On the nature of pad cratering

Intent was to study the effects and interactions of the main process and environmental factors which are likely to affect pad performance. Real time observation of crack propagation under the pad achieved by cross-sectioning very carefully to the middle of the pad and then subjecting it to cyclic loading revealed some important location dependencies. Experimentation also involved cyclic bending of prepared samples with different preconditioning levels of reflow, moisture and cycling, followed by measurement of the crack area under the pad, post cycling. This shed light on the complex degradation mechanisms at play which did not necessarily have linear dependencies nor were they as basic intuition may have led us to believe. An effort was made to develop an analytical model with the help of multiple regression techniques.