Thermo-mechanical properties of Isotropic Conductive Adhesive filled with Metallized Polymer Spheres

The thermo-mechanical properties of Isotropic Conductive Adhesives (ICAs) containing Metallized Polymer Spheres (MPS) with a diameter of 30 μm and 15 μm as conductive fillers have been investigated, denoted ICA-30μm and ICA-15 μm respectively. The MPS are coated with an approximately 150 nm thick layer of Ag. The coefficient of thermal expansion (CTE) below Tg for ICA-30μm and ICA-15μm was found to be 50 ppm/°C and 53 ppm/°C, respectively. DMA measurements show a relatively large increase in loss modulus when 30 μm MPS are added to the epoxy matrix. The thermal conductivity with different volume fillings of MPS for both ICA-30μm and ICA-15μm has been investigated. Thermal conductivity of the ICA was modeled by using the Pal model for core-shell particles with reasonable accuracy especially at lower volume fillings. A thermal conductivity of 1 W/mK can be achieved by using approximately 1.4 vol% of silver. Using ICA with conventional silver flakes/particles, approximately 16 vol% of silver has to be used to achieve the corresponding thermal conductivity, which clearly illustrates the cost benefits of using ICA with MPS.