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Do tinned tracks interfere with RF signals?

A comment in another thread made me wonder: when people design RF circuits (not my own area), do they take care to avoid tinning tracks on PCB's, so the impedance of the tracks is not affected by the solder's skin effect?

This is more a theoretical question as it's rare to see tinned tracks these days. But the question intrigued me and I don't have a "feel" for whether this would be a significant problem in RF work. And it's going to vary with type of solder, amount of tinning, frequencies employed etc so there cannot be a definitive answer, just a qualitative debate.

A related question - at what frequency would you advise switching away from tinned wires to carry signals?

Interested to hear folks' views on this 8)

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Nemo
Reply to
Nemo
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My norm is solder mask over bare copper.

Bob

Reply to
<castlebravo242

If you have stopped thinking of it as a "signal line" and started thinking of it as a "stripline" or "microstrip". OTOH at those frequencies tinning will be among the least of your potential loss sources.

Mark L. Fergerson

Reply to
alien8er

At really high frequencies, GHz, skin effect becomes a major loss factor. But most of the current in a microstrip is on the bottom of the trace, which typically has a "black oxide" treatment to enhance adhesion, and is horrible for skin losses.

Stripline is of course not solder coated.

Below a GHz or so, solder coating the top side probably won't make a measurable difference.

But as noted, most boards are SMOBC these days anyhow.

John

Reply to
John Larkin

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