| 摘要 |
PROBLEM TO BE SOLVED: To provide a compatibility between insulation of an insulating layer formed on the upper layer of a ceramic circuit board and solder wettability of a conductive layer for connection formed on the top of the insulating layer. SOLUTION: A ceramic circuit board is comprised of an upper-layer conductive layer 22 (upper layer resistor layer 23), a conductive layer 26 for connection and a double-layer insulating layer between them. An upper insulating layer 25 of the double-layer insulating layer is formed of glass ceramic, containing a relatively small amount of glass and exhibiting low density. A lower insulating layer 25 is formed of a glass ceramic, containing a relatively large amount of glass and exhibiting a high density. Since the upper insulating layer 25 is formed of the glass ceramic containing a relatively small amount of glass and exhibiting a low density, glass components diffusing from the upper insulating layer 25 to the conductive layer 26 for connection are few and the surface of the conductive layer 26 for connection does not becomes rich in glass. Its solderability can be maintained in a high level. If a lower insulating layer 24 is formed of a glass ceramic exhibiting high density, necessary level of insulation can be ensured without increasing the thickness of the insulating layers 24 and 25.
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