PATENT DOCUMENT

Publication Number: US-11419231-B1
Application Number: US-201815886203-A
Country: US
Kind Code: B1

Title: Forming glass covers for electronic devices

Abstract:
A cover for an electronic device includes a glass cover defining a substantially planar first surface, a substantially planar second surface opposite the first surface, an opening extending through the glass cover, and a raised wall surrounding the opening and defining a portion of an interior surface of the opening.

Claims:
What is claimed is: 
     
       1. A notebook computer, comprising:
 a monolithic glass sheet defining:
 a substantially planar first sheet surface; 
 a substantially planar second sheet surface opposite the first surface; 
 an opening extending through the monolithic glass sheet; and 
 a wall surrounding and extending from the opening; and 
 
 a key comprising:
 a glass key cover positioned at least partially within the opening and defining:
 a molded top surface having a concave shape and defining an exterior surface of the key; and 
 a substantially planar machined bottom surface; 
 
 a sub-structure coupled to the glass key cover; and 
 a support mechanism movably supporting the sub-structure and the glass key cover relative to a base structure. 
 
 
     
     
       2. The notebook computer of  claim 1 , wherein:
 the first sheet surface defines an exterior surface of the notebook computer; and 
 the wall extends a distance relative to the second sheet surface. 
 
     
     
       3. The notebook computer of  claim 2 , wherein the wall defines a top wall surface that is substantially parallel with the second sheet surface. 
     
     
       4. The notebook computer of  claim 3 , wherein:
 the top wall surface is a machined surface; and 
 the wall has an unmachined exterior surface and an unmachined interior surface. 
 
     
     
       5. The notebook computer of  claim 1 , wherein:
 the opening is a first opening; 
 the wall is a first wall; and 
 the monolithic glass sheet has a second opening and defines a second wall surrounding and extending from the second opening. 
 
     
     
       6. The notebook computer of  claim 5 , wherein the first and second walls extend substantially the same height above the second surface. 
     
     
       7. A notebook computer, comprising:
 a display portion; and 
 a housing portion flexibly coupled to the display portion by a hinge, the housing portion comprising:
 a base structure; 
 a cover coupled to the base structure and defining a keyboard region having a plurality of apertures; and 
 a key in the keyboard region and comprising:
 a glass key cover positioned at least partially within an aperture of the plurality of apertures and defining:
 a molded top surface having a concave shape and defining an exterior surface of the key; and 
 a substantially planar machined bottom surface; 
 
 a sub-structure coupled to the glass key cover; and 
 a support mechanism movably supporting the sub-structure and the glass key cover relative to the base structure. 
 
 
 
     
     
       8. The notebook computer of  claim 7 , wherein:
 the glass key cover further comprises a raised feature extending from the molded top surface. 
 
     
     
       9. The notebook computer of  claim 7 , wherein:
 a thickness at a central region of the glass key cover is between about 0.3 mm and about 0.5 mm; and 
 a thickness at an outer region of the glass key cover is between about 0.6 mm to about 0.75 mm. 
 
     
     
       10. The notebook computer of  claim 7 , wherein the glass key cover is coupled to the sub-structure with adhesive. 
     
     
       11. The notebook computer of  claim 7 , wherein the glass key cover has a substantially square outer perimeter. 
     
     
       12. The notebook computer of  claim 7 , wherein the input device comprises a collapsible dome below the sub-structure, the collapsible dome biasing the sub-structure and glass key cover towards a biased position. 
     
     
       13. The notebook computer of  claim 12 , wherein the sub-structure is configured to contact the collapsible dome to collapse the collapsible dome in response to a user input. 
     
     
       14. The notebook computer of  claim 7 , wherein the cover is formed of glass.

Description:
CROSS-REFERENCE TO RELATED APPLICATION(S) 
     This application is a continuation patent application of U.S. patent application Ser. No. 15/710,352, filed Sep. 20, 2017 and titled “Forming Glass Covers for Electronic Devices,” which is a nonprovisional patent application of and claims the benefit of U.S. Provisional Patent Application No. 62/398,483, filed Sep. 22, 2016 and titled “Forming Glass Covers for Electronic Devices,” the disclosures of which are hereby incorporated herein by reference in their entireties. 
    
    
     FIELD 
     The present invention relates generally to forming glass covers for electronic devices, and more particularly to forming shaped glass sheets and removing portions of the sheets to form openings in glass covers. 
     BACKGROUND 
     Electronic devices are ubiquitous in society and can be found in everything from wristwatches to computers. Many hand-held devices include input devices such as buttons, keys, touch-sensitive input devices (e.g., trackpads, touchscreens), as well as output devices such as displays, that facilitate user interactions with the device. In certain applications, glass or other transparent covers are positioned over the input and/or output devices, or over other portions of the electronic device. The covers may protect sensitive components and may define interface surfaces that directly receive physical inputs, such as touches and presses. 
     SUMMARY 
     A cover for an electronic device includes a glass sheet defining a substantially planar first surface, a substantially planar second surface opposite the first surface, an opening extending through the glass sheet, and a wall surrounding and extending from the opening. 
     The wall may extend a distance relative to the second surface. The wall may define a top surface that is substantially parallel with the second surface, and the first surface may define an exterior surface of an electronic device. The top surface may be a machined surface, and wall may have an unmachined exterior surface and an unmachined interior surface. 
     The opening may be a first opening, the wall may be a first wall, and the glass sheet may further define a second opening extending through the glass sheet, and a second wall surrounding and extending from the second opening. The first and second walls may extend substantially the same height above the second surface. 
     A cover for an electronic device includes a glass sheet defining a first surface, a second surface parallel to and set apart from the first surface by a thickness, and a third surface defining a sidewall of an opening that extends through the glass sheet and having a height that is greater than the thickness of the glass sheet. 
     The glass sheet may further define a raised wall surrounding the opening, the third surface may define an inner surface of the raised wall, and a fourth surface may define an outer surface of the raised wall. The opening may be substantially rectangular. 
     The glass sheet may be incorporated with an electronic device including a housing, a processor within the housing, and a touch-sensitive input device within the housing and below the glass sheet. The glass sheet may define an input surface for the touch-sensitive input device. The glass sheet may facilitate capacitive coupling between the touch-sensitive input device and an object in contact with the input surface. 
     A method of forming a glass cover for an electronic device includes positioning a glass sheet on a shaped mold, conforming the glass sheet to the shaped mold, solidifying the glass sheet to form a shaped glass sheet comprising a surface defining a high relief portion and a low relief portion, and removing at least a portion of the high relief portion, thereby forming a glass cover defining an opening for the electronic device. Removing the portion of the high relief portion may include grinding the shaped glass sheet with a grinding tool. 
     The surface may be a first surface, the glass sheet may further comprise a second surface opposite the first surface, and the second surface may define an exterior surface of the electronic device. 
     Prior to removing the portion of the high relief portion, the shaped glass sheet may be removed from the shaped mold. Conforming the glass sheet to the mold may comprise applying pressure to the glass sheet. Conforming the glass sheet to the mold may comprise applying a vacuum to the glass sheet through the shaped mold, thereby drawing the glass sheet against a surface of the shaped mold. 
     The shaped mold may be a first shaped mold having a first set of contours corresponding to the high relief portions and low relief portions of the glass sheet, applying the pressure to the glass sheet may include contacting the glass sheet with a second shaped mold having a second set of contours that is complementary to the high relief portions and the low relief portions of the glass sheet. 
     A method may include positioning a contoured glass sheet in a fixture, the contoured glass sheet including a first portion, a second portion recessed relative to the first portion, and a joining segment joining the second portion to the first portion. The method may further include separating the second portion from the first portion by cutting along the joining segment, thereby forming a perforated sheet from the first portion. The method may further include coupling the perforated sheet to a housing of an electronic device. 
     The cutting may include directing a cutting beam onto the joining segment. The cutting beam may be a laser beam. 
     The perforated sheet may include an opening corresponding to the second portion which was removed from the contoured glass sheet, and the method may further include positioning the second portion in the opening and coupling the second portion to an input device within the electronic device and below the opening of the perforated sheet. The input device may be a force-sensitive input device. The input device may be a touch-sensitive input device. The input device may be a mechanical input device. 
     The method may further include positioning the perforated glass sheet over a touch-sensitive input device. The touch-sensitive input device may be a touch-sensitive display. 
     A method of forming a glass cover for an electronic device may include conforming a glass sheet to a shaped mold defining at least one contour, and cooling the glass sheet to form a shaped glass sheet defining at least one indented portion corresponding to the at least one contour in the shaped mold, and a flange portion surrounding the at least one indented portion. The method may further include removing the shaped glass sheet from the shaped mold and separating the at least one indented portion from the flange portion to form at least one glass cover for an electronic device. 
     The separating may include machining the flange portion of the shaped glass sheet to singulate the at least one indented portion. The separating may include machining the at least one indented portion of the shaped glass sheet to produce a perforated glass sheet. The machining the at least one indented portion may include grinding the at least one indented portion. 
     The at least one glass cover may be coupled to an input device within the electronic device. The input device may be a force-sensitive device. The force-sensitive device may be a trackpad of a laptop computer. 
     The flange portion may define a perforated glass sheet. The method may further include coupling the perforated glass sheet to a housing of an electronic device. 
     An electronic device may include a housing, a base structure, a cover coupled to the housing and having aperture, and an input device. The input device may include a glass button cover positioned within the aperture of the cover and defining a molded top surface defining an exterior surface of the input device and a machined bottom surface. The input device may further include a sub-structure coupled to the glass button cover, and a support mechanism movably supporting the sub-structure and the glass button cover relative to the base structure. The machined bottom surface may be substantially planar. The cover may be formed of glass. 
     The molded top surface may have a concave shape, and the glass button cover may further include a raised feature extending from the molded top surface. The glass button cover may be coupled to the sub-structure with adhesive. 
     A thickness at a central region of the glass button cover may be between about 0.3 mm and about 0.5 mm, and a thickness at an outer region of the glass button cover may be between about 0.6 mm to about 0.75 mm. The glass button cover may have a substantially square outer perimeter. 
     The input device may include a collapsible dome below the sub-structure, the collapsible dome biasing the sub-structure and glass button cover towards a biased position. 
     A method may include positioning a glass sheet on a shaped mold, conforming the glass sheet to the shaped mold, solidifying the glass sheet to form a shaped glass sheet defining a protrusion extending above a web portion, and separating the protrusion from the web portion, thereby forming a perforated glass sheet corresponding to the web portion and an input device cover corresponding to the protrusion. Separating the protrusion from the web portion may include cutting a joining segment connecting the protrusion to the web portion with a wire saw. The method may further include attaching the input device cover to a sub-structure of an input device. The method may further include positioning the perforated glass sheet over a touch-sensitive input device. 
     The shaped mold may contact substantially an entire bottom surface of the glass sheet during the conforming, and conforming the glass sheet to the shaped mold may further include applying a partial mold to less than an entire top surface of the glass sheet prior to solidifying the glass sheet. The partial mold may contact the web portion of the shaped glass sheet. 
    
