June 6, 2017 at 2:30 p.m. PST
The iPhone is a durable device, however, it could be improved. This article examines why the iPhone isn’t made with sapphire glass.
Sapphire glass is an extremely durable material. In fact, the windows on modern military helicopters are often constructed of sapphire glass. Given its durability, sapphire glass seems to be an excellent option for smartphone screens. Unfortunately, cost is the main reason why the iPhone isn’t made with sapphire glass.
Prior to the iPhone 6 launch, rumors indicated that Apple’s upcoming phone would be constructed of sapphire glass. This didn’t prove to be true. In fact, the iPhone 6, 6S and 7 are all constructed with Gorilla Glass. Apple’s investment in a sapphire glass manufacturing plant turned out to be for the Apple Watch. The Apple Watch uses sapphire glass, however, it’s a fairly small screen. It’s simply too expensive to use sapphire glass for a smart phone screen. We’ll cover the cost analysis later in this article.
How Sapphire Glass is Made
Sapphire glass is a synthetically made “boule” of sapphire. It is basically identical to the gem. Sapphire glass is extremely hard and durable. Only diamonds are harder than sapphire. Making sapphire glass is expensive and takes a lot of time.
The first step in making sapphire glass is to place a hockey-puck sized seed in a molybdenum crucible. Corundum and uncrystallized sapphire are then added to the crucible. The crucible is placed inside a furnace which also contains a cooling mechanism, to prevent the sapphire seed from melting. The furnace is sealed and becomes a vacuum as it heats up to 2200º C. This allows the materials to melt together. A long process of heating and cooling, which takes up to 17 days, causes the sapphire to gradually crystallize. The end result is a sapphire glass boule. Specialized cutting and polishing tools transform the sapphire glass into usable components.
Apple’s Sapphire Glass Manufacturing Facility Experienced Problems
Apple invested in a sapphire glass manufacturing facility in Arizona, in partnership with GT Advanced Technologies. The plant was capable of producing enough sapphire glass to cover iPhone production. Unfortunately, poor design of the plant led to production shortfalls. The facility experienced several power outages which ruined batches of sapphire glass. Furthermore, some production runs were blighted by contamination. This not only led to production shortfalls, but also increased the cost of the end product. To further complicate matters, the plant did not have appropriate equipment to cut the boules.
Conflict between Apple and GT arose, as the latter had to file for bankruptcy. GT couldn’t produce the quantities of sapphire glass that Apple needed, resulting in Apple purchasing less of the material than expected. No contract held Apple accountable to purchase a specific quantity of sapphire glass. Details of the court case show that Apple cut corners when constructing the facility. For example, there was no back up power supply and they purchased inappropriate boule cutting and polishing tools.
Apple actually intended to construct the iPhone 6 out of sapphire glass. Due to production problems, they could only manufacture enough sapphire glass for Apple Watches. The iPhone 6 used Gorilla Glass, which is still the screen material used in all iPhones. Touch ID sensors and cameras are protected by small patches of sapphire glass. But if your iPhone’s screen was made of the same material, it would be virtually impossible to scratch.
Is Sapphire Glass Better than Gorilla Glass?
Sapphire Glass is much harder than Gorilla Glass, however, it’s also more brittle. At 9 on the Mohs hardness scale, sapphire glass is almost as scratch resistant as a diamond. Unfortunately, the material is much more brittle than glass. This presents a tradeoff. Sapphire glass is scratch resistant, but it may be more prone to shattering than Gorilla Glass. Advancements in sapphire glass technology may overcome this problem.
Device construction also matters. Sapphire glass can shatter because it is not flexible. If a smartphone features a sturdy enough frame, it may prevent a sapphire glass screen from shattering when dropped.
It’s important to note that Corning’s Gorilla Glass also benefits from technological advancements. New versions of Gorilla Glass can survive a 1.6 meter fall onto a rough surface 80% of the time. Unfortunately, Gorilla Glass is still susceptible to scratches. Corning’s new Gorilla Glass SR+ is both durable and scratch resistant.
Sapphire Glass Costs More than Gorilla Glass
Cost is the main factor preventing sapphire glass from adorning the iPhone. At its current price, sapphire glass costs five times as much as Gorilla Glass. Manufacturing advances, such as reusable crucibles, may reduce the cost. Even with these improvements, sapphire glass would still cost three times as much as Gorilla Glass.
Future iPhones Probably Won’t Use Sapphire Glass
The future of the iPhone is unclear. As material technologies continue to evolve, Apple will be forced to make some hard decisions. They can’t always go with the best material. Apple needs enough components to construct almost 100 million iPhones. Prohibitive costs and huge demand make it difficult for Apple to get everything they want. For example, Apple took years before they could offer an OLED iPhone display. No manufacturer could scale to meet their demand. Given that sapphire glass takes a long time to manufacture, Apple will probably avoid the material. There’s simply too much uncertainty involved in the process.
Shortly after launching Gorilla Glass 5, Corning followed up with Gorilla Glass SR+. This new material offers the shatter resistance of Gorilla Glass, with the scratch resistance of sapphire glass. Additionally, the material features favorable optical properties, providing greater brightness. This saves battery life on mobile devices.
Although the cost of Gorilla Glass SR+ is unavailable, it is intended for use in wearables. This indicates that Corning assumes the price is too expensive for most smartphones. It’s possible that Apple may want something special for the 10th anniversary of the iPhone. The rumored iPhone 8 or iPhone X will carry a hefty price tag. If Apple was willing to splurge on sapphire glass for the iPhone 6, they may opt for opulence with the next iPhone. I expect Apple to use this material in future Apple Watches. They may even use it in future iPhones.
Given the available information, my best guess is that the next iPhone will use Gorilla Glass 5. It may feature an all-glass construction similar to the iPhone 4, but with a much sleeker and sophisticated profile. That said, Apple is still capable of surprising people, despite the prevalence of rumors. If the next iPhone is to have glass on the front and back, Gorilla Glass SR+ will prevent it from scratching.