Processing method and processing system for hard and brittle material workpiece

Abstract

The invention relates to a machining method and system for a hard and brittle material workpiece. In one aspect, the machining method comprises the steps that a viscous medium is applied to the to-be-machined surface of a workpiece; and the fixed abrasive tool makes contact with the to-be-machined surface and generates relative movement for grinding machining, in the grinding machining process, abrasive particles falling off from the fixed abrasive tool in the grinding machining process are captured by the viscous medium and suspended at the contact interface of the fixed abrasive tool and the workpiece, so that a free abrasive layer is formed, and the free abrasive layer is separated from the to-be-machined surface. And therefore, the abrasive particles in the free abrasive material layer perform in-situ grinding on the to-be-machined surface. Therefore, the cutter lines are reduced or even eliminated, and the surface machining quality of the workpiece is improved.

Description

Technical Field

[0001] This disclosure relates to the field of semiconductor manufacturing technology, and more specifically, to a method and system for processing workpieces made of hard and brittle materials. Background Technology

[0002] With the rapid development of the semiconductor optoelectronic industry, hard and brittle materials such as silicon carbide (SiC) are widely used in applications such as chip substrates, precision optical windows, and electronic devices due to their excellent physicochemical properties. However, their high hardness and brittleness make machining these materials quite difficult.

[0003] In the processing technology of related technologies, the surface smoothing of hard and brittle workpieces, or the forming of specific geometric structures (such as annular grooves, stepped surfaces, etc.), mainly relies on CNC machine tools in conjunction with bonded abrasive tools (usually called cutting tools) for grinding. Bonded abrasive tools refer to grinding tools in which abrasive particles (referred to as abrasive grains) are fixed on the tool matrix by a bonding agent (such as ceramics, resins, etc.).

[0004] However, in actual manufacturing processes, especially when machining hard and brittle material workpieces with structures such as annular grooves, the relevant processing technologies face severe challenges. Specifically, after the annular groove is machined, obvious periodic textures (commonly known as tool marks) often remain on the bottom or wall surface of the groove. The presence of these tool marks not only affects the appearance quality of the product, but also introduces deep subsurface damage because the tool marks themselves are actually microcracks and stress concentration areas on the material surface, affecting the yield of subsequent processes such as polishing and epitaxial growth.

[0005] In response, attempts to improve workpiece surface quality have often focused on replacing grinding wheels with finer-grit ones, adjusting the hardness of the bonding agent, or changing grinding parameters. However, these improvements have yielded limited results and are unlikely to effectively reduce or eliminate tool marks. Summary of the Invention

[0006] This section is based on the general summary of this disclosure, and not on a full disclosure of the entire scope or all features of this disclosure.

[0007] According to one aspect of this disclosure, a method for machining a workpiece made of hard and brittle material is provided. The method includes: applying a viscous medium to the surface of the workpiece to be machined; and bringing a bonded abrasive tool into contact with the surface to be machined and generating relative motion to perform grinding. During grinding, the viscous medium captures and suspends abrasive grains detached from the bonded abrasive tool during grinding at the interface between the bonded abrasive tool and the workpiece, forming a free abrasive layer, thereby allowing the abrasive grains in the free abrasive layer to perform in-situ grinding of the surface to be machined.

[0008] According to another aspect of this disclosure, a machining system is also provided. This machining system implements the above-described machining method for workpieces made of hard and brittle materials. The machining system includes a CNC machine tool, a bonded abrasive tool, and a media supply unit. The CNC machine tool includes a first drive device for driving the workpiece and a second drive device for driving the bonded abrasive tool. The bonded abrasive tool is mounted on the second drive device for grinding the surface of the workpiece mounted on the first drive device. The media supply unit is configured to supply a viscous media to the surface to be machined.

