Introduction
In modern manufacturing, lightweighting, high efficiency, and cost reduction are indispensable factors for maintaining and enhancing competitiveness. The evolution of electric vehicles, EVs, renewable energy-related equipment, and high-performance electronic devices, in particular, places new demands on material technology. Against this backdrop, “aluminum-copper composite materials,“ which combine metals with different properties—aluminum and copper—are attracting significant attention due to their excellent electrical and thermal conductivity, lightweight properties, and economic advantages.
Copper boasts high electrical and thermal conductivity, but its high specific gravity leads to increased product weight, and price fluctuations are also a challenge. On the other hand, aluminum is lightweight and inexpensive but has lower electrical and thermal conductivity compared to copper. By optimally combining these two metals, aluminum-copper composite materials can maximize the strengths of each and compensate for their weaknesses, potentially becoming a key material in next-generation manufacturing.
This article will provide a detailed explanation for Japanese manufacturing executives and procurement managers on the mechanisms of electrical and thermal conductivity in aluminum-copper composite materials, diverse application examples, and the innovative solutions offered by Daiwa Aluminum Vietnam. We will demonstrate how aluminum-copper composite materials can contribute to urgent challenges such as cost reduction, quality improvement, and lead time reduction, based on specific numerical data.
Electrical and Thermal Conductivity Properties of Aluminum-Copper Composite Materials
To understand the true value of aluminum-copper composite materials, it is essential to first grasp the properties of the individual constituent metals. Copper is known for its excellent electrical and thermal conductivity. Specifically, the electrical conductivity of copper at room temperature is approximately 5.8 x 107 S/m, Siemens per meter, and its thermal conductivity reaches approximately 400 W/, m·K, Watts per meter per Kelvin,. These are top-class performances among metallic materials. However, copper has a high specific gravity of 8.96 g/cm3 and is also relatively expensive.
In contrast, aluminum’s electrical conductivity is approximately 3.5 x 107 S/m, and its thermal conductivity is about 200 W/, m·K, which are inferior to copper. However, aluminum’s greatest advantage is its lightness. Its specific gravity is 2.70 g/cm3, about one-third that of copper, and its price is also more stable compared to copper. This lightweight property and economic advantage are why aluminum is used in a wide range of fields.
Aluminum-copper composite materials aim to leverage the benefits of both metals by joining them. For example, copper can be placed in areas requiring high electrical conductivity, while aluminum can be used in parts where lightweighting and cost reduction are crucial. This allows for the creation of materials with an optimal balance of properties that are difficult to achieve with single materials.
Mechanism of Improved Electrical and Thermal Conductivity through Compositing
The electrical and thermal conductivity properties in composite materials are not simply an average of the constituent materials. The quality of the bonding interface is extremely important. In ideal composite materials, the high conductivity of copper and the lightweight properties of aluminum create a synergistic effect. For example, the copper layer can serve as the primary path for current and heat, while the aluminum layer provides structural support and lightweighting. This can achieve over 30% weight reduction while maintaining equivalent electrical and thermal conductivity performance.
Impact of Interfacial Resistance on Properties and Reduction Technologies
The biggest challenge when joining aluminum and copper is the “interfacial resistance“ between dissimilar metals. Interfacial resistance refers to the electrical or thermal resistance that occurs at the interface where different metals meet. If this resistance is high, the overall conductivity of the composite material significantly decreases. Aluminum and copper have different coefficients of thermal expansion, copper: approx. 17 x 10-6 /K, aluminum: approx. 23 x 10-6 /K, making them prone to stress at the interface during heating and cooling cycles, which can lead to interfacial delamination and increased resistance.
To reduce this interfacial resistance, advanced joining technologies are essential. For example, Friction Stir Welding, FSW, utilizes the plastic flow generated at the joint to achieve strong bonding at the atomic level. Explosion Bonding is a technique that uses the energy of explosives to instantaneously apply high pressure, joining metals at the atomic level, and can form a very strong and low-resistance interface. Diffusion Bonding is also a method that uses atomic diffusion under high temperature and pressure to join materials, resulting in a uniform interface. With these technologies, the target value for interfacial resistance in composite materials is set at tens of nΩ·cm2 or less, and achieving this level allows for maintaining conductivity properties close to those of single materials.
Balance of Specific Gravity and Conductivity in Composite Materials
In the design of aluminum-copper composite materials, the balance between specific gravity and conductivity is extremely important. For example, EV battery busbars require both lightweighting and the ability to handle high current densities. While the specific gravity of typical copper busbars is 8.96 g/cm3, aluminum-copper composite busbars can maintain electrical conductivity performance close to that of pure copper while keeping the specific gravity at around 4.0-6.0 g/cm3 by adjusting the aluminum ratio. This contributes to the overall lightweighting of the vehicle and improves fuel efficiency and cruising range. For instance, one EV manufacturer reported a case where the overall weight of the battery pack was reduced by approximately 15% by using composite busbars.
Key Applications of Aluminum-Copper Composite Materials
Aluminum-copper composite materials are being innovatively applied across various industrial sectors due to their unique properties. Their adoption is accelerating particularly in fields where high efficiency, lightweighting, and cost reduction are strongly demanded.
