Interpretation of connector parameters
Insulation resistance refers to the resistance value that appears when a voltage is applied to the insulating portion of the connector to generate a leakage current in or on the surface of the insulating portion. It is mainly affected by insulation materials, temperature, humidity, and insults. The insulation resistance value provided on the connector sample is generally the index value under the standard atmospheric conditions. In some environmental conditions, the insulation resistance value will have a degree of decline. Also pay attention to the insulation resistance test voltage value. According to the insulation resistance (MΩ) = the voltage applied to the insulator (V)/the leakage current (μA), different voltages are applied, resulting in different results. In the connector test, the applied voltage is generally 10V, 100V, 500V third gear.
The withstand voltage is the critical voltage that can withstand higher than the rated voltage in the specified time, between the insulated parts of the contact pair or between the insulated part and the ground, without causing a breakdown phenomenon. It is mainly affected by the contact pair spacing and creepage distance and geometry, insulator material as well as ambient temperature and humidity, atmospheric pressure.
Any connector can not be separated from the current when it is working, and there is a danger of fire. Therefore, not only is the connector required to prevent ignition, it is also required to be able to self-extinguish in a short time in the event of ignition and fire. When choosing, pay attention to the use of flame-retardant, self-extinguishing insulating material electrical connectors.
1）Single leg separation force and total separation force
The contact pressure in the connector is an important indicator. It directly affects the size of the contact resistance and the wear amount of the contact pair. In most structures, direct measurement of contact pressure is quite difficult. Therefore, the contact pressure is often measured indirectly through a single-leg separation force. For a round pinhole contact pair, a standard pin having a prescribed weight is generally used to verify the ability of the female contact member to hold the weight. Generally, the diameter of the standard pin is the lower limit of the diameter of the male contact and is -5 μm. The total separation force is generally twice the sum of the on-line separation forces. When the total separation force exceeds 50 N, manual insertion and removal are already quite difficult. Of course, for some test equipment or certain special occasions, zero insertion force connectors, automatic disconnect connectors, etc. can be selected.
The environmental parameters include ambient temperature, humidity, rapid temperature change, atmospheric pressure, and corrosive environment. The environment in which the connector is used, stored, and transported has a significant effect on its performance, so the appropriate connector must be selected based on the actual environmental conditions.
The connector's metallic and insulating materials determine the connector's operating ambient temperature. High temperatures can destroy edge materials, causing a decrease in insulation resistance and pressure resistance; for metals, high temperatures can cause contact pairs to lose their elasticity, accelerate oxidation, and degrade plating. Typical ambient temperatures are -55 to 100°C. Higher requirements may be required for special applications.
Relative humidity greater than 80% is the cause of electrical breakdown. The wet environment causes the absorption and diffusion of water vapor on the surface of the insulator, which easily lowers the insulation resistance to below MΩ level. Under long-term conditions in high-humidity environment, it will cause physical deformation, decomposition, escaping products, and producing respiratory effects and electrolysis and corrosion and cracks. Especially in the connector outside the device, it is often necessary to consider the environmental conditions of moisture, water infiltration and pollution, in which case the sealed connector should be used. For watertight, dust-tight connectors generally use GB4208 shell protection level to represent.
3）Rapid temperature change
The Humidity Change Test simulates the actual use of the connector device in a cold environment to switch to a warm environment, or simulates a situation in which the space temperature of the spacecraft and the detector rapidly changes. A sudden change in temperature may cause cracking or delamination of the insulating material.
At a high altitude in the air, the plastic emits gas to contaminate the contact pairs, increase the tendency of corona generation, decrease the withstand voltage performance, and cause the circuit to produce a short-circuit fault. When the air reaches a certain value, the plastic performance deteriorates. Therefore, when using non-sealed connectors at high altitude, derating must be used.
According to the different corrosive environments of the connector, the connectors of the corresponding metal, plastic, and plating structure are used. As in the connector used in the salt spray environment, if there is no antiseptic metal surface, the performance will deteriorate rapidly. In the presence of considerable concentrations of SO2, it is not appropriate to use silver-plated contacts. In hot areas, mold is also an important issue.