Top 10 Wiring Harness Materials: Selection Guide for Engineers
A comprehensive guide to wire harness materials—from conductors and insulation to connectors, terminals, and protective jacketing. Learn how to select the right materials for your application's requirements.
Table of Contents
Introduction: Why Material Selection Matters
The materials used in a wire harness directly determine its performance, reliability, and lifespan. A harness that functions perfectly in a climate-controlled office will fail rapidly under the hood of a vehicle or in an industrial plant. Understanding material properties and matching them to your application's demands is fundamental to successful wire harness design.
This guide covers the 10 essential material categories in wire harness construction: from the copper conductors carrying current to the protective sleeving keeping everything together. For each category, we'll discuss material options, properties, and selection criteria to help you make informed decisions.
Key Factors in Material Selection:
- Operating temperature range
- Environmental exposure (moisture, chemicals)
- Electrical requirements (voltage, current)
- Mechanical stress (flex cycles, vibration)
- Fire safety and smoke requirements
- Regulatory compliance (UL, RoHS, etc.)
1. Conductor Materials
The conductor is the heart of any wire—it carries the electrical current from source to load. Material selection affects conductivity, flexibility, weight, and cost.
| Material | Conductivity | Weight | Cost | Best Applications |
|---|---|---|---|---|
| Bare Copper (ETP) | 100% IACS | 8.9 g/cm³ | $$ | General purpose, most applications |
| Tinned Copper | 98% IACS | 8.9 g/cm³ | $$$ | Corrosive environments, soldering |
| Silver-Plated Copper | 103% IACS | 8.9 g/cm³ | $$$$ | High-frequency RF, aerospace |
| Nickel-Plated Copper | 95% IACS | 8.9 g/cm³ | $$$ | High temperature (>200°C) |
| Aluminum | 61% IACS | 2.7 g/cm³ | $ | Weight-critical (aerospace, EV) |
| Copper-Clad Aluminum | 75% IACS | 3.6 g/cm³ | $$ | Weight/cost compromise |
Copper Advantages
- Superior electrical conductivity
- Excellent flexibility and ductility
- Easy to crimp and solder
- Stable resistance over time
Aluminum Considerations
- 60% lighter than copper
- Lower material cost
- Requires special terminations
- Forms oxide layer (connection issues)
"Copper is our default recommendation for 95% of applications. The cost difference with aluminum rarely justifies the extra engineering effort for proper termination. The exception is aerospace and EV applications where every gram matters—there, aluminum makes sense with the right terminal technology."
— Hommer Zhao, WireHarnessProduction
2. Insulation Materials
Insulation surrounds the conductor to prevent short circuits, protect against electrical shock, and shield the wire from environmental factors. The right insulation depends on temperature, chemical exposure, flexibility needs, and cost constraints.
| Material | Temp Range | Flexibility | Chemical Resist. | Cost |
|---|---|---|---|---|
| PVC | -20°C to +105°C | Good | Good | $ |
| XLPE | -40°C to +125°C | Moderate | Excellent | $$ |
| Silicone | -60°C to +200°C | Excellent | Moderate | $$$ |
| PTFE (Teflon) | -70°C to +260°C | Stiff | Outstanding | $$$$ |
| FEP | -70°C to +200°C | Good | Excellent | $$$ |
| ETFE (Tefzel) | -70°C to +150°C | Excellent | Excellent | $$$ |
| TPE | -40°C to +105°C | Excellent | Good | $$ |
| Kapton (Polyimide) | -269°C to +400°C | Stiff | Excellent | $$$$$ |
Insulation Material Deep Dive
PVC (Polyvinyl Chloride)
The industry workhorse for general-purpose applications. PVC offers good electrical properties, flame retardance, and resistance to oils and acids at the lowest cost. However, it becomes brittle at low temperatures and releases toxic chlorine gas when burned.
Best for: Indoor applications, general electronics, appliances, building wire
XLPE (Cross-Linked Polyethylene)
A "step up" from PVC with superior temperature performance and mechanical properties. The cross-linking process creates a thermoset material that won't melt under heat. XLPE is the standard for automotive wire (TXL/GXL types) and can be manufactured with LSZH properties.
Best for: Automotive, industrial, outdoor, underground cable
PTFE (Teflon)
Premium insulation for extreme environments. PTFE handles the highest temperatures, resists virtually all chemicals, and has excellent electrical properties. The downsides are high cost, stiffness (poor for tight bend radii), and difficulty stripping without nicking conductors.
