PATENT DOCUMENT

Publication Number: US-9983342-B2
Application Number: US-201514881067-A
Country: US
Kind Code: B2

Title: Backlight structures for an electronic device with sensor circuitry

Abstract:
A display may be mounted within an electronic device housing. The display may deflect inwardly when pressed by a user. A sensor formed from a flexible printed circuit may measure capacitance changes associated with inward deflection of the display. A backlight for the display may have a backlight plate on which the printed circuit is mounted. The backlight plate may be formed from a fiber-composite material such as carbon fiber. Multiple carbon-fiber layers may be sandwiched together to form the backlight plate. An electromagnetic shield layer may be used to electromagnetically the printed circuit. The backlight plate may have an opening in which conductive material is placed to short the electromagnetic shield layer to a ground pad on the printed circuit.

Claims:
What is claimed is: 
     
       1. An electronic device, comprising:
 a housing, wherein the housing comprises a rectangular housing having two opposing short edges and two opposing long edges that are longer than the short edges; 
 a display mounted within the housing; 
 backlight structures that supply backlight to the display, wherein the backlight structures include a fiber-composite plate and a light guide plate, wherein the fiber composite plate comprises: 
 two outer unidirectional carbon-fiber layers; and 
 two inner unidirectional carbon-fiber layers sandwiched between the two outer unidirectional carbon fiber layers, wherein the two outer unidirectional carbon-fiber layers have fibers running between the two opposing long edges parallel to the short edges, and wherein the two inner unidirectional carbon-fiber layers have fibers running between the two opposing short edges parallel to the long edges; and 
 a flexible printed circuit that is supported on the fiber-composite plate and is interposed between the fiber-composite plate and the light guide plate. 
 
     
     
       2. The electronic device defined in  claim 1  wherein the fiber-composite plate comprises at least first and second unidirectional fiber-composite layers having respective fibers that are perpendicular to each other. 
     
     
       3. The electronic device defined in  claim 1  further comprising an electromagnetic shield layer that shields the flexible printed circuit. 
     
     
       4. The electronic device defined in  claim 3  wherein the electromagnetic shield layer comprises a layer selected from the group consisting of: a layer of conductive adhesive and a layer of metal foil. 
     
     
       5. The electronic device defined in  claim 4  further comprising a first layer of adhesive between the flexible printed circuit and the shield layer and a second layer of adhesive between the shield layer and the fiber-composite plate. 
     
     
       6. The electronic device defined in  claim 3  wherein the fiber-composite plate has a surface and wherein the electromagnetic shield layer comprises a metal coating on the surface. 
     
     
       7. The electronic device defined in  claim 6  further comprising a layer of adhesive between the electromagnetic shield layer and the flexible printed circuit. 
     
     
       8. The electronic device defined in  claim 3  wherein the flexible printed circuit has a surface and wherein the electromagnetic shield layer comprises a metal layer on the surface. 
     
     
       9. The electronic device defined in  claim 8  further comprising a layer of adhesive between the metal layer and the fiber-composite plate. 
     
     
       10. The electronic device defined in  claim 3  wherein the electromagnetic shield layer comprises a layer of metal foil embedded within the fiber-composite plate. 
     
     
       11. The electronic device defined in  claim 10  wherein the layer of metal foil has first and second opposing surfaces and wherein a portion of the first surface is exposed to conductive material that shorts the metal foil to a ground pad in the flexible printed circuit. 
     
     
       12. The electronic device defined in  claim 3  wherein the flexible printed circuit has a ground trace, wherein the fiber-composite layer has an opening, and wherein the electronic device further comprises conductive material in the opening that shorts the electromagnetic shield layer to the ground trace. 
     
     
       13. The electronic device defined in  claim 12  wherein the conductive material comprises a polymer with embedded metal particles. 
     
     
       14. The electronic device defined in  claim 3  wherein the display has a surface that is deflected by application of pressure from a finger of a user and wherein the flexible printed circuit measures the deflection of the display. 
     
