We did a big JLC order and inclued a bunch of 6" square pieces of double-side gold-plated 1oz copper FR4, for dremeling prototypes.
I sheared off a strip and measured its resistance. The result corresponds to 0.7 oz copper. I've seen worse.
Maybe most of their boards start out 0.7 and get plated up some, when they plate the vias.
Copper *is* expensive lately.
John Larkin Highland Tech Glen Canyon Design Center Lunatic Fringe Electronics
The resistivity of the plated copper may not be what you expect for bulk copper, either due to impurities or internal stress. Have you checked the weight?
John
Electroless coatings are usually of higher bulk resistivity than electroplated, and electroplated also varies with how it's done.
If the copper and gold have higher bulk resistivity due to impurities, won't that translate into a thinner coating than actual if one computes assuming ideal purity?
Joe
I'd assume that the base copperclad is mechanically fabricated, not plated. The ENIG is plated, but that's microinches. Maybe the rolled foil has higher resistivity than virgin bulk copper, stress or something.
I don't have a good way to check the weight of the copper.
0.7 oz electrical equivalent isn't bad. Just good to know. We sometimes care about trace resistance.John Larkin Highland Tech Glen Canyon Design Center Lunatic Fringe Electronics
It is not impurities that raise the resistance, but structure of the metal. Electroplating grows crystals of metal and the current flows from crystal to crystal, following a longer path than it would take if the crystals were bashed together.
I've often wondered if a pulsed laser could be used to briefly melt a local spot of surface crystals into the liquid phase without heating a large enough volume to get the substrate too hot.
It's a rubber stamp ordered from Amazon.
John Larkin Highland Tech Glen Canyon Design Center Lunatic Fringe Electronics
Have something to add? Share your thoughts — no account required.
Ask the community — no account required