A method for polycrystalline diamond grinding based on pressure regulation

Abstract

The application discloses a polycrystalline diamond grinding method based on pressure regulation. The polycrystalline diamond grinding processing parameter setting is performed through pressure regulation. The polycrystalline diamond to be processed is divided into multiple layers according to height. The processing load of each layer is set according to the critical fracture strength of the material and the processing area. The load of the whole processing process is in the critical state of causing cracks and other damages of the material. The processing efficiency is maximized. Meanwhile, the cracks and other damages of the subsurface are not caused in the grinding process. The method has the characteristics of rapidness, low cost and strong operability and can be used for grinding and processing of polycrystalline diamonds in different growth modes and different sizes. The method has certain guiding significance for optimizing material processing parameters, shortening processing time and improving the yield.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of polycrystalline diamond processing, and particularly relates to a polycrystalline diamond grinding method based on pressure adjustment. BACKGROUND

[0002] Diamond has some of the most extreme physical, optical and mechanical properties of any material, such as the lowest friction coefficient, the lowest compressibility, the highest bulk modulus and thermal conductivity, wide optical transparency from deep ultraviolet (UV) to far infrared, and extreme mechanical hardness and wear resistance. Diamond is widely used in modern industry, such as cutting tools, optical windows, heat dissipation, etc., and is considered as an ideal material for manufacturing high-performance semiconductor electronic components. The industrial applications of diamond all require high-precision planarization to obtain ultra-smooth and damage-free surfaces. In addition, the characteristics of high hardness, wear resistance and anisotropy make the processing of diamond extremely difficult. Therefore, the principles, processes and equipment types of diamond ultra-precision polishing technology have always been the focus of attention of the academic and industrial communities.

[0003] The initial surface of polycrystalline diamond is rough, the diameter is large, and the thickness deviation is large, which brings unprecedented imbalance to efficiency and quality. Grinding processing is an important means of planarization processing of large-size polycrystalline diamond. The conventional grinding processing method usually adopts a specific pressure for processing, which does not take into account the thickness deviation of the sample. The grinding of materials in the academic field mostly focuses on the uniformity of the grinding track and the development of new tools, and there are few reports on the grinding pressure for the thickness deviation of the material. However, pressure is an important parameter for adjusting the processing efficiency and quality of the material. The industry adopts fixed pressure processing for the whole process for the processing of large-size wafers. When the pressure is set too small for the grinding of diamond, the material removal rate is too low, which increases the processing time. When the pressure is too large, the pressure per unit area of the material in the early stage of processing may exceed the ultimate strength of the material, which undoubtedly increases the breakage of the material and reduces the yield. At present, large-size polycrystalline diamond is expensive, which undoubtedly greatly increases the production cost.

[0004] Therefore, it is meaningful to adopt a grinding method based on pressure adjustment for parameter setting for the grinding processing of polycrystalline diamond material. SUMMARY

[0005] The purpose of the present application is to overcome the shortcomings of the prior art. The fracture strength of the material is obtained by using the indentation method. The contour line obtained according to the fracture strength and height information of the material is used to divide the sample to be processed into layers and calculate the load required for grinding, so as to optimize the load in the whole grinding process, improve the processing efficiency, the yield of production and save the production cost.

[0006] To solve the above technical problems, the technical scheme adopted by the present application is:

[0007] A method for polycrystalline diamond grinding based on pressure regulation, comprising the following steps:

[0008] (1) Selecting a polycrystalline diamond sample, cutting it into small pieces after polishing, and then performing an indentation test on the sample using an indentation method to obtain the minimum load F0 at which the diamond produces a crack;

[0009] (2) Selecting 2-50 μm diamond as the diamond abrasive in the polycrystalline diamond grinding fluid, and the effective radius of the diamond abrasive is equal to the radius of the indenter tip used in step a indentation method;

[0010] (3) Calculating the number N of effective abrasive particles participating in grinding in the diamond grinding fluid during the grinding process;

[0011] (4) Calculating the critical pressure P of the diamond producing a crack under the action of the abrasive during the grinding process,

[0012] P=F0*N / A0,

[0013] Where A0 is the area of the diamond being ground;

[0014] (5) Detecting the surface type of the polycrystalline diamond to be ground and calculating the contour lines, with an interval of m;

[0015] (6) Calculating the area An of each contour line envelope, and n≥1, then the actual area Ai of each layer being processed is:

[0016] When the processed surface is convex, Ai=An;

[0017] When the processed surface is concave, Ai=S-An, where S is the area of the sample being processed;

[0018] Then the load required for grinding under each contour line

[0019] F n = a *P*A i ,

[0020] Where a is the safety load factor;

[0021] (7) Calculating the area A i , the load Fn is applied, the material removal rate R of the grinding process, and the material removal rate R is the volume of material removed per unit time under this process parameter, then the time T n required for processing at this contour line interval is:

[0022] T n = 0.5*m*Ai / R;

[0023] (8) the load F required for processing each contour line n and processing time T n input into the numerical control system of the grinding machine tool;

[0024] (9) processing the polycrystalline diamond to be ground in step (5) according to the program set in step (8).

