Rolled copper: Copper foil is obtained by extrusion. It is characterized by good bending resistance, but its conductivity is weaker than electrolytic copper. It is mainly used for cameras in flip phones.
Electrolytic copper: Pre-made blister copper (99% copper content) into thick plates as the anode, pure copper into thin sheets as the cathode, with a mixed solution of sulfuric acid (H2SO4) and copper sulfate (CuSO4) as electrolyte. After electricity is applied, copper dissolves from the anode into copper ions (Cu) and moves to the cathode. After reaching the cathode, electrons are obtained and pure copper (also called electrolytic copper) is precipitated at the cathode. The active iron and zinc impurities in blister copper will dissolve into ions (Zn and Fe) together with the copper. Since these ions are not difficult to precipitate compared to copper ions, these ions can be prevented from precipitating on the cathode by appropriately adjusting the potential difference during electrolysis. Impurities that are less reactive than copper, such as gold and silver, are deposited at the bottom of the electrolytic tank. The copper plates produced in this way are called "electrolytic copper". They are of high quality and can be used to make electrical products. The sediment deposited at the bottom of the electrolyzer is likened to "anode mud". It is rich in gold and silver and is a very valuable object. Taking it out and reprocessing it has extremely high economic value.
The copper foil materials used for flexible circuit boards are mainly divided into two types: rolled copper (RA) and electrolytic copper (ED). It is a conductor layer bonded to the cover film insulating material. After various processes Processing and etching into the required pattern. The choice of what type of copper material to use as the conductor of a flexible circuit board needs to be considered in terms of product application range and circuit accuracy.
In terms of performance comparison, rolled copper materials have better stretchability and bending resistance than electrolytic copper materials. The elongation of rolled materials reaches 20-45%, while electrolytic copper materials only have 4-40%. However, the electrolytic copper material is formed by electroplating. Its copper particle crystal structure can easily form vertical line edges during etching, which is very conducive to the production of fine wires. In addition, because the crystals themselves are arranged neatly, the plating layer formed and the final surface treatment are formed. The surface is relatively flat. On the contrary, due to the processing technology of the rolled material, the layered crystal structure is recrystallized. Although the rolling performance is good, irregular cracks and unevenness will appear on the surface of the copper foil, causing the copper surface roughness problem in the industry.
To address the shortcomings of electrolytic materials, material suppliers have developed high-ductility electrolytic materials. After conventional processing, the materials are subjected to heat treatment and other processes to recrystallize copper atoms, so that they can achieve the characteristics of rolled materials.