In this study, flip‐chip (FC) assemblies on printed circuit board (PCB) and flex, with bump heights of 4, 20 and 40μm, and with a constant copper pad height were compared by modelling of the bonding process and of thermal cycling from –40 to 1258C. The stress distributions of the assemblies were analysed and it was found that the largest stresses occurred for the smallest bump height. The stresses in the anisotropic conductive film for the FC‐on‐flex assembly were also found to be generally larger than for the FC‐on‐PCB.

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Isotropic conductive adhesives (ICA) have been considered as replacement materials for lead-tin solder alloys. In this paper, the post-impact shear strength of ICA surface mount (SM) joints was obtained experimentally and compared with that of SM lead-tin joints. The dynamic impact energy was provided in the form of three-point bending on the PCB using equipment called the split Hopkinson bar. Strain rates of over 4000/s were used for the impact bending test. The action of impact bending was used to simulate the effect on the PCB and the interconnection as a result of high energy impact on an electronic equipment. Shear test was then performed to examine the change in strength of the ICA joints as a result of impact damage. It was found that the SM ICA joints failed due to impact at a strain rate just over 4000/s. Microstructural examination carried out using a scanning electron microscope revealed that the interface between the ICA and copper pad on the PCB was the weakest region of the joint.

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Finite element analysis was used to model the transient heat transfer problem and the mechanical influence of the conducting particle in the anisotropic conductive adhesive (ACF). Three-dimensional (3D) brick element was performed for the transient heat transfer analysis, and the result was found that heat was transferred and spread from the die to the ACF and its conducting particle very quickly; in around 0.5 sec the ACF can reach the bonding temperature of 220°C. For the mechanical stress analysis of the conducting particle, the degree of the deformation was increased as the bonding force increased. The conducting particle was subjected to the larger stress level as the smaller of the particle size. The stress concentration was located at the edge area and diminished at the center area. It was also found that the cracks were found at the four corners of the conducting particles which was due to the highest stress level subjected on that location. Moreover, if only considering the plastic particle, the stress level was concentrated at the center area and vanished at the edge area.