Evaluating CAF Failure Risk via Ion Migration Rate Testing

1. CAF Mechanism & Ion Migration

• ElectrochemICal Path:
  $\text{Anode:}\mathrm{C}\mathrm{u}\to \mathrm{C}{\mathrm{u}}^{2+}+2{\mathrm{e}}^{-}\text{Cathode:}2{\mathrm{H}}_2\mathrm{O}+2{\mathrm{e}}^{-}\to 2\mathrm{O}{\mathrm{H}}^{-}+{\mathrm{H}}_2$
  

• Ion Migration Rate (K):
  $K=\frac{\mathrm{\Delta }L}{\mathrm{\Delta }t\cdot E}(\text{Unit:}\mu {\mathrm{m}}^2\mathrm{/}\mathrm{V}\cdot \mathrm{s})$
  

  • $\mathrm{\Delta }L$: Dendrite length (μm)

  • $\mathrm{\Delta }t$: Test duration (h)

  • $E$: Electric field (V/mm)

2. Test Standards & Acceleration Model

2.1 Accelerated Conditions

2.2 Lifetime Prediction

• Arrhenius Model:
  $t_{\mathrm{f}\mathrm{a}\mathrm{i}\mathrm{l}}=A\cdot e^{\frac{E_a}{RT}}\cdot V^{-n}\cdot d^m$
  

  • $E_a$: 0.8±0.1eV

  • $V$: Voltage (V), $n$≈1.7

  • $d$: Spacing (mm), $m$≈2.2

3. Test Structure Design

4. Test Procedure

4.1 Key Parameters

5. Risk Classification

6. Material & Process Improvements

7. Test Report Essentials

1. Migration Path Analysis: SEM/EDS dendrite composition (Cu/O>1:1 confirms CAF)

2. Leakage Current-Time Curve: Record first >1μA timepoint (t₀)

3. Acceleration Factor: Extrapolate 25℃/60%RH life from 85℃/85%RH data

4. Material CTI: Comparative Tracking Index (IEC 60112) >250V