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March 2002

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Subject:
From:
"Crepeau, Phil" <[log in to unmask]>
Reply To:
TechNet E-Mail Forum.
Date:
Thu, 7 Mar 2002 12:00:02 -0800
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hi,

it seems to me that you need to have the customer sign a letter stating that they accept all responsibility for issues related to the reliability of this assembly.  if they do that, then party on.  if they don't do that, you should refuse this work.

phil

-----Original Message-----
From: d. terstegge [mailto:[log in to unmask]]
Sent: Thursday, March 07, 2002 8:48 AM
To: [log in to unmask]
Subject: [TN] Flattening a board during assembly


Hi Technetters,

We've got a batch of boards here that's really twisted (about 1.5 % when measured according to IPC-TM-650) due to imbalanced design. The customers is not willing to change the design, and we discussed with them the possibility of using a carrier-frame for flattening these boards while they are processed through our SMT-line.

My worry is that this results in unacceptable stress in the solder joints as soon as the board is released from the carrier. Fortunately there's no BGA on this board, but it does have a small QFP and some 40 mm long SMT-connectors. It's supposed to be a high-reliability military product.

Does anyone have any data on the effects of such internal stresses ?
Also other comments are welcome.

Best regards.

Daan Terstegge
SMT Centre
Thales Communications
Unclassified mail
Personal Website: http://www.smtinfo.net

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