Hitachi, Ltd.

Masahiro Gooda

Tasao Soga

Fumiyuki Kobayashi

Masahiro Okamura

Takaya Suzuki

Tadao Kushima

Toshitaka Yamamoto

A method of forming a number of discrete solder layers on a semiconductor wafer of a large area. A number of regions which are easy to be wetted with solder are formed on one of the major surfaces of the wafer. A solder foil is positioned on the one major surface and a plate-like jig including a plate and projections formed on one surface thereof is disposed on the solder foil with the projections facing the latter. By heating the stacked assembly at a sufficiently high temperature for the solder foil to be molten, a number of the discrete solder layers having a uniform thickness are formed on the semiconductor wafer.

Method of forming a number of solder layers on a semiconductor wafer

This invention provides a thermal fatigue resistant, low-melting point solder alloy consisting of 13 to 20% by weight Bi, 42 to 50% by weight, Pb, the balance being Sn. This solder alloy is suited for lap joints of electronic parts into or onto a printed substrate or a hybrid substrate.

Thermal fatigue resistant low-melting point solder alloys

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Hitachi, Japan

Masahiro Gooda