Who makes copper foil for AI data centers

Copper foil is the conductor inside a printed circuit board. It arrives as a very thin sheet, bonded to the resin-and-glass core to make copper-clad laminate, and the etching process removes everything that is not a trace. Foil comes in rolled and electrodeposited grades with different grain structures and surface treatments, and at high frequency the surface treatment matters as much as the copper itself. That is the part worth understanding. Signals at high speed travel near the surface of the conductor, so a rough foil surface — which is what makes foil bond well to resin — costs signal loss. The industry's answer has been successive generations of low-profile foil that keep adhesion while flattening the surface, and those grades are a much narrower supply base than copper foil in general. AI hardware pushes on this from two directions at once: accelerator boards and high-radix switch boards run more layers at higher per-lane rates, and both need the low-loss grades. The same foil supply also feeds battery makers, which is a genuinely competing demand on the same production assets. What to look for is grade rather than tonnage — commodity foil availability says little about the availability of the low-profile grades a high-speed board needs — and where the treatment step happens, since that is where much of the value sits.