Single sided pcb: that is, only one side of the PCB board has lines (may have holes or no holes), and the other side is covered with substrate or direct insulating ink, without any lines and under strong light, the whole board is light-transmitting (except for individual sided pcb). Special requirements for plates and processes). Only the side with the lines on the cross section contains copper foil.

Double sided pcb: It is a common circuit with two sides, relying on copper holes as a "bridge" on both sides of the link board, and placing the entire PCB board under strong light to transmit light (except for individual boards and special process requirements). The cross-section only contains copper foil on the outermost two sides of the PCB.

Multilayer PCB: On the basis of the double-sided board, it is like a "sandwich" and there is a sandwich PCB in the middle (generally, the number of layers of mobile phones, computers, home appliances, and automotive pcb is 4 to 12 layers. For military or aviation, the number of layers of positioning equipment pcb is 8 to 20 layers. The number of layers of PCBs such as satellites, navigation, rockets, etc. can reach more than 60 layers, and its precision can be imagined. In fact, CPU can also be understood as an ultra-precise "PCB" in microelectronics.) In the middle The interlayer is generally referred to as the "inner layer". Multilayer PCB is opaque to the whole board or partially transparent and inconspicuous under strong light. The outermost ends and the middle position of the cross section contain copper foil.

In the case of single sided, double sided and multilayer PCB using the same board and the same volume, the weight of multilayer PCB is greater than that of double sided pcb, and the weight of double sided pcb is greater than that of single sided pcb.