IDC2D – A Bitmap Based 2d Copper Plane Current Density Simulation

History

- 9 May 2007 Initial release. Still at a beta stage – usable, but not thoroughly debugged or the results verified with measurements.

- 21 Oct 2007 – A new developer has added new features to the project: faster threaded calculations, and saving calculation results. As well, preliminary measurements in one case (on a section of a backplane) show close agreement with calculated values.

- 22 Nov 2007 – Many new features have been added such as the ability to zoom into the bitmap images and examine the current density and voltage of the associated pixels.

- 28 Jan 2008 – Version 0.3 introduced which rolls up contributions of all developers and updates the GUI. A color picker saves some time in defining colors and associated meanings. Added temperature input that applies to all materials.

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Wiki

Introduction

IDC2D is a entry level program to estimate the current density within the power plane of a PCB. Power distribution in a PCB circuit is often done through layers of copper embedded in the circuit board. Voids are created in this layer to allow for other signals and component leads to pass through the board. To ensure that enough copper remains to carry the required current, a 2d (2 dimensional) simulation can be run. Commercial products are available to do these calculations based on extracting the required information from the PCB design software. They often use a mesh representation to create a 2d or 3d model as an input to a finite element analysis program. While computationally more efficient than the approach taken here, the setup and learning curve for these products makes the effort too great for many smaller projects.

Features

• 24-bit bitmap input. Bitmaps can be created using ‘Paint’ or by doing a screen capture.
• Default current sources are defined by green pixels (R=0,G=255,B=0), drain is blue (R=0,G=0,B=255), and copper is red (R=255,G=0,B=0). NOTE: BMP transfer of images from computer to computer may use different color maps.
• Reports effective dc resistance between current source and sink.

• Reports peak current density.
• Multiple conductive materials can be simulated within a single image.
• Save computed bitmaps as well as exporting data for other mathematics packages.
• Zoom to view details in bitmaps.

Screenshots

Limitations

• Single ideal source and drain exaggerate current densities of the closest source and drain points.
• Thermal effects are not accounted for. All parts of the copper are at the same temperature – current density and board components can have some affect on local copper temperature.

Future Work

• Of course there are many possibilities, but adding too much effort will provide functions which overlap currently available software.
• Adding thermal effects. May also do time simulation to view speed at which heating and current redistribution occurs.
• Define current source as a surface contact rather than ideal voltage source within 2D plane.
• Additional user inputs: automatic placement of a source and drain (eg left edge, top edge, etc.).
• Multiple sources and drains each with a defined source impedance.
• A 2.5D or 3D version could be useful for electro-migration studies.