Hi Bill!

I'd like to echo Tom's comments about the ability of vapor phase, or
condensation soldering to overcome a lot of thermal mass. I suppose you would have to
use solder pre-forms to accomplish the soldering for pin-through-hole devices
as in your case. My experience with vapor phase has only been with SMT
assemblies though. Tom is right about the price of the vapor phase fluid too...can
run around $600 a gallon!!

A company named Solvaysolexis (formerly known as Aussimont) makes something
they call Galden PFPE (perfluoropolyether) fluids that has boiling points that
range from 150 C. to 260 C.

http://www.solvaysolexis.com/pdf/gald_vapor.pdf

Vapor Phase systems are sold by one of our own Technetters, Graham Naisbitt
of Concoat (http://www.concoat.co.uk/), and there's a company here in the
states called R & D Technical Services (http://www.rdtechnicalservices.com/) that
sell systems.

When you say you use a Airvac solder volcano, are you talking about a Airvac
PCBRM-12? Dynamic solder pot with a bunch of different sized nozzles? I have
one of those here, and I'm having occasional trouble reworking connectors on
some thick back-planes...not as thick as your .250" boards, but I feel your
pain.

I had posted yesterday asking about a Zephyrtronics (http://www.zeph.com)
ZT-6 "Airfountain" to help me with pre-heating and rework, and I got a response
from a colleague of yours who works at Northrop Grumman Xetron, who has a ZT-6
and several ZT-1's. He said they're the next best thing to sliced bread when
it comes to soldering or reworking things on a big, thick, heavy copper board.
Personally, I'm going to try and get a demo unit in here as soon as everyone
gets back from APEX.

Hope this helps,

-Steve Gregory-

> Thanks a lot Tom.
>
> -----Original Message-----
> From:   Tom Gervascio [mailto:[log in to unmask]]
> Sent:   Wednesday, February 25, 2004 8:01 AM
> To:     [log in to unmask]
> Subject:        Re: [TN]
>
> In a previous life, we used to use a Centech vapor phase reflow to
> reflow large backplanes. May have issues with thermal shock due to the
> large temperature gradient generated when the vapor phase fluid (which
> is very expensive) condenses on the board and gives up the latent heat
> (heats up the board). On the positive side, it is impossible to overheat
> the board and can heat up large thermal masses quickly.
>
>
> Also maybe a preheat of a board before running the boards thru the
> solder wave with some topside flux application (just make sure that the
> flux gets properly activated and cleaned off).
>
> Hope this helps
>
> Tom Gervascio
> Senior Process Engineer
> Sparton Electronics
> (352) 540-4040
>
> >>> [log in to unmask] 02/24/04 02:50PM >>>
> Hi everyone,
>
> I am a Manufacturing Engineering in an area that builds test equipment
> for
> airborne radar systems.  For the past several months Design Engineering
> has
> been giving us a variety of "thick" boards to which to solder thru
> hole
> components.  The boards range in thickness up to .250".  We have been
> substituting press-in sockets where possible, but they are not always
> available in the sizes we need.  So far, in the most difficult
> situations, I
> have been using an Airvac solder volcano.  This works fairly well, but
> can't
> be used in all situations, and doesn't always result in flow thru to
> the
> other side.
>
> Is there any other system that would be more appropriate for thick
> boards
> where flow thru is a problem?  We are working to            J-Std-001B
> Class
> 3.  We are ready to go back to the designers (and have gone back to
> them),
> but I would like to find out if there are other possibilities first.
>
> Thanks for any help you can give,
>
> Bill Mengers
> Mfg. Engineer
> Northrop Grumman Corp.
> Baltimore
>




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