ECCA wire (Enameled Copper Clad Aluminum Wire) is one of the most important composite conductor materials**in high-frequency, lightweight, and energy-saving applications in the 21st century. It is composed of a three-layer structure of aluminum core + copper skin + paint film insulation layer, which combines the light weight and cheapness of aluminum with the excellent conductive, weldable, and high-frequency characteristics of copper.
It is made of copper-clad aluminum wire (CCA) by coating an aluminum core with copper strips and then metallurgically bonding (welding, rolling, extruding), and then coating the surface with an insulating paint film (PE, PEI, PAI, PI, PU, etc.). ECCA concentrates the advantages of “copper surface + aluminum heart”.
1.2 Five core advantages of ECCA line
Advantages
Physical basis
Engineering significance
Lightweight
Aluminum density 2.7 vs copper 8.96 g/cm³
50-65% weight reduction
Low cost
Aluminum price is only 1/8-1/12 of copper price
Material cost reduced by 40-65%
High frequency excellence
Skin effect (current concentration in the copper layer)
100 kHz performance is almost the same as pure copper
Good paint film
The surface is a copper layer and the paint film has good adhesion
The paint film adhesion is close to that of pure copper enameled wire
Solderability
The surface is a copper layer and can be soldered with a soldering iron
The weldability is better than that of pure aluminum enameled wire
1.3 3 major application fields of ECCA line
-High frequency electronics: switching power supply, UPS, inverter, rectifier
– New energy: electric vehicle OBC, photovoltaic inverter, wind power converter
– 5G Communications: Base Station AAU, Filter, Balun Coil
II. Detailed explanation of the cross-sectional structure of the ECCA line
2.1 Three mainstream structures of ECCA lines
Structure type
Sectional view
Copper distribution
Features
Concentric structure
🔵 Copper skin evenly surrounds the aluminum core
360° equal thickness coating
Mainstream, stable performance
Eccentric structure
Uneven copper thickness
One side is thicker and the other is thinner
Performance is degraded and eliminated
Embedded construction
Copper embedded in aluminum core
Partial copper plating
Special applications
2.2 Typical cross-section (concentric circles)
Paint film insulation layer (0.02-0.08 mm)
┌────────────────────┐
│ Copper layer (10-30%) │ ← Main path of current
│ ┌───────────────┐ │
│ │ │ │
│ │ Aluminum core │ │ ← Weight body
│ │ (70-90%) │ │
│ │ │ │
│ └───────────────┘ │
└─────────────────────┘
2.3 Functional division of 3-layer structure
Layer
Material
Thickness
Function
Layer 1 (outer)
Paint film
0.02-0.08 mm
Electrical insulation
Layer 2 (Medium)
Copper
0.05-0.30 mm
Conductive (100% current carrying at high frequencies)
Layer 3 (inner)
Aluminum
Diameter 0.10-8.0 mm
Mechanical support, cost reduction
2.4 Matching of copper thickness and frequency
Operating frequency
Skin depth
Minimum copper thickness
Remarks
50 Hz
9.3 mm
Not required (full cross-section)
No advantage to copper-clad aluminum
1 kHz
2.1 mm
Not required
Power frequency advantage area
10 kHz
660 μm
0.7 mm
Close
100 kHz
210 μm
0.25 mm
Copper-clad aluminumThe starting point of advantages
1 MHz
66 μm
0.08 mm
Best Advantage Area
10 MHz
21 μm
0.03 mm
Fully utilized
III. Detailed explanation of the physical properties of ECCA lines
3.1 Conductive properties
Properties
Pure Copper
ECCA (20% Copper)
ECCA (25% Copper)
ECCA (30% Copper)
DC resistivity (μΩ·cm)
1.724
2.78
2.55
2.40
Conductivity (% IACS)
100%
62%
67%
72%
50 Hz AC resistance
1.0×
1.61×
1.45×
1.40×
10 kHz AC resistance
1.0×
1.10×
1.05×
1.03×
100 kHz AC resistance
1.0×
1.02×
1.01×
1.00×
1 MHz AC resistance
1.0×
1.01×
1.00×
1.00×
10 MHz AC resistance
1.0×
1.00×
1.00×
1.00×
Key Finding: Above 100 kHz, the AC resistance of ECCA wire (30% copper) is exactly the same as pure copper**. This is the physical basis for ECCA lines to replace pure copper in switching power supplies and UPS.
