Metallic bond diamond grinding wheel, preparation method thereof and thinning method

Abstract

The invention belongs to the technical field of grinding, and particularly relates to a metallic bond diamond grinding wheel, a preparation method of the metallic bond diamond grinding wheel and a thinning method. The diamond grinding block comprises a porous diamond grinding material, a metal binding agent and a pore forming agent. The porous diamond abrasive is prepared by carrying out a thermochemical corrosion method on diamond; the metal bonding agent comprises copper-tin alloy powder, graphite powder, nano Al2O3, cadmium powder and polyimide resin. Compared with the prior art, the problem that in the prior art, the thinning technological parameters of the grinding wheel are not suitable for the novel grinding wheel with the fine granularity is solved. According to the scheme, the novel grinding wheel with the fine granularity is provided, the thinning parameters are researched on the basis of the novel grinding wheel, and therefore better machining efficiency and silicon wafer surface quality can be obtained under the grinding wheel and the thinning process parameters.

Description

Technical Field

[0001] The invention belongs to the technical field of grinding, and in particular relates to a metal bond diamond grinding wheel and a preparation method thereof and a thinning method. Background Art

[0002] Single crystal silicon is the main substrate material for more than 95% of semiconductor devices and more than 99% of integrated circuits in the world. As the scale of integrated circuits increases, the application of silicon materials in semiconductor component manufacturing continues to expand, becoming the foundation of the chip and electronic equipment manufacturing industry.

[0003] The process of manufacturing silicon wafer substrates includes the following steps: melting quartz sand and refining it into single crystal silicon rods, which are then stretched to form silicon rods, cut and rolled to form cylindrical silicon rods, cut the silicon rods into thin slices, chamfer, grind and etch them, polish them using CMP technology, and finally clean them to make silicon wafer substrates.

[0004] After the silicon wafer has completed wafer processing and manufacturing through a series of processes, during the IC packaging and testing phase, in order to reduce the chip packaging volume, improve the chip heat dissipation efficiency and electrical performance, etc., the back of the silicon wafer needs to be thinned before the chip is packaged to remove excess substrate material.

[0005] Thinning is an ultra-precision grinding technology that uses a grinding wheel with ultra-hard abrasives with high hardness to grind the workpiece efficiently. The stability of the grinding process can be ensured by actively controlling the workpiece surface processing accuracy using a high-rigidity and high-precision drive device. Since the contact length, contact area and cutting angle between the grinding wheel and the workpiece are constant, micron-level processing accuracy and micron or even nanometer-level surface roughness can be obtained.

[0006] However, in early studies, due to limited research conditions, the grinding wheel speed was relatively low (≤3000r / min), the grinding wheel feed rate was relatively small (≤0.5mm / s), and the grinding wheel grit was coarse (≥M2.5 / 5). However, with the development of materials science, finer-grained grinding wheels have emerged, and the technology of grinding equipment has also been improved. Therefore, based on new fine-grained grinding wheels, it is necessary to study the effects of grinding wheel speed, grinding feed rate, grinding wheel diamond grit, and grinding wheel volume density on silicon wafer thinning. Summary of the invention

[0007] The purpose of the present invention is to provide a metal bond diamond grinding wheel and a preparation method thereof and a thinning method in order to solve at least one of the above problems, so as to solve the problem that the thinning process parameters of the grinding wheel in the prior art are not suitable for a new type of grinding wheel with fine grains. This solution proposes a new type of fine-grained grinding wheel, and based on it, studies the thinning parameters, and then obtains better processing efficiency and silicon wafer surface quality under the grinding wheel and thinning process parameters.

[0008] The purpose of the present invention is achieved through the following technical solutions:

[0009] The first aspect of the present invention discloses a metal bond diamond grinding wheel, comprising a grinding wheel base and a diamond grinding block bonded to the grinding wheel base;

[0010] The diamond grinding block comprises the following components in percentage by mass: 60-70% porous diamond abrasive, 20-30% metal binder and 5-15% pore-forming agent;

[0011] The porous diamond abrasive is prepared by subjecting diamond to thermochemical etching;

[0012] The metal binder comprises the following raw materials in percentage by mass: 95-98% copper-tin alloy powder, 0.5-3% graphite powder, 0.5-2% nano-Al2O3, and 0.5-2% cadmium powder and polyimide resin; in the copper-tin alloy powder, tin accounts for 40-55% by mass, and the rest is copper; in the cadmium powder and polyimide resin, cadmium powder accounts for 20-30% by mass, and the rest is polyimide resin.

