| 摘要 |
PURPOSE:To enhance insulation strength and improve reliability by making it difficult to concentrate electrical field in the periphery of metallized layer. CONSTITUTION:A metallized layer 3 is provided at the center of front and rear surfaces of alumina insulation plate 2 on an insulated substrate 4. Since a circular pattern is used for the layer 3 of substrate 4 in the case of such an insulated power transistor 15, concentration of field is alleviated at the periphery of layer 3 and thereby an insulation strength of substrate 4 is remarkably inproved. It is also possible to employ the structure that a rectangular pattern is employed for the layer 3 and four corners are gradually rounded and thereby concentration of electric field at the corners can be alleviated. Moreover, a polygonal pattern may also be employed for the layer 3. |
