Mitsui Kinzoku Company, Limited (President: Takeshi Nou; “Mitsui Kinzoku”) announces that the technological development of MicroThin™, which had been previously announced in the “Mitsui Kinzoku Rolls Out MicroThin™ for Use as Flexible PCBs” news release dated November 11,2025, has been completed. MicroThin™ is the thinnest copper foil with a carrier that permits peeling even in high-temperature processes.
MicroThin™, an extremely thin electrodeposited copper foil with a carrier, is a product of Mitsui Kinzoku combining a copper foil thickness ranging from 1.5 μm to 5 μm suitable for forming fine circuits with multiple types of fine-roughening treatment. It has been traditionally mainly used for semiconductor package substrates and motherboards for smartphones (HDI printed circuit boards). Recently, there has been a new application for MicroThin™: flexible PCBs.
Newly developed as the thinnest copper foil with a carrier for high-temperature applications, MicroThin™ can be applied even to PCBs with excellent dielectric characteristics, such as MPI, LCP, and PTFE PCBs that require high-temperature processes, having a high-temperature-resistant peeling layer that can be stably peeled even at 350 °C or more. MicroThin™ is expected to be introduced as a material that realizes fine circuit formation, thinning, and increased reliability even for PCBs that require high-level electrical characteristics, such as those used in next-generation mobile devices.
Mitsui Kinzoku will contribute to the realization of a sustainable society by implementing its vision for 2030, “Building new businesses －and the future－ with our material intelligence,” based on its purpose, “We promote the well-being of the world through a spirit of exploration and diverse technologies.”
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Mitsui Kinzoku Completes Technological Development of MicroThin™ for High-temperature Applications