Senju Metal Industry Co., Ltd.

Kabushiki Kaisha Toshiba

Rikiya Katoh

Yoshitaka Toyoda

Toshihiko Taguchi

Osamu Munekata

Takayuki Suzuki

Izuru Komatsu

Masahiro Tadauchi

Kouichi Teshima

Mitsuyoshi Hirayama

Jun Sugimoto

A lead-free solder paste suitable for soldering chip parts includes a powder of a twin-peak Sn-based solder alloy containing 0.2-1.0 mass % of Ag and a flux. The solder alloy has a first peak of heat absorption in a differential scanning calorimeter curve at the start of melting and a second peak when the major portion of the alloy subsequently melts.

Lead-free solder paste

A lead-free solder alloy which has a relatively low melting temperature and which is suitable for soldering electronic devices consists essentially of from 5 to 9 mass % of Zn, from 2 to 15 mass % of Bi, optionally from 0.001 to 1 mass % of P or from 0.001 to 0.1 mass % of Ge, and a balance of Sn. The solder alloy has a liquidus temperature of at most 220&deg; C.

Lead-free solder alloys

Disclosed is a method of joining metallic members together. The metallic members are coated with an undercoat composed of an alloy of tin and zinc and contacted with each other through a mixture containing a solder comprising tin and zinc and a flux, while heating the metallic members to melt the solder. Then the molten solder is solidified to join the metallic members. Here, the ratio of zinc in the undercoat is represented by x (% by weight), the ratio of zinc in the solder is represented by y (% by weight), and the ratio, x, and the ratio, y, are values within an area enclosed by the line A or B in FIG.,which satisfies the formulas: 1&lE;x&lE;20, 3&lE;y&lE;13 and 3&lE;(x&plus;y)/2&lE;13, or formulas: 0.1&lE;x&lE;25, 2&lE;y&lE;15 and 2&lE;(x&plus;y)/2&lE;15.

Method of joining metallic members, and joined metallic members

A solder paste suitable for use in reflow soldering of chip components having good soldering properties without causing tombstoning comprises a solder powder admixed with a viscous flux. The solder powder is comprised of a twin peak solder alloy consisting essentially, on a weight basis, of: 60-65% Sn, 0.1-0.6% Ag, 0.1-2% Sb, and a balance of Pb, and having a liquidus temperature below 200.degree. C.

Solder paste for chip components

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Sohka, Japan

Rikiya Katoh