clarifying:
1. there is no such report, I 'developed' the method myself in desperation
to find why and where we got interrupts in superBGA solder joints. Dip in
LN2, simple as making a cup of tea, just put the board into the LN2, wait
until boiling stops, then the board is at -196 centigrades. The solder
joints are brittle now. You can easily shear or prey the BGA off the board.
It's of course a destructive test. Furthermore, if you are playing with a
large board, it is recommended to cut out the specific BGA site with a
diamond saw before doing the investigation. My method is primitive and
violent, but can be useful if the ordinary methods don't fit. I recommend
trying on some scrap samples before testing the actual sample. I had our
model shop to make some simple steel blades for the shear machine or hand
preying. I'll see if they exist still. If so, I'll send a pic to Steve's
wall.
2. the report I sent to Ioan shows a little of the separation of BGA from
board when preying it off. Not so remarkable stuff, there must be lots of
similar articles in the technet arcive.
Ingemar
----- Original Message -----
From: "Victor G. Hernandez" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Thursday, June 22, 2006 4:14 PM
Subject: Re: [TN] How to know if a BGA is properly soldered?
I am very interested in receiving document of LN2 technique/method for
detecting BGA solder bump integrity. Where can I acquire a copy of the
complete report.
Victor,
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Hfjord
Sent: Thursday, June 22, 2006 9:05 AM
To: [log in to unmask]
Subject: Re: [TN] How to know if a BGA is properly soldered?
10an,
I love violent methods. Depending on whether you can sacrifice the
board or
not, also depending on thickness of board, you may do following. Dip
board
in liquid nitrogen until stopped boiling, then bend board slightly. If
there
is a tiny 'ping' , the BGA is ready to be lifted off. Otherwise, use a
shear
tool and a knee pressure equipment to shear it off. You have to control
the
move, which ought to be just a fraction of a ball diameter. If you don't
have control on shear move, you'll smear the solder ruptures and get no
useful sample.
I'll send to you some pages out of 185 page report I wrote some years
ago
about superBGA problems. In that short version I send to you, just have
a
look at the first pages where you can see how the BGA separated from the
board, and how the ruptures look like.
Hope this will confuse you still, but at a higher level...
Ingemar Hernefjord
Ericsson Microwave Systems
----- Original Message -----
From: "Tempea, Ioan" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Friday, June 16, 2006 3:05 PM
Subject: [TN] How to know if a BGA is properly soldered?
Hi,
first it was the cracked capacitor question, thanks to all who answered.
Now I have another one on the ethernal dilemma: is the BGA poorly
soldered
or there is a design issue?
The question is: how can I assess whether the BGA that fails test is
properly soldered? I do not have a 5DX and whatever I can see with the
Ersascope looks OK. Needless to say, I cannot get the location of the
failed
pin.
Will cross sectioning parallel to the surface of the board tell me
anything?
Can this be done? Any particularities regarding the polishing of the
surfaces?
What to look for?
Thanks,
Ioan
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