Investigation Of EMI In High-speed Package

With the rapid increase of data rate and bandwidth,electromagnetic compatibility(EMC)problems are becoming more challenging for package design.Electromagnetic interference(EMI),as the core issue in EMC field,has attracted much attention of researchers both in industry and academia.Therefore,based on commercial packaging technologies,some potential EMI problems caused by high-speed signal are investigated,and the corresponding solutions are proposed in this paper.First,the EMI characteristics in high-speed transimission are explored based on typical wire-bonded quad flat package(WB-QFP)and wire-bonded ball grid array package(WB-BGA).The details of results are discussed and analysed using the electric field limit of unintentional radiation as the major criterion,combined with S parameters,surface current and electric field distribution.Bonding wires,thickness of substrate and dielectric constant are found to be the major contributors of EMI emissions for WB-QFP package.And for WB-BGA package,lid and bonding wires are the most important factors below 25 GHz.In order to predict the resonant frequencies accurately,the equivalent circuit of bonding wires are developed with good agreement to the full-wave simulation.Then,several practical solutions are proposed to solve the EMI problems in WB-BGA package,including a novel type of package lid based on electromagnetic bandgap(EBG)structures,resistive vias,a resistive lid and return path of bonding wires.And all these techniques can suppress radiation significantly.In particular,a suppression over 8 dB?V/m is achieved from 3 GHz to 25 GHz by using a resistive lid.Finally,two broadband EMI shielding structures based on periodic graphene resistive patterns are designed in combination with the conventional EMI shielding structures and the unique electrical properties of graphene,which achieve 95%absorption from 39.2 GHz to 200 GHz.The characteristics of parameters and the physical mechanisms are analyzed in detail.