An evaluation of board-mounted power module packages

We compare the characteristics of four BMP packages with a focus on thermal performance. Using experimental and simulation methods, the air-flow regime is found to be particularly important in determining which package provides superior thermal performance. For single-board medium-power designs, air flow velocities of less than 200 fpm allow potted modules to run cooler while air velocities greater than 400 fpm tend to allow open-frame modules to operate cooler. For dual-board designs, however, open-frame modules appear to outperform potted modules even at natural convection. Other attributes that are of interest to BMP users, such as cost, manufacturability, and ease of use, are discussed. We also propose a new method to obtain thermal derating characteristics of open-frame modules.