user8769: I made a simple circuit controlled by the ATMEGA IC then tried to encase it in resin. It died. What is the thing that caused it to die? I've had other circuits working fine in resin. I want to try again, what steps can I take to prevent this?
I've looked for obvious shorts but can find none. 
Resin heats up when it cures, could that be the issue?


user4358: Potting of circuits can lead to various issues. It can't be told exactly what caused your device to fail until you uncover it like an archeologist.
Common problems are:

Resin entering a spring loaded contact and canceling out contact forces
Resin exsuding corrosive substances ruining contacts
Resin expanding during curing and opening spring contacts or even breaking up solder contacts
Same effect after cool down of resin

Later and often unexpected problems are:

thin gaps around potted objects (i.e. no surface contact) literally sucking in water. 
potting material producing water itself during curing.

Many of these problems can be circumvented by applying conformal coating, as suggested by comments and apparently proven right by your experiments. 
If it is not necessary refrain from using sockets and solder connections directly to the components. You won't be able to salvage them, anyway.

8769: <p>I made a simple circuit controlled by the ATMEGA IC then tried to encase it in resin. It died. What is the thing that caused it to die? I've had other circuits working fine in resin. I want to try again, what steps can I take to prevent this?</p>

<p>I've looked for obvious shorts but can find none. </p>

<p>Resin heats up when it cures, could that be the issue?</p>

<p><a href="https://i.stack.imgur.com/WaMDY.jpg" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/WaMDY.jpg" alt="enter image description here"></a></p>
 4358: <p>Potting of circuits can lead to various issues. It can't be told exactly what caused your device to fail until you uncover it like an archeologist.</p>

<p>Common problems are:</p>

<ul>
<li>Resin entering a spring loaded contact and canceling out contact forces</li>
<li>Resin exsuding corrosive substances ruining contacts</li>
<li>Resin expanding during curing and opening spring contacts or even breaking up solder contacts</li>
<li>Same effect after cool down of resin</li>
</ul>

<p>Later and often unexpected problems are:</p>

<ul>
<li>thin gaps around potted objects (i.e. no surface contact) literally sucking in water. </li>
<li>potting material producing water itself during curing.</li>
</ul>

<p>Many of these problems can be circumvented by applying conformal coating, as suggested by comments and apparently proven right by your experiments. 
If it is not necessary refrain from using sockets and solder connections directly to the components. You won't be able to salvage them, anyway.</p>
