Understanding Annular Rings in PCB Design

PCB designs must take into account many factors, including the size and placement of components, the routing of traces, and the use of appropriate materials. One critical aspect of the design phase that is often overlooked is the annular ring.

An annular ring is the area of copper that surrounds a through-hole or via on a PCB. It is the space between the edge of the hole and the edge of the copper pad. Annular rings play a crucial role in ensuring the reliability and functionality of circuits, as they help to ensure proper connectivity between different layers of the board.

Calculating Annular Ring Size

The size of the annular ring is determined by the size of the hole and the size of the pad. The larger the hole and pad, the larger the annular ring. The size of the annular ring is also affected by the manufacturing process used to create the board. Different processes have different tolerances and limitations, which can affect the size of the annular ring. Talk to your manufacturer!

It is essential to consider the size of the annular ring during the design phase of the board. The size of the hole, the size of the pad, and the manufacturing process used all play a role in determining the appropriate size of the annular ring. If the annular ring is too small, it can lead to poor connectivity and unreliable operation of the board. Conversely, if the annular ring is too large, it can cause problems during the manufacturing process, such as over-etching.

It is ideal for designers to ensure that their annular rings are located dead-center with the holes. This ensures the best possible connection between the vias and the layers. To calculate the perfect width for the annular ring, designers can use the following formula:

Annular ring width = (Diameter of the pad – Diameter of the finished hole) / 2

For instance, if the pad diameter is 20 mils and the hole diameter is 8 mils, the width is calculated as follows: (20 - 8) / 2 = 6 mils.

Designing for Appropriate Annular Ring

A general rule of thumb is to use an annular ring that is at least 0.1 mm larger than the diameter of the hole. This ensures that there is enough copper to create a reliable electrical connection.

It is also essential to ensure that the annular ring is centered around the hole. If the annular ring is off-center, it can lead to poor connectivity and unreliable operation of the board.

Annular rings are a critical aspect of PCB design. They ensure proper connectivity between different layers of a board, which is essential for the reliable operation of electronic devices. The size of the annular ring is determined by the size of the hole, the size of the pad, and the manufacturing process used.

Happy annular ring designing!