GRINDING DEVICE FOR SURFACE MACHINING OF WORKPIECES

Description

CROSS REFERENCE

The present application claims the benefit under 35 U.S.C. § 119 of German Patent Application No. DE 10 2024 203 417.7 filed on Apr. 12, 2024, which is expressly incorporated herein by reference in its entirety.

FIELD

The present invention relates to a grinding device for surface machining of workpieces, which is characterized by particularly good monitoring of the grinding process and of grinding elements arranged on the grinding device, in order to make a high surface quality of the workpieces possible.

BACKGROUND INFORMATION

A grinding device is described in German Patent Application No. DE 10 2020 214 459 A1. The surface of workpieces can be machined or smoothed using this conventional grinding device, which comprises a grinding wheel that can be rotated about a horizontally arranged axis. In order in particular to recognize in due time so-called grinding burns, which can not only lead to a poorer-quality surface on the workpieces but possibly also to damage or pre-damage to the grinding wheel, the conventional grinding device comprises at least one sensor element that detects a parameter used for detecting the desired impairment or disruption and feeds it to an evaluation device. Furthermore, German Patent Application No. DE 10 2020 214 459 A1 mentions that the sensor element should be arranged as close as possible to the grinding wheel in the region of the machining surface.

Further information, in particular with regard to the exact arrangement of the at least one sensor element, cannot be found in the specified document.

In addition, the basic structure of a grinding device for machining the back side of wafers is described in German Patent Application No. DE 10 2009 011 491 A1.

SUMMARY

A grinding device according to the present invention for surface machining of workpieces, in particular for surface machining of back sides of wafers, may have the advantage that it makes possible the arrangement of at least one, typically a plurality of sensor elements and optionally machining elements on the grinding device in an advantageous constructive manner in order to detect at least one parameter that is relevant with regard to the quality of the grinding process and/or the quality or geometry of grinding elements.

The present invention is based on the idea of providing a carrier device, which is arranged at a short distance from the grinding elements of the grinding wheel and serves to arrange or position the at least one sensor element. In particular, the carrier device according to the present invention also makes it possible to simultaneously position a plurality of sensor elements and/or machining elements for grinding elements, which sensor elements and/or machining elements are arranged at different locations on the carrier device.

Against the background of the above explanations, a grinding device according to an example embodiment of the present invention for surface machining of workpieces includes a grinding wheel that is mounted rotatably about a first axis and that has at least one grinding element. Furthermore, at least one sensor element that interacts at least indirectly with the grinding element is provided for detecting a parameter of the grinding element, wherein the parameter can preferably be fed to an evaluation device. According to an example embodiment of the present invention, in the grinding device, the at least one grinding element is arranged at a radial distance from the first axis, in that the at least one grinding element is surrounded, on the side radially facing and/or radially facing away from the first axis, by a carrier element that at least in regions covers the at least one grinding element, and in that the at least one sensor element is arranged on the carrier element. The grinding wheel is preferably disk-shaped with a grinding end face. The grinding end face of the grinding wheel is aligned in the grinding device substantially in parallel with a workpiece end face of the preferably disk-shaped workpiece. Preferably, the first axis of the grinding wheel is arranged in parallel with a second axis of a workpiece holding wheel receiving the workpiece, in such a way that the grinding end face of the grinding wheel at least partially covers and/or engages the workpiece end face of the workpiece. Particularly preferably, the grinding wheel is arranged relative to the workpiece in such a way that the grinding end face covers a surface of the workpiece end face from the circumference to the second axis of the workpiece.

Advantageous developments of the grinding device according to the present invention for surface machining of workpieces are disclosed herein.

With regard to the preferred intended use of the grinding device, the surface machining of flat workpieces such as wafers, according to an example embodiment of the present invention, it is preferably provided that the grinding wheel comprises a plurality of grinding elements that are arranged at equal angular intervals about the first axis and the machining surfaces of which, interacting with the workpiece to be machined, are arranged in a plane running perpendicularly to the first axis, and that the carrier element comprises at least one annular carrier wall that is arranged perpendicularly to the machining surfaces of the grinding elements.

