Annular Rings – An Indispensable Part Of A PCB - Miracle Electronics

1. Annular Rings – An Indispensable Part Of A PCB - Miracle Electronics In a basic PCB construction, vias are created by drilling holes through the copper pad etched on each layer of the board. An annular ring is the area between the edge of the drilled via and copper pad. The greater the width of the ring, the greater the copper connection around the via will be. The amount of copper left around the via on both the top and bottom sides of the board is the annular ring. This annular ring is one of the biggest concerns of almost every PCB designer. Importance of annular rings In spite of the annular ring being a matter of concern for every designer, it does not mean that the ring is something trivial. Annular rings are essential for a PCB because they give room for reliable electrical connections on the board. Establishing excellent connections, they serve as anchors for the PCB. Without annular rings, there won’t be desired electrical connections. But at the same time, as an annular ring can provide such benefits, issues with them can be problematic too and can heavily affect trace continuity. Also, it may negatively affect the functionality of the entire board.

2. Problems associated with annular rings Let’s now take a look at some of the most common problems associated with a PCB annular ring. Tangency– The moment a drill misses its desired mark, the resulting hole edges towards the pad’s size; and the moment the spot gets to touch the edge of the place, it brings an annular ring tangency. Breakouts– If the drilling deviates more than just missing the desired mark, it brings about instances of breakouts, which is even more dangerous! Such instances are most commonly seen when the lamination causes parts of a PCB to move away from where they must be. Rupturing– An aging circuit board can result in the annular ring to rupture. Also, annular ring de-wetting, contamination on the holes, and excessive mechanical stress are other reasons for breakage. How can such problems be avoided? To avoid the issues mentioned above, first and foremost, it is very important to consider seriously the design and shape of the annular rings. Also, the size of the annular ring, in terms of width and diameter, is equally important. Next, while drilling these rings, accuracy is important in a way that the drilling stays on the mark. The best annular ring is achieved by accurately drilling at the center of the via pad; and the drilling accuracy depends on the equipment that the

3. manufacturer uses. Drilling the rings at the dead-center of the board ensures excellent conductivity between the layers and the vias. Another factor to consider while designing an annular ring is the application in which the PCB is to be used. For instance, you need to identify if the PCB needs to be used in any critical environments like high temperature, excessive moisture, sensitivity, etc. For such special requirements, high-quality specialized PCB annular rings are required. Without the right design criteria for annular rings, you may end up with a board with poor functionality. Calculating the size of the annular ring The minimum diameter of an annular ring depends on a lot of factors. Small rings can result in annular breakouts, thus putting the vias at risk. Similarly, larger rings are also not feasible. Thus, it is important to come up with the right size design. Without the right ring size, the overall functionality of the board is at risk. The accurate annular ring width is the difference between the finished hole’s diameter and the copper pad divided by two. As per the IPC- 2221A standards, the calculation of the minimum PCB annular ring size is as follows – Minimum Annular Ring = (Minimum Ringer Border)x2 + (Tolerance) + (Hole Size) Considerations as an end user With all of the above being so technical, there is not much you can do as a layman without knowledge. But, as an end user, there are certainly a few things that you can consider. For instance,

4. High quality materials need to be used. Prototypes need to be made before the actual production to check for any flaws. If there is longer usage or excessive mechanical stress on the PCBs, make sure to replace them before they wear out, or at the least, keep maintaining them from time to time. Most importantly, a genuine manufacturer (https://www.miracle.net.in/blog/8- recommended-tips-find-best-pcb-assembly- manufacturer/) needs to be hired. You need to ensure that you work with a designer who values Design for Manufacturability, if you want to achieve the best and most desirable annular rings for your PCB. One such manufacturer is Miracle Electronics, who is highly experienced and expertized for offering almost every kind of PCB assembly from India for every kind of application and industry. and experienced For more Information: https://www.miracle.net.in/