METHOD FOR ELECTROLYSIS-ASSISTED OXIDATIVE REGENERATION OF ALKALINE COPPER-AMMONIA CHLORIDE ETCHING WORKING SOLUTION, AND APPARATUS USING SAME

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation application of PCT application No. PCT/CN2024/071780 filed on Jan. 11, 2024, which claims the benefit of Chinese Patent Application No. 202310061500.5 filed on Jan. 13, 2023. The contents of all of the aforementioned applications are incorporated by reference herein in their entirety.

TECHNICAL FIELD

The present disclosure belongs to the technical field of etching processes for printed circuit boards, and specifically relates to a method for electrolysis-assisted oxidative regeneration of an alkaline copper-ammonia chloride etching working solution, and an apparatus using the same.

BACKGROUND

The etching processes for printed circuit boards are divided into acidic etching processes and alkaline etching processes. The alkaline etching processes are primarily alkaline copper-ammonia chloride etching processes. In the industry, an etching solution in an etching machine is commonly referred to as an etching working solution. An etching working solution adopted in the alkaline copper-ammonia chloride etching process, namely, an alkaline copper-ammonia chloride etching working solution, mainly includes an ammonia source, ammonium chloride, and a copper-ammonia chloride complex (Cu(NH₃)₄Cl₂), and may also include other ammonium salt additives and/or other additives. The traditional alkaline copper-ammonia chloride etching working solution mainly adopts ammonia water as the ammonia source. To improve the etching performance, a novel alkaline copper-ammonia chloride etching working solution formula, namely, a weakly-alkaline etching solution, has emerged in the industry. In this weakly-alkaline etching solution, ammonium bicarbonate and/or ammonium carbonate are/is adopted as the major ammonia source. This weakly-alkaline etching solution has a lower pH than the traditional alkaline copper-ammonia chloride etching solution, which can reduce the volatilization and pollution of free ammonia during an etching process.

During an etching production process, a desired replenishment solution needs to be continuously fed into an etching machine to balance and stabilize a concentration of each component and a ratio of components in an etching working solution, thereby maintaining the etching performance. Such a replenishment solution is referred to as an etching replenisher. An alkaline copper-ammonia chloride etching replenisher mainly includes an ammonia source and ammonium chloride, and may also include other ammonium salt additives and/or other additives. During the continuous etching production of printed circuit boards, because a large amount of an etching replenisher is fed into an etching machine, an etching working solution overflows from a tank to be outside the etching machine to produce an overflow solution, which is referred to as a spent etching solution.

A copper-etching agent in the alkaline copper-ammonia chloride etching working solution is a divalent copper-ammonia chloride complex Cu(NH₃)₄Cl₂. During an etching process, the divalent copper-ammonia complex reacts with metallic copper and is converted into a monovalent copper-ammonia complex Cu(NH₃)₂Cl accordingly (as shown in the following equation), resulting in the loss of copper-etching performance:

To maintain a stable etching rate, a substantial amount of an etching replenisher must be introduced, such that, under the action of an oxidant, a monovalent copper-ammonia complex in an etching working solution can be oxidatively regenerated into a divalent copper-ammonia complex as a copper-etching agent. The corresponding reaction principle is as follows:

For the oxidative regeneration of the alkaline copper-ammonia chloride etching working solution, the following technology is currently adopted: Oxygen in air is adopted as an oxidant. Fresh air is introduced into an etching machine under a negative pressure induced by extraction ventilation, an etching working solution is atomized through spraying to produce liquid droplets, and the liquid droplets are then allowed to contact the fresh air, such that the oxidative regeneration of a copper-etching agent is achieved through oxygen in the fresh air. On the typical alkaline etching machine, a spray device and a tail gas treatment device are arranged, which together constitute a spray-oxygen absorption-exhausting system. The spray device is configured to spray an etching working solution on a printed circuit board to be etched. The tail gas treatment device is configured to neutralize a gas discharged from an etching machine. In the spray-oxygen absorption-exhausting system, a fan is typically adopted as a power source for introducing fresh air into an etching machine, and the fan is commonly arranged at a position of the tail gas treatment device.

However, the above technology presents the following deficiencies:

1. Due to the solution turbulence caused by a spraying operation, an ammonia gas is constantly released from an etching working solution. To meet the oxidative regeneration demand of a copper-etching agent, fresh air needs to be introduced into an etching machine at a high flow rate. Consequently, a large amount of an ammonia gas will be extracted from the etching machine by a high-flow-rate extraction operation of the spray-oxygen absorption-exhausting system, resulting in the waste of an ammonia water raw material and even the potential etching performance failure due to ammonia deficiency in the etching working solution.

2. Due to the release of ammonia, a significant amount of an ammonia gas is present in a tail gas discharged during an etching process and requires an environmental treatment, which increases the production cost.

3. When a weakly-alkaline etching process is adopted, due to a low pH of an etching working solution adopted for the weakly-alkaline etching process, the reducibility of a monovalent copper-ammonia chloride complex Cu(NH₃)₂Cl in the etching working solution is weakened, resulting in a low oxidation reaction rate of the monovalent copper-ammonia chloride complex with oxygen in air. As a result, the regeneration efficiency of a copper-etching agent by the existing technology for oxidative regeneration of a copper-etching agent is low, and can hardly meet the production requirements.

To address the shortcomings of the existing technology for oxidative regeneration of a copper-etching agent in an alkaline copper-ammonia chloride etching working solution, the essential auxiliary oxidative regeneration process improvement is required, such that an etching rate can meet the production etching rate requirement or the ammonia utilization can be effectively optimized and the ammonia pollution can be reduced.

SUMMARY

A first objective of the present disclosure is to provide a method for electrolysis-assisted oxidative regeneration of an alkaline copper-ammonia chloride etching working solution. In this method, a regenerated copper-etching agent is oxidatively regenerated from an etching working solution through electrolysis, which can effectively improve the etching efficiency and/or reduce the ammonia pollution and enhance the ammonia utilization.

A second objective of the present disclosure is to provide an apparatus for electrolysis-assisted oxidative regeneration of an alkaline copper-ammonia chloride etching working solution.

The first objective of the present disclosure is achieved through the following technical solutions:

A method for electrolysis-assisted oxidative regeneration of an alkaline copper-ammonia chloride etching working solution is provided, where the alkaline copper-ammonia chloride etching working solution is used for etching on an etching machine, and the method includes the following steps:

(1) selecting an electrolytic cell provided with an electrolytic cell separator, where the electrolytic cell is divided by the electrolytic cell separator into an anode cell zone and a cathode cell zone; an anode is provided in the anode cell zone and is connected to a positive electrode of an electrolytic power supply; and a cathode is provided in the cathode cell zone and is connected to a negative electrode of the electrolytic power supply;

(2) with the alkaline copper-ammonia chloride etching working solution as an anode electrolyte, conducting electrolysis in the electrolytic cell, where a reaction of oxidatively regenerating a copper-etching agent occurs in the anode cell zone; and

• • during the electrolysis, the alkaline copper-ammonia chloride etching working solution circularly flows between the etching machine and the anode cell zone of the electrolytic cell; and

(3) during the electrolysis, controlling an oxidation-reduction potential (ORP) value of the anode electrolyte at 300 mV or less, and feeding an etching replenisher into the alkaline copper-ammonia chloride etching working solution to participate in the reaction of oxidatively regenerating the copper-etching agent, such that a pH value and/or a copper ion concentration of the alkaline copper-ammonia chloride etching working solution on the etching machine are/is controlled within a set process range.

The method of the present disclosure is applicable to the oxidative regeneration of various alkaline copper-ammonia chloride etching working solutions with a copper ion concentration of 60 g/L to 170 g/L and a pH value of 7 to 9. In addition to the traditional alkaline copper-ammonia chloride etching working solutions, the present disclosure also includes other alkaline copper-ammonia chloride etching working solutions each including both an ammonia source and a chloride ion, such as weakly-alkaline etching solutions.

In the step (2), the circulation of the etching working solution between the etching machine and the anode cell zone of the electrolytic cell refers to the circulation of the etching working solution between an etching machine and the anode cell zone of the electrolytic cell.

In the step (3), the etching replenisher can be added to the anode cell zone and/or the etching machine and/or a container connected to either of the anode cell zone and the etching machine and/or a solution mixing junction of the anode cell zone and the etching machine.

The etching machine of the present disclosure is provided with a spray-oxygen absorption-exhausting system. Through multiple repeated experiments, the inventors have discovered that, during the electrolysis-assisted oxidative regeneration of an alkaline copper-ammonia chloride etching working solution in the present disclosure, through different combinations of an electrolytic cell separator and electrolytes and varying electrolyte parameters, oxidants such as oxygen and/or chlorine and/or a hydroxyl radical can be generated on the electrolytic anode. These oxidants promote the oxidative regeneration of a monovalent copper-ammonia complex in an etching working solution into a copper-etching agent, namely, a divalent copper-ammonia chloride complex Cu(NH₃)₄Cl₂. As a result, a concentration of the copper-etching agent in the alkaline copper-ammonia chloride etching working solution can be guaranteed, and the etching efficiency can also meet the production requirements. Consequently, while effectively enhancing the etching efficiency, the present disclosure can significantly mitigate the raw material waste and ammonia pollution issues by reducing a flow rate of fresh air supplied during an etching process. Further, when the etching working solution has a relatively low pH value, a monovalent copper-ammonia chloride complex Cu(NH₃)₂Cl exhibits weak reducibility and can hardly be oxidized. In this case, a rate of electrolytic oxidation of the monovalent copper-ammonia chloride complex is higher than a rate of oxygen-exchange oxidation. Thus, the method of the present disclosure can remarkably enhance an etching rate of an alkaline copper-ammonia chloride etching working solution with pH of less than or equal to 8.5, thereby meeting the production requirements.