[0025] In step (3), the number of diamonds on the grinding disc can be obtained by the total concentration and flow rate of the grinding liquid, and the number of effective abrasive grains N participating in the grinding can be obtained according to the proportion by the size of the grinding disc and the size of the diamond.

[0026] In step (1), the growth method of the polycrystalline diamond sample includes but is not limited to the MPCVD method, the direct current arc method, and the hot wire method.

[0027] In step (2), the form of the indenter includes but is not limited to the Vickers indenter, the Rockwell indenter, the spherical indenter, and the triangular pyramid indenter.

[0028] In step (6), the safety factor of processing a is set to 0.5-0.9.

[0029] The beneficial effects of the present application are:

[0030] The polycrystalline diamond grinding method based on pressure adjustment disclosed in the present application sets the polycrystalline diamond grinding processing parameters through pressure adjustment, divides the polycrystalline diamond to be processed into multiple layers according to the height, sets the processing load of each layer according to the critical fracture strength of the material and the processing area, makes the load of the entire processing process in the critical state of causing cracks and other damages to the material, maximizes the processing efficiency, ensures that no sub-surface cracks and other damages are caused during the grinding process, has the characteristics of rapidity, low cost, and strong operability, can be used for grinding and processing polycrystalline diamonds of different growth methods and different sizes, has certain guiding significance for optimizing material processing parameters, shortening processing time, and improving the yield rate. BRIEF DESCRIPTION OF DRAWINGS

[0031] Figure 1 The size of the diamond indenter and the cross blade used for the indentation test of the present application;

[0032] Figure 2 The concave contour line graph of the polycrystalline diamond sample to be ground in Example 1;

[0033] Figure 3 The surface effect graph after processing the original surface flatness for different times in Example 1;

[0034] Figure 4 A comparison chart of the time length consumed for processing 2-4 inch samples using the present application and the conventional method. DETAILED DESCRIPTION

[0035] The following specific examples illustrate the implementation of the present application, and those skilled in the art can easily understand other advantages and effects of the present application from the disclosure of the specification.

[0036] The following will be specifically described in conjunction with examples:

[0037] Example 1

[0038] The present application provides a polycrystalline diamond grinding method based on pressure regulation, as shown in Figures 1 to 4 .

[0039] The polycrystalline diamond grinding method based on pressure regulation comprises the following steps:

[0040] a. Selecting polycrystalline diamond obtained by MPCVD growth as a sample, polishing the sample, the surface roughness after polishing is less than 10 nm, the sample thickness is 1 mm, cutting into small pieces by an infrared nanosecond laser, the size is 10*10 mm 2 , using a Vickers hardness tester to perform an indentation test on the sample, using a Vickers indenter, the cross blade of the indenter is 1 μm, as shown in Figure 1 , record the displacement load curve during the indentation process, when the load changes suddenly, it is considered that the material has been fractured, and the average load F0=0.35±0.03N when the diamond cracks is recorded;

[0041] b. Selecting a 10 μm diameter diamond abrasive grain as the diamond in the grinding liquid for grinding polycrystalline diamond, according to the empirical formula, the effective radius of the abrasive grain is 1 / 10 of its diameter, the effective radius of the diamond abrasive grain is equal to the tip radius of the indenter used in step a indentation method;

[0042] c. Calculate the number of effective abrasive grains on the unit grinding disc according to the flow rate and concentration of the grinding liquid; that is, the number N of effective abrasive grains in the diamond grinding liquid participating in the grinding during the grinding process, N can be obtained through the concentration of diamond abrasive grains in the grinding liquid, the flow rate of the grinding liquid, and the contact area of the sample;

[0043] d. Calculate the critical pressure P of the diamond under the action of the 10 μm abrasive grain during the grinding process, the calculation formula is P=F0*N / A0=0.15Mpa.

[0044] e. Detecting the surface type of the 2 inch polycrystalline diamond to be ground, the flatness is 18 μm, and calculating the contour line, the interval of the contour line is m=3 μm, as shown inFigure 2 The area of each contour envelope An is calculated, n = 6, and the actual area of each layer to be processed Ai is calculated.

[0045] f. The area An of each contour envelope is calculated, n = 6, and the actual area of each layer to be processed Ai is calculated:

[0046] Since the processed surface is concave, Ai = S - An, where S is the area of the processed sample, and An and Ai can be calculated by software; where S = 1290.32 square millimeters, Ai = 489.68 square millimeters when i = 1, Ai = 786.73 square millimeters when i = 2, and all values of Ai are obtained by software.

[0047] The load F required for grinding processing under each contour is n :

[0048] F n = a *P*An,

[0049] wherein a = 0.9, the selection of the coefficient is based on the uniformity of the fracture strength of the sample, the average fracture of a single indentation F0 = 0.35 ± 0.03 N, the fluctuation is 0.03 / 0.35 = 8.57%, to improve the safety of the sample, and the interval of the contour is considered, the coefficient is 0.9; F1 = 66.1 N, F2 = 106.2 N, and all values of F1-F6 are obtained in turn.

