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PCB elements: HOLES TYPES
04.08.2017
Łukasz Romik

Due a big variety of functions and applications of printed circuits the different types of the holes can be present in their structure. They can be classified in a general way – metalized / non-metalized or because of their shape or function etc. 

The classification considering most types of holes types used in printed circuits is presented below.

 

Basic classification:

  • vias/metalized holes
    • standard – diameter from 0.2 mm
    • micro-vias – diameter below 0.2 mm (typical: 0.1 mm; 0.15 mm)
  • non-metalized holes: diameter from 0.25 mm
    • without annular ring
    • with the annular ring moved from the hole edge
    • with the annular ring up to the hole edge.

 

Classification by what layers they pass through / what layers they connect:

  • PTH/NPTH – they pass through the entire thickness of the PCB;
  • blind/backdrilling – vias/holes drilled to the depth (visible from outside but only on one side of the PCB);
  • buried vias – vias connecting the internal layers (not visible from outside).

 

Classification by a finishing method:

  • not covered by a soldermask – without cover or covered with the protection layer e.g. HAL, ENIG etc.
  • covered with a soldermask (usually not plugged)
  • filled (copper, dielectric)
  • filled and covered with a soldermask (standard)
  • filled and covered with a soldermask (flat, bigger degree of filling).

 

Non-typical:

  • slotholes:
  1. special case: slotholes 2D - the slothole length (L) is smaller or equal double it width (2D)

L ≤ 2*D  sinkholes (beveled).

 

 

 

 

  • sinkholes (beveled)

 

 

 

 

 

Classification by the diameter tolerance (examples):

  •  standard, typically: + 0.1 mm / - 0.05 mm
  •  pressfit: e.g. + 0.05 mm / - 0.05 mm.

 

The parameters and application of individual types of holes will be presented in the forthcoming articles.

 
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