Prior to the GTAT Fiasco, Apple had invented a New Way to Manufacture near Defect-Free Sapphire for the iPhone
A little under 10 months ago Apple's one-time Sapphire supplier GTAT shockingly filed for bankruptcy. Countless problems in the manufacturing process failed to produce the sapphire that Apple wanted to use for the iPhone 6's cover glass. Today the U.S. Patent & Trademark Office published a patent application from Apple that reveals a very sophisticated method to manufacture sapphire parts, and in particular to using a laser and more than one gas medium to cut a sapphire substrate and to produce a sapphire part. The sapphire part was to be for a protective cover for a portable electronic device. Whether Apple's invention will surface in a partnering plant or simply be scrapped is unknown at this time.
Apple's Patent Background
Corundum is a crystalline form of aluminum oxide and is found in various different colors, most of which are generally referred to as sapphire. Sapphire is a hard and strong material with a hardness of 9.0 on the Mohs scale, and, as such, is capable of scratching nearly all other minerals. Because of its hardness and strength, sapphire may be an attractive alternative to other translucent materials like glass or polycarbonate. However, due to its brittle nature, sapphire is susceptible to dramatic strength reductions as a result of small defects in the surface or edge of the part. It is generally desirable to minimize small defects that may occur during manufacturing to produce a sapphire part that is durable and long lasting.
Manufacturing a near defect-free sapphire part may present unique challenges. The strength of a brittle material, such as sapphire, is limited due to flaw population on the surface or edges of the part. An inconsistent or inadequate surface or edge finish can lead to the propagation of micro cracks and result in a weakened part.
Traditional translucent materials like silicate glass are able to be chemically strengthened to a significant depth to minimize the effect of these flaws, but on extremely hard materials such as sapphire, a similar process is not readily available. Sapphire's hardness makes cutting and polishing the material both difficult and time consuming when using conventional processing techniques. Further, conventional processing tools, such as cutters, experience relatively rapid wear when used on sapphire. This further increases the resource demand when surface finishing sapphire parts.
In general, there is a need for a system and method for producing sapphire parts having minimal micro-defects on the edges and surface of the part resulting in improved strength and to reliability over time. There is also a need for a system and method for producing high-quality edge cuts on sapphire parts in a rapid, repeatable fashion while using an efficient amount of resources.
Apple's Invention Title: System and Method for Laser Cutting Sapphire using Multiple Gas Media
Apple's invention generally related to manufacturing a sapphire part and in particular to using a laser and more than one gas medium to cut a sapphire substrate and to produce a sapphire part. The sapphire part may be used as a protective cover for a portable electronic device.
A sapphire substrate is obtained for performing a laser cutting operation. The sapphire substrate is cut along a cut profile using a laser and a first gas medium. The first gas medium is substantially comprised of an inert gas. The sapphire substrate is then irradiated at or near the cut profile using the laser and a second gas medium.
The second gas medium is different than the first gas medium and comprises at least 15% oxygen by volume. The sapphire part is eventually separated from the sapphire substrate. In some embodiments, the inert gas is nitrogen gas. In some cases, the first gas medium comprises at least 99% inert gas by volume.
In some embodiments, a final cut is performed on the sapphire substrate using the laser. The final cut may result in the separation of the sapphire part from the sapphire substrate or, alternatively the final cut may remove additional material from the sapphire part. In some cases, the final cut is performed after the sapphire substrate has been irradiated using the second gas medium. In other cases, the final cut is performed before the sapphire substrate has been irradiated using the second gas medium.
In some embodiments, the irradiating using the second gas medium is performed at an irradiation laser power that is less than a cutting laser power used for cutting the sapphire substrate using the first gas medium. In some cases, the cutting laser power is less than 950 watts and the irradiating laser power is at least 500 watts less than the cutting laser power.
In some embodiments, the final cut is performed using a final-cut laser power that is greater than a cutting laser power used for cutting the sapphire substrate using the first gas medium.
In one example embodiment, cutting the sapphire substrate along the cut profile includes (1) melting a portion of the sapphire substrate along the cut profile using the laser and (2) removing the portion of the sapphire substrate along the cut profile by blowing a stream of the first gas medium on the portion of the sapphire substrate that has been melted.
