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سجل التغييرات الكاملالمحرّك 1.18.3

Via Current & Resistance

المسارات والنحاس

Cross-section, resistance and current capacity of a via, and how many you need.

هذه الصفحة غير مترجمة بالكامل بعد. الأجزاء غير المترجمة معروضة بالإنجليزية.

المدخلات

ملف اللوحة

Fills Board thickness (barrel length) وOperating temperature وFinished hole diameter from your board profile.

IPC-6012: 20 µm average for Class 2, 25 µm for Class 3
A
°C
°C

النتائج

1 ناجحة
Vias required
4
ناجح

المعيار: 4 vias ≥ the 4 needed for a 10 °C rise, IPC-2221B §6.2, k = 0.024
أظهر خطوات الحساب
  1. Barrel cross-section, an annulusA = π × (d + t_p) × t_p = π × 0.325 mm × 25 µm = 0.02553 mm² = 39.56 mil²
  2. Current per via, IPC-2221I = k × ΔT^0.44 × A^0.725 = 0.024 × 10^0.44 × 39.56^0.725 = 951.2 mA
  3. Vias requiredN = ⌈I / I_via⌉ = ⌈3 / 0.9512⌉ = 4
  4. Resistance of 4 in parallelR = (ρ × T / A) / N = 1.1 mΩ / 4 = 275.5 µΩ
Resistance per via
1.1mΩ
Current capacity per via

for 10 °C rise, k = 0.024
951.2mA
Voltage drop across transition
826.4µV
كل النتائج (4)
Barrel cross-section

39.6 mil², a tube, not a rod
25500µm²
4 vias in parallel
275µΩ
Power in the via field
2.479mW
Aspect ratio

standard fabrication
5.33:1
4 vias at 750 mA each, inside the 951.2 mA per-via limit. Minimum required: 4.

Spread the vias along the current path. A tight cluster shares heat and runs hotter than this calculation assumes.

إلى أي حد نعرف هذا الرقم

من أين تأتي الطريقة
  • IPC-2221B §6.2 (2012)

IPC-2221B, Generic Standard on Printed Board Design, §6.2 (2012) معايرة على قياسات

صادقة ضمن
  • Barrel plating thickness 5 µm to 100 µm

Barrel plating thickness Barrel plating far outside the usual 15 to 35 µm is a different process from the one assumed here.

مدى دقتها
The IPC-2221 trace curve applied to the barrel cross-section.

It ignores the heat the barrel sheds into the planes it crosses, so the current it reports is conservative.

IPC-2221B §6.2

يُقاس مقابل

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المسح البارامتري

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المقطع العرضي

المبدأ

A plated hole carries current in a thin copper tube, not the whole hole. A 0.3 mm via with 25 µm plating has about the cross-section of a 0.7 mm trace in 1 oz copper.

Barrel cross-sectional area
A=π(d+tp) tpA = \pi (d + t_p)\, t_p
Mean diameter d + tp. For 0.3 mm and 25 µm, A ≈ 0.0255 mm² (about 40 mil²).
Barrel resistance
Rvia=ρ lA=ρ tboardπ(d+tp)tpR_{via} = \frac{\rho\, l}{A} = \frac{\rho\, t_{board}}{\pi (d+t_p) t_p}
Typically 0.5–2 mΩ on a 1.6 mm board.
Current capacity (IPC-2221 applied to the barrel)
I=k ΔT0.44A[mil2]0.725I = k\,\Delta T^{0.44} A_{[\t{mil}^2]}^{0.725}
N vias in parallel
RN=RviaN,Iper=INR_N = \frac{R_{via}}{N}, \qquad I_{per} = \frac{I}{N}
Thermal resistance of one via
Rθ,via=tboardkCuAR_{θ,via} = \frac{t_{board}}{k_{Cu} A}
The same formula with copper’s thermal conductivity in place of its electrical conductivity. About 163 °C/W for the example above.
  • ddfinished (plated) hole diameter
  • tpt_pcopper plating thickness in the barrel, typically 20–30 µm
  • llbarrel length = board thickness
  • NNnumber of vias sharing the current
تفاصيل إضافية

Treating the barrel as a trace of the same cross-section is conservative: it is bonded to copper at both ends and sheds heat better than a free trace.

Power vias. Spread them along the path rather than clustering, and add at least one more than the calculation needs. An open barrel is a field failure.

Fabrication limits

  • Aspect ratio (board thickness ÷ hole) above about 8:1 makes plating hard; 10:1 is the practical limit for standard processes.
  • Plating class. IPC-6012 Class 2 requires 20 µm average in the hole, Class 3 requires 25 µm. If your capacity assumes 25 µm, put it on the drawing.
  • Filled vias. Copper-filled vias conduct much better; epoxy-filled ones conduct no better than plain.
References: IPC-6012 (qualification and performance of rigid boards, plating thickness classes), IPC-2221B §6.2 for the current capacity relation.

إصدار المحرك ⁨1.18.3⁩