How to choose PCB materials and electronic components correctly?

1. Selection of PCB materials

For normal electronic products, you can choose FR4 epoxy fiberglass substrate; for high ambient temperature or flexible circuit board, you can choose polyimide fiberglass substrate; for high frequency circuits, you can choose Polytetrafluoroethylene fiberglass wiki board; for electronic products requiring high heat dissipation, you can choose Metal substrate.

Factors to be considered when selecting PCB materials:

(1) Substrates with higher glass transition temperature (Tg) should be appropriately selected, and Tg should be higher than the operating temperature of the circuit.

(2) Low coefficient of thermal expansion (CTE) is required. Because the thermal expansion coefficient of X, Y and thickness direction is inconsistent, it is easy to cause the deformation of PCB, and in serious cases, it will cause the fracture of metallized holes and damage components.

(3) High heat resistance is required. PCB is generally required to have 250℃ / 50S heat resistance.

(4) Good flatness is required. The PCB warpage of THE SMT must be less than 0.0075mm/mm.

(5) In terms of electrical performance, materials with high dielectric constant and small dielectric loss are required for high-frequency circuits. Insulation resistance, voltage resistance and arc resistance should meet product requirements.

2. Selection of electronic components

In addition to meeting the requirements of electrical performance, the components should also meet the requirements of surface assembly. The packaging form, size and packaging form of components should also be selected according to the equipment conditions of the production line and the technological process of the product. For example, thin and small-sized components need to be selected for high-density assembly; and if the mounting machine does not have a wide-size braided tape feeder, the BRaided SMD devices cannot be selected.