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January 2005

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Subject:
From:
Lee Parker <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Lee Parker <[log in to unmask]>
Date:
Thu, 6 Jan 2005 14:51:04 -0500
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text/plain (71 lines)
Roger

What solderability finish is on the bare board and has anything been
done to certify its quality?

Best regards

Lee

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Roger Stoops
Sent: Thursday, January 06, 2005 1:19 PM
To: [log in to unmask]
Subject: [TN] Solder Joint Failures after Short-term Vibration

Hello all,

We are having an ongoing problem with solder joint failures on a 144-pin
PQFP processor, after short-term vibration. The board layout and
mechanical mounting apparatus were designed with vibration in mind, and
have passed vibration testing in the past. The same processor is used on
a dozen other assemblies, none of which have this problem.

The solder joints appear to exhibit dewetting, although there is a toe
and heel fillet.  The heel fillet is unusually large, and the top of the
PQFP lead has a grainy appearance instead of a matte or shiny
appearance.  Some leads can be pushed off the solder joint with very
little pressure.  Sn62Pb36Ag2 solder is being used, and our EMS provider
continues to claim that boards meet IPC-A-610 class 2 requirements.

Any ideas as to what may be causing solder joint failures?

Also, any suggestions or recommendations (preferred) for a test house to
provide x-ray, microsection and composition analysis?

TIA & Best Regards,

Roger M. Stoops, CID+
Trimble Navigation Ltd., Dayton, OH, USA
Ph: +01 937.245.5288
Fax: +01 937.233.7511

Oh, and BTW, changing EMS providers is not an option...

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