The patch capacitor is one of the most widely used components in the circuit boards of electronic equipment nowadays. In order to meet the needs of high-speed, miniaturization and low-cost development of electronic products, patch capacitors are also developing rapidly. But the patch capacitor must play its own role in the circuit board to ensure the safety of use. What are the technical specifications of SMC?
1. Capacity and error:
Maximum deviation range between nominal capacitance and actual capacitance. Similar to the identification method of resistors, the accuracy level of commonly used patch capacitors is generally expressed in English letters. Grade D, +0.5%; Grade F, +1%; Grade G, +2%; Grade J, +5%; Grade K, +10%; Grade M, +20%.
2. Insulation resistance:
Indicators indicating the size of leakage. The smaller the capacity of the patch capacitor, the larger the insulation resistance, the smaller the leakage. Usually in hundreds of mega-ohms to several giga-ohms. Generally, the insulation resistance of electrolytic capacitors is small. The smaller the leakage, the better the performance of the patch capacitor.
3. Temperature coefficient:
Capacitance varies with temperature. Within a certain temperature range, the relative change of capacitance value for each temperature rise of one degree Celsius. For patch capacitors, the smaller the temperature coefficient, the better.
4. Rated operating voltage:
In the circuit, the capacitor can work stably for a long time to withstand the maximum DC voltage. For patch capacitors with the same other conditions, the higher the rated operating voltage, the larger the volume.
5. loss:
In the circuit, each patch capacitor consumes energy due to heating. It usually comes from dielectric loss and metal loss.
6. Frequency characteristics:
The characteristics of the patch capacitance changing with different electric field frequencies. Because of the change of dielectric constant, the capacitance value decreases correspondingly, and the loss increases with the increase of frequency. When working in high frequency circuit, the substrate resistance and inductance of the patch capacitor will affect its performance. This also makes it necessary to consider the frequency characteristics of the circuit board when choosing the patch capacitor.
7. Storage time
For very stable capacitors, the capacitance value changes little with storage time. But for some unstable capacitors, the change of capacitance value can be as high as 5%~10% per 1000 hours. But this kind of change is reversible. If the capacitor is preheated at 150 C for one hour before use, the capacitance will return to normal.
These are the technical specifications of some patch capacitors, familiar with the various characteristics of capacitors, in the selection of patch capacitors will not only consider the price and volume, but also lead to errors in the selection of capacitors, thereby affecting the performance of the entire circuit.
