1、 By application scope

1. Copper clad laminate (CCL) and copper foil for printed circuit board (PCB)

CCL and PCB are widely used fields of copper foil. First, copper foil and resin impregnated adhesive sheet are hot pressed into copper clad laminate, which is used to make printed circuit boards. At present, PCB has become an indispensable main component for most electronic products to achieve circuit interconnection. At present, copper foil has become the key material of PCB that plays the role of supporting and interconnecting components in electronic products. It is compared to the "neural network" of electronic product signal and power transmission and communication. Since the 1990s, the development of IT product technology has promoted the development of PCB in the direction of multi-layer, thin, high-density and high-speed. It also requires that copper foil, which has entered a new era of technological development, be more high-performance, high-quality and reliable. At present, most of the applications in CCL and PCB industries are Electrolytic copper foil 。

2. Copper foil for lithium ion secondary battery

According to the working principle and structural design of lithium ion battery, graphite, petroleum coke and other negative materials need to be coated on the conductive collector. Copper foil has become the negative collector of lithium ion battery due to its good conductivity, soft texture, mature manufacturing technology and relatively low price. Copper foil is not only the carrier of negative active material, but also the collector and conductor of negative electrons in lithium ion batteries. At the initial stage of the development of lithium ion batteries, the copper foil used as the collector of negative electrode is mostly Calendered copper foil 。 But because lithium ion batteries Price of rolled copper foil The negative electrode coated with active substances has poor operability in drying, roller and other manufacturing processes, and is prone to wrinkles and even fractures. At the same time, the rolled copper foil has some defects, such as complex manufacturing process, long process, low production efficiency, etc. For this reason, in recent years, with the improvement of the physical, chemical, mechanical and metallurgical properties of electrolytic copper foil, as well as the advantages of easy production operation, high productivity and relatively cheap price, the use of high-performance electrolytic copper foil instead of calendered copper foil has been applied in the actual production of lithium ion batteries. At present, most lithium ion battery manufacturers at home and abroad use electrolytic copper foil as the battery cathode collector.

3. Copper foil for electromagnetic shielding

It is mainly used in some fields requiring electromagnetic shielding such as hospitals, communications and military affairs. Due to the limitation of the width of the rolled copper foil, the electromagnetic shielding copper foil is mostly electrolytic copper foil.

2、 Divided by production process

1. Calendered copper foil

The copper foil is made of copper plate by smelting and processing, then the copper plate is rolled repeatedly to make the original foil, and then the original foil is subject to a series of surface treatments such as roughening treatment, heat treatment and anti oxidation treatment according to requirements. As the rolled copper foil is limited by the processing technology, the width of the rolled copper foil is difficult to meet the production requirements of rigid CCL and lithium-ion battery cathode plates. In addition, the poor thermal stability and operability of the rolled copper foil also limit its application in the lithium-ion secondary battery industry.

However, the rolled copper foil belongs to lamellar crystalline structure, so it is superior to electrolytic copper foil in strength and toughness,

Therefore, rolled copper foil is mostly used for flexible printed circuit board. In addition, due to the high density and smooth surface of the rolled copper foil, which is conducive to the rapid transmission of signals after the printed circuit board is made, some rolled copper foils are also used on the printed circuit board for high-frequency high-speed transmission and fine wiring.

2. Electrolytic copper foil

The copper foil is made by dissolving the copper into copper sulfate electrolyte, and then electrodepositing the copper sulfate electrolyte in the 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-resistant treatment and anti oxidation treatment are carried out on the original foil according to the requirements. The electrolytic copper foil is different from the calendered copper foil. The crystal morphology of both sides of the original electrolytic foil is different, and the side close to the cathode roll is smooth, becoming a smooth surface. The other side 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 rolled copper foil. As electrolytic copper foil belongs to columnar crystal structure, its strength and toughness are inferior to those of calendered copper foil. At present, electrolytic copper foil is mostly used in the production of rigid copper clad laminate and negative pole carrier of lithium ion secondary battery.

3、 Classified according to the way of surface treatment

1. Single side treated copper foil

Among electrolytic copper foils, one side surface treated copper foils are the ones with large production volume. They are not only a type of electrolytic copper foils with large usage in the manufacturing of copper clad laminates and multilayer boards, but also copper foils with large application range. Among these products, a low profile copper foil (LP) emerged in the mid-1990s.

2. Double sided (inverted) copper foil

Multilayer circuit board, mainly used for fine circuit, has a low profile on its smooth surface. The copper clad plate made by pressing this surface with the substrate can maintain a high precision circuit after etching. The demand for such copper foil is growing.

