Brazing Aluminum to Copper | Chalco Aluminum

The melting points, thermal conductivity, and expansion rates of copper and aluminum are very different. This makes brazing between them technically challenging.

Differences in thermal expansion can cause joints to weaken or crack over time.

That's why choosing the right filler metal, flux, and brazing temperature is critical for a strong, long-lasting bond.

brazing aluminum to copper

Why choose brazing to join aluminum and copper?

In industrial manufacturing, aluminum and copper each offer distinct advantages. But due to their physical differences, direct welding between them is difficult. Brazing has become one of the most efficient and cost-effective ways to bond these two metals.

Brazing creates a metallurgical bond between copper and aluminum using filler metal, making it ideal for joining dissimilar metals with reliable strength.
It uses lower temperatures than fusion welding, so it doesn't melt the base metals—this helps preserve material properties and is safer for heat-sensitive parts.
The brazed joint has some ductility, which helps absorb stress caused by the metals' differing expansion rates, reducing the risk of cracking over time.
Induction brazing offers fast, localized heating and high automation—perfect for high-volume, continuous production.
Compared to pure copper systems, brazed copper-aluminum joints significantly reduce both cost and weight, especially in HVAC systems, batteries, and electrical assemblies where conductivity matters.
It's also ideal for bonding thin-walled copper-aluminum busbars, often used in battery modules, busbars, and power terminals.

Tip: While brazing aluminum to copper is economical and suitable for mass production, the joint's conductivity is lower and it's not ideal for high-stress or corrosive environments. Smart design and surface protection are essential for long-term reliability.

Key parameters for brazing aluminum to copper

The filler metal must have a melting point lower than both copper (1085°C) and aluminum (660°C). Filler alloys with a melting range of 450–600°C, such as aluminum-silicon, are commonly used.
The copper and aluminum surfaces must be thoroughly cleaned of oxides using mechanical abrasion or acid pickling, then coated with a flux based on ammonium fluoride or ammonium chloride.
Heat the joint to the filler's melting point carefully—avoid overheating the base metals to prevent damage.

How to choose the right filler metal for brazing aluminum to copper

Choosing the right filler metal is critical when brazing aluminum to copper. It directly affects joint strength, conductivity, corrosion resistance, and process stability.

You need to consider filler type, melting point, wetting ability, flux compatibility, and the specific application.

Filler alloy type	Melting range	Key features	Recommended applications
Aluminum-silicon alloys e.g. Al-Si 12 (AA4047), AlSi10	577–585°C	Excellent flow and wetting; helps avoid overheating aluminum and reduces brittle Cu-Al interface	Heat exchangers, thin copper busbars, battery modules
Zinc-aluminum alloys e.g. ZnAl15, ZnAl22	380–420°C	Good conductivity, low cost, low melting point; rare earths can improve corrosion resistance	Low-voltage connections, power terminals, humid environments
Super Alloy No.1	Above 600°C	High joint strength, excellent pressure resistance and stability	High-pressure systems, HVAC circuits
Sn-Zn alloys	198–260°C	Lead-free, eco-friendly, good wetting, aluminum-like appearance	Electronics, light-duty electrical joints
Sn-Pb alloys	183–270°C	Proven performance, low cost, easy to process	General low-temp joints in non-corrosive settings
Tin-coated filler	232°C	Low melting point, easy to work with	Signal lines, low-stress sampling points

Chalco offers a wide range of aluminum-silicon, zinc-aluminum, and flux products for brazing aluminum to copper—widely used in heat exchangers, battery modules, and electrical assemblies.Quick Quote

Aluminum to Copper Brazing Rod

Chalco's aluminum to copper brazing rod ensures strong, reliable joints for HVAC and electrical use.

Aluminum Brazing Welding Material

Chalco's best-selling aluminum brazing materials include clad aluminum brazing alloys and self-fluxing aluminum products.

AL 822 Aluminum Brazing Rod

AL 822 aluminum brazing rod offers excellent flowability and wetting performance.

Brazing rings

Flux

Welding wire

Preparation steps for brazing aluminum to copper

Oxide removal

Use mechanical abrasion or chemical cleaning (acid pickling) to remove oxides and contaminants from aluminum and copper surfaces. This ensures proper metal-to-metal contact.

Flux application

Apply flux to improve wetting and bonding between the filler metal and base metals. It also prevents re-oxidation and helps form a clean, strong joint.

Surface cleaning

Thoroughly clean both aluminum and copper to remove dirt, grease, and any remaining oxides. A clean surface is key to effective brazing.

Heat source selection

Choose from flame heating (flexible, ideal for small parts), resistance/induction heating (uniform and efficient for automated or batch production), or oven heating (for simultaneous multi-joint brazing).

Heat source selection

Methods and processes for brazing aluminum to copper

Flame brazing

Uses aluminum-silicon filler metal (such as Al-Si 12 / AA4047), ideal for small parts and on-site operations.
Focus the flame on the copper side to avoid overheating the aluminum.
Advantage: Fast and efficient for light-duty joints, minimizes aluminum damage.

Super Alloy brazing (Super Alloy No.1)

Used in the refrigeration industry to join copper and aluminum tubes. It relies on a special liquid flux and brazing rod to create a strong, durable joint that withstands up to 20, 000 PSI.

Preheat the copper tube, apply heat and flux, then feed in filler metal.
Advantage: Highly reliable and pressure-resistant, perfect for HVAC systems.

