Yoshiro Takahashi

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.

High-density build-up wiring boards using conventional printed wiring boards process

To keep pace with the downsizing of electronic communication equipment and acceleration of transmission speed, the printed wiring board (PWB) must have finer wiring and thinner plating. While various means have been developed to produce these high density boards, we have also developed a process that enables the production of upper and lower surface conductor interconnections on Build-Up substrates using metallic via-posts. The features of the via-post type boards are as follows: (a) it is possible to make them high density, because of the very small via-post developed; (b) Any type of resin can be used; (c) Stacks are possible; that is, mounting a post directly above another post; (d) wirebonding to a pad is possible by use of the via-post. We developed high density, high quality, lower costing, and easier to enable via-post type Build-Up PWBs for Card PCs using conventional PWB equipment. The following is a report on our investigation and the result of trial PWB evaluations.