The plastic insulating material and conductive parts of the terminal are directly related to the quality of the terminal, and they determine the insulation performance and conductivity of the terminal respectively. Failure of any terminal will lead to failure of the entire system engineering. It is said that prevention is the purpose and analysis is the foundation. From the point of view of use, the function that the terminal block should achieve is: the place where the contact part should be conducted must be conducted, and the contact is reliable. The place where the insulation part should not be connected must be insulated reliably.
There are three common fault forms of terminal blocks:
01. Poor contact
The metal conductor inside the terminal block is the core part of the terminal, which transmits the voltage, current or signal from the external wire or cable to the corresponding contact of the matching connector. Therefore, the contact must have an excellent structure, stable and reliable contact retention and good electrical conductivity. Due to the unreasonable structural design of the contact piece, wrong material selection, unstable mold, out-of-tolerance processing size, rough surface, unreasonable surface treatment process such as heat treatment and plating, improper assembly, harsh storage, and use environment, and improper operation and use, all of them will be damaged in the contact piece. The contact part and the mating part cause poor contact.
02. Poor insulation
The role of the insulator is to keep the contacts in the correct position and to insulate between the contacts and between the contacts and the housing. Therefore, insulating parts must have excellent electrical properties, mechanical properties and process-forming properties. Especially with the widespread use of high-density and miniaturized terminals, the effective wall thickness of the insulator is getting thinner and thinner. This puts forward more stringent requirements on insulating materials, injection mold precision and molding process. Due to the presence of excess metal on the surface or inside of the insulator, surface dust, flux and other pollution, organic material precipitates and harmful gases, the adsorption film fuses with the surface water film to form an ionic conductive channel, moisture absorption, mold growth, and aging of insulating materials. Will cause short circuits, leakage, breakdown, low insulation resistance and other poor insulation.
03. Poor fixation
The insulator not only plays an insulating role, but also usually provides precise centering and protection for the protruding contacts, and also has the functions of installation, positioning, locking and fixing on the equipment. Poor fixation will affect the reliability of contact in the slightest and cause instantaneous power failure, and the serious one will be the disintegration of the product. Disintegration refers to the abnormal separation between the plug and the socket, between the pin and the jack caused by unreliable structure due to materials, design, process and other reasons when the terminal is in the mated state, which will cause the power transmission of the control system and Serious consequences of interruption of signal control. Unreliable design, wrong material selection, improper selection of molding process, poor quality of heat treatment, mold, assembly, welding and other processes, improper assembly, etc. will cause poor fixation.
In addition, poor appearance due to coating peeling, corrosion, bruises, molded case flash, cracks, rough processing of contacts, deformation, etc. Poor interchange caused by large and other reasons is also a common and frequently-occurring disease. These kinds of faults can generally be found and eliminated in time during inspection and use.
Without reliable terminals, there will be no reliable system engineering. Failure and reliability are two aspects of a contradictory body that are corresponding and interrelated. Through the reliability screening of terminal blocks, various failure modes and failure mechanisms can be found, which can lead to a large number of lessons learned and eliminate various hidden dangers, and provide a scientific basis for improving design, process, inspection and use. It is also important to revise and formulate the technical conditions of terminal blocks. in accordance with. It is the ultimate goal of failure analysis to find measures to prevent failure and realize the transformation from failure to reliability.
