robertferanec , 02-12-2018, 07:29 PM
When they are building your PCB, they can use different materials. What they would like to probably know is, what is thickness of copper on your top and bottom layers.
Copper thickness is important especially in cases when your tracks will be carrying higher currents or if you need impedance controlled PCB.
If you are not sure, standard safe copper thickness is 1oz (or 35um). Very often you can use 1/2oz (18um) on signal layers.