| 摘要 |
PROBLEM TO BE SOLVED: To provide a highly reliable circuit board which has little in warpage after heat history and moreover is superior in heat cycle. SOLUTION: This circuit board in which the thickness of an Ag layer where solids are diffused to the side of a radiation copper plate is 10μm or thicker than that on the side of a copper circuit, in one where a copper circuit is joined to one side of a ceramic board and a radiation copper plate is jointed to the other side, using solder materials including Ag components and active metallic components, respectively. The copper circuit is made on one side of the ceramic board, and the radiation copper plate on the other side, and the volume rate of the radiation copper plate to the copper circuit is 30-90%, and moreover the planarity in compliance with JIS B0621 after conducting five times of furnace passage test in which 350 deg.C×5 minutes and 25 deg.C×five minutes constitutes a cycle in air.
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