The aspect ratio plays a crucial role in the manufacturing process of Multi-Layered PCBs. If neglected, they can leave you with a tattered circuit board barely able to form proper connection points for your via plating, or even electronic component placement.
What is the PCB Aspect Ratio
An aspect ratio is the PCB thickness to the diameter of the drilled via. This ratio affects the plating that is within the vias, altering reliability and sturdiness.
PCB with a thickness of 0.2”
Drill diameter of 0.02”
Aspect ratio = 10:1
As this ratio increases, the greater the risk of cracking.
Keeping your PCB aspect ratio lower will ensure consistency and strength of the Printed Circuit Board.
Microvia Before Aspect Ratios for PCBs
Microvia are holes that are drilled through the traces of Printed Circuit Board layers, best done with a laser drilling a vias, with the sole purpose of connecting to another trace on another layer. They are often present in HDI multi-layered PCBs which require each layer to be connected in one way or another. There are a few variations of microvia that come in the form of blind, buried, and through-hole microvias.
Blind Microvias connect an outer layer of the Printed Circuit Board to an internal layer of the Circuit but do not go any further. So if we have a four-layered Printed Circuit Board, the first two layers will have a drilled hole through the traces, but not the third or fourth.
After these microvias are properly designed into the Circuit Board, it’s now time to drill through each via location.
This is where annular rings come into play.
The annular ring is the copper ring left around the drilled hole portion of the via which gives us our connective surface in which to either mount components onto or fill in to give us a nice plated via. The larger the annular ring, the larger the connection surface we have. A simple, yet very crucial, piece to the manufacturing puzzle.
More in our Microvia Drilling Informative Article Series
Micron Laser specializes in Microvia Laser Drilling Services
Contact Micron Laser Technology to see how our Microvia laser drilling processes can advance your PCB designs utilizing microvias and avoid the pitfalls of underprocessed, overprocessed, and poor plating adhesion that lead to downstream reliability issues.
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