[SI-LIST] Shape factors for sheet resistance based estimations
- From: "Jerry Martinson" <jmartinson@xxxxxxxxxxxxxxxxx>
- To: <si-list@xxxxxxxxxxxxx>
- Date: Mon, 28 Apr 2003 15:03:30 -0700
Hi,
I'd like to figure out the resistance between two points on a PCB. I've
used the sheet resistance "square" trick before for trivially simple
shapes but now I'm looking at a shape that I'm not really sure how to
turn into component squares. I know that the correct technique involves
drawing "curvilinear squares" or rectangles but this is an art that I've
never acquired a good feel for. I'm also not exactly sure how to
gracefully handle this when one of the points from which I want to
determine the resistance from is deep inside the shape.
I have a vague recollection (or fantasy?) from college days about "shape
factors" that might make this process easier. This is where there is a
chart of common shapes that correspond to a precomputed "shape factor",
S, that is equal to some fraction or multiple of a dimensionless
square. From this chart one can effectively synthesize the answer for a
complex shape using easy "cubist" art rather than the much more
difficult "groovy" art of curvilinear squares.
I was wondering if someone knew of references to:
1. A chart for 2d sheet resistance shape factors
2. More instruction on how to use the sheet resistance method (or
curvilinear square drawing/estimation) in general so I don't
accidentally use it incorrectly and so I could perhaps construct my own
library of pre-computed shapes if necessary
3. Whether this process is simple and accurate enough to be useful
4. Whether the exact same rules apply for the concept of "sheet
inductance"
Thanks,
Jerry
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