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 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 wea
lth 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
---------------------------------------------------
Technet Mail List provided as a service by IPC using LISTSERV 15.0
To unsubscribe, send a message to [log in to unmask] with following text in
the BODY (NOT the subject field): SIGNOFF Technet
To temporarily halt or (re-start) delivery of Technet
send e-mail to
[log in to unmask]: SET Technet NOMAIL or (MAIL)
To receive ONE mailing per day of all the posts: send e-mail to
[log in to unmask]: SET Technet Digest
Search the archives of previous posts at: http://listserv.ipc.org/archives
Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16 for
additional information, or contact Keach Sasamori at [log in to unmask] or
847-615-7100 ext.2815
-----------------------------------------------------
---------------------------------------------------
Technet Mail List provided as a service by IPC using LISTSERV 15.0
To unsubscribe, send a message to [log in to unmask] with following text in
the BODY (NOT the subject field): SIGNOFF Technet
To temporarily halt or (re-start) delivery of Technet send e-mail to
[log in to unmask]: SET Technet NOMAIL or (MAIL)
To receive ONE mailing per day of all the posts: send e-mail to
[log in to unmask]: SET Technet Digest
Search the archives of previous posts at: http://listserv.ipc.org/archives
Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16 for
additional information, or contact Keach Sasamori at [log in to unmask] or
847-615-7100 ext.2815
-----------------------------------------------------
---------------------------------------------------
Technet Mail List provided as a service by IPC using LISTSERV 15.0
To unsubscribe, send a message to [log in to unmask] with following text in
the BODY (NOT the subject field): SIGNOFF Technet
To temporarily halt or (re-start) delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL or (MAIL)
To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest
Search the archives of previous posts at: http://listserv.ipc.org/archives
Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16 for additional information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100 ext.2815
-----------------------------------------------------
|
