Roger,
Do you have a photograph of the solder joint failure that you could get Steve to post on his web site.?
Regards,
George
George M. Wenger (908)-546-4531
Reliability / FMA Engineer
Base Station and Subsystems Group
Andrew Corporation, 40 Technology Drive, Warren, NJ 07059
[log in to unmask]
-----Original Message-----
From: TechNet [mailto:[log in to unmask]]On Behalf Of Roger Stoops
Sent: Thursday, January 06, 2005 1:57 PM
To: [log in to unmask]
Subject: Re: [TN] Solder Joint Failures after Short-term Vibration
Sorry I did not provide more parameters...
No wave solder. Process is: 1) Screen paste bottom side. 2) place comps. 3) reflow. 4) screen paste top side. 5) place comps. 6) reflow. 7) clean. (etc, etc.). And the bottom side joints look pretty good.
I do not have more process info such as reflow profile.
And thanks Dave, we will need to have a cross-section FA done to really get at the bottom of this, but I will now be able to put together some specific questions that need to be asked of the EMS.
Have a conference call tonight, means I'll have to tape CSI...
Rgds,
Roger
-----Original Message-----
From: TechNet [mailto:[log in to unmask]]On Behalf Of Cheryl Tulkoff
Sent: Thursday, January 06, 2005 1:28 PM
To: [log in to unmask]
Subject: Re: [TN] Solder Joint Failures after Short-term Vibration
Roger -
Does this board go through the wave solder process after SMT? You could be
seeing secondary reflow of the SMT joint at the wave. This happens when the
temperature of the wave process is sufficient to remelt topside joints. It
usually happens only on fine pitch QFPs(smaller joints with less solder
volume). To avoid this, most people will run the wave solder temperature
lower (240-250 C rather than 260C) and the conveyor faster (5.5 ft/min or
higher).
I can send more info if you're interested in checking it out.
Thanks,
Cheryl Tulkoff
Phone:(512) 683-8586
Fax: (512) 683-8847
National Instruments
11500 N. Mopac Expressway
Building A
Austin, TX 78759-3504
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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