In PCB design, the concept of pads is crucial, and PCB engineers must have a solid understanding of it. However, even among those who are familiar, many engineers possess only a limited knowledge of pads. The following sections will provide a detailed overview of the types and design standards for pads in PCB design.
1. Types of pads
Generally, pads can be categorized into seven types, distinguished by their shapes as follows:
**Square pads**—These are typically used when the components on the printed circuit board are large and sparse, with simple wiring. This type of pad is particularly convenient for hand-made PCB fabrication.
**Circular pads**—Commonly found on single and double-sided printed boards with regularly arranged components. If the board’s density permits, the pads can be made larger to ensure they remain intact during soldering.
**Island-shaped pads**—These pads feature an integrated connection between them. They are frequently utilized in installations with vertical and irregular arrangements. For example, such pads are commonly used in tape recorders.
**Teardrop pads**—These are often employed when the traces connecting to the pads are thin, helping to prevent pad delamination and ensuring the traces do not detach from the pads. Teardrop pads are particularly prevalent in high-frequency circuits.
**1. Pad Types in PCB Design**
– **Polygonal pads** are utilized to differentiate pads with similar outer diameters but varying apertures, facilitating easier processing and assembly.
– **Oval pads** provide sufficient area to enhance anti-stripping capabilities, often employed in dual in-line devices.
– **Open-shaped pads** are designed to ensure that pad holes, which may require manual repair post-wave soldering, are not sealed by solder.
**2. Design Standards for Pad Shape and Size in PCB Layout**
1. The minimum dimension for any single side of pads must not be less than 0.25mm, and the maximum diameter should not exceed three times the component aperture.
2. It is advisable to maintain a distance greater than 0.4mm between the edges of two pads.
3. In high-density wiring scenarios, oval and oblong connection pads are recommended. The diameter or minimum width of a single-sided board pad should be 1.6mm; for weak-current circuit pads on double-sided boards, an additional 0.5mm should be added to the hole diameter. Oversized pads may lead to unnecessary solder bridging. If the hole diameter exceeds 1.2mm or if the pad diameter is greater than 3.0mm, pads should be designed in a diamond or quincunx configuration.
4. For plug-in components, to prevent copper foil from breaking during soldering, single-sided connection pads must be entirely covered with copper foil; double-sided panels should have teardrop fillings as a minimum requirement.
5. All machine-inserted parts should feature drip pads aligned with the bent leg direction to ensure complete solder joints at the bend.
6. Pads on large copper areas should be chrysanthemum-shaped to avoid soldering. In cases where there are significant ground and power lines on the PCB (exceeding 500 square millimeters), windows should be partially opened or designed to fill with a grid pattern.
**3. PCB Manufacturing Process Requirements for Pads**
1. Test points should be incorporated if the ends of chip components are not connected to plug-in components. The diameter of these test points should be at least 1.8mm to facilitate testing with an online tester.
2. For IC pads with closely spaced pins that are not connected to manual plug-in pads, test pads must be added. For chip ICs, test points should not be placed within the chip IC silk screen, and the diameter must also be at least 1.8mm for online testing purposes.
3. If the distance between pads is less than 0.4mm, a white oil must be applied to reduce the risk of solder bridging during wave crest soldering.
4. Both ends of SMD components should be designed with lead-tin, with a recommended width of 0.5mm wire and a length of typically 2 to 3mm.
5. For hand-soldering components on single-sided boards, the tin bath should be removed in the opposite direction to the tin flow, and the viewing hole width should range from 0.3mm to 1.0mm.
6. The spacing and size of conductive rubber keys should align with the actual conductive rubber keys. The PCB connected to this should be designed with gold fingers, specifying the appropriate gold plating thickness.
7. The dimensions and spacing of pads should closely match the size of the surface-mounted components.
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1. Types of pads
Generally, pads can be categorized into seven types, distinguished by their shapes as follows:
**Square pads**—These are typically used when the components on the printed circuit board are large and sparse, with simple wiring. This type of pad is particularly convenient for hand-made PCB fabrication.
**Circular pads**—Commonly found on single and double-sided printed boards with regularly arranged components. If the board’s density permits, the pads can be made larger to ensure they remain intact during soldering.
**Island-shaped pads**—These pads feature an integrated connection between them. They are frequently utilized in installations with vertical and irregular arrangements. For example, such pads are commonly used in tape recorders.
**Teardrop pads**—These are often employed when the traces connecting to the pads are thin, helping to prevent pad delamination and ensuring the traces do not detach from the pads. Teardrop pads are particularly prevalent in high-frequency circuits.
**1. Pad Types in PCB Design**
– **Polygonal pads** are utilized to differentiate pads with similar outer diameters but varying apertures, facilitating easier processing and assembly.
– **Oval pads** provide sufficient area to enhance anti-stripping capabilities, often employed in dual in-line devices.
– **Open-shaped pads** are designed to ensure that pad holes, which may require manual repair post-wave soldering, are not sealed by solder.
**2. Design Standards for Pad Shape and Size in PCB Layout**
1. The minimum dimension for any single side of pads must not be less than 0.25mm, and the maximum diameter should not exceed three times the component aperture.
2. It is advisable to maintain a distance greater than 0.4mm between the edges of two pads.
3. In high-density wiring scenarios, oval and oblong connection pads are recommended. The diameter or minimum width of a single-sided board pad should be 1.6mm; for weak-current circuit pads on double-sided boards, an additional 0.5mm should be added to the hole diameter. Oversized pads may lead to unnecessary solder bridging. If the hole diameter exceeds 1.2mm or if the pad diameter is greater than 3.0mm, pads should be designed in a diamond or quincunx configuration.
4. For plug-in components, to prevent copper foil from breaking during soldering, single-sided connection pads must be entirely covered with copper foil; double-sided panels should have teardrop fillings as a minimum requirement.
5. All machine-inserted parts should feature drip pads aligned with the bent leg direction to ensure complete solder joints at the bend.
6. Pads on large copper areas should be chrysanthemum-shaped to avoid soldering. In cases where there are significant ground and power lines on the PCB (exceeding 500 square millimeters), windows should be partially opened or designed to fill with a grid pattern.
**3. PCB Manufacturing Process Requirements for Pads**
1. Test points should be incorporated if the ends of chip components are not connected to plug-in components. The diameter of these test points should be at least 1.8mm to facilitate testing with an online tester.
2. For IC pads with closely spaced pins that are not connected to manual plug-in pads, test pads must be added. For chip ICs, test points should not be placed within the chip IC silk screen, and the diameter must also be at least 1.8mm for online testing purposes.
3. If the distance between pads is less than 0.4mm, a white oil must be applied to reduce the risk of solder bridging during wave crest soldering.
4. Both ends of SMD components should be designed with lead-tin, with a recommended width of 0.5mm wire and a length of typically 2 to 3mm.
5. For hand-soldering components on single-sided boards, the tin bath should be removed in the opposite direction to the tin flow, and the viewing hole width should range from 0.3mm to 1.0mm.
6. The spacing and size of conductive rubber keys should align with the actual conductive rubber keys. The PCB connected to this should be designed with gold fingers, specifying the appropriate gold plating thickness.
7. The dimensions and spacing of pads should closely match the size of the surface-mounted components.
If you have any PCB manufacturing needs, please do not hesitate to contact me.Contact me
