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What are the functions of the "lead" of SMD capacitors?

Date: 2024-09-06
At present, new products such as the automotive industry, medical equipment, household appliances, and consumer electronics are emerging in an endless stream, and SMD capacitors will be used in these fields. The main function of SMD capacitors is beneficial to electronic products. For example, bypass, coupler, filtering, storage capacity, etc., and its small size and large storage capacity are beneficial. SMD capacitors include SMD ceramic capacitors, SMD tantalum capacitors, and SMD aluminum electrolytic capacitors. What is the function of the lead of SMD capacitors? The following related content is for reference.

The interpretation of the "lead" function of SMD capacitors is as follows
1.When using SMD capacitors to suppress electromagnetic interference, the simplest problem is the effect of capacitor leads on the filtering effect. 
The capacitive reactance of the capacitor is inversely proportional to the frequency. Using this characteristic, the capacitor is connected in parallel between the signal line and the ground line to bypass high-frequency noise. In actual engineering, many people find that this method cannot filter noise as expected, and they are powerless in the face of stubborn electromagnetic noise. One of the reasons is that the effect of capacitor leads on the bypass function is ignored.

2.The impedance of the chip capacitor decreases with the increase of frequency. At lower frequencies, the characteristics of the capacitor, that is, the resistance decreases with the increase of frequency, and resonance occurs at a certain point. At this time, the impedance of the capacitor and other equivalent series resistance ESR occur. Above the resonance point, due to the effect of ESL, the capacitance impedance increases with the increase of frequency, resulting in the impedance characteristics of the inductor. 
Above the resonance point, due to the increase of capacitor impedance, the bypass effect on high-frequency noise is weakened.

3.The resonant frequency of the capacitor is determined by ESL and C-. The larger the capacitor and inductance, the lower the resonant frequency, that is, the worse the high-frequency wave effect of the capacitor. ESL is not only related to the type of capacitor, but also the length of the capacitor wire is a very important parameter. 
The longer the wire length, the larger the inductance, and the lower the capacitor resonant frequency. In actual engineering, the wire of the capacitor should be as short as possible, and the accurate and inaccurate installation methods of the capacitor should be improved.
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