Best for: Aerospace, medical autoclaves, chemical processing, high-frequency RF
Silicone Rubber
Combines high temperature performance with excellent flexibility. Silicone maintains its properties across a wide temperature range and is inherently flame retardant. However, it has lower mechanical strength and is more susceptible to cut-through damage.
Best for: High-flex applications, medical devices, lighting, heating elements
Temperature Ratings Are Not Absolute
Published temperature ratings assume specific conditions (usually 10,000-hour life). Continuous operation at rated temperature shortens life. For long-term reliability, design to 80% of rated temperature. Transient peaks can exceed ratings briefly, but sustained operation above ratings causes rapid degradation.
3. Connector Housing Materials
Connector housings protect terminals, provide mechanical interfaces, and often include sealing features. The housing material must withstand the application's temperature, chemicals, and mechanical stresses while maintaining dimensional stability.
| Material | Max Temp | Properties | Common Applications |
|---|---|---|---|
| Nylon (PA66) | 120°C | Good mechanical, absorbs moisture | Consumer electronics, appliances |
| PBT | 150°C | Low moisture absorption, dimensional stability | Automotive under-hood |
| PPA | 180°C | High strength, chemical resistant | EV battery, exhaust area |
| LCP | 220°C | Thin walls, very stable | SMT connectors, high-density |
| PEEK | 250°C | Premium performance, chemical resistant | Aerospace, oil & gas, medical |
For connector selection guidance, see our article on Wire Harness Design Guide.
4. Terminal & Contact Materials
Terminals and contacts form the electrical interface in connectors. They must provide reliable electrical contact, resist corrosion, and withstand mechanical forces during mating and environmental stress.
| Base Material | Properties | Plating Options | Applications |
|---|---|---|---|
| Brass (CuZn) | Good conductivity, easy forming | Tin, nickel, gold | Low-cost general purpose |
| Phosphor Bronze | High spring force, fatigue resistant | Tin, silver, gold | High-reliability connectors |
| Beryllium Copper | Highest spring force, best fatigue life | Gold, silver | Aerospace, military, high-cycle |
Plating Materials
Tin Plating
- • Lowest cost option
- • Good solderability
- • 10-50 mating cycles
- • Can form whiskers
Gold Plating
- • Best reliability
- • Low contact resistance
- • 500+ mating cycles
- • Highest cost
Silver Plating
- • Best conductivity
- • High current capacity
- • Tarnishes over time
- • Moderate cost
5. Shielding Materials
Shielding protects sensitive signals from external interference (EMI/RFI) and prevents radiated emissions from the cable. Shielding effectiveness depends on material, coverage percentage, and construction type.
| Shield Type | Coverage | Flexibility | Best For |
|---|---|---|---|
| Braided Copper | 85-95% | Good | Low-frequency EMI, general purpose |
| Aluminum Foil | 100% | Limited flex | High-frequency, static installations |
| Foil + Braid | 100% | Moderate | Full-spectrum EMI protection |
| Spiral Wrap | 75-85% | Excellent | High-flex, robotic cables |
| Conductive Tape | 100% | Fair | Low-cost shielding |
For coaxial cable assemblies, shielding is integral to impedance control. For general wire harnesses, shielding is added to specific conductors or the entire bundle as needed.
6. Jacketing Materials
The outer jacket provides mechanical protection, abrasion resistance, and environmental sealing for multi-conductor cables. Jacketing material selection follows similar criteria to insulation but focuses more on mechanical and environmental protection.
Standard Jackets
- PVC: Low cost, good abrasion resistance, general indoor use
- PE: Excellent moisture resistance, outdoor/direct burial
- PUR: Superior abrasion and oil resistance, industrial
- TPE: Good flex life, wide temperature range
Specialty Jackets
- LSZH: Low smoke, no toxic halogen gases when burned
- Silicone: High temperature, flexible, clean room
- PTFE: Extreme temperature, chemical resistant
- Metal Armor: Crush and rodent protection
LSZH (Low Smoke Zero Halogen) Requirements
LSZH jackets are increasingly required by code and specification in:
- Mass transit vehicles
- Commercial aircraft
- Ships and marine vessels
- Data centers
- Healthcare facilities
- High-rise buildings (plenum spaces)
7. Protective Sleeving
Protective sleeving bundles wires together and provides additional protection against abrasion, heat, and chemicals. The right sleeving depends on the harness routing environment.
