A near-net forming method for ultra-thin diamond / copper composite materials

Abstract

The present invention provides a near-net forming method for ultra-thin diamond / copper composite materials, and ultra-thin diamond / copper composite materials obtained by the method. The preparation method comprises the following steps: 1) powder loading: tungsten-coated diamond powder and copper powder are placed in an agate mortar, mixed evenly with alcohol as a medium, and placed in a graphite mold in a wet powder state, and a piece of copper foil or a layer of copper powder is added to each of the upper and lower surfaces; 2) drying: the mold obtained in step 1 is vacuum dried at a temperature of 80 to 100°C; 3) sintering: the assembled mold after drying is placed in a furnace chamber of a spark plasma sintering system, pressure is applied, and sintering is performed after vacuuming; 4) polishing: the composite material sintered in step 3 is simply polished with sandpaper to remove the carbon paper and excess copper on the surface, and an ultra-thin diamond / copper composite material can be obtained. The method has a simple preparation process, convenient operation, and good repeatability.

Description

Technical Field

[0001] The invention relates to a method for preparing a high thermal conductivity composite material, and in particular to a near-net-shape forming method for forming an ultra-thin diamond / copper composite material by spark plasma sintering. Background Art

[0002] In order to solve the problem of low thermal conductivity of electronic packaging materials, researchers in the field of heat dissipation materials have developed a high thermal conductivity material with a thermal expansion coefficient that matches that of semiconductor chips - diamond / copper composite materials. Generally, the theoretical thermal conductivity of the composite material is above 740W / (m·K), and its thermal conductivity increases with the increase of diamond content. However, due to the poor wettability of the diamond and copper interface, its thermal conductivity deteriorates significantly. The thermal conductivity of the composite material prepared in the laboratory generally does not exceed 700W / (m·K). At the same time, due to the high hardness and large particle size of diamond, the composite material is difficult to process and has a rough surface. In practical applications, the thickness of the composite material needs to reach 0.3mm, and laser cutting is usually used to process such high thermal conductivity materials. However, laser cutting is not only expensive and inefficient, but also carbonizes the diamond surface, thereby reducing the thermal conductivity of the diamond / copper composite material. Therefore, it is crucial to develop a near-net-shape forming technology for diamond / copper composite materials that are free from subsequent processing, have high surface flatness and high thermal conductivity. Summary of the invention

[0003] The present invention aims at the problem that diamond / copper is difficult to process and has a rough surface, and provides a near-net-shape forming method for an ultra-thin diamond / copper composite material, which comprises the following steps:

[0004] Step 1: Powder loading: Put tungsten-coated diamond powder and copper powder into an agate mortar, use alcohol as a medium, mix them evenly, put them into a graphite mold in a wet powder state, and add a piece of copper foil or a layer of copper powder on the upper and lower sides of the mixed powder, wherein the particle sizes of the diamond powder and copper powder are 150-220 μm and 60-80 μm respectively;

[0005] Step 2: Drying: Place the mold obtained in step 1 in a vacuum drying oven and vacuum dry it at a temperature of 80-100°C;

[0006] Step 3: Sintering: Place the dried assembled mold into the spark plasma sintering system (SPS) furnace chamber, apply pressure, evacuate the vacuum, and then sinter with electricity;

[0007] Step 4: Grinding: Grind the composite material sintered in step 3 with sandpaper to remove the carbon paper and excess copper on the surface, thereby obtaining an ultra-thin diamond / copper composite material.

[0008] Preferably, the ultra-thin diamond / copper composite material has a thickness of 0.2 to 2.0 mm, preferably 0.3 to 1.0 mm.

[0009] Preferably, the weight ratio of the tungsten-coated diamond powder to the copper powder in step 1 is 1:1 to 1:15, preferably 1:2 to 1:12.

[0010] Preferably, in step 1, the thickness of the copper foil or copper powder on the upper and lower surfaces of the mixed powder is 0.1 mm to 0.3 mm respectively.

[0011] Preferably, the thickness of the wet powder filling in step 2 is greater than 0.2 mm and less than 2.0 mm, more preferably greater than 0.3 mm and less than 1.5 mm.

[0012] Preferably, the sintering process parameters in step 3 are set as follows:

[0013] Axial pressure: 30~40MPa;

[0014] Heating rate: 60-80℃ / min to 850-950℃, keep warm for 5-10min;

[0015] Sintering temperature: 850~950℃;

[0016] Cooling rate: After the insulation is completed, the current is cut off and the furnace is cooled to room temperature.

