6

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?

enter image description here

  • How much current does it use currently? What's that black stuff underneath the IC? I don't think heat is an issue, as the ATMega has a temperature range of -40C to 85C. – Gerben Nov 22 '15 at 20:00
  • The black thing is an ic holder, like the one on UNO boards. I powered it at 3.3v and it worked fine in air. – futurebird Nov 22 '15 at 20:01
  • 2
    I asked for current, not voltage. I the future I'd solder wires directly to the IC, instead of using a IC holder. – Gerben Nov 22 '15 at 20:02
  • 1
    For your next try, use a conformal coating (and test it) before molding it into the resin. Replace any switches with corresponding jumpers – James Waldby - jwpat7 Nov 22 '15 at 20:04
  • 2
    One could easily imagine resin seeping into the ic pin - socket interface and pushing the contacts out of contact. – Chris Stratton Nov 22 '15 at 20:53
3

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.

| improve this answer | |

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.