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March 1999

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Tue, 2 Mar 1999 18:28:01 -0500
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no clean can be classified as two types: no residue or low residue.. For no
residue type you may be able to use it most of the time (still leave
residue, but it is very small quantity).  The low residue type can not be
used on any assemblies which may be used as intermediate stage (definite not
for tinning the components, you asking for troubles).  The low residue no
clean flux will oxidize and almost behave like conformal coat (actually,
some of the Japanese product is spray on and form a conformal coat like
material after solder)... In addition, using cleaning method (e.g. in the
case of rework) may activate the "cured" no clean surface, cause potentially
reliability concerns...
before you fully implement the no-clean, get your yield high and minimize
the rework.  Make sure select the right type of flux for the right steps of
the job...good luck...
kl
At 09:44 AM 3/2/99 -0500, you wrote:
>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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