PATENT DOCUMENT

Publication Number: US-10406634-B2
Application Number: US-201514788897-A
Country: US
Kind Code: B2

Title: Enhancing strength in laser cutting of ceramic components

Abstract:
A ceramic material, such as sapphire, is irradiated using a laser-based process to form a cut. In some implementations, a region of the ceramic material adjacent to the cut may be heated. The region may be removed to form an edge feature. In various implementations, the region of the ceramic material adjacent to the cut may be shielded from an outer portion of a laser beam used in the laser-based process using a shield, such as a polyethylene film. This removal and/or shielding operations may improve the mechanical strength of the ceramic material.

Claims:
What is claimed is: 
     
       1. A method for forming a ceramic component, comprising:
 irradiating a ceramic material to form a cut having a first depth using a first laser-based process having a first laser beam at a first power, the first laser-based process defining a diameter of the cut; 
 heating a region of the ceramic material adjacent to the cut by irradiating the region with the first laser beam subsequent to forming the cut; and 
 removing the region of the ceramic material by forming an edge feature having a second depth that is less than the first depth, the edge feature formed using a second laser-based process having a second laser beam at a second power that is less than the first power and that is directed at the region of the ceramic material adjacent to the cut. 
 
     
     
       2. The method of  claim 1 , wherein:
 the operation of heating heats the region of the ceramic material with an outer portion of the first laser beam; and 
 the outer portion has an energy insufficient to cut the ceramic material during the operation of irradiating. 
 
     
     
       3. The method of  claim 1 , wherein the operation of heating the region of the ceramic material forms a defect in the ceramic material. 
     
     
       4. The method of  claim 1 , wherein the operation of heating the region of the ceramic material forms micro-cracks in the ceramic material. 
     
     
       5. The method of  claim 4 , wherein the operation of removing the region of the ceramic material removes the micro-cracks in the ceramic material. 
     
     
       6. The method of  claim 4 , wherein the operation of removing the region of the ceramic material introduces additional micro-cracks in the ceramic material that are smaller than the micro-cracks. 
     
     
       7. The method of  claim 1 , wherein the operation of removing the region of the ceramic material removes a section of the ceramic material having a depth of approximately 15-25 microns. 
     
     
       8. The method of  claim 1 , wherein the first power is approximately 30-45 watts and the second power is approximately 10-25 watts. 
     
     
       9. The method of  claim 1 , wherein the first laser beam is produced for approximately 7-15 pulses and the second laser beam is produced for approximately 1 pulse. 
     
     
       10. The method of  claim 1 , wherein the second laser-based process includes a shorter duration pulse than the first laser-based process. 
     
     
       11. A method for forming a ceramic component, comprising:
 irradiating a ceramic material with a first laser-based process having a first laser beam to form a cut having a first depth, the irradiating with the first laser-based process defining a diameter of the cut; 
 shielding, with a shield, a region of the ceramic material adjacent to the cut from an outer portion of the first laser beam; 
 heating the region of the ceramic material through the shield by irradiating the region using an operation of the first laser-based process subsequent to forming the cut; and 
 removing a defect formed in the ceramic material to form an edge feature having a second depth less than the first depth, the edge feature formed by the irradiating using a second laser beam that is directed at the region of the ceramic material adjacent to the cut and that has a lower power by at least 5 watts average power, or a shorter pulse duration than the first laser beam. 
 
     
     
       12. The method of  claim 11 , further comprising absorbing, with the shield, at least part of an energy of the outer portion of the first laser beam to reduce thermal stress within the region. 
     
     
       13. The method of  claim 11 , further comprising applying the shield to the ceramic material before the operation of irradiating the ceramic material. 
     
     
       14. The method of  claim 11 , wherein the operation of shielding comprises shielding the region of the ceramic material with a plastic film. 
     
     
       15. A method for forming a ceramic component, comprising:
 irradiating a ceramic material to form a cut having a first depth using a first laser-based process having a first laser beam applied for a first duration, the first laser-based process defining a diameter of the cut and 
 heating a region of the ceramic material adjacent to the cut by irradiating the region using the first laser beam subsequent to forming the cut; and 
 removing the region of the ceramic material adjacent to the cut to form an edge feature having a second depth that is less than the first depth, the edge feature formed using a second laser-based process having a second laser beam that is directed at the region of the ceramic material adjacent to the cut and applied for a second duration that is less than the first duration. 
 
     
     
       16. The method of  claim 15 , wherein the first duration is at least seven times longer than the second duration. 
     
     
       17. The method of  claim 15 , wherein application of the second laser beam for the second curation removes less of the ceramic material than application of the first laser beam for the first duration. 
     
