A method for vacuum pressure sintering porous aluminum powder on an aluminum-based silicon carbide matrix

Abstract

The present invention provides a method for vacuum pressure sintering porous aluminum powder on an aluminum-based silicon carbide matrix, comprising the following steps: mechanically polishing the surface of an aluminum-based composite material reinforced with silicon carbide particles to be sintered to obtain an aluminum-based silicon carbide matrix; immersing the aluminum-based silicon carbide matrix in acetone for cleaning to remove grease from the surface of the aluminum-based silicon carbide matrix; placing the cleaned aluminum-based silicon carbide matrix in an ultrasonic cleaning machine for ultrasonic cleaning; pouring aluminum powder into a graphite mold and scraping it flat to ensure close contact between the aluminum powder and the aluminum-based silicon carbide matrix; placing the sintered assembly in a vacuum pressure sintering machine for pressure sintering, wherein under the action of high temperature and pressure, the contact surfaces approach each other, and after a certain holding time, the aluminum powder atoms gradually diffuse into the aluminum-based silicon carbide to form a reliable connection. The present invention successfully sintered porous aluminum powder on the aluminum-based silicon carbide matrix under appropriate sintering temperature and applied pressure, with good capillary action.

Description

Technical Field

[0001] The invention belongs to the field of powder sintering, and in particular relates to a method for vacuum pressure sintering porous aluminum powder on an aluminum-based silicon carbide matrix. Background Art

[0002] As electronic devices and semiconductor integrated circuits develop toward high reliability, high integration, high density, and lightweight design, the number of microelectronic components is increasing, their integration density is increasing, and their heat density is increasing. Consequently, the heat dissipation requirements for microelectronic component housings are becoming increasingly stringent. Traditional molybdenum-copper alloys and tungsten-copper alloys, due to their high specific gravity and low thermal conductivity, are gradually failing to meet performance requirements. Therefore, aluminum-based composites reinforced with high volume fractions of silicon carbide particles (Al / SiCp) have become an ideal alternative to traditional electronic packaging materials.

[0003] Silicon carbide particle-reinforced aluminum-based composites (Al / SiCp) are widely used in aerospace and other structural devices requiring high strength and high temperature resistance due to their low density, low thermal expansion coefficient, high specific strength and specific stiffness, high elastic modulus and good wear resistance. By changing the ratio of Al to SiC while maintaining high strength, their CTE can be customized to better match third-generation semiconductors such as gallium nitride (GaN) and silicon carbide (SiC). Summary of the Invention

[0004] In response to the above-mentioned technical problems in the prior art, the present invention provides a method for vacuum pressure sintering porous aluminum powder on an aluminum-based silicon carbide matrix. This method sinters the aluminum powder on the surface of aluminum-based silicon carbide with different thermal expansion coefficients, and has good bonding force and capillary properties, which can provide a channel for preparing heat dissipation devices.

[0005] To achieve the above object, the present invention provides a method for vacuum pressure sintering porous aluminum powder on an aluminum-based silicon carbide substrate, comprising the following steps:

[0006] Step S1, mechanically grinding the surface of the silicon carbide particle reinforced aluminum matrix composite material to be sintered to break the oxide film coated on the surface of the silicon carbide particle reinforced aluminum matrix composite material to obtain an aluminum-based silicon carbide matrix;

[0007] Step S2, immersing the aluminum-based silicon carbide substrate in acetone for cleaning to remove grease on the surface of the aluminum-based silicon carbide substrate, first immersing it in 10% NaOH for about 3 minutes, and then immersing it in 10% HNO3 for about 3-5 minutes to remove the residual oxide film by chemical reaction;

[0008] Step S3, placing the cleaned aluminum-based silicon carbide substrate into an ultrasonic cleaning machine for 3-5 minutes to clean the surface acid, alkali and SiC particles;

[0009] Step S4, pouring aluminum powder into a graphite mold and then flattening it to ensure that the aluminum powder is in close contact with the aluminum powder and with the aluminum-based silicon carbide matrix to obtain a sintered assembly consisting of aluminum-based silicon carbide-aluminum powder-graphite grinding tool;

[0010] In step S5, the sintered assembly consisting of aluminum-based silicon carbide, aluminum powder, and graphite abrasive is placed in a vacuum pressure sintering machine and the program is set to perform pressure sintering. Under the action of high temperature and pressure, the contact surfaces approach each other. After a certain holding time, the aluminum powder atoms gradually diffuse into the aluminum-based silicon carbide to form a reliable connection.

