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What are Mounting Holes? | PCB Knowledge

by: Apr 11,2023 3112 Views 0 Comments Posted in PCB Basic Information

Mounting Holes

Summary:       PCB Mounting Holes

What are Mounting Holes?

Mounting holes are holes that are drilled through a PCB to provide a location for mounting the board to a chassis or enclosure. They are typically larger in diameter than other types of holes on the board and are often placed at the corners of the board or in other critical locations. Mounting holes are usually surrounded by a copper pad or annular ring that provides a stable connection between the board and the mounting hardware.

Figure1: Mounting Holes

Two Types of Mounting Holes

Depending on whether they have a conductive layer or not, mounting holes can also be classified as plated and un-plated mounting holes.


Plated mounting holes are necessary when electrical connections are required between different layers of the PCB. For example, if a PCB has a ground plane on a different layer than the top layer, plated mounting holes may be necessary to connect the top layer to the ground plane. Additionally, plated mounting holes can provide a reliable anchor point for screws, bolts, or other hardware, helping to keep components firmly attached to the board


Unlike plated mounting holes, which are used to provide electrical connections between layers of a PCB, un-plated mounting holes are primarily used for mechanical purposes. They are typically isolated from other components and traces on the board and may require a keep-out zone to ensure that they do not interfere with other parts of the circuit.


Mounting Holes with Vias Surrounded

In many cases, you may find mounting holes surrounded by tiny vias, but what are these vias used for? These vias are typically placed in the annular ring or the thermal relief pads of the mounting holes and are mainly used for three reasons.

First, distribute the mechanical stress caused by mounting the PCB to a larger area. Vias provide additional support and prevent the mounting holes from becoming loose or damaged over time due to mechanical stress or vibration.

Second, create a grounding connection between different layers of the PCB. This helps to reduce electromagnetic interference and noise, which can be especially important in sensitive or high-frequency circuits.

Third, the vias can be used to connect a copper plane or heatsink to the mounting hole, which can help to dissipate heat from the PCB. The vias create a direct thermal path between the PCB and the heatsink, allowing for efficient heat transfer.

Figure2: Mounting Holes with Vias Surrounded



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