     
       15. An electronic device, comprising:
 a rectangular housing, wherein the rectangular housing has two opposing short edges and two opposing long edges; 
 a display with backlight structures that include a light guide and a fiber-composite plate having at least some fibers that span the rectangular housing, wherein the fiber-composite plate comprises a pair of outer unidirectional carbon-fiber layers and a pair of inner unidirectional carbon-fiber layers sandwiched between the pair of outer unidirectional carbon-fiber layers, and wherein the outer unidirectional carbon-fiber layers have carbon fibers that run between the two opposing long edges; 
 a flexible printed circuit supported on the fiber-composite plate; and 
 an electromagnetic shield layer that is interposed between the fiber-composite plate and a portion of the flexible printed circuit that is interposed between the light guide and the fiber-composite plate. 
 
     
     
       16. The electronic device defined in  claim 15  further comprising an opening in the fiber-composite plate and conductive material in the opening that shorts the electromagnetic shield layer to a ground pad on the flexible printed circuit.

Description:
This application claims the benefit of provisional patent application No. 62/155,989 filed on May 1, 2015, which is hereby incorporated by reference herein in its entirety. 
    
    
     BACKGROUND 
     This relates generally to electronic devices and, more particularly, to display backlight structures for electronic devices with displays and sensor circuitry. 
     Electronic devices often include displays. Displays include arrays of pixels that present images to a user. Some displays such as organic light-emitting diode displays have pixels containing light-emitting diodes. Other displays such as liquid crystal displays are backlit. In a typical configuration, a backlight unit for a display emits light that passes through an array of liquid crystal display pixels. The backlight unit may contain light-emitting diodes that emit light into the edge of a light guide plate. The light guide plate may distribute the light from the light guide plate across the display. Scattered light from the light guide plate may serve as backlight for the liquid crystal display. 
     It may be desirable to incorporate a sensor into a display. For example, some displays include touch sensor arrays. Challenges may arise when incorporating components such as sensors into devices that have displays. For example, it may be difficult to ensure that the electrical and mechanical properties of a sensor are compatible with an associated display and backlight structures. 
     It would therefore be desirable to be able to provide improved display structure such as improved backlight structures for an electronic device with a sensor. 
     SUMMARY 
     An electronic device may be provided with a rectangular housing having a pair of opposing short edges and a pair of opposing long edges. A display may be mounted within the housing. The display may deflect inwardly when pressed by a user. A flexible printed circuit with sensor electrode structures may measure capacitance changes associated with inward deflection of the display. 
     The display may be backlight using backlight structures. The backlight structures may include a backlight plate on which the flexible printed circuit is mounted. The backlight plate may be formed from a fiber-composite material such as carbon fiber. 
     Multiple carbon-fiber layers may be sandwiched together to form the backlight plate. The carbon-fiber layers may include a pair of inner unidirectional layers having fibers that span the short edges and a pair of outer unidirectional layers having fibers that run between the long edges parallel to the short edges. 
     An electromagnetic shield layer may be used to electromagnetically shield the flexible printed circuit. The backlight plate may have an opening in which conductive material such as a polymer that contains embedded metal particles is placed to short the electromagnetic shield layer to a ground pad on the flexible printed circuit. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of an illustrative electronic device having a display in accordance with an embodiment. 
         FIG. 2  is a cross-sectional side view of an illustrative liquid crystal display in accordance with an embodiment. 
         FIG. 3  is a cross-sectional side view of an illustrative electronic device having a display with a backlight and a sensor formed using a flexible printed circuit mounted on a backlight plate in accordance with an embodiment. 
         FIG. 4  is an exploded perspective view of an illustrative backlight plate in accordance with an embodiment. 
         FIG. 5  is a cross-sectional side view of an illustrative backlight plate in which a shield layer is formed from a layer of conductive adhesive that is grounded to a flexible printed circuit on the backlight plate in accordance with an embodiment. 
         FIG. 6  is a cross-sectional side view of an illustrative backlight plate in which a shield layer is formed from a metal coating on the backlight plate that is grounded to a flexible printed circuit on the backlight plate in accordance with an embodiment. 
         FIG. 7  is a cross-sectional side view of an illustrative backlight plate in which a shield layer is formed from a conductive layer on a flexible printed circuit mounted to the backlight plate in accordance with an embodiment. 
