Newsgroups: comp.robotics
Path: brunix!uunet!wupost!csus.edu!netcom.com!nagle
From: nagle@netcom.com (John Nagle)
Subject: Re: Epoxy on Wire Wrap
Message-ID: <1993Jan17.062530.6401@netcom.com>
Organization: Netcom - Online Communication Services  (408 241-9760 guest) 
References: <1993Jan15.155453@vinnie.cuc.ab.ca>
Date: Sun, 17 Jan 1993 06:25:30 GMT
Lines: 36

jonathan@vinnie.cuc.ab.ca (Jonathan Levine) writes:
>H. Y. Firooznia -- (hfir_cif@uhura.cc.rochester.edu) writes:
>>I've heard of people protecting wire-wrapped circuits by encasing them
>>in epoxy, or some sort of resinous substance, that when heated is fluid
>>enough to flow over and through all the nooks and crannies of a circuit,
>>yet hardens when it cools, to a solid, durable casing.  Does anyone know
>>of such a substance, and where I can find it?  What other techniques are
>>there for protecting wire-wrapped stuff, other than simply encasing 
>>a circuit in a box?

       If you're worried about humidity, you can use a conformal coating,
like Fine-L-Kote, to seal the board.  You mask the connectors and spray
it on; it glows in UV, so you can check that you covered everything.  
This leaves a light, tough, transparent coating.  Cheap, easy to apply,
and simple.  Takes a day to dry to non-tacky state, though.
Removable, with "Fine-L-Kote Remover", if you need to fix something.
"Protects against salt, water, dilute acids, limited resistance to lower
aliphatic alcohols, ketones, esters, petroleum spirits, and is mold and
fungus resistant," says the can.  From Tech Spray.  About $8 per can.
Often used on military electronics.

       There are heavier conformal coatings, which resemble shrink-wrap
after the material dries.  These are normally applied by dipping.  I've
seen these used for automotive electronics, but I haven't used them
myself.

       Sometimes one sees board covers on military electronics, sheet metal
covers that protect the components from rough handling.  You have to allow
some margin around the perimeter of the board for the cover.  Don't
know where to get these, but they'd make sense for wire-wrapped boards.

       Casting electronics into a solid block of plastic is possible,
but I haven't seen it done in years.

					John Nagle

