An elastic grinding head and a grinding method for grinding ultra-thin hard and brittle materials

Abstract

The application discloses an elastic grinding head for grinding super-thin hard and fragile materials, which comprises a coaxial guide cylinder, a return spring, a T-shaped grinding head, a pressure spring and a plug, the T-shaped grinding head is arranged in the guide cylinder and extends from the bottom of the guide cylinder, the plug is installed on the top of the guide cylinder, the pressure spring is installed between the plug and the top of the T-shaped grinding head, and the return spring is sleeved on the T-shaped grinding head; the pressure spring of the application plays a role in conducting the pressure of the main shaft of a machine tool on one hand and plays a role in controlling the rigid contact pressure between the workpiece and the grinding head on the other hand, so that the elastic grinding head has elasticity, when encountering an abnormal convex point on the surface of the workpiece, the elastic grinding head is lifted by a certain distance, the load of the cutter at the abnormal convex point is effectively reduced, the concentration of the machining stress at the abnormal convex point is reduced, the occurrence of cracks is reduced, and the yield is improved.

Description

Technical Field

[0001] This invention relates to the field of precision machining technology for hard and brittle materials, specifically to an elastic grinding head and grinding method for grinding ultra-thin hard and brittle materials. Background Technology

[0002] Semiconductor manufacturing equipment contains numerous precision ceramic and quartz components made of silicon carbide, silicon nitride, alumina, and aluminum nitride. These components are characterized by high hardness and brittleness, yet require extremely precise machining. They belong to a class of hard, brittle, and difficult-to-machine materials. Traditional mechanical grinding processes are essentially head-on collisions, making the workpiece highly sensitive to external stimuli. The vibrations generated during the process can cause uneven material removal from the workpiece surface, significantly impacting grinding quality. Furthermore, these vibrations often lead to workpiece cracking, chipping, and incomplete machining. Therefore, increasing the machining accuracy of the equipment to reduce the excitation force can mitigate vibration. However, excessively pursuing equipment complexity and precision requirements can drastically increase manufacturing costs.

[0003] In recent years, high-frequency, low-amplitude ultrasonic-assisted machining technology has become increasingly mature. The principle of this technology is that the tool holder generates high-frequency, high-intensity impact force under the action of the ultrasonic converter, which drives the grinding rod to intermittently impact the surface of the part, causing the surface of the part to produce tiny vibrations. The local stress of the part far exceeds the brittle fracture stress of the material, thereby reducing the cutting force by up to 40%, the cutting heat by up to 30%, and improving the processing efficiency and yield. It provides an excellent solution for machining hard and brittle materials.

[0004] However, for ultra-thin, hard, and brittle ceramic components with a thickness of less than 0.5 mm, such as ceramic phone cases, ultra-thin ceramic heat sinks, SiC edge rings, irregularly shaped Al2O3 sealing sheets, and SiC spray discs, there are characteristics of high clamping difficulty, small machining allowance, and low fracture load. Referring to the three-point bending strength of typical hard and brittle ceramics from Kyocera, Japan, when the material thickness is 0.5 mm, the span is 30 mm, and the width is 3.0 mm, the fracture load of the material is less than 10 N, as shown in the table below.

[0005]

[0006]

[0007] The yield rate of such parts processed with ultrasonic assistance remains very low. One possible reason is that although the impact load applied to the part under ultrasonic assistance can achieve the purpose of material removal with very small impact load, for ultrathin and brittle materials, the impact load is very likely to exceed the fracture load limit, causing the material to fracture brittlely. Another possibility is that ultrasonic vibration-assisted processing simply changes the traditional constant load hard-on processing method to intermittent hard-on impact load. This impact load is very likely to cause local stress concentration in the part, generating more subsurface microcracks. Due to the cross-sectional size effect of ultrathin and brittle materials, the path for the steady-state development of microcracks is extremely short. That is, the material will not fracture brittlely. However, the crack will propagate under impact fatigue until the crack length exceeds the thickness of the ultrathin material. This explains that in the initial stage of ultrathin material processing, the material is intact, but as the material is further thinned, the crack gradually elongates and enlarges, eventually leading to fracture. Summary of the Invention

[0008] To address the aforementioned problems in the prior art, this invention provides an elastic grinding head and grinding method for grinding ultrathin, hard, and brittle materials, thus solving the problem of low yield in ultrasonic-assisted processing of ultrathin, hard, and brittle ceramic parts.

