Hi David,

The original premise was that no-clean's won't be cleaned; therefore,
many no-clean fluxes were not formulated to assist the cleaning process.
Add a long residence time and cleaning is likely even more difficult.
Today you can buy cleanable-no-clean's...

In addition to what Rudy shares regarding acids, we have seen the
organic acids in the water soluble flux adhere to the resin mixture of
the no-clean "low residue" flux.  The water soluble flux "sticks" to the
no-clean residue.  The water-soluble/no-clean's organic-acid/resin
mixture then becomes very difficult to remove with water.  At that
point, our recommendation is to remove both the no-clean and water
soluble flux with an appropriate  wash chemistry.

What part of the part is the acid unfriendly to?

Have a Great Week!

Shean Dalton
Austin American Technology
www.aat-corp.com <http://www.aat-corp.com>
512-335-6400


-----Original Message-----
From: R Sedlak
Sent: 6/27/2005 12:02 PM
To: [log in to unmask]
Subject: Re: [TN] Flux residues--Why


David: No-clean residue is SUPPOSED to be hard to remove, this means it
is unreactive, and thus will not corrode the part....

When you mix it with water soluble flux (which usually contain small
amounts of strong acid), you reactivate the organic acids in the
residues, and they can be quite corrosive, and unlike the water soluble
flux acids, they do not vaporize during soldering, and this organic acid
combined with the acid in the water soluble flux can work together to
corrode.

Hope this helps.

Rudy Sedlak
RD Chemical Company

David Tremmel <[log in to unmask]> wrote:
Technetters,

I have received some microBGAs which I have to reball and they have a
no-clean flux residue which is difficult to remove. Also, when it comes
in
contact with our water-soluble flux it creates an acid which is not very
'friendly' to the part.

Would any of the chemical gurus care to edify one of the uneducated ones
why
no-clean flux, when dried and allowed to set for a couple of months is
so
difficult to completely remove and what possible acids or chemicals are
created when it is combined with water-soluble flux (type ORM1)?

As always, I appreciate the responses I receive.

David Tremmel
Technical Manager
BT Mexico

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