Simulation for the contact resistance of a single anisotropic conductive adhesive particle with rough surface

In anisotropic conductive adhesive (ACA) bonding, the components´ surfaces are not completely smooth and there are a great number of individual micro spots on the contact surfaces between particles and metal pads. However, most of the previous studies about contact resistance of ACA joints have neglected the roughness of contact surfaces between particles and metal pads and thus it may underestimate the contact resistance. This paper presents a model to analyze the effects of the roughness on the contact resistance of an ACA joint with Au coated polymer particles. The rough surface is constructed with micro cylinders and the roughness is represented with asperity density, asperity height and asperity radius. The model finds that the contact resistance increases obviously with the decrement of asperity density and asperity radius, while it is not sensitive to asperity height. In addition, the bulk resistance of asperities should be considered if the asperity radius is too small, and it even may play a major role on the contact resistance. In conclusion, the roughness of contact surfaces should be considered to calculate contact resistance accurately, otherwise, the contact resistance may be underestimated.