[0009] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0010] On one hand, an elastic grinding head for grinding ultra-thin, hard, and brittle materials is provided, which includes a coaxial guide cylinder, a pull-back spring, a T-shaped grinding head, a pressure spring, and a plug. The T-shaped grinding head is disposed inside the guide cylinder and extends from the bottom of the guide cylinder; the plug is installed on the top of the guide cylinder; the pressure spring is installed between the plug and the top of the T-shaped grinding head; and the pull-back spring is sleeved on the T-shaped grinding head.

[0011] The pressure spring of this invention serves two purposes: firstly, it transmits the pressure of the machine tool spindle, and secondly, it controls the rigid contact pressure between the workpiece and the grinding head. This makes the elastic grinding head elastic, and when it encounters abnormal protrusions on the workpiece surface, the elastic grinding head lifts upward a certain distance, effectively reducing the load on the tool at the abnormal protrusions, reducing the concentration of processing stress at the abnormal protrusions, reducing the occurrence of cracks, and improving the yield.

[0012] Furthermore, the T-type grinding head includes a connected T-shaped platform, a square-section long shank, and a round-section grinding end;

[0013] The pressure spring is installed between the plug and the upper surface of the T-shaped platform; the return spring is sleeved on the square-section long shank; the square-section long shank and the round-section grinding end extend from the pre-set square hole at the bottom of the guide cylinder.

[0014] Furthermore, the stiffness of the compression spring is 15 N / mm to 35 N / mm; the stiffness of the pull-back spring is one-tenth of the stiffness of the compression spring.

[0015] Furthermore, a pressure sensor is installed on the lower surface of the plug.

[0016] On the other hand, a grinding method based on an elastic grinding head for grinding ultrathin, hard, and brittle materials includes the following steps:

[0017] Step S1: Clamping. Clamp the workpiece with the surface to be ground facing upwards on the grinding machine. Collect and record the height value of the surface to be ground, and evaluate the flatness of the workpiece clamping.

[0018] Step S2: Establish a coordinate system at the center of the workpiece surface to be ground.

[0019] Step S3: Depth of cut measurement. Install the elastic grinding head on the machine tool spindle and slowly reduce the Z value. When the pressure sensor inside the elastic grinding head reports a pressure of 2 Newtons, record the Z value.

[0020] Step S4, Programming and Machining: Using the Z value recorded in step S3 as the depth of cut, program the workpiece surface to be ground by running the entire XY plane as a subroutine.

[0021] Furthermore, the method for establishing the coordinate system in S2 is as follows: take the lowest point of the height value collected in step S1 as the origin of the Z-axis, and take the center of the workpiece surface to be ground as the origin of the coordinate system.

[0022] Furthermore, the method for grinding the surface of the workpiece in step S4 is as follows: if the pressure sensor feeds back pressure information, and if the pressure fed back by the pressure sensor exceeds 1 Newton during the execution of this subroutine, then the Z-axis feed is zero, and the subroutine is executed repeatedly.

[0023] If the pressure returned by the pressure sensor is less than 1 Newton during the execution of this subroutine, the program will terminate.

[0024] Furthermore, in step S4, the spindle speed is set to 800-18000 r / min, and the feed speed in a certain direction in the XY plane is 3-300 mm / min.

[0025] This invention discloses an elastic grinding head and grinding method for grinding ultrathin, hard, and brittle materials, the beneficial effects of which are:

[0026] 1. The pressure spring of the present invention serves two purposes: firstly, it transmits the pressure of the machine tool spindle, and secondly, it controls the rigid contact pressure between the workpiece and the grinding head. This makes the elastic grinding head elastic. When it encounters abnormal protrusions on the workpiece surface, the elastic grinding head lifts upward a certain distance, effectively reducing the load on the tool at the abnormal protrusions, reducing the concentration of processing stress at the abnormal protrusions, reducing the occurrence of cracks, and improving the yield.