3.2 Physical and mechanical properties
Properties
Pure Copper
ECCA (Copper 20%)
ECCA (Copper 25%)
ECCA (Copper 30%)
Density (g/cm³)
8.96
3.40
3.65
3.85
Tensile strength (MPa)
220-300
100-130
110-140
130-160
Elongation (%)
30-40%
15-22%
18-25%
20-28%
Modulus of elasticity (GPa)
110-120
70-80
75-85
80-90
Thermal conductivity (W/(m·K))
401
200
215
230
Coefficient of thermal expansion (10⁻⁶/K)
16.5
21
22
22.5
Melting point (°C)
1085
660 (Aluminum)
660
660
Weldability
Excellent
Good
Good
Good
3.3 Chemical Properties
Properties
Pure Copper
ECCA Wire
Atmospheric corrosion resistance
Good (patina generation)
Good (copper layer protection)
Salt spray corrosion resistance
General
General (protected by the copper layer, the aluminum core is exposed after the copper layer corrodes under salt spray)
Acidic environment
Good
Good (copper layer is acid-resistant)
Alkaline environment
Excellent (copper is alkali resistant)
Good (copper layer is alkali resistant)
Moist heat aging
Excellent
Good
UV resistant
Good
Good
3.4 Paint film adhesion performance (core advantage)
Paint film type
Pure copper substrate
ECCA wire (outside copper skin)
Remarks
PE (polyester)
Excellent
Excellent
ECCA paint film adhesion is close to that of pure copper
PEI (Polyesterimide)
Excellent
Excellent
Close to pure copper
PAI (polyamideimide)
Excellent
Excellent
Close to pure copper
PI (Polyimide)
Excellent
Excellent
Close to pure copper
PU (Polyurethane)
Excellent
Excellent
Close to pure copper
Modified primer
Normally none
Optional coupling agent enhancement
Further improvements
ECCA’s core advantage: Because the surface is a copper layer (not an aluminum layer), the paint film adhesion is almost the same as that of pure copper enameled wire, which is one of the biggest advantages of ECCA over pure aluminum enameled wire.
IV. ECCA wire vs pure copper wire vs pure aluminum wire vs CCA bare wire
4.1 Comprehensive comparison of 4 major materials
Performance
Pure copper enameled wire
ECCA enameled wire
Pure aluminum enameled wire
CCA bare wire
Density (g/cm³)
8.96
3.40-3.85
2.70
3.40-3.85
DC resistivity (μΩ·cm)
1.724
2.40-2.78
2.83
2.40-2.78
100 kHz AC resistance
1.0×
1.00-1.02×
–
–
Paint Adhesion
Excellent
Excellent
Difficult
No Paint
Weldability
Excellent
Good
Difficult
Difficult
Tensile strength (MPa)
220-300
100-160
70-110
100-160
Weight
Baseline
55-65% off
70% off
55-65% off
Price
High
Medium (Save 40-65%)
Low
Medium
Applicable frequency
Full frequency band
> 20 kHz
> 50 kHz
Requires enameling
4.2 ECCA vs CCA bare wire
ECCA = CCA + paint film
Difference
CCA bare wire
ECCA enameled wire
Insulation
None
Paint film (PE/PEI/PAI/PI)
Application
Additional insulation required
Directly wound coil
Craft
Simple
Paint + Bake
Cost
Low
Medium (increased paint film cost)
Applicable
Shielding, grounding
Transformers, motor windings
4.3 Selection decision table
Application scenarios
Recommended materials
Reasons
Power frequency transformer (50/60 Hz)
Pure copper
Large DC resistance is a disadvantage
High Frequency Transformers (>20 kHz)
ECCA
BEST CHOICE
100 kHz inductor
ECCA
Same performance as pure copper
1 MHz Inductor
ECCA
Optimum
