A new technique to check the correct mounting of the power module heatsinks

Abstract

Temperature management is a non-secondary aspect in the design of power circuits and systems. As a matter of facts, changes in the junction temperature have significant effects on the semiconductor device behavior; furthermore, a high junction temperature accelerates the failure mechanisms of power devices used in the power module and reduces their lifetime. Therefore, it is often necessary to introduce a suitable heat dissipation system able to keep the junction temperature within the device operating limits. Passive heatsinks represent the most widely used strategy. However, an incorrect mounting of the heatsink may cause an unacceptable junction temperature increase in a power module. Even though the heatsink was initially properly assembled, it may be affected by defects during its working lifetime. Thus, it is necessary to devise effective strategies for testing the heatsink mounting at the end of the printed circuit board production and during the operational phase. In this paper, a method to test the heatsink mounting on power module is discussed. The proposed solution does not require thermal measurements, but only electrical ones and can be performed both at the end of the power module production, by means of an automatic test equipment, and in mission using a dedicated test circuit included in the system. The method was experimentally assessed on a DC-DC buck converter, validating the proposed solution.