[0017] Preferably, in step 4, the mesh numbers of the sandpaper are 100 mesh, 800 mesh, and 2000 mesh, respectively, and the surface of the composite material is polished until it is smooth.

[0018] According to a second aspect of the present invention, there is provided an ultra-thin diamond / copper composite material prepared according to the method of the present invention.

[0019] Preferably, the ultra-thin diamond / copper composite material has a thickness of 0.2 to 2.0 mm, preferably 0.3 to 1.0 mm.

[0020] Preferably, the ratio of thermal conductivity of the ultra-thin diamond / copper composite material to that of copper is greater than 1.060, more preferably greater than 1.065;

[0021] Preferably, the thermal expansion coefficient of the ultra-thin diamond / copper composite material at room temperature is 7.0*10 -6 ~8.0*10 -6 K -1 , more preferably 7.28*10 -6 ~8.0*10 -6 K -1 .

[0022] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0023] 1. According to the method of the present invention, the powder mixing method using ethanol medium for grinding avoids the problem of uneven powder mixing caused by the difference in particle size and density of diamond powder and copper powder.

[0024] 2. According to the method of the present invention, a piece of copper foil or a layer of copper powder is added to the upper and lower surfaces when filling the powder, which solves the problem of uneven surface of the diamond / copper composite material. And after demoulding, only simple grinding is required, so it has the advantages of high efficiency, time saving and labor cost saving.

[0025] 3. According to the method of the present invention, ultra-thin high thermal conductivity diamond / copper composite materials can be directly prepared, thereby saving the high laser processing costs.

[0026] 4. According to the method of the present invention, the preparation process is simple, easy to operate, has good repeatability, stable products and good batch consistency.

[0027] The method of the present invention has universal applicability and can be widely applied to the preparation of other metal-based diamond composite materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 This is a photo of a diamond / copper composite material with a thickness of 0.3 mm prepared according to Example 1. DETAILED DESCRIPTION

[0029] In order to make the purpose, technical solution and effect of the present invention clearer and more specific, the present invention is further described in detail by enumerating the following embodiments. It should be noted that the embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0030] Copper powder and diamond powder are purchased from Sinopharm Group.

[0031] Example 1

[0032] Preparation of diamond / copper composite material with a thickness of 0.3 mm

[0033] 0.037 g of tungsten-coated diamond powder with a particle size of 200 μm and 0.378 g of copper powder with a particle size of 75 μm were put into a mortar and mixed evenly using 5 ml of alcohol; the wet powder was loaded into a graphite mold with a diameter of 13 mm, the filling height was 0.4 mm, and a piece of copper foil with a thickness of 0.2 mm was added to the upper and lower sides of the mixed powder.

[0034] Then, the loaded graphite mold was placed in a vacuum drying oven and vacuum dried at 80° C. for 3 h.

[0035] After drying, the dried graphite mold is placed in the furnace of the spark plasma sintering system to quickly shape the mixed powder by spark plasma sintering.

[0036] Axial pressure: 30MPa;

[0037] Heating rate: 60℃ / min to 900℃, keep warm for 8min;

[0038] Sintering temperature: 900℃;

[0039] Cooling rate: After the insulation is completed, the current is cut off and the furnace is cooled to room temperature.

[0040] Next, the obtained diamond / copper composite material was polished with 100 mesh, 800 mesh, and 2000 mesh sandpapers respectively until the surface of the composite material was smooth.

[0041] The thickness of the diamond / copper composite material is 0.3 mm.

[0042] Test sample performance:

[0043] Thermal conductivity (thermal conductivity of "diamond / copper composite material" / thermal conductivity of copper): the measurement result with glue pad is 1.085, and the measurement result without glue pad is 1.073 (measured by comparing with pure copper of the same size through thermal resistance method).

[0044] Thermal expansion coefficient: The test result at room temperature is 7.60*10 -6 K -1 (The testing equipment is a thermomechanical analyzer, model TMA402F3).

[0045] Example 2

[0046] Preparation of diamond / copper composite material with a thickness of 0.5 mm

[0047] 0.074 g of tungsten-coated diamond powder with a particle size of 200 μm and 0.283 g of copper powder with a particle size of 75 μm were put into a mortar and mixed evenly using 5 ml of alcohol; the wet powder was loaded into a graphite mold with a diameter of 13 mm, the filling height was 0.6 mm, and a piece of copper foil with a thickness of 0.2 mm was added to the upper and lower sides of the mixed powder.

[0048] Then, the loaded graphite mold was placed in a vacuum drying oven and vacuum dried at 100 °C for 2 h.

