Investigation of thermal fatigue life scatter of IVH in PWB

In this study, Printed Wiring Board (PWB) specimens with Interstitial Via Hole (IVH) were exposed to thermal cycling test, and the thermal fatigue life scatter of IVH was investigated by Finite Element Analysis (FEA), taking into consideration the influence of interactions between different processes during manufacturing. Focusing on laminated structure of PWB, the FEA was conducted with detailed modeling of glass cloth shape. The validity of the FEA model was confirmed by comparing the results of analysis with crack condition and order of fatigue fracture of IVH in thermal cycling test. The validated model was used to investigate a technique for evaluation of fatigue life scatter. It was revealed that the scatter factors in laminating process and drilling process influence the thermal fatigue life scatter of IVH. It was also found that in order to evaluate thermal fatigue life scatter of IVH by FEA, it is necessary to use a strain value which is representative of the equivalent plastic strain range that occurs all over IVH, instead of the equivalent plastic strain range extracted at a local point where the value is maximum.