution's and the bath's use, and subsequently a second single solution, itself useful for both the makeup and replenishment of a plating bath is used for a different plating purpose. That is, one solution is used for makeup and replenishment for a first purpose and then a second solution is added for a second purpose, where the second solution is further used as a replenisher for the bath.

In another embodiment multiple solutions may be used for makeup for the first purpose, multiple solutions of a second type may be used for replenishment, then multiple solutions of a third type may be used for a second purpose.

The present invention serves to solve a problem which has vexed the industry for decades. By way of example, high phosphorous plating baths, required for plating in select applications, tend to have a very short life, on the order of 5 or fewer metal turnovers (MTOs) of an EN bath containing 6 grams per liter of nickel. Each formulated bath has expense and by having a bath with a short life, the overall expenses ramp up quickly. Further, the bath ultimately has to be disposed of and because of the chemical makeup of the bath, disposal can also be expensive and have an environmental impact. Benefits are clear if a bath's life can be extended. The present invention attempts to do so by re-purposing the bath to a less-than-high phosphorous bath to be used to plate applications not requiring a high phosphorous EN coating which the used bath is no longer able to produce in an effective, efficient, or economical way.

Though the present invention primarily focuses on electroless nickel phosphorus plating systems, other plating systems fall within the spirit and intent of this invention. Other relevant examples of systems and baths include, but are not limited to:

• • All electroless plating baths
  • All electroless nickel plating baths
  • All nickel-phosphorous alloy ratios
  • Electroless nickel-boron
  • Poly alloys
  • Electroless cobalt
  • EN systems resulting in different levels of brightness
  • EN plating that is subsequently blackened
  • Non-metal stabilized plating systems
  • Metal stabilized plating systems
  • Heavy metal stabilized plating systems
  • Composite plating systems
  • Electroless copper, palladium, gold, and/or silver
  • Alloys/combinations thereof

The solution of the present invention may contain some quantity of one or more of the materials that are ordinarily added to the plating bath as auxiliary solutions.

Although the present invention may include components for stability, brightness, fume control, pit reduction, or other alterations to the properties of the coatings, in some situations, platers may add additional auxiliary solutions to the plating bath for modified stability, brightness, fume control, pit reduction, or other alterations to the properties of the coatings resulting from the plating baths.

The present invention includes embodiments directed to similar practices and solutions used for electroless nickel phosphorous, nickel boron, nickel boron phosphorous, nickel tungsten phosphorous, cobalt boron, cobalt phosphorous, copper phosphorous, and other types of plating baths.

Typically, the plater (the end user of the plating bath) buys the solutions needed to make up and replenish the plating baths from a supplier (a manufacturer or distributor) of such solutions.

When such solutions with pH levels different than the pH level of the plating bath are added to a plating bath, there is an inherent acid-base reaction. That acid base reaction can cause a precipitation of materials such as nickel hydroxide or other precipitates in the plating bath. Such precipitation is known to cause defects in the plated layer, such as roughness, pitting, reduced brightness, lower corrosion resistance, and other defects. This precipitation also includes degeneration of at least some or all of the bath components in advance of subsequent plating.

This phenomenon is amplified by the greater the difference between the pH of the solution(s) and the pH of the plating bath.

The importance of pH compatibility between the plating bath and any solutions or materials added to the plating bath is amplified by the elevated temperature of the plating bath. At such temperatures, the volatile reaction of components containing alkaline materials such as but not limited to ammonia and other hydroxides or carbonates and the like are problematic to the worker who is tasked with making such replenishments to the plating bath. As the task is not pleasant from an odor, safety, and other reasons, having a single solution with a pH compatible with the plating bath is desirable.

For the reasons disclosed herein, the compatibility of the pH of the solution to the plating bath of the present invention is advantageous in the industry. It is desirable that the pH of the solution be similar to that of the plating bath during operation, such as but not limited to within 3 pH of one another. It is desirable that the pH of the solution be acidic if the plating bath is acidic. It is desirable that the pH of the solution is not more than three pH units different than the plating bath. Also, during operation of the bath, certain characteristics of the bath might be regularly measured, such as but not limited to temperature, pH, and metal content or density.

As will become evident in the examples below, the present invention includes multiple combinations of ingredients in various ranges of quantities/percentages in a single solution useful to both makeup and maintain the composition of ingredients in the plating bath. In general, the present invention is comprised of a family of solutions each of which affords an improved ease of use and also extends the life of typical plating baths.

Single component electroless nickel plating systems overcome a number of factors which have limited manufacturers and users of plating baths to use plating bath systems with multiple solutions instead of a single solution. These factors are disclosed in U.S. Pat. Nos. 10,006,126, 10,731,257, and 10,731,258, which are incorporated herein by reference.

A key measure of the quality and suitability of solutions for making up and replenishing electroless plating baths is the resulting plating rate and lifetime of the plating bath.

The plating rate corresponds to the thickness of the coating achieved from a plating bath over a period of time. For example, microns of thickness per hour is a typical measure of plating rate. There are generally accepted ranges of plating rates for various types of plating baths and these rates might differ based on the quantity and/or types of articles being plated. For example, a typical low to medium phosphorous plating bath typically plates at a rate of 15 to 25 microns per hour. A typical high phosphorous electroless nickel plating bath plates at a rate of 7 to 12 microns per hour. The plating rate of a given plating bath depends upon operating temperature, bath loading, pH, agitation, age of the bath, and other factors. The choice of type of phosphorous also depends on a variety of factors, including particularly the articles being plated and the purpose of the plating.

