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October 2011

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Subject:
From:
Steve Gregory <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Steve Gregory <[log in to unmask]>
Date:
Mon, 31 Oct 2011 10:00:15 -0400
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text/plain (109 lines)
Here's a photo of some raised vias at another company that I had experienced
in the past;

http://stevezeva.homestead.com/files/Raised_Vias.jpg

We almost rejected the boards, but the project was so hot we thought that we
would try one and see what we wound up with.

Surprisingly, they went together okay. The customer accepted the boards
knowing what the bare boards looked like. It was just lucky that the raised
vias were within the solder paste footprint.

The PCB fabricator got a butt chewing and was told that they needed to do a
better job of planarizing them, and to never send us boards that looked like
that again. They got the message...

Steve

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Stadem, Richard D.
Sent: Monday, October 31, 2011 9:50 AM
To: [log in to unmask]
Subject: Re: [TN] maximum height of artifacts above the soldermask

Amol, you are correct, I have run into the same issue. Our board fabricator
took steps to correct this issue after it was discovered, and our paste
printing issues disappeared. It can be done.
dean 

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Amol Kane
Sent: Friday, October 28, 2011 7:45 AM
To: [log in to unmask]
Subject: [TN] maximum height of artifacts above the soldermask

Dear Technetters,
Is there a spec/guidance/industry best practice recommendation on the
maximum height of artifacts (like silkscreen, via tents etc.,) above the
soldermask surface?. Assuming the stencil foil sits squarely on the
soldermask, any height above that will induce a (localized) standoff if any
such artifact is near the pad. We have some boards in which the via tents
are 7 mils above the rest of the mask surface. Some of these vias are close
to fine pitch devices. I am afraid that I won't be able to control the
volume of paste during printing leading to shorts. The board house saying I
won't have an issue (big surprise there! :)). Is there something I can use
as a basis of my push back ?

Thanks in advance!!


Amol Kane | Process Engineer
Catalyst Manufacturing Services, Inc.
941 Route 38, Owego NY 13827
Phone: (607) 687-7669 Extn 349 | Website:
www.catalystems.com<http://www.catalystems.com/>


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