Conductivity of conductive polymer for flip chip bonding and BGA socket

Abstract

Numerous experimental studies on electrically conductive polymer have showed that the flip chip bonding and BGA socket with conductive polymers have a certain amount of contact resistance between contact pad and conductive polymer and among fillers, in addition to bulk resistance of fillers themselves. The ingress of insulating films into the contact area results in an increase of contact resistance. Conductive polymer generally consists of conductive filler and adhesive polymer matrix. Its conductivity depends not only on filler material, filler ratio, and operating environment, but also on filler packing structure, voltage drop and mechanical stress due to the mismatch of materials’ coefficients of thermal expansion, which results in the deformation of the chip, substrate and printed circuit board. In this paper, an analysis, based on fundamental electrical contact physics, material kinetics and particle packing structure, was conducted to deepen our understanding into the correlation between the conductivity of polymer bonding system and such key variables as filler packing configuration, stress, voltage drop and operating environment.