A bath life is typically measured in “metal turn-overs”, or MTOs. Different baths can have different MTO lifetimes depending on a number of factors such as but not limited to the type of plating bath, the operation and maintenance of the plating bath, the quantity and types of articles plated, the base metal of the articles being plated, and other factors. One MTO represents the use of a plating bath over a period of time where parts are plated, the cumulative quantity of the metal salt in the bath at makeup is used (deposited onto parts immersed in the plating bath) and replenished into the plating bath. For example, if a one-liter electroless nickel plating bath is made up with 6 grams of nickel metal (coming from a metal salt like nickel sulfate), parts are plated therein until 0.6 grams of nickel are depleted, the bath is replenished with 0.6 grams of nickel, and this process is repeated 9 more times for a total depletion and replenishment of 6 grams of nickel, then this bath has achieved one MTO. Of course, it is not only the nickel salt that is consumed and replenished in the course of usage. Any and all reducing agent(s), stabilizer(s), brightener(s), and all other ingredients must be maintained in proper concentration in the plating bath, otherwise plating bath performance, life, and resulting plating quality will suffer. Adding too much or too little of certain ingredients can also reduce the bath life. Another factor influencing the bath life is the gradual buildup of byproducts in the plating bath as a result of the plating reaction. A maximum bath life is important to the plater since the solutions used for plating baths are a significant cost to the plater; it is time consuming, inconvenient, and costly for the plater to dispose of a used bath and replace it with a new bath; treatment of a used bath is costly and can have environmental implications. Therefore, it is important to the plater that the solutions used for bath makeup and replenishment are formulated in a way as to maximize bath life and performance, where a measure of bath life is the number of MTOs.

When evaluating solutions for the makeup and replenishment of an electroless plating bath, achieving at least one MTO with proper performance and results is a significant threshold to validate the composition(s) of the solution(s). Although some plating bath systems exist for the perpetual use of the plating bath, accomplished by removal of byproducts from the bath and replenishment with select materials, such baths are generally not considered practical nor economical for widespread commercial use, and therefore the life of an electroless plating bath in terms of the number of MTOs achievable is an important factor in the utility of an electroless plating bath. Further, in the industry these types of baths are referred to as “regenerative” and not “replenishable” baths.

Generally speaking, the number of MTOs for a bath is limited by the chemical composition of the bath as one important factor. For example, and significant to this invention, a commercial high phosphorous bath is limited to around 5 MTOs, whereas a medium phosphorous bath can achieve more MTOs. Of course, the performance requirements of the objects to be plated dictate whether a bath is high, medium, or low phosphorous.

As plating baths are used to plate articles and the baths increase in the number of metal turnovers, ultimately the bath reaches a point where, because of byproduct accumulation, the bath must be disposed of. This disposal is typically further due to the buildup of contaminants in the plating bath. These contaminants can include byproducts of the plating reaction such as sodium orthoposphite in the case of electroless nickel, other material build-up such as a zincate solution introduced to the plating bath from the pretreatment of aluminum articles prior to plating, or other contaminants from the chemical process such as the drag-in from articles immersed into the plating bath, and even material in the plating shop that can otherwise migrate into the plating bath.

As such materials build-up in the plating bath, they can cause deleterious effects to both the bath and the plating including but not limited to a reduced plating rate and/or quality problems with the plated deposit such as poor adhesion, pitting, roughness, lack of uniformity, altered physical properties, and other defects.

Therefore, plating baths are normally disposed of at a certain number of metal turnovers before the plating becomes poor. One reason for this commercial practice is that metal turnovers are easier to measure than the cumulative amount of known or unknown contamination. Moreover, it is general practice in the plating industry to try and dispose of a plating bath just before costly quality problems occur on the articles being plated. For example, if a plating shop anticipates adhesion problems on the plating on aluminum articles from a plating at around four to seven metal turnovers due to the buildup contamination of zinc in the plating bath from the pretreatment process of plating on aluminum, the plating shop may discard a plating bath at three metal turnovers to avoid such potential problems and then makeup a new plating bath.

There is a method, known as “bleed and feed” that is rarely if ever practiced in advance of the present invention and not practiced commercially. In this method, as a plating bath reaches a certain number of metal turnovers, a portion of the bath is removed, that portion is replaced with a newly formed plating bath and mixed into the unremoved portion of the bath. In other words, some of the byproducts together with some of the other elements in the bath are removed as a vehicle to extend the bath's life. This method effectively dilutes the plating bath with new plating bath and thereby reduces the concentration of contaminants in the plating bath so the plating bath can continue to be used to plate articles with consistent performance and plating results. Of course, it also requires disposal of useful but unused chemicals as well. For example, if a plating bath were made up and used to a total of four metal turnovers and then 25% the plating bath was removed and replaced with a newly made-up plating bath, the resulting plating bath would effectively be at 3 metal turnovers in terms of bath age and the amount of contamination. The benefits of such a method are that a plating bath can be used at a more steady-state in terms of parameters (such as plating rate, stability, temperature, pH, etc.) and plating quality (such as adhesion, corrosion resistance, stress, color, quality, etc.).

Despite these benefits, the bleed and feed method are rarely if ever practiced commercially. There are a number of reasons for this lack of commercial acceptance. These include the additional cost of materials as traditionally the cost to makeup new bath with multiple components is greater than the cost to replenish an existing bath. There is the added time and labor cost to perform the bleed and feed process, especially with multiple components needed to make up the new portion of the bath. In addition, the bleed and feed process may result in more waste for disposal, as well as more frequent disposals of materials.

Single component electroless nickel solutions make a version of the bleed and feed method commercially viable and advantageous. As an example below demonstrates, the novel utility of a single solution for both the makeup and replenishment of a plating bath solves this problem. As a single solution for both the makeup and replenishment of a plating bath, this enables a plating shop to perform the bleed and feed method using fewer chemicals, or less of various chemicals, that is cheaper, easier, faster than it would be with a multiple solution system. The plating shop is able to bleed a portion of the plating bath and either 1) replace this portion with the same volume of a newly made-up plating bath or 2) replace this portion with just the required amount of the single solution of a present invention and dilute the plating bath up to the operating volume. This second option, facilitated by the present invention, is essentially just a large replenishment to the plating bath which is made practical by the use of a single solution for its simplicity and compatibility with the plating bath for the reasons explained in this disclosure.

