High-density diamond / copper composite material and preparation method thereof

Abstract

The invention provides a high-density diamond / copper composite material, a preparation method of the high-density diamond / copper composite material and a heat dissipation device comprising the high-density diamond / copper composite material. The preparation method comprises the following steps that (1) the surface of a coated diamond is plated with copper through an electroplating method to obtain a copper weight increasing diamond, and the mass of a copper layer accounts for 50%-200% of the mass of the coated diamond; (2) the obtained copper weight increasing diamond and copper powder are mechanically and evenly mixed; (3) the mixed powder obtained in the step (2) is weighed and put into a graphite mold to be pre-pressed; 4) putting the assembled graphite mold into a spark plasma sintering system for heating, pressurizing and sintering; 5, the sintered block in the step 4 is demolded, taken out, cut and polished, and the relative density of the diamond / copper composite material is 99% or above. The diamond / copper composite material has high density, can achieve high diamond volume fraction, and is good in performance and low in cost.

Description

Technical Field

[0001] The present invention relates to the field of composite materials, and more specifically, to a high-density diamond / copper composite material and a preparation method thereof. This composite material has a high density and a high thermal conductivity. Background Art

[0002] As a fourth-generation electronic packaging material, diamond / copper composite materials have excellent performance and a huge future market. They are applied in the fields of third-generation semiconductor packaging, high-power semiconductor device packaging, advanced packaging, radar, optical communication, and consumer electronics.

[0003] The industrialization process routes suitable for diamond / copper composite materials can be divided into three types, namely pressure infiltration, spark plasma sintering, and hot pressing sintering. Analyzing from the principle, each has its own advantages and disadvantages.

[0004] The infiltration method is to raise the temperature above the melting point of copper, melt the copper, and use gas pressure and capillary force to squeeze the copper into the diamond gaps. The prepared diamond / copper composite material has a high volume fraction content, which can reach more than 65 vol%, and a high density. However, due to the slow heating rate, high forming temperature, low production efficiency, the product surface cannot be covered with a metal layer, and the surface processing is difficult.

[0005] Both spark plasma sintering and hot pressing sintering are to apply a certain temperature and pressure to the diamond / copper mixed powder to press it into shape. The forming temperature is lower than the melting point of copper, and the sintering pressure is generally 30 - 50 MPa. The difference lies in the different heating principles of pulsed current pressurized sintering and hot pressing sintering. Spark plasma sintering directly passes a pulsed current through the mixed powder and the graphite mold, and Joule heat is generated between the powders, with a fast heating rate. Generally, a furnace of diamond / copper composite materials can be sintered in 1 - 2 hours. While hot pressing sintering is to heat the graphite mold through an external heating body, thereby raising the temperature of the mixed powder. The heating rate is slow and the production efficiency is low. Generally, it takes 12 hours to produce a furnace, and it takes 1 - 2 days for large-diameter samples. Therefore, compared with hot pressing sintering, spark plasma sintering has a high production efficiency for diamond / copper composite materials, and the performance of large-size samples is more uniform.

[0006] However, compared with pressure infiltration, in spark plasma sintering and hot pressing sintering, since the forming temperature is lower than the melting point of copper, copper particles cannot enter the tiny diamond gaps through capillary force. Therefore, it is impossible to prepare a diamond / copper composite material with a high diamond volume fraction and densification. Summary of the Invention

[0007] Technical Problem In view of the problems existing in the prior art, the present invention provides a method for rapidly preparing a high-density diamond / copper composite material by spark plasma sintering technology, a high-density diamond / copper composite material prepared by this method, and a heat dissipation device including this diamond / copper composite material.

[0008] Technical solution According to the present invention, a high-density diamond / copper composite material and a preparation method thereof are provided.

[0009] According to the first aspect of the present invention, a method for preparing a high-density diamond / copper composite material is provided, which includes the following steps: Step 1: Copper is plated on the surface of coated diamond by electroplating to obtain copper-weighted diamond, wherein the mass of the copper layer is 50% - 200% of the mass of the coated diamond; Step 2: The copper-weighted diamond obtained in Step 1 is mechanically mixed evenly with copper powder; Step 3: Weigh the mixed powder obtained in Step 2, put it into a graphite mold, and perform pre-pressing; Step 4: Put the assembled graphite mold in Step 3 into a spark plasma sintering system for heating and pressure sintering; Step 5: Demold and take out the sintered block in Step 4, and cut and polish it. Among them, the relative density of the diamond / copper composite material is more than 99%.

