What is Annular Ring

By Bester PCBA

Last Updated: 2023-07-26

Annular Ring Definition

An annular ring in the PCB industry is the area of copper pad around a drilled and finished hole, which is used to establish a good connection between a via and the copper trace. It is calculated based on the outer layer pad diameter, plated hole diameter, and tool size. The size of the annular ring is defined as the distance between its outer diameter and the inner diameter, which is the difference in their radii. It is a crucial part of any printed circuit board, especially in multilayer PCBs, and serves as an anchor for the circuit.

Frequently Asked Questions

It is recommended that the annular ring for microvias/laser drills should be at least 2 mils, while for mechanically drilled vias it should be at least 4 mils. It is important to note that the annular ring measurement in the CAM software is based on the drilled hole size, not the finished hole size.

What is the minimum annular ring on a PCB?

The minimum width for annular rings on the inner layer of a PCB is 0.1mm, while for those on the outer layer, it is 0.05mm.

Do vias need annular rings?

In a multi-layer PCB, it is important to ensure that there is sufficient copper surrounding the via to create a strong connection between the copper traces and the via. The primary objective of an annular ring is to establish a reliable connection between the via and the copper trace.

What is outer layer annular ring?

The region that is situated between the outer edge of the solder pad and the solder hole may experience a break in the annular ring if the hole is drilled off-center. The occurrence of this depends on the nominal diameter of the hole in comparison to the nominal outer diameter of the solder pad.

What is the purpose of the annular ring?

An annular ring refers to the region between the conductive copper pad’s edge and the hole drilled into a via. Vias are utilized as interconnecting nodes between various layers on a PCB.

What size is a standard annular ring?

The annular ring’s minimum width is usually 0.15mm (6mil), and the CNC drill size can vary from 0.2mm to 6.3mm.

What is the annual ring in PCB?

When designing a multilayer PCB, it is common to use vias to route traces from one layer to another. These vias are created by drilling holes through the copper pads on the surface of the PCB. The annular ring refers to the amount of copper that remains around the via on both the top and bottom sides of the PCB.

What is the maximum allowable PCB deflection?

According to the IPC standard, the maximum allowable deformation for a PCB board with surface mount device is limited to 0.75%, while for a PCB board without surface mount, the maximum allowable deformation is 1.5%.

What is standard PCB hole tolerance?

The tolerance for holes in Printed Circuit Boards (PCBs) is typically specified by manufacturers as ±0.004. It is important to note that the lead, regardless of whether it is at the upper or lower end of the tolerance range, must fit properly into the hole.

What is the difference between Class 2 and Class 3 annular rings?

According to the specifications, Class 2 permits a void in 5% of the holes, while Class 3 does not allow any voids. Additionally, the plating thickness requirement for Class 2 is 0.8 mil, which is lower than the 1 mil requirement for Class 3. These are some of the variations in requirements between Class 2 and Class 3.

What is the difference between annular and circular?

An annulus is a flat two-dimensional shape that is circular in form and is created by two concentric circles. The space or area that is enclosed between these two circles is known as the annulus. As it is a circular figure, the boundaries are formed by two circles that share the same center.

How do you calculate the annular ring of via?

To determine the width of an annular ring, the following formula can be used: (pad diameter – via diameter) ÷ 2. This formula helps in measuring and calculating the annular ring accurately.

What size is a through hole annular ring?

The standard minimum annular ring size is commonly 0.05mm. To calculate the pad diameter, you can add 0.05mm to 0.3mm, double the result, and then add it to the hole size. This will give you the required pad diameter.

What is the inner layer of the annual ring?

The xylem, which is responsible for transporting water throughout the tree, is formed from the cambium cells located on the inner side. The annual rings that we observe in trees are a result of the formation of these xylem layers.

What is annular ring shank?

Nails with annular rings or ring shanks are designed with rings on the shank to provide improved grip and additional resistance when used in timber. These types of nails are suitable for use in stud walls or deck boards due to the resistant feature of the annular rings on the nail shank.

Why is it called annular?

The term “annular” is derived from the Latin word “annulus,” which means ring. Annular eclipses are named after their maximum or darkest point, even if it occurs for a brief moment. An eclipse is classified as an annular solar eclipse if the distinct ring of fire is visible from at least one location.

Why is it called annulus?

The term “annulus” (plural – annuli) originates from the Latin language and translates to “little ring”. An annulus refers to the region situated between two concentric circles that are positioned in the same plane and share the same center.

What is the difference between annulus and annular?

An annulus, which can be referred to as annuli or annuluses in plural, is a mathematical term used to describe the area between two circles that share the same center. It has a ring-like or hardware washer-like shape. The term “annulus” is derived from the Latin word “anulus” or “annulus” which means ‘little ring’. Additionally, the adjective form of annulus is annular, as seen in the term “annular eclipse”.

What is the aspect ratio of a PCB?

The definition of PCB aspect ratio pertains to the relationship between the depth and diameter of a through-hole. Specifically, it is the ratio of the hole depth to the hole diameter. To illustrate, a circuit board with a through-hole diameter of 0.020 inches and an aspect ratio of 3 to 1 would have a board thickness of 0.062 inches.

What are the different types of ring sizes?

To determine the appropriate ring size, it is important to note that standard ring sizes increase by 0.4 millimeters for every half-size. For example, a ring with a size of 3 measures 14 mm, while a ring with a size of 3.5 measures 14.4 mm. Similarly, a ring with a size of 4 measures 14.8 mm. Typically, women’s rings range from sizes 3 (14 mm) to 9 (19 mm), while men’s rings are usually sized between 8 (18.2 mm) and 14 (23 mm).