You may wonder why we create the outer layers using a copper foil, which is not the same as the final copper thickness. Due to the processes used, copper is plated on to the board. This means that, for example, the use of an 18μm copper foil results in 35μm nominal final copper thickness.
The final copper thickness is governed by the tables stated in IPC 2221A above. Please note that the actual thickness of your copper PCB may be thinner. In the PCB industry, we use the terminology, final copper thickness, however this is nominal and the actual result may turn out thinner. This is not the rule, but can occur in the standard process. If you need to define your PCB copper thickness, we encourage you to send us an enquiry to firstname.lastname@example.org. We will pass your request on to your local Würth CBT representative.