Copper foil is a very thin copper material. It can be divided by process into two types: rolled(RA) copper foil and electrolytic(ED) copper foil. Copper foil has excellent electrical and thermal conductivity, and has the property of shielding electrical and magnetic signals. Copper foil is used in large quantities in the manufacture of precision electronic components. With the advancement of modern manufacturing, the demand for thinner, lighter, smaller and more portable electronic products has led to a wider range of applications for copper foil.
Rolled copper foil is referred to as RA copper foil. It is a copper material that is manufactured by physical rolling. Due to its manufacturing process, RA copper foil has a spherical structure inside. And it can be adjusted to soft and hard temper by using the annealing process. RA copper foil is used in the manufacture of high-end electronic products, especially those that require a certain degree of flexibility in the material.
Electrolytic copper foil is referred to as ED copper foil. It is a copper foil material that is manufactured by a chemical deposition process. Due to the nature of the production process, electrolytic copper foil has a columnar structure inside. The production process of electrolytic copper foil is relatively simple and is used in products that require a large number of simple processes, such as circuit boards and lithium battery negative electrodes.
RA copper foil and electrolytic copper foil have their advantages and disadvantages in following espects:
RA copper foil is purer in terms of copper content;
RA copper foil has better overall performance than electrolytic copper foil in terms of physical properties;
There is little difference between the two types of copper foil in terms of chemical properties;
In terms of cost, ED copper foil is easier to mass produce because of its relatively simple manufacturing process and is less expensive than calendered copper foil.
Generally, RA copper foil is used in the early stages of product manufacturing, but as the manufacturing process becomes more mature, ED copper foil will take over in order to reduce costs.
Copper foil has good electrical and thermal conductivity, and it also has good shielding properties for electrical and magnetic signals. Therefore, it is often used as a medium for electrical or thermal conduction in electronic and electrical products, or as a shielding material for some electronic components. Due to the apparent and physical properties of copper and copper alloys, they are also used in architectural decoration and other industries.
The raw material for copper foil is pure copper, but the raw materials are in different states due to different production processes. Rolled copper foil is generally made from electrolytic cathode copper sheets that are melted and then rolled; Electrolytic copper foil needs to put raw materials into sulfuric acid solution for dissolving as copper-bath, then it is more inclined to use raw materials such as copper shot or copper wire for better dissolution with sulfuric acid.
Copper ions are very active in the air and can easily react with oxygen ions in the air to form copper oxide. We treat the surface of copper foil with room temperature anti-oxidation during the production process, but this only delays the time when the copper foil is oxidized. Therefore, it is recommended to use copper foil as soon as possible after unpacking. And store the unused copper foil in a dry, light-proof place away from volatile gases. The recommended storage temperature for copper foil is about 25 degrees Celsius and the humidity should not exceed 70%.
Copper foil is not only a conductive material, but also the most cost-effective industrial material available. Copper foil has better electrical and thermal conductivity than ordinary metallic materials.
Copper foil tape is generally conductive on the copper side, and the adhesive side can also be made conductive by putting conductive powder in the adhesive. Therefore, you need to confirm whether you need single-sided conductive copper foil tape or double-sided conductive copper foil tape at the time of purchase.
Copper foil with slight surface oxidation can be removed with an alcohol sponge. If it is a long time oxidation or large area oxidation, it needs to be removed by cleaning with sulfuric acid solution.
CIVEN Metal has a copper foil tape specifically for stained glass that is very easy to use.
In theory, yes; however, since material melting is not conducted in a vacuum environment and different manufacturers use varying temperatures and forming processes, combined with differences in production environments, it is possible for different trace elements to be mixed into the material during forming. As a result, even if the material composition is the same, there can be color differences in the material from different manufacturers.
Sometimes, even for high-purity copper foil materials, the surface color of copper foils produced by different manufacturers can vary in darkness. Some people believe that darker red copper foils have higher purity. However, this is not necessarily correct because, in addition to the copper content, the surface smoothness of the copper foil can also cause color differences perceived by the human eye. For example, copper foil with a high surface smoothness will have better reflectivity, making the surface color appear lighter, and sometimes even whitish. In reality, this is a normal phenomenon for copper foil with good smoothness, indicating that the surface is smooth and has low roughness.
Electrolytic copper foil is produced using a chemical method, so the finished product surface is free of oil. In contrast, rolled copper foil is produced using a physical rolling method, and during production, mechanical lubricating oil from the rollers can remain on the surface and inside the finished product. Therefore, subsequent surface cleaning and degreasing processes are necessary to remove oil residues. If these residues are not removed, they can affect the peel resistance of the finished product's surface. Particularly during high-temperature lamination, internal oil residues may seep to the surface.
The higher the surface smoothness of the copper foil, the higher the reflectivity, which may appear whitish to the naked eye. Higher surface smoothness also slightly improves the material's electrical and thermal conductivity. If a coating process is required later, it is advisable to choose water-based coatings as much as possible. Oil-based coatings, due to their larger surface molecular structure, are more likely to peel off.
After the annealing process, the overall flexibility and plasticity of the copper foil material are improved, while its resistivity is reduced, enhancing its electrical conductivity. However, the annealed material is more susceptible to scratches and dents when it comes into contact with hard objects. Additionally, slight vibrations during the production and conveyance process can cause the material to deform and produce embossing. Therefore, extra care is needed during subsequent production and processing.
Because the current international standards do not have accurate and uniform testing methods and standards for materials with a thickness of less than 0.2mm, it is difficult to use traditional hardness values to define the soft or hard state of copper foil. Due to this situation, professional copper foil manufacturing companies use tensile strength and elongation to reflect the material's soft or hard state, rather than traditional hardness values.
Annealed Copper Foil (Soft State):
- Lower hardness and higher ductility: Easy to process and form.
- Better electrical conductivity: The annealing process reduces grain boundaries and defects.
- Good surface quality: Suitable as a substrate for printed circuit boards (PCBs).
Semi-Hard Copper Foil:
- Intermediate hardness: Has some shape retention capability.
- Suitable for applications requiring some strength and rigidity: Used in certain types of electronic components.
Hard Copper Foil:
- Higher hardness: Not easily deformed, suitable for applications requiring precise dimensions.
- Lower ductility: Requires more care during processing.
The tensile strength and elongation of copper foil are two important physical performance indicators that have a certain relationship and directly affect the quality and reliability of the copper foil. Tensile strength refers to the ability of copper foil to resist breaking under tensile force, typically expressed in megapascals (MPa). Elongation refers to the ability of the material to undergo plastic deformation during the stretching process, expressed as a percentage.
The tensile strength and elongation of copper foil are influenced by both thickness and grain size. To describe this size effect, the dimensionless thickness-to-grain size ratio (T/D) must be introduced as a comparative parameter. The tensile strength varies differently within different thickness-to-grain size ratio ranges, while elongation decreases as thickness decreases when the thickness-to-grain size ratio is constant.