[0009] According to the above technical solution, by introducing a viscous medium, the wear characteristic of bonded abrasive tools during grinding is utilized to capture and suspend the detached abrasive grains at the contact interface between the bonded abrasive tool and the workpiece, thus transforming these abrasive grains into abrasive media. This transforms the machining process from a single mode of grinding using bonded abrasive tools to a composite mode of grinding using both bonded abrasive tools and abrasive media, thereby reducing or even eliminating tool marks and improving the surface finish of the workpiece. Attached Figure Description

[0010] The features and advantages of embodiments of the present disclosure will become more readily understood from the following description with reference to the accompanying drawings. The drawings are not drawn to scale and some features may be enlarged or reduced to show details of specific components.

[0011] In the attached diagram: Figure 1 This is a schematic diagram illustrating the processing of hard and brittle material workpieces using related technologies.

[0012] Figure 2 This is a flowchart of a processing method for a hard and brittle material workpiece according to an embodiment of the present disclosure.

[0013] Figure 3 This is a schematic diagram showing the cross-sectional positional relationship when machining an annular groove on a workpiece using a bonded abrasive tool.

[0014] Figure 4 This is a schematic diagram of the abrasive grain distribution in the grinding zone when no viscous medium is applied.

[0015] Figure 5 This is a schematic diagram of the abrasive grain distribution in the grinding area after the application of a viscous medium.

[0016] Figure 6 This is a schematic diagram of a processing system according to an embodiment of the present disclosure.

[0017] In the accompanying drawings, the same or corresponding technical features, parts or components are represented by the same or corresponding reference numerals. Detailed Implementation

[0018] The present disclosure will now be described in detail with reference to the accompanying drawings and exemplary embodiments. It should be noted that the following detailed description of the present disclosure is for illustrative purposes only and is not intended to limit the scope of the disclosure.

[0019] It should be noted that, for clarity, not all features of a particular embodiment are described or shown in the specification and drawings. Furthermore, to avoid unnecessary details obscuring the technical solutions of interest in this disclosure, only the device structures and parts closely related to the technical solutions of this disclosure are described and shown in the specification and drawings, while other details that are not closely related to the technical content of this disclosure and are known to those skilled in the art are omitted.

[0020] To better understand the technical solution of this disclosure, the following will first refer to... Figure 1 This paper provides a brief introduction to the processing of hard and brittle material workpieces using related technologies.

[0021] It is understandable that, for hard and brittle materials, in addition to silicon carbide, it can also be sapphire, gallium nitride (GaN), etc., without any restrictions.

[0022] Typically, CNC machine tools are used to machine workpieces made of hard and brittle materials. For example... Figure 1 As shown, the CNC machine tool 100' may be equipped with a first drive unit 120' and a second drive unit 140'. The first drive unit 120' is typically a rotary table, used to carry the workpiece 20' and drive it to rotate about a first axis X'. The second drive unit 140' is typically the spindle of the CNC machine tool 100', used to hold the bonded abrasive tool 200' and drive it to rotate about a second axis Y', and drive it to perform feed motion in a desired direction. For example, as... Figure 1 As shown, the first axis X' is the rotation center axis of the turntable or workpiece 20'; the second axis Y' is the rotation center axis of the bonded abrasive tool 200'. In annular groove machining, the second axis Y' can be orthogonal to the first axis X', and the desired feed direction can be orthogonal to both the first and second axis directions. Alternatively, in some embodiments, the second axis Y' can also be parallel to the first axis X'. For example, the bonded abrasive tool 200' can be a columnar structure with a long axis (the top of the columnar structure is the grinding part, and the lower part is the fixed structure). During operation, the bonded abrasive tool 200' is vertically fixed and driven by the second drive device 140' to rotate along the direction of the second axis Y' (i.e., along the long axis direction) to perform grinding.

[0023] The workpiece 20' is typically fixed on the tooling fixture 30', which is placed on the first drive device 120'. Thus, the first drive device 120' drives the tooling fixture 30' to rotate, thereby causing the workpiece 20' to rotate.