[0013] Preferably, the pore former is a PE / CeO2 / Cu composite.

[0014] Preferably, the grinding wheel substrate is an aluminum substrate.

[0015] The second aspect of the present invention discloses a method for preparing a metal bond diamond grinding wheel as described above, comprising the following steps:

[0016] S1: Preparation of metal binder:

[0017] The copper-tin alloy powder, graphite powder, nano-Al2O3, cadmium powder and polyimide resin are uniformly mixed, dried, ball-milled and sieved to obtain a metal binder;

[0018] S2: Preparation of porous diamond abrasive:

[0019] S21: ball milling and mixing diamond and an etchant under a protective atmosphere, pressing the obtained mixed powder into a block and calcining;

[0020] S22: washing the calcined sample with aqua regia, mixed acid and distilled water in sequence, and drying to obtain a porous diamond abrasive;

[0021] S3: mixing the porous diamond abrasive, the metal binder and the pore-forming agent and hot pressing them to obtain a diamond grinding block;

[0022] S4: bonding the diamond grinding block to the grinding wheel substrate to obtain the metal bond diamond grinding wheel.

[0023] Preferably, in step S1, the drying temperature is 95-105° C., the ball milling is to obtain powder with a diameter of 4-6 mm, and the sieving is to pass through a 200-250 mesh sieve.

[0024] Preferably, in step S21, the protective atmosphere is an argon atmosphere at 1 atmosphere, the mass ratio of diamond to corrosive agent is 1:6, the corrosive agent is Fe, Fe2O3 or Fe / Fe2O3, the pressure for pressing into blocks is 30 MPa, and the calcination is carried out by heating the mixture to 900-1000°C at a rate of 5°C / min and calcining for 2-4 hours.

[0025] Preferably, in step S22, the mixed acid is concentrated sulfuric acid, perchloric acid and concentrated nitric acid mixed in a volume ratio of 5:3:1.

[0026] Preferably, in step S3, the temperature of the hot pressing molding is 550°C.

[0027] The third aspect of the present invention discloses a thinning method, which uses any of the metal bond diamond grinding wheels described above to perform grinding and thinning.

[0028] Preferably, the grinding and thinning process satisfies one or more of the following conditions:

[0029] i) The grinding wheel speed is 3500-5000r / min;

[0030] ii) Feed speed is 1.0-1.4 μm / s;

[0031] iii) The grinding wheel grit is M2 / 4, M1.5 / 3, M1 / 2 or M0.5 / 1;

[0032] iv) Grinding wheel bulk density is 1.2-2.2g / cm 3 .

[0033] Compared with the prior art, the present invention has the following beneficial effects:

[0034] Previous research on improving the grinding efficiency of fine-grained diamond abrasives has mainly focused on improving self-sharpening by increasing the internal defects of diamond. Therefore, compared with ordinary diamond, the porous diamond used in the present invention has a large number of fine cutting edges, which can significantly improve its self-sharpening and grinding efficiency, and help disperse cutting heat and stress, and improve the surface processing quality of the workpiece. The metal bond porous diamond grinding wheel of the present invention is used for thinning, which effectively improves the grinding accuracy and efficiency.

