When designing PCB pads in PCB board design, it is necessary to design strictly in accordance with relevant requirements and standards. Because PCB pad design is very important in SMT processing, pad design will directly affect the weldability, stability and heat transfer of components, related to the quality of SMT processing, so what is the DESIGN standard of PCB pad?

Design standard of shape and size of PCB pad:

1. Call PCB standard packaging library.

2, the minimum unilateral pad is not less than 0.25mm, the maximum diameter of the whole pad is not more than 3 times the aperture of the component.

3. Try to ensure that the distance between the edges of the two pads is greater than 0.4mm.

4. Pads with diameters exceeding 1.2mm or 3.0mm shall be designed as diamond or plum pads

5. In the case of dense wiring, oval and oblong connecting plates are recommended. The diameter or minimum width of single panel pad is 1.6mm; Double panel weak current line pad only need hole diameter plus 0.5mm, too large pad easy to cause unnecessary continuous welding.

Two, PCB pad through hole size standard:

The inner hole of the pad is generally not less than 0.6mm, because it is not easy to process when the hole is less than 0.6mm. Usually, the diameter of the metal pin plus 0.2mm is used as the inner hole diameter of the pad. If the metal pin diameter of the resistance is 0.5mm, the inner hole diameter of the pad is 0.7mm, and the diameter of the pad depends on the inner hole diameter.

Key points of reliability design of PCB pad

1. Symmetry, in order to ensure the surface tension balance of molten solder, both ends of the pad must be symmetrical.

2. Pad spacing, pad spacing is too large or too small will cause welding defects, so make sure the component ends or pins are properly spaced from the pad.

3. Residual size of pad. The residual size of component end or pin after lap with pad must ensure that the solder joint can form meniscus surface.

4. The width of the pad should be basically the same as the width of the component end or pin.

The correct PCB pad design, if there is a small amount of skew during SMT machining, can be corrected during reflow welding due to the surface tension of the molten solder. If the PCB pad design is not correct, even if the mounting position is very accurate, it is easy to appear component position deviation, suspension bridge and other welding defects after reflow welding. Therefore, PCB pad design should be paid attention to when designing PCB.