3.1 μ m ultra-thin PET copper plated film | Accurate selection of flexible conductive materials from square resistance data as substrate thickness approaches physical limits

1、 What does 3.1 μ m mean? ——The engineering value of ultra-thin substrates

The thickness of PET film has been reduced from the conventional 25 μ m and 12 μ m to 4.5 μ m and 3.1 μ m - each thickness crossing is redefining the physical boundaries of flexible electronic design.

The 3.1 μ m PET substrate poses multiple challenges in tension control, temperature control accuracy, and coating uniformity in roll to roll continuous coating production. PET film itself has excellent mechanical strength, chemical stability, and low moisture absorption. The ultra-thin specification of 3.1 μ m further amplifies the flexibility advantage of PET - smaller bending radius, lower bending stress, and lighter weight per unit area.

In the hinge cable of foldable screen phones, for every 1 μ m reduction in substrate thickness, the design space of the hinge mechanism can be released one more minute; In the micro sensors of wearable devices, the thinner the substrate, the higher the comfort of wearing the device. The thickness of 3.1 μ m approaching the physical limit is precisely in response to these engineering requirements of "space as performance".

Advanced Institute Technology uses vacuum magnetron sputtering technology to deposit high-purity oxygen free copper conductive layer on a 3.1 μ m ultra-thin PET substrate. The thickness of the copper layer can be precisely processed according to customer requirements. By using roll to roll continuous coating technology, the flatness and coating uniformity of ultra-thin substrates during high-speed operation are ensured.

2、 Product Matrix from Square Resistance Data: Four Copper Layer Thicknesses, Four Performance Positions

Conductivity is the core functional indicator of PET copper plated film, and sheet resistance is the most direct parameter for measuring conductivity performance. The lower the square resistance, the smaller the signal transmission loss and the higher the conductivity efficiency under the same conditions.

Advanced Institute Technology's 3.1 μ m PET copper plated film series offers four copper layer thickness options, covering the complete performance range from high-frequency bending to high conductivity:

The relationship between copper layer thickness and square resistance is not simply a linear decrease. The theoretical resistance of the 0.7 μ m model (0.4 Ω) is actually higher than that of the 0.3 μ m model (0.1 Ω), which is not abnormal - the combined effect of the copper layer grain structure and deposition process determines the final conductivity. Overly thick copper layers on ultra-thin substrates may cause grain coarsening due to stress accumulation, which in turn affects the efficiency of the conductive path.

Among the four models, 3.1 1PET copper plated film achieved a measured square resistance of 40-50m Ω with a 1 μ m copper layer, making it the most conductive model in the series and suitable for scenarios with strict requirements for low resistance. 3.1 0.3PET copper plated film achieves the best balance between conductivity and flexibility with a measured resistance of 225m Ω, making it the universal main model of this series.

3、 From 40m Ω to 520m Ω: Different square resistances correspond to different scenarios

3.1 1PET Copper Coating (40-50m Ω) - High Conductivity Type

The 1 μ m copper layer and measured square resistance as low as 40-50m Ω are the "ceiling" of the conductivity performance of this series. Ultra low impedance means extremely low signal transmission loss and stronger current carrying capacity. In electromagnetic shielding scenarios that require high conductivity, low impedance directly corresponds to higher shielding effectiveness. In high-frequency signal transmission lines, low impedance ensures signal integrity. Advanced Institute Technology can control the square resistance within the range of 0.01-1 Ω/□ by adjusting the sputtering power or chemical plating time. 40-50m Ω is close to the lower limit of this process and is suitable for scenarios with extreme conductivity requirements - high-frequency antenna lines, high current flexible circuits, and high-performance electromagnetic shielding layers.

3.1 0.3PET Copper Plating Film (225m Ω) - Balanced Universal Type

A 0.3 μ m copper layer and a measured square resistance of 225m Ω have found the optimal balance between conductivity and flexibility. The copper layer thickness of 0.3 μ m ensures sufficient conductive path density without significantly affecting the bending performance of the substrate due to excessive thickness. The interface bonding strength between copper layer and PET substrate can be optimized through pretreatment process, and the peel strength can reach ≥ 1.5N/mm. A square resistance of 225m Ω is sufficient to meet the conductivity requirements of the vast majority of flexible circuits and electromagnetic shielding scenarios, making it the most widely applicable model in this series - flexible circuit boards, electromagnetic shielding films, and conductive lines for wearable devices.

3.1 0.7PET Copper Plated Film (380m Ω) - Highly Reliable and Durable Type

0.7 μ m copper layer, measured square resistance of 380m Ω. Although the theoretical square resistance (0.4 Ω) is higher than the 0.3 μ m model, a thicker copper layer means better wear resistance and scratch resistance. In scenarios that require repeated insertion, friction, or exposure to slight mechanical wear, the 0.7 μ m copper layer provides an additional 'safety margin'. After 96 hours of salt spray test, there is no corrosion standard. The surface of the copper layer can be further improved for corrosion resistance through electroplating or chemical passivation treatment - industrial control equipment interfaces, vehicle electronic connectors, and maintenance cover sealing surfaces that require frequent operation.

3.1 0.1PET copper plated film (520m Ω) - extremely flexibleType

0.1 μ m copper layer, measured square resistance of 520m Ω. The copper layer is the thinnest and has the least impact on the flexibility of the substrate. In scenarios that require extremely small bending radii and high-frequency bending, ultra-thin copper layers mean lower bending stresses and longer fatigue life. Laboratory tests have shown that the optimized PET copper plated film has a resistance change rate of less than 2% after 1000 cycles of bending. The 0.1 μ m copper layer is designed to maximize the bending life advantage of foldable screen hinge cables, flexible sensors, and dynamic flexible circuits that require repeated bending.

4、 Process guarantee: Vacuum magnetron sputtering and roll to roll continuous coating

Advanced Institute Technology produces 3.1 μ m PET copper plated film using vacuum magnetron sputtering technology. In a highly vacuum environment, copper atoms sputtered by magnetic field control are uniformly deposited on the surface of PET film, forming a dense and low defect conductive film. The controllability of copper layer thickness reaches ± 0.1 μ m.

In response to the special challenge of 3.1 μ m ultra-thin substrate, the company has achieved precise tension control and temperature control management on the roll to roll continuous coating production line. The adhesion of the copper layer can reach level 5B according to ASTM D3359 testing. The surface roughness of the copper layer can be optimized according to the requirements. In response to the high frequency loss sensitivity in the 5G communication field, the surface roughness can be reduced to Ra ≤ 50nm.

Advanced Institute Technology supports customized copper layer thickness and substrate specifications as needed. Whether it requires ultra-thin design to meet the strict requirements of space and weight for precision electronic devices, or thicker design to enhance conductivity, precise matching can be achieved.

5、 Selection suggestion: How to choose the most suitable model for your application?

When selecting, it is necessary to comprehensively evaluate factors such as the working temperature range (PET substrate heat resistance of about 120 ℃), bending frequency and radius, environmental corrosion risk (salt spray, humidity), etc. Advanced Institute Technology provides full process technical support from sample trial production to batch delivery.

PET copper plated film cleverly combines the flexibility of polymer films with the excellent conductivity of copper. Driven by the popularization of flexible electronics, the explosion of wearable devices, and the continuous growth of electromagnetic shielding demand, the 3.1 μ m ultra-thin PET copper plated film is providing engineers with precise matching of conductive substrates for different scenarios with a complete coverage range from 40-50m Ω to 520m Ω.