Hi,
Wow, wonderful pics.
Question:
Could this problem even exist with a HASL finish?
Bob Kondner
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Werner Engelmaier
Sent: Saturday, February 27, 2010 11:01 AM
To: [log in to unmask]
Subject: Re: [TN] Hackneyed?
Hi Inge,
Yes, I have seen this before-not with those absolutely great pictures, but
with very similar elemental distributions.
In that case, the assembly saw nine (9!!!) soldering exposures.
I looks to me, your assembly was either exposed to soldering temperatures
too often and/or too long.
Werner
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Inge
Sent: Wednesday, February 24, 2010 2:54 PM
To: [log in to unmask]
Subject: [TN] Hackneyed?
Hi Folks,
am asking you to sacrifice a minute on a topic that may make you sick, as
much as it has been discussed. Have a look at the SEM images that
(hopefully) will be beamed by our most honorable guy, Dr Gregory. By
order:
1. Pic 38 BGA ball after the preying off the 560 ball BGA from the board.
SEI mode.
http://stevezeva.homestead.com/files/XILINX_Daniel_38.jpg
2. pic 39, same at x 5,000
http://stevezeva.homestead.com/files/XILINX_Daniel_39.jpg
3. pic 40,samet at x 10,000
http://stevezeva.homestead.com/files/XILINX_Daniel_40.jpg
4.pic, 41 same at x 20,000
These four show the face of the pulled-off balls. The package/board was
sectioned into halv by half inch pieces with a thin blade diamond saw and
then each BGA section was separated from the board
by means of a steel.
http://stevezeva.homestead.com/files/XILINX_Daniel_41.jpg
After SEM 1-4 I made EDS, which can be seen below.
5. http://stevezeva.homestead.com/files/XILINX_Backlund_Ball_2.doc
As you can see, there is nearly no Lead (!), a high w/% Nickel, a little Tin
and lots of Phosphorous. Clearly, the separation has been in a
Now, continue with having a look at the board pads after the preying-off.
6. pic 44, Board pad at low magnification and SEI mode.
http://stevezeva.homestead.com/files/XILINX_Daniel_44.jpg
7.pic 46, same at x 5,000
http://stevezeva.homestead.com/files/XILINX_Daniel_46.jpg
8.pic 48, same at x 10,000
http://stevezeva.homestead.com/files/XILINX_Daniel_48.jpg
9. pic 50, same at x 20,000
http://stevezeva.homestead.com/files/XILINX_Daniel_50.jpg
10. pic 51, same but with BS mode
http://stevezeva.homestead.com/files/XILINX_Daniel_51.jpg
11. XILINX_backlund_pad_1.doc
http://stevezeva.homestead.com/files/XILINX_Backlund_Pad_1.doc
As you can see here, there is more Lead, a high w/% Nickell, much more Tin
and still lots of Phosphorous.
Discussion:
Obviously, real and reliable solder joints are only in the circumperipheric
of the whole (best understood with pic 10). How strong the adhesion was in
the main part of the joint, we don't know. From the function (final)
electrical testing, we have experienced several cases with disturbed
signals. Many a times, we have had to remove the BGA and supersede with a
fresh one. The test engineer told me, that by slightly add pressure to the
BGA, he may get the signal through again. He thinks we have an issue with
the uvias, others think there is a problem with the BGAs, myself I'm
committed to my theory that this has to do with the rotten interface between
the Tin/Lead and the ENIG pads.
Question:
Is anyone familiar with the said? What is your opinion about the
demonstrated solder joints? Can yoy get cracks and electrical misfunction,
despite that hundreds of balls are holding the BGA close to the board in a
'iron grip' ?
Wayne? Steve? Dave? George W? Vlad?
Thanks in advance. You'll have to wait for Steve to fix the exhibition.
/Inge
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