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Common faults and preventive measures in terminal


         
        

The plastic insulation materials and conductive parts of the terminals are directly related to the quality of the terminals, which determine the insulation performance and the conductivity of the terminals. Any failure of the terminal will result in the failure of the entire system project. This is a profound lesson at home and abroad.

Prevention is the goal, analysis is the foundation. In a sense, preventing failure is more important than analyzing failure. It is more realistic to guarantee the quality and reliability of terminals.

From the point of use of the terminal, the function that should be reached is that the contact area should be guided and reliable. The place where the insulation should not be conductive must be insulated and reliable. There are three common types of fatal failure modes:

Poor contact

Terminals within the metal conductor is the core of the terminal part, it will come from external wires or cables voltage, current or signal to the corresponding contact element matching connector. The contact must have excellent structure, stable and reliable contact strength and good electrical conductivity. Due to the unreasonable contact element structure design, material selection error, the mold is not stable, processing out-of-tolerance size, surface roughness, plating surface treatment such as heat treatment process is unreasonable, improper assembly, storage conditions and improper operation, will be in contact with a contact part of the cause poor contact and cooperate with the parts.

Insulation fault

The insulator's effect is to keep the contacts in the right position, and to keep contact between contact and contact between the contact and the shell. The insulation must have excellent electrical performance, mechanical properties and process molding performance. Especially with high density, miniaturization terminal is widely used, the effective wall of insulator is thinner and thinner. This paper puts forward more stringent requirements for insulation materials, injection mold precision and molding process. Due to the insulator surface or within the metal tailings, surface dust, flux, such as pollution of be affected with damp be affected with damp, organic material deposition and harmful gas adsorption film with surface water membrane fusion to form ionic conductive channel, absorption of moisture, mold, insulation aging, can cause short circuit, leakage, breakdown, low insulation resistance insulation fault phenomenon.

Fixed bad

Insulators insulation effect not only, also usually provide accurate outstretched contact for protection, and at the same time also has the installation position, the function of the lock is fixed on the device. Fixed bad, the light person affects the contact reliable causes the instant power failure, serious is the product disintegrates. Refers to the disintegration of terminals in close state, due to the material, design, technology and so on reasons for structure between plug and socket caused by unreliable, abnormal separation between pin and socket, will cause control system and signal control in power transmission interrupted serious consequences. Unreliable due to design, select material errors, incorrect molding process, heat treatment, mould, assembly, welding process of poor quality, such as fixed assembly does not reach the designated position, etc can cause adverse.

In addition, due to the coating peeling, corrosion, bruising, molded case flash, rupture, contact a rough machining, the deformation causes such as the appearance of the poor, due to the positioning lock tight fit size out-of-tolerance, consistency processing quality is poor, total separation force is too large to causes such as reversal, is also a common disease, frequently-occurring disease. These kinds of failures are usually found out in the process of inspection and use.

Prevention of failure reliability screening test.

In order to ensure the quality and reliability of terminals, to prevent the deadly fault occurs, proposal according to the product technical conditions, formulate the corresponding filter technical requirements, carry out the following reliability test targeted to prevent failure.

Prevention of exposure

1) guided test

In 2012, the general terminal production manufacturer's product acceptance test will not be this project, and the user will normally need to conduct the conducting test. Therefore, it is suggested that the manufacturer should increase the point-by-point conducting test by 100% for some key models.

2) transient detection

Some terminals are used in dynamic vibration environments. The experimental results show that only the test static contact resistance is qualified, and it is not guaranteed to be reliable in dynamic environment. Because, often qualified connector contact resistance in the vibration, impact, such as simulation test is a momentary power outages, so for some high reliability requirements of terminals, best can 100% contact dynamic vibration test to assess its reliability.

3) single hole separation test

The single hole separation force refers to the separation force of the intercalation state, which is the separation force of motion, which is used to characterize the contact between the insertion needle and the socket. The experiment shows that the single hole separation force is too small, and it can cause the signal to be instantaneous in vibration and shock load. The method of single hole separation force is used to check the contact reliability ratio. Check to find the hole of the single hole separation force, and the measurement contact resistance is usually qualified. For this purpose, the factory in addition to developing a new generation of flexible plugged into close contact with stable and reliable contact element, the should not be used to model focused on automatic insertion force tester more neat, deal with finished goods for 100% of the check point by point puckering separation force, prevent interruptions caused by individual jack relaxation signals.

Prevention of insulation

1) insulation inspection

The quality of raw materials has great effect on insulation performance of insulators. So for the choice of raw materials manufacturers especially important, should not blindly to reduce costs and loss of the material quality. Should choose metal material with good credit. And check carefully for each batch of material incoming inspection batch number, material certificate, and other important information. Traceability information materials to use.

2) insulation resistance check

To 2012, there are some factory assembly process into finished products after the detection performance, the results due to the insulation resistance is unqualified, insulator to the whole batch of finished product scrap. Reasonable process should be done in the state of insulator parts 100% process to ensure the electrical performance is qualified.

Prevention of fixation

1) interchangeability check

Cross-checking is a dynamic check. It requires the same series matching plug and socket can be inserted with connection each other, to find whether there is due to the insulator, such as pieces of contact parts size out-of-tolerance, causes such as missing parts or assembly does not reach the designated position cannot be inserted, positioning and locking, even in the rotating force under the action of disintegration. The other function of the interchangeability check is to find out whether there is any metal residue that can affect insulation performance in time. Therefore, the terminals of some important USES should be inspected 100% to avoid such major fatal failure accidents.

2) resistance to torque

Resistance to torque is a very effective way to check the reliability of terminal structure. For example, the standard of MIL -l-39012 of the U.S. military, the standard should be tested by the standard for the inspection of the moment in time to detect the problem in time.

3) connect the pass of the conductor

It is often found that individual cores are not being sent in place, or when they are put in place, the contact is not reliable. The analysis is due to the fact that individual holes have burrs or dirty CARDS. Especially use factory has denso to a connector at the end of the several mounting holes, found that the defects after illness had to have installed other discharge hole pressure welding wire, to replace the connector. In addition, due to the improper coordination of wire diameter and pressure, the failure of pressure welding process can also result in the failure of the pressure connection. For this purpose, the factory in the plug of the finished product before delivery to the delivery of the goods (a) the sample of the all mounting holes to test, with loading and unloading tools will have pressure to pin the wires or jack simulation to send in place, check whether to lock up. According to the requirement of the product technology, the check of the pulling force is carried out by the root pressing wire.

Without reliable terminals, there is no reliable system engineering. Failure and reliability are two aspects of a paradox that correspond to one another.

Through the terminal reliability screening found various failure modes and failure mechanism, can lead to a lot of lessons and eliminate all kinds of hidden dangers, to improve the design, process, inspection and provide scientific evidence for use, it is also revise and formulate the important basis of terminal technology conditions. It is the ultimate aim of failure analysis to find the measures to prevent failure.