# Maximum Trace Current

Discussion in 'The Projects Forum' started by CurrentFlow, Apr 12, 2011.

1. ### CurrentFlow Thread Starter New Member

Apr 12, 2011
1
0
Hello all,

How would one measure the maximum allowed current through a PCB trace? So far I'm thinking about keeping the voltage constant while increasing the current limit... Also thinking about measuring temperature and other measurements. Any ideas on quantifying these?

Thanks.

2. ### retched AAC Fanatic!

Dec 5, 2009
5,201
313
I did a google for "max pcb trace current" and came up with this calculator as the first hit.

http://www.desmith.net/NMdS/Electronics/TraceWidth.html

The formula follows convention, but I have never used it.

It incorporates temperature in the formula, and there is a link on the same page to an article about temperature and trace-width.

There are also tables to be had from the same list of search results.

3. ### SgtWookie Expert

Jul 17, 2007
22,183
1,729
Roman Black's site is hosting PCBtemp, a freeware utility that used to be supported by UltraCad. Support has been discontinued, but it is still a very handy calculator.

4. ### THE_RB AAC Fanatic!

Feb 11, 2008
5,435
1,305
Yep I will second PCBtemp. It's a good little program.

Just be aware you need to know if your PCB is 1oz or 2oz copper (thickness of the copper layer itself) and be careful as many manufactured PCBs can skimp on the copper layer.

As a test you can run 1 amp (measured) through x inches of a PCB trace and measure the voltage drop over those inches. I have done this on occasion and compared with PCBtemp, and it's usually pretty close.

That's also a good test to see if your PCB maker skimped on your copper, they do that sometimes as the copper is a big \$\$ cost to them.