[0035] Further research on the effects of wheel speed, grinding feed rate, grinding wheel diamond grit, and grinding wheel volume density on silicon wafer thinning showed that: with the increase of grinding wheel speed, silicon wafer processing efficiency will first increase and then decrease, with the critical point being 3800r / min. At the same time, the increase of grinding wheel feed rate can improve silicon wafer processing efficiency, but will cause the surface roughness of silicon wafer to gradually increase. The reduction of grinding wheel diamond grit will reduce the surface roughness of silicon wafer. Finally, appropriately increasing the grinding wheel volume density will help extend the service life of the grinding wheel. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 The effect of grinding wheel speed on average current and surface roughness in test example 1;

[0037] Figure 2 The effect of grinding wheel speed on average machining time in test example 1;

[0038] Figure 3 The effect of grinding feed rate on average current and surface roughness in test case 2;

[0039] Figure 4 The effect of grinding feed speed on average machining time in test case 2;

[0040] Figure 5 The effect of grinding wheel grain size on average current and surface roughness in test example 3;

[0041] Figure 6 The effect of grinding wheel grain size on average machining time in test example 3;

[0042] Figure 7 The effect of volume density on average current and surface roughness in Test Example 4;

[0043] Figure 8 This is the effect of volume density on average processing time in Test Example 4. DETAILED DESCRIPTION

[0044] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments.

[0045] In the following description, unless otherwise specified, the reagents used are conventional commercially available products, and the methods used are well known in the art.

[0046] A metal bond diamond grinding wheel comprises a grinding wheel base and a diamond grinding block bonded to the grinding wheel base;

[0047] The grinding wheel matrix is ​​an aluminum matrix;

[0048] The diamond grinding block comprises the following components in percentage by mass: 60-70% porous diamond abrasive, 20-30% metal binder and 5-15% pore-forming agent;

[0049] The porous diamond abrasive is prepared by subjecting diamond to thermochemical etching;

[0050] The metal binder comprises the following raw materials in percentage by mass: 95-98% copper-tin alloy powder, 0.5-3% graphite powder, 0.5-2% nano-Al2O3, and 0.5-2% cadmium powder and polyimide resin; in the copper-tin alloy powder, tin accounts for 40-55% by mass, and the rest is copper; in the cadmium powder and polyimide resin, cadmium powder accounts for 20-30% by mass, and the rest is polyimide resin;

[0051] The pore-forming agent is a PE / CeO2 / Cu composite.

[0052] in,

[0053] The metal binder is obtained by the following steps:

[0054] Copper-tin alloy powder, graphite powder, nano-Al2O3, cadmium powder and polyimide resin are mixed uniformly, dried (95-105 degrees Celsius), ball-milled (with a diameter of 4-6 mm), and sieved (200-250 mesh) to obtain a metal binder.

[0055] Porous diamond abrasive is prepared by thermochemical etching:

[0056] Under the protection of argon at 1 atmosphere, diamond and etchant (Fe, Fe2O3 or Fe / Fe2O3) are uniformly mixed in a mass ratio of 1:6 using a ball mill. The uniformly mixed powder is pressed into blocks under a pressure of 30MPa, filled into a corundum crucible, and then placed in a tube furnace. After completing the above operations, under the protection of argon at 1 atmosphere, diamond and etchant are heated to the experimental temperature (900-1000℃, corrosion 2-4h) at a heating rate of 5℃ / min. Then cool in the furnace under the protection of argon at 1 atmosphere.

[0057] The prepared samples were then soaked in aqua regia (concentrated hydrochloric acid: concentrated nitric acid = volume ratio 3:1) for 1 hour at room temperature to remove residual Fe and Fe2O3. Then, the powders were rinsed with deionized water until they were neutralized. After that, they were rinsed with mixed acid (concentrated sulfuric acid: perchloric acid: concentrated nitric acid = volume ratio of 5:3:1) to remove the residual graphite on the samples (aqua regia is a strong acid made by mixing concentrated hydrochloric acid and concentrated nitric acid in a certain proportion, which can react with carbon in diamond to generate carbon dioxide gas and graphite). Finally, the diamond powder was washed with distilled water to neutralize it, and the sample was dried to obtain diamond abrasive.

[0058] Diamond grinding blocks are obtained through the following steps:

[0059] The porous diamond abrasive, metal binder and pore-forming agent are mixed and hot-pressed at 550°C to prepare a diamond grinding block by hot-pressing sintering.

[0060] Metal bond diamond grinding wheel is obtained through the following steps:

[0061] The diamond grinding block is bonded to an aluminum substrate to obtain a metal bond diamond grinding wheel.

