Types Of Holes on PCBs: A Comprehensive Guide

Types Of Holes on PCB
Types Of Holes on PCBs: A Comprehensive Guide

The Printed Circuit Boards (PCBs) serve as the base for connecting various electronic components that drive the performance of electrical circuits. One of the most important aspects of PCB design is incorporating holes, which serve different functions depending on their types and placements. These holes facilitate component mounting, electrical connections, and mechanical stability. When it comes to the types of holes, it is so important to understand the types of holes on PCBs for effective PCB design and manufacturing. This post will delve into the various types of holes found in PCBs and their respective roles.

An In-Depth Look at PCB Hole Varieties

This section explores the different types of holes on PCBs. Let’s go through it and understand what exactly they are and their functions:

  1. Through-Hole: These are the most common type of holes found on PCBs. They pass entirely through the board from the top to the bottom. These holes are mainly used in lead assemblies, which are supported by older PCB technologies. There are two primary types of through-holes:
    • Plated Through Holes (PTH): These holes have a conductive coating on the inner surface, which helps connect traces on different layers of the PCB. They are used for mounting components with leads, like resistors and capacitors, and for vias, which are conductive pathways between different PCB layers.
    • Non-Plated Through-Holes (NPTH): These holes do not have a conductive coating and are used for mechanical purposes to secure the PCB with screws or provide alignment during assembly.
  2. Buried Via: This type of hole connects two or more inner layers of a PCB without extending to the outer layers. They are invisible from the surface and enhance the routing density of multi-layer PCBs further. Buried vias are also standard in high-density interconnect (HDI) designs, where maximizing the available area for routing is essential.
  3. Blind Via: This PCB hole connects an outer layer of the PCB to one or more inner layers but does not go through the entire board. Blind vias save space and allow for more complex routing on multi-layer PCBs. They are crucial in HDI PCBs, where board real estate is at a premium.
  4. Countersink and Counterbore Holes: These holes are mechanical features that accommodate fasteners.
    • Counterbore Holes: This counterbore hole is a standard screw hole that is cylindrical in shape. It is drilled into the board's surface to securely fit a typical socket cap screw with a moderately rounded head. These holes are distinguished by their diameter and depth.
    • Countersink Holes: This countersink hole is conical in shape, just opposite the counterbore hole. To drill this cone-shaped hole, more calculation and precision are required compared to a counterbore hole. As a consequence, a flathead screw can be screwed into the hole and leave it completely flush with the surface of the board. It keeps the surface of the board smoother and will not interfere with the flow of the board’s design. Countersinks are measured by their diameter and angle.
  5. Tool Hole: This hole helps connect the circuit board to its test fixture or operating position. These holes are not plated and are insulated from traces or electronic components on the PCB board.
  6. Microvia: They are a subset of vias characterized by their small size, typically with a diameter of less than 0.15 mm. They are used in HDI PCBs to connect different layers in the board.
  7. Sidestep Hole: These holes are drilled before through holes. They are generally used to fix or weld some professional parts.
  8. Crimp Holes: They are partially drilled holes used for interconnecting wires to the PCB during hand soldering. These holes allow wire to be crimped onto the board.
  9. Slot Holes: These holes are used for components with non-standard lead shapes or to create specific mechanical features in the PCB design. Depending on their purpose, slots can be either plated or non-plated. Plated slots may be used for connectors or other components that require a more robust mechanical bond.

Importance of Proper Hole Design

The design and placement of holes on a PCB are critical for several reasons:

Understanding the different types of holes on PCBs and their functions is crucial as each type of hole serves a specific purpose, from providing electrical connections to ensuring mechanical stability. If you have been considering partnering with a trusted and experienced PCB assembly service, you can consider Twisted Traces. You can contact the experts at the company to discuss your PCB designs and the types of holes used in them.

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