[0027] 2. In this invention, the stiffness of the pressure spring is 15N / mm to 35N / mm, which effectively controls the load applied by the elastic grinding head to the ultra-thin hard and brittle material workpiece. This load is less than the ultimate bending load of the ultra-thin hard and brittle material workpiece and will not cause the material to bend and break.

[0028] 3. In the grinding method for ultra-thin hard and brittle materials in this invention, the method for determining the depth of cut and the determination of program termination greatly improve the grinding accuracy of ultra-thin hard and brittle materials. Attached Figure Description

[0029] Figure 1 This is a schematic diagram of the structure of an elastic grinding head for grinding ultra-thin, hard, and brittle materials according to the present invention.

[0030] Figure 2 This is a cross-sectional schematic diagram of an elastic grinding head for grinding ultra-thin, hard, and brittle materials according to the present invention.

[0031] Figure 3 This is a schematic diagram of the guide cylinder of the present invention.

[0032] Figure 4 This is a schematic diagram of the structure of the T-type grinding head of the present invention.

[0033] Among them, 1. guide cylinder; 11. square hole; 2. pull-back spring; 3. T-shaped grinding head; 31. T-stage; 32. square cross-section long shank; 33. round cross-section grinding end; 4. pressure spring; 5. plug; 51. pressure sensor. Detailed Implementation

[0034] The present invention is described in detail with reference to specific embodiments to enable those skilled in the art to understand the invention. However, it should be understood that the invention is not limited to the scope of the specific embodiments. For those skilled in the art, various changes are obvious as long as they are within the spirit and scope of the invention as defined and determined by the appended claims. All inventions utilizing the concept of the present invention are protected.

[0035] Example 1

[0036] This embodiment provides an elastic grinding head for grinding ultrathin, hard, and brittle materials. Its purpose is to solve the problem of low yield in ultrasonic-assisted machining of ultrathin, hard, and brittle ceramic parts. (Refer to...) Figures 1-4 The specific structure of this embodiment will be described in detail below.

[0037] An elastic grinding head for grinding ultrathin, hard and brittle materials includes a coaxial guide cylinder 1, a pull-back spring 2, a T-shaped grinding head 3, a pressure spring 4, and a plug 5.

[0038] The T-shaped grinding head 3 is located inside the guide cylinder 1 and extends from the bottom of the guide cylinder 1; the plug 5 is installed on the top of the guide cylinder 1; the pressure spring 4 is installed between the plug 5 and the top of the T-shaped grinding head 3; and the pull-back spring 2 is sleeved on the T-shaped grinding head 3.

[0039] In this embodiment, the T-shaped grinding head 3 is inserted from the top of the guide cylinder 1, and the grinding head end of the T-shaped grinding head 3 extends from the bottom of the guide cylinder 1. Then, the plug 5 is installed on the top of the guide cylinder 1 by thread, and the pressure spring 4 is installed between the plug 5 and the top of the T-shaped grinding head 3, acting between the T-shaped grinding head 3 and the top of the guide cylinder 1. The pull-back spring 2 is sleeved on the T-shaped grinding head 3, acting between the T-shaped grinding head 3 and the bottom of the guide cylinder 1. Thus, the pressure spring 4 plays a role in transmitting the pressure of the machine tool spindle on the one hand, and on the other hand, it plays a role in controlling the rigid contact pressure between the workpiece and the grinding head. This makes the elastic grinding head elastic. When encountering abnormal protrusions on the workpiece surface, the elastic grinding head lifts up a certain distance, effectively reducing the load on the tool at the abnormal protrusions, reducing the concentration of processing stress at the abnormal protrusions, reducing the occurrence of cracks, and improving the yield.

