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.
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?
Maybe make a Matryoshka potting job with the SD card in the middle container (and no potting compound) and an outer potting box with epoxy.
Change of dimension as the epoxy cures and with temperature on a non-compressible material might cause the connections to be unreliable.
If you seal the inner vessel with silicone, be sure to use electronic grade, the acetic acid cured type (smells like vinegar) is not compatible with reliability in electronic devices.
You could just use blue tack / white tack. You can easy remove it if needs be, but you can create an airtight seal that will stay in place.
Edit: I think a better solution would be to use something like a project box to keep it waterproof. What is the reason for preventing removal? For vibration or similar, you could seal around the slot to keep it in place.
