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A soft solder of Pb alloy for semiconductor devices that contains 1 to 65 wt % of Sn or In or both, the balance being Pb and incidental impurities which include less than 50 ppb of radioisotopes and the count of radioactive alpha-particles being not more than 0.5 CPH/cm.sup.2. The solder exhibits high adhesive strength and good wettability. The properties of this material may be further improved by addition of 1 to 10 wt % of Ag.

Inventors: Naoyuki Hosoda, Naoki Uchiyama, Ryusuke Kawanaka
Original Assignees: Mitsubishi Kinzoku Kabushiki Kaisha, Mitsubishi Denki Kabushiki Kaisha
Current U.S. Classification: 420/563; 257/E21.505; 257/E23.023; 420/1; 420/557; 420/558; 420/566; 420/570
International Classification: B32D 1502

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Citations

Cited PatentFiling dateIssue dateOriginal AssigneeTitle
US2711484Jun 21, 1955PREPARATION OF RADIOACTIVE OBJECTS
US2811721Dec 15, 1954Oct 29, 1957 FRITTS ETAL
US2883330May 26, 19551959LIQUID METAL COMPOSITIONS CONTAINING
US4396677Mar 11, 1981Aug 2, 1983Metal, carbon, carbide and other composites thereof

Referenced by

Citing PatentFiling dateIssue dateOriginal AssigneeTitle
US4654275Nov 27, 1985Mar 31, 1987Allied CorporationStorage life of Pb-In-Ag solder foil by Sn addition
US5011658May 31, 1989Apr 30, 1991International Business Machines CorporationCopper doped low melt solder for component assembly and rework
US5051316May 24, 1990Sep 24, 1991Taiho Kogyo Co., Ltd.Overlay alloy or plain bearing
US5066614Sep 28, 1990Nov 19, 1991Honeywell Inc.Method of manufacturing a leadframe having conductive elements preformed with solder bumps
US5161729Jul 11, 1991Nov 10, 1992Honeywell Inc.Package to semiconductor chip active interconnect site method
USRE33313Sep 12, 1989Aug 28, 1990Cominco Ltd.Method for making low alpha count lead

Claims

1. A soft solder of Pb alloy for semiconductor devices that contains 1 to 65 wt% of Sn or In or both, the balance being Pb and incidental impurities which include less than 50 ppb of radioisotopes and the count of radioactive alpha-particles being not more than 0.5 CPH/cm.sup.2.

2. A soft solder of Pb alloy for semiconductor devices that contains 1 to 65 wt% of Sn or In or both and 1 to 10 wt% of Ag, the balance being Pb and incidental impurities which include less than 50 ppb of radioisotopes and the count of radioactive alpha-particles being not more than 0.5 CPH/cm.sup.2.

Drawings