         FIG. 8  is a cross-sectional side view of an illustrative backlight plate containing a layer of metal foil that serves as a shield for a sensor flexible printed circuit that has been mounted on the plate in accordance with an embodiment. 
         FIG. 9  is a cross-sectional side view of an illustrative backlight plate in which a conductive shield layer has a shelf region that assists in forming a low resistance grounding path between the conductive shielding layer and a ground in a sensor flexible printed circuit on the backlight plate in accordance with an embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     An illustrative electronic device of the type that may be provided with a display is shown in  FIG. 1 . Electronic device  10  may be a computing device such as a laptop computer, a computer monitor containing an embedded computer, a tablet computer, a cellular telephone, a media player, or other handheld or portable electronic device, a smaller device such as a wrist-watch device, a pendant device, a headphone or earpiece device, a device embedded in eyeglasses or other equipment worn on a user&#39;s head, or other wearable or miniature device, a television, a computer display that does not contain an embedded computer, a gaming device, a navigation device, an embedded system such as a system in which electronic equipment with a display is mounted in a kiosk or automobile, equipment that implements the functionality of two or more of these devices, or other electronic equipment. In the illustrative configuration of  FIG. 1 , device  10  is a portable device such as a cellular telephone, media player, tablet computer, wrist device, or other portable computing device. Other configurations may be used for device  10  if desired. The example of  FIG. 1  is merely illustrative. 
     In the example of  FIG. 1 , device  10  includes a display such as display  14  mounted in housing  12 . Housing  12 , which may sometimes be referred to as an enclosure or case, may be formed of plastic, glass, ceramics, fiber composites, metal (e.g., stainless steel, aluminum, etc.), other suitable materials, or a combination of any two or more of these materials. Housing  12  may be formed using a unibody configuration in which some or all of housing  12  is machined or molded as a single structure or may be formed using multiple structures (e.g., an internal frame structure, one or more structures that form exterior housing surfaces, etc.). 
     Display  14  may be a touch screen display that incorporates a layer of conductive capacitive touch sensor electrodes or other touch sensor components (e.g., resistive touch sensor components, acoustic touch sensor components, force-based touch sensor components, light-based touch sensor components, etc.) or may be a display that is not touch-sensitive. Capacitive touch screen electrodes may be formed from an array of indium tin oxide pads or other transparent conductive structures. A touch sensor may be formed using electrodes or other structures on a display layer that contains a pixel array or on a separate touch panel layer that is attached to the pixel array (e.g., using adhesive). 
     Display  14  may include an array of pixels formed from liquid crystal display (LCD) components, an array of electrophoretic pixels, an array of plasma pixels, an array of organic light-emitting diode pixels or other light-emitting diodes, an array of electrowetting pixels, or pixels based on other display technologies. Configurations in which display  14  is a backlit liquid crystal display are sometimes described herein as an example. The use of liquid crystal display pixels to form display  14  is merely illustrative. Display  14  may, in general, be formed using any suitable type of pixels. 
     Display  14  may be protected using a display cover layer such as a layer of transparent glass or clear plastic. Openings may be formed in the display cover layer. For example, opening may be formed in the display cover layer to accommodate a button such as button  16 , a speaker port such as speaker port  18 , or other components. Openings may be formed in housing  12  to form communications ports (e.g., an audio jack port, a digital data port, etc.), to form openings for buttons, etc. 
     A cross-sectional side view of an illustrative configuration for display  14  is shown in  FIG. 2 . As shown in  FIG. 2 , display  14  may include backlight structures such as backlight unit  42  for producing backlight  44 . During operation, backlight  44  travels outwards (vertically upwards in dimension Z in the orientation of  FIG. 2 ) and passes through display pixel structures in display layers  46 . This illuminates any images that are being produced by the display pixels for viewing by a user. For example, backlight  44  may illuminate images on display layers  46  that are being viewed by viewer  48  in direction  50 . 
     Display layers  46  may be mounted in chassis structures such as a plastic chassis structure and/or a metal chassis structure to form a display module for mounting in housing  12  or display layers  46  may be mounted directly in housing  12  (e.g., by stacking display layers  46  into a recessed portion in housing  12 ). Display layers  46  may form a liquid crystal display or may be used in forming displays of other types. 
