| 摘要 |
PURPOSE:To make the circumferential portion of an insulating plae thicker than the portion directly under a wiring metallic plate thereof for reducing the tehrmal resistance between a semiconductor element and a metallic fan without affecting dielectric strength. CONSTITUTION:A wiring metallic plate 13 is selver-soldered 12 on an insulating plate 11 of ceramic for example. While the thickness D of the circumferential portion of said insulating plate 11 is kept at a value necessary for obtaining a dielectric strength, that (d) directly under said wiring metallic plate 13 thereof is lessened for lowering thermal resistance thereof. With excessive decrease in said thickness (d), however, the problem of the dielectric breakdown of said insulating plate 11 occurs. In the case of ceramic, therefore, the lower limit of said thickness (d) is 0.3mm when dielectric strength is 2.000VAC. Thereby, dielectric strengrh depends on creeping discharge that considerably depends on said thickness D so that dielectric strength can be increased. On the other hand, heat conducgivity can be radised by lessening said thickness (d). |