It is important to note the difference between extending the life of a plating bath in terms of time versus extending the life of a plating bath in terms of MTOs or metal turnovers. The present invention extends the number of MTOs obtainable from a plating bath.

The present invention provides utility to a plating shop where zinc build up in the plating bath from plating on aluminum substrates is problematic. Prior to the present invention, a plating shop's ability to use a plating bath beyond the point when the zinc concentration reaches a level at which plating additional aluminum substrates would be impossible depended on the plating shop's ability to plate on substrates made of materials other than aluminum such as steel, stainless steel, copper alloys, and others that do not go through a zincate type of pretreatment and therefore do not introduce zinc to the plating bath. Prior to the present invention, a plating shop may be able to do this only if they have parts made of a material other than aluminum that require the same type of plating as the plating applied to the aluminum parts. This is because the additional non-aluminum parts can be plated in the plating bath without further increasing the zinc concentration in the plating bath and not subject to the adhesion problems that would be inherent in plating onto additional aluminum substrates. By using the present invention, a plating shop may have additional opportunities to continue to use the same plating bath on parts other than aluminum by changing the plating bath to produce a different type of coating which may be more useable on these non-aluminum parts.

It is also demonstrated in the examples of the present invention that the modification of a plating bath from one purpose to another purpose can include modifying the pH of an electroless nickel plating bath, say from acid to alkaline, or from alkaline to acid. Whereas the vast majority of electroless nickel plating baths are operated at acidic pH levels, some electroless nickel plating baths are operated at alkaline pH levels. Such alkaline electroless nickel plating baths are used in the plating of aluminum substrates. As described above, the process of plating aluminum substrates leads to the buildup of zinc in the plating bath. By using an alkaline electroless nickel plating bath for a thin “strike” or “flash” layer before transferring the substrate into an acid electroless nickel plating bath for the full plated layer, the zinc is contained in the alkaline bath instead of the acid bath. The alkaline bath has a higher tolerance to zinc contamination. This dual plating bath process of an alkaline bath before the acid bath, extends the life of the acid plating bath. By using the present invention to be able to convert a plating bath from acid to alkaline, or alkaline to acid, the plating shop is able to optimize the utility and lifetime of one or more plating baths; as they can decide when a plating bath has reached the end of its useful life for one purpose, but then repurpose the plating bath so it can be used for another purpose that may still be possible.

In summary, the present invention introduces multiple plating processes all directed to extending bath life and resulting in a plurality of coating compositions and/or plating a plurality of objects. Some embodiments utilize a single solution for makeup and replenishment followed by a second solution for plating a second type of object (or resulting in a somewhat different coating). Some solutions serve the same effect but are not single solutions. Other embodiments include an interim step of removing a portion of the bath after a determined amount of time or plating before adding solution to create at least a second coating type or plating at least a second type of object.

When evaluating solutions for the make-up and replenishment of an electroless plating bath, verification of the physical properties of the coatings resulting from this plating bath is significant to validate the composition(s) of the solution(s). Such physical properties of the coatings include, but are not limited to, composition, hardness, corrosion resistance, thickness, uniformity, electrical conductivity and resistivity, porosity, appearance, brightness, reflectivity, adhesion, stress, elasticity, tensile strength, elongation, density, coefficient of thermal expansion, wear resistance, coefficient of friction, and/or other properties.

In U.S. Pat. No. 5,609,767 (“Eisenmann”) Eisenmann discloses an experimental rejuvenation type of plating bath which is different than the replenishment type of plating bath for the present invention, but Eisenmann is directed to plating only one type of object or one type of coating.

The present invention uses multiple solutions to, in some embodiments, extend the life of a plating bath by changing the purpose of the plating bath by enabling the plating bath to produce more than one type of coating during its overall lifetime. Eisenmann, by contrast, uses equipment and non-plating processes to extend the life of a plating bath through rejuvenation to remove byproducts in the plating bath so the plating bath can be used, potentially for an infinite lifetime to produce a same one type of coating over the course of the entire lifetime of the plating bath.

The present invention is directed to electroless plating baths that are made-up and replenished over the course of the plating bath's lifetime without rejuvenation or other methods of extracting byproducts from the plating bath with the intention of such extraction and subsequent chemical additions to extend the life of the plating bath. Rejuvenation processes in the EN plating industry are exceptionally rare. Nearly all EN plating in the world is by a replenishment method, not with rejuvenation. The goal, method, and chemical formulations used for such rejuvenation type plating systems as well as the extensive equipment that is required to enact the rejuvenation process is substantially different than the vastly more commonly used replenishment type plating baths in the plating industry. Whereas the present invention is, in part, directed to extending the life of an electroless plating bath, the present invention is not a rejuvenation type process. The present invention is not intended to remove byproducts from the plating bath nor provide for a plating bath with an essentially endless life as is the objective of rejuvenation type processes.

products from the plating bath nor provide for a plating bath with an essentially endless life as is the objective of rejuvenation type processes.

Once the bath has been prepared, it is ready for use in the electroless plating process of the present invention. This involves contacting the surface of an article to be plated or coated with the electroless metallizing bath. However, the article to be coated may require preliminary preparation prior to this contact in order to enable the autocatalytic plating deposition on the surface of the article. This preparation includes the removal of surface contaminants. For example, this process may involve any of, but not limited to, degreasing, alkaline cleaning, electrocleaning, zincating, water or solvent rinsing, acid activation, pickling, ultrasonic cleaning, physical modification of the surface, vapor or spray treatments, etc.

An electroless plating bath is typically operated generally according to the following practices related to the equipment, and operation of the bath.