     Display layers  46  may include a liquid crystal layer such as liquid crystal layer  52 . Liquid crystal layer  52  may be sandwiched between display layers such as display layers  58  and  56 . Layers  56  and  58  may be interposed between lower polarizer layer  60  and upper polarizer layer  54 . 
     Layers  58  and  56  may be formed from transparent substrate layers such as clear layers of glass or plastic. Layers  58  and  56  may be layers such as a thin-film transistor layer and/or a color filter layer. Conductive traces, color filter elements, transistors, and other circuits and structures may be formed on the substrates of layers  58  and  56  (e.g., to form a thin-film transistor layer and/or a color filter layer). Touch sensor electrodes may also be incorporated into layers such as layers  58  and  56  and/or touch sensor electrodes may be formed on other substrates. 
     With one illustrative configuration, layer  58  may be a thin-film transistor layer that includes an array of pixel circuits based on thin-film transistors and associated electrodes (pixel electrodes) for applying electric fields to liquid crystal layer  52  and thereby displaying images on display  14 . Layer  56  may be a color filter layer that includes an array of color filter elements for providing display  14  with the ability to display color images. If desired, layer  58  may be a color filter layer and layer  56  may be a thin-film transistor layer. Configurations in which color filter elements are combined with thin-film transistor structures on a common substrate layer in the upper or lower portion of display  14  may also be used. 
     During operation of display  14  in device  10 , control circuitry (e.g., one or more integrated circuits on a printed circuit) may be used to generate information to be displayed on display  14  (e.g., display data). The information to be displayed may be conveyed to a display driver integrated circuit such as circuit  62 A or circuit  62 B using a signal path such as a signal path formed from conductive metal traces in a rigid or flexible printed circuit such as printed circuit  64  (as an example). 
     Backlight structures  42  may include a light guide plate such as light guide plate  78 . Light guide plate  78  may be formed from a transparent material such as clear glass or plastic. During operation of backlight structures  42 , a light source such as light source  72  may generate light  74 . Light source  72  may be, for example, an array of light-emitting diodes. 
     Light  74  from light source  72  may be coupled into edge surface  76  of light guide plate  78  and may be distributed in dimensions X and Y throughout light guide plate  78  due to the principal of total internal reflection. Light guide plate  78  may include light-scattering features such as pits or bumps. The light-scattering features may be located on an upper surface and/or on an opposing lower surface of light guide plate  78 . Light source  72  may be located at the left of light guide plate  78  as shown in  FIG. 2  or may be located along the right edge of plate  78  and/or other edges of plate  78 . 
     Light  74  that scatters upwards in direction Z from light guide plate  78  may serve as backlight  44  for display  14 . Light  74  that scatters downwards may be reflected back in the upwards direction by reflector  80 . Reflector  80  may be formed from a reflective material such as a layer of plastic covered with a dielectric mirror thin-film coating. 
     To enhance backlight performance for backlight structures  42 , backlight structures  42  may include optical films  70 . Optical films  70  may include diffuser layers for helping to homogenize backlight  44  and thereby reduce hotspots, compensation films for enhancing off-axis viewing, and brightness enhancement films (also sometimes referred to as turning films) for collimating backlight  44 . Optical films  70  may overlap the other structures in backlight unit  42  such as light guide plate  78  and reflector  80 . For example, if light guide plate  78  has a rectangular footprint in the X-Y plane of  FIG. 2 , optical films  70  and reflector  80  may have a matching rectangular footprint. If desired, films such as compensation films may be incorporated into other layers of display  14  (e.g., polarizer layers). 
     It may be desirable to incorporate a touch sensor and other sensors into device  10  to capture input from a user. For example, an array of capacitive touch sensor electrodes may be formed under the display cover layer for device  10  (i.e., between layers  46  and the outermost layer of display  14 ). If desired, force sensing technology may be incorporated into display  14  (e.g., to measure how firmly a user is pressing against display  14 ). 
     A cross-sectional side view of device  10  in an illustrative configuration in which device  10  includes a force sensor that detects pressure from a user&#39;s fingers or other external object is shown in  FIG. 3 . In the illustrative arrangement of  FIG. 3 , device  10  includes a display such as display  14  having display layers  46  (e.g., a liquid crystal display of the type shown in  FIG. 2 ) mounted under a display cover layer such as display cover layer  90  (e.g., a layer of clear glass, transparent plastic, sapphire, a combination of these materials, or other materials). Display cover layer  90  may be mounted on the front face of housing  12 , so that a user (e.g., fingertip  102  or other external object) may press downwards on display cover layer  90  in direction  104  to provide input to device  10 . 
