TECHNET Archives

December 2008

TechNet@IPC.ORG

Options: Use Monospaced Font
Show Text Part by Default
Show All Mail Headers

Message: [<< First] [< Prev] [Next >] [Last >>]
Topic: [<< First] [< Prev] [Next >] [Last >>]
Author: [<< First] [< Prev] [Next >] [Last >>]

Print Reply
Subject:
From:
"Stadem, Richard D." <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Stadem, Richard D.
Date:
Mon, 22 Dec 2008 13:25:44 -0600
Content-Type:
text/plain
Parts/Attachments:
text/plain (135 lines)
Also, for all of you. Please note that many BGAs and uBGAs have temperature sensor devices built into them that cause the BGA to stop operating above a certain temperature. I once had a test tech that would put his finger on the BGA to make it fail, just to show me it had "bad solder joints". His body temperature was enough to cause the temp sensor circuit to switch it off. 

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Phillip Bavaro
Sent: Monday, December 22, 2008 1:17 PM
To: [log in to unmask]
Subject: Re: [TN] What could be the root cause for a failed board that passed functiona test after going through reflow for the 2nd time?

Whereas Werner mentioned testing at an elevated temperature, my instinct would have been to test it at lower temperature, in order to see if you can make it fail due to shrinkage, if in fact you have a microcrack.
Pressing lightly on a suspect component can sometimes give a failed unit continuity to pass

I just went through a situation in which a failed unit would pass after reheating the connection but after the unit had fully cooled to ambient, it would fail again.
Initially the SMT process was blamed, but after closely evaluating the solder joints of the LGA in question, we determined this was a test limit issue relative to temperature, and nothing was wrong with the solder joints

Cross section analysis (I know, destructive) is what most would do if we want to determine the root cause....otherwise we are just guessing.

Phil



At 01:50 PM 12/22/2008 -0500, Werner engelmaier wrote:
>  Hi Rudolph,
>Sounds like you have a failure that only shows up under certain 
>conditions---this could include fractured vias, pad cratering with 
>trace fracture, pillow-on-head, brittle interfacial failures, etc.
>You might try to test the assembly at elevated T [say 50C], or while 
>slightly bending or vibrating it.
>
>Werner
>
>
>
>
>
>
>
>-----Original Message-----
>From: Rudolph yu <[log in to unmask]>
>To: [log in to unmask]
>Sent: Mon, 22 Dec 2008 1:34 pm
>Subject: [TN] What could be the root cause for a failed board that 
>passed functiona test after going through reflow for the 2nd time?
>
>
>
>
>
>
>
>
>
>
>Hi:
>
>We have a proto assembly that passed the functional test initially.  
>But after we shipped it to the customer, it failed at the their site 
>for the same kind of test.  After we received the board back, we 
>reflowed it using the same reflow profile, and the board would 
>funcation once again...
>We checked the boards under 5DX  after we received it back from the 
>customer and found no defects on it.
>
>What could be causing this? and why the assembly would pass the test in 
>the first place?
>
>Here iare couple areas that I could think of...but not sure if they are valid.
>
>1.  Certain parts (microBGA) may be better off to have underfill 
>underneath for thermal mismatch? ( Need to check spec) 2.  During 
>handling and shipping, the board may be stressed to a degree that a 
>microfacture is formed.
>
>  What other areas could cause this problem.
>
>Thanks
>Rudolph
>
>
>
>
>
>
>_________________________________________________________________
>Life on your PC is safer, easier, and more enjoyable with Windows Vista®.
>http://clk.atdmt.com/MRT/go/127032870/direct/01/
>---------------------------------------------------
>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
-----------------------------------------------------

---------------------------------------------------
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
-----------------------------------------------------

ATOM RSS1 RSS2