Pick up your smartphone. Touch its screen. It’s smooth, crystal-clear, and amazingly resilient. Chances are your smartphone is protected by a sheet of Corning Gorilla Glass. But what exactly is this Gorilla Glass? How is it fabricated and what makes it so strong?
But electronics have improved in other ways, too. Processor speeds have risen dramatically, following Moore’s Law. Screen resolution is sharper and more vibrant than ever. And some companies spend almost as much time on aesthetics as they do engineering. But there’s one improvement that you can’t really see.
Ion exchange is a chemical strengthening process where large ions are “stuffed” into the glass surface, creating a state of compression. Gorilla Glass is specially designed to maximize this behavior. The glass is placed in a hot bath of molten salt at a temperature of approximately 400°C. Smaller sodium ions leave the glass, and larger potassium ions from the salt bath replace them. These larger ions take up more room and are pressed together when the glass cools, producing a layer of compressive stress on the surface of the glass. Gorilla Glass’s special composition enables the potassium ions to diffuse far into the surface, creating high compressive stress deep into the glass. This layer of compression creates a surface that is more resistant to damage from everyday use. –Gorilla Glass Website.
Why mobile devices?
Fast forward to 2006, when Steve Jobs and the Apple crew were testing their new iPhone prototype. They noticed normal things like keys or coins that were present in the pocket would damage the device’s plastic screen. Determined to find a suitable replacement material, Jobs sent an email to a contact of his at Corning, Wendell Weeks. He tasked Mr. Weeks with finding a suitable glass for his new device. What Jobs didn’t know that a full year prior to his request, Corning had begun exploring that concept.
In 2005, the Motorola RAZR V3 got the folks at Corning thinking. Could an industry such as mobile phones be a market for their shelved Chemcor product? The ubiquitous flip phone was selling well, and the folks at Corning were wondering if they had a place in that market. The RAZR used an ultra-thin glass rather than the impact plastic that was the standard at the time. As mobile phones were getting thinner, they could use a glass that was durable. Chemcor was great, but had it’s challenges. The specialty glass had only been manufactured to a thinness of 4mm, which simply would not do for a mobile device.
As Apple became enamored with the idea of using this type of glass, they started feeding Corning their desired specs. They needed a glass at 1.3mm, well below half of what Corning ever achieved with Chemcor. A thing Corning hadn’t shared with Apple was that Chemcor had never been mass produced. Apple also wanted this glass, which they had no idea didn’t really exist, in six months time. But Weeks took a cue from Jobs’ book — he took the risk and said yes to the project. He tasked his scientists with fulfilling a glass that could meet the demands of Apple. They named it Project Gorilla Glass.
With fusion draw complete, the material produced so far is cut down to size and then placed into a 400 degree C bath of molten salt. This is all part of a process called ion exchange, a standard purification technique in many industries, but here the extreme heat is used to draw out sodium atoms from the surface of the glass, replacing them with larger potassium atoms.
Talking about swapping “smaller” and “larger” atoms may sound rather irrelevant, but it does make a very real difference. The end result is a surface coating which is far more compressed at the atomic level, making it significantly more resistant to scratches.
What’s more, while regular glass has a major problem with crack propagation – the way defects will spread and grow – Gorilla Glass’s state of permanent compression means the material is always pushing together, which means it’s far less likely to experience any cracks in the first place.
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Information Brought To You By Biovolt Corporation.