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Date: | Fri, 21 May 1999 09:18:37 -0700 |
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Jack,
The hotter the trace, the less current it can carry. So when you solve for
trace width, you have to know the hottest environment your board in which
your PCB is still expected to work. Commercial temperatures are around 85
deg. C and military are 125 deg. C max. From that max figure, subtract the
ambient temperature of your PCB environment, which can vary from room temp
to an enclosed box with no air flow. That will be your temperature rise
allowable for traces.
David J. Ricketts
Pertek Engineering
voice> 949-475-4485
-----Original Message-----
From: TechNet [mailto:[log in to unmask]]On Behalf Of Jack Olson
Sent: Friday, May 21, 1999 9:00 AM
To: [log in to unmask]
Subject: [TN] Temperature Curves for PCB Traces
Sorry for posting this here (after already trying the designer council) but
if I don't get a logical scientifical semi-provable response I will be
forced to use the dreaded "10 degree curve" for the rest of my designs....
ouch!
I can't figure out how to select the appropriate temperature curve when
calculating PCB trace widths versus current requirements.
If you use the chart in IPC-D-275 or IPC-2221, you have to select a curve to
get your minimum trace width.
If you use a calculator, it will solve for the temperature rise, but you
still must know if it is acceptable.
So what is acceptable? Anything that won't make the material hit Tg?
I'm trying to avoid the dreaded "Just use the worst case"...
Am I missing something?
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