PCBパターン幅 計算ツール
IPC-2221準拠の電流容量計算
Required Parameters
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Quick Answer
Use this to calculate how wide a copper trace must be to safely carry a specific current without overheating (based on IPC standards).
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Design Notes
The IPC-2221 standard equations used here provide a safe baseline, but modern high-density boards often rely on the newer IPC-2152 standard. External layers dissipate heat into the air efficiently, meaning they can be thinner than internal layers for the same current. If routing power planes or high-current motor drivers, consider using thicker copper (e.g., 2oz) or removing solder mask to apply solder directly over the trace to lower resistance.
Common Mistakes
- 1
Using internal layer calculations for external traces (results in overly wide traces).
- 2
Ignoring the effect of via bottlenecks: A 50-mil trace won't handle 5A if it connects to the next layer through a single 0.3mm via. Use via arrays.
- 3
Assuming 1oz copper is exactly 1oz thick everywhere: Plating processes can vary copper thickness by up to 20%.
Engineering Handbox
1. Find Cross Section: A = (3 / (0.048 × 10^0.44))^(1/0.725) ≈ 39.5 mil² 2. Given 1oz = 1.378 mils thick 3. Width = 39.5 / 1.378 = 28.6 mils (0.726 mm)
Knowledge Base
IPC-2221の公式は？
I = k × ΔT^b × A^c。Aは断面積（mil²）。外層：k=0.048、内層：k=0.024。
1Aに必要なパターン幅は？
1oz銅箔外層、温度上昇10°Cで約10mil（0.25mm）。内層はその2倍。
銅箔厚の影響は？
1oz = 35µm。2ozにすると同じ電流で必要なパターン幅が半分に。
許容温度上昇は？
標準設計：10°C。パワー基板：20〜30°C。FR4のTgは130〜170°C。
ビアは同じ電流を流せる？
いいえ。標準ビア（0.3mm）は0.5〜1A程度。大電流にはビアアレイを使用。