Charles:

There are two factors to consider:
Water vapor transfer and absorption.
Heat transfer.
Water protection requires high-density encapsulants like organic waxes
or gelled oils. Lower density plastics or epoxies will allow both
moisture transfer and absorption with time. Unfortunately the plastic
products do not have good thermal conductivity. Loaded epoxies can have
higher thermal conductivity.
Inorganic encapsulants like silicone have fair moisture characteristic
and good thermal conductivity.
If you use loaded silicone encapsulants the heat transfer will be even
better than with air.
Thickness helps delay the moisture transfer but also delays heat
transfer.

- Wayne Foletta
BMI - Saratoga, CA

> ----------
> From:         Charles Laforge[SMTP:cjoachim@HOTMAIL.COM]
> Reply To:     pic microcontroller discussion list
> Sent:         Friday, January 30, 1998 8:27 AM
> To:   PICLIST@MITVMA.MIT.EDU
> Subject:      Encasing Pic in Epoxy
>
> Hi Guys
>
> Just doing a little thinking here and I was wondering what my options
> are to protect circuitry from the elements.  I was thinking of
> encassing
> the whole controller (PIC, crystal, regulator, adc, etc..) in epoxy to
> protect it from rain, snow, etc...  I'm just curious if this would
> cause
> the components to overheat and eventually breakdown. Please, if you
> have
> experience with this sorta thing let me know what you've tried and
> whats
> been succesfull.
>
> Thank you
>
> Charles
>
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