1. Copper clad laminate and copper foil for printed circuit board
Copper clad laminate and PCB are the most widely used fields of copper foil. Firstly, the adhesive sheet of copper foil and impregnated resin is hot-pressed to make copper-clad laminate, which is used to make printed circuit boards. At present, PCB has become an indispensable part of most electronic products to realize circuit interconnection. At present, copper foil has become the key material of PCB which plays the role of supporting and interconnecting components in electronic products. It is compared to the "neural network" for the signal and power transmission and communication of electronic products. Since 1990s, the development of IT product technology has promoted the development of PCB to multilayer, thin, high density and high speed. It is also required that the copper foil entering the new technological development period has higher performance, higher quality and higher reliability. At present, the products used in copper clad laminate and PCB industry are mostly electrolytic copper foil.
2. Copper foil for lithium ion secondary battery
According to the working principle and structural design of lithium ion battery, it is necessary to coat the conductive current collector with graphite, petroleum coke and other negative materials. Copper foil has become the first choice for negative current collectors of lithium-ion batteries because of its good conductivity, soft texture, mature manufacturing technology and relatively low price. Copper foil is not only the carrier of negative active materials, but also the collector and conductor of negative electrons in lithium ion batteries. At the early stage of lithium ion battery development, the copper foil used as negative current collector was mostly rolled copper foil. However, due to the high price of rolled copper foil for lithium ion batteries, the negative electrode coated with active materials has poor operability in the manufacturing processes such as drying and rolling, and is prone to wrinkles and even cracks. At the same time, the rolled copper foil has some defects, such as complex manufacturing process, long process and low production efficiency. Therefore, in recent years, with the improvement of physical, chemical, mechanical and metallurgical properties of electrolytic copper foil, as well as the advantages of simple production operation, high productivity and relatively low price, the use of high-performance electrolytic copper foil instead of calendered copper foil has been applied to the actual production of lithium-ion batteries. At present, most lithium-ion battery manufacturers at home and abroad use electrolytic copper foil as the negative current collector of the battery.
3. Copper foil for electromagnetic shielding
Mainly used in hospitals, communications, military and other fields that need electromagnetic shielding. Due to the limited width of rolled copper foil, electromagnetic shielding copper foil is mostly electrolytic copper foil.
Second, according to the production process
1. Rolling copper foil
Copper foil is made of copper after smelting, and then the copper plate is repeatedly rolled into the original foil, and then the original foil is subjected to a series of surface treatments such as roughening, heat resistance and oxidation resistance as needed. Due to the limitation of processing technology, the width of rolled copper foil is difficult to meet the production requirements of rigid copper clad laminate and negative pole piece of lithium ion battery. In addition, the poor thermal stability and operability of rolled copper foil also limit its application in lithium-ion secondary battery industry.
Rolling copper foil belongs to flaky crystal structure, so it is superior to electrolytic copper foil in strength and toughness.
Therefore, calendered copper foil is mostly used in flexible printed circuit boards. In addition, because the rolled copper foil has high density and smooth surface, it is beneficial to the rapid transmission of signals after being made into printed circuit boards, so some rolled copper foils are also used in printed circuit boards with high-frequency and high-speed transmission and thin lines.
2. Electrolytic copper foil
Copper foil is made by dissolving copper in copper sulfate electrolyte, and then electrodepositing copper sulfate electrolyte in special electrolytic equipment under the action of direct current to make the original foil. Then a series of surface treatments such as roughening treatment, heat resistance treatment and oxidation resistance treatment are carried out on the original foil as needed. Electrolytic copper foil is different from calendered copper foil, and the crystal morphology of both sides of electrolytic green foil is different, and the side close to cathode roller is smooth and becomes smooth. On the other hand, it presents a convex-concave crystal structure, which is rough and becomes a rough surface. The surface treatment of electrolytic copper foil is also different from that of calendered copper foil. Because electrolytic copper foil belongs to columnar crystal structure, its strength and toughness are not as good as those of rolled copper foil. Electrolytic copper foil is now mainly used to produce rigid copper-clad laminates and negative carriers for lithium-ion secondary batteries.
Three, according to the surface treatment can be divided into
1. Single sided copper foil
Among the electrolytic copper foils, one-sided surface treated copper foil is the largest variety, which is not only the most widely used electrolytic copper foil in the manufacture of copper clad laminate and multilayer board, but also the most widely used copper foil. Among these products, low profile copper foil (LP) appeared in the mid-1990s.