[0011] Preferably, the sintering is divided into two processes, the first sintering process is the sintering between aluminum powders;

[0012] In step 4, the aluminum powder is flattened to form a spatial stack of aluminum powder and aluminum powder in the mold. In step 5, a specific pressure is applied to increase the contact area and pressure between the aluminum powder and the thin oxide layer on the surface of the aluminum powder. The pressure is then crushed, and the movement of aluminum atoms in the oxide layer of the aluminum powder is promoted by high temperature. The aluminum atoms diffuse through the pressure-crushed oxide layer on the surface and enter other aluminum powders to form an effective sintering connection. The pressure (30-50Mpa) and temperature (500-540℃) are matched to ensure that the pressure-temperature combination can destroy the aluminum oxide on the outside of the aluminum powder, form effective contact between the aluminum powders, and rapidly diffuse the aluminum atoms. This avoids problems such as the collapse of the porous structure of the aluminum powder due to excessive pressure, the inability to crush the oxide layer due to insufficient pressure, which affects the diffusion of aluminum atoms, the melting of the aluminum powder due to excessive temperature, and the slow diffusion rate of aluminum atoms due to excessively low temperature.

[0013] The second sintering process is the sintering between aluminum powder and aluminum-based silicon carbide matrix;

[0014] The aluminum powder is flattened in step 4, and in step 5, pressure is applied to effectively contact the substrate, breaking down the oxide layer on the aluminum powder's surface. In step 5, high temperature promotes the diffusion of aluminum atoms from the aluminum powder into the substrate. Aluminum atoms and silicon carbide particles in the substrate also diffuse into the aluminum powder, forming an effective sintered connection between the aluminum powder and the aluminum-based silicon carbide substrate. The temperature and pressure are matched to break down the oxide layers on the aluminum powder and substrate, forming effective contact between the aluminum powder and the substrate, and rapidly diffusing aluminum atoms under the combined effects of pressure and temperature, achieving diffusion sintering.

[0015] In step 5, appropriate pressure and temperature can ensure effective contact between aluminum powder and aluminum powder, and between aluminum powder and the matrix, ensure a certain contact area and still have a certain gap, ensure that aluminum atoms can effectively diffuse between aluminum powder and aluminum powder, and between aluminum powder and the matrix, and ensure that aluminum atoms diffuse to form an effective sintering connection rather than aluminum powder melting to form recasting.

[0016] Preferably, the temperature formula for diffusion in step S5 is T=(0.6-0.8)Tm, where Tm is the lowest melting point of aluminum.

[0017] Preferably, in step S1, mechanical polishing is performed using sandpaper with a mesh size of 200-2000, and the oxide film coated on the surface of the silicon carbide particle reinforced aluminum-based composite material is removed using a mixed solution of hydrochloric acid and nitric acid and a sodium hydroxide solution.

[0018] Preferably, after the aluminum-based silicon carbide substrate is immersed in acetone for cleaning in step S2, an ultrasonic cleaning machine is used again to ultrasonically clean the grease, and the ultrasonic cleaning time is 3-5 minutes.

[0019] Preferably, in step S1, the aluminum-based composite material is regulated by adjusting the proportions of the components, and its physical properties comprehensively absorb the advantages of the metal matrix and the reinforcement, resulting in new excellent performance.

[0020] Preferably, the particle size of the aluminum powder in step S4 is 10-100 μm.

[0021] Preferably, in step S5, the holding temperature is set at 500-540° C. for 1-2 hours, and the applied pressure is set at 30-50 MPa until the sintered component cools down to room temperature along with the furnace.

[0022] The beneficial effects of the present invention are: under the action of high temperature and pressure, the aluminum powder is diffused when in contact with the aluminum-based silicon carbide matrix, so that the aluminum powder is sintered on the aluminum-based silicon carbide matrix to form a reliable connection. The method of vacuum pressure sintering porous aluminum powder on the aluminum-based silicon carbide matrix can sinter the aluminum powder on the surface of aluminum-based silicon carbide with different thermal expansion coefficients, and has good bonding force and capillary properties, which can provide a channel for preparing heat dissipation devices. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is a scanning electron microscope photograph of the vacuum pressure sintering of porous aluminum powder on an aluminum-based silicon carbide matrix according to the present invention.

[0024] Figure 2 This is a scanning electron microscope photograph of porous aluminum powder under 0 MPa pressure in the prior art.

[0025] Figure 3 This is a scanning electron microscope photograph of porous aluminum powder at 580°C in the prior art. DETAILED DESCRIPTION

[0026] To facilitate understanding of the technical means, inventive features, objectives, and effectiveness of the present invention, the following examples, combined with accompanying figures, specifically illustrate a method for vacuum pressure sintering porous aluminum powder on an aluminum-based silicon carbide substrate. These examples are intended only to illustrate the present invention and are not intended to limit its scope.

