International Conference on Soldering & Reliability (SMTA), Toronto, Ontario, Canada, 20-22 May, 2009

Reliability of SAC305 and Sn3.5Ag Solders under High Temperature Thermal Cycling

Elviz George2, Diganta Das2, Michael Osterman2, and Michael Pecht1, 2
1City University of Hong Kong, Hong Kong, China
2Center for Advanced Life Cycle Engineering (CALCE)
University of Maryland, College Park, MD, USA 20742


Certain applications have operating temperatures higher than the reliable operating ranges for eutectic SnPb solders leading to reliance on expensive specialized solders. But the ban on lead in the majority of electronics has increased the use of lead-free solders (such as SAC305 and Sn3.5Ag). Due to their higher melting temperatures, they are a possible alternative to specialized solders in these applications. Previous studies have shown that during temperature cycling up to 125°C, the lead free solders performed as well or better than eutectic SnPb solder. However, literature on the thermal cycling reliability of lead-free solders at peak temperatures higher than 150°C is very limited. This paper presents the results of a study to assess the effects of temperature cycling with a peak temperature of 185°C on PBGAs, QFPs, and surface mount resistor packages assembled with SAC305 and Sn3.5Ag solder pastes on ENIG and Sn-based proprietary board finishes. The durability data of the components with different solder pastes and board finishes are then compared based on which recommendations are provided.

Keywords: high temperature, thermal cycling, ball grid array (BGA), lead-free solder, reliability.

Complete article available to CALCE consortium members

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