Peter,
As MoonMan says, this type of problem is preventable by using proper DFM
procedures, but then folks in the repair business like us would have nothing
to do!
Removing warp is actually rather simple, and is an IPC documented procedure.
I've attached a link to our online procedure with more details. We find that
about 80% of the time we can remove warp and bring bare, or assembled,
boards into spec. However, sometimes the inherent stress in the remaining
20% is just too great to overcome.
Bow and Twist Repair Procedure
http://www.circuittechctr.com/guides/3-2.htm
Jeff Ferry
CEO
Circuit Technology Center, Inc.
www.circuittechctr.com
[log in to unmask]
978-374-5000
Sign up for our Free E-mail Newsletter at:
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-----Original Message-----
From: <Peter George Duncan> [mailto:[log in to unmask]]
Sent: Thursday, November 15, 2001 9:11 PM
To: [log in to unmask]
Subject: [TN] Board Warp
Hi, All,
We have received a number of 12 layer ENIG-finished MLB's with blind via
hole groups, and which are destined to have BGA's (1.27mm pitch) populated
onto them. The boards measure 8.2" x 5.7" and they are warped to the extent
of one corner being raised by between 1.5mm and about 3mm. The axis of the
warp is the long side of a triangle whose other two sides measure about 5.7
x 5.7.
In this age of sensitive boards, does a technology or technique exist for
straightening the boards back into spec - they are class 3 boards - or is
this an area where angels still fear to tread?
The boards are desperately urgent, which is why I'm asking this rather than
simply rejecting them and having them re-made (which takes about a month).
TIA for any help.
Peter Duncan
[This e-mail is confidential and may also be privileged. If you are not the
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