Application and Working Principle of Surface Mount Electrolytic Capacitors

PublishTime： 2024-10-23 Article Source：XIANGRU ELECTRONICS Official Website

Surface Mount Electrolytic Capacitors are usually made of metal foil (aluminum/tantalum) as the positive electrode, and the insulating oxide layer of the metal foil (aluminum oxide/tantalum pentoxide) as the dielectric. Surface mount electrolytic capacitors are divided into surface mount aluminum electrolytic capacitors and tantalum electrolytic capacitors based on their different positive electrodes. The negative electrode of the surface mount aluminum electrolytic capacitor is composed of thin paper/film or electrolyte polymer immersed in electrolyte solution (liquid electrolyte); The negative electrode of tantalum electrolytic capacitors is usually made of manganese dioxide. Due to the use of electrolytes as negative electrodes (distinguishing them from dielectrics), surface mount electrolytic capacitors are named after them.

Polarized surface mount electrolytic capacitors are commonly used in power circuits or mid - and low-frequency circuits for power filtering, decoupling, signal coupling, time constant setting, DC isolation, and other purposes. Surface mount electrolytic capacitors are generally not suitable for use in AC power circuits. When used as filtering capacitors in DC power circuits, their anode (positive pole) should be connected to the positive terminal of the power supply voltage, and their cathode (negative pole) should be connected to the negative terminal of the power supply voltage, and cannot be reversed, otherwise the capacitor will be damaged. Non polarized surface mount electrolytic capacitors are commonly used in speaker frequency divider circuits, TV S-calibration circuits, and single-phase motor starting circuits. Surface mount electrolytic capacitors are widely used in household appliances and various electronic products, with a large capacity range of generally 1-1000 μ F and a rated operating voltage range of 6.3-450V. Its disadvantages are high dielectric loss, large capacity error (maximum allowable deviation is+100%, -20%), poor high temperature resistance, and easy failure after long storage time. The polarity of surface mount electrolytic capacitors should be observed with a "-" on the side of the capacitor, which is the negative pole. If the positive and negative poles of the electrolytic capacitor are not marked, it can also be judged based on the length of its pins. When the positive pole of the electrolytic capacitor is connected to the positive power supply (black probe in resistance mode) and the negative terminal is connected to the negative power supply (red probe in resistance mode), the leakage current of the surface mount electrolytic capacitor is small (large leakage resistance). On the contrary, the leakage current of the electrolytic capacitor increases (leakage resistance decreases). When measuring, first assume that a certain pole is the "+" pole, connect it to the black probe of the multimeter, and connect the other electrode to the red probe of the multimeter. Record the scale at which the probe stops (the resistance value is higher on the left side of the probe), then discharge the capacitor (i.e. touch the two leads), swap the two probes, and measure again. In the two measurements, the black probe was connected to the positive terminal of the surface mount electrolytic capacitor on the one where the needle stayed to the left (with a high resistance value).

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