The basic performance of electrical wire connectors can be divided into three categories: mechanical performance, electrical performance and environmental performance. Another important mechanical property is the mechanical life of the connector. Mechanical life is actually a durability index. It is based on a single engagement and separation as a cycle, and judges whether the connector can normally complete its connection function (such as contact resistance value) after the specified engagement and separation cycle.
1. As far as the connection function is concerned, the pull-out force is an important mechanical performance. Plugging force is divided into insertion force and pull-out force (pull-out force is also called separation force), the requirements of the two are different. The maximum insertion force and minimum separation force are stipulated in the relevant standards, which indicates that the insertion force is smaller from the point of view of use (hence the structure of LIF with low insertion force and ZIF without insertion force), and if the separation force is too small, the reliability of contact will be affected. The insertion force and mechanical life of the connector are related to the contact structure (positive pressure), the coating quality (sliding friction coefficient) at the contact area and the dimensional accuracy (alignment) of the contact arrangement.
2. The main electrical properties of electrical wire connectors include contact resistance, insulation resistance and electrical strength.
(1)High quality electrical wire connectors should have low and stable contact resistance. The contact resistance of the connector varies from several milliohms to tens of milliohms.
(2) Insulation resistance is an index to measure the insulation performance between the contacts of electrical wire connectors and between the contacts and the outer shell. Its magnitude ranges from hundreds to thousands of mega-ohms.
(3) Electrical resistance, or withstand voltage or dielectric withstand voltage, is the ability to withstand rated test voltage between connector contacts or between contacts and shell.
(4) Other electrical properties. The electromagnetic interference leakage attenuation is to evaluate the shielding effect of the connector. The electromagnetic interference leakage attenuation is to evaluate the shielding effect of the connector. It is generally tested in the frequency range of 100 MHz to 10 GHz. For radio frequency coaxial connectors, there are also electrical indicators such as characteristic impedance, insertion loss, reflection coefficient, 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, namely high-speed signal connector, has emerged. Accordingly, in terms of electrical performance, besides characteristic impedance, there are also some new electrical indicators, such as crosstalk, transmission delay, skew and so on.
3. Common environmental properties include temperature resistance, humidity resistance, salt spray resistance, vibration and impact resistance.
(1) The highest working temperature of the connector at present is 200 (- 65 C), except for a few high temperature special connectors. When the connector works, the current generates heat at the contact point, which leads to temperature rise. Therefore, it is generally considered that the working 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 at rated operating current is specified explicitly.
(2) Invasion of moisture resistance will affect the insulation performance of connection h and corrode metal parts. The constant humidity and heat test conditions are 90%~95% (according to product specifications, up to 98%) and temperature + 40 +20 C. The test time is at least 96 hours according to product specifications. Alternating humidity and heat tests are more rigorous.
(3) When the salt fog resistant connector works in the environment containing moisture and salt, the surface treatment layer of its metal structure and contact parts may produce electrochemical corrosion, which affects the physical and electrical properties of the connector. In order to evaluate the ability of electrical wire connectors to withstand this environment, salt spray test is prescribed. The connector is suspended in a temperature controlled test box, and sprayed with compressed air with a prescribed concentration of sodium chloride solution to form a salt mist atmosphere. Its exposure time is prescribed by product specifications for at least 48 hours.
(4) Vibration and shock resistance are important properties of electrical wire connectors. They are especially important in special application environments such as aerospace, railway and highway transportation. They are important indicators to test the mechanical structure and electrical contact reliability of electrical wire connectors. There are clear provisions in the relevant test methods. The peak acceleration, duration, impulse waveform and time of electrical continuity interruption should be specified in impact test. Other environmental performance according to the use requirements, the other environmental performance of electrical wire connectors are sealing (air leakage, liquid pressure), liquid impregnation (the ability to withstand the evil habits of specific liquids), low pressure and so on.