What is the difference between a solder pad and an overbore?
Pad and Via play different roles in electronics manufacturing and PCB (Printed Circuit Board) design, and the main differences between them are in definition, principle, function and design details.The following is a detailed comparison of the two:
I. Definition
Pad: pad is the basic unit of surface mount assembly, used to constitute the circuit board pad pattern (land pattern), that is, a variety of special component types designed for the combination of pads.Pad is divided into pin pads and surface mounted pads, where the pin pads have weld holes, mainly used for welding pin components; and surface mounted pads do not have weld holes, mainly used for welding surface mounted components, located on the surface of the PCB.
Through-hole: through-hole, also known as metallised holes, is an important component in the manufacture of PCBs.In the double-sided board and multilayer board, in order to connect the printed wires between the various layers, in the various layers need to be connected to the intersection of the wires drilled on a public hole, that is, through-hole, can be located in any layer of the PCB.
Second, the principle
Solder Pad: The design of the solder pad should ensure that the components can be correctly and firmly soldered on the circuit board.Functionally, Land is a two-dimensional surface feature for components that can be surface mounted; and Pad is a three-dimensional feature for components that can be plugged in.The structural design of the pads is critical to the formation of solder joints, and incorrect construction may result in poor soldering.
Through-hole: Through-hole passes through the entire PCB board through the metal layer within the board layer to realise the electrical connection of circuits between different layers.In the process, the hole wall of the hole in the cylindrical surface of the chemical deposition method of plating a layer of metal, to connect the middle layers need to be connected to the copper foil.Through-hole parameters are mainly the outer diameter of the hole and the size of the drill hole.
Third, the role of
Pad: welding component pins, pads not only play the role of electrical connection, but also play a role in mechanical fixation.It ensures that the components can be stably fixed on the circuit board, and maintain good electrical contact.
Vias: connecting different layers of the circuit, the main role of the vias is electrical connection, it helps signal transmission and current conduction between electronic devices.In addition, vias can also serve as heat sinks in some cases.
IV. Design Details
Aperture: the aperture of the aperture is generally small, usually as long as the board processing technology can be done is enough.The pad aperture in the drilling will increase the size of a certain amount to ensure that the solder can be fully filled when welding.
Surface treatment: the surface of the aperture can be coated with solder resist ink or not.The surface of the pads usually needs to be kept clean and smooth so that the solder can adhere well when soldering.
Solder ring width: The minimum width of the solder ring of the hole is usually 0.15mm (in case of universal process) to ensure that the copper plating can be reliably sunk.The minimum width of the pad's solder ring is usually 0.20mm (in the case of general-purpose technology), to ensure that the pad's adhesion force.
In summary, the pads and holes in the PCB design and manufacturing each has its unique role and design requirements.Proper understanding and application of them is critical to ensure the performance and reliability of the circuit board.
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