Design independent lifetime assessment method for PCBs under low cycle fatigue loading conditions

In this work a method was worked on that assesses the lifetime of printed circuit boards (PCBs) under low cycle fatigue conditions. The method was based on finite element models and low cycle fatigue experiments. Verifying it, two significantly different PCB designs and several different PCB built ups were analyzed. Doing so, for the numerical part the individual layer materials were characterized, material models were defined and simulation models were built. A submodelling technique had to be applied in order to evaluate the local loading situation. For the experimental part corresponding PCBs were manufactured and a statistically relevant number of boards were tested in a board level cyclic bend test (BLCBT) while the critical connections were monitored. Based on the results of one PCB a correlation model describing the dependence of the cycles to failure on the local loading situation was formulated and used for the lifetime assessment of the other boards. A very good agreement between predicted and measured results could be shown.