[sci.electronics] "potting" electronic circuits

bert@athens.iex.com (Bert Campbell) (08/03/89)

Back when I had absolutely no use for it I read an article about
"potting", encasing in epoxy/plastic/whatever small electronic
circuits.  Whay would one do such a thing?  Well, if you were building
a very small point-to-point gizmo in a small enclosure and you want
to freeze everything where it is positionally (to guard against shorts),
it would seem like a good method. RTV (silicone sealant to u) might
work but I'd rather use something hard.

Has anyone had experience doing this trick?  Can you use garden-variety
epoxy?  I think I have seen ads for materials designed for this purpose,
any sources?  Special thermal characteristics required?  Pointers, hints
kinks, sarcastic comments solicited, preferably by email.

Thanks well in advance,
Bert Campbell   {uunet,convex}!iex!bert

wiz@xroads.UUCP (Mike Carter) (08/03/89)

Several years ago I made my pocket money by creating "Frozen Wildlife"
abd glow-in-the-dark-key-chain-danglers.
Go catch a few Huntsman spiders, douse them in Chloroform and pin them out
until they started to dry.
Next, the local hobby shop stocked a good supply of Resin and catalyst.
Add the two in the prescribed way, drop "herman" into mold and pour.
 
You can buy plastic moulds or make one out of plasticene (SIlly Putty)
and hobby knife it to the shape desired. One thing to watch for is 
adding too much or too little catalyst. If you add too much the 
thermic reaction cooks whatever's inside and bubbles form. Too little and
the stupid thing may never fully catalyze and remain sticky.
Far too much catalyst caused the plastic to crack while curing.
You can also purchase dyes or colorants to add to the goop just before
pouring.
 
	
Several manufacturer's use this in an attempt to force premature obsoleteness
of modem & multiplexer power supplies and rip both of your arms off for a
replacement. Of course, the cure is ACID.
 
	-Mike
-- 
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= Mike Carter  N7GYX, Phoenix AZ| Q: Why did the Chicken cross the road  ?  =
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