On the difference between thermal cycling and thermal shock testing for board level reliability of soldered interconnections

In this work, the endurance behavior of a ball grid array package is determined at two different temperature cycle conditions: a thermal cycle test and a thermal shock test. The observed failure distributions and failure modes allow deriving a translation factor between the two test conditions. Finite element analyses are carried out to design a predictive simulation model for the fatigue lifetime. Using an isothermal approach, a discrepancy is found between the experimental and simulated results. Incorporating the experimentally measured temperature gradients into a semi-transient model leads to a better match with the observed lifetimes. In particular for the fast thermal shock loading this turns out to be necessary. The results prove that temperature gradients in BGA-packages play an important role in board level reliability testing.