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Author Vianco, P. T.
Sponsorship US Department of Energy (US)
Source United States Department of Energy Office of Scientific and Technical Information
Content type Text
File Format PDF
Language English
Subject Keyword MATERIALS SCIENCE ♦ METALLURGICAL FLUX ♦ IMPURITIES ♦ SOLDERING ♦ TRACE AMOUNTS ♦ POLLUTION SOURCES ♦ TIN BASE ALLOYS ♦ LEAD ALLOYS
Abstract There are two sources of contamination in solder alloys. The first source is trace elements from the primary metals used in the as-manufactured product, be that product in ingot, wire, or powder form. Their levels in the primary metal are determined by the refining process. While some of these trace elements are naturally occurring materials, additional contamination can result from the refining and/or forming processes. Sources include: furnace pot liners, debris on the cutting edges of shears, rolling mill rollers, etc. The types and levels of contaminants per solder alloy are set by recognized industrial, federal, military, and international specifications. For example, the 63Sn-37Pb solder purchased to the ASTM B 32 standard can have maximum levels of contamination for the following metals: 0.08(wt.)%Cu, 0.001 %Cd, 0.005%Al, 0.25%Bi, 0.03%As, 0.02%Fe, and 0.005 %Zn. A second cause of contamination in solders, and solder baths in particular, is their actual use in soldering operations. Each time a workpiece is introduced into the bath, some dissolution of the joint base metal(s), protective or solderable coatings, and fixture metal takes place which adds to contamination levels in the solder. The potential impurities include Cu; Ni; Au or other noble metals used as protective finishes and Al; Fe; and Zn to name a few. Even dissolution of the pot wall or liner is a source of impurities, typically Fe.
Educational Use Research
Learning Resource Type Article
Publisher Date 1999-02-22
Publisher Place United States
Journal Welding Journal
Technical Publication No. SAND99-0463J
Organization Sandia National Labs., Albuquerque, NM (US) ♦ Sandia National Labs., Livermore, CA (US)
Page Count 7


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