Soldered Joint Reliability for Interstitial Pin Grid Array Packages

The reliability of solder joints and plated‐through‐hole (PTH) copper structure was investigated for 503 I/O interstitial pin grid array packages with two different pin diameters. Each package type was wave soldered to printed wiring boards having two different surface finishes and PTH sizes, by using the 63Sn–37Pb alloy. Accelerated thermal cycling with continuous monitoring was used in conjunction with metallographic analysis to determine reliability and to elucidate the failure threshold. The microstructural features and failure modes were found to be similar among the solder joints despite the physical differences. The measured solder joint fatigue lifetimes varied from 2450 to 3700 thermal cycles, depending on pin and PTH combinations. The reliability of PTH copper exceeded 4000 thermal cycles regardless of the PTH size. The solder joint fatigue results were used to predict the reliability under operating conditions.