PCB vias and hole sizes: what you can order
How big a hole must be for a component or a screw, what the drill limits are and how to use vias for signals, current and heat.
What a via is
A via is a plated hole that connects copper on different layers. A through-hole via passes through the whole board. Blind vias connect an outer layer to an inner one, buried vias connect inner layers only. Both add process steps and cost.
At PCB-ELECTRA the standard range is plated through-hole vias. If your design needs blind or buried vias, contact us before you finish the layout.
Drill limits
- Smallest drill: 0.3 mm with a pad of 0.5 mm.
- Largest drill: 6.4 mm. Larger holes are produced by milling.
- Aspect ratio: board thickness divided by hole diameter should stay below roughly 10 : 1 for reliable plating.
- Annular ring: give pads a real margin around the hole; tight rings are the most common source of yield loss.
- Plating: copper plating reduces the finished diameter by roughly 0.05 mm compared with the drill. Specify the finished hole size in your drill file and tell us whether holes are plated or not.
Hole sizes for leads and screws
| Use | Finished hole |
|---|---|
| Component lead 0.6 mm | 0.8 to 0.9 mm |
| Component lead 0.8 mm | 1.0 to 1.1 mm |
| Component lead 1.0 mm | 1.2 to 1.3 mm |
| M2 screw | 2.2 to 2.4 mm |
| M3 screw | 3.2 to 3.4 mm |
| M4 screw | 4.3 to 4.5 mm |
As a rule, the hole is 0.2 to 0.3 mm larger than the lead so that it can be soldered reliably.
Vias for signals, current and heat
- Signals: use the standard via of 0.3 mm drill and 0.5 mm pad, or larger when space allows — larger vias are more forgiving in production.
- Current: use several vias in parallel; one via is the weak point of a power connection. See the trace width and current guide.
- Heat: a field of vias under a power component conducts heat to a copper area on the other side, which then acts as a heat spreader.
- Via in pad: avoid placing vias inside solder pads of fine-pitch parts unless you have agreed it with us first; solder can flow into the hole.
What to send
Gerber layers plus separate Excellon drill files for plated and non-plated holes, in millimetres (see the Gerber guide). Slots and large cut-outs belong on the outline layer. Configure the board in the price calculator.
Frequently asked questions
What is the smallest drill diameter?
0.3 mm, with a pad of at least 0.5 mm.
What happens with holes larger than 6.4 mm?
Holes above the maximum drill diameter of 6.4 mm are milled instead of drilled.
Do I need separate drill files for plated and non-plated holes?
Yes. Separate files let us give each hole the right treatment, so keep them apart and specify the finished diameters.
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