Thermal stress analysis of tape automated bonding packages and interconnections

The stresses and strains in tape automated bonding (TAB) assemblies have been studied using a nonlinear three-dimensional finite-element method. Detailed stress distributions in the TAB assembly beam leads, polyimide rings, gold bumps, silicon chips, and solder joints are presented. Due to the flexibility of the beam lead and the unequal thermal expansion and stiffness difference of all the parts of the TAB assembly, the beam lead was subjected to the largest deformation. Bending of the silicon chip and printed circuit board was very small compared with that of the beam lead, because of their much larger section moments of inertia. Due to their small thickness, the TAB beam leads, unlike the case of conventional surface mount technology assemblies, are more likely to fail than the solder joints. There is excellent agreement between the analytically predicted and the experimentally observed failure mechanisms. The results presented should be useful in understanding and designing more reliable advanced surface-mount assemblies