[0024] During the machining process, the bonded abrasive tool 200' is slowly lowered so that its bottom surface contacts the surface to be machined of the workpiece 20', and relative motion is generated by the rotation of the bonded abrasive tool 200' and the workpiece 20', thereby realizing the grinding process on the surface to be machined.

[0025] In the machining of hard and brittle materials, when using bonded abrasive tools (such as ceramic-bonded diamond wheels, i.e., ceramic cutters) to grind annular grooves on workpieces (such as silicon carbide products), even with high-precision CNC machine tools, the bottom of the groove often still shows marks of varying depths. The inventors discovered that during dry grinding or wet grinding using conventional grinding fluids (such as water), the diamond grains on the surface of the bonded abrasive tool act like tiny ploughshares tracing the workpiece surface. Because the abrasive grains are fixed in the bond, their movement trajectory mirrors that of the machine tool, thus the scratches left on the workpiece surface are periodically repeated. This repeated layering easily forms macroscopically visible textures.

[0026] Furthermore, the inventors discovered that as processing progresses, abrasive grains can detach due to wear or breakage of the bonding agent. These detached abrasive grains are thrown out of the processing area by the centrifugal force generated by rotation, or carried away by the flushing fluid. As a result, these detached abrasive grains cannot continue to participate in effective material removal; moreover, a few abrasive grains that are not thrown out may roll or get stuck uncontrollably between the workpiece and the tool, causing random deep scratches and further deteriorating the surface quality.

[0027] In view of this, according to embodiments of the present disclosure, a method for machining workpieces made of hard and brittle materials is provided. Hereinafter, referring to... Figures 2 to 5 The processing method will be described in detail.

[0028] The processing method includes the following steps: Step S110: Apply an adhesive medium 40 to the surface 22 to be machined on the workpiece 20; and Step S120: Make the bonded abrasive tool 200 come into contact with the surface 22 to be processed and generate relative motion to perform grinding.

[0029] The viscous medium 40 can capture and suspend the abrasive grains 202 that fall off the bonded abrasive tool 200 during grinding at the contact interface between the bonded abrasive tool 200 and the workpiece 20 to form a free abrasive layer 50, thereby enabling the abrasive grains 202 in the free abrasive layer 50 to perform in-situ grinding on the surface 22 to be processed.

[0030] like Figure 3 As shown, an example is taken where a bonded abrasive tool 200 using, for example, a ceramic-bonded diamond tool (such as a grinding wheel) grinds an annular groove (i.e., the surface 22 to be machined) of a workpiece 20.

[0031] In step S110, an operator or automated coating device uniformly applies a layer of viscous medium 40 to the bottom and sidewalls of the annular groove 22 of the workpiece 20. After the application of the viscous medium 40 is completed, the substantive grinding stage begins in step S120. In this step, the bonded abrasive tool 200 is moved to the annular groove 22 of the workpiece 20, bringing it into contact with the groove 22. At this time, the pre-applied viscous medium 40 is compressed and filled in the gap between the bonded abrasive tool 200 and the groove wall and bottom. Subsequently, a CNC machine tool can be started to create relative movement between the bonded abrasive tool 200 and the workpiece 20. For example, this relative movement includes the workpiece 20 rotating around... Figure 6 The rotation of the first axis X and the consolidation of the abrasive tool 200 around it are shown. Figure 6 The rotation of the second axis Y shown.

[0032] pass Figure 4 and Figure 5 The diagram illustrates the changes that occur at the contact interface between the bonded abrasive tool 200 and the workpiece 20 during the machining process with and without the application of a viscous medium. For example, the bonded abrasive tool 200 of a ceramic-bonded diamond tool possesses "self-sharpening" properties, meaning that its surface can maintain a sharp or acute state through its own wear during operation. In the initial stage of grinding, the abrasive grains 202 on the surface of the bonded abrasive tool 200 cut the workpiece 20. As cutting progresses, the edges of the abrasive grains 202 wear down and become blunt, increasing the cutting resistance. When the resistance exceeds the retention limit of the ceramic bond, the bond undergoes micro-fracture, the old abrasive grains 202 fall off, and new abrasive grains 202 are exposed to continue participating in the grinding process.

