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

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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 wont 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.
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• Problems associated with annular rings
• Lets 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 pads
  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

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• 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 holes 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,

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• 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 and experienced
  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 value
  s 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.
• For more Information https//www.miracle.net.in/