Do you know how to correctly design the shape of PCB pads when designing a PCB? How should the standards for the size of these pads be designed?

Pads are the basic building blocks of surface - mount assembly on a PCB. On a printed circuit board, the electrical connections of almost all surface - mount device (SMD) components are made through pads. So, how should the shape of pads be designed in PCB design? What are the standards for the design size? PCBMATER will explain the techniques involved for you.

I. Pad Shapes

The design of PCB pads can be basically divided into 7 categories according to their shapes as follows:

1. Square Pads

This type of pad design can be used when the components on the printed circuit board are large in volume, small in overall quantity, and the printed wires on the printed circuit board are simple.

2. Round Pads

Widely used in single - and double - sided printed circuit boards where components are arranged regularly.

3. Island - shaped Pads

The connections between pads are integrated into one. It is commonly used in vertical and irregularly arranged installations.

4. Teardrop - shaped Pads

Often adopted when the connected lines are thin, and commonly used in high - frequency PCBs.

5. Polygonal Pads

Used to distinguish pads with similar outer diameters but different hole diameters, which is convenient for processing and assembly.

6. Oval Pads

This type of pad has enough area to enhance the anti - peeling ability and is commonly used for dual - in - line packages.

7. Plum - blossom - shaped Pads

When the fixing hole needs to be metallized and connected to GND, if the fixing hole is fully metallized, it is easy to block the hole during reflow soldering. Using an internal metal screw hole may cause poor grounding due to installation or multiple disassembly and assembly. However, with a plum - blossom - shaped pad, good grounding can be ensured regardless of how the stress changes.  

II. Design Standards for Pad Shapes and Sizes

1. The minimum unilateral size of all pads should not be less than 0.25mm, and the maximum diameter of the entire pad should not be more than 3 times the component hole diameter.

2. The distance between the edges of two pads should be greater than 0.4mm as much as possible.

3. In the case of dense wiring, oval and oblong pads are recommended.

4. For plug - in components, to avoid the phenomenon of copper foil breakage during soldering, the single - sided connection pads should be completely covered with copper foil, and for double - sided boards, at a minimum, teardrops should be added.

5. All machine - inserted parts should be designed as teardrop - shaped pads along the direction of the bent pins to ensure full solder joints at the bent - pin positions.

6. Pads on large - area copper planes should adopt chrysanthemum - shaped pads to prevent cold soldering.

The above are the relevant requirements for the design standards of pad shapes and sizes in PCB design introduced to you by PCBMASTER. Hope it helps you.