• • The plating tank is typically constructed of polypropylene, stainless steel (Type 316) or mild steel with a suitable tank liner depending on bath in use and other considerations. Stainless steel tanks may be anodically protected.
  • Filtration through a 10-micron or finer rated polypropylene filter bag system is suggested. Polypropylene wound cartridge filters are also permissible, but generally are not as easy to use as filter bags. The filtering pump system should turn the bath over at a rate of at least 10 times per hour.
  • Agitation is useful in maintaining bath homogeneity and for providing a consistent finish for the coating. Air spargers with air from a high volume, low-pressure air blower is recommended. Compressed air is not recommended due to potential oil contamination. Other types of agitation, may also be used.
  • Heating of the bath may be accomplished by various methods including heat exchangers and immersion heaters. The bath temperature should be monitored and maintained closely.
  • Cooling of the bath with an appropriate cooling apparatus should be done rapidly at the end of a shift or any time the bath will not be used for an extended period of time.
  • Rack, barrel, and fixturing devices are typically constructed of compatible materials such as polypropylene, chlorinated polyvinyl chloride (CPVC), stainless steel, PTFE, Viton, silicone rubber, and others that can withstand the chemicals and temperature of the plating bath and pretreatment process. Maskants may be used to protect fixtures from being plated.
  • Masking is typically accomplished with compatible materials such as certain vinyl tapes, stop-off paints, plugs and gaskets made of Viton, silicone rubber, and others that can withstand the chemicals and temperature of the plating bath and pretreatment process.
  • The plating tank should be clean and passivated. The most common method is with a solution of 40-50% nitric acid for 2-3 hours at room temperature, followed by rigorous rinsing and neutralizing of the tank and verification that no nitrate contamination remains.
  • The plating bath is typically maintained to be within 80% and 100% concentration of nickel, hypophosphite, stabilizers, or other chemicals based on the initial makeup concentration of these ingredients. Tighter control further helps performance.
  • Titration of the plating bath is typically before and after every batch of parts that is plated. Replenishing is normally done during plating cycles if the workload will lower the nickel concentration to 90% or less for optimal bath performance and plating quality.
  • Continual and accurate measurement of bath temperature, pH, and bath solution level is important and typically done. Evaporation will reduce bath volume and give false indication of actual concentration. Adding DI water as needed during the plating cycle is useful to keep solution at proper level.
  • The deposition rate of a given plating bath depends upon operating temperature, bath loading, pH, agitation, age of the bath, and other factors.

Although the examples detailed below depict specific combinations of components, time, and control, the reader should recognize that the present invention is not limited to the specific materials and metrics in the examples. For example, plating different goods may require different quantities or combinations. The pH of the plating bath can vary by application but is preferably in a range of 4.0 to 9.0. The plating bath temperatures can preferably be in the range of 20 to 100 degrees Celsius. The duration of the cycle times can be in any range required to provide the coating thickness and properties desired.

The solution of the present invention's contents may vary based on the plating needs, such as but not limited to, the type of plating necessary, and the types of objects being plated. Preferably, the solution is directed to electroless nickel plating, but other types of plating may also lend themselves to a single solution, such as but not limited to other types of electroless nickel plating.

In U.S. Pat. No. 10,006,126, among many other prior art references in the field of electroless nickel plating, plating baths and processes are limited to a plating bath of a singularly defined type that produced a coating of a singularly defined type for the lifetime of the plating bath. For example, a high phosphorus plating bath would be made-up, articles would be coated in said plating bath with a high phosphorous electroless nickel plated layer, and the plating bath would be replenished with one or more components designed to produce a similar and consistent high phosphorus coating until the end of the plating bath's useful lifetime. This lifetime in the number of metal turnovers or MTOs that the plating bath is able to achieve before it is no longer physically or commercially viable to continue the use of this plating bath, as described herein.

Such end of bath life causes can include an unacceptably slow plating rate of the plating bath; or unacceptable properties of the coating itself such as undesirable hardness, phosphorus content, corrosion resistance, stress, physical appearance, and other properties.

The present invention instead teaches a method and plating bath whereby a plating bath is:

• • 1) made-up with one or more chemical solutions and ingredients to produce a first coating of a specific one or more physical parameters,
  • 2) articles are coated with said first specific physical parameters characteristics,
  • 3) the plating bath is replenished with one or more chemical solutions and ingredients in order to continue to produce the same first specific physical parameters of the coating on additional articles from said plating bath, and then
  • 4) the bath is subsequently replenished with a different (“second”) one or more chemical solutions and ingredients in order to produce a different one or more physical parameters of the coating on additional articles plated in the same plating bath.

Said another way, a first bath for a first purpose is used and subsequently refunctioned for a second purpose merely be adding a second combination of chemical solutions, thereby extending the overall life off the bath.

The benefits of the present invention include, but are not limited to, methods whereby:

• • 1) Multiple types of coatings may be produced from the same plating bath,
  • 2) A plating bath's life can be extended so as to improve utilization of components and extend the lifetime the plating bath, and
  • 3) Reducing the amount of waste generated from plating.

Extending the lifetime of a plating bath is of great interest for commercial, profitability, productivity, waste reduction, convenience, and other benefits to the day-to-day operation of one or more planting baths in a plating shop. While there are many ways in which users of plating baths routinely work to extend the lifetime or MTO's of plating baths, but these methods differ from the present invention's multi-purpose function. Such methods include, but are not limited to:

• • 1. Insuring proper maintenance of the chemical ingredients in the plating bath through accurate replenishment of the plating bath,
  • 2. Utilizing a single component replenishment solution instead of multiple components to enable the ingredients in the plating bath to stay within a defined range and ratio with the other ingredients,
  • 3. Avoiding contamination of the plating bath,
  • 4. Diligent maintenance of the plating tank and equipment,
  • 5. Avoiding defects in the coating of articles that would necessitate reworking of the articles and therefore additional redundant usage of the plating bath and reduction of its lifetime,
  • 6. Cooling heated plating baths at the end of a work shift,
  • 7. Filtration of the plating baths to avoid particulate that could lead to excessive plating within the plating bath and or the tank and equipment within the plating tank,
  • 8. As well as many other methods within commercial use.

