I'm working on a hydraulic valve driver board for some heavy equipment, and am toying with the idea of potting them in epoxy, pourable RTV, etc. The main reason is mechanical in nature; I'm using two small PCB's, 90 degrees to the main card as the user interface, potting it would make in into a brick which would secure the small boards. This might seem overkill, but these machines have very severe vibration and any hanging mass is vulnerable to destruction. Also protection from moisture, hydraulic fluid, etc. is a secondary reason. I put a drawing which might explain the setup better at:
In the past, I've only done this with prototypes or one-offs using regular epoxy. The commercially available stuff from MG Chemicals and Loctite looks to be very good quality, and designed specifically for potting, but it's much more expensive that I would have guessed. $100 - $150 per gallon.
I'm sure someone out there has come across this problem as well. Any hints? Is this stuff commercially available for other applications at a better price? Standard gallon jugs of epoxy (from the hardware or craft store) supposedly have a lot of shrinking as they cure which can shear parts off the board. I've read that some people "cut" the epoxy with sand to control this and act as a cheap filler, has anyone had experience with this?
Thanks!
Chris