Effect of die-attach material on performance and reliability of high-power light-emitting diode modules

Heat dissipation for packaging high-power light-emitting diodes is critically important to performance and reliability of LED lighting modules. The first thermal interface encountered by the heat flow is a die-attach material between the diode chip and its substrate. In this study, three different types of die-attach materials were used to construct 1-Watt GaN LED single-chip modules: a silver epoxy processed by curing; a lead-free solder paste by reflowing; and a nanosilver paste by low-temperature sintering. The modules were aged in an 85°C/85% relative humidity chamber and temperature-cycled between -40°C and 150°C. Luminous fluxes of the aged and cycled modules were measured to determine the effect of die-attach material. Results showed that the LED modules with chips joined by the low-temperature sintered nanosilver paste gave the best performance and long-term stability. This is attributed to high thermal conductivity of the sintered silver joint for improved heat dissipation.