Classification of flexible pcb board copper foil

Classification of flexible pcb board copper foil

The types of copper foil are:

1. According to the thickness, it can be divided into thick copper foil (more than 70μm), conventional thickness copper foil (more than 18μm and less than 70μm), thin copper foil (more than 12μm and less than 18μm), ultra-thin copper foil (less than 12μm);

2. According to the surface conditions, it can be divided into single-sided treated copper foil (single-sided wool), double-sided treated copper foil (double-sided rough), smooth-treated copper foil (double-sided wool), and double-sided smooth copper foil (dual gloss) And very low profile copper foil (VLP copper foil) copper foil, etc.

(1) Single-sided treated copper foil (single-sided wool): Among the electrolytic copper foils, the single-sided surface treated copper foil is the most produced variety, which is not only the most used type in the manufacture of copper clad laminates and multilayer boards Electrolytic copper foil, and it is the copper foil with the largest application range.

(2) Double-sided treated copper foil (double-sided thick): Mainly used in multi-layer circuit boards for fine circuits, the smooth surface has a low profile, and this surface is laminated with the base material to make the copper clad laminate. After etching, a high-precision circuit can be maintained. The demand for such copper foil is increasing.

3. Divided according to the scope of application:

(1) Copper clad laminate (CCL) and copper foil for printed circuit boards (PCB): CCL and PCB are the most widely used areas of copper foil. PCB has now become an indispensable main component for most electronic products to achieve circuit interconnection. Copper foil has now become a key material for PCBs that play a role in supporting and interconnecting components in electronic products. At present, most of the applications in CCL and PCB industries are electrolytic copper foil.

(2) Copper foil for lithium-ion secondary batteries: According to the working principle and structural design of lithium-ion batteries, anode materials such as graphite and petroleum coke need to be coated on the conductive current collector. Because of its good electrical conductivity, soft texture, mature manufacturing technology, and relatively low price, copper foil has become the first choice for the negative electrode current collector of lithium-ion batteries.

(3) Copper foil for electromagnetic shielding: Mainly used in hospitals, telecommunications, military and other areas that require electromagnetic shielding. Due to the limitation of the width of rolled copper foil, the electromagnetic shielding copper foil is mostly electrolytic copper foil.

4. According to the production method, it can be divided into electrolytic copper foil and rolled copper foil.

(1) Electrolytic copper foil is formed by depositing copper ions in the electrolyte on a smooth rotating stainless steel plate (or titanium plate) round cathode drum. The side of the copper foil that is close to the surface of the cathode drum is called the smooth surface, and the other side It is called a rough surface.

The electrolytic copper foil is different from the rolled copper foil. The surface of the electrolytic copper foil has different crystal morphologies. The side close to the cathode roll is smoother, called the smooth surface; the other side presents a concavo-convex crystal structure, which is rougher, called the matte surface. There are also certain differences in the surface treatment of electrolytic copper foil and rolled copper foil. Because the electrolytic copper foil has a columnar crystalline structure, the strength and toughness are inferior to the rolled copper foil, so the electrolytic copper foil is mostly used in the production of rigid copper clad laminates, and then made into rigid printed boards.

The technical performance requirements for electrolytic copper foil (including roughened ones) mainly include thickness, standard quality, appearance, tensile strength, peel strength, high temperature oxidation resistance, and copper foil quality resistivity. In addition to the above 7 main performance requirements, manufacturers in some countries and regions have other performance requirements, such as elongation, folding resistance, hardness, elastic coefficient, high temperature elongation, surface roughness, etching, and solderability , The adhesion of UV ink and the color of copper foil are equal.

(2) Rolled copper foil is generally made of copper ingots as raw materials, and is made by processes such as hot pressing, tempering toughening, scaling, cold rolling, continuous toughening, pickling, calendering and degreasing and drying.

Calendered copper foil is rarely used on rigid copper clad laminates. Since the bending resistance and elasticity coefficient of rolled copper foil are greater than that of electrolytic copper foil, it is suitable for flexible copper clad laminates. Its copper purity (99.9%) is higher than that of electrolytic copper foil (99.89/5), and it is smoother than electrolytic copper foil on the rough surface, which is conducive to the rapid transmission of electrical signals. Therefore, in recent years, rolled copper foil has been used on the base material of high-frequency and high-speed signal transmission and thin-wire printed boards in foreign countries. It is used as the substrate of the printed circuit board on the audio equipment, and can also improve the sound quality effect. It is also used to reduce the thermal expansion coefficient (TCE) of multi-layer circuit boards with thin wires and high-levels. In recent years, Japan has also introduced new varieties of rolled copper foil, such as: high toughness rolled copper foil, a rolled copper foil with low-temperature crystallization characteristics. Due to its high bending resistance, it is suitable for flexible boards. The other is oxygen-free rolled copper foil, its characteristic is that the oxygen content is only O. 001%, with high tensile strength, it can be used on printed circuit boards that require high lead strength in TAB and printed boards of audio equipment.

5. Other types of copper foil:

(1) Coated copper foil: mainly includes glued copper foil (ACC) and back glued copper foil (RCC). The glued copper foil is roughened on the electrolytic copper foil and then coated with a resin layer on the roughened surface , It is mainly used in the manufacture of paper-based copper clad laminates.

(2) Carrier copper foil: The production of ultra-thin copper foil mostly uses a metal supporting foil with a certain thickness as the cathode, and copper is electrodeposited on it, and then the plated ultra-thin copper foil is heated together with the supporting metal foil of the cathode. Press, solidify and press on the insulating material board, and then peel off the metal supporting foil used as the cathode by chemical or mechanical methods. This ultra-thin copper foil electrodeposited on the carrier is called carrier copper foil.

(3) Untreated copper foil: IPC-4562 stipulates that there are two types of untreated copper foil, one is the copper foil that does not carry out enhanced bonding treatment on the surface of the copper foil and does not carry out anti-rust treatment (code N); one It is a copper foil (code P) on which the surface of the copper foil is not treated with enhanced adhesion but is treated with rust prevention. Generally, the latter type of copper foil is widely used, such as some copper foils for lithium-ion batteries and shielding copper foils.

(4) Low-profile copper foil (LP copper foil): Mainly used for multilayer circuit boards, it requires the surface roughness of copper foil to be smaller than that of ordinary copper foil. IPC-4562 stipulates that the profile of both sides of LP copper foil should not be greater than 10.2 microns.