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June 2006

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TechNet E-Mail Forum <[log in to unmask]>, Hfjord <[log in to unmask]>
Date:
Thu, 22 Jun 2006 16:04:48 +0200
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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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