Printed circuit boards (PCBs) are used to carry electronic components and provide circuits to connect the components. From a structural point of view, PCBs are divided into single-sided, double-sided and multi-layer boards.
Single-sided is the most basic PCB, where the parts are concentrated on one side and the wires are concentrated on the other side. Because the wires only appear on one side, we call this PCB a single-sided board. Because single-sided boards have many strict restrictions on designing circuits (because there is only one side, the wiring cannot cross and must go around a separate path), only early circuits use this type of board.
The wiring diagram of a single-sided board is mainly screen printing, that is, a resist is printed on the copper surface, and after etching, a mark is printed with a solder mask, and finally the part guide holes and shape are completed by punching. In addition, some products produced in small quantities and in large quantities use a photographic method that forms a pattern with a photosensitive resist.
Double-sided board is a printed circuit board with copper on both sides, including the top and bottom. Both sides can be wired and soldered, and there is an insulating layer in the middle. It is a commonly used printed circuit board. Both sides can be wired, which greatly reduces the difficulty of wiring, so it is widely used.
There are wiring on both sides of the double-sided board, but to use the wires on both sides, there must be a proper circuit connection between the two sides.
This “bridge” between circuits is called a guide hole. A guide hole is a small hole filled or coated with metal on the PCB board, which can be connected to the wires on both sides. Because the area of a double-sided board is twice that of a single-sided board, the double-sided board solves the difficulty of wiring interlacing in a single-sided board (it can be connected to the other side through the hole), and it is more suitable for more complex circuits than a single-sided board.
PCB multilayer board refers to a multi-layer circuit board used in electrical products. Multilayer boards use more wiring boards of single-sided or double-sided boards. A printed circuit board with one double-sided inner layer and two single-sided outer layers or two double-sided inner layers and two single-sided outer layers, alternating through a positioning system and insulating adhesive materials and interconnecting conductive patterns according to design requirements, becomes a four-layer or six-layer printed circuit board, also known as a multi-layer printed circuit board. Common multi-layer boards are generally 4-layer boards or 6-layer boards, and complex multi-layer boards can reach dozens of layers.
Features:
The biggest difference between PCB multi-layer boards and single-sided and double-sided boards is the addition of internal power layers (maintaining the internal power layer) and ground layers, and the power and ground network are mainly wired on the power layer. However, the wiring of multi-layer boards is mainly based on the top and bottom layers, supplemented by the middle wiring layer. Therefore, the design of multi-layer boards is basically the same as that of double-sided boards. The key lies in how to optimize the wiring of the internal power layer to make the wiring of the circuit board more reasonable and have better electromagnetic compatibility.
The difference between double-sided boards and multi-layer boards
In terms of process, the difference between double-sided boards and multi-layer boards is as follows:
1. The pressing materials of double-sided boards are only P sheets and Cu foils; the pressing materials of multi-layer boards include P sheets and two outermost Cu foils, as well as inner layers between P sheets.
2. The production of multi-layer boards includes the production of inner layers. The production of inner layers is roughly similar to that of outer layers.