4、 By performance

Copper foil for CCL and PCB can be divided into standard copper foil, high temperature and high elongation copper foil, high elongation copper foil, transfer resistant copper foil, low profile copper foil, etc.

1. Standard copper foil

It is mainly used to press 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, after the copper foil is roughened, a layer of special adhesive is also applied. The roughened surface of this copper foil is relatively rough, and the thickness of the copper foil is generally about 35-70um, Various performance requirements are not very high. For the copper foil used for glass fiber cloth copper clad plate, in addition to the necessary roughening treatment, heat resistance treatment (such as galvanizing, brass plating, etc.) should also be carried out, and special heat resistance and oxidation resistance treatment should be carried out. It has a high adhesion with the base material, and the heat resistance temperature reaches about 200 ℃. It is mainly made of 18um copper foil.

2. High temperature and high extensibility copper foil (THE copper foil)

It is mainly used on multilayer printed boards. Because the heat of multilayer printed boards during pressing will cause the copper foil to recrystallize, it is necessary to have the same high elongation at high temperature (180 ℃) as at normal temperature. Therefore, it is necessary to have high-temperature extensibility copper foil to ensure that there is no ring cracking during the production of printed boards.

3. High elongation copper foil (HD)

It is mainly used on the flexible circuit board and requires high folding resistance, so it must have high density and necessary heat treatment.

4. Transfer resistant copper foil

It is mainly used on printed circuit boards with high insulation requirements. If copper ions transfer after the copper foil is made into circuit boards, it will have a considerable impact on the insulation reliability of the substrate. Therefore, special treatment (such as nickel plating) must be carried out on the surface of copper foil to prevent further ionization and transfer of copper.

5、 Other types of copper foil

1. Low profile copper foil (LP copper foil), very low profile copper foil (VLP copper foil)

It is mainly used on multilayer circuit boards. It requires that the surface roughness of copper foil is smaller than that of ordinary copper foil. In addition, the surface of copper foil used in some high-frequency circuits is almost smooth, that is, ultra-low profile copper foil (VLP copper foil). Its surface roughness is smaller than that of ordinary copper foil. It is specified in IPC-4562 that the profile of both sides of LP copper foil is not more than 10.2 μ m, and the profile of both sides of VLP copper foil is not more than 5.1 μ m.

2. Glued copper foil

Adhesive coated copper foil mainly includes adhesive coated copper foil (ACC) and adhesive backed copper foil (RCC). The adhesive coated copper foil is coated with resin layer on the roughened surface after the electrolytic copper foil is roughened. It is mainly used in the manufacture of paper-based copper clad laminates. The adhesive backed copper foil is composed of copper foil with roughened, heat-resistant, oxidation resistant surface and resin in phase B. The resin layer of the adhesive backed copper foil has the same processibility as the FR-4 adhesive sheet. Therefore, some people also believe that RCC is a new CCL product without glass fiber, which is convenient for laser, plasma and other etching treatment.

3. Carrier copper foil

The production of ultra-thin copper foil mostly uses the metal support foil with a certain thickness as the cathode, on which copper is electrodeposited, then the coated ultra-thin copper foil and the support metal foil of the cathode are hot pressed, solidified and pressed on the insulating material plate, and then the metal support foil used as the cathode is stripped off by chemical or mechanical methods. The ultra-thin copper foil electrodeposited on the carrier is called carrier copper foil. The metals used as the electrodeposition carrier can include stainless steel, nickel, lead, zinc, chromium, copper, aluminum, etc., but some of the above metals are not easy to process into foil materials; Some processed into foil is too expensive; Some processed foil has too many sand holes; Some surfaces are difficult to handle and pollute the copper foil. Therefore, aluminum foil is a practical and economical support. 4. Untreated copper foil

IPC-4562 stipulates that there are two kinds of untreated copper foils. One is the copper foil (code N) whose surface is not subject to enhanced bonding treatment or rust prevention treatment; One is the copper foil (code P) whose surface is not subject to reinforcement bonding treatment but is subject to rust prevention treatment. Generally, the latter copper foil is widely used, such as copper foil for some lithium ion batteries, shielding copper foil, etc.

There are many kinds of electrolytic copper foil according to different classifications. With the development of electronic and electronic information technology, a lot of newer and higher requirements have been put forward for the variety and quality of electrolytic copper foil, which promotes the faster development of copper foil technology, and the variety and specification of electrolytic copper foil are also increasing.