In the layer structure of a PCB board, there are several important concepts.
PP (Prepreg): Prepreg is a semi-cured sheet, also known as prepreg material, a thin sheet material that impregnated with resin and cured to an intermediate degree. It is mainly used as the bonding material and insulation material for inner conductive patterns of multilayer printed circuit boards. After being laminated with Prepreg, the semi-cured epoxy resin is squeezed out, begins to flow, and solidifies, bonding the multilayer circuit boards together and forming a reliable insulating layer. In the PCB industry, Prepreg can be likened to glue, used to bond several cores together using the lamination method to create multilayer boards.
PP Type:1080(3.1mil), 3313(4.2mil), 2116(5.4mil), 7628(7.7mil).

Core: Core is a rigid material with specific thickness and copper on both sides.
The pressing materials for multilayer boards mainly consist of Prepreg and Core.

The differences between the two are:
- Prepreg is a material used in PCBs, with a semi-solid texture similar to cardboard, while core is a rigid material similar to copper.
- Prepreg functions as both an adhesive and insulator, whereas core serves as the foundational material for PCBs, with entirely different functional roles.
- Prepreg can be flexible, while core cannot be bent.
- Prepreg is non-conductive, whereas core has copper layers on both sides, serving as the conductive medium for the printed circuit board.

In other special cases or Advanced PCBs (you need to choose "Customized Services and Advanced Options" and Custom stackup or Impedance control):
1. If you need custom stackup or control impedance, we will manufacture according to your requirement.
2. After place order,we will calculate whether it meets the requirements based on the stackup , material and impedance information.Also we will confirm with you.

For flexible PCB stackup, please check "Stack-up for FPC".

For rigid PCB, in response to customer demand, PCBWay has added a variety of laminate structures to our products (currently, we have added 298 and will continue to update them), which can greatly satisfy product structural design and impedance requirements.