     
       18. The method of  claim 15 , wherein the first duration comprises multiple pulses.

Description:
FIELD 
     The described embodiments relate generally to manufacture of ceramic components, such as sapphire. More particularly, the present embodiments relate to enhancing strength in ceramic components that are cut using a laser-based process. 
     BACKGROUND 
     Consumer or non-consumer devices may include components (such as protective coverings, windows, and/or surfaces) formed from ceramic materials. One example of such a ceramic material is corundum. 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. Sapphire may also be produced in thin sheets and polished to achieve exceptional optical performance. 
     Compared to other optically clear materials like traditional polycarbonate or other types of plastic, ceramic materials (such as sapphire) may offer improved scratch resistance and strength. However, ceramic materials may be difficult to machine because of their hardness. Embodiments described herein are directed to manufacturing ceramic materials without the drawbacks of some traditional techniques. 
     SUMMARY 
     The present disclosure relates to forming a ceramic component using laser cutting. A ceramic material, such as sapphire, may be irradiated using a laser-based process to form a cut. A region of the ceramic material adjacent to the cut may be heated and may be removed to form an edge feature in various implementations. The region of the ceramic material adjacent to the cut may be shielded from an outer portion of a laser beam used in the laser-based process using a shield in some implementations. Such removal and/or shielding may improve the mechanical strength of the ceramic material. 
     In various embodiments, a method for forming a ceramic component may include irradiating a ceramic material using a laser-based process to form a cut, heating a region of the ceramic material adjacent to the cut, and removing the region of the ceramic material. 
     In some examples, the operation of irradiating and the operation of heating may occur at different times. In various examples, the operation of heating may heat the region of the ceramic material with an outer portion of a laser beam used in the laser-based process and the outer portion may have an energy insufficient to cut the ceramic material during the operation of irradiating. 
     In various examples, the operation of irradiating may include irradiating the ceramic material through a first laser-based process using a first laser beam and the operation of removing the region of the ceramic material may include removing the region of the ceramic material through a second laser-based process using a second laser beam. The second laser beam may have a lower power than the first laser beam. The second laser-based process may include a shorter duration pulse than the first laser-based process. 
     In some examples, the operation of heating the region of the ceramic material may form a defect such as micro-cracks in the ceramic material. The operation of removing the region of the ceramic material may remove the micro-cracks in the ceramic material. The operation of removing the region of the ceramic material may introduce additional micro-cracks in the ceramic material that are smaller than the micro-cracks. The operation of removing the region of the ceramic material may remove a section of the ceramic material having a depth of approximately 15-25 microns. 
     In some embodiments, a method for forming a ceramic component may include irradiating a ceramic material with a laser beam to form a cut and shielding a region of the ceramic material adjacent to the cut from an outer portion of the laser beam using a shield (such as a plastic film). 
     In various examples, the method may further include absorbing, with the shield, at least part of the energy of an outer portion of the laser beam to reduce thermal stress within the shielded region. In some examples, the method may further include applying the shield to the ceramic material before irradiating the ceramic material. 
     In various examples, the method may also include heating the region through the shield to form a defect in the ceramic material and removing the defect using an additional laser beam. 
     In various embodiments, a ceramic component (such as at least one of sapphire, zirconia, or glass) may include a surface formed by laser cutting the ceramic component and an edge feature (such as at least one of a chamfer, a bezel, a shelf, a curve, or a rounding) formed along the surface by removing a thermally stressed region of the ceramic component. 
     In some examples, the ceramic component may be formed by shielding a region of the ceramic component with a shield from an outer portion of a laser beam used in the laser cutting. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The disclosure will be readily understood by the following detailed description in conjunction with the accompanying drawings, wherein like reference numerals designate like structural elements, and in which: 
         FIG. 1A  shows a front isometric view of an example electronic device; 
         FIG. 1B  shows a rear isometric view of an example electronic device; 
         FIG. 2  shows a flow chart of a first example process for forming a ceramic component; 
         FIG. 3  shows a flow chart of a second example process for forming a ceramic component; 
         FIGS. 4A-4H  show cross-sectional views of a ceramic material undergoing a process of forming a ceramic component for an electronic device such as is depicted in  FIGS. 1A-B . The process may be the first example process of  FIG. 2 ; and 
         FIGS. 5A-5D  show cross-sectional views of a ceramic material undergoing a process of forming a ceramic component for an electronic device such as is depicted in  FIGS. 1A-B . The process may be the second example process of  FIG. 3 . 
     
    
    
