Miniaturized high frequency fundamental MCF for IF filters in mobile radio systems

This paper describes a miniaturized high frequency fundamental monolithic crystal filter (HFF-MCF), which is suitable for the intermediate frequency (IF) filter in the mobile phones. Miniaturization of this HFF-MCF has been achieved with a face-down bonding technique. HFF-MCF chips are housed in a ceramic package with a cantilevered beam structure using a silicone-based conductive paste. Miniaturized HFF-MCFs of 71 MHz to 110 MHz are housed in ceramic packages with external dimensions of 3.8 mm×3.8 mm×0.9 mm. Results of frequency responses, thermal characteristics and reliability tests for the face-down HFF-MCFs are shown in this paper. For higher frequency applications, a 265 MHz HFF-MCF is also presented, which is housed in a package of 3.0 mm×3.0 mm×0.8 mm