Design standards of pads in PCB design

When designing PCB pads in PCB design, it is necessary to design them in strict accordance with relevant requirements and standards. Because the design of PCB pads is very important in SMT chip processing, which will directly affect the solderability, stability and heat transfer of components and the quality of chip processing, what is the PCB pad design standard? 1. Design standard of PCB pad shape and size: 1. Call PCB standard package library. 2. The minimum single side of the bonded pad is not less than 0.25mm, and the maximum diameter of the whole bonded pad is not more than 3 times of the component aperture. 3. Try to ensure that the distance between the edges of two pads is greater than 0.4mm. 4. Pads with an aperture of more than 1.2mm or a diameter of more than 3.0mm should be designed as diamond or quincunx pads. 5. In case of dense wiring, oval and oblong connecting pads are recommended. The diameter or minimum width of a single panel pad is 1.6mm; The weak current circuit pad of the double panel only needs the hole diameter plus 0.5mm Excessive pad is easy to cause unnecessary welding. Second, PCB pad via size standard:
The inner hole of the pad is generally not less than 0.6mm, because the hole smaller than 0.6mm is not easy to process when punching. Usually, the diameter of the metal pin plus 0.2mm is used as the inner hole diameter of the pad. For example, when the metal pin diameter of the resistor is 0.5mm, the inner hole diameter of the pad corresponds to 0.7mm, and the pad diameter depends on the inner hole diameter.  
3. Key points of reliability design of PCB pads: 1. Symmetry. To ensure the surface tension balance of molten solder, the pads at both ends must be symmetrical. 2. Pad spacing. Too large or too small a pad spacing will cause welding defects, so it is necessary to ensure the proper spacing between the terminal or pin of the component and the pad. 3. The remaining size of the pad, the remaining size of the component end or pin after overlapping with the pad must ensure that the solder joint can form a meniscus. 4. The width of the pad should be basically the same as the width of the component end or pin. Correct PCB pad design, if there is a small amount of skew during chip processing, can be corrected by the surface tension of molten solder during reflow soldering. However, if the PCB pad design is not correct, even if the mounting position is very accurate, soldering defects such as component position deviation and suspension bridge will easily occur after reflow soldering. Therefore, great attention should be paid to PCB pad design during PCB design.