1. The main manifestations of chip capacitor failure
In the actual maintenance of SMD capacitors, the main failures of capacitors are as follows:
- Open circuit failure caused by pin corrosion.
- Open circuit failure of desoldering and virtual welding.
- Low capacity or open circuit failure caused by liquid leakage.
- Leakage, serious leakage and breakdown faults
2. The parameters to be considered in the selection of chip capacitors
In circuit design, it is particularly important to choose the right chip capacitor. There are many parameters for chip capacitors. What kinds of parameters need to be considered in order to choose a suitable chip capacitor for the circuit? The following are the parameters of chip capacitors that need to be considered:
- Packaging of chip capacitors In each circuit, there should be fixed packaged chip capacitors, otherwise it will cause material loss due to uneven package size. Like common chip capacitor packages: 0201, 0402, 0603, 0805, 1206, 1210, 1812 , 2010, 2512, etc. However, in the actual industry, the chip capacitor of the package size should be selected according to the specific length, width and height of the appropriate circuit.
- The capacity of the chip capacitor The capacity parameter of the chip capacitor is also very important. Don’t think that the larger the chip capacitor is, the better, you should choose the appropriate chip capacitor capacity according to the actual circuit needs. The common units of the chip capacitor capacity are pF, nF and uF , Several capacity units can be converted mutually, and the conversion formula is: 1uF=1000nF=1000000pF.
- Error accuracy of chip capacitors The capacity error of the SMD capacitor is called the error accuracy of the SMD capacitor. The accuracy grades of the commonly used SMD capacitors are represented by letters. The accuracy of the numbers represented by different letters is different, respectively: D range 0.5%; F range ±1 %; J file ±5%; K file ±10%; M file ±20%, the allowable error of high-precision precision chip capacitors is small.
- The temperature coefficient of the chip capacitor When considering the parameters of chip capacitors, purchasers often ignore the temperature coefficient parameter. In fact, when we choose chip capacitors, we should properly consider the temperature coefficient of chip capacitors. Normally, within a certain temperature range, Every time the temperature changes by 1℃, the relative performance of the capacitor will also change accordingly. In fact, the smaller the temperature coefficient of the chip capacitor, the better.
- Frequency characteristics of chip capacitors It is the property that the electrical parameters of the capacitor change with the frequency of the electric field. The chip capacitor working under high frequency conditions, because the dielectric constant is lower at high frequency than at low frequency, the capacity of the chip capacitor is also reduced correspondingly, and the loss will also be Increase with increasing frequency. In addition, when working at high frequencies, other distribution parameters of the chip capacitor will affect the performance of the chip capacitor. For example, COG chip capacitors are more suitable for circuits in high frequency environments.