[0027] The present invention adopts the following technical solution: a method for vacuum pressure sintering porous aluminum powder on an aluminum-based silicon carbide matrix, comprising the following steps:

[0028] Mechanically grind the base metal to be welded with 200-2000 mesh sandpaper to break the oxide film covering the surface of aluminum-based silicon carbide;

[0029] Immerse the aluminum-based silicon carbide substrate in acetone to remove grease from the surface of the aluminum-based base material, immerse it in 10% NaOH for about 3 minutes, and immerse it in 10% HNO3 for about 3-5 minutes to remove the residual oxide film by chemical reaction;

[0030] After cleaning, place the aluminum-based silicon carbide substrate in an ultrasonic cleaning machine for 3-5 minutes to clean the surface acid, alkali and SiC particles;

[0031] Pour 140-mesh aluminum powder into the graphite mold and then scrape it flat to ensure that the aluminum powder is in close contact with the aluminum-based silicon carbide matrix;

[0032] The sintered assembly consisting of aluminum-based silicon carbide, aluminum powder, and graphite abrasive was placed in a vacuum pressure sintering machine. The program was set to sinter the aluminum powder on the surface of the aluminum-based silicon carbide at a heating temperature of 500°C and an applied pressure of 20 MPa. After keeping warm for 1 hour, the aluminum powder atoms gradually diffused into the aluminum-based silicon carbide to form a reliable connection.

[0033] This method utilizes the diffusion of aluminum powder when in contact with an aluminum-based silicon carbide matrix under the action of high temperature and pressure, thereby sintering the aluminum powder on the aluminum-based silicon carbide matrix to form a reliable connection.

[0034] This method can achieve the sintering of aluminum powders with various pore sizes on silicon carbide reinforced aluminum-based composites with different volume fractions. The process is simple, the surface properties are good, the connection is reliable, and good capillary force can be provided.

[0035] Preferably, the sintering is divided into two processes, the first sintering process is the sintering between aluminum powders;

[0036] In step 4, the aluminum powder is flattened to form a spatial stack of aluminum powder and aluminum powder in the mold. In step 5, a specific pressure is applied to increase the contact area and pressure between the aluminum powder and the aluminum powder, and the thin oxide layer on the surface of the aluminum powder is crushed by pressure. The high temperature promotes the movement of aluminum atoms in the oxide layer of the aluminum powder, and the aluminum atoms diffuse through the pressure-crushed oxide layer on the surface into other aluminum powders to form an effective sintering connection. The pressure and temperature are matched to ensure that the pressure-temperature combination can destroy the aluminum oxide on the outside of the aluminum powder, form effective contact between the aluminum powders, and rapidly diffuse the aluminum atoms, without causing problems such as collapse of the porous structure of the aluminum powder due to excessive pressure, inability to crush the oxide layer due to insufficient pressure to affect the diffusion of aluminum atoms, melting of the aluminum powder due to excessive temperature, and slow diffusion of aluminum atoms due to excessive temperature.

[0037] The second sintering process is the sintering between aluminum powder and aluminum-based silicon carbide matrix;

[0038] The aluminum powder is flattened in step 4, and in step 5, pressure is applied to effectively contact the substrate, breaking down the oxide layer on the aluminum powder's surface. In step 5, high temperature promotes the diffusion of aluminum atoms from the aluminum powder into the substrate. Aluminum atoms and silicon carbide particles in the substrate also diffuse into the aluminum powder, forming an effective sintered connection between the aluminum powder and the aluminum-based silicon carbide substrate. The temperature and pressure are matched to break down the oxide layers on the aluminum powder and substrate, forming effective contact between the aluminum powder and the substrate, and rapidly diffusing aluminum atoms under the combined effects of pressure and temperature, achieving diffusion sintering.

[0039] In step 5, appropriate pressure and temperature can ensure effective contact between aluminum powder and aluminum powder, and between aluminum powder and the matrix, ensure a certain contact area and still have a certain gap, ensure that aluminum atoms can effectively diffuse between aluminum powder and aluminum powder, and between aluminum powder and the matrix, and ensure that aluminum atoms diffuse to form an effective sintering connection rather than aluminum powder melting to form recasting.

[0040] like Figure 1 FIG. 1 is a scanning electron microscope photograph of the present invention for vacuum pressure sintering porous aluminum powder on an aluminum-based silicon carbide substrate. Figure 2 For Beijing General Research Institute of Nonferrous Metals, published in 2022, Zhang Jueling. Research on the preparation process of integrated aluminum-based capillary wicks for flat heat pipes, or Dai Zhiwei, published in 2019 by Soochow University. Research on the preparation and mechanical properties of porous aluminum-based composite materials, or Zhang Jueling, Wang Linshan, Zheng Fengshi, etc., published in Materials Review in 2023. Scanning electron microscope photos of porous aluminum powder at 0MPa pressure. Insufficient pressure cannot break the oxide layer and increase the contact area, resulting in loose particles-particles and particles-substrate. Figure 3As shown in some foreign literature (Nuruzzaman DM, Kamaruzaman FF, Azmi N M. Effect of sintering temperature on the propertiesof aluminium-aluminium oxide composite materials[J]. International Journal ofEngineering Materials and Manufacture, 2016, 1(2): 59-64.), scanning electron microscope photos of porous aluminium powder at 580°C show that when the temperature is too high, the aluminium powder melts and sinters into blocks, and the porous structure collapses.

