The final hole size
is the diameter of the final hole including all metal depositions.
The drill size
is the diameter of the drilling tool, which must be larger than the
final hole size.
Drill size and hole size
D
Drill size
H
Final hole size
The drilling tool diameter depends on:
- tolerance of hole diameter
- type of hole (plated, non plated)
- type of surface (electroless, HAL, ...)
- copper plating (25 µm or more)
- tolerance of annular ring
- board thickness
- aspect ratio
Hole size / drill size
Drill type
Electroless surface
Hot air leveling or PbSn reflowed
Board thickness ≤ 3.5 mm
Board thickness > 3.5 mm
Component drill
+ 0.10 mm
+ 0.15 mm
+ 0.20 mm
Through via
+ 0.10 mm
+ 0.10 mm
+ 0.15 mm
Blind via (SBU)
+ 0.00 mm
+ 0.00 mm
+ 0.00 mm
Buried via
+ 0.00 mm
+ 0.00 mm
+ 0.00 mm
Micro via (laser drilled)
+ 0.00 mm
+ 0.00 mm
+ 0.00 mm
Blind via (depth controlled)
+ 0.00 mm
+ 0.00 mm
+ 0.00 mm
The table assumes standard copper plating of 25 µm (+ 100%).
If more plating is needed you must increase the tool diameter.
For depth controlled blind vias and micro vias the aspect ratio is maximal 1:1.
Component drills
Component drills pick up components. Usually these hole sizes have a + tolerance.
When you have set the drill size according to the table above, you must check
pad size, annular ring and aspect ratio.
Non plated drills
Non plated component drills are usually drilled 0.05 mm bigger than the required hole size.
Through vias, blind vias, buried vias, micro vias
These drills are used for electrical connection between two or more layers.
In this case there is no + tolerance needed.
