Terminal blocks are common connection accessories in the industrial automation industry. They are wide-ranging and fully functional, and have absolute advantages in wire connection and signal transmission. Termination refers to the way the terminal contacts the wire or cable.

From the point of view of the use of the terminal, the function that should be achieved is that the contact area must be conductive and the contact is reliable. The place where the insulation should not be turned on must be insulated and reliable. Prevention is the purpose and analysis is the foundation. In a sense, preventing failures is more important than analyzing failures. It has a more realistic meaning for ensuring the quality and reliability of the terminals.

There are three common types of fatal faults in terminal blocks:

Poor contact

The metal conductor inside the terminal is the core part of the terminal that transfers the voltage, current or signal from the external wire or cable to the corresponding contact of the mating connector. Therefore, the contact member must have an excellent structure, stable and reliable contact retention and good electrical conductivity. Due to the unreasonable design of the contact structure, the wrong selection of materials, unstable mold, poor processing size, rough surface, unreasonable surface treatment process such as heat treatment plating, improper assembly, poor storage and use environment, improper operation, will be in the contact parts. Contact and fitting parts cause poor contact.

 2. Poor insulation

Due to metal impurities on the surface or inside of the insulator, surface dust, flux and other pollution are damp, organic material precipitates and harmful gas adsorption film and surface water film fuse to form ionic conductive channels, moisture absorption, mildew, insulation material aging and other reasons, It will cause short circuit, leakage, breakdown, low insulation resistance and other insulation problems.

 3. Bad fixation

The insulator not only acts as an insulator, but also provides precise centering and protection for the extended contacts, as well as mounting and locking to the device. Poor fixing, light contact affects reliable momentary power outage, and serious product disintegration. Due to unreliable design, incorrect material selection, improper selection of molding process, poor quality of heat treatment, mold, assembly, welding, etc., assembly failure, etc. will result in poor fixation.

In addition, due to coating peeling, corrosion, bumping, plastic shell flashing, cracking, rough processing of contact parts, deformation and other reasons caused by poor appearance, due to the positioning of the locking fit, the processing quality is poor, the total separation force Poor exchange caused by a large number of reasons is also a common disease and frequently-occurring disease. These kinds of faults can generally be found in the inspection and use process in time.

Reliability screening test for prevention of failure

In order to ensure the quality and reliability of the terminal block and prevent the occurrence of the above-mentioned fatal fault, it is recommended to study and formulate the corresponding screening technical requirements according to the technical conditions of the product, and carry out the following reliability test for the prevention of failure.

1. Prevent contact failure

1) Instantaneous detection

Some terminals are used in a dynamic vibration environment. The experiment proves that it is only qualified to check whether the static contact resistance is qualified, and it cannot guarantee the reliable contact in the dynamic environment. Because the connector with good contact resistance often exhibits instantaneous power failure during vibration, shock and other simulated environmental tests, it is better to test the dynamic vibration test of some high reliability terminals. Contact reliability.

 2) Single hole separation force detection

The single-hole separation force refers to the separation force in which the contact member in the engaged state changes from static to moving, and is used to characterize that the pin and the socket are in contact. Experiments show that the single-hole separation force is too small, which may cause signal transients when subjected to vibration and shock loads. It is effective to check the contact reliability by measuring the single hole separation force to measure the contact resistance. Check that the single hole separation force is too poor, the measured contact resistance is still qualified.

 2. Prevent insulation failure

1) Insulation inspection

The quality of raw materials has a great influence on the insulation properties of insulators. Therefore, the choice of raw material manufacturers is particularly important, and the cost can not be reduced and the quality of materials should be lost. And for each batch of materials to be inspected, carefully check the inspection lot number, material certification and other important information, and make traceable information on the use of materials.

 2) Insulation insulation resistance inspection

At present, some of the production plant processes are required to be assembled into finished products and then tested for electrical properties. As a result, the insulation of the insulator itself is unqualified, and only the entire batch of finished products is scrapped. A reasonable process should be 100% process screening in the state of the insulator parts to ensure electrical performance.

 3. Prevention of poor fixation

1) Interchangeability check

Interchangeability checks are a dynamic check. It requires that the same series of plugs and sockets can be mated to each other, and it is found that there is no difference in the size of the insulators, contacts, etc., the missing parts or the assembly is not in place, etc., which cannot be inserted, positioned and locked. Even under the action of the rotating force, it causes disintegration. Another function of the interchangeability check is to find out whether there are metal surpluses that affect the insulation performance through plugging and unplugging, such as threads and bayonet. Therefore, for some important applications, the terminal should be 100% checked to avoid such major fatal failures.

 2) General measurement of crimped wires

In the electrical installation, it is often found that the individual core crimping wires are not in place, or cannot be locked after being sent to the position, and the contact is unreliable. The reason for the analysis is that there are burrs or dirt stuck in the screw holes of the individual mounting holes. Before the finished product leaves the factory, all the mounting holes of the sample of the plug (seat) of the delivery shall be tested. That is, the wire crimped with the pin or the socket may be sent to the position by the loading and unloading tool to check whether it can be locked. According to the technical requirements of the product, the pull-out force of the crimping wires is checked one by one.