Measurement of deflections experienced by electronic chips during soldering

Electronic chips may experience, during the soldering process to a circuit board, out-of-plane displacements whose magnitude is not compatible with technological requirements on good bonding. This paper presents an experimental procedure based on the projection computer-aided moire (PCAM) system in order to contour the distorted shape of electronic chips undergoing a thermal cycle which simulates the soldering process. The PCAM system is an integrated system where a pattern of fringes is transformed via software into a continuous phase distribution from which the distorted shape of the chip can be recovered. In this study, a number of chips have been heated at different temperatures ranging between 120 and 220 degrees C in order to reproduce conditions that may occur during the real soldering process. Since measurements are carried out when the thermal field has become uniform, the chip deforms in the fashion of a quadric surface (i.e. a hyperboloid). Analysis of the chip's deformed shape reveals that the largest displacement gradients experienced by the chips tested in this study are such that requirements on good bonding of the welded assembly are met. This finding, together with the fact that handling and investigation of electronic chips usually require special care, supports the conclusion that the PCAM approach may be successfully applied in the industry for the non-destructive testing of delicate components.