Thermal management of integrated circuits in burn-in environment

Burn-in screening test technology has been an important method to ensure integrated circuits (IC) quality and reliability. But there are many problems remains to be solved during burn-in and accurate junction temperature of IC during burn-in is one of these problems. Leakage currents are rapidly increasing with CMOS IC technology scaling, and this will lead to high junction temperature of IC in burn-in environment. Positive feedback between junction temperature and leakage currents result in continual junction temperature increases, and thermal runaway will probably happen. In addition, differences of frequency during burn-in and variation of device parameters, all these lead to the junction temperature of IC not the same even in the same burn-in environment. To solve these problems, a closed-loop temperature controlled system and corresponding integrated IC's case temperature acquired method are presented in this paper. Under the ambient temperature of burn-in oven, each socket is a microenvironment managed by closed-loop temperature controlled system. Several small thermal resistors which measure the temperature of different areas of the IC are mounted on the surface of the IC in the burn-in socket and we choose measured maximum temperature as the feedback signal of the temperature controlled system. Compared with junction temperature of IC without temperature controlled system, junction temperature of different IC with temperature controlled system in burn-in environment almost the same, and steady state error is in the range of 0.2°C which is far less than differences of junction temperature without temperature controlled system. Rise time and dynamic response time are all much faster. All these advantages make burn-in process reliable and integrated circuits of great reliability.