### Hole Aspect ratio

The aspect ratio rule defines the criteria for a manufacturer to properly plate a hole for reliable connectivity of the hole consistently. A hole that is too small will not allow the material used to plate the entire hole to fully plate the hole, leaving a disconnect in the circuitry. The aspect ratio can be defined as:
- Minimum hole size based on the thickness of the number of layers. That can be expressed as ratio of the total thickness of the layers a pin or via spans, excluding the mask layers to the finished hole diameter.
Graphical description is shown below.
Example
The Ratio is defined as 6:1 The uVia finished hole diameter is .007 The drill spans layer 1 and layer 2. The dielectric layer and the layer1 and layer 2 copper thicknesses are combined To equal .0128. .0128 / .007 = 1.814 The ratio is less than 6, so the via passes. Now another via (.007 diameter) spans layers 1 thru 8 layers, overall thickness of layer and dielectric = .047 .047/ .007 = 6.714 The ratio is greater than 6, so this drill gets a DRC.
This rule is applicable to any via or thru hole pins.