PCB, short for printed circuit board, is the supplier of electronic components and electronic interconnections. The key advantage of PCBs lies in its capability to greatly reduce the errors of routing and assembly and to increase the degree of automation and fabrication efficiency. Due to decades' development, PCBs have been constantly contributing to the improvement and progress of people's modern life.

PCBs can be classified into different categories according to different classification standards. Based on the number of layers, PCBs can be classified into single-layer PCBs (also called single-sided PCBs), double-layer PCBs (also called double-sided PCBs) and multi-layer PCBs. Based on the substrate material, PCBs can be classified into rigid PCBs, flexible PCBs and flex-rigid PCBs. Based on application fields, PCBs can be divided into low-frequency PCBs and high-frequency PCBs. With the development of technology and the advent of new substrate, some special types of PCBs come into being, such as metal core PCBs, SMT PCBs, high-Tg PCBs, carbon-film PCBs, etc. Each type of PCBs is applied in different fields owing to their advantages together with consideration of their disadvantages.