[0041] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. It should be pointed out that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A method for vacuum pressure sintering porous aluminum powder on an aluminum-based silicon carbide matrix, characterized by: The steps include: Step S1, mechanically grinding the surface of the silicon carbide particle reinforced aluminum matrix composite material to be sintered to break the oxide film coated on the surface of the silicon carbide particle reinforced aluminum matrix composite material to obtain an aluminum-based silicon carbide matrix; Step S2, immersing the aluminum-based silicon carbide substrate in acetone for cleaning to remove grease on the surface of the aluminum-based silicon carbide substrate, first immersing it in 10% NaOH for 3 minutes, and then immersing it in 10% HNO3 for 3-5 minutes to remove the residual oxide film by chemical reaction; Step S3, placing the cleaned aluminum-based silicon carbide substrate into an ultrasonic cleaning machine for 3-5 minutes to clean the surface acid, alkali and SiC particles; Step S4, pouring aluminum powder into a graphite mold and then flattening it to ensure that the aluminum powder is in close contact with the aluminum powder and with the aluminum-based silicon carbide matrix to obtain a sintered assembly consisting of aluminum-based silicon carbide-aluminum powder-graphite grinding tool; In step S5, the sintered assembly consisting of aluminum-based silicon carbide, aluminum powder, and graphite abrasive is placed in a vacuum pressure sintering machine and the program is set to perform pressure sintering. Under the action of high temperature and pressure, the contact surfaces approach each other. After a certain holding time, the aluminum powder atoms gradually diffuse into the aluminum-based silicon carbide to form a reliable connection.

2. The method for vacuum pressure sintering porous aluminum powder on an aluminum-based silicon carbide substrate according to claim 1, characterized in that: Sintering is divided into two processes. The first sintering process is the sintering between aluminum powders; In step 4, the aluminum powder is flattened in the mold to form a spatial stack of aluminum powder and aluminum powder. In step 5, the contact area and pressure between the aluminum powder and the aluminum powder are increased by a preset pressure value, and the thin oxide layer on the surface of the aluminum powder is broken by pressure. The high temperature promotes the movement of aluminum atoms in the oxide layer of the aluminum powder, and the aluminum atoms diffuse through the pressure-broken oxide layer on the surface into other aluminum powder to form an effective sintering connection. The second sintering process is the sintering between aluminum powder and aluminum-based silicon carbide matrix; The aluminum powder is flattened in step 4 and effectively contacts the substrate through pressure in step 5, and the oxide layer on the surface of the aluminum powder is broken. In step 5, the aluminum atoms in the aluminum powder are promoted to diffuse into the substrate through high temperature, and the aluminum atoms and silicon carbide particles in the substrate also float and diffuse into the aluminum powder at the same time, forming an effective sintering connection between the aluminum powder and the aluminum-based silicon carbide substrate.

3. The method for vacuum pressure sintering porous aluminum powder on an aluminum-based silicon carbide substrate according to claim 2, characterized in that: The temperature formula for diffusion in step S5 is T=(0.6-0.8)Tm, where Tm is the lowest melting point of aluminum.

4. The method for vacuum pressure sintering porous aluminum powder on an aluminum-based silicon carbide substrate according to claim 3, characterized in that: In step S1, mechanical polishing is performed using sandpaper with a mesh size of 200-2000, and the oxide film coated on the surface of the silicon carbide particle reinforced aluminum-based composite material is removed using a mixed solution of hydrochloric acid and nitric acid and a sodium hydroxide solution.

5. The method for vacuum pressure sintering porous aluminum powder on an aluminum-based silicon carbide substrate according to claim 4, characterized in that: In step S2, the aluminum-based silicon carbide substrate is immersed in acetone for cleaning, and then ultrasonic cleaning is performed again using an ultrasonic cleaning machine to clean the grease. The ultrasonic cleaning time is 3-5 minutes.

6. The method for vacuum pressure sintering porous aluminum powder on an aluminum-based silicon carbide substrate according to claim 5, characterized in that: The particle size of the aluminum powder in step S4 is 10-100 μm.

7. The method for vacuum pressure sintering porous aluminum powder on an aluminum-based silicon carbide substrate according to claim 6, characterized in that: In step S5, the holding temperature is set at 500-540° C. for 1-2 hours, and the applied pressure is set at 30-50 MPa until the sintered component cools down to room temperature along with the furnace.

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