One example of a benefit of the present invention in extending the lifetime of a plating bath is due to the difference in lifetime typically achieved in electroless nickel phosphorus plating baths based on the type of plating bath being used. High phosphorous electroless nickel plating baths are generally understood in the plating to industry to be useful for a lifetime of approximately 4-6 mental turnovers before the plating bath has reached the end of its useful life. This range of MTOs is based on an EN plating bath having 6 grams per liter of nickel. Plating baths with less than 6 grams per liter of nickel can achieve a higher number of MTOs because less nickel and other chemical ingredients are needed to achieve each MTO. The amount of plating produced from a plating bath (measured in terms of grams of metal deposited and/or mil-square feet) depends on both the number of MTO's and the concentration of metal(s) in the plating bath. One reason for the end of the high phosphorus plating bath's useful lifetime between 4-6 metal turnovers is because by that time in the life of a high phosphorus electroless nickel plating bath, the plating rate becomes significantly slower than the initial plating rate of the plating bath when it was newly made-up, at least in part consequential to the existence of byproducts at a growing rate, and that the plating rate at 4-6 MTOs becomes slower than commercially desirable. A second important reason why plating shops will stop using a high phosphorous electroless nickel plating bat at around 4-6 MTOs is because the nickel phosphorus alloy coating achieved from a plating bath at that late stage in that the plating bath's life will no longer have the optimal physical properties required for commercial applications. For example, at that point in a high phosphorus plating bath's life, the coating will have different levels of hardness, stress, corrosion resistance, and other properties, compared to the levels of these parameters produced by the same plating bath when it was initially made up and/or had less MTOs. Consequently, at that point in the bath's life, the high phosphorous bath is no longer adequate for commercial plating.

Inadequate corrosion resistance of the plating from such a plating bath at this late stage of the bath's lifetime is significant because high levels of corrosion resistance are one of the primary reasons that a high phosphorus nickel alloy would be specified for a commercial application, and therefore why a high phosphorus type electroless nickel plating bath is used instead of using a low or medium phosphorus electroless nickel plating bath.

There are many reasons why a plating shop would prefer to use a low or medium phosphorous electroless nickel plating bath, rather than a high phosphorous electroless nickel plating bath. One such reason is the inherently faster plating rate of low and medium phosphorous electroless nickel plating baths compared to high phosphorous baths.

There are two most common methods used in the plating industry to test the corrosion resistance of plated layers, other than use of plated parts in actual usage conditions.

The first is a salt spray test where the plated part is enclosed in a chamber with a continual spray of a salt fog at defined temperature, humidity and salt concentration for a number of hours to determine the salt spray corrosion resistance of the coating. There are many flaws with this method as successful salt spray resistance depends on not only the plating, but also the substrate, the pretreatment of the substrate prior to plating, as well as the plating bath chemistry and how it is operated. Moreover, salt spray testing is a method to indicate the corrosion resistance of a plated layer, but this method generally does not represent the actual environmental conditions to which an actual plated part will be used in its actual application.

The second method to test the corrosion resistance of a plated layer is commonly known as the ‘nitric acid test’. The standard way this test is employed is to immerse a plated panel into concentrated nitric acid to see if there is any discoloration (corrosion) of the plating. A plated layer is considered to pass the nitric acid test if the plating can withstand 30 seconds of immersion in this nitric acid without discoloring. The nitric acid test is commonly used in the plating industry as test of corrosion resistance, which is also a verification of the percentage of phosphorous in an electroless nickel coating. In general, a high phosphorous electroless nickel coating will pass the nitric acid test. Low and medium phosphorous electroless nickel coatings will not.

A high phosphorus electroless nickel plating bath typically plates at a rate of 10 to 12 microns per hour at the outset of a new plating bath's life as made-up, and this rate typically gradually decreases to about 7 to 9 microns per hour after a number of metal turnovers.

By contrast, a typical medium phosphorus electroless nickel plating bath will have an initial plating rate between 18 and 25 microns per hour. As a typical medium phosphorus plating bath is used, the plating rate will normally decrease to about 15 microns per hour by the time the plating bath reaches eight or more metal turnovers.

A typical low phosphorus electroless nickel plating bath will have an initial plating rate between 20 and 25 microns per hour. As a typical low phosphorus plating bath is used, the plating rate will normally decrease to about 15 microns per hour by the time the plating bath reaches eight or more metal turnovers.

Users of such plating baths are able to counteract the inherent decrease in plating rate over the lifetime of a plating bath by adjusting parameters such as pH and temperature of the plating bath. However, these adjustments are only able to decrease the plating rate to a limited extent. Moreover, such adjustments may have consequences for the operation of the plating bath that are undesirable such as less stability of the plating bath, plate out onto the tank and auxiliary equipment, and so on. Plate out is a term used to describe the plating onto the tank, a tank liner if used, any auxiliary equipment in the plating tank such as pumps, pipes, and so on. Plate out is problematic for a number of reasons including the waste of chemicals used in plating these surfaces that are not desired to be coated, reducing the stability of the plating bath, affecting the plating quality on the coating on actual parts or substrates where quality coating is desired, the need to strip the plating from the tank, pumps, pipes and other auxiliary plated out surfaces, interruption of the plating schedule, reduction in plating bath life, additional waste treatment, and other problems known in the plating industry associated with plate out.

The percentage of phosphorus in the electroless nickel coating inversely correlates directly to the plating rate of the plating bath. As noted, the plating rate of high phosphorus electroless nickel plating baths is inherently slower than the plating rate of medium phosphorus or low phosphorus plating baths. The slow plating rate of high phosphorus plating bath is one of the key ways that high phosphorus plating baths are able to produce high phosphorus coatings.

The percent phosphorus in an electroless nickel coating can be adjusted to some extent in any type of plating bath (low, medium, or high phosphorus) by adjusting parameters such as the temperature, pH, plating bath age, surface area loading in the tank, agitation, and other factors. Practically, however, the amount of phosphorus in the electroless nickel coating that can be modified by adjusting these plating bath parameters is relatively small (essentially only by a few percent of phosphorus in the coating). Adjusting these parameters would not, for example, be able to convert what is typically understood to be a low phosphorus electroless nickel plating bath for example into a high phosphorus electroless nickel plating bath, similarly just by changing these parameters; it is not practical that a high phosphorus plating bath could be adjusted in order to produce a low phosphorus electroless nickel coating.

