PATENT DOCUMENT

Publication Number: US-8982547-B2
Application Number: US-201314094600-A
Country: US
Kind Code: B2

Title: Electronic devices with component mounting structures

Abstract:
Electronic devices are provided that have components. A housing protrusion may be interposed between a display cover layer and display components. A button may have a button member. A support structure for a dome switch in the button may have a screw hole. A housing may have screw holes through which a screw passes. The screw may also pass through the screw hole of the support structure to hold the switch structure near the button member. A clip may have a spring. A metal plate may prevent the clip from becoming worn by the spring. A display may be mounted on a ledge in a device housing. The ledge may have gaps with supports and removed corners.

Claims:
What is claimed is: 
     
       1. An electronic device, comprising:
 a display having a cover layer, a thin-film transistor layer, and a plurality of additional layers, wherein the thin-film transistor layer is physically coupled to the cover layer through the plurality of additional layers in the display; 
 a housing having a protrusion that is interposed between the cover layer and the thin-film transistor layer, wherein the housing comprises a rear housing surface, wherein the thin-film transistor layer is interposed between the cover layer and the rear housing surface, and wherein the housing and the protrusion are formed from one piece; and 
 an electronic component coupled to the display, wherein the protrusion extends over a cavity in the housing and wherein the electronic component is located within the cavity. 
 
     
     
       2. The electronic device defined in  claim 1  wherein the housing comprises peripheral regions adjacent to a side of the cover layer, the electronic device further comprising adhesive joining the protrusion of the housing and the cover layer together. 
     
     
       3. The electronic device defined in  claim 1  wherein the cover layer is located on a first side of the housing protrusion and wherein the display comprises display components located on a second side of the housing protrusion. 
     
     
       4. The electronic device defined in  claim 1  wherein the display comprises display components and wherein the housing protrusion defines a cavity within which at least some portion of the display components are disposed. 
     
     
       5. The electronic device defined in  claim 1  wherein there is at least one direct line between the cover layer and the thin-film transistor layer that does not include any air gaps. 
     
     
       6. An electronic device, comprising:
 a display having a cover layer and a thin-film transistor layer; 
 a housing having a protrusion that is interposed between the cover layer and the thin-film transistor layer, wherein the housing comprises a rear housing surface, wherein the thin-film transistor layer is interposed between the cover layer and the rear housing surface, and wherein the housing and the protrusion are formed from one piece; 
 a flex circuit that has an end that is attached to the thin-film transistor layer, wherein the protrusion is interposed between the end of the flex circuit and the cover layer; and 
 an electronic component coupled to the display, wherein the protrusion extends over a cavity in the housing and wherein the electronic component is located within the cavity. 
 
     
     
       7. The electronic device defined in  claim 6  wherein the cover layer comprises a layer of cover glass that is attached to the protrusion with adhesive. 
     
     
       8. The electronic device define in  claim 7  further comprising a color filter layer adjacent to the thin-film transistor layer, wherein the thin-film transistor layer has an edge, wherein the protrusion is interposed between the edge of the thin-film transistor layer and the layer of cover glass, and wherein the color filter layer has an edge that is recessed with respect to the edge of the thin-film transistor layer. 
     
     
       9. The electronic device defined in  claim 8  further comprising:
 a support structure around which a portion of the flex circuit bends, wherein the electronic component comprises a capacitor that is connected to the flex circuit. 
 
     
     
       10. The electronic device defined in  claim 7  wherein the adhesive comprises pressure sensitive adhesive. 
     
     
       11. An electronic device, comprising:
 a display having an exterior layer and at least one interior layer; 
 a housing having a protrusion that is interposed between the exterior and interior layers, wherein the housing comprises a rear housing surface, wherein the interior layer is interposed between the exterior layer and the rear housing surface, and wherein the housing and the protrusion are formed from one piece; 
 adhesive that attaches the exterior layer to the protrusion; and 
 a capacitor coupled to the display, wherein the protrusion extends over a cavity in the housing and wherein the capacitor is located within the cavity. 
 
     
     
       12. The electronic device defined in  claim 11  wherein the exterior layer comprises a layer of cover glass. 
     
     
       13. The electronic device defined in  claim 11  wherein the exterior layer comprises a cover layer. 
     
     
       14. The electronic device defined in  claim 11  wherein the interior layer comprises a thin-film transistor layer. 
     
     
       15. The electronic device defined in  claim 11  wherein the adhesive comprises pressure sensitive adhesive. 
     
     
       16. The electronic device defined in  claim 11  further comprising a flex circuit that has an end that is attached to the interior layer, wherein the protrusion is interposed between the end of the flex circuit and the exterior layer. 
     
     
       17. The electronic device define in  claim 16  further comprising a color filter layer adjacent to the interior layer, wherein the interior layer has an edge, wherein the protrusion is interposed between the edge of the interior layer and the exterior layer, and wherein the color filter layer has an edge that is recessed with respect to the edge of the interior layer. 
     
     
       18. The electronic device defined in  claim 17  further comprising:
 a support structure around which a portion of the flex circuit bends, wherein the capacitor is connected to the flex circuit.

Description:
This application is a divisional of patent application Ser. No. 12/870,769, filed Aug. 27, 2010, which is hereby incorporated by referenced herein in its entirety. This application claims the benefit of and claims priority to patent application Ser. No. 12/870,769, filed Aug. 27, 2010. 
    
