I would like to know whether it is possible to completely cover/pot a microSD card inserted in a slot (which is soldered on a pcb) with an epoxy resin. Will the sd card continue working properly? Will the card's contacts work without problem with the epoxy? If this could be done but not with epoxy, please suggest other potting compound or technique.

My reasons for doing this are to prevent microSD removal from the slot and also waterproofing.

  • \$\begingroup\$ What you need to worry about would be the contact later between said SD card and the holder. \$\endgroup\$ – winny Jul 8 '18 at 10:40
  • 1
    \$\begingroup\$ Get a waterproof SD card compartment and pot that \$\endgroup\$ – PlasmaHH Jul 8 '18 at 11:55

I wouldn't recommend it.

So, here's my theory:

SD card contacting depends on spring contacts in the SD card holder.

If your potting compound creeps into the gap between SD card and holder contacts before it hardens, it's game over.

But even if it's too viscous to creep in before it sets, chances are you now have removed all springiness from the contacts. Now, imagine your PCB gets colder: the potting beneath the contacts shrink. Since they are mechanically restricted by the potting in the direction of shrinkage, they might not be sliding along the SD card contacts while doing so, but simply go "away" from these contacts (my hypothesis here is that the potting compound will have similar thermal properties as the PCB, and thus lower thermal expansion per Kelvin; thus, it will "drag" the contacts towards the PCB surface, and not along the axes they will usually be following when contracting). That way, you might be breaking your contact.

Are you sure that microSD is the technology of choice if you need non-exchangeable memory? Wouldn't using a simple eMMC chip not be cheaper than soldering on a complex SD card holder?

  • \$\begingroup\$ Thanks for your answer. I have an existing design that I need to "waterproof" but I may consider a design change as you suggest since it looks like what I intended to do will not work. \$\endgroup\$ – Kozuch Jul 8 '18 at 11:54
  • 2
    \$\begingroup\$ I might help to cover the SD-card holder (with card inserted) in RTV silicone before potting. \$\endgroup\$ – brhans Jul 8 '18 at 14:06

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.