I assume you have some assemblies that work properly. If you do, test
one and verify it is working, and collect the test data. Carefully
remove the BGA at the site you are having trouble with. Place an
emulation socket in that location and reflow it in place. Use a socket
with crowned pins (not spring coil contacts) so you can test BGAs with
or without solder balls. After cleaning the old solder balls away from
the original BGA, place it in the socket and re-run the test to verify
the assembly is still good. If it is OK, use this assembly as a "golden
unit" to test the different lots of Xilinx 4013s. You can use this
golden unit to screen incoming parts and create "known-good BGAs" to
populate your production boards, as well as for debugging the issues
with the bad parts. Compare the test data of the good BGAs with the
failed BGAs to determine the root cause of the BGA malfunction. This is
a good way to document the failure so as to return the failed BGAs. Note
however that the failed BGAs may meet the test definitions at Xilinx,
they may just not work perfectly in your particular circuits.
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Inge
Sent: Saturday, March 10, 2007 1:05 PM
To: [log in to unmask]
Subject: [TN] FPGA (DSP)
Hi all,
TechNet member's knowhow got no limits, so I try this, despite not usual
PWB topic. Have some FPGAs for DSP that don't work at all. CLK A and B
are OK, checked with a scope on the inputs, all 5V Vcc's are OK, but
when I apply stimuli on the various inputs, I get no reaction on any
data outputs. Very primitive test method, I know, but I thought that at
least something would come out to show that the device isn't completly
dead. The flash memory is external, I've tried with both disabled and
enabled flash, nothing helps. I can't remove the FPGAs, so I have to
test them on the assembled board. I've tried various triggers too. An
advanced troubleshooting would include logic analysers, external pattern
generators and a special test adapter. That's for a logic specalist,
which I'm not. My question is this: Does anyone of you have a proposal
how to test, simple way, if the FPGAs are dead or alive? The FPGAs are
Xilinx 4013, made in numbers of 'millions', very popular some years ago.
A fresh board costs 30,000 USD, hoped to escape that cost.
Inge
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