[0010] Coated diamond refers to diamond whose surface is coated with a layer of metal through surface treatment, that is, diamond with a metal coating on its surface.

[0011] Preferably, the coated diamond is one or more selected from chromium-coated diamond, tungsten-coated diamond, titanium-coated diamond, and zirconium-coated diamond.

[0012] Preferably, the particle size of the coated diamond is 50 - 1000 μm.

[0013] Preferably, the coating thickness of the coated diamond is 30 - 200 nm.

[0014] Preferably, the coated diamond is prepared by magnetron sputtering method.

[0015] Preferably, the mass of the copper layer in the copper-weighted diamond is 80% - 150% of the mass of the coated diamond.

[0016] The electroplating can be carried out by conventional methods. For example, the following electroplating process can be used for electroplating: Stir and wash the coated diamond with high-purity water → Cook with alkaline water to remove impurities → Stir and wash with high-purity water → Immerse in an electroplating solution containing copper ions → Electrolyze with electricity, and adjust the pH value regularly during the process → Take out, stir and wash with high-purity water, and vacuum dry.

[0017] Preferably, in step 2, the particle size of the copper powder is 0.5 - 100 μm.

[0018] Preferably, in the mixed powder obtained in step 2, the volume fraction of the coated diamond accounts for 10% - 70%, preferably 50% - 70%.

[0019] Preferably, the equipment used for mixing in step 2 is a V-type mixer, the mixing time is 12 h, the rotation speed is 25 r / min, and the mass ratio of the balls to the materials used is 0.5 - 2:1.

[0020] Preferably, the pre-pressing pressure in step 3 is 5 - 15 MPa.

[0021] Preferably: The sintering process in step 4 is as follows: The sintering temperature is 900 - 1050 °C; Heating stage: In the stage of RT - 600 °C, the heating rate is 40 - 55 °C / min; the pressure is 5 - 15 MPa; Above 600 °C, to the sintering temperature stage, the heating rate is 25 - 35 °C / min, and the pressure is 25 - 35 MPa; After reaching the sintering temperature, keep it warm for 40 - 80 min; Cooling stage: In the stage of sintering temperature to 800 °C, the pressure is 25 - 35 MPa, and the cooling rate is 15 - 25 °C / min; Below 800 °C, to the RT stage, the pressure is 0 MPa, and the cooling method is furnace cooling.

[0022] Preferably, in step 5, laser cutting is used, and a sandblasting machine is used to remove surface dirt and burrs.

[0023] According to the second aspect of the present invention, a diamond / copper composite material is provided, which is prepared by the method for preparing a diamond / copper composite material according to the present invention.

[0024] Preferably, the flexural strength of the diamond / copper composite material is above 300 MPa, preferably above 340 MPa.

[0025] Preferably, the thermal conductivity of the diamond / copper composite material is 650 W / (m·K) or more, preferably 660 W / (m·K) or more, more preferably 670 W / (m·K) or more, even more preferably 680 W / (m·K) or more, even more preferably 690 W / (m·K) or more, and further more preferably 700 W / (m·K) or more.

[0026] According to the third aspect of the present invention, a heat dissipation device is provided, which includes the diamond / copper composite material according to the present invention.

[0027] Beneficial effects 1. Aiming at the problem of poor density caused by the preparation of high-volume fraction diamond / copper composite materials by the spark plasma sintering technology in the prior art, the present invention pre-coats a thick copper layer on the surface of the diamond, realizing the preparation of high-volume fraction and high-density diamond / copper composite materials, with good performance and low cost.

[0028] 2. The present invention uses spark plasma sintering to prepare diamond / copper composite materials, with easy operation of the equipment, simple process, high efficiency and low cost; 3. The diamond / copper composite material products prepared by the present invention have stable performance and high repeatability. Description of the drawings

[0029] Figure 1 SEM photograph of the chromium-plated diamond used in Example 1 according to the present invention before the copper thickening treatment.

[0030] Figure 2 SEM photograph of the fracture surface of the diamond / copper composite material prepared according to Example 2.

[0031] Figure 3 SEM photograph of the fracture surface of the diamond / copper composite material prepared according to Comparative Example 2. Specific embodiments

[0032] Source of raw materials: The chromium-plated diamond is sourced from Changsha Moben New Materials Co., Ltd., with a particle size of 300 μm and a coating thickness of 50 - 100 nm; The copper powder is purchased from Anhui Nalomit New Materials Technology Co., Ltd., with a particle size of 1 - 5 μm.

