Julie,
I don't believe that the component sagging has anything to do with the "dewetting". If this is only happening with one vendor's component then I would be very suspicious that the electrolytic Ni/Au surface finish on the substrate has problems. The electrolytic Ni on some lands may not have been properly cleaned or protected by the Au over plating allowing passivation of the Ni especially around the perimeter of the land resulting in a solder attachment but poor wetting. During the second reflow the Ni at the edges of the poorly wet land oxidizes further and the solder "dewets" from the land.
Regards,
George
George M. Wenger
Senior Principal Reliability / FMA Engineer
Andrew Corporation - Wireless Network Solutions
40 Technology Drive, Warren, NJ 07059
(908) 546-4531 Office (732) 309-8964 Mobile
E-mail: [log in to unmask]
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Julie Silk
Sent: Thursday, June 30, 2011 8:57 PM
To: [log in to unmask]
Subject: Re: [TN] BGA ball dewet from substrate
I agree it's very strange. I don't have cross-sections after the first reflow yet. The raw parts show very nice joints between ball and substrate. The faulty balls are mostly at the interior rows (empty center, no balls there). It is one part, one supplier -- but nothing fishy on the raw part. Looks like electrolytic Ni/Au on the substrate. Steve Gregory is posting a picture. Could the upside-down part sag so much in the middle during reflow that it pulls away??
--------------------------------
Julie Silk
Environmental Compliance Technical Program Manager
Agilent Technologies
707-577-4296
[log in to unmask]
-----Original Message-----
From: [log in to unmask] [mailto:[log in to unmask]]
Sent: Thursday, June 30, 2011 3:49 PM
To: TechNet E-Mail Forum; SILK,JULIE (A-Sonoma,ex1)
Subject: RE: [TN] BGA ball dewet from substrate
Is this random with respect to location? Is it particular to one part/supplier?
It seems very strange that a properly reflowed BGA solderball connection would "dewet" itself during a subsequent reflow operation.
A cross section after the first reflow will probably explain what happened.
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Julie Silk
Sent: Thursday, June 30, 2011 3:29 PM
To: [log in to unmask]
Subject: Re: [TN] BGA ball dewet from substrate
The substrate pad shows an intermetallic layer, demonstrating that there had been a metallurgical bond. Also, the surface of both pad and ball are smooth -- not a fracture, but as if reflowed. I have a good picture from the FA report to share once I figure out how. I believe that if you were to analyze the very first layer on the BGA substrate pad, it would have a layer of solder.
---------------------------------------------------
Technet Mail List provided as a service by IPC using LISTSERV 16.0
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
For additional information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100 ext.2815
-----------------------------------------------------
------------------------------------------------------------------------------
This message and any attachments are solely for the use of the addressee and may contain L-3 proprietary information that may also be defined as USG export controlled technical data. If you are not the intended recipient, any disclosure, use or distribution of its content is prohibited. Please notify the sender by reply e-mail and immediately delete this message and any attachments.
______________________________________________________________________
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 16.0
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
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 16.0
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
For additional information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100 ext.2815
-----------------------------------------------------
|
