Effects of power/ground via distribution on the power/ground performance of C4/BGA packages

The effects of the distribution of power and ground vias in C4/BGA type packages are studied. Two types of via distributions are evaluated. One type has vias concentrated in the core area. The other type has vias uniformly distributed across the package. The performances of package power and ground supplies are evaluated through their resonance characteristics, impedances and effective inductances. It is found that the lowest package resonant frequency is increased by adding power and ground vias to the package. It is also found that there are no significant differences in the lowest resonant frequencies between the two types of via distributions, but the centered via distribution results in substantially lower effective package inductance.