Method of manufacturing metal substrate

A method of manufacturing a metal substrate, comprising:

• providing a first single-sided substrate structure comprising a first insulating substrate and a first metal layer, wherein the first insulating substrate has a first surface and a second surface opposite to the first surface, and the second surface is between the first surface and the first metal layer;
• performing a first modification process on the first surface;
• providing a second single-sided substrate structure comprising a second insulating substrate and a second metal layer;
• and
• bonding the first single-sided substrate structure on the second single-sided substrate structure, wherein the second insulating substrate is between the first surface and the second metal layer,
• wherein each of the first insulating substrate and the second insulating substrate is made of a material selected from the group consisting of PI, PET, Teflon, LCP, PE, PP, PS, PVC, Nylon, acrylic resin, ABS, phenolic resin, epoxy resin, polyester, silicone, PU, PAI and a combination thereof, and the first surface has an original surface roughness, and the original surface roughness has a variation substantially less than 10% after the first surface is released from the second insulating substrate.