    
     
       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. 
         FIG. 1  shows an example electronic device. 
         FIG. 2A  shows an exploded view of the electronic device of  FIG. 1 . 
         FIG. 2B  shows a partial cross-sectional view of an input device of the electronic device of  FIG. 1 . 
         FIGS. 3-5  show an example process for forming a glass cover. 
         FIG. 6A  shows a partial cross-sectional view of a shaped glass sheet, viewed along line  4 B- 4 B in  FIG. 4A , showing the glass sheet during a material removal operation. 
         FIG. 6B  shows a partial cross-sectional view of a glass sheet, viewed along line  6 B- 6 B in  FIG. 5 . 
         FIG. 6C  is a detail view of a portion of the glass sheet in  FIG. 6B . 
         FIG. 7A  shows a partial cross-sectional view of a shaped glass sheet, viewed along line  7 A- 7 A in  FIG. 4A . 
         FIGS. 7B-7C  show partial cross-sectional views of a glass sheet, viewed along line  7 B- 7 B in  FIG. 5 . 
         FIGS. 8A-8B  show another example process for forming a glass cover. 
         FIG. 9  shows a perspective view of an example molding apparatus. 
         FIGS. 10A-10C  show partial cross-sectional views of the molding apparatus of  FIG. 9 . 
         FIG. 11  shows a perspective view of another example molding apparatus. 
         FIG. 12  shows a partial cross-sectional view of the molding apparatus of  FIG. 11 . 
         FIG. 13A  shows a perspective view of a shaped glass sheet. 
         FIG. 13B  shows a cross-sectional view of the shaped glass sheet of  FIG. 13A . 
         FIGS. 14A-14B  show a shaped glass sheet at various stages of a singulation process. 
         FIG. 15  shows a shaped glass sheet undergoing another singulation process. 
         FIGS. 16A-16C  show example post-processing steps for a button cover. 
         FIGS. 17A-17B  show a glass sheet at various stages of a forming process. 
         FIGS. 18A-18B  shows a cross-sectional view of a pressing process to form a glass sheet. 
         FIG. 19  shows a glass sheet undergoing a machining process. 
         FIGS. 20A-20C  show a glass sheet at various stages of a singulation process. 
         FIGS. 21A-21B  show example button covers. 
         FIG. 22  shows another example electronic device. 
         FIG. 23  shows a partial cross-sectional view of the electronic device of  FIG. 22 , viewed along line  23 - 23  in  FIG. 22 . 
         FIGS. 24A-24D  show an example process for forming a cover for the electronic device of  FIG. 22 . 
         FIG. 25  shows an example process of forming a glass cover. 
     
    
    