[0050] g. The material removal rate R = 0.12 mm 3 / min (obtained by grinding experiment of small size sample) when the area is Ai and the load is Fn, then the time required for processing at this contour interval is Tn = 0.5*m*Ai / R; then T1 = 6.2 min, T2 = 9.7 min, and T1-T6 are calculated in turn.

[0051] wherein the time required for contour interval processing Tn is simplified, assuming that the height difference within the contour is continuous and uniform, then the material volume can be considered as half of the contour multiplied by the area; the volume can also be accurately calculated by integration, the material removal volume is:, wherein x, y are the sample coordinate values within the contour area, the zero point of the coordinate is the center of the lowest point of the contour envelope area, and z is the height value relative to the center point, then the processing time is T = V / R; in this embodiment, the simplified calculation is adopted.

[0052] h. The load F n and the processing time T n required for processing each contour are input into the numerical control system of the grinder;

[0053] i. Polycrystalline diamond that needs to be processed in e is processed according to the procedure set in h, such as Figure 3 The surface topography of a 2-inch sample with a flatness of 18 μm after different processing times is shown in Fig. 2, and Figure 4 Fig. 3 shows different sizes of polycrystalline diamond samples grown under the same process, and the time required for processing to a flatness of 1 μm using the conventional method and the method of the present application is compared. It can be seen from the figure that the processing time is greatly reduced.

[0054] The polycrystalline diamond processing parameter setting method with pressure regulation adopted by the present application can divide the polycrystalline diamond to be processed into multiple layers according to height, set the processing load of each layer according to the critical fracture strength of the material and the processing area, so that the load of the entire processing process is at the critical state of causing damage such as cracks in the material, the processing efficiency is maximized, and damage is not caused. It has the characteristics of being fast, low cost, and easy to operate, and can be used for the processing of polycrystalline diamond of different growth methods and different sizes. It has certain guiding significance for optimizing material processing parameters, shortening processing time, and improving yield.

[0055] The basic principles, main features and advantages of the present application are shown and described above. Those skilled in the art should understand that the present application is not limited by the above examples, and the above examples and descriptions in the specification are only to illustrate the principles of the present application. Without departing from the spirit and scope of the present application, various changes and improvements can be made to the present application, and these changes and improvements all fall within the scope of the claimed invention. The scope of protection of the present application is defined by the appended claims and equivalents thereof.

[0056] In the description of the present application, it should be understood that the terms "front", "back", "left", "right", "center", etc. indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as limiting the scope of protection of the present application.

Claims

1. A method of polycrystalline diamond grinding based on pressure regulation, characterized by, The method comprises the following steps: (1) selecting a polycrystalline diamond sample, cutting the sample into small pieces after polishing, and then performing an indentation test on the sample using an indentation method to obtain the minimum load F0 at which the diamond generates a crack; (2) selecting 2-50 μm diamond as the diamond abrasive in the polycrystalline diamond grinding liquid, and the effective radius of the diamond abrasive is equal to the radius of the tip of the indenter used in step a; (3) calculating the number N of effective abrasives participating in the grinding in the diamond grinding liquid during the grinding process; (4) calculating the critical pressure P at which the diamond generates a crack under the action of the abrasives during the grinding process, P = F0*N / A0, where A0 is the area of the diamond being ground; (5) detecting the surface type of the polycrystalline diamond to be ground and calculating the contour lines, with an interval of m; (6) calculating the area An of each contour line envelope, and n≥1, so that the actual area Ai of each layer being processed is: Ai = An when the surface being processed is convex; Ai = S-An when the surface being processed is concave, where S is the area of the sample being processed; and the load required for grinding under each contour line is F n = a *P*A i , wherein a is the safety load factor; (7) the area is A i , the material removal rate R of the polishing process is the volume of the material removed per unit time under the process parameters, and the time T required for processing between the contour intervals is: n ​ T n = 0.5*m*A i / R; (8) Load F required to machine each contour n and machining time T n to the numerical control system of the grinding machine (9) processing the polycrystalline diamond to be ground in step (5) according to the program set in step (8).

2. The method of claim 1, wherein the pressure is regulated. In step (3), the number of diamonds on the grinding disc can be obtained from the total concentration and flow rate of the grinding liquid, and the number N of effective abrasives participating in the grinding can be obtained according to the proportion based on the size of the grinding disc and the size of the diamond.

3. The method of claim 1, wherein the pressure is regulated. In step (1), the growth method of the polycrystalline diamond sample includes but is not limited to the MPCVD method, the direct current arc method, and the hot wire method.

4. The method of claim 1, wherein the pressure is regulated. In step (2), the form of the indenter includes but is not limited to the Vickers indenter, the Rockwell indenter, the spherical indenter, and the triangular pyramid indenter.

5. The method of claim 1, wherein the pressure is regulated. In step (6), the safety factor of the processing a Set it to 0.5-0.9.

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