PATENT DOCUMENT

Publication Number: US-10361384-B2
Application Number: US-201615068279-A
Country: US
Kind Code: B2

Title: Displays with shared flexible substrates

Abstract:
An electronic device may be provided with a display such as an organic light-emitting diode display. The display may include an array of display pixels formed on a polymer substrate layer. The polymer substrate layer may include an contiguous layer of polyimide that forms a substrate layer in additional structures such as a polymer film and a flexible printed circuit. A first transition region may be interposed between the display and the polymer film, and a second transition region may be interposed between the polymer film and the flexible printed circuit. Metal traces may be formed on the polymer film and on the flexible printed circuit. A display driver integrated circuit may be mounted to the traces on the polymer film. The polymer film may form a U-shaped bend. The flexible printed circuit may be coupled to a printed circuit board in the device using hot bar solder connections.

Claims:
What is claimed is: 
     
       1. An electronic device, comprising:
 a polymer substrate having a curved portion between first and second planar portions; 
 an array of organic light-emitting diode display pixels on the first planar portion of the polymer substrate; 
 a flexible printed circuit having multiple layers including a conductive layer and an insulating layer, wherein the second planar portion of the polymer substrate is interposed between the conductive layer and the insulating layer; and 
 at least one metal layer on the curved portion of the polymer substrate. 
 
     
     
       2. The electronic device defined in  claim 1  wherein the first planar portion of the polymer substrate extends under the entire array of organic light-emitting diode display pixels. 
     
     
       3. The electronic device defined in  claim 1  further comprising a buffer layer and a passivation layer on the first planar portion of the polymer substrate. 
     
     
       4. The electronic device defined in  claim 3  wherein the buffer layer and the passivation layer are interposed between the array of organic light-emitting diode display pixels and the first planar portion of the polymer substrate. 
     
     
       5. The electronic device defined in  claim 3  wherein the buffer layer and the passivation layer do not extend onto the second planar portion of the polymer substrate. 
     
     
       6. The electronic device defined in  claim 1  wherein the flexible printed circuit comprises a conductive via and wherein the polymer substrate overlaps the conductive via. 
     
     
       7. The electronic device defined in  claim 1  further comprising an adhesive layer and a layer of coverlay formed over the at least on metal layer on the curved portion of the polymer substrate. 
     
     
       8. The electronic device defined in  claim 7  wherein the adhesive layer and the layer of coverlay do not extend onto the second planar portion of the polymer substrate. 
     
     
       9. The electronic device defined in  claim 1  wherein the first planar portion of the polymer substrate overlaps the second planar portion of the polymer substrate. 
     
     
       10. An electronic device, comprising:
 a display having at least first and second layers; 
 a printed circuit having at least first and second layers; and 
 a flexible substrate having a first portion interposed between the first and second layers of the display, a second portion interposed between the first and second layers of the printed circuit, and a curved portion between the first and second portions, wherein the first portion overlaps the second portion. 
 
     
     
       11. The electronic device defined in  claim 10  wherein the display comprises an organic light-emitting diode display, wherein the first layer in the display comprises organic emissive material and the second layer in the display comprises a polymer support structure. 
     
     
       12. The electronic device defined in  claim 11  wherein the first and second layers in the printed circuit comprise first and second metal layers. 
     
     
       13. The electronic device defined in  claim 12  wherein the first and second metal layers do not extend onto the first portion of the flexible substrate and wherein the organic emissive material and the polymer support structure do not extend onto the second portion of the flexible substrate. 
     
     
       14. An electronic device, comprising:
 a substrate having first and second regions; 
 a display comprising an organic emissive layer and thin-film transistor array on the first region of the substrate; 
 a printed circuit having multiple layers including a metal layer and a polymer layer, wherein the second region of the substrate is interposed between the metal layer and the polymer layer, wherein the metal layer and the polymer layer do not extend onto the first region of the substrate and wherein the organic emissive layer and the thin-film transistor array do not extend onto the second region of the substrate; and 
 a support layer that supports the first region of the substrate, wherein the substrate is interposed between the support layer and the organic emissive material. 
 
     
     
       15. The electronic device defined in  claim 14  wherein the substrate comprises a flexible polymer substrate having a bend and wherein the first region of the substrate overlaps the second region of the substrate. 
     
     
       16. The electronic device defined in  claim 14  wherein the printed circuit comprises signal traces that convey signals to the thin-film transistor array. 
     
