Track width 20A

[leonel]

Hi...
I want to build a pcb, but i have to have one track that has to support a corrent of 20A.
My doubt it's how much width has to be my track to support 20A ?
Regards

 

[Oznog]

It depends on the thickness of the copper.
Also is it an issue of the trace overheating, or the trace's resistance being too high? On overheating you need to consider the thinnest point- likely right at the component pad- as the limiting factor.

 

[stevez]

As a place to start, 12 (AWG) ga wire is often the choice to carry a 20 amp current. It has a cross sectional area of .00513 square inches or 3.31 square millimeters. It would seem that the thinnest cross section of a copper trace would have to be about this cross section or greater. I would think that voltage drop might also be a consideration.

 

[Oznog]

It would not necessarily need the cross section of a 12 ga wire. There are 3 factors here- the resistivity per unit length of the conductor, the thermal dissipation coefficient of the conductor (which is a factor of surface area and insulation thickness), and how hot the insulation can get before failing.

For a PCB trace, the dissipation of a wide trace can be large with relatively little copper, and it is not covered with a great deal of insulation.

Is this a 20 amp continuous load, or intermittent? What are you trying to do?

 

[bloki]

Here you have PCB Trace Calculator:

 

[Klaus]

Here you have PCB Trace Calculator:

I can't see a "calculate" button with this program. Anybody got it to work on a macintosh computer?
Klaus

 

[Russlk]

I found that if I click on the temperature after entering the current, the results show up. Just entering the current does nothing.

 

[leonel]

The current it's intermitent.
Sorry my ignorance, but what is a "12 (AWG) ga wire"? It's a pcb track with 12mm width?

Using the calculator it gives me on the internal result 29mm and in the external result 10mm of about 38.8mm of track lenght.

 

[Russlk]

AWG stands for "American Wire Guage". #12 is .0808 inches in diameter and is rated 14 amps for a 25 foot length. The fusing current (at which it melts) is 235 amps.

 

[bloody-orc]

when the track must carry large currents then a thick coat of tin is added to it. this makes the wire "fat" and therefore you dont need to have a inch wide track. it is made so in PC power suply's etc.