Mechanical stability and insulation reliability of polymeric layers constructed by thermal fusion of polymer shell particles heterocoagulated on conductive nickel‐plated core particles

Abstract

AbstractIn this study, the mechanical stability and insulating reliability of polymeric layers constructed on the surface of nickel‐plated particles for anisotropic conductive films were measured by means of a microcompression test. The polymeric layers were constructed by heterocoagulation between the nickel‐plated core particles and the polymeric shell particles and successive thermal fusion. Uniform core‐shell particles with a coverage of approximately 60%–70% were prepared at NaCl concentrations near the critical coagulation concentrations of the shell particles. Continuous polymeric layers were successfully formed by heating the heterocoagulates at a temperature slightly higher than the glass transition temperature of the shell particles. The microcompression test was applied to measure the compression displacement until the heterocoagulates were electrically connected. The larger the shell particles and the higher the coverage of heterocoagualtes, the greater the displacement, reaching a maximum displacement of 0.72 μm for heterocoagulates with shell particles of 217 nm before heating. Heating the heterocoagulates and thermally melting adjacent shell particles could further improve the insulating properties of polymeric layer. Thermal melting of shell particles of heterocoagulates with a coverage more than 60% by 152 or 217 nm shells resulted in the disappearance of zero‐point conductive particles.