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Common causes of electronic components failure

Electronic components refer to finished products that do not change the molecular composition during production and processing in the factory. They are often composed of several parts. The family of electronic components is very extensive and large, including things that are quite complex, including resistors, relays, capacitors, transformers, potentiometers, tubes, heat sinks, electromechanical components, potentiometers, connectors, and so on. Today, Xiaobian will choose the most contacted resistors, capacitors, inductors and transformers in electronic circuits to focus on the causes of failure and common detection methods.
1, resistor class
As the name suggests, a resistor can be used as a current limiting function in a circuit. Secondly, a resistor can also generate heat by the thermal effect of current. In daily life, it is generally called a resistor, and is an energy consuming component. The bulbs, heating wires, etc. that we commonly use can be expressed as resistors.
The number of resistors used in electronic equipment is large, and the ratio of failures of electronic equipment caused by resistor failure is relatively high, accounting for about 15%. The failure mode and cause of the resistor are closely related to the structure, process characteristics and use conditions of the product. There are four types of resistor failure:
(1) Lead breakage, matrix defects, poor uniformity of the film layer, groove defect of the film layer, poor contact between the film material and the lead end, contamination of the film and the substrate, and the like.
(2) unevenness of the resistive film, cracking of the resistive film, poor lead wires, decomposition of the resistive film, migration of silver, reduction of resistive oxide, electrostatic charge, wire breakage, corona discharge, and the like.
(3) Poor contact, current corrosion, poor lead wires, poor insulation of wires, melting of solder joints, etc.
(4) Poor contact, poor soldering, contact reed rupture or lead drop, impurity contamination, poor epoxy glue, shaft tilt, etc.
(5) Poor heat dissipation, burnout caused by excessive moisture or defects during manufacturing
(6) The circuit is abnormal, such as short circuit, overload, etc., causing the resistor to burn out.
(7) The contact pressure is too small, the reed stress is relaxed, the sliding contact is off track or conductive layer, the mechanical assembly is improper, or a large mechanical load (such as collision, drop, etc.) causes deformation of the contact spring.
(8) The conductive layer or the contact track forms various non-conductive film layers at the contact due to oxidation and contamination.
2, capacitors
A capacitor, also known as "capacitance," is a device that holds a charge and is an energy storage component. The simplest structure of a capacitor can be composed of two layers of insulating material sandwiched between two adjacent metal plates, so the type of capacitor is mainly determined by the electrode and the insulating medium.
The common fault phenomena of capacitors mainly include breakdown, open circuit, electrical parameter degradation, electrolyte leakage and mechanical damage, which are closely related to various types of materials, structural differences, manufacturing processes and environmental conditions, and working stress. The main reasons for these failures are as follows:
(1) Breakdown. Defects, defects, impurities or conductive ions in the medium; aging of the dielectric material; electrochemical breakdown of the dielectric; arcing of the inter-electrode edge under high humidity or low pressure; instantaneous short circuit of the dielectric under mechanical stress; migration of metal ions Forming a conductive channel or edge arcing discharge; dielectric air gap breakdown inside the dielectric material causes electrical breakdown of the medium; mechanical damage of the medium during the manufacturing process; changes in the molecular structure of the dielectric material and the applied voltage is higher than the rated value.
(2) Open the road. Breakdown causes electrode and lead insulation; electrolytic capacitor anode lead foil is corroded (or mechanically broken); lead wire and electrode contact point oxide layer to cause low level open circuit; lead wire and electrode contact poor or insulated; electrolytic capacitor anode lead The metal foil is opened due to corrosion; the dry or frozen working electrolyte; the instantaneous open circuit between the electrolyte and the dielectric under mechanical stress.
(3) Degradation of electrical parameters. Moisture and dielectric aging and thermal decomposition; metal ion migration of electrode materials; existence and change of residual stress; surface contamination; self-healing effect of metallized electrode of material; volatilization and thickening of working electrolyte; electrolytic corrosion or chemical corrosion of electrode; Lead and electrode contact resistance increases; impurities and harmful ions.
(4) The temperature stress in the circuit promotes surface oxidation, accelerates the influence of aging, accelerates the degradation of electrical parameters, and causes the electric field strength to decrease, accelerating the early arrival of dielectric breakdown.

3, inductive coil class
An inductive coil is a device that operates on the principle of electromagnetic induction. It is an energy storage component that converts electrical energy into magnetic energy and stores energy in a magnetic field.
The reason why the inductor is burnt out can be said to be very much. We can consider prevention from the following factors:
(1) The quality problem of the enameled wire, the manufacturer used an enameled wire with a temperature resistance of 130 ° C to 150 ° C or less in order to reduce the cost of production.
(2) The reaction force between the suction of the induction coil; when the voltage is low, the suction will become difficult, the operation time of the induction coil is long, and the time for the induction coil to withstand the strong current becomes longer, and the inductance coil is heated more. Make the suction more obvious and the suction is more difficult until it can not be sucked. When the inductor coil operates at a high temperature, the resistance increases and the current will become very large.
(3) The working voltage range of the product design is not wide enough. Once the voltage is 80%~85%, there is a possibility that the hot state cannot be sucked. When the voltage is higher than 120%, the inductor coil is easy to overheat.
(4) The control process is not strict or out of control; during production, the inner layer of the winding of the inductor coil is not sufficiently immersed in the paint, and the drying is not thorough, which may cause poor soldering of the lead wire joint and incomplete insulation, resulting in inter-turn and layer. Short circuit and loss of insulation.
(5) Insufficient coil winding process is insufficient; when the winding machine is in production, the winding tension should not be too loose or too tight, otherwise the enameled wire will be elongated, resulting in partial insulation withstand voltage drop.
(6) In the process of use, the insulation part of the inductor coil is damaged or mechanically damaged, causing the inductance coil to short-circuit or hit the ground, so that a large short-circuit current is generated in the inductor coil, causing the temperature to rise sharply and the heat is transferred. When you reach the adjacent line, it will eventually burn the entire coil.
(7) Human causes; when the user is unfamiliar with the use of non-inductive coils, the voltage regulation is often incorrect; the installation process is poor, the inspection of the inductor coil is not careful, causing the inductor to be mixed with other impurities, and the operation and maintenance are not In place, the relevant use technology is not strictly implemented. During the period from installation to burnout, most of the inductor coils have not undergone routine routine maintenance and dirt treatment, resulting in poor heat dissipation conditions of the inductor coil and burning.
4, transformers
The transformer is a device that uses the principle of electromagnetic induction to change the AC voltage. The main components are the primary coil, the secondary coil and the magnetic core. Generally, the transformer has two or more windings.
In terms of current technology, there are two factors that have the greatest impact depending on the type of transformer: the use of insulating materials and temperature.
(1) Using materials
The insulation material used in the transformer must comply with the high temperature resistance and oxidation resistance. Because the transformer has been operating in a harsh environment for many years, under the action of electricity, heat, chemical and electric power, the insulation material is likely to lose more than a certain limit. The mechanical properties and insulation properties are gradually aging, so it can be said that the basic life of the transformer can be said to be determined by the high temperature resistance and oxidation resistance of the insulating material.
(2) Temperature
Practice and research have shown that the relationship between the operating temperature of the transformer and the life has an 8 °C rule: the transformer runs for a long time beyond the temperature rise limit, and the service life of the transformer is shortened by half for every 8 °C increase.

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