Bing,

Can you provide any additional info: What is the time delay between
soldering and cleaning?

Is this a new problem with an old material or a new process?

What is the temperature of you wash water?

If you have a new "Water Soluble" Solder paste, you need to check that it is
WATER SOLUBLE not Water WASHABLE.

You state that you drain the wash tank after each shift. This is not perhaps
the most appropriate process because your residues are acid and you tank
will become an acid bath with processing only a few assemblies. This is why
full cascade systems are preferred.

As to adding chemistry, be careful. In order to keep your process under
control, you MUST keep the wash chemistry away from the rinse section. If
your equipment is NOT designed with an extended wet isolation section, you
may make life even more complicated for yourself.

My recommendation is to make sure that: the paste is water Soluble, that
your wash temp is around 120 deg F and your rinse is less than 10
microsiemens.

Hope this helps

Regards, Graham Naisbitt

[log in to unmask]

Concoat Ltd             Phone: +44 1276 691100
Alasan House          Fax:      +44 1276 691227
Albany Park
CAMBERLEY
GU15 2PL UK

Any opinions expressed are those of this employer.

-----Original Message-----
From: Melanie Racuya <[log in to unmask]>
To: [log in to unmask] <[log in to unmask]>
Date: 24 August 1998 11:18
Subject: [TN] white residue


Hello netters
We're using a with clean solder paste in the manufacturing of our
flex and I'm encountering  white residues  as seen after aqueous
cleaning. Can this be an effect of the flux content of the solder
paste that we are using? Or is it the cleanliness of the DI water
beign used by the aqueous cleaning machine (which is drained and
changed every end of the shift)? We tried reloading it in the aqueous
cleaner but it doesnt suffice cleaning the white residues. Will I be
needing another chemical or solvent to clean it up first before
reloading it in the aqueous machine?
By the way, did anybody among you have encountered this problem
before?
I need your help!

Thanks,
Bing

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