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August 2007

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Subject:
From:
Leo Higgins <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Leo Higgins <[log in to unmask]>
Date:
Wed, 15 Aug 2007 09:05:02 -0700
Content-Type:
text/plain
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text/plain (76 lines)
Would it be possible to stencil print, or dispense dots of an appropriate epoxy paste to form small mechanical stand offs  only at the location of the offending PTH components?



Best regards,
Leo

          
Leo M. Higgins III, Ph.D.
Sr. Vice President, Engg and Technology
ASAT, Inc. 
13809 Research Blvd., Suite 635
Austin, Texas     78750

office phone   512-249-4758
mobile           512-423-2002
[log in to unmask]
www.asat.com



-----Original Message-----
From: TechNet [mailto:[log in to unmask]]On Behalf Of Phil Nutting
Sent: Wednesday, August 15, 2007 9:59 AM
To: [log in to unmask]
Subject: [TN] Solder mask as an insulator


Let me start with, I know that we should not rely on the LPI solder mask
as an insulator.  So I need recommendations for a simple and cost
effective solution.

Problem parameters; 0.062 thick FR-4 with 2 oz copper and LPI mask.  PTH
components laying on traces that go under the parts.  PTH parts are
shorting to the traces.

Our fab house is against adding a second layer of LPI mask.  On face
value a second layer sounds good and easy, but I know there are issues
too long to list.

Short of raising the components above the board, applying an insulator
under the components or a new board layout is there a better way of
preventing this shorting problem?

Thanks in advance.

Phil Nutting
Design for Manufacturing Engineer
Kaiser Systems, Inc.
126 Sohier Road
Beverly, MA 01915
voice: 978-922-9300 x1310
fax: 978-922-8374
e-mail: [log in to unmask] 
www.kaisersystems.com

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