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One of the boards I have has these surface traces that run a lot of current through. I believe they are called power planes. Does anyone know a typical copper thickness (35 um?) ? Also, what is the type of lamination on the top (lighter green color) and what's could be the thickness?

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A typical PWB copper thickness is "1 ounce". This is how much one square foot of plating weighs. 1 oz = 35 micro-meters. https://pcbprime.com/pcb-tips/copper/

A power supply board might use 2 or 3 oz copper, but I don't think that this board does.

The green layer is the "solder mask". It keeps the molten solder from straying beyond the pads. It also provides some protection to the traces. If there is a standard thickness I don't know it.

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There is a wide variation in designs.

35 um is std 1oz copper lam.(ination) Then 0.5, 0.25, 2,3,4... oz

Outer layer is typ 0.5 oz.(18 um) then 0.5 oz plating added, but can be any sub-multiple or bare with organic coating.

The clear tint is a polymer called "soldermask" that protects the traces also has a wide variance from dry to wet film might typically be 20 to 25 um which is your choice.

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The copper can have various thicknesses; 1 oz. copper (short for one ounce per square foot) is 35 μm thick, but 2 oz. is also common for boards that handle higher power.¹ Some boards have 0.5 oz. copper, too. Inner layers are usually thinner than outer layers in a multi-layered board.

Note that all copper in a given layer will have the same thickness; there's no practical method to make a power plane thicker than other traces on the same layer. You would just make the whole layer thicker.

The soldermask (the green stuff) doesn't usually have a defined thickness; its purpose is to simply act as a physical barrier between the metal traces and the environment, to prevent solder from sticking where you don't want it to and to prevent oxidation of the copper. This function doesn't strongly depend on thickness, and it's not expensive to procure or to deposit (unlike the metal layers) so its thickness will vary between fabs that use different equipment and different soldermask materials.

The parts of the copper traces that are not covered by soldermask are typically coated in something as well. For the cheapest boards, this is just a quick dunk in molten solder followed by a blast of hot air to get off all but a little bit of it (referred to as a HASL finish, "hot air solder levelling"). HASL finishes are not typically of a controlled thickness, and I couldn't tell you what a typical thickness is. Slightly more expensive boards, or ones where flatness is a big concern (HASL can be fairly bumpy, relative to what's needed to reliably attach certain surface-mount parts), will use ENIG (for "Electroless Nickel/Immersion Gold"), where a thin plating of nickel is applied, followed by an even thinner layer of gold. Typical thicknesses for ENIG are around 200 μ" (yes, that's microinches. That's about 5 μm.) of nickel, followed by 1-3 μ" (25 to 75 nm) of gold. There are other finishes, but those are by far the most common.


¹The PCB fab that I use for prototype runs actually offers as thick as 13-ounce copper for outer layers, if you're okay with paying hundreds of dollars more and waiting the better part of a month for your boards to ship. I have no idea what you would use such a board for. That's nearly half a millimeter of copper!

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