[0049] After drying is complete, the dried graphite mold is placed in the furnace chamber of the spark plasma sintering system to use spark plasma sintering to quickly shape the mixed powder;

[0050] Axial pressure: 30MPa;

[0051] Heating rate: 80℃ / min to 950℃, keep warm for 10min;

[0052] Sintering temperature: 950℃;

[0053] Cooling rate: After the insulation is completed, the current is cut off and the furnace is cooled to room temperature.

[0054] Next, the obtained diamond / copper composite material was polished with 100 mesh, 800 mesh, and 2000 mesh sandpapers respectively until the surface of the composite material was smooth.

[0055] The thickness of the diamond / copper composite material is 0.5 mm.

[0056] Test sample performance:

[0057] Thermal conductivity (thermal conductivity of "diamond / copper composite material" / thermal conductivity of copper): the measurement result with glue pad is 1.070, and the measurement result without glue pad is 1.066 (measured by comparing with pure copper of the same size through thermal resistance method).

[0058] Thermal expansion coefficient: The test result at room temperature is 7.28*10 -6 K -1 (The testing equipment is a thermomechanical analyzer, model TMA402F3).

Claims

1. A near-net-shape forming method for ultra-thin diamond / copper composite material, comprising the following steps: Step 1: Powder loading: Put the tungsten-coated diamond powder and copper powder into an agate mortar, use alcohol as the medium, mix them evenly, put them into a graphite mold in a wet powder state, and add a piece of copper foil or a layer of copper powder on the upper and lower sides of the mixed powder. The particle sizes of the diamond powder and copper powder are 150-220 μm and 60-80 μm respectively; Step 2: Drying: Place the mold obtained in step 1 in a vacuum drying oven and vacuum dry it at a temperature of 80-100°C; Step 3: Sintering: Place the dried and assembled mold into the furnace chamber of the spark plasma sintering system, apply pressure, evacuate the vacuum, and then sinter with power on. The sintering process parameters are set as follows: Axial pressure: 30~40MPa; Heating rate: 60-80℃ / min to 850-950℃, keep warm for 5-10min; Sintering temperature: 850~950℃; Cooling rate: After the insulation is completed, the current is cut off and the furnace is cooled to room temperature; Step 4: Grinding: Grind the composite material sintered in step 3 with sandpaper to remove the carbon paper and excess copper on the surface to obtain an ultra-thin diamond / copper composite material. The thickness of the ultra-thin diamond / copper composite material is 0.2-2.0 mm.

2. The method according to claim 1, wherein: The weight ratio of the tungsten-coated diamond powder to the copper powder in step 1 is 1:1 to 1:

15.

3. The method according to claim 2, wherein: The weight ratio of the tungsten-coated diamond powder to the copper powder in step 1 is 1:2 to 1:

12.

4. The method according to claim 1, wherein: In step 1, the thickness of the copper foil or copper powder on the upper and lower surfaces of the mixed powder is 0.1 mm to 0.3 mm respectively.

5. The method according to claim 1, wherein: The thickness of the wet powder filling in step 1 is greater than 0.2 mm and less than 2.0 mm.

6. The method according to claim 5, wherein: The thickness of the wet powder filling in step 1 is greater than 0.3 mm and less than 1.5 mm.

7. The method according to any one of claims 1 to 6, wherein: In step 4, the mesh numbers of the sandpaper are 100 mesh, 800 mesh, and 2000 mesh, respectively, and the surface of the composite material is polished until it is smooth.

8. An ultra-thin diamond / copper composite material obtained by the method according to any one of 1 to 5.

9. The ultra-thin diamond / copper composite material according to claim 8, wherein: The thickness of the ultra-thin diamond / copper composite material is 0.3-1.0 mm.

10. The ultra-thin diamond / copper composite material according to claim 8, wherein: The ratio of thermal conductivity of the ultra-thin diamond / copper composite material to that of copper is greater than 1.

060.

11. The ultra-thin diamond / copper composite material according to claim 10, wherein: The ratio of thermal conductivity of the ultra-thin diamond / copper composite material to that of copper is greater than 1.

065.

12. The ultra-thin diamond / copper composite material according to claim 8, wherein: The thermal expansion coefficient of the ultra-thin diamond / copper composite material at room temperature is 7.0*10 -6 ~8.0*10 -6 K -1 .

13. The ultra-thin diamond / copper composite material according to claim 8, wherein: The thermal expansion coefficient of the ultra-thin diamond / copper composite material at room temperature is 7.28*10 -6 ~8.0*10 -6 K -1 .

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