Electronic – Conformal coating and micro SD card sockets


I have a embedded computer design which uses a low profile micro sd card socket as an extra option in addition to an on board solid state disk as storage/booting mediums. In manufacture the board is coated with conformal coating but i'm in a bit of a pickle regarding the SD card socket and the coating.

The SD card socket should be masked i assume before coating is applied, otherwise it may seep into the connector i suspect, but then i am creating a bit of a weakness against moisture. It seems this particular weakness is inherent to the SD card socket.

Has anyone found a good solution for this on a professional level, or are these two things simply incompatible (card sockets and coatings/materials). Have you operated exposed sd card sockets in moist environments with a long durability ?.

What i'm mostly afraid of is that if i have the pin connections protruding from the chassis coated, the coating will seep into the socket. Expecting workers to be careful while hand coating stuff like this is probably too much and asking for trouble later.


Best Answer

You could try loading a dummy card while coating to act as a mask for the contacts. In my experience, SD cards themselves are quite hardy to moisture but unless you seal the SD card into the socket you'll have a potential for water ingress to the contacts. I've only dealt with conformal coatings a few times and usually the boards only have pigtails to avoid this sort of issue with connectors.

That said, I have potted boards with connectors installed for prototype systems and the epoxy never broke the contact. You might be fine installing the final SD cards prior to coating as long as you don't intend to access/remove them.