Roger,
It almost sounds like you have a QFP lead plating problem....
The EMS is probably right and these meet the spec...
However for your application IPC is not enough...
The reason the top of the lead is grainy is because that is the reflowed
condition of the QFP plating...
I would guess that
1) If x-rayed you have micro-voids in the solder under the leads
2) Your pads are the same width as the leads on the QFPs for the failing lot
You need to get full height toe fillets on the QFP leads...otherwise they
will fail...
It is possible to do but requires secondary operations...
Paul
Paul Edwards
Process Engineering
[log in to unmask]
Tel: 408-433-4700
FAX: 408-433-9988
Surface Art Engineering
81Bonaventura Dr.
San Jose, CA 95134
DUNS: 944740570
CAGE/NCAGE: 1XZ48
-----Original Message-----
From: Roger Stoops [mailto:[log in to unmask]]
Sent: Thursday, January 06, 2005 10:19 AM
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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