     As shown in  FIG. 3 , backlight unit  42  (e.g., the backlight structures of  FIG. 2 ) may be located under lower surface  108  of display layers  46  and may be mounted in a support structure such as a chassis formed from plastic structures  94  and  96  and backlight plate  98 . Structures  94  and  96  may be formed from white and black shots of molded plastic respectively or may be formed from other plastic structures. Structures  94  and  96  may form a rectangular ring-shaped frame into which display structures such as backlight unit  42  and display layers  46  may be mounted. Unit  42  and layers  46  may have a rectangular outline when viewed from the front of device  10  and structures  94  and  96  may form all or part of a plastic rectangular ring or display  14  may have other shapes (e.g., display  14  may be round, etc.). 
     Plastic structures  94  and  96  may be supported by a supporting member such as backlight plate  98  (sometimes referred to as a backlight unit plate or M-chassis, etc.). Structures  94  and  96  may be attached to plate  98  using a layer of adhesive (e.g., pressure sensitive adhesive or liquid adhesive such as adhesive cured using room temperature curing, elevated temperature curing, moisture curing, curing by application of ultraviolet light or other light, curing using catalyst, or other curing techniques, etc.). The thickness of the adhesive used to attach structures  94  and  96  to plate  98  may be 10-60 microns, more than 5 microns, less than 70 microns, or other suitable thickness. Plate  98  may form a structural support for backlight  42  and may be formed from metal, plastic, fiber-composite material such as carbon fiber materials, other materials, or combinations of these materials. Plate  98  may be solid (i.e., plate  98  may form a substantially rectangular member without openings) or plate  98  may have one or more openings. 
     A flexible printed circuit for a force sensor (sometimes referred to as a “sensor flex”) such as sensor flex  100  may be mounted on plate  98 . Sensor flex  100  may include one or more electrodes that make capacitance measurements. The capacitance signals measured by the electrode structures on sensor flex  100  are proportional to the distance G between the sensor flex electrodes and the conductive structures of thin-film transistor layer  58  on lower surface  108  of display layers  46 . The measured capacitance may be lowest when finger  102  is not pressing downwards on display cover layer  90 . In this configuration, layer  90 , surface  108  of display layer  46 , and backlight unit  42  are undeflected (i.e., these layers are planar). When a user presses finger  102  downwards on the upper surface of layer  90  in direction  104 , layer  90 , display layers  46 , and backlight unit  42  may deflect downwards towards the electrode structures of sensor flex  100 . The reduction in the distance G between the conductive electrode structures formed from thin-film transistor layer  58  and the conductive electrode structures in sensor flex  100  results in an increase in the measured capacitance. The change in capacitance that is sensed in this way is proportional to the amount of downward force by finger  102  and therefore can be used as a force sensor output signal. 
     Satisfactory operation of the force sensor that measures the capacitance between deflecting display layer  46  and sensor flex  100  can be ensured by forming backlight plate  98  from a rigid layer. When plate  98  is sufficiently rigid, plate  98  and therefore sensor flex  100  will exhibit minimal deflection or no deflection when a user presses in direction  104  on display  14 . As a result, the deflection of display  14  (e.g., surface  108 ) relative to the conductive sensor electrodes on sensor flex  100  can be accurately measured. Plate  98  may be formed from one or more layers of rigid material such as metal, plastic, ceramic, etc. With one suitable arrangement, plate  98  is formed from a fiber-based composite such as carbon fiber material. 
     As shown in  FIG. 3 , electrical components  110  may be mounted within the interior of housing  12 . Electrical components  110  may include integrated circuits, wireless circuitry, and other devices that produce electromagnetic signals that have the potential to interfere with the operation of the force sensor formed from sensor flex  100  and other components in device  10 . To reduce interference, it may be desirable to interpose an electromagnetic shield between components  108  and the force sensor electrode structures of sensor flex  100 . For example, a layer of conductive material may be incorporated into plate  98 , may be mounted on plate  98 , or may be incorporated into sensor flex  100  (e.g., on the lower surface of flex  100 ) to serve as an electromagnetic shield. 
