The acids you are talking about are not strong acids, but are also often more reactive than many strong acids (ie: Form insoluble salts) and the correct choice of resin in the column can insure rapid removal of the acid.
Rudy Sedlak
RD Chemical Company
--- On Mon, 4/23/12, Robert Kondner <[log in to unmask]> wrote:
From: Robert Kondner <[log in to unmask]>
Subject: Re: [TN] No-Clean Flux
To: [log in to unmask]
Date: Monday, April 23, 2012, 8:46 AM
Karen,
OK thanks.
One more general chemistry question:
If you have weak acids in solution, and you pass that solution through a DI
column, will the weak acid be removed from solution as quickly as a strong
acid?
Thanks,
Bob Kondner
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Karen Tellefsen
Sent: Monday, April 23, 2012 11:32 AM
To: [log in to unmask]
Subject: Re: [TN] No-Clean Flux
The acids in no clean fluxes are usually sparingly soluble in water,
particularly adipic. The pH paper is a qualitative test. Spraying
phenolphthalein on .the board will contaminate it and the board will need to
be cleaned even if excess acid is not found.
If you want a quantitative test, use IC. There are ways to extract small
areas if you want to look for localized contamination.,
Karen Tellefsen - Electrical Testing
[log in to unmask]
908-791-3069
Re: [TN] No-Clean Flux
Robert Kondner
to:
TechNet
04/23/2012
11:10 AM
Sent by:
TechNet <[log in to unmask]>
Please respond to rkondner
Karen,
Thanks. Are these acids soluble in water? Can a collection of rinse water
be used to determine the "Quality" of the heating process?
Kind of like a simplified ionic contamination test? Maybe a rinse with a
basic phenolphthalein solution (pink) and if it turns clear "You Have Acid".
Is there any way to calculate if such a test would have sufficient accuracy
in the range of interest?
Bob K.
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Karen Tellefsen
Sent: Monday, April 23, 2012 10:52 AM
To: [log in to unmask]
Subject: Re: [TN] No-Clean Flux
pH paper slightly dampened with DI water. I've used it and it works.
Some of the organic acid activators will be left behind after soldering, but
most of them should have sublimed during processing. Additionally, some
organic acids are worse than others; malic is worse than succinic is worse
than adipic.
Karen Tellefsen - Electrical Testing
[log in to unmask]
908-791-3069
Re: [TN] No-Clean Flux
Robert Kondner
to:
TechNet
04/23/2012
10:43 AM
Sent by:
TechNet <[log in to unmask]>
Please respond to rkondner
Hi,
Are there any spray on chemical indicator that can be used to detect for
activated flux? Something like a litmus or phenolphthalein solution?
Bob K.
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Brian Ellis
Sent: Monday, April 23, 2012 10:28 AM
To: [log in to unmask]
Subject: Re: [TN] No-Clean Flux
I agree 100% with Doug. The important point is to ensure that the carboxylic
acids are sublimed. This starts to happen at temperatures around 180°C but
it takes time as well as temperature. It is therefore essential to limit the
quantity to the minimum necessary to do the job and confine to the joint
area. What is positive is that soldering irons operate at a higher
temperature than wave or reflow, so that residues that spread outside the
joint area will probably be heated sufficiently to ensure sufficient
sublimation. Another important point is to ensure that all the alcohol has
evaporated before starting the retouch, so that the latent heat of
evaporation would otherwise cool down the flux and allow it to spread before
sublimation takes place. This requires the operator to wait a few minutes
between dosing the flux and picking up the soldering iron. It is common to
have a row of fluxed assemblies and, as one is added at one end, a circuit
is picked up at the other end for soldering. I don't know whether it is
still available, but a flux with a crimson dye showed where unheated flux
was applied and was quite common in days of yore. The dye sublimated with
the activators.
Brian
On 23/04/2012 16:42, Woolley, Mark D. (Mark) wrote:
> I have an issue with one of the assembly houses we use. They are
> using a No-clean flux that contains adipit and succinic acids (per the
> MSDS) in an alcohol base.
>
> Is it allowed to leave flux on the PWB that HAS NOT BEEN DEACTIVATED
> BY HIGH TEMPERATURES OF SOLDERING?
>
> I am not talking about the flux used in the solder paste or wave
> soldered flus. I am talking about the flux used at rework and
> touch-up of the PWB.
>
>
>
> I havce seen papers detailing corrosion on PWBs using "no-clean"
> fluxes and I have seen it on some of our products. This usually
> pccurs near the periphery of the PWB where the wave solder flux is
> protected by the pallet used to pass the PWB through the solder wave.
>
>
>
> Any opinions and references will be appreciated. I can give the
> manufacturer and flux type to individuals, but don't want to put it in
> a global email.
>
>
>
> Thanks
>
> mark
>
>
>
>
>
> mark
>
> Mark Woolley |PTRL Laboratory | Avaya | 1300 West 120th Ave |
> Westminster, CO 80234 USA |
>
> Voice (Lab): (303) 538-2166 | email: [log in to unmask] |
>
>
>
>
> ______________________________________________________________________
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