     
       17. The electronic device defined in  claim 14  wherein the support layer and the substrate each comprise polymer. 
     
     
       18. The electronic device defined in  claim 14  further comprising a polarizer on the first region of the substrate, wherein the organic emissive material is interposed between the substrate and the polarizer.

Description:
This application claims priority to U.S. patent application Ser. No. 14/172,488, filed Feb. 3, 2014, and provisional patent application No. 61/769,686, filed Feb. 26, 2013, which are hereby incorporated by reference herein in their entireties. 
    
    
     BACKGROUND 
     This relates generally to electronic devices, and more particularly, to electronic devices with displays. 
     Electronic devices often include displays. For example, cellular telephones and portable computers often include displays for presenting information to a user. An electronic device may have a housing such as a housing formed from plastic or metal. Components for the electronic device such as display components may be mounted in the housing. 
     It can be challenging to incorporate a display into the housing of an electronic device. Size and weight are often important considerations in designing electronic devices. If care is not taken, displays may be bulky or may be surrounded by overly large borders. The housing of an electronic device can be adjusted to accommodate a bulky display with large borders, but this can lead to undesirable enlargement of the size and weight of the housing and unappealing device aesthetics. 
     It would therefore be desirable to be able to provide improved displays for electronic devices. 
     SUMMARY 
     An electronic device may be provided with a display such as a light-emitting diode display. The light-emitting diode display may include an array of organic light-emitting diode display pixels formed on a substrate such as a polymer substrate layer. The polymer substrate layer may extend out from the display and may form a layer in additional structures in the electronic device such as a polymer film and a flexible printed circuit. 
     The polymer substrate layer may be a contiguous layer of polyimide having a first region that forms a display substrate layer in the display, a second region that forms a polymer film substrate layer in a polymer film, and a third region that forms a flexible printed circuit layer in a flexible printed circuit. 
     A first transition region may be interposed between the display and the polymer film. A second transition region may be interposed between the polymer film and the flexible printed circuit. 
     The first transition region may include layers that are shared with the display and may include layers that are shared with the polymer film such as one or more layers of metal. For this reason, the first transition region may be thicker than the polymer film. 
     The second transition region may include layers that are shared with the polymer film and may include layers that are shared with the flexible printed circuit. For this reason, the second transition region may be thicker than the polymer film and may be thicker than the flexible printed circuit. 
     The polymer film may include one or more layers of metal and the flexible printed circuit may include one or more layers of metal. The flexible printed circuit may, for example, include more layers of metal than the polymer film. The flexible printed circuit may include metal layers formed on one surface of the shared flexible polymer substrate layer and additional metal layers formed on an opposing surface of the shared flexible polymer substrate layer. Vertical conductive structures such as conductive vias may be used to form electrical connections between metal layers in the flexible printed circuit. 
     The array of display pixels may be formed on a first region of the flexible polymer substrate layer and a plurality of metal traces may be formed in a second region of the flexible substrate layer. A display driver integrated circuit may be mounted to the metal traces in the second region. The flexible polymer substrate layer may include U-shaped bend such that the first region of the flexible polymer substrate layer overlaps the display driver integrated circuit in the second region of the flexible polymer substrate layer. At least a portion of the display may overlap the display driver integrated circuit. 
     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 such as a laptop computer with a display in accordance with an embodiment of the present invention. 
         FIG. 2  is a perspective view of an illustrative electronic device such as a handheld electronic device with a display in accordance with an embodiment of the present invention. 
         FIG. 3  is a perspective view of an illustrative electronic device such as a tablet computer with a display in accordance with an embodiment of the present invention. 
         FIG. 4  is a perspective view of an illustrative electronic device such as a computer display with display structures in accordance with an embodiment of the present invention. 
         FIG. 5  is a circuit diagram of a portion of an illustrative pixel array that may be used in a display of the type shown in  FIGS. 1-4  in accordance with an embodiment of the present invention. 
         FIG. 6  is a cross-sectional side view of an illustrative display such as an organic light-emitting diode display in accordance with an embodiment of the present invention. 
