PCB, that is, printed circuit board, can be divided into single-sided PCB, double-sided PCB, and multi-layer PCB according to the number of layers; according to hardness, it can be divided into rigid PCB, flexible PCB, and rigid-flex PCB; according to the conductivity of holes, it can be divided into Through-hole PCB, blind-hole PCB, buried-hole PCB, plated-through-hole PCB, and non-plated-through-hole PCB.