PERM DoD Consortium Phase 3 Pb-free Solder Thermal Cycle Reliability

Tim Pearson, David Hillman, Ross Wilcoxon,
Julie Mills, Leela Herena
Collins Aerospace
IA, USA

Pb-free soldering processes and materials have been implemented in the commercial electronics sector due to the European Union Waste Electrical and Electronic Equipment (WEEE) and Reduction of Hazardous Waste (RoHS) Directives. These environmental legislative directives were targeted at industrial and commercial electronic products but had an unintended impact on aerospace/defense products due to global supply chain transition actions. A group of industry, academic, and government agencies initiated a Pb-free solder alloy reliability investigation, building on previous activities, to characterize and understand various aspects of Pb-free solder joint integrity under -55°C to +125°C thermal cycle conditions. The goal of the testing was to generate reliability data for test vehicles that were representative of IPC Class III High Performance Electronic products.

The continuity of using the same test vehicle design and components in a follow-on test provides a unique opportunity to compare thermal cycle test results over time. Table 3 compares the IPC/PERM DoD Pb-free Electronics Project Phase 3/Part 1 study, the Joint Council on Aging Aircraft/Joint Group on Pollution Prevention (JCAA/JGPP) Pb-free Solder Project [1] and NASA DoD Phase 2 Pb-free Solder Project [2] results for the TQFP-144 component. Nearly 16 years span the different test results but overall, there is consistency in the Weibull N63 value for both SnPb solder and for the Pb-free solder alloys. Small changes in the component material composition and the assembly processes account for small differences in thermal cycles for the SnPb solder alloys. For the Pb-free solder alloys, the primary difference is the change in solder alloy composition across the different program phases.