Routing micro coaxial cables efficiently and reliably within compact electronic devices, dense PCBs, or tight mechanical enclosures requires careful planning and specific techniques. Improper routing can lead to signal degradation, electromagnetic interference (EMI), physical damage, and device failure. Follow these essential practices:
1. Plan Meticulously Before Routing:
- Map the Path: Create a detailed diagram of the entire cable path from source to destination connector. Identify tight bends, pinch points, proximity to heat sources, moving parts, and other high-risk areas.
- Determine Minimum Bend Radius: Establish the absolute minimum bend radius for your specific micro coax cable (usually specified as a multiple of the cable diameter, e.g., 5x – 10x the outer diameter). Never exceed this limit. Routing below minimum bend radius damages internal conductors and shield, causing impedance changes and signal loss.
- Consider Strain Relief: Plan secure anchoring points at cable ends and periodically along the route to prevent pulling forces from transferring to connectors.
2. Master Handling Techniques:
- Avoid Sharp Bends: Use smooth, sweeping curves. Form gentle bends using your fingers; never crease or kink the cable.
- Leverage Conduits & Tubes: Route cables through flexible plastic sleeving, spiral wrap, or small-diameter silicone tubing. This provides abrasion resistance, prevents pinching, and simplifies routing through crowded areas.
- Utilize Guides & Ties:
- Adhesive Backed Cable Ties: Securely anchor cables to enclosures or PCBs without drilling. Choose low-profile options.
- Cable Clips & Clamps: Use tiny plastic or metal clips designed for micro coax to hold the cable securely against surfaces.
- Self-Adhesive Hook-and-Loop (Velcro) Ties: Ideal for temporary bundling or organizing runs before final securing; easy to adjust and reuse.
- Cable Channels/D-Rings: Route cables along dedicated low-profile channels integrated into the chassis or PCB for organization and protection.
- Employ Routing Tools: Use soft-tipped non-conductive tools (like nylon tweezers, spudgers, or specialized coax routing hooks) to gently guide cables through confined spaces without damaging insulation.
3. Shielding & EMI Management:
- Maintain Shield Integrity: Avoid excessive flexing or crushing that could tear or deform the shield braid/foil. Ensure connectors provide full 360-degree shielding continuity.
- Distance from Noise Sources: Route micro coax paths as far away as physically possible from:
- Switching power supplies.
- High-speed digital lines/clocks.
- Motors and other high-current devices.
- Grounding: Ensure connectors and associated metal enclosures are properly grounded per design specifications to drain EMI effectively. Avoid creating ground loops.
- Cross at Right Angles: If crossing over other conductive traces or power cables is unavoidable, do so at right angles (90 degrees) to minimize inductive coupling.
4. Securing & Protecting Connections:
- Pre-Bend Before Termination: Form the necessary bend in the cable before attaching the connector. Avoid flexing stress directly at the connector solder points.
- Proper Strain Relief at Connectors: Use epoxy, silicone adhesive, heatshrink with glue lining, or dedicated strain relief boots designed for micro coax connectors. This prevents flexing and stress directly on the solder joints.
- Avoid Compression/Pinch Points: Ensure cables are not squeezed between flat surfaces or forced under heavy components. Use spacers if needed.
5. Testing and Validation:
- Continuity & Shorts: Verify continuity of center conductor and shield separately before and after routing. Check for any shorts between conductors.
- Impedance & VSWR: Use a Vector Network Analyzer (VNA) if possible to check characteristic impedance and Voltage Standing Wave Ratio (VSWR) after routing. Significant deviations indicate damage or poor routing.
- Signal Integrity Testing: Test actual signal transmission through the routed path under operating conditions if feasible (e.g., using oscilloscopes, Bit Error Rate Testers – BERTs) to catch subtle degradation or intermittent issues caused by routing stress.
Pro Tips for Success:
- Use Dedicated Micro Coax: Don’t try to use standard RG coax where micro coax is required. Micro coax is specifically designed for the tight spaces and flexibility demands.
- Work Slowly & Carefully: Rushing increases the risk of damaging delicate cables.
- Perform Route Validation: Power down the device and gently manipulate cables along their routed path while monitoring your test equipment for intermittents.
- Document: Update your diagram with the final routing path for future reference and troubleshooting.
By meticulously planning the route, handling the delicate cables with care, employing appropriate supports and protection strategies, managing EMI effectively, securing endpoints correctly, and rigorously testing the final installation, you can successfully route micro coaxial cables even in the most demanding tight spaces while ensuring optimal signal integrity and long-term reliability.
