The plastic insulating material and conductive parts of the terminal are directly related to the quality of the terminal, which determine the insulation performance and electrical conductivity of the terminal respectively. The failure of any terminal will lead to the failure of the entire system engineering. The painful lessons that have occurred at home and abroad in this regard are very profound.
Prevention is the goal, analysis is the foundation. In a sense, preventing failure is more important than analyzing failure. It has more practical significance for ensuring the quality and reliability of terminal blocks.
From the point of view of use, the functions that the terminal should achieve are: the place where the contact part should be turned on must be turned on, and the contact is reliable. The place where the insulating part should not be turned on must be insulated and reliable. There are three common fatal failure forms of terminal blocks:
1. Poor contact
The metal conductor inside the terminal is the core part of the terminal, which transmits the voltage, current or signal from the external wire or cable to the contact piece corresponding to the matching connector. Therefore, the contact piece must have an excellent structure, stable and reliable contact retention and good electrical conductivity. Due to unreasonable structure design of the contact piece, wrong material selection, unstable mold, excessive processing size, rough surface, unreasonable surface treatment such as heat treatment and electroplating, improper assembly, poor storage and use environment and improper operation and use, it will cause poor contact at the contact part and the matching part of the contact piece.
2. Poor insulation
The function of the insulator is to keep the contacts in the correct position, and to insulate the contacts from each other, and between the contacts and the shell. Therefore, the insulating parts must have excellent electrical properties, mechanical properties and process molding properties. Especially with the widespread use of high-density, miniaturized terminals, the effective wall thickness of the insulator is getting thinner and thinner. This puts forward stricter requirements for insulating materials, injection mold accuracy and molding process. Due to the presence of metal excess on the surface or inside of the insulator, surface dust, flux and other pollution are damp, organic material precipitates and harmful gas adsorption films fuse with the surface water film to form ionic conductive channels, moisture absorption, mildew growth, aging of insulating materials and other reasons, will cause short circuit, leakage, breakdown, low insulation resistance and other poor insulation phenomena.
3. Poor fixation
The insulator not only plays an insulating role, but also usually provides precise neutralization protection for the protruding contacts. At the same time, it also has the functions of installation and positioning, locking and fixing on the equipment. If the fixing is poor, the lighter one will affect the reliability of the contact and cause instant power failure. The serious one is the disintegration of the product. Disintegration refers to the abnormal separation between the plug and the socket and the pin and the jack caused by the unreliable structure of the terminal in the plug-in state due to materials, design, technology and other reasons, which will cause serious consequences for the interruption of power transmission and signal control of the control system. Due to unreliable design, wrong material selection, improper selection of molding process, poor quality of heat treatment, mold, assembly, welding and other processes, and inadequate assembly will cause poor fixation.
In addition, due to the appearance of the coating peeling, corrosion, bumping, plastic shell flash, cracking, rough processing of the contact parts, deformation and other reasons, due to the excessive size of the positioning and locking fit, the consistency of the processing quality is poor, and the total separation force is too large. Poor exchange caused by such reasons is also a common disease and frequently occurs. These kinds of faults can generally be found and eliminated in time during inspection and use.
