0.75& max for an SMT assembly.

Reference IPC-J-STD-001D Section 9.3.

Test method is per IPC-TM-650 method 2.4.22.  You can download this method
for free at:
 http://tinyurl.com/22trj9


-----Original Message-----
From: McGlaughlin, Jeffrey A [mailto:[log in to unmask]] 
Sent: Thursday, March 08, 2007 7:05 AM
To: [log in to unmask]
Subject: [TN] Post Assembly Bow and Twist

Technet and DesignersCouncil Gurus -

I have been asked by our mechanical engineering group to find out if there
is a standard or specification for post assembly flatness of printed circuit
cards.  This has never been an issue for functional failure but a new design
requires that a row of LEDs mate to a display panel mask such that no light
leaks from one LED cell to the next. Their concern is that post assembly bow
and twist will over stress solder joints and board copper if they
mechanically stress the cards by pressing/pulling them flat to an assembly
frame.  Can anyone direct me to a standard or advise me on the maximum
allowable bow and twist for this type of situation?


Jeffrey McGlaughlin, CID
Engineering Designer
Battelle
505 King Avenue
Columbus Ohio 43201-2693
(614)424-7582 Phone
(614)458-7582 Fax 

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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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