2. Double-sided (reverse) copper foil
A multilayer circuit board mainly used for fine circuits has a smooth surface with a low profile, and a copper-clad laminate made by pressing the surface with a substrate can maintain a high-precision circuit after etching. The demand for this kind of copper foil is increasing.
Fourth, according to performance.
Copper foil for CCL and PCB can be divided into standard copper foil, high temperature high ductility copper foil, high ductility copper foil, transfer resistant copper foil and low profile copper foil according to their properties.
1. Standard copper foil
Mainly used for pressing paper-based phenolic resin copper clad laminate and epoxy resin glass fiber cloth copper clad laminate. For the copper foil used for paper-based copper clad laminate, in order to improve the bonding strength between the copper foil and the substrate, the copper foil should be coated with a special adhesive after roughening. The coarsened surface roughness of this kind of copper foil is relatively large, and the thickness of copper foil is generally about 35-70μ m, so various performance requirements are not very high. For the copper foil used for glass fiber cloth copper clad laminate, in addition to the necessary roughening treatment, heat-resistant treatment (such as zinc plating, brass plating, etc.) should be carried out. ), special high-temperature anti-oxidation treatment, strong adhesion to the substrate, heat-resistant temperature of about 200℃. Mainly made of 18um copper foil.
2. High temperature and high ductility copper foil (copper foil)
Mainly used for multilayer printed boards. Because the heat of multilayer printed board will recrystallize copper foil, it needs to have the same high elongation at high temperature (180℃) as at normal temperature, so it needs high-temperature malleable copper foil to ensure that there is no ring crack in the manufacturing process of printed board.
3. High ductility copper foil
Mainly used in flexible printed circuit board, it requires high folding resistance, so it must have high density and undergo necessary heat treatment.
4. Anti-transfer copper foil
Mainly used for printed circuit boards with high insulation requirements. If copper ions are transferred after the copper foil is made into a circuit board, it will have a considerable impact on the insulation reliability of the substrate. Therefore, the surface of copper foil must be specially treated (such as nickel plating) to inhibit further ionization and transfer of copper.
Five, other types of copper foil
1. Low profile copper foil (LP copper foil), very low profile copper foil (VLP copper foil)
Mainly used for multilayer circuit boards, the surface roughness of copper foil is required to be less than that of ordinary copper foil. In addition, the surface of copper foil used in some high-frequency lines is almost smooth, that is, ultra-low profile copper foil (VLP copper foil), and its surface roughness is smaller than that of ordinary copper foil. IPC-4562 stipulates that the contour of LP copper foil is not more than10 ... 2 microns, and that of VLP copper foil is not more than 5.65438 0 microns.
2. Glued copper foil
Coated copper foil mainly includes coated copper foil (ACC) and coated copper foil (RCC). Glued copper foil is made by roughening electrolytic copper foil and then coating resin layer on the roughened surface, which is mainly used to manufacture paper-based copper clad laminate. Adhesive-backed copper foil is composed of copper foil with rough surface, heat resistance and oxidation resistance and B-grade resin. The resin layer of adhesive-backed copper foil has the same manufacturability as FR-4 adhesive sheet, so some people think that RCC is a new type of copper clad laminate product without glass fiber, which is convenient for laser and plasma etching.
3. Carrier copper foil
In the production of ultra-thin copper foil, a metal supporting foil with a certain thickness is used as the cathode, and copper is electrodeposited on it. Then, the coated ultra-thin copper foil and the supporting metal foil of the cathode are hot-pressed, cured and pressed on the insulating material plate, and then the metal supporting foil used as the cathode is peeled off by chemical or mechanical methods. This ultra-thin copper foil electrodeposited on the carrier is called carrier copper foil, and the metals used as electrodeposition carrier may include: stainless steel, nickel, lead, zinc, chromium, copper, aluminum and so on. , but some of the above metals are not easy to be processed into foil; Some processed into foil are too expensive; Some are processed into foil, and there are too many sand holes and pinholes; Some surfaces are difficult to treat, which will pollute the copper foil. So at present, the most practical and economical support is aluminum foil. 4. Untreated copper foil
According to IPC-4562, there are two kinds of untreated copper foil, one is copper foil (code N) whose surface has not been treated with anti-rust treatment to enhance adhesion; One is copper foil (code P), the surface of which is not treated to enhance adhesion, but is treated to prevent rust. Usually the latter copper foil is widely used, such as copper foil of some lithium ion batteries and shielding copper foil.
There are many kinds of electrolytic copper foil according to different methods. With the development of electronic information technology, newer and higher requirements are put forward for the variety and quality of electrolytic copper foil, which promotes the faster development of copper foil technology and more and more varieties and specifications of electrolytic copper foil.