     DETAILED DESCRIPTION 
     Reference will now be made in detail to representative embodiments illustrated in the accompanying drawings. It should be understood that the following descriptions are not intended to limit the embodiments to one preferred embodiment. To the contrary, it is intended to cover alternatives, modifications, and equivalents as can be included within the spirit and scope of the described embodiments as defined by the appended claims. 
     Laser cutting of ceramic materials, such as sapphire, may thermally stress ceramic materials in ways that affect the mechanical strength of the ceramic materials. For example, many laser beams have a Gaussian energy distribution (e.g., high energy concentration at a core of the laser beam that tapers to zero at the outside portions of the laser beam). As a result, the core of the laser beam may have sufficient energy to cut a ceramic material, but outer portions outside of the core of the laser beam may have insufficient energy to cut within the time of the cutting operation. Though these lower energy outer portions of the laser beam may not have sufficient energy to cut the ceramic material, they may still heat and thermally stress regions of the ceramic material adjacent to the cut. This heating may form micro-cracks or other defects in the affected region of the ceramic material. Such defects may reduce the mechanical strength of the ceramic material, such as bending strength. These defects may spread when the ceramic material is stressed (such as micro-cracks that spread or otherwise weak areas in which micro-cracks may form), such as when the ceramic material experiences an impact or shock. 
     As discussed herein, in accordance with various embodiments, ceramic components (such as sapphire) can be manufactured using a laser cutting process that may reduce or eliminate some issues related to manufacturing ceramic components. 
     The present disclosure relates to forming a ceramic component using a laser-based process. A ceramic material may be irradiated using a laser-based process to form a cut. In some implementations, a region of the ceramic material adjacent to the cut may be heated and the region may be removed to form an edge feature (such as a chamfer, a bezel, a shelf, a curve, a rounding, and so on). In various implementations, the laser-based process may use a laser beam and the region of the ceramic material adjacent to the cut may be shielded from an outer portion of the laser beam using a shield. The shield may be formed of polyethylene or another plastic and/or any material operable to shield the ceramic material from an outer portion of the laser beam. The shield may shield the ceramic material by absorbing and/or blocking at least part of the outer portion of the laser beam. Such an outer portion may have insufficient energy to cut the ceramic material during the irradiating. This removal and/or shielding may improve the mechanical strength of the ceramic material. 
     In accordance with various embodiments,  FIGS. 1A-B  show a device having one or more example ceramic components or parts that may be manufactured according to the techniques discussed herein. In this example, the ceramic components may be multiple hard protective sheets formed of sapphire, zirconia, glass, or other ceramic material on the exterior of the device. Such protective sheets may provide outstanding scratch resistance and enhance the mechanical integrity of the device. A protective sheet may also function as an optically transmissive window and provide visibility to underlying components, such as display screens or graphical elements. In a typical implementation, both the optical and mechanical properties of the protective sheets may be important to perception of quality and performance of the device. 
     As shown in  FIG. 1A , the device  10  includes protective cover sheet  11  formed from a ceramic component and used as an optically transmissive protective layer. The cover sheet  11  is typically attached to the device  10  using an optically transmissive adhesive or other bonding technique. In this example, the cover sheet  11  is attached using a pressure sensitive adhesive (PSA) film. The cover sheet  11  may be attached to the face of the display screen  20  and protect the display screen  20  from scratches or other physical damage. The display screen  20  may include a liquid crystal display (LCD), organic light emitting diode (OLED) display, or similar display element. Because the cover sheet  11  overlays the display screen  20 , optical clarity, a polished surface finish, material thickness, and physical strength may be useful aspects of the cover sheet&#39;s  11  functionality, alone or in conjunction with other such aspects. The cover sheet  11  may also be attached to, or be integrated with, a transparent electronic sensor that overlays the display screen  20 . In some cases, the electronic sensor covers the entire display screen  20  and is used as the main input device for the user. In some implementations, the cover sheet  11  may be integrated with a touch sensor configured to detect finger or stylus touches on the surface of the cover sheet  11 , a force sensor configured to determine a force exerted on the cover sheet  11 , or other sensors that detect interactions with the cover sheet  11 . 
     As shown in  FIG. 1A , the front surface of the device  10  also includes a button sheet  12  used to protect the surface of the control button  22 . In this example, the button sheet  12  is formed from a ceramic component and is used as an optically transmissive protective layer. The button sheet  12  protects the surface of the control button  22  and allows visibility of any graphical elements that are printed on the control button  22 . In some cases, it is not necessary that the button sheet  12  be optically transmissive. For example, the button sheet  12  may be opaque and itself printed with a graphical element or symbol. In this case, the button sheet  12  is a flat sheet, but in other embodiments, the button sheet  12  may be formed as a contoured or curved surface. 
     The button sheet  12  may enhance the mechanical strength of control button  22 , which is used as an input to the device  10 . In the present example, the control button  22  includes a tactile switch which is operated by depressing the control button  22 . The control button  22  may also include or be associated with an electronic touch sensor, such as a capacitive touch sensor or biometric sensor. The button sheet  12  may be attached directly to a housing of the control button  22  and may, alternatively be attached or integrated with the electronic touch sensor of the control button  22 . Similarly, a ceramic component can be used as a protective cover for a variety of input mechanisms, including a slide, wheel, key, and the like. 
     As shown in  FIG. 1B , the back surface of the device  10  is protected by a back sheet  13 . Similar to the cover sheet  11 , the back sheet  13  is also formed from a ceramic component and is used as an optically transmissive protective layer. In this case, the back sheet  13  provides visibility of graphical elements printed on the back face of the device  10 . In this case, the back sheet  13  covers the entire back of the device  10 , except for the area near the camera lens  24 . A separate ceramic component may be used to protect the camera lens  24 . In an alternative embodiment, the back sheet  13  also covers the camera lens  24  and a separate ceramic component is not used. 
