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February 2004

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Subject:
From:
Steve Gregory <[log in to unmask]>
Reply To:
TechNet E-Mail Forum.
Date:
Mon, 9 Feb 2004 13:54:49 EST
Content-Type:
text/plain
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text/plain (57 lines)
Hi Sue!

I had problems with solder mask a few weeks ago that I posted about. In my
case, I was seeing it after cleaning. Also in my case it wasn't merely flaking,
it was like a snake sheding its skin...mask was coming off in huge slabs. I
still have some pictures of it on my web page at:
http://www.stevezeva.homestead.com/

Look at the "Mask Peel" pictures there...it was ugly! What it turned out to
be was that the pumice scrub before mask application hadn't been done on one
panel hadn't been done, even though the production paperwork at the fab vendor
had been signed
off that had been done. This was a dry film solder mask over bare cooper by
the way...

The problem only affected 2 boards because it was built in a 2-up panel. For
some reason, only one panel out of the lot that got built didn't get scrubbed
as it should have been. The boards passed our tape test at incoming inspection
too. It wasn't until the boards got thermally shocked at wave solder, and
then washed, did the poor adhesion because of the bad surface prep show itself.

-Steve Gregory-



> I know this was up for a discussion a few weeks ago. Can anyone tell me
> what the root cause was determined to be?
>
> I am experiencing solder mask flaking on a group of boards manufactured
> by one certain supplier. It is a random occurrence for example 10 out of
> the 100 boards we had this occurr. Then a different board we ran 8 out
> of 40 were flaking same supplier as previous one.
>
> Supplier runs samples at his facility and he see's no flaking. We
> changed our solder temperature from 500 degrees to 450 degrees at the
> suppliers suggestion and flaking still occurs. He then states maybe were
> not using enough flux but review shows plenty of flux if anything maybe
> were using to much flux from the way the boards look coming out of the
> wave and washer.
>
> Thanks
> Sue Foulkes
> QA Manager
> AESCO Mfg.
>


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