[SI-LIST] : Trace Capacitance

Farrokh Mottahedin ([email protected])
Mon, 21 Jun 1999 08:59:22 -0700

I hope someone can explain what is happening with the following capacitance
measurement. A friend asks if capacitance is directly proportional to
surface area, why doesn't his measurement scale linearly. On a pcb made
specifically for trace characteristics measurement, he measures
1) 10 pf for a 10 cm long trace that is 5 mils (.12 mm) wide
2) 25 pf for a 10 cm long trace that is 20 mils (.50 mm) wide
3) Both traces are far apart from each other and from other components.
4) Both traces are over a solid ground plane.
5) Equipment is HP 4285A Precision LCR meter set at 1 MHz


Farrokh Mottahedin
Quantum Corporation
(408) 324-7934
[email protected]

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