         FIG. 7  is a perspective view of a display, a first transition region, a polymer film, a second transition region, and a flexible printed circuit that share a flexible polymer substrate layer in accordance with an embodiment of the present invention. 
         FIG. 8  is a cross-sectional side view of a portion of a display, a first transition region, a polymer film, a second transition region, and a flexible printed circuit that share a flexible polymer substrate layer in accordance with an embodiment of the present invention. 
         FIG. 9  is a cross-sectional side view a portion of an illustrative electronic device in which a contiguous flexible polymer substrate layer forms part of a display, a polymer film, and a flexible printed circuit and in which the contiguous flexible polymer layer is connected to a printed circuit board using solder in accordance with an embodiment of the present invention. 
         FIG. 10  is a diagram illustrating how a flexible printed circuit that shares a layer with a display may be soldered to a printed circuit board using hot bar soldering tools in accordance with an embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     Electronic devices may include displays. The displays may be used to display images to a user. Illustrative electronic devices that may be provided with displays are shown in  FIGS. 1, 2, 3, and 4 . 
       FIG. 1  shows how electronic device  10  may have the shape of a laptop computer having upper housing  12 A and lower housing  12 B with components such as keyboard  16  and touchpad  18 . Device  10  may have hinge structures  20  that allow upper housing  12 A to rotate in directions  22  about rotational axis  24  relative to lower housing  12 B. Display  14  may be mounted in upper housing  12 A. Upper housing  12 A, which may sometimes referred to as a display housing or lid, may be placed in a closed position by rotating upper housing  12 A towards lower housing  12 B about rotational axis  24 . 
       FIG. 2  shows how electronic device  10  may be a handheld device such as a cellular telephone, music player, gaming device, navigation unit, or other compact device. In this type of configuration for device  10 , housing  12  may have opposing front and rear surfaces. Display  14  may be mounted on a front face of housing  12 . Display  14  may, if desired, have openings for components such as button  26 . Openings may also be formed in display  14  to accommodate a speaker port (see, e.g., speaker port  28  of  FIG. 2 ). 
       FIG. 3  shows how electronic device  10  may be a tablet computer. In electronic device  10  of  FIG. 3 , housing  12  may have opposing planar front and rear surfaces. Display  14  may be mounted on the front surface of housing  12 . As shown in  FIG. 3 , display  14  may have an opening to accommodate button  26  (as an example). 
       FIG. 4  shows how electronic device  10  may be a computer display or a computer that has been integrated into a computer display. With this type of arrangement, housing  12  for device  10  may be mounted on a support structure such as stand  19 . Display  14  may be mounted on a front face of housing  12 . 
     The illustrative configurations for device  10  that are shown in  FIGS. 1, 2, 3, and 4  are merely illustrative. In general, electronic device  10  may be 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, 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. 
     Housing  12  of device  10 , which is sometimes referred to as a case, may be formed of materials such as plastic, glass, ceramics, carbon-fiber composites and other fiber-based composites, metal (e.g., machined aluminum, stainless steel, or other metals), other materials, or a combination of these materials. Device  10  may be formed using a unibody construction in which most or all of housing  12  is formed from a single structural element (e.g., a piece of machined metal or a piece of molded plastic) or may be formed from multiple housing structures (e.g., outer housing structures that have been mounted to internal frame elements or other internal housing structures). 
     Device  10  may have one or more displays such as display  14 . Display  14  may be an organic light-emitting diode (OLED) display or other suitable display. Display  14  may, if desired, include capacitive touch sensor electrodes for a capacitive touch sensor array or other touch sensor structures (i.e., display  14  may be a touch screen). Touch sensor electrodes may be provided on a touch panel layer that is interposed between organic light-emitting diode display structures and a transparent cover layer (e.g., a cover glass layer), may be formed on the underside of a cover layer, or may otherwise be incorporated into display  14 . 
     As shown in  FIGS. 1, 2, 3, and 4 , display  14  may be characterized by a central active region such as active region AA in which an array of display pixels is used in displaying information for a user. Active region AA may be surrounded by an inactive region such as inactive border region IA. Active region AA may have a rectangular shape. Inactive region IA may have a rectangular ring shape that surrounds active region AA (as an example). Portions of display  14  in inactive region IA may be covered with an opaque masking material such as a layer of black ink (e.g., a polymer filled with carbon black) or a layer of opaque metal. The opaque masking layer may help hide components in the interior of device  10  in inactive region IA from view by a user. 
