A method for preparing a copper-based composite material with uniform diamond particle reinforcement

Abstract

This invention relates to the technical field of composite material preparation, specifically to a method for preparing a diamond particle uniformly reinforced copper-based composite material. The steps are as follows: diamond particles are uniformly coated onto the surface of a pure copper sheet, and uncoated pure copper sheets are stacked and rolled; after each rolling pass, the copper sheet is folded in half and then rolled again; the resulting sample is hydraulically compressed to a certain deformation, wherein the hydraulic compression direction is perpendicular to the rolling direction; the resulting sample is hot-rolled at a certain temperature, then cooled to room temperature, and the above steps are repeated multiple times. The sample after the final cooling is taken, and surface impurities are removed to obtain the diamond particle uniformly reinforced copper-based composite material. The diamond particle uniformly reinforced copper-based composite material prepared by this invention is dense, has good interfacial bonding, and the diamond particles are uniformly distributed in the matrix. It exhibits good thermal conductivity and a low coefficient of thermal expansion, showing promising application prospects in the field of electronic packaging materials.

Description

Technical Field

[0001] This invention relates to the technical field of composite material preparation, and specifically to a method for preparing a copper-based composite material with uniform diamond particle reinforcement. Background Technology

[0002] Copper-based composite materials are artificially formed composite materials using copper metal and its alloys as the matrix, combined with one or more metallic or non-metallic reinforcing phases. Diamond has the highest thermal conductivity in nature (2200-2600 W / (m·K)) and a low coefficient of thermal expansion (1.7×10⁻⁶ K). -1 Copper is a non-metallic material with excellent thermal conductivity, good processability, and low cost. Diamond / copper composites, with diamond as the reinforcing phase and copper as the matrix material, are expected to simultaneously possess high thermal conductivity and a low coefficient of thermal expansion, making them a highly competitive new electronic packaging material.

[0003] Currently, there are many methods for preparing diamond-reinforced copper-based composite materials. From the perspective of matrix state, they can be divided into: (1) solid-state methods: powder metallurgy, hot pressing, cumulative rolling, spark plasma sintering, etc.; (2) liquid-state methods: co-spray deposition, in-situ self-generation, liquid metal impregnation, etc.; (3) gaseous methods: physical vapor deposition, chemical vapor deposition, etc. The traditional process for preparing diamond / copper electronic packaging materials has the following problems: (1) poor wettability between diamond and copper, resulting in poor interfacial bonding of the composite material. (2) when the content of the reinforcing phase is high, the diamond segregation phenomenon is serious, resulting in poor overall thermal performance.

[0004] Cumulative rolling is a type of intense plastic deformation process that uses continuous multi-pass rolling to prepare ultrafine-grained materials. Currently, using cumulative rolling to prepare metal matrix composites presents challenges such as interlayer bonding problems. Furthermore, due to the enormous deformation, particle-reinforced composites can develop cracks, leading to breakage and detachment. Therefore, researchers typically employ low-pass (usually less than 20 passes) cumulative rolling methods to prepare composites. However, since the dispersion and interfacial bonding of diamond and the copper matrix largely depend on the number of rolling passes, lower passes cannot effectively disperse diamond particles or improve interfacial bonding, thus hindering the preparation of high-performance composites. Summary of the Invention

[0005] The purpose of this invention is to provide a method for preparing a copper-based composite material with uniform diamond particle reinforcement. This method is simple, low-cost, and beneficial for large-scale industrial applications. The prepared composite material is dense, has good interfacial bonding, and features uniformly distributed diamond particles within the matrix. It exhibits good thermal conductivity and a low coefficient of thermal expansion, showing promising application prospects in the field of electronic packaging materials.

[0006] The solution adopted by this invention to achieve its objective is: a method for preparing a copper-based composite material with uniform diamond particle reinforcement, comprising the following steps:

[0007] (1) Take a cleaned pure copper sheet and coat the surface of the pure copper sheet with diamond particles evenly; stack the pure copper sheets coated with diamond particles and those not coated with diamond particles, with the diamond particles located inside the stack, and roll them; after each rolling pass, fold the copper sheet in half and then roll it again; repeat the folding-rolling process until the required number of passes is reached.

[0008] (2) The sample obtained in step (1) is hydraulically compressed to a certain amount of deformation, wherein the hydraulic compression direction is perpendicular to the rolling direction;

[0009] (3) The sample obtained in step (2) is hot rolled at a certain temperature. The hot rolling direction is consistent with the rolling direction in step (1). Then it is cooled to room temperature. The above steps are repeated several times. After the last cooling, the sample is taken and surface impurities are removed to obtain the diamond particle uniformly reinforced copper matrix composite material.

