Considering the use requirements of reliability derating, it is usually required that the actual working voltage should be less than 80% of the rated voltage.
2. Selection of capacitor working voltage: The pulse voltage and withstand voltage of the capacitor are limited by the rated current of the capacitor because of the loss of the thin-film capacitor. If a large current passes through the capacitor, the thin-film capacitor itself will heat up, and in severe cases, there will be dangers such as thermal breakdown (smoke, breakdown).
When using, ensure that these two voltages are within the allowable range.
If the actual working voltage (current) waveform cannot be determined, it can be determined by the temperature rise of the capacitor itself. Generally, for polyester capacitors, the self-temperature rise is allowed to be lower than 10C.
For polypropylene capacitor, it is allowed to be used under the condition that its temperature rise is less than 5℃
(The actual measurement shall be carried out on the surface of the lead welding part of the capacitor end face) 3. Selection of capacitor capacity and lead span: 1) The selection of capacity must be within the range of E24 series values: 1.0,1.2,1.3,65438+. 2.4, 2.7, 3.0, 3.3, 3.6, 3.9, 4.3, 4.7, 5. 1, 5.6, 6.2, 6.8, 7.5, 8.2, 9. 1 * * 24, in which E6554 is in.
2) The range of capacity values should conform to the range given in the general specifications of various capacitors: the specifications provided by different manufacturers may have slightly different upper and lower limits of capacity, but if the selected capacity value is obviously lower than the lower limit value of this category, it should be selected from ceramic capacitors; conversely, if the selected capacity value is higher than the upper limit value of this category, it should be selected from electrolytic capacitors.
3) Selection of lead molding foot distance: The conventional lead spacing p of different types and specifications of thin film capacitors has a certain value in the manufacturer's manual, but in actual use, according to the PCB assembly requirements, the manufacturer can be required to supply lead molding, and the size requirements of the molding foot spacing f are given.
However, because the user does not consider the actual value of the natural pin spacing p of the capacitor and arbitrarily sets the value of the molding pin spacing f, the molding size is unreasonable, which not only affects the process assembly effect, but also causes great difficulties for suppliers, and must be highly valued by users. It is required that the molding needle pitch f be as close as possible to the conventional needle pitch p of capacitors, and the following molding standards must be followed: when P≥F, P-F≤8mm(F value is an integer multiple of 2.5) when P.