1. Structural Dimensions: The dimensions of the connector are crucial. Connections within a product are subject to space constraints, especially connectors on a single board, which cannot interfere with other components. Based on the available space and installation location, select the appropriate mounting method (front/rear mounting, screws, retaining rings, rivets, or quick-locking mechanism within the connector itself, etc.) and shape (straight, bent, T-type, round, square).
2. Matching Resistor: Some signals require impedance, especially radio frequency signals, which have stricter requirements for matching resistors. Impedance mismatch can cause signal reflection, thus affecting signal transmission. Generally, signal transmission does not have special requirements for connector impedance.
3. Shielding: With the development of communication products, electromagnetic compatibility is receiving increasing attention. When selecting connectors, a metal shell is required, and the cable needs a shielding layer to connect to the connector's metal shell, achieving a shielding effect. The cable shielding layer can also be made by wrapping the plug with copper foil.
4. Preventing Mis-Insertion: Preventing mis-insertion has two aspects: First, if the connector itself rotates 180 degrees, incorrect connection will occur, leading to signal connection errors. In this case, carefully select connectors to avoid incorrect insertion, or adjust the relative positions of the connectors for unique installation. Second, to reduce material usage, several signals may use the same connector, potentially resulting in a situation where connector A is plugged into connector B. It's important to note that if this situation leads to serious consequences (not just a simple alarm, but catastrophic), then connectors A and B must be plugged into different types of sockets.
5. Connector reliability: Connectors are used to connect signals, so the connection points must be reliable (e.g., surface contact is better than point contact, and pinhole is better than leaf spring, etc.).
6. Operating Environment: When the connector is used in outdoor, indoor, high temperature, high humidity, salt spray, mildew, or extremely cold environments, special requirements are placed on the connector.
7. Practicality: When selecting connectors, try to choose universal parts, especially within the same product series. Choosing practical connectors can reduce the variety of materials, increase quantity, lower costs, and reduce supply risks.
8. Locking function: To prevent the connector from falling off during the mating process and to ensure good contact, the connector needs to have a locking function.
9. Cost: Cost is also a key factor in the selection process. With increasingly fierce market competition, it is necessary to fully consider the correct selection of connectors, their own costs, and production costs.
10. Supply: The supply of connectors is affected by many factors. For example, the supply of general-purpose connectors is better than that of non-general-purpose connectors, and the supply of domestically produced connectors is better than that of foreign ones.
11. Rated Voltage. Rated voltage, also known as operating voltage, primarily depends on the insulation material used in the connector and the distance between the contact pairs. When the voltage is lower than its rated voltage, some components or devices may not function properly. The rated voltage of a connector should actually be understood as the manufacturer's recommended maximum operating voltage. Connectors can theoretically operate normally below their rated voltage. It is generally recommended to select the rated voltage reasonably based on the connector's withstand voltage (dielectric strength) rating, the operating environment, and safety requirements. That is, the same withstand voltage rating can be used with different maximum operating voltages depending on different operating environments and safety requirements. This approach is more in line with objective usage.
12. Rated Current. Rated current, also known as operating current, is generally used below the rated current, similar to rated voltage. During connector design, the rated current requirement is met through thermal design because the contacts heat up when current flows due to conductor and contact resistance. If this heat exceeds a certain limit, it can damage the connector's insulation, causing contact failure, softening the surface coating, and ultimately, failure. Therefore, limiting the rated current is essential; in fact, it's necessary to limit the internal temperature rise of the connector to within the designed value. A key consideration when selecting connectors is that the rated current must be dated for multi-core connectors. This is especially important in high-current applications. For example, a φ3.5 mm contact pair typically has a rated current of 50A, but for five cores, the derating must be 33%, meaning each core's rated current is only 38A. The more cores, the greater the derating.
