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In PCB design, pads play a crucial role. While PCB engineers are well-acquainted with them, let's delve into the various types of pads and their design standards.

A pad is a conductive area on a PCB designed to connect components to the circuit board. It's a fundamental building block of surface mount assembly, forming the land pattern for various components.

1. Types of PCB Pads
Common Pads

1. Square Pads: Commonly used when components on the board are large, few, and the circuit traces are simple. These pads are easy to implement in handmade PCBs.
2. Circular Pads: Widely used in single and double-sided PCBs with regularly arranged components. Larger pads are preferred when board density allows, reducing the risk of detachment during soldering.
3. Island Pads: The connecting lines between pads are integrated into the pad itself. Often used for vertical, irregular arrangement mounting.
4. Polygon Pads: Used to differentiate between pads with similar outer diameters but different hole sizes, facilitating processing and assembly.
5. Oval Pads: These pads have sufficient area to enhance peel resistance and are commonly used for dual-in-line packages.
6. Open Pads: Often used to ensure that manually soldered pad holes are not sealed by solder after wave soldering.

4. Special Pads

1.  Plum Blossom Pad: Typically used for large via ground connections. This design prevents the hole from being blocked during reflow soldering, ensures good grounding, and accommodates stress variations.
2. Cross Pad: Also known as thermal pad or hot air pad. It reduces heat dissipation during soldering, preventing cold solder joints or PCB lifting.
3. Tear Drop Pad: Commonly used when the connected trace is thin, preventing the pad from lifting and the trace from disconnecting.

3. Design Standards for PCB Pads
Shape and Size

1. Utilize standard PCB footprint libraries.
2. Minimum pad width should not be less than 0.25mm, and the maximum diameter should not exceed 3 times the component hole diameter.
3. Ensure a minimum spacing of 0.4mm between pad edges.
4. Pads with a hole diameter exceeding 1.2mm or a pad diameter exceeding 3.0mm should be designed as diamond or plum blossom shapes.
5. For dense routing, elliptical or oblong pads are recommended. Single-sided pad diameter or minimum width is 1.6mm; for double-sided weak electrical circuit pads, the hole diameter plus 0.5mm is sufficient. Larger pads can cause unnecessary solder bridging.

1. The inner hole of the pad is generally no smaller than 0.6mm. Typically, the inner hole diameter is the diameter of the metal pin plus 0.2mm. For example, if the metal pin diameter of a resistor is 0.5mm, the corresponding inner hole diameter of the pad is 0.7mm. The pad diameter depends on the inner hole diameter.

1. Symmetry: Ensure symmetry for balanced molten solder surface tension.
2. Pad spacing: Excessive or insufficient pad spacing can cause soldering defects. Ensure appropriate spacing between component ends or pins and pads.
3. Remaining pad size: The remaining size after the component end or pin overlaps with the pad must ensure the formation of a solder fillet.
4. Pad width: Should be consistent with the width of the component end or pin.