MANUFACTURE OF VOLTAGE DEPENDENT NONLINEAR RESISTOR

PURPOSE:To stabilize insulation resistance and varistor voltage, and to increase lighting surge resistance by calcining a mixture onto the side face of an element assembly and applying a mixture for a side-face high resistance layer prepared through crushing. CONSTITUTION:A zinc oxide raw material and a fixed quantity of an additive such as Bi2O3, Co3O4, etc., are mixed. The mixture is granulated, molded in a predetermined shape, and decreased, and a molded form is temporarily calcined. Fixed quantities of a bismuth compound, an antimony compound and a silicon compound are mixed and calcined onto the side face of a calcined body and crushed, and coated with mixture paste for a side-face high resistance layer, to which ethyl cellulose, butyl carbitol, n butyl acetate, etc., are added as an organic binder, in thickness of 60-300mum. The temperature of the crushed calcined body is increased up to 1100-1250 deg.C at a temperature elevating rate 40-60 deg.C/hr, held for three or seven hr, and cooled at a temperature lowering rate of 30-200 deg.C/hr up to 800 deg.C. Accordingly, the hygroscopicity of a side-face high resistance layer is improved, varistor voltage and insulation resistance are stabilized, lightening surge resistance is increased, and a change with time of an element is also enhanced.