Aluminum nitride (AlN) is a kind of integrated high performance new ceramic material, has excellent thermal conductivity, a reliable electrical insulation, low dielectric constant and dielectric loss, non-toxic and matching with the silicon thermal expansion coefficient, and a series of excellent features. And it is considered as a new generation of high degree of the semiconductor substrate and the ideal materials of the electronics packaging , and has received wide attention by the researchers at home and abroad. In theory, the thermal conductivity of AlN is 320 W/(m), actual thermal conductivity of industrial preparation of polycrystalline aluminum nitride can be up to 100 ~ 250 W/(m), the numerical value is 5 ~ 10 times to a traditional alumina substrate, close to the thermal conductivity of beryllium oxide, but because of the high toxic, beryllium oxide was gradually stopped to be used in the industrial production. Compared with several other ceramic materials, comprehensive performance of aluminum nitride ceramic is good, very suitable for the semiconductor substrate and structural packaging material with an enormous application potentiality in the electronic industry.

　　High resistivity, high heat conductivity and low dielectric constant are the most basic requirements of substrate in integrated circuit for packages. Encapsulation should match well with silicon substrate with good thermal matching, easy to be formed, high surface smoothness, easy to be metalized , easy processed characteristics and certain mechanical properties and low cost, etc. Most ceramics is ionic bond and covalent bond strong material, has excellent comprehensive performance and is commonly used in electronic packaging substrate materials, has high insulation performance and excellent high frequency characteristics. At the same time, linear expansion coefficient and electronic components are very similar with stable chemical performance and high thermal conductivity. For a long time period, most of the high power hybrid integrated circuit substrate material used A1203 and BeO ceramic, but A1203 substrate has the characteristics of low thermal conductivity and thermal expansion coefficient and Si mismatching; BeO, although it has excellent comprehensive performances, its high production cost and virulent disadvantage limit its application. Therefore, from the factors such as performance, cost and environmental protection, both of them can not fully meet the needs of the development of modern power electronic devices.

　　Electronic thin film material is the basis of microelectronics technology and electronic technology, thus the study of all kinds of new electronic thin film materials is becoming a hot attention spot to many researchers. AlN, found in the 1860 s, can be used as electronic thin film materials, and has wide application. In recent years, wide bandgap semiconductor material and the electronic devices represented by Ⅲ A family of nitrides have a fast development, known as third generation of semiconductor after the first generation represented by Si semiconductor and the second generation represented by GaAs semiconductor. A1N as typical Ⅲ A family of nitride obtained more and more the attentions of the researchers at home and abroad. At present, countries compete to invest a lot of manpower and material resources to study AlN thin films. Because the A1N has many excellent properties including wide band gap, strong polarization, 6.2 eV forbidden band width to make it have a broad application prospect in the machinery, microelectronics, optical, and electronic components, surface acoustic wave (SAW) device manufacture, high frequency broadband communications and power semiconductor devices and other fields. A variety of excellent properties of AlN determine its various applications, as piezoelectric thin film, has been widely used. As electronic devices and integrated circuit encapsulation, dielectric isolation and insulation material, it has important application prospect; as the blue light, ultraviolet light-emitting material, it is current research hotspot.

　　In order to improve the current brittleness of ceramic material, many researches have been conducted. Among them by adding the second phase, the third phase particles to form duplex ceramic toughness of ceramic materials has become the baby means. This method, compared with adding whisker, fiber and other methods, has the characteristics of low cost, easy preparation ,and etc. Silicon carbide materials by Ding Jigao hardness, high strength, wear resistance, corrosion resistance, small density and other excellent properties has won a large number of applications in machinery, chemical industry, energy and military industry. But due to its low room temperature strength and insufficient toughness, its applications have the limitations to certain extend. In order to improve the strength and toughness of silicon carbide ceramic materials, the adding methods according to the theory of metal dispersion strengthened by the second phase particles have made some achievements such as SiC/TiC, SiC/A1203 and SiC/TlB, etc.

　　Aluminum nitride (AlN) with high thermal conductivity, 320 W/(m K) in theory, the actual value can be up to 260 W/(m K), 10 ~ 15 times of alumina ceramics, With so many superior performances, such as the relative low dielectric constant (about 8.8) and reliable electrical insulation resistivity (> 1016 q m. - 1), high temperature resistance, corrosion resistance, non-toxic, good mechanical properties and thermal expansion coefficient of matching with the silicon (20 ℃ ~ 500 ℃, 4.6 x 10-6 K - 1) and etc., AlN has been used in more and more high technology fields, which in many cases require AlN for abnormity and micro parts, but the traditional mold and isostatic pressing process cannot be prepared for complex shapes of ceramic parts, plus the AlN ceramic material inherent low resilience and brittleness and processing difficulties make traditional machining method difficult to prepare the AlN ceramic parts of complex shapes. In order to give full play to the performance advantages of AlN and broaden its application scope, problems settlement of the complex shape of AlN ceramic forming technology is one of crucial nodes.

