6B-6 An Ultra Small SAW RF Filter using Wafer Level Packaging Technology

Since a multitude of surface acoustic wave (SAW) filters are the key components for wireless communications, they play an important role in today´s mobile phone evolution. Increasing the levels of functional integration and size reduction are therefore the major driving forces in recent SAW radio frequency (RF) filter development. This paper presents a pioneering work for design and fabrication of ultra small SAW filter package. A novel wafer level packaging technology based on through-wafer interconnection and wafer-to-wafer bonding is designed to achieve highly miniaturized SAW RF filters. Based on this technology, SAW RF filters for mobile phone systems are developed in the world´s smallest size of 1.0 times 0.8 times 0.25 mm³. It is shown that our newly developed SAW RF filter offers equal frequency characteristics compared with the conventional chip-sized package. And the reliability test result of hermetically sealed SAW filter package will be presented to verify its application to mobile phones. As a result of these developments, wafer-level packaged SAW RF filters will offer considerable advantages over conventional chip-sized packages in many aspects of performance and production, including size, cost, and further integration