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What is the PCB pad design standard

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 pad is very important in SMT chip processing, which will directly affect the solderability, stability and heat transfer of components and the chip processing quality, what is the design standard of PCB pad?

 I. design standards for the shape and size of PCB pads:

      1. call PCB standard packaging library.
      2. The minimum single side of the bonding pad is not less than 0.25mm, and the maximum diameter of the whole bonding 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 exceeding 1.2mm or a pad diameter exceeding 3.0mm shall be designed as diamond or quincunx pads

      5. In the case of dense wiring, it is recommended to use oval and oblong connection pads. The diameter or minimum width of single panel pad is 1.6mm; The weak current circuit pad of double panel only needs hole diameter plus 0.5mm, too large pad will easily lead to unnecessary connection welding.

 Ⅱ. PCB pad via size standard:

he inner hole of the pad is generally not less than 0.6mm, because holes smaller than 0.6mm are difficult 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.

Ⅲ. reliability design points of PCB pads:

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

2. The gap between pads, which is too large or too small, will cause welding defects. Therefore, it is necessary to ensure that the gap between component ends or pins and pads is appropriate.

3. The remaining size of the pad, the remaining size after the component end or pin is overlapped with the pad, must ensure that the solder joint can form 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 due to the surface tension of molten solder during reflow soldering. However, if the PCB pad design is incorrect, even if the mounting position is very accurate, welding defects such as component position deviation and suspension bridge will easily occur after reflow soldering, so it is necessary to pay great attention to the PCB pad design.


Post time: Sep-14-2020