Matters Needing Attention in Selection of Thin Film Capacitor(II)

3. Selection of capacitor capacity and lead span:

1) the capacity selection shall be in accordance with the E24 series values of: 1.0, 1.1, 1.2 / 1.31,1.51.6, 1.8,2.0, 2.2, 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 a total of 24 levels, in which the following crossbar values are E12 series values, which are the preferred series values.

2) the range of capacity values shall be in accordance with the capacity range given in the generic specification for all types of capacitors:

The upper and lower limits of capacity may vary slightly from the specifications provided by different manufacturers, but if the capacity selection value is significantly lower than the lower limit of the class, it should be selected in ceramic capacitors, On the contrary, if the capacity value is higher than the upper limit of this category, it should be selected in the electrolytic capacitor.

3) how to select the foot distance of wire forming:

For different types of thin film capacitors of different specifications, the normal lead spacing P has definite values in the manufacturer's specifications, but in practical use, according to the PCB assembly requirements, manufacturers can be required to form and supply. The size requirement of the foot distance F is given. However, because the user does not consider the actual value of the natural foot distance P of the capacitance, and makes the forming foot distance F value at will, many unreasonable molding dimensions exist, which affect the effect of the process assembly and cause great difficulties for the supplier to supply. This shall attract the attention of the user and require that the molding foot distance F should be as close as possible to the conventional foot spacing of the capacitance, and must comply with the following molding criteria:

When P ≥ F, P F ≤ 8mm(F is 2. 5 times;

When P < F, F-P ≤ 5mm(F is 2. 5 times).

In conclusion, the selection of thin film container must be based on the full understanding of the characteristic parameters of all kinds of capacitors and can determine the working conditions of the circuit. At the same time, the principle of standardization and generalization must be taken into account.