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SMD aluminum electrolytic capacitors are also known as chip capacitors, commonly used are multi-layer ceramic capacitors, high-frequency cylindrical capacitors, chip-like polyester capacitors, chip-like electrolytic capacitors, chip-like tantalum electrolytic capacitors, chip-like micro-adjustable capacitors and so on. It is widely used in circuit design. This paper introduces some matters needing attention in the use of chip capacitors.
Flake capacitor is also called chip capacitor, commonly used are multi-layer ceramic capacitor, high-frequency cylindrical capacitor, chip-like polyester capacitor, chip-like electrolytic capacitor, chip-like tantalum electrolytic capacitor, chip-like fine-tuning capacitor and so on.
Attention should be paid to the use of flake capacitors.
(1) the working voltage of the capacitor must be lower than the rated voltage and should not exceed the rated voltage. For example, when the working voltage is 12V, the rated voltage is 16-25V; when the working voltage is 5V, the rated voltage is 6-10V; when the working voltage is 3.3V, the rated voltage is 4-6V. In addition, the capacitance of the capacitor is also related to the voltage value. For example, the flake tantalum capacitor withstands voltage 4-50V, 0.1-4.7uF small capacity capacitor has rated voltage of 50V, and 10 pF above, withstand voltage value higher than 25V is rarely seen. Therefore, attention should be paid to circuit design.
(2) chip capacitors can replace small voltages with large voltages. For example, the circuit needs a 10V 1UF capacitor, which can be replaced by the 1UF capacitor of 16V.
(3) capacitor accuracy and material category should be chosen reasonably. The accuracy of commercial chip capacitors below 0.01 uF can reach J (+5%); above 0.01 uF, J class is less, with K class (+lO%) more; above 0.1 uF, M class (+20%) more.
(4) The capacity specifications (series) of the chip capacitors with size code 0805 are the most complete on the market, and some of the capacity of 0603 may be out of stock. When the production lot size is small, in order to prevent the shortage of the market and affect production, the pad can be slightly extended, so that it can be applied to 0603 and 0805, to avoid the absence of parts and stop production.
(5) Flaky multi-layer ceramic capacitors are all rolled-in, the type is on the tape disc, and there is no sign on the capacitor. Although the capacity can be measured by measuring methods, it is difficult to distinguish the accuracy grade of material categories. Therefore, be careful when using it, especially manual assembly.
(6) Open-type slice-type fine-tuning capacitor can not be welded by wave soldering, but closed-type slice-type fine-tuning capacitor can be welded by wave soldering.
(7) Lamellar capacitors are generally multi-layer structure, some people use soldering iron manual welding, at this time must pay attention to the welding speed, avoid overheating, resulting in a large temperature difference and fracture of the base end, so that capacity decline.
(8) chip capacitors are made of ceramic substrates, thin and crisp. Some of the circuit boards are thin, and the force will be deformed when they are installed, which will easily cause the capacitor to break. Solution: In addition to improving the design process, can also easily cause breakage in places where the use of tubular capacitor, because the strength of tubular capacitor is high, not easy to break.