[0033] Testing method The testing method for the coefficient of thermal expansion is the linear expansion method, and the testing equipment is a thermal dilatometer produced by Netzsch, Germany; The testing method for the thermal conductivity is the laser flash method, and the testing equipment is a laser thermal conductivity meter produced by Netzsch, Germany, model LFA350; The testing method for the flexural strength is the three-point bending method, and the testing equipment is a universal testing machine.

[0034] The density test method is the Archimedes drainage method.

[0035] Example 1 The diamond / copper composite material was prepared through the following steps Step 1: Copper was electroplated on the surface of chromium-plated diamond through the electroplating method to obtain copper-weighted diamond. Among them, the electroplating process was as follows: The chromium-plated diamond was stirred and cleaned with high-purity water → cooked with alkaline water to remove impurities → stirred and cleaned with high-purity water → placed in an electroplating solution containing copper ions and soaked → electroplated by energizing after soaking, during which the pH value was adjusted regularly → taken out, stirred and cleaned with high-purity water, and vacuum dried. Among them, the mass of the copper layer was 100% of the mass of the chromium-plated diamond.

[0036] Step 2: The copper-weighted diamond obtained in Step 1 and copper powder were mechanically mixed evenly using a V-type powder mixer. The mixing process was as follows: The mixing time was 12 h, the rotation speed was 25 r / min, and the mass ratio of the balls to the materials used was 1:1; Step 3: Weigh 36.74 g of the diamond-copper mixed powder obtained in Step 2, where the volume fraction of diamond was 50 vol%. The mixed powder was loaded into a graphite mold and pre-pressed. The pre-pressing pressure was 10 MPa. The inner diameter of the graphite mold used was 50 mm, and the height was 30 mm; Step 4: The materials assembled in Step 3 were put into a spark plasma sintering system for heating and pressure sintering. The sintering process was as follows: The sintering temperature was 980 °C; Heating stage: In the RT-600 °C stage, the pressure was 10 MPa, and the heating rate was 45 °C / min; Above 600 °C, to the 980 °C stage, the pressure was 30 MPa, and the heating rate was 30 °C / min; Keep the pressure and hold for 60 min at the sintering temperature; Cooling stage: In the 980 °C to 800 °C stage, apply a pressure of 30 MPa, and the cooling rate was 20 °C / min; Below 800 °C, to the RT stage, the pressure was 0 MPa, and the cooling method was furnace cooling.

[0037] Step 5: Take out the sintered block in Step 4. The size of the prepared diamond / copper composite material was Ø50*3 mm, and then cutting, grinding and testing were carried out.

[0038] Figure 1 To show the SEM photo of the chromium-plated diamond used in Example 1 according to the present invention before the copper thickening treatment, it was observed that the thickness of the chromium layer on the diamond surface was 75 nm, and the thickness was uniform.

[0039] Example 2 Prepare diamond / copper composites through the following steps Step 1: Copper-plated diamond is obtained by electroplating copper on the surface of chromium-plated diamond. The electroplating process is as follows: Stir and wash the chromium-plated diamond with high-purity water → Boil in alkaline water to remove impurities → Stir and wash with high-purity water → Immerse in an electroplating solution containing copper ions → Electrolyze after immersion, adjust the pH value regularly during the process → Take out, stir and wash with high-purity water, and vacuum dry. Among them, the mass of the copper layer is 100% of the mass of the chromium-plated diamond.

[0040] Step 2: Mechanically mix the copper-increased diamond obtained in Step 1 and copper powder evenly using a V-type powder mixer. The mixing process is as follows: The mixing time is 12 h, the rotation speed is 25 r / min, and the mass ratio of the balls to the materials used is 1:1; Step 3: Weigh 33.54 g of the diamond-copper mixed powder obtained in Step 2, where the volume fraction of diamond is 60 vol%. Load the mixed powder into a graphite mold and perform pre-pressing. The pre-pressing pressure is 10 MPa. The inner diameter of the graphite mold used is 50 mm and the height is 30 mm.; Step 4: Put the materials assembled in Step 3 into a spark plasma sintering system for heating and pressure sintering. The sintering process is as follows: The sintering temperature is 1010 °C; Heating stage: In the RT-600 °C stage, the pressure is 15 MPa and the heating rate is 50 °C / min; Above 600 °C, up to the 1010 °C stage, the pressure is 25 MPa and the heating rate is 25 °C / min; Maintain the pressure and keep the temperature for 60 min at the sintering temperature; Cooling stage: In the 1010 °C to 800 °C stage, the pressure is 25 MPa and the cooling rate is 20 °C / min; Below 800 °C, down to the RT stage, the pressure is 0 MPa and the cooling method is furnace cooling; Step 5: Demold and take out the sintered block in Step 4. The size of the prepared diamond / copper composite material is Ø50*3 mm, and then perform cutting, grinding and testing.

