Electronic components and electromechanical components have electrical contacts. The electrical connection between two discrete contacts is called interconnection. The electronic equipment must be interconnected according to the circuit schematic diagram to realize the predetermined function.
Interconnection mode of circuit board 1. Welding mode a printed board, as an integral part of the whole machine, generally cannot constitute an electronic product, and there must be external connection problems. For example, electrical connections are required between printed boards, between printed boards and components outside the board, and between printed boards and equipment panels. It is one of the important contents of PCB design to select the connection with the best combination of reliability, manufacturability and economy. There can be many ways of external connection, which should be flexibly selected according to different characteristics.

The connection mode has the advantages of simplicity, low cost, high reliability, and can avoid the failure caused by poor contact; The disadvantage is that the exchange and maintenance are not convenient enough. This method is generally applicable to the case where there are few external leads of components.
1. PCB wire welding
This method does not require any connectors, as long as the external connection points on the PCB are directly welded with the components or other components outside the board with wires. For example, the horn and battery box in the radio.
During interconnection and welding of circuit board, attention shall be paid to:
(1) The bonding pad of the welding wire shall be at the edge of the PCB printed board as far as possible, and shall be arranged according to the unified size to facilitate welding and maintenance.
(2) In order to improve the mechanical strength of wire connection and avoid pulling off the solder pad or printed wire due to wire pulling, drill holes near the solder joint on the PCB to let the wire pass through the through hole from the welding surface of the PCB, and then insert the solder pad hole from the component surface for welding.
(3) Arrange or bundle the conductors neatly, and fix them with the board through wire clips or other fasteners to avoid the breakage of the conductors due to movement.
2. PCB layout welding
The two PCB printed boards are connected by flat wires, which is both reliable and not prone to connection errors, and the relative position of the two PCB printed boards is not limited.
Printed boards are directly welded. This method is usually used for the connection between two printed boards with an included angle of 90 °. After connection, it becomes an integral PCB component.

Interconnection mode 2 of circuit board: connector connection mode
Connector connection is often used in complex instruments and equipment. This “building block” structure not only ensures the quality of mass production, reduces the cost of the system, but also provides convenience for debugging and maintenance. In case of equipment failure, the maintenance personnel do not need to check the component level (that is, check the cause of the failure and trace it to the specific components. This work takes a lot of time). As long as they judge which board is abnormal, they can immediately replace it, eliminate the failure in the shortest time, shorten the downtime and improve the utilization of the equipment. The replaced circuit board can be repaired in sufficient time and used as a spare part after repair.
1. Printed board socket
This connection is often used in complex instruments and equipment. This method is to make a printed plug from the edge of the PCB printed board. The plug part is designed according to the size of the socket, the number of connections, the contact distance, the position of the positioning hole, etc., so that it matches the special PCB printed board socket.
During plate making, the plug part needs gold plating to improve wear resistance and reduce contact resistance. This method has the advantages of simple assembly, good interchangeability and maintenance performance, and is suitable for standardized mass production. Its disadvantage is that the cost of printed board is increased, and the manufacturing precision and process requirements of printed board are high; The reliability is slightly poor, and poor contact is often caused by oxidation of the plug or aging of the socket * *. In order to improve the reliability of external connection, the same outgoing line is often led out in parallel through the contacts on the same side or both sides of the circuit board.
PCB socket connection mode is commonly used for products with multi board structure. There are two types of socket and PCB or backplane: * * type and pin type.
2. Standard pin connection
This method can be used for external connection of printed boards, especially for pin connection in small instruments. The two printed boards are connected by standard pins. Generally, the two printed boards are parallel or vertical, which is easy to realize mass production.