Electronic Ceramic Insulation Device

Electronic ceramic insulation device

Referred to as device porcelain, it has excellent electrical insulation properties and is used as electronic ceramics for structural parts, substrates and casings in electronic equipment and devices. Insulation device porcelain includes various insulators, coil frames, tube holders, band switches, capacitor support brackets, integrated circuit substrates and packaging shells. The basic requirements for this type of porcelain are low dielectric constant ε, small dielectric loss tanδ, high insulation resistivity ρ, high breakdown strength E, and good dielectric temperature characteristics and frequency characteristics. In addition, higher mechanical strength and chemical stability are also required.

Among these types of ceramics, talc porcelain and alumina porcelain are the most widely used. Their main crystalline phase components are and respectively. Talc porcelain has excellent electrical insulation and low cost, and is a typical high-frequency device porcelain used in radio frequency bands. Alumina porcelain is a kind of high-frequency, high-temperature and high-strength device porcelain with better electrical insulation. Its electrical and physical properties increase with the increase of aluminum oxide content. Commonly used are high alumina porcelain containing 75%, 95%, and 99% alumina. In some highly demanding integrated circuits, even pure corundum porcelain with an aluminum oxide content of 99.9% is used, whose properties are similar to sapphire single crystals. The disadvantages of high alumina porcelain, especially pure corundum porcelain, are difficulty in manufacturing, high firing temperature and high price.

There is also a type of high thermal conductivity porcelain represented by beryllium oxide (BeO) in the device porcelain. The room temperature thermal conductivity of beryllium oxide porcelain containing BeO95% is the same as that of metal. Beryllium oxide also has good dielectric properties, temperature resistance and high mechanical strength. The disadvantage is that the raw material of BeO is very toxic, and the ceramic material has a high firing temperature, which limits its application. Boron nitride (BN) porcelain and aluminum nitride (AlN) porcelain are also high thermal conductivity porcelains. Although their thermal conductivity is not as good as that of beryllium oxide porcelain, they are non-toxic, processability and dielectric properties are good, and can be used for high-frequency and high-power transistors. Used for heat dissipation and insulation in large-scale integrated circuits.

Developed a kind of hot-pressed ceramics with SiC as the base material and doped with a small amount of BeO and other impurities. This kind of ceramic has excellent insulation properties, and its thermal conductivity is higher than that of beryllium oxide porcelain with a purity of 99%. Its thermal expansion coefficient is close to that of silicon single crystals in a wide temperature range, and is expected to be used in large-scale integrated circuits with large power dissipation.

Low-alkali feldspar porcelain, which is used as the matrix of carbon film and metal film resistors, is also an important and inexpensive device porcelain, but its dielectric loss is large and it is not suitable for use at high frequencies.