    
     BACKGROUND 
     This relates generally to electronic devices, and, more particularly, to electronic device component mounting features that enhance the performance of electronic devices. 
     Electronic devices may have displays. Displays may be mounted near to the edges of device housings. 
     Buttons are used in electronic devices to control device functions such as media playback functions. Buttons are typically mounted in openings in device housings. 
     Spring-loaded clips may be provided on electronic devices that allow the devices to be attached to items of clothing. Clips may be mounted to device housings using hinges 
     Displays may be provided with cover glass layers that rest on housing ledges. The housing ledges may have gaps to accommodate structures such as screws. 
     Electronic devices with features such as these may have shortcomings. Device housings may not be configured in a way that allows displays to be placed sufficiently close to device housing edges, button mounting structures may be overly large, spring-loaded clips may have parts that are subject to undesired wear, and display cover layers may be subject to unwanted damage when devices are dropped. 
     It would therefore be desirable to be able to provide improved electronic device structures. 
     SUMMARY 
     A housing for an electronic device may have a protrusion that is interposed between a display cover layer and display components. The display cover layer may be a layer of cover glass. The display components may include a flex circuit cable and a driver integrated circuit. The protrusion may lie over a cavity in a housing. The flex circuit may have a bent portion that is supported by a support structure within the cavity. Capacitors on the flex circuit may be mounted in the cavity. 
     A button may have a button member. A device housing may have an opening through which the button member passes. A support structure may be provided for a switch such as a dome switch. The dome switch may be actuated when the button member is pressed. The support structure for the dome switch may have a screw hole. A housing may have screw holes through which a screw passes. The screw may also pass through the screw hole in the support structure. This holds the switch structure near the button member. 
     An electronic device may have a clip. The clip may have a clip member that is attached to a housing structure in the electronic device by a hinge. The hinge may have a torsion spring. A metal plate in the hinge may be interposed between the clip member and the spring to prevent the clip member from becoming worn by the spring. 
     A display may be mounted on a ledge in a device housing. The ledge may have a ledge surface and gaps. Support structures may be provided in the gaps. The support structures may have recesses that accommodate screws in the device. The support structures may have upper surfaces that lie flush with the ledge surface. 
     Further features of the invention, its nature and various advantages will be more apparent from the accompanying drawings and the following detailed description of the preferred embodiments. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of an illustrative electronic device that may be provided with a display and display mounting structures in accordance with an embodiment of the present invention. 
         FIG. 2  is a cross-sectional side view of an electronic device of the type shown in  FIG. 1  in accordance with an embodiment of the present invention. 
         FIG. 3  is a cross-sectional side view of an illustrative electronic device of the type shown in  FIGS. 1 and 2  in accordance with an embodiment of the present invention. 
         FIG. 4  is a perspective cross-sectional view of the illustrative electronic device of  FIG. 3  in accordance with an embodiment of the present invention. 
         FIG. 5  is perspective interior view of a portion of a display in a device of the type shown in  FIGS. 3 and 4  in accordance with an embodiment of the present invention. 
         FIG. 6  is a diagram of a conventional button mounted in an opening in a device housing. 
         FIG. 7  is a cross-sectional side view of an illustrative button in an electronic device in accordance with an embodiment of the present invention. 
         FIG. 8  is an exploded perspective view of an illustrative screw and support structure that may be used in supporting a button switch in an electronic device in accordance with an embodiment of the present invention. 
         FIG. 9  is a perspective view of an interior portion of an electronic device housing showing holes that may be provided in the housing to receive an elongated cylindrical member such as a screw of the type shown in  FIG. 8  in accordance with an embodiment of the present invention. 
         FIG. 10  is an exploded perspective view of an illustrative electronic device housing, a button, and button support structures in accordance with an embodiment of the present invention. 
         FIG. 11  is a perspective view that shows a button and button support structures such as a button and button support structures of the type shown in  FIG. 10  mounted in an electronic device housing such as an electronic device housing of the type shown in  FIG. 10  in accordance with an embodiment of the present invention. 
         FIG. 12  is a perspective view of an illustrative electronic device that may have a spring-loaded clip and structures in the clip to provide durability in accordance with an embodiment of the present invention. 
         FIG. 13  is an exploded perspective view of an electronic device of the type shown in  FIG. 12  in accordance with an embodiment of the present invention. 
         FIG. 14  is a cross-sectional side view of a portion of an electronic device of the type shown in  FIGS. 12 and 13  in the vicinity of a spring in accordance with an embodiment of the present invention. 
         FIG. 15  is an exploded perspective view of an electronic device of the type shown in  FIG. 12  in accordance with an embodiment of the present invention. 
         FIG. 16  is an exploded perspective view of an illustrative electronic device that has a display in accordance with an embodiment of the present invention. 
         FIG. 17  is a top view of a portion of an electronic device housing showing how the housing may have a ledge on which a cover layer in a display may rest in accordance with an embodiment of the present invention. 
         FIG. 18  is a perspective view of an interior portion of an electronic device of the type shown in  FIG. 16  showing how a support structure may be used to bridge gaps in a housing ledge in accordance with an embodiment of the present invention. 
         FIG. 19  is a cross-sectional side view of a portion of the housing of  FIG. 18  taken through an illustrative portion of a housing ledge that does not have a gap in accordance with an embodiment of the invention. 
         FIG. 20  is a cross-sectional side view of a portion of the housing of  FIG. 18  taken through an illustrative portion of a housing ledge that has a gap and an associated display support structure in accordance with an embodiment of the invention. 
         FIG. 21  is a perspective view of an illustrative electronic device that may be provided with a display cover layer in accordance with an embodiment of the present invention. 
         FIG. 22  is a cross-sectional side view of an illustrative electronic device of the type shown in  FIG. 21  taken along a central portion of a display edge in accordance with an embodiment of the present invention. 
         FIG. 23  is a cross-sectional side view of an illustrative electronic device of the type shown in  FIG. 21  taken at a corner portion of a display edge in accordance with an embodiment of the present invention. 
         FIG. 24  is a perspective view of a housing for an electronic device of the type shown in  FIG. 21  showing how corner portions may be removed from a housing ledge on which the edges of a display cover layer are mounted in accordance with an embodiment of the present invention. 
         FIG. 25  is a perspective view of a housing for an electronic device of the type shown in  FIG. 21  showing how corner portions may be removed from a housing ledge on which the edges of a display cover layer are mounted in accordance with an embodiment of the present invention. 
         FIG. 26  is a perspective view of an illustrative spacer and flex circuit in accordance with an embodiment of the present invention. 
         FIG. 27  is a cross-sectional end view of an illustrative spacer to which a flex circuit has been attached in accordance with an embodiment of the present invention. 
         FIG. 28  is a side view showing how layers of flex circuit material may be bonded together to form a flex circuit and showing how a stiffener may be thermally bonded to the flex circuit using a heated press in accordance with an embodiment of the present invention. 
         FIG. 29  is a side view of a screen printing tool of the type that may be used in forming a patterned adhesion promotion layer such as a patterned coating of ink on the surface of a flex circuit in accordance with the present invention. 
         FIG. 30  is a side view of an oven that is being used to heat a flex circuit with a patterned adhesion promotion layer of the type that may be formed using the equipment of  FIG. 29  in accordance with an embodiment of the present invention. 
         FIG. 31  is a side view of an illustrative spacer to which a flex circuit is being attached using ultraviolet-light-cured adhesive that is being launched into the interior of the spacer in accordance with an embodiment of the present invention. 
         FIG. 32  is a flow chart of illustrative steps involved in attaching a flex circuit to a support structure in accordance with an embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     Electronic devices are sometimes provided with displays. Displays may be used to present visual information to a user such as pictures and menu items. If desired, displays may be provided with touch sensors to gather user touch input. 
