Making of varistor from thick film

Abstract

Abstract PURPOSE:To provide a varistor for thick film integrated circuit with a high load capacity and a good stability, by dissolving a metal oxide in an acid and then dropping a base into the solution to produce a deposit and making varistor powder from the deposit and binding the varistor powder with glass. CONSTITUTION:A simple or doped metal oxide, for example, zinc oxide is dissolved in an appropriate amount of formic acid etc. A base is dropped into the solution while the solution is stirred. Thereby, a deposit is produced. The deposit is washed in water and then dried. Thereafter, the deposit is treated with heat at a temperature of 300 deg.C so that the varistor powder is produced. For instance, 60 % by weight of the varistor powder is mixed with 40 % by weight of glass powder. A vehicle is added to the mixture to make this mixture like paste. The paste-like mixture is printed on a heat-resisting insulator substrate and then baked at a temperature of 650 to 900 deg.C, thereby making a thick-film varistor. Because the varistor has no acute angles due to crushing, the form of the boundary layer (glass layer) between the varistor powder granis is stabilized and the surge resistance and the load capacity are raised. A desired grain size of varistor powder can be obtained by setting depositing conditions.

Inventors

• 👤 Masaru Oda

Bibliographic Details