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May 2007

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TechNet E-Mail Forum <[log in to unmask]>, Steve Gregory <[log in to unmask]>
Date:
Fri, 4 May 2007 16:01:25 -0400
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TechNet E-Mail Forum <[log in to unmask]>, Vladimir Igoshev <[log in to unmask]>
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Vladimir Igoshev <[log in to unmask]>
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Hi Inge,

NONE of the joints you pictured look like a typical "Brittle Fracture"
type of failure on ENIG boards. Do you happen to have some
cross-sectional images of the bad (lifting) lids? 


You are right, there are areas of exposed electroless Ni in Fig. 4
(didn't get, though your reference to a P peak as there is no EDS
spectra).

As far as "Sn spheres" is concerned, then... I wouldn't jump to such a
conclusion right away. From image 6 I can tell that the cross-section is
slightly etched (probably you used silica) and the presence of the
spheres could be related to the polishing procedure.

Regards,

Vladimir

AMD

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Steve Gregory
Sent: Friday, May 04, 2007 2:45 PM
To: [log in to unmask]
Subject: 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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