Hi Victor,
no etching is used. How could the polishing create all these perfectly
rounded balls? I have seen hundreds of Tin/Lead cross sections, but never
like this ones. Polishing is done with diamond spray 1/4 micron grade.
I agree, doesn't look typical brittle, more like ductile, as said Werner,
but not typical ductile either if you refer to the high magnification
photos. Instead they look more like solder joints that have gone through
severe grain growth and sliding, leading to creep and rupture. I can't
determine that either.
Inge
----- Original Message -----
From: "Vladimir Igoshev" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Friday, May 04, 2007 1:01 PM
Subject: Re: [TN] Metalurgists, need assistance
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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