[0040] Specifically, the T-shaped grinding head 3 includes a connected T-shaped platform 31, a square-section long shank 32, and a round-section grinding end 33. A pressure spring 4 is installed between the plug 5 and the upper surface of the T-shaped platform 31. A pull-back spring 2 is sleeved on the square-section long shank 32. The square-section long shank 32 and the round-section grinding end 33 extend from the square hole 11 pre-set at the bottom of the guide cylinder 1.

[0041] In this embodiment, the square hole 11 matches the cross-sectional shape of the square-section long shank 32, so that the square-section long shank 32 and the round-section grinding end 33 of the T-shaped grinding head 3 axially pass through the pull-back spring 2 and the square hole 11 pre-set at the bottom of the guide cylinder 1 and extend out. The cross-sectional area of ​​the T-stage 31 is larger than the area of ​​the square hole 11, so that a pressure spring 4 is set between the upper surface of the T-stage 31 and the plug 5, and a pull-back spring 2 is set between the lower surface of the T-stage 31 and the bottom end of the guide cylinder 1, thereby controlling the rigid contact pressure between the workpiece and the grinding head.

[0042] Specifically, the stiffness of the compression spring 4 is 15N / mm to 35N / mm; the stiffness of the pull spring 2 is one-tenth of the stiffness of the compression spring 4.

[0043] In this embodiment, the material to be ground is an ultrathin hard and brittle material, such as brittle ceramics or glass, with a thickness of less than 0.5 mm. The flatness or unevenness difference of the surface to be ground is less than 0.08 mm. The safety factor for the fracture strength of brittle materials is generally taken as 2 to 3.5. According to Hooke's Law, the following formula (1) can be obtained:

[0044]

[0045] in:

[0046] F 断 —Material fracture strength, taken as 10N;

[0047] F 预压 —The pre-pressure of the grinding material is 2N;

[0048] α—Safety factor for brittle materials (α1 = 3.5, α2 = 2.0);

[0049] λ — the flatness or unevenness difference of the surface to be ground is less than 0.08 mm, and the value is 0.08.

[0050] C represents the design stiffness of the compression spring, which can be calculated to be 10.625 N / mm ≤ C ≤ 37.5 N / mm.

[0051] In this embodiment, the design stiffness of the pressure spring 4 is 15N / mm to 35N / mm, which effectively controls the load applied by the elastic grinding head to the ultra-thin hard and brittle material workpiece. This load is less than the ultimate bending load of the ultra-thin hard and brittle material workpiece and will not cause the material to bend and break.

[0052] To reduce the risk of brittle fracture of ultra-thin materials during processing and improve the stability of the elastic grinding head, the stiffness of the pressure spring 4 of the elastic grinding head is 35 N / mm, the number of support coils is 2.5, and the number of effective coils is 4 to 8; the stiffness of the pull spring 2 is 3.5 N / mm.

[0053] Specifically, a pressure sensor 51 is installed on the lower surface of the plug 5.

[0054] In this embodiment, the plug 5 is plugged into the top of the guide cylinder 1 by a threaded structure. A pressure sensor 51 is installed on the lower surface of the plug 5. The pressure sensor 51 is a strain gauge pressure sensor, which is used to feed back the pressure information of the pressure spring 4. In this embodiment, when the elastic grinding head is not working, the pull-back spring 2 is in a compressed state and the pressure spring 4 is in a free state.

[0055] Example 2

[0056] Based on Example 1, this example provides a grinding method using an elastic grinding head for grinding ultrathin, hard, and brittle materials. The purpose is to solve the problem of low yield in ultrasonic-assisted processing of ultrathin, hard, and brittle ceramic parts. The specific steps in this example will be described in detail below.

[0057] A grinding method based on an elastic grinding head for grinding ultrathin hard and brittle materials, wherein the workpiece is a silicon nitride ceramic blank with a thickness of 0.44±0.04mm and a flatness of 0.083, and the flatness of the blank is ground to be less than 0.03;

[0058] An elastic grinding head is selected, with a pressure spring stiffness of 35 N / mm, a support coil number of 2.5, and an effective coil number of 4; the stiffness of the return spring 2 is 3.5 N / mm.