5G communications
ECCA
Weight reduction and cost reduction
Electric vehicle OBC
ECCA
High frequency, high power density
Photovoltaic inverter
ECCA
Cost reduction, high efficiency
Pure DC application
Pure copper
Not suitable for copper-clad aluminum
Shielding, grounding
CCA bare wire
High cost performance
V. International standards of ECCA line
5.1 ASTM B566 (Copper Clad Aluminum Bare Wire Standard)
Project
Required Content
Range
Round copper-clad aluminum wire, diameter 0.10-8.00 mm
Optional coupling agent primer (enhances adhesion)
Main paint application
4-12 coats
6-12 coats
Baking temperature
350-450°C
330-420°C (avoid interface diffusion)
Baking time
10-30 s/lane
12-35 s/lane
Paint film thickness
Grade 1/2/3
Grade 1/2/3
Line speed
50-200 m/min
40-180 m/min
6.5 Key process differences
Compared with pure copper enameled wire, ECCA:
Difference
Pure Copper
ECCA
Reason
Primer
Normally none
Optional
Further enhances adhesion
Baking temperature
Higher
Slightly lower
Prevent interface diffusion
Baking time
Shorter
Slightly longer
Paint film fully cured
Annealing temperature
Higher
Slightly lower
Prevent excessive softening of aluminum
VII. Key performance indicators of ECCA line
7.1 Paint film grade and thickness
Paint film grade
Paint film thickness (μm)
ECCA use
Grade 1
18-30
High frequency small signal coil
Grade 2
30-50
General high frequency transformer
Grade 3
50-80
Medium and high voltage windings
Grade 4
> 80
High voltage special applications
7.2 Breakdown voltage
Paint film grade
Breakdown voltage (kV)
Breakdown voltage (V/mil)
Grade 1
4-6
1,000-1,500
Grade 2
6-10
1,500-2,500
Grade 3
10-15
2,500-3,800
Grade 4
> 15
> 3,800
7.3 Temperature level
Temperature grade
Paint film
Long-term operating temperature
Short-term extreme temperature
Class 130 (B)
PE
130°C
150°C
Class 155 (F)
PEI
155°C
175°C
Class 180 (H)
PEI
180°C
200°C
Class 200 (R)
PAI
200°C
220°C
Class 220 (N)
PAI / PI
220°C
240°C
Class 240 (C)
PI
240°C
260°C
7.4 Lifetime Prediction (200°C)
Paint film
Lifespan (200°C)
Lifespan (180°C)
PE
1,000-2,000 h
5,000-10,000 h
PEI
3,000-5,000 h
15,000-20,000 h
PAI
8,000-12,000 h
25,000-40,000 h
PI
10,000-20,000 h
30,000-50,000 h
VIII. Five typical applications of ECCA lines
8.0 Application Overview and Selection Quick Check
A quick guide to selecting ECCA lines for different applications:
Application
Frequency
Power
Recommended specifications
Recommended copper ratio
Recommended paint film
Switching power supplies
50-500 kHz
5-500 W
AWG 24-36
20-25%
PEI/PAI
UPS
20-100 kHz
1-100 kVA
AWG 18-30
20-25%
PAI
Electric Vehicle OBC
50-200 kHz
3.3-22 kW
AWG 16-30
20-25%
PAI
5G AAU
700 MHz-6 GHz
10-100 W
AWG 28-40
15-20%
PAI/PI
Photovoltaic inverter
20-100 kHz
1-100 kW
AWG 16-26
25-30%
PAI
Wireless Charging
85-200 kHz
1-22 kW
AWG 16-30
20-25%
PAI
Server Power Supplies
100-500 kHz
500-3000 W
AWG 20-32
20-25%
PAI/PI
Industrial power supplies
20-100 kHz
1-50 kW
AWG 18-30
25-30%
PAI
8.1 Application 1: Switching power supply high frequency transformer
8.1.1 Application background
Switching mode power supplies (SMPS), operating at frequencies 20-500 kHz, are the most important applications of ECCA lines**.
