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April 2008

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Subject:
From:
Donald Vischulis <[log in to unmask]>
Reply To:
Donald Vischulis <[log in to unmask]>
Date:
Mon, 28 Apr 2008 17:26:28 -0500
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Over the years, I've seen thickness specified about every possible way: over laminate, over copper before plating, maximum thickness for any point on the board including solder resist, over gold plated fingers, and tight tolerances in a defined area of the board.  The thing to remember is that laminate for one and two sided applications (generally > .030) is sold as a nominal thickness over copper.  Thinner materials intended for multilayer are sold as nominal thickness over laminate.  

You need to specify what you need for your application.  Along with the specification, you need to understand how you and your supplier will verify the thickness of the finished product.  The tighter the tolerance, the higher the cost.  Working with your fabricator(s) will allow you to understand the cost impact of the specification choices.

Don Vischulis

-----Original Message-----
>From: Phil Nutting <[log in to unmask]>
>Sent: Apr 25, 2008 2:51 PM
>To: [log in to unmask]
>Subject: [TN] Specifying board thickness
>
>Hi Technetters,
>
>We are reviewing how we specify finished circuit board thickness to make sure we get what we think we specified.  Recent events have placed what we specify under scrutiny.  I've looked through IPC-2221, IPC-2222, IPC- 4101B, IPC-6012B and IPC-7351A with no luck.
>
>Currently our documentation calls for 0.059" finished board thickness without measuring the thickness of the copper.  Presumably when the copper is added we get to 0.062" finished thickness which is important when we start stacking circuit boards on standoffs.
>
>How do others specify circuit board thickness?
>
>Is there an IPC spec I can quote chapter and verse?
>
>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
>
>Note: All the information contained in this e-mail and its attachments is proprietary to Kaiser Systems, Inc. and it may not be reproduced without the prior written permission of sender.  If you have received this email in error, please immediately return it to sender and delete the copy you received.
>
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Search the archives of previous posts at: http://listserv.ipc.org/archives
Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16 for additional information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100 ext.2815
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