Subject: | |
From: | |
Reply To: | |
Date: | Mon, 26 Jul 2010 21:55:55 -0400 |
Content-Type: | text/plain |
Parts/Attachments: |
|
|
WOW.
This brings me back to the days gone by of Ceramic Leadless Chip Carriers, CLCCs. When they were 16 pin (or terminal or castellation...) they were fine, soldered great. Then they got bigger and heavier, lowered solder joint thickness and we saw failures. There were neat "stand-offs" to ensure height and even clever dry soldermask stackers to maintain the .003 min solder joint height. We would bond our components prior to reflow; white was standard epoxy and pink had .004 ceramic balls to ensure that min condition. Then came the gull wing friendly passives and the issue pretty much went away, came back with BGAs again and again went away.
If your components are displacing the paste and sitting right on the copper check the process. Maybe some is has a heavy hand on a semi-automatic pick and place. Also buy a COTS board and look at that, just as a sanity check. I don't think I answered your question, hopefully rendered some insight.
Thank you for your service and diligence to solid product.
Boston Brad
----- Original Message -----
From: Hart, Dale L CTR USAF AFMC AFRL/RXSA<mailto:[log in to unmask]>
To: [log in to unmask]<mailto:[log in to unmask]>
Sent: Tuesday, July 20, 2010 9:23 AM
Subject: [TN] solder joint height
We have been doing a some analysis of cca's for the Air Force consisting of
SMT. The visual inspection of the solder joints looks very good all
characteristics above the suggest minimum for class 3 of 610. The solder
fillets in some instances could be characterized as being robust. In
cross-sectional analysis however, the solder joint height of the components
electrical termination above the land has been perhaps 0.025 mm to the point
of needing a SEM to look at the land-solder-component lead interface.
Closer examination in these areas revealed small cracks in the grain
boundaries. I used the term grain boundaries because the solder in these
areas do not resemble the colonies observed in the bulk solder of the
fillet. In some of these instances the land is often deformed in the shape
of the component lead.
Would these joints although stronger be more susceptible to fatigue or
overload failure?
What are the implications if these cca's are encapsulated?
What suggestions could be offered to the manufacturer?
Dale L. Hart
Universal Technology Corporation (UTC)
Failure Analysis
1270 North Fairfield Road
Dayton, Ohio 45432-2600
(937) 656-9165
Fax (937) 656-4600
Email: <mailto:[log in to unmask]<mailto:[log in to unmask]>> [log in to unmask]<mailto:[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]<mailto:[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]<mailto:[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]<mailto:[log in to unmask]>: SET Technet Digest
Search the archives of previous posts at: http://listserv.ipc.org/archives<http://listserv.ipc.org/archives>
Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16<http://www.ipc.org/contentpage.asp?Pageid=4.3.16> for additional information, or contact Keach Sasamori at [log in to unmask]<mailto:[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
-----------------------------------------------------
|
|
|