| 摘要 |
A circuit board including a plurality of substrates fixed on a main substrate with solder, wherein the plurality of substrates include a substrate having a smaller thermal expansion coefficient than the main substrate, and wherein the plurality of substrates are made by bonding together a ceramic substrate and a substrate having a higher strength than the ceramic substrate, with the higher-strength substrate bonded to the main substrate side of the ceramic substrate. Since a substrate having a higher strength than a ceramic substrate is bonded to the main substrate side of the ceramic substrate, it is possible to reduce the thermal stress applied to the ceramic substrate side of the circuit board so as to prevent cracking in the ceramic substrate, thus improving the reliability of the circuit board against a thermal stress.
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