SMD capacitors, also known as SMD capacitors, surface mount capacitors, are usually yellow, black or light blue in appearance. It can be divided into two types: non-polar and polar. This article mainly discusses the difference between the positive and negative poles of polarized chip capacitors.

The positive and negative poles of the SMD aluminum electrolytic capacitor are distinguished and the black block with the mark on the measuring capacitor is the negative pole. There are two semicircles on the capacitor position on the PCB, and the pin corresponding to the colored semicircle is the negative pole. It is also useful to use the length of the pins to distinguish the positive and negative long legs as positive and the short legs as negative.

When we do not know the positive and negative poles of the capacitor, we can measure it with a multimeter. The medium between the two poles of the capacitor is not an absolute insulator, and its resistance is not infinite, but a finite value, generally above 1000 megohms. The resistance between the two poles of a capacitor is called insulation resistance or leakage resistance. The leakage current of the electrolytic capacitor is small (large leakage resistance) only when the positive terminal of the electrolytic capacitor is connected to the positive power supply (black test pen when the electric block is used) and the negative terminal is connected to the negative power supply (the red test pen when the electric block is used). On the contrary, the leakage current of the electrolytic capacitor increases (the leakage resistance decreases). In this way, we first assume that a certain pole is the "+" pole, the pointer multimeter selects R*100 or R*1K block, and then the assumed "+" pole is connected to the black test lead of the multimeter, and the other electrode is connected to the red test lead of the multimeter. Connect, write down the scale at which the needle stops (the resistance value of the needle on the left is large), (for a digital multimeter, the reading can be read directly.) Then discharge the capacitor (touch the two leads), then switch the two test pens, and repeat Measurement. In the two measurements, when the last position of the watch needle is to the left (or the resistance value is large), the black watch lead is connected to the positive electrode of the electrolytic capacitor.

One is a common tantalum capacitor, which is in the shape of a cuboid, and the end marked with "-" is positive. You can take a look at the pictures I posted;

There is also a silver surface mount capacitor, which should be aluminum electrolysis. The top is round and the bottom is square, which is very common on optical drive circuit boards. This kind of capacitance is marked with "-" and the end is negative.

Polar capacitors are what we usually call electrolytic capacitors. Generally, we usually use aluminum electrolytic capacitors the most. Because the electrolyte is aluminum, its temperature stability and accuracy are not very high. It is close to the circuit board, so the temperature stability is required to be high, so the chip capacitors are mostly tantalum capacitors. According to their different withstand voltages, the chip capacitors can be divided into four series: A, B, C, and D. :

Type Package Withstand Voltage

A. 3216, 10V

B. 3528, 16V

C. 6032, 25V

D. 7343, 35V

The package of chip tantalum capacitors is divided into A type (3216), B type (3528), C type (6032), D type (7343), E type (7845). The beveled angle indicates the positive pole.

It can be judged from the feet, the long one is the positive pole and the short one is the negative pole. On the capacitor body, the one with half of the color paint is the negative pole.