Micro Coaxial Cable factory

Semi-Rigid Coaxial Cable Handling: Critical Precautions for Optimal P...

1. ‌Mechanical Stress Management‌
   ‌A. Bending and Shaping Guidelines‌
   Semi-rigid cables are designed for ‌one-time bending‌. Improper shaping can crack the outer conductor, causing signal leakage or impedance mismatches.

Cable Diameter (mm) Minimum Bend Radius (Static) Maximum Bend Angle (per 10cm length)
2.2 8 mm 90°
3.0 12 mm 60°
5.0 20 mm 45°
‌Tools‌: Use mandrel benders (e.g., Times Microwave SMB-2200) to ensure uniform curvature.

‌B. Avoiding Fatigue Fractures‌
‌Vibration-Prone Environments‌: Secure cables with clamps every 15–20 cm (per MIL-STD-348).
‌Do NOT Re-bend‌: Once shaped, re-adjusting bends risks metal fatigue. Replace deformed sections.

2. ‌Thermal Considerations‌
   ‌A. Temperature Limits During Installation‌
   ‌Operating Range‌: -55°C to +165°C (PTFE dielectric).
   ‌Soldering/Assembly‌: Keep localized heat below 300°C to prevent dielectric melting. Use heat sinks on connectors.
   ‌B. Thermal Expansion Mismatch‌
   Example: A 3.0mm aluminum-jacketed cable in a satellite payload failed due to CTE (Coefficient of Thermal Expansion) mismatch with a steel chassis.

‌Solution‌:

Use flexible transition sections (e.g., braided jumpers).
Match materials (e.g., copper cables with copper brackets).

3. ‌Connector Installation Best Practices‌
   ‌A. Soldering Techniques‌
   ‌Flux Selection‌: Non-corrosive rosin flux (e.g., Kester 1544) to avoid residue-induced corrosion.
   ‌Soldering Iron‌: 60W with a chisel tip (350–400°C) for rapid heat transfer.
   ‌Step-by-Step‌:

Clean the cable end with isopropyl alcohol.
Tin the inner conductor and connector pin.
Solder within 3 seconds to prevent dielectric damage.
‌B. Connector Alignment‌
Misalignment causes impedance spikes (>2.0 VSWR at 18 GHz).

‌Tool‌: Use alignment jigs (e.g., Southwest Precision SNAPA-LOK).
‌Verification‌: Test with a vector network analyzer (VNA) post-installation.

4. ‌Grounding and Shielding Integrity‌
   ‌A. Grounding the Outer Conductor‌
   ‌Direct Grounding‌: Solder the cable’s outer conductor to a low-impedance ground plane.
   ‌Avoid Paint/Coating‌: Scrape off anodized layers on mounting surfaces for metal-to-metal contact.
   ‌B. Shield Continuity Testing‌
   ‌Method‌: Use a milliohm meter to measure resistance between cable shield and chassis (<5 mΩ).
   ‌Failure Case‌: A radar system EMI issue traced to a 120 mΩ ground discontinuity in a 5.0mm cable.
5. ‌Environmental Protection‌
   ‌A. Moisture and Corrosion‌
   ‌Sealing‌: Apply silicone sealant (e.g., Dow Corning 732) at connector interfaces in humid environments.
   ‌Material Choice‌: Opt for silver-plated copper in salt-spray conditions (per ASTM B117).
   ‌B. Abrasion Resistance‌
   ‌Sleeving‌: Protect cables in high-friction zones with PTFE sleeving (e.g., Gore Tex GORE™ Protective Sleeve).
6. ‌Common Mistakes and Fixes‌
   Mistake Consequence Solution
   Over-tightening clamps Outer conductor crushing Torque to 0.6–0.8 Nm
   Using non-mandrel tools Oval deformation Replace damaged section
   Skipping post-installation VNA test Undetected impedance mismatch Re-solder or replace connector
7. ‌Case Study: Aerospace Antenna Feed Failure‌
   ‌Issue‌: A bent 2.2mm semi-rigid cable in a UAV’s phased array antenna caused 6 dB loss at 15 GHz.
   ‌Root Cause‌: Hand-bent beyond 8mm radius, cracking the outer conductor.
   ‌Fix‌: Replaced with a pre-shaped section and added vibration-damping mounts.
8. ‌Industry Standards Summary‌
   Standard Focus Area Key Requirement
   MIL-STD-348 RF connector interfaces VSWR <1.3 up to 18 GHz
   IEC 60169 Soldering and grounding Shield continuity <5 mΩ
   NASA-STD-8739.4 Spacecraft cable assembly No sharp bends, 2x thermal cycle testing