A preferred development of the present invention described above provides that the at least one carrier wall comprises a transverse wall running in parallel with and below the machining surface. The carrier element can thus be designed to be either L-shaped or U-shaped in cross-section. In particular, the lower transverse wall serves, on the one hand, to make possible a protected arrangement of the at least one sensor element and, on the other hand, for example in connection with the use of liquid media, to make possible an easy removal of the medium from the region of the carrier device by the medium being discharged or drained via the lower transverse wall. For this purpose, the lower transverse wall may, for example, also be arranged at an angle to the horizontal in order to ensure that the medium drains toward a drain.

In addition, according to an example embodiment of the present invention, it is particularly preferred if the at least one sensor element is arranged in the region of an opening of the carrier element. Thus, the sensor element can be arranged through the opening in the direction of the grinding element at any desired small distance, wherein the carrier element can simultaneously serve, for example, for fastening the sensor element.

A further preferred development of the grinding device of the present invention provides that a machining device for machining the at least one grinding element is arranged in the region of the carrier element. Such a machining device typically comprises an actuator or an element that is designed to make possible either cleaning of the grinding element or of the machining surface of the grinding element, or the creation or maintenance of a desired contour of the machining surface on the grinding element. Such cleaning elements may, for example, comprise mechanical contact by brushes or the use of a pressurized water jet or the like. Such an actuator may also be provided as an ultrasonic oscillator in order, for example, to make cleaning possible by coupling ultrasonic vibrations (typically between 20 kHz and 150 kHz) into the liquid. Alternatively, such an actuator can also be used to mechanically couple the vibrations into the grinding wheel in order to improve the quality of the workpiece surface being machined.

In particular, according to an example embodiment of the present invention, it may also be provided that the carrier element is designed in the shape of a circular ring segment, and that the carrier element projects beyond the grinding elements on the side facing the machining surfaces. This makes it possible, in particular, to position the grinding elements in overlap with the workpiece surfaces of the workpieces to be machined, without the carrier element being in the way.

According to an example embodiment of the present invention, it may also be provided that the at least one sensor element is designed to detect a temperature and/or a frequency of the at least one grinding element as a parameter. Typically, either structure-borne sound sensors for frequencies >50 KHz, ultrasonic sensors for a frequency range between 20 kHz and 50 kHz or vibration sensors for frequency ranges <20 kHz are used for this purpose.

According to an example embodiment of the present invention, the at least one sensor element may also be designed to detect a geometric size of the at least one grinding element as a parameter. For example, by detecting the height of the grinding element, it can be concluded that the grinding element is worn or, in general, if the dimensions deviate significantly from the target values, that a grinding element has broken.

Preferably, according to an example embodiment of the present invention, it is provided that the grinding wheel comprises a workpiece holding wheel that positions at least one workpiece relative to the grinding wheel and is mounted rotatably about a second axis running in parallel with the first axis, and that the grinding wheel and the workpiece holding wheel can be driven in different directions about the axes. Such a grinding device as described so far is preferably used for machining the back sides of the surfaces of wafers.

Further advantages, features, and details of the present invention can be found in the following description of preferred embodiments of the present invention and with reference to the figures.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective representation of a grinding device according to an example embodiment of the present invention.

FIG. 2 is a sectional representation of the grinding device according to FIG. 1.

FIG. 3 to FIG. 9 are each longitudinal sections in the region of a carrier element for explaining different geometric designs of the carrier element and arrangement of sensor elements, according to example embodiments of the present invention.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS

Identical elements or elements which have the same function are provided with the same reference signs in the figures.

FIGS. 1 and 2 show a grinding device 100 for surface machining of workpieces 1, in particular for surface machining of back sides of wafers 2. The grinding device 100 comprises a grinding wheel 10, which is rotatable (continuously) about a vertically arranged first axis 12 in the direction of the arrow 14, for example clockwise, by means of a drive (not shown). Furthermore, the grinding device 100 comprises a workpiece holding wheel 20, which is rotatable about a second axis 22, which is arranged in parallel with the first axis 12, in the direction of the arrow 24, likewise by means of a drive (not shown). It is essential that the direction of rotation of the two arrows 14, 24 is different, i.e., that the workpiece holding wheel 20 is rotated in the counterclockwise direction (continuously) in the exemplary embodiment shown, wherein the rotational angular speeds of the grinding wheel 10 and of the workpiece holding wheel 20 may be different.

