How It's Made: Optimal SMT Launches For QFN Packaged MMIC Filters

In my previous tech note exploring TDR as a method for optimizing surface mount footprints, we determined the root cause of the evaluation circuit’s performance degradation and added an inductive taper to the launch to improve impedance matching. By optimizing the PCB launch into the package, insertion loss and return loss performance significantly improved (Figure 1). In this tech note, we will break down surface mount packaging parasitic sources and present solutions to combat these undesirable parasitics