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September 1998

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Subject:
From:
Bev Christian <[log in to unmask]>
Reply To:
TechNet E-Mail Forum.
Date:
Wed, 2 Sep 1998 08:03:28 -0400
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text/plain
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text/plain (71 lines)
Rudolph,
Most criteria for cosmetic acceptance of no-clean boards are pretty
subjective.  One absolute no-no is flux residue in the holes of edge
connectors.  Other than that, we have not really had an issue with flux
residues since the early nineties. I'm not quite sure I know what you mean
by a "stain", but at most we will see some residue around the PTH leads of
massive parts (those with a large thermal mass), other than that we do not
see much of anything.  Nitrogen helps, but should not be necessary to reach
this stage.  I would also recommend the newer spray fluxers as opposed to
wave, foam or the old drum spray fluxers.  These are my personal preferences
showing through.  Also, I would definitely talk to your flux supplier about
this issue.  Perhaps he/she can give some suggestions as to your profile or
perhaps you need to change fluxes.

Corrosive material in no-clean fluxes!!?  Ahhh, where's a tall building to
jump off of?  That is a very inflammatory statement (pun, unless you are
talking VOC free  :)  )  I will start by asking the philosophical question
of "what is small?" (no smart comments, please).  If you are talking about
ppb or maybe ppm. OK, but there shouldn't be "significant " amounts of
corrosive materials in the no-clean fluxes of reputable manufacturers.  If
there is, we're in trouble, because we have had product out in the field
with no-cleans since the late 80's.

regards,
Bev Christian
Nortel

> ----------
> From:         Rudolph Yu[SMTP:[log in to unmask]]
> Sent:         Tuesday, September 01, 1998 3:56 PM
> To:   [log in to unmask]
> Subject:      [TN] Inspection criteria for no clean assembly?
>
> Currently we accept no clean assembly as long as we can not see stain
> mark or powder residue on the assembly within 2 feet after the wave
> soldering process.  What is yours like?
>  Is there a need to check for contamination level on no clean assembly?
> If the answer is yes, then what measurement should I test it against?
> What tester in the market does serve this function?
>  The reason why i ask the question is because I heard that even no clean
> flux does contain small amount of corrosive material, thus can affect
> the product in long run.
> Thank you
>
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