How do you choose a solder suitable for welding copper-aluminum composite sheets?

Release time:

2026-01-16

When selecting solder for welding copper-aluminum composite sheets, the key considerations are as follows: The solder’s melting point must be lower than that of aluminum (660℃), it must have good fluidity, the joint strength must be high, its electrical conductivity must be excellent, and it must also be capable of inhibiting the formation of brittle phases.

I. Core Criteria for Selecting Solder Alloys
Melting point: Select a solder with a melting range of 550–650℃ (such as BCuZn-Si or Al-Si-Zn) to avoid melting the aluminum.
Fluidity: Solder with good fluidity (such as XR-FC22) can fill gaps and is suitable for workpieces with large gaps.
Strength and Conductivity: Tensile strength ≥ 80 MPa, weld resistance ≤ 30 μΩ, meeting the requirements of power equipment.
Corrosion resistance: To prevent electrochemical corrosion, select zinc-based or aluminum-based solder alloys.
II. Recommended Solder Types

Flux-cored wire:

XR-FC22: Moderate fluidity, high strength, suitable for workpieces with large gaps.
XR-FC20A: Excellent conductivity, suitable for welding copper and aluminum pipes.
WE CuAl-Q303: Comes with flux, easy to operate, and no post-weld cleaning required.

Solid-core welding wire + flux:

M51+M51-F: Low-temperature soldering (179℃), suitable for small workpieces.
HL501: Specifically designed for scratch welding, suitable for welding cast bars.
III. Operational Precautions
Surface Treatment: Thoroughly clean before welding to prevent oxidation from affecting the bond.
Process Control: Brazing requires strict control of temperature and time to prevent the formation of brittle phases.