     As shown in  FIGS. 1A-B , the device  10  is a portable electronic device. The device  10  may be any one of a variety of devices utilizing a hard substrate as a covering, window, and/or surface. For example, the device  10  may be a portable electronic device, such as a mobile phone, portable media player, wearable electronic device, health monitoring device, and/or other portable appliance. Similar types of protective covers may be applied to other electronic devices, including, for example, tablet computers, notebook computers, and various wearable devices. Additionally, the protective covers may be applied to other types of devices including non-electronic devices, such as mechanical watches which utilize an optically transmissive face over the dial. Alternatively, the protective covers may be integrated with any device that includes a hard exterior surface, particularly if the surface includes a display screen, camera, or other optical element. 
     As discussed above with respect to  FIGS. 1A-B , various components (e.g., cover sheet  11 , button sheet  12 , and back sheet  13 ) of an electronic device may be formed from ceramic material, which may include various forms of aluminum oxide. Such ceramic materials may undergo a plurality of processes (e.g., laser cutting) in order to form one or more ceramic components used as a protective sheet for electronic device  10 . Such processes may include various techniques discussed herein that improve the mechanical strength of the ceramic material. 
     Techniques of forming ceramic components or parts using laser cutting will now be described. While the following examples are provided with respect to an ablation laser cutting process, the systems and techniques may also be applicable to other types of laser-based processes including, for example, laser fusion, laser etching, physical etching, laser scribing, laser stress cracking, and the like. 
       FIG. 2  shows a flow chart of a first example process  200  for forming a ceramic component. Such a ceramic component may be a component such as the cover sheet  11 , the button sheet  12 , and/or the back sheet  13  of  FIGS. 1A-1B . 
     At  210 , a ceramic material may be irradiated using a laser-based process to form a cut. The laser-based process may use a laser beam. In some cases, the irradiation may be performed using an ablation laser cutting process where the laser beam heats a portion of the ceramic material corresponding to the cut until the portion evaporates, sublimates, or is converted to plasma and is thus removed to form the cut. 
     In a non-limiting example, a laser may be used in an ablation laser cutting process to form the cut. The laser may include one or more of a variety of lasers that are suitable for providing a laser beam capable of forming the cut in the ceramic material, as discussed herein. In some embodiments, the laser cut is performed using a laser that is configured to produce a laser beam at wavelengths centered at approximately 1070 nanometers and pulse durations ranging from 1 to 20 picoseconds. The laser may be configured to produce a laser beam with a power ranging from 10 watts to 100 watts average power. The laser produces multiple laser pulses in order to form the cut by evaporating portions of the ceramic material, sublimating portions of the ceramic material, and/or converting portions of the ceramic material to plasma. The laser may be configured to produce a laser beam ranging from 10 watts to 100 watts average power and may pulse the laser beam one time in order to remove a region adjacent to the cut. 
     The laser beam may have a Gaussian energy distribution or otherwise does not have a uniform energy distribution. The laser beam may have a core portion of a higher energy and one or more outer portions outside the core with lower energy than the core. The higher energy of the core portion may be sufficient to cut the ceramic material. The lower energy of the one or more outer portions may be insufficient to cut the ceramic material during the irradiating. However, the lower energy of the one or more outer portions may still heat the region of the ceramic material adjacent to the cut. This heating may create a thermally induced stress and may form micro-cracks and/or other defects that may adversely impact the mechanical strength (such as bending strength) of the ceramic material. 
     At  220 , the region of the ceramic material adjacent to the cut may be heated and/or a thermal stress therein may be otherwise induced. The region may be heated by the laser-based process. The heating of the region of the ceramic material may form a defect in the ceramic material, such as one or more micro-cracks. In some implementations, the region may be heated at the same time the cut is formed. However, in other implementations, the irradiating to form the cut and the heating may occur at different times. For example, the laser-based process may involve multiple passes of a laser, one or more of which may heat the region. By way of another example, various other processes performed after the irradiating may heat the region of the ceramic material. 
     At  230 , an edge feature (such as a chamfer, a bezel, a shelf, a curve, a rounding, and so on) may be formed on the region of the ceramic material adjacent to the cut by removing at least a portion of the region. The removal of the region may remove ceramic material thermally stressed by the heating and thus remove micro-cracks or other defects or fill micro-cracks or other defects caused by the cutting with molten ceramic material. The removal of the region may also change the impact geometry of the region of the ceramic material such that an impact or shock to the ceramic material is less likely to cause present micro-cracks or other defects to spread and/or otherwise improve the mechanical strength of the ceramic material. 
     In some cases, the removal of the region may be performed using a laser-based process. The laser-based process may be the laser-based process of  210  and/or may be another laser-based process. For example, the laser-based process of  210  may be a first laser-based process using a first laser beam and the removal may be performed using a second laser-based process using a second (or additional) laser beam. In some implementations where first and second laser-based processes are used, the second laser beam used in the second laser-based process may have a lower power than a first laser beam used in the first laser-based process. In some implementations, the second laser-based process may include a shorter duration pulse than the first laser-based process. 
     In other cases, the removal of the region may be performed by a variety of different processes. Such processes may include machining, grinding, lapping, polishing, abrasion, blasting, etching, and/or any other process capable of removing the region. 