8.1.2 Selection Guide
Parameters
Recommended values
Specifications
AWG 22-38 (0.40-0.08 mm)
Paint film
PEI / PAI (180-200°C)
Copper volume ratio
15-25%
Paint film grade
Grade 1-2
8.1.3 Typical cases
A 200 W laptop power supply, the main transformer operates at 100 kHz, and uses AWG 30 ECCA wire (20% copper). Compared to pure copper, the weight is reduced by 45%, the cost is reduced by 50%, and the efficiency remains at 92%.
8.2 Application 2: UPS uninterruptible power supply
8.2.1 Application background
Inverters, rectifiers, transformers in UPS, operating frequency 20-100 kHz.
8.2.2 Typical cases
A 10 kVA online UPS uses ECCA wirewound power transformers and high-frequency inductors. The weight of the entire machine is reduced from 80 kg to 50 kg, while the efficiency remains at 95%.
8.3 Application 3: Electric Vehicle OBC
8.3.1 Application background
EV on-board charger (OBC) operates at 50-200 kHz frequency and 3.3-22 kW power.
8.3.2 Selection Guide
Parameters
Recommended values
Specifications
AWG 16-30 (1.30-0.25 mm)
Paint film
PAI (200°C)
Copper volume ratio
20-25%
Paint film grade
Grade 2
8.3.3 Typical cases
An 11 kW OBC using ECCA wire wound high frequency transformer. Power density increased by 30%, cost reduced by 25%.
8.4 Application 4: 5G communication base station
8.4.1 Application background
5G AAU, filter, Balun coil, frequency 700 MHz-6 GHz.
8.4.2 Typical cases
A 5G AAU uses ECCA enameled Litz wire to wind Balun coils at a frequency of 3.5 GHz. 60% weight reduction, 55% cost reduction.
8.5 Application 5: Photovoltaic inverter
8.5.1 Application background
Photovoltaic inverter operating frequency 20-100 kHz, power 1-100 kW.
8.5.2 Typical cases
A 10 kW string inverter uses an ECCA wire-wound high-frequency transformer. The weight of the whole machine is reduced by 30% and the cost is reduced by 40%.
8.6 Application 6: Server and Data Center Power Supplies
8.6.1 Application background
Server power supplies and data center PSUs operate at a frequency of 100-500 kHz and a power of 500-3000 W, which have extremely high requirements for efficiency and power density.
8.6.2 Selection Guide
Parameters
Recommended values
Specifications
AWG 20-32 (0.81-0.20 mm)
Paint Film
PAI / PI (200-220°C)
Copper volume ratio
20-25%
Paint film grade
Grade 2
8.6.3 Typical cases
A 2000 W server PSU with a main transformer operating at 200 kHz, using ECCA wire (22% copper). Compared with the pure copper solution, the efficiency is increased from 94% to 95%, the weight is reduced by 40%, and the temperature rise is reduced by 8°C.
8.7 Application 7: Industrial frequency converter
8.7.1 Application background
The operating frequency of industrial frequency converters is 4-16 kHz and the power is 1-500 kW.
8.7.2 Typical cases
For a 22 kW industrial frequency converter, the output filter inductor is wound using ECCA wire. The weight of the entire machine is reduced by 25%, the cost is reduced by 30%, and the efficiency remains above 97%.
