# Cap2D

## 2D PCB layer capacitance calculation

Resist2D page

I am starting a new topic, targeting high frequency PCB design. The Gerber Viewer will be a base for it. But for now, my targets are more abstract and more related to general electrotechnic or electromagnetism. I have already realized that the equation system solving is going to be the main difficulty, due to the size of the unknown variable set. So I am learning.

My latest milestone, I am happy to share, is a 2D capacitance solver, which could be used to calculate the capacitance between two layers of metal traces or planes.

This simple program reads a bitmap (e.g. png) representing the shape of the capacitor plates. Red and green color channels are used to represent the top and bottom plates, respectively. Overlapped areas are visible as yellow, due to the additive mix of the red and green channels.

Additional information, that is bitmap-pixel-scale and distance between plates, can be set in the "Params" dialog.

The program solves capacitance of defined 2.5D structure.

On the left window/picture there is a charge density map, also numerically readable by the mouse pointer. There are 3 charge density map views: both plates (R-Y-G colors), top and bottom. In particular, there is a cross-section selection line, controlling the cross-section view.

The cross-section view on the right window/picture: Thin red (top) and green (bottom) lines represent the capacitor plates. All over around, the window shows the electric-potential color-map. At the mouse pointer, there is the Electric field vector displayed. Corresponding electric-potential value and the electric-field absolute value are displated numerically, below. Assuming the voltage on the top and bottom plates to be +1 and -1 Volt. Color mappings can be changed, using the right mouse click or in the "View" menu.

At the moment there is no calculation for a dielectric influence!
However, it is still possible use the program to solve the real-life PCB capacitances, multiplying the capacitance value by relative permittivity (Εr):

• for internal PCB layers - more exact
• for top/bottom PCB layers - as estimation only - up to 50%error

The software is to be download in two versions. 32-bit and 64-bit. The reason for this is that the equation solving part, for now, is a straightforward Gaussian elimination, suitable only for relative small amount of variables, limited by n² storage requirement. To make it a bit better, 64-bit version can access much bigger memory, available now on the standard PC.
The program starts with preloaded demo.

### »» Cap2D_32.exe 32 bit Windows ««

For a secure download, the exe files are signed using my certificate (Rafal Powierski).