Friction welding

No filler metal needed. Minimal joint prep. The aluminum and copper surfaces are bonded by heat generated through rotational friction.

Explosion welding

Copper and aluminum are bonded by a high-pressure explosive force that fuses the metals at the interface.

Alloy bonding method

During brazing, a controlled aluminum-copper alloy layer forms at the joint. A stainless steel sleeve may be added to reinforce the structure.

We offer a full range of copper-aluminum joining solutions, including Al-Si brazing wire, Super Alloy rods, friction weld parts, and explosion bonding technology.

Contact us for technical support and custom product recommendations.Quick Quote

Copper Clad Aluminum

Chalco offers a one-stop copper clad aluminum solution, covering a full range of products including plates, strips, wires, and busbars.

Copper Clad Aluminum Wire CCA

Combines the high conductivity of copper with the lightweight nature of aluminum. Widely used in telecommunications, cables, and electronic wiring.

Copper Clad Aluminium busbar CCA

Delivers excellent conductivity and reduced weight. Ideal for high-current transmission in new energy systems and electrical equipment.

Copper Clad Aluminum Plate

Integrates copper’s superior conductivity with aluminum’s light weight and cost efficiency.

Copper Clad Aluminum Strip

Used in connectors, grounding straps, and composite conductors—balancing performance and cost in both electrical and electronic applications.

Large and medium-sized copper-aluminum friction welded components

Designed for high-strength applications, offering reliable bonding of dissimilar metals.

0.5” ∅ x 2.5” copper-aluminum welded part

Compact friction-welded joint ideal for precision electrical or thermal connections.

Copper-Aluminium Bimetal Clad Cable Lugs

Copper-Aluminium Bimetal Clad Washer

Copper Aluminum Flexible Connectors

High Speed Rail Grounding Blocks

Copper Aluminum Composite Hardware Components

Copper aluminum bimetallic LiB terminal

Applications of brazing aluminum to copper

HVAC & Refrigeration

Brazing aluminum to copper is widely used in joining heat exchangers and refrigeration system tubing—for outdoor units, condensers, evaporators, and more.

Automotive & Aerospace

Ideal for producing lightweight, high-performance parts such as fuel lines, radiators, and air conditioning modules.

Electrical & Construction

Plays a vital role in manufacturing electrical components and structural parts—used in wire tabs, cable terminals, and mechanical fittings.

Electric Vehicles & Energy Storage

As EV, HEV, PHEV, and energy storage systems grow, so does the demand for reliable connections between aluminum cathodes and copper anodes.

Common issues and solutions in brazing Aluminum to copper

By applying proper brazing techniques and process control, you can ensure strong, reliable copper-aluminum joints. Key factors include preventing galvanic corrosion, controlling heat input, and selecting the right filler materials.

Overheating the joint

Excessive heating can cause unwanted diffusion and lead to low-melting-point Al-Cu alloys (e.g., Al-Cu33, melts at 548°C), which may result in perforation or corrosion.

Solution: Avoid direct flame contact with the joint. Use indirect heating to melt the filler metal, and remove the heat source immediately once flow begins.

Melting point difference between aluminum and copper

Aluminum melts at around 650°C, while copper exceeds 1000°C. Heat transfer from copper to aluminum can cause the aluminum to melt too quickly and damage its structure.

Solution: Aim the flame at the copper side to concentrate heat there. Remove heat as soon as the aluminum nears melting.

Poor filler metal wetting

Weak wetting and flow reduce joint integrity and coverage.

Solution: Adjust the temperature or joint gap. Use a filler alloy with better wetting performance for both metals.

Porosity in the joint

Pores can compromise joint strength and sealing.

Solution: Maintain precise temperature control and reduce air entrapment. Improve joint design for better filler distribution.

Galvanic corrosion

Copper and aluminum have different electrochemical potentials, which can cause corrosion over time.

Solution: Apply anti-corrosion coatings or isolation layers between the metals to prevent electrochemical reactions.

Chalco offers a complete range of materials, technical support, and solutions for aluminum to copper brazing.

Safety and best practices for brazing aluminum to copper

Keep the workspace well-ventilated to avoid inhaling harmful fumes.
Wear heat-resistant gloves, safety goggles, and flame-retardant clothing.
Use fume extraction or work in an area with proper airflow.
Equip the area with fire extinguishers (dry powder or CO₂) and remove flammable materials. Provide a safe cooling zone for hot tools and parts.
After brazing, clean flux residues with warm water or solvents. Inspect joints for cracks, voids, or cold welds.
Apply nickel plating or corrosion-resistant coatings to prevent galvanic corrosion between copper and aluminum.

User guide: practical tips and future outlook for brazing aluminum to copper

In practice, users should follow proven techniques: thoroughly clean and deoxidize the surfaces, select compatible filler metals like Al-Si or Zn-Al alloys, and aim the flame at the copper side to avoid overheating the aluminum.

Always follow personal protection guidelines and ensure proper ventilation to maintain safety and weld quality.

To improve brazing skills, users should practice on scrap materials, use appropriate tools and materials, and seek guidance from experienced professionals.

Stay up to date with industry innovations—such as low-temperature alloys and automated brazing systems—which can greatly improve consistency and joint quality.

Mastering the brazing process takes time, refinement, and hands-on experience. For manufacturers and engineers aiming for high reliability and product performance, mastering aluminum-to-copper brazing is a key step toward competitive advantage.