8.8 Application 8: Wireless charging system
8.8.1 Application background
The working frequency of wireless charging for electric vehicles is 85 kHz, and the wireless charging frequency of mobile phones is 100-200 kHz.
8.8.2 Typical cases
An 11 kW wireless charging system for an electric vehicle uses ECCA enameled Litz wire (20% copper) in both the primary and secondary coils. The system is 92% efficient and weighs 35% less than a pure copper solution.
IX. Five engineering suggestions for ECCA line selection
9.1 Suggestion 1: Frequency determines material selection
Operating frequency
Recommended materials
50/60 Hz power frequency
Pure copper
400 Hz
Pure copper or ECCA
1-20 kHz
Pure copper or ECCA
20-100 kHz
ECCA Advantages Starting Point
100 kHz-1 MHz
ECCA Best Advantage Area
> 1 MHz
ECCA Litz wire / silver plated
9.2 Recommendation 2: Choose copper ratio based on power density
Power density (W/cm²)
Recommended copper volume ratio
< 1
10-15%
1-5
15-20%
5-10
20-25%
> 10
25-30%
9.3 Suggestion 3: Choose paint film according to temperature
11.2 Can ECCA wire completely replace pure copper?A: It cannot be completely replaced, but it is the best choice in certain scenarios:
High frequencies above 100 kHz: alternative
50/60 Hz power frequency: cannot be replaced
11.3 What is the advantageous frequency range of ECCA lines?
Answer: 100 kHz-1 MHz is the best advantage range of ECCA lines:
– In this frequency band, skin depth < copper thickness
– Electric current flows completely in the copper layer
– ECCA has almost the same AC resistance as pure copper
11.4 What is the lifespan of ECCA wires?
Paint film
200°C life
180°C life
PEI
3,000-5,000 h
15,000-20,000 h
PAI
8,000-12,000 h
25,000-40,000 h
PI
10,000-20,000 h
30,000-50,000 h
How much does the 11.5 ECCA line cost?
Usually price comparison (taking pure copper enameled wire as 1.0):
– Pure copper enameled wire: 1.0
– ECCA wire (copper 20%): 0.4-0.5
– ECCA wire (copper 25%): 0.5-0.6
– Pure aluminum enameled wire: 0.15-0.25
11.6 What situations should be avoided when using ECCA lines?
To ensure long-term reliable operation of the ECCA line, the following situations should be avoided:
Long-term overtemperature work: The operating temperature should not exceed the rated temperature level of the paint film (PEI 180°C, PAI 200°C, PI 220°C). Overtemperature will accelerate interface diffusion and paint film aging.
Long-term high-humidity environment: In hot and humid environments, galvanic corrosion may occur at the copper-aluminum interface. Moisture-proof measures should be taken or a fully sealed structure should be adopted.
Frequent hot and cold cycles: Under repeated hot and cold cycles, the difference in thermal expansion coefficients between copper and aluminum (copper 16.5, aluminum 23.0 ×10⁻⁶/K) will accelerate interface delamination
Strong vibration environment: Under continuous vibration, the fatigue life of the copper-aluminum interface is reduced, and vibration reduction installation should be used
Strong acid and alkali environment: Acid and alkali will corrode the copper layer, thereby exposing the aluminum core and accelerating corrosion.
Long-term large current overload: Long-term overload will produce overheating, accelerate interface diffusion and paint film aging
11.7 How are ECCA lines stored and transported?
Storage and shipping considerations for ECCA lines:
Ambient temperature: -10°C to 40°C, avoid direct sunlight
Relative Humidity: < 75%, avoid getting wet
Packaging: Original factory sealed packaging, should be used as soon as possible after opening
Avoid mechanical damage: Handle with care to avoid damage to the paint film caused by collision and extrusion.
