Glass with incredibly thin layers is an appealing concept for several engineering applications. For instance, coating steel components in glass could provide corrosion protection, whereas overlaying microelectronic circuits with glass might provide dielectric protection.
However, making incredibly thin bits of glass can be difficult, especially using traditional methods such as float glass manufacturing. Alternatively, glass can be placed directly onto surfaces to form a coating for this application.
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Thin Glass Films vs. Thick Glass Films
Glass films are categorized into two types: thick films and thin films. While thin glass films are normally thinner than thick glass films, there is some crossover, therefore, a “thick film” can be thinner than a “thin film” in some instances.
Thin and thick glass films are often distinguished by the manufacturing technique employed. Thin glass films with thicknesses ranging from sub-nanometer to several microns are often manufactured using vapor deposition techniques, in which vaporized silicon compounds are oxidized and the resulting silicon oxide (glass) condenses on a substrate.
The thickness of thick glass films, on the other hand, can range from a few microns to several millimeters, and they are typically deposited as suspensions such as slurries, pastes, or inks. Screen printing and tape-casting are two examples of thick film processes.
Applications of Thick Glass Films
Glass is often employed as a sealing material due to its tunable coefficient of thermal expansion.1 This leads to glass seals that can be adjusted to meet the thermal expansion properties of the components they create a seal between, resulting in a dependable seal in thermal cycling applications.
Thick film processes help create glass seals. Glass is first manufactured as a powder, with the composition and particle sizes tailored to the application. Powdered glass is combined with an agglomeration agent before being applied directly to a component via robotic dispensers, tape casting, or screen printing. The entire assembly is heated in a furnace for many hours to melt and vitrify the glass powder into a bonded glass seal.2
Glass seals are frequently employed in energy storage, particularly in solid oxide fuel cells and metal ion and thermal batteries, where seal integrity over a broad range of temperatures is crucial. Glass is also employed in high-temperature sensors and sensitive perovskite photovoltaic cells to create high-performance seals.
Glass films for electronics are made using a process known as tape casting, in which a suspension of powdered glass or ceramic is cast across a flat surface in a thin, “tape”-like layer before drying and sintering.
These tape-cast coatings are useful in creating single-layer or laminated microelectronic circuits and components because glass has strong anti-corrosion qualities and great dielectric capabilities.3 Thick glass films are extensively utilized for thick film resistors, the most commonly seen resistors today.4
Glass coatings can be applied directly to stainless steel to safeguard against corrosion and high-temperature oxidation. These coatings are normally employed to make corrosion-resistant steel tanks and silos. Glass coatings, such as glass seals, can be tuned for both mechanical and thermal compatibility with a substrate, making them ideal for a broad range of materials, including titanium and titanium superalloys.5
Applications of Thin Glass Films
Vapor deposition methods, such as physical vapor deposition (PVD) and chemical vapor deposition (CVD), can vaporize solid materials into individual molecules. To create a thin glass film, the vaporized material can either condense on a substrate (PVD) or interact chemically with the substrate (CVD).
In the case of glass, vapor deposition processes frequently begin with a precursor compound that contains silicon, such as hexamethyldisilane. It is possible to heat these precursors to create vapor, which is later oxidized to create silicate (the major ingredient of glass) and deposited on a substrate.
Vapor deposition processes yield exceptionally pure glass. When compared to traditionally made glass, vapor-deposited glass is also exceptionally stable. Both of these characteristics give vapor-deposited glass an edge in specialist applications.
Vapor-deposited glass is commonly used to manufacture specialized optical components such as optical fibers and telescope mirrors. Thin glass films made by vapor deposition are extremely advantageous in electronics applications and are already employed in OLED displays and cellphone screens, with organic electronics (such as photovoltaics) applications anticipated to flourish.
Mo-Sci specializes in creating specialized glass solutions for practically any application while working with clients from various industries. Mo-Sci has unrivaled competence in glass production and processing, including thin and thick glass film technologies, from prototyping to commercialization.
References and Further Reading
- Sealing Glass – Mo-Sci.
- Processing technologies for sealing glasses and glass‐ceramics – Pablos‐Martín – 2020 – International Journal of Applied Glass Science – Wiley Online Library. https://ceramics.onlinelibrary.wiley.com/doi/full/10.1111/ijag.15107.
- Yu, T., Ju, K., Liu, J. & Li, Y. Tape casting and dielectric properties of SiO 2 -filled glass composite ceramic with an ultra-low sintering temperature. Journal of Materials Science: Materials in Electronics 25, (2014).
- Thin and Thick Film | Resistor Materials | Resistor Guide. https://eepower.com/resistor-guide/resistor-materials/thin-and-thick-film/.
- Chen, M., Li, W., Shen, M., Zhu, S. & Wang, F. Glass coatings on stainless steels for high-temperature oxidation protection: Mechanisms. Corrosion Science 82, 316–327 (2014).
This information has been sourced, reviewed and adapted from materials provided by Mo-Sci.
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