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The plastic insulating material and conductive parts of the terminal are directly related to the quality of the terminal, and they respectively determine the insulation and conductivity of the terminal. In order to ensure the quality and reliability of the terminal and prevent the occurrence of poor insulation, poor contact, and poor fixing, it is recommended to study and formulate corresponding screening technical requirements according to the technical conditions of the product, and carry out the following targeted reliability inspections to prevent failure.

At present, some production plants require that the electrical properties are tested after assembly into finished products. As a result, the entire batch of finished products has to be scrapped because the insulation resistance of the insulator itself is unqualified. A reasonable process should be 100% process screening in the state of insulator parts to ensure qualified electrical performance.

2. Measures against "bad contact"

1) Continuity detection

At present, the general terminal manufacturer's product acceptance test does not have this item, and users generally need to conduct continuity testing after installation. Therefore, it is recommended that manufacturers add 100% point-by-point conduction detection to some key models of products.

2) Transient detection

Some terminal blocks are used in dynamic vibration environment. The experiment proves that it is only used to check whether the static contact resistance is qualified, and it cannot guarantee the reliability of the contact in dynamic environment. Because connectors with qualified contact resistances often suffer from instantaneous power failure during simulated environmental tests such as vibration and impact, it is best to perform dynamic vibration tests on some terminals with high reliability requirements. Contact reliability.

3) Single hole separation force detection

The single-hole separation force refers to the separation force of the contact member in the inserted state from being stationary to moving, which is used to characterize the contact between the pin and the socket. Experiments show that if the separation force of a single hole is too small, it may cause instantaneous signal interruption when subjected to vibration and shock loads. The method of measuring the separation force of a single hole is more effective than measuring the contact resistance. Inspect the jacks where the single-hole separation force is out of tolerance, and the contact resistance is often still qualified. For this reason, in addition to the development of a new generation of flexible plug-in contact, the manufacturer should not use automatic plug-in force testing machines for multi-point simultaneous testing of key models, and should conduct 100% point-by-point orders for finished products. Check the hole separation force to prevent instantaneous signal interruption caused by the loosening of individual jacks.

3. Measures against "bad fixation"

1) Through test of crimping wire

In electrical installation, it is often found that individual core crimped wires cannot be delivered in place, or cannot be locked after delivery, and the contact is unreliable. The reason for the analysis is that there are burrs or dirt stuck on the threads of individual mounting holes. Especially when using the last few mounting holes that the factory has installed on a plug seat, if the defect is found, the crimping wires of the other holes that have been installed have to be unloaded one by one, and the plug seat is replaced. In addition, due to the improper selection of the wire diameter and the crimping aperture, or the error in the crimping process, it will also cause the crimping end to be weak. For this reason, the manufacturer must conduct a thorough test on all the mounting holes of the delivered plug (seat) sample before the finished product leaves the factory, that is, use the loading and unloading tool to simulate the wire crimped with the pin or socket to check whether it can be Locked. According to the product technical conditions, check the pull-off force of each crimped wire.

2) Interchangeability check

The interchangeability check is a dynamic check. It requires that the matching plugs and sockets of the same series can be mated and connected to each other, and it can be found whether there is any failure to be inserted, positioned and locked due to the out-of-dimension of insulators, contacts and other parts, missing parts or improper assembly. , And even cause disintegration under the action of rotating force. Another function of the interchangeability check is to detect in time whether there is any metal excess that affects the insulation performance through plug connections such as threads and bayonets. Therefore, 100% of the wiring terminals of some important purposes should be checked for this item to avoid such major fatal failure accidents.

3) Torque check

Torque inspection is a very effective inspection method to assess the reliability of the terminal structure. For example, the U.S. military standard MIL-L-39012 standard stipulates. According to the standard, samples should be sampled and tested for torque resistance in each batch to find problems in time.

summary

Without reliable wiring terminals, there is no reliable system engineering. Failure and reliability are two aspects of a contradictory body that are corresponding and interrelated. Finding various failure modes and failure mechanisms through the reliability screening of terminal blocks can draw a lot of experience and lessons and eliminate various hidden dangers, and provide scientific basis for improving design, process, inspection and use. It is also an important part of revising and formulating technical conditions for terminal blocks. in accordance with. Finding measures to prevent failures and realizing the transformation from failure to reliability is the ultimate goal of failure analysis.