[0062] Example 1

[0063] The mass ratio of metal binder is: copper-tin alloy powder: 96%, graphite powder: 2%, nano-Al2O3: 1%, cadmium powder and polyimide resin (cadmium powder accounts for 25%, and the rest is polyimide resin): 1%; among them, in the copper-tin alloy powder, tin accounts for 50%, and the rest is copper.

[0064] Then, the copper-tin alloy powder, graphite powder, nano-Al2O3, cadmium powder and polyimide resin are mixed evenly, dried (95 degrees Celsius), ball-milled (ball diameter 5 mm), and sieved (200 mesh sieve) to obtain a metal binder.

[0065] The new porous diamond abrasive was prepared by thermochemical etching method, and the etching parameters are shown in No. #1 in Table 1.

[0066] Under the protection of argon at 1 atmosphere, diamond and etchant were uniformly mixed in a ball mill. The uniformly mixed powder was pressed into blocks under a pressure of 30 MPa, filled into a corundum crucible, and then placed in a tube furnace. After completing the above operations, diamond and etchant were heated to the experimental temperature at a heating rate of 5°C / min under the protection of argon at 1 atmosphere. Then they were cooled in the furnace under the protection of argon at 1 atmosphere.

[0067] The prepared samples were then soaked in aqua regia (concentrated hydrochloric acid: concentrated nitric acid = volume ratio 3:1) at room temperature for 1 hour to remove residual Fe and Fe2O3. Then, the powders were rinsed with deionized water until they were neutralized. After that, they were rinsed with mixed acid (concentrated sulfuric acid: perchloric acid: concentrated nitric acid = volume ratio of 5:3:1) to remove the residual graphite on the samples. Finally, the diamond powder was washed with distilled water to neutralize it, and the sample was dried to obtain pure diamond abrasive.

[0068] In the metal bond diamond grinding wheel (by mass), the proportion of metal bond is: 20%, porous diamond abrasive: 65%, pore-forming agent: 15%.

[0069] PE / CeO2 / Cu composite was used as pore former.

[0070] The diamond grinding block with the size of 110×50×10 mm was prepared by hot pressing and sintering at 550°C.

[0071] The aluminum substrate is used as the grinding wheel substrate, and then the diamond grinding block is bonded to the aluminum substrate.

[0072] Example 2

[0073] The mass ratio of metal binder is: copper-tin alloy powder: 97%, graphite powder: 1.5%, nano-Al2O3: 1%, cadmium powder and polyimide resin (cadmium powder accounts for 25%, and the rest is polyimide resin): 0.5%; among them, in the copper-tin alloy powder, tin accounts for 50%, and the rest is copper.

[0074] Then, the copper-tin alloy powder, graphite powder, nano-Al2O3, cadmium powder and polyimide resin are mixed evenly, dried (95 degrees Celsius), ball-milled (ball diameter 5 mm), and sieved (200 mesh sieve) to obtain a metal binder.

[0075] The new porous diamond abrasive was prepared by thermochemical etching method, and the etching parameters are shown in No. #2 in Table 1.

[0076] Under the protection of argon at 1 atmosphere, diamond and etchant were uniformly mixed in a ball mill. The uniformly mixed powder was pressed into blocks under a pressure of 30 MPa, filled into a corundum crucible, and then placed in a tube furnace. After completing the above operations, diamond and etchant were heated to the experimental temperature at a heating rate of 5°C / min under the protection of argon at 1 atmosphere. Then they were cooled in the furnace under the protection of argon at 1 atmosphere.

[0077] The prepared samples were then soaked in aqua regia (concentrated hydrochloric acid: concentrated nitric acid = volume ratio 3:1) at room temperature for 1 hour to remove residual Fe and Fe2O3. Then, the powders were rinsed with deionized water until they were neutralized. After that, they were rinsed with mixed acid (concentrated sulfuric acid: perchloric acid: concentrated nitric acid = volume ratio of 5:3:1) to remove the residual graphite on the samples. Finally, the diamond powder was washed with distilled water to neutralize it, and the sample was dried to obtain pure diamond abrasive.