[0041] Comparative Example 1 Prepare diamond / copper composites through the following steps Step 1: Mechanically mix chromium-plated diamond and copper powder evenly using a V-type powder mixer. The mixing process is as follows: The mixing time is 12 h, the rotation speed is 25 r / min, and the mass ratio of the balls to the materials used is 1:1; Step 2: Weigh 36.74 g of the diamond-copper mixed powder obtained in Step 1, where the volume fraction of diamond is 50 vol%. Load the mixed powder into a graphite mold and perform pre-pressing. The pre-pressing pressure is 10 MPa. The inner diameter of the used graphite mold is 50 mm and the height is 30 mm; Step 3: Put the material assembled in Step 2 into a spark plasma sintering system for heating and pressure sintering. The sintering process is as follows: The sintering temperature is 980 °C; Heating stage: In the stage of RT - 600 °C, the pressure is 10 MPa and the heating rate is 45 °C / min; Above 600 °C, to the 980 °C stage, the pressure is 30 MPa and the heating rate is 30 °C / min; Maintain the pressure and keep the temperature for 60 min at the sintering temperature; Cooling stage: In the stage of 980 °C to 800 °C, apply a pressure of 30 MPa and the cooling rate is 20 °C / min; Below 800 °C, to the RT stage, the pressure is 0 MPa and the cooling method is furnace cooling.

[0042] Step 4: Take out the sintered block in Step 3. The size of the prepared diamond / copper composite material is Ø50 * 3 mm, and then perform cutting, grinding and testing.

[0043] Comparative Example 2 Prepare a diamond / copper composite material through the following steps Step 1: Mechanically mix the chromium-plated diamond and copper powder evenly using a V-type powder mixer. The mixing process is as follows: The mixing time is 12 h, the rotation speed is 25 r / min, and the ball-to-material mass ratio used is 1:1; Step 2: Weigh 33.54 g of the diamond-copper mixed powder obtained in Step 1, where the volume fraction of diamond is 60 vol%. Load the mixed powder into a graphite mold and perform pre-pressing. The pre-pressing pressure is 10 MPa. The inner diameter of the used graphite mold is 50 mm and the height is 30 mm.; Step 3: Put the material assembled in Step 2 into a spark plasma sintering system for heating and pressure sintering. The sintering process is as follows: The sintering temperature is 1010 °C; Heating stage: In the stage of RT - 600 °C, the pressure is 15 MPa and the heating rate is 50 °C / min; Above 600 °C, to the 1010 °C stage, the pressure is 25 MPa and the heating rate is 25 °C / min; Maintain the pressure and keep the temperature for 60 min at the sintering temperature; Cooling stage: From 1010 °C to 800 °C, the pressure is 25 MPa and the cooling rate is 20 °C / min. Below 800 °C to RT, the pressure is 0 MPa and the cooling method is furnace cooling.

[0044] Step 4: Demold and take out the sintered block in Step 3. The size of the prepared diamond / copper composite material is Ø50*3 mm, and then cutting and grinding tests are carried out.

[0045] Table 1 Performance table of the diamond / copper composite material prepared in Example 1

[0046] Figure 2 SEM photograph of the fracture surface of the diamond / copper composite material prepared for Example 2. From Figure 2 it can be observed that there are no obvious holes and gaps formed due to diamond accumulation on the fracture surface, and the interface between diamond and copper is tightly bonded. Therefore, the prepared diamond / copper composite material has high density and good performance. Figure 3 The diamond / copper composite material prepared for Comparative Example 2. From Figure 3 it can be observed that the copper particles cannot completely fill the voids formed by diamond accumulation (such as Figure 3 the part circled by the circle in). After a large amount of diamond accumulation, there are many pores inside the diamond / copper composite material, the density difference is poor, and the performance is low.

