The design of electronic products tends to be more and more modular. The combination of different functional modules can quickly create high-quality products with different performances. The connection of the modules is particularly important. The following are some shared by a senior hardware engineer. Experience about connector selection.

The connector is like a functional interface of the program. The design is reasonable. In the future, product maintenance, upgrades, and transplants will do more with less, so that the product maintains a lasting vitality. The unreasonable design causes difficulties in future maintenance and upgrades. Eventually, the product loses its competitiveness, and the importance of the connector is self-evident.

1. Pins and spacing

The number of pins and the pitch of pins are the basic basis for selecting a connector. The number of pins selected depends on the number of signals to be connected. For some SMD connectors, as shown in the figure below, the number of pins should not be excessive. Because during the soldering process of the placement machine, due to the effect of high temperature, the connector plastic will be deformed by heat and expand in the middle, resulting in the virtual soldering of the pins.

2. Electrical performance

The electrical properties of the connector mainly include: limit current, contact resistance, insulation resistance and electrical strength. When connecting a high-power power supply, please pay attention to the limit current of the connector. When transmitting high-frequency signals such as LVDS and PCIe, please pay attention to the contact resistance. The connector should have a low and constant contact resistance, usually tens to hundreds of mΩ.

 3. Environmental performance

The environmental performance of the connector mainly includes: temperature resistance, humidity resistance, salt spray resistance, vibration, impact and so on. Choose according to the specific application environment. If the application environment is relatively humid, the moisture resistance and salt fog resistance of the connector are very high, so as not to corrode the metal contacts of the connector. In the field of industrial control, the connector has high resistance to vibration and shock to prevent the connector from falling during vibration.

4. Mechanical properties

The mechanical properties of the connector include tension, mechanical foolproof, etc. Mechanical foolproofing is very important to the connector. After reverse insertion, it may cause irreversible damage to the circuit!

The insertion force is divided into insertion force and separation force. The relevant standard specifies the maximum insertion force and minimum separation force. From the perspective of use, the insertion force should be small and the separation force should be large. If the separation force is too small, it will reduce the reliability of the contact. However, for connectors that often need to be inserted and removed, excessive separation force increases the difficulty of extraction and shortens the mechanical life.