[0078] In the metal bond diamond grinding wheel (by mass), the proportion of metal bond is: 20%, porous diamond abrasive: 70%, pore-forming agent: 10%.

[0079] PE / CeO2 / Cu composite was used as pore former.

[0080] The diamond grinding block with the size of 110×50×10 mm was prepared by hot pressing and sintering at 550°C.

[0081] The aluminum substrate is used as the grinding wheel substrate, and then the diamond grinding block is bonded to the aluminum substrate.

[0082] Example 3

[0083] The mass ratio of metal binder is: copper-tin alloy powder: 98%, graphite powder: 1%, nano-Al2O3: 0.5%, cadmium powder and polyimide resin (cadmium powder accounts for 25%, and the rest is polyimide resin): 0.5%; among them, in the copper-tin alloy powder, tin accounts for 50%, and the rest is copper.

[0084] Then, the copper-tin alloy powder, graphite powder, nano-Al2O3, cadmium powder and polyimide resin are mixed evenly, dried (100 degrees Celsius), ball-milled (ball diameter 5 mm), and sieved (200 mesh sieve) to obtain a metal binder.

[0085] The new porous diamond abrasive was prepared by thermochemical etching method, and the etching parameters are shown in No. #3 in Table 1.

[0086] Under the protection of argon at 1 atmosphere, diamond and etchant were uniformly mixed in a ball mill. The uniformly mixed powder was pressed into blocks under a pressure of 30 MPa, filled into a corundum crucible, and then placed in a tube furnace. After completing the above operations, diamond and etchant were heated to the experimental temperature at a heating rate of 5°C / min under the protection of argon at 1 atmosphere. Then they were cooled in the furnace under the protection of argon at 1 atmosphere.

[0087] The prepared samples were then soaked in aqua regia (concentrated hydrochloric acid: concentrated nitric acid = volume ratio 3:1) at room temperature for 1 hour to remove residual Fe and Fe2O3. Then, the powders were rinsed with deionized water until they were neutralized. After that, they were rinsed with mixed acid (concentrated sulfuric acid: perchloric acid: concentrated nitric acid = volume ratio of 5:3:1) to remove the residual graphite on the samples. Finally, the diamond powder was washed with distilled water to neutralize it, and the sample was dried to obtain pure diamond abrasive.

[0088] In the metal bond diamond grinding wheel (by mass), the proportion of metal bond is: 25%, porous diamond abrasive: 70%, pore-forming agent: 5%.

[0089] PE / CeO2 / Cu composite was used as pore former.

[0090] The diamond grinding block with the size of 110×50×10 mm was prepared by hot pressing and sintering at 550°C.

[0091] The aluminum substrate is used as the grinding wheel substrate, and then the diamond grinding block is bonded to the aluminum substrate.

[0092] Example 4

[0093] The mass ratio of metal binder is: copper-tin alloy powder: 98%, graphite powder: 0.5%, nano-Al2O3: 0.5%, cadmium powder and polyimide resin (cadmium powder accounts for 25%, and the rest is polyimide resin): 1%; among them, in the copper-tin alloy powder, tin accounts for 50%, and the rest is copper.

[0094] Then, the copper-tin alloy powder, graphite powder, nano-Al2O3, cadmium powder and polyimide resin are mixed evenly, dried (105 degrees Celsius), ball-milled (ball diameter 5 mm), and sieved (200 mesh sieve) to obtain a metal binder.

[0095] The new porous diamond abrasive was prepared by thermochemical etching method, and the etching parameters are shown in No. #4 in Table 1.

[0096] Under the protection of argon at 1 atmosphere, diamond and etchant were uniformly mixed in a ball mill. The uniformly mixed powder was pressed into blocks under a pressure of 30 MPa, filled into a corundum crucible, and then placed in a tube furnace. After completing the above operations, diamond and etchant were heated to the experimental temperature at a heating rate of 5°C / min under the protection of argon at 1 atmosphere. Then they were cooled in the furnace under the protection of argon at 1 atmosphere.

