High thermal dissipation and high reliability performance of wafer level high power light-emitting diodes

In this paper we present the thermal analysis and reliability performance of high power light-emitting diodes (LEDs) with silicon carrier packages. The junction temperature of LEDs is an essential reliability parameter. Exceeding the maximum raised junction temperature could lead to light output degradation and sometimes even to destructive failure. Therefore thermal management and proper thermal characterization of high power LEDs is very important for mass production with good optical and reliability performance. Leaf-frame, ceramic and organic material are used as conventional structure. The thermal resistance is 13≃20°C/W and 8≃12°C/W respectively. It will be a drawback for thermal dissipation for high power LEDs especially for outdoor lighting application. Silicon material is a widely investigation material in recently. Low thermal resistance (3≃5°C/W), low cost and high current capacity are good for high power LEDs. Furthermore, the wafer form assembly method is a trend in the future for high volume mass production. Traditionally, silver paste adhesive is used as die attach material. Voids and low thermal conductive are critical issues for high power LEDs due to most of the thermal will cross the chip and raising the silicone material temperature then result in phosphor thermal decay. Here we use eutectic die attach process instead of paste to enhance the thermal dissipation. In the meantime, we use thermal simulation to predict the thermal resistance of the package and also testing the real package. The thermal resistance is 3.9°C/W and 2.77°C/W respectively. Finally, the package reliability also performed such as temperature cycling test (TCT) 1000 cycles, Temperature Humidity Test (THT) 1000Hrs, room temperature life testing and high temperature life testing. The results show the luminous flux decay ≤ 4% which is high reliability performance. And SAT also shows no delamination within the package.