SOLDER AND PACKAGING THEREFROM

WIPO Patent Application WO/2004/004967

A1

An unleaded solder that exhibits the same workability, use conditions and bonding reliability as those of the conventional Sn-37 wt.% Pb eutectic solder. In particular, a solder comprising 7 to 10 wt.% of zinc, 0.001 to 6 wt.% of bismuth, 0.001 to 0.1 of silver and the remainder of tin. The solidus temperature thereof is not lower than the melting point of Sn-37 wt.% Pb eutectic solder, and the difference between the liquidus temperature thereof and the melting point of Sn-37 wt.% Pb eutectic solder is about 10 to 20ºC. Therefore, electronic components can be mounted by means of the same reflow furnace as in the use of conventional Sn-37 wt.% Pb eutectic solder. The contained silver increases the tensile strength of solder and inhibits the formation of unfavorable intermetallic compounds. Consequently, a circuit substrate unit of high bonding reliability having a mechanical strength greater than in the use of Sn-37 wt.% Pb eutectic solder can be produced without the need to introduce a new reflow furnace capable of uniform heating over the entire surface of substrate.

FUNAYA TAKUO (JP)
MYOHGA OSAMU (JP)
OKADA YOSHITSUGU (JP)
KUBOTA HIROSHI (JP)
SAKURAI JUNYA (JP)

PCT/JP2003/008361

January 15, 2004

July 01, 2003

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NEC CORP (JP)
FUNAYA TAKUO (JP)
MYOHGA OSAMU (JP)
OKADA YOSHITSUGU (JP)
KUBOTA HIROSHI (JP)
SAKURAI JUNYA (JP)

B23K35/22; B23K35/26; C22C13/00; H05K3/34; (IPC1-7): B23K35/26

JPH09277082A	1997-10-28
JPH0994687A	1997-04-08
EP1196015A1	2002-04-10
JP2002224880A	2002-08-13

Amano, Hiroshi (40-4 Shiba 3-chom, Minato-ku Tokyo, JP)

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