4D-2 High Volume Production of a Fully Matched 5050 PCS-CDMA-BAW Duplexer

Since 2001 bulk acoustic wave (BAW) technology is highly investigated due to its silicon-based technology for further integration in the RF part of e.g. mobile phones. At the IEEE UFFC Symposium 2005 in Rotterdam EPCOS presented the very first results of several CDMA related components like 3838 PCS BAW duplexer, full-band Tx-filter and Rx diversity filter using the solidly mounted resonator (SMR) technique and packaged using EPCOS' proprietary CSSPlus technology [Schmidhammer, E, et al.]. Meanwhile we have successfully started the high-volume production of a fully matched 5050 PCS BAW Duplexer, a component, which was requested by various customers. This BAW duplexer has been specifically designed to match the impedance network commonly employed at the PA output path, transforming the PA output impedance level of approx. 3 Omega into the 50 Omega reference level. Qualification tests according to JEDEC and IEC standards show a high reliability of the component with respect to temperature-shocks (-40deg/125deg), damp heat steady state tests (85 degC/85% relative humidity) and high temperature storage (125 degC). These quality levels were mainly achieved by employing a newly developed Ni-based UBM. The presented results show clearly our continuing improvements within SMR-BAW technology. Our process flow using a 200 mm manufacturing line uses only the minimum number of process steps by still keeping a high yield in combination with high process stability and high process robustness. EPCOS is the first component supplier worldwide deploying high-volume production based on 200 mm wafers