Thermal resistance analysis of high power LED module under power cycling test

High junction temperature is always a big concern for the LED products since it is generally associated with the product's reliability. Therefore, the way to maintain an adequate cooling capacity is extremely important for LED module. It is no doubt that thermal resistance is one of critical indicators restricting the heat dissipation. In this work, one LED module with ceramic carrier is submitted to power cycling test, and T3ster transient thermal analysis tester is employed to measure the electrical and thermal properties of LED module. During the power cycling testing, the temperature and thermal resistance are monitored, with a goal to analyze the thermal resistance rise at different layer inside LED module. The result indicates the total thermal resistance of the LED module climbs dramatically after power cycling test, in which the increased thermal resistance of the solder joint layer shows a crucial contribution obviously. Based on the experimental investigation, the increased thermal resistance of the solder joint is key reason that leads to the increasing junction temperature of LED package. It's concluded the solder joint layer should be regarded as a key role on reducing the total thermal resistance of LED module. The material and structure of solder joint layer should be designated based on the thermal resistance performance during the long time operating in order to enhance the reliability of LED module.