     The removal of ceramic material during the formation of the edge feature may be lower energy, performed for a shorter duration, and/or with any other parameters otherwise less likely to produce a thermal gradient that may thermally stress the ceramic material than the removal of ceramic material during the irradiating to form the cut. For example, if irradiating uses 7-15 pulses of a laser beam at 30-45 watts average power, the formation of the edge feature using the laser beam may use one pulse of the laser beam at 10-25 watts average power. By way of another example, the formation of the edge feature may remove less ceramic material than the irradiating and thus use less energy, such as where the ceramic material is cut through a thickness of 0.3 millimeters and a section of the ceramic material having a depth of approximately 15-25 microns is removed to form the edge feature. The lower energy of the edge feature formation compared to the irradiating may prevent formation of additional micro-cracks during the edge feature formation or introduce additional micro-cracks that are smaller than the micro-cracks formed by the irradiating. By way of still another example, the formation of the edge feature may be performed for a smaller amount of time than the irradiating, thus being less likely to produce a thermal gradient that may thermally stress the ceramic material. 
     Although the example process  200  is illustrated and described as including particular operations performed in a particular order, it is understood that this is an example. In various implementations, various orders of the same, similar, and/or different operations may be performed without departing from the scope of the present disclosure. For example, in some implementations, one or more operations discussed with respect to  FIG. 3  below may be performed without departing from the scope of the present disclosure. 
     In one example of the process  200 , a section of ceramic material may be cut from a larger piece of ceramic material by irradiating the ceramic material using a laser beam. The laser beam may be directed around a section of the larger piece of ceramic material to irradiate around a shape of the section of ceramic material (which may be round, square, oval, rectangular, triangular, irregular, and/or any other shape) to form a cut between the section of ceramic material and the larger piece of ceramic material. The section of ceramic material may thus be separated from the larger piece of ceramic material. The laser beam may then be directed around the outside region of the section of ceramic material adjacent to the cut to irradiate the region and form an edge feature by removing at least part of the region. 
       FIG. 3  shows a flow chart of a second example process  300  for forming a ceramic component. Such a ceramic component may be a component such as the cover sheet  11 , the button sheet  12 , and/or the back sheet  13  of  FIGS. 1A-1B . 
     At  310 , a shield may be disposed on a ceramic material. In some cases, the shield may be a polyethylene or other plastic and/or any other material operable to shield the ceramic material from an outer portion of a laser beam. Such an outer portion may have insufficient energy to cut the ceramic material, may have insufficient energy to cut the ceramic material completely or in a desired manner during irradiating, and/or may be shielded for other reasons. Such materials may include a polyester sheet, plastic film, paint (e.g., ink), curable opaque material (polymer spray), or other suitable material. The shield may be optically transparent or translucent, opaque, partially opaque, and so on. The shield may be disposed on the ceramic material using a variety of different processes such as a lamination process, a physical vapor deposition (PVD) process, a printing process, a painting process, or other technique for disposing the shield on the ceramic material. 
     At  320 , a ceramic material may be irradiated with a laser beam to form a cut. The ceramic material may be cut using a laser beam as part of an ablation laser cutting operation (and/or another laser-based process such as laser fusion). At  330 , a region of the ceramic material adjacent to the cut may be shielded during the irradiating using the shield disposed on the ceramic material. This shielding may reduce and/or eliminate the thermal stress of the laser beam on the region of the ceramic material adjacent to the cut. 
     In some cases, the shield may absorb at least part of the energy of one or more outer portions of the laser beam (such that the shield reduces thermal stress within the shielded region) and/or otherwise block at least part of the energy of such outer portions from the ceramic material. As the shield absorbs or blocks at least part of such outer portions, thermal stress of such portions on the region of the ceramic material adjacent to the cut may be reduced and/or eliminated (though such outer portions of the laser beam may still heat and/or otherwise induce some amount of thermal stresses in the region). The mechanical strength of the ceramic material may thus be improved by the reduction and/or elimination of the thermal stress. 
     In various cases, the shield may be formed of a material that does not burn or melt from irradiation by the outer portion of the laser beam to which the shield is exposed. This may enable the shield to optimally shield the region of the ceramic material adjacent to the cut and/or prevent molten portions of the shield from adhering to the ceramic material. In other cases, the shield may be sacrificial. As the shield may be removed in such cases, it may not matter if the shield burns or melts. 
     The shield may also perform various other functions during the irradiating operation. For example, the irradiating operation may scatter molten portions of ceramic material and the shield may protect the surface of the ceramic material on which it is disposed from such scattering molten portions of ceramic material. By way of another example, the shield may prevent scratching of the ceramic material and/or other damage during handling. 
     In various implementations, the process  300  may optionally include one or more additional operations, such as  340  and  350 . At  340 , the shield may be removed. The shield may be removed by a variety of different processes, such as peeling the shield from the ceramic material, dissolving the shield using a solvent, and/or any other such removal process. 
     At  350 , an edge feature may be formed on the region of the ceramic material adjacent to the cut by removing at least a portion of the region. In some cases, the shield may not totally protect the region of the ceramic material adjacent to the cut from being thermally affected by the laser beam. In such cases, the mechanical strength of the ceramic material may be further improved by forming an edge feature in such regions. 
     For example, a first laser-based process may be used at  320  to form the cut and heat the region through the shield to form a defect in the ceramic material and the defect may be removed using a second laser-based process. In other examples, the same laser-based process may both form and remove the defect. In yet other examples, a laser-based process may be used to form the cut and one or more mechanical processes (such as machining, grinding, lapping, polishing, abrasion, blasting, etching, and/or any other process) may be used to remove a region adjacent to the cut. 
     Although the example process  300  is illustrated and described as including particular operations performed in a particular order, it is understood that this is an example. In various implementations, various orders of the same, similar, and/or different operations may be performed without departing from the scope of the present disclosure. 
