Title: Heatsinks behave as an antenna a source of EMI problems

Abstract

The active/passive heatsinks have recently garnered much attention due to their benefit to keep the temperature of the electronic device and PCB/ICs in a certain range. A heatsink is expected both to perform a maximum cooling thermally and to have a minimum of the radiation in electromagnetic terms since it causes electromagnetic interference (EMI) in devices around. In this talk, many studies discussing the EMI and thermal performance (TP) of that in the literature are going to be discussed. We will look the natural convection heatsinks for thermal and electromagnetic (EM) performances in details. Especially in devices operating at high frequencies, these structures behave like antennas if their electrical dimensions are comparable to the interval of λ - λ/20 wavelengths. Analysis show that the heatsinks act as both a monopole antenna and a patch antenna. To eliminate the EMI from a heatsink, the grounding, shielding, and filtering techniques are studied. In the literature, the grounding methods are studied up to 2GHz and it is determined that it provides improvement up to 12dB. For 1-40 GHz it is possible to have up to 20dB improvements in EMI by using absorbers and shielding methods. The proposed solution approaches in the literature and their results are compared and the advantages and disadvantages of each approach are discussed. The base height of the heat sink is pre-dominant both from the heat dissipation and electromagnetic emission point of view in comparison to other parameters. Both the feeding point and type of feeding can be destructive or restorative for heat sinks from the antenna behavior point of view as well as its dimensions. In conclusion, heat sink performance in terms of temperature cannot be the only point to be taken into account, but their quasi-antenna behavior should also be taken into account.