An annular ring PCB is a type of PCB that has a circular pattern etched into its surface. Indicates the area between the hole drilled in the via and the edge of the conductive copper pad.
To understand the basics of an annular ring, you need to know how to construct a through-the-hole. During PCB manufacturing, the PCB is etched and left through pads that are aligned with each other on different layers. A hole is drilled to form a hole and copper is deposited on the walls of the hole by electroplating.
When you view the PCB from the top, the drilled vias appear as a ring pattern. They are called annular rings. The annular rings are of different sizes. Some PCB designers choose to use thicker annular rings, while others assign thinner annular rings due to space constraints.
How to Measure?
For any combination of multiple manufacturing processes, overlapping small errors often occur. Specifically, when the process of etching copper traces on a PCB and the process of drilling through said traces are combined, your drill holes are often not perfectly aligned in the center of those traces and will cause you to slightly Deviate from neatness. But fear not. Has little effect!
First, by identifying manufacturer-specific tolerances, they will be able to accommodate errors, and by identifying minimum widths, you can confidently reduce risk throughout your manufacturing process, ensuring that minimum values are always met.
In short, be aware that there will be some manufacturing errors along the way, but designing for those errors will get you beyond the bare minimum, especially for a drilled annular ring.
The Size of the Annular Ring Is Calculated by the Following Formula.
Ring size = (pad diameter – drill diameter) / 2
Frequently Asked Questions about Annular Rings
Since vias are an important part of PCB manufacturing, if there is a problem with the annular ring, it can affect the continuity of the traces.
In theory, the perfect annular ring is formed by drilling a hole in the center of the via pad. The accuracy of drilling depends on the machine used.
If a ring fracture occurs, it will affect the continuity of the via. When the copper area of the connection holes and pads is small, the current will be affected. This problem is more pronounced when the affected channel is used to deliver more current. When a ring crack is detected, more copper filler is usually added around the exposed area to secure it.
The calculation of the ring width plays an important role in PCB manufacturing. If the ring is not wide enough, the hole may touch the border of the pad, a condition called “tangent”. In extreme cases, the hole may lie outside the pad boundary, known as a “breakout”. Both of these should be avoided during PCB manufacturing.
English