Gary,
Great answer with greater clarification. But I do have few questions being a
mechanical guy.

(1) Does trace width has to do anything with the frequency or it's the
length of the trace only beside rise time.?

(2)Rise time - Is there any rise time number for FR4 material as this test
is being performed at bare board level?

(3) Why you are saying that it's good that TDR test often occurs at a higher
frequency than you desire?

Hope you understand my level of understanding on the subject!

re,
ken patel

At 09:43 PM 8/30/1999 EDT, you wrote:
>Ken,
>
>The measuring frequency is dependent on the rise time and the length of the
>signal trace. As the trace becomes shorter the TDR tester increases the
>frequency so that it can obtain a good sampling along the shorter trace. The
>frequency at which the test occurs is not really within the operators control
>If you wish to control the test frequency, then you must provide the
>fabricator with a test trace length that is calculated to force the TDR
>tester to test at a given frequency. your fabricator should be able to
>provide that information to you for a given design. Rather than ask for a
>specific frequency, you may wish to ask at what frequency did the test occur.
>Often it occurs at a higher frequency than you desire, which may be good.
>
>Regards,
>
>Gary Ferrari
>Executive Director
>IPC Designers Council
>860-350-9300
>
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______________________________________________________
Ken Patel                       Phone:  (408) 490-6804
1708 McCarthy Blvd.             Fax:    (408) 490-6859
Milpitas, CA 95035              Beeper: (888) 769-1808

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