Electronic equipment must be in accordance with the circuit schematic diagram interconnection, in order to achieve the predetermined function, if the connection error will lead to the entire circuit board is invalid, so the choice of reliability, technology and economy with the best connection, is one of the important content of circuit board design. There are many ways to connect to the outside world. You should choose flexibly according to different characteristics. The following two methods are the most common.
The welding way
The advantages of this method are simple operation, low cost, high reliability, can avoid the fault caused by poor contact; Disadvantages are interchange, maintenance is not convenient. This method is generally applicable to parts with fewer external leads.
1. PCB wire welding
There is no need for any connector, as long as the external connection point on the circuit board and the components or other components outside the board are directly welded with wires.
Attention should be paid to the interconnection welding of circuit board:
(1) the welding pads of the welding wires shall be placed on the edge of the circuit board as far as possible and arranged in uniform size to facilitate welding and maintenance.
(2) in order to improve the mechanical strength of wire connection and avoid pulling the solder pad or printed wire out of the wire, drill a hole near the solder spot on the circuit board and let the wire pass through the through hole on the solder surface of the PCB and insert the solder pad hole into the component surface for welding.
(3) arrange or tie the wires neatly, and fix them with wire CARDS or other fasteners and plates to prevent the wires from breaking due to movement.
2. PCB line welding
The two circuit boards are connected by line, which is reliable and not prone to connection errors, and the relative position of the two circuit boards is not limited.
Direct welding between the PCB, this method is often used for the two PCB between the Angle of 90 degrees, connected to become a whole circuit board components.
Connector connection mode
In more complex instruments and equipment, plug – in connection is often used. This “building block” structure not only ensures the quality of mass production of products, reduces the cost of the system, and provides convenience for debugging and maintenance. When equipment fails, maintenance personnel do not have to check the component level (that is, check the cause of the failure, trace the root to the specific component. This work requires quite a lot of time), as long as the judgment is which board is abnormal can be immediately replaced, in the shortest time to eliminate the fault, shorten the downtime, improve the utilization of equipment. The replaced circuit board can be repaired in sufficient time and used as spare parts after repair.
1, printed board socket
This connection is often used in more complex instruments and equipment. This method is to make printed plug from the edge of the circuit board. The plug part is designed according to the size of the socket, the number of points, the distance between the contacts and the position of the positioning hole, so as to match the socket of the special circuit board.
When making the plate, the plug part needs to be gold-plated to improve wear resistance and reduce contact resistance. This method of assembly is simple, interchangeability, good maintenance performance, suitable for standardized mass production. The disadvantage is that the cost of PCB increases and the manufacturing precision and process requirements of PCB are higher. Reliability is a little poor, often because the plug part is poor contact oxidation. In order to improve the reliability of external connection, the same lead wire is often drawn out in parallel through the contacts on the same side or both sides of the circuit board.
2. Standard pin connection
This method can be used for external connection of printed board, especially in small instruments, pin connection is often used. Two printed boards are connected by a standard pin. The two printed boards are generally parallel or vertical, which is easy to realize mass production.