In the selection of ultra-thin PET copper plated film, engineers are faced with a seemingly simple choice: since the goal is "thinner and lighter", why not directly choose a substrate of 2.3 μ m or even thinner?

The answer lies at the intersection of process yield and engineering reliability. The 2.3 μ m PET substrate is approaching the physical limit of an independent film - during vacuum magnetron sputtering, the heat capacity of the film is extremely small, and even small temperature fluctuations can cause shrinkage or even melting; The winding tension window is extremely narrow, and slight tension deviation can cause wrinkles or tensile deformation. Industry data shows that the thickness of ultra-thin PET substrates that can be used for stable copper plating is usually above 3 μ m. Although 2.3 μ m is feasible in the laboratory, it still faces significant challenges in terms of mass production yield and batch consistency.

2、 Roll to roll vacuum magnetron sputtering: constructing precision conductive layer on 3.1 μ m substrate

The copper layer preparation of 3.1 μ m PET copper plated film adopts roll to roll vacuum magnetron sputtering process. In a highly vacuum environment, copper with a purity of 99.999% is used as the target material. High energy ions bombard the copper target material to sputter copper atoms, which are uniformly deposited on the surface of PET film under the action of electric and magnetic fields, forming a copper layer with uniform thickness and strong adhesion. On this basis, Advanced Institute Technology adopts a dry wet combination process of "magnetron sputtering as the base and pulse electroplating for thickening": the magnetron sputtering layer provides a high adhesion and low defect seed layer, while the pulse electroplating layer provides low resistivity and high density.

Copper plating on ultra-thin substrates with a thickness of 3.1 μ m faces a series of technical challenges that are far more stringent than conventional thickness substrates:

3、 Copper layer thickness: Performance range from 0.1 μ m to 1 μ m

Based on 3.1 μ m PET substrate, copper plated film products with different copper layer thicknesses can be prepared by precise control of sputtering and electroplating process parameters. The thickness of the copper layer varies from 0.1 μ m to 1 μ m, and different thicknesses correspond to different performance focuses:

When selecting, engineers should weigh the requirements of conductivity, bending life, and processing accuracy comprehensively: the thinner the copper layer (0.1-0.3 μ m), the better the flexibility, and the higher the etching accuracy, which is suitable for high-precision thin circuits and transparent applications; The thicker the copper layer (0.7-1 μ m), the lower the square resistance, and the stronger the current carrying capacity and shielding effectiveness. Advanced Institute Technology's copper layer thickness covers 0.1-8 μ m, supporting flexible customization from ultra-thin to thickened. The typical value of square resistance for 1 μ m copper thickness is ≤ 18m Ω/□, and for 4 μ m copper thickness, the square resistance is ≤ 4.5m Ω/□.

4、 Key performance: 3.1 μ m specification technical foundation

ComprehensiveAdvanced Institute of TechnologyAccording to official website information, the key performance characteristics of 3.1 μ m PET copper plated film are as follows:

• Conductivity performance.The copper layer endows PET film with excellent conductivity. The square resistance of 1 μ m copper thickness is ≤ 18m Ω/□, and when the copper thickness is ≥ 2 μ m, the square resistance is ≤ 0.05 Ω/□. Square resistance uniformity within ± 5%, suitable for FPC and antenna applications that require high conductivity consistency.
• Coating adhesion.The adhesion of the coating reaches grade 5B (the highest grade of ASTM D3359), and the peel strength is ≥ 8N/cm (180 ° peel test). According to laboratory tests, the resistance change rate of the copper plated film after 1000 cycles of bending is less than 2%.
• Bending resistance performance.Under a bending radius of R0.5, it can withstand ≥ 100000 dynamic bending cycles, with a resistance change of less than 10% after bending.
• Heat resistance.Under the condition of 160 ° C/30min, there were no bubbles or delamination, and the simulated reflow soldering process was validated. The temperature range for the use of PET substrate is -40 ° C to 120 ° C.
• Pinhole density.≤ 0.1 pieces/m ², fully inspected for online defect detection to ensure the integrity of the coating on ultra-thin substrates.
• Square resistance uniformity.Within ± 5%, better than the industry standard of ± 10% - ± 15%, suitable for FPC and antenna applications with strict requirements for signal attenuation consistency.

5、 Core application scenario: From composite current collectors to high-density FPC

6、 Selection considerations: from copper layer thickness to application scenarios

When engineers choose 3.1 μ m PET copper plated film, the following dimensions deserve special attention:

• Selection of copper layer thickness.The thinner the copper layer (0.1-0.3 μ m), the better the flexibility and suitability for high-precision thin circuits; The thicker the copper layer (0.7-1 μ m), the lower the square resistance, and the stronger the conductivity and shielding effectiveness. 3.1 1PET is the standard specification for lithium battery composite current collectors; 3.1 0.1PET and 3.1 0.3PET are more suitable for high-density FPC and sensor electrodes.
• Bending life requirements.For dynamic applications that require frequent bending, thinner copper layer schemes should be preferred to reduce the risk of copper layer fatigue fracture. Advanced Institute Technology's copper plating film has undergone ≥ 100000 bending radii at R0.5, and the resistance change after bending is less than 10%.
• Current carrying capacity requirements.Applications that require carrying a certain amount of current should choose a thicker copper layer scheme. 3.1 The 1 μ m copper layer of 1PET provides the conductive pathway required for the composite current collector.
• Processing adaptability.3.1 μ m thin films require high processing accuracy in subsequent etching, bonding, and other processes. Advanced Institute Technology supports continuous roll to roll production, with each production line equipped with online resistance, thickness, and defect detection systems. Each roll of copper plated film comes with a factory inspection report, and the batch can be traced.

7、 Conclusion

The essence of 3.1 μ m PET copper plated film is to find an engineering balance point between the physical limits of PET film and the feasibility of mass production. It is thinner than 4 μ m or 6 μ m, bringing tangible weight reduction and space benefits to lithium battery composite current collectors and high-density FPCs; At the same time, it retains sufficient process margin to ensure stable operation of coil to coil magnetron sputtering copper plating within an acceptable yield range.

From the measured results of BYD's patent data showing a 3.3% increase in energy density of 3 μ m composite copper foil, to the engineering implementation of advanced institute technology's low-temperature and low stress deposition process on ultra-thin substrates - behind the thickness figure of 3.1 μ m is a complete process system from substrate tension control, temperature management to coating uniformity and adhesion guarantee. For engineers, understanding why it is 3.1 μ m instead of 2.3 μ m or 4 μ m - the answer to this question is precisely the technological watershed for ultra-thin PET copper plated films to move from "capable plating" to "precision plating".