     A perspective view of an illustrative electronic device that may be provided with a display is shown in  FIG. 1 . As shown in  FIG. 1 , device  100  may have a housing such as housing  102 . Housing  102  may be formed from plastic, metal, carbon fiber composite material, other composites, glass, ceramics, other materials, or combinations of these materials. Housing  102  may be formed from multiple pieces of material or may be formed using a unibody construction in which housing  102  is substantially formed from a single structure (e.g., machined or cast metal, plastic, etc.). Device  100  may be a media player, a cellular telephone, a computer, or other suitable electronic device. 
     Display  104  may be mounted to the front face of device  100 . Portions of housing  102  such as portions  128  may surround display  104 . Portions  128  may be integral portions of housing  102  or may be separate structures. For example, portions  128  may be provided by creating a rectangular lip in housing  102  that surrounds all four edges of display  104  or, if desired, portions  128  may be formed from a separate rectangular ring member that is attached to other housing structures. Portions  128  may serve as a cosmetic trim for display  104  and may sometimes be referred to as a bezel structure or a device bezel. 
     To improve device aesthetics and reduce device size, it may be desirable to minimize the width of bezel  128 . At the same time, sufficient interior space should be provided within device  100  to accommodate the components that make up display  104 . A cross-sectional side view of an illustrative layout that may be used to mount display  104  and its associated structures within device  100  is shown in  FIG. 2 . As shown in  FIG. 2 , display  104  may include multiple layers such as layers  110 ,  108 , and  106 . These layers may form an image pixel array for displaying images for a user. The layers may include a touch sensor array based on capacitive sensors, resistive sensors, acoustic sensors, piezoelectric sensors, or other sensors. 
     As shown in  FIG. 2 , the exposed outer surface of display  104  may be covered with a transparent protective member such as planar transparent cover layer  106 . Layer  106  may be formed from plastic, glass, ceramic, or other transparent substances. In a typical scenario, layer  106  may be formed from glass. Layer  106  may therefore sometimes be referred to as a cover glass layer. The use of glass to form protective cover layer  106  is, however, merely illustrative. Other materials may be used in protective layer  106  if desired. 
     Display  104  may be an organic light-emitting diode (OLED) display, a plasma display, a liquid crystal display (LCD) or other suitable display. The use of LCD technology is sometimes described herein as an example. 
     In an LCD display arrangement, layer  110  may include a thin-film transistor layer. The thin-film transistor layer may include an array of thin-film transistors formed on a glass substrate. Layer  108  may be a color filter layer that includes an array of colored filter elements. Touch sensor layers may also be incorporated into layer  108  or may be placed adjacent to layer  108 . A layer of liquid crystal material may be interposed between layer  108  and layer  110 . Electrodes may be used to apply electric fields to image pixels in the liquid crystal layer. Thin-film transistor circuitry on the thin-film layer may be used in driving signals onto the electrodes. A backlight structure and other structures may also be included in display  104 . 
     Driver integrated circuit (IC)  120  may be formed on the outermost surface of thin-film transistor layer  110  (i.e., on the outermost surface of a thin-film transistor substrate layer). Thin-film transistors and other circuitry for display  104  may be formed on the outermost surface of thin-film transistor layer  110  in the portion of display  104  that is adjacent to color filter layer  108 . This circuitry forms an array of image pixel circuits for an image pixel array in display  104 . Conductive traces on the surface of layer  110  may be used to interconnect driver IC  120  to the thin-film transistors in the image pixel array. It is generally desirable to form driver IC  120  on the surface of layer  110  to ensure that control signals from driver IC  120  can be driven into the image pixel array without experiencing undesirable parasitic capacitances. 
     Device  100  may have one or more printed circuit boards such as printed circuit board  112 . Circuit board  112  may be formed from a rigid printed circuit board material such as fiberglass-filled epoxy (as an example). Integrated circuits and other components  130  may be mounted on printed circuit board  112 . To interconnect the circuitry of board  112  to display  104 , a cable such as cable  114  may have one end (end  116 ) that is connected to board  112  and may have another end (end  118 ) that is connected to thin-film transistor layer  110 . Cable  114  may, if desired, be implemented using a flexible printed circuit (“flex circuit”) formed from a sheet of flexible polymer such as polyimide. Flex circuit cable  114  may include a number of conductive traces. Each end of flex circuit cable  114  may be provided with contacts that make electrical connections with mating contacts on board  112  and thin-film transistor layer  110 . Connector structures (e.g., flex circuit connectors) may be used in connecting flex circuit cable  114  to traces on board  112  at end  116  and in connecting flex circuit cable  112  to thin-film transistor layer  110  at  118 . Connections between cable  112  and the conductive traces on board  112  and thin-film transistor layer  108  may also be formed using conductive adhesive (sometimes referred to as anisotropic conductive film). 
     Edge  132  of color filter layer  108  (i.e., the color filter glass substrate and any touch sensor electrode substrate and other touch sensor structures that are adjacent to the color filter glass substrate) is preferably recessed by a distance R with respect to edge  124  of thin-film transistor layer  110 . This serves to form an exposed region in thin-film transistor layer  110  upon which driver IC  120  may be mounted. The exposed region preferably has a sufficient area to accommodate driver IC  120  and attachment of end  118  of flex circuit cable  114 . 
     To minimize the size of bezel region  128  of housing  102 , housing  102  may have a protruding structure such as structure  126 . Protrusion  126  serves as a support structure for cover layer  106 . On the left-hand edge of cover layer  106  (in the orientation of  FIG. 2 ), pressure sensitive adhesive  122  may be used to attach cover layer  106  to protrusion  126 . Along the other edges of cover layer  106  (e.g., along the right-hand edge of cover layer  106  in the orientation of  FIG. 2 ), pressure sensitive adhesive  122  may be used to connect cover layer  106  to other portions of housing  102 . To facilitate assembly, the pressure sensitive adhesive that is used to attach cover layer  106  may be placed on cover glass  106  along the left-hand edge prior to assembly and may be placed on housing  102  along the other three edges. Attaching the pressure sensitive adhesive to cover glass  106  along its left-hand edge may help prevent the left-hand edge of cover glass  106  from catching on the pressure sensitive adhesive during assembly. 
     Because structure  126  has the shape of a protrusion, the region directly below protrusion  126  forms a cavity that can be used to accommodate components in device  100  such as display components. As shown in  FIG. 2 , for example, there is a region  134  that lies under protrusion  126  (i.e., a region that is located in a more interior location within housing  102  than protrusion  126 ) and that is available for internal device components. In the  FIG. 2  example, cavity region  134  is used to accommodate the left-hand edge of thin-film transistor glass  110 , flex circuit cable  114 , and the left-hand edge of printed circuit board  112 . If desired, other components may be mounted under housing protrusion  126  in region  134 . The  FIG. 2  arrangement is merely illustrative. 
       FIG. 3  is a cross-sectional side view of an illustrative arrangement that may be used for electronic device  100 . As shown in  FIG. 3 , display layers  104  may include cover glass  106 , optically clear adhesive  152 , touch sensor array  150  (e.g., a glass substrate with an array of clear electrodes such as indium tin oxide electrodes), optically clear adhesive  146 , upper polarizer  148 , color filter layer  108 , thin-film transistor layer  110 , and lower displayer layers  154  (e.g., backlight structures including a back reflector and diffuser layer, a lower polarizer, etc.). 
     Flex cable  114  may have a bend such as bend  142 . Support structure  138  may help support flex cable  114  at bend  142  (e.g., by ensuring that flex cable  114  has a defined minimum acceptable bend radius). Stiffeners such as stiffener  140  may be used in supporting flex cable  114  (e.g., to prevent bends that would weaken solder joints on cable  114 ). Stiffener  140  may be, for example, a metal stiffener that is formed from a material such as stainless steel. Support structure  138  may be formed from a material such as plastic. For example, support structure  138  may be formed from polycarbonate. Bracket  136  may be formed from a metal such as stainless steel and may be used for mounting plastic support structure  138 . Adhesive  156  may be used in attaching flex circuit cable  112  to support structure  138 . 
     Electrical components such as capacitors  160  may be mounted to flex circuit cable  112  and may be accommodated (along with the other structures shown in  FIG. 3 ) within cavity region  134  under protrusion  126 .  FIG. 4  is a cross-sectional perspective view of device  100  showing how capacitor  160  may be mounted in the cavity under protrusion  126 . 
     As shown in  FIG. 3 , portions of display  104  such a portion  162  of backlight layers  154  (sometimes referred to as a p-chassis) may also be accommodated in the cavity (i.e., cavity region  134 ) that is formed below the overhanging protrusion (protrusion  126 ). 