[0010] Preferably, in step (1), the diamond particles account for a volume percentage of 0 and less than or equal to 60% of the pure copper sheet, and the particle size of the diamond particles is 30 to 100 μm.

[0011] Preferably, in step (1), there are at least two pure copper sheets. When there are more than two pure copper sheets, there is at least one diamond particle layer. When there are multiple diamond particle layers, the diamond particle layers are evenly distributed in the stack.

[0012] Preferably, in step (1), the deformation of the sample in the thickness direction is controlled to be 50% to 70% in each rolling pass, and the cumulative rolling passes are 30 to 50.

[0013] Preferably, in step (2), the deformation of the sample is controlled by hydraulic pressure to be 20% to 30%.

[0014] Preferably, in step (1), the rolling speed is 100-300 mm / min.

[0015] Preferably, in step (2), the hydraulic pressure is 100-200 kN.

[0016] Preferably, in step (3), the hot rolling temperature is 550-650°C.

[0017] Preferably, in step (3), the reduction in thickness of the hot-rolled sample is ≤30% each time, repeated at least four times, and the total reduction in thickness of the hot-rolled sample is ≥65%. Generally, the total reduction in thickness of the hot-rolled sample is controlled to be 65% to 75%.

[0018] Preferably, in step (3), the cooling process is as follows: first, cooling is performed at 100-200°C, and then air cooling is performed to room temperature.

[0019] The principle of this invention is as follows: diamond particles are sandwiched between copper sheets and continuously rolled multiple times at room temperature without lubrication. With each rolling pass, the diamond particles gradually disperse on the rolling surface as the sample lengthens during rolling, and also gradually disperse in the thickness direction of the sample. Sufficient rolling passes can uniformly disperse the diamond particles and achieve good bonding between the diamond and the copper matrix. To prevent breakage, sticking to the mill, and loss due to detachment of the composite material, a steel plate is used to encase the composite material during rolling. Even after room temperature rolling and uniform dispersion, many cracks and interlayer inconsistencies still exist in the final sample. To further improve sample density and eliminate cracks and interlayer inconsistencies, the room temperature rolled sample undergoes hydraulic shaping and cumulative hot rolling. Due to the heat treatment during cumulative hot rolling and rolling at high temperatures, defects in the composite material are eliminated, and the interlayer bonding becomes stronger.

[0020] The present invention has the following advantages and beneficial effects:

[0021] 1. The preparation method of the present invention is simple to operate, requiring only multi-pass rolling, hydraulic and cumulative hot rolling treatment, and the equipment is an industrial rolling mill, hydraulic press and muffle furnace, which can realize industrial-scale production.

[0022] 2. This invention can effectively disperse diamond particles in composite materials, preventing them from agglomerating, and can disperse nanodiamond particles with a volume fraction of up to 60%.

[0023] 3. This invention can effectively promote the bonding between diamond and copper matrix, with no detachment or pores at the bonding interface.

[0024] 4. The diamond particle uniformly reinforced copper matrix composite material prepared by this invention is dense, has good interfacial bonding, and the diamond particles are uniformly distributed in the matrix. It has good thermal conductivity and low coefficient of thermal expansion, and has good application prospects in the field of electronic packaging materials. Attached Figure Description

[0025] Figure 1 These are schematic diagrams of the rolling process in embodiments 1, 2, and 3 of the present invention;

[0026] Figure 2 These are optical micrographs of the uniformly reinforced copper matrix composite material with diamond particles at different magnifications in Examples 1, 2, and 3 of the present invention; wherein (a) and (b) are optical micrographs of Example 1, (c) and (d) are optical micrographs of Example 2, and (e) and (f) are optical micrographs of Example 3.

[0027] Figure 3The thermal diffusivity of the diamond particle-reinforced copper matrix composite material obtained in Examples 1, 2, and 3 of this invention;

[0028] Figure 4 The thermal expansion coefficient diagrams are shown for the diamond particle-reinforced copper matrix composites obtained in Examples 2 and 3 of this invention. Detailed Implementation

[0029] To better understand the present invention, the following embodiments are further illustrations of the present invention, but the content of the present invention is not limited to the following embodiments.

[0030] Example 1

[0031] Diamond particles were used as the reinforcement and pure copper sheets as the matrix. In this embodiment, the copper sheet dimensions were: 100mm long, 50mm wide, and 0.1mm thick. The diamond particles were 100μm in size. An industrial rolling mill was used, with a rolling speed of 187mm / min. A hydraulic press was used, with a hydraulic pressure of 150kN. A muffle furnace was used, with a holding temperature of 600℃ and a cooling temperature of 150℃.

