You might have to use micro-ohm-meter to detect the resistance between the contact. http://www.home.agilent.com/agilent/product.jspx?pn=34420A


  _____

From: TGAsia on behalf of Patricia Lui
Sent: Sat 8/22/2009 7:26 PM
To: [log in to unmask]
Subject: Re: [TGAsia] ??: [TGAsia] Holes Desmear I ssue


Hi James Liu,

In additional to the photos the single photo on the right is taken form a board which had been picked just after the assembly, it had not gone through 48hrs of functional test. As for the 3 photos on the left they are boards picked up during the 48hrs functional test run and also from boards after running for a few months in the field.

I noticed that the boards which have run for a long time then pick up as rejects have a more severe desmear look. So actually I suspect in the initial stage these boards might already have the same or minor desmear conditon but it is still able to let current pass through. But as the boards run for a much longer time, due to expand and contraction the desmear area worsen so it die off after 3 to 6 months running. I cannot confirm is this possible as it is all only as per my suspect condition.

Now my biggest problem is how do I pick up this problem boards from the good boards, I cannot let it run for 3 to 6 months then wait for it to fail to identify them. I hope that you can give me some direction or advise.

As a PCB factory I have already done 100% etesting, this issue cannot be picked up in the PCB factory, where can this issue normally be picked up? is it the PCB factory responsible or the PCB assembly house responsible to pick up this issue boards? I believe this desmear issues only surface up after reflow.

Really appreciate to you have your advise on it.

Thanks & Best Regards
Patricia Lui



--- On Fri, 21/8/09, James Liu <[log in to unmask]> wrote:



From: James Liu <[log in to unmask]>
Subject: [TGAsia] ??: [TGAsia] Holes Desmear Issue
To: [log in to unmask]
Date: Friday, 21 August, 2009, 10:20 PM


Would you mind attaching some photos about the holes?


Best Regards,

James Liu ???
Director, Technology & Standardization ???????
IPC China
??????????1088?2303?
Suite 2303,#1088 West Yan'an Rd., Changning, Shanghai 200052 PRC
Tel:   +86 21 5497 3435
Fax:  +86 21 5497 3437
MP:   +86 136 0133 3491
[log in to unmask]<[log in to unmask]" target="_blank">http:[log in to unmask]><mailto:[log in to unmask]<[log in to unmask]" target="_blank">http:[log in to unmask]>>
www.ipc.org.cn<http://www.ipc.org.cn<http://www.ipc.org.cn/>>
________________________________
???: TGAsia [[log in to unmask]<[log in to unmask]" target="_blank">http:[log in to unmask]>] ?? Patricia Lui [[log in to unmask]<[log in to unmask]" target="_blank">http:[log in to unmask]>]
????: 2009?8?21? 19:50
???: Listserv TGAsia
??: [TGAsia] Holes Desmear Issue

Dear Friends,

Currently I am facing the following issue which I hope to have your expertise advise:

Issue:
I have boards rejected and found that the 1.2mm holes of some of the boards have desmear and we have confirmed that it was caused by the 1.2mm drill bit blunt at the tip area. Only 6% of the boards are affected.

The boards have all passed 1) Etest in my factory  2) 48hrs functional test.
But it have failed after 3 to 6 months on the field due to desmear in different location of the 1.2mm holes. Currently customer is rejecting 100% of the boards because they have no confident to use the boards.

I hope to have your expertise on what other test (non-distructive) I can conduct to be able to 100% pick up this type of issue boards which had passed the functional test. Baring in mind that 1) the boards are already assembled with components, 2) the boards have passed the standard test listed above. 3) The boards can fail after 3 to 6 months running.

Hope to have your expertise advise. Thanks

Best Regards
Patricia Lui
Xuan Technologies
Tel: 65-97227602







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