In early February we learned about Apple's new Sapphire manufacturing equipment arriving at their new Arizona plant for processing sapphire materials. We learned days later that Apple's Arizona Plant could manufacture synthetic sapphire at two times the current worldwide capacity. And at the top of this month, Apple's CEO Tim Cook stated that their new sapphire plant wasn't for creating iPhone display covers but rather reserved for a secret project. Today we learn more about Apple's sapphire processing methods and systems through two new patent applications published by the US Patent Office. The patent covers special laser cutting techniques and specialized furnaces. And while the Arizona plant may not be used for making sapphire iPhone display covers, some other plant will, as the patent clearly illustrates the process in context with the iPhone as noted in our cover graphic.
Apple's Patent Background
Corundum is a crystalline form of aluminum oxide and is found in various different colors, all of which are generally commonly referred to as sapphire except for red corundum which is commonly known as ruby and pinkish-orange corundum which is known as padparadscha.
Transparent forms of corundum are considered precious stones or gems. Generally, corundum is extraordinarily hard with pure corundum defined to have 9.0 Mohs and, as such, is capable of scratching nearly all other minerals. For the present purposes, the terms "corundum" and "sapphire" may be used interchangeably to refer generally to the crystalline form of aluminum oxide.
As may be appreciated, due to certain characteristics of corundum, including its hardness and transparent characteristics, among others, it may be useful in a variety of different applications.
However, the same characteristics that are beneficial for particular applications commonly increase both the cost and difficulty in processing and preparing the sapphire for those applications. As such, beyond costs associated with it being a precious stone, the costs of preparing the corundum for particular uses is often prohibitive.
For example, the sapphire's hardness makes the cutting and polishing of the material both difficult and time consuming when conventional processing techniques are implemented. Further, conventional processing tools such as cutters experience relatively rapid wear when used on corundum.
Apple Invents Laser Cutting Techniques & Other Processes Related to Sapphire
Apple invents systems and methods related to cutting polished hard materials and more specifically, systems and methods related to cutting polished corundum (sapphire).
Methods related to efficient processing of sapphire are discussed in Apple's patent filing which are expected to both speed manufacture of corundum for applications and make the use of conundrum cost effective.
In particular, one embodiment may take the form of a method of cutting a hard transparent material having a polished surface. The method includes roughening a portion of the polished surface, directing a laser beam on the roughened portion of the surface to melt and, thereby, cut through the hard material.
Another embodiment may take the form of a system for processing corundum including a roughening apparatus and a laser. The roughening apparatus initially receives a corundum member and roughens a polished surface of the corundum member. The laser then cuts through the corundum member by directing the laser at the portions of the polished surface that have been roughened.
Yet another embodiment may take the form of a method for cutting polished corundum including a surface preparation step and a cutting step. In the surface preparation step, a polished portion of the surface of the corundum is prepared for subsequent cutting through in-coupling of laser energy. In the cutting step, a laser is directed to the portion of the polished surface of the corundum that has been prepared.
A Laser Process
Apple's patent FIG. 3C noted below illustrates an embodiment in which the laser #123 is used to roughen the surface of the sapphire. As illustrated in FIG. 3C, the laser may move relative to the sapphire member so as to create a cutting pattern #124 on the surface of the sapphire. The movement and positioning of the laser may be precisely controlled so as to create the pattern (dashed line) of a desired sapphire member, which is a display cover as noted further below.
In a roughening technique, the polished surface #120 is chemically etched. A mask may initially be provided to cover portions of the polished surface that are not to be roughened and a non-masked portion of the polished surface generally takes the form of the desired sapphire member shape. An etching agent is applied to the surface (or the surface is exposed to the etching agent) to roughen the non-masked portions of the polished surface. A cleansing step may be implemented to remove or neutralize the etching agent before or after the mask is removed.
A Cutting Process
Turning to Apple's patent FIG. 5 noted below, a cutting step is illustrated. In the cutting step, a laser #130, such as a microsecond fiber laser, is focused on the roughened spot #121 to laser cut the sapphire ribbon #120. The laser may implement different pulse lengths, frequencies, pulse energies, and varying average power levels than the laser #123 of FIG. 3C of the roughening step.
