# Current capacity for PCB vias

1. ## thumb rule current through a pcb via

Hi, I'm wondering if anyone can share the experience/ rule of thumb of the current capacity for vias in PCB layouts. THanks

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2. ## Re: Current capacity for PCB vias

Hi,

Check this pdf for above subject,

Hope this helps you.

Regards

Ramesh

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3. ## Re: Current capacity for PCB vias

I was just looking up this topic the other day and found this website:

http://circuitcalculator.com/wordpre...ia-calculator/

You can calculate the resistance of the via which you can then apply to your own current usage and see what kind of loss and heat generation will occur.

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4. ## Current capacity for PCB vias

Thanks, Ramesh, but that paper doesn't give any rule of thumb to do it.

Hey, OradFarez, thanks for sharing the tools. Could you give me an idea what's criteria to choose the via size using that tool, i mean, what's maximum loss is allowed??

For myself, I just use the circumlength of the fininshed via as the trace width, then using this tool to check it:

h**P://circuitcalculator.com/wordpress/2006/01/31/pcb-trace-width-calculator/

Do you guys think it's correct??

5. ## Re: Current capacity for PCB vias

running2k

I suggest to you the reading of book "The Circuit Designer's Companion" by Tim Willians. In this book you can read "the characteristic impedance for a copper track over a ground plane on a double-side work out around 100-150 ohm for narrow tracks on 1.6 mm thickness, reducing to around 75-100 ohm on 0.7 mm". The book includes figures that show the theoretical resistance for various thickness of copper track per centimetre, etc.

Regards, svicent

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6. ## Current capacity for PCB vias

Rule of thumb:
A via of x diameter will carry the same current as a track on the same board of 3x width.

7. ## Re: Current capacity for PCB vias

Hi,

Btbass,could you please shed some light on the rule of thumb ur talking about,do appreciate if could upload the link for the same.

Regards

Ramesh

8. ## Current capacity for PCB vias

The Circumference of a circle is Pi x Dia.
If you could straighten out your via, you would have a track through the board of Pi x Dia width.

Simplified? yes, but it is a rule of thumb.

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