     The organic light-emitting diode display structures (sometimes referred to as the OLED display structures, the OLED structures, the organic light-emitting diode structures, the organic light-emitting diode layer, the light-generating layers, the image-generating layers, the display layer, or the image pixel layer) may have a planar rectangular active region in its center that forms active area AA of display  14 . The rectangular active region includes an array of organic light-emitting diode pixels. The edges of the organic light-emitting diode layer surround the active center region and form a rectangular peripheral ring. This border region contains circuitry such as signal lines and display driver circuitry that does not emit light and is therefore referred to as the inactive portion of the display. The inactive portion of the display is shown as inactive border region IA in  FIGS. 1, 2, 3, and 4 . 
     A portion of the active region in display  14  is shown in  FIG. 4 . As shown in  FIG. 4 , the active region may include an array such as array  21  of organic light-emitting diode display pixels  23 . Pixels  23  may be arranged in rows and columns in array  21  and may be controlled using a pattern of orthogonal control lines. The control lines in pixel array  21  may include gate lines  27  and data lines  25 . 
     Each pixel may include a light-emitting element such as organic light-emitting diode  31  and associated control circuitry  29 . Control circuitry  29  may be coupled to the data lines and gate lines so that control signals such as data line signals and gate line signals may be received from driver circuitry such as a display driver integrated circuit. Data line signals on data lines  25  may be provided to the columns of display pixels  23  in pixel array  21 . Gate line signals on gate lines  25  may be provided to the rows of pixels  23  in pixel array  21 . 
     Driver circuitry may include on-display driver circuits such as one or more gate line drivers implemented using low-temperature polysilicon transistors formed in the inactive portion of the display. The driver circuitry may also include a driver integrated circuit. The driver integrated circuit may be mounted in the inactive region of display  14  or may be mounted on a printed circuit or film that is electrically coupled to display  14 . The display driver integrated circuit may, for example, be mounted on a polymer film that shares a flexible polymer substrate layer with display  14 . 
     A cross-sectional side view of an illustrative organic light-emitting diode display such as display  14  is shown in  FIG. 6 . As shown in  FIG. 6 , display  14  may include image-generating layers such as organic light-emitting diode display structures  30 . Display structures  30  may be mounted on a display substrate layer such as display substrate layer  32 . Display substrate layer  32  may be mounted on a support layer such as support layer  36  using an adhesive such as adhesive  34 . 
     If desired, additional layers may be included in display  14 . For example, display  14  may include a display cover layer (e.g., a flexible or rigid cover layer formed from plastic or glass), a touch-sensitive layer having touch-sensitive circuitry (e.g., capacitive touch electrodes or other touch-sensitive circuitry configured to detect the location of one or more touches or near touches on display  14 ), and/or other display layers not shown in  FIG. 6 . 
     Organic light-emitting diode structures  30  may include multiple layers such as organic emissive layer  44 , an adhesive layer such as adhesive layer  42 , an encapsulation layer such as encapsulation film layer  40 , and a polarizer such as polarizer  38 . 
     Organic emissive layer  44  may include a layer of organic emissive material integrated into a thin-film transistor matrix. The thin-film transistor matrix may include an array of electrodes such as thin-film transistor electrodes  48 . Organic emissive material in layer  44  may be formed from organic plastics such as polyfluorene or other organic emissive materials. Encapsulation film layer  40  may be configured to encapsulate organic emissive layer  44 . Encapsulation film layer  40  may be formed from a layer of metal foil, metal foil covered with plastic, other metal structures, a glass layer, a thin-film encapsulation layer formed from materials such as silicon nitride, a layered stack of alternating polymer and ceramic materials, a layered stack of alternating polymer and ceramic materials, or other suitable material for encapsulating organic emissive material  44 . Encapsulation layer  40  protects organic emissive material  44  from environmental exposure by preventing water and oxygen from reaching organic emissive materials within display  14 . 
     Image light from the organic light-emitting diode pixels in layer  44  is emitted upwards through adhesive  42 , encapsulation film  40 , and polarizer  38 . Polarizer  38  may be a circular polarizer configured to suppress reflections from the metal signal lines in layer  44  that might otherwise be visible to a user. 
     Thin-film transistor circuitry  48  may be formed on the surface of a display substrate such as display substrate layer  32 . If desired, a passivation layer such as passivation layer  46  may be formed on the surface of display substrate layer  32  (e.g., interposed between organic emissive layer  44  and display substrate layer  32 ). Display substrate layer  32  may be mounted on support structure  36 . 
