The R/F world gets more interesting all the time. What doesn't.

Do what you've always done to calculate impedance requirements for microstrip or stripline. Specify
the impedance, dielectric thickness, material Dk, line width & tolerance, conductor thickness, and
place the specified construction requirements on the master drawing. I strongly suggest "hanging"
quality conformance test circuitry as specified by IPC and require the fabrication facility to x-
section and run TDR testing.

The fab facility should use the appropriate test coupons, as part of the test circuitry, to perform
testing. Corelation is easily and objectively made between TDR and findings in x-section. You will
see and corelate the results and be able to make changes. You may perform the TDR testing in house
also, if required.

Certs are a matter of choice. If the above requirements are met by a carefully evaluated and
qualified fab facility, the certs are the test results you receive by request in the contract. Some
capabilities provide certs as a matter of doing business as material, chemical, and other
certifiable elements and processes.

Except in certain instances, the fab capability should be free to use preferred laminate, core, and
prepreg material. Of course, as an R/F person, you know certain materials perform better than others
especially at very high speeds and you will want concurrence with whoever does the job.

Earl Moon

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