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March 1999

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Subject:
From:
Bev Christian <[log in to unmask]>
Reply To:
TechNet E-Mail Forum.
Date:
Tue, 2 Mar 1999 10:56:38 -0500
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Ted,
Our company has done a little compatibility testing between previously
approved fluxes and never found a failure.  Note, I mentioned that the
fluxes were previously approved. By this I mean that they have passed the
chloride ion, copper mirror, SIR and electromigration requirements of
Bellcore GR-78-CORE.  In addition the latter was done with stripes of
various solder masks across the coupons as we have found some mask/flux
incompatibilities.  This flux/mask testing we do for all chemicals that are
going to come in contact with the bare PCB or the completed PCBA.  However,
as far as doing a complete matrix of all fluxes with every board vendor
source of a particular mask or a matrix of all flux combinations, we
wouldn't even try that nightmare - too many combinations.

For SIR the Bellcore test is 96 hours and I think the IPC test is 7 days and
the Bellcore electromigration test is 500 hours (~4 weeks).  An 8 week SIR
test?  I am not familiar with this one.  My store of Circuit Assembly mags
does not stretch back to 1992.

regards,
Bev Christian
Materials Engineering Lab
Carrier Solutions
Nortel Networks
613-967-5407
> -----Original Message-----
> From: Ted Labowski [SMTP:[log in to unmask]]
> Sent: Tuesday, March 02, 1999 9:45 AM
> To:   [log in to unmask]
> Subject:      [TN] No Clean Flux Compatability
>
> My company is making a slow transition to No Clean chemistry in our SMT,
> Wave, and Post Wave operations.
>
>  We are taking a systematic approach and thought we were on a smooth
> path until I ran across a June 1992 article published in Circuit
> Assembly and authored by several Engineers at the Foxboro Company
> (Foxboro, MA).
>
> The article was written specifically about No Clean materials  and it
> warns about "incompatibilities between similar solder flux products
> supplied by different vendors." The conclusion is rather frightening
> "The potential for intermittent and ultimately catastrophic failure of a
> circuit over time due to flux incompatibility is cause for serious
> concern."
>
> I have contacted several industry experts and all downplay the
> significance of compatibility issues, although none have performed
> independent testing to qualify their "opinions".
>
> Does anyone have any first hand experience with No Clean flux
> incompatibilities?  Additionally, is there any material published on
> this subject other than the one I ran across?
>
> Barring any new information, I am prepared to undertake a regimen of
> testing which will verify the compatibility of the No Clean materials
> which are currently approved by MPI.  The testing will be similar to
> that performed in the Foxboro article ( SIR using IPC-B-25 coupons, 40
> degrees C/95% RH, 30 V bias, measured incrementally during the 8 week
> cycle).
>
>
> Ted Labowski
> Vice President - Quality
> Microboard Processing, Inc.
>
> Email : [log in to unmask]
>
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