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Butcher
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Epoxy Potting RF Components

09/05/2008 4:05 PM

I am a mechanical engineer and want to get some electrical guidance on epoxy potting an RF board. I need to package a small radio that consists of two stacked PC boards about the size of a credit card. Part of one board is a radio, so it has several analog and RF components and an SMA connector. No high voltages are involved. Heat dissipation could be an issue, but please disregard that for now, it's not what I need help on. One option I'm looking at is potting the entire unit, but I know that the dielectric properties of the potting compound will screw up the RF components by shifting filter and transmit frequencies, etc. Has anyone successfully potted RF electronics? If so, please let me know how you got around this problem. Thanks, Butcher
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Pathfinder Tags: electrical epoxy housing potting RF
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Sparkstation
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#1

Re: Epoxy Potting RF Components

09/05/2008 6:34 PM

Hello Butcher

It is not regarded as advisable to "directly epoxy pot" over the RF components.

What is normally done is to place the RF area of the circuit, including all the RF components inside a thin metal case, which case is connected to the "ground plane" of the printed wiring.

Once the circuit has been proven to work correctly, and no further adjustment is required, the complete assembly may then be safely epoxy potted, and there will thus be no alteration in frequency etc. in the RF circuitry.

If you are unsure, look at a typical TV tuner RF section of a TV card for a computer, and you'll see the RF section inside the "metal can connected to the RF ground plane", although those particular cards are not epoxy potted - Note the picture at left.

Kind Regards....

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aurizon
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#2
In reply to #1

Re: Epoxy Potting RF Components

09/06/2008 8:06 AM

hold on, there are many types of epoxy and other potting compounds. Then there are the fillings of them. For low frequency you have more latitude, and many potting material and fillers will be acceptable. As you increase the frequency the properties of the filler as well as the compound can influence resonance, "Q", and coupling. If this is going to be in an adverse atmosphere you might consider sparky's tin cans, but solder all seams and fill all vias so you have a steel pot with air inside. some ideas are found here

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Butcher
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#3

Re: Epoxy Potting RF Components

09/06/2008 8:50 AM

Thanks guys, that is helpful and gives me some more confidence in what I've found looking around on my own. I'll post back once I try it (probably not for a few months, unfortunately). Thanks, Butcher
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Anonymous Poster
#4

Re: Epoxy Potting RF Components

03/02/2009 11:08 AM

Hi Butcher,

I am experiencing a similar issue with a microelectronics board that needs to be potted. I would like to speak with you by email or phone about your findings. What's the best way to get in touch with you?

-Marc

marcshin@gmail.com
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Mok Thye Linn
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#5

Re: Epoxy Potting RF Components

04/29/2020 10:23 PM

For this application, you need a flexible potting material. The hardness is critical for the RF transmission also. Kindly refer to the following information.

Feel free to send in your request if found interested: enquiry@penchem.com
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spanz
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#6

Re: Epoxy Potting RF Components

08/20/2020 12:07 PM

RF will get effected by potting. Microwaves even more so.

Unless you are launching a high voltage power supply into outer space, i seldom see potting used for any RF products today.

what is used is common FR4 pc boards, and some sort of slightly ductile epoxy coating. Google "Glob top" component sealing

if all you care about is moisture, there are "conformal coats" that go on very thin that work too
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Anonymous Poster (1); aurizon (1); Butcher (1); Mok Thye Linn (1); spanz (1); Sparkstation (1)

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