Effects of silica filler and diluent on material properties and reliability of non-conductive pastes (NCPs) for flip-chip applications

Abstract

The material properties of Non-Conductive Pastes (NCPs) for electronic packaging interconnection materials were investigated to improve reliability and processability of flip chip on organic substrate using NCP in this study. The paste materials composed of low temperature rapid curing epoxy resin, latent curing agent, ceramic fillers and reactive diluents. For the characterization of NCP composites with different content of non-conducting fillers and diluents, differential scanning calorimeter (DSC), thermomechanical analysis (TMA), dynamic mechanical analysis (DMA), thermogravimetric analysis (TGA), HAAKE rheometer, and Brookfield viscometer were used. As the ceramic filler content increased, CTE values decreased and storage modulus at room temperature increased. Also, glass transition temperature increased. As the diluent content increased, viscosity decreased and thixotropic index increased but thermo-mechanical properties such as modulus, CTE, and $T_g$ deteriorated. Daisy chain resistance changes were measured during reliability tests such as thermal cycling, high temperature storage, and high temperature and humidity test. Also, cumulative distribution of connection resistance changes was measured during thermal cycling and high temperature storage test. The reliability results were significantly influenced by CTEs and modulus of NCPs. Especially the reliability result of thermal cycling test was analyzed by Suhir’s model to investigate shear strain induced adhesive layer. The induced shear strain during flip chip assembly process affected the thermal cycling reliability.