What Is PCB Core?
- The Core of a PCB is rigid or flexible base material laminated with copper on one or two sides. A CORE is used for manufacturing single- and double- sided printed circuit boards (PCBs) but is also used to multilayer PCB production. Core also refers to CCL, FCCL or laminate.
- In HDI PCB stack-up with i+N+i structure, the “N” can also be treated as a HDI core with through-hole PCB structure. The buried vias are drilled through the “Core”.
PCB Core vs. Prepreg
The laminate of the PCB is what holds the layers together. Traditionally, there are four layers that make up the board: Core, Copper foil, PP, Solder mask, and Silkscreen (from bottom to top). The laminates are developed by curing under pressure and temperatures of cloth using thermoset resin to create the final piece of uniform thickness.
PCB cores and laminates are similar and, in some ways, quite different. Your core is effectively one or more prepreg (PP) laminates that are pressed, hardened, and cured with heat, and the core is plated with copper foil on each side. The prepreg material is impregnated with a resin, where the resin is hardened but left uncured. Most manufacturers describe the prepreg as the glue that holds core materials together; when two cores are stacked on each side of a prepreg laminate, exposing the stack to heat causes the resin to begin bonding to the adjacent layers. The hardened resin slowly cures through crosslinking, and its resulting material properties start to approach those of the core layers.