Technet people,
I have an engineer who would like verification on his calculations to this question.
If any of you would have any knowledge of this, please post to the forum.
Thank you,
 Karl Bates
 [log in to unmask]

The issue I need resolved is the Sheet Resistivity Characteristic of 1 oz. copper.

I am astounded that none of the PC design manuals in our possesion has any numbers about this.

Let me describe a hypothetical problem.

Suppose I need a copper trace of exactly 0.1 ohms, plus or minus a reasonable percentage.  How would I do that?

It seems that there should be standard curves available giving resistance per unit length for various trace widths.  Mathematically, though, it can be expressed as

  R = Rs X (L/W)

where:

 - R is the  Resistance of the trace.
- Rs is the sheet resistance of the copper layer in ohms/square
- L is the trace length
- W is the trace width.

Rs is simply the Bulk resistivity of copper divided by the layer's thickness.

For 1 oz. copper, the published thickness is 0.035mm (ANSI/IPC-L-108B, REVB, Table 2), and the bulk resistivity is 1.724e-6 ohm*cm (ITT Reference Data for Radio Engineers, 1975, page 421, Table 12).

The ratio of these two numbers gives a sheet resistivity of .4926 ohms/square.  But as confident I am in my math, I would feel a lot better if someone else has published that result also.  Besides, there may be second order effects that I have not anticipated.

Do any of your contacts have an answer or a reference?


With best regards,


Michael A. Banak 

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