Development of heat dissipation structure for face-down bonded devices

We developed a heat dissipation structure for face-down bonded surface acoustic wave (SAW) filter packages. This structure enables compact packages at low cost. Heat dissipation from the transmission (Tx) SAW filter and filter sealing are important factors in enhancing package reliability. Tx and reception (Rx) SAW filters were bonded on a printed wiring board (PWB) with a branching circuit, and the filters were sealed with a metallic lid using conductive adhesive. High thermal conductivity adhesive was used to fill between the Tx SAW filter and the metallic lid, enabling the heat of the Tx SAW filter to be dissipated. The filter properties of the package using this high thermal conductivity adhesive were not changed after 500 hour operation with 5 W input RF signals. Results following the performance of thermal shock tests also confirmed characteristics indicating an extremely tight seal, with a rate of helium leakage of only 10/sup -8/ atm/spl middot/cc/s. Thus, as indicated in detail by these results, we concluded that the structure which we developed has been proven to be suitable for application to SAW filter packages.