In the dynamic realm of Flexible Printed Circuit (FPC) technology, the performance of copper foil plays a pivotal role. As a key material in FPC manufacturing, copper foil's properties directly influence the overall functionality and reliability of FPCs. Shenzhen Huaruixin Electronics Co., Ltd., a professional designer and producer of FPC&PCB&Rigid - Flex Printed Boards, deeply understands the significance of these parameters. Let's explore the crucial performance parameters of FPC copper foil.

1. Electrical Conductivity Parameters

Resistivity

Meaning: Resistivity, measured in ohm - meter (Ω·m), is a fundamental parameter for gauging the electrical conductivity of copper foil. It represents the resistance value of a unit - length and unit - cross - sectional - area copper foil at a specific temperature. A lower resistivity indicates superior electrical conductivity. In applications involving high - frequency signal transmission, such as 5G communication modules or high - speed data transfer in data centers, low - resistivity copper foil is essential. For instance, in high - speed serial interfaces like PCIe (Peripheral Component Interconnect Express), where maintaining proper impedance matching is crucial for reliable data transfer, low - resistivity copper foil can effectively reduce signal attenuation during transmission, ensuring the integrity and accuracy of high - frequency signals.

Surface Resistance

Meaning: Surface resistance, with the unit of ohm per square (Ω/sq), reflects the conductive characteristics of the copper foil's surface. It has a significant impact on circuit connections and signal transmission in FPCs. A lower surface resistance enables smooth current flow on the copper foil surface, minimizing signal distortion or transmission failures caused by excessive surface resistance. In the fabrication of FPCs with fine - line circuits, especially in high - density interconnection (HDI) boards used in advanced smartphones or high - end tablets, strict control of surface resistance is of utmost importance. Even a slight change in surface resistance can significantly affect the overall performance of the intricate circuit.

2. Flexibility Parameters

Bend Radius

Meaning: The bend radius, usually measured in millimeters (mm), refers to the minimum radius at which the FPC copper foil can be bent without suffering damage such as cracking, breaking, or performance degradation. A smaller bend radius implies better flexibility, allowing the copper foil to adapt to more complex bending and folding scenarios. In wearable devices like smartwatches or the flexible displays of foldable smartphones, which require frequent bending with the user's movement, copper foil with a small bend radius is essential. For example, in a smartwatch FPC, a copper foil with a bend radius of 1mm can endure thousands of daily bends, ensuring the stable operation of functions like heart - rate monitoring and activity tracking.

Bending Fatigue Life

Meaning: Bending fatigue life represents the number of times the copper foil can withstand repeated bending under specific conditions (such as a certain bend radius, bend angle, and bend frequency) without experiencing failures like open - circuit, short - circuit, or significant performance decline. It is a crucial indicator for evaluating the flexibility and durability of copper foil. In applications where FPCs are frequently bent, such as the flexible circuit boards in foldable smartphones, high - bending - fatigue - life copper foil is necessary. Some advanced copper foils can endure over 1 million bending cycles, greatly extending the service life of the device and enhancing user experience.

3. Thickness Parameters

Nominal Thickness

Meaning: Nominal thickness, typically measured in microns (μm), is the standard thickness set during the production of copper foil. Common nominal thicknesses for FPC copper foil include 9μm, 12μm, 18μm, and 35μm. The thickness of copper foil has a direct bearing on its electrical and mechanical properties. Thicker copper foil, with lower resistance, can carry larger currents and is suitable for circuits that require high - current transmission, such as power - supply circuits in industrial equipment or high - power consumer electronics. On the other hand, thinner copper foil offers better flexibility and is more suitable for applications with high - flexibility requirements and relatively lower current - carrying demands, like the FPCs in miniaturized electronic devices such as wireless earphones.

4. Tensile Strength Parameters

Tensile Strength

Meaning: Tensile strength, measured in megapascals (MPa), is the maximum tensile stress that the copper foil can withstand before being stretched and broken. It reflects the copper foil's ability to resist tensile damage. In the use of FPCs, especially in environments where external pulling forces may be encountered, such as in the FPC connection parts of industrial equipment, sufficient tensile strength can ensure that the copper foil does not break easily, maintaining the integrity and normal operation of the circuit. Additionally, high tensile strength also facilitates the processing operations in FPC manufacturing, such as lamination and stamping, helping the copper foil better maintain its shape and performance.

Elongation

Meaning: Elongation is the percentage of the elongation at break to the original length of the copper foil in a tensile test. It indicates the ability of the copper foil to undergo plastic deformation without breaking when subjected to tensile forces. A higher elongation means that the copper foil can absorb energy through its own deformation when under tensile stress, avoiding sudden fracture. In applications where FPCs are subject to dynamic tensile stress, such as in the FPC connections of movable components in some mechanical devices, copper foil with high elongation can better adapt to tensile deformation, improving the reliability and service life of the FPC.

5. Chemical Stability Parameters

Corrosion Resistance

Meaning: Corrosion resistance refers to the ability of copper foil to resist the erosion of chemical substances in the surrounding environment. It is usually evaluated by immersing the copper foil in specific corrosive media (such as acid, alkali, or salt solutions) and observing the degree of corrosion on the copper foil surface, mass changes, or resistance changes. Good corrosion resistance can ensure that in harsh chemical environments, such as outdoor electronic devices exposed to moisture, humidity, and chemicals, or industrial equipment in chemical plants, the copper foil in FPCs will not experience performance degradation due to corrosion, such as increased resistance or short - circuits, thereby extending the service life and reliability of the FPC.

Oxidation Resistance

Meaning: Oxidation resistance is the ability of copper foil to resist oxidation by oxygen. Copper easily reacts with oxygen in the air to form copper oxide, and the resistance of copper oxide is higher than that of pure copper, which can affect the electrical conductivity of the copper foil. By applying anti - oxidation treatments (such as coating an anti - oxidation layer on the surface) and testing the copper foil in accelerated oxidation environments such as high - temperature and high - humidity conditions, the oxidation resistance of the copper foil can be evaluated. In high - temperature and high - humidity working environments, such as in industrial ovens or steam equipment, copper foil with good oxidation resistance can maintain stable electrical conductivity, ensuring the normal operation of the circuit.

Shenzhen Huaruixin Electronics Co., Ltd. has been at the forefront of the FPC industry, leveraging its in - depth understanding of these copper - foil performance parameters. Through continuous research and development, strict quality control, and the application of advanced manufacturing technologies, the company ensures that its FPC products meet the highest standards. Whether it's achieving optimal electrical conductivity for high - speed data transfer or ensuring excellent flexibility for wearable device applications, Shenzhen Huaruixin Electronics Co., Ltd. has the expertise to deliver.

We warmly welcome new and old friends in the industry to engage in exchanges and learning. Together, we can explore the latest trends in FPC technology, share insights on copper - foil applications, and drive the continuous innovation and development of the FPC industry.