Improved Heat Dissipation Through Copper Bricks for High Turns Ratio Planar Transformers

Planar transformers are easy to manufacture and enable low tolerance electromagnetic and thermal properties. Hence they are of great interest for a large scale production of power electronic converters. In planar transformers the maximum board temperature is limited by the glass transition of the board laminate material. To increase the current capability of the transformer a good heat dissipation from the transformer windings is beneficial. The thermal limitations of a basic transformer design with a high turns ratio are presented using a finite element analysis (FEA). In order to enhance the heat dissipation of the transformer windings, this paper analyzes the effect of thermal vias and in a second step, copper bricks are introduced on the outer layers to improve the lateral heat transfer. The accuracy of the analysis and the effectiveness of this design approach are verified experimentally.