Thermal characterisation of electrically conductive adhesive flip-chip joints

In this paper, we present simulation results of the thermal characteristics of epoxy-based anisotropically conductive adhesive (ACA) flip-chip joints. The results are compared with the thermal characteristics of isotropically conductive adhesive (ICA) flip-chip joints, soldered flip-chip modules and wire bonded modules. The simulated thermal parameters are the overall thermal resistance from the active chip surface down to the substrate as well as the unsteady/transient state characteristics time constant. In modern telecommunication applications, the thermal behaviour (temperature response) caused by electronic high power pulses are of great interest. The unsteady state characteristics are discussed and presented as time constants under different conditions. The thermal simulation software used is an IVF-developed software designed for electronic packaging applications. In order to study the effect of different ACA joint shapes on the thermal characteristics, a joint thermal crack model was developed and simulated for various sets of parameters. The purpose of the investigation of a nonperfect ACA joint is to see how thermal characteristics are affected by ACA joint shape. Simulation of isotropically electrically conductive adhesive joints was done for 35 μm thick joints. Simulations were made for two different bondline thicknesses for soldered flip-chip modules. Finally, simulations have been done on a wire bonded module and on an ideally contacted ACA mounted flip-chip module with 400 I/Os in order to compare the two cases