     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. 
     Glass covers may be used to cover various different portions of electronic devices. For example, glass covers may be positioned over a touch-sensitive input device or a force-sensitive input device to provide an interface surface for the touch- or force-sensitive input devices. Glass covers may have beneficial structural properties that make them well suited for such applications, such as high hardness, a smooth surface, and suitable dielectric properties to facilitate detection of force or touch inputs applied to the covers. Moreover, where the glass covers overlie displays or other visual output devices, the transparency of the glass allows the displays to be viewed while also protecting the display. Glass covers may either be fully transparent, such as when they overlie a display, or they may be textured using a secondary surface treatment or any other suitable texturing process. 
     Glass covers for electronic devices may include openings or apertures therethrough. For example, a glass cover for a mobile phone may include openings over audio components, such as speakers and microphones, to allow sound to pass through the cover. As another example, an electronic device may have a camera lens that extends through an opening in a glass cover. As yet another example, a button, or part of a button, may be positioned in an opening in a glass cover. 
     Described herein are techniques for forming glass covers for electronic devices. For example, a glass sheet may be positioned over a shaped mold and then heated to the transition temperature (e.g., the softening point) of the glass material. At the transition temperature, the glass sheet will soften and slump over the shaped mold. In the slumping process, the glass sheet conforms to the shape (e.g., the contours) of the mold and is cooled, thereby forming a contoured sheet. More particularly, the shaped mold may have a surface defining bumps, depressions, recesses, areas of high relief, areas of low relief, or other shapes or contours. When the glass is slumped over the surface of the mold and cooled, the resulting glass sheet corresponds to the shape (e.g., the areas of high and low relief) of the mold. For example, a bump or protrusion on the surface of the mold may produce a corresponding bump or protrusion in the shaped glass sheet. Once the shaped glass sheet is cooled, it may be removed from the shaped mold. 
     The contours of the shaped glass sheet may define areas that are formed into apertures or openings in a finalized glass cover. For example, a sheet of glass may be slumped over a mold that has a protruding portion, resulting in a shaped glass sheet with a corresponding protrusion. In order to form an aperture or opening, the protrusion can be removed to produce a perforated glass sheet. The removal of the protrusion can be by grinding the protrusion with a grinding or lapping tool, or by cutting the protrusion from the remaining portion of the sheet with a laser beam (e.g., cutting beam), wire saw, or other suitable cutting tool or technique. 
     The perforated sheet can then be coupled to an electronic device such that the aperture (or apertures) formed by removing protruding portions align with certain components of an electronic device. For example, an aperture may align with a speaker, button, key, optical lens, or any other suitable component of the electronic device. A portion of the glass sheet may also cover input devices, displays, or other components of an electronic device. 
     Furthermore, the cover glass can be coupled to input devices of the electronic device, such as force-sensitive and touch-sensitive input devices. For example, the protruding portion that is cut from the shaped glass sheet may be incorporated for used to cover input devices, such as a button or a touch-sensitive input device (e.g., a touch-sensitive display). The shape of the cover glass may be circular, rectangular, or any shape that will conform with the input device and permit coupling with the electronic device. In a further example, the shaped glass may be formed in such a way that a piece of glass removed to form an aperture in the shaped glass sheet may be used as a cover for an input device. For example, a cover may have an opening that corresponds to a button, and the piece of glass removed to form the opening may be used as a cover for the button. 
     Although one or more of these processes may be described in detail in the context of handheld devices, such as mobile phones, laptops, and notebooks, the embodiment disclosed should not be interpreted or otherwise used as limiting the scope of the disclosure, including the claims. In addition, one skilled in the art will understand that the following description has broad application. Accordingly, the discussion of any embodiment is meant only to be exemplary and is not intended to suggest that the scope of the disclosure, including the claims, is limited to these embodiments. 
       FIG. 1  shows an example device  100 . The device  100  shown in  FIG. 1  is a mobile phone (e.g., a smartphone), but this is merely one representative example of a device that may be used in conjunction with the ideas disclosed herein. Other example devices include, without limitation, music/media players, tablet computers, laptop computers, wearable electronic devices, watches (e.g., mechanical, electrical, or electromechanical), keyboards, and the like. Moreover, while the ideas disclosed herein are primarily described with reference to glass covers for electronic devices, the ideas are also applicable to glass (or other material) covers for other devices or applications. 
       FIG. 1  illustrates a handheld device  100 , such as a mobile phone. The electronic device  100  includes a housing  150  and a cover  110 , which may cover or otherwise overlie a display and/or a touch-sensitive input device (e.g., a touchscreen). The cover  110  may be made of a material such as glass, plastic, sapphire, or any other suitable material. The device  100  may also include internal components, such as processors, memory, circuit boards, batteries, sensors, and the like. Such components may be disposed within an internal volume defined at least partially by the housing  150 . 
     The cover  110  may have one or more openings or apertures to accommodate input and/or output devices. For example, as shown in  FIG. 1 , a first opening  120  may be provided for an input device (e.g., a button, fingerprint sensor, or the like) to enable mechanical inputs to be received by the central processor. This input device may respond to mechanical pressure and may control operations of the device  100  in response to detected inputs. For example, the input device may control applications that are operating on the device  100 , cause the device  100  to power-on or unlock, or the like. The cover  110  may also define a second opening  140 , which may be adjacent or proximate a speaker. For example the second opening  140  may allow audio to pass through the cover  110  and to a user. 
     Non-perforated glass covers may also be provided to cover input devices such as buttons, fingerprint sensors, and the like. For example, a button cover  130  may overlie or be coupled to an input device such as a button. The button cover  130  may fit within the first opening  120  in the cover  110  (or an opening in any other component or structure of an electronic device). The button cover  130  may optionally include a raised feature  121 , which may allow the user to tactilely locate the button and/or differentiate the button from surrounding areas of the cover  110  or the device  100  more generally. The button cover  130  may have a substantially planar external surface (e.g., the surface that is pressed by a user to actuate the button), or it may be contoured, such as convex or concave. Further, while the button cover  130  is shown as having a substantially square shape, other shapes are also contemplated, such as circular, rectangular, and the like. Although non-perforated glass covers are discussed in the context of an input device of an electronic device, the glass cover concept may be applied to a variety of peripheral devices, such as pressure-sensitive displays, gaming controllers, and so on. 
     The cover  110 , with its exemplary openings, and the button cover  130  may be produced from the same sheet of glass by a method disclosed herein. For example, a glass sheet may be slumped over a mold to form a glass sheet with contours that correspond to the desired openings. A portion of the contoured sheet that is removed to form an opening (and thereby form the cover  110 ) may be used as a cover for an input device on the same electronic device as the cover  110  (e.g., the button cover  130 ). In other cases, the cover  110  and/or the button cover  130  may be formed from different sheets of glass. For example, as described herein, multiple button covers may be formed from a single sheet of glass. 
     While embodiments are disclosed herein where the handheld device  100  is discussed in the context of a mobile phone, the handheld device  100  may take a variety of forms, such as a laptop computing system, a personal digital assistant, an electronic notebook, a portable gaming system, and so on. 
       FIG. 2A  is an exploded view of the handheld device  100  of  FIG. 1 , showing the cover  110  and the button cover  130  removed from the housing  150 . As shown in  FIG. 2A , the cover  110  overlies and may be coupled to a display  202  that is positioned within and coupled to the housing  150 . The display  202  may be a touch-sensitive and/or force-sensitive display, as described above, and may include display components (e.g., lighting elements, filters, polarizers, liquid crystal layers) as well as input sensing components (e.g., capacitive sensors, resistive sensors, piezoelectric sensors). 
     The button cover  130  overlies and may be part of or coupled to an input device  204 , and is positioned in the first opening  120 . The input device  204  may include electrical and mechanical components, such as dome switches, spring members, haptic actuators, and/or other mechanisms to provide mechanical or tactile button functions, as described with respect to  FIG. 2B . Additionally or alternatively, the input device  204  may include touch- and/or force-sensitive components, such as capacitive, resistive, or optical sensors (or other types of sensors) that detect user inputs and control operations of the device  100 . In some cases, the touch- and/or force-sensitive components detect the presence and/or proximity of an implement such as a finger, stylus, or the like, by electrically sensing the implement. Accordingly, the button cover  130  (or any glass cover described herein that overlies a touch- and/or force-sensitive input) may be formed from a dielectric material, such as glass, sapphire, or any other material that facilitates or otherwise does not interfere with a sensor&#39;s ability to electrically sense objects applied thereto. 
     The button cover  130  may have any suitable dimensions. For example, the button cover  130  may be configured to be operated (e.g., pressed) by one finger of a user, and as such may have a size that is convenient and comfortable for one-finger operation. For example, where the button cover  130  is a square (as shown) or rectangle, the button cover  130  may have a length along each side between about 1.0 cm and about 2.0 cm. Where the button cover  130  is a circle, the button cover  130  may have a diameter between about 1.0 cm and about 2.0 cm. Other shapes and dimensions are also possible. 
     The button cover  130  may be coupled to a sub-structure of the input device  204 , which may in turn be coupled to mechanical support structures such as hinges, guides, pivoting and/or articulating mechanisms, and the like. For example,  FIG. 2B  shows a partial cross-sectional view of the electronic device  100 , viewed along line  2 B- 2 B in  FIG. 1 , showing details of the input device  204 . The input device  204  includes the button cover  130 , which may be coupled to a sub-structure  208 . The sub-structure  208  may be any suitable material, such as plastic, and the button cover  130  may be coupled to the sub-structure  208  in any suitable way, such as with adhesives, mechanical interlocking structures, threaded fasteners, clips, and the like. In some cases, interstitial components or materials may be between the sub-structure  208  and the button cover  130 , such as adhesives, glues, bonding agents, polymer layers, fabrics, or the like. 
     The sub-structure  208  (or the button cover  130  itself, if the sub-structure  208  is not used) may be movably supported relative to a base structure, such as the housing  150 , by a support mechanism  210 . As shown, the support mechanism  210  includes linked members that may guide the button cover  130  along a substantially linear path. Other types of support mechanisms  210  may also be used, such as telescoping guides, scissor mechanisms, hinges, or the like. 
     The input device  204  may also include a switching component that produces a signal or other detectable event when the input device is actuated (e.g., when the button cover  130  is pressed by a user). For example, as shown in  FIG. 2B , the input device  204  includes a collapsible dome  212 . The collapsible dome  212  may be formed from any suitable material or materials, such as rubber, plastic, metal, or the like. When collapsed, deformed, or deflected by downward movement of the button cover  130  and sub-structure  208 , the collapsible dome  212  may close an electrical circuit. The electronic device  100  may detect the closure of the circuit and register an input (and perform a function or operation in response to registering the input). The collapsible dome  212  may also provide a biasing force that biases the sub-structure  208  and button cover  130  towards a biased or unactuated position (e.g., an upward force, as shown in  FIG. 2B ). The collapsible dome  212  may also provide a desired tactile response to the button cover  130  when the button cover  130  is actuated, such as a click or detent. 
     Returning to  FIG. 2A , this figure also illustrates the relative positioning of the second opening  140  with respect to a speaker  206  (or a speaker port coupled to a speaker). As noted above, the opening  140  may be configured to communicate with the speaker  206  to allow sound to pass from the interior of the electronic device  100  through the cover  110 . 
       FIGS. 3-5  illustrate an example process for forming a monolithic glass cover, such as the cover  110 , for an electronic device.  FIG. 3  shows a glass sheet  300  positioned over a shaped mold  302 . As shown, the glass sheet  300  is substantially planar and has a substantially uniform thickness. For example, the glass sheet may have a substantially uniform thickness between about 0.02 mm and about 3.0 mm. 
     The glass sheet may be formed from or may include any suitable glass, such as borosilicate glass, aluminosilicate glass, soda lime glass, chemically strengthened glass, or any other suitable glass. The glass sheet  300  may be formed from or may include materials other than glass, such as sapphire or any other material that may be formed by the molding process described herein. 
     The shaped mold  302  may have contours (e.g., protrusions, cavities, channels, depressions, or the like) that are configured to form corresponding contours in the glass sheet  300 . For example, the shaped mold  302  includes a first recess  304  and a second recess  306 . The first recess  304  may be configured to produce a recess or indentation in the glass sheet  300  that will ultimately be removed to form an aperture or opening (e.g., the first opening  120 ,  FIG. 1 ) for a button cover. Similarly, the second recess  306  may be configured to produce a recess or indentation in the glass sheet  300  that will ultimately be removed to form an aperture (e.g., the second opening  140 ,  FIG. 1 ) for a speaker or other audio component. 
     The glass sheet  300  may be formed against the mold  302 . This process may be referred to as slumping, and may include heating the glass sheet  300  and/or the mold  302 , applying the glass sheet  300  to the mold  302 , and causing the glass to conform to the shape of the mold  302  (e.g., by applying pressure from another mold part or with a vacuum molding system). After the glass sheet  300  is formed against the mold  302  and hardened (e.g., by cooling), the glass sheet  300 , now a monolithic shaped glass sheet, may be removed from the mold  302  for further processing. 
       FIG. 4A  shows a shaped glass sheet  401  corresponding to the glass sheet  300  after molding. The shaped glass sheet  401  includes a first recess  408  (corresponding to the first recess  304  in the mold  302 ) and a second recess  410  (corresponding to the second recess  306  in the mold  302 ). The shaped glass sheet  401  may also have a border or flange portion  412  where the glass sheet  300  conformed to an outer edge of the mold  302 . As described herein, the recesses  408 ,  410 , or indented portions, of the shaped glass sheet  401  may be removed to form apertures or openings, thereby forming a perforated glass sheet. 
       FIG. 4B  shows a partial cross-sectional view of the shaped glass sheet  401 , viewed along line  4 B- 4 B in  FIG. 4A .  FIG. 4B  illustrates how the glass sheet  300  conforms to the recesses in the mold  302 . In particular, the shaped glass sheet  401  includes the second recess  410 , which was formed by the glass conforming to the second recess  306  in the mold  302 . The shaped glass sheet  401  may also include a border portion  412  where the glass sheet  300  conformed to an outer edge of the mold  302 . 
     A top surface  402  of the shaped glass sheet  401  may be configured to define an exterior surface of an electronic device (e.g., the electronic device  100 ), and may also define an input surface of an input device (e.g., a touchscreen of the electronic device  100 ). A bottom surface  404  of the shaped glass sheet  401  may be configured to face an interior portion of the electronic device  100 . The top surface  402  and the bottom surface  404  may be substantially planar. 
     The shaped glass sheet  401  may be formed so that any grinding or machining that is used to remove the recessed portions and form the openings occurs only on or adjacent the bottom surface  404 . Accordingly, the top surface  402  is not marred or otherwise subjected to physical operations that may scratch or otherwise damage the top surface  402 . 
