Because of the special structure, metal matrix composite has great advantage in heat transfer performance. Among them, diamond / aluminum composite has become a hot research and development direction in the field of thermal management due to its advantages of low density, high heat conduction and adjustable thermal expansion coefficient. For example, as a heat management material with excellent thermal conductivity, it can coordinate the increasing power density and the temperature difference between the surrounding environment, realize high-efficiency heat dissipation and reduce the target which does not match the thermal expansion coefficient of chip materials To improve the stability and reliability of the system.
The thermal conductivity of diamond / aluminum composite depends on the preparation process to a large extent. Therefore, the composite process is very important in the material research. There are many kinds of preparation methods of metal matrix composites. With the progress of technology and equipment, more and more new methods and new processes have been gradually derived. At present, the main methods of diamond / aluminum composite materials are non pressure infiltration, vacuum pressure infiltration and extrusion casting, discharge plasma sintering, vacuum hot pressing sintering, etc.
1. No pressure infiltration
The preparation process of non pressure infiltration was proposed by LANXIDE company in 1989 based on the direct metal oxidation process. The main process is to first make the reinforced powder into preform by adhesive or pre sintering, and then place the base metal in the upper part or lower part of the reinforcement, and heat it under the atmosphere to make the metal melt into the gap of the preform spontaneously. The most important process is to make the metal melt into the gap of the preform automatically After cooling and solidification. The non pressure infiltration method can realize the low cost preparation of composite materials with large plane size and complex surface shape, which is suitable for mass production. However, the key to limit the performance of the process is density generation. Therefore, the properties of the composites prepared without pressure infiltration are very sensitive to the preparation process parameters. At the same time, the higher preparation temperature also makes it difficult to control the interface reaction between diamond and aluminum matrix Degree.
2. Vacuum pressure infiltration
Vacuum pressure infiltration is to put the preform in the mold, use vacuum to remove the gas in the preform, and then inject inert gas into the melting furnace according to a certain pressure, squeeze liquid metal into the mold cavity, infiltrate the pore of the preform, and obtain the composite blank. The process has no limitation on the types, forms and alloy types of the reinforcing phase. The net forming of the material can be realized by die design, and the insufficient and density problems without pressure infiltration are overcome, and the casting defects are few.
3. Squeeze casting
Extrusion casting is a method of using external pressure to infiltrate liquid or semi liquid metal matrix into the preform with reinforced phase, and solidify to obtain composite materials. The process has no limit on the shape, type and composition of the matrix alloy, so it can be used in the composition design in a wide range. Because the composite is solidified under high pressure, the requirement of alloy wettability is reduced, and the defects of casting structure are also less.
4. Plasma sintering by discharge
The technology of spark plasma sintering, also known as "plasma activated sintering", originated from the "pulse sintering technology" introduced in the United States in 1930s. Later, Japan developed a more advanced EDM sintering based on this technology and obtained corresponding patents, but it was not widely used because of its low production efficiency; until 1988, Japan first developed the technology The first SPS equipment with a maximum sintering pressure of 5 tons has been popularized in the field of new materials research. The process is that the direct current can produce Joule heat in a moment by pre loading the metal and ceramic particles in the mold. It has the advantages of uniform heating, high heating rate, low sintering temperature, short sintering time and high production efficiency. The density, microstructure defects (such as particle damage, impurities) and interface bonding state of diamond / aluminum composites prepared by SPS are the key factors affecting their thermal conductivity.
SPS equipment developed and produced by Shanghai Haoyue
5. Vacuum hot pressing sintering
Vacuum hot pressing sintering is a traditional powder metallurgy method to prepare metal matrix composites. Its preparation process mainly includes screening, mixing, cold pressing consolidation, degassing, hot pressing sintering, and then pressing to obtain aluminum matrix composites. The results show that the composite obtained by vacuum hot pressing sintering technology has micron scale diffusion bonding interface, which is conducive to the improvement of thermal conductivity.
Vacuum hot press furnace developed and produced by Haoyue in Shanghai
Haoyue technology is a high-tech enterprise integrating R & D, production and sales of electric furnace. The company has been focusing on the four fields of semiconductor materials, carbon materials, advanced ceramics and composite materials and lithium battery materials, with rich industry experience and professional technology, dedicated to serving customers and providing perfect integrated industrial solutions.
