PCB pad – a basic guide for beginners

PCB Pad A Basic Guide for Beginners

PCB pad, the basic constituent unit of surface mount assembly, is used to form the land pattern of the circuit board, that is, various pad combinations designed for special component types. In this article, let’s dive into the types, and design standards of PCB pads. Keep reading!

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    What is PCB pad?

    PCB Pad
    PCB Pad

    A PCB pad, is a small area on a PCB where electronic components are mounted or connected. It’s like a landing spot for components, allowing them to be soldered onto the board. These pads provide electrical connections between the component and the PCB, ensuring that the circuit functions properly.

    Types of PCB pads

    1. Square pads – used when the components on the printed board are large and few, and the printed wires are simple. When making a PCB by hand, it is easy to use this PCB pad.

    2. Circular pads – widely used in single and double-sided PCBs where components are regularly arranged. If the density of the board allows, the pad can be larger so that it will not fall off during soldering.

    3. Island-shaped pads – the pads and the connections between the pads are integrated into one. Commonly used in vertical irregular arrangement installation.

    4. Polygonal pads – used to distinguish pads with similar outer diameters but different apertures, which is convenient for processing and assembly.

    5. Elliptical pad – This pad has enough area to enhance the anti-stripping ability, and is often used in dual in-line devices.

    6. Open-shaped pads – commonly used to ensure that the pad holes of manual repair soldering are not sealed by solder after wave soldering.

    Types of PCB Pads

    Design standards for pads in PCB design

    PCB Pad Design
    PCB Pad Design

    Design standards for the shape and size of PCB pads

    1. Call the PCB standard package library.

    2. The minimum single side of the pad is not less than 0.25mm, and the diameter of the entire PCB pad is not greater than 3 times the aperture of the component.

    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 exceeding 1.2mm or a pad diameter exceeding 3.0mm should be designed as diamond-shaped or plum-shaped pads.

    5. In the case of dense wiring, it is recommended to use oval and oblong connection pads. The diameter or minimum width of the single-sided pad is 1.6mm; the weak current line pad of the double-sided PCB only needs to add 0.5mm to the hole diameter, and the pad is too large to cause unnecessary continuous welding.

    PCB pad via hole size standard

    The inner hole of the pad is generally not less than 0.6mm, because the hole smaller than 0.6mm is not easy to process when punching. Usually, the diameter of the metal pin plus 0.2mm is used as the diameter of the inner hole of the pad. For example, when the diameter of the metal pin of the resistor is 0.5mm, the diameter of the inner hole of the pad corresponds to 0.7mm. Pad diameter depends on bore diameter.

    Reliability design of PCB pads

    1. Symmetry, in order to ensure the balance of the surface tension of molten solder, the PCB pads at both ends must be symmetrical.

    2. Pad spacing, if the spacing of the pads is too large or too small, it will cause welding defects, so it is necessary to ensure that the spacing between the component terminals or pins and the pads is appropriate.

    3. The remaining size of the pad, the remaining size after the component end or lead and the pad overlap must ensure that the solder joint can form a meniscus.

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

    FAQ-about PCB

    A pad is the exposed region of metal on a circuit board that the component lead is soldered to. Multiple pads in conjunction are used to generate the component footprint or land pattern on the PCB. The two types of pads available are through-hole and surface mount pads.

    Contact pads or bond pads are small, conductive surface areas of a printed circuit board (PCB) or die of an integrated circuit. They are often made of gold, copper, or aluminum and measure mere micrometres wide. Pads are positioned on the edges of die, to facilitate connections without shorting.

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