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Copper foil tin plating, oxidation resistance and weldability scheme
Copper is one of the most commonly used conductive materials in the electronics industry, with conductivity second only to silver and a much lower cost. But copper has an inherent weakness: it is chemically reactive.
In humid air, copper reacts with oxygen, water vapor, and carbon dioxide to form cuprous oxide and copper oxide on the surface, which in turn forms green basic copper carbonate - copper green. The oxide layer is a semiconductor or even an insulator, which increases contact resistance, deteriorates conductivity, causes signal attenuation, and accumulates heat. Even more tricky is that the oxidized copper surface cannot be wetted by solder - even if it is reluctantly soldered, the solder joints are unreliable.
The oxidation of copper directly threatens the service life of electronic devices that require long-term reliable operation. Tin plating was born to solve this problem - by covering the surface of copper foil with a layer of tin metal, tin forms a dense tin dioxide film in the air, effectively preventing further oxidation of copper.
Core proposition:Tin plating was born to solve the problem of copper oxidation - covering the surface of copper foil with a layer of tin metal, tin forms a dense tin dioxide film in the air, effectively preventing further oxidation of copper.
The value of tin plating on copper foil is reflected in two aspects:
The chemical stability of tin is much better than that of copper. The tin plating layer forms a dense physical barrier on the surface of the copper foil, isolating the copper from the external environment (oxygen, water vapor, salt spray). Even if there is slight oxidation on the surface of the tin layer, the generated tin dioxide film is still dense and stable, which can continue to protect the underlying copper foil from erosion. Industry practice has shown that electroplating a 2-3 micron tin layer on the surface of copper foil can effectively suppress copper oxidation in conventional environments.
Tin is one of the most commonly used soldering metals in electronic manufacturing. The surface of tinned copper foil naturally has good solderability - solder can quickly wet and form reliable solder joints. This means that engineers can directly solder wires, components, or grounding wires onto tinned copper foil without the need for additional flux or polishing treatment. For scenarios that require welding connections, tin plated copper foil is a necessary condition.
The performance of copper foil tin plated products depends not only on the tin layer, but also on the thickness of the copper foil substrate itself. The three specifications of 12 microns, 18 microns, and 33 microns each have their own focus:
| Copper foil thickness | Typical characteristics | flexibility | Current-carrying capacity | Typical application scenarios |
|---|---|---|---|---|
| 12 microns | Extremely thin, highly flexible, lightweight | optimal | lower | High density FPC thin lines, wearable devices, miniature sensors |
| 18 microns | Thin, good flexibility, moderate conductivity | good | moderate | Conventional FPC signal lines, electromagnetic shielding layers, flexible connections |
| 33 microns | Thicker, higher strength, higher current carrying capacity | general | higher | High current FPC, power lines, cable shielding, automotive electronics |
Selection logic:The selection of copper foil thickness is essentially a balance between flexibility and current carrying capacity. 12 microns is suitable for thin and flexible scenarios, 18 microns is the most widely used balanced specification, and 33 microns is aimed at high current and high reliability scenarios.
Advanced Institute of Technology:We can provide customized tin plating services for copper foils with substrate thicknesses ranging from 12 microns to 33 microns, supporting both single-sided and double-sided tin plating options. The thickness of the tin plating layer can be controlled at 2-3 microns according to actual needs.
The resistivity of copper foil substrate is generally 1.7-1.8 × 10 Ω· m. The tin plating layer does not significantly affect the overall conductivity, and the conductive impedance of the adhesive surface is usually ≤ 0.05 Ω.
The tin plating layer forms a dense tin dioxide film in the air, effectively preventing further oxidation of the copper foil. Copper foil treated with tin plating has significantly better corrosion resistance than bare copper in humid and salt spray environments.
The surface of tinned copper foil has good solderability, and the solder can quickly wet and form reliable solder joints. The tin content can be adjusted between 65% and 92% to meet different welding process requirements.
The shielding effectiveness of copper foil tin plated products can reach 78-100dB in the frequency range of 30MHz-1GHz. The tin plated layer provides antioxidant protection without weakening the electromagnetic shielding ability of the copper foil.
The most classic application. Tin plated copper foil serves as a shielding layer for data communication cables, control cables, and coaxial cables, effectively resisting electromagnetic interference. Used as a high-speed direct copper cable shielding layer in scenarios such as AI computing power and data centers to ensure the stability of high-capacity data transmission. It is also widely used in high-definition TV data cables, military shielding materials, and communication engineering.
Used for making high-density flexible circuit boards, especially suitable for products that require repeated folding, such as smartphones and tablets. Tin plated copper foils with specifications of 12 microns and 18 microns are widely used in the production of FPC thin lines.
Used in the wiring harness of new energy vehicles for high-voltage cables, signal cables, and motor windings, providing stable conductivity, corrosion resistance, and high temperature resistance. The application of tin plating on copper foil is increasing in the manufacturing of lithium-ion batteries.
Used for pins or contact areas of various terminals, connectors, relays, and other components to improve solderability, reduce contact resistance, and prevent copper substrate oxidation. In PCB solder pads or lead materials, tin plating can protect copper foil from oxidation, ensuring excellent soldering performance even after long-term storage.
Advanced Institute (Shenzhen) Technology Co., Ltd. was established in 2016 and is a national high-tech enterprise specializing in flexible substrate coating, shielding materials, absorbing materials, and precious metal pastes. The company has passed the ISO9001 quality management system certification.
In the field of copper foil tin plating, Advanced Institute Technology provides the following core capabilities:
Supports rolled copper foil and electrolytic copper foil, with customizable substrate thicknesses of 12 microns, 18 microns, 33 microns, and other specifications.
Supports single-sided tin plating and double-sided tin plating, with a typical tin layer thickness of 2-3 microns.
Adopting electroplating tin process, the thickness of the coating is adjusted by precise control of electroplating time and current density.
Support on-demand cutting to meet the width requirements of different application scenarios.
Quality control throughout the entire process of cleaning, drying, and inspection.
The essence of tin plating on copper foil is to establish a unified material solution between the high conductivity of copper and the oxidation resistance and weldability of tin. It is not replacing copper with tin, but protecting copper with tin - building a dense protective barrier on the surface of copper foil, while making tin's solderability convenient for engineering operations.
12 microns provide ultimate flexibility and lightweight, 18 microns strike a balance between flexibility and conductivity, and 33 microns cater to high current and high reliability scenarios - three thickness specifications cover the complete application spectrum from wearable devices to automotive electronics. Understanding the selection logic of different copper foil thicknesses and the dual value of tin plating layers is the key to upgrading copper foil tin plating from a "roll of metal foil" to an "engineering decision".
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