Everything that you need to learn regarding printed circuit board annular rings

19 Feb, 2022

By ren

According to Printed circuit board news, annular rings are an essential component of any printed circuit board (PCB industry), yet they provide a significant difficulty to Printed circuit board suppliers. With such fine work, it's possible to make mistakes when drilling this via, which might lead to supply chain boards malfunctions. This may affect total semiconductor sales.

You should stay up to date on printed circuit board trends and updates to have a better grasp of Printed circuit board assembly. PCB designers must use caution when considering size and location while doing PCB fabrication. In this post, we'll go over all you would need to know regarding annular rings, including the specific problems they provide and how to get them just right.

This annular ring is a printed circuit board (PCB) component that surrounds a completed hole or through. Passive components are openings on circuit boards that serve as nodes linking the various layers. The annular ring spans the space between both the via's border and the metal pad that surrounds the hole.

What are annular rings used for? Annular rings aid in the stability of the electronics circuit between both the via and the metal pad. They also provide designers some leeway if the opening isn't exactly centered, assuring conductivity.

A PCB Annular Ring's Composition

An annular ring is a circular or ring in form. The word "annulus" derives from the mathematics term for the gap between two concentric rings. The annular ring surrounds a hole inside the metal plate of a PCB by which a via passes. The objective of the Printed circuit engineering association is to advance circuit board engineering as a career and to stimulate, enable, and encourage the sharing of knowledge via the incorporation of innovative design concepts.

You must guarantee that perhaps the layers of a multi-layer circuit board interface flawlessly with both the copper wires. The copper-plated via transmit current between the layers. The copper circle that surrounds the via through each layer is referred to as the annular ring.

Annular rings come in a variety of diameters, and a bigger annular ring is often more effective in preventing breakouts. Before we get into breakout difficulties, let's speak about annular ring PCB diameters.

How Do You Determine Annular Size?

 One purpose of making an annular ring is to drill directly through the center. The more precise the hole, the much more easily electricity flows through all of it.

The basic equation may be used to determine the width of an annular ring:

 (Copper Pads Size – Size of Completed Hole/Via) / 2 = Annular Ring Width

So users take the size of the metal pad (the outermost circle) and subtract it from the size of the via (the innermost circle). Split that figure in half to get the ideal width for your annular rings.

 What is the Importance of Annular Ring Size?

The diameter of the annular ring is important since it impacts how well your conductivity works. Although you don't want it to be too wide because you're working with a small area, it does need to be big enough just to maintain a good connection.

As we all know, annular rings are used to provide a stable electrical connection between the PCB and the circuit board today announced. Thus, the ring size must, first and foremost, enable cords to flow smoothly through it. An additional thing to keep in mind would be that the annular ring's smallest amount must be more than or equal to an overall stated design.

If any of the foregoing requirements are not met, it leads to anomalies such as "tangency," "breakout," and an unwanted annular ring. One of the most important things to remember while building a PCB board is that all of the annular rings must be meticulously built. Surface mount technology PCB is a technique for mounting electrical components and circuitry on printed circuit boards (PCBs). Only this one will culminate in the circuit operating properly.

How to Determine the Correct Annular Ring Size?

During the PCB production process, each PCB manufacturer will specify the tolerances for the annular ring. To get onto the safe place, you must always add a little extra room. Most designers advise raising the size from the manufacturer's requirements by 1.0mm. The modest extra breadth will aid in the prevention of future problems.

The diameter of your annular rings will be determined by the purpose of the board. The Association of Printed Circuit Boards classifies PCBs into three categories: Category 1, Category 2, and Category 3. So because bulky PCBs are greater in size, large annular rings were required. Class iii PCBs need heavier-duty annular rings.

In PCB, and what's the smallest annular ring?

Certain PCBs have to be able to sustain heavy-duty equipment and areas, while others must be exceedingly small. Consider PCBs in cellphones or other tiny technology devices.

The minimal annular ring in this scenario must be proportionately small. But how tiny are we willing to go? Inlet and outlet annular rings have varying design limits, according to industry leading standards.

1. The minimum width for annular rings on a PCB's inner layer is 0.1mm.

2. The minimum width for annular rings on a PCB's outer layer is 0.05mm.

What's the Distinction Between a PCB Annular Ring and a Through-Hole?

When you hear the phrase PCB, you most often envision the through-hole approach. It is a method of mounting electrical components. Electronic components are inserted into holes drilled in a printed circuit board (PCB).

Although through-holes are a sort of via, they are not the only type of via. Through-holes produce conduction by inserting wires through the hole and afterward soldering them to the metal pad. Annular rings, on either hand, generate conductance by connecting directly the copper-plated via to the metal pad.

What Exactly Is a Teardrop Annular Ring?

A teardrop annular ring is formed like a teardrop in PCB fabrication. Rather than creating a complete circle, you add additional copper to join the ring's outside corners. The extra copper adds strength to the ring.

The major reason for using teardrop annulus rings is if the drill bit deviates significantly while drilling. This issue might result in the removal of too much metal, jeopardizing the connections.

 Common Issues with PCB Annular Rings

As you indicated at the outset, annular rings can be difficult to master. With the annular ring, PCB manufacturers may encounter any of the following challenges.

The fabrication of annular rings, like any other electrical component, is not without flaws. This implies that, in addition to the fundamental concerns of Tangency, Breakout, and Unwanted Annular Ring, there are other frequent challenges.

This covers the via's misregistration. As previously stated, annular rings must be cut in the absolute center of the pad for effective operation. However, in some circumstances, the ring's minimum width is uneven, resulting in marginal interconnections, dependability issues, and higher resistance. All of these issues may be resolved by properly positioning the annular ring PCB.

 Unwanted Annular Ring

An annular ring that is too big on a tiny PCB may prevent the board from functioning properly. A circular ring may pose problems, especially if the copper pad is tiny. According to Printed circuit board news, in this case, is to use prototypes while designing and fabricating a PCB.


 \A tangency arises whenever a hole is accidentally drilled off-center. A tangency occurs but you're so far off-center that now the hole hits the edge of the pad. Tangency can also be caused by an annular ring that is too narrow for the hole. Tangencies impair communication and might even be harmful.


A breakout occurs when the holes go outside of the border of the annulus ring and the copper pad, similar to the next step of tangency. It erupts.

Breakouts occur most frequently when the levels of the board do not fit correctly, resulting in the hole not aligning through every layer. Again, the best strategy to avoid breakouts is to make sure the annular ring is large enough to contain the hole.


Annular rings, like everything else, can be stressed and disintegrate with time. A rupture occurs when an annular ring splits or fractures. Rupture can occur as a result of aging, mechanical forces, or even stressors. The easiest strategy to avoid rupture is to utilize high-quality materials and repair your PCB as it matures.


Annular rings are an important component of every printed circuit board, but they may be difficult to get properly. Just use these instructions to learn about the annular ring as well as how to create them. Annular rings are a major source of worry for PCB designers. You know how you can put your via in the middle of the pad in the configuration items, but it doesn't mean you won't get tangencies or, worst, breakout.


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