Effects of plating stubs on the electrical performance of wirebond PBGA packages

In order to continue using some of the cost-effective and conventional packaging technologies for high speed applications, it becomes increasingly important to accurately model and characterize some of the unique package structures alongside wirebonds, vias, solder balls or pins. In this paper, we study the effects of plating stubs on the electrical behaviors of plastic ball-grid-array (PBGA) packages over a wide frequency range. Quasi-static and fullwave analyses of several PBGA package designs with different layouts and lengths of plating stubs are performed. The scattering parameters obtained from fullwave analyses are then used to perform frequency- and time-domain simulations to determine the degradation of the package performance due to the plating stubs. The effects of wirebonds, substrate traces, vias, and plating stubs on the signal nets are also studied using quasi-static models. The transfer curves and the eye diagrams of the simulated waveforms of the PBGA packages with and without the plating stubs are compared The simulation results are correlated with measurement data that are used to improve the accuracy of the models.