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4 μ m PET aluminum plated film · Ultra thin metallization and composite current collector scheme
In the selection of ultra-thin PET aluminum 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 the vacuum evaporation process, the heat capacity of the film is extremely small, and 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 ultra-thin PET substrates that can be used for stable metallization typically have a thickness of 4 μ m or more.
Core proposition:4 μ m is in a "just right" position in engineering: it is significantly thinner than 6 μ m, bringing considerable volume efficiency and weight reduction benefits to the composite current collector of metalized thin film capacitors and lithium batteries; At the same time, it retains sufficient mechanical strength and thermal capacity margin, enabling roll to roll vacuum deposition to operate stably within an acceptable yield range.Advanced Institute of TechnologyThe PET film produced is aluminum plated, with a thickness range of 4.5 to 188 microns, a width of up to 250mm to 1200mm, and supports customization according to demand. Although 4 μ m is slightly lower than the conventional production limit, advanced technology can achieve stable supply in this thickness range through process optimization.
In metallized film capacitors, PET film serves as the dielectric, and its thickness directly determines the volumetric efficiency of the capacitor. The capacitance of a capacitor is inversely proportional to the thickness of the dielectric - the thinner the film, the greater the capacitance within the same volume. The commonly used dielectric film thickness for thin film capacitors is usually 1 to 20 μ m, and the thinner the film, the higher the capacity density.
4 μ m is at a critical balance between high volumetric efficiency and process feasibility. The capacitor with PET as the dielectric is called Mylar capacitor, with a dielectric constant of about 3.0 to 3.2, a higher capacity density than polypropylene capacitor, and a working temperature range covering -40 ° C to 125 ° C. The thickness of the metallized electrode is only 50 to 100nm, which not only reduces contact resistance but also has a certain self-healing ability. When the dielectric partially breaks down, the extremely thin metal layer rapidly evaporates around the breakdown point, allowing the capacitor to resume normal operation.
Polyester film capacitors use PET film as the dielectric, and the electrodes are made of vacuum deposited aluminum or zinc aluminum alloy layers, which are packaged by winding and forming. Metallized polyester film capacitors have high capacity density and self-healing properties, while also ensuring small size and light weight. The mass production capability of 4 μ m PET aluminum coated film is a crucial step in the direction of ultra-thin technology, moving from being "feasible" to being "user-friendly".
The application of 4 μ m PET aluminum coated film in the field of lithium battery composite current collectors is one of the most concerned technological directions in recent years.
The composite current collector adopts a sandwich structure of "metal conductive layer polymer material support layer metal conductive layer". Composite aluminum foil mainly adopts vacuum coating technology. It is first coated with 8-15nm metal aluminum oxide through an evaporation kettle, and then thickened with about 1 μ m aluminum layer. Considering the adhesion of aluminum ions, the base film of composite aluminum foil is mainly made of PET material. In industry practice, a layer of 50 to 80nm metal is deposited on the surface of a plastic film with a thickness of 4 μ m using magnetron sputtering and vacuum evaporation. Then, the metal layer is thickened to 1 μ m by electroplating with water to produce a composite metal foil with a total thickness of 6 to 8 μ m, which is used to replace the traditional current collector with a thickness of 4 to 13 μ m.
The density of PET substrate is only about 1/2.7 of aluminum. Replacing part of the aluminum layer with 4 μ m PET significantly reduces the surface density of the current collector. Under the trend of lightweight, PET composite aluminum foil can achieve a current collector thickness of less than 8 μ m, which plays an important role in the lightweighting of power batteries.
Security Enhancement:In terms of safety, the polymer substrate in the middle has flame-retardant properties, and the metal conductive layer is relatively thin. When short circuited, it will melt like a fuse and quickly melt before thermal runaway. The burr size generated by the composite current collector is small, and the short-circuit current can be greatly reduced in a short period of time due to the short-circuit effect caused by the heating of the polymer material layer. Composite current collector is a new technology for power batteries, which uses ultra-thin PET as the substrate and double-sided synchronous vacuum coating technology to make composite functional layers. Compared with traditional pure aluminum foil, it has the advantages of high safety, energy saving and environmental protection, and low cost.
The aluminum layer of 4 μ m PET aluminum coated film was prepared using vacuum evaporation technology. Vacuum evaporation is the process of placing a roll of film in a vacuum chamber. When the vacuum degree reaches 4 × 10 ⁻⁴ mbar or higher, the evaporation boat is heated to 1300 to 1400 ° C, and then aluminum wire with a purity of 99.9% is continuously sent to the evaporation boat for evaporation. The aluminum vapor condenses and deposits on the surface of the PET film to form a coating.
Vacuum deposition on ultra-thin substrates with a thickness of 4 μ m faces a series of technical challenges that are far more stringent than conventional thickness substrates:
If the winding tension is too high, the film will be "squeezed" out, wrinkled, or even stretched and deformed; If the tension is too low, it is easy to cause detachment. The thinner the substrate thickness, the narrower the tension control window. Advanced vacuum aluminum plating technology can form a uniform and dense aluminum layer on the surface of PET film, ensuring the stability and consistency of material properties.
The temperature resistance of PET film is about 180 ° C, while the evaporation temperature of aluminum can reach 1200 to 1400 ° C. The evaporation process requires temperature control, and excessive substrate temperature can cause defects such as deformation, uneven surface thickness, or cracking. The modern production line adopts a computer control system, which precisely controls the matching relationship between the evaporation rate and the substrate operating speed to control the substrate temperature rise within a safe range.
