How to choose electronic components

The selection of components should be based on the circuit requirements of the specific product, as well as the size of the PCB, the density and type of the assembly, the grade of the product and the cost of the input.

1. Selection of SMC.

A. Pay attention to the size and accuracy of the size, and consider satisfying the functions of the placement machine.

B. Tantalum and aluminum electrolytic capacitors are mainly used where the capacitance is the largest.

C. Film capacitors are used in places with high heat resistance requirements

D. Mica capacitors are used in mobile communications with high Q values

E. The wave soldering process must choose a three-layer metal electrode soldered end structure chip component

2.SMD selection.

A. Small outline package transistor: SOT23 is the most commonly used transistor package, SOT143 is used for RF.

B.SOP, SOJ: It is a reduced version of DIP, which is similar to DIP.

C. QFP: Large occupied area, pins are easily deformed and easy to lose coplanarity; but the flexibility of the pins can help release stress and improve the reliability of solder joints. The minimum pitch of QFP pins is 0.3mm, currently 0.5mm has been widely used, 0.3mm, 0.4mm solder joint reliability. QFP is gradually being replaced by BGA. When selecting, you should pay attention to whether the accuracy of the placement machine meets the requirements.

D. PLCC: small area, pin is not easy to deform, but detection is not convenient

E.LCCC: Expensive, mainly used for high reliability and military products. CET issues between devices and circuit boards should be considered. .

F.BGA, CSP: suitable for circuits with high I / O

3.Selection of chip electromechanical components

Chip electromechanical components are mainly used in high-density, small-volume, light-weight electronic products.

4.THC (Insert Components) The selection of high-power devices, electromechanical components and special devices is not yet mature, and we must use insert components.