[0059] Includes the following steps:

[0060] Step S1: Clamping. Clamp the workpiece with the surface to be ground facing upwards on the grinding machine. Collect and record the height value of the surface to be ground, and evaluate the flatness of the workpiece clamping. The flatness of the workpiece clamping is required to be ≤0.08mm. Otherwise, re-clamp. In this embodiment, the flatness of the workpiece clamping is 0.05mm.

[0061] Step S2: Establish a coordinate system at the center of the workpiece surface to be ground.

[0062] Specifically, the method for establishing the coordinate system in step S2 is as follows: take the lowest point of the height value collected in step S1 as the origin of the Z-axis, and take the center of the workpiece surface to be ground as the origin of the coordinate system.

[0063] Step S3, Depth of cut measurement: Install the elastic grinding head on the machine tool spindle and slowly reduce the Z value. When the pressure sensor 51 inside the elastic grinding head reports a pressure of 2 Newtons, record the Z value.

[0064] Step S4, Programming and Machining: Using the Z value recorded in step S3 as the depth of cut, program the workpiece surface to be ground by running the entire XY plane as a subroutine.

[0065] The method for grinding the surface of the workpiece in step S4 is as follows: the pressure sensor 51 feeds back pressure information. If the pressure fed back by the pressure sensor 51 is greater than 1 Newton during the operation of this subroutine, the Z-axis feed is zero and the subroutine is executed repeatedly.

[0066] If the pressure reported by pressure sensor 51 is less than 1 Newton during the execution of this subroutine, the program will end.

[0067] In step S4, the spindle speed is set to 800-18000 r / min, and the feed speed in a certain direction in the XY plane is 3-300 mm / min. In this embodiment, the spindle speed is set to 18000 r / min, and the feed speed in a certain direction in the XY plane is 300 mm / min.

[0068] Coordinate measuring machine (CMM) measurement: The flatness of the processed silicon nitride wafer is 0.02 mm.

[0069] Example 2

[0070] Based on Example 1, this example provides a grinding method using an elastic grinding head for grinding ultrathin, hard, and brittle materials. The purpose is to solve the problem of low yield in ultrasonic-assisted processing of ultrathin, hard, and brittle ceramic parts. The specific steps in this example will be described in detail below.

[0071] A grinding method based on an elastic grinding head for grinding ultrathin hard and brittle materials, wherein the workpiece is a silicon nitride ceramic blank with a thickness of 0.3+0.1mm and a flatness of 0.092, and the flatness of the workpiece is ground to be less than 0.015;

[0072] An elastic grinding head is selected, with a pressure spring stiffness of 40 N / mm, a support coil count of 2.5, and an effective coil count of 8; the stiffness of the return spring 2 is 4 N / mm.

[0073] Includes the following steps:

[0074] Step S1: Clamping. Clamp the workpiece with the surface to be ground facing upwards on the grinding machine. Collect and record the height value of the surface to be ground, and evaluate the flatness of the workpiece clamping. The flatness of the workpiece clamping is required to be ≤0.08mm. Otherwise, re-clamp. In this embodiment, the flatness of the workpiece clamping is 0.05mm.

[0075] Step S2: Establish a coordinate system at the center of the workpiece surface to be ground.

[0076] Specifically, the method for establishing the coordinate system in step S2 is as follows: take the lowest point of the height value collected in step S1 as the origin of the Z-axis, and take the center of the workpiece surface to be ground as the origin of the coordinate system.

[0077] Step S3, Depth of cut measurement: Install the elastic grinding head on the machine tool spindle and slowly reduce the Z value. When the pressure sensor 51 inside the elastic grinding head reports a pressure of 2 Newtons, record the Z value.

[0078] Step S4, Programming and Machining: Using the Z value recorded in step S3 as the depth of cut, program the workpiece surface to be ground by running the entire XY plane as a subroutine.

[0079] The method for grinding the surface of the workpiece in step S4 is as follows: the pressure sensor 51 feeds back pressure information. If the pressure fed back by the pressure sensor 51 is greater than 1 Newton during the operation of this subroutine, the Z-axis feed is zero and the subroutine is executed repeatedly.