[0097] The prepared samples were then soaked in aqua regia (concentrated hydrochloric acid: concentrated nitric acid = volume ratio 3:1) at room temperature for 1 hour to remove residual Fe and Fe2O3. Then, the powders were rinsed with deionized water until they were neutralized. After that, they were rinsed with mixed acid (concentrated sulfuric acid: perchloric acid: concentrated nitric acid = volume ratio of 5:3:1) to remove the residual graphite on the samples. Finally, the diamond powder was washed with distilled water to neutralize it, and the sample was dried to obtain pure diamond abrasive.

[0098] In the metal bond diamond grinding wheel (by mass), the proportion of metal bond is: 30%, porous diamond abrasive: 65%, pore-forming agent: 5%.

[0099] PE / CeO2 / Cu composite was used as pore former.

[0100] The diamond grinding block with the size of 110×50×10 mm was prepared by hot pressing and sintering at 550°C.

[0101] The aluminum substrate is used as the grinding wheel substrate, and then the diamond grinding block is bonded to the aluminum substrate.

[0102] Table 1 Corrosion parameters of Examples 1-4

[0103]

[0104] In the following, four groups of silicon wafer thinning and grinding tests were carried out on a DISCO DFG850 thinning machine to explore the effects of grinding wheel speed, grinding feed rate, grinding wheel grit size, and grinding wheel volume density on silicon wafer thinning processing.

[0105] Test Example 1

[0106] The metal bond diamond grinding wheel prepared in Example 1 was used to carry out a uniaxial fine grinding test on the back side thinning of an 8-inch silicon substrate.

[0107] In order to study the effect of grinding wheel speed on silicon wafer thinning grinding, the grinding wheel speed was taken as a single variable, the grinding wheel with a grit of M4 / 8 was used, the grinding feed rate of the thinning machine was 0.6 mm / s, the ceramic chuck speed of the back thinning machine was 40 r / min, and 100 silicon wafers were processed at grinding wheel speeds of 3000, 3400, 3800, 4200, 4600, and 5000 r / min. The results are shown in Figure 2. Figure 1 and 2 shown.

[0108] Depend on Figure 1 It can be seen that as the grinding wheel speed increases, the load characterization current of the thinning machine spindle continues to increase. At a grinding wheel speed of 5000r / min, the load characterization current occasionally exceeds the upper limit set by the machine tool. The roughness of the surface of the ground silicon wafer decreases as the grinding wheel speed increases. As the grinding wheel speed increases, the cutting speed will also increase, and the speed at which the silicon wafer is cut will also increase, making the surface roughness smoother. However, during high-speed thinning, excessively high grinding wheel speeds may cause the grinding wheel to wear faster, generating more heat and vibration, which may lead to an increase in surface roughness.

[0109] Depend on Figure 2 It can be seen that the speed of 3800r / min is the turning point of the average processing time. At this speed, the processing efficiency is the highest.

[0110] Test Example 2

[0111] The metal bond diamond grinding wheel prepared in Example 2 was used to carry out a uniaxial fine grinding test on the back side thinning of an 8-inch silicon substrate.

[0112] In order to study the effect of grinding feed rate on silicon wafer thinning grinding, the grinding feed rate was taken as a single variable, the ceramic chuck speed was 40r / min, the grinding wheel speed was 3400r / min, and 100 silicon wafers were processed at grinding feed rates of 0.2, 0.6, 1.0, and 1.4μm / s. The experimental results are shown in Figure 2. Figure 3 and 4 shown.

[0113] Depend on Figure 3It can be seen that as the grinding wheel feed rate increases, multiple parameters in the silicon wafer thinning process change, including the average current and surface roughness. Figure 4 , as the feed speed increases, the average processing time becomes shorter and the processing efficiency improves. Further analysis shows that the increase in the grinding wheel feed rate will deepen the abrasive cutting depth, increase the grinding resistance of the grinding wheel and the resistance of the spindle, and thus lead to an increase in the load characterization current. Although shortening the processing time is conducive to improving production efficiency, if the feed rate is too high, it will cause problems such as burning and cracking on the surface of the silicon wafer, thereby affecting the processing quality. Therefore, in the thinning of silicon wafers, it is necessary to weigh the feed rate and processing quality according to the specific situation, and select the appropriate feed rate to achieve the best processing effect.

