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Saturn PCB Calculator how good is it?

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Anonymous_Ricky

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Hi All,

I have just gone through Saturn PCB Calculator for calculating current carrying capacity of traces.
But I doubt how accurate is it, as it gives almost same result for Internal and External Layer traces. I underastand that no calculator can give exact results but from my previous experiences I think there has to be some differences in current carrying capacities of internal and external traces.
Please correct me if I am wrong.

Regards,
Ricky
 

irish634

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The reason you are getting the same results is because he uses the "Internal and External" charts. These charts are actually the charts for the 3 oz copper weight, external conductors.

Quoting the standard:
"Internal and external conductors operate very close to the same temperature rise for the same applied current and cross sectional area. Conductors in a vacuum environment operate at higher temperatures than in air for the same size conductor and applied current." (Section A.2 pg 18)
Charts listed in 5.1 and 5.2 of the IPC-2152 are the 3 oz. external charts. External and internal conductors experience approximately the same temperature rise when current is applied to them. This is true in both still-air and vacuum environments. The 3 oz. charts show the least current carrying capacity when compared to the 1⁄2 oz., 1 oz., and 2 oz. charts; therefore they were selected as the single chart to be included in the main document.
The spreadsheet in the link was created by Jack Olson. He was on the committee for the standard and is extremely knowledgeable on the subject. He told me that the way the Saturn calculator is programmed, there really is no way to do it accurately. I actually refer to Jack's spreadsheet calculator while I am creating my own. Keep in mind that most calculators will "get you in the ball park." Some of the results (current, impedance, etc) in the Saturn calculator are a bit suspect to me. But it'll get you in the ball park.

To answer your question, yes there are differences between internal and external, still air and vacuum, that's why there are 60+ charts in the IPC-2152. The calculator is in effect, giving you conservative numbers.

Craig
 
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