Pad design in PCB design

When designing PCB pads in PCB board design, it is necessary to design strictly accordance with relevant requirements. Because in the SMT processing, the design of the PCB pad is very important, the pad design will directly affect the solderability, stability and thermal energy transfer of the component, ralated to the SMT quality. So what is PCB pad design standard?

First, the design criteria of the shape and size of the PCB pad:

1. Refer to the PCB standard package library.
2. There is a minimum of 0.25mm on one side of the pad, and the maximum diameter of the whole pad is not more than 3 times the aperture of the element.
3. Try to ensure that the distance between the edges of the two pads is greater than 0.4mm.
4. Pads with a hole diameter of more than 1.2 mm or a pad diameter of more than 3.0 mm should be designed as diamond or plum-shaped pads.
5. In the case of dense wiring, it is recommended to use oval and oblong lands. The diameter or minimum width of the single-panel pad is 1.6mm; the weak-circuit pad of the double-panel requires only 0.5mm of the hole diameter, and the excessively large pad may cause unnecessary soldering.

Second, the 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 difficult to process when punching, and the metal pin diameter value plus 0.2mm is usually used as the hole diameter of the pad, such as when the metal pin diameter is 0.5 mm of the resistor, the hole diameter of the pad corresponds to 0.7 mm, and the diameter of the pad depends on the diameter of the inner hole.

Third, the reliability of the PCB pad design points:

1. Symmetry: in order to ensure the balance of the surface tension of the molten solder, the pads at both ends must be symmetrical.
2. Pad pitch: if the pitch of the pad is too large or too small, it will cause soldering defects, so we need to make sure that the component terminals or pins are properly spaced from the pads.
3. The remaining dimensions of the pad: the remaining dimensions of the component terminals or pins after bonding to the pads must ensure that the solder joints can form a meniscus.
4. The pad width should be substantially the same as the width of the component terminals or pins.

The correct PCB pad design, if there is a small amount of crook during the processing of the SMT, it can be corrected by the surface tension of the molten solder during reflow. If the PCB pad design is not correct, even if the placement position is very accurate, after the reflow, it is easy to have component position offset, suspension bridge and other soldering defects. Therefore, when designing the PCB, the PCB pad design needs pay a lot of attention.

Kindly please feel free to contact Kola@sdy-pcb.com or our engineer if you want more information on Pad design in PCB design.