One of the reasons for this limitation is that high phosphorus plating baths used commercially in the planting industry are typically made without certain stabilizers and without sulfur ingredients, which can act as accelerators of the plating rate. Such sulfur based and other plating rate accelerating ingredients are commonly used in low and medium phosphorus electroless nickel plating baths. It is well known in the industry that cross contamination between low or medium phosphorous electroless nickel plating baths must be avoided into high phosphorus electrochemical plating baths. If the sulfur, or other ingredients contained in the low or medium high phosphorus bath, is allowed to contaminate the high phosphorus plating bath, sulfur and the like can impact the physical properties of the coating made by the high phosphorus electroless nickel plating bath. This impact can include the corrosion resistance of the coating which is especially problematic for the reasons noted herein that high corrosion resistance is one of the primary reasons for using a high phosphorus electroless nickel plating bath.

Manufacturers of electroless nickel plating solutions must also be careful to avoid sulfur and other ingredients from contaminating the plating solutions that are used in high phosphorus electroless nickel plating applications.

Extending the life of a plating bath is an important environmental consideration to avoid or delay wasting a plating bath before it is absolutely necessary to do so and then environmentally treat a plating bath. Waste treatment of a plating bath requires materials, energy, expense, labor, overhead, documentation and many other costs, so it is desirable to minimize the amount or frequency of plating baths that need to be waste treated. When a plating bath reaches the point that it is no longer considered commercially or technically useful for continued use, and therefore has reached the end of its useful lifetime, the plating bath is typically called used, spent, waste, or other such terms. These terms can be used interchangeably. Depending on location used, EN baths may or may not be considered hazardous waste according to regulatory agencies.

Waste treatment of spent electroless nickel plating baths is typically handled in the electroless nickel plating industry by one of several different methods. One method is to have the plating bath hauled away for treatment or disposal elsewhere. This method requires paying one or more third parties to remove and treat or dispose of the used plating bath in consistency with applicable regulations, among other reasons. Depending on the quantity of such used plating baths generated by a plating shop and depending on the location of the plating shop and the regulatory requirements of that locale, there may be permitting and other regulatory administrative requirements the plating shop would need to comply with. This is another possible expense of time and resources for the plating shop and therefore another reason why extending the plating bath lifetime would be advantageous.

A second method for treating a spent electroless nickel plating bath is to perform a procedure generally known as “plateout.” In this procedure, certain chemicals are added to the plating bath such as a pH adjuster to increase the pH of the plating bath, and/or such as additional reducing agent to the plating bath in order to increase the activity level of the plating bath. This is done so that when a load of parts, typically steel, or steel wool with a high surface area is immersed in the plating bath, the plating activity is so high that essentially all of the nickel metal in the plating bath will be plated out onto the steel or the like. This method is intended to remove the nickel from the plating bath, so that the remaining liquid of the plating bath will free or essentially free of nickel. Thus, the remaining liquid may then be treated separately by other methods such as ion exchange, precipitation, neutralization, reverse osmosis, or dilution with other waste streams in order to dispose of it. There are regulatory issues involved with this method as well.

A third method of treating a spent electroless nickel plating baths is to evaporate the plating bath. Naturally this takes time, energy, equipment, and disposal of the resulting dry material or sludge which also must be dealt with. Regulatory issues are also involved with this method.

Fourth, there are methods to chemically treat a spent electroless nickel plating bath that involve adding chemicals such as flocculants or absorbents to precipitate or otherwise separate the nickel from the plating bath. Such a precipitation method, like the plateout method, is often complicated by certain ingredients within a typical electroless nickel plating bath such as ammonium hydroxide and other complexing agents that are included in the plating bath for plating functionality, but complicate the ability to then remove the nickel from the plating bath. While such a precipitation method is able to be accomplished on a spent electroless nickel plating bath, and the nickel is entirely or essentially removed, the remaining liquid of the plating bath still needs to be treated by one or more of the methods noted above, in addition to still dealing with regulatory issues.

The present invention is a significant deviation from the prior art where the objective of the prior art plating solutions was to maintain a consistent type of coating over the entire course of the plating bath's lifetime. The present invention represents a novel method of using a plating bath to produce coatings of a specific type and then being able to continue to use the same initial plating bath that has been used for plating to produce coatings of a first specific type to then be able to produce coatings of a second specific, or different, type or kind. This is achieved in the present invention by using one or more chemicals or solutions in the initial phase of a plating bath's lifetime; and then at a point in time in the plating bath's lifetime, preferably but not exclusively at or near the bath's end of life, the plating bath is replenished with one or more chemicals or solutions that are different to some extent from the chemicals or solutions used in the plating bath in the initial phase of the plating bath's lifetime, thereby extending the bath's life beyond its nominal end of life.

One of the many practical advantages of the present invention relates to the issues disclosed above, and widely understood in the worldwide electroless nickel plating industry, is about overcoming the significantly shorter bath life achievable from a high phosphorus electroless nickel plating bath compared to the bath life achievable from a low or medium phosphorus electroless nickel plating bath. This significant difference in plating baths'lifetimes is widely understood and widely accepted in the electroless nickel plating industry. People knowledgeable about the electroless nickel plating industry understand why this differential in plating bath lifetimes makes high phosphorus electroless nickel plating more expensive, more wasteful, less productive, and with other inherent comparative deficiencies.

