Inductance and SSN performance comparison of a 225 plastic BGA and a 208 plastic QFP

This paper focuses on the simultaneous switching noise (SSN) performance comparison between two compatible packages: a conventional leadframe plastic 208 QFP and a plastic 225 BGA with planar designed structures for power and ground. Self and mutual lead inductance (L) of the 208 QFP, hence its L matrix, was experimentally characterized by using a network analyzer based measurement technique. The same technique and formulation were extended to characterize the power and ground L of the 225 BGA which consists of multiple sources/sinks planar structures. To compare their SSN performance, the effective L of these two packages was calculated from the measured self/mutual L and power/ground L data by assuming certain switching conditions and pin assignments. It was discovered that effective L of the leadframe QFP decreases proportionally with increasing number of assigned power/ground pins, but effective L of the planar designed BGA does not exhibit this trend due to the current sharing and crowding in its power/ground planes. The study was further extended by constructing complete circuit models of these two packages including connection to bond wire, driver, chip power bus, and board-level interconnect models for full SPICE simulations