Development of the residual stresses in an organic adhesive, alumina filled epoxy (EPO-TEK H65-175MP) during curing process has been studied in-situ. The effect of the adhesive’s thickness was evaluated by preparing samples and analyzing residual stresses. Samples were prepared by applying a layer of the epoxy in various thicknesses on the back side of the silicon die. The topology changes of the die’s surface during curing process and cooling of the epoxy were monitored by digital image analysis enhanced moire´ interferometry (DIAEMI). Residual stresses were calculated from the curvature changes of the surface of the die. The results show that the stress buildup is mainly caused by the mismatch in coefficient of thermal expansion between the adhesive and the die. Relaxation of the residual stress was found while the samples were kept in an open environment at room temperature. Such reduction in stress may be attributed to moisture absorption by the epoxy that results in expansion of the epoxy.

During the die-attach process, residual stresses are methods. Due to mismatch in the coefficient of thermal expandeveloped in components of the die-attach assembly due to the mismatch of coefficients of thermal expansion of different materials. To properly assess the service life of the assembly, those stresses must be taken into account. Several test dies, with and without chip's protective coating, were prepared, and two different bonding materials, "low-stress" and "high-stress," were used for analysis of the die-attachment induced stresses. An experimental technique, the digital image analysis enhanced moire interferometry (DIAEMI), was utilized to observe the initial and final (after die-attach) surface contour patterns of dies. This information was used to obtain the in-situ out-ofplane displacements of the die due to the die-attach process, and the induced stresses were calculated by a hybrid finite element method. The results show that stresses in die induced by highstress bonding materials are on average five times higher than the stresses induced by low-stress materials; during the process some of residual stresses induced by the chip's coating were released. By comparing the results with the straightforward finite element method prediction, it is shown that the induced stresses are much lower than those stresses predicted by the straightforward finite element calculation.

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