Volume 1, Issue 2 (March 1973)
Fatigue Behavior of Solders Used in Flip-Chip Technology
This paper surveys the mechanical fatigue behavior of 5/95 Sn/Pb solder and solder with copper, silver and palladium impurities at different temperatures and on-off cycling frequencies. Presence of copper in 5/95 Sn/Pb creates hard and relatively brittle intermetallics which also significantly decrease the fatigue life of solder. The fatigue cracks were observed to propagate through grain boundaries, although some slip striations were observed within individual grains. There is a significant decrease in the fatigue life of 5/95 Sn/Pb in the temperature range of 85 C to 150 C. The fatigue life of solder decreases with a decrease in cycling frequency. Results have shown that the frequency exponent is equal to ⅕. Cyclic strain softening was observed in the specimens which were tested under constant total strain control conditions.