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Positive and negative pole judgment method of SMD aluminum Electrolytic capacitor


When we don't knowcapacitanceWhen measuring the positive and negative poles, a multimeter can be used to measure. The medium between the two poles of a capacitor is not an absolute insulator, and its resistance is not infinite, but a finite value, usually above 1000 megaohms. The resistance between the two poles of a capacitor is called insulation resistance or leakage resistance. Only the positive terminal of the Electrolytic capacitor is connected to the positive side of the power supply (black probe in resistance gear), and the negative terminal is connected to the negative side of the power supply (red probe in resistance gear),Electrolytic capacitorThe leakage current is only small (the leakage resistance is large). On the contrary, the leakage current of Electrolytic capacitor increases (the leakage resistance decreases). In this way, we first assume that a certain pole is the "" pole, and the multimeter uses R * 100 or R * 1K gear. Then, connect the assumed "" pole to the black lead of the multimeter, and the other pole to the red lead of the multimeter. Record the scale at which the needle stops (the resistance value on the left side of the needle is high), and for a digital multimeter, the reading can be directly read. Then discharge the capacitor (touch the two leads), and then switch the two probes to perform a new measurement. In the two measurements, the black probe is connected to the positive pole of the Electrolytic capacitor when the last position of the probe is left (or the resistance is high).


Differentiation between positive and negative electrodes of SMD capacitors

One is the common tantalum capacitor, which is in the shape of Rectangular cuboid, and the end marked with "-" is positive;

Additionally, there is a silver surface mount capacitor, presumably aluminum electrolysis. The top is circular and the bottom is square, which is common on optical drive circuit boards. This type of capacitor has a negative end marked with "-".


Capacitance: can be divided into two categories: non-polar and polar:

The following two types of packages are most common for non-polar capacitors, namely 0805 and 0603;

Polar capacitors, also known as what we usually callElectrolytic capacitorGenerally, aluminum Electrolytic capacitor is the most commonly used one. Since its electrolyte is aluminum, its temperature stability and accuracy are not very high. However, since the patch element is close to the circuit board, it requires high temperature stabilityChip capacitorwithTantalum capacitorAccording to their different withstand voltages, SMD capacitors can be divided into four series: A, B, C, and D, with specific classifications as follows:

Type, packaging form, withstand voltage

A 3216 10V

B 3528 16V

C 6032 25V

D 7343 35V

  Chip tantalum capacitorThe packaging is divided into A type (3216), B type (3528), C type (6032), D type (7343), and E type (7845). The one with a diagonal angle represents the positive pole, (the one with a small triangle represents the positive pole? I don't know!)

Dial switch, crystal oscillator: Different specifications of SMD packaging can be found in the market, and their performance and price will be related to their pin coating, nominal frequency, and segment.

You can tell from your feet that the long one is the positive pole and the short one is the negative pole On the capacitor body, the negative electrode is coated with half of the color

The term solid-state electrolysis or liquid capacitor refers to the material used for its cathode. The advantage of using electrolyte as a cathode is that the capacitance can be very large. However, electrolyte is prone to volatilization and leakage in high-temperature environments, which greatly affects its lifespan and stability. Solid state capacitors use functional conductive polymers as dielectric materials, which do not cause slurry explosion when energized without long-term use. Moreover, at low temperatures, solid-state capacitors will not fail to achieve their expected characteristics and functions due to the slow movement of electrolyte ions. Compared to liquid electrolytes, solid-state capacitors have superior characteristics such as environmental protection, low impedance, high and low temperature stability, high ripple resistance, and high reliability.


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