[0114] Test Example 3

[0115] The metal bond diamond grinding wheel prepared in Example 3 was used to carry out a uniaxial fine grinding test on the back side thinning of an 8-inch silicon substrate.

[0116] In order to study the influence of diamond grit of grinding wheel on the thinning grinding of silicon wafers, based on the results of the previous two groups of tests, the grinding process parameters of ceramic chuck speed 40r / min, grinding wheel speed 3400r / min, and grinding wheel feed rate 1.0μm / s were selected. Grinding wheels with grit sizes of M4 / 8, M2 / 4, M1.5 / 3, M1 / 2, and M0.5 / 1 were used to process 100 silicon wafers respectively.

[0117] Effects of different grit diamond grinding wheels on silicon wafer grinding Figure 5 and 6 As shown in the figure, as the abrasive particle size of the grinding wheel decreases, the roughness of the ground silicon wafer surface gradually decreases, but the characterization current gradually increases and the processing time increases, and the average processing time increases. The reason for this phenomenon is that as the abrasive particle size increases, the abrasive cutting depth when the grinding wheel grinds the silicon wafer also increases.

[0118] After grinding silicon wafers with M1 / 2 and M0.5 / 1 grinding wheels, the surface roughness Ra obtained was found to be similar. This shows that when the diamond grit of the grinding wheel reaches a certain fineness, its influence on the surface roughness of the silicon wafer will be reduced. When the diamond grit of the grinding wheel reaches a certain fineness, its influence on the surface roughness of the silicon wafer is reduced. This is because the influence of the abrasive agglomeration phenomenon becomes significant. In practical applications, it is necessary to comprehensively consider the relationship between the diamond grit of the grinding wheel and the cutting effect to obtain the best processing results.

[0119] Test Example 4

[0120] In order to study the effect of grinding wheel volume density on silicon wafer thinning grinding, the grinding process parameters of ceramic chuck speed 40r / min, grinding wheel speed 3400r / min, grinding wheel feed rate 1.0μm / s and grinding wheel diamond grain size of M4 / 8 were selected. Grinding wheels with different volume densities were used to process 100 silicon wafers respectively.

[0121] Effects of different volume density diamond wheels on grinding silicon wafers Figure 7 and 8 As shown in the figure, the average processing current of diamond grinding wheels with different volume densities is not much different when grinding silicon wafers, but the wear ratio of the grinding wheels is significantly different. With the increase of the volume density of the grinding wheel, the wear ratio of the grinding wheel also tends to increase. However, there is no obvious trend in the effect of volume density on the processing time.

[0122] Generally speaking, the higher the volume density of the grinding wheel, the greater its strength and hardness, and the higher its wear resistance and heat resistance. Therefore, high-density grinding wheels usually have a longer service life. In addition, the volume density of the grinding wheel also affects the roughness and hardness of its surface. When the volume density of the grinding wheel is low, its surface will be relatively rough, and it is difficult to achieve the requirements of high-precision processing. When the volume density of the grinding wheel is high, its surface is smoother and harder, which can better achieve high-precision processing.

[0123] In summary, the results show that with the increase of grinding wheel speed, the silicon wafer processing efficiency will first increase and then decrease, and the critical point is 3800r / min. At the same time, the increase of grinding wheel feed rate can improve the silicon wafer processing efficiency, but it will cause the surface roughness of silicon wafer to gradually increase. The reduction of grinding wheel diamond grain size will reduce the surface roughness of silicon wafer. Finally, appropriately increasing the grinding wheel volume density will help to extend the service life of the grinding wheel. It is worth noting that if the speed is too high, the machine tool spindle load will increase and even cause shutdown. Therefore, in order to obtain better processing efficiency and surface quality, it is necessary to weigh the above factors and select appropriate process parameters. Appropriate process parameters can be selected in the following range: i) grinding wheel speed is 3500-5000r / min; ii) feed rate is 1.0-1.4μm / s; iii) grinding wheel grain size is M2 / 4, M1.5 / 3, M1 / 2 or M0.5 / 1; iv) grinding wheel volume density is 1.2-2.2g / cm 3 .

