PCBA Tech - What are the factors for PCBA to select capacitors

What are the factors for PCBA to select capacitors
1, PCBA processing capacitance selection

In electronic circuits, the capacitance is determined according to certain performance indicators. When determining the capacitance, it should be selected according to the nominal series. If the capacity value of the capacitor cannot be found through the nominal series, it can be solved by series-parallel method or by modifying other parameters in the design scheme. When replacing the capacitor in the circuit, it is best to select the capacitor with the original parameter or the component whose performance index is better than that of the original circuit capacitor.

2, PCBA processing capacitor withstand voltage selection

When selecting capacitors for PCBA processing, the withstand voltage of the components must be higher than the working voltage in the actual circuit. It is especially worth noting that the high voltage that may be generated in the electronic circuit should be considered.

3. PCBA processing capacitor medium selection

Different capacitors have different characteristics and different uses. When choosing the medium of the capacitor, we must first understand the characteristics of each medium, and then determine which occasion it is suitable for.

Electrolytic capacitors use metals such as aluminum as the positive electrode, and an oxide film is formed on its surface as the medium. The medium and the electrode become an inseparable whole; the negative electrode is a solid or non-solid electrolyte. Since the materials of the two electrodes constituting the electrolytic capacitor are different, its positive and negative electrodes are marked separately. When using, the positive terminal must be connected to the high potential of the circuit, and the negative terminal must be connected to the low potential of the circuit, otherwise it will cause damage to the capacitor. According to the different electrode materials, there are aluminum electrolytic capacitors, tantalum electrolytic capacitors and niobium electrolytic capacitors.

Mica capacitors are capacitors with mica sheets as the medium. It has good insulation performance, low loss, good temperature stability, and high capacitance accuracy. It is commonly used in high-frequency oscillation circuits.

The medium of the ceramic capacitor is ceramic, and it can be divided into high frequency ceramic capacitor and low frequency ceramic capacitor according to the different ceramic composition (high frequency is represented by CC, and low frequency is represented by CT). The capacitance of high-frequency ceramic dielectric capacitors is between a few tenths of a picofarad to a few hundred picofarads. It is often used in occasions that require low loss and stable capacitance and as tuning capacitors, tank capacitors and temperature compensation capacitors in high-frequency circuits. There are several types of capacitor withstand voltage such as 160V, 250V and 500V. The capacity error is divided into 2%, 5%, 10% and 20%. The capacitance of low-frequency ceramic capacitors ranges from 300pF to 22000pF, suitable for low-frequency circuits.
The production process of paper dielectric capacitors is simple, low cost, and wide voltage range; the disadvantage is that the capacitance is not easy to control, the loss is large, the stability is poor, and the inductance is the largest, and it is usually not suitable for use at high frequencies.

Polyester capacitors are also called polyester capacitors. It is a capacitor with polyester film as the medium. It can be used in the coupling, decoupling, bypass, DC blocking and other circuits of various electronic instruments, televisions, and radios. At present, the country has higher and higher requirements for environmental protection and greater efforts in link governance. This is a challenge but also an opportunity for PCB factories. If PCB factories are determined to solve the problem of environmental pollution, then FPC flexible circuit board products can be at the forefront of the market, and PCB factories can get opportunities for further development.