Optimization of InGaN-based LED Package Structure for Automotive Adaptive Driving Beam Headlamp

Abstract

We investigated the luminance, thermal, and thermo-mechanical properties of vertical (V)-LED and flip-chip (FC)-LED packages with different white silicones for a vehicle head lamp application. The FC-LED package showed higher equivalent maximum stress than the V-LED package. For example, the equivalent maximum stresses for the FC-LED package with white silicone (WR-3020) were 6.05 and 2.45 MPa at -45 and 125 degrees C, respectively, whereas those for the V-LED one with WR-3001 were 1.09 and 1.56 MPa. Irrespective of currents, the V-LED packages exhibited lower thermal resistance (R-th) than the FC-LED package. The V-LED package showed 25.3% lower R(th)value (junction to PCB) at 1000 mA than the FC-LED package. The FC-LED packages illustrated higher luminous flux drop-rate at 85 degrees C than the V-LED package. The V-LED packages revealed lower surface temperature than the FC-LED package. The contrast ratio depended on the package structures and white silicone coating widths. The packages with the wider edge-coating width had higher luminance and the V-LED packages exhibited higher luminance. The luminous flux maintenance rate was degraded by 0.9%-2.9% after 1000 h. The V-LED package with WR-3001 showed the best performance, while the FC-LED package with WR-3020 displayed the lowest performance.