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October 2005

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From:
Mel Parrish <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Mel Parrish <[log in to unmask]>
Date:
Mon, 3 Oct 2005 16:21:29 -0500
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Hey Doug,
Great to hear from the great cleaning O Guru always informative and interesting. 
As I'm sure you pointed out many times, a bevy (lots) of in-service failures have been created through the use of no clean/low residue flux with point to point (soldering irons) or localized flow like selective solder, after the initial soldering/cleaning process, since the normally temperature volatized residues don't see required temperatures as they disperse from the heat source toward the cooler periphery. Rework (touchup) or Touchup (rework) is often a traceable source. I suppose that the key is to know what the brew is in the intended flux. As Doug says, "good" flux may be OK, but there are others, and they may require testing as there are a lot of different brews available these days. 


Mel Parrish
STI Electronics Inc.
102 Tribble Drive
Madison, AL 35758
256 705 5530
256 461 9566 Fax
[log in to unmask]
www.stielectronicsinc.com
 

-----Original Message-----
From: TechNet [mailto:[log in to unmask]]On Behalf Of Douglas O. Pauls
Sent: Monday, October 03, 2005 2:49 PM
To: [log in to unmask]
Subject: Re: [TN] Mixing Fluxes: Water Sol and Rosin


Hoping to hear from Mr Pauls...

Well, Kevin, Mr. Pauls is my Dad, but I am willing to take a shot at it.

Your basic question of whether you CAN mix flux types on a single assembly
can be answered by  Yes you can.  See, I can answer a question with
something besides "It Depends".  I shall now pause whilst some individuals
pick themselves up off the floor.  You have received some good advance so
far.  I like George Wenger's answer about the order in which you use
fluxes.

The key to it all, as with most things in electronics manufacturing is
knowing what you are doing.  If you don't know what you are doing, then
mixing flux Bad Idea Kimosabe.  Understanding the residues and their
effects really dictates what you can and cannot do.  Understanding how much
flux is needed for any particular task is also important.  I have seen
companies use "dangerous" fluxes and produce reliable product and I have
seen companies use "safe" fluxes and produce garbage.  If you have the data
that shows you know what you are doing, and your process is robust, then
you can use almost anything.

Your customer says water solubles, but only rosin fluxes with topical
cleaning after that.  I am not a big fan of this approach either.
Operators have a little flux residue, smear it all over with a topical
cleaner and minimal rinsing and "poof" it is magically clean.  Anyone who
believes this should get their glasses, either prescription or safety, put
a drop of oil on one lense, then smear it around over a large area.  How
clean are the lenses?  Partial cleaning leads to more failures than no
cleaning.  What we do here at Rockwell is to use low solids fluxes and
pastes, clean them with an appropriate aqueous cleaner, and in selected
programs, use a good low residue flux and leave it in place.  Works great
for us.

So, that is a long winded way of saying "It Depends".

Doug Pauls




             Kevin
             <[log in to unmask]
             COM>                                                       To
             Sent by: TechNet          [log in to unmask]
             <[log in to unmask]>                                          cc

                                                                   Subject
             10/03/2005 11:34          [TN] Mixing Fluxes: Water Sol and
             AM                        Rosin


             Please respond to
              TechNet E-Mail
                   Forum
             <[log in to unmask]>
             ; Please respond
                    to
                   Kevin
             <[log in to unmask]
                   COM>






Is it acceptable to mix flux types on a single piece of hardware?  I have
background in MIL/AERO requirements of the "rosin only" creedo.  My past
experience is with rosin types only, to avoid all the emotional customer
issues and testing requirements.  However, I am now working for a company
and their SOPs dictate use of WS at first solder, followed by water
clean.  They then dictate rosin for any touchup, with hand clean only.  Is
there a risk in mixing water sol and rosin on a single piece of hardware?
What about resin and rosin?

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