value and unit of static current conduction

[wisnu24]

I try to implement a static current conduction analysis on PCB. I already got the result of it and saw the weird value on the volume current and joule heating. I attached the pictures and sif of my simulation. from the legend of both volume current Magnitude and joule heating, I get a very very big number. what is the unit of them, is that Ampere and Joule respectively? if yes that doesn't make sense and that will burn the PCB down. Did I put the number of current density incorrectly? I thought that how to get the number is current / area of the sink, the area of the sink is 0.09 mm^2 x 8 boundaries = 0.72 mm^2. So if I wanna sink 1.5 Amps, I got around 2083333. and put the negative on that since the current goes from the sink to the source. Can someone help with a better explanation on my understanding, please?

I also put all the project in my drive feel free to see that https://drive.google.com/file/d/14ZKvtr ... sp=sharing

regards,
Wisnu

[raback]

Hi

The SI units would be A/m^2 and J/m^3.

If you work with CAD geometries are off by 1000^n then the plausible explanation is that you created your case in mm's but ElmerSolver assumes the unit to be in metres (or does not expect but then you should take care of the units youself, i.e. current density becomes A/(mm)^2 etc. The solution for this is to scale the mesh with factor 1.0e-3.

-Peter

[wisnu24]

Hi peter! thank you for your answer, I thought that I already set everything up to a meter. I convert it by myself like 0.072 mm^2 to 0.072 e^-6 m^2. even with the A/m^2 it kind of turns my PCB into ashes.

[wisnu24]

Hi

The SI units would be A/m^2 and J/m^3.

so from JH.png at small area that has a white color, it can be said that area has 10000000 J/m^3 or 5200 deg Celsius???

[kevinarden]

You are calculating the joule heating but not the temperature. Your system has no heat loss anywhere. You can add the heat equation calculate temperature and account for heat loss.
Kelvin

temperature.png

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mcase.sif

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[wisnu24]

thankyou kelvin that's help a lot