Basic Performance of Connectors

The basic performance of connectors is categorized into three main types: mechanical, electrical, and environmental properties. Another crucial mechanical property is the mechanical life of a connector. Mechanical life is essentially a durability metric, referred to as "mechanical operation" in the Chinese National Standard GB5095. It is measured in cycles, where one cycle consists of one insertion and one extraction. The evaluation criterion is whether the connector can still properly fulfill its connection function (e.g., maintaining the specified contact resistance) after a designated number of mating cycles.

1. Mechanical PerformanceIn terms of connection function, mating force is a critical mechanical property. Mating force is divided into insertion force and extraction force (also known as separation force), and the requirements for the two are different. Relevant standards specify the maximum insertion force and minimum separation force. This indicates that, from a user's perspective, the insertion force should be small (leading to the development of Low Insertion Force (LIF) and Zero Insertion Force (ZIF) structures). However, if the separation force is too small, it will compromise contact reliability. The mating force and mechanical life of a connector depend on the contact structure (magnitude of normal force), the plating quality of the contact area (coefficient of sliding friction), and the dimensional accuracy of the contact arrangement (alignment).

2. Electrical PerformanceThe primary electrical properties of connectors include contact resistance, insulation resistance, and dielectric withstanding voltage.

① Contact Resistance: High-quality electrical connectors should exhibit low and stable contact resistance. The contact resistance of connectors typically ranges from a few milliohms to several tens of milliohms.

② Insulation Resistance: This is an indicator measuring the insulation performance between contacts, as well as between contacts and the shell. Its magnitude generally ranges from several hundred megohms to several thousand megohms.

③ Dielectric Withstanding Voltage (also known as withstand voltage or medium withstand voltage): This characterizes the ability of the connector to withstand a rated test voltage between contacts, or between contacts and the shell.

④ Other Electrical Properties: EMI (Electromagnetic Interference) leakage attenuation evaluates the EMI shielding effectiveness of a connector, which is typically tested within a frequency range of 100MHz to 10GHz. For RF coaxial connectors, electrical parameters also include characteristic impedance, insertion loss, reflection coefficient, and Voltage Standing Wave Ratio (VSWR). With the development of digital technology, a new category of high-speed signal connectors has emerged to connect and transmit high-speed digital pulse signals. Correspondingly, in terms of electrical performance, besides characteristic impedance, new electrical metrics have been introduced, such as crosstalk, transmission delay, and skew.

3. Environmental PerformanceCommon environmental properties include temperature resistance, moisture resistance, salt spray resistance, vibration, and shock.

① Temperature Resistance: Currently, the maximum operating temperature for general connectors is 200°C (excluding a few special high-temperature connectors), and the minimum operating temperature is -65°C. Because current generates heat at the contact points during operation, causing a temperature rise, it is generally considered that the operating temperature equals the ambient temperature plus the contact temperature rise. Certain specifications explicitly define the maximum allowable temperature rise of a connector under its rated operating current.

② Moisture Resistance: The intrusion of moisture can affect the insulation performance of the connector and cause rusting of metal parts. The conditions for a steady-state damp heat test are a relative humidity of 90%~95% (up to 98% depending on product specifications) and a temperature of +40±2°C. The test duration is specified by the product, with a minimum of 96 hours. Cyclic damp heat tests are even more stringent.

③ Salt Spray Resistance: When operating in environments containing moisture and salt, the metal structural components and the surface treatment layers of the contacts may undergo electrochemical corrosion, affecting the physical and electrical performance of the connector. A salt spray test is specified to evaluate the connector's ability to withstand such environments. The connector is suspended in a temperature-controlled test chamber, and a specified concentration of sodium chloride solution is sprayed out using compressed air to create a salt spray atmosphere. The exposure time is stipulated by product specifications, lasting for at least 48 hours.

④ Vibration and Shock Resistance: Resistance to vibration and shock is a vital property for electrical connectors, especially in special application environments such as aerospace, as well as railway and highway transportation. It is a key indicator for verifying the robustness of the connector's mechanical structure and the reliability of its electrical contacts. Relevant testing methods have explicit provisions for this. In shock testing, the peak acceleration, duration, shock pulse waveform, and the permitted duration of electrical continuity interruption must be specified.

⑤ Other Environmental Properties: Depending on application requirements, other environmental properties of electrical connectors may include sealing performance (air leakage, liquid pressure), liquid immersion (resistance to degradation by specific fluids), and low air pressure.