Abstract: The present invention relates to a bus bar assembly comprising a high power transistor module directly mounted to a bus bar. The bus bar has an improved solderability characteristic and is designed so that a solid, effective soldered connection results during a conventional soldering process in which the high power transistor module is securely mounted to the bus bar to form the bus bar assembly of the present invention. Accordingly, the soldering process involves soldering a pin which is a part of the high power transistor module to a surface of the bus bar using sufficient heat. The improved solderabilty of the present bus bar results by forming a soldering island in the bus bar at predetermined points thereof. The soldering island comprises a central soldering opening, which receives the soldering pin, and a plurality of thermal barrier openings distributed around the soldering opening.