Introduction to basic performance of common connectors
The basic performance of connectors can be divided into three categories: mechanical performance, electrical performance, and environmental performance.
1. In terms of connection function, blockage force is an important mechanical property. Insertion force and withdrawal force are divided into insertion force and withdrawal force (withdrawal force is also known as separation force), and their requirements are different. There are provisions in the relevant standards regarding the maximum insertion force and minimum separation force, which indicates that from a usage perspective, the insertion force is relatively small (hence the structure with low insertion force LIF and no insertion force ZIF). If the separation force is too small, it will affect contact reliability.
Another important mechanical performance is the mechanical lifespan of the connector. Mechanical lifespan is actually a durability indicator, referred to as mechanical operation in the national standard GB5095. It takes one insertion and one extraction as a cycle, and is judged based on whether the connector can complete its connection function (such as contact resistance value) normally after the specified insertion and extraction cycle.
The insertion and extraction forces of connectors, as well as their mechanical lifespan, are related to the contact structure (positive pressure), the coating quality of the contact part (sliding friction coefficient), and the dimensional accuracy (alignment) of the contact device.
The main electrical properties of connectors include contact resistance, insulation resistance, and dielectric strength.
① Electrical connectors with high-quality contact resistance should have low and stable contact resistance. The contact resistance of the connector varies from a few milliohms to several tens of milliohms.
② Insulation resistance is an indicator that measures the insulation performance between the contacts of an electrical connector, as well as between the contacts and the housing. Its magnitude ranges from a few hundred megaohms to several thousand megaohms.
③ Dielectric strength, also known as withstand voltage and dielectric withstand voltage, refers to the ability to withstand the rated test voltage between connector contacts or between contacts and the housing.
④ Other electrical performance.
Electromagnetic interference leakage attenuation is an evaluation of the electromagnetic interference shielding effect of a connector, and the amount of electromagnetic interference leakage attenuation is an evaluation of the electromagnetic interference shielding effect of a connector, usually tested in the frequency range of 100MHz to 10GHz.
For RF coaxial connectors, there are also electrical indicators such as characteristic impedance, insertion loss, reflection coefficient, voltage standing wave ratio, etc. Due to the development of digital technology, a new type of connector, namely the high-speed signal connector, has emerged to connect and transmit high-speed digital pulse signals. Therefore, in terms of electrical performance, in addition to characteristic impedance, there are also some new electrical indicators, such as crosstalk, transmission delay, and delay.
3. Common environmental performance includes temperature resistance, humidity resistance, salt spray resistance, vibration resistance, and impact resistance.
① The current maximum working temperature for connectors is 200 ℃ (except for a few special high-temperature connectors), and the minimum temperature is -65 ℃. When the connector is working, the current generates heat at the contact point, causing the temperature to rise. Therefore, it is generally believed that the operating temperature should be equal to the sum of the ambient temperature and the contact temperature rise. In certain specifications, the maximum allowable temperature rise of connectors at rated operating current is clearly specified.
② Moisture resistance can affect the insulation performance of connection h and cause rusting of metal components. The constant humidity and heat test conditions are relative humidity of 90%~95% (up to 98% according to product specifications), temperature of+40 ± 20 ℃, and test time of at least 96 hours according to product specifications. The alternating humidity and heat test is more stringent.
③ When salt spray resistant connectors work in environments containing moisture and salt, their metal structure and surface treatment layer of contacts may produce electrochemical corrosion, which can affect the physical and electrical performance of the connectors. In order to evaluate the ability of electrical connectors to withstand this environment, salt spray testing is required. Hang the connector in a temperature controlled test chamber and spray a specified concentration of sodium chloride solution with compressed air to form a salt spray atmosphere. The exposure time is specified by the product specifications.