The failure of the terminal is mainly due to poor contact, poor insulation and poor fixation. The plastic insulating materials and conductive parts of the terminal are directly related to the quality of the terminal. They determine the insulation and conductivity of the terminal respectively, which is the material cause of the failure. The failure of any terminal will lead to the failure of the whole system engineering. From the perspective of use, the function of the wiring terminal should be: the place where the contact part is connected must be connected, and the contact is reliable. Where the insulation part should not be connected, the insulation must be reliable. Common fatal fault forms of terminal blocks are:
   1. The metal conductor inside the wiring terminal of the poor contact connector is the core part of the terminal, which transmits the voltage, current or signal from the external wire or cable to the contact corresponding to its matching connector. Therefore, the contact must have excellent structure, stable and reliable contact holding force and good electrical conductivity. Due to unreasonable contact structure design, wrong material selection, unstable mold, out of tolerance of processing size, rough surface, unreasonable surface treatment processes such as heat treatment and electroplating, improper assembly, poor storage and use environment and improper operation and use, poor contact will be caused at the contact part and mating part of the contact.
   2. The function of poorly insulated insulator is to keep the contact in the correct position and arrangement, and to insulate the contact from the contact and the contact from the shell. Therefore, the insulating parts must have excellent electrical performance, mechanical performance and process molding performance. Especially with the wide use of high-density and miniaturized wiring terminals, the effective wall thickness of insulators becomes thinner and thinner. This puts forward more stringent requirements for insulating materials, injection mold accuracy and molding process. Short circuit, electric leakage, breakdown, low insulation resistance and poor insulation will be caused due to the presence of metal residues, surface dust, solder and other pollution and moisture on the surface or inside of the insulator, the fusion of organic material precipitates and harmful gas adsorption film with the surface water film to form an ionic conductive channel, moisture absorption, mildew growth, aging of insulating materials and other reasons.
   3. The poorly fixed connector also learned that the insulator not only plays the role of insulation, but also usually provides accurate centering protection for the protruding contact, but also has the functions of installation, positioning, locking and fixing on the equipment. Poor fixation will affect the reliable contact, resulting in instantaneous power failure and serious product disassembly. Disassembly refers to the abnormal separation between plug and socket, pin and Jack caused by unreliable structure due to materials, design, process and other reasons when the wiring terminal is in the plugged state, which will cause serious consequences of interruption of power transmission and signal control of the control system. Poor fixation will be caused by unreliable design, wrong material selection, improper selection of forming process, poor process quality such as heat treatment, mold, assembly and welding, and inadequate assembly. In addition, poor appearance caused by coating peeling, corrosion, bruise, plastic shell flash, fracture, rough contact processing, deformation and other reasons, poor exchange caused by excessive positioning and locking fit size, poor consistency of processing quality and excessive total separation force are also common and frequently occurring diseases. These faults can generally be found and eliminated in time during inspection and use.