     Air gaps such as air gaps  144  and cover layer lower chamfer  158  may help prevent damage to cover layer  106 . Cover layer  106  may have an upper surface that is raised above the uppermost surface of housing  102 . 
     A perspective view of cover layer  106  and associated components as viewed from the interior of device  100  (in an unassembled state) is shown in  FIG. 5 . As shown in  FIG. 5 , flex circuits such as circuits  114  and  114 ′ may be provided with bends and may have portions that run vertically (i.e., parallel to vertical axis  164 , which is perpendicular to the plane of planar cover layer  106  and the other planar layers of planar display  104 ). 
     Electronic devices often contain buttons. For example, buttons may be used to make volume adjustments and other media playback adjustments, to make menu selections, to turn the power in a device on and off, and to provide other control functions. 
     A conventional button is shown in the cross-sectional side view of  FIG. 6 . As shown in  FIG. 6 , button  200  is formed in an opening in electronic device housing  202 . Button  200  has button member  204  that reciprocates along axis  222  during operation. When pressed downwards in direction  224 , lower button member surface  210  presses against upper portion  212  of dome switch  214 . This collapses dome switch  214  and shorts electrical contacts associated with dome switch  214 , “closing” the switch. 
     Dome switch  214  is mounted on dome switch support member  216 . Dome switch support member  216  is attached to the interior surface  226  of housing wall  202  using adhesive  220 . 
     To ensure proper operation of button  200 , the dimensions of the structures in  FIG. 6  should be well controlled. In particular, the spacing between lower surface  210  of button member  204  and upper surface  212  of dome switch  214  should be accurately controlled. If this spacing is too small, switch  214  may be inadvertently activated. If this spacing is too large, the button may feel loose or it may be difficult to properly close the switch when button member  204  is moved in direction  224 . 
     The distance between lower surface  210  and upper surface  212  is determined by the location of surface  212  and the location of surface  210 . 
     The location of surface  212  relative to housing  202  is affected by the location of inner surface  226  of housing wall  202  and the shape of support  216 . This is because surface  218  of support  216  is attached to surface  226 . Variations in the location of surface  226  affect the location of surface  218  and therefore the location of surface  212  of switch  214 . 
     The location of surface  210  relative to housing  202  is affected by the location of surface  208  of housing  202 . This is because surface  206  of button member  204  bears against surface  208  when button member  204  is not depressed. Careful control of the location of surfaces  226  and  208  and use of accurate dimensions in support structure  216  will ensure that button  200  functions properly. 
     In compact button designs, there may not be sufficient space available to accommodate a button support structure such as conventional support structure  216  of  FIG. 6 . A button arrangement of the type shown in  FIG. 7  may therefore be used to ensure accurate button operation. 
     As shown in  FIG. 7 , button  250  may be formed from a button member such as button member  254  that is mounted in an opening in electronic device housing  252 . Button  250  may be actuated when a user presses on surface  284  in direction  282 . This pushes button member  254  in direction  282  so that inner button member surface  286  presses against outermost surface portion  260  of dome switch  262 . When dome switch  262  is collapsed, a conductive inner dome surface in switch  262  may short a pair of switch terminals to each other, thereby closing the switch. 
     The distance between surface  286  of button member  284  and surface  260  of dome switch  262  affects the operation of button  250 . Accurate button operation may be achieved by accurately controlling this distance. 
     The distance between surface  286  and surface  260  is controlled by the location of surface  286  and the location of surface  260 . 
     The location of surface  286  relative to housing  252  is affected by the location of inner surface  256  of housing wall  252 . This is because surface  258  of button member  254  bears against surface  256  when button member  254  is not depressed (i.e., when button member  254  is in its unactuated position). 
     The location of surface  260  of dome switch  262  relative to housing  252  is controlled by the location of surface  270  of support structure  288 . This is because dome switch  262  and its associated flex circuit substrate  272  are mounted on surface  270  (e.g., using pressure sensitive adhesive). The location of surface  270  along dimension  280  therefore controls the location of surface  260  along dimension  280 . 
     To ensure that the location of surface  270  is well controlled relative to housing  252 , support structure  288  may be mounted within electronic device housing  252  (and the electronic device formed using housing  252 ) using one or more elongated members such as screw  264 . 
     Screw  264  may have a head such as head  290  that is attached to a shaft such as shaft  276 . Portion  278  of shaft  276  may be smooth (unthreaded) and may pass through an unthreaded cylindrical opening with smooth sidewalls in portion  252 ′ of housing  252 . Portion  266  of shaft  276  may be threaded and may engage threads in support structure  288 . Portion  274  of shaft  276  may be smooth (unthreaded) and may be received in an unthreaded cylindrical opening in housing  252 . 
     The outer diameter of shaft  276  in regions  278  and  274  and the corresponding inner diameter of the openings through support structure  288  and housing  252  can be accurately controlled during manufacturing, which allows the position of surface  270  along dimension  280  (and therefore the position of surface  260 ) to be accurately determined. 
       FIG. 8  is an exploded perspective view showing how screws such as screw  264  may be inserted into holes such as hole  300  in support structure  288  along an axis such as axis  294 .  FIG. 8  also shows how dome switch  262  and dome switch flex circuit  272  to which dome switch  262  is connected may be mounted on front surface  270  of support structure  288 . A layer of adhesive such as pressure sensitive adhesive  302  may be used in attaching flex circuit  272  to support  288 . Front surface  270  may be a planar surface that lies parallel to longitudinal axis  294  of screw  264 . 
       FIG. 9  is a perspective view of a portion of housing  252  showing how housing  252  may have an opening such as opening  298  to accommodate button member  254 . As shown in  FIG. 9 , screw  264  ( FIG. 8 ) may pass through opening  292  in housing portion  252 ′ along axis  294 . When inserted through opening  292  of housing portion  252 ′ and through opening  300  in support structure  288  of  FIG. 8 , tip portion  274  of screw  264  will be received within hole  296  in housing  252 , thereby holding support structure  288  and dome switch  262  in place within device housing  252 . Device housing  252  may form a housing for an electronic device such as a cellular telephone, music player, computer, or other electronic equipment. 
       FIG. 10  is an exploded perspective view of buttons such as button  250  of  FIGS. 7 ,  8 , and  9  that may be mounted in an electronic device (such as device  100  of  FIG. 1 ). As shown in  FIG. 10 , device  100  may include three buttons of the type shown in  FIGS. 7 ,  8 , and  9 . Dome switches  262 A,  262 B, and  262 B for the three buttons may be mounted on a circuit such as flex circuit  712 . Flex circuit  712  may be connected to circuitry in device  100 . As one example, flex circuit  712  may be connected to circuit  711 . Circuit  711  may, if desired, be connected to audio jack connector  710 . 
     Support structure  288  may include four holes  300  with threads. Screws  264  may screw into holes  300  and engage the threads of holes  300 . 
     Device  100  may include openings in device housing  252  such as openings  700 ,  702 ,  704 A,  704 B, and  704 C. As examples, opening  700  may be an opening for a 30-pin connector, opening  702  may be an opening for an audio plug, opening  704 A may be an opening for button member  254 A (e.g., a lock/unlock button), opening  704 B may be an opening for button member  254 B (e.g., an up button that may be used as a volume up button), and opening  704 C may be an opening for button member  254 C (e.g., a down button that may be used as a volume down button). 
     Button members  254 A,  254 B, and  254 C may be respectively biased into openings  704 A,  704 B, and  704 C of device housing  252 . 
     A perspective view of the buttons and electronic device of  FIG. 10  in an at least partially assembled state is shown in  FIG. 11 . As shown in  FIG. 11 , flex circuit  712  may include portions that wrap around support structure  288 . If desired, flex circuit  712  may be coupled to support structure  288  (e.g., flex circuit  712  may be coupled to support structure  288  with adhesive). 
     Electronic devices may be provided with spring-loaded clips. For example, small portable devices such as music player devices may be provided with clips that allow the devices to be attached to articles of clothing. 
       FIG. 12  is a perspective view of an illustrative electronic device that may be provided with a clip. Electronic device  400  of  FIG. 12  may be a media player, a cellular telephone, or other electronic equipment. As shown in  FIG. 12 , electronic device  40  may have a main body such as housing  402 . Housing  402  may be formed from one or more structures such as plastic structures, metal structures, glass structures, composite structures, ceramic structures, or combinations of such structures. Housing  402  may include control circuits, a battery, and user interface components (e.g., buttons, displays such as touch screen displays and non-touch displays, status indicator lights, speaker and microphone ports, audio jacks, input-output port connectors, etc.). 
