Waterproofing Circuits

[alvarop]

I found an old RSA SecurID and decided to open it to see what was inside.

The whole thing seems to be inside molded plastic. And what I mean is that they assembled the circuit, then poured the plastic around it and let it solidify. I couldn't really take it apart. (Without destroying the whole thing, which I did)

They did leave a nice window for programming though.

I was just wondering if anyone here has worked with such designs and could share some information as to how it's done. I'm interested in waterproofing some circuits, but I don't really know what the materials used are. I would also assume there can be some serious heat problems if done wrong.

Thanks!

[joelby]

The technique is known as 'potting' and usually uses epoxy. Heat conductivity and expansion are definitely things to consider. There's a lot of information at http://www.pottingsolutions.com/my%20site/Technology/potting_hints.htm .

[saturation]

If you don't have potting compounds, and your design does not generate much heat; you can DIY pot it with liquid tape.

Here's a good list of possible substitutes:

http://answers.hackaday.com/what-is-a-good-low-cost-dielectric-potting-material-for-high-voltage-electronics/

[tecman]

Also look for "casting compounds" which is a common term for fully encapsulating electronics.

paul

[Time]

Thats yours or you found it?  They still use those things.  You might get a reward if you return it.

[alvarop]

Thanks for the help! Now I know what to look for.

I used it to log in to my online banking, but I no longer have an account for that bank. Not to mention that the RSA database is out, so these are not as secure as they used to be.