Effect of Thermal Annealing on the Electrical Conductivity of Copper-Tin Polymer Composites

Polyvinylidene fluoride (PVDF) copolymer conductive composites containing 40 vol % copper (Cu) and tin (Sn) fillers are prepared by injection molding. Postmolding thermal annealing is found to increase the electrical conductivity of the composites by an order of magnitude. The volume ratio between Cu and Sn is found to have a significant effect on filler distribution but a weaker effect on electrical conductivity compared to the annealing conditions. Synchrotron X-ray tomography is used to visualize and quantitatively analyze the morphology and distribution of the filler particles, indicating that higher conductivity can be attributed to better dispersion of the low-melting-point Sn filler, which provides better interparticle contact in the Cu network.