| 摘要 |
PROBLEM TO BE SOLVED: To provide an insulating substrate whose withstand voltage is high and whose reliability is high. SOLUTION: An insulating substrate 1 is provided with plural overlapped insulating ceramics layers 2a and 2b, intermediate layer 4 made of materials other than those of the insulating ceramics layers 2a and 2b which is arranged between the upper and lower insulating ceramics layers 2a and 2b, so that the insulating ceramics layers 2a and 2b can be jointed with each other, and conductive layers 5 and 6 respectively arranged on the surface of the insulating ceramics layer 2a in the uppermost stage and the back face of the insulating ceramics layer 2b in the lowermost stage. When the ceramics layers 2 and 2b whose strength is below designed strength are present, the insulating ceramics layers 2a and 2b are damaged, and electric breakdown is generated due to thermal stress, the other insulating ceramics layers 2a and 2b are sound. Thus, the problem of a withstand voltage cannot be generated in the insulating substrate 1. |