The alkaline copper-ammonia chloride etching working solution (hereinafter also referred to as an etching working solution) includes a large number of chloride ions. As a result, during the electrolysis-assisted oxidative regeneration of the etching working solution, these chloride ions are easily oxidized at the electrolytic anode to produce chlorine and/or a hypochlorite ion in a solution. Subsequently, depending on the ease of electron losses of reductive substances in the etching working solution during an oxidation reaction, the chlorine and/or the hypochlorite ion will undergo a chemical reaction with these reductive substances sequentially. The chlorine and the hypochlorite ion generated during the electrolysis will preferentially react with the monovalent copper-ammonia complex in the etching working solution.

However, when there are uneven concentrations locally in a reaction solution during the electrolysis, the chlorine and the hypochlorite ion may further react with ammonia and ammonium ions in the etching working solution. Moreover, when the etching working solution further includes at least one of a carbonate, a bicarbonate, and a reducing additive, these substances also participates in the above reaction. The addition of the etching replenisher is intended to compensate those components consumed in the reaction of oxidatively regenerating the copper-etching agent in the etching working solution. However, the components additionally consumed by the chlorine and the hypochlorite ion in the etching working solution cannot be routinely compensated through the etching replenisher due to irregular patterns of consumption and substantial consumption. Correspondingly, the original balance among concentrations of various substances in the etching working solution is disrupted, and a pH value of the etching working solution abnormally decreases, resulting in the imbalance in a chemical reaction for copper etching on the etching machine. Therefore, during the electrolysis, the control of the ORP value of the anode electrolyte at 300 mV or less can ensure the effective regeneration of the copper-etching agent in the etching working solution while effectively preventing the oxidative consumption of reductive substances other than the monovalent copper-ammonia complex in the etching working solution.

When oxygen is generated at the electrolytic anode, the following electrochemical reaction takes place: 4[OH]⁻−4e⁻→2H₂O+O₂↑. In this case, the following chemical reactions occur in the anode electrolyte:

When chlorine is generated at the electrolytic anode, the following chemical reactions occur in the anode electrolyte:

A hydroxyl radical —OH is also generated in the anode electrolyte of the present disclosure during the electrolysis, and similarly, the following chemical reaction of oxidatively regenerating the copper-etching agent occurs:

Based on the above reaction mechanisms for copper etching and copper-etching agent regeneration, the etching working solution has a pH value continuously decreasing and a specific gravity value constantly increasing during the etching and regeneration processes. Therefore, at least one parameter of the above two process parameters can be adopted as a control basis. The etching replenisher is fed into the etching working solution based a change of the at least one parameter to control and maintain the continuous etching production.

The electrolytic cell separator in the step (1) is a material capable of effectively blocking entrance of copper ions and ammonium ions from the anode cell zone into the cathode cell zone, and is preferably at least one selected from the group consisting of a bipolar membrane, a reverse osmosis membrane, an anion-exchange membrane, a proton exchange membrane, and an ion selectivity-free membrane. The electrolytic cell separator can be further used in combination with a filter cloth. The reverse osmosis membrane is specifically a reverse osmosis membrane sheet, which generally has a lower price than the bipolar membrane, the ion-exchange membrane, and the proton exchange membrane and thus is economical and practical. More preferably, when the reverse osmosis membrane is adopted as the electrolytic cell separator, a pH value of an electrolyte in the electrolytic cell should be less than or equal to 11 to extend a service life of the reverse osmosis membrane.

The cathode electrolyte in the cathode cell zone may be any ammonia and/or ammonium-containing alkaline solution. An etching working solution, an etching replenisher, and a spent etching solution that include ammonia and/or ammonium adopted in an alkaline etching process all can be adopted as the ammonia and/or ammonium-containing alkaline solution. At the electrolytic cathode of the present disclosure, the following electrolytic reaction of water to produce hydrogen mainly occurs: 4H⁺+4e⁻→2H₂↑, and/or an electrochemical reaction of reducing a high-valence ion into a low-valence ion or a metal occurs. That is, when the cathode electrolyte includes a copper ion, a copper metal may be generated at the electrolytic cathode during the electrolysis.

Preferably, the cathode electrolyte in the cathode cell zone of the electrolytic cell is one or a mixed solution of two or more selected from the group consisting of a spent alkaline copper-ammonia chloride etching solution, an alkaline copper-ammonia chloride etching replenisher, an alkaline copper-ammonia chloride etching working solution, a copper-ammonia complex solution, ammonia water, an ammonium bicarbonate solution, and an ammonium carbonate solution.

Oxygen does not react with ammonia or ammonium ions, and exhibits a significantly lower reaction rate with carbonates, bicarbonates, and most reducing additives than chlorine. Consequently, any of the following preferred embodiments is adopted. Through a specific combination of an electrolytic cell separator and a cathode electrolyte, an electrochemical reaction environment favorable for oxygen evolution is created, such that an electrochemical reaction of electrolyzing water primarily occurs at the electrolytic anode of the electrolytic cell to produce oxygen. As a result, chloride ions can be effectively prevented from being oxidized through an electrochemical reaction at the anode to produce chlorine, thereby minimizing the generation of chlorine and hypochlorite ions and further protecting reductive substances other than the monovalent copper-ammonia complex in the etching working solution from oxidative consumption:

(1) The electrolytic cell separator is at least one selected from the group consisting of a reverse osmosis membrane, a bipolar membrane, a proton exchange membrane, and an ion selectivity-free membrane, and a cathode electrolyte is an ammonia and/or ammonium-containing alkaline solution.

(2) The electrolytic cell separator is an anion-exchange membrane, and the cathode electrolyte is ammonia water.

In the embodiment (1), when the bipolar membrane is adopted as the electrolytic cell separator, water molecules in the bipolar membrane are ionized to produce hydroxide ions and hydrogen ions during the electrolysis. The hydroxide ions migrate from an inside of the bipolar membrane into the anode electrolyte under an attraction action of an electric field, and thus are enriched, which promotes the electrochemical reaction of converting hydroxide ions into oxygen for evolution at the electrolytic anode. When the reverse osmosis membrane is adopted as the electrolytic cell separator, only water, hydrogen ions, and hydroxide ions are allowed to pass through due to special material properties. Thus, during the electrolysis, hydroxide ions in the cathode electrolyte pass through the electrolytic cell separator and enter the anode electrolyte under an attraction action of an electric field, and thus are enriched, which promotes the electrochemical reaction of converting hydroxide ions into oxygen for evolution at the electrolytic anode. When the proton exchange membrane is adopted as the electrolytic cell separator, hydrogen ions and hydronium ions are primarily allowed to pass through due to special material characteristics, which promotes the water electrolysis and oxygen evolution at the electrolytic anode during the electrolysis. When the ion selectivity-free membrane is adopted as the electrolytic cell separator, a pore size of the ion selectivity-free membrane blocks large ions while permitting small ions or molecules such as hydrogen ions and hydroxide ions to pass through, which promotes the occurrence of water electrolysis and oxygen evolution primarily at the electrolytic anode during the electrolysis. The ion selectivity-free membrane is a porous membrane or a porous film.

In the embodiment (2), when the anion-exchange membrane is adopted as the electrolytic cell separator and the ammonia water is adopted as the cathode electrolyte, during the electrolysis, hydroxide ions in the cathode electrolyte pass through the electrolytic cell separator and enter the anode electrolyte under an attraction action of an electric field, and thus are enriched, which promotes the electrochemical reaction of converting hydroxide ions into oxygen for evolution at the electrolytic anode.

Preferably, in the preferred embodiment (1), the electrolytic cell separator is the reverse osmosis membrane and/or the bipolar membrane and/or the ion selectivity-free membrane, and the cathode electrolyte of the electrolytic cell is a spent etching solution from the same etching solution system as the anode electrolyte. For example, a spent etching solution from the same etching machine as the anode electrolyte can be adopted, which can prevent the hydrogen evolution in the cathode cell zone during the electrolysis to avoid the generation of a new hazard source.

In order to effectively avoid the excessive rapid consumption of reductive substances other than a monovalent copper-ammonia complex in the alkaline copper-ammonia chloride etching working solution, such as ammonia, ammonium ions, carbonates, bicarbonates, and reducing additives, the present disclosure may take at least one of the following improvement measures when a consumption rate of a reductive substance or some reductive substances other than the monovalent copper-ammonia complex exceeds a preset value during an etching production process:

Measure 1: During the electrolysis, the ORP value of the anode electrolyte is reduced. Preferably, the ORP value of the anode electrolyte is controlled at less than or equal to 280 mV.

