Broadband BGA-Via Transitions for Reliable RF/Microwave LTCC-SiP Module Packaging

This letter presents two broadband ball grid array-via transition structures applicable in reliable radio frequency/microwave low-temperature co-fired ceramic system-in-package (LTCC-SiP) module packaging from dc up to the K-band. The first transition provides better electromagnetic shielding, while the second one exhibits 40% wider bandwidth by including an air-cavity in the LTCC module. To specifically address board-level reliability, novel plastic-core solder balls as large as 1100 mum were employed. The measured 1-dB cutoff frequencies of the transition structures, all the way from the printed circuit board up to the top surface of the module package, were 19 and 27 GHz. In addition, equivalent circuit models for the transitions were developed.