     For example, although  340  and  350  are illustrated and described as removing the shield after irradiating the ceramic material and then removing the region of the ceramic material adjacent to the cut, it should be understood that this is an example. In some implementations, the edge feature may be formed before the shield is removed, thus also removing a region of the shield. In other implementations, the shield may not be removed, such as in cases where the shield functions as a surface treatment (such as a scratch resistant coating, an oleophobic coating, a hydrophobic coating, a glare resistant coating, and so on) for the ceramic material. 
     By way of another example, the process  300  is illustrated and described as disposing the shield on (and/or otherwise applying the shield to) the ceramic material before irradiating the ceramic material. However, in other implementations, irradiating may be performed iteratively and the shield may be applied partway through the iterative irradiating process. 
       FIGS. 4A-4H  show cross-sectional views of a ceramic material  401  undergoing a process of forming a ceramic component for an electronic device such as the cover sheet  11 , the button sheet  12 , and/or the back sheet  13  of  FIGS. 1A-B . The process may correspond to the first example process  200  of  FIG. 2 . 
       FIG. 4A  illustrates a ceramic material  401 , such as sapphire, having a surface  402 . One or more portions of the ceramic material  401 , such as the surface  402 , may be subjected to one or more treatments such as grinding, palling, and polishing for a variety of purposes such as achieving a fine surface finish on the surface  402 . Additionally, the ceramic material  401  may undergo various pre-processing procedures prior to a laser cutting operation. In a non-limiting example, the ceramic material  401  may be sliced from a boule, ground down to a particular thickness, and/or polished to provide a particular surface finish. 
       FIG. 4B  illustrates irradiation of a portion of the surface  402  using a first laser-based process. The first laser-based process may use a laser beam  492  produced by a laser  491 . The ceramic material  401  is irradiated with the laser beam  492  to form a cut  406 , as shown in  FIG. 4C .  FIGS. 4B and 4C  may correspond to operations  210 - 220  of  FIG. 2 . 
     As illustrated in  FIGS. 4B and 4C , the laser beam  492  produced by the laser  491  may have a core  493  and one or more outer portions  494  outside of the core  493 . The core  493  may have a higher energy density than the outer portions  494  such that the energy of the core  493  is sufficient to cut the ceramic material  401  whereas the lower energy of the outer portions  494  to which one or more regions (corners  405 , or edges) adjacent to the cut  406  are subjected is insufficient to cut the ceramic material  401  during irradiating. For example, the core  493  may have a power ranging from 10 watts to 100 watts, the outer portions  494  may have a power below 10 watts, and a power below 10 watts may be insufficient to cut the ceramic material  401  during irradiating. Though the outer portions  494  of the laser beam  492  have insufficient energy to cut the ceramic material  401 , they may still heat (or otherwise induce thermal stresses in) the side surfaces  404  or other regions of the ceramic material  401  adjacent to the cut  406 , particularly the corners  405  of the surface  402  that is irradiated by the laser beam  492 . 
     Described another way, the laser beam  492  may have a non-uniform (e.g., Gaussian) energy distribution such that a first region of the ceramic material  401  is irradiated with sufficient energy that the first part evaporates, sublimates, or is converted to plasma (or melts or is otherwise cut) whereas a second region of the ceramic material  401  is irradiated with only enough energy to heat (and/or only partially evaporate, sublimate, convert to plasma, melt, and/or otherwise cut) the second region of the ceramic material  401 . The first region of the ceramic material  401  may correspond to the cut  406  that is subjected to the core  493 . The second region of the ceramic material  401  may correspond to the corners  405  that are subjected to the outer portions  494 . 
       FIG. 4D  is a detail view of one of the corners  405  of the surface  402 . As illustrated, the heating of the ceramic material  401  by the outer portions  494  of the laser beam  492  may form micro-cracks  410  or other defects in the ceramic material  401 . 
       FIG. 4E  illustrates removal of a region of one of the corners  405  of the surface  402  to produce an edge feature  407  on one of the side surfaces  404  of the ceramic material  401 .  FIG. 4F  shows the ceramic material  401  after formation of an edge feature  407  on the other corner  405 .  FIGS. 4E and 4F  may correspond to operation  230  of  FIG. 2 . 
     As shown in  FIGS. 4E and 4F , the formation of the edge feature  407  may be performed using a laser-based process (whether the first laser-based process or another, second laser-based process) that uses the laser beam  492 . The formation of the edge feature  407  may remove at least part of the portions of the region of the ceramic material heated by the laser beam  492 , thus removing at least part of the micro-cracks  410  and improving the mechanical strength of the ceramic material. The formation of the edge feature  407  may also cause molten ceramic material  401  to flow into some of the micro-cracks  410 , sealing those micro-cracks  410  and improving the mechanical strength of the ceramic material. The formation of the edge feature  407  may further change the geometry of the side surfaces  404  to reduce contact point sharpness, thus reducing the possibility that the side surfaces  404  will be affected by an impact or shock that will transfer to weaknesses such as present micro-cracks  410  and improving the mechanical strength of the ceramic material  401 . 
     The formation of the edge feature  407  may be a lower energy and/or shorter duration process than the irradiating to form the cut such that the formation of the edge feature  407  does not introduce additional micro-cracks  410  in the ceramic material and/or introduce additional micro-cracks  410  in the ceramic material that are smaller than the micro-cracks formed by the irradiating. In some cases, this may be accomplished by configuring the laser  491  to produce the laser beam  492  differently during formation of the edge feature  407  than during irradiating. For example, the laser  491  may produce the laser beam  492  at 30-45 watts average power for 7-15 pulses during irradiating and at 10-25 watts average power for 1 pulse during formation of the edge feature  407 . In other cases, this may be accomplished by the formation of the edge feature  407  removing a smaller amount of the ceramic material  401  than is removed by the irradiating. For example, the cut  406  may be formed through 0.3 millimeters of the thickness of the ceramic material  401  whereas the edge features  407  may be formed approximately 15-25 microns in depth into the surface  402  and from the side surfaces  404 . 
