iNEMI Pb-Free Alloy Characterization Project Report: Part VIII - Thermal Fatigue Results for High-Ag Alloys at Extended Dwell Times
Authors: Richard Coyle, Richard Parker, Elizabeth Benedetto, Keith Howell, Keith Sweatman, Stuart Longgood, Joseph Smetana, Aileen Allen, Peter Read, Babak Arfaei, and Francis Mutuku Company: Alcatel-Lucent, iNEMI, Hewlett-Packard Co., Nihon Superior Co., Delphi, Alcatel-Lucent, Hewlett-Packard Co., Universal Instruments, Binghamton University Date Published: 9/28/2014
Abstract: The Pb-Free Alloy Characterization Program sponsored by International Electronics Manufacturing Initiative (iNEMI) is conducting an extensive investigation using accelerated temperature cycling (ATC) to evaluate ball grid array (BGA) thermal fatigue performance of 12 commercial or developmental Sn-based, Pb-free solder alloys. This paper presents the findings from a specific subset of the temperature cycling test matrix derived from the alloys with higher Ag content that contain approximately 2 wt. % Ag or more. Temperature cycling data are presented for two different BGA components and comparisons are made with multiple temperature cycles. The temperature cycling variables include different cyclic temperature ranges (?T) and temperature extremes. This study focuses on the results from tests that used extended, 60 minute upper and lower temperature dwell times. Extended dwell times are more representative of service conditions and are known to reduce the reliability in ATC tests relative to shorter dwell times and cycles. The failure data are reported as characteristic life ? (number of cycles to 63.2% failure) and slope ? from a two-parameter Weibull analysis. The ATC data and failure analysis are discussed in terms of the alloy composition and the initial as well as evolving microstructures that result from temperature cycling. The relative performance of the various alloys under multiple ATC conditions, and how this may impact acceleration behavior, is discussed.