Grinding Device for Surface Machining of Workpieces

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.

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.

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.

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.

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

show a grinding devicefor surface machining of workpieces, in particular for surface machining of back sides of wafers. The grinding devicecomprises a grinding wheel, which is rotatable (continuously) about a vertically arranged first axisin the direction of the arrow, for example clockwise, by means of a drive (not shown). Furthermore, the grinding devicecomprises a workpiece holding wheel, which is rotatable about a second axis, which is arranged in parallel with the first axis, in the direction of the arrow, likewise by means of a drive (not shown). It is essential that the direction of rotation of the two arrows,is different, i.e., that the workpiece holding wheelis rotated in the counterclockwise direction (continuously) in the exemplary embodiment shown, wherein the rotational angular speeds of the grinding wheeland of the workpiece holding wheelmay be different.

The workpiece holding wheelfurther comprises holding means in the form of suction devices or suction bores (not shown), which are designed to fix the workpieceor the waferagainst the upper side of the cylindrical workpiece holding wheel. During the grinding process, for example, the grinding wheelis moved in the direction of the first axistoward the workpiece holding wheelin order to achieve material removal on the workpiece.

The grinding wheelcomprises, as can be seen in particular in, a plurality of grinding elementsarranged at equal angular intervals about the first axis. The grinding elementsare arranged on a pitch circle diameterabout the first axisand are in each case approximately designed in the shape of a ring segment. Free spacesare formed between the grinding elements. The grinding elementscomprise, on the side facing the workpiece surface of the workpieceto be machined, a machining surface() that runs in parallel with the surface of the workpiece.

As can also be seen in particular in, the diameters of the grinding wheeland of the workpiece holderand the distance between the two axes,are coordinated in such a way that the grinding wheelonly partially covers the workpiece holding wheel.

The grinding elementsare fastened in the region of an exemplary annular workpiece carrierof the grinding wheel, in particular by insertion into receptaclesof the workpiece carrier. As can be seen in, below the workpiece carrieron their outer sides facing radially away from the first axisand/or on their inner sides facing radially toward the first axis, the grinding elementsare furthermore surrounded by an annular carrier element. In, it can also be seen that the carrier elementis arranged only in the partial region of the grinding wheelthat does not overlap with the workpiece holding wheel.

In the embodiment according to, the carrier elementis U-shaped in cross-section with a radially inner carrier walland a radially outer carrier wallin relation to the first axis, which walls are arranged in parallel with and at a short distance from the grinding elements. Below the machining surfaces, the two carrier walls,are connected to one another by means of a transverse wall.

The carrier elementaccording to, in contrast, is designed to be L-shaped in cross-section with, for example, an inner carrier walland a transverse wall. In contrast, the carrier elementaccording tocomprises only an inner carrier walland the carrier elementaccording tocomprises an inner carrier walland an outer carrier wallbut no transverse wall. The carrier elementserves to arrange or position at least one sensor elementand optionally at least one machining device.

shows the case in which ultrasound is coupled into water as a medium by means of two water nozzles,arranged in the region of openings on the inner carrier walland the outer carrier wall, in order to excite the grinding elementsto vibrate in order to improve the quality of the grinding process. Thus, the water nozzles,form actuators.

shows the case in which an electrodeis arranged between the two transverse walls,below the grinding elementsas a machining devicefor the electrochemical cleaning of the machining surfacesof the grinding elements.

shows the case in which structure-borne sound of the grinding elementscan be detected by means of two structure-borne sound sensors,as the sensor elementhaving the water nozzles,, 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 elementis designed as a temperature sensor or as a sensor elementfor detecting a geometric size of the grinding elements, in particular the height or the dimension of the grinding elements.

Generally speaking, at least one parameter P is detected by means of the at least one sensor element, which parameter can be fed at least indirectly to an evaluation device() of the grinding devicein 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.

The grinding devicedescribed 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 wallis arranged at an incline relative to the horizontal in order to allow medium to drain out of the region of the carrier device(not shown). Furthermore, the grinding deviceis not to be limited to the use of wafersas workpieces.