Measure 2: During the electrolysis, an effective electrolytic area of the anode in the electrolytic cell is increased. When etching requirements are met, the smaller the current density per unit area of the anode, the better. Similarly, at a same electrolysis power, the larger the surface area of the anode, the better. A method for increasing the effective electrolytic area of the anode includes, but is not limited to, increasing a volume of the anode, using an anode with a hollow or network structure, providing a protrusion at the anode, and adding an electrical conductor that is in contact with the anode and is not easily soluble in the anode electrolyte. The electrical conductor that is not easily soluble in the anode electrolyte is preferably at least one selected from the group consisting of gold, platinum, graphite, and a titanium-based coated insoluble anode.

Measure 3: A solution circulation flow rate between the anode cell zone of the electrolytic cell and the etching machine is increased to allow solution exchange and mixing, such that Cu(NH₃)₂Cl in the etching working solution is more likely to approach the anode and be oxidatively regenerated into a copper-etching agent Cu(NH₃)₄Cl₂.

Measure 4: A solution mixing-exchange tank is provided on a connecting pipeline between the anode cell zone of the electrolytic cell and the etching machine, and the solution mixing-exchange tank is connected to the anode cell zone of the electrolytic cell and the etching machine. A solution circulation flow rate between the anode cell zone of the electrolytic cell and the solution mixing-exchange tank is increased or a solution circulation flow rate between the anode cell zone of the electrolytic cell and the etching machine and the solution circulation flow rate between the anode cell zone of the electrolytic cell and the solution mixing-exchange tank are increased to allow solution exchange and mixing. As a result, Cu(NH₃)₂Cl in the etching working solution is more likely to approach the anode and be oxidatively regenerated into a copper-etching agent Cu(NH₃)₄Cl₂.

The above measures all can maintain a high concentration of the reductive substance Cu(NH₃)₂Cl in the anode electrolyte surrounding the anode, which leads to the additional advantage that the oxidant nitrogen trichloride can hardly be generated during the electrolysis. In the measure 4, the solution mixing-exchange tank can temporarily store a substantial amount of a solution in which a copper-etching agent has been oxidatively regenerated, such that an electrolysis-assisted oxidative regeneration system can rapidly respond to a change in an etching production load.

The present disclosure can be improved as follows: At least two parameters selected from the group consisting of an ORP value, the pH value, and a specific gravity value of the alkaline copper-ammonia chloride etching working solution on the etching machine are detected and monitored, and operations of the electrolytic cell and a feeding device for the etching replenisher are controlled based on detected parameter results. In this way, the electrolysis-assisted oxidation is added to the traditional oxidative regeneration process based on spray-oxygen absorption. Further, a control mode of combining an etching reaction of the etching machine and an electrochemical reaction of an electrolysis apparatus is adopted to stabilize the balance of an etching working solution, thereby enabling the continuous etching production of the etching working solution. Specifically, an output working current or start/stop of the electrolytic power supply of the electrolytic cell is controlled according to a measured ORP of the etching working solution on the etching machine, and/or a flow rate of an etching working solution produced from the electrolysis in the anode cell zone of the electrolytic cell to enter the etching machine is controlled, and the feeding of an etching replenisher and/or an etching solution raw material and/or water is controlled based on a measured pH and/or specific gravity value of the etching working solution on the etching machine.

Preferably, a temperature of the etching working solution on the etching machine is detected and monitored to control the temperature of the etching working solution.

Preferably, the ORP value of the anode electrolyte in the electrolytic cell and/or an ORP value of a solution in the solution mixing-exchange tank are/is detected and monitored, and an output working current or start/stop of the electrolytic power supply of the electrolytic cell is controlled according to a preset ORP value for the anode electrolyte and/or a preset ORP value for the solution in the solution mixing-exchange tank, so as to achieve the safe production and exert the performance of the electrolysis apparatus.

Preferably, at least one selected from the group consisting of an ORP value, a pH value, and a specific gravity value of the cathode electrolyte is detected and monitored to control an electrochemical reaction in the cathode cell zone.

Preferably, a feeding signal of a printed circuit board to be etched on the etching machine is used as a safety interlock for the electrolysis apparatus. When no additional printed circuit board to be etched is fed, the electrolytic power supply in the electrolysis-assisted oxidation apparatus is shut down within a safe time interval.

The present disclosure can also be improved as follows: A measure is taken to make an exhaust air volume in a spray-oxygen absorption-exhausting system on the etching machine adjustable, which reduces a fresh air supply volume while enabling the reaction of oxidatively regenerating a copper-etching agent and optimizes overall production conditions for a spray-oxygen absorption reaction based on a fresh air supply and discharge of an ammonia-polluted tail gas.

The second objective of the present disclosure is achieved through the following technical solutions:

An apparatus for electrolysis-assisted oxidative regeneration of an alkaline copper-ammonia chloride etching working solution using the method described above is provided, including an etching machine, an etching replenisher tank, and an electrolytic cell.

An electrolytic cell separator is provided in the electrolytic cell, and the electrolytic cell is divided by the electrolytic cell separator into an anode cell zone and a cathode cell zone. An anode is provided in the anode cell zone and is connected to a positive electrode of an electrolytic power supply. A cathode is provided in the cathode cell zone and is connected to a negative electrode of the electrolytic power supply. The anode cell zone of the electrolytic cell is connected to the etching machine through a pipeline to allow a liquid circulation flow between the anode cell zone of the electrolytic cell and the etching machine, such that the alkaline copper-ammonia chloride etching working solution undergoes an oxidative regeneration reaction in the electrolytic cell during the liquid circulation flow.

The etching replenisher tank is connected to the etching machine and/or the anode cell zone of the electrolytic cell, and is configured to store an etching replenisher. During the oxidative regeneration reaction, the etching replenisher is added to the anode cell zone and/or the etching machine and/or a container connected to either of the anode cell zone and the etching machine and/or a solution mixing junction of the anode cell zone and the etching machine.

The etching machine adopts an alkaline copper-ammonia chloride etching solution for printed circuit board etching. In addition to the conventional alkaline copper-ammonia chloride etching solution, the alkaline copper-ammonia chloride etching solution includes an etching solution including both an ammonia source and a chloride ion, such as a weakly-alkaline etching solution. The etching machine is provided with a spray device and a tail gas treatment device, which together constitute a spray-oxygen absorption-exhausting system. The tail gas treatment device is configured to treat a gas discharged from an etching machine or a polluted tail gas released during a reaction in a solution in each tank/cell of the apparatus of the present disclosure.

The etching replenisher tank is provided with a feeding device configured to feed the etching replenisher into the etching machine and/or the anode cell zone of the electrolytic cell for a copper-etching chemical reaction. The feeding device includes a feeding pipeline and a pump.

Preferably, the etching machine is connected to the anode cell zone of the electrolytic cell through at least two pipelines, and at least one of the at least two pipelines is provided with a pump to achieve a circulation flow of an etching working solution.

The electrolytic cell separator is a material capable of effectively blocking entrance of copper ions and ammonium ions from the anode cell zone into the cathode cell zone. Preferably, the electrolytic cell separator is at least one selected from the group consisting of a bipolar membrane, a reverse osmosis membrane, an anion-exchange membrane, a proton exchange membrane, and an ion selectivity-free membrane. More preferably, the electrolytic cell separator is the reverse osmosis membrane and/or the bipolar membrane and/or the ion selectivity-free membrane.

In the electrolytic cell, the anode is an insoluble anode, and the cathode is an electrical conductor. Preferably, an anode material is at least one selected from the group consisting of gold, platinum, graphite, and a titanium-based coated insoluble anode, and a cathode material is at least one selected from the group consisting of gold, platinum, graphite, titanium, copper, and stainless steel.

The present disclosure can be improved as follows: At least one pipeline between the anode cell zone of the electrolytic cell and the etching machine is provided with a solution mixing-exchange tank. The solution mixing-exchange tank is connected to each of the etching machine and the anode cell zone of the electrolytic cell through a pipeline, and is connected to at least one of the etching machine and the anode cell zone of the electrolytic cell through at least two pipelines to form a liquid flow circulation, such that solutions in the solution mixing-exchange tank, the etching machine, and the anode cell zone of the electrolytic cell undergo mixing and exchange. The storage of an etching solution produced after oxidative regeneration with a large-volume solution mixing-exchange tank can well respond to a change in an etching chemical reaction and create conditions to allow the rapid entrance of Cu(NH₃)₂Cl from an etching working solution into the anode cell zone of the electrolytic cell for oxidation. In this improved solution, the etching replenisher tank is connected to at least one of the etching machine, the anode cell zone of the electrolytic cell, and the solution mixing-exchange tank. During the oxidative regeneration reaction, the etching replenisher is fed through the feeding device to one or more of the etching machine, the anode cell zone of the electrolytic cell, and the solution mixing-exchange tank.

The present disclosure can be improved as follows: A temporary storage tank is further provided to store a material or serve as a chemical reaction tank. The temporary storage tank is connected to at least one of the etching machine, the electrolytic cell, and the solution mixing-exchange tank through a pipeline, or is arranged on a connecting pipeline between any two of the etching machine, the electrolytic cell, and the solution mixing-exchange tank.

