The chip capacitor is the most used component in SMT processing. In order to meet the needs of electronic products in the development direction of high-speed, miniaturization and low-cost, chip capacitors are also developing rapidly. The chip capacitor must play its role in the circuit board and ensure safe use.
What are the technical indicators of chip capacitors?
1. Capacity and deviation range
The maximum deviation range is between the nominal capacitance and the actual capacitance. Similar to the identification method of resistors, the accuracy grades of commonly used for chip capacitors are generally represented by English letters. Grade D, ±0.5%; Grade F, ±1%; Grade G, ±2%; Grade J, ±5%; Grade K, ±10%; Grade M, ±20%.
2. Insulation resistance
Indicating the degree of the current leakage. The smaller the capacity of the chip capacitor, the greater the insulation resistance, the smaller the leakage current. Generally in the range of several hundred megaohms to several gigaohms. Generally, the insulation resistance of electrolytic capacitors is small. The smaller the leakage, the better the performance of the chip capacitor.
3. Temperature coefficient
The change of capacitance value with temperature. Within a certain temperature range, the relative change value of the capacitance value for every temperature rise by one degree Celsius. For chip capacitors, the smaller the temperature coefficient, the better.
4. Rated working voltage
In the circuit, the maximum DC voltage that the capacitor can withstand for long-term stable operation. For chip capacitors with the same other conditions, the higher the rated working voltage, the larger the volume size.
5. Loss
In the circuit, the energy consumed by each chip capacitor due to heat. Generally comes from dielectric loss and metal loss.
6. Frequency characteristics
The characteristic that the value of the capacitance changes with different electric frequencies. For capacitors working in high-frequency circuits, because of the change in dielectric constant, the capacitance value will decrease accordingly, and the loss will increase with the increase in frequency. When working in a high-frequency circuit, the chip capacitor's own resistance, inductance and other factors will affect its performance. This also makes it necessary to consider the frequency characteristics of the circuit board when selecting chip capacitors.
7. Storage time
For very stable capacitors, the capacitance value does not change much with storage time. But for some unstable capacitors, the change in capacitance value can be as high as 5%~10% per 1000 hours of storage. But this kind of change is reversible. Before using the capacitor, preheat the capacitor in an environment of 150°C for 1 hour, and the capacitance value will return to normal.
The above technical indicators of chip capacitors used in SMT chip processing. After familiar with the various characteristics of capacitors, when choosing chip capacitors, you will not only consider price and volume, which will lead to incorrect selection of capacitors, which will affect the performance of the entire circuit.