     From the perspective of the top surface  402 , the first and second recesses  408 ,  410  are recessed relative to the top surface  402 . However, from the perspective of the bottom surface  404 , the first and second recesses  408 ,  410  appear as protrusions. More particularly, from the perspective of the bottom surface  404 , the second recess  410  defines an area of high relief  411 , while the non-recessed portions (e.g., those portions that are not intended to form openings) define an area of low relief  414 . Similarly, the border portion  412  may be an area of high relief. As used herein, areas of high relief and low relief on a sheet are described relative to a surface that is subjected to a removal operation (e.g., grinding, milling, laser cutting, etc.), regardless of the profile of the opposite side of the sheet. For example, with reference to  FIG. 4B , the area of high relief  411  is removed (using a cutting operation directed to the bottom surface  404 ) to form a perforated cover. Thus, the area  411  is referred to as an area of high relief even though, as viewed from the top surface  402 , it may appear as a recess or area of low relief. 
       FIG. 5  shows a perforated glass sheet  502 , corresponding to the shaped glass sheet  401  after the border or flange portion  412  has been removed, and after the bottom portions of the recesses  408 ,  410  have been removed to form openings  506 ,  504  (corresponding to the openings  120 ,  140  in  FIG. 1 ). The perforated glass sheet  502  (which may be monolithic) may be used as a cover for an electronic device, such as the cover  110  shown in  FIGS. 1 and 2 . 
     By slumping the glass to form recesses and corresponding protruding portions (e.g., the portions of the recesses that protrude from the bottom surface of the sheet), openings can be formed by grinding away or otherwise removing the protruding portions of the glass. This process may enable new and varied techniques for forming openings in monolithic glass sheets. For example, multiple openings, even openings of different sizes and shapes (such as the openings  120 ,  140  in  FIGS. 1-2 ) can be formed simultaneously by applying a flat grinding tool to the shaped glass sheet. By contrast, with other cutting and machining processes (such as directing a laser perpendicularly onto a glass sheet or using an end mill that is perpendicular to the glass sheet) it may be difficult to machine or cut multiple openings having different sizes or shapes in an efficient manner. For example, it may be difficult to position all of the necessary tooling adjacent the glass sheet at the same time, thus mandating slower processes such as forming the openings serially. 
       FIG. 6A  shows a partial cross-sectional view of the shaped glass sheet  401 , viewed along line  4 B- 4 B in  FIG. 4A , during a machining operation to remove at least some of the high relief portion  411  and (optionally) the border portion  412 . In particular,  FIG. 6A  shows a rotating tool  600 , such as a grinding wheel or milling bit, removing part of the high relief portion  411  to form the opening (e.g., the second opening  506 ,  FIG. 5 ) in the shaped glass sheet  401  and thereby form the perforated glass sheet  502  ( FIG. 5 ). While  FIG. 6A  shows a rotating tool, other cutting tools are also contemplated, such as wire saws. 
     The tool  600  may be configured to only contact the high relief portion  411 , and not to make contact with the low relief portion  414 , thereby avoiding scratches and/or tool marks on the low relief portion  414 . For covers where the low relief portion  414  covers a display, this may help preserve the transparency and optical properties of the low relief portion  414 . Moreover, the tool  600  may form the opening  506  without contacting an inner surface  603  ( FIGS. 6B-6C ) of the opening  506 . For example, a typical drilling or milling operation may form an opening by penetrating through the sheet substantially perpendicularly to the surfaces of the sheet, thus machining the inner surface  603  by contacting the inner surface  603  with the tool. On the other hand, the shape and configuration of the high relief portion  411  allows the opening  506  to be formed without having to machine the sidewalls (e.g., the inner surface  603 ) of the opening  506  directly. When this technique is applied to forming a cover for an electronic device, as described herein, the machined surface is positioned out of view and out of reach of a user of the electronic device (e.g., it faces and/or is oriented towards an interior portion of the electronic device, and is not reachable by a user under normal operation of the device). This may reduce the processing steps required to produce a desired shape and surface finish for the inner surface  603  of the opening  506 , as the additional processing steps to turn the raw machined surface into a suitable final form (e.g., grinding, machining, polishing, buffing) may be reduced or omitted. 
       FIG. 6B  shows a partial cross-sectional view of the perforated glass sheet  502 , viewed along line  6 B- 6 B in  FIG. 5 . As shown, the high relief portion  411  ( FIG. 6A ) and the border portion  412  ( FIGS. 4A-4B ) have been removed from the shaped glass sheet  401  to form the perforated glass sheet  502  defining the opening  506 . In some cases, high relief portions corresponding to other openings may be removed at substantially the same time as the high relief portion  411  (e.g., simultaneously). For example, the tool  600  may be configured to contact all of the high relief areas of a shaped glass sheet at substantially the same time. In one example, the tool  600  is a grinding wheel with a substantially flat or planar axial side that is large enough to substantially simultaneously contact all of the high relief surfaces of a shaped glass sheet. One or more shaped glass sheets (e.g., the shaped glass sheet  401 ) may be placed in contact with the axial side of the grinding wheel until the high relief portions (e.g., the high relief portions  411  and the border portion  412 , and any other high relief portions, such as one corresponding to the first recess  408 ) are removed and the openings are formed. 
     In some cases, the high relief portions are not entirely removed from the shaped glass sheet  401  such that part of the material that defined the high relief portions is left extending from the bottom surface of the perforated glass sheet  502 .  FIG. 6C  is a detail view of the area  602  in  FIG. 6B , illustrating the shape of the opening  506 , where the opening  506  includes some of the unremoved material from the high-relief portion. 
     In particular, the recesses may be at least partially defined by joining segments  407  ( FIG. 4B ) that join the bottom or recessed portion of the recess to the main portion of the sheet  401 . Returning to  FIG. 6C , a portion of the joining segment  407  ( FIG. 4B ) that was not fully removed from the perforated glass sheet  502  forms a wall  604  (which may extend a distance relative to the bottom surface of the glass) that surrounds and extends from the opening  506 . The glass sheet  502  may be a monolithic component that includes the wall  604  (and optionally other walls) as well as the substantially planar portions. 
     The wall  604  defines an interior surface of the opening  506 . That is, the interior surface (or sidewall) of the opening  506  may define at least part of an inner surface  603  of the wall  604 , and an outer or exterior surface  607  of the wall may extend at an angle to the bottom surface of the glass sheet  502  (e.g., the outer surface of the wall may extend substantially perpendicularly from the bottom surface). The wall  604  also defines a top surface  605 . The top surface  605  may be a machined or ground surface, as a result of the removal of the high relief portion  411 . A machined or ground surface may have grooves, channels, cracks, ridges, or other patterns or features formed into the surface as a result of a machining or grinding operation (or any other physical ablation or removal operation). These features or patterns may be substantially regular or repeating, as may occur during a grinding or machining or other physical ablation operation (e.g., when a rotating grinding wheel or oscillating cutting tool is used to cut the material). 
     The wall  604  may increase the strength and/or rigidity of the perforated glass sheet  502 , particularly in the area of the opening  506 . In particular, the wall  604  acts as a stiffening member by increasing the size and/or the second moment of inertia of the perforated glass sheet  502  in the areas of the opening  506 . Similar walls may be formed around any of the apertures or openings that are formed using the described processes. For example, a wall similar to the wall  604  may surround the opening  504  ( FIG. 5 ). 
     In addition to strengthening and/or stiffening the sheet  502 , the walls (e.g., the wall  604 ) around the openings may also make the glass appear thicker than its actual thickness. For example, because the walls defining the openings extend at an angle from a primary surface of the glass sheet (e.g., the glass sheet curves downward around the edge of the opening  506 , as shown in  FIG. 6C ), the height of the walls (e.g., the length of the surface that defines the inner surface of the opening) may be greater than the thickness of the sheet itself. Accordingly, when an opening is viewed so that the walls are visible, the walls may give the appearance that the glass sheet has a thickness corresponding to the height of the walls, rather than the actual thickness of the glass sheet. 
     Also, the slumping process may produce smooth, rounded contours at the edges of the openings without requiring additional machining or polishing processes to form the smooth, rounded contours. For example, when the glass conforms to a recess or a protrusion in a mold, the surface of the glass that is opposite the mold (e.g., that does not contact the mold) may form substantially continuous, rounded edges where the glass relaxes around the mold contours. For example,  FIG. 6C  shows a continuous, rounded edge surface  606  extending between a top surface of  508  of the sheet  502  and the portion of the sheet  502  defining the wall  604 . These rounded edges may be smoother to the touch, thereby providing a more desirable tactile sensation when a user contacts the edges of the openings (e.g., when pressing the button cover  130  to actuate the button input, or when the user places the device  100  to an ear, thus placing the opening  140  near or on the user&#39;s ear). Additionally, the interior and exterior surfaces  603 ,  607  of the wall  604  may be formed and shaped during the molding or slumping process, and thus may not require additional machining or grinding or other bulk material removal processes. In some cases, they may not even require polishing, as the unmachined surfaces may be sufficiently smooth after the molding or slumping process. 
     Because the rounded edges are formed during the slumping process rather than by a machining or grinding operation, the resulting perforated glass sheet  502  may be stronger and/or more durable than perforated sheets formed via other processes. For example, while a rounded edge may be produced by milling, grinding, drilling, or other machining or ablation techniques, these processes may produce cracks (e.g., micro-cracks) or other surface irregularities that act as stress concentration points where larger cracks may initiate. By forming the rounded edges with a slumping operation (or another operation where the glass is allowed to relax and naturally form its outer surface), the rounded or contoured edges may be formed without cracks or other stress concentrators. 
     Regardless of whether the edges of the openings are rounded or contoured, or whether they are defined by discontinuous edges (e.g., right angle edges or corners), the slumping process may produce edges that do not require additional machining to form the edges. Thus, the edge, and indeed the entire inner surface of the opening may be unmachined. For example, the edge and the inner surface may not be milled or drilled to form the opening or to finish the surface. Where the edge and/or inner surface are formed without machining, they may be polished or buffed to produce a desired surface finish. Even in these cases, however, the machining operation that forms the openings may not require or result in contact between the machining tool and the edge or the inner surface. 
     The operation of removing the high relief portions described above with respect to  FIGS. 6A-6B  results in the destruction of the high relief portions of the shaped glass sheet. In some cases, a high relief portion of a shaped glass sheet may itself be useful as a cover for an electronic device or a component thereof. For example, when removing a recessed portion of a shaped glass sheet to form an opening for a button (such as the opening  506 ,  FIG. 5 ), the removed portion of the sheet may be used as a cover for the button. In such cases, a high relief portion of a shaped glass sheet may be removed in a nondestructive process.  FIG. 7A  shows a partial cross-sectional view of the shaped glass sheet  401 , viewed along line  7 A- 7 A in  FIG. 4A , illustrating the sheet  401  at various stages of a process of removing a recessed portion of the sheet  401 .  FIGS. 7B-7C  show partial cross-sectional views of the perforated glass sheet  502 , viewed along line  7 B- 7 B in  FIG. 5 , illustrating the perforated sheet  502  after removal of a recessed portion of the shaped glass sheet  401 . The result of the process shown in these figures is a first cover with an opening (such as the cover  110 ,  FIG. 1 ) and a second cover corresponding to the portion that was removed to form the opening (such as the button cover  130 ,  FIG. 1 ). 
       FIG. 7A  shows the shaped glass sheet  401  with a cut line  701  extending through joining portions  703  that join a high relief portion  710  to a low relief portion  712 .  FIG. 7B  shows the shaped glass sheet  401  after the high relief portion  710  has been separated from the shaped glass sheet  401  along the cut line  701 . The high relief portion  710  may be separated or singulated from the shaped glass sheet  401  in any suitable way, such as with a laser beam, electron beam, water jet, wire saw, cutting tool, or the like. For example, a laser beam may be directed onto the joining portions  703  from the side (e.g., substantially perpendicular to the joining portions  703  and/or substantially parallel with the low relief portion  712 , though other angles are also contemplated). 
     After removal, the high relief portion  710  may be further processed, such as by removing the outer edges of the high relief portion  710  (e.g., the portions of the joining portions  703  that remained attached to the high relief portion  710 ). For example,  FIG. 7B  shows cut lines  702  where the high relief portion  710  may be cut to remove the joining portions  703 . The joining portions  703  may be removed from the high relief portion  710  in any suitable way, such as with a laser beam, electron beam, water jet, machining tool, or the like. 
     The high relief portion  710  may be shaped so that it fits in the opening  506  that was created by the removal of the high relief portion  710 . For example, where the opening  506  is adjacent or overlies an input device (e.g., the input device  204 ,  FIG. 2A ), the high relief portion  710  may be used to form a cover for the input device that fits within the opening  506  (e.g., the button cover  130 ,  FIGS. 1-2 ).  FIG. 7C  shows a cover  706  that is formed from the high relief portion  710  and is configured to fit within the opening  506 . Thus, when the perforated glass sheet  502  is coupled to a housing and the cover  706  is coupled to an input device, the cover  706  may be positioned within the opening  506 . The cover  110  and the button cover  130  of  FIGS. 1-2  may correspond to the perforated glass sheet  502  and the cover  706  described with respect to  FIG. 7C . In some cases, instead of using the glass from the aperture to use as a button cover inside the aperture, the button cover  130  may be formed from a separate sheet than the cover  110 . For example,  FIGS. 9-20C  show an example in which multiple button covers are formed on a single sheet, where the remaining portion of the sheet is not used as a cover for an electronic device. 
       FIGS. 3-5  describe forming a contoured glass sheet by allowing the glass sheet to relax into a mold with recesses that correspond to recesses to be formed in the glass sheet. However, recesses may also be formed using a mold that has protrusions, where the protrusions form the recesses in the glass sheet (e.g., the glass sheet relaxes around the protrusion of the mold).  FIGS. 8A-8B  illustrate an example process for forming a glass cover, such as the cover  110 , for an electronic device, where the recesses in the glass are formed by mold protrusions, rather than mold recesses. 
       FIG. 8A  shows a glass sheet  800  positioned over a shaped mold  802 . As shown, the glass sheet  800  is substantially planar and has a substantially uniform thickness. The shaped mold  802  includes a first protrusion  804  and a second protrusion  806 . The first protrusion  804  may be configured to produce a recess or indentation in the glass sheet  800  that will ultimately be removed to form an aperture or opening (e.g., the opening  120 ,  FIGS. 1-2 ) for a button cover, while the second protrusion  806  may be configured to produce a recess or indentation in the glass sheet  800  that will ultimately be removed to form an opening for a speaker or other audio component (e.g., the speaker  206 ,  FIG. 2A ). The shaped mold  802  may also have a flange region  809  that forms a flange or border region on the glass sheet  800 . Thus, the shaped mold  802  may form a shaped glass sheet  801  ( FIG. 8B ) that has the same or similar shape as the shaped glass sheet  401  formed by the shaped mold  302 . 
     The shaped glass sheet  801  may be further processed to remove at least part of the recesses  808 ,  810  to form openings, such as the openings  506 ,  504  ( FIG. 5 ) in the shaped glass sheet  801 . For example, the recesses may be machined, ground, cut, or otherwise removed from the remaining portion of the shaped glass sheet  801 , as described with respect to  FIGS. 6A-7C  (or in any other suitable manner). 
     The forming process described with respect to  FIGS. 3-5  may be used to produce a cover where the exterior or interface surface was not in contact with the shaped mold  302  during a molding or slumping operation. On the other hand, the exterior surface of a cover formed by the process described with respect to  FIGS. 8A-8B  may have been in contact with the surface of the mold  802 . In the latter case, the surface of the mold  802  that contacts the glass to form the exterior surface of the cover may have a particular surface polish, finish, or texture that will be replicated on the exterior surface of the cover. 
       FIGS. 3-8B  illustrate recesses and openings having particular shapes. For example, the first recesses  408 ,  808  (and the corresponding openings) and the second recesses  410 ,  810  (and the corresponding openings) are substantially rectangular. These are merely example shapes, however, and other shapes are also contemplated for the openings in a perforated glass sheet and for the covers optionally formed by removing high relief portions from the sheets, such as circles, rectangles, rounded rectangles, ovals, pill- or lozenge-shapes, oblong shapes, or the like. 