The present disclosure can be improved as follows: A sensor is provided in at least one of the etching machine, the electrolytic cell, the solution mixing-exchange tank, and the temporary storage tank, and the sensor is one or more selected from the group consisting of an ORP meter, a pH meter, a liquid level meter, a thermometer, and a gravimeter. The ORP meter configured to test the anode electrolyte is arranged at a position where an ORP value can be timely and accurately detected. Preferably, an automatic detection/feeding controller is further provided. A control signal output terminal of the automatic detection/feeding controller is connected to a control signal input terminal of at least one pump and/or the feeding device and/or the electrolytic power supply in the apparatus of the present disclosure. The automatic detection/feeding controller is configured to control according to a preset time program and/or a value measured by the sensor. After the automatic detection/feeding controller is provided, a corresponding process can be automated.

The present disclosure can also be improved as follows: A liquid flow buffer tank is provided to solve the liquid flow problem between tanks/cells, such that a solution can flow smoothly between devices. The liquid flow buffer tank is connected to at least one of the etching machine, the electrolytic cell, the solution mixing-exchange tank, and the temporary storage tank through a pipeline, or is arranged on a connecting pipeline between any two of the etching machine, the electrolytic cell, the solution mixing-exchange tank, and the temporary storage tank.

The present disclosure can also be improved as follows: At least one of the electrolytic cell, the solution mixing-exchange tank, and the temporary storage tank is provided with a heat exchanger to control a working temperature of a corresponding solution.

The present disclosure can also be improved as follows: A solid-liquid separator is provided to separate and remove solid impurities from a reaction solution. The solid-liquid separator is connected to at least one of the etching machine, the electrolytic cell, the solution mixing-exchange tank, the temporary storage tank, and the liquid flow buffer tank through a pipeline, or is arranged on a connecting pipeline between any two of the etching machine, the electrolytic cell, the solution mixing-exchange tank, the temporary storage tank, and the liquid flow buffer tank.

The present disclosure can also be improved as follows: A variable-frequency fan is provided in the spray-oxygen absorption-exhausting system or the original fan is replaced with a variable-frequency fan to make an exhaust air volume adjustable, and/or a gas flow-regulating valve is provided on a gas extraction pipeline of the spray-oxygen absorption-exhausting system. Accordingly, an exhaust air volume of the spray-oxygen absorption-exhausting system in the prior art can be adjusted to control a discharged polluted ammonia gas.

The present disclosure can also be improved as follows: At least one of the electrolytic cell, the solution mixing-exchange tank, and the temporary storage tank is provided with a liquid flow circulation stirrer to make a concentration and temperature of a corresponding solution uniform and controllable.

Compared with the prior art, the present disclosure has the following beneficial effects:

1. The electrolysis-assisted oxidation method of the present disclosure accelerates an oxidative regeneration reaction for an alkaline copper-ammonia chloride etching working solution, thereby improving the etching production efficiency.

2. The electrolysis-assisted oxidation method of the present disclosure does not rely entirely on a spray-oxygen absorption-exhausting system of an etching machine for oxygen supply, and thus can reduce a flow rate of fresh air supplied during an etching process, thereby mitigating the ammonia pollution.

3. The electrolysis-assisted oxidation method of the present disclosure can reduce the waste of ammonia and improve the utilization efficiency of an ammonia raw material.

4. The apparatus using the electrolysis-assisted oxidation method of the present disclosure has a simple structure, is safe and reliable, and involves small investments and rapid returns.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of an apparatus and process flow for electrolysis-assisted oxidative regeneration of an alkaline copper-ammonia chloride etching working solution in Example 1 of the present disclosure;

FIG. 2 is a schematic diagram of an apparatus and process flow for electrolysis-assisted oxidative regeneration of an alkaline copper-ammonia chloride etching working solution in Example 2 of the present disclosure;

FIG. 3 is a schematic diagram of an apparatus and process flow for electrolysis-assisted oxidative regeneration of an alkaline copper-ammonia chloride etching working solution in Example 3 of the present disclosure;

FIG. 4 is a schematic diagram of an apparatus and process flow for electrolysis-assisted oxidative regeneration of an alkaline copper-ammonia chloride etching working solution in Example 4 of the present disclosure; and

FIG. 5 is a schematic diagram of an apparatus and process flow for electrolysis-assisted oxidative regeneration of an alkaline copper-ammonia chloride etching working solution in Example 5 of the present disclosure.

• • Reference numerals: 1—etching machine, 2—electrolytic cell, 3—electrolytic cell separator, 4—electrolytic anode, 5—electrolytic cathode, 6—electrolytic power supply, 7—sealing cell cover with a feeding and exhaust port for the electrolytic cell, 8—etching replenisher tank, 9—sensor, 10—automatic detection/feeding controller, 11—heat exchanger, 12—solid-liquid separator, 13—temporary storage tank, 14—liquid flow buffer tank, 15—liquid flow circulation stirrer, 16—impeller stirrer, 17—solution mixing-exchange tank, 18—hydrogen high-altitude discharge pipe, 19—valve, 20—pump, 21—etching replenisher, 22—spent etching solution, 23—etching working solution, 24—solution that has undergone a reduction treatment at the electrolytic cathode, 25—cathode electrolyte, 26—printed circuit board to be etched, 27—tail gas treatment device, 28—metallic copper, 29—gas flow-regulating valve, 30—variable-frequency fan, 31—acidic reaction solution for a tail gas treatment, and 32—nozzle.

DETAILED DESCRIPTION OF THE EMBODIMENTS

The present disclosure is further described below through specific embodiments.

The electrolytic cell, the temporary storage tank, the liquid flow buffer tank, the liquid flow circulation stirrer, the etching replenisher tank, the hydrogen high-altitude discharge pipe, and the solution mixing-exchange tank adopted in the following embodiments all are products of Yegao Environmental Protection Equipment Manufacturing Co., Ltd., Foshan City, Guangdong Province, China. YH-510A is an alkaline etching reducing additive product marketed by Yegao Chemical Co., Ltd. The etching machine, the heat exchanger, the electrolytic power supply, the sensor, the automatic detection/feeding controller, the valve, the pump, and the chemical raw material all are commercially-available products. Other products with similar properties to the products listed in the present disclosure may also be adopted by those skilled in the art according to conventional selection, which all can achieve the objectives of the present disclosure.

Example 1

FIG. 1 shows an apparatus and process flow for electrolysis-assisted oxidative regeneration of an alkaline copper-ammonia chloride etching working solution in this example. The apparatus includes an etching machine 1, an electrolytic cell 2, an electrolytic cell separator 3, an electrolytic power supply 6, an etching replenisher tank 8, sealing cell covers 7-1 and 7-2 each with a feeding and exhaust port for the electrolytic cell, sensors 9-1, 9-2, and 9-3, a hydrogen high-altitude discharge pipe 18, an etching replenisher 21, an etching working solution 23, a cathode electrolyte 25, a printed circuit board to be etched 26, a tail gas treatment device 27, a gas flow-regulating valve 29, a valve, and a pump.

The electrolytic cell 2 is divided by the electrolytic cell separator 3 into an anode cell zone and a cathode cell zone. The anode cell zone is connected to the etching machine 1 through two pipelines for a liquid flow circulation. The sealing cell covers 7-1 and 7-2 each with a feeding and exhaust port for the electrolytic cell are arranged for the anode cell zone and the cathode cell zone, respectively. The etching replenisher tank 8 is connected to the etching machine 1 through a pipeline.

The electrolytic cell separator 3 is an anion-exchange membrane. An electrolytic anode is a titanium-based coated electrode, and an electrolytic cathode is a stainless steel. The cathode electrolyte 25 is 12% ammonia water. The etching working solution is a mixed solution of main components of copper-ammonia chloride, ammonia water, and ammonium chloride. Specific process parameters are listed in Table 1.

In this example, a spray-oxygen absorption-exhausting system is provided, which is a treatment apparatus combining a spray device and the tail gas treatment device 27. The spray device includes pipelines arranged on the etching machine, a pump 20-2, and a nozzle 32, and is configured to direct the etching working solution to be above the spray device for spray atomization. The tail gas treatment device 27 is configured to receive waste gases from the etching machine 1, the electrolytic cell 2, and the etching replenisher tank 8 through gas pipelines. The gas flow-regulating valve 29 is arranged on a gas pipeline of the etching machine 1.

The sensor 9-1 is an ORP meter, the sensor 9-2 is a gravimeter, and the sensor 9-3 is an ORP meter.

In this example, operation steps for the electrolysis-assisted oxidative regeneration of an alkaline copper-ammonia chloride etching working solution in this example were as follows:

1. The etching working solution 23 was fed into the etching machine 1 and the anode cell zone of the electrolytic cell 2, with the etching working solution circularly flowing between the etching machine and the anode cell zone of the electrolytic cell. 12% ammonia water was fed into the cathode cell zone of the electrolytic cell 2. The gas flow-regulating valve 29 was maintained at the original fully-open state.

