Double check the data-sheets for the LEDs about processing. In my experience most of these radial LEDs are not reflow rated. Some are, most are not.
Statement direct from data-sheet of one such LED by Nichia:
Direct soldering onto a PCB board should be avoided. Mechanical stress to the resin may be caused by warping of the PC board of from the clinching or cutting of the leadframes. When it is absolutely necessary, the LEDs may be mounted in this fashion, but the User will assume responsibility for any problems. Direct soldering should only be done after testing has confirmed that no damage, such as wire bond failure or resin deterioration, will occur. Nichia's LEDs should not be soldered directly to double sided PCB board because the will deteriorate the epoxy resin.
-----Original Message-----
From: Woolley, Mark D. (Mark) [mailto:[log in to unmask]]
Sent: Monday, June 14, 2010 10:38 AM
To: [log in to unmask]
Subject: Re: [TN] LED wiring bonding
Steve,
It appears that the LED die itself may be delaminated from the
leadframe. If so, it probably moved with the encapsulant, possibly
during reflow, causing the bondwire break.
Check out the bond between the dieattach and the leadframe. If it was
not processed correctly it may be so weak that there was an adhesive
rather than a cohesive failure as well as the delamination of the
encapsulant. The amount of moisture LEDs can pick up is much higher
than an IC, so they must be treated as more moisture sensitive than
other similar components. Obviously in the lens area they do not have
any fillers to assist in limiting the thermal expansion during reflow.
mark
mark
Mark Woolley |PTRL Laboratory | Avaya | 1300 West 120th Ave |
Westminster, CO 80234 USA |
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Thayer, Wayne - IIW
Sent: Monday, June 14, 2010 6:08 AM
To: [log in to unmask]
Subject: Re: [TN] LED wiring bonding
Steve-
One more thing, although it is probably unimportant:
Your pix show the easiest to observe wire defect, the necking down. But
the mass of wire missing from the broken or necked down area had to go
somewhere, or the distance between the leadframe components had to have
increased permanently.
If the distance increased permanently, that would be possible if the
fixture holding these LED components moved while the molding compound
was above Tg.
In similar constructs, I have seen the extra wire at the top of the
ball: It sheared the wire off in the heat affected zone.
Wayne
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Steven Creswick
Sent: Sunday, June 13, 2010 12:22 PM
To: [log in to unmask]
Subject: Re: [TN] LED wiring bonding
Victor,
I have posted a few pictures on the IPC site -
http://ipc-technet.groupsite.com/galleries
I am probably way down at the bottom under "Mold Delamination from LED's
and
Leadframes"
I had to crop them to hide the guilty, etc., but I believe they will
still
get the point across
I've shown delamination of the mold compound from the lead frame and
surface
of the LED as well as necking of the wire due to CTE issues.
Steve Creswick
http://www.linkedin.com/in/stevencreswick
______________________________________________________________________
This email has been scanned by the MessageLabs Email Security System.
For more information please contact helpdesk at x2960 or
[log in to unmask]
______________________________________________________________________
---------------------------------------------------
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
-----------------------------------------------------
This e-mail and any files transmitted with it may be proprietary and are
intended solely for the use of the individual or entity to whom they are
addressed. If you have received this e-mail in error please notify the
sender.
Please note that any views or opinions presented in this e-mail are
solely those of the author and do not necessarily represent those of ITT
Corporation. The recipient should check this e-mail and any attachments
for the presence of viruses. ITT accepts no liability for any damage
caused by any virus transmitted by this e-mail.
______________________________________________________________________
This email has been scanned by the MessageLabs Email Security System.
For more information please contact helpdesk at x2960 or
[log in to unmask]
______________________________________________________________________
---------------------------------------------------
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
-----------------------------------------------------
______________________________________________________________________
This email has been scanned by the MessageLabs Email Security System.
For more information please contact helpdesk at x2960 or [log in to unmask]
______________________________________________________________________
---------------------------------------------------
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
-----------------------------------------------------
______________________________________________________________________
This email has been scanned by the MessageLabs Email Security System.
For more information please contact helpdesk at x2960 or [log in to unmask]
______________________________________________________________________
---------------------------------------------------
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
-----------------------------------------------------
|
