Home > Nanotechnology Columns > HZO > Protective Nanocoating Methodologies
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Mallory McGuinness Content Specialist HZO |
Abstract:
While there are numerous ways to deposit nanocoatings, this article provides a high-level overview, including the benefits and drawbacks, of some of the most popular application methods, including dipped, sprayed, and plasma-enhanced chemical vapor deposition (PECVD).
February 9th, 2021
Protective Nanocoating Methodologies
Protective nanocoatings are thin layers (with a thickness of a few tens to a few hundreds of nanometers) applied to electronic substrates to improve or create functionalities such as corrosion protection, dielectric strength, liquid protection, and thermal management. These valuable benefits for industrial, medical, IoT, consumer electronics, and automotive applications have inspired manufacturers to incorporate the functionalized films into their electronic products.
While there are numerous ways to deposit nanocoatings, this article provides a high-level overview, including the benefits and drawbacks, of some of the most popular application methods, including dipped, sprayed, and plasma-enhanced chemical vapor deposition (PECVD).
Spraying/Dispensed
Spraying or dispensed application is a technique used for larger production runs, ensuring quality and avoiding yield loss. Typically automated, this thin-film sprayed layer formation can be compared to stacking individual droplets in succession, functioning as a continuous layer. The deposition method operates within the wet regime, ultimately achieving dry layers with reasonable thickness control. Spray gun settings, such as material flow rate, nozzle-to-sample distance, and atomizing gas (N2) pressure may be varied to attain required spray attributes.
Automated spraying is a popular technique for more efficient and accurate nanocoating applications. Products including organic photo-detecting devices, organic thin-film transistors, and light-emitting polymer and organic thin-film transistors are good candidates for this technique.
Advantages include the potential for a lower material loss during deposition, low-cost fabrication using simple coating techniques, and easier thickness control of materials.
Disadvantages include the effort that must be invested into achieving optimal fluid properties, the use of solvents that can create sustainability issues, and the fact that some material options are halogenated.
Dipping
Dip coating refers to immersing a substrate into a coating tank, removing the component from the immersion tank, and allowing it to drain. After this process, which can be automated or manual, the substrate can be dried by baking or force-drying. Often, an integrated pumping and filter system ensures control of material purity so that the material is delivered to the tank in the right format. Coating thickness is contingent upon withdrawal and immersion speeds.
Dip coating is often used to apply specialized coatings to bulk products, including devices in the biomedical field, in small-batch experiments, and for research on protein coatings, tribological coatings, and protective coatings.
Advantages include efficient application - coating all sides of a substrate at once. Dip coating is also adaptable between high-precision batch processes and large-scale processes. Limitations of dip coating include challenges in coating curved or flexible substrates, material shrinkage that can lead to cracks in films, and high levels of material waste as much of the coating material will ultimately not be used.
Plasma-enhanced Chemical Vapor Deposition (PECVD)
PECVD uses plasma energy as a catalyst to deposit nanocoatings for ultra-thin, flexible electronic protection. The plasma may be created by radiofrequency or direct current discharge between two electrodes. PECVD equipment utilizes a mixture of free electrons, excited atoms, ions, radicals, and molecules to deposit the coatings. Various materials may be applied, including polymers (fluorocarbons, silicone, hydrocarbons), oxides, and metal nitrides. Film properties may easily be controlled to produce organic nanocoatings on large substrates with varying mechanical, electrical, thermal, optical, and chemical properties.
The breadth of materials that PECVD can use makes it suitable for many applications, including semiconductor devices, solar cells, and optically active device applications.
Advantages include tight control of film composition and uniformity, controlled and efficient usage of precursor materials with few by-products. The resulting chemistry of nanocoatings produced by PECVD is unique and cannot be attained by standard wet deposition techniques. Disadvantages include the fact that ion bombardment during the process could damage some sensitive substrates.
Conclusion
This high-level overview has provided the reader with the groundwork to make a more informed decision about which nanocoating process to choose. The next article will discuss the exciting capabilities of the PECVD process in more detail.
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