Effective Methods and Techniques for Testing Micro Coaxial Cables

 

Key Challenges and Objectives

1. ​Miniature Structure Limitations: Diameters <0.5mm increase risks of short circuits or mechanical damage during probing.
2. ​High-Frequency Signal Validation: Requires GHz-level precision for impedance matching, insertion loss, and return loss.
3. ​Mechanical Reliability Testing: Must replicate real-world bending, stretching, and fatigue conditions.

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Testing Procedures and Methods

1. ​Visual and Structural Inspection

• ​Tools:
  • High-magnification microscope (200×+)
  • X-ray micro-CT scanner
• ​Key Checks:
  • ​Conductor Defects: Inspect silver plating uniformity and surface scratches under microscope (Fig. 1).
  • ​Dielectric Layer Consistency: Measure circumferential thickness variation using laser micrometer (±2μm tolerance).

2. ​Electrical Performance Testing

• ​Tools:
  • Vector Network Analyzer (VNA, up to 40GHz)
  • Precision LCR meter
• ​Critical Tests:
  • ​Impedance Matching:
    • Measure characteristic impedance (50Ω/75Ω) using calibrated VNA (±5% tolerance).
  • ​Insertion Loss:
    • Validate loss at target frequency (e.g., <0.3dB/cm @10GHz).
  • ​Shielding Effectiveness:
    • Compare SNR with/without EMI exposure (shielded vs. unshielded configurations).

3. ​Mechanical Reliability Testing

• ​Equipment:
  • Dynamic bending tester
  • Micro-tensile machine
• ​Test Protocols:
  • ​Bending Endurance:
    • 100,000 cycles at 0.5mm radius; post-test resistance change ≤5%.
  • ​Stretch Resistance:
    • Apply 0.5N tensile force; elongation before breakage must exceed 15%.

4. ​Material Analysis

• ​Techniques:
  • SEM-EDS (Scanning Electron Microscopy with Energy Dispersive Spectroscopy)
  • Differential Scanning Calorimetry (DSC)
• ​Analysis Targets:
  • ​Dielectric Thermal Stability: Verify PTFE withstands -200°C~260°C.
  • ​Jacket Chemical Resistance: No swelling after 24h immersion in pH 2–12 solutions.

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Recommended Tools and Precautions

1. ​Probing Solutions:
   • Use micro-spring probes (e.g., Hirose UFF series) with <0.1N contact force.
2. ​Calibration Requirements:
   • Perform VNA calibration with 3.5mm/1.0mm kits to eliminate fixture errors.
3. ​ESD Protection:
   • Maintain 40%~60% humidity; deploy ionizers to neutralize static charges.

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Case Study and Data

• ​Medical Catheter Application:
  • A 0.2mm-diameter cable showed insertion loss increase from 0.25dB/cm to 0.28dB/cm after 100,000 bends, compliant with ISO 13485 medical standards.

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Conclusion

Effective testing of Micro coaxial cables demands precision instrumentation, standardized protocols, and advanced material analysis. Future advancements in non-destructive techniques like terahertz imaging will revolutionize quality control while preserving cable integrity.

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Visualization Recommendations:

1. ​Microscopic Conductor Surface Image: Annotate plating defects and scratches.
2. ​VNA Measurement Screenshot: Display S11/S21 parameters across 1–40GHz.
3. ​Dynamic Bending Tester Animation: Demonstrate multi-axis bending simulation.

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