Step one is to put a rework flux under the BGA and then reflow using a
PDR IR rework station.
If that doesn't cure it then we remove the device, check the pads and
replace with new.
We only reuse devices when expensive or rare and we send out for laser
reballing as that doesn't use a 'life'.
We purchased the machine as we had a big contract where it was a
contractural requirement to x-ray every bga and qfn and store all
results, and work to the requirements for voids in IPC610 d. The machine
was paid for in 30 days!!!!
We use the x-ray machine to verify processes, we hardly see any voiding
any where near the limit in IPC610, and I don't think voiding is
anything like the problem its air time might indicate.
We do put down some power pad devices and x-ray is the only tool for
confirming the heat will be removed.
We do not use it for 100% inspection for BGAs any more, it is only used
for process confirmation.
Regards
Rex 

-----Original Message-----
From: Blair Hogg [mailto:[log in to unmask]] 
Sent: 07 October 2009 13:20
To: [log in to unmask]; Rex Waygood
Subject: Re: BGA X-Ray Defect Detection Capabilities

Just out of curiosity, when you detect an open on a BGA, what do you do?
I'm suspecting it is not practical to rework just the open sj, can you
reflow the entire BGA to get the open sj to form a connection, or remove
and reattach? 
Do you re-use the removed device or replace with a new one? 

Is the x-ray inspection really useful, or is it just to confirm a defect
found in test? Or does it detect defects before test so that they can be
reworked prior to testing?

Is the x-ray inspection useful for getting the profile parameters
correct, and then once the process is in control the inspection no
longer adds value?

Thanks,

Blair

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