Impedance z is one of the four basic parameters of capacitor, to be exact, it is equivalent series resistance ESR. Because the ESR of electrolytic capacitor is relatively large, it is directly replaced by impedance, and impedance z is the composite value of capacitive reactance, inductive reactance and equivalent series resistance.

The significance of testing impedance lies in:

1, large impedance means large charging and discharging resistance, which will affect the charging and discharging speed and easily lead to insufficient power supply when responding quickly;

2. The large impedance means that the capacitor consumes more electric energy to generate heat when working, which leads to the decrease of ripple resistance of the capacitor, which is not conducive to the design of the filter circuit.

Capacitive impedance consists of three parts:

1, material impedance, including the material of the pin, and the conductivity of different metal materials is different. During the test, the fixture clamps two leads. Generally speaking, copper-silver plating is the best, followed by pure copper tin plating, copper-clad steel tin plating and iron tin plating. Of course, due to the cost, most capacitors use tin-plated iron leads;

2, electrolyte impedance, mainly refers to the electrolyte, because the electrolyte is the actual cathode of the capacitor, that is to say, the negative charge is concentrated on the electrolyte, so the impedance of the electrolyte is dominant for the electrolytic capacitor. After the conductive polymer is used to replace the electrolyte in the solid-state capacitor, the impedance of the electrolyte becomes very low.

3. The structural impedance, as the name implies, is the influence caused by the processing technology, mainly including the tightness of the winding, the pinning impedance of the lead and aluminum foil, and so on.

Then from the above description, we can clearly understand the factors that lead to the change of capacitance impedance:

1. lead material decreases with the increase of lead conductivity;

2. When the electrolyte dries up, the smaller the electrolyte fullness, the greater the impedance;

3. The type of electrolyte, bad electrolyte formula or polluted electrolyte will increase the impedance;

4. If the winding is not tight, the ability of electrolytic paper to store electrolyte will decrease, which is similar to the principle of electrolyte drying, and the impedance will increase;

5, poor nailing, large impedance;

6. Another possibility is local burr short circuit, which leads to the formation of negative aluminum foil and the increase of ESR during charging.

To sum up, the abnormal impedance of the capacitor is mostly formed in the production stage, and the electrolyte is mainly exhausted at the user end, which means that the service life will be exhausted.

PS: After typing so many words, you gave too few points.