| 摘要 |
PROBLEM TO BE SOLVED: To obtain a highly reliable circuit board capable of not only significantly reducing occurrence of cracks in solder and a ceramic substrate, but also peeling and break of bonding wires and plated films. SOLUTION: A circuit board is constituted by forming a circuit on one surface of a ceramic substrate and a heat sink on the other surface of the substrate, and the circuit and heat sink are made of Al or an Al alloy and have thicknesses of 100μm or larger and Vickers hardness of 15 kgf/mm2 or smaller. The ceramic substrate is composed of aluminum nitride, and the Al or Al alloy is composed of rolled Al containing 99.99 wt.% Al or higher. In addition, the volumetric ratio of the circuit to the heat sink is adjusted to be in the range of 0.80-1.2.
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