Electronics > Projects, Designs, and Technical Stuff
EMI foam on top of ICs
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subliti:
Hi
I saw this teardown video from Dave (https://youtu.be/sKcH4JxnxbQ?t=992) and some of the chips had some kind of emi foam on top of it. I never saw this before and i find it interesting. Does this only work for low freq and does something similar exist for high freq ? And what is high or low freq in this context ?
I was wondering....could one reduce the overall noise floor of a rf radio chip that is in the same enclosure with a bunch of other chips lika a mcu etc if i put this foam on top of the mcu etc, could this improve something ? Even if the rf section is already shielded by a metal case, could this improve something ?
Kleinstein:
A closed metal can is a RF resonator. For the really high frequency stuff (> 1 GHz) sometimes addition absorbers are added to dampen the resonances. The higher the frequency the more important it gets.
Having this in a low frequency meter is odd. I am a bit with Daves guess - maybe a desperate late addition to meet EMI requirements.
coppercone2:
those digital chips can make high frequency emissions (MCU).
If the converter has a pass transistor built into it then maybe? It could maybe have a high impedance some where that is being modulated by digital signals to effect a power rail (acting as a RF amplifier mainlining noise into the power rail at low impedance).
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