| 摘要 |
PROBLEM TO BE SOLVED: To provide a silicon nitride-based circuit board which is excellent in both of thermal conductivity and strength and is excellent in productivity without requiring a special sintering operation. SOLUTION: This circuit board is formed by disposing a metallic circuit board via a joint layer on a silicon nitride sintered compact. This silicon nitride sintered compact contains an Ma component and/or Ca component at <=7.0wt.% in total in terms of oxide. More particularly, the number of the grain boundaries observed at the polished surface of the silicon nitride sintered compact is <=10 pieces per 10μm length of the straight line drawn in an arbitrary direction on the polished surface. Further, the Al of the impurities included in the silicon nitride sintered compact is <=0.25wt.% in terms of metal and F is <=0.3wt.% in terms of metal. |
