Hi, Linda
I think what you may be seeing is more commonly called pad cratering, a common issue with lead-free soldering. This shows up mostly on BGAs with their relatively non-compliant connections, rather than gullwing leads. However, I have seen it happen on gullwing connectors, where the body of the connector is fastened to the PWB such that the compliant leads pull so hard as to lift the pads during reflow and cooldown. This can be confirmed using shadow moiré photography, where the image is strobed a number of times during the temperature cycle in order to show the physical movement that takes place.
Rather than pursuing the visible confirmation of lead coplanarity during reflow using shadow moiré photography, you may be better off researching the cause/corrective actions of pad cratering.
Simply search the archives of Technet or Google up the term "pad cratering" and you will get a wealth of information, causes, and corrective measures to eliminate the issue. It can be caused by a number of design and process factors working together.

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Linda Langley
Sent: Tuesday, October 13, 2009 9:02 AM
To: [log in to unmask]
Subject: [TN] Lifted Leads

Linda

I know that you are signed on TechNet

Could you please post question to all experts for me:

We are reflowing 50pins CF card SMT connector and having high rate of the lifted leads (they are gull wings leads). We measured leads co planarity using CMM before reflow and it seems that all leads are meeting the spec. 

My guess is that the component body is bowing during reflow process (we are dong Pb free reflow with the peak of 234°C) causing lifted leads.

Somebody told me that there is a lab who can measure leads co planarity during reflow cycle. Is anybody aware of such as test?

Thank you

 

Can anyone share some information, any help will be greatly appreciated.

 

 

Linda Langley CIT

Training Specialist

Jabil Circuit

248-292-6176


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