Insulating ceramics are also called device ceramics. Used as various insulators, insulating structural parts, band switches and capacitor support supports, electronic component packaging shells, integrated circuit substrates and packaging shells, etc. The basic requirements for insulating ceramics are small dielectric constant, low dielectric loss, high insulation resistivity, high electric strength, high mechanical strength, good thermal shock resistance, high thermal conductivity and good temperature, humidity and frequency. stability etc. In addition, high-voltage electrical ceramics used in high-voltage electrical equipment also belong to insulating ceramics. Commonly used insulating ceramics are alumina ceramics, steatite ceramics, mullite ceramics, cordierite ceramics, forsterite ceramics, etc. Among them, alumina ceramics and steatite ceramics are the most widely used. Alumina ceramics are a kind of high-frequency, high-temperature, high-strength device ceramics with good electrical insulation properties. The main features 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.