     Display substrate layer  32  and support structure  36  may be polymer-based layers formed from thin plastic films. Examples of materials that may be used to form display substrate layer  32  and/or support structure  36  include polyimide, polyethylene naphthalate (PEN), polyethylene terephthalate (PET), other suitable polymers, a combination of these polymers, etc. Other suitable substrate materials that may be used to from layer  32  and/or layer  36  include glass, metal foil covered with a dielectric, a multi-layer polymer stack, a thin glass film bonded to a thin polymer, a polymer composite film comprising a polymer material combined with nanoparticles or microparticles dispersed therein, etc. In one suitable arrangement that is sometimes described herein as an example, display substrate layer  32  is formed from a layer of polyimide. Polyimide layer  32  may have a thickness of 10-25 microns, 14-40 microns, 15-20 microns, or more than 5 microns. 
     Thin-film transistor circuitry  48  may receive control signals via signal lines in layer  44  (e.g., via gate lines  27  and data lines  25  of  FIG. 5 ). Signals applied to the thin-film transistors in organic emissive layer  44  selectively cause portions of emissive layer  44  to emit display light and thereby display images on display  14  in the active area. 
     In conventional electronic devices, a display driver integrated circuit is mounted in the inactive area of a display. The inactive area includes space for fanning out control lines from a centralized location at which a signal cable for the driver circuitry is attached. The signal cable routes signals from a main logic board or other printed circuit board to the driver circuitry. Typically, a conductive adhesive is used to mount one end of the signal cable to the display. A board-to-board connector is often used to connector the opposing end of the signal cable to the main logic board. This type of configuration often requires a significant amount of inactive border area and can also lead to a bulky and aesthetically unappealing device. Moreover, connecting structures such as adhesive attachment structures increase the risk of disconnection between parts which in turn can lead to display failure. 
     To minimize the inactive area of a display while also reducing the need for connecting structures such as adhesives and board-to-board connectors, a polymer substrate layer such as flexible polymer substrate layer  32  may extend beyond the edge of support layer  36  and may be used as a substrate layer for additional structures such as polymer films having photolithographically patterned traces and flexible printed circuits (e.g., flexible printed circuits having traces, vias, hot bar pads, etc.). By using a single contiguous layer of flexible polymer such as polyimide as a base layer (e.g., a substrate layer) for multiple structures in device  10 , the need for additional connecting structures and the risk of unintentional disconnections may be minimized. 
     As shown in  FIG. 6 , region A of flexible polymer substrate  32  forms a substrate layer in display  14 . Region A of flexible polymer substrate layer  32  may sometimes be referred to as flexible polymer substrate layer  32 A. Organic light-emitting diode pixels  23  ( FIG. 5 ) may be formed on flexible polymer substrate layer  32 A (i.e., region A of flexible polymer substrate layer  32 ). 
       FIG. 7  shows how flexible polymer substrate layer  32  may form a layer in additional structures such as a polymer film and a flexible printed circuit. As shown in  FIG. 7 , portion  32 A of substrate layer  32  forms a layer in display  14  (region A), portion  32 C of substrate layer  32  forms a layer in polymer film  84  (region C), and portion  32 E of substrate layer  32  forms a layer in flexible printed circuit  86  (region E). Portion  32 B of substrate layer  32  forms a layer in transition region  81  (region B) where display  14  transitions into polymer film  84 . Portion  32 D of substrate layer  32  forms a layer in transition region  83  (region D) where polymer film  84  transitions into flexible printed circuit  86 . 
     For simplicity,  FIG. 7  does not show the individual layers that make up display  14 , transition region  81 , polymer film  84 , transition region  83 , and flexible printed circuit  86 . However, it should be understood that display  14  includes additional layers and structures coupled to region A of substrate layer  32  (sometimes referred to herein as substrate layer  32 A); transition region  81  includes additional layers and structures coupled to region B of substrate layer  32  (sometimes referred to herein as substrate layer  32 B); polymer film includes additional layers and structures coupled to region C of substrate layer (sometimes referred to herein as substrate layer  32 C); transition region  83  includes additional layers and structures coupled to region D of substrate layer  32  (sometimes referred to herein as substrate layer  32 D); and flexible printed circuit includes additional layers and structures coupled to region E of substrate layer  32  (sometimes referred to herein as substrate layer  32 E). The individual layers that make up display  14  are described in the illustrative configuration of  FIG. 6 . The individual layers that make up transition region  81 , polymer film  84 , transition region  83 , and flexible printed circuit  86  are shown in  FIG. 8  and will be described in greater detail in connection with  FIG. 8 . 
