static current on thin copper sheet. Votage drop is huge and converge not good

[dSilverEC]

Hi,
I am trying to implement static current, there are 2 issues now,

Version : Elmer 9.0

1. the converge is not good. so I have to relax to 1e-3.
2. The voltage drop is huge. the potential(violtage) drop to 0 in the middle of the power plane. so it is wrong, it cannot be such high drop.

Electric Conductivity is changed to 47e6 S/M^2 for PCB copper,
BC1 : Pad1 potential 5V
BC2 : Pad2 current density 7500 on 400 amp/mm^2

the mesh unv is created by SALOME-9.10.0. My guess is that prbably the unit in the mesh is wrong, from mm to m, so it has 1000 scale. I don't know hot to check the mesh unit. I attached the mesh, sif and results.

thank you if you can give me advise.

[dSilverEC]

I just did a simple experiment, it looks like the step file need to scale down to meter.
More checks are under process...

[Rich_B]

Hello,

To check the dimensions of the mesh, there are two simple methods. After running ElmerGrid to convert the mesh from unv format into Elmer mesh format, you could:

1. Open the mesh.nodes in a spreadsheet program and create charts such as x versus y coordinates, or x versus z coordinates.

2. Open the mesh files in ElmerGUI, and click on Model, Summary, and look for the bounding box dimensions.

Using the second method, here are the results:

BOUNDING BOX
X-coordinate: [ -0.0676753 , 0.0878975 ]
Y-coordinate: [ -0.0871058 , 0.0869226 ]
Z-coordinate: [ 0 , 5.4e-05 ]

Looks like the unv file was converted into meters. Note that the width to thickness ratio is 0.174 m / 5.4e-5 m = 3,222.

Rich.

[Rich_B]

Hello,

Attached is another sif file, this one uses the direct solver, umfpack.

Edit: updated the sif file, to more closely match the original case.sif file. Looks like the unv file was converted by ElmerGUI, which means that the default action will be '-autoclean'. The smaller pad is boundary number 26, and the larger pad is boundary number 25.

volume-current.png (57.52 KiB) Viewed 331 times

potential.png (44.16 KiB) Viewed 331 times

Rich.