Abstract
In this study, in order to investigate the effect of the heterogeneity of the laminated structure in a FR-4 on the thermal fatigue life of the Interstitial Via Hole (IVH) in a Printed Wiring Board (PWB), we suggest a practical technique for investigating the variation factors that affect thermal fatigue life. On the basis of the technique, the variation factors were investigated using a thermal cycling test and Finite Element Analysis (FEA). The FEA was conducted with detailed modeling of the plain fabric glass cloth in a PWB, and the analysis results agreed well with the crack conditions and order of fatigue fractures which were observed in the thermal cycling test. We found that differences in the laminating conditions of the glass cloth and differences in the IVH position relative to the glass cloth at certain laminating conditions affect the thermal fatigue life of the IVH. These differences are the variation factors of the thermal fatigue life of an IVH, and combinations of the variation factors will affect the thermal fatigue life of an IVH.
