Pinsheng Electronics Co.,Ltd
When designing the PCB pad, the PCB pad needs to be designed in strict accordance with the relevant standards.
Because the design of PCB pads is very important in SMT SMT processing, the design of the pads will directly affect the weldability, stability and heat transfer of the components, and affect the quality of SMT processing. What is the design standard of PCB pads?
I. design standards for shape and size of PCB pads:
1. Call the PCB standard package library.
2. The single side of the welding plate shall be no less than 0.25mm, and the diameter of the whole welding plate shall be no more than 3 times of the element aperture.
3. Try to ensure that the distance between the edge of the two pads is greater than 0.4mm.
4. Welding pads with an aperture of more than 1.2mm or a pad diameter of more than 3.0mm shall be designed as diamond or plum pads
5. Oval and oblong connection plates are recommended for tight wiring.
The diameter or minimum width of the single panel pad is 1.6mm;
Only 0.5mm of hole diameter is needed for the weak-current line welding pad of double panel. Too large welding pad is easy to cause unnecessary welding.
Ii. Standard of overhole size of PCB pad:
Generally, the inner hole of the welding plate is not less than 0.6mm, because it is not easy to process when the die punching hole is smaller than 0.6mm. Usually, the diameter of the metal pin plus 0.2mm is taken as the diameter of the inner hole of the welding plate.
3. Key points of reliability design of PCB pad:
1. Symmetry. In order to ensure the balance of surface tension of molten solder, both ends of solder plates must be symmetrical.
2. Pad spacing, too large or too small pad spacing will cause welding defects, so make sure that the element end or pins are properly spaced from the pad.
3. The remaining dimensions of the pad, and the remaining dimensions of the component end or pin after lap joint with the pad must ensure that the welding spot can form a curved surface.
4. The width of the pad should be basically consistent with the width of the component end or pin.
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Correct PCB pad design. If there is a small amount of skew during patch processing, it can be corrected during reflow soldering due to surface tension of molten solder.
However, if the design of the PCB pad is not correct, even if the mounting position is very accurate, the component position deviation, suspension bridge and other welding defects will easily occur after the re-flow welding. Therefore, great attention should be paid to the design of the PCB pad during PCB design.
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