Copper foil is a flat metallic material of very small thickness, made from almost pure copper. Copper foil is used when high electrical conductivity, good thermal conductivity or effective electromagnetic shielding is required. Due to these properties, copper foil is a central functional material in electrical engineering, electronics, EMC shielding, battery technology and printed circuit board manufacturing.
Copper foil is not a standardised unitary product. Properties, quality and suitability depend strongly on the manufacturing process, purity, thickness and surface condition.
Technical properties and fundamentals
Copper as a material
Copper is a non-ferrous metal with very high electrical and thermal conductivity. Copper foils are typically made from high-purity copper grades.
Relevant basic characteristics of copper:
- Very high electrical conductivity
- High thermal conductivity
- Good formability
- Good corrosion resistance in many environments
These properties make copper particularly suitable for conductive and shielding applications.
Thickness ranges of copper foil
Copper foil is typically used in thicknesses from a few micrometres to several tenths of a millimetre. Thickness influences:
- Electrical resistance
- Mechanical stability
- Shielding effectiveness
- Processability
Very thin copper foils are mechanically sensitive and require adapted processing.
Manufacturing processes for copper foil
Rolled foil
Rolled foil is produced by mechanically rolling copper sheet down to very small thicknesses.
Typical properties of rolled copper foil:
- Very uniform material structure
- High mechanical strength
- Good bending properties
- Smooth surface
Rolled foil is preferred for high-quality electronic applications.
Electrolytically produced copper foil
Electrolytic copper foil is produced by galvanic deposition on rotating drums.
Typical properties:
- Cost-efficient production
- One rough side, one smooth side
- Good adhesion to substrates
This copper foil is often used in printed circuit boards and batteries.
Surface treatment
Copper foil can additionally be surface-treated to improve specific properties:
- Oxidation protection
- Adhesion improvement
- Corrosion resistance
Such treatments affect electrical conductivity and must be evaluated in relation to the application.
Electrical and thermal properties
Electrical conductivity
Copper foil has a very low specific electrical resistivity. It is therefore excellently suited for:
- Current conduction
- Ground planes
- Shielding
- Contacting
The effective conductivity depends on thickness, purity and temperature.
Thermal conductivity
Copper foil can distribute or dissipate heat efficiently. It is therefore also used as a heat spreader, particularly in power electronics.
Thin foils have a lower heat capacity but respond quickly to temperature changes.
Applications and areas of use
Printed circuit boards and electronics
Copper foil is a central base material in printed circuit board technology. It serves as the conductor track material and as ground plane.
Adhesion to the substrate is critical for reliability.
EMC shielding
Copper foil is often used for EMC shielding. Due to its high conductivity, it effectively reflects and absorbs electromagnetic fields.
Typical applications:
- Enclosure shielding
- Cable shielding
- Shielding films in sealing systems
The shielding effect depends strongly on continuous electrical contact.
Battery technology
In lithium-ion batteries, copper foil is used as the current collector on the anode side. High purity and defined surface structures are required here.
Electrical and energy engineering
Copper foil is used in transformers, windings and busbars when low installation height or flexible geometries are required.
Processing copper foil
Cutting and stamping
Copper foil can be cut or stamped mechanically. Thin foils require sharp tools and low cutting forces to avoid burr formation.
Bending and forming
Copper foil is highly formable. With very small bend radii, however, there is a risk of material fatigue.
Bonding and laminating
Copper foil is frequently laminated onto plastics or composite materials. Adhesion depends on surface treatment and adhesive system.
Limits and constraints
Copper foil is subject to technical limits:
- Surface oxidation
- Mechanical sensitivity at low thickness
- Weight compared with aluminium
- Costs at high material purity
These aspects must be considered during design.
Comparison with aluminium foil
Copper foil offers significantly higher electrical conductivity than aluminium foil. Aluminium foil is lighter and more cost-effective but does not achieve the same shielding or conduction performance at the same thickness.
Selection depends on the application.
GOBA Takeaway
Copper foil is a highly functional material for electrical, thermal and EMC-relevant applications. Its high conductivity, good processability and versatile applications make it an indispensable material in electrical engineering and electronics.
The suitability of copper foil arises not solely from the copper material itself, but from the interplay of manufacturing process, thickness, surface condition and processing.