Understanding how to model difficult features and related physical effects in electrical packages

We investigate and provide solutions for a number of features that are simple and occur frequently in electrical package analysis, yet are difficult to model accurately. We also describe physical effects where the results seem unusual and suspect, but actually are physically based. We consider the current spread from vias, apparent shielding ineffectiveness of ideal conductive enclosures, negative inductance in coupled line structures, situations where adding small valued decoupling capacitors actually increases noise, and gridding and convergence issues.