Ted Labowski 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?

Yes.  One of our competitor's pastes just does not get
along with one of our liquid fluxes, as a customer discovered.
This flux works relatively well with most of our solder pastes.
Of course, I'll never formally publish this, so this sort of
information can be quite hard to find.  I routinely
test our pastes, liquid fluxes and core-fluxed wire for compatability
wrt electrical reliability and provide customers with the data.
I don't usually test our materials with competitor's products.
I doubt the competition does either.

It's my job to make sure Alpha products are compatable with
other Alpha products.
A mixture of different vendor's products may work well together,
but it's the user's job to ensure that they do.

> 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).

This test should point out any material incompatabilities.  It's a very
good idea to run this sort of test, though I'm not sure you'll learn more
with a 1000 hour test than a 200 hour test, because gross incompatabilities
usually show up fairly early.  Frequent measurements, at least 1 or 2X a day,
is a good idea.

Here's hoping your material work well together (they probably do).

Karen Tellefsen
Alpha Metals

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