[0047] In the present invention, a thin metal coating and a thick copper layer are pre-coated on the surface of diamond, and then a diamond / copper composite material is prepared by spark plasma sintering, and the obtained composite material has excellent performance. The thin metal coating can reduce the interfacial thermal resistance between diamond and copper, and the thick copper layer makes the coated diamond form a "core-shell diamond" structure with a copper shell and diamond particles as the core. This "core-shell diamond" particle has a certain plasticity during the solid-phase sintering process, which greatly improves the density of the prepared diamond / copper composite material and has superior performance. From the results of the examples and comparative examples, it can be seen that compared with the diamond / copper composite material treated with chromium plating, the thermal conductivity of the copper-thickened diamond / copper composite material is greatly improved, and a thermal conductivity of up to 750 W / (m·K) and a composite material density greater than 99% can be achieved.

Claims

1. A method for preparing a high-density diamond / copper composite material, comprising the following steps: Step 1: Copper is plated on the surface of the coated diamond by electroplating to obtain copper-weighted diamond, where, The mass of the copper layer is 50% - 200% of the mass of the coated diamond; Step 2: Mechanically mix the copper-weighted diamond obtained in Step 1 and copper powder evenly; Step 3: Weigh the mixed powder obtained in Step 2 and load it into a graphite mold for pre-pressing; Step 4: Place the assembled graphite mold in Step 3 into a spark plasma sintering system for heating and pressure sintering; Step 5: Demold and take out the sintered block in Step 4, and cut and polish it; Among them, the relative density of the diamond / copper composite material is more than 99%.

2. The method for preparing a high-density diamond / copper composite material according to claim 1, wherein The coated diamond is one or more selected from chromium-coated diamond, tungsten-coated diamond, titanium-coated diamond and zirconium-coated diamond; And / or, the particle size of the coated diamond is 50 - 1000 μm; And / or, the coating thickness of the coated diamond is 30 - 200 nm; And / or, the coated diamond is prepared by magnetron sputtering.

3. The method for preparing the high-density diamond / copper composite material according to claim 1 or 2, wherein, The mass of the copper layer in the copper-weighted diamond is 80% - 150% of the mass of the coated diamond.

4. The method for preparing a high-density diamond / copper composite material according to any one of claims 1 to 3, wherein The particle size of the copper powder in Step 2 is 0.5 - 100 μm; And / or, in the mixed powder obtained in Step 2, the volume fraction of the coated diamond accounts for 10% - 70%, preferably 50% - 70%; And / or, the equipment used for mixing in Step 2 is a V-type mixer, the mixing time is 12 h, the rotation speed is 25 r / min, and the mass ratio of the balls to the materials used is 0.5 - 2:

1.

5. The method for preparing a high-density diamond / copper composite material according to any one of claims 1 to 4, wherein In the mixed powder obtained in Step 2, the volume fraction of the coated diamond accounts for 50% - 70%; And / or, the pre-pressing pressure in Step 3 is 5 - 15 MPa.

6. The method for preparing a high-density diamond / copper composite material according to any one of claims 1 to 5, wherein The sintering process in Step 4 is: The sintering temperature is 900 - 1050 °C; Heating stage: In the RT - 600 °C stage, the heating rate is 40 - 55 °C / min; the pressure is 5 - 15 MPa; Above 600 °C, to the sintering temperature stage, the heating rate is 25 - 35 °C / min, and the pressure is 25 - 35 MPa; After reaching the sintering temperature, keep it warm for 40 - 80 min; Cooling stage: From the sintering temperature to the 800 °C stage, the pressure is 25 - 35 MPa, and the cooling rate is 15 - 25 °C / min; Below 800 °C, to the RT stage, the pressure is 0 MPa, and the cooling method is furnace cooling.

7. The method for preparing a high-density diamond / copper composite material according to any one of claims 1 to 6, wherein In Step 5, laser cutting is used, and a sandblasting machine is used to remove surface dirt and burrs.

8. A diamond / copper composite material, which is prepared by the method for preparing a high-density diamond / copper composite material according to any one of claims 1 to 7.

9. The diamond / copper composite material according to claim 8, wherein the flexural strength of the diamond / copper composite material is 300 MPa or more, preferably 340 MPa or more; and / or, the thermal conductivity of the diamond / copper composite material is 650 W / (m·K) or more, preferably 660 W / (m·K) or more, more preferably 670 W / (m·K) or more, even more preferably 680 W / (m·K) or more, even more preferably 690 W / (m·K) or more, and further more preferably 700 W / (m·K) or more.

10. A heat dissipation device, which comprises the diamond / copper composite material according to claim 8 or 9.

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