PCB Technical - The interconnection between PCB printed circuit boards

PCB components and electromechanical components have electrical contacts, and the electrical connection between two discrete contacts is called interconnection. The electronic devices must be interconnected in accordance with the PCB circuit schematic diagram to achieve the predetermined function.

As an integral part of the whole machine, a printed circuit board generally cannot constitute a PCB product, and there is bound to be an external connection problem. For example, electrical connections are required between printed boards, printed boards and external components, printed boards and equipment panels. It is one of the important contents of the printed board design to select the connection with the best coordination of reliability, manufacturability and economy. There are many ways of external connection, which should be selected flexibly according to different characteristics.

The interconnection method of the circuit board

The advantages of this connection method are simplicity, low cost, high reliability, and can avoid failures caused by poor contact; the disadvantage is that interchange and maintenance are not convenient enough. This method is generally suitable for components with fewer external leads.

1. PCB wire welding

This method does not require any connectors, as long as the external connection points on the PCB printed board are directly welded to the components or other parts outside the board with wires. For example, the horn and battery box in the radio.

Pay attention to the interconnection welding of the circuit board:

(1) The soldering wire pads should be as close as possible to the edge of the PCB printed board and arranged in a uniform size to facilitate soldering and maintenance.

(2) In order to improve the mechanical strength of the wire connection and avoid pulling off the pad or printed wire due to the wire being pulled, drill holes should be drilled near the solder joints on the PCB printed board to allow the wires to pass through the soldering surface of the printed board. Go through the through hole, and then insert the pad hole from the component surface for soldering.

(3) Arrange or bundle the wires neatly, and fix them to the board with wire clips or other fasteners to prevent the wires from breaking due to movement.

2. PCB cable welding

The two PCB printed boards are connected by a flat cable, which is reliable and not prone to connection errors, and the relative position of the two PCB printed boards is not restricted.

The printed boards are directly welded. This method is often used for connecting two printed boards at a 90-degree angle. After connection, it becomes a whole PCB printed board part.

Circuit board interconnection mode two: connector connection mode

In more complicated instruments and equipment, connector connections are often used. This "building block" structure not only guarantees the quality of mass production of products, reduces the cost of the system, and provides convenience for debugging and maintenance. When the equipment fails, the maintenance personnel do not have to check the component level (that is, check the cause of the failure and trace the source to the specific component. This work takes a lot of time), as long as it is judged which board is abnormal. It can be replaced immediately, troubleshooting in the shortest time, shortening downtime, and improving equipment utilization. The replaced circuit board can be repaired within ample time and used as a spare part after repair.

1. Printed board socket

In more complex instruments and equipment, this type of connection is often used. This method is to make a printed plug from the edge of the PCB printed board, and the plug part is designed according to the size of the socket, the number of contacts, the distance of the contacts, the location of the positioning hole, etc., to match the special PCB printed board socket.

When making the board, the plug part needs to be gold-plated to improve the wear resistance and reduce the contact resistance. This method is simple to assemble, has good interchangeability and maintenance performance, and is suitable for standardized mass production. The disadvantage is that the cost of the printed board is increased, and the manufacturing precision and process requirements of the printed board are higher; the reliability is slightly worse, and the contact is often poor due to the oxidation of the plug part or the aging of the socket reed. In order to improve the reliability of external connections, the same lead wire is often led out in parallel through the contacts on the same side or on both sides of the circuit board.

PCB socket connection method is often used in products with multi-board structure. There are two types of reed type and pin type for socket and printed board or bottom plate.

2. Standard pin connection

This method can be used for external connection of printed boards, especially pin connections are often used in small instruments. The two printed boards are connected through standard pins. The two printed boards are generally parallel or perpendicular, which is easy to achieve mass production.