In one example embodiment, irradiating the sapphire substrate along the cut profile includes (1) heating a portion of the sapphire substrate along the cut profile using the laser, and (2) immersing the portion of the sapphire substrate being heated in the second gas medium.
In some embodiments, the sapphire part may be installed as a protective cover on a portable electronic device. In some cases, the portable electronic device is any one of: a mobile telephone, a portable media player, a wearable device, or a tablet computing device.
One example embodiment is directed to a system for producing a sapphire part. The system includes a gas delivery device that is configured to provide a stream of gas to a portion of a sapphire substrate that is irradiated by a laser beam. The system also includes a laser configured to produce the laser beam incident on the portion of the sapphire substrate. In some cases, the laser is further configured to irradiate the sapphire substrate along a cut profile while a first gas medium is provided by the gas delivery device. The first gas medium is substantially comprised of an inert gas. The laser is further configured to irradiate the sapphire substrate along the cut profile while a second gas medium is provided by the gas delivery device. The second gas medium is different than the first gas medium and comprises at least 15% oxygen by volume. In some embodiments, the laser is an infrared laser having a maximum power of 1,500 watts and a variable pulse duration ranging from 0.2 ms to 10 ms.
Exemplary System for Producing a Sapphire Part
Apple's patent FIG. 4 noted below depicts a schematic view of an exemplary system for producing a sapphire part.
2As shown in Apple's patent FIG. 4 noted above, system #400 includes a laser #402 and a gas delivery device #404 comprising a coaxial gas delivery nozzle #404a and a side gas delivery nozzle #404b.
The system also includes a controller #410 used to control the laser and the gas delivery device. The system also typically includes a support structure or positioning mechanism for holding and positioning a sapphire substrate #300 below the laser.
In the present example, the laser is a fiber laser configured to produce a laser beam at wavelengths centered at approximately 1070 nm and pulse durations ranging from 0.2 to 10 ms. Due to the fact that the sapphire substrate may absorb emissions near 1070 nm, the laser is configured to heat and cut the sapphire substrate. Typically, the laser can be configured to produce a laser beam at a power ranging from 10 watts to 150 watts average power (with a maximum of 1,500 watts of maximum power).
The system also includes a mechanism for directing the laser beam produced by the laser onto the surface of the sapphire substrate. The mechanism may position the laser, position the sapphire substrate, manipulate the path of the laser beam, or any combination of the three. In general, mechanism is able to direct the laser beam along one or more cut paths (302, 304) on the surface of the sapphire substrate.
As shown in FIG. 4, the system also includes a gas delivery device having a coaxial gas delivery nozzle 404a and a side gas delivery nozzle 404b for directing a stream or streams of a gas medium onto the surface of the sapphire substrate. Typically, the gas delivery device is configured to direct a stream of gas at or near the location where the laser beam is incident on the surface of the sapphire substrate. Thus, the laser beam and the surface of the sapphire substrate near the incident laser beam are immersed in the gas media provided by the gas delivery device. The gas delivery device is generally configurable to provide a range of flow velocities and mass flow rates to facilitate etching, cutting, and irradiating operations in accordance this invention.
Specifically, the coaxial gas delivery nozzle 404a is configured to produce a stream of gas media at a pressure with a range from 5 bar to 15 bar using a nozzle having a diameter ranging from 0.1 mm to 0.5 mm. In one example, the gas delivery device is configured to produce a coaxial gas stream at a pressure of 8 bar using the coaxial gas delivery nozzle 404a having a diameter of 0.3 mm.
Apple's patent FIG. 2 depicts an example process for manufacturing a sapphire part; Apple's patent FIG. 3A depicts a sapphire substrate that has been cut; and FIG. 3B depicts a sapphire substrate that has been cut and irradiated.
Apple credits Michael Li, Anthony Richter and Dale Memering (Apple's Manager for Product Design Materials) as the inventors of patent application 20150209903 which was originally filed in Q1 2014. Considering that this is a patent application and the fact that GTAT filed for bankruptcy, the timing of bringing such system to market is unknown at this time.
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