EMI problems caused by the presence of heatpipe/heatspreader and heatsink structures in a high-speed design are well known in engineering practice. High-frequency noise can be coupled from IC packages to an electrically conductive heatsink or heatspreader attached to the IC, which then is radiated, or the energy coupled to an enclosure cavity mode. This EMI coupling path was modeled with the finite-difference time-domain (FDTD) method, and a mitigation approach was investigated. Good agreement between measurements and FDTD modeling is demonstrated, indicating FDTD is a suitable tool for analysis and design. Then, several grounding schemes suitable for a heatsink or heatspreader were compared using FDTD modeling. The results indicate that sufficiently connecting the heatspreader or heatsink to the top layer of the PCB, even without further electrically connecting to the PCB ground plane, can result in appreciable EMI reduction. Good electrical connection of the heatsink or heatspreader to the PCB ground plane through an SMT-mount approach can achieve a 10-25 dB reduction for EMI attributable to the proposed coupling path.
C. Wang et al., "Grounding of Heatpipe/Heatspreader and Heatsink Structures for EMI Mitigation," Proceedings of the IEEE International Symposium on Electromagnetic Compatibility (2001, Montreal, Quebec), vol. 2, pp. 916-920, Institute of Electrical and Electronics Engineers (IEEE), Aug 2001.
The definitive version is available at http://dx.doi.org/10.1109/ISEMC.2001.950507
IEEE International Symposium on Electromagnetic Compatibility (2001: Aug. 13-17, Montreal, Quebec)
Electrical and Computer Engineering
Electromagnetic Compatibility (EMC) Laboratory
Keywords and Phrases
EMI Coupling Path; EMI Mitigation; FDTD; IC Packages; PCB; SMT; Earthing; Electrical Connection; Electrically Conductive Heatsink; Electromagnetic Interference; Enclosure Cavity Mode; Finite Difference Time-Domain Analysis; Finite-Difference Time-Domain Method; Grounding Schemes; Heatpipe; Heatsink; Heatspreader; High Frequency Noise Coupling; High-Speed Design; Printed Circuits; Finite Difference Method; Heat Pipes; Heat Sinks; Printed Circuit Boards; Time Domain Analysis; Cavity Modes; Signal Interference
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Article - Conference proceedings
© 2001 Institute of Electrical and Electronics Engineers (IEEE), All rights reserved.