Shielding Effectiveness Simulation of SMT EMI Gaskets Utilizing ANSYS HFSS

Abstract

Abstract As more components populate smaller board areas, the risk of unwanted coupling between components increases. Shielding and radiated emissions tests outlined by IEEE standards such as IEC 61000-4-21 and ASTM4935D identify measurement techniques to quantify shielding effectiveness. In a PCB topology, shields enclose components to create a Faraday cage, but necessitate a method to ground and fasten the shield to the PCB. Typical methods include the use of gaskets, sealants and clips. This paper reviews a gasket methodology and validates a parameterized ANSYS HFSS simulation with the measured relationship between gasket configuration and shielding effectiveness. Surface mount, rectangular, compressible gaskets manufactured by W.L. Gore & Associates, Inc. are used in several configurations to shield a PCB radiator. Radiated emissions measurements are performed in an ETS-Lindgren reverberation chamber to evaluate shielding effectiveness for each configuration. ANSYS HFSS, a full wave Finite Element Method (FEM) electromagnetic simulation solver, is used to simulate each geometric configuration and is verified with measured results.