Suggestion: Just about every copper layer is assumed to contain the same finished copper excess weight Unless of course otherwise specified in your fabrication notes. A four-layer board with an outlined weight of 1oz, is assumed to possess a completed copper thickness of 1.37mils (or maybe more) on each individual https://six-layer-high-frequency73827.blogscribble.com/31287097/how-six-layer-long-and-short-gold-finger-pcb-circuit-board-can-save-you-time-stress-and-money