Why 1.5mm via only rated to 7.48 Amps

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Faringdon:
Hi,
The following via calculator...

https://circuitcalculator.com/wordpress/2006/03/12/pcb-via-calculator/

...shows a power dissipation of 30mW when carrying 12 Amps (for a via as follows..

drill = 1.5mm diam
Board thickness = 1.6mm
1 ounce copper

......so why does it calculate  that "Ampacity" is only 7.48 Amps?

***Also, i am certain that a   4 layer board with 1 ounce copper , does not have 1 ounce copper in the via side walls, unless they are plated up with an extra process, which is very expensive.....do you  concur?
A standard 1 ounce copper board, would only have half ounce copper in the via walls...(unless plated up with the extra expensive plating process)

thm_w:
Read his comment on that page, he explains why

--- Quote ---I added an estimate of the via’s ampacity based on the article in reference [2] above and IPC-2221 guidelines. It should be stressed that no detailed studied were done and this is only an estimate so please read all the following disclaimers. My approach is to assume that the via is equivalent to a trace of the same cross-sectional area, and then apply the ampacity guidelines of IPC-2221. In calculating the ampacity, I chose to use the equation for external traces and a conservative temperature rise allowance of 10 degree C. For these assumptions to hold, the board should have at least one full copper plane and the via should be connected to a trace or plane that can also handle the current. Also be aware that temperature rises stack up for all heat sources in close proximity. So, if you put a bunch a vias close together, each one may contribute a 10 degree C rise if running at the estimated ampacity.
--- End quote ---

free_electron:
use SaturnPCB toolkit . and those 2221 curves are total bunk based on a flawed military empiric test.

Faringdon:
Thanks, it would be great if there was software that could upload a gerber file and tell what the trace resistance was from A to B?

free_electron:

--- Quote from: Faringdon on June 16, 2022, 08:37:05 am ---Thanks, it would be great if there was software that could upload a gerber file and tell what the trace resistance was from A to B?

--- End quote ---
that exists. it is called a PDN analyser. CST makes that. you probably don't want to know what it costs though ...
ZofZ has an experimental free one