Mechanical and electrical properties investigation of micro-size single metal-coated polymer particle

Micro-sized metal coated polymer particles are widely used in the anisotropic conductive adhesive (ACA). The mechanical properties of the metal coated polymer particles are crucial important for the processing and reliability performance of ACA materials in driver IC package application. In this paper, mechanical characterization and electrical property of individual Ni/Au coated micro-size polymer particles were investigated by using the compression tester equipped with a flat indenter. There are three different diameters of metal coated polymer particles (3µm, 5µm, 10µm) selected to be evaluated the mechanical characterization. The mechanical properties of particles such as recovery rate, compression ratio and compression modulus, K value, were discussed through force-displacement curve by using micro-compression tester machine. The relationship between mechanical properties and different loading rate (0.5∼5.0 mN/sec.), loading force (10∼100mN) and particle size (3µm, 5µm, 10µm) were discussed in the research work. Due to the high temperature bonding process in driver IC package application, the stable mechanical property of metal particles of ACA at high temperature is important. The particular particle displays significantly force-displacement curve at the higher temperature (150°C) because of the polymer characterization. The electrical property of a metal-coated polymer particle is also important for ACA interconnection process. Contact resistance characteristic of a single metal-coated polymer particle was evaluated in this work. The contact resistance of a single metal-coated polymer particle through different thickness of metal coating layer, different loading force, and different loading rates from the micro-compressor was investigated. The electrical resistant influence through difference deformation of particles was discussed here. The electrical conductivity mostly depends on the metallic coating materials and deformation of particles. The investigation here would like apply a significant guiding to the manufacture design of metal coated polymer particle for the Anisotropic Conductive Adhesive packaging applications.