PWB solder joint life calculations under thermal and vibrational loading

The goal of automating printed wiring board (PWB) solder joint fatigue life calculations into a design environment is to make reliability assessment information available to the designer as early as possible, in an easily understood and implemented manner. The assumptions and details of the fatigue life calculations under a combined thermal and vibrational load are discussed. A methodology to evaluate the combined effects of simultaneous vibration and thermal cycling of solder joints is presented. This combined loading situation is simulated by superposing the effects of the vibrational and thermal loads. The damage due to each load type acting individually is determined and then superposed to assess the overall effective fatigue life of the joint. As a first-order approximation, the Palmgren-Miner linear superposition rule is utilized