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Protecting components from surrounding dielectric constant

 
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Koen
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Joined: 06 Jan 2016
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PostPosted: Wed Jan 06, 2016 5:34 pm    Post subject: Protecting components from surrounding dielectric constant Reply with quote

Hello,

I would like to pot a PCB including RF inductors and capacitors. The potting compound has an Er of 4.6, similar to FR4. It impacts the capacitance of the RF components and I would like to shield these with a bubble of air to reduce these changes. Would you have an idea of the necessary shielding space needed around 0402 components ? Would a few millimeters left, right and above be enough or is much more volume needed ?

Thank you !
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admin
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Joined: 03 Jan 2007
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PostPosted: Wed Jan 06, 2016 6:06 pm    Post subject: Reply with quote

3mm would be more than enough for 0402s.

The fields on capacitors are pretty tightly bound so I wouldn't expect a huge change in capacitance. Inductors won't be affected unless you are near their self resonant frequency.

I would say 0.5mm surrounding the components would be more than sufficient
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Koen
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PostPosted: Mon Jan 25, 2016 6:25 am    Post subject: Reply with quote

Thank you for your answer ! I will try to surround the components by a thin layer of air and report of the results as I had a terrible time finding literature about this problem.
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