Reference sheet
Via current
How much current a via carries, and when to use several
PCB via current capacity
Rough single-via guide from IPC-2221's own internal-conductor formula (I = 0.024 · ΔT0.44 · A0.725), treating the plated barrel as a trace of width π·d and thickness = the plating — assuming 25 µm of barrel plating (IPC-6012 Class 2's typical minimum is 20 µm) and a 10°C rise, no thermal relief. Real capacity depends on plating thickness, board stack-up, and ambient conditions; when a single via isn't enough, use several in parallel rather than assuming a bigger drill scales linearly — the exponent on area is 0.725, well short of linear.
| Drill diameter | Approx. current |
|---|---|
| 0.2 mm (8 mil) | ≈ 0.67 A |
| 0.3 mm (12 mil) | ≈ 0.90 A |
| 0.4 mm (16 mil) | ≈ 1.11 A |
| 0.5 mm (20 mil) | ≈ 1.30 A |
| 0.6 mm (24 mil) | ≈ 1.48 A |
| 0.8 mm (31 mil) | ≈ 1.83 A |
| 1.0 mm (39 mil) | ≈ 2.15 A |
