| 摘要 |
<p>PROBLEM TO BE SOLVED: To improve solderability by suppressing adhesion of silicon compound on electrodes on the outer surface of a varistor by blending the varistor device mainly containing zinc oxide and having electrodes on its outer surface and silicon powder and by heat-treating the blend in a gas flow. SOLUTION: A varistor device 2 and SiO2 powder as Si powder are put into a cylindrical alumina porcelain container 1 having gas ventilating openings, are blended and are heat-treated at 900 deg.C for 2 hours. After forming specimens by a gas flow, the varistor device 2 and the Si powder 3 are separated and the varistor device 2 is barrel polished by using SiC and Zr balls. After that, the varistor device 2 is coated with electrolytic Ni plating and electrolytic solder plating in sequence. When the gas flow is performed during the heat treatment operation at a flow speed of 5 mm/min. or higher, forming of Bi atmosphere is suppressed, grain boundary of the varistor is prevented from being reduced and solderability failures can be reduced.</p> |
