| 摘要 |
PROBLEM TO BE SOLVED: To enhance reliability by arranging a metal circuit specifically with respect to the fringe of a ceramic substrate and specifying the ratio of circumferential fringe length on the plane of the metal circuit thereby reducing crack without sacrifice of heat dissipation properties and dielectric breakdown strength of the circuit board. SOLUTION: A point B on the fringe of a ceramic substrate closest to an arbitrary point A on the fringe of a metal circuit plane is determined and a tangent L1 to the fringe of the metal circuit plane is drawn at the point A. A tangent L2 and a normal L3 to the fringe of the seramic circuit board are drawn at the point B. Smaller oneθof the angles formed by the line L1 and the lines L2, L3 is then determined. Subsequently, the total circumferential length d on the fringe of the metal circuit plane is determined for the angleθin the range of 10-45 deg.. Overall circumferential length D on the fringe of the metal circuit plane is also determined and the ratio R (%) of the overall length D to the total length d is determined according to a formula R=d/D×100. A circuit board for module is constituted by setting the R at 30% or above.
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