Apple Lands US Patent for Precise ‘Laser-Cutting’ of Sapphire Parts for iPhones
Apple landed a U.S. patent Tuesday describing methods for the precise “laser-cutting” of sapphire parts for iPhones using “multiple gas media,” Patent and Trademark Office records show. Sapphire is a “hard and strong material” that’s capable of scratching “nearly all other minerals” except diamonds, but cutting the material using conventional production processes is problematic, says the patent (9,844,833), which names three Silicon Valley inventors and is based on an application filed in January 2014.
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Though iPhone lovers long told Apple that a scratch- and crack-resistant sapphire-glass screen was the feature they wanted most in a future phone (see 1408150058), Apple never followed through, but instead uses sapphire for the crystal on some Apple Watch models and as the lens cover material for the cameras on many of its phones, including on the iPhone X. Because of its hardness and strength, sapphire “may be an attractive alternative to other translucent materials like glass or polycarbonate,” the patent says. But sapphire’s “brittle nature” makes the material “susceptible to dramatic strength reductions as a result of small defects in the surface or edge of the part,” it says.
That’s why it’s “generally desirable to minimize small defects that may occur during manufacturing to produce a sapphire part that is durable and long lasting,” the patent says. But manufacturing sapphire parts that are “near defect-free” presents “unique challenges,” it says. “An inconsistent or inadequate surface or edge finish can lead to the propagation of micro cracks and result in a weakened part,” it says. More conventional “translucent” materials like “silicate glass” can be chemically strengthened to “minimize the effect of these flaws, but on extremely hard materials such as sapphire, a similar process is not readily available,” it says.
Sapphire's hardness also makes cutting and polishing it “difficult and time consuming when conventional processing techniques are implemented,” it says. Conventional “cutters” are also susceptible to “rapid wear” when used on sapphire, further increasing “the resource demand when surface-finishing sapphire parts,” it says.
Those problems show the need for “a system and method for producing sapphire parts having minimal micro-defects on the edges and surface of the part” that can result in the part’s "improved strength and reliability over time,” the patent says. There's also a need for a method for “producing high-quality edge cuts on sapphire parts in a rapid, repeatable fashion while using an efficient amount of resources,” it says.
The patent envisions using a “fusion laser-cutting process” to produce a sapphire part “having acceptable edge and surface finish,” it says. During a fusion cut, a laser beam is used to heat and partially melt a portion of the sapphire material, it says: “A directed stream of gas is then used to remove the melted material leaving a void or depression in the sapphire material. The efficiency and edge finish produced by a fusion cut may be superior to other types of laser cutting techniques, including, for example, ablation laser cutting techniques or laser scribing.” Apple didn’t comment on possible commercial uses of the invention described in the patent.