Modular integration of RF SAW filters

A desire to incorporate multiple functions into a single component continues to drive product size reduction in the wireless electronics industry. In the radio portion of wireless handsets, many of the functions have been modularized. Because surface acoustic wave (SAW) devices are built using a piezoelectric substrate, they require unique packaging in order to ensure their functionality. Some form of a hermetic cavity over the active area of the SAW die is necessary to avoid damage or mass loading to the unpassivated surface. This paper reviews the nature of the RF SAW filters and current packaging approaches. A novel encapsulation process for these filters is discussed. The active area of the filter is protected at the wafer level by a low profile hermetic lid. It can thereafter be tested, singulated and integrated along with other devices into a module. Examples of modules used in wireless products with integrated SAW filters are given.