     As described above with respect to  FIGS. 7A-7C  button covers may be formed from a piece of glass that was removed from a larger piece of glass when forming an aperture in the larger glass, where the aperture itself surrounds or is aligned with the button or other input device. In other cases, button covers (or covers for other types of input devices) may be formed from a different sheet than the sheet that is used for the cover, or they may be used in devices without a glass cover. For example, multiple button covers may be formed on a single sheet, and the button covers may be singulated from the sheet. The button covers may be used to cover or couple to input devices, while the remaining portion of the sheet may be discarded, or may be destroyed as a result of the singulation and/or further processing of each button cover.  FIGS. 9-20C  show various techniques for forming button covers in this way. Of course, any of the described techniques may be used separately or in conjunction with other techniques, processes, or methods described herein. 
       FIG. 9  illustrates an example molding apparatus that may be used to form a single sheet having multiple protrusions from which multiple glass button covers may be produced. For example, a shaped mold  902  may include a plurality of protrusions  904 . When a glass sheet  910  is molded or slumped against the shaped mold  902 , the protrusions  904  may produce corresponding protrusions in the glass sheet  910 . These protrusions may be removed from the remaining portion of the glass sheet  910 , as described herein, and used as covers for buttons or other input devices (such as the button cover  130 ,  FIG. 1 ). 
     The protrusions  904  of the shaped mold  902  may be configured to produce button or input device covers of any particular shape, and with any particular features. For example, the top surfaces of the protrusions  904  may be concave, such that the corresponding features molded into the glass sheet  910  may also be concave. As another example, if the top surfaces of the protrusions  904  are substantially flat or planar, the corresponding features molded into the glass sheet  910  may also be substantially flat or planar. As shown in  FIG. 9 , the top surface of the glass sheet  910  (e.g., the surface that is not against the shaped mold  902  during molding) may form the exterior or user-facing surfaces of the glass button covers. Thus, a concave top surface of the protrusions  904  will produce a concave user-facing surface in the corresponding glass button cover. The shaped mold  902  may form such features in the glass sheet  910  by contacting substantially the entire bottom surface of the glass sheet  910 , thereby transferring the shape of the shaped mold  902  to the glass sheet  910 . 
     As noted above, in some cases a glass button cover may optionally include a raised feature  121  ( FIG. 1 ). In such cases, the protrusions  904  may have mold features  906  that are configured to form a raised feature in the glass sheet  910  (and ultimately to form the raised feature of a button cover).  FIG. 9  shows some protrusions  904  that lack the mold features  906 , and others that include the mold features  906 . In other examples, the protrusions  904  may all have the mold features  906  (e.g., all button covers produced therefrom will have the raised features), or they may all exclude the mold features  906  (e.g., no button covers produced therefrom will have the raised features). 
     The molding apparatus shown in  FIG. 9  may also include a top mold  920 . The top mold  920  may be used to apply pressure to the glass sheet  910  during the molding process. As shown, the top mold  920  may be a partial mold that includes web portions  922  defining openings  924 . The web portions  922  may be aligned with the recessed areas between the protrusions  904  of the shaped mold  902 , and may force portions of the glass sheet  910  into the recessed areas during molding. This process, depicted in greater detail in  FIGS. 10A-10C , may help mold the glass sheet  910  onto and around the protrusions  904 , thereby producing more consistent shapes and helping force the glass sheet  910  into intimate contact with the shaped mold  902 . 
     Further, the webbed design of the partial top mold  920  increases the molding pressure between the glass sheet  910  and the shaped mold  902  without contacting the top surface  912  on the portions that form the top or user-facing surfaces of the button covers. This may help avoid imparting any textures or imperfections, which may be present in a top mold, into the user-facing surface of the button covers. This may also help maintain a desired structural or cosmetic surface on the button covers, and reduce or eliminate other processing steps such as polishing or machining that may otherwise be required to remove textures or other remnants of a top mold. 
     While  FIG. 9  shows a molding apparatus that will produce a sheet with a 2×2 grid or array of button covers, this is merely exemplary, and the molding apparatus may instead be configured to produce sheets with more button covers, such as a 3×3 grid, 4×4 grid, 5×5 grid, or any other arrangement or quantity of button covers. 
       FIG. 10A  depicts a cross-sectional view of the molding apparatus of  FIG. 9 , viewed along line  10 A- 10 A in  FIG. 9 .  FIG. 10A  shows how the shaped mold  902  and the top mold  920  cooperate to mold protrusions  1004 ,  1006  into the glass sheet  910 . For example, the top mold  920  may contact the glass sheet  902  in a region between the protrusions  904  of the shaped mold  902  (e.g., it may contact what becomes a web portion of the glass sheet). The pressure of the top mold  920  on the web portion of the glass sheet  910  may help pull the glass sheet  910  against the shaped mold  902 , thus increasing the quality of the replication of the shape of the shaped mold  902  in the glass sheet  910 . 
     Further, while the top mold  920  does not contact the entire top surface of the glass sheet  910 , the top mold  920  (e.g., the web portions  922  of the top mold) effectively increases the tension in the glass sheet  910 , which helps draw the glass sheet  910  into close contact with the top and side surfaces of the protrusions  904 . This additional force or tension may also help form consistent corner features or shapes in the glass sheet  910 . For example, the additional force and stretching caused by the top mold  920  (as compared to a slumping or molding process without a top mold) may cause an edge region  1005  of the glass sheet  910  to form a target radius, spline, or other contour, even without any mold surface actually contacting the exterior or top surface of the edge region  1005 . 
     As noted above, the protrusions  906  are configured to form raised features  1008  in the glass sheet  910 . The additional force provided by the top mold  920  may also increase the quality or consistency of replication of the protrusions  906  in the glass sheet  910 , as the glass sheet  910  may be forced to more intimately contact the protrusions  906  and thus form a more distinct raised features  1008  (as compared to a slumping or molding process without a top mold, for example). 
     The top mold  920  thus may increase the quality of replication of the shaped mold&#39;s features into the glass sheet  910 . Because the top mold  920  does not contact the external (e.g., top) surface of the protrusions  1004 ,  1006 , these surfaces may avoid being marred, shaped, textured, or otherwise affected by a mold surface. Further, because the glass sheet  910  is heated during the molding process, the absence of a top mold in contact with these surfaces may allow these surfaces to form smooth, continuous surfaces. These surfaces may require less post-processing (e.g., grinding, machining, lapping, polishing) to achieve a desired surface finish than molding processes that directly contact the surfaces. In some cases, the surface may be sufficiently smooth after the molding process that no further polishing of the user-facing surfaces (e.g., top, side, and edge surfaces) is necessary prior to a button cover being integrated with an input device or electronic device. 
     In some cases, the shaped mold  910  may also include vacuum lines  1002  in the mold  910 . Together with a vacuum source, the vacuum lines  1002  may draw the glass sheet  910  against the molding surface of the shaped mold  910  to conform the glass sheet  910  to the features of the shaped mold  910 . In some cases, the area above the glass sheet  910  may be pressurized to produce a greater pressure differential on the opposite sides of the glass sheet  910 . In such cases, the vacuum source may be omitted or used in conjunction with pressurization on the top surface of the glass sheet  910 . For example, any pressure differential between the top and bottom surfaces of the glass sheet  910  may force the glass sheet  910  against the molding surface of the shaped mold  910 . 
     As described above, the glass sheet  910  may be heated prior to being molded by the shaped mold  902  and the top mold  920 . For example, the glass sheet  910  may be heated (e.g., in a furnace, by flame, or any other suitable technique) and then placed on the shaped mold  902  and subjected to molding forces (e.g., by gravity, vacuum, pressure differential, the top mold  920 , etc.) to produce a shaped glass sheet. 
       FIG. 10B  depicts a cross-sectional view of another molding apparatus, similar to that shown in  FIG. 9 . Instead of a top mold with a web configuration and openings that correspond to the mold protrusions  904 , the top mold  1010  in  FIG. 10B  forms an enclosed mold cavity. For example, the top mold  1010  includes protrusions  1014 , which provide the same or similar functions as the web portions  922  of the top mold  920 , as described above. The top mold  1010  also includes top walls  1015  spanning the areas between the web portions  922  and defining an enclosed mold cavity. The top walls  1015  may be recessed relative to the protrusions  1014  such that the top walls  1015  do not contact the glass sheet  910  during the molding process, instead leaving a space  1012  above the glass sheet  910 . As such, while the top mold  1010  fully encloses or covers the glass sheet  910  (or at least the portions of the glass sheet  910  that are being formed to produce the button covers). This may allow for greater pressure control inside the mold during molding. For example, the top mold  1010  may include air lines  1016 , which may be used to increase (or decrease) the pressure on the top side of the glass sheet  910  to produce a pressure differential on the opposing sides of the glass sheet  910  to force the glass sheet  910  into intimate contact with the shaped mold  902 . 
       FIG. 10C  depicts a cross-sectional view of another molding apparatus, similar to that shown in  FIG. 9 , but with a top mold  1020  that is configured to substantially completely contact the glass sheet  910  during molding. For example, the top mold  1020  may be complementary to the shaped mold  902 , having web portions  1026  and recessed portions  1024  that both contact the top surface of the glass sheet  910  during molding. The top mold  1020  also includes a complementary recess  1028 , corresponding to the protrusion  906 , to help form a raised feature on the glass sheet  910  (e.g., corresponding to the raised feature  121 ,  FIG. 1 ). 
     The top mold  1020  may be used in cases where it is desired to impart a shape or texture to the top surface of the glass sheet  910  that is not achieved with natural slumping or relaxation of the glass sheet  910  over the shaped mold  902 . For example, without a directly opposing mold surface, the top surface of the glass sheet  910  may not exactly replicate the protrusion  906 . Accordingly, the resulting raised feature may not be adequately distinguished from the adjacent portions of the top surface of the glass sheet  910 . Accordingly, a top mold  1020  may be used to impart a desired shape to the raised feature, as well as any other portion of the glass sheet  910 . 
     As another example, it may be desirable to use the top mold  1020  to impart a particular texture or surface finish to the top surface of the glass sheet  910 . For example, the mold surfaces of the top mold  1020  may be shaped or textured, and those shapes or textures may be imparted to the glass sheet  910 . The textures or shapes may include ridges, pebbling, bumps, or any other suitable texture. Because the top surface of the glass sheet  910  (as depicted in  FIG. 10C ) may form an exterior or user-facing surface of an input device, the texturing or surface finish may be used to form a consistent tactile feel across different input devices on a given electronic device, as well as across input devices of different electronic devices (e.g., so that each smartphone from a particular manufacturer, for example, has a consistent look and feel). 
       FIG. 11  shows another example molding apparatus that may be used to form shaped glass sheets from which multiple button covers may be produced. As shown in  FIG. 11 , a shaped mold  1102  may include a plurality of recesses  1104 , each configured to produce a protrusion on the glass sheet  1110  that will ultimately be formed into a button cover. Thus, the surface of the glass sheet that ultimately becomes the exterior or user-facing surface of the button covers faces is in contact with recesses in the shaped mold  1102 , rather than facing upward and being uncontacted by a mold surface (as described with respect to  FIGS. 10A-10B , for example). 
     The recesses  1104  of the shaped mold  1102  may be configured to produce button covers of any particular shape, and with any particular features. For example, the bottom surfaces of the recesses  1104  may be convex, such that the corresponding features molded into the glass sheet  1110  may be concave (once the features are singulated and formed into button covers). As another example, if the bottom surfaces of the recesses  1104  are substantially flat or planar, the corresponding features molded into the glass sheet  1110  may also be substantially flat or planar. 
     As noted above, in some cases a button cover may optionally include a raised feature  121  ( FIG. 1 ). In such cases, the recesses  1104  may have mold features  1106  (e.g., recesses in the bottom surface that defines the recess  1104 ) that are configured to form a raised feature in the glass sheet  1110  (and ultimately to form the raised feature of a button cover).  FIG. 11  shows some recesses  1104  that lack the mold features  1106 , and others that include the mold features  1106 . In other examples, the recesses  1104  may all have the mold features  1106  (e.g., all button covers produced therefrom have the raised features), or they may all exclude the mold features  1106  (e.g., no button covers produced therefrom have the raised features). 
     The molding apparatus shown in  FIG. 11  may optionally include a top mold  1120 . The top mold  1120  may be used to apply pressure to the glass sheet  1110  during the molding process. As shown, the top mold  1120  has protrusions  1122  that correspond to and/or are aligned with the recesses  1104  in the shaped mold  1102 . The protrusions  1122  may be configured to force portions of the glass sheet  1110  into the recesses  1104  during molding. This process, depicted in greater detail in  FIG. 11 , may help mold the glass sheet  1110  into the recesses  1104 , thereby producing more consistent shapes and helping force the glass sheet  1110  into intimate contact with the shaped mold  1102 . In some cases, however, the top mold  1120  may be omitted, and the glass sheet  1110  may be allowed to relax and slump against the shaped mold  1102  and into the recesses  1104  either without additional force (e.g., using only gravity), or using only fluid pressure differential (e.g., a vacuum system in the shaped mold  1102  and/or increased pressure on the opposite side of the mold). 
     While  FIG. 11  shows a molding apparatus that will produce a sheet with a 2×2 grid or array of button covers, this is merely exemplary, and the molding apparatus may instead be configured to produce sheets with more button covers, such as a 3×3 grid, 4×4 grid, 5×5 grid, or any other arrangement or quantity of button covers. 
       FIG. 12  depicts a cross-sectional view of the molding apparatus of  FIG. 11 , viewed along line  12 - 12  in  FIG. 11 .  FIG. 12  shows how the shaped mold  1102  and the top mold  1120  cooperate to mold protrusions  1105  into the glass sheet  1110 . The protrusions  1105  may appear as recesses in  FIG. 12  because the glass sheet  1110  is essentially being molded upside down as compared to  FIGS. 9-10C , for example. Nevertheless, for consistency in the description and because the bottom surface of the glass sheet  1110 , as shown in  FIG. 12 , forms the exterior, user facing surfaces of the button covers (e.g., the top and side surfaces), the protrusions  1105  are referred to herein as protrusions instead of recesses. 
       FIG. 12  shows the protrusions  1122  of the top mold  1120  in contact with the glass sheet  1110 , forcing the glass sheet  1110  into intimate contact with the recesses  1104  of the shaped mold  1102 . In cases where raised features are to be formed in the glass sheet  1110 , the protrusions  1122  may include complementary protrusions (e.g., the protrusion  1203 ) that force the glass into the recess  1106  that forms the raised feature. 
     As shown, the top mold  1120  may be configured so that parts of the mold do not contact the glass sheet  1110 . For example, the top mold  1120  may include recesses or channels that form spaces  1202  above the glass sheet  1110  during molding. The spaces  1202  between the protrusions  1122  may reduce the strain or force on the glass sheet  1110  during molding. 
     In order to assist in shaping the glass sheet  1110 , the shaped mold  1102  and the top mold  1120  may include vacuum lines  1205 ,  1206 , respectively. The vacuum lines  1205 ,  1206  may be used to increase or decrease a fluid pressure on the glass sheet  1110  to help force the sheet  1110  into contact with desired portions and/or surfaces of the molds. 
     While  FIG. 12  shows the shaped mold  1102  being used in conjunction with a particular top mold  1120 , other configurations of top molds may also be used. For example, a top mold that substantially entirely contacts the top surface of the glass sheet  1110  may be used. In other cases, the top mold may be omitted altogether. 