     The electromagnetic shield may be grounded by coupling the electromagnetic shield to a suitable source of ground potential. With one illustrative arrangement, sensor flex  100  contains a ground (e.g., one or more metal traces patterned to form ground contacts) and a conductive path is used to short the electromagnetic shield layer to the ground. The conductive path may be formed from a conductive polymer. The conductive polymer may be formed by incorporating metal particles or other conductive particles into a polymer binder. The binder (resin) may be a liquid polymer that is cured at room temperature, that is cured using a catalyst, that is cured by applying heat, and/or that is cured by applying ultraviolet light, light at other wavelengths, or other energy to cure and harden the conductive polymer. With one suitable arrangement, the conductive polymer that is used to ground the shield layer to the ground traces in sensor flex  100  is curable liquid polymer that includes silver particles. Other conductive structures may be used to ground the shield to the ground traces of sensor flex  100  or other source of ground potential in device  10  if desired. 
     Backlight plate  98  may be formed from fiber composite materials such as carbon fiber materials or fiber composites with other types of fiber impregnated in a polymer binder (sometimes referred to as a matrix) such as epoxy or other curable resin. One or more layers of fiber-composite material may be used in forming plate  98 . The fiber-composite material may be formed from unidirectional fibers, from woven fibers, from multiple layers each having fibers and/or fabric formed from fibers that are oriented in different directions, or other types of fiber-composite structures. If desired, fiber-composite layers may be combined with plastic sheets, metal sheets, and/or other layers of material. Configurations in which backlight plate  98  has been formed from multiple unidirectional sheets of carbon fiber material are sometimes described herein as an example. This is, however, merely illustrative. Plate  98  may be formed from any suitable materials. 
     An exploded perspective view of an illustrative set of carbon fiber layers that may be used in forming plate  98  is shown in  FIG. 4 . In the example of  FIG. 4 , plate  98  has been formed from four carbon fiber layers  98 - 1 ,  98 - 2 ,  98 - 3 , and  98 - 4 . Initially, these layers may be provided in the form of partly cured material (sometimes referred to as prepreg). Plate  98  may by formed by compressing these layers together (with or without intervening layers of adhesive) under heat and pressure until the prepreg is cured and forms a rigid support member. The thickness of plate  98  (e.g., the collective thickness of layers  98 - 1 ,  98 - 2 ,  98 - 3 , and  98 - 4  or other such layers) may be 0.2-0.4 mm, more than 0.1 mm, less than 0.7 mm, less than 0.6 mm, less than 0.4 mm, etc. 
     Each layer in plate  98  may be a unidirectional carbon fiber layer having carbon fibers that run along one of its lateral dimensions. In the example of  FIG. 4 , the two outermost layers of the stack of layers in  FIG. 4  (i.e., upper layer  98 - 1  and lower layer  98 - 4 ) preferably each have carbon fibers  112  that run parallel to their shorter lateral dimension (i.e., dimension X, which corresponds to the width of display  14  from left to right in device  10  of  FIG. 1 ). Fibers  112  in the outer layers therefore run between the two opposing long edges of housing  12 . The diameters of fibers  112  may be about 10 microns, less than 25 microns, 5-15 microns, more than 2 microns, less than 15 microns, or other suitable size. The two innermost layers of the stack of layers in  FIG. 4  (i.e., middle layers  98 - 2  and  98 - 3 ) preferably each have carbon fibers  112  that run parallel to their longer lateral dimension (i.e., dimension Y, which corresponds to the length of display  14  from its lower edge to its upper edge in device  10  of  FIG. 1 ). The innermost layers therefore span the two opposing shorter edges of housing  12  and run parallel to the longer edges of housing  12 . 
     Because the fibers in different layers are oriented perpendicular to each other, the rigidity of plate  98  is enhanced. Rigidity is further enhanced in the arrangement of  FIG. 4  by placing the layers whose fibers  112  span the shorter lateral dimension of plate  98  (i.e., layers  98 - 1  and  98 - 4 ) at the outermost layer positions in the stack of layers. In this position, the width-spanning fibers  112  of layers  98 - 1  and  98 - 4 , which can be supported by portions of device  10  such as housing  12  and structures  94  and  96  of  FIG. 3 , are farthest from the center of plate  98  (i.e., farthest in vertical dimension Z from the center of plate  98  in vertical dimension Z) and are therefore most effective at resisting bending of plate  98  out of the X-Y plane. Because the layers of  FIG. 4  are vertically symmetrical (i.e., because layers  98 - 1  and  98 - 2  form a mirror image of layers  98 - 3  and  98 - 4 ), the neutral stress plane of plate  98  may be aligned with the middle of plate  98 , thereby helping to reduce and balance stresses within plate  98  when plate  98  is deflected. 
       FIG. 5  is a cross-sectional side view of plate  98  and sensor flex  100  showing how an electromagnetic shield may be formed from a conductive adhesive layer between plate  98  and sensor flex  100 . Sensor flex  100  may have ground traces  114  that form one or more ground contacts such as illustrative ground pad  114 ′. Traces  114  may be coupled to a source of ground potential within device  10 . Electromagnetic shield  116  may be formed from a layer of conductive material interposed between sensor flex  100  and backlight plate  98 . With one suitable arrangement, electromagnetic shield  116  may be formed from a layer of conductive adhesive (e.g., a polymer containing conductive particles such as metal particles). With another suitable arrangement, electromagnetic shield  116  may be formed from a layer of metal foil (e.g., copper foil, aluminum foil, or other metal foil). 
