Common terminal failure prevention measures

From the point of view of use of the terminal block, the function that should be achieved is: the conducting part of the contact part must be conducted and the contact is reliable. Insulation should not be conducted where the insulation must be reliable.

There are three types of fatal faults that are common to terminal blocks:

1. Bad Contact The metal conductor inside the terminal is the core part of the terminal. It transmits the voltage, current or signal from the external wire or cable to the corresponding contact of the connector. Therefore, the contacts must have a good structure, stable and reliable contact retention and good electrical conductivity. Due to the unreasonable contact structure design, material selection error, mold instability, processing size, surface roughness, heat treatment plating and other surface treatment process is unreasonable, improper assembly, poor storage environment and improper operation, will be in the contact Contact and fittings cause poor contact.

2. Insufficient insulation The role of the insulator is to keep the contacts in the correct position and to insulate the contacts from the contacts and between the contacts and the housing. Therefore, the insulator must have excellent electrical properties, mechanical properties and process forming properties. In particular, with the widespread use of high-density, miniaturized terminals, the effective wall thickness of the insulator becomes thinner and thinner. This puts forward more stringent requirements for insulation materials, injection mold accuracy and molding process. Due to the existence of metal extraneous materials on the surface or inside of the insulator, surface dust, flux and other pollution damp, the organic material precipitates and harmful gas adsorption film and the surface water film fuse to form an ionic conductive path, moisture absorption, mold, insulation material aging and other reasons, Can cause short circuit, leakage, breakdown, low insulation resistance and other poor insulation phenomena.

3. Insufficient fixed insulators not only provide insulation, but they also provide precise centering and protection for protruding contacts. They also have the function of mounting and locking and fixing on the device. Poorly fixed, light affect the contact and reliable cause an instant power failure, the serious is the product disintegration. Disassembly refers to the disconnection between the plug and the socket and between the pin and the jack caused by the unreliability of the structure due to the material, design, and process due to the connection terminals. The serious consequences of signal control interruptions. Due to unreliable design, incorrect material selection, improper selection of molding process, poor quality of heat treatment, mold, assembly, welding, etc., and poor assembly may cause poor fixation.

In addition, due to the coating peeling, corrosion, bumps, plastic shell flash, cracking, contact processing rough, deformation and other causes of poor appearance, due to positioning and locking with the size of the poor, poor consistency of processing quality, the total separation force over Disadvantages caused by large-scale exchanges are also common and frequently-occurring diseases. These kinds of faults can be found in the inspection and use process in time.

Preventive Failure Reliability Screening Inspection To ensure the quality and reliability of the terminal blocks and to prevent the above-mentioned fatal failures, it is recommended that according to the technical conditions of the products, research and development of corresponding screening technical requirements be carried out to carry out the following targeted failure prevention reliability. test.

1. Prevention of poor contact 1 Conduction test At present, the general terminal manufacturer product acceptance test does not have this item, and users generally need to conduct conduction test after installation. Therefore, it is recommended that the manufacturer should increase 100% point-by-point conduction testing for some key models of products.

2 Instantaneous Break Detection Some terminal blocks are used in a dynamic vibration environment. The experiment proves that it is only qualified to test the static contact resistance, and it can not guarantee the reliable use of the contact in the dynamic environment. Because, often, connectors that meet acceptable resistance still experience momentary power failures when they are subjected to vibration, impact, or other simulated environmental tests, it is advisable to perform dynamic vibration tests on 100% of the terminals that require high reliability. Contact reliability.

3 Single-hole separation force detection The single-hole separation force refers to the separation force from the rest state to the movement of the contact state in the engagement state, which is used to indicate that the pin and the jack are in contact. Experiments show that: the separation force of single hole is too small, and it may cause the signal to break when subjected to vibration and impact load. It is more effective to measure the contact reliability than to measure the contact resistance by measuring the separation force of the single hole. It was found that jacks with poor single-hole separation force were detected and the contact resistance was often still acceptable. For this reason, in addition to the development of a new generation of flexible plug-in contact with stable and reliable contact parts, the manufacturer should not use the automatic insertion force testing machine for key models to perform multiple point tests and respond to the finished product 100% point by point. The hole separation force is checked to prevent the signal from being broken due to the looseness of individual jacks.

2. Prevention of poor insulation 1 Insulating materials Checking the quality of raw materials has a great influence on the insulating properties of insulators. Therefore, it is very important for the selection of raw material manufacturers, not to reduce the cost and to lose the quality of the material. We should select the reputable manufacturers. We must carefully check the batch number, material proof and other important information. Material traceability data.

2 insulation insulation resistance inspection At present, some of the production plant process requirements after the assembly of finished products to detect electrical performance, the results of the insulator itself as insulation resistance is not qualified, only the entire batch of finished products scrapped. A reasonable process is to screen the process for 100% of the insulator parts to ensure that the electrical properties are acceptable.

3. Prevention of poor fixation 1 interchangeability inspection Interchangeability examination is a dynamic examination. It requires that the same series of matching plugs and sockets can be mated and connected to each other, from which it can be found out whether due to the size of insulators, contact parts and other parts of the size of the poor, lack of parts or assembly is not in place and other reasons can not be inserted, positioning and locking , even under the influence of rotational force disintegration. The other function of the interchangeability inspection is to find out if there are metal extraneous materials that may affect the insulation performance by inserting and removing the connection through screws, bayonet, etc. Therefore, 100% of the terminals of some important applications should be checked for this project to avoid such fatal fatal accidents.

2 Torque Check Torque Check is a very effective method of checking the reliability of the terminal structure. Such as the US military standard MIL-L-39012 standard. According to the standard should be tested in each batch of samples to check the torque resistance, timely detection of problems.

3 Press-fit wire pass-through test When the power is installed, it is often found that the individual core crimped wire is not sent in place, or it cannot be locked after being delivered, and the contact is not reliable. The reason for the analysis is that there are burrs or dirt stuck on the individual mounting holes. In particular, the use of the factory has been installed in the last few mounting holes of a plug connector. It was discovered that after the defect, only the crimped wires of the other holes that had been installed had to be unloaded and the plug connector was replaced. In addition, due to improper selection of wire diameters and crimp apertures, or due to misoperation of the crimping process, it can also result in an unstuck crimping accident. For this purpose, the manufacturer shall test all the mounting holes of the delivered plugs (seats) before the finished products leave the factory. That is, using the loading and unloading tools, the wires to which the pins or jacks are crimped are sent to the place and checked for compliance. Locked. According to the technical specifications of the product, the pull-off force shall be checked for the crimped conductors one by one.

Without reliable terminal blocks, there is no reliable system engineering. Failure and reliability are two aspects of a contradictory body that correspond to and relate to each other. 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. It provides a scientific basis for improving design, technology, inspection and use, and it is also important for revising and formulating the technical conditions of the terminal blocks. in accordance with. The ultimate goal of failure analysis is to find measures to prevent failures and achieve transformation from failure to reliability.