Mitsui Mining & Smelting holds about 98% of the market for ultra-thin copper foil, which is heading into a supply gap much like the ABF substrate squeeze. It is already running at extremely high utilization as 800G silicon-photonics and upcoming 1.6T optical modules shift to mSAP processes and memory substrates add bits and layers. Optical modules alone could reach 3% of global demand in 2026 and 7% in 2027, and the high-end tightness will spill into the mid-to-low end of copper foil. x.comÂ

