High-voltage chip capacitors are mainly used for power supply filtering, power supply voltage reduction, voltage doubling, and surge protection. The basic working principle is charging and discharging, and of course rectification, oscillation and other functions. It is used in power supply circuits to achieve bypass, decoupling, filtering and energy storage. It is often used in module power supplies, LCD high-voltage boards, resistor-capacitor step-down power supplies, (RR) inverters, automotive xenon lamps (electronic ballasts), Among products such as voice splitters, R Ethernet interfaces, digital camera flashes, Christmas light strings, energy-saving lamps, high-frequency electrodeless lamps, electronic ballasts and other products, SMD varistor C products are widely used in the fields of mobile phones and computer motherboards. Broad application prospects.
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Travel charger, desktop/desktop charger, car charger, corded charger, single B charger, dual port B charger, multi-port B charger, port C. Car charger fast charging car charging Device. Dual port car charger fast charging car charger, double B car charger fast charging car charger, single port B car charger. car charger, single port B car charger car charger, pull ring B car charger car charger special patch Ceramic capacitors replace tantalum capacitors with higher voltage resistance and more stable anti-breakdown performance.
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Special chip capacitors for air purifiers to replace electrolytic capacitors
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Quality control and failure analysis
< Passive components (&c)& occupy a very important position in electronic products. Although the material value of many passive components in the entire electronic product is not high, the failure of any insignificant component may lead to the failure of the entire system. The ratio of active components (C) and passive components in general electronic products is approximately:. This data illustrates the importance of quality control of passive components.
There are many types of passive components, and multilayer ceramic capacitors () are the most important and one of the most widely used products. In the typical structure, the conductor is generally a ceramic dielectric or a ceramic dielectric, which is formed by high-temperature sintering and multi-layer ceramic structure. The terminal coating of the device is generally sintered /, and then a barrier layer is prepared (to block the internal / material to prevent it from reacting with the outside), and then a layer B is prepared on the layer for welding. In recent years, products using C on the terminal have also appeared.
Classification
According to the capacitance value and stability, it is divided into, &R, &, etc. According to the size, it can be divided into equal parts.
Multilayer ceramic capacitors () have excellent inherent reliability and can be used stably for a long time. But if the device itself has defects or defects are introduced during the assembly process, it will have a serious impact on its reliability.
Intrinsic factors causing defects
. Cavities in ceramic media
The main factor causing voids is ceramic Organic or inorganic contamination in the powder, improper control of the sintering process, etc. The generation of cavities can easily lead to leakage, which in turn causes local heating inside the device, further reducing the insulation performance of the ceramic dielectric and resulting in increased leakage. This process occurs cyclically and continues to deteriorate. In severe cases, it can lead to serious consequences such as cracking, explosion, or even burning of multilayer ceramic capacitors.
. Sintering cracks&(r&c) Sintering cracks often originate from one end of the electrode and expand in the vertical direction. The main reason is related to the cooling rate during the sintering process. Cracks and hazards are similar to voids.
.Layering
The sintering of multilayer ceramic capacitors is the co-firing of multi-layer material stacks. The sintering temperature can be as high as ℃ or above. The interlayer bonding force is not strong, internal pollutants volatilize during the sintering process, and improper control of the sintering process may lead to delamination. Delamination has similar hazards to voids and cracks, and is an important inherent defect in multilayer ceramic capacitors.
.Temperature shock cracks (r&c)
Mainly caused by the temperature shock the device undergoes during soldering, especially wave soldering, and improper repair. An important cause of temperature shock cracks.
Multilayer ceramic capacitors are characterized by being able to withstand large compressive stress, but have poor resistance to bending. Any operation that may cause bending deformation during device assembly may cause device cracking. Common stress sources include: patch centering, people, equipment, gravity and other factors during the circuit board operation and circulation during the process, through-hole component insertion circuit testing, single board segmentation circuit board installation, circuit board positioning, riveting screw installation, etc. This type of crack generally originates from the upper and lower metallized ends of the device and propagates toward the interior of the device along the °C angle. This type of defect is also the most common type of defect that actually occurs.
(Chip multilayer ceramic capacitors, monolithic capacitors, chip capacitors, chip capacitors or chip capacitors)&Device failure analysis methods
< br/> Scanning Ultrasonic Analysis:
The scanning ultrasonic method is the most important non-destructive testing method for analyzing multilayer ceramic capacitors. Can detect voids, delaminations and horizontal cracks very effectively. Since the analysis principle of ultrasonic is mainly plane reflection, the resolution ability of vertical cracks such as most sintering cracks and bending cracks with large vertical components is not strong. At the same time, the detection of multilayer ceramic capacitors generally requires higher ultrasonic frequencies.
Methanol leak detection method:
For severe delamination or cracking, the methanol leak detection method can be used, that is, the failed device is immersed in methanol solution middle. Since methanol is a polar molecule and has strong penetrating power, it can penetrate into severely delaminated or cracked areas through capillary action. When powered on, a large leakage current is generated, which can aid in diagnosis.
Metallographic section method:
Metallographic section is not only the most classic but also the most effective failure analysis method for ceramic capacitors. The advantage is that through cross-section and corresponding optical or scanning electron microscope inspection, the composition, morphology and other fine structures of the failed parts can be obtained, thereby assisting in the analysis of the failure mechanism. However, its disadvantages are that the preparation is relatively complex, the preparation technology requirements are relatively high, and it is a destructive detection method. Figure & shows a typical case of metallographic cross-section analysis of the failure of multilayer ceramic capacitors.
Quality control of (chip multilayer ceramic capacitors, monolithic capacitors, chip capacitors, chip capacitors or chip capacitors)
Multilayer ceramic capacitors are characterized by superior reliability without inherent defects and without other defects introduced by the assembly process. But if defects exist, whether intrinsic or extrinsic, they can have a serious impact on device reliability. At the same time, potential defects in assembled ceramic capacitors are difficult to detect through non-destructive, online inspection, etc. Therefore, the quality control of multilayer ceramic capacitors must mainly be solved through preventive measures. Common preventive measures include:
. Carefully select suppliers, conduct regular sampling testing of their products, etc.
. Carefully analyze and effectively control all operations that may cause thermal stress and mechanical stress in the assembly process.
Taking into account the characteristics of multilayer ceramic capacitors, the detection of the device can mainly include:
Structural analysis: & that is, using gold Samples were sampled by means of phase profiling. You can have a comprehensive understanding of the manufacturing level and inherent defects of the device.
. Scanning ultrasonic analysis&:& can be very effective in detecting defects such as voids, delaminations, and horizontal cracks. Temperature resistance test examines device cracking and/or layering that may be caused by high temperature and temperature shock. Exposed defects. Bending test: &Assemble the device on the specified printed circuit board in accordance with relevant standards, and conduct a bending test to examine the device's ability to resist bending. Of course, there are many other testing indicators for ceramic capacitors, and inspection items can be added or reduced according to specific circumstances to achieve the most effective control at the lowest cost.
Main inspection and control items in the assembly process:
.Reflow or wave soldering temperature curve, general device
manufacturers will provide relevant suggestions curve. Through the accumulation and analysis of assembly yield, an optimized temperature curve can be obtained.
. In the assembly process, special attention needs to be paid to the operation and circulation of printed circuit boards, especially manual insertion, rivet connection, and manual cutting. If necessary, the product design may even need to be modified to maximize the avoidance of multilayer ceramic capacitors from areas that may generate greater mechanical stress during the process.
.Inspecting the electrical detection & C process during the assembly process, attention must be paid to minimizing the mechanical stress caused by mechanical contact at the test point.
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