The workpiece holding wheel 20 further comprises holding means in the form of suction devices or suction bores (not shown), which are designed to fix the workpiece 1 or the wafer 2 against the upper side of the cylindrical workpiece holding wheel 20. During the grinding process, for example, the grinding wheel 10 is moved in the direction of the first axis 12 toward the workpiece holding wheel 20 in order to achieve material removal on the workpiece 1.

The grinding wheel 10 comprises, as can be seen in particular in FIG. 2, a plurality of grinding elements 26 arranged at equal angular intervals about the first axis 12. The grinding elements 26 are arranged on a pitch circle diameter 28 about the first axis 12 and are in each case approximately designed in the shape of a ring segment. Free spaces 33 are formed between the grinding elements 26. The grinding elements 26 comprise, on the side facing the workpiece surface of the workpiece 1 to be machined, a machining surface 34 (FIGS. 3 to 6) that runs in parallel with the surface of the workpiece 1.

As can also be seen in particular in FIGS. 1 and 2, the diameters of the grinding wheel 10 and of the workpiece holder 20 and the distance between the two axes 12, 22 are coordinated in such a way that the grinding wheel 10 only partially covers the workpiece holding wheel 20.

The grinding elements 26 are fastened in the region of an exemplary annular workpiece carrier 36 of the grinding wheel 10, in particular by insertion into receptacles 38 of the workpiece carrier 36. As can be seen in FIGS. 3 to 6, below the workpiece carrier 36 on their outer sides facing radially away from the first axis 12 and/or on their inner sides facing radially toward the first axis 12, the grinding elements 26 are furthermore surrounded by an annular carrier element 40. In FIGS. 1 and 2, it can also be seen that the carrier element 40 is arranged only in the partial region of the grinding wheel 10 that does not overlap with the workpiece holding wheel 20.

In the embodiment according to FIGS. 2 and 3, the carrier element 40 is U-shaped in cross-section with a radially inner carrier wall 42 and a radially outer carrier wall 44 in relation to the first axis 12, which walls are arranged in parallel with and at a short distance from the grinding elements 26. Below the machining surfaces 34, the two carrier walls 42, 44 are connected to one another by means of a transverse wall 46.

The carrier element 40 according to FIG. 4, in contrast, is designed to be L-shaped in cross-section with, for example, an inner carrier wall 42a and a transverse wall 46. In contrast, the carrier element 40 according to FIG. 5 comprises only an inner carrier wall 42b, and the carrier element 40 according to FIG. 6 comprises an inner carrier wall 42 and an outer carrier wall 44 but no transverse wall 46. The carrier element 40 serves to arrange or position at least one sensor element 48 and optionally at least one machining device 50.

FIG. 7 shows the case in which ultrasound is coupled into water as a medium by means of two water nozzles 52, 54 arranged in the region of openings on the inner carrier wall 42 and the outer carrier wall 44, in order to excite the grinding elements 26 to vibrate in order to improve the quality of the grinding process. Thus, the water nozzles 52, 54 form actuators.

FIG. 8 shows the case in which an electrode 56 is arranged between the two transverse walls 42, 44 below the grinding elements 26 as a machining device 50 for the electrochemical cleaning of the machining surfaces 34 of the grinding elements 26.

FIG. 9 shows the case in which structure-borne sound of the grinding elements 26 can be detected by means of two structure-borne sound sensors 58, 60 as the sensor element 48 having the water nozzles 62, 64, in order to make possible a statement about the process state (e.g., for the recognition of cracks).

Cases are also possible in which the sensor element 48 is designed as a temperature sensor or as a sensor element 48 for detecting a geometric size of the grinding elements 26, in particular the height or the dimension of the grinding elements 26.

Generally speaking, at least one parameter P is detected by means of the at least one sensor element 48, which parameter can be fed at least indirectly to an evaluation device 66 (FIG. 9) of the grinding device 100 in order to make possible either a (qualitative) statement about the grinding process or a statement about a quality or the state of one or more of the grinding elements 26.

The grinding device 100 described thus far can be altered or modified in many ways without deviating from the idea of the present invention. In particular, it may be provided that the transverse wall 46 is arranged at an incline relative to the horizontal in order to allow medium to drain out of the region of the carrier device 40 (not shown). Furthermore, the grinding device 100 is not to be limited to the use of wafers 2 as workpieces 1.