     Although the edge features  407  are shown as being formed with a particular geometry, it is understood that this is an example. In various implementations, the edge features  407  may be formed with a variety of different geometries without departing from the scope of the present disclosure. For example,  FIGS. 4G  and H show the edge features  407  with a shelf geometry with rounded corners and a shelf geometry with sharp corners, respectively. 
       FIGS. 5A-5D  show cross-sectional views of a ceramic material  501  undergoing a process of forming a ceramic component for an electronic device such as the cover sheet  11 , the button sheet  12 , and/or the back sheet  13  of  FIGS. 1A-B . The process may correspond to the second example process  300  of  FIG. 3 . 
       FIG. 5A  illustrates disposition of a shield  502  on a surface  503  of a ceramic material  501 . By way of example, in some implementations, the shield  502  may be a polyethylene or other plastic film. However, in other implementations, the shield  502  may be any material that absorbs, blocks, and/or otherwise shields outer portions of a laser beam (such as those outer portions with energy insufficient to cut the ceramic material  501  during irradiating) from the ceramic material. The shield  502  may be disposed on the surface  503  of the ceramic material  501  by lamination, PVD, printing, painting, or other disposition process. By way of non-limiting example, the ceramic material  501  may have a thickness of approximately 0.3 millimeters and the shield may have a thickness of approximately 0.15-0.25 millimeters for a total thickness of approximately 0.45-0.55 millimeters.  FIG. 5A  may correspond to operation  310  of  FIG. 3 . 
       FIG. 5B  illustrates irradiating a portion of the shield  502  and the surface  503  using a laser beam  592  produced by a laser  591  to form a cut  506 . The laser beam  592  has a core  593  with an energy sufficient to cut the ceramic material  501  and one or more outer portions  594  outside of the core  593  with energy insufficient to cut the ceramic material  501  during irradiating. As shown, the shield  502  shields or blocks the side surfaces  504  adjacent to the cut  506  or other regions from the outer portions  594  (and/or absorbs at least part of the energy of the outer portions  594  and/or otherwise protects the side surfaces  504  from the outer portions  594 ), preventing or reducing thermal stress of the outer portions  594  on the side surfaces  504  of the ceramic material  501  and thus reducing or eliminating formation of micro-cracks or other defects. As a result, the mechanical strength of the ceramic material  501  is improved over a cut made without the shield  502 .  FIG. 5B  may correspond to operations  320  and  330  of  FIG. 3 . 
     As shown, the material of the shield  502  may not burn or melt from irradiation by the outer portions  594  of the laser beam  592 . This may allow the shield  502  to shield the ceramic material  501  during the entire irradiating process as opposed to burning away or melting and exposing portions of the side surfaces  504  of the ceramic material  501  partway through. This may also prevent molten portions of the shield  502  from adhering to the ceramic material  501 . 
     Although  FIGS. 5A-5B  illustrate the laser beam  592  cutting the shield  502  as well as the ceramic material  501 , it is understood that this is an example. In various implementations, the shield  502  may be configured with one or more gaps that correspond to the core  593 . As such, the portions of the shield  502  around the gap shield the ceramic material  501  from the outer portions  594  but the shield  502  is not irradiated by the core  593  and is not cut during cutting of the ceramic material. Various procedures are possible and contemplated. 
       FIG. 5C  illustrates optional removal of the shield  502  from the ceramic material  501  that may be performed in some implementations.  FIG. 5C  may correspond to the optional operation  340  of  FIG. 3 . 
       FIG. 5D  illustrates optional removal of a region of one of the corners (edges) of the surface  503  by laser ablating using the laser beam  592  produced by the laser  591  to produce an edge feature  507  on one of the side surfaces  504  of the ceramic material  501 . In some cases, the shield  502  may not completely shield the side surfaces  504  from the laser beam  592  and the side surfaces  504  may still be heated and/or thermal stresses may be otherwise induced therein that may form one or more defects. By forming the edge feature  507 , damage caused to the ceramic material  501  by the irradiating may be partially or fully mitigated and the mechanical strength of the ceramic material may be further improved.  FIG. 5D  may correspond to operation  350  of  FIG. 3 . 
     Although a particular process is illustrated and described with respect to  FIGS. 5A-5D , it is understood that this is an example. In various implementations, various combinations of the same, similar, and/or different operations may be performed in a variety of orders without departing from the scope of the present disclosure. For example, in some implementations, the edge feature  507  may be formed prior to removal of the shield  502  and/or removal of the shield  502  may be omitted. 
     By way of another example, although  FIG. 5D  illustrates removal of the region using the laser beam  592 , it should be understood that this is an example. In various implementations, such removal may be performed using one or more mechanical processes, such as machining, grinding, lapping, polishing, abrasion, blasting, etching, and/or any other process capable of removing the region. 
     As described above and illustrated in the accompanying figures, the present disclosure relates to forming a ceramic component using laser cutting. A ceramic material may be irradiated using a laser-based process to form a cut. In some implementations, a region of the ceramic material adjacent to the cut may be heated and the region may be removed to form an edge feature (such as a chamfer, a bezel, a shelf, a curve, a rounding, and so on). In various implementations, the laser-based process may use a laser beam and the region of the ceramic material adjacent to the cut may be shielded from an outer portion of the laser beam using a shield (which may be formed of polyethylene or another plastic and/or any material operable to shield the ceramic material from an outer portion of the laser beam, such as by absorbing and/or blocking at least part of the outer portion of the laser beam, with insufficient energy to cut the ceramic material during irradiating). This removal and/or shielding may improve the mechanical strength of the ceramic material. 
     The foregoing description, for purposes of explanation, used specific nomenclature to provide a thorough understanding of the described embodiments. However, it will be apparent to one skilled in the art that the specific details are not required in order to practice the described embodiments. Thus, the foregoing descriptions of the specific embodiments described herein are presented for purposes of illustration and description. They are not targeted to be exhaustive or to limit the embodiments to the precise forms disclosed. It will be apparent to one of ordinary skill in the art that many modifications and variations are possible in view of the above teachings.

