Abstract New soldering-interface failure-analysis method based on the transient thermal response of the LED packages proposed. This method is based on the physical properties that the operating voltage of the LED packages is inversely proportional to the junction temperature and the change of the junction temperature, which is monitored by voltage, represents the change of thermal gradient in the LED packages. Fast time-domain algorithm for failure-sensitivity enhancement was developed. And the feasibility of this algorithm was verified using a two-point measurement method during a thermal shock test.