     Shield  116  (e.g., conductive adhesive, metal foil, or other conductive material) may be sandwiched between upper and lower layers of adhesive such as upper pressure sensitive adhesive layer  126  and lower pressure sensitive adhesive layer  118  (e.g., pressure sensitive adhesive layers or other adhesive layers that are not conducting). Aligned openings may be formed within layers  126 ,  116 ,  118 , and  98  to form a cylindrical opening or other hole such as opening  122 . Opening  122  penetrates from rear surface  128  of plate  98  to the lower surface of sensor flex  100 , thereby exposing ground pad  114 ′. This allows conductive material  124  (e.g., a conductive material such as a curable liquid polymer containing metal particles) to be placed into opening  122 . Conductive material  124  creates a short circuit path such as path  120  that shorts shield  116  to ground pad  144 ′, thereby grounding shield  116 . 
     If desired, the size and/or shape of the openings in the layers of  FIG. 5  may be different. For example, the sizes and shapes of the openings formed through layers  98 ,  118 ,  116 , and  126  to create the hole that exposes pad  114 ′ need not be of identical shapes and sizes. For example, the openings in adhesive layers  118  and/or  126  may be larger than the opening in shield layer  116  to help create additional exposed surfaces on shield layer  116 . These exposed surfaces may help form a satisfactory electrical connection between material  124  and shield  116 . 
     As shown in the illustrative configuration of  FIG. 6 , shield  116  may be formed by depositing a metal coating on upper surface  130  of plate  98 . The metal layer that is used in forming shield  116  may be deposited using physical vapor deposition (e.g., evaporation or sputtering), may be formed using electrochemical deposition (e.g., using electroplating or electroless deposition techniques), and/or by otherwise applying a conductive coating to upper surface  130  of plate  98 . Opening  122  may be filled with conductive material  124  to short shield  116  to ground pad  114 ′, as illustrated by conductive path  120 . 
     Another illustrative arrangement for forming shield  116  between plate  98  and sensor flex  100  is shown in  FIG. 7 . In the configuration of  FIG. 7 , shield  116  has been formed from a metal coating layer on lower surface  132  of sensor flex  100 . Shield  116  may be coupled to ground traces  114  in sensor flex  100 , thereby grounding shield  116 . Shield  116  may be formed from a planar region of metal traces (e.g., a blanket metal film) that is formed as part of the process of fabricating sensor flex  110 . A layer of adhesive such as pressure sensitive adhesive  126  may be interposed between plate  98  and sensor flex  100  and may be used to attach sensor flex  100  to plate  98 . With this type of approach, ground traces  114  may be coupled to shield  116  directly without need for additional conductive material such as conductive material  124 . 
     In the illustrative arrangement of  FIG. 8 , shield  116  has been formed from a metal layer such as a layer of metal foil (e.g., at thin sheet of metal having a thickness of 1-100 microns, 5-20 microns, 10-12 microns, 10-200 microns, less than 200 microns, less than 100 microns, more than 5 microns, or other suitable thickness). Shield  116  may be interposed between layers  98 - 1  and  98 - 2  of plate  98  and layers  98 - 3  and  98 - 4  of plate  98  or may be sandwiched between any other pair of layers in plate  98 . The layers of plate  98  may be formed from carbon fiber prepreg that binds to shield  116  when cured under heat and pressure to form plate  98  and/or shield  116  may be coupled to the layers of plate  98  using layers of adhesive. Conductive material  124  in opening  122  may be used to electrically coupled shield  116  to ground pad  114 ′, as indicated by conductive path  120 . 
     As shown in the illustrative configuration of  FIG. 9 , the size of opening  122  may be enlarged as opening  122  passes through one or more of the layers adjacent to shield layer  116 . Shield layer  116  of  FIG. 9  may be, for example, a layer of metal foil or other metal layer that has been embedded between layers  98 - 2  and  98 - 3  of plate  98 . Plate  98  may be attached to sensor flex  100  using pressure sensitive adhesive layer  126 . In the example of  FIG. 9 , the opening in layers  98 - 1  and  98 - 2  of plate  98  is larger than the opening in layers  98 - 3  and  98 - 4 . This exposes surface  140  of shield  116  (e.g., a circular ring-shaped surface that surrounds openings  122  or other exposed surface of shield  116 ) to conductive material  124  and helps form a low-resistance path (path  120 ) between shield  116  and ground pad  114 ′. Openings such as opening  122  of  FIG. 9  may be formed using a milling tool (e.g., a mechanical machining tool), an etching tool, a laser drilling tool, or other suitable equipment for forming openings in plate  98  that expose metal surfaces such as surfaces  140 . 
     The foregoing is merely illustrative and various modifications can be made by those skilled in the art without departing from the scope and spirit of the described embodiments. The foregoing embodiments may be implemented individually or in any combination.

