A simple filtering approach to improve the return loss of a PCB to DIE transition trough a PBGA package for over GHz applications

We present in this paper, based on HFSS simulation studies, a simple way to improve a PCB to DIE transition (trough a Plastic Ball Grid Array (PBGA) package) for a 50 Ohm impedance of reference. The method uses well known technique for the synthesis of Low Pass (LP) filter based on Standard Engineering normalized tables. A II model of the PBGA transition at high frequency is used as one of the embedded building block of a typical LC ladder filter. The additional LC sections around the PBGA transition are distributed (microstrip) elements on the PCB side and lumped elements on the DIE side. Such simple filtering technique improves in very significant way the return loss (RL) margin over the accepted -10 dB threshold in the RF industry.