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Date: | Tue, 09 Jul 1996 16:25:25 -0700 |
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As I was browsing through some previous discussions, I came across the
following question (yeah, I'm quoting myself). It was regarding the use
of Figure 3-4 in IPC-D-275 to determine an appropriate trace width based
on current.
> As an example, say I need 5amps and 20 degrees over ambient is a safe
> assumption. The chart gives ABOUT 100 square mils, which corresponds to
> ABOUT a 75mil trace width on the 1oz copper curve.
> OK, how many of you use 75mils? How safe is this number?
Many of you responded (THANK YOU) but one issue was never brought up and
I am still curious about it.
According to IPC-RB-275 Table 7, a conductor width can be reduced 20% by
a nick or scratch for a length of 0.5 inches and still be acceptable,
plating thickness can vary (as well as the 1oz copper stock), traces can
be over-etched, etc.
So does the chart indicate that I should use 75mil aperture in my CAD
system, or is my goal to take all factors into account and try to ensure
the END RESULT is 75 mils minimum?
Am I splitting hairs? Jack
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