Backed refined copper foil and copper-clad laminates not over 0.15 mm thick (excluding the backing) are classified under 741021. Once the laminate is further processed into a finished PCB with circuitry, it moves out of this heading entirely. The thickness of the copper layer, not the overall board thickness, governs classification here.

The 0.15 mm limit applies to the copper layer only, explicitly excluding any backing. A foil that is 0.10 mm thick bonded to a 0.5 mm paper backing still qualifies as foil under 7410 because the copper itself does not exceed the threshold.