Investigation on relative merits of different fringe analysis procedures in ESPI measurement on electronic components

This work describes the application of Phase Shifting Electronic Speckle Pattern Interferometry (PS-ESPI) systems in measuring full-field in-plane strains on Surface Mounted Technology electronic components (SMT). The thermal expansion rates of the materials making up the Electronic Packaging (EP) may be so different that mechanical failure occurs because of variable thermal stresses within the loading cycles. ESPI is particularly suitable for such a measurement because it allows performing non-contact test on non-flat surfaces made up of different materials. Besides, Phase Shifting Techniques (PST) usually improve significantly the accuracy of results. In this paper, experimental investigations have been carried out on voltage stabilizers widely used for supplying power stage to common electronic devices. A preliminary study on three-point-bending suggested the most suitable optical setup and allowed choosing the PS procedure able to get the best visibility of fringes. Further information was gathered by comparing experimental results with finite element analyses. The results obtained suggest the application of PS-ESPI techniques for better understanding failure mechanisms. This may be particularly helpful in the different design stages of special applications for electronics