Earl,
1) There is no way that a good paraffin wax "works it way" into a solid
solder joint.
2) Are you sure that liquid high boiling hydrocarbons from a cheap wax (not
properly separated in the first place in the refinery) have left the wax and
slithered their way into mechanical switches and other moving parts on the
circuit boards instead?
3) If you really are finding hydrocarbons in cracked joints, then they
cracked first and then the migration happened.
4) You will note I used a lot of adjectives - good chemist "weasel words".
All bets are off if you have some weird, corrosive "goo".
5) Peter's suggestion and component warning were correct.  I would add the
usual safety cautions regarding proper ventilation and static spark
generation.
6) I think you mean methylene chloride (CH2Cl2).  You use that and are
worried about paint thinner?  Methylene chloride is a suspected carcinogen
and has a low boiling point (104F, 40C if I did my math correctly for those
of us who are not in the hegemony of the US, Liberia and Yemen who have not
gone metric  :)  ).   Of course "paint thinner" is pretty generic and it can
range from a mixture of hydrocarbons to mixtures that contain acetates and
toluene to those that contain some rather nasty ketones that I don't want
going up my nostrils (and into my liver)!
7) It sure sounds like the contact cement is more likely your villain,
especially since you can see its effects.
8) Anybody out there got a good suggestion for Earl with regards to
softening/dissolving (possible?) the contact cement?
9) I would worry about the effect of methylene chloride on some of the
plastics used for components.
10) You can buy some neat little batch reflow ovens from Tomken Industries.
http://www.tomkenindustries.com/reflow.htm They market a Techno HA-02 and
06.  I am sure there are others.

Hope this helps.

regards,
Bev Christian
Research in Motion


-----Original Message-----
From: Earl A. Pruitt [mailto:[log in to unmask]]
Sent: March 15, 2002 10:07 PM
To: [log in to unmask]
Subject: [TN] Contaminated solder


I am an electronics tech servicing 10+ year old amateur radio gear.  The
trouble I am having is with a single sided through-hole board.  Areas of
the board are covered with wax.  Over time the boards malfunction as the
wax works its way into the solder.  Hand resoldering is a nightmare as the
wax continues to wick towards the connection.  Heating the board and
draining the wax away does not help as some wax residue is left.  Also,
components become damaged from the air gun.  The boards are also covered
in contact cement that has become corrosive and conductive.  Currently we
are using Methaline Chloride to soften the glue and then pick it away.
Questions are as follows: 1) How can the wax be completely removed? 2) How
can the glue be removed without using such a toxic substance as paint
stripper? 3) Is there an economical device that can be purchased to reflow
these old boards without hand resoldering hundreds of cold/contaminated
connections?  Any help would be greatly appreciated!

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