Additionally, the laser may be focused at the roughened spot on the surface or at some point below the roughened spot. That is, the laser may be focus at some point in the middle of the sapphire member or near a back surface of the sapphire member, rather than on the surface which that was roughened.
In one case, the laser may cause the sapphire to melt when it in-couples and heats the sapphire. Once the laser has in-coupled and begun to melt the sapphire, it may move away from the position of the roughened spot and continue to melt the sapphire. In a second case, the laser may cause material removal through an ablation process, where layers of sapphire are ablated over multiple cutting passes.
Apple further notes that pressurized gas, such as air, nitrogen gas or other suitable gas #132 is directed at the melted sapphire to remove it, leaving a cut #126 through the sapphire ribbon.
Apple's patent FIG. 8 illustrates an example electronic device, an iPhone, in which the sapphire member #136 may be implemented. It just happens to be illustrating an iPhone with a bezel-free edge-to-edge display design.
In Apple's patent FIG. 9 we're able to see an illustration of a sapphire wafer #160 from which many sapphire members may be cut. Generally, the sapphire wafer may be sliced from a grown sapphire boule.
One or both sides of the wafer may be polished prior to cutting out sapphire members #164. In particular, a top surface #162 of the sapphire boule may be polished. As such, each of the sapphire members may have at least one polished side upon being cut from the wafer. The cutting of sapphire the members from the wafer may be performed through a roughening step followed by a laser cutting/melting step, as discussed above.
Apple's Sapphire Growth & Processing System
And lastly, in Apple's patent FIG. 10 noted above we're able to see an example sapphire growth and processing system #170 which includes a sapphire growth furnace #172, which may take any suitable form such as an EFG furnace for example.
Additionally, the system may include preprocessing equipment such as slicers and polishers #174. Additionally, an annealing furnace may be provided to help cure any defects in the sapphire crystal from the growth phase.
The system includes a cutting system #176 that includes a roughener #178 and a laser cutter #180. As discussed above, the laser cutter may be configurable such that its power level and/or focal point may be adjusted so that it may serve dual purposes as a roughener and cutter.
The system further may include equipment for one or more post-processing steps such as grinding and polishing. An annealing furnace may also be provided after cutting the sapphire members to cure any defects that resulted from the cutting and/or other processing steps.
Apple notes that the system is believed to achieve efficiencies based on the equipment and processes performed in creating a sapphire member for use in electronic devices. In particular, the laser cutting of the sapphire is anticipated to save costs in the long run as it will not experience wear in the same way a mechanical cutter would. Additionally, the speed at which the laser cutter may operate may provide for increased production. Moreover, the processes and systems described herein may scale well and may be configurable to achieve further efficiencies. In particular, for example, one or more rougheners may feed a single laser cutter or a single roughener may feed multiple laser cutters.
Apple credits Anthony Richter, Dale Memering and Vincent Yan as the inventors of patent application 20140076299 which was originally filed in Q3 2012.
Second Invention: Heat Exchangers in Sapphire Processing
A second sapphire processing related patent surfaced today under patent application number 20140080081 noting inventors Christopher Prest and Dale Memering.
Apple's patent abstract states that their invention is about "Systems and methods for efficient heating during production of corundum. One embodiment takes the form of a system for processing corundum including a first furnace and a second furnace. The first and second furnaces are sequentially arranged and heat from the first furnace is subsequently used to heat the second furnace."
Apple's patent FIG. 1 noted below illustrates a Kyropoulos process for sapphire growth; FIG. 3 illustrates a VHGF process for sapphire growth; and patent FIG. 4B illustrates an alternative system for recycling heat in sapphire processing by passing heat directly between two furnaces after heating phases for the furnaces wherein a single growth furnace supplies heat to two annealing furnaces.
To review more of the details behind Apple's second sapphire related patent, click here.
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