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October 2011

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Subject:
From:
"Wenger, George M." <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Wenger, George M.
Date:
Mon, 24 Oct 2011 08:40:52 -0500
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I believe Richard is correct and it would be very easy to prove.  Simply do an XRF measurement on a via with a discoloration and one without and  it the discolored pad shows no nickel and the non-discolored one does you have your proof.

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 Stadem, Richard D.
Sent: Monday, October 24, 2011 9:34 AM
To: [log in to unmask]
Subject: Re: [TN] Discoloration on plated over vias

What you are seeing is referred to as a nickel skip, or skip plating. If the nickel deposit is too thin or not there at all, the copper will migrate up through the gold and cause it to look a bright orange in color. The gold thickness is redundant, the problem is insufficient nickel.

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Chuck Brummer
Sent: Saturday, October 22, 2011 10:17 AM
To: [log in to unmask]
Subject: Re: [TN] Discoloration on plated over vias

Ioan,

Two micro inches of Gold isn't very much.  Is there a Nickel barrier 
layer?  If not that is probably copper migrating up through your gold. 
Heat or time will do that to gold over copper.

Chuck


Charles W. Brummer | 3M Manufacturing Engineer
3M Electronic Solutions Division
3M Canoga Park, 8357 Canoga Ave. | Canoga Park, CA 91304
Office: 818 734 4930
[log in to unmask] | www.3M.com


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From:
Ioan Tempea <[log in to unmask]>
To:
<[log in to unmask]>
Date:
10/21/2011 02:14 PM
Subject:
[TN] Discoloration on plated over vias
Sent by:
TechNet <[log in to unmask]>



Dear Technos and Smarts,

 

I got this issue, see http://ipc-technet.groupsite.com/gallery/21662

 

So 6 layer, 2oz Cu per layer PCB, epoxy filled vias and plated over. After 
assembly we see 4-5 vias having reddish stains, on most boards. Had it 
analyzed, no trouble with via integrity, no cracks in cover plating, no 
migration of fluids from inside out. FTIR does not detect any surface 
contamination.

 

Au plating thickness stands at 2.09 micro inches.

 

Nothing special detected in the stains, so the lab concluded what we see 
is an optical effect due to a certain roughness of the Cu. The logical 
conclusion is no issue, cosmetic defect.

 

However, our end customer, high reliability, want to know what the stains 
are and want absolute confirmation that long term reliability is not 
affected. Also, we've been warned that no such issues will be tolerated on 
future lots.

 

My questions to your infinite knowledge is: have you seen this before? How 
can I convince the customer everything is OK? What is the root cause and 
how can I get rid of the issue?

 

Many thanks,

 

Ioan Tempea, ing.
Ingénieur Principal de Fabrication / Senior Manufacturing Engineer
T | 450.967.7100 ext.244
E | [log in to unmask] <mailto:[log in to unmask]> 
W | www.digico.cc <http://www.digico.cc/> 

 
 N'imprimer que si nécessaire - Print only if you must

 


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