     Device  400  may have a clip such as clip  404 . Clip  404  may have a clip member such as clip member  450 . Hinge  406  and hinge pin  408  may allow clip member  450  to pivot about clip rotational axis  410 . When a user presses end  412  of member  450  towards housing  402  in direction  414 , end  416  of member  450  is forced away from housing  402  in direction  418 . This opens gap  422  to receive an item of clothing or other object. When end  412  is released, a spring in hinge  406  may bias member  450  so that end  416  moves in direction  420  towards housing  402  and grips the item of clothing or other object within gap  422 . 
     The spring in hinge  406  may be a torsion spring such as torsion spring  428  in  FIG. 13 . Spring  428  may be formed from music wire having a diameter of 0.65 mm (as an example). As shown in  FIG. 13 , housing  402  may include structures  402 A and  402 B. Structure  402 A may be a cover, a display, a control panel, or other structure. Structure  402 B may be a lower housing body structure in which printed circuit boards and other components for device  400  are mounted. 
     Screws  424  may pass through holes  452  in housing  402 B and may be received by threaded holes  454  in hinge block structure  426 . This attaches hinge block structure  426  to housing  402 B. 
     Member  450  may have a tooth structure such as tooth  434  to help member  450  when grasping items of clothing. Hinge pin support structure  436  may have holes  438  that receive press-fit hinge pins  408  along axis  410 . Pins  408  also are received in holes  456  on hinge block structure  426 . This holds structure  426  over spring  428  and captures spring  428  between structure  426  and surface  432  of member  450  in hinge structure  436 . 
     Spring  428  may have end portions that engage clip  450  and structure  426 . For example, spring  428  may have a bent end such as end  442  that bears against plate  430  on surface  432  of member  450 . Spring  428  may also have a bent end such as bent end  440  that engages recess  427  in structure  426 . Because structure  426  is attached to housing  402 B, end  440  is fixed with respect to housing  402 B. 
     When clip member  450  is rotated around axis  410  to open clip  404 , spring  428  twists. The torsion that is produced by the twisted shape of spring  428  produces a restoring force that tends to close clip  404 . For this reason, hinge  406  may sometimes be referred to as a torsion hinge or torsion-spring hinge. 
     As shown in  FIG. 14 , plate  430  may be attached to clip member  450  by a layer of adhesive such as adhesive  444 . Adhesive  444  may be, for example, a layer of pressure sensitive adhesive that attaches the unexposed underside of plate  430  to member  450 . Other attachment mechanisms may be used if desired (e.g., welds, fasteners, slots, etc.). 
     When end  412  of member  450  is pushed in direction  414  to open clip  404 , exposed surface  446  of plate  430  pushes upwards in direction  414  and bears against end  442  of spring  428 . End  440  of spring  428  may be received within hole  427  (or other suitable engagement feature) in hinge block structure  426  and is therefore held at a fixed position with respect to housing  402 B. As torsion builds in spring  428 , the pressure between end  442  and plate  430  increases. 
     Plate  430  is preferably formed from a durable material that can withstand pressure from end  442  of spring  428  without becoming worn. For example, plate  430  may be formed from a thin sheet of a hard metal such as stainless steel. The metal of plate  430  is preferably harder and more durable than the metal and that forms member  450 , thereby enhancing the durability of member  450  and clip  404 . In a typical arrangement, member  450  and housing body  402 B may be formed from relatively soft materials such as aluminum, other soft metals, or other soft materials such as plastic. By forming plate  430  from a material that is harder than member  450 , the surface of member  450  is protected from wear due to contact with end  442  of spring  428 . Plate  430  may be formed from stainless steel, tungsten, molybdenum, stiff alloys of materials such as these, or any other material that is harder than member  450 . 
       FIG. 15  is an exploded perspective view of an electronic device such as device  400  of  FIG. 12  that may include a clip such as clip  404 . As shown in  FIG. 15 , device  400 , housing structure  402 B, clip  404 , and tooth  434  may have rounded edges. Clip  404  may be mounted to housing structure  402 B using four screws  424  (as an example). Housing structure  402 B may include four holes  452  (shown in  FIG. 25 ). Screws  424  may pass through holes  452  and thread into holes  454  of hinge block structure  426 . 
     Electronic devices that include displays may have housings with ledges (see, e.g., protrusion  126  of  FIG. 2 , which forms a ledge that supports lip-shaped cover layer  106 ). The ledges may be used to support the edges of a display cover layer. It may sometimes be desirable to form gaps within a ledge. For example, it may be desirable to form a gap in a ledge to accommodate a screw or other device component. If care is not taken, the presence of gaps in the ledge may create a failure point that makes the cover layer in the display subject to cracking (i.e., because the display cover layer is not supported by the ledge in the gap region). 
     This failure mechanism can be at least partly eliminated by providing display support structures. An illustrative device of the type that may be provided with display support structures within housing ledge gaps is shown in  FIG. 16 . As shown in  FIG. 16 , electronic device  500  may include a housing such as housing  508 . Housing  508  may be formed using a unibody construction or may be formed from one or more separate housing members. Materials that may be used for forming housing  508  include metal, plastic, carbon fiber composites and other composites, ceramics, glass, other materials, and combinations of these materials. In a typical arrangement, housing  508  may be formed from a piece of metal that has been machined to form solid or protrusion-shaped ledges (e.g., ledge structures  510  and associated ledge support surfaces  512 ). 
     Device  500  may have a display such as display  534 . Display  534  may include a display module such as display module  504 . Module  504  may include liquid crystal display (LCD) layers such as color filter and thin-film transistor layers and an optional touch sensor layer. Touch sensor capabilities may be provided using capacitive touch sensors, acoustic touch sensors, piezoelectric touch sensors, resistive touch sensors, or other touch sensors. Display module  504  may be protected by cover layer  502 . Cover layer  502  may be formed from a transparent sheet of material such as glass or plastic. Glass structures can provide good scratch resistance and transparency, but can be subject to cracking if device  500  is dropped. Plastic, ceramics, and other transparent cover layer material may also be subject to breakage if device  500  is dropped. 
     When display  534  is mounted in device  500 , the periphery of cover layer  502  rests on ledge surface  512  of ledge  510  and is surrounded by bezel region  518 . To ensure that display  534  and cover layer  502  are sufficiently protected against damage, weaknesses in the mounting arrangement for display  534  may be reduced or eliminated. One possible weakness in an arrangement of the type shown in  FIG. 16  is the presence of gaps such as gap  514  in ledge structure  510 . Gaps such as gaps  514  may be formed to accommodate design constraints (e.g., to make room for screws such as screws  516  or other components). When gaps  514  are present, however, the continuity of ledge surface  512  is disrupted. This creates an unsupported portion along the edge of cover layer  502  that can cause layer  502  to crack if device  500  is dropped or subjected to other impact events. 
       FIG. 17  is a top view of ledge  510  showing how incorporation of gap  514  into ledge  510  to accommodate screw  516  results in a discontinuity in ledge surface  512 . 
       FIG. 18  shows how device  500  may be provided with support structures such as support structures  520 . Structures  520  may have shapes with cavities that accommodate screws  516  or other such components. The size of structures  520  may be configured so that the upper surface of each support structure  520  lies flush with ledge surface  512 . Support structures  520  may be attached to housing  508  using pressure sensitive adhesive or other adhesives, fasteners, engagement features, welds, or other suitable attachment mechanisms. Materials that may be used to form support structures  520  include plastic, metal, composites, etc. With one suitable arrangement, housing  508  may be formed from machined metal such as machined aluminum and support structures  520  may be formed from plastic. 
     Because the upper surface of support structure  520  lies flush with ledge surface  512  of housing ledge portion  510 , the ledge surface that supports the periphery of cover layer  502  is substantially continuous. In this respect, support structures  520  serve to help support display cover layer  502  and may therefore sometimes be referred to as display support structures, cover glass support structures, or cover layer support structures. 
     A cross-sectional view of device  500  of  FIG. 18  (including display cover layer  502 ) that is taken along line  530  of  FIG. 18  and that is viewed in direction  532  is shown in  FIG. 19 . As shown in  FIG. 19 , in portions of ledge  510  that do not contain gaps, ledge surface  512  supports interior surface  524  of cover layer  502 . 
