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PCB annular ring in printed circuit board design

PCB annular ring - a key term in PCB and PCBA

A PCB has a number of important parts and one of them-PCB annual ring. If you get it wrong, it can be quite troublesome. Not to mention, it can influence the continuity of the trace and even influence the functionality of the circuit.

What is PCB annular ring?

An PCB annular ring is fundamentally a term and it describes and depicts an area between the via’s hole and the edge of the copper pad. It can be said that vias work just like interconnecting nodes between multiple layers on a printed circuit board.

During the manufacturing process of PCBs, a PCB is typically etched. It tends to leave via pads aligned on different layers. In addition, the pad is drilled to make a hole where copper is usually deposited at the hole’s wall with electroplating.

Typically, when we look at the PCB from the top, we can see ring-shaped patterns on it that are basically created and developed by the drilled vias. We call them annular rings and it should be noted that they are different in size.

In addition to it, some designers consider having thicker annular rings whereas others might consider having thinner annular rings because of space limitations and constraints.

What’s the structure of an annular ring?

It is important to note that when there is a need or requirement to connect different traces in a board that is multi-layered, copper pads are placed and positioned on the copper pads. After that, vias are drilled on them. It is necessary to make connections. Once the drilling process is complete, the structure and shape of the PCB annual ring are set by the outer ring that tends to surround the via.
What's the structure of an annular ring

What is the purpose of the annular ring?

In the board, different holes are drilled when the PCB is being developed and constructed. These holes might be utilized for the installation, as vias for multi layer PCB, or for the use of through-hole technology. Actually, PCB annual rings have an objective and that is all about creating a good connection between copper traces and vias.

In addition to it, PCB annular rings tend to provide the surface area, which is necessary for connecting wires and even leading to different electronic components and parts. They work like an anchor for the circuit.

What is the significance of an annular ring in scale?

There is no doubt that an PCB annular ring has great significance in scale. Without the right size, the desired results may never be achieved. For instance, when the dimension of an annular ring is less than the required value, it can affect the attachment of the component.

In addition to it, it can lead to the breakout of the pad. In fact, it is a condition that is related to the region where the pad is penetrated or entered by the circuit. In fact, it is even capable affecting and reducing the capacity of a circuit to carry current.

How do you calculate the annular ring?

When it comes to the positioning of the PCB annular rings, they are often located and placed in the center. This position is generally considered to ensure that a suitable connect is developed. Meanwhile, the calculation of the annular ring and its width is as follow.
How do you calculate the annular ring
Width of PCB Annular Ring = (Diameter of the pad – Diameter of the finished hole) / 2

There is definitely a need to ensure that precise measurements and calculations are made. Otherwise, it can mess up the printed circuit board and even the connectivity of components.

What is minimum annular ring in PCB?

The minimum annular ring in a PCB means the minimum amount of copper between the edge of the hole and the edge of the land once the finished hole has been plated. It is important to note that it is also recognized as a supported hole.

There are times when traces on a PCB are needed to be interlinked to another layer. The traces, in such cases, end up on a pad. On the pad, the via helps the trace in moving from the pad and connect to another layer.

How big should the PCB annular ring be?

There is no fixed size of annular rings. It should be noted that an PCB annular ring’s size relies to a significant extent on the designer but still, it cannot be overlooked that the ring’s minimum width is often 0.1 millimetres.

Meanwhile, when it comes to the minimum width of annular rings on the outer layer of a printed circuit board, it is 0.05 mm. The size of the annular ring itself will rely to a significant extent on the purpose of the board. The maximum width of an PCB annular ring is generally 6.3 mm.

How does annular ring affect PCB and PCBA?

There is no doubt that the annular ring influences both the PCBA and PCB. For instance, the width indicates just how much space can be moved by a PCB and even how much space can be used by a drill. The functional connectivity is affected to a great extent by an annular ring in both PCB and PCBA.

Consideration about annular ring when PCB design

Consideration about annular ring when PCB designThere exist a number of considerations to be focused upon in a PCB design. There are several types of vias and shapes of PCB annular rings. There is a need to identify which shape and type are more suitable for the PCB.Deciding which ones to use generally are the primary consideration. Without selecting the right types and shapes, the desired output may never be achieved.

What’s the relationship between PCB annular ring, pad, and via?

Usually, a via is made or created by precisely drilling a hole through a copper pad that is etched on all layers of a printed circuit board. As far as the PCB annular ring is concerned, it represents the surface area between the drilled via and the pad’s edge. Therefore, without a via, an PCB annular ring cannot be really created. When there is an increase in the width of the PCB annular ring, the copper connection right around the drilled via will also be greater.


The above is the introduction of the PCB hole ring, I hope that will be helpful to you. Also, if you want to know more about PCB and PCBA, you can visit our IBE website. If you are looking for a one-stop PCBA manufacturer, please contact us directly.



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