Journal of SMT Article

The Influence of Alloy Composition and Temperature Cycling Dwell Time on the Reliability of a Quad Flat No Lead (QFN) Package

Authors: Richard Coyle, Peter Read, Heather McCormick, Richard Popowich, and Debra Fleming
Company: Alcatel-Lucent
Date Published: 1/30/2012   Volume: 25-1

Abstract: The thermal fatigue performance of SnAgCu (SAC) Pb-free and SnPb eutectic solders was compared using accelerated temperature cycling (ATC). The Pb-free solder alloys were SAC405, SAC305, and SAC105. The cycling tests were performed with a 7 mm x 7 mm Quad Flat No-Lead (QFN) (BGA) test vehicle with 0/100 ºC temperature cycling using dwell times of both 10 and 60 minutes. The initial results from this study were published in an earlier paper [1]. The current paper addresses some assembly deficiencies in the previous work and presents new temperature cycling data to complete the objectives of the original study. The test results show a direct relationship between characteristic fatigue life and Ag content, with the higher Ag content alloys outperforming those with the lowest Ag content. The characteristic lifetime of the SnPb solder assemblies exceeds that of the Pb-free solders, but the characteristic lifetimes of the high Ag alloys are relatively high. As expected, there is a consistent inverse relationship between fatigue life and dwell time for all solders including the SnPb eutectic.

Keywords: 

Pb-free solder, SnPb solder, QFN, SAC, dwell time



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