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February 2009

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Subject:
From:
"Thayer, Wayne" <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Thayer, Wayne
Date:
Wed, 11 Feb 2009 16:42:23 -0500
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text/plain
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text/plain (206 lines)
 Am I measuring correctly?  According to that 20micron scale in the cross section, the nickel is about 7microns(approx 280micro inches) thick?  Could that be the reason the structure is so brittle? I guess the plater was having a big sale on nickel that day?

Wayne Thayer

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Stadem, Richard D.
Sent: Wednesday, February 11, 2009 4:31 PM
To: [log in to unmask]
Subject: Re: [TN] CRACKED ENIG PADS

Vladimer is correct. They are cracks in the nickel/gold layer that extend down to the copper and stop there. The reason is that the nickel is a much more brittle or non-ductile material than either the gold or the copper. The copper will bend somewhat if the board is stressed, but the nickel will not, it cracks. The gold is so thin on true ENIG (3-5
uinches) that when the nickel cracks the gold is literally torn apart.
The copper does not crack easily.
So the board was subject to some type of flexural stress that caused the nickel to crack, and the direction of the flexure determines the portion of the annular ring upon which the hard nickel is going to crack. That is why in this particular picture the cracks are concentrated on one side of the annular ring.

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Vladimir Igoshev
Sent: Wednesday, February 11, 2009 2:41 PM
To: [log in to unmask]
Subject: Re: [TN] CRACKED ENIG PADS

Lee,

Without seeing the actual cross-sections it's impossible to say what is the root cause. If you are not happy with the lab report, you can send me the part and I'll do it.

Regards,

Vladimir
SENTEC
11 Canadian Road, Unit 7.
Scarborough, ON M1R 5G1
Tel: (416) 899-1882
Fax: (905) 882-8812
www.sentec.ca


-----Original Message-----
From: Lee Whiteman <[log in to unmask]>

Date:         Wed, 11 Feb 2009 14:41:46
To: <[log in to unmask]>
Subject: Re: [TN] CRACKED ENIG PADS


Victor, George, Vladimir, and Company

Steve should be attaching the cross-section photograph. Since I did not supervise the cross-sectioning activity, I will not vouch on the quality of the cross-section.

I do see a layer (crack?) between the ENIG plating and the copper surface, but the report that I received indicated that there was "no evidence of a lack of bonding" - the lab reports words. That layer
(crack?) seems more pronounced than similar ENIG cross-sections I have seen.

Lee Whiteman, PMP
Senior Member Engineering Staff
L-3 Communications East
Telephone: (856) 338-3508
FAX: (856) 338-2906
E-Mail: [log in to unmask]


-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Victor Hernandez
Sent: Wednesday, February 11, 2009 2:23 PM
To: [log in to unmask]
Subject: Re: [TN] CRACKED ENIG PADS

Can you share the photos of the cross section?



-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Wenger, George M.
Sent: Wednesday, February 11, 2009 12:51 PM
To: [log in to unmask]
Subject: Re: [TN] CRACKED ENIG PADS

Lee,

When you say "Evidently" that you have done cro


Lee,

When you say "Evidently" that you have done cross sectioning and see that the cracks are only in the Ni and Au and not in the Cu?  Since you said "There was no evidence of a lack of bonding between the copper and the ENIG finish" that implies to me that you did cross section but since I wasn't sure I thought I'd ask.

Regards,
George
George M. Wenger
Andrew Wireless Solutions
Senior Principal FMA/Reliability Engineer 40 Technology Drive, Warren, NJ 07059
(908) 546-4531 (Office) (732) 309-8964 (cell) [log in to unmask]

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Steve Gregory
Sent: Wednesday, February 11, 2009 1:42 PM
To: [log in to unmask]
Subject: Re: [TN] CRACKED ENIG PADS

Hi Lee!

Have your pictures posted. They are here:

http://stevezeva.homestead.com/files/THROUGH_HOLE_CRACKS-1.jpg

http://stevezeva.homestead.com/files/THROUGH_HOLE_CRACKS-2.jpg

I have to let those that know more about plating than I do answer this one...

Steve

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Lee Whiteman
Sent: Wednesday, February 11, 2009 12:20 PM
To: [log in to unmask]
Subject: [TN] CRACKED ENIG PADS

I have asked Steve to put up a pair of pictures I received. They are of cracks within the ENIG finish of a PWB. I know that the board failed, based on IPC-6011 and IPC-6012.

My question is what would cause the cracking? Evidently, it is in the Nickel layer and the copper layer was not compromised. There was no evidence of a lack of bonding between the copper and the ENIG finish.
These boards are fresh from the supplier.

Just curious...

Thanks in advance.

Lee Whiteman, PMP
Senior Member Engineering Staff
L-3 Communications East
Telephone: (856) 338-3508
FAX: (856) 338-2906
E-Mail: [log in to unmask]


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