[0033] In such Figure 4 In the related technologies shown without the application of a viscous medium, these detached abrasive grains 202 are partially or completely washed away or thrown out of the processing area, resulting in these abrasive grains 202 being distributed mainly on the outer side or edge of the contact interface, and the distribution is not uniform enough. Not only do they not participate in the effective grinding of the surface to be processed, but they also cause tool marks.

[0034] In this embodiment, such as Figure 5 As shown, the detached abrasive grains 202 are captured by the surrounding viscous medium 40. Due to the huge viscous resistance provided by the viscous medium 40, these abrasive grains 202 cannot be thrown off, but are confined at the contact interface, thus becoming more evenly distributed, and more abrasive grains 202 will participate in the effective grinding of the surface to be processed.

[0035] As more and more abrasive grains 202 detach and are captured, a free abrasive layer 50, consisting of abrasive grains 202 and viscous media 40, gradually forms between the bonded abrasive tool 200 and the workpiece 20 (see...). Figure 5 The free abrasive layer 50 acts like a flexible grinding pad. Driven by the high-speed rotation of the bonded abrasive tool 200, the free abrasive particles 202 in the free abrasive layer 50 undergo complex rolling and sliding movements within the contact interface to continuously impact and grind the microscopic protrusions on the surface of the workpiece 20 within the contact interface, as well as smooth out the scratches left by the bonded abrasive tool 200, thus achieving more uniform in-situ grinding.

[0036] In this way, the entire grinding process performed within the contact interface includes and integrates two processes: "dimensional grinding" performed by the bonded abrasive tool 200 and "surface polishing" performed by the free abrasive layer 50. As a result, compared with the grinding process of the aforementioned related technologies, the grinding of the surface 22 of the workpiece 20 can be carried out more effectively and uniformly, thereby reducing or even eliminating periodic textures and thus improving the surface finish of the workpiece 20.

[0037] Understandably, the viscous medium 40 may not contain any abrasive particles before being applied to the surface 22 to be processed.

[0038] This design not only reduces costs, but also enables adaptive machining because the abrasive grains in the viscous medium 40 will be entirely derived from the detached abrasive grains 202 of the subsequently used bonded abrasive tool 200.

[0039] Therefore, whether coarse-grained bonded abrasive tools are used in the roughing stage or fine-grained bonded abrasive tools are used in the finishing stage, the particle size of the free abrasive captured in the viscous medium 40 always perfectly matches the current machining accuracy requirements, eliminating the need to frequently change viscous medium 40 of different specifications.

[0040] However, it is also conceivable that the viscous medium 40 contains abrasive particles before being applied to the surface 22 to be processed. This disclosure does not limit this.

[0041] For example, the viscous medium 40 may be an emulsified paste. The emulsified paste may include an oil phase component, an aqueous phase component, and an emulsifier.

[0042] The oil phase component provides lubrication at the contact interface under high contact stress. In the grinding contact area, oil phase molecules can form a physical adsorption film or a chemical reaction film on the surface of the workpiece 20, preventing dry friction between the abrasive grains 202 and the workpiece 20. Exemplarily, the oil phase component may include one or more of hydrocarbons (such as petrolatum, mineral oil, etc.), vegetable oils, and fatty alcohols.

[0043] The aqueous phase is the matrix of the paste, in which important functional additives are dissolved. For example, to prevent the paste from drying out during heat generation during processing, the aqueous phase includes a humectant, such as at least one of glycerin (glycerol) and propylene glycol. These polyols have strong hygroscopic properties, locking in moisture and ensuring that the paste maintains stable rheological properties during prolonged processing.