     A cross-sectional view of device  500  of  FIG. 18  (including display cover layer  502 ) that is taken along line  526  of  FIG. 18  and that is viewed in direction  528  is shown in  FIG. 20 . As shown in  FIG. 20 , in portions of ledge  510  that contain gaps (gaps  514  of  FIGS. 16 ,  17 , and  18 ), ledge surface  512  is substantially reduced or is absent and is therefore unable to support interior surface  524  of cover layer  502 . To prevent display cover layer  502  from cracking, support for interior surface  524  of cover layer  502  may be provided by outer ledge surface  522  of support structure  520 . Structures  520  are therefore able to bridge gaps in ledge  510  and ensure that display cover layer  502  is satisfactorily supported around its periphery. 
     It may be desirable to provide an electronic device with a display cover layer have a surface that protrudes slightly from the surface of the housing in which the display cover layer is mounted.  FIG. 21  is a perspective view of an illustrative electronic device that may be provided with a display of this type. As shown in  FIG. 21 , device  600  may have a housing such as housing  602 . Housing  602  may be formed from plastic, metal, carbon fiber composite material, other composites, glass, ceramics, other materials, or combinations of these materials. Housing  602  may be formed from multiple pieces of material or may be formed using a unibody construction in which housing  602  is substantially formed from a single structure (e.g., machined or cast metal, plastic, etc.). 
     Display  604  may be mounted to the front face of device  600 , so that outer (exterior) surface  608  of display  604  (i.e., the surface of a layer of display cover material such as display cover glass) is located at an elevated distance PX above housing surface  606  (i.e., surfaces  606  and  608  are not flush with each other because surface  608  protrudes outwards past surface  606 ). Surface  606  may, for example, be associated with a bezel structure that serves as a cosmetic trim for display  604 , a metal band such as a housing band or other structure that surrounds display  604 , a portion of a unibody housing or multipart housing that surrounds display  604 , or other device structures. 
     The elevation of surface  608  of display  604  above surface  606  of housing  602  may enhance device aesthetics, but may make display  604  more likely to crack when dropped or subjected to other shock events. In a drop event, device  600  may strike the ground front-face down (i.e., with display  604  facing the ground). When device  600  falls, one corner of display  604  may strike the ground before others. This may cause an opposing corner of display  604  to experience a whip-like motion in which the opposing corner of display  604  strikes the ground with a magnified force. Particularly in devices such as device  600  of  FIG. 21  that have elevated display surfaces (or other such elevated layers), display  604  may be prone to damage if not designed properly. 
     To prevent damage during drop events, device  600  may have display mounting ledges that run along only portions of the periphery of device  600 . Near the corners of device  600  in which display  604  may be subject to a whip-like strike, the display mounting ledges may be absent to accommodate potential flexing of display  604  (i.e., flexing in a display cover layer such as a display cover glass layer). This type of arrangement is illustrated in more detail in  FIGS. 22 and 23 .  FIG. 22  is a cross-sectional view of the right-hand edge of device  600  of  FIG. 21  taken along line  628  of  FIG. 21  and viewed in direction  630 .  FIG. 23  is a cross-sectional view of the right-hand edge of device  600  of  FIG. 21  taken along line  624  and viewed in direction  626 . 
     The cross-sectional view of  FIG. 22  corresponds to a portion of device  600  in which a display mounting ledge is present and is used to mount display  604 . As shown in  FIG. 22 , display  604  may include cover layer  632  and display module structures  612 . Display module  612  may include layers that form an image pixel array for displaying images for a user of device  600 . If desired, display module layers  612  may include a touch sensor array based on capacitive sensors, resistive sensors, acoustic sensors, piezoelectric sensors, or other sensors. The layers of display module  612  may also include a backlight, polarizers, a color filter layer, a liquid crystal layer, a thin-film transistor layer, and other display layers. Display module  612  may be an organic light-emitting diode (OLED) display module, a plasma display module, a display module using liquid crystal display (LCD) technology, or other suitable display. 
     As shown in  FIG. 22 , the exposed outer surface of display  604  may be covered with a transparent protective member such as planar transparent cover layer  632 . Layer  632  may be formed from plastic, glass, ceramic, or other transparent substances. In a typical scenario, layer  632  may be formed from glass. Layer  632  may therefore sometimes be referred to as a cover glass layer. As with the other electronic device arrangements described herein, the use of glass to form protective cover layer  632  is merely illustrative. Other materials may be used in protective layer  632  if desired. 
       FIG. 22  shows how the edge of cover layer  632  may have a lower edge surface such as surface  616  that is mounted on a ledge in housing  602  such as ledge surface  620 . A layer of adhesive such as pressure sensitive adhesive  610  may be interposed between lower cover layer surface  616  and upper surface  620  of the housing ledge. The housing ledge may be formed from a portion of housing  602  such as protrusion  602 A or other suitable housing structures. Module  612  may have a smaller planar area than cover layer  632  (i.e., a smaller footprint when viewed from the front face of device  600 ), so that the edges of module  612  are somewhat recessed from the edges of cover layer  632 . Strips of adhesive such as pressure sensitive adhesive  610  may run along each of the four peripheral edges of display  604 . 
     Protrusion  602 A and display mounting ledge surface  620  are preferably absent from the four corners of device  600 , as shown in the cross-sectional view of  FIG. 23 . As shown in  FIG. 23 , the inner surfaces of housing  602  in the corners of housing  602  are configured to form a cavity (opening  614 ) under each lower edge surface  616  of display cover layer  632 . 
     Ledge-shaped protrusion  602 A and ledge surface  620  of  FIG. 22  (which are present along the center of the edges of the display) are not present at the corners of display  604  and device  600 . As a result of the absence of support from an underlying ledge, cover layer  632  is free to flex somewhat in the event that cover layer  632  experiences an inward force during a drop event. If, for example, exposed surface  608  of cover layer  632  experiences an inward force because of a drop event, the corner of cover layer  632  and the associated lower surface  616  in the corner of display  604  can flex inward in direction  618  without being impeded by protrusion  602 . Cover layer  632  is then able to rebound without cracking after the drop event is over. 
     The amount of each corner that is free of ledge surface  620  and protrusion  602 A can be, for example, 1-30% of the length of each edge, 5-10% of the length of each edge, less than 25% of the length of each edge, or other suitable amount of the edge length in device  600 .  FIG. 24  shows an illustrative arrangement that may be used for device  600 . As shown in  FIG. 1 , housing structures such as protrusions  602 A or other portions of housing  602  may serve as ledges that form ledge surfaces  620 . Each ledge surface may run along a respective edge of housing  602 . If desired, surface  620  on each edge may be interrupted by one or more gaps that are filled with support structures as described in connection with support structures  520  of  FIG. 18 . Corner openings (cavities)  614  may be formed at each corner of device  600 , so that each of the four corners of display cover layer  632  are unsupported (as shown in  FIG. 23 ) and do not rest on protrusion  602 A of  FIG. 22 . 
       FIG. 25  is a perspective view of an electronic device such as device  600  of  FIG. 21  that may include display mounting ledges that run along only portions of the periphery of device  600 .  FIG. 25  shows an illustrative arrangement in which housing structures such as protrusions  602 A or other portions of housing  602  serve as ledges that form ledge surfaces  620 . In the  FIG. 25  example, ledge surface  620 A is relatively narrow (e.g., surface  620 A may be narrower than ledge surfaces  620 B,  620 C, and  620 D), ledge surface  620 B is formed in multiple sections (e.g., to allow passage of screws into openings  621 ), ledge surface  602 C is formed along a relatively short length of the edge of housing  602  (e.g., surface  602 C may be shorter in overall length that ledge surfaces  620 A,  620 B, and  620 D), and ledge surface  620 D may be formed adjacent to opening  620 D (e.g., a 30-pin opening). 
     It may be desirable to use adhesion promotion materials to help securely mount flex circuit structures such as the cable formed from flex circuit  114  of  FIG. 3  to support structures such as support structure  138 . To ensure adequate adhesion between flex circuit  114  and support structure  138 , a patterned coating of an adhesion promotion material may be formed on the flex circuit. 
       FIG. 26  is an exploded perspective view of an illustrative support structure (sometimes referred to as a spacer) and associated flex circuit with an adhesion promotion layer. As shown in  FIG. 26 , support structure  138  may have curved surface  802 . Surface  802  may help define a known and acceptable bend radius for bend  142  in flex circuit  114 . Support structure  138  may be formed from a material that is transparent to light such as clear polycarbonate, other clear plastics, glass, etc. Support structure  138  may, for example, be formed from optically clear polycarbonate that is transparent at ultraviolet (UV) wavelengths. The use of a UV-transparent material for support structure  138  may help distribute ultraviolet light that can be used in curing adhesive (e.g., UV-cured epoxy or other UV adhesive). 
