Electronic components mainly include components and devices. Electronic components are finished products whose molecular components are not changed during production and processing, such as capacitors, resistors, and inductors. Electronic devices are finished products whose molecular structure changes during the production process, such as electron tubes, integrated circuits, etc.
Resistive components
The failure of resistance components accounts for a large proportion of electronic equipment. Resistance can be divided into functions such as shunting, step-down, load, and impedance matching. According to different structures, resistance components can be divided into wire-wound resistors and non-wire-wound resistors.
The main ways of failure of resistance components are contact damage, open circuit and mechanical damage to the lead.
The influence of temperature change on the resistance is mainly that when the temperature rises, the thermal noise of the resistance increases, the resistance value deviates from the nominal value, and the allowable dissipation probability decreases. But we can also take advantage of this characteristic of resistors. For example, there are specially designed resistors: PTC (Positive Temperature Coefficient Thermistor) and NTC (Negative Temperature Coefficient Thermistor). Their resistance is affected by temperature. Very big.
Mechanical vibration will loosen solder joints and crimping points, resulting in mechanical damage such as poor contact.
Capacitor components
The main failure modes of capacitor components include breakdown, mechanical damage, and electrolyte leakage.
The main reasons for capacitor breakdown are:
1. The medium has defects, impurities and conductive ions;
2. The medium is aging;
3. The dielectric material has electrical and air gap breakdown;
4. The medium is mechanically damaged during manufacturing and processing;
5. The molecular structure of the medium changes;
6. The migration of metal ions forms a conductive channel or edge flashover discharge.
Capacitor failure may also be caused by an open circuit. Oxidation of the lead wire and the capacitor contact point leads to a low-level open circuit, poor contact between the lead wire and the electrode, and the metal foil of the electrolytic capacitor anode leads to an open circuit failure due to mechanical breaking. For this reason, the capacitor may also fail due to electrical parameter degradation failures, such as: the migration of metal ions in the electrode material, the self-healing effect of the metalized electrode of the material, the electrolytic and chemical corrosion of the electrode, humidity, surface pollution, etc., may all cause the capacitor. Degradation of electrical parameters.
Inductance components
Inductance components involve transformers, inductors, filter coils, oscillating coils, etc. Most of the failures of inductance components are caused by external factors, such as: the temperature rise of the transformer, the short-circuit of the load, the excessive current passing through the coil, etc., will cause the coil to short-circuit, short-circuit, and breakdown.
In an integrated circuit, no matter which part has a problem, the whole cannot operate normally, such as: electrode short circuit, open circuit, mechanical wear, poor solderability, etc., will all fail. Failures are mainly divided into complete damage and poor thermal stability. Thermal stability failures mainly occur at high temperatures or low temperatures, and fail if they exceed the operating temperature range of the device.
Solution
How to effectively find the failed electronic components and replace or repair the problem?
During debugging, when there is a problem that the circuit cannot work or does not work properly. First, through the dynamic observation method, that is, when the line equipment is energized, the faults of the electronic components are judged by listening, watching, touching, and smelling. For example: listen to whether there is any abnormal sound from the equipment. Look carefully for smoke and sparks in the circuit; touch the components and circuits for hotness; smell for burns and other odors.
It can also be judged by measuring the on-off conditions in the circuit with a multimeter, and by measuring various values in normal and abnormal circuits.
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