A novel thermally conductive transparent die attach adhesive for high performance LEDs

High thermal conductivity, low viscosity and high transparency are desired properties of die attach adhesives (DAA) for LEDs to achieve high thermal and optical performance as well as good reliability. However, it is challenging for DAAs with thermally conductive fillers to keep a low viscosity and high transparency. In this paper, a novel DAA with designed hyper-branched epoxy-silicone and surface modified fused silica was formulated to improve the thermal conductivity without sacrificing high transparency and low viscosity. Compared with a widely used commercial DAA, 165% thermal conductivity improvement and 83% viscosity reduction are achieved, resulting in 26% thermal resistance reduction, 7% light extraction enhancement, and 14% less lumen degradation in accelerate aging test for mid-power LED packages.