Prepeg is the abbreviation for Preimpregnated and means pre-impregnated. The term prepeg is used in printed circuit board technology for pre-impregnated intermediate layers of multilayerprinted circuit boards and HDI printed circuit boards.
Prepregs are flexible laminates consisting of resin and glass fiber. They are between 50 µm and 175 µm thick and act as a kind of adhesive between the solid core layers. After lamination, the adhesive cures.
Thicker prepregs have a higher type designation and provide greater stability in multilayer PCBs. The resin content of prepregs depends on the prepreg type and is between 75 % and approx. 50 %. To ensure that the characteristic HF properties of the printed circuit boards are not impaired, prepregs must have the same flame retardancy as the core boards.