What is CUPAL?

CUPAL is a plating of copper on aluminum. The two metals are inseparably welded together in a special process. CUPAL is therefore not an alloy, but a composite material from the group of non-ferrous metals. CUPAL is tested in many ways and proven over many years as a replacement material for pure copper, Tombak and brass.

CUPAL combines the advantages of light metals - low specific weight (low dead weight), easy workability, etc. - with the advantages of copper, such as corrosion resistance, the property of being soldered and electroplated, special features for electrical purposes. The copper or aluminum properties of CUPAL are both in chemical and physical terms like those of pure copper and pure aluminum. CUPAL enables corrosion-resistant connections between heavy and light metals. CUPAL is characterized by good thermal conductivity. The electrical conductivity of CUPAL is favourable and reaches a conductance equal to that of pure copper for high frequency currents. The contact values are even better than those of pure copper.
CUPAL metal sheets can be processed by drawing, pressing, embossing, driving, bending, folding, riveting etc., in a simple way they can be soldered and electroplated like pure copper.


CUPAL is particularly suitable for electrical engineering (connecting elements between light and heavy metal conductors, power and contact material for a variety of purposes of electric power, light-current and high frequency engineering), in apparatus and mechanical engineering (containers, housings, services) and for the large area of metal products (quality products, fine notions, craft).

Product Information

CUPAL is a cold rolled and plated composite material between aluminum as the carrier material and copper as 
Cladding material. This composite material is use in the electrical industry as a contact or transition element between conductors of aluminum and copper. Due to the connection of CUPAL, the contact resistance between the different metals is shifted to the composite plate and is thus protected from atmospheric influences.


Manufacturing process

The CUPAL composite material is produced by cold roll bonding. After a surface preparation adapted to the particular material, aluminum and copper are tightly connected by high pressure in a plating and rolling frame. The material solidification caused in this way must be reduced by an appropriate heat treatment to achieve the desired properties. Here, the adhesion strength between aluminum and copper is improved as a result of a diffusion bonding at the same time. By limiting the annealing time and annealing temperature, an uncontrolled alloy layer formation is suppressed.

Due to the submicroscopically thick alloy layer, CUPAL can be further processed by cold forming, such as folding, flanging, bending, embossing, shaping, stretch and deep drawing. In case of a strong increase in strength due to cold forming, the original formability can be obtained again by a heat treatment. The heat treatment should, however, not exceed 260 degrees Celsius/4 h.

Application technology

Switchgear and apparatus engineering Use as washers, inserts and cable lugs
Overhead line construction Rapping tape or sleeve-like inserts in terminal connections
Batteries Connection between printed circuit boards and batteries

Advantages of CUPAL metal sheets

Its low specific weight results in benefits for accelerated masses, such as for switches.

For high-frequency currents, only thin copper cladding is necessary to achieve a conductivity corresponding to the all-copper material on account of the skin effect. This leads to its use in capacitors and components for transmitting and receiving equipment.

Mechanical and physical properties

Properties Unit Alu/Copper (80/20) Alu/Copper (70/30)
Density g/cm3 4,00 4,6
Electrical conductivity m/Ohm*mm2) 39,6 41,9
Specific resistance Ohm*mm2/m 0,0252 0,0239
Requ. cross section with respect to Cu 1,46 1,41
Requ. cross section with respect to Al 0,937 0,906
Thermal conductivity W/(m+K) 247 265
Linear thermal expansion coefficient 10-6/K 22,5 21,8
Modulus of elasticity kN/mm2 76 81
Tensile strength N/mm2 110-160 130-180

Chemical Composition of CUPAL Materials

Aluminum: AL 99,5 | AL 99.5 | material no. 3.0255 according to DIN 17007 | 1050 alloy according to Int. Reg. Record

Copper: E1-Cu58 | material no. 2.0065 according to DIN 1787 | CU/a1 according to NFA 53-100 | CU 99.9%

Aluminum is often used to reduce costs and weight compared to copper. The electric conductivity of aluminum versus volume is slightly lower than that of copper. However, the electric conductivity versus mass is higher. In practice, this means that a conductor line of aluminum requires an approximately one and a half times larger cross-section than a conductor line made of copper in order to achieve the same current-carrying capacity. On the other hand, this conductor line made of aluminum is then considerably lighter and cheaper than the thinner conductor line made of copper.A disadvantage of aluminum is that it cannot be soldered because of its passivating surface layer and, for the same reason, because a transition resistance is created when using screw and clamp connections. In this case, a highly conductive connecting element can be interconnected when using clamps or sleeves made of Cupal, where aluminum surfaces are pressed together and the copper surface is still connected with the usual electrical connecting techniques.