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AssigneeHitachi, Ltd.
InventorsMasahide Harada, Akihiro Ando, Ryohei Satoh, Akira Yabushita, Naoya Kanda, Kazuhiko Horikoshi
Estimating the term…
A solder bonding metal layer which is formed on a circuit board comprises a metal layer having a mixture of first metal which is easily wetted with metals constituting the solder and which easily forms alloy or intermetallic compounds and of second metal which is not wetted easily with the above solder and not melted. In this case, a concentration gradient that the concentration of the first metal is high on the bonding surface may be formed in the metal layer. A circuit board having a solder bonding metal layer which keeps good bonding even after many times of repairs and improves the reliability is realized.
A circuit board for mounting an electronic part by solder bonding which comprises a substrate and a solder bonding metal layer formed on said substrate, said solder bonding metal layer comprising a mixture of first metal which is easily wetted with metals constituting a solder to be bonded to said solder bonding metal layer and which easily forms alloy or intermetallic compounds with the metals constituting the solder and of second metal which is not wetted easily with said metals constituting the solder and which is not melted during solder bonding wherein a concentration gradient exists in said solder bonding metal layer so that the concentration of said first metal constituting the solder bonding metal layer is higher than the second metal on a surface of the solder bonding metal layer.
Dependencies are inferred from the claim text.