[0044] In addition, the aqueous phase component may also include a water-soluble polymeric thickener. For example, the water-soluble polymeric thickener may include carbomer. Carbomer is a cross-linked acrylic resin that, when dispersed in water and neutralized, has its molecular chains that stretch dramatically due to the repulsion of like charges, forming a large three-dimensional network structure. This network structure imparts a high yield stress to the paste, enabling it to support denser abrasive grains and prevent them from settling, thereby achieving a suspension effect on the abrasive grains.

[0045] Emulsifiers are used to mix aqueous and oil phase components to form a stable dispersion system, that is, to stably combine immiscible oil and water phases to achieve a stable viscous form. For example, emulsifiers may include glyceryl stearate, triglyceride diisostearate, etc.

[0046] Of course, other implementations of the viscous medium 40 can also be envisioned, as long as it can capture and suspend the abrasive grains 202 that fall off the bonded abrasive tool 200 during grinding at the contact interface between the bonded abrasive tool 200 and the workpiece 20 to form a free abrasive layer 50.

[0047] In some embodiments, in order to maintain the continuity of this grinding effect, it is conceivable that during the processing, for example, if it is found that the viscous medium 40 dries out or is lost, fresh viscous medium 40 can be continuously or intermittently replenished to the contact interface to maintain the lubrication state and suspension ability at the contact interface.

[0048] On the other hand, to implement the above-described processing method, according to embodiments of this disclosure, a processing system is also provided. Hereinafter, referring to... Figure 6 The processing system 10 will be described in detail.

[0049] The machining system 10 includes a CNC machine tool 100, a bonded abrasive tool 200, and a media supply unit 300.

[0050] Similar to the previously mentioned CNC machine tool 100', the CNC machine tool 100 includes a first drive unit 120 and a second drive unit 140. The first drive unit 120 may be, for example, a rotary table, for carrying the workpiece 20 and driving the workpiece 20 to rotate about a first axis X. The second drive unit 140 may be, for example, the spindle of the CNC machine tool 100, for holding the bonded abrasive tool 200 and driving the bonded abrasive tool 200 to rotate about a second axis Y, and driving it to perform feed motion in a desired direction.

[0051] The bonded abrasive tool 200 is mounted on the second drive device 140 and is used to perform grinding on the surface 22 of the workpiece 20 to be processed, which is mounted on the first drive device 120.

[0052] It should be noted that the arrangement of the bonded abrasive tool 200 is not limited to... Figure 6 The state shown can also be vertically arranged. In some embodiments, the bonded abrasive tool 200 can be a columnar structure with a long axis, the top of which is the grinding part and the bottom part is the fixing structure. During operation, the lower part of the bonded abrasive tool 200 is vertically fixed to the second drive device 140, and the second axis Y, which serves as the rotation center axis of the bonded abrasive tool 200, is parallel to the first axis X, that is, the bonded abrasive tool 200 rotates along its long axis to grind the surface 22 to be processed.

[0053] Apart from the above arrangement, the other specific components and working mechanisms of the bonded abrasive tool 200 have been described above and will not be repeated here.

[0054] The medium supply unit 300 is configured to supply a viscous medium 40 to the surface 22 of the workpiece 20 to be processed.

[0055] For example, the media supply unit 300 may be a nozzle integrated next to the second drive device 140, and the media supply unit 300 may deliver viscous media 40 to the processing area quantitatively and at regular intervals according to the instructions of the control system to ensure the stable operation of the grinding process.

[0056] It is conceivable that, in view of the characteristics of hard and brittle materials that are easily broken and deformed, the workpiece 20 can be fixed on the tooling fixture 30 by means of wax, and the tooling fixture 30 is fixed on the first driving device (e.g., turntable) 120 by vacuum adsorption.

[0057] Industrial adhesive wax has good filling properties in the molten state, which can adapt to the microscopic unevenness on the back of the workpiece 20. After cooling and solidification, it provides uniform surface contact support, thereby avoiding stress concentration and workpiece deformation caused by point contact.