Power Electronics Sector
Power electronics is a technology for power conversion and control, indispensable for EV inverters, industrial motor drives, and power converters in renewable energy systems. In these devices, large currents flow, making heat generation a significant challenge. To cool semiconductor elements such as IGBT, Insulated Gate Bipolar Transistor, modules, excellent thermal conductivity and lightweight heat dissipation materials are required.
Aluminum-copper composite materials can leverage the high thermal conductivity of copper while reducing the overall weight of the module with the lightweight properties of aluminum. For example, using composite materials for heatsinks and baseplates can achieve up to 25% weight reduction compared to conventional copper parts, while maintaining or improving heat dissipation performance. This contributes to system miniaturization and improved energy efficiency. The global EV market is expected to grow at an annual rate of over 20%, Source: Society of Automotive Engineers of Japan, and the demand for power electronics components is rapidly increasing accordingly.
Battery Packs, Busbars, Current Collectors,
With the widespread adoption of electric vehicles, EVs, improving battery pack performance is an urgent issue. Battery packs are composed of numerous cells connected in series and parallel, and busbars and current collectors are used for these connections. While conventional busbars were mainly made of copper, they can account for about 20% of the total weight of the battery pack, posing a significant barrier to lightweighting.
Aluminum-copper composite busbars can leverage the excellent electrical conductivity of copper while using the lightweight properties of aluminum to potentially reduce the overall weight of the battery pack by more than 10%. This directly leads to extended EV cruising range and improved power efficiency. Furthermore, replacing copper busbars with composite busbars is estimated to reduce material costs by 15% to 30%, offering significant benefits for EV manufacturers. Composite busbars demonstrate their true value particularly in EV battery systems that handle high voltage and high current.
Heat Dissipation Components, Heatsinks, Heat Exchangers,
As electronic devices become more powerful, the amount of heat generated increases. Many devices, such as CPUs, GPUs, and LED lighting, require efficient heat dissipation, and the performance of heatsinks and heat exchangers determines the stable operation of the system. Aluminum-copper composite materials combine the high thermal diffusivity of copper with the lightweight and processability of aluminum, achieving heat dissipation performance and lightweighting that are difficult to achieve with conventional single materials.
For example, by using copper for the part in contact with the heat source and aluminum for the fin part, the heat conduction path can be optimized while reducing the overall weight. This contributes to the miniaturization, longer lifespan, and improved reliability of electronic devices. Applications are particularly expected in environments with strict weight restrictions, such as the aerospace and automotive electronics fields.
Wires and Cables
From power transmission and distribution lines to internal wiring in home appliances, wires and cables form the foundation of social infrastructure. Conventional wires were mainly made of copper, but rising copper prices and weight issues have always been a concern. Aluminum-copper composite materials achieve significant lightweighting and cost reduction while maintaining conductivity equivalent to copper by coating the surface of copper with aluminum, or vice versa.
For example, in overhead power transmission lines, using aluminum-copper composite stranded wires instead of conventional aluminum conductor steel reinforced, ACSR, wires can achieve both increased transmission capacity and lightweighting of supporting structures. In automotive wire harnesses, the adoption of composite materials can reduce the overall vehicle weight by several kilograms, contributing to improved fuel efficiency. One estimate suggests that the weight of wire harnesses per car can be reduced by approximately 20%.
Lightweighting and Cost Reduction Effects
Common to all the application examples mentioned above are the two major benefits that aluminum-copper composite materials bring: “lightweighting“ and “cost reduction.“ Considering that the specific gravity of copper is approximately 3.3 times that of aluminum, the more copper can be replaced by aluminum, the more dramatically the overall product weight decreases. This directly leads to reduced transportation costs, improved fuel efficiency, and enhanced performance of the final product.
Furthermore, since the market price of copper is higher than that of aluminum, the adoption of composite materials also contributes to reducing material costs. Especially in situations where copper prices are unstable, the adoption of composite materials also functions as a supply chain risk hedge. For example, assuming copper market price is $10,000 per ton and aluminum is $2,500, if the use of copper can be reduced by 30% through compositing, material costs will be significantly suppressed.
Conclusion
Aluminum-copper composite materials are emerging as one of the key material solutions helping manufacturers achieve multiple objectives simultaneously, including weight reduction, improved electrical and thermal conductivity, optimized material costs, and enhanced product competitiveness. By combining the strengths of both aluminum and copper, these composites deliver outstanding performance in applications such as electric vehicles (EVs), energy storage systems, power electronics, heat dissipation components, busbars, electrical wiring, and many other advanced industrial fields.
However, to fully realize the benefits of aluminum-copper composite materials, manufacturers must do more than simply select the right material. Optimized component design, reliable bonding between the two metals, and an appropriate manufacturing process are equally critical. These factors directly determine the performance, durability, and long-term reliability of the final product.
With extensive expertise in aluminum casting and the development of high-performance aluminum components, Daiwa Aluminum Vietnam supports customers throughout every stage of the process—from material selection and design optimization to the production of precision aluminum castings that meet the stringent quality standards of Japan and global markets. We help manufacturers identify the most suitable solutions to balance performance, weight, cost, and mass-production efficiency, enabling products to remain competitive from the earliest design stage.
If your company is looking for solutions to reduce component weight, improve thermal management, or optimize costs for electrical, electronic, automotive, industrial, or energy applications, contact Daiwa Aluminum Vietnam today. Our engineering team is ready to provide customized solutions tailored to your specific requirements and support the development of high-quality products that meet the evolving demands of the global manufacturing supply chain.