The basic performance of connectors

The basic performance of connectors can be classified into three major categories: mechanical performance, electrical performance and environmental performance. Another important mechanical performance is the mechanical life of the connector. Mechanical life is actually a durability index. In the national standard GB5095, it is called mechanical operation. It is defined as one insertion and one extraction as a cycle, and the judgment basis is whether the connector can normally complete its connection function (such as contact resistance value) after the specified number of insertion and extraction cycles.

1. Mechanical performance: In terms of connection function, insertion and extraction force is an important mechanical performance. Insertion and extraction force are divided into insertion force and extraction force (extraction force is also called separation force), and the requirements for the two are different. In relevant standards, there are maximum insertion force and minimum separation force regulations. This indicates that from the perspective of use, the insertion force should be small (hence there are low insertion force LIF and zero insertion force ZIF structures), while if the separation force is too small, it will affect the reliability of contact. The insertion and extraction force and mechanical life of connectors are related to the structure of the contact (the size of the normal pressure), the quality of the coating on the contact surface (the sliding friction coefficient), and the dimensional accuracy of the contact arrangement (alignment).

2. Electrical performance: The main electrical performance of connectors includes contact resistance, insulation resistance and dielectric strength.
① Contact resistance: High-quality electrical connectors should have low and stable contact resistance. The contact resistance of connectors ranges from several milliohms to tens of milliohms.
② Insulation resistance: It is an indicator to measure the insulation performance between the contact pieces and between the contact pieces and the housing of the electrical connector, and its order of magnitude is from hundreds of megohms to thousands of megohms.
③ Dielectric strength or withstand voltage, dielectric breakdown voltage, is a characteristic that represents the ability of the connector's contact pieces or the contact pieces and the housing to withstand the rated test voltage.
④ Other electrical performance: Electromagnetic interference leakage attenuation is used to evaluate the electromagnetic interference shielding effect of the connector. Electromagnetic interference leakage attenuation is generally tested in the frequency range of 100 MHz to 10 GHz. For RF coaxial connectors, there are also electrical indicators such as characteristic impedance, insertion loss, reflection coefficient, and voltage standing wave ratio (VSWR). Due to the development of digital technology, in order to connect and transmit high-speed digital pulse signals, a new type of connector, high-speed signal connector, has emerged. Correspondingly, in terms of electrical performance, in addition to characteristic impedance, some new electrical indicators have also emerged, such as crosstalk, transmission delay, and skew.

3. Environmental performance: Common environmental performances include temperature resistance, humidity resistance, salt spray resistance, vibration resistance and shock resistance, etc.
① Temperature resistance: The maximum operating temperature of connectors is 200℃ (except for a few high-temperature special connectors), and the minimum temperature is -65℃. Due to the generation of heat at the contact point when the connector is working, causing temperature rise, it is generally believed that the operating temperature should be equal to the sum of the ambient temperature and the temperature rise at the contact point. In some specifications, the maximum allowable temperature rise of the connector under the rated operating current is clearly specified.
② Humidity resistance: The invasion of moisture will affect the insulation performance of the connector and rust the metal parts. The constant damp heat test conditions are a relative humidity of 90% to 95% (up to 98% according to product specifications), a temperature of +40 ± 20℃, and the test time is specified by the product, with a minimum of 96 hours. The alternating damp heat test is more severe.
③ Salt spray resistance: When connectors work in an environment containing moisture and salt, the metal structural parts and the surface treatment layer of the contact pieces may undergo electrochemical corrosion, affecting the physical and electrical performance of the connector. To evaluate the connector's ability to withstand this environment, a salt spray test is specified. It involves suspending the connector in a temperature-controlled test chamber and spraying a specified concentration of sodium chloride solution with compressed air to form a salt spray atmosphere. The exposure time is specified by the product, with a minimum of 48 hours. ④ Vibration and shock resistance Vibration and shock resistance are important performance characteristics of electrical connectors, especially in special application environments such as aviation and aerospace, railway and road transportation. They are important indicators for testing the mechanical structure's sturdiness and electrical contact reliability of electrical connectors. In relevant test methods, there are clear regulations. In shock tests, peak acceleration, duration, and shock pulse waveform should be specified, as well as the time of electrical continuity interruption.
⑤ Other environmental performance According to usage requirements, other environmental performance of electrical connectors also include sealing (air leakage, liquid pressure), liquid immersion (resistance to deterioration in specific liquids), low air pressure, etc.