Assessment of PCB pad cratering resistance by joint level testing

Cracking of the laminate under the solder connect pads, known as pad craters, is a reliability issue related to mechanical stresses generated from either mechanical or thermal loading. The current study aims to establish a mechanistic understanding of pad cratering through the use of joint-level testing techniques. Both strength and cyclic loading lifetime are considered, and the results indicate that these two loading modes are not correlated. The individual crack paths within a crater are found to differ with laminate material, glass style (if any), and micro-via details. Various degradation mechanisms are found to have a significant effect on this failure mode with both thermal and moisture exposure showing decreased laminate performance. Finally, the relationship between joint-level testing is compared to the performance in board level drop test. Here we see that joint-level testing is far more general, in terms of qualifying the robustness of the laminate.