2. The spray-oxygen absorption-exhausting system of the etching machine was started. The printed circuit board to be etched 26 was fed into the etching machine 1 for etching. The feeding of the etching replenisher 21 was controlled according to a value detected by the sensor 9-2 as a gravimeter to ensure that the etching working solution met the set process parameters. If a value detected by the sensor 9-1 as an ORP meter was 150 my or less, the electrolytic power supply 6 was turned on for electrolysis to allow the oxidative regeneration for the etching working solution. The turn-off of the electrolytic power supply 6 was controlled based on a value detected by the sensor 9-3 as an ORP meter and a set safety threshold of 150 mv. During the electrolysis, a monovalent copper-ammonia complex in an anode electrolyte was oxidized into a copper-etching agent Cu(NH₃)₄Cl₂, and hydrogen was electrodeposited at the cathode 5.

3. During an etching process, with an exhaust flux in the spray-oxygen absorption-exhausting system undiminished, electrolysis-assisted oxidation was adopted in combination to achieve the oxidative regeneration of the copper-etching agent, thereby enhancing an etching rate.

4. A polluted waste gas from each cell/tank in the apparatus was directed to the tail gas treatment device 27 for an environmental treatment.

5. Hydrogen from the cathode cell zone was directed to the hydrogen high-altitude discharge pipe for safe discharge.

According to the etching working solutions shown in Table 1, an etching working solution was subjected to oxidative regeneration with the traditional spray-oxygen absorption system. A measured etching rate was recorded in Table 1. Then, the electrolysis apparatus was started, and with the oxidative regeneration scheme of “traditional spray-oxygen absorption system+electrolytic oxidative regeneration apparatus” in the present disclosure, the etching working solution was subjected to oxidative regeneration according to the above steps. A measured etching rate was recorded in Table 1.

The etching rates of the above two processes were compared. The addition of the electrolysis-assisted oxidation apparatus without diminishing an exhaust flux in the traditional spray-oxygen absorption-exhausting system improved the etching production efficiency by 14%.

Test results showed that, after long-term etching and electrolysis-assisted oxidative regeneration, contents of ammonia water and ammonium ions in the etching working solution did not significantly change.

Specific process parameters were listed in Table 1.

Example 2

FIG. 2 shows an apparatus and process flow for electrolysis-assisted oxidative regeneration of an alkaline copper-ammonia chloride etching working solution in this example.

The apparatus includes an etching machine 1, an electrolytic cell 2, an electrolytic cell separator 3, an electrolytic power supply 6, an etching replenisher tank 8, sealing cell covers 7-1 and 7-2 each with a feeding and exhaust port for the electrolytic cell, sensors 9-1, 9-2, and 9-3, a liquid flow buffer tank 14, an etching replenisher 21, an etching working solution 23, a cathode electrolyte 25, a printed circuit board to be etched 26, a tail gas treatment device 27, a gas flow-regulating valve 29, a valve, and a pump.

The electrolytic cell 2 is divided by the electrolytic cell separator 3 into an anode cell zone and a cathode cell zone. The sealing cell covers 7-1 and 7-2 each with a feeding and exhaust port for the electrolytic cell are arranged for the anode cell zone and the cathode cell zone, respectively. The anode cell zone is connected to the etching machine 1 through the liquid flow buffer tank 14, and the etching machine 1 is connected to the anode cell zone through another pipeline, thereby achieving a liquid flow circulation between the anode cell zone and the etching machine. The etching replenisher tank 8 is connected to the etching machine 1 through a pipeline.

The electrolytic cell separator 3 is a bipolar membrane. An electrolytic anode is a platinum electrode, and an electrolytic cathode is a stainless steel. The cathode electrolyte 25 is a copper-ammonia complex solution. The etching working solution is a mixed solution of copper-ammonia chloride, ammonium chloride, ammonium carbonate, and YH-510A. Specific process parameters are listed in Table 1.

In this example, a spray-oxygen absorption-exhausting system is provided, which is a treatment apparatus combining a spray device and the tail gas treatment device 27. The spray device includes pipelines arranged on the etching machine, a pump 20-2, and a nozzle 32, and is configured to direct the etching working solution to be above the spray device for spray atomization. The tail gas treatment device 27 is configured to receive waste gases from the etching machine 1, the electrolytic cell 2, and the etching replenisher tank 8 through gas pipelines. The gas flow-regulating valve 29 is arranged on a gas pipeline of the etching machine 1.

The sensor 9-1 is an ORP meter, the sensor 9-2 is a gravimeter, and the sensor 9-3 is an ORP meter.

In this example, operation steps for the electrolysis-assisted oxidative regeneration of an alkaline copper-ammonia chloride etching working solution in this example were as follows:

1. The etching working solution 23 was fed into the etching machine 1 and the anode cell zone of the electrolytic cell 2, with the etching working solution circularly flowing between the etching machine and the anode cell zone of the electrolytic cell. The copper-ammonia complex solution 25 was fed into the cathode cell zone of the electrolytic cell 2. The gas flow-regulating valve 29 was maintained at the original fully-open state.

2. The spray-oxygen absorption-exhausting system of the etching machine was started. The printed circuit board to be etched 26 was fed into the etching machine 1 for etching. The feeding of the etching replenisher 21 was controlled according to a value detected by the sensor 9-2 as a gravimeter to ensure that the etching working solution met the set process parameters. If a value detected by the sensor 9-1 as an ORP meter was 280 my or less, the electrolytic power supply 6 was turned on for electrolysis to allow the oxidative regeneration for the etching working solution. The turn-off of the electrolytic power supply 6 was controlled based on a value detected by the sensor 9-3 as an ORP meter and a set safety threshold of 280 mv. During the electrolysis, a monovalent copper-ammonia complex in an anode electrolyte was oxidized into a copper-etching agent Cu(NH₃)₄Cl₂, and metallic copper 28 was electrodeposited at the cathode 5.

3. During an etching process, with an exhaust flux in the spray-oxygen absorption-exhausting system undiminished, electrolysis-assisted oxidation was adopted in combination to achieve the oxidative regeneration of the copper-etching agent, thereby enhancing an etching rate.

4. A polluted waste gas from each cell/tank in the apparatus was directed to the tail gas treatment device 27 for an environmental treatment.

The copper-ammonia complex solution in this example was a tetraamminecopper (II) hydroxide solution. According to the etching working solutions shown in Table 1, an etching working solution was subjected to oxidative regeneration with the traditional spray-oxygen absorption system. A measured etching rate was recorded in Table 1. Then, the electrolysis apparatus was started, and with the oxidative regeneration scheme of “traditional spray-oxygen absorption system+electrolytic oxidative regeneration apparatus” in the present disclosure, the etching working solution was subjected to oxidative regeneration according to the above steps. A measured etching rate was recorded in Table 1.

The etching rates of the above two processes were compared. The addition of the electrolysis-assisted oxidation apparatus without diminishing an exhaust flux in the spray-oxygen absorption-exhausting system improved the etching production efficiency by 14%. Test results showed that, after long-term etching and electrolysis-assisted oxidative regeneration, contents of ammonium ions, ammonium carbonate, and YH-510A in the etching working solution did not significantly change.

Specific process parameters were listed in Table 1.

Example 3

FIG. 3 shows an apparatus and process flow for electrolysis-assisted oxidative regeneration of an alkaline copper-ammonia chloride etching working solution in this example. The apparatus includes an etching machine 1, an electrolytic cell 2, an electrolytic cell separator 3, an electrolytic power supply 6, an etching replenisher tank 8, sensors 9, a solid-liquid separator 12, a temporary storage tank 13, a liquid flow buffer tank 14, a hydrogen high-altitude discharge pipe 18, an etching replenisher 21, an etching working solution 23, a cathode electrolyte 25, a printed circuit board to be etched 26, a tail gas treatment device 27, a variable-frequency fan 30, and a plurality of valves and pumps.

The electrolytic cell 2 is divided by the electrolytic cell separator 3 into an anode cell zone and a cathode cell zone. The sealing cell covers 7-1 and 7-2 each with a feeding and exhaust port for the electrolytic cell are arranged for the anode cell zone and the cathode cell zone, respectively. The anode cell zone is connected to the etching machine 1 and the temporary storage tank 13 through the liquid flow buffer tank 14, and the etching machine 1 is connected to the anode cell zone through the solid-liquid separator 12, thereby achieving a liquid flow circulation between the anode cell zone and the etching machine 1. The etching replenisher tank 8 is connected to the etching machine 1 through a pipeline.

The electrolytic cell separator 3 is a reverse osmosis membrane, the electrolytic anode 4 is a graphite electrode, and the electrolytic cathode 5 is graphite. The cathode electrolyte 25 is a 10% ammonium carbonate solution. The etching working solution 23 is a mixed solution of copper-ammonia chloride, ammonia water, ammonium chloride, ammonium bicarbonate, and YH-510A. Specific process parameters are listed in Table 1.

A sensor 9-1 is a liquid level meter, a sensor 9-2 is a pH meter, a sensor 9-3 is a gravimeter, a sensor 9-4 is an ORP meter, and a sensor 9-5 is an ORP meter.

In this example, a spray-oxygen absorption-exhausting system is provided, which is a treatment apparatus combining a spray device and the tail gas treatment device 27. The spray device includes pipelines arranged on the etching machine, a pump 20-2, and a nozzle 32. The tail gas treatment device 27 is configured to receive waste gases from the etching machine 1, the electrolytic cell 2, the etching replenisher tank 8, and the temporary storage tank 13 through gas pipelines.

