Solder Fatigue Impacts of Conformal Coating for Tin Whisker Mitigation on Chip-Scale Thin Small Outline Packages

This study explores the impact of polyurethane conformal coating on the solder fatigue life of 0.5 mm pitch, thin small outline package (TSOP) components. Test samples were subjected to temperature cycling from −40°C to + 100°C. Uncoated samples were tested in addition to sets with 10, 13, and 20 μm thick coatings. Solder joint failure data fit to 3-parameter Weibull distributions demonstrate characteristic fatigue life reductions of 30% with increasing coating thickness but relatively subtle changes to the failure distribution shape.