       FIGS. 13A-13B  illustrate a shaped glass sheet  1300  that may result from molding a glass sheet using the apparatuses and techniques described with respect to  FIGS. 9-12 .  FIG. 13A  shows the shaped sheet  1300  in perspective view, and  FIG. 13B  shows a cross-sectional view of the sheet  1300 , viewed along line  13 B- 13 B in  FIG. 13A . The sheet includes protrusions  1302  and  1304  extending above a web portion  1305 , with the protrusions  1304  each having a raised feature  1306 . The protrusions  1302 ,  1304  may be removed from the shaped glass sheet  1300  (or simply “sheet  1300 ”) to form button covers (or covers for other types of input devices).  FIGS. 14A-16C  illustrate example techniques for singulating the protrusions  1302 ,  1304   
       FIG. 14A  shows the sheet  1300  being subjected to a singulating process in which the protrusions  1302 ,  1304  are removed with a wire saw ( 1402  or  1404 ). In particular, a wire saw, which may be a wire coated with an abrasive such as diamond particles, may be moved through the sheet  1300  in a direction that is substantially parallel to the plane of the sheet  1300 .  FIG. 14B , which shows a cross-section of  FIG. 14A  viewed along line  14 B- 14 B in  FIG. 14A , shows example paths  1406 ,  1408  of a wire saw through the sheet  1300 . Each path  1406 ,  1408  may effectively singulate the protrusions  1302 ,  1304  from the web portion  1305 . The path  1406  may remove some of the bottom of the protrusions  1302 ,  1304 , while the path  1408  may not contact or traverse through the protrusions  1302 ,  1304 , but instead cut through a joining portion  1410  that extends from the web portion  1305  to the main portion of the protrusions  1302 ,  1304 . 
     Returning to  FIG. 14A , a wire saw may be traversed through the material of the sheet  1300  along various possible directions. For example, a first wire saw  1404  is shown being moved perpendicularly to a straight or linear side of the protrusions  1302 ,  1304 . As another example, a second wire saw  1402  is shown being moved at an angle relative to the straight side of the protrusions  1302 ,  1304 . More particularly, the wire saw  1402  is moved so that it enters the sheet  1300  at a corner of one of the a protrusions  1302 . Moving the wire saw  1402  in this direction may reduce the number of times that the wire saw  1402  must exit and re-enter the material of the sheet  1300  while singulating the protrusions of the sheet  1300 . This may reduce stress on the cutting wire, the sheet  1300 , and the individual protrusions being singulated, as the tension and shape of the wire may not vary as significantly throughout the cutting process as compared to a perpendicular cutting direction. This angled cutting technique may also reduce chipping, breakage, and other damage to the protrusions  1302 ,  1304  and the cutting wires. 
       FIG. 15  illustrates another singulating process for the sheet  1300 . More particularly,  FIG. 15  shows how the protrusions  1302 ,  1304  may be singulated by cutting around the protrusions along a direction that is substantially perpendicular to the plane defined by the sheet  1300 . For example, a cutting tool (e.g., wire saw, milling bit, cutting wheel, scribe, etc.) or cutting beam (e.g., laser beam, plasma beam, etc.) may be directed onto the sheet  1300  and along the paths  1502  around the protrusions  1302 ,  1304  to singulate the protrusions from the sheet  1300 . 
       FIGS. 16A-16C  illustrate the singulated protrusions at various stages of processing after singulation.  FIG. 16A , for example, shows a cross section of a singulated protrusion  1600  (corresponding to the protrusion  1302 , for example). The singulated protrusion  1600  defines a top surface  1604 , a bottom surface  1605 , and joining portions  1602  (corresponding to the joining portion  1410 ,  FIG. 14 ). Where a singulating process removes the joining portions  1602 , and optionally part of the bottom of the protrusion  1600 , the singulated protrusion may instead resemble the button cover  1607  shown in  FIG. 16B  immediately after singulation. Also, as noted above, the top surface  1604  may correspond to the exterior or user-facing surface of a button cover, and may be a molded surface. In particular, the top surface  1604  may have a desired shape and surface texture or polish after molding and without machining, grinding, lapping, polishing, and/or other processing. In other cases, only a polishing step is required to produce a final surface finish on the top surface  1604 . Similarly, the side surfaces  1603  (and the spline or edge  1601  where the top surface  1604  meets the side surfaces  1603 ) may have a desired shape, texture, or polish after molding and without further processing (e.g., without machining). Thus, the surfaces of the button cover  1607  that are or may be exposed to a user may be fully formed by the molding and/or slumping process. Moreover, because the top and side surfaces  1604 ,  1603  of the button cover  1607  are molded, they may not have sharp or defined apices at the edges where the top surface  1604  meets the side surfaces  1603 . By contrast, where the top and side surfaces of glass button covers are formed or shaped by cutting, machining, and/or grinding the glass material, the button covers may have edges with sharp or well defined apices, which may be unattractive, prone to chipping, and may risk accidentally cutting or scraping users. In such cases, the edges (and optionally the top and side surfaces) may be dulled, machined, shaped, or otherwise dulled. 
     Returning to  FIG. 16A , after singulation, the joining portions  1602  may need to be removed from the singulated protrusion  1600  (e.g., where the singulating operation does not fully remove the joining portions). Optionally, some of the bottom surface of the singulated protrusion  1600  may also be removed to produce the desired thickness and shape of the resulting button cover. Removing the joining portions  1602  and the portion of the bottom surface of the singulated protrusion  1600  (e.g., up to the line  1606 ) may be achieved by any suitable process, including lapping, machining, grinding, or the like. After removing the joining portions  1602  and forming the bottom surface, the singulated protrusion  1600  may be subjected to a polishing step in which the bottom surface is polished to produce a desired surface polish or texture. The polishing process may remove or mitigate scratches, cracks, or other damage caused by the removal of the joining portions  1602  and any optional grinding or lapping of the bottom surface of the singulated protrusion  1600 . 
     After the joining portions  1602  are removed and the bottom surface is polished to a desired surface roughness, the singulated protrusion may resemble the button cover  1607  shown in  FIG. 16B . The button cover  1607  defines a top surface  1604 , which may be a user-facing surface having a shape that was defined by a mold surface or by the natural slumping of the glass material over the mold (as described above with respect to  FIGS. 9-12 , for example). As shown, the top surface  1604  defines a concave shape, which may provide a smooth, contoured, attractive interface surface to a button or other input device. The button cover  1607  also defines a bottom surface  1608 , which may be substantially planar and suitable for coupling to a sub-structure of a button or other input device. As noted above, the bottom surface  1608  of the button cover may be a machined surface. For example, the bottom surface  1608  may be formed (and made substantially planar, or any other suitable shape) by any combination of wire cutting, lapping, polishing, machining, grinding, or the like. As noted above, a surface that is machined or ground (or otherwise subjected to a physical material removal operation) may have grooves, channels, cracks, ridges, or other patterns or features formed into the surface. These features or patterns may be substantially regular or repeating. 
     The button cover  1607  may have any suitable dimensions. For example, at the outer edges or outer region, the button cover  1607  may have a thickness between about 0.5 mm and about 1 mm, or between about 0.6 mm and about 0.75 mm. At the center or central region, the button cover  1607  may have a thickness between about 0.3 mm and about 0.6 mm, or between about 0.4 mm and about 0.55 mm. Of course, other thicknesses are also possible. 
     In some cases, the button cover  1607  may be subjected to further processing to change the shape of one or more of the edges. For example, the top edges  1611  and/or the bottom edges  1612  may be chamfered or rounded with additional machining or other material removal process(es). The chamfered or rounded edges may be less prone to chipping, cracking, or other damage than a raw edge. In some cases, only edges that are formed or affected by a machining or lapping process are chamfered or rounded. For example, as noted above, the top edges  1611  may be fully shaped by molding or slumping, without further post processing such as grinding or lapping, and thus may not form an edge with a sharp apex. On the other hand, a lapping or grinding process applied to the bottom of the button cover  1607  may result in an edge with a sharp apex. The rounding or chamfering may thus be applied to the bottom edges  1612  to remove or dull the apex. 
       FIGS. 17A-20C  relate to another technique for forming glass covers for buttons or other input devices. In particular,  FIGS. 17A-20C  relate to a process in which grooves are formed in a glass sheet to define an array or group of protrusions, and a mold or press is applied to the protruding regions to impart a shape and optionally a texture to a top surface of the protrusions. The shape of the molding apparatus, and thus the shape of the top surfaces of the protrusions, may correspond to a target shape for a button cover, or a cover of any other suitable type of input device. After the shaping, the protrusions may be singulated from the sheet and further processed to remove excess material and ultimately produce final glass button covers. 
       FIG. 17A  shows a glass sheet  1700  prior to having grooves formed therein. The glass sheet  1700  may be similar to any of the glass sheets described herein, and may be substantially planar and featureless. A grinding tool  1702  may be applied to the top surface  1703  of the glass sheet  1700  to form a pattern of grooves or recesses that define protrusions. The grinding tool  1702  is only shown as a grinding wheel for simplicity of illustration, and it instead may be any other suitable tool, such as an end mill, a wire saw, or the like. Other types of tools or processes may be used to form the grooves, such as laser etching, plasma etching, or the like. 
       FIG. 17B  shows the glass sheet  1700  after the grinding tool  1702  has formed grooves  1706  in the top surface  1703  of the glass sheet  1700 . The grooves may define protrusions  1704 , which may have a shape that substantially corresponds to the shape of the button covers that are to be formed from the glass sheet  1700 . For example, as shown in  FIG. 17B , the protrusions  1704  (and thus the button covers produced from the protrusions  1704 ) may be substantially square. More particularly, they may have a substantially square outer perimeter. Other shapes are also possible, such as circles, rectangles, or any other suitable shape. 
       FIG. 18A  shows a cross-sectional view of the glass sheet  1700 , viewed along line  18 A- 18 A in  FIG. 17B . The glass sheet  1700  may have any suitable thickness such as between about 1.0 mm and about 3.0 mm. As shown, the grooves  1706  extend only partly through the sheet  1700 . The grooves  1706  may be any suitable depth, such as about 250 microns to about 1.0 mm, and the protrusions  1704  may have any suitable width, such as between about 250 microns to about 1.0 mm. Other dimensions are also possible. Because the protrusions  1704  are not formed by slumping or molding a glass sheet over a mold (as described above), the cross-section of the glass sheet  1700  after the grooves  1706  are formed may be different than that of a slumped or molded glass sheet. For example, the thickness of a shaped glass sheets that is molded or slumped (e.g., the shaped glass sheet  1300 ,  FIG. 13A ) may be substantially continuous or equal at different locations of the glass sheet, and the protrusions on one side of the molded or slumped sheet may have complementary recesses on the opposite side. By contrast, the protrusions in the glass sheet  1700  may not correspond to or be formed in part by recesses in the opposite surface, and the thickness of the sheet  1700  varies due to the machined or ground grooves  1706 . 
     The grooves  1706  formed in the glass sheet  1700  may serve several functions. For example, the grooves  1706  may substantially define the shape of at least the top surfaces of the button covers that are to be formed from the glass sheet  1700 . Further, as shown in  FIGS. 18A-18B , the grooves may provide a relief area into which glass may flow or extend when a mold or press is applied to the top surfaces of the protrusions  1704  to impart a shape (e.g., a concave shape) to the protrusions and thus produce a desired shape for the user-facing surface of the button covers. 
       FIGS. 18A-18B  illustrate an example process in which a press  1800  is applied to the top surfaces of the protrusions  1704  to impart a desired shape to the protrusions  1704 . As noted above, one advantageous shape for a button cover is a concave shape that may feel comfortable when pressed by a user&#39;s finger. Accordingly, the press  1800  may have press surfaces  1802 ,  1804  with convex shapes that will, when pressed against the glass sheet  1700  (after the sheet is heated, for example), form complementary concave shapes in the top surfaces of the protrusions  1704 . The press surfaces may also include other shapes, contours, or features that may form complementary features on the top surfaces of the protrusions  1704 . For example, as noted above, raised features may be included on the surfaces of button covers to provide a tactilely perceptible feature that a user may easily detect with a finger. The press surface  1804  includes a recess  1806  that is configured to form a raised feature (e.g., the raised feature  121 ,  FIG. 1 ) on the glass sheet  1700 . 
       FIG. 18B  shows the press  1800  in contact with the glass sheet  1700 . The glass sheet  1700  may have been heated prior to the press  1800  being applied, such as in a furnace, with a flame, or using any other suitable technique. Alternatively, the glass sheet  1700  may be heated by the press  1800  itself as the press  1800  is applied to the glass sheet  1700 . The press surfaces  1802 ,  1804  imprint a concave shape into the protrusions  1704 , thus forming a top surface with a desired or target shape (and optionally forming the raised feature with the recess  1806 ). During the pressing or forming process, some of the glass of the protrusions  1704  may be forced outward, around the periphery of the protrusions  1704  and into the grooves  1706 . For example, excess material  1808  may be forced outward due to the force from the press  1800 . If the grooves  1706  were not present, the glass sheet  1700  may be deformed in a different way, which may make further processing inconvenient or difficult. For example, if a glass sheet without grooves were used, the force of the press  1800  may cause the glass to bubble or dome upwards in the regions between the presses, which may make singulation and further processing more difficult. Also, glass without the grooves  1706  may not take on and maintain the shape of the press surfaces  1802 ,  1804  as well as glass with the grooves  1706 . 
     In some cases, after the press  1800  imparts a desired shape to the protrusions of a glass sheet (e.g., the glass sheet  1700 ), the shaped protrusions may be further processed or shaped. For example,  FIG. 19  shows the glass sheet  1700  undergoing a process in which the sides of the protrusions  1704  are machined or otherwise processed to round the corners of the protrusions. For example, a machining tool  1902  (e.g., an end mill) may be traversed along the corners and/or sides of the protrusions  1704  to round the corners of the protrusions  1704  (as shown on the protrusion  1704  in the lower left of  FIG. 19 ). 
     The machining tool  1902  may extend to any suitable depth in the glass sheet  1700 . For example, the machining tool  1902  may extend just to the bottom of the grooves  1706 . In other examples, the machining tool  1902  may extend past the bottom of the grooves  1706 , effectively forming deeper channels. In yet other examples, the machining tool  1902  may extend to a depth that is less than the depth of the channels. The depth to which the machining tool  1902  extends may depend at least in part on the target thickness for the button covers being produced from the glass sheet  1700 . For example, the machining tool  1902  may extend to or only slightly beyond the depth that corresponds to a target thickness of the button covers. 
     In some cases, instead of or in addition to rounding the corners of the protrusions  1704 , the machining tool  1902  removes all or some of the excess material  1808  formed during the pressing process. In such cases, the machining tool  1902  may be positioned so as to remove only the excess material  1808 , leaving the grooves  1706  having substantially the same thickness (and substantially parallel and planar sidewalls) as the grooves  1706  after their initial formation. In other cases, the machining tool  1902  removes more material, leaving the grooves  1706  wider than their initial size, and reducing the overall dimensions of the protrusions  1704  (and thus producing smaller button covers). 
     After the pressing operation ( FIG. 18B ), and optionally after further machining operations ( FIG. 19 ), the button covers may be singulated from the glass sheet  1700 .  FIGS. 20A-20C  illustrate an example singulation process for the glass sheet  1700 . As shown in  FIG. 20A , the glass sheet  1700  may be mounted to a support structure or fixture  2002  and positioned relative to wire saws  2004 . The wire saws  2004  may be aligned with the grooves  1706 , or otherwise positioned so that the wire saws  2004  form an edge or side of a button cover. That is, the wire saws  2004  may be configured to cut the button covers to their target peripheral dimensions. In some cases, a single wire is used along each groove, such that one side of a cutting wire cuts a side of one protrusion, and an opposite side of the cutting wire cuts a side of a second, adjacent protrusion. In other cases, multiple wires are used along each groove, with a first wire cutting a side of one protrusion, and a second wire cutting a side of a second, adjacent protrusion. Further,  FIG. 20A  shows a series of cutting wires  2004 , such that multiple parallel cuts may be made in the glass sheet  1700  substantially simultaneously. In other cases, fewer wire saws  2004  may be used, and cuts may be made serially. Either or both of the wire saws  2004  and the fixture  2002  may be moved to bring the wire saws  2004  and the glass sheet  1700  into contact with one another, thus separating the glass sheet  1700  into at least two segments  2008 . 