[0032] (1) Cut pure copper sheets of size 100×50×0.1mm, take 8 sheets as the original substrate, and use laser ablation to remove surface impurities.

[0033] (2) Based on the volume of the pure copper sheet used, after calculation, diamond particles with a volume fraction of 10% were added to an appropriate amount of ethanol, cleaned with an ultrasonic cleaner, and then dried with hot air. The dried diamond particles were divided into seven parts and added to the surface of seven copper plates respectively.

[0034] (3) Stack 7 copper sheets with diamond particles on the surface and 1 copper sheet without diamond particles on the surface to ensure that there is a layer of diamond particles between every two layers of the 8 copper sheets.

[0035] (4) Use a folded stainless steel plate to hold the pure copper sheet and feed it between two rolls for rolling. Adjust the distance between the two rolls to ensure that the sample reduction is about 50%. After each rolling pass, fold it in half along the rolling direction and roll it again. Repeat the above steps (the rolled copper sheet is surface treated, and no diamond particles are added) to roll it until the number of rolling passes reaches 20.

[0036] (5) The copper tube with graphite paper wrapped inside is filled evenly with the composite material sample after cumulative rolling, and the copper tube is sealed with graphite paper. The pressure of the hydraulic press is adjusted to 150kN, and the copper tube is sealed by hydraulic pressure. The reduction of the thickness of the copper tube sample during hydraulic pressure is ≥20%.

[0037] (6) Wrap the sealed composite copper tube with a stainless steel sheet and place it in a muffle furnace at 600℃ for 10 minutes. Immediately remove it and roll it, ensuring the sample's compression is no more than 30%. After rolling, place it in a muffle furnace at 150℃ for slow cooling. After cooling for 15 minutes, remove the sample and air-cool it to room temperature. Replace the stainless steel sheet and place the composite material back into the muffle furnace at 600℃ for heat treatment. Repeat the above steps at least four times to ensure the final compression of the sample is no less than 70%.

[0038] (7) Take the sample after the last cooling, remove the outer copper tube by wire cutting, and remove the surface impurities by laser ablation to obtain the final composite material.

[0039] Figure 1 The rolling process shown in Embodiments 1, 2, and 3 of the present invention is mainly divided into three steps: pretreatment, cumulative stacking rolling, and cumulative hot rolling. Figure 2 a and b in the figure are optical micrographs of the composite material in Example 1 of the present invention at different magnifications. It can be seen from the figure that the diamond is uniformly dispersed in the copper matrix and the interface between the diamond and the copper matrix is ​​well bonded. Figure 3 The thermal diffusivity of the composite material prepared in Example 1 of this invention was determined; Figure 4 The figure shows the coefficient of thermal expansion of the composite material prepared in Example 1 of the present invention. It can be seen from the figure that the sample has a lower coefficient of thermal expansion at lower temperatures.

[0040] In this embodiment, after 20 rolling passes and 4 cumulative hot rolling processes, the final copper matrix composite material with uniformly reinforced 10% volume fraction diamond particles has a thermal conductivity of 214.54 W / (m·K) and its coefficient of thermal expansion matches that of the silicon chip substrate (0.000006-0.000008 / K).

[0041] Example 2

[0042] Diamond particles were used as the reinforcement and pure copper sheets as the matrix. In this embodiment, the copper sheet dimensions were: 100mm long, 50mm wide, and 0.1mm thick. The diamond particles were 100μm in size. An industrial rolling mill was used, with a rolling speed of 187mm / min. A hydraulic press was used, with a hydraulic pressure of 150kN. A muffle furnace was used, with a holding temperature of 600℃ and a cooling temperature of 150℃.

[0043] (1) Cut pure copper sheets of size 100×50×0.1mm, take 8 sheets as the original substrate, and use laser ablation to remove surface impurities.

[0044] (2) Based on the volume of the pure copper sheet used, after calculation, diamond particles with a volume fraction of 20% were added to an appropriate amount of ethanol, cleaned with an ultrasonic cleaner, and then dried with hot air. The dried diamond particles were divided into seven parts and added to the surface of seven copper plates respectively.

[0045] (3) Stack 7 copper sheets with diamond particles on the surface and 1 copper sheet without diamond particles on the surface to ensure that there is a layer of diamond particles between every two layers of the 8 copper sheets.

[0046] (4) Use a folded stainless steel plate to hold the pure copper sheet and feed it between two rolls for rolling. Adjust the distance between the two rolls to ensure that the sample reduction is about 50%. After each rolling pass, fold it in half along the rolling direction and roll it again. Repeat the above steps (the rolled copper sheet is surface treated, and no diamond particles are added) to roll it until the number of rolling passes reaches 30.

