PCB substrate selection from the electrical performance, reliability, processing process requirements, economic indicators, etc. There are many substrates used for PCB, mainly including two categories: organic and inorganic. Organic substrates are made of reinforced materials such as glass fiber cloth impregnated with resin binder, then coated with Copper foil after drying, through high temperature and high pressure, which is also known as Copper Clad Laminations (CCL), inorganic substrates mainly ceramic and enamel coated steel substrates.
The printed circuit board is divided into rigid printed circuit board, flexible printed circuit board and rigid – flexible printed circuit board. Rigid printed circuit board refers to the printed circuit board which is made of copper foil layer pressed on the surface of the substrate which is not easy to bend. Flexible printed circuit board refers to the printed circuit board made of copper foil layer pressed on the surface of flexible substrate. It has good heat dissipation and is ultra-thin. It can not only bend, fold and wind, but also move and expand arbitrarily in 3d space.
Rigid printed circuit board and flexible printed circuit board are combined to form rigid-flexible printed circuit board, which is mainly used for the electrical connection of rigid printed circuit board and flexible printed circuit board.
PCB can be divided into single panel, double panel and multilayer board according to the number of layers of copper foil. Single panel refers to the surface of the insulation substrate only one side covered with conductive graphics printed circuit board. Double panel refers to the printed circuit board with conductive graphics covered on both sides of the insulation substrate, that is, the conductor on both sides of the circuit is connected through the welding pad and through the hole. Multilayer board refers to a layer of copper foil and a layer of insulation substrate alternately bonded printed circuit board. If there are four layers of copper foil, it is called four layers of plate, if there are six sides covered with copper foil, it is called six layers of plate, the electrical interconnect between the plate layer through the welding pad, through hole, blind hole and buried hole. Most of the motherboard is 4-8 layers structure, the current international highest level can achieve nearly 100 layers.