| 摘要 |
PROBLEM TO BE SOLVED: To improve the reliability of a circuit board by using metallic plates respectively composed of plural layers including Al and Cu layers for metallic circuits and metallic heat sinks, and bonding the Al layer to an aluminum nitride substrate with an Al-Si-Mg or Al-Cu-Mg bonding material. SOLUTION: A circuit board is formed in such a way that metallic plates are laid on both the front and rear surfaces of an aluminum nitride substrate and bonded to the substrate, by evenly perpendicularly pressing the metallic plates against the substrate at a temperature of 550-635 deg.C in a vacuum atmosphere by using a jig which presses the metallic plates against the substrate by thrusting carbon plates into the substrate. Then an etching resist is screen- printed and etching is performed with an FeCl3 solution. In addition, the resist is removed and electroless Ni-P plating is performed to the thickness of 3μm. The circuit board thus formed has metallic heat sinks using metallic plates each composed of two or more layers including Al and Cu layers. The Al layer is bonded to the aluminum nitride substrate by using an Al-Si-Mg bonding material, etc.
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