[0047] (5) The copper tube with graphite paper wrapped inside is filled evenly with the composite material sample after cumulative rolling, and the copper tube is sealed with graphite paper. The pressure of the hydraulic press is adjusted to 150kN, and the copper tube is sealed by hydraulic pressure. The reduction of the thickness of the copper tube sample during hydraulic pressure is ≥20%.

[0048] (6) Wrap the sealed composite copper tube with a stainless steel sheet and place it in a muffle furnace at 600℃ for 10 minutes. Immediately remove it and roll it, ensuring the sample's compression is no more than 30%. After rolling, place it in a muffle furnace at 150℃ for slow cooling. After cooling for 15 minutes, remove the sample and air-cool it to room temperature. Replace the stainless steel sheet and place the composite material back into the muffle furnace at 600℃ for heat treatment. Repeat the above steps at least four times to ensure the final compression of the sample is no less than 70%.

[0049] (7) Take the sample after the last cooling, remove the outer copper tube by wire cutting, and remove the surface impurities by laser ablation to obtain the final composite material.

[0050] Figure 1 The rolling process shown in Embodiments 1, 2, and 3 of the present invention is mainly divided into three steps: pretreatment, cumulative stacking rolling, and cumulative hot rolling. Figure 2 c and d in the figure are optical micrographs of the composite material in Example 2 of the present invention at different magnifications. It can be seen from the figure that diamond is uniformly dispersed in the copper matrix and the interface between diamond and copper matrix is ​​well bonded. Figure 3 The thermal diffusivity of the composite material prepared in Example 2 of this invention was determined; Figure 4 The figure shows the coefficient of thermal expansion of the composite material prepared in Example 2 of the present invention. It can be seen from the figure that the sample has a lower coefficient of thermal expansion at lower temperatures.

[0051] In this embodiment, after 20 rolling passes and 4 cumulative hot rolling processes, the final copper matrix composite material with uniformly reinforced 20% volume fraction diamond particles has a thermal conductivity of 238.61 W / (m·K) and its coefficient of thermal expansion matches that of the silicon chip substrate (0.000006-0.000008 / K).

[0052] Example 3

[0053] Diamond particles were used as the reinforcement and pure copper sheets as the matrix. In this embodiment, the copper sheet dimensions were: 100 mm long, 50 mm wide, and 0.1 mm thick. The diamond particles were 100 μm in size. An industrial rolling mill was used, with a rolling speed of 187 mm / min. A hydraulic press was used, with a hydraulic pressure of 200 kN. A muffle furnace was used, with a holding temperature of 600°C and a cooling temperature of 150°C.

[0054] (1) Cut pure copper sheets of size 100×50×0.1mm, take 8 sheets as the original substrate, and use laser ablation to remove surface impurities.

[0055] (2) Based on the volume of the pure copper sheet used, diamond particles with a volume fraction of 40% were added to an appropriate amount of ethanol and cleaned with an ultrasonic cleaner, then dried with hot air. The dried diamond particles were divided into seven portions and added to the surface of seven copper plates respectively.

[0056] (3) Stack 7 copper sheets with diamond particles on the surface and 1 copper sheet without diamond particles on the surface to ensure that there is a layer of diamond particles between every two layers of the 8 copper sheets.

[0057] (4) Use a folded stainless steel plate to hold the pure copper sheet and feed it between two rolls for rolling. Adjust the distance between the two rolls to ensure that the sample reduction is about 50%. After each rolling pass, fold it in half along the rolling direction and roll it again. Repeat the above steps (the rolled copper sheet is surface treated, and no diamond particles are added) to roll it until the number of rolling passes reaches 35.

[0058] (5) Fill the copper tube with graphite paper on the inner wall evenly with the composite material sample after cumulative rolling, and seal the copper tube with graphite paper. Adjust the pressure of the hydraulic press to 200kN, and use the hydraulic press to seal the copper tube. The reduction of the copper tube sample thickness during hydraulic pressure is ≥20%.

[0059] (6) Wrap the sealed composite copper tube with a stainless steel sheet and place it in a muffle furnace at 600℃ for 10 minutes. Immediately remove it and roll it, ensuring the sample's compression is no more than 30%. After rolling, place it in a muffle furnace at 150℃ for slow cooling. After cooling for 15 minutes, remove the sample and air-cool it to room temperature. Replace the stainless steel sheet and place the composite material back into the muffle furnace at 600℃ for heat treatment. Repeat the above steps at least four times to ensure the final compression of the sample is no less than 70%.

