Via Current Calculator
Calculate maximum current capacity for PCB vias. Get resistance, power dissipation, and parallel via recommendations.
Calculator
How to Use This Calculator
This via current calculator estimates the maximum current a PCB via can safely carry based on its physical dimensions and thermal constraints.
- Select a Preset or Enter Dimensions — Choose a common via size or input custom values
- Set Plating Thickness — Typical values are 25µm (1oz) to 50µm (2oz)
- Enter Board Thickness — The via length equals your PCB thickness
- Set Temperature Limits — Define allowed temperature rise and ambient
- Add Parallel Vias — For higher currents, use multiple vias
- Click Calculate — Get current capacity and resistance
Via Current Theory
A via is essentially a hollow copper tube connecting different PCB layers. Its current-carrying capacity depends on the cross-sectional area of the copper plating and the ability to dissipate heat.
Key Factors
- Copper Cross-Section: Larger diameter and thicker plating = more copper = more current
- Via Length: Longer vias have higher resistance
- Temperature Rise: Current causes I²R heating; limit temp rise to avoid damage
- Thermal Path: Heat dissipates through copper to traces and planes
Resistance Formula
Cross-Section Area
Current Capacity
Maximum current is limited by the allowed temperature rise. The formula balances I²R power dissipation against the via's thermal resistance. Conservative estimates use 10-20°C rise above ambient.
Via Types and Sizes
Standard Via Sizes
| Via Type | Drill Size | Typical Current | Use Case |
|---|---|---|---|
| Signal Via | 0.2-0.3mm | 0.3-0.5A | Signal routing, low power |
| Standard Via | 0.4-0.5mm | 0.7-1.0A | General purpose |
| Power Via | 0.6-0.8mm | 1.0-1.5A | Power distribution |
| Heavy Current Via | 1.0-1.2mm | 1.5-2.5A | High current paths |
Via Plating Thickness
| Plating | Thickness | Notes |
|---|---|---|
| Standard | 20-25µm | Most common, adequate for signal vias |
| Heavy | 35-50µm | Power vias, higher current capacity |
| IPC Class 3 | ≥25µm | High-reliability applications |
Design Tips
Using Multiple Vias
- Current Sharing: Multiple vias share current, but not equally
- √n Rule: Use √n scaling for parallel vias (4 vias ≈ 2× current, not 4×)
- Spacing: Space vias apart to avoid thermal coupling
- Array Pattern: Use via arrays for power planes and high-current paths
Via Placement for Power
- Place power vias close to IC power pins
- Use multiple vias for each power connection
- Connect vias to wide traces or copper pours
- Avoid routing high-speed signals near power via arrays
Thermal Considerations
- Vias help transfer heat between layers
- Thermal vias under hot components improve cooling
- Filled vias have better thermal conductivity
- Consider copper pour around via arrays for heat spreading
Example: 5A Power Supply
| Single 0.4mm via | ~0.8A capacity |
| Required for 5A | ~10 vias (conservative) |
| Alternative: 0.8mm vias | ~4-5 vias |
| Best: 1.0mm filled vias | ~3-4 vias |
Frequently Asked Questions
How accurate is this calculator?
This calculator provides conservative estimates based on thermal models. Real-world current capacity depends on many factors including PCB material, copper quality, and thermal environment. Use these values as guidelines and add safety margins for production designs.
Should I fill my power vias?
Filled vias (with conductive or non-conductive fill) can carry more current because the fill adds thermal mass and reduces thermal resistance. However, filled vias are more expensive. For most designs, using more standard vias is more cost-effective than fewer filled vias.
Why does the calculator use √n for parallel vias?
Current doesn't divide equally among parallel vias due to unequal resistance paths and thermal coupling. The √n scaling provides a conservative estimate. For critical designs, simulate current distribution or add more vias.
What plating thickness should I use?
Standard 25µm plating is adequate for most signal vias. For power vias carrying more than 0.5A per via, consider specifying 35-50µm plating. Check with your PCB manufacturer for available options and costs.
How do I verify via current in my design?
Use thermal simulation or IR camera measurements on prototypes. Check via temperature rise under load. If vias get hot (more than 20°C above ambient), add more vias or increase via size.
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