     Flex circuit  114  may be formed from one or more sheets of flexible dielectric such as one or more sheets of polyimide or other polymer layers. Patterned conductive lines such as traces of copper or other metal may be incorporated into the layers of flex circuit  114  to form signal pathways for signals in device  100 . The patterned lines in flex circuit  114  may be used to form a serial bus, a parallel bus, radio-frequency transmission lines, paths for control signals, paths for display data, and other electrical paths. 
     Adhesives such as thermally cured adhesives and light-cured adhesives (e.g., UV adhesives) may be used in attaching flex circuit  114  to support structure  138 . The process of thermally bonding a structure to flex circuit  114  may involve elevated temperatures. For example, thermal-bonding adhesives may form durable bonds when elevated to temperatures of about 150° C. (e.g., 100° C. or more, 150° C. or more, 100-200° C., etc.). At the same time, some structures in device  100  (e.g., display structures associated with display  104 ) may be sensitive to elevated temperatures. As an example, display  104  may have a light reflector layer that is subject to warping if elevated to temperatures above 70° C. 
     The use of elevated adhesive curing temperatures may be avoided in some situations by using UV adhesive. UV adhesive can be cured by application of UV light without involving the application of heat. Nevertheless, it may be difficult or impossible to achieve desired adhesion strengths when using UV adhesive to bond structures directly to flex circuit  114 , due to the inherently weak nature of UV-adhesive-to-polyimide bonding. 
     To address this potential bonding weakness and thereby ensure that flex circuit  114  is well attached to support structure  138 , a layer of adhesion promotion material such as material  800  may be interposed between flex circuit  114  and an adhesive that helps bond flex circuit  114  to the surface of support structure  138 . By using a coating of material  800 , adhesion may be increased sufficiently that UV adhesive can be used to attach flex circuit  114  to support structure  138 , avoiding the need to use potentially damaging elevated temperatures. Adhesion promotion material  800  may be formed from a substance such as ink (e.g., a coating of black ink such as Taiyo® SW400 black ink having a thickness of less than 0.5 mm or less than 0.1 mm or other suitable thicknesses). 
     The application of ink  800  to flex circuit  114  can increase the brittleness of flex circuit  114 . It may therefore be desirable to limit the application of ink  800  to portions of flex circuit  114  that are away from bend region  142 , where flex circuit  114  is flexed during assembly. As shown in the cross-sectional view of  FIG. 27 , for example, ink  800  can be patterned so as to cover only region  810  along the side of support structure  138 , not end region  812  of structure  138  in the vicinity of bend  142 . 
     After ink layer  800  has been formed, an adhesive such as UV adhesive may be used to attach flex circuit  114  to support structure  138 . As shown in  FIG. 27 , for example, adhesive  806  may be used to attach ink  800  and flex circuit  112  to side  138 L of support structure  138 . The same type of bonding approach may be used to attach flex circuit  114  to side  138 R of support structure  138  or, as shown in  FIG. 27 , stiffener  140  may be attached to flex circuit  114  using thermally cured adhesive  802  (e.g., adhesive that forms a bond upon application of an elevated temperature). With this type of approach, adhesive  802  may form a strong bond between stiffener  140  and flex circuit  114 . Stiffener  140  may be formed from a material such as stainless steel, plastic, glass, or other materials that exhibit satisfactory adhesion to UV adhesive. This allows stiffener  140  may be attached to surface  138 R of support structure  138  using adhesive  804  such as UV adhesive. Because adhesive layers such as adhesive layer  806  on surface  138 L and adhesive layer  804  on surface  138 R of support structure  138  can be formed using UV adhesive, it is not necessary to subject support structure  138  or the other structures in device  100  (e.g., display structure  104 ) to elevated temperatures when attaching flex circuit  114  to support structure  138  in device  100 . 
       FIGS. 28 ,  29 ,  30 , and  31  show equipment and processes that may be used in attaching flex circuit  114  to support structure  138 . 
     To form desired electrical pathways in flex circuit  114 , one or more layers of flex circuit  114  may be provided with patterned traces such as traces  814  of  FIG. 28 . Flex circuit  114  may be formed from one or more layers of polyimide or other polymers (as examples). Stiffener  140  may be attached to the uppermost layer of flex circuit  114  using thermally curing adhesive  802 . The layers of flex circuit  114  may be bonded together (e.g., using adhesive) while stiffener  140  is attached to the uppermost layer of flex circuit  114  by application of heat and pressure. For example, heated plates  816  of a heated press may be moved towards each other to compress and bond together stiffener  140 , thermal adhesive  802 , and the individual layers of flex circuit  114 . Heated plates  816  may raise the temperature of adhesive  802  to a temperature of about 100° C., to about 150° C., or to other temperatures sufficient for curing thermal adhesive  802 . 
     After flex circuit  114  and bonded stiffener  114  are removed from the heated press, a patterned layer of ink or other adhesion-promotion layer may be formed on flex circuit  114 . As shown in  FIG. 29 , for example, squeegee  818  may be moved in direction  822  to force ink  800  through patterned openings such as opening  824  in screen  820 . This deposits ink  800  in a pattern (e.g., a rectangular shape of the type shown in  FIG. 26 ) on the upper surface of flex circuit  114 . 
     An oven or other heating tool may then be used to heat and dry layer  800 , so that layer  800  forms a satisfactory bond to flex circuit  114  (see, e.g., oven  826  of  FIG. 30 ). 
     Once patterned ink layer  800  has been formed on flex circuit  114 , flex circuit  114  may be attached to support structure  138  using layers of adhesive such as UV adhesive layer  806  and UV adhesive layer  804  of  FIG. 31 . Light source  828  (e.g., a UV light source such as a UV lamp) may be used to introduce UV light  830  into the interior of support structure  138 . Support structure  138  may be formed from a material with sufficient transparency to allow a substantial fraction of the light that has been launched into support structure  138  to pass into UV adhesive layers  804  and  806 . As light  830  illuminates layers  804  and  806 , the adhesive of layers  804  and  806  is cured. Using this approach, adhesive  806  can attach ink  800  and flex circuit  114  to surface  138 L of support structure  138 . Adhesive  804  can attach stiffener  140  and flex circuit  114  to surface  138 R of support structure  138 . Tip region  812  at the end of support structure  138  near bend  142  may be ink free to help avoid making flex circuit  114  undesirably brittle where flex circuit  114  is being flexed to bend around support structure  138 . 
     Illustrative steps involved in using equipment of the type shown in  FIGS. 28 ,  29 ,  30 , and  31  to attach a flexible structure such as flex circuit  114  to a support structure such as support structure  138  are shown in  FIG. 32 . 
     At step  832 , layers of polyimide or other sheets of flexible material that contain patterned conductive traces may be bonded together (e.g., using a tool such as a press with plates  816  of  FIG. 28 ). Stiffener  140  may be thermally bonded to flex circuit  114  by heating plates  816  to an elevated temperature (e.g., above 70° C., about 150° C., etc.). 
     At step  834 , patterned ink layer  800  may be formed on flex circuit  114 . Patterned ink  800  may be formed by screen printing, pad printing, brush application, spraying, dripping, ink-jet printing, etc. An oven such as oven  826  may be used to bake ink  800  to flex circuit  114 . 
     To complete the assembly of support structure  138  and flex circuit  114  into device  100  (as shown, for example, in  FIG. 3 ), UV-curable liquid adhesive layers  804  and  806  may be formed on support structure  138  and flex circuit  114  may be wrapped around end  142  of support structure  138  (step  836 ). Some or all of the wrapping operations involved in bending flex circuit  114  around end  142  of support structure  138  may occur after support structure  138  has been mounted within the housing of device  100 . For example, flex circuit  114  may be wrapped around support structure  138  when assembling components within the housing of device  100  such as components that are attached to the ends of flex circuit  114  (e.g., a display, display driver circuits, logic boards, etc.). 
     During the operations of step  836 , adhesive layers  804  and  806  may be cured by exposure to UV light  830  from UV light source  828  (e.g., after flex circuit  114  and support structure  138  have been placed within device  110 ). No elevated temperatures are needed to UV cure layers  804  and  806 , so flex circuit  114  may be attached to support structure  138  without elevating the temperature of device  100  and potentially fragile structures such as display  104 . 
     The foregoing is merely illustrative of the principles of this invention and various modifications can be made by those skilled in the art without departing from the scope and spirit of the invention. The foregoing embodiments may be implemented individually or in any combination.