In this example, operation steps for the electrolysis-assisted oxidative regeneration of an alkaline copper-ammonia chloride etching working solution in this example were as follows:

1. The etching working solution 23 was fed into the etching machine 1 and the anode cell zone of the electrolytic cell, and the cathode electrolyte 25 was fed into the cathode cell zone of the electrolytic cell. A rotational speed of the variable-frequency fan 30 arranged at the tail gas treatment device 27 was reduced from the original 1,400 rpm to 1,200 rpm. A spray pump 20-2 arranged on the etching machine 1 was turned on to make the etching working solution undergo an oxidation reaction with oxygen in air during a spray atomization process. Pumps 20-3 and 20-4 were turned on to make the etching working solution circularly flow between the etching machine 1 and the anode cell zone of the electrolytic cell 2. During the circulation flow, solid impurities in the etching working solution were removed through the solid-liquid separator 12.

2. The printed circuit board to be etched 26 was fed into the etching machine 1 for etching, during which a specific gravity value of the etching working solution continuously increased and an ORP value of the etching working solution decreased. A pump 20-1 was controlled to feed the etching replenisher 21 into an etching machine based on a value detected by the sensor 9-3 as a gravimeter. An operation of the electrolytic cell 2 was controlled based on a value detected by the sensor 9-4 as an ORP meter. The turn-off of the electrolytic power supply 6 was controlled based on a value detected by the sensor 9-5 as an ORP meter and a set safety threshold of 80 mv. The turn-on of a pump 20-5 was controlled based on a value detected by the sensor 9-1 as a liquid level meter to discharge a solution as a spent etching solution. When the electrolytic cell 2 was started to enable electrolysis-assisted oxidation, a monovalent copper-ammonia complex in an anode electrolyte underwent an electrochemical oxidation reaction at the anode to regenerate a copper-etching agent, and hydrogen was electrodeposited at the cathode.

3. During an etching process, the rotational speed of the variable-frequency fan 30 was reduced to decrease the emission of an ammonia-containing waste gas, and a process for electrolysis-assisted oxidative regeneration of a copper-etching agent was adopted in combination, thereby maintaining the original etching rate.

4. Hydrogen electrodeposited at the cathode was directed to a hydrogen high-altitude discharge pipe and discharged.

5. A polluted waste gas from each cell/tank in the apparatus was directed to the tail gas treatment device 27 for an environmental treatment.

According to the etching working solutions shown in Table 1, an etching working solution was subjected to oxidative regeneration with the traditional spray-oxygen absorption system, in which case the rotational speed of the variable-frequency fan 30 was 1,400 rpm. A measured etching rate was recorded in Table 1. Then, the electrolysis apparatus was started, and with the oxidative regeneration scheme of “traditional spray-oxygen absorption system+electrolytic oxidative regeneration apparatus” in the present disclosure, the etching working solution was subjected to oxidative regeneration according to the above steps. A measured etching rate was recorded in Table 1. According to the comparison of etching rates in Example 3, when the efficiency of the traditional spray-oxygen absorption system to regenerate the copper-etching agent was directly lowered after the reduction in the rotational speed of the variable-frequency fan 30 (the reduction in a flow rate of fresh air), the addition of the electrolysis-assisted oxidative regeneration apparatus to facilitate the oxidative regeneration of the copper-etching agent can meet the original etching production requirements. According to test results, in the present disclosure, after the electrolysis-assisted oxidation was adopted in combination with the adjustment of the spray-oxygen absorption system, an ammonia gas loss caused by extraction was reduced by 50%. After long-term etching and electrolysis-assisted oxidative regeneration, contents of ammonia water, ammonium ions, ammonium bicarbonate, and YH-510A in the etching working solution did not significantly change.

Specific process parameters were listed in Table 1.

Example 4

FIG. 4 shows an apparatus and process flow for electrolysis-assisted oxidative regeneration of an alkaline copper-ammonia chloride etching working solution in this example.

The apparatus includes an etching machine 1, an electrolytic cell 2, an electrolytic cell separator 3, an electrolytic anode 4, an electrolytic cathode 5, an electrolytic power supply 6, sealing cell covers 7 with a feeding and exhaust port for the electrolytic cell, an etching replenisher tank 8, seven sensors 9, an automatic detection/feeding controller 10, a heat exchanger 11, a solid-liquid separator 12, two temporary storage tanks 13, three liquid flow buffer tanks 14, a liquid flow circulation stirrer 15, a solution mixing-exchange tank 17, an etching replenisher 21, a spent etching solution 22, an etching working solution 23, a solution 24 that has undergone a reduction treatment at the electrolytic cathode, a cathode electrolyte 25, a printed circuit board to be etched 26, a tail gas treatment device 27, a gas flow-regulating valve 29, a variable-frequency fan 30, and a plurality of valves and pumps.

The electrolytic cell 2 is divided by the electrolytic cell separator 3 into an anode cell zone and a cathode cell zone. The sealing cell covers each with a feeding and exhaust port for the electrolytic cell are arranged for the anode cell zone and the cathode cell zone, respectively. The anode cell zone is connected to the solution mixing-exchange tank 17 through two pipelines to allow a liquid flow circulation. The cathode cell zone is connected to a temporary storage tank 13-2 through a liquid flow buffer tank 14-3. The etching machine 1 is connected to the solution mixing-exchange tank 17 through two pipelines to allow a liquid flow circulation. The etching machine 1 is additionally connected to the cathode cell zone through a liquid flow buffer tank 14-1 and a temporary storage tank 13-1. The etching replenisher tank 8 is connected to the etching machine 1 through a pipeline.

The electrolytic cell separator 3 is a bipolar membrane. The electrolytic anode 4 is a titanium-based coated insoluble anode, and the electrolytic cathode 5 is a titanium metal block. The cathode electrolyte 25 is the spent etching solution 22 produced after an etching operation in this example.

The etching working solution is a mixed solution of copper-ammonia chloride, ammonia water, ammonium chloride, and YH-510A. Specific process parameters are listed in Table 1.

A sensor 9-1 is a thermometer, a sensor 9-2 is a gravimeter, a sensor 9-3 is an ORP meter, a sensor 9-4 is a thermometer, and sensors 9-5, 9-6, and 9-7 all are ORP meters.

In this example, a spray-oxygen absorption-exhausting system is provided, which is a treatment apparatus combining a spray device and the tail gas treatment device 27. The spray device includes pipelines arranged on the etching machine, a pump 20-4, and a nozzle 32. The tail gas treatment device 27 is configured to receive waste gases from the etching machine 1, the electrolytic cell 2, the etching replenisher tank 8, the solution mixing-exchange tank 17, and the temporary storage tanks 13-1 and 13-2 through gas pipelines. The gas flow-regulating valve 29 is arranged on a gas pipeline of the etching machine 1.

In this example, a detection signal input terminal of the automatic detection/feeding controller 10 is connected to a detection signal output terminal of each sensor, and a control signal output terminal of the automatic detection/feeding controller 10 is connected to control signal input terminals of each pump, the electrolytic power supply 6, and the heat exchanger 11.

In this example, operation steps for the electrolysis-assisted oxidative regeneration of an alkaline copper-ammonia chloride etching working solution in this example were as follows:

1. A power supply for the entire apparatus was turned on. Under the control of the automatic detection/feeding controller 10, the on-site detection was conducted through various sensors. The detected data was transmitted to the automatic detection/feeding controller 10 for processing. After the processing, a command was issued according to a program to make each device run.

2. An opening of the gas flow-regulating valve 29 was set to 80% of the original fully-open opening. The etching working solution 23 was fed into the etching machine 1, the anode cell zone of the electrolytic cell, and the solution mixing-exchange tank 17. The spent etching solution 22 was fed into the cathode cell zone. The pump 20-4 on the etching machine was started to make the etching working solution undergo an oxidation reaction with oxygen in air through spray atomization. Pumps 20-5 and 20-6 were started to make the etching working solution circularly flow between the etching machine 1 and the solution mixing-exchange tank 17. Pumps 20-7 and 20-8 were started to make a solution in the solution mixing-exchange tank 17 circularly flow between the solution mixing-exchange tank and the anode cell zone of the electrolytic cell.

3. The printed circuit board to be etched 26 was fed into the etching machine for etching. A pump 20-1 was controlled to feed the etching replenisher 21 based on data detected by the sensor 9-2 as a gravimeter. A concentration of a copper-etching agent in the etching working solution was monitored by the sensor 9-3 as an ORP meter, and an etching rate was adjusted accordingly. The sensor 9-5 as an ORP meter was started to monitor ORP of the etching working solution, and a working current or turn-off of the electrolytic power supply 6 was controlled accordingly. For the sensor 9-6 as an ORP meter, a safety threshold of 50 my was set as a safety interlock for controlling the turn-off of the electrolytic power supply 6.

After the electrolytic cell 2 was started to allow electrolysis-assisted oxidation, a monovalent copper-ammonia chloride complex in the anode electrolyte was oxidatively regenerated into the copper-etching agent Cu(NH₃)₄Cl₂, and an ORP value of the cathode electrolyte decreased due to an electrochemical reduction reaction. An ORP value of 15 mV was set for the sensor 9-7 as an ORP meter to control the feeding of the spent etching solution 22 into the cathode cell zone by the pump 20-2. If overflowing from the cathode cell zone, the cathode electrolyte was directed to a temporary storage tank 13-2 for temporary storage. A reduction reaction of divalent copper ions mainly occurred at the electrolytic cathode 5 without metallic copper deposited.

