A coaxial probe system for measuring Z-direction electrical resistivity of conductive polymers

A novel coaxial Kelvin probe technique has been developed to measure the z-axis electrical resistivity of conductive polymer adhesives. The approach uses a very simple test structure, comprising of a sandwich of the conductive adhesive material between two Copper conductors. The coaxial probe includes an outer region through which the current is forced, and an inner probe which senses the surface voltage drop, and is hooked to a nano-voltmeter to enable micro-ohms resistance measurements with high sensitivity. This is followed by detailed finite element modeling of the sample and probe set-up configuration to extract an accurate value for the effective z-axis resistivity of the conductive adhesive, as well as its bulk and interfacial z-resistivity values. This technique has been demonstrated on two candidate conductive materials as well as solder (as a reference). It has the potential to enable rapid optimization and development of conductive polymer adhesive systems for different interfaces and for various applications.