The practice prior to the present invention in the electroless nickel industry was to operate high phosphorus plating baths up to a lifetime of approximately 4-6 metal turnovers before resorting to waste treatment of the plating bath by the methods described herein or others that may be available to the plating shop. The present invention provides an opportunity to obtain further useful productive plating from such a plating bath that would have previously been considered spent or waste or no longer commercially useful. In one embodiment of the present invention, the present invention achieves this important benefit by replenishing a fully or partially used high phosphorus electroless nickel plating bath with one or more chemicals or solutions that are able to essentially transform the planting bath into a medium phosphorus electroless nickel plating bath. By doing so, the plating bath does not need to be removed from use and waste treated prematurely. Instead, the plating bath is able to continue to be used productively by producing a medium phosphorus electroless nickel alloy coating for additional metal turnovers of the plating bath and at a higher plating rate than the plating bath was providing during its initial period of use as a high phosphorus electroless nickel plating bath.

As demonstrated in the examples of the present invention, the transformation of the high phosphorus plating bath to a medium phosphorus plating bath drastically increases the lifetime of the plating bath and reduced the amount of waste required for treatment.

The plating bath in Example 1 was able to produce more than 5 additional MTOs of medium phosphorous EN plating after the same bath had already been used for 5.06 MTOs of high phosphorous plating. This achievement of the present invention cut the waste treatment of this bath by more than half.

As also demonstrated in the examples of the present invention, such as Example 2, the utility of the present invention is greatly enabled by the use of chemicals or solutions in each the multiple phases of the plating bath's lifetime where these chemicals or solutions are compatible with each other. This is especially true when the chemicals or solutions used in each of the multiple phases of the plating bath lifetime are as identical to each other as possible, other than, for example, the phosphorous levels and related chemicals.

Moreover, the utility of the present invention is also greatly enabled by the use of single component solutions in each of the phases of the plating bath's lifetime, as this provides the benefits inherent in the use of single component plating solutions as described herein, such as Examples 1, 2, 4, 6, 7, 8, 9, and 10.

For example, the transformation from the high phosphorus stage of a plating bath's lifetime to a medium phosphorus plating bath is facilitated when a high phosphorous single component electroless nickel solution is used for the initial bath makeup and subsequent replenishment in the first stage of its lifetime to produce high phosphorus electroless nickel coatings; and then when a medium phosphorous single component electroless nickel solution is used to replenish the bath in the second stage of its lifetime to produce medium phosphorus electroless nickel coatings is as close to identical as possible with the high phosphorous single component solution used in the first phase of the bath's lifetime. This is achievable when the two single component solutions have identical types and concentrations of the bulk ingredients such as metal salt, reducing agent, pH adjusters, complexing agents, and others as in Examples 1, 2, 6, 7, 8, 9, and 10.

These bulk ingredients represent typically more than 95% of the composition of a single component solution. When the only difference between the replenishment solution in the first stage of the plating bath's life and the replenishment solution in the second stage of the plating bath's life is the type or concentration of stabilizers, accelerators, brighteners, particulate matter stabilizers, and the like, then the effectiveness of transforming the plating bath from a plating bath capable of producing one type of plated layer to a plating bath capable of producing a different type of plated layer is dramatically increased. This improvement includes the effectiveness of transforming the plating bath from a high phosphorus planting bath to a medium phosphorus plating bath mid-use is dramatically increased.

Maximum consistency in the chemicals or solutions used in the multiple phases of a plating bath's lifetime in the present invention is also important not only for the performance of the plating bath, but also the physical characteristics of the resulting plating onto articles. The plating itself must meet various requirements such as appearance, uniformity, level of brightness, and so on. The compatibility of the replenishment solution from the first phase of the plating bath life to the replenishment solution in the second phase of the plating bath life can significantly improve the ability of the plating bath in the second phase to produce coatings that meet the various physical properties required as has also been discussed herein.

The use of auxiliary chemicals to facilitate any or all aspects of the plating bath performance and or properties of the plated layers is certainly viable within the scope of the present invention. Such auxiliary chemicals maybe added to the plating bath in addition to the one or more premixed solutions as discussed in the present invention. Such auxiliary chemicals may also be added to the one or more premixed solutions for the purposes described herein.

In addition to the utility of producing different phosphorous concentrations in the electroless nickel plated alloy from a plating bath by employing the present invention, there are other properties such as but not limited to hardness, stress, magnetics, conductivity, resistivity, porosity, reflectivity, wear resistance, coefficient of friction, adhesion, elasticity, elongation, density, and coefficient of thermal expansion, that are important relative to the finished product and which can be varied in the different phases of use in a plating bath used according to the present invention. These and other properties differ at least between low, medium, and high phosphorus. Even changes in the brightness and aesthetic appearance of plating can be altered between different stages in a plating bath used according to the present invention.

It is important to point out that the present invention can also be used simply for extending the life of a plating bath even if changing one or more physical parameters of the coating from a first type to a second type of a plating bath life is not necessary. There is utility in extending a plating bath for the reasons disclosed herein.

The present invention can be practiced with one or multiple solutions for the makeup and/or replenishment of the plating bath in one phase of the plating bath's lifetime, and one or multiple other solutions for the replenishment of the plating bath in a subsequent phase of its lifetime.

EXAMPLES

FIG. 1, incorporated herein, includes several examples of different plating baths'performance over time applicable to the present invention. FIG. 1 discloses the relevant operational parameters, plating bath performance, and plating results data for a number of plating bath systems.

In each of the examples in FIG. 1:

• • 1. An electroless nickel bath was formed.
  • 2. Mild agitation was introduced to each plating bath.
  • 3. The pH of each of the baths was maintained at values as noted.
  • 4. The operating temperature of each of the baths was maintained at temperatures as noted.
  • 5. Substrates made of steel, stainless steel, copper and/or aluminum alloys were cleaned and otherwise pretreated and immersed into the plating baths formed by the solutions listed in (in FIG. 1).
  • 6. The surface area of the substrate(s) was maintained within the range appropriate for each plating bath according to the manufacturer's specifications in square feet of substrate surface area to gallons of plating bath.
  • 7. The substrates were left in each of the plating baths for cycle times as noted, during which time the pH, temperature and agitation of each of the plating baths were monitored and maintained.
  • 8. The plated layers on the substrates were analyzed at relevant bath usage increments for uniformity, appearance, hardness, phosphorous content, and the industry standard nitric acid test. Any data points not presented in FIG. 1, can be inferred by one skilled in the art to be consistent with adjacent data points in the plating bath system. In those examples, where insoluble particulate matter was included in the solution used in each of these plating baths, the resulting platings were analyzed by cross sectional examination to verify the incorporation of these particulate materials in the plating.
  • 9. The details of the plated layer parameters are listed in FIG. 1
  • 10. The plating baths were analyzed.
  • 11. Each of the plating baths were analyzed for the metal salt, reducing agent, and other ingredients'concentration and replenished with either:
    • a. The required quantity of the exact same solution or solutions or a compatible solution or solutions as used in the makeup of the respective plating bath to return metal salt, reducing agent, and other ingredients'concentration of the plating bath to the respective concentrations required to produce the same type of plated layer as preciously produced by the plating bath on one or more additional substrates; or
    • b. The required quantity of a different solution or solutions as used in the makeup and previous replenishment of the respective plating bath to adjust the metal salt, reducing agent, and/or other ingredients of the plating bath to produce a different type of plated layer as preciously produced by the plating bath.
  • 12. The replenishment of the plating bath was made during and/or after the substrates were being plated in the plating bath.
  • 13. This process of plating substrates, analyzing the substrates, analyzing the baths, and replenishing the baths was continued until each of the baths reached the number of metal turnovers as noted. This process was implemented at timing consistent with conventional plating practice in order to maintain the concentration of materials in the plating bath in a useful range.

Throughout the process, the pH, temperature and agitation were maintained, and the plating reaction was observed by the bubbles evolving from the substrates. This process was performed on each of the plating baths in FIG. 1 over the course of a number of days with the baths cooled at the end of use on one day and reheated to the operating temperature on the following day. Filtration of the plating baths was employed. This process is representative of the typical usage of a plating bath in commercial practice.

These examples demonstrate the following combinations of multi-purpose plating baths, as accomplished by the present invention:

• • High phosphorous to medium phosphorous
  • High phosphorous to low phosphorous
  • Low phosphorous to medium phosphorous
  • Medium phosphorous to medium phosphorous with PTFE
  • High phosphorous to medium phosphorous with boron nitride
  • High phosphorous to medium phosphorous with diamond
  • A single component system to a multiple component system
  • A single component system to a single component system.
  • A multiple component system to a single component system
  • The use of auxiliary solutions
  • Acid to alkaline
  • Alkaline to acid
  • Useless to useful
  • Lower hardness to higher hardness
  • Compressive stress to tensile stress
  • Slower plating rate to higher plating rate
  • Higher corrosion resistance to lower corrosion resistance

These examples include the use of the following plating solutions:

• • One-Plate® 2001Q-2.0 as sold by Surface Technology, Inc. of Ewing, NJ USA.
  • One-Plate® 1001Q as sold by Surface Technology, Inc. of Ewing, NJ USA.
  • One-Plate® 1001S as sold by Surface Technology, Inc. of Ewing, NJ USA.
  • One-Plate® 3001Q-2.0 as sold by Surface Technology, Inc. of Ewing, NJ USA.
  • Ni-Plate® 201 A, B, and C as sold by Surface Technology, Inc. of Ewing, NJ USA.
  • Ni-Plate® 100 A and C as sold by Surface Technology, Inc. of Ewing, NJ USA.
  • Ni-Plate® 300 A, B, and C as sold by Surface Technology, Inc. of Ewing, NJ USA.
  • Ni-Plate® 161 E and C as sold by Surface Technology, Inc. of Ewing, NJ USA.
  • Ni-Slip® 500 D-NPF as sold by Surface Technology, Inc. of Ewing, NJ USA.
  • Ni-Slip® 25 D as sold by Surface Technology, Inc. of Ewing, NJ USA.
  • Composite Diamond Coating CDC® D-2 as sold by Surface Technology, Inc. of Ewing, NJ USA.

Other combinations and utility can further be achieved according to the novel method of the present invention whereby a single plating bath is operated to provide for multiple purposes.

A sample technical data sheets associated with these solutions is attached as Appendix 1, incorporated herein by reference.

A sample safety data sheets associated with solutions is attached as Appendix 2, also incorporated herein by reference.

It was observed in Experiment 7, that the plated layer looked unique for an electroless nickel-boron nitride coating compared to the conventional appearance for such a coating in the plating industry. Rather than the traditional semi-bright or matte nickel finish, the plated layer in this example of the present invention had a matte gray/blue appearance similar to a typical electroless nickel-PTFE coating. Moreover, the electroless nickel-boron nitride coating of this example also had a physical appearance and tactile feel more consistent with a typical electroless nickel-PTFE coating. Upon microscopic examination of the electroless nickel-boron nitride coating of Experiment 7, the surface of the coating exhibited a surface profile with a texture similar to electroless nickel-PTFE consistent with what is often described as an orange peel surface. As there are certain deficiencies and concerns with the use of PTFE in general, and in plating applications specifically, an alternative to PTFE has long since been desirable. The use of boron nitride has been the most commercially preferred alternative to PTFE in the electroless nickel industry. While the use of boron nitride has some advantages over PTFE to the plater as well as the plated layer, the surface finish of the typical plated layer of electroless nickel with boron nitride is often not as useful to applications requiring low friction and release properties because such coatings lack the surface profile of electroless nickel-PTFE coatings. Therefore, the plating conditions including plating rate and other parameters of the present invention have benefits to producing electroless nickel-boron nitride coatings with improved properties.

Example 9 demonstrates the utility of the present invention to transform an acid type EN plating bath with a high number of MTOs, that was no longer useful for its initial purpose to produce a medium phosphorous EN coating, into an alkaline EN plating bath that was able to be used for a different purpose. This different purpose was to serve as a “strike” or “flash” plating bath for plating aluminum substrates as disclosed in the present invention. This is an additional example of how the present invention can avoid the make up of additional plating baths, reduce waste, increase utility to the plating operator, and other benefits. Example 10 similarly demonstrates such utility.