John,
As far as I know most people do not use SEC for PCBAs manufactured using
no-clean fluxes, pastes, etc. The reason for this is that the "high"
readings are mainly from relatively benign weak organic acids. The real key
of course is how much halide, sulfate, etc. is in the soup. So the
technique will not tell you if you have a potential corrosion problem and is
therefore not speced in any standard.
What it can do for you is give you an idea of what level of loading of flux
you are putting on your assembly. This will have consequences as far as
flux usage, residues in edge connectors and cosmetics. When we looked at
this eight years ago we typically saw values in the range of 2.5 to 4.5 SOD.
What you can do is set yellow and red light limits for the amount of residue
you want on your packs.
I would caution you about one potential problem with using this equipment
with soldered packs - many no-clean flux residues do not like a 50/50 or
75/25 IPA/DI water environment and you can end up with some pretty awful
looking packs with a white residue everywhere! Keeping your flux
application technique in control and going to spray fluxing are better
things to do than fooling around with SEC.
regards,
Bev Christian
Nortel
> ----------
> From: John Barton[SMTP:[log in to unmask]]
> Sent: Monday, August 10, 1998 9:47 AM
> To: [log in to unmask]
> Subject: [TN] No-clean Fluxes + Omegameters
>
> Technetters,
> Can anyone help with 2 questions that were sent my way re no-clean fluxes?
>
> > >>
> > >> Question 1 Is the Omegameter used on No-Clean PCAs. If so
> what are
> the
> > >> typical ug of NaCl levels found on the PCBs and what would be the
> > >> frequency of inspection be.
> > >>
> > >> Question 2 If you dont use an Omegameter, what process
> control do you
>
> > >> have in place for the control of contamination on No-Clean PCAs.
> >
> Thanks,
> John Barton
>
> ___________________________________________________________
> John Barton AKA JohnnyB
> NMRC, Lee Maltings, Phone : +353-21-904088
> Prospect Row, Fax : +353-21-270271
> Cork, Ireland. e-mail: [log in to unmask]
> "Whenever I'm faced with a difficult problem, I always think to
> myself 'How would MacGyver deal with this?'"
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