What are the design standards for PCB solder pads in surface mount processing?

Below, the electronic technician will organize and introduce for you.

1、 Design standards for the shape and size of PCB pads:

Call the PCB standard packaging library.

The minimum unilateral diameter of the solder pad shall not be less than 0.25mm, and the maximum diameter of the entire solder pad shall not exceed three times the aperture of the component.

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

Solder pads with apertures exceeding 1.2mm or pad diameters exceeding 3.0mm should be designed as diamond or plum shaped pads.

In the case of dense wiring, it is recommended to use elliptical and elongated connection plates. The diameter or minimum width of the single panel solder pad is 1.6mm; for the weak current circuit solder pad of the double-sided board, only the hole diameter needs to be increased by 0.5mm. If the solder pad is too large, it can easily cause unnecessary soldering.

2、 PCB pad via size standard:

The inner diameter of the solder 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 solder pad inner hole is calculated by adding 0.2mm to the diameter of the metal pin. For example, when the diameter of the metal pin of a resistor is 0.5mm, the corresponding diameter of the solder pad inner hole is 0.7mm, and the diameter of the solder pad depends on the diameter of the inner hole.

3、 Key points for reliability design of PCB pads:

Symmetry, in order to ensure the balance of surface tension of molten solder, the two end pads must be symmetrical.

The spacing between solder pads, whether too large or too small, can cause solder defects, so it is important to ensure that the distance between the component ends or pins and the solder pads is appropriate.

The remaining size of the solder pad, after the component end or pin overlaps with the solder pad, must ensure that the solder joint can form a meniscus.

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

The correct PCB pad design can be corrected during reflow soldering due to the surface tension of the molten solder if there is a small amount of skew during installation. If the PCB pad design is incorrect, even if the mounting position is very accurate, it is easy to have component position deviation, suspension bridge and other welding defects after reflow soldering. Therefore, great attention should be paid to the PCB pad design.

In SMT surface mount processing, the design of PCB pads is very important. The design of pads directly affects the solderability, stability, and heat transfer of components, and is related to the quality of surface mount processing. Therefore, when designing PCB pads, it is necessary to strictly follow the relevant requirements and standards for design