Copper-aluminum composite conductors are essential for electrical equipment lightweighting and BOM cost reduction. However, different manufacturing techniques yield dramatically different metallurgical interfaces. Selecting the wrong bonding method risks interface delamination during forming or resistance spikes from thick intermetallic compound (IMC) growth under thermal cycling.
Four Core Cu-Al Cladding Technologies & Microstructural Comparison
1. **Liquid-Solid Continuous Casting (CUNECTRA Process)**: Under controlled protective atmosphere, molten aluminum solidifies against pure copper strip under precision roll pressure, creating an ultra-thin 300~500nm nanoscale eutectic layer (Al₂Cu/Al₄Cu₉). The metallurgical bond exhibits peel strength >148 N/mm and survives severe 90° cold bending without micro-cracking.
2. **Flash Butt Welding**: High-temperature melting and forging generates a thick 10~50μm brittle IMC layer with an extensive heat-affected zone, making it brittle under bending and suitable only for simple end-to-end joints.
3. **Friction Stir Welding (FSW)**: Solid-state mechanical stirring produces strong localized seams but operates on a piece-by-piece cycle time that cannot support high-speed progressive busbar stamping.
4. **Explosive Cladding**: Designed for heavy plates; wavy interface geometry results in wide thickness tolerances (±0.5mm) incompatible with SMT coplanarity requirements.
Comparative Test Data: Peel Strength, Conductivity, and Fatigue
In compliance with GB/T 32468 and DL/T 217 standards, liquid-solid cast eutectic busbars demonstrate decisive electrical and mechanical performance advantages:
- Interface Peel Strength: Liquid-solid casting > 148 N/mm (12x higher than GB/T standard ≥ 12 N/mm)
- DC Resistivity at 20°C: ≤ 0.02350 Ω·mm²/m (delivering 86% the ampacity of pure copper by volume)
- 90° Cold Bending: Zero delamination or micro-cracking at bend radius R = 0.5t
- Density & Weight: 3.94 g/cm³ (44% of pure copper), cutting overall busbar weight by 56%
Type-Testing Certifications by STRI & National Electric Control Center
CUNECTRA's complete catalog of 51 rectangular eutectic busbar sizes (15×3mm to 125×12mm) is certified by the National Testing Center for Electric Control Equipment (Tianjin) and the Shanghai Electrical Apparatus Research Institute (STRI) under 50K, 60K, and 70K temperature rise regimes.