　　Selected from the "The Research And Application Development of Aluminum Nitride Ceramic" Author：Hu Youjing， Yan Xiaoyan

Aluminum nitride (AlN) is a kind of integrated high performance new ceramic material, has excellent thermal conductivity, a reliable electrical insulation, low dielectric constant and dielectric loss, non-toxic and matching with the silicon thermal expansion coefficient, and a series of excellent features. And it is considered as a new generation of high degree of the semiconductor substrate and the ideal materials of the electronics packaging , and has received wide attention by the researchers at home and abroad. In theory, the thermal conductivity of AlN is 320 W/(m), actual thermal conductivity of industrial preparation of polycrystalline aluminum nitride can be up to 100 ~ 250 W/(m), the numerical value is 5 ~ 10 times to a traditional alumina substrate, close to the thermal conductivity of beryllium oxide, but because of the high toxic, beryllium oxide was gradually stopped to be used in the industrial production. Compared with several other ceramic materials, comprehensive performance of aluminum nitride ceramic is good, very suitable for the semiconductor substrate and structural packaging material with an enormous application potentiality in the electronic industry.

　　High resistivity, high heat conductivity and low dielectric constant are the most basic requirements of substrate in integrated circuit for packages. Encapsulation should match well with silicon substrate with good thermal matching, easy to be formed, high surface smoothness, easy to be metalized , easy processed characteristics and certain mechanical properties and low cost, etc. Most ceramics is ionic bond and covalent bond strong material, has excellent comprehensive performance and is commonly used in electronic packaging substrate materials, has high insulation performance and excellent high frequency characteristics. At the same time, linear expansion coefficient and electronic components are very similar with stable chemical performance and high thermal conductivity. For a long time period, most of the high power hybrid integrated circuit substrate material used A1203 and BeO ceramic, but A1203 substrate has the characteristics of low thermal conductivity and thermal expansion coefficient and Si mismatching; BeO, although it has excellent comprehensive performances, its high production cost and virulent disadvantage limit its application. Therefore, from the factors such as performance, cost and environmental protection, both of them can not fully meet the needs of the development of modern power electronic devices.

　　Electronic thin film material is the basis of microelectronics technology and electronic technology, thus the study of all kinds of new electronic thin film materials is becoming a hot attention spot to many researchers. AlN, found in the 1860 s, can be used as electronic thin film materials, and has wide application. In recent years, wide bandgap semiconductor material and the electronic devices represented by Ⅲ A family of nitrides have a fast development, known as third generation of semiconductor after the first generation represented by Si semiconductor and the second generation represented by GaAs semiconductor. A1N as typical Ⅲ A family of nitride obtained more and more the attentions of the researchers at home and abroad. At present, countries compete to invest a lot of manpower and material resources to study AlN thin films. Because the A1N has many excellent properties including wide band gap, strong polarization, 6.2 eV forbidden band width to make it have a broad application prospect in the machinery, microelectronics, optical, and electronic components, surface acoustic wave (SAW) device manufacture, high frequency broadband communications and power semiconductor devices and other fields. A variety of excellent properties of AlN determine its various applications, as piezoelectric thin film, has been widely used. As electronic devices and integrated circuit encapsulation, dielectric isolation and insulation material, it has important application prospect; as the blue light, ultraviolet light-emitting material, it is current research hotspot.

　　In order to improve the current brittleness of ceramic material, many researches have been conducted. Among them by adding the second phase, the third phase particles to form duplex ceramic toughness of ceramic materials has become the baby means. This method, compared with adding whisker, fiber and other methods, has the characteristics of low cost, easy preparation ,and etc. Silicon carbide materials by Ding Jigao hardness, high strength, wear resistance, corrosion resistance, small density and other excellent properties has won a large number of applications in machinery, chemical industry, energy and military industry. But due to its low room temperature strength and insufficient toughness, its applications have the limitations to certain extend. In order to improve the strength and toughness of silicon carbide ceramic materials, the adding methods according to the theory of metal dispersion strengthened by the second phase particles have made some achievements such as SiC/TiC, SiC/A1203 and SiC/TlB, etc.

　　Aluminum nitride (AlN) with high thermal conductivity, 320 W/(m K) in theory, the actual value can be up to 260 W/(m K), 10 ~ 15 times of alumina ceramics, With so many superior performances, such as the relative low dielectric constant (about 8.8) and reliable electrical insulation resistivity (> 1016 q m. - 1), high temperature resistance, corrosion resistance, non-toxic, good mechanical properties and thermal expansion coefficient of matching with the silicon (20 ℃ ~ 500 ℃, 4.6 x 10-6 K - 1) and etc., AlN has been used in more and more high technology fields, which in many cases require AlN for abnormity and micro parts, but the traditional mold and isostatic pressing process cannot be prepared for complex shapes of ceramic parts, plus the AlN ceramic material inherent low resilience and brittleness and processing difficulties make traditional machining method difficult to prepare the AlN ceramic parts of complex shapes. In order to give full play to the performance advantages of AlN and broaden its application scope, problems settlement of the complex shape of AlN ceramic forming technology is one of crucial nodes.

　　Selected from the "The Research And Application Development of Aluminum Nitride Ceramic" Author：Hu Youjing， Yan Xiaoyan