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May 2007

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Subject:
From:
"David D. Hillman" <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, [log in to unmask]
Date:
Fri, 4 May 2007 16:55:51 -0500
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Hi Vlad! If I am interpreting Inge's photo number 4 correctly [realize I 
didn't get to see it on the SEM in person : - ) ], I see the nickel 
surfaces which have no wetting of solder. Gold dissolves into solder at 
100 uinches per second (Bader data) there should be no gold on those 
surfaces. In brittle interface fracture, I expect to see very few regions 
of nonwetting - the failure is due to the poor properties of the Sn/Ni 
intermetallic (e.g I get good wetting, its just not a strong interface). 
In cases of black pad, I expect to see very few regions of good wetting, 
the nickel surface has been corrupted such that I don't form the Sn/Ni 
intermetallic (e.g I get terrible wetting and never form a good 
interface). Thus my comments for picture 4.

Dave



Vladimir Igoshev <[log in to unmask]> 
Sent by: TechNet <[log in to unmask]>
05/04/2007 04:12 PM
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Vladimir Igoshev <[log in to unmask]>


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Subject
Re: [TN] Metalurgists, need assistance






Hi Dave,

I'm lost:-) how come you know there was no Au in the areas where we see 
Ni?

Brittlle Failed ENIG joints wqill have a similar "muddy" appearance

Regards,

Vladimir

-----Original Message-----
From: TechNet
To: [log in to unmask]
Sent: Fri May 04 16:45:09 2007
Subject: Re: [TN] Metalurgists, need assistance

Hi folks and thank you Steve for being "TechNet Picture Central"!  Sorry 
but just to warn everyone but I am going to use the "B" word shortly. Inge 

- take a close look at picture 4. As Werner pointed out the gold is 
non-wetting the nickel  in number of locations. What really jumped out at 
me is that "mud flat" appearance on some of the nickel surface regions - a 

"mud flat" appearance is a classic indication of black pad! I recommend 
you complete a cross-section to confirm that you have nickel grain 
boundary attack. 

But since it is Friday, go have a beer and worry about this on Monday!

Dave Hillman
Rockwell Collins
[log in to unmask]




Steve Gregory <[log in to unmask]> 
Sent by: TechNet <[log in to unmask]>
05/04/2007 01:45 PM
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Re: [TN] Metalurgists, need assistance






Hi Inge!

Got your pictures posted. Took me a bit, I was swapping our wave
solderpot from 63/37 to HMP. Done now. I'm getting quicker, I can do it
in 20-minutes now. Took me about 45-minutes when I first did it...

Anyways, here's the links:

http://stevezeva.homestead.com/files/Pic1.jpg
http://stevezeva.homestead.com/files/Pic2.jpg
http://stevezeva.homestead.com/files/Pic3.jpg
http://stevezeva.homestead.com/files/Pic4.jpg
http://stevezeva.homestead.com/files/Pic5.jpg
http://stevezeva.homestead.com/files/Pic6.jpg

-Steve-

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Hfjord
Sent: Friday, May 04, 2007 12:22 PM
To: [log in to unmask]
Subject: [TN] Metalurgists, need assistance

Have an issue with (randomly) lifted FPGA leads.
Pic 1: good joint after pull test
Pic 2: ditto but high magnification
Pic 3: "rotten" joint after pull test
Pic 4: ditto but high magnification
Pic 5: "rotten" cross section
Pic 6: ditto but high magnification

60Sn on ENIG, obviously a brittle region. Suspect Kirkendall voids, but
the pockets with zillions of Tin spheres (0.1 to 2 um in size) points at
insufficient peak temperature to make 100% melt and good solidifying. If
these little balls were Lead, I could understand, but they are Tin!
Never seen like. Any "quickhead" out there, need fast advice. 

Note: Pic 2, you can see the underlying board pad nickel as dark areas. 
An experienced analyst will hopefully recognize. No Phosphorous peaks!

My Friday headache.

Inge

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