Thermal Management Estimations for B2itTM Printed Wiring Boards with Bump (Filled Via Hole) Interconnection

We have developed B2itTM (Buried Bump interconnection technology) printed wiring boards (PWB's) for high density and high performance wiring boards or substrates. Ordinary PWB's have low thermal conductivity because of their organic materials, compared with ceramic substrates and so on. The B2itTM PWB's have filled via holes by silver paste bumps to connect wiring lines between neighbor layers. The feature is different from ordinary PWB's having copper-plated through holes. This paper reports the thermal management properties for the B2itTM PWB's by measuring the thermal resistance of several filled via hole situation. And a thermal conductivity of the via hole material was simulated from the measurement values. As the results, the thermal conductivity of the via hole was very high to compare with that of the normal printed silver paste, and the B2itTM PWB's had good thermal management property enough to high density packaging.