Chip scale package for SAW filter on the oxidized porous silicon using flip-chip bonding and Cu plated metal wall

Abstract

Chip scale package (CSP) for surface acoustic wave (SAW) filter has been implemented on silicon with thick oxidized porous silicon (OPS) layer using the thick plated metal wall and flip-chip bonding technique and the RF performance of SAW filter was measured. The key approach of this article was that the SAW filter and semiconductor RFICs were packaged on same substrate (OPS) with same packaging method (epoxy molding) at the same time. In packaging the SAW filter, the surface should be maintained in hermetic void for the performance reliability, and this has been solved by metal wall and epoxy molding compound. The silicon with thick OPS layer had good RF performance. The transmission line loss was below 0.1 dB/mm in L-band. flip-chip bonded SAW filter on OPS layer showed the -2.6 dB passband loss and 0.95 dB maximum ripple in 865-895 MHz range and the stopband attenuation was below -50 dB. For the demonstration of CSP SAW filter, we have developed the dual mode (CDMA and AMPS) receiver module where the SAW filter was interconnected between low noise amplifier (LNA) and down mixer which was also assembled on OPS layer using multichip module technology.