EEVblog #732 – PCB Sheet Resistance

Fundamentals Friday
What is Sheet Resistance?
Did you know that the resistance of a square copper PCB trace is the same regardless of the size?
Dave explains the theory behind this rather counter-intuitive concept called Sheet Resistance, and demonstrates that it is in fact true.
What is the ohms per square of 1oz copper-clad PCB material and how can you use this concept to calculate the resistance of a PCB trace?
Thin Film Precision Resistor Network video HERE
Forum HERE

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    • Johm

      I still have some nuances:

      I suppose by saying square means the biggest square you can get? What about a copper sheet with an irrational ratio (i.e. DIN A4)? Or a circular sheet, there are infinite squares… Nice approach though, I missed FF.

    • hdavis

      Fundamental Fridays are my favorite. Also your 741st video is fast approaching. Do you have any special plans honoring the op amp we grew up with?

    • tlhIngan

      Another way to “think about it” is let’s say a square is simplified to a resistor with resistance R. Now you double each side, so now you have 4 squares of R – two in parallel, two in series. Analyze that as simple parallel/series resistors and you still have R.

      So if you have a 1×1 square of resistance R, a 2×2 or 3×3 or higher array of resistors also produces the same resistance, R.

      • Synthetase

        Exactly. I enjoyed Dave’s comment about squares in the thin film resistor video because it prompted me to pause the vid and think about it – and I came up with the same solution as you, in that I considered it from a series/parallel circuit point of view.

    • I agree with the previous poster, it’s really easy to comprehend if you just think of a square as being a fixed resistance and stack series “rows” in parallel ladders with each other.

    • Erick Moraes

      FF are my favorite segment, hands down.

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