[0080] If the pressure reported by pressure sensor 51 is less than 1 Newton during the execution of this subroutine, the program will end.

[0081] In step S4, the spindle speed is set to 800-18000 r / min, and the feed speed in a certain direction in the XY plane is 3-300 mm / min. In this embodiment, the spindle speed is set to 8000 r / min, and the feed speed in a certain direction in the XY plane is 3 mm / min.

[0082] Coordinate measuring machine (CMM) measurement: The flatness of the processed silicon nitride wafer is 0.01 mm.

[0083] Although specific embodiments of the invention have been described in detail with reference to the accompanying drawings, this should not be construed as limiting the scope of protection of this patent. Various modifications and variations that can be made by a person skilled in the art without inventive effort within the scope described in the claims still fall within the scope of protection of this patent.

Claims

1. An elastic grinding head for grinding ultra-thin hard and brittle materials, characterized in that: It comprises a coaxial guide cylinder (1), a return spring (2), a T-shaped grinding head (3), a pressure spring (4) and a plug (5); The T-shaped grinding head (3) is arranged in the guide cylinder (1) and extends from the bottom of the guide cylinder (1); the plug (5) is installed on the top of the guide cylinder (1); the pressure spring (4) is installed between the plug (5) and the top of the T-shaped grinding head (3); and the return spring (2) is sleeved on the T-shaped grinding head (3). The rigidity of the pressure spring (4) is 15 N / mm-35 N / mm, and the rigidity of the return spring (2) is one-tenth of the rigidity of the pressure spring (4).

2. The flexible polishing head for polishing ultra-thin hard and brittle materials according to claim 1, wherein: The T-shaped grinding head (3) comprises a T-shaped table (31), a square-section long handle (32) and a circular-section grinding end (33) connected with each other. The pressure spring (4) is installed between the plug (5) and the upper surface of the T-shaped table (31); the return spring (2) is sleeved on the square-section long handle (32); and the square-section long handle (32) and the circular-section grinding end (33) extend from the square hole (11) at the bottom of the guide cylinder (1).

3. The elastomeric polishing head for polishing ultra-thin hard and brittle materials of claim 1, wherein: The lower surface of the plug (5) is provided with a pressure sensor (51).

4. A method of lapping an elastic lapping head for lapping an ultra-thin hard and brittle material according to any one of claims 1 to 3, characterized in that, The method comprises the following steps: Step S1, clamping, clamping the workpiece surface to be ground horizontally upwards on the grinding machine, collecting and recording the height value of the workpiece surface to be ground, and evaluating the clamping flatness of the workpiece; Step S2, establishing a coordinate system, establishing a coordinate system at the center of the workpiece surface to be ground; Step S3, back engagement amount determination, installing the elastic grinding head on the machine tool spindle, slowly reducing the Z value, when the pressure sensor (51) in the elastic grinding head feedbacks a pressure of 2 Newton, recording the Z value; Step S4, programming and processing, programming with the back engagement amount of the Z value recorded in step S3, running the entire XY surface as a subroutine, and grinding the workpiece surface to be ground.

5. The method of claim 4, wherein the method is characterized by: The method for establishing a coordinate system in step S2 is that the lowest point of the height value collected in step S1 is taken as the Z-axis origin, and the center of the workpiece surface to be ground is taken as the coordinate system origin.

6. The method of claim 4, wherein the method is characterized by: The method for grinding the workpiece surface to be ground in step S4 is that the pressure information is fed back by the pressure sensor (51), if there is a stage in which the pressure fed back by the pressure sensor (51) is greater than 1 Newton during the running of the subroutine, the Z-direction feed is zero, and the subroutine is repeatedly executed; If the pressure fed back by the pressure sensor (51) is less than 1 Newton during the running of the subroutine, the program running is ended.

7. The method of claim 6 wherein the method further comprises the step of: In step S4, the spindle speed is set to 800-18000 r / min, and the feed speed in a certain direction in the XY plane is 3-300 mm / min.

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