Numerical study on thermal management of high power LED die bonding technology

Thermal management of high power LED packages is crucial to realize a reliable lighting performance. It is known that the die attach materials acts as a bottleneck that impedes the heat flow from the junction to the heat sink. Bonding quality and techniques, thus, are important in thermal management of packaging and require detail study. Due to the difficulty in measurements, numerical simulation is a practical way to perform the thermal analysis. In this manuscript, a new low-temperature die bond material is studied. With low melting temperature of the die attach material, the LED can avoids the possible damages. The thermal analysis is carried out numerically by the finite element method. A standard surface mount high power LED is used as the reference model. The thermal impacts using different LED die bonding technology is investigated, including the localized laser pulse heating and the blanket heating. The influences of the spill of attach materials are also studied. The results indicate that low-temperature bonding materials in the laser bonding have low thermal impacts compared to the conventional bonding materials (Au-Sn) with high process temperature (330°C). The time revolution is also simulated for the heating process and the following diffusion process to raise the melting temperature to avoid the re-melting of the die attach material. The power of the laser pulse needs to be control to prevent the overheating. The blanket heating method is shown having larger time constant than the pulsed laser heating. This will be a drawback in mass production. To conclude, the new die bond materials are very suitable for reducing the thermal management issues for LEDs die bond in low-temperature laser attach technology applications.