Metadata:
Filing Date: 20150701
Publication Date: 20190910
Grant Date: 20190910
Priority Date: 20150701
Inventors: LI, MICHAEL M.
CHINNAKARUPPAN, PALANIAPPAN
SUN, YULEI
HUM, PHILLIP W.
RAMMAH, MARWAN
Assignee: APPLE INC
CPC Classifications: [{"code": "B23K26/402", "inventive": true, "first": false, "tree": "[]"}, {"code": "B23K26/18", "inventive": true, "first": false, "tree": "[]"}, {"code": "B23K26/361", "inventive": true, "first": false, "tree": "[]"}, {"code": "B23K26/0624", "inventive": true, "first": false, "tree": "[]"}, {"code": "B23K26/38", "inventive": true, "first": true, "tree": "[]"}, {"code": "B23K26/38", "inventive": true, "first": true, "tree": "[]"}, {"code": "B23K26/361", "inventive": true, "first": false, "tree": "[]"}, {"code": "B23K26/402", "inventive": true, "first": false, "tree": "[]"}, {"code": "B23K2103/52", "inventive": false, "first": false, "tree": "[]"}, {"code": "B23K26/0624", "inventive": true, "first": false, "tree": "[]"}, {"code": "B23K2103/52", "inventive": false, "first": false, "tree": "[]"}, {"code": "B23K26/18", "inventive": true, "first": false, "tree": "[]"}, {"code": "B23K26/18", "inventive": true, "first": false, "tree": "[]"}, {"code": "B23K26/0624", "inventive": true, "first": false, "tree": "[]"}, {"code": "B23K2103/52", "inventive": false, "first": false, "tree": "[]"}, {"code": "B23K26/361", "inventive": true, "first": false, "tree": "[]"}, {"code": "B23K26/402", "inventive": true, "first": false, "tree": "[]"}, {"code": "B23K26/38", "inventive": true, "first": true, "tree": "[]"}]
Family ID: 57683458