Ioan,
Lapping (X-sectioning parallel to the board) won't help you. A reliable technique which would allow one to assess whether a crack in a given BGA ball is present is yet to be discovered.
In general, it's a complex issue and solder joints are not always the ones to blame. There is always a chance that either the component itself, or another component in the circuitry is causing the problem.
Vladimir
RIM
Sent from my Blackberry Wireless
Vladimir Igoshev, 519-888-7465 ext.5283
----- Original Message -----
From: TechNet <[log in to unmask]>
To: [log in to unmask] <[log in to unmask]>
Sent: Fri Jun 16 14:03:58 2006
Subject: Re: [TN] How to know if a BGA is properly soldered?
If the board is heated to about 150 deg C for about 60 min, the
BGA may be able to be peeled or pried off the board with pads still
connected to the BGA balls. Once it is off with everything intact, do a
visual with a Scope.
Regards,
Ramon
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Wayne Thayer
Sent: Friday, June 16, 2006 1:45 PM
To: [log in to unmask]
Subject: Re: [TN] How to know if a BGA is properly soldered?
Ioan, the chances are that you don't care about trying to salvage the IC
at this point. It sounds like you know which ball is the problem, but
since its not on an outside row you can't see it.
If you have access to a rotary tool such as a Dremel and a decent
10x-30x stereoscope, then just buy a cylindrical diamond burr from the
McMaster Carr company (www.mcmaster.com) and grind through the device
down to the suspect connection. Use a little DI or distilled water to
lubricate the cut and remove debris. You need some hand skills for this
job, but it's really pretty easy. Just don't ding the board.
Wayne Thayer
>>> [log in to unmask] 6/16/2006 9:05 am >>>
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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