Idea: Every single copper layer is assumed to have the exact same concluded copper bodyweight Except otherwise specified in your fabrication notes. A four-layer board with a defined body weight of 1oz, is assumed to have a concluded copper thickness of 1.37mils (or more) on just about every copper layer. https://landentvwyx.csublogs.com/37999130/indicators-on-arduino-uno-medical-pcb-you-should-know