Metadata:
Filing Date: 20151012
Publication Date: 20180529
Grant Date: 20180529
Priority Date: 20150501
Inventors: SCHLAUPITZ, ALEXANDER D.
HOWE, JACQUELINE M.
Assignee: APPLE INC
CPC Classifications: [{"code": "H05K1/0393", "inventive": false, "first": false, "tree": "[]"}, {"code": "H05K1/16", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F2203/04107", "inventive": false, "first": false, "tree": "[]"}, {"code": "H05K2201/10151", "inventive": false, "first": false, "tree": "[]"}, {"code": "H05K1/0393", "inventive": false, "first": false, "tree": "[]"}, {"code": "H05K1/0216", "inventive": false, "first": false, "tree": "[]"}, {"code": "G06F2203/04107", "inventive": false, "first": false, "tree": "[]"}, {"code": "H05K1/0216", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02B6/0051", "inventive": false, "first": false, "tree": "[]"}, {"code": "H05K2201/10151", "inventive": false, "first": false, "tree": "[]"}, {"code": "H05K1/16", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02B6/0065", "inventive": true, "first": false, "tree": "[]"}, {"code": "H05K1/0216", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02B6/0035", "inventive": true, "first": true, "tree": "[]"}, {"code": "H05K2201/10151", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02B6/0065", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F3/044", "inventive": true, "first": false, "tree": "[]"}, {"code": "H05K1/16", "inventive": true, "first": false, "tree": "[]"}, {"code": "H05K1/0393", "inventive": false, "first": false, "tree": "[]"}, {"code": "G06F2203/04107", "inventive": false, "first": false, "tree": "[]"}, {"code": "G06F3/044", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02B6/0055", "inventive": true, "first": true, "tree": "[]"}, {"code": "G02B6/0051", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02B6/0035", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02B6/0055", "inventive": true, "first": true, "tree": "[]"}, {"code": "G06F3/044", "inventive": false, "first": false, "tree": "[]"}]
Family ID: 57204789