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October 2009

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Tue, 13 Oct 2009 12:43:09 -0500
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TechNet E-Mail Forum <[log in to unmask]>, "Stadem, Richard D." <[log in to unmask]>
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I agree with that assessment.  Board warpage can be a contributing factor also.



 



From: [log in to unmask] [mailto:[log in to unmask]] 

Sent: Tuesday, October 13, 2009 12:37 PM

To: [log in to unmask]; Stadem, Richard D.; [log in to unmask]

Subject: Re: [TN] Lifted Leads



 



Hi Linda & Dean,

While I take Linda by her words, 'pad cratering' is not out of the question, since the leads on connectors, whether they are gullwing-shaped or not are notoriously on-compliant.



In either case, the underlying root cause is connector body warping; for 'lifted leads' on heating and for 'pad cratering' on cooling.



Werner



 



-----Original Message-----

From: Stadem, Richard D. <[log in to unmask]>

To: [log in to unmask]

Sent: Tue, Oct 13, 2009 10:23 am

Subject: Re: [TN] Lifted Leads



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 time

s 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] <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 th

at 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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