Copper foil, as a fundamental conductive raw material for producing printed circuit boards (PCBs) and lithium-ion batteries, serves as the carrier for assembling various electronic components. Since the untreated raw foil produced by electrodeposition consists of exposed copper crystal grains, its anti-peeling strength with resin laminates under high-temperature pressing is low, leading to easy detachment and scrap. Additionally, its poor high-temperature oxidation resistance may result in copper diffusion, posing risks of short circuits in later PCB production. Direct etching of raw foil also carries high risks of side etching and circuit breakage. Therefore, electrolytic copper foil requires a series of post-treatment processes in practical PCB applications, including pretreatment, roughening, stabilization, alloying, passivation, and silanization, to meet the requirements of emerging electronic components.

‌Roughening‌ increases active sites on the copper foil surface. Typically, electrodeposition is performed at limiting current density in a high-acid, low-copper electrolyte to form uniformly distributed fine copper nodules, replacing smooth contour peaks and enhancing adhesion to resin boards.

‌Stabilization‌, slightly different from roughening, aims to encapsulate and reinforce the dendritic roughened nodules to prevent detachment. This involves coating a layer of copper over the loose roughened particles to improve anti-peeling strength with resin boards.

‌Alloying‌ typically involves plating one or more layers of dissimilar metals after roughening and stabilization. The alloy layer enhances the heat resistance and anti-peeling strength of copper-clad laminates, preventing copper diffusion into resin substrates during lamination and side leakage during etching.

‌Passivation‌ forms a protective film on the copper foil surface. Traditional passivation uses chromate due to chromium’s exceptional hardness. During passivation, chromium metal forms a dense basic chromate oxide film, improving abrasion resistance, oxidation resistance, and storage stability.

‌Silanization‌ involves hydrolyzed silanol groups from silane coupling agents reacting with hydroxyl groups on the copper oxide surface to form Si—O—Me bonds, significantly enhancing adhesion between resin boards and copper foil while providing additional protection.

In practice, most copper foil manufacturers only include passivation in post-treatment processes. Traditional chromic acid-glucose immersion passivation uses toxic hexavalent chromium, which is carcinogenic and harmful to ecosystems and human health. With tightening environmental regulations, developing chromium-free green passivation technologies for lithium battery copper foil has become imperative.

Environmentally friendly passivators fall into two categories: organic and inorganic.
‌Organic passivators‌ include organic acids (phytic acid, citric acid, phosphonic acid), heterocyclic compounds (azoles, imidazoles, thiazoles), and silane coupling agents (amino silanes, epoxy silanes), forming protective films to prevent oxidation.
‌Inorganic passivators‌ include molybdate, tungstate, silicate, and rare earth salts, forming metal oxide films for oxidation resistance. Combining multiple corrosion inhibitors further enhances protective performance.

‌Jiujiang Defu Technology Co., Ltd.‌ disclosed a patent (A Chromium-Free Passivation Method for Lithium Battery Copper Foil), using methyl benzotriazole as the main film-forming agent to create a protective coordination bond film on copper foil.

‌Fogang Kingboard Industrial Co., Ltd.‌ patented (Copper Foil Anti-Oxidation Treatment Liquid, Preparation Method, and Equipment), containing hydroxybenzotriazole (HBTA), 2-mercaptobenzotriazole (MBT), sodium molybdate, and phosphoric acid. Post-treatment copper foil exhibits no discoloration at 150°C for 30 minutes, with uniform appearance and no defects.

‌Anhui Tongguan Copper Foil Co., Ltd.‌ published a study (Silanization Treatment of Copper Foil and Its Corrosion Resistance), using γ-APT (γ-aminopropyl triethoxysilane) to form self-assembled films under acidic conditions, optimizing corrosion resistance after curing at 100°C for 1 hour.

‌Frank Technology (Shenzhen) Co., Ltd.‌ patented (A Benzotriazole-Containing Nano-Silicon Corrosion Inhibitor and Preparation Method), synthesizing a benzotriazole-silane nano-inhibitor with enhanced copper protection and structural stability.

‌Hubei Jianghan New Materials Co., Ltd.‌ patented (3-(N-Imidazolyl)Propyltriethoxysilane and Synthesis Method), used for metal surface treatment, resin adhesion improvement, and corrosion inhibition.

‌Gewuzhi New Materials Co., Ltd.‌ specializes in R&D and production of copper foil chemicals, providing high-performance surface treatment solutions for electronics and lithium batteries. Through proprietary NEOS, PCU, and 110 series products, the company enhances copper foil stability, tensile strength, and oxidation resistance while advancing chromium-free processes for green manufacturing. With technical expertise and customized services, Gewuzhi has become a key domestic supplier, supporting localization of high-end materials in 5G communication and new energy battery industries.