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Re: Production testing of 6400 BGA pc boards with Xray and/or JTAG?

Started by Jeff Brower December 1, 2007
Peter-

> Anyone have any tips on production testing techniques for pc boards
> using the C64xx BGA chip?

Several years ago my company used to make DSP module functional test systems for
Sanmina Viking-InterWorks... here are a few comments. I apologize in advance if my
comments are redundant with Mike Dunn's.

> i.e. is Xray inspection of the BGA contacts standard?

No. Only if a number of boards tend to fail and/or a failure pattern develops, for
example in a 2-sided board one side has more DSP failures.

> Are there test programs using JTAG that can check for opens/shorts and
> do external memory bus testing?

Yes, boundary scan is used often. However, functional test is the gold standard.
You can run boundary scan all day and not find many types of failures with a DSP
board. Our thinking was that boundary scan served as an assembled PCB electrical
test, nothing more.

> Has anyone gotten advice from TI in doing design-for-test with the C64xx
> that they could share?

TI provides some good board layout advice for individual devices, but I've not seen
anything from them specifically addressing DFT. There are tons of stuff I could
recommend, mostly proprietary, here are a few general categories:

-JTAG access and chain configuration options are
critical. DSP and other JTAG chains (FPGA, uP,
etc) can't be shared

-a number of test points are crucial such as CLKOUT;
these plus boot mode configuration Rs should be
accessible by the test equipment; i.e. not buried
on the bottom side of the board

-heat is a huge issue with the larger TI DSPs; the
test fixture needs to address this

-the test fixture may need precise control over
voltage rail ramp-up sequence and shape

-test fixture may need to address line-length and
signal integrity issues for high speed interfaces
(PCI, SRIO, serial ports, etc)

-Jeff