Package-level electromagnetic interference analysis

Electromagnetic Interference (EMI) is becoming more problematic as both the number of components in a system and operating speed increase. This paper introduces possible EMI problems at the package level, and various package stack-up structures and templates are compared. In addition, die shielding, package edge shielding, and package lid shielding effects on EMI are discussed. Primarily, the package lid is used for heat spreading and warpage control. However, the impact of EMI is significant, and properly grounding the lid is a very important. A major contributor of EMI in the package is cavity resonance. The package structure, along with the lid, can create a rectangular resonant cavity, where the resonant frequency of its TMzxx0 modes can be calculated using equations based on the substrate material and package geometry. The resonant frequency is related to the dielectric material properties and substrate size. This phenomenon was verified through simulation using a full 3M EM field solver. Furthermore, a test vehicle was fabricated and compared to the simulation results. These analyses help identify possible weak spots in the package and device and determine the most effective solution for improving package-level EMI problems.