For modular circuits, the selection of connectors plays a pivotal role, so when choosing connectors, what angles should we consider the connectors suitable for hardware use?

1. Pin, pitch

The number of pins and pin spacing are the basic basis for connector selection. The number of pins chosen for the connector depends on the number of signals that need to be connected. For some SMD connectors, such as SMD pin headers, the number of pins should not be too many. Because in the welding process of the placement machine, due to the high temperature, the plastic of the connector will be deformed by heat, and the middle part will bulge, resulting in virtual welding of the pins. In the early stage of development, our programmer used this kind of pin header and female header for inter-board connection. As a result, the pins of the prototype pin header were soldered in a large area. After changing to 2 pin headers with half the number of pins, there is no false soldering.

Nowadays, electronic equipment is developing towards miniaturization and precision, and the pin pitch of connectors has also changed from 2.54mm to 1.27mm to 0.5mm. The smaller the pin pitch, the higher the production process requirements. The pin spacing should be determined according to the company's production technology level. The blind pursuit of small spacing will cause difficulties in production and maintenance.

2. Electrical properties

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

3. Environmental performance

The environmental performance of the connector mainly includes: temperature resistance, humidity resistance, salt spray resistance, vibration, shock, etc. Choose according to the specific application environment. If the application environment is relatively humid, the requirements for the connector's moisture resistance and salt spray resistance are high, so as to prevent the metal contacts of the connector from being corroded. In the field of industrial control, the requirements for the anti-vibration and shock performance of the connector are high, so as to prevent the connector from falling off during the vibration process.

4. Mechanical properties

The mechanical properties of the connector include plugging force, mechanical foolproofness, etc. Mechanical foolproofing is very important for connectors. Once inserted backwards, it is likely to cause irreversible damage to the circuit!

The pull-out force is divided into insertion force and separation force. Relevant standards stipulate the maximum insertion force and the 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, the reliability of the contact will be reduced. However, for the connector that needs to be plugged and unplugged frequently, if the separation force is too large, it will increase the difficulty of pulling out and reduce the mechanical life.