[0058] In this disclosure, the terms "first," "second," etc., are used merely for descriptive purposes and should not be considered restrictive. Furthermore, although this disclosure has been described with reference to exemplary embodiments, it should be understood that this disclosure is not limited to the specific embodiments described and shown herein. Various changes to the exemplary embodiments can be made by those skilled in the art without departing from the scope defined by the claims of this disclosure.

[0059] The features mentioned and / or shown in the foregoing description of exemplary embodiments of this disclosure may be combined in the same or similar manner with one or more other embodiments, combined with features in other embodiments, or substituted for corresponding features in other embodiments. Such combinations or substitutions should also be considered as including within the scope of protection of this disclosure.

Claims

1. A method for machining workpieces made of hard and brittle materials, characterized in that, The processing method includes: Applying an viscous medium to the surface of the workpiece to be processed; and The bonded abrasive tool is brought into contact with the surface to be processed, and relative motion is generated to perform grinding. In the grinding process, the viscous medium captures and suspends the abrasive grains that fall off the bonded abrasive tool during the grinding process at the contact interface between the bonded abrasive tool and the workpiece to form a free abrasive layer, thereby enabling the abrasive grains in the free abrasive layer to perform in-situ grinding on the surface to be processed.

2. The processing method for hard and brittle material workpieces according to claim 1, characterized in that, The viscous medium does not contain abrasive particles before being applied to the surface to be processed, and the abrasive particles in the free abrasive layer are all abrasive particles that have detached from the bonded abrasive tool.

3. The processing method for hard and brittle material workpieces according to claim 1, characterized in that, The viscous medium is an emulsified paste, and the emulsified paste comprises: The oil phase component, including at least one of hydrocarbons, vegetable oils and fatty alcohols, is used to provide lubrication at the contact interface; The aqueous phase components, including humectants and water-soluble polymeric thickeners, are used to provide the viscous resistance required to suspend the abrasive particles; and Emulsifiers are used to mix the aqueous phase components with the oil phase components to form a stable dispersion system.

4. The processing method for hard and brittle material workpieces according to claim 3, characterized in that, The water-soluble polymer thickener includes carbomer, and the humectant includes at least one of glycerin and propylene glycol.

5. The processing method for hard and brittle material workpieces according to claim 3, characterized in that, The emulsifier includes at least one of glyceryl stearate and triglyceride diisostearate.

6. The processing method for hard and brittle material workpieces according to claim 1, characterized in that, The bonded abrasive tool is a ceramic-bonded diamond tool. During the grinding process, the binder on the surface of the ceramic-bonded diamond tool breaks down to release the diamond abrasive grains.

7. The processing method for hard and brittle material workpieces according to claim 1, characterized in that, The hard and brittle material is silicon carbide, sapphire, or gallium nitride.

8. The processing method for hard and brittle material workpieces according to claim 1, characterized in that, The surface to be processed is an annular groove on the workpiece, the grinding part of the bonded abrasive tool extends into the annular groove, and the viscous medium fills the space between the grinding part and the annular groove.

9. The processing method for hard and brittle material workpieces according to claim 1, characterized in that, It also includes continuously or intermittently replenishing the viscous medium to the contact interface during the grinding process.

10. The processing method for hard and brittle material workpieces according to claim 1, characterized in that, The relative motion includes: the workpiece rotating about a first axis and the bonded abrasive tool rotating about a second axis.

11. The processing method for hard and brittle material workpieces according to claim 1, characterized in that, The workpiece is fixed to the tooling fixture by wax adhesion, and the tooling fixture is fixed to the machine tool turntable by vacuum adsorption.

12. A processing system, characterized in that, The machining system performs the machining method for hard and brittle material workpieces according to any one of claims 1 to 11, the machining system comprising: A CNC machine tool includes a first drive unit for driving the workpiece and a second drive unit for driving the bonded abrasive tool. The bonded abrasive tool is mounted on the second driving device and is used to perform grinding on the surface of the workpiece to be processed, which is mounted on the first driving device; and A medium supply unit is configured to supply the viscous medium to the surface to be processed.

Images