Research On Electromagnetic Radiation And Suppression Method Of System In Package

As consumer electronic devices rapid move toward miniaturization and high speed,the development of packaging in the future will always be accompanied by serious electromagnetic interference(EMI)problem.This resrarch is based on the prevailing Wire Bonded Ball Grid Array(WB-BGA)package that is a kind of system in package(Si P)and the new Si P with sputtering coating shielding scheme,the EMI problem is studied.Aiming at the WB-BGA package that has been widely used in consumer electronic devices,this article provides an accurate modeling method for the package,especially the current research involves less on-chip inductance modeling.Then,based on the accurate modeling of the package simulation model,the far-field radiation results of the on-chip inductance and the off-chip structure are obtained by simulation.Through the comparison results,it is determined that the main reason for the excessive radiation of the WB-BGA package near 10 GHz is the on-chip inductance.This research is helpful to analyze other packages with on-chip inductors through simulation modeling,and guides the future design of packages in consumer electronic devices.Based on the actual commercial Si P with sputter coating shielding scheme,this research studies the EMI problem of near-field shielding performance problems.Through the combination of theoretical analysis and full-wave simulation,multiple influencing factors of its electromagnetic shielding performance are explored,mainly including the thickness of t coating thickness,conductivity,defects,uniformity,direct current resistance from coating to ground,solder ball distribution,etc.According to the previous research results of electromagnetic shielding performance influencing factors,the radiation leakage in the Si P with the sputter coating shielding scheme mainly comes from the radiation leakage of the BGA layer.According to the previous research results on the influencing factors of the electromagnetic shielding performance of the Si P with sputter coating shielding scheme,the radiation leakage of the package mainly comes from the ball grid array(BGA)layer,so this research proposes two optimization schemes.Therefore,two optimization schemes are proposed in this paper.Firstly,the following optimization strategies can be adopted for the distribution of solder balls:(1)the spacing of the ground solder balls should gradually increase with the increase of the distance from the radiation source,thereby reducing the electromagnetic field intensity of the face with holes;(2)Ground solder balls should be distributed in all directions to avoid the situation that the gap between the coating film and the ground plane is not cut off.The optimized ball distribution can improve the shielding performance by over 20 d B.Secondly,based on the gap waveguide theory,the mushroom-shaped electromagnetic bandgap(EBG)is applied between the package and the ground plane,which can reduce the electromagnetic field intensity at the gap between the coating and the ground plane,thereby improving the shielding performance.The simulation results show that both the mushroom and spiral EBG can significantly improve the shielding performance in the working frequency band.