Solidification shrinkage defects in electronic solders

Abstract

Alloys that undergo solidifi cation over a wide range of temperatures generally exhibit a difference in the contraction behavior of the ensuing solid and liquid phases. Furthermore, dissolution of substrate metals during process refl ow can lead to shifts in phase composition, additional primary phases, and volumetric contraction artifacts. The extent and frequency of surface roughness, shrinkage voids, fi llet lifting, and hot tearing seen in lead-free solders are different than for eutectic tin lead solder. Shrinkage effects have been reported in Sn/Pb, Sn/Pb/Ag, Sn/Ag/Cu, and Sn/Cu/Ni solders for various components, but few studies have examined their impact on solder joint reliability. Nevertheless, they warrant proper identifi cation due to the shift toward lead-free solders. This article is a review of the effects of shrinkage in Sn-Pb and lead-free solders as well as a discussion of some of the factors that contribute to their formation. Visit the site regularly and click on "What's New" to fi nd out the most up-to-date information on meetings, publications, membership activities, and more. www.tms.org ■ CMS-Plus is available to accept abstracts for the 2006 TMS Annual Meeting. http://cmsplus.tms.org ■ The Members Only site has been updated and reorganized. http://members.tms.org/members/mempage.asp ■ The Metal-Matrix Composites database is now available as a member benefi t. http://members.tms.org/MMCDatabase/MMC.asp

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