Chemical Isolation: Keep away from acids, alkalis, and organic solvents
Storage Period: Use within 12 months of original packaging, use within 3 months after opening
Stacking method: Vertical or horizontal shaft installation to avoid paint film pressure loss
XII. Future Trend: Development of ECCA Line Technology
12.1 Trend 1: Higher copper volume ratio
Current mainstream: 15-25% copper volume ratio
Future direction: 25-40% copper volume ratio
Meaning: Performance closer to pure copper
12.2 Trend 2: Nano coating technology
Copper surface nano-coating (Ni, Ag, Au)
Nano fillers are added to the paint film
Interfacial nano-diffusion barrier layer
12.3 Trend 3: New energy drive
New energy vehicles: OBC, DC-DC, motor controller
Energy storage: battery management system
Photovoltaic: Inverter
Wind power: converter
12.4 Trend 4: Expansion of high-frequency applications
5G/6G communication base station
Satellite communications
Wireless charging
millimeter wave
12.5 Trend 5: Smart Manufacturing
Online defect detection (vision + AI)
Digital twin
Full process traceability
Intelligent quality control
XIII. Conclusion: ECCA wire is the “King of Composite Conductors” for high frequency and lightweight
As a key material for high-frequency lightweight applications in the 21st century, ECCA wire (Enameled Copper Clad Aluminum Wire) plays an irreplaceable role in switching power supplies, UPS, new energy vehicles, 5G communications, photovoltaic inverters, wireless charging and other fields.
ECCA Core Values:
– Lightweight: 55-65% lighter than pure copper
– LOW COST: 40-65% cheaper than pure copper
– High frequency excellence: almost the same as pure copper above 100 kHz
– Good paint film: The outer layer of copper skin makes the paint film adhesion close to that of pure copper
– Weldability: The surface is a copper layer, and the weldability is better than that of pure aluminum
LP Winding Wireprovides a full range of ECCA wire products with specifications AWG 8-44 (0.08-3.20 mm), copper volume ratio 10-30%, and paint films covering the full range of PE/PEI/PAI/PI. All products are certified by ASTM B566, IEC 60317, UL, VDE, TÜV, and CCC.
XIV. Appendix: Key Parameters Cheat Sheet
14.1 Quick check on copper volume ratio
Copper volume ratio
Conductivity (% IACS)
Density (g/cm³)
Applicable frequency
Typical applications
10%
50-55%
3.0-3.2
> 100 kHz
High frequency small signal
15%
58-62%
3.2-3.4
> 50 kHz
High frequency transformer
20%
62-66%
3.4-3.6
> 20 kHz
SMPS Mainstream
25%
66-70%
3.6-3.8
> 10 kHz
General high frequency
30%
70-72%
3.8-4.0
Power frequency-high frequency
High-end application
14.2 Quick check on paint film selection
Paint Film
Abbreviation
Temperature Class
Weldability
Cost
Typical Applications
Polyester
PE
130°C
Weldable
Low
General Motors
Polyesterimide
PEI
180°C
Difficult to solder
Medium
SMPS
Polyamide-imide
PAI
200°C
Weldable
Medium to high
High end
Polyimide
PI
220°C
Difficult to solder
High
High temperature
Polyurethane
PU
155°C
Easy to weld
Medium
Coil
14.3 Quick check on diameter specifications
AWG
Diameter (mm)
Cross-sectional area (mm²)
Typical applications
22
0.644
0.326
SMPS Transformer
24
0.511
0.205
SMPS Transformer
26
0.405
0.129
High frequency inductor
28
0.321
0.081
High frequency inductor
30
0.255
0.051
SMPS Mainstream
32
0.202
0.032
Communication Coil
34
0.160
0.020
Communication Coil
36
0.127
0.013
Tiny coil
38
0.101
0.008
Tiny coil
40
0.080
0.005
Tiny Coil
14.4 Selection process
1.Determine operating frequency: Decide whether ECCA is suitable
2. Determine power density: Determine copper volume ratio
3. Determine the temperature level: Determine the paint film
4. Determine voltage level: Determine paint film thickness
