Archive of the former Yahoo!Groups mailing list: Homebrew PCBs

I didn't get the start of this thread so I'm getting in late. I take it
that the object is to make some custom connectors. I do this routinely to
make connectors that will fit into the recesses of my models. I also use
vacuum equipment to make castings and laminates (and on occasion a spy
satellite) so I have some experience with that process as well.

First, as far as safety is concerned, a pressurized vessel is far more
dangerous than a vacuum vessel. I was the safety officer for our autoclave.
To make me more attentive to the safety concerns, my office was in a direct
line with the autoclave door. If the thing blew, I'd go right along with it
across I-95. I made sure it wouldn't blow. Everyone probably has several
dozen vacuum chambers in their homes in the form of light bulbs. Failure of
a vacuum chamber results in things being drawn into the chamber, away from
the operator. As long as the structure doesn't shatter (like a light bulb)
not much harm can come of it. A pressure vessel failure can cause major
distruction even at relatively low pressures.

For potting connectors, there is probably no need for either vacuum or
pressure pots. There are epoxy formulations which will degas with little or
no assistance. The biggest problem is keeping the uncured epoxy in place
while not contaminating the electrical contacts. I've used Epon 814 and
Versamid 104 mixed at a @:1 ratio to pot circuit boards. This is not the
recommended mix ratio, but cured at 105°F overnight it produces a bubble
free solid matrix. If you can construct a 2 part mold and figure out how to
keep the resin from leaking out the bottom, it should be fairly easy to
produce your custom connectors.

For my purposes, since each connector is unique, I just plug headers and
sockets together (I use perf board to position the parts and major cutting
and fitting is usually required) then I use a brush to coat them with a
thixotropic epoxy paste. I then stick the whole mess into the spot where
they will have to fit (mold released of course) and let them cure. Do this
once for the male side and once for the female side and I have a connector
fitted to the particular installation.