     Because display  14 , polymer film  84 , flexible printed circuit  86 , and transition regions  81  and  83  are formed from different layers and different combinations of layers, display  14 , polymer film  84 , flexible printed circuit  86 , and transition regions  81  and  83  may have different thicknesses. For example, display  14  may have a thickness T 1  (in a first region of display  14 ), transition region  81  may have a thickness T 2 , polymer film  84  may have a thickness T 3 , transition region  83  may have a thickness T 4 , and flexible printed circuit  86  may have a thickness T 5 . 
     Thickness T 1  of display  14  may, for example, be between 0.3 mm and 0.5 mm, between 0.1 mm and 0.9 mm, between 0.4 mm and 0.6 mm, less than 1.0 mm, or greater than 1.0 mm. Thickness T 2  of transition region  81  may, for example, be between 0.08 and 0.12, between 0.05 and 0.15, less than 0.2 mm, or greater than 0.2 mm. Thickness T 3  of polymer film  84  may, for example, be between 0.05 mm and 0.09 mm, between 0.03 mm and 0.1 mm, less than 0.1 mm, or greater than 0.1 mm. Thickness T 4  of transition region  83  may, for example, be between 0.1 mm and 0.15 mm, between 0.05 mm and 0.2 mm, between 0.8 mm and 0.3 mm, between 0.1 mm and 0.2 mm, less than 0.3 mm, or greater than 0.3 mm. Thickness T 5  of flexible printed circuit  86  may, for example, be between 0.1 mm and 0.15 mm, between 0.08 mm and 0.2 mm, less than 0.2 mm, or greater than 0.2 mm. 
     As shown in  FIG. 7 , display control circuitry such as display driver integrated circuit  88  may be mounted on polymer film  84  in region C of substrate  32 . Metal traces such as photolithographically patterned traces  90  may be formed on substrate layer  32 C. Display driver integrated circuit  88  may be mounted to traces  88 . Traces  88  may be used to convey electrical signals between display  14  and display driver integrated circuit  88  (e.g., between organic light-emitting diode pixel array  21  of  FIG. 5  and display driver integrated circuit  88 ). Polymer film  84  may be flexible and may be configured to bend about a bend axis. In one suitable embodiment, polymer film  84  makes a 180° bend such that polymer film  84  overlaps itself (e.g., in a U-shaped or C-shaped bend). If desired, display driver integrated circuit  88  may be mounted before the bend (e.g., to lie in the same plane as display  14 ), in the bend (e.g., in a portion of polymer film  84  that runs perpendicular or nearly perpendicular to display  14 ), or after then bend (e.g., such that a portion of display  14  overlaps circuit  88 ). Bending polymer substrate layer  32  in this way may help minimize the inactive border of display  14 . 
     Electrical components such as components  92  may be mounted on flexible printed circuit  86 . Components  92  may include integrated circuits, discrete components such as resistors, capacitors, and inductors, and other electronic components. Flexible printed circuit  86  may include patterned conductive traces  96  (e.g., conductive traces on flexible sheets of substrate such as polyimide sheets). Patterned conductive traces  96  may form signal lines that convey signals from a printed circuit board in device  10  (e.g., from integrated circuits or other components on a main logic board in device  10 ) to display circuitry such as display driver circuitry  88  on polymer film  84 . Driver circuitry  88  may distribute signals to the display pixels of display  14  via traces such as traces  90 . Flexible printed circuit  86  may also include a hot bar pad such as hot bar pad  94  for electrically connecting traces  96  to a printed circuit board (e.g., a main logic board or other suitable printed circuit in device  10 ). 
     Display  14 , polymer film  84 , and flexible printed circuit  86  share a common substrate layer (layer  32 ). Display  14 , polymer film  84 , and flexible printed circuit  86  may have additional shared layers and/or may each have additional layers that are unique to that structure. For example, display  14  may have layers that are located only in portion A of substrate  32 , polymer film  84  may have layers that are located only in portion C of substrate  32 , and flexible printed circuit  86  may have layers that are located only in portion E of substrate  32 . 
     A cross-sectional side view of flexible printed circuit  86 , transition region  83 , polymer film  84 , transition region  81 , and a portion of display  14  is shown in  FIG. 8 . As shown in  FIG. 8 , flexible printed circuit  86 , transition region  83 , polymer film  84 , transition region  81 , and display  14  each include a portion of substrate layer  32 . In each of regions A, B, C, D, and E, additional layers and/or structure are coupled to substrate layer  32 . 
     Display  14 , for example, includes region  1 A and region  2 A. In region  1 A, light-emitting diode display structures  30  may be coupled to substrate layer  32 A. A passivation layer such as passivation layer  46  and a buffer layer such as buffer layer  50  may be interposed between light-emitting diode display structures  30  and substrate layer  32 A. In region  2 A, an optional layer of flexible polymer  52 A may