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Method for preparing aluminum nitride ceramic powder

wallpapers Tech 2021-01-14
Aluminum nitride (AlN) is a hexagonal crystal, pure AlN is blue-white, usually gray or off-white. As a new ceramic material with excellent comprehensive performance, aluminum nitride ceramics have excellent thermal conductivity, reliable electrical insulation, low dielectric constant and dielectric loss, non-toxic and thermal expansion coefficient matching silicon, etc. Excellent characteristics, considered to be an ideal material for a new generation of highly integrated semiconductor substrates and electronic device packaging
Preparation method of aluminum nitride ceramic
The preparation process is basically similar to other ceramic materials. There are 3 preparation processes: powder synthesis, molding, and sintering.
1. Preparation of AlN powder
Aluminum nitride powder is used as the raw material to prepare the final ceramic product. Its purity, particle size, oxygen content and other impurity content have an important impact on the thermal conductivity, subsequent sintering, and molding process of the subsequent product. It is the performance of the final product. cornerstone. The synthesis methods of aluminum nitride powder are as follows:
①Direct nitriding method: In a high temperature nitrogen atmosphere, aluminum powder is directly combined with nitrogen to produce aluminum nitride powder. The reaction temperature is generally 800°C to 1200°C.
②Carbothermal reduction method: The mixed powder of alumina powder and carbon powder undergoes reduction and nitridation reaction in flowing nitrogen at high temperature (1400℃~1800℃) to produce AlN powder.
③Self-propagating high-temperature synthesis method: This method is the direct nitridation of aluminum powder, which makes full use of the characteristics of direct nitridation of aluminum powder as a strongly exothermic reaction. The aluminum powder is placed in the middle of nitrogen and then the high temperature between aluminum and nitrogen is used. The heat of the chemical reaction sustains the reaction on its own and synthesizes AlN.
④Chemical vapor deposition method: Use aluminum volatile compounds to react with nitrogen or ammonia to precipitate aluminum nitride powder from the gas phase; depending on the choice of aluminum source, it is divided into inorganic (aluminum halide) and organic (aluminum alkyl) ) Chemical vapor deposition method.
2. AlN molding process
There are many molding processes for aluminum nitride powder, and traditional molding processes such as molding, hot pressing, and isostatic pressing are all applicable. Due to the strong hydrophilicity of aluminum nitride powder, in order to reduce the oxidation of aluminum nitride, contact with water should be avoided as much as possible during the molding process. In addition, although hot pressing and isostatic pressing are suitable for preparing high-performance bulk aluminum nitride ceramic materials, their high cost and low production efficiency cannot meet the increasing demand of the electronics industry for the amount of aluminum nitride ceramic substrates. In order to solve this problem, in recent years, people have adopted the casting method to form aluminum nitride ceramic substrates. The tape casting method has also become the main basic molding process for aluminum nitride ceramics used in the electronics industry.

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