Metal Core PCB Circuit Board Production Thick Copper Printed Circuit Board Manufacturer ♦ What is Metal Core PCB ? A Metal Core PCB (MCPCB)—also called an IMS (Insulated Metal Substrate)—is a printed-circuit board whose base layer is a thick metal plate (almost always aluminum, sometimes copper or steel) instead of the traditional FR-4 fiberglass. A thin dielectric (5–150 µm) is bonded on top of the metal to isolate the copper circuit layer while still conducting heat