The lack of active functional groups on the surface of PET material and insufficient adhesion between the metal coating and the substrate can lead to the detachment of the aluminum layer during subsequent processing or capacitor operation. The plasma pretreatment process of Advanced Institute Technology effectively improves the bonding strength between PET and aluminum layer, ensuring that the adhesion of the coating meets the application requirements.
On a 4 μ m ultra-thin substrate, any tiny substrate defects or dust particles can become penetrating pinholes. Advanced Institute Technology conducts plasma activation pretreatment on PET film, introducing active sites without damaging the substrate, while minimizing pinhole defects to the greatest extent possible.
Based on a 4 μ m PET substrate, aluminum plated film products with different aluminum layer thicknesses can be prepared by precisely controlling the evaporation process parameters. The thickness of the aluminum layer is usually characterized by optical density (OD), with higher OD values indicating thicker aluminum layers and lower light transmittance. Industry data shows that the OD value of metallized PET film is usually between 1.62 and 3.6, and can be customized. The thickness of the aluminum layer is generally between 20 and 100 nanometers, which can be adjusted according to different application requirements.
Different thicknesses correspond to different performance focuses:
| Product Type | Optical Density (OD) | Key Characteristics | Typical Applications |
|---|---|---|---|
| 4 0.1PET aluminum plated film | ~0.1 OD | Extremely thin aluminum layer, semi transparent, extremely flexible | Ultra thin capacitors, precision optical films, low barrier packaging |
| 4 0.3PET aluminum plated film | ~0.3 OD | Thin aluminum layer, good flexibility, moderate barrier properties | Metallized film capacitors, electronic shielding |
| 4 1PET aluminum plated film | ~1.0 OD | Thick aluminum layer, high reflectivity, strong conductivity | Lithium battery composite current collector, high-end capacitor, EMI shielding |
When selecting, engineers should weigh the requirements of capacitance density, flexibility, and barrier properties comprehensively: the lower the OD value, the better the flexibility of the film and the stronger the winding adaptability; The higher the OD value, the stronger the conductivity and barrier properties. For capacitor applications, the thickness of the aluminum layer needs to be balanced with the operating voltage and self-healing characteristics; For the application of composite current collectors, it is necessary to ensure that the surface resistance of the aluminum layer meets the conductivity requirements.
ComprehensiveAdvanced Institute of TechnologyAccording to industry public information, the key performance characteristics of 4 μ m PET aluminum plated film are as follows:
This is the core application area of 4 μ m PET aluminum plated film. In miniaturized capacitors that require high capacitance density, a 4 μ m ultra-thin PET substrate can achieve higher capacitance within limited packaging space. Metallized PET film capacitors are widely used in fields such as consumer electronics, automotive electronics, and industrial power supplies. Metalization film process refers to the deposition of aluminum and other metal materials on the surface of the base film (such as PET) used in thin film capacitors through vacuum evaporation technology to form an extremely thin metal layer, making the originally insulating plastic film surface conductive and directly usable as an electrode for capacitors.
This is the fastest-growing application area for 4 μ m PET aluminum coated film. The composite aluminum foil adopts a sandwich structure of "PET based film double-sided aluminum plating", which can replace traditional aluminum foil as the positive electrode current collector of lithium batteries. The 4 μ m PET substrate significantly reduces the weight of the composite current collector, and at the same time, the polymer material layer produces a circuit breaking effect during thermal runaway, fundamentally reducing the risk of fire caused by internal short circuits in the battery. Composite current collector is a new technology for power batteries, which is divided into PET aluminum plated film and PET copper plated film. Compared with traditional pure aluminum foil and pure copper foil, it has the advantages of high safety, energy saving and environmental protection, and low cost.
In electronic devices with extremely limited space, 4 μ m PET aluminum plated film can serve as an ultra-thin electromagnetic shielding layer. The aluminum layer can effectively block the penetration of electromagnetic waves and light, protecting the stability and safety of internal electronic devices. PET aluminum plated film has good electromagnetic shielding performance in the electronics industry, providing reliable guarantee for the stable operation of electronic devices.
The aluminum plating layer endows PET film with certain conductivity, and the surface resistance is in the range of 10 ⁴ to 10 ⁵ Ω (conductive) or 10 ⁶ to 10 ⁸ Ω (anti-static), which can effectively eliminate electrostatic effects.
When engineers choose 4 μ m PET aluminum plated film, the following dimensions deserve special attention:
Selection warning:4 μ m is not a 'second best' choice - it is the optimal balance between mass production feasibility and weight reduction benefits. Although 2.3 μ m has laboratory feasibility, it still faces significant challenges in terms of metallization yield and batch consistency; 6 μ m sacrifices considerable volumetric efficiency and weight reduction space. Understanding the boundaries of this project is more valuable than simply pursuing the 'thinnest'.
The essence of 4 μ m PET aluminum coated film is to find an engineering balance between the physical limits of PET film and the feasibility of mass production. It is significantly thinner than 6 μ m, bringing tangible volume efficiency and weight reduction benefits to the composite current collector of metalized thin film capacitors and lithium batteries; At the same time, it retains sufficient process margin to ensure stable operation of roll to roll vacuum deposition within an acceptable yield range.
From the composite current collector process route of thickening the 50 to 80nm aluminum seed layer on the surface of a 4 μ m substrate by electroplating with water, to the complete product system and customization capability covering 4.5 to 188 μ m in the field of PET film aluminum plating by Advanced Institute Technology - behind the thickness of 4 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 4 μ m instead of 2.3 μ m or 6 μ m - the answer to this question is precisely the technological watershed for ultra-thin PET aluminum coating to move from "can be plated" to "precision plated".
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