In modern electronic devices, surface mount capacitors are widely used in various circuits due to their small size, light weight, and excellent electrical performance. However, like other electronic components, surface mount capacitors can also fail during use, which can not only affect the normal operation of electronic devices but also lead to equipment malfunctions in severe cases. A thorough understanding of the main causes of surface mount capacitor failure is crucial for improving the reliability and stability of electronic devices.
Failure due to electrical stress
Overvoltage breakdown
Surface mount capacitors all have a rated operating voltage. When the voltage applied across a surface mount capacitor exceeds its rated voltage, overvoltage breakdown may occur. This is because excessively high voltage causes the internal insulating dielectric to experience an excessively strong electric field, leading to a decrease in insulation performance and ultimately breakdown. In some power supply circuits, voltage transients or surges, such as lightning strikes or voltage fluctuations during power switching, can cause surface mount capacitors to withstand excessively high voltages. For example, at the power input of an electronic device, a nearby lightning strike could generate a high-voltage surge that is conducted through the power lines to the surface mount capacitor, causing it to break down and rendering the entire power supply circuit malfunction.
Overcurrent damage
Although surface-mount capacitors are primarily used for storing and releasing charge, their current-carrying capacity is relatively limited. When an abnormally large current occurs in the circuit, such as an overcurrent caused by a short circuit, the surface-mount capacitor may be damaged due to overheating. Overcurrent causes a large amount of heat to be generated in the capacitor's internal metal electrodes and leads. If this heat cannot be dissipated in time, it will lead to changes in the capacitor's structure and performance. Prolonged overcurrent may also melt the capacitor's solder joints, causing the capacitor to detach from the circuit board. In a power amplifier circuit of an electronic device, a short circuit caused by transistor breakdown allows excessive current to flow through the surface-mount capacitor, ultimately causing it to overheat and fail, affecting the normal operation of the entire amplifier circuit.
Failure caused by mechanical stress
Welding stress
Soldering is a critical step in the installation of surface mount capacitors. Improper soldering techniques, such as excessively high soldering temperature, excessive soldering time, or excessive mechanical force applied during soldering, can generate stress within the capacitor. This stress may damage the internal structure of the capacitor, such as loosening the connection between the electrodes and the dielectric, thus affecting the capacitor's electrical performance. During reflow soldering, if the temperature profile is not set appropriately, or if the surface mount capacitor remains at high temperatures for too long, a difference in thermal expansion between the ceramic body and the metal electrodes can occur, inducing internal stress and leading to open circuits or short circuits during subsequent use.
Vibration and shock
Electronic devices may be subjected to vibration and impact during use, such as mobile phones being dropped during daily use or industrial equipment experiencing mechanical vibration during operation. When surface-mount capacitors are subjected to vibration and impact, their solder joints and the circuit board will bear additional stress. If this stress exceeds the solder joint's withstand capacity, it may cause the solder joint to crack, interrupting the electrical connection between the capacitor and the circuit board. Long-term vibration may also gradually loosen the internal structure of the capacitor, affecting its stability. In some automotive electronic devices, due to the bumps and vibrations during vehicle operation, the solder joints of surface-mount capacitors are prone to fatigue cracking, leading to capacitor failure and affecting the normal operation of the vehicle's equipment.
Failure due to environmental factors
Temperature effect
Temperature is a crucial environmental factor affecting the performance of surface mount capacitors. At high temperatures, dielectric losses increase, leading to a higher equivalent series resistance (ESR) and consequently, increased heat generation. Excessive heat can also alter the capacitance and even degrade the capacitor's insulation performance. In some industrial equipment, due to high operating temperatures, surface mount capacitors are constantly exposed to high temperatures, causing their capacitance to gradually decrease and eventually fail to meet circuit requirements. Conversely, at low temperatures, the electrolyte may solidify or thicken, resulting in poor performance and even open circuits. In electronic devices used in cold regions, such as outdoor surveillance cameras, surface mount capacitors may fail at low temperatures, affecting the device's normal monitoring functions.
Humidity
The impact of humidity on surface-mount capacitors cannot be ignored. When electronic devices are in high-humidity environments, moisture may penetrate the capacitors. Moisture reacts chemically with the metal electrodes inside the capacitor, causing corrosion. Corrosion increases electrode resistance and can even lead to electrode breakage, resulting in capacitor failure. Moisture can also affect the capacitor's insulation performance, leading to increased leakage current. In electronic devices located in coastal areas, where air humidity is high, surface-mount capacitors are particularly susceptible to humidity-related issues, such as corrosion and leakage, reducing the reliability of the equipment.
Failure due to manufacturing defects
Material quality issues
The materials used in the manufacture of surface mount capacitors play a crucial role in their performance and reliability. Quality issues with the capacitor's dielectric or electrode materials, such as insufficient purity of the dielectric or poor conductivity of the electrode materials, can lead to capacitor failure during use. Low-quality dielectric materials can cause unstable insulation performance, making the capacitor prone to breakdown under electric fields. Quality problems with the electrode materials can result in weak connections between the electrodes and the dielectric, making them susceptible to separation under electrical or mechanical stress. In some low-cost electronic devices, the use of inferior surface mount capacitors significantly increases the probability of capacitor failure after a period of use.
Production process deviation
In the production of surface mount capacitors, deviations in the manufacturing process can also lead to capacitor failure. During manufacturing, uneven electrode thickness or positional deviations during electrode printing can affect the capacitor's electrical performance. Defects in the packaging process, such as poor bonding between the packaging material and the capacitor body, can allow moisture and impurities to penetrate the capacitor, causing failure. Improper process control during capacitor cutting and forming can create microcracks inside the capacitor. These microcracks may gradually expand during subsequent use, eventually leading to capacitor failure.
The failure of surface mount capacitors is caused by a combination of factors. Electrical stress, mechanical stress, environmental factors, and manufacturing defects can all affect the performance and reliability of surface mount capacitors, leading to their failure. To improve the reliability of electronic equipment, these factors need to be fully considered during the design, manufacturing, and use of electronic equipment, and corresponding measures need to be taken, such as rational circuit design, optimized soldering processes, and improved operating environments, to reduce the probability of surface mount capacitor failure and ensure the stable operation of electronic equipment. With the continuous development of electronic technology, the requirements for the performance and reliability of surface mount capacitors are becoming increasingly stringent. Future research needs to further investigate the failure mechanisms of surface mount capacitors, continuously improve manufacturing processes and materials, and enhance the quality and reliability of surface mount capacitors.