| Type | Material | Properties | Applications |
|---|---|---|---|
| Braided Sleeve | PET, Nylon, Nomex | Expandable, abrasion resistant | Automotive, industrial |
| Corrugated Tubing | PA, PP, PE | Flexible, crush resistant | Automotive, appliances |
| Heat Shrink | Polyolefin, Viton, PTFE | Seals, strain relief | Connectors, splices |
| Spiral Wrap | PE, PA | Easy installation, serviceable | General bundling |
| Fiberglass Sleeve | Glass fiber, silicone coated | Extreme heat protection | Exhaust, engine harnesses |
8. Tapes & Adhesives
Tapes serve multiple functions in wire harnesses: bundling, insulation, abrasion protection, and noise reduction. Select tape based on temperature rating, adhesive type, and specific function needed.
Harness Tapes
- PVC Tape: General bundling, marking (-20°C to +80°C)
- Cloth/Fleece: Noise damping, abrasion protection
- Kapton: High temperature, electrical insulation
- Silicone: Self-fusing, waterproof repair
Adhesive Considerations
- Rubber: Good initial tack, general purpose
- Acrylic: Better temperature and UV resistance
- Silicone: Highest temperature performance
- Hot Melt: Fast bonding, potting applications
9. Materials by Industry Application
Different industries have distinct material requirements based on their operating environments and regulatory demands. Here's a quick reference guide:
Automotive
High temperature under hood, vibration, fluids exposure
Aerospace
Extreme temperature range, weight critical, high reliability
Medical Devices
Biocompatibility, sterilization, patient safety
Industrial/Robotics
High flex cycles, oil/coolant exposure, EMI immunity
For industry-specific guidance, see our articles on Automotive vs Industrial Wire Harness and Medical Wire Harness Manufacturers.
10. Frequently Asked Questions
What is the best wire insulation material for high temperature applications?
PTFE (Teflon) offers the highest temperature rating up to 260°C continuous. Silicone rubber handles up to 200°C with better flexibility. For moderate high-temp (125°C), XLPE provides a cost-effective solution. Choose based on your maximum temperature, flexibility needs, and budget.
Should I use copper or aluminum wire for my wire harness?
Copper is the standard choice for most applications due to superior conductivity, flexibility, and ease of termination. Aluminum is 60% lighter and cheaper, making it attractive for weight-sensitive applications like aerospace and EVs, but requires special termination techniques and is less flexible.
What is LSZH cable and when should I use it?
LSZH (Low Smoke Zero Halogen) cable produces minimal smoke and no toxic halogen gases when burned. It's required for enclosed spaces with limited ventilation—transit systems, aircraft, ships, data centers, and buildings with fire safety requirements. Many building codes now mandate LSZH in certain applications.
What connector housing material is best for high-temperature automotive applications?
PBT (Polybutylene Terephthalate) is the standard for under-hood automotive connectors, handling up to 150°C. For extreme temperatures near exhaust systems or EV battery packs, PPA (Polyphthalamide) handles up to 180°C. PEEK offers the highest performance up to 250°C but is significantly more expensive.
How do I choose between PVC and XLPE wire insulation?
PVC is lower cost and suitable for general applications up to 70-105°C with good chemical resistance. XLPE costs more but offers better temperature performance (up to 125°C), superior mechanical strength, and moisture resistance. For automotive wire (TXL/GXL), XLPE is the standard. Use PVC for cost-sensitive general applications; XLPE for demanding environments.
Conclusion
Wire harness material selection is a balancing act between performance requirements, environmental conditions, regulatory compliance, and cost. There's rarely a single "best" material—the right choice depends on your specific application's demands.
Use this guide as a reference when specifying materials, but always validate selections with your manufacturer and conduct appropriate testing for your application. The tables and comparisons here provide starting points—actual performance can vary based on specific formulations, processing, and operating conditions.
Need Help Selecting Wire Harness Materials?
Our engineering team can help you select the optimal materials for your wire harness application, balancing performance, cost, and compliance requirements.
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Hommer Zhao
Founder & Technical Director, WireHarnessProduction
With over 15 years in wire harness manufacturing, Hommer has extensive experience with materials across automotive, medical, industrial, and aerospace applications. He helps engineering teams select optimal materials for their specific requirements.