1. Yes, same pattern on other boards.
2. One other board sees pretty much the same vibration (mounted typically the same place on the machine too).
3. Have the impression that this was done on earlier batch, which batch was put in the field with few failures, if any.
4. Dewetting symptoms appear on 3 sides of PQFP, and at other random locations on board (topside).
5. Checked resonance a few years ago, which lead to tripling the number of mounting locations. Board then survived "shake table" test and subsequent field test.
Good questions, thanks.
Roger
-----Original Message-----
From: TechNet [mailto:[log in to unmask]]On Behalf Of
[log in to unmask]
Sent: Thursday, January 06, 2005 1:53 PM
To: [log in to unmask]
Subject: Re: [TN] Solder Joint Failures after Short-term Vibration
Roger,
If this part isn't having problems elsewhere, have you verified the same
pad pattern exists on all PWBs? I am assuming the same automated
soldering process is used on all these other assemblies. Do the other
assemblies see the same levels of vibration? Have you visually verified
the solder joints prior to vibration? Do all of the leads appear to have
this dewetting, or are there specific locations with the issue. If none
of these issues lead you anywhere, it would seem to point back to a
mechanical issue (resonance?) on this particular assembly.
Good luck!
Jim Carlson
Reliability/Quality Engineer
Rockwell Collins
Roger Stoops <[log in to unmask]>
Sent by: TechNet <[log in to unmask]>
01/06/2005 01:19 PM
Please respond to TechNet E-Mail Forum; Please respond to Roger Stoops
To: [log in to unmask]
cc:
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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