Micro Coaxial Cable factory

What is the Maximum Operating Voltage for Standard Micro Coaxial Cable Assemblies?

This is a crucial question when designing or using tiny coaxial cables (“micro coax”) in applications like medical devices, miniature sensors, high-speed digital connections, or aerospace systems. Pushing these delicate cables beyond their voltage limits risks failure, signal loss, and even safety hazards like arcing or fire.

The Short, Essential Answer:

There is ​no single universal “standard” maximum operating voltage for all micro coaxial assemblies. ​Typically, it ranges between 30 volts (V) AC/DC and 100 volts (V) AC/DC for common miniature coax cables used in signal transmission applications. However, ​you MUST always consult the specific manufacturer’s datasheet for the exact cable assembly you are using. Relying on a generic range without checking is unsafe and unreliable.

Why is there a Range? What Factors Dictate the Maximum Voltage?

The maximum operating voltage a micro coax cable can handle depends on several critical engineering factors:

1. ​Conductor Size (AWG): Thicker inner conductors (like 36 AWG) generally handle slightly more voltage than extremely fine ones (like 44 AWG).
2. ​Insulation Material & Thickness: This is arguably the most critical factor.
   • ​Dielectric Strength: The core insulation separating the center conductor from the shield must withstand high electric fields without breaking down. Common materials like FEP (Fluorinated Ethylene Propylene) and PTFE (Teflon) have excellent dielectric strength.
   • ​Insulation Thickness: Thicker insulation directly increases the breakdown voltage. However, micro coax is designed to be micro, so insulation is inherently very thin.
3. ​Shielding Construction: While primarily for EMI protection, the shield integrity also influences the electrical path and potential breakdown points.
4. ​Jacket Material (if present): An outer jacket provides additional environmental protection but minimal direct contribution to voltage withstand within the cable itself.
5. ​Environmental Conditions: Temperature extremes, humidity, chemical exposure, and flexing can degrade insulation properties over time, effectively lowering the safe operating voltage.

Understanding Typical Ranges (with Caveats!)

• ​Low-End (Common for Fine Wire/Gigahertz Signals): Many assemblies using 40 AWG to 44 AWG conductors with thin FEP insulation are rated around ​30V to 50V AC/DC (RMS). For example, MMCX assemblies or very fine micro-coax might fall here.
• ​Mid-Range (Common for General Signal Transmission): Assemblies using 36 AWG to 40 AWG with standard FEP or PTFE insulation often have ratings around ​50V to 100V AC/DC (RMS). This covers a large portion of commonly used miniature coax assemblies (like smaller RG-178 assemblies, micro-SMA).
• ​Higher End (Less Common for “Micro”): Specialized cables with thicker insulation might approach ​150V or higher, but pushing into this territory is less typical for assemblies truly classified as “micro coax” (which prioritize small size and high frequency over high voltage).

Crucial Safety & Reliability Notes

1. ​Operating Voltage ≠ Test Voltage: Manufacturers specify a Working Voltage (Continuous Operating Voltage). They often also specify a much higher Test Voltage (Withstand Voltage) used briefly during production testing or qualification (e.g., 500V or 1000V DC for 60 seconds). ​NEVER confuse the withstand voltage with the safe operating voltage.
2. ​DC vs. AC: Voltages are usually specified for both direct current (DC) and alternating current (AC – given as RMS value). An AC rating might be slightly lower than its DC counterpart for the same cable.
3. ​Peak Voltage Matters: For pulsed or high-frequency AC signals, the peak voltage (which is √2 times the RMS voltage for sine waves) must also stay below the maximum operating voltage rating. Ensure your system considers peak voltage.
4. ​Derating: Voltage ratings are often given at room temperature (e.g., 20-25°C/68-77°F). Operating at higher temperatures significantly reduces the safe voltage the insulation can handle. Consult derating curves in the datasheet.
5. ​Power Delivery vs. Signal: Micro coax is primarily designed for signal transmission where currents are very low. Using it for significant DC power delivery requires special attention to both voltage rating and current carrying capacity (which is very limited in micro coax).

Key Takeaways for Safe Use

• ​Forget Generic “Standard” Answers: Voltage capability is highly specific.
• ​Mandatory: ​ALWAYS check the manufacturer’s datasheet for the exact cable assembly (part number and revision) you intend to use. This is non-negotiable for safety and reliability.
• ​Know Your Environment: Factor in temperature, humidity, and potential chemical exposure.
• ​Signal vs. Power: Understand the distinction; micro coax excels at signals, not power.
• ​Safety Margin: If possible, design with a safety margin below the maximum rated voltage, especially for critical applications.

By understanding these factors and prioritizing datasheet consultation, you ensure your micro coaxial assemblies perform reliably and safely within their true electrical capabilities. Never gamble on the voltage rating – always verify with the specific manufacturer specifications.