Steve,

We still do that here.  Enough so that if it is called out on the drawing we
don't question it.  It sounds like the mask didn't hold up through the
fusing of the tin-lead. Probably LPI versus dry film.

Thanks,
Jim

-----Original Message-----
From: TechNet [mailto:[log in to unmask]]On Behalf Of Steve Gregory
Sent: Wednesday, March 31, 2004 4:41 PM
To: [log in to unmask]
Subject: [TN] Solder mask over Tin/Lead...


Hi All!

I'm just wondering if I'm missing something. Is there any performance reason
whatsoever, that requires solder mask over Tin/Lead instead of using SMOBC
(Solder Mask Over Bare Copper)?

Got a board in receiving inspection that I got called back to look at
because
the mask was failing tape test. When I saw the board, it was solder mask
over
Tin/Lead, just like it was called out on the drawing. The mask had already
lost adhesion in a few places, but we hadn't done anything to it yet
assembly-wise...

I see didn't see this particular boards drawing before we went out and
bought
it, otherwise I would have thrown-up a red flag then. What suprised me
though, is that our fab vendor didn't say anything before they built it. Is
anything
other than SMOBC being used regularly. I thought solder mask over Tin/Lead
was ancient stuff, and that everybody learned not to do that anymore...

-Steve Gregory-

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