Metadata:
Filing Date: 20131202
Publication Date: 20150317
Grant Date: 20150317
Priority Date: 20100827
Inventors: SANFORD EMERY
ALVAREZ FELIX
LYNCH STEPHEN BRIAN
Assignee: APPLE INC
CPC Classifications: [{"code": "H10D86/481", "inventive": true, "first": false, "tree": "[]"}, {"code": "H10D86/60", "inventive": true, "first": false, "tree": "[]"}, {"code": "H10D86/60", "inventive": true, "first": false, "tree": "[]"}, {"code": "H10D86/481", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F1/1626", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01L27/1255", "inventive": true, "first": true, "tree": "[]"}, {"code": "G02F1/13452", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02F2001/133317", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02F2001/133314", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02F1/13452", "inventive": true, "first": true, "tree": "[]"}, {"code": "G02F1/133317", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02F1/133314", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02F1/133317", "inventive": false, "first": false, "tree": "[]"}, {"code": "G06F1/1626", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F1/16", "inventive": true, "first": true, "tree": "[]"}, {"code": "G02F1/13452", "inventive": true, "first": false, "tree": "[]"}, {"code": "Y10T428/31504", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01H13/04", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F1/1637", "inventive": true, "first": false, "tree": "[]"}, {"code": "Y10T428/31504", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01H13/10", "inventive": true, "first": true, "tree": "[]"}, {"code": "G06F1/1626", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01H13/52", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02F1/13", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01H2223/024", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02F1/133314", "inventive": false, "first": false, "tree": "[]"}, {"code": "G06F1/1637", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F1/1626", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02F1/13452", "inventive": true, "first": false, "tree": "[]"}, {"code": "Y10T428/24628", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02F1/133314", "inventive": false, "first": false, "tree": "[]"}, {"code": "Y10T428/24628", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09F9/00", "inventive": true, "first": false, "tree": "[]"}, {"code": "Y10T428/31507", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02F1/133317", "inventive": false, "first": false, "tree": "[]"}, {"code": "Y10T428/31507", "inventive": false, "first": false, "tree": "[]"}]
Family ID: 44588242