[0124] The above description of the embodiments is to facilitate the understanding and use of the invention by those skilled in the art. It is obvious that those skilled in the art can easily make various modifications to these embodiments and apply the general principles described herein to other embodiments without creative work. Therefore, the present invention is not limited to the above embodiments, and improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the present invention should be within the scope of protection of the present invention.

Claims

1. A metal bond diamond grinding wheel, characterized in that: It includes a grinding wheel base and a diamond grinding block bonded to the grinding wheel base; The diamond grinding block comprises the following components in percentage by mass: 60-70% porous diamond abrasive, 20-30% metal binder and 5-15% pore-forming agent; The porous diamond abrasive is prepared by subjecting diamond to thermochemical etching; The metal binder comprises the following raw materials in percentage by mass: 95-98% copper-tin alloy powder, 0.5-3% graphite powder, 0.5-2% nano-Al2O3, and 0.5-2% cadmium powder and polyimide resin; in the copper-tin alloy powder, tin accounts for 40-55% by mass, and the rest is copper; in the cadmium powder and polyimide resin, cadmium powder accounts for 20-30% by mass, and the rest is polyimide resin.

2. A metal bond diamond grinding wheel according to claim 1, characterized in that: The pore-forming agent is a PE / CeO2 / Cu composite.

3. A metal bond diamond grinding wheel according to claim 1, characterized in that: The grinding wheel matrix is ​​an aluminum matrix.

4. A method for preparing a metal bond diamond grinding wheel as claimed in any one of claims 1 to 3, characterized in that: The steps include: S1: Preparation of metal binder: The copper-tin alloy powder, graphite powder, nano-Al2O3, cadmium powder and polyimide resin are uniformly mixed, dried, ball-milled and sieved to obtain a metal binder; S2: Preparation of porous diamond abrasive: S21: ball milling and mixing diamond and an etchant under a protective atmosphere, pressing the obtained mixed powder into a block and calcining; S22: washing the calcined sample with aqua regia, mixed acid and distilled water in sequence, and drying to obtain a porous diamond abrasive; S3: mixing the porous diamond abrasive, the metal binder and the pore-forming agent and hot pressing them to obtain a diamond grinding block; S4: bonding the diamond grinding block to the grinding wheel substrate to obtain the metal bond diamond grinding wheel.

5. The method for preparing a metal bond diamond grinding wheel according to claim 4, characterized in that: In step S1, the drying temperature is 95-105° C., the ball milling is to obtain powder with a diameter of 4-6 mm, and the sieving is to pass through a 200-250 mesh sieve.

6. The method for preparing a metal bond diamond grinding wheel according to claim 4, characterized in that: In step S21, the protective atmosphere is an argon atmosphere at 1 atmosphere, the mass ratio of diamond to corrosive agent is 1:6, the corrosive agent is Fe, Fe2O3 or Fe / Fe2O3, the pressure of pressing into blocks is 30MPa, and the calcination is carried out by heating the temperature to 900-1000°C at a rate of 5°C / min and calcining for 2-4h.

7. The method for preparing a metal bond diamond grinding wheel according to claim 4, characterized in that: In step S22, the mixed acid is concentrated sulfuric acid, perchloric acid and concentrated nitric acid mixed in a volume ratio of 5:3:

1.

8. The method for preparing a metal bond diamond grinding wheel according to claim 4, characterized in that: In step S3, the temperature of the hot pressing molding is 550°C.

9. A thinning method, characterized in that: The metal bond diamond grinding wheel as described in any one of claims 1 to 3 is used for grinding and thinning.

10. A thinning method according to claim 9, characterized in that: The grinding and thinning process satisfies one or more of the following: i) The grinding wheel speed is 3500-5000r / min; ii) Feed speed is 1.0-1.4 μm / s; iii) The grinding wheel grit is M2 / 4, M1.5 / 3, M1 / 2 or M0.5 / 1; iv) Grinding wheel bulk density is 1.2-2.2g / cm 3 .

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