Tin pest in electronics?
Circuit World, 33(1),
Purpose - To review the literatures, and to consider the latest results regarding the formation of tin pest in lead-free solders and interconnections. Design/methodology/approach - Previous work, over almost a century, on tin pest formation in tin and its alloy has been critically analysed. Samples of the new generation of lead-free solders, which have experienced long term storage at - 18 and - 40 degrees C, have been examined. Findings - Tin pest has been observed in bulk samples of tin - 0.5 (wt%) copper solder after exposure at - 18 degrees C although not at - 40 degrees C. Other leadfree alloys (Sn-3.5Ag, Sn-3.8Cu-0.7Cu and Sn-Zn-Bi) have been immune to date. Large-scale model joints exhibit tin pest but actual joints may be resistant due to the limited free solder surface available and the constraint of intermetallic compounds and components. Research limitations/implications - The possibility of tin pest formation in joints remains. It seems that impurities are essential protection against it, but for long term applications there is no certainty that tin pest and joint deterioration will never occur. Originality/value - The paper considers the various factors that may affect tin pest formation and demonstrates its existence in one of the more popular new lead-free alloys.
||This paper is an abbreviated version of a review to be published in Materials Science and Engineering. That paper was prepared in January, 2006. Recent observations at the Open University have shown that: tin pest forms in Sn-3.5Ag and Sn-3.8Ag-0.7 Cu bulk alloys at −18°C and in Sn-0.5Cu at −40°C. The cat is amongst the pigeons!
||Mathematics, Computing and Technology > Design, Development, Environment and Materials
||16 Apr 2009 11:04
||02 Dec 2010 20:26
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