In a message dated 98-01-22 14:15:28 EST, [log in to unmask] writes:

<< Hi People,

 Does anyone have precise methods of isolating locations of shorts and opens
 inside a finished PWB. Electrical Test, Probots and Micro-Ohmmeters hint at
the
 areas of the defects, but dont reveal the actual location. I am wondering if
 anyone has tried Infared Thermal Imaging, High Resolution x-ray or Tracing
high
 frequency signals through a board. New project and little frustrated, Thanks
 for any help.

 Dave Kleinman
 Optical Inspection Engineer
 Raytheon-TI Austin, TX
 512-250-7141 >>

Hi Dave,

     I'm assuming when you say "finished PWB" that means completely assembled.
I'm not a test type, but at a past employer we evaluated a Nicholet X-ray
machine for a couple of months.

     We were evaluating it mainly for doing solder joint x-ray's. But one day
after we had it for a while, one of our test technitions came over to our
surface mount area looking kinda' frustrated...he had been trying to de-bug
the boards that accumulated in what we called our "dog-pile". He had one board
with him that he had been trying to find a open in for a couple of hours and
asked if it was possible to put the board into the machine and look in a
certain area of the board to try and find a open trace.

     We put it into the machine and found the open trace in about 2-minutes.
After that, he was using the x-ray machine more than we did in SMT for the
remainder of the time we had the machine on evaluation...so it seems to me
that it was a pretty good tool for that. We didn't keep the machine
unfortunately, it only looks straight down through the PCB, unlike a Four Pi
x-ray laminography machine, and it was difficult to tell exactly where the
voids in a solder joint were when we spotted them...which was the main reason
for buying the equipment.

                                                               -Steve Gregory-
                                                                 Zevatech Inc.

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