Thermal effects of die-attach void fraction and position in high-power LED packages: a three-dimensional finite-element study

Purpose This study aims to quantify the effects of die-attach void fraction and in-plane position on heat flow in a high-power phosphor-converted LED package. Design/methodology/approach The model was run in MATLAB R2025b with the Partial Differential Equation Toolbox. Nineteen configurations covered six void fractions and three positions, plus the void-free case. Mesh, energy-balance, transient, material, convection, source-partition, shape and aspect-ratio checks were completed. The 18 voided cases were examined as a 6 × 3 fraction–position grid. Findings The 30% corner-directed void raised junction temperature by 5.50 °C and package resistance by 39.37%. It also made the chip-top field strongly non-uniform. The corner penalty remained 5.39–5.61 °C over the conversion-layer heat sweep. Heat was redirected laterally, and the position penalty grew with void fraction. Practical implications A limit based only on total void area can miss a large defect located near the edge or corner of the bond. Originality/value Moving a void while keeping its projected area unchanged produced different temperature and resistance values. The heat-flux maps relate this position effect to the loss of the direct through-thickness path and increased lateral flow through the remaining bonded area.