[SI-LIST] Re: board level test to dig out the failure of the component
- From: Mike Brown <bmgman@xxxxxxxxxx>
- To: si-list <si-list@xxxxxxxxxxxxx>
- Date: Fri, 02 Jul 2010 09:28:14 -0500
Vincent Zeng wrote:
>Hello
>
>I have a question and would like to hear some idea. Oftenly we found some
>board level test failure and after a long time process of debuging, we found
>the failure is indeed casued by $2 component, like oscillator. Some frequency
>shiffting is the root cause. Do you have some idea to distuiguish component
>level failure on board level test?
>
>Any idea will be really appreciated!!
>
>best regards
>
>Vincent
>
>
>
>------------------------------------------------------------------
>
>
Vincent,
This sounds to me like a marginal design in some fashion. I've been out
of the design and troubleshooting business for several years now, but I
have spent the better part of 50 years chasing those kind of bugs. My
sense tells me that the culprit is yet to be identified.
The fact that it took a long time to find the "problem" (if, indeed the
problem has been found) tells me that everything works but the system.
I have serious doubt that any board level test is going to find the
"failed" component. This because the component is not really failed,
but is being stimulated, on some occasions, in some abnormal fashion due
PERHAPS to SI or noise issues. Real root-cause analysis of the failure
is needed, then design changes incorporated as needed.
I always advocate not blaming the component until there is rather
conclusive evidence that it is not performing to spec. This takes a lot
of looking and a lot of analysis, and no small amount of skill and
persistence. A good dose of luck doesn't hurt either. When you have
found what the stimulus is that causes the failure, you may be able to
program operations which avoid that stimulus and run successfully for
many hours, then run a case which hits the bad stimulus and get a quick
failure. That's pretty conclusive proof that you know what the culprit is.
Best of luck to you in isolating the culprit(s)!
Mike
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