Peter,
These comments sound very similar to some research papers and articles our
company has published on white residues & their sources. I will add that
certain soldermasks do have a propensity to absorb water and cleaning
chemistries and show a visible white residue after a cleaning process.
Here are links to some of our studies on white residues - hopefully they can
help in determining what is going on.
http://www.residues.com/pdf/processRx_6-04.pdf
http://www.residues.com/pdf/white_residue1.pdf
http://www.residues.com/pdf/white_residue2.pdf
Regards,
Sara Rice
Foresite Inc.
www.residues.com
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Joe Russeau
Sent: Tuesday, August 16, 2005 9:24 AM
To: [log in to unmask]
Subject: Re: [TN] White residues at wave soldering
Hi Peter,
The white residues may be leftover flux. I have seen several instances
where some flux formulations turn white after being exposed to water. It
does not necessarily mean it is going to cause you a problem, but it is more
times a process indicator. It may be that your flux application process
needs to be dialed back. Keep in mind that you only want to apply enough
flux to get the soldering job done. If too much flux is applied then the
wave may not be fully activating all of the flux on the board, which can
result in white residues post cleaning.
As far as why the residues become insoluble? In my experience it is more the
case that too much flux has been applied and the cleaning process either
doesn't have any saponifier or enough saponifier to tackle the cleaning job
or the belt feed through the cleaner is too fast or maybe the temperature of
the water or saponifier mixture is too low, not necessarily that the
residues are insoluble. My suggestion would be to review the spray
application process and determine if the amount of flux can be reduced.
Maybe look at a few boards post wave and determine if there is flux
remaining, it may appear clear. If there is alot of flux residue post wave,
this is an indicator that more flux than is needed is being applied. I would
also review my cleaning process to determine if the deionized water
(assuming that you are using DI) is acceptable (2-10 Megohm-cm) or that your
saponifier concentration is sufficient or that you have the correct
temperatures for the saponifier you are using.
In terms of soldermask attack, maybe, but not enough information for me to
draw such a conclusion. Best of luck.
Best Regards,
Joe Russeau
Process Analyst
Precision Analytical Laboratory, Inc.
4106 Cartwright Dr. Ste. A
Kokomo, IN 46902
P: 765-455-1993
F: 765-455-1996
E: [log in to unmask]
----- Original Message -----
From: "Peter Lee" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Monday, August 15, 2005 11:20 PM
Subject: [TN] White residues at wave soldering
> Technet,
>
> I have a question on white residues formation at wave soldering. We have
> recently run experiments to test the performance of various halide-free
> water soluble fluxes (ORH0 under JSTD-004). The flux was applied through a
> spray fluxer and all PCAs were immediately washed after wave soldering in
> in-line cleaner, with DI water only.
>
> Surprisingly, we've identified several PCAs built with flux A from one
> vendor exhibiting white residues at various T/H leads on the boards. See
> images below.
>
> http://members.shaw.ca/ppwlee1/Images/White_residues1.JPG
> http://members.shaw.ca/ppwlee1/Images/White_residues2.JPG
>
> What could be the cause and forming mechanism of the residues? What causes
> it to become (sometimes) insoluble in water? In general what approach can
be
> taken to minimize or prevent formation of white residues?
>
>
> Rgds,
> Peter
>
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