       FIG. 20B  shows the glass sheet  1700  after cutting by the wire saws  2004  in  FIG. 20A . In particular, the glass sheet  1700  has been separated into two segments  2008 . As shown in  FIG. 20B , an additional series of wire saws  2006  (which may be the same saws as shown in  FIG. 20A , with either the fixture  2002  or the wires saws  2004  rotated ninety degrees) above the two segments  2008 . The wire saws  2006  may be oriented substantially perpendicularly to the wire saws  2004  in  FIG. 20A  to produce substantially perpendicular cuts on the two segments  2008  of the glass sheet. As described above, either or both of the wire saws  2006  and the fixture  2002  may be moved to bring the wire saws  2006  and the glass sheet  1700  into contact with one another. 
     After the additional cutting process shown in  FIG. 20B , the individual button covers may be formed.  FIG. 20C  shows the glass sheet after the cutting process in  FIG. 20B , with four separated button covers  2010  still attached to the fixture  2002 . The button covers  2010  may have exterior peripheral dimensions that are substantially equal to the target dimension. For example, additional machining or forming process may not be necessary, after the singulation steps in  FIGS. 20A-20B , to produce the target peripheral size. In cases where further machining or processing is required to form the peripheral shape of the button covers, such processing may occur while the button covers  2010  are still attached to the fixture  2002 . (The glass sheet  1700 , and thus the button covers  2010 , may be attached to the fixture in any suitable way, such as with adhesive, wax, cement, mechanical retention features, or the like.) 
       FIGS. 21A-21B  show example button covers produced using the techniques described with respect to  FIGS. 17A-20C , after singulation and optional post processing (e.g., polishing, machining, chamfering, lapping, etc.).  FIG. 21A  shows an example button cover  2100  having a contoured (e.g., concave) top surface  2102 , formed at least in part by a press, such as the press  1800 ,  FIG. 18A . The button cover  2100  may have substantially straight sides  2104  that join other sides at corners  2106  having defined apices (e.g., sharp corners). The sides  2104  and apices may be formed as a result of a singulation process. For example, where wire saws are used to singulate button covers from a sheet, as described with reference to  FIGS. 20A-20C , the wire saws may produce sharp corners as a result of the cutting action of the wires. As noted above, further processing (e.g., polishing) may be performed on the sides  2104  and corners  2106  to slightly dull the edges formed by the cutting process, which may help reduce danger to user&#39;s fingers and also mitigate micro-cracks or other imperfections that may have been produced during cutting. 
       FIG. 21B  shows another example button cover  2110  that may be produced using the techniques described with respect to  FIGS. 17A-20C . In particular,  FIG. 21B  shows an example button cover  2110  having a contoured (e.g., concave) top surface  2112 , formed at least in part by a press, such as the press  1800 ,  FIG. 18A . The button cover  2110  may have sides  2114  that join other sides at corners  2116 . While the button cover  2100  in  FIG. 21A  has sharp corners, a top portion of each of the corners  2116  in  FIG. 21B  has been rounded or contoured, such as with the machining process described with respect to  FIG. 19 . As shown, the rounded portion does not extend a full height of the corners  2116 , but instead only extends only part way towards the bottom surface of the button cover  2110 , thus forming ledges  2118  where the top portions of the corners  2116  (e.g., the rounded portions) meet the bottom portions of the corners  2116  (e.g., the portions that have sharp edges or well-defined apices). This configuration may result from a machining step (e.g., as described with respect to  FIG. 19 ) in which the machining tool only rounds the corners to less than the complete thickness of the final button cover. 
     In some cases, the ledges  2118  may be used to help retain the button cover to an electronic device, and may provide an upstop that defines or sets the maximum travel of the button (or other input device). For example, if the button cover  2110  were used as the button cover  130  in  FIG. 1 , the ledges  2118  may be below the cover  110  and, and a biasing force (e.g., from a collapsible dome beneath the button cover  2110 ) may force the ledges  2118  into contact the bottom surface of the cover  110 . In other cases, the button cover  2110  may be incorporated with an electronic device or input device such that the ledges  2118  are visible (e.g., they do not overlap with a bottom surface of a cover). 
       FIGS. 3-21C  refer generally to covers and/or button covers for a handheld electronic device, such as a smartphone. However, the processes and principles for forming those covers may also be used to make covers for other electronic devices or input devices. For example,  FIG. 22  shows an example of another electronic device  2200  that may include a glass cover formed in accordance with the ideas described herein. In the illustrated embodiment, the electronic device  2200  is implemented as a laptop or notebook computer. The electronic device  2200  includes a housing  2204  and a display  2202  within and/or coupled to the housing  2204 . The electronic device  2200  may also include a touch- and/or force-sensitive input device, such as a trackpad  2208 , within and/or coupled to the housing  2204 . The trackpad may be positioned in an opening in a top cover  2206 . The top cover  2206  may be formed from or include any material, such as glass, metal, or the like. The top cover  2206  may also define a plurality of openings in which keys or keycaps may be disposed. The top cover  2206  may be formed in any suitable way, such as using the techniques described herein. 
     The trackpad  2208  may receive and/or detect inputs, such as touches, taps, gestures, and the like, and may include a cover  2210  that defines an exterior or interface surface of the trackpad  2208 . The cover  2210  may be formed from or include a glass material, and may be formed in a manner similar to the covers described above (e.g., the cover  110  or the button cover  130 ). 
       FIG. 23  shows a partial cross-sectional view of the electronic device  2200 , and more particularly the trackpad  2208 , viewed along line  23 - 23  in  FIG. 22 . The trackpad  2208  includes a touch sensor  2304  positioned below the cover  2210 . The touch sensor  2304  may include various components for detecting touch inputs applied to the cover  2210 . For example, the touch sensor  2304  may include capacitive sensing layers, resistive sensing layers, inductive sensing layers, filters, shields, dielectric layers, compliant layers (e.g., to allow the cover  2210  to move when a force input is applied), processors, and the like. The cover  2210  may be formed from or include any appropriate material that allows the touch sensor  2304  to sense objects applied to or near the cover  2210 . For example, the cover  2210  may be glass, sapphire, a dielectric, or any other suitable material. 
     The trackpad  2208  may also include one or more force sensors  2302 . In  FIG. 23 , the force sensors  2302  support the cover  2210  at an outer edge of the cover  2210 , though this is merely one example configuration, and many other configurations are possible. For example, force sensors (or force sensing components) may be positioned below a central portion of the cover  2210 , such as under, over, or integrated with the touch sensor  2304 . The force sensors used in the trackpad  2208  (e.g., the force sensors  2302 ) may include components for any suitable force sensing system, such as piezoelectric sensors, strain gauges, capacitive force sensors, optical sensors, and the like. 
       FIGS. 24A-24D  illustrate an example process for forming a glass cover, such as the cover  2210 .  FIG. 24A  shows a glass sheet  2400  positioned over a mold  2402 .  FIG. 24B  shows a shaped glass sheet  2401  formed by molding (e.g., slumping) the glass sheet  2400  over the mold  2402 . The mold  2402  defines a recess  2404 , which produces a corresponding recess  2406  in the shaped glass sheet  2401 . 
       FIG. 24B  shows a cross section of the shaped glass sheet  2400  viewed along line  24 C- 24 C in  FIG. 24B . From the perspective of the bottom of the shaped glass sheet  2401 , the recess  2406  defines a high relief portion  2408  and a low relief portion  2407 . A joining segment  2410  joins the high relief portion  2408  (e.g., the recess) to a border or flange portion  2411 . 
       FIG. 24B  shows a cut line  2412  extending through the joining segment  2410 , indicating where the shaped glass sheet  2401  is cut to singulate the high relief portion  2408  to be used as a cover for the trackpad  2208  ( FIG. 22 ), or a different device. The high relief portion  2408  may be cut along the cut line  2412  using any appropriate tool or technique, such as a laser beam, electron beam, water jet, milling tool, or the like. As shown, the high relief portion  2408  is separated from the low relief portion  2407 , and the low relief portion  2407  is not destroyed (e.g., it is simply cut away from the high relief portion  2408 ). In some cases, the low relief portion  2407  may be machined, ground, or otherwise removed from the high relief portion  2408  by a destructive process, leaving only the high relief portion  2408  (e.g., the recessed portion). 
       FIG. 24C  shows a perforated glass sheet  2414  (corresponding to the low relief portion  2407 ) and a cover  2416  (corresponding to the high relief portion  2408 ), both formed from the shaped glass sheet  2401 . The cover  2416  may be used as a cover for the trackpad  2208 , or for any other electronic device or input device. The perforated glass sheet  2414  may be discarded or it may be used as a cover for an electronic device or input device. For example, the perforated glass sheet  2414  may be used as the top cover  2206  ( FIG. 22 ), and the opening in the perforated glass sheet  2414  may frame or otherwise define an opening for the trackpad  2208  or another input device or mechanism. 
     The cut line  2412  may be positioned such that parts of the joining segments  2410  remain on the cover  2416  when the cover  2416  is singulated from the low relief portion  2407 . This remaining material may form a wall  2418  around the outer perimeter of the cover  2416 . The wall  2418  may be removed from the cover  2416  to form a substantially planar cover  2416 , or it may be left on the cover  2416 . Where the wall  2418  is left on the cover  2416 , it may increase the stiffness of the cover  2416  by acting as a structural web element that reduces bending, flexing, or other deformations of the cover  2416  (e.g., by increasing the second moment of inertia of the cover  2416 ). Also, the wall  2418  may make the cover  2416  appear thicker than the actual thickness of the glass sheet. For example, even if the glass sheet is 0.5 mm thick, if the wall  2418  is 1.0 mm in length, the cover  2416  may appear to be 1.0 mm thick when viewed from the side or at an angle. 
       FIG. 25  shows an example process for forming a glass cover, such as the glass cover  110  or the button cover  130  of  FIGS. 1-2 , or the cover  2210  of  FIG. 22 . In operation  2500 , a glass sheet (e.g., the glass sheet  300 ) is positioned on a shaped mold (e.g., the shaped mold  302 ) which defines at least one contour, recess, protrusion, or the like. For example, the glass sheet can be positioned over the shaped mold as illustrated in  FIG. 3 . The positioning can be performed by hand, as well as by robotic processes. 
     In operation  2520 , the glass sheet is heated to a temperature that allows the glass to conform to the shape of the mold (e.g., a softening temperature). For example, the glass sheet may be heated to a glass transition temperature of the material of the glass sheet. The heating can take place in a furnace, an oven, kiln, electric melter, day tank, a pot furnace or any other unit that can be heated to the desired temperature, at the desired rate, for the requisite duration. 
     The heating can be accomplished by raising the temperature of the sheet (or the environment of the sheet) at a given rate to the softening temperature, and then holding the glass at that temperature for a given duration. The heating process may have multiple steps, such that the glass is heated to a first temperature and then maintained at the first temperature for a duration. Then, the glass may be heated to a second temperature and then held at the second temperature for a duration. The first and second temperatures, as well as the durations for which those temperatures are maintained, may be any suitable temperatures and durations. 
     In operation  2540 , the glass sheet is conformed to a shape of the shaped mold. For example, once heated to the softening temperature, the glass sheet can be slumped over the shaped mold (e.g., forming the shaped glass sheet shown in  FIG. 4 ). The glass sheet slumps over the features of the mold and adopts the contours of the shaped mold. A first shaped mold may have a first set of contours, and a second shaped mold may have a second set of contours. The contours may include recesses (e.g., the recesses  304 ,  306 ,  FIG. 3 ) that are configured to form recesses relative to a substantially planar portion of the sheet, or protrusions (e.g., the protrusions  804 ,  806 ,  FIG. 8A ) that are configured to form protrusions relative to a substantially planar portion of the sheet. The contours may also include at least one indented portion (e.g., the recess  2404 ,  FIG. 24 ) surrounded by a flange portion. 
     Optionally, in operation  2540 , pressure may be applied to the glass sheet to assist the conforming process. Pressure may be applied to assist the conforming of the glass sheet. The pressure may be applied by contacting the heated glass sheet with a second shaped mold (e.g., an upper shaped mold). The upper shaped mold may have protrusions corresponding to a pattern that is complementary to the contours of the lower shaped mold (e.g., the shaped molds  302 ,  802 ,  2402 ). The second or upper shaped mold applies pressure to the heated glass sheet forcefully conforming the glass sheet to the contours (e.g., recesses and/or indentations) of the lower shaped mold. In another example, pressure may also be applied by applying a vacuum to the glass sheet in a vacuum chamber and/or through a vacuum mold. The vacuum may be applied through the shaped mold through lines or channels in the shaped mold providing assistance for the conforming of the glass sheet to the shaped mold. In this example, the glass sheet is drawn against the shaped mold. 
     In operation  2560 , the glass sheet is cooled to form a shaped glass sheet. The cooling may be performed at any suitable cooling rate, and may be assisted, for example, by passing a cooling fluid (e.g., air, water) over the glass sheet. 
     The shaped glass sheet may have at least one indented (e.g., recessed) portion corresponding to a feature in the shaped mold. For example, the shaped glass sheet may have a recessed portion that corresponds to a location of a button or other input or output device, such as described with respect to in  FIGS. 1-8B  above. As another example, the shaped glass sheet may have at least one recessed portion and a flange portion surrounding the recessed portion, such as described with respect to  FIGS. 22-24D  above. 
     In operation  2580 , the shaped glass sheet is removed from the shaped mold. The removal may be facilitated by the addition of a release agent, such as born nitride, on the shaped mold prior to heating the glass sheet. For example, removal of the shaped glass sheet from the shaped mold after cooling may be performed individually in a serial fashion, or using robotics to remove many shaped glass sheets in parallel. 
     In operation  2590 , at least a portion of the of the high relief portion of the shaped glass sheet is removed to form a glass cover defining an opening or aperture for the electronic device. For example, an area of high relief may be removed by positioning the shaped glass sheet in a fixture and grinding a portion of the shaped glass sheet with a grinding machine, as shown in  FIG. 6A , or otherwise machining it away. Removal may destroy the portion of the shaped glass sheet that is ground off by the grinding operation. By removing the high relief portion, the low relief portion may form a perforated sheet, and may be used as a cover glass on an electronic device such as a mobile phone, laptop computer, tablet computer, or other electronic device. 
     On the other hand, the removal may be accomplished by cutting the shaped glass sheet with a laser beam. For example, as shown in  FIGS. 7A-7C , separation of a first portion (e.g., the low relief portion  414 ,  FIG. 7A ) and a second portion (e.g., the high relief portion  411 ,  FIG. 7A ) can be accomplished without destruction of either portion by cutting the shaped glass sheet with a laser beam or other suitable cutting technique. The laser beam may be directed on a joining portion (e.g., the joining portions  703 ,  FIG. 7A ) that joins the first portion (e.g., the low relief portion  414 ) and the second portion (e.g., the high relief portion  411 ) that is recessed or offset relative to the first portion.  FIG. 7C  illustrates the products of cutting a contoured glass sheet (e.g., a sheet having at least one recessed portion relative to a first portion), showing a cutting beam (e.g., laser beam) to form a perforated sheet corresponding to the first portion of the contoured glass sheet and a glass cover corresponding to the second portion of the contoured glass sheet. 
     While the present disclosure has been described with reference to various examples, it will be understood that these examples are illustrative and that the scope of the disclosure is not limited to them. Many variations, modifications, additions, and improvements are possible. More generally, examples in accordance with the present disclosure have been described in the context or particular embodiments. Functionality may be separated or combined in blocks differently in various embodiments of the disclosure or described with different terminology. These and other variations, modifications, additions, and improvements may fall within the scope of the disclosure as defined in the claims that follow 
     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. For example, while the methods or processes disclosed herein have been described and shown with reference to particular operations performed in a particular order, these operations may be combined, sub-divided, or re-ordered to form equivalent methods or processes without departing from the teachings of the present disclosure. Moreover, structures, features, components, materials, steps, processes, or the like, that are described herein with respect to one embodiment may be omitted from that embodiment or incorporated into other embodiments.