[0060] (7) Take the sample after the last cooling, remove the outer copper tube by wire cutting, and remove the surface impurities by laser ablation to obtain the final composite material.

[0061] Figure 1The rolling process shown in Embodiments 1, 2, and 3 of the present invention is mainly divided into three steps: pretreatment, cumulative stacking rolling, and cumulative hot rolling. Figure 2 In the figure, e and f are optical micrographs of the composite material in Example 3 of the present invention at different magnifications. It can be seen from the figure that diamond is uniformly dispersed in the copper matrix and the interface between diamond and copper matrix is ​​well bonded. Figure 3 The thermal diffusivity of the composite material prepared in Example 3 of this invention was determined.

[0062] In this embodiment, after 20 rolling passes and 4 cumulative hot rolling processes, the thermal conductivity of the copper matrix composite material with uniform diamond particle reinforcement of 40% volume fraction is 247.03 W / (m·K).

[0063] Table 1 shows the calculated thermal conductivity values ​​of the composite materials prepared in Examples 1-3 of the invention. As can be seen from the table, the thermal conductivity of the samples increases with the increase of the diamond volume fraction.

[0064] Table 1. Calculated thermal conductivity values ​​of the composite materials prepared in Examples 1-3

[0065]

[0066] Comparing embodiments 1, 2, and 3 of this invention, it can be seen that through multi-pass cumulative rolling, diamond particles of different volume fractions can be uniformly dispersed in the copper matrix, and the interface bonding is good, without defects such as pores or cracks. From Table 1, Figure 4 It can be seen that the diamond-reinforced copper-based composite material prepared by this invention has high thermal conductivity and a thermal expansion coefficient that matches the low temperature of silicon plates.

[0067] The above description is merely a preferred embodiment of the present invention, and should not be construed as limiting the scope of the invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications are also considered to be within the scope of protection of the present invention.

Claims

1. A method for preparing a copper-based composite material with uniform diamond particle reinforcement, characterized in that, Includes the following steps: (1) Take a cleaned pure copper sheet and coat the surface of the pure copper sheet with diamond particles evenly; stack the pure copper sheets coated with diamond particles and those not coated with diamond particles, with the diamond particles located inside the stack, and roll them; after each rolling pass, fold the copper sheet in half and then roll it again; repeat the folding-rolling process until the required pass is reached. (2) The sample obtained in step (1) is hydraulically compressed to a certain amount of deformation, wherein the hydraulic compression direction is perpendicular to the rolling direction; (3) The sample obtained in step (2) is hot rolled at a certain temperature. The hot rolling direction is consistent with the rolling direction in step (1). Then it is cooled to room temperature. The above steps are repeated several times. After the last cooling, the sample is taken and the surface impurities are removed to obtain the diamond particle uniformly reinforced copper matrix composite material. In step (3), the hot rolling temperature is 550~650℃; the reduction of the thickness of the hot-rolled sample is ≤30% each time, and it is repeated at least four times, with the total reduction of the thickness of the hot-rolled sample being ≥65%; the cooling process is as follows: first, cooling is carried out at 100~200℃, and then air cooling is carried out to room temperature.

2. The method for preparing the uniformly reinforced copper-based composite material with diamond particles according to claim 1, characterized in that: In step (1), the diamond particles account for a volume percentage of the pure copper sheet that is greater than 0 and less than or equal to 60%, and the particle size of the diamond particles is 30~100μm.

3. The method for preparing the uniformly reinforced copper-based composite material with diamond particles according to claim 1, characterized in that: In step (1), there are at least two pure copper sheets. When there are more than two pure copper sheets, there is at least one diamond particle layer. When there are multiple diamond particle layers, the diamond particle layers are evenly distributed in the stack.

4. The method for preparing the uniformly reinforced copper-based composite material with diamond particles according to claim 1, characterized in that: In step (1), the deformation of the sample in the thickness direction is controlled to be 50%~70% in each rolling pass, and the cumulative rolling passes are 30~50.

5. The method for preparing the uniformly reinforced copper-based composite material with diamond particles according to claim 1, characterized in that: In step (2), the deformation of the sample is controlled by hydraulic pressure to be 20%~30%.

6. The method for preparing the uniformly reinforced copper-based composite material with diamond particles according to claim 1, characterized in that: In step (1), the rolling speed is 100~300 mm / min.

7. The method for preparing the uniformly reinforced copper-based composite material with diamond particles according to claim 1, characterized in that: In step (2), the hydraulic pressure is 100~200kN.

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