Methodology for Efficient Modeling of BGA Packages at RF/microwave Frequencies

This contribution presents a methodology for efficient modeling of ball grid array (BGA) packages at RF/microwave frequencies. Since even remarkably small package discontinuities may cause signal integrity (SI) problems at these operating frequencies, our methodology focuses on thorough RF modeling of each package interconnecting segment along the entire signal path (from chip to board). It commences with a segmentation of the signal path into various interconnecting segments, taking into consideration the discontinuity effects, rather than just the physical discontinuities themselves. This is then followed by electromagnetic (EM) and equivalent circuit modeling of each segment up to a frequency of 25GHz, thereby providing an in-depth understanding of the parasitic nature of the interconnecting segments. In order to validate these models, test structures were designed, fabricated and measured. For each segment, a good correlation was obtained between measurement and simulation results. Finally, all the separately extracted models were then combined to generate a wideband model of the complete signal path, which can be used to track down SI problems caused by each interconnecting segment.