4. A polluted tail gas from each cell/tank in the apparatus was directed to the tail gas treatment device 27 for an environmental treatment. A rotational speed of the variable-frequency fan 30 arranged at the tail gas treatment device 27 was reduced from the original 1,400 rpm to 1,300 rpm.

According to the etching working solutions shown in Table 1, an etching working solution was subjected to oxidative regeneration with the traditional spray-oxygen absorption system, in which case the gas flow-regulating valve 29 was fully open and the rotational speed of the variable-frequency fan 30 was 1,400 rpm. A measured etching rate was recorded in Table 1. Then, the electrolysis apparatus was started, and with the oxidative regeneration scheme of “traditional spray-oxygen absorption system+electrolytic oxidative regeneration apparatus” in the present disclosure, the etching working solution was subjected to oxidative regeneration according to the above steps. A measured etching rate was recorded in Table 1.

According to the comparison of etching rates of the two processes in Example 4, the measure of reducing an opening of the gas flow-regulating valve 29 to 80% of the original fully-open opening and reducing the rotational speed of the variable-frequency fan 30 (reducing a flow rate of fresh air) not only diminished the ammonia pollution, but also reduced the spray oxidation effect. On this basis, the present disclosure adopted an apparatus for electrolysis-assisted oxidative regeneration of the copper-etching agent, such that the original etching production efficiency could be maintained. Thus, the present disclosure achieved the energy conservation and emission reduction while guaranteeing the production efficiency. According to test results, in the present disclosure, after the electrolysis-assisted oxidation was adopted in combination with the adjustment of the spray-oxygen absorption system, an ammonia gas loss caused by extraction was reduced by 60%. After long-term etching and electrolysis-assisted oxidative regeneration, contents of ammonia water, ammonium ions, and YH-510A in the etching working solution did not significantly change.

Specific process parameters were listed in Table 1.

Example 5

FIG. 5 shows an apparatus and process flow for electrolysis-assisted oxidative regeneration of an alkaline copper-ammonia chloride etching working solution in this example. The apparatus includes an etching machine 1, an electrolytic cell 2, an electrolytic cell separator 3, an electrolytic anode 4, an electrolytic cathode 5, an electrolytic power supply 6, sealing cell covers 7 with a feeding and exhaust port for the electrolytic cell, an etching replenisher tank 8, nine sensors 9, an automatic detection/feeding controller 10, two heat exchangers 11, two temporary storage tanks 13, three liquid flow buffer tanks 14, a liquid flow circulation stirrer 15, a solution mixing-exchange tank 17, an etching replenisher 21, a spent etching solution 22, an etching working solution 23, a solution 24 that has undergone a reduction treatment at the electrolytic cathode, a cathode electrolyte 25, a printed circuit board to be etched 26, two tail gas treatment devices 27, electrodeposited metallic copper 28, a variable-frequency fan 30, and a plurality of valves and pumps.

The electrolytic cell 2 is divided by the electrolytic cell separator 3 into an anode cell zone and a cathode cell zone. The sealing cell covers for the electrolytic cell are arranged for the anode cell zone and the cathode cell zone, respectively. The anode cell zone is connected to the solution mixing-exchange tank 17 through two pipelines to allow a liquid flow circulation. The cathode cell zone is connected to a temporary storage tank 13-1 through a liquid flow buffer tank 14-3. The etching machine 1 is connected to the solution mixing-exchange tank 17 through two pipelines to allow a liquid flow circulation. The etching machine 1 is connected to a temporary storage tank 13-2. The etching replenisher tank 8 is connected to the etching machine 1 through a pipeline.

The electrolytic cell separator 3 is a reverse osmosis membrane, the electrolytic anode 4 is gold, and the electrolytic cathode 5 is a copper metal plate. The cathode electrolyte 25 is the spent etching solution 22 produced after an etching operation in this example.

The etching working solution is a mixed solution of copper-ammonia chloride, ammonia water, ammonium chloride, ammonium carbonate, ammonium bicarbonate, and YH-510A. Process parameters are listed in Table 1.

The electrolytic cathode 5 is a removable cathode copper plate. After a specified weight of a copper metal is electrodeposited, the cathode copper plate is taken out and recovered, and another cathode copper plate is placed in the cathode cell zone to continue an operation.

A sensor 9-1 is a thermometer, a sensor 9-2 is a pH meter, a sensor 9-3 is a gravimeter, a sensor 9-4 is an ORP meter, a sensor 9-5 is a thermometer, a sensor 9-6 is a liquid level meter, a sensor 9-7 is an ORP meter, a sensor 9-8 is an ORP meter, and a sensor 9-9 is a gravimeter.

The heat exchanger 11 is configured to control a temperature of the etching working solution to ensure the etching performance of the etching working solution.

In this example, a spray-oxygen absorption-exhausting system is provided, which is a treatment apparatus combining a spray device and a tail gas treatment device 27-1. The spray device includes pipelines arranged on the etching machine, a pump 20-2, and a nozzle 32. The tail gas treatment device 27-1 belongs to a specialized traditional spray-oxygen absorption-exhausting system, and is provided with the variable-frequency fan 30. The tail gas treatment device 27-1 is configured to receive a waste gas from the etching machine 1 through a gas pipeline. A tail gas treatment device 27-2 is configured to receive waste gases from the tail gas treatment device 27-1, the electrolytic cell 2, the etching replenisher tank 8, the solution mixing-exchange tank 17, and the temporary storage tanks 13-1 and 13-2 through gas pipelines. In this example, a detection signal input terminal of the automatic detection/feeding controller 10 is connected to a detection signal output terminal of each sensor, and a control signal output terminal of the automatic detection/feeding controller 10 is connected to control signal input terminals of each pump, the electrolytic power supply 6, and the heat exchanger 11.

In this example, operation steps for the electrolysis-assisted oxidative regeneration of an alkaline copper-ammonia chloride etching working solution in this example were as follows:

1. A power supply for the entire apparatus was turned on. Under the control of the automatic detection/feeding controller 10, the on-site detection was conducted through various sensors. The detected data was transmitted to the automatic detection/feeding controller 10 for processing. After the processing, a command was issued according to a program to make each device run.

2. A rotational speed of the variable-frequency fan 30 was reduced from the original 1,400 rpm to 1,300 rpm. The etching working solution 23 was fed into the etching machine 1, the anode cell zone of the electrolytic cell, and the solution mixing-exchange tank 17. The spent etching solution 22 was fed into the cathode cell zone. The pump 20-2 on the etching machine was started to make the etching working solution undergo an oxidation reaction with oxygen in air through spray atomization. Pumps 20-4 and 20-5 were started to make the etching working solution circularly flow between the etching machine 1 and the solution mixing-exchange tank 17. Pumps 20-6 and 20-7 were started to make a solution in the solution mixing-exchange tank 17 circularly flow between the solution mixing-exchange tank and the anode cell zone of the electrolytic cell.

3. The printed circuit board to be etched 26 was fed into the etching machine for etching. An operation of the heat exchanger 11-1 was controlled based on data detected by the sensor 9-1 as a thermometer. A pump 20-1 was controlled to feed the etching replenisher based on data detected by the sensor 9-2 as a pH meter. A concentration of copper ions in the etching working solution was monitored by the sensor 9-3 as a gravimeter. An etching rate was adjusted according to a set value for the sensor 9-4 as an ORP meter. The heat exchanger 11-2 was controlled based on data detected by the sensor 9-5 as a thermometer to stabilize a temperature of the etching working solution. A pump 20-3 was controlled to discharge the spent etching solution 22 based on the sensor 9-6 as a liquid level meter. An operation of the electrolytic cell 2 was controlled based on data detected by the sensor 9-7 as an ORP meter. For the sensor 9-8 as an ORP meter, a safety threshold of 180 my was set as a safety interlock for the turn-off of the electrolytic power supply. A specific gravity value of 1.08 g/L was set for the sensor 9-9 as a gravimeter to control the feeding of the spent etching solution 22 into the cathode cell zone by a pump 20-10. During the electrolysis, a Cu(NH₃)₂Cl complex in the anode electrolyte was oxidized into a copper-etching agent Cu(NH₃)₄Cl₂, and the metallic copper 28 was electrodeposited at the cathode.

4. A polluted tail gas from each cell/tank in the apparatus was directed to the tail gas treatment device 27-2 for an environmental treatment. A tail gas from an etching machine was directed to the tail gas treatment device 27-1 with an adjustable exhaust air volume for a treatment, and a waste gas from the tail gas treatment device 27-1 was further directed to the tail gas treatment device 27-2 for an environmental treatment.

According to the etching working solutions shown in Table 1, an etching working solution was subjected to oxidative regeneration with the traditional spray-oxygen absorption system, in which case the rotational speed of the variable-frequency fan 30 was 1,400 rpm. A measured etching rate was recorded in Table 1. Then, the electrolysis apparatus was started, and with the oxidative regeneration scheme of “traditional spray-oxygen absorption system+electrolytic oxidative regeneration apparatus” in the present disclosure, the etching working solution was subjected to oxidative regeneration according to the above steps. A measured etching rate was recorded in Table 1.

