Structural insulating ceramics
Aluminum oxide ceramics, silicon nitride ceramics, zirconia ceramics
The main characteristics of structural insulating ceramics are high mechanical strength, high thermal conductivity, wear resistance, excellent insulation performance at high temperature and high frequency, stable chemical and physical properties, and electrical and physical properties increase with the increase of Al2O3 content. Commonly used are high-alumina ceramics containing 75% (mass percentage, the same below), 96% and 99% Al2O3 (alumina ceramics with an Al2O3 content greater than 75% are collectively called high-alumina porcelain, and those with a content higher than 95% are called corundum porcelain). In some extremely demanding integrated circuits, pure corundum porcelain with an Al2O3 content of 99.9% is also used, and its performance is similar to that of sapphire single crystal. The main crystal phase composition of talc ceramics is MgSiO3, which has the advantages of high mechanical strength, small dielectric loss, and good process performance. It can be used to manufacture most device parts. , A typical high-frequency device porcelain suitable for the radio frequency band. With the development of the electronics industry, especially the increase in the integration and power of thick and thin film hybrid integrated circuits and microwave integrated circuits, higher requirements are placed on the thermal conductivity of ceramics, so ceramics with high thermal conductivity have been developed, such as Beryllium oxide ceramics, boron nitride ceramics, aluminum nitride ceramics, silicon carbide ceramics, etc. The biggest feature of beryllium oxide ceramics is high thermal conductivity, which is close to metal aluminum, and has good dielectric properties. It is a good material for making high-power transistor shells, heat sinks, high-power integrated circuits and microwave integrated circuit substrates. . However, the raw material of beryllium oxide is poisonous, and the firing temperature of porcelain is high, thus limiting its application. Boron nitride ceramics and aluminum nitride ceramics are also high thermal conductivity ceramics. Although its thermal conductivity is not as good as that of beryllium oxide ceramics, it is non-toxic, has good processability and dielectric properties, and can be used for heat dissipation and insulation in high-frequency high-power transistors and hybrid integrated circuits.