Nippon Metal Industry Co., Ltd.

Hirotaka Tanaka

Masaaki Yoshikawa

Haruo Aoyama

An Sn&#x2014;Zn lead-free solder alloy according to the present invention is constructed in a manner such that it is an Sn-based solder alloy indispensably containing 6 to 10 wt % zinc at least, and further containing 0.0015 to 0.1 wt % magnesium, said magnesium content being effective quantity for forming a protective magnesium oxide film on the solder surface and also for destroying said oxide film during soldering. When solder paste is preserved, the inside of solder particle is protected by the protective magnesium oxide film formed on the surface of solder particle, and a reaction between zinc and an activator is suppressed, so that preservation stability is improved, and at elevated temperature during soldering, a state where said protective oxide film is easily destroyed is obtained, so that good wettability is held.

Sn&#x2014;Zn lead-free solder alloy, its mixture, and soldered bond

An Sn&#x2014;Zn lead-free solder alloy according to the present invention is constructed in a manner such that it is an Sn-based solder alloy indispensably containing 6 to 10 wt % zinc at least and further containing 0.0015 to 0.03 wt % magnesium and 0.0010 to 0.006 wt % aluminum. Upon preservation of solder paste not only under refrigeration but also at a room temperature or higher, the inside of solder particle is protected by the protective magnesium/aluminum oxide film formed on the solder particle surface, and a reaction between zinc and an activator is suppressed, so that preservation stability is improved, and at the elevated temperature during soldering, the solder alloy enters a state where said protective oxide film is easily destroyed, so that good wettability is held.

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Sagamihara, Japan

Hirotaka Tanaka