Component failures on circuit boards are often related to the working environment (such as temperature, humidity, vibration), electrical stress (such as voltage, current overload), and their own aging characteristics. The following are the most prone components to malfunction and their common causes of failure:
Table of Contents
1、 Electrolytic capacitor
-Fault manifestations: bulging, leakage, capacity decay, and increased internal resistance.
-Easy to malfunction reasons:
-The electrolyte of electrolytic capacitors will gradually evaporate with increasing temperature, and high-temperature environments (such as areas near high-power components) will accelerate aging, with a typical lifespan of about 2000-10000 hours (positively correlated with temperature).
-Long term operation under excessive ripple current, reverse voltage, or overvoltage can lead to increased internal heating, causing electrolyte expansion and ultimately resulting in swelling and leakage.
-Common scenarios: power circuits (such as motherboard power supply modules, graphics card power supply parts), motor drive circuits, etc.
2、 Resistor
-Fault manifestations: open circuit, increased/decreased resistance, burnt out (appearance blackened).
-Easy to malfunction reasons:
-If the power exceeds the rated value (such as circuit overload causing excessive current), the resistor will heat up and burn out.
-Carbon film/metal film resistors experience poor contact and resistance drift due to vibration or poor welding.
-Thin film resistors may experience leakage in humid environments, leading to abnormal resistance values.
-Common scenarios: in current limiting circuits, voltage divider circuits, and load circuits.
3、 Semiconductor devices (diodes, transistors, MOSFETs, IGBTs, etc.)
-Fault manifestations: breakdown short circuit, open circuit, performance degradation (such as decreased amplification).
-Easy to malfunction reasons:
-Voltage/current overload (such as power surge, load short circuit) causes PN junction breakdown.
-Poor heat dissipation (such as high-power tubes without heat sinks) can cause thermal breakdown due to high temperatures.
-Electrostatic damage (especially in MOS transistors, where the gate oxide layer is thin and susceptible to electrostatic breakdown).
-Common scenarios: rectifier circuit (diode), switch circuit (MOS/IGBT), amplifier circuit (transistor).
4、 Connectors and connectors
-Fault manifestations: poor contact, oxidized pins, looseness and detachment.
-Easy to malfunction reasons:
-Frequent plugging and unplugging can cause pin wear or deformation, resulting in increased contact resistance.
-In humid or dusty environments, pins may oxidize and rust (such as copper pins forming an oxide layer).
-Vibration environment (such as automobiles and industrial equipment) causes loose connectors.
-Common scenarios: power interface, data interface (such as USB, HDMI), board to board connector, terminal block.
5、 Relays and contactors
-Fault manifestations: contact erosion and adhesion, coil burnout, mechanical jamming.
-Easy to malfunction reasons:
-When the contact passes through a high current, an arc is generated, which can cause oxidation or melting of the contact after long-term use (especially for inductive loads such as motors and solenoid valves).
-The coil voltage is too high or has been powered on for a long time, causing the enameled wire to overheat and burn out.
-Environmental dust and humidity cause mechanical parts to jam, making it impossible to engage/disconnect normally.
-Common scenarios: power switching circuits, motor control circuits, industrial automation equipment.
6、 Fuses (fuses) and fuse resistors
-Fault manifestation: circuit breaker (open circuit).
-Easy to malfunction reasons:
-Short circuit or excessive load in the circuit can cause the current to exceed the rated value, triggering the protection fuse.
-Self aging or poor contact (such as oxidation of the fuse seat) can cause accidental melting.
-Function: As a protective component, faults often involve sacrificing oneself to protect other circuits, and it is necessary to investigate the underlying causes of overload (such as short circuits, component damage).
7、 Light Emitting Diodes (LEDs)
-Fault manifestations: no light (open circuit), brightness attenuation, flashing.
-Easy to malfunction reasons:
-Excessive reverse voltage can cause PN junction breakdown, or excessive forward current can cause chip overheating and burnout.
-Long term high temperature work leads to aging of fluorescent powder and brightness degradation (especially for white LED).
8、 Crystal oscillator and ceramic resonator
-Fault manifestations: vibration stoppage, frequency deviation, abnormal output waveform.
-Easy to malfunction reasons:
-Vibration or impact can cause internal crystal fragmentation (crystal oscillators are precision components with poor resistance to mechanical stress).
-Poor soldering (virtual soldering) or moisture on the pins can cause unstable circuit contact.
-Abnormal peripheral capacitance parameters (such as capacitance deviation) affect the oscillation frequency.
Summarize
The core causes of component failures can be summarized as: overstress (voltage/current/temperature), aging, mechanical damage (vibration/impact), and environmental erosion (humidity/dust). Among them, electrolytic capacitors, connectors, and semiconductor devices are the “hardest hit areas” for circuit board failures due to their own characteristics or working environment, and are also the priority targets for troubleshooting during maintenance.
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