Impact Resistance of SM Joints Formed with ICA

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.