From: email@example.com (Bob Wilson)
Subject: Re: PCB routing
Date: Fri, 25 Oct 2002 04:20:01 -0000
Organization: Your Organization
X-Newsreader: WinVN 0.99.9 (Released Version) (x86 32bit)
In article <191C91BDFE8ED411B84400805FBE794C2DA011B9@pfs21.ex.nus.edu.sg>,
>How do we determine thickness of line width to route when dealing with
>or signal traces on a PCB? Does the location ( either surface layer or
>sandwitch in between dielectric) changes the properties of the thickness of
>normally what is the size of a min via drill to use for power or signal?
>also what is the clearance to use for these via if it's surrounded by a
>thanks for your expertise.
There is no simple answer.
Trace width can be limited by voltage drop in low voltage high current
circuits, or by power (heat) in higher voltage lines. To clarify, a width
that is selected to prevent excessive heat caused by current flow, may work
well at higher voltages, but at low voltages this may cause an unacceptable
voltage drop. For example, it may be that a half-volt drop will result from
a trace width that stays withing the acceptable limits for heating. At (say)
50 volts, this is no big deal, but if the trace has only 3 volts on it,
half a volt loss is catastrophic.
Similarly, you can get away with very thin traces for a short distance
(where total heat is insigificant, and where component leads act as heat
sinks), but for longer traces, far greater widths are needed.
The answer to your question is basically that you need to use your head and
consider the particular parameters involved, and make a judgement for
yourself under the particular conditions. There is no early "no-brainer"