It seems that, in my more than slightly dimmed memory, there was a paper put out by Kester at APEX many years ago warning people about exactly these issues.
I'll search and if I can find I'll post.
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Bob Wettermann
Sent: Tuesday, December 15, 2015 2:45 PM
To: Technet <[log in to unmask]>
Subject: Re: [TN] IPC 7095 and Liquid Fluxes for Rework
Richard:
Thanks for your reply. I read the following:
They form
> particulates in the solder joints, they run all over, and they like to
> penetrate and boil. Many people do not realize that is one of the main
> causes of lifted pads.
Any pictures or a paper to back this up (I am a Reaganite-trust but verify)
Have a great new year!
Bob/BEST
On Tue, Dec 15, 2015 at 2:32 PM, Joyce Koo <[log in to unmask]> wrote:
> http://www.smtnet.com/express/200005/soldering/soldering.pdf
>
> > I'm going to come right out and make this statement. You can laugh
> > all
> you
> > want, but the data proves that liquid fluxes are terrible!
> >
> > Not only for BGA rework, but pretty much any type of rework! They
> > form particulates in the solder joints, they run all over, and they
> > like to penetrate and boil. Many people do not realize that is one
> > of the main causes of lifted pads.
> >
> > Let the screaming and moaning and hysterical laughing begin. I
> > really don't care.
> >
> > I have been training operators in the companies I work for years and
> years
> > to use only tacky fluxes for touchup, for simple rework, and for hot
> > air or hot gas rework, as well as for molten solder fountain rework.
> > I have qualified the use of tacky fluxes to replace liquid many,
> > many times. The cleanliness results of both water soluble and
> > cleaned RMA tacky fluxes
> are
> > several times better than for liquid fluxes. The tacky fluxes seem
> > to promote wetting much better than any liquid flux I have ever
> > used, and I think I have used them all.
> >
> > Because the tacky fluxes are developed for worst-case conditions
> > (hot gas and solder fountain rework) they actually work much better
> > than any
> liquid
> > flux I have ever tried.
> >
> > And they typically are much easier to confine to just the solder
> > joint(s) you are trying to touchup or solder.
> >
> > And they don't evaporate or burn off before you even reach liquidus.
> >
> > And for about 10,000 other reasons, but one of the biggest is that
> > once the operators try using tacky flux for all rework and touchup,
> > they never go back.
> >
> > If the REACH folks decreed that there would be no more liquid flux
> > allowed, beginning yesterday, it would not mean a thing to me. I
> > would say, "Good riddance".
> >
> > Most liquid fluxes on the market today were developed for wave
> > solder or selective solder use; they were never intended to be used
> > as a benchtop flux. People adapted them for compatibility reasons.
> >
> > My feeling is that they should be limited to wave or selective
> > solder processes.
> >
> > Use a good tacky flux of the same chemistry for everything else.
> > Those from one particular solder company have always worked best for
> > me. God
> is
> > the ____ and the Omega.
> >
> > But always qualify, qualify, qualify.
> >
> > dean
> >
> >
> > -----Original Message-----
> > From: TechNet [mailto:[log in to unmask]] On Behalf Of Bob Wettermann
> > Sent: Tuesday, December 15, 2015 10:40 AM
> > To: [log in to unmask]
> > Subject: [TN] IPC 7095 and Liquid Fluxes for Rework
> >
> > Dear Technetters:
> >
> > In reviewing the IPC 7095 BGA guidelines I noticed a mention of
> > liquid based fluxes for BGA rework. Has anyone heard of liquid
> > fluxes being robust enough for Sn63 or lead-free rework processes?
> >
> >
> > ____________________________________________________________________
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> > --
> > Thanks
> >
> > Bob Wettermann/BEST
> >
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>
>
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Bob Wettermann
BEST Inc
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