Metadata:
Filing Date: 20180201
Publication Date: 20220816
Grant Date: 20220816
Priority Date: 20160922
Inventors: LANCASTER-LAROCQUE, SIMON R.
CAO, ROBERT Y.
MATHEW, DINESH C.
Manjunath, A C
JONES, CHRISTOPHER D.
PREST, CHRISTOPHER D.
MILLER, ARI P.
BIR, KARAN
KIM, GENIE
Assignee: APPLE INC
CPC Classifications: [{"code": "H01H3/12", "inventive": false, "first": false, "tree": "[]"}, {"code": "G06F1/169", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F1/1684", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F1/1626", "inventive": true, "first": false, "tree": "[]"}, {"code": "C03B23/0357", "inventive": true, "first": false, "tree": "[]"}, {"code": "C03B23/0355", "inventive": true, "first": false, "tree": "[]"}, {"code": "C03B23/0352", "inventive": true, "first": false, "tree": "[]"}, {"code": "C03B23/0305", "inventive": true, "first": false, "tree": "[]"}, {"code": "C03B23/0302", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04M2250/22", "inventive": false, "first": false, "tree": "[]"}, {"code": "H04M1/23", "inventive": true, "first": true, "tree": "[]"}, {"code": "H04M1/0266", "inventive": false, "first": false, "tree": "[]"}, {"code": "G06F1/1626", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F1/1643", "inventive": true, "first": false, "tree": "[]"}, {"code": "C03B11/08", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04M1/0266", "inventive": true, "first": false, "tree": "[]"}, {"code": "H05K5/03", "inventive": true, "first": true, "tree": "[]"}, {"code": "G06F3/041", "inventive": true, "first": false, "tree": "[]"}, {"code": "C03B11/08", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04M1/0266", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F1/1626", "inventive": true, "first": false, "tree": "[]"}, {"code": "H05K5/03", "inventive": true, "first": true, "tree": "[]"}, {"code": "G06F3/041", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F1/1643", "inventive": true, "first": false, "tree": "[]"}]
Family ID: 82802867