Three basic properties of RJ45 connectors

The three basic properties of RJ45 connectors are mechanical, electrical, and environmental. 1． Mechanical properties: As far as the connection function is concerned, the insertion and extraction force is an important mechanical property. Insertion force is divided into insertion force and extraction force (extraction force is also called separation force), and the requirements of the two are different. The maximum insertion force and the minimum separation force are specified in the relevant standards, which indicates that, from the point of view of use, the insertion force should be small (thus there are structures with low insertion force LIF and no insertion force ZIF), and if the separation force is too small, it will affect the reliability of contact. Another important mechanical property is the mechanical life of the connector. Mechanical life is actually a durability index, which is called mechanical operation in the national standard GB5095. It takes one insertion and one withdrawal as a cycle, and judges whether the connector can normally complete its connection function (such as contact resistance value) after the specified insertion and withdrawal cycle. The insertion and extraction force and mechanical life of the connector are related to the contact structure (positive pressure), the coating quality of the contact part (sliding friction coefficient) and the dimensional accuracy of the contact arrangement (alignment).

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2． Electrical performance: The main electrical performance of the connector 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 the connector varies from a few milliohms to tens of milliohms. ② Insulation resistance is an index to measure the insulation performance between the contacts of electrical connectors and between the contacts and the shell, and its order of magnitude ranges from hundreds of megohms to thousands of megohms. ③ Dielectric strength, also known as withstand voltage and dielectric withstand voltage, refers to the ability to withstand the rated test voltage between the connector contacts or between the contacts and the shell. ④ Other electrical properties. Electromagnetic interference leakage attenuation is to evaluate the electromagnetic interference shielding effect of the connector, and the electromagnetic interference leakage attenuation is to evaluate the electromagnetic interference shielding effect of the connector, which is generally tested within the frequency range of 100MHz ~ 10GHz. For RF coaxial connectors, there are also electrical indicators such as characteristic impedance, insertion loss, reflection coefficient, voltage standing wave ratio and so on. 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. Accordingly, in terms of electrical performance, in addition to the characteristic impedance, there are also some new electrical indicators, such as crosstalk, transmission delay, time lag and so on.

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3． Environmental performance: Common environmental performance includes temperature resistance, humidity resistance, salt spray resistance, vibration and shock resistance, etc. ① Temperature resistance At present, the maximum working temperature of connectors is 200 ℃ (except for a few high-temperature special connectors), and the minimum temperature is -65 ℃. When the connector works, the current generates heat at the contact point, resulting in temperature rise, so it is generally believed that the working temperature should be equal to the sum of the ambient temperature and the temperature rise of the contact point. In some specifications, the maximum allowable temperature rise at the rated operating current of the connector is specified. ② Resistance to the invasion of moisture will affect the insulation performance of the connection and rust the metal parts. Steady damp heat test conditions are 90% ~ 95% relative humidity (up to 98% according to the product specification), temperature + 40 & # 177; 20 ℃, and the test time is 96 hours at least according to the product specification. The alternating damp heat test is more severe. ③ When the salt-spray-resistant connector works in the environment containing moisture and salt, the surface treatment layer of its metal structural parts and contacts may produce galvanic corrosion, which will affect the physical and electrical properties of the connector. In order to evaluate the ability of electrical connectors to withstand this environment, a salt spray test is specified. The connector is suspended in a temperature-controlled test chamber and sprayed with compressed air with a specified concentration of sodium chloride solution to form a salt spray atmosphere with an exposure time specified by the product specification of at least 48 hours. ④ vibration and shock resistance is an important performance of electrical connectors, especially in special application environments such as aviation and aerospace, railway and highway transportation, which is an important index to test the robustness of electrical connector mechanical structure and the reliability of electrical contact. There are clear provisions in the relevant test methods. The peak acceleration, duration, and shock pulse waveform, as well as the time of interruption of electrical continuity, shall be specified in the shock test. ⑤ Other environmental properties According to the use requirements, other environmental properties of electrical connectors include sealing (air leakage, liquid pressure), liquid immersion (resistance to deterioration of specific liquids), low air pressure, etc.

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