Ruddiph,
Putting a failing assembly through an additional re-flow is a worst case scenario for troublshooting. You should have done analysis on the assmbly to find the problem.
If that was done properly (you'd need a right perosn/company for the job, though) than you would have guess whether it was the PWB or the assembly problem.
I usually say: not try to fix a problem without knowing the root cause.
Regards,
Vladimir
----- Original Message -----
From: TechNet <[log in to unmask]>
To: [log in to unmask] <[log in to unmask]>
Sent: Tue Dec 23 16:11:56 2008
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?
You got that right Joyce,
And, at the same time, the they point blame to process or material that
are up or down stream from themselves!
I don't tend to like to be constrained by political correctness, but, in
the sprit season, and in deference to those of all faiths...
Have a Happy Holidays Everyone!
Paul Reid
-----Original Message-----
From: Joyce Koo [mailto:[log in to unmask]]
Sent: Tuesday, December 23, 2008 10:38 AM
To: [log in to unmask]; Paul Reid
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?
Paul, my old age tells me usually the pwb house point finger to
interconnect, the mfg point to material, and so on. That is why the
expert make their money. The mgr want to hear the independent view they
paid too dollar for.
--------------------------
Sent using BlackBerry
----- Original Message -----
From: TechNet <[log in to unmask]>
To: [log in to unmask] <[log in to unmask]>
Sent: Tue Dec 23 08:18:22 2008
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?
Hi Rudolph,
All experts find a problem that relates to their area of expertise. If
you are sick and you go to a cardiologist you find you have a heart
condition. Next go to the endocrinologist and there is a hormonal
imbalance causing a heart condition. The dietitian finds a nutritional
deficiency due to imbalanced diet that is expressed as hormonal
imbalance that causes the heart condition. The heck of it is, they can
all be correct.
I am a PWB guy, so I will find a PWB problem. Werner mentioned
interconnect failure and I agree that is a strong possibility. The signs
you describe support interconnect failure.
Well here's my input. We found discrepant microvias and capped buried
vias that where temperature and pressure sensitive. At ambient they are
closed, at operational temperatures they are open. Manually twisted they
open, release they close.
If either is present in your PCB design, I would investigate the
reliability of microvias and capped buried vias. Both interconnects can
produce a failure mode that is self healing at ambient . Barrel cracks
and interconnect separation is less prone to be self healing at ambient
and are further down the list of suspect interconnect structures.
Sincerely,
Paul Reid
Program Coordinator
PWB Interconnect Solutions Inc.
235 Stafford Rd., West, Unit 103
Nepean, Ontario
Canada, K2H 9C1
613 596 4244 ext. 229
Skype paul_reid_pwb
[log in to unmask] <mailto:[log in to unmask]>
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Rudolph yu
Sent: Monday, December 22, 2008 1:35 PM
To: [log in to unmask]
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(r).
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
-----------------------------------------------------
---------------------------------------------------------------------
This transmission (including any attachments) may contain confidential
information, privileged material (including material protected by the
solicitor-client or other applicable privileges), or constitute
non-public information. Any use of this information by anyone other than
the intended recipient is prohibited. If you have received this
transmission in error, please immediately reply to the sender and delete
this information from your system. Use, dissemination, distribution, or
reproduction of this transmission by unintended recipients is not
authorized and may be unlawful.
---------------------------------------------------
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
-----------------------------------------------------
|
