Isolation transformers are critical safety devices in power systems and electronic equipment. Their core functions are to achieve electrical isolation, suppress common-mode interference, and protect personal safety. As the core material for isolation transformer windings, the quality of soft annealed copper foil directly affects the transformer’s insulation performance, anti-interference capability, and operational reliability.
I. Technical Definition of Soft Annealed Copper Foil
1.1 Basic Concepts
Soft annealed copper foil (O-state copper foil) is pure copper material that has undergone full annealing treatment, resulting in fully grown grains and maximum plasticity. Compared to hard or semi-hard copper foil, soft-annealed copper foil has:
- Highest plasticity: Elongation ≥25%, suitable for complex shape winding
- Lowest hardness: Hardness 35-55 HV, easy to process and shape
- Optimal conductivity: IACS value ≥101%, lowest resistance
- No internal stress: Eliminates residual stress from rolling
1.2 Special Working Conditions
- Insulation safety level: Strict insulation matching, sufficient electrical clearance
- Moisture resistance: Maintain insulation in humid environments
- Low leakage capacitance: Minimize parasitic capacitance
- High frequency characteristics: Consider skin effect in high frequency applications
II. Technical Specifications
2.1 Grades and Chemical Composition
| Grade | Copper+Silver | Conductivity | Typical Applications |
|---|---|---|---|
| C11000 (ETP) | ≥99.90% | ≥101% IACS | General Isolation transformer |
| C10100 (OFC) | ≥99.99% | ≥101.5% IACS | High-Performance |
| C10200 (TPA) | ≥99.95% | ≥101% IACS | Precision Electronics |
2.2 Key Performance Parameters
Electrical Performance:
- Conductivity: IACS≥101% (annealed)
- Resistivity: 0.01724 Ω·mm²/m (20°C)
- Temperature Coefficient: 0.00393/°C
Mechanical Properties:
- Tensile strength: 200-260 MPa (O state)
- Elongation: ≥25% (A50mm)
- Hardness: 35-55 HV
- Surface roughness: Ra≤0.8μm
III. Application Requirements
3.1 Insulation Coordination Design
- Copper foil to core: Nomex paper, polyester film, or epoxy resin
- Interlayer insulation: Mylar film or phenolic paper
- Clearance: ≥3mm from edge to core
3.2 Low Parasitic Capacitance Design
- Thin insulation design
- Interleaved winding to reduce interlayer capacitance
- Copper foil width optimization based on frequency
3.3 Winding Process Parameters
| Parameter | Recommended Value |
|---|---|
| Winding Tension | 5-15 N/mm² |
| Winding Speed | 20-50 m/min |
| Annealing Temperature | 400-650°C |
| Insulation Baking | 120-180°C |
IV. Industry Standards and Certifications
| Standard | Description |
|---|---|
| IEC 60325 | Copper Foil for Transformers |
| GB/T 5231 | Processed Copper and Copper Alloys |
| ASTM B152 | Copper Sheets, Strips, and Foils |
| JIS H3100 | Copper and Copper Alloy Strips and Foils |
V. Quality Inspection
| Inspection | Method | Standard |
|---|---|---|
| Chemical Composition | Spectroscopy | Cu≥99.90% |
| Tensile Strength | Tensile Test | 200-260 MPa |
| Elongation | Tensile Test | ≥25% |
| Thickness Tolerance | Thickness Gauge | ±0.02mm |
| Conductivity | Eddy Current | IACS≥101% |
VI. Supplier Selection Criteria
- Full-process production line (melting → rolling → annealing → slitting)
- Atmosphere-protected annealing to avoid oxidation
- Thickness control accuracy: ±0.02mm
- ISO 9001/14001/45001 certified
- Monthly capacity: ≥200 tons
VII. Product Specifications
| Grade | Thickness | Width | Temper | Conductivity |
|---|---|---|---|---|
| C11000 | 0.1-2.0mm | 20-500mm | O | ≥101% IACS |
| C10100 | 0.05-1.5mm | 10-400mm | O | ≥101.5% IACS |
| C10200 | 0.1-2.5mm | 20-600mm | O | ≥101% IACS |
Conclusion
When selecting soft annealed copper foil for isolation transformers, focus on ductility, conductivity, and thickness uniformity. Prioritize suppliers with strong annealing process control and thickness accuracy.
Our company has 30 years of experience exporting electrical wire and metal foil. We provide C11000/C10100/C10200 series soft annealed copper foil with customized sizes and global sample shipping.
Contact:
Email: office@cnlpzz.com
WhatsApp: 0086-19337889070
The technical parameters described are general reference values. Please consult our technical team for specific selections based on your isolation transformer design requirements.