A wafer level encapsulated FBAR chip molded into a 2.0 mm × 1.6 mm plastic package for use as a PCS full band Tx filter

A high performance 2.0 mm × 1.6 mm × 1.0 mm full band filter is demonstrated. The small filter size is achieved by: 1) encapsulating the die in a chip scale hermetic package; and by 2) molding that chip scale package into a plastic chip-on-board package. This new packaging scheme reduces the filter cost and allows for further size reduction. The filter has a minimum insertion loss of ∼ 1 dB, is guaranteed to have a 3.5 dB worst-case insertion loss in the Tx band (1850-1910 MHz), and typically exhibits 35 dB of rejection in the Rx band (1930-1990 MHz). The filter comprises high-Q FBAR resonators that enable it to make a sub-10 MHz transition from the pass to stop band. Hence the required rolloff within the 20 MHz (1%) guard band can be achieved while accounting for both manufacturing variations and operating temperature drifts. The filter achieves ∼ 25 dB of rejection at the second harmonic (3700-3820 MHz) and typically 15 dB of rejection at the third harmonic (5550-5730 MHz).