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 71MHz to 110MHz are housed in ceramic packages with external dimensions of 3.8mm x 3.8mm x 0.9mm. 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 265MHz HFF-MCF is also presented, which is housed in a package of 3.0mm x 3.0mm x 0.8mm.