According to the comparison of etching rates of the two processes in Example 5, the reduction in the supply of fresh air caused by the reduction in the rotational speed of the variable-frequency fan 30 in the traditional spray-oxygen absorption-exhausting system directly affects the chemical reaction of oxidatively regenerating the copper-etching agent. On this basis, an apparatus for electrolysis-assisted oxidative regeneration of the copper-etching agent was added, which could enhance the etching production efficiency while reducing the emission of an ammonia-containing waste gas to improve the environment. According to test results, in the present disclosure, after the electrolysis-assisted oxidation was adopted in combination with the adjustment of the spray-oxygen absorption system, an ammonia gas loss caused by extraction was reduced by 40%. When there was a low solution circulation flow rate between the anode cell zone of the electrolytic cell and the solution mixing-exchange tank, after long-term etching and electrolysis-assisted oxidative regeneration, contents of ammonia water, ammonium ions, ammonium carbonate, ammonium bicarbonate, and YH-510A in the etching working solution slightly decreased. When a solution circulation flow rate between the anode cell zone of the electrolytic cell and the solution mixing-exchange tank was increased or the solution circulation flow rate between the solution mixing-exchange tank and the anode cell zone of the electrolytic cell and a solution circulation flow rate between the solution mixing-exchange tank and the etching machine were increased, after long-term etching and electrolysis-assisted oxidative regeneration, contents of ammonia water, ammonium ions, ammonium carbonate, ammonium bicarbonate, and YH-510A in the etching working solution did not significantly change. Specific process parameters were listed in Table 1.

Example 6

The apparatus in Example 2 was adopted, and the method in Example 2 was repeated. This example was different from Example 2 in that: The electrolytic cell separator 3 was an ion selectivity-free membrane, and the turn-off of the electrolytic power supply 6 was controlled based on a value detected by the sensor 9-3 as an ORP meter and a set safety threshold of 300 mv.

According to the etching working solutions shown in Table 1, an etching working solution was subjected to oxidative regeneration with the traditional spray-oxygen absorption system. A measured etching rate was recorded in Table 1. Then, the electrolysis apparatus was started, and with the oxidative regeneration scheme of “traditional spray-oxygen absorption system+electrolytic oxidative regeneration apparatus” in the present disclosure, the etching working solution was subjected to oxidative regeneration according to the above steps. A measured etching rate was recorded in Table 1.

According to test results, when there was a low solution circulation flow rate between the anode cell zone of the electrolytic cell and the etching machine, after long-term etching and electrolysis-assisted oxidative regeneration, contents of ammonium ions, ammonium carbonate, and YH-510A in the etching working solution slightly decreased with a low decline rate, indicating controllability. When a solution circulation flow rate between the anode cell zone of the electrolytic cell and the etching machine was increased, after long-term etching and electrolysis-assisted oxidative regeneration, contents of ammonium ions, ammonium carbonate, and YH-510A in the etching working solution did not significantly change. In this example, when the effective electrolytic area of the electrolytic anode increased, after long-term etching and electrolysis-assisted oxidative regeneration, contents of ammonium ions, ammonium carbonate, and YH-510A in the etching working solution did not significantly change.

Example 7

The apparatus in Example 4 was adopted, and the method in Example 4 was repeated. This example was different from Example 4 in that: The electrolytic cell separator 3 was a proton exchange membrane, and for the sensor 9-6 as an ORP meter, a safety threshold of 100 my was set as a safety interlock for controlling the turn-off of the electrolytic power supply 6.

According to the etching working solutions shown in Table 1, an etching working solution was subjected to oxidative regeneration with the traditional spray-oxygen absorption system, in which case the gas flow-regulating valve 29 was fully open and the rotational speed of the variable-frequency fan 30 was 1,400 rpm. A measured etching rate was recorded in Table 1. Then, the electrolysis apparatus was started, and with the oxidative regeneration scheme of “traditional spray-oxygen absorption system+electrolytic oxidative regeneration apparatus” in the present disclosure, the etching working solution was subjected to oxidative regeneration according to the above steps. A measured etching rate was recorded in Table 1. Test results showed that, after long-term etching and electrolysis-assisted oxidative regeneration, contents of ammonia water, ammonium ions, and YH-510A in the etching working solution did not significantly change.

During an etching process, the etching replenisher was fed into the etching machine, the solution mixing-exchange tank, and the anode cell zone of the electrolytic cell separately for testing. An identical etching effect was achieved.

Comparative Example 1

The apparatus in Example 2 was adopted, and the method in Example 2 was repeated. This comparative example was different from Example 2 in that: The electrolytic cell separator 3 was an ion selectivity-free membrane, and the turn-off of the electrolytic power supply 6 was controlled based on a value detected by the sensor 9-3 as an ORP meter and a set safety threshold of 400 mv. This comparative example was different from Example 6 in that there was a different set safety threshold for the sensor 9-3 as an ORP meter.

According to test results, after long-term etching and electrolysis-assisted oxidative regeneration, contents of ammonium ions, ammonium carbonate, and YH-510A in the etching working solution significantly decreased. Even after a solution circulation flow rate between the anode cell zone of the electrolytic cell and the etching machine increased and the effective electrolytic area of the electrolytic anode increased, the additional consumption of the above components remained excessive and uncontrollable, making it difficult to maintain the stable composition of the etching working solution.

TABLE 1
				Etching rate
				when the	Etching rate when the
				oxidative	oxidative regeneration
				regeneration is	is conducted with the
				conducted with	traditional spray-
		ORP value		the traditional	oxygen absorption
		of an	Composition	spray-oxygen	system + the
	Etching working	anode	of a cathode	absorption	electrolytic oxidative
Example	solution	electrolyte	electrolyte	system	regeneration apparatus	Remarks

1

Copper ion

Upper

12% ammonia

56

μm/min

64

μm/min

The original fully-open

	concentration:	limit of a	water			opening of the gas flow-
	170 g/L	set value				regulating valve 29 in the
	pH value: 8.4	for an				traditional spray-oxygen
		ORP meter				absorption-exhausting system
		9-3: 150				remains unchanged
		mv

2

Copper ion

Upper

Copper ion

21

μm/min

24

μm/min

The original fully-open

	concentration: 60	limit of a	concentration			opening of the gas flow-
	g/L	set value	in a copper-			regulating valve 29 in the
	YH-510A	for an	ammonia			traditional spray-oxygen
	concentration:	ORP meter	complex			absorption-exhausting system
	2.5 mol/L	9-3: 280	solution:			remains unchanged
	pH value: 7	mv	70 g/L
			pH value: 8.2

3

Copper ion

Upper

10%

51

μm/min

52

μm/min

A rotational speed of the

	concentration:	limit of a	ammonium			variable-frequency fan 30 is
	140 g/L	set value	carbonate			reduced from the original
	YH-510A	for an	solution			1,400 rpm to 1,200 rpm
	concentration:	ORP meter
	1.2 mol/L	9-5: 80 mv
	pH value: 8.2

4

Copper ion

Upper

Spent etching

60

μm/min

61

μm/min

An opening of the gas flow-

	concentration:	limit of a	solution			regulating valve 29 in the
	110 g/L	set value	produced after			traditional spray-oxygen
	YH-510A	for an	an etching			absorption-exhausting system
	concentration:	ORP meter	operation in			is reduced to 80% of the
	0.00004 mol/L	9-6: 50 mv	this example			original fully-open opening,
	pH value: 9					and a rotational speed of the
						variable-frequency fan 30 is
						reduced from the original
						1,400 rpm to 1,300 rpm

5

Copper ion

Upper

Spent etching

35

μm/min

42

μm/min

A rotational speed of the

	concentration: 90	limit of a	solution			variable-frequency fan 30 is
	g/L	set value	produced after			reduced from the original
	YH-510A	for an	an etching			1,400 rpm to 1,300 rpm
	concentration:	ORP meter	operation in
	0.7 mol/L	9-8: 180	this example
	pH value: 7.4	mv

6

Copper ion

Upper

Copper ion

21

μm/min

25

μm/min

The original fully-open

	concentration: 60	limit of a	concentration			opening of the gas flow-
	g/L	set value	in a copper-			regulating valve 29 in the
	YH-510A	for an	ammonia			traditional spray-oxygen
	concentration:	ORP meter	complex			absorption-exhausting system
	2.5 mol/L	9-3: 300	solution: 70			remains unchanged
	pH value: 7	mv	g/L
			pH value: 8.2

7

Copper ion

Upper

Spent etching

60

μm/min

63

μm/min

An opening of the gas flow-

	concentration:	limit of a	solution			regulating valve 29 in the
	110 g/L	set value	produced after			traditional spray-oxygen
	YH-510A	for an	an etching			absorption-exhausting system
	concentration:	ORP meter	operation in			is reduced to 80% of the
	0.00004 mol/L	9-6: 100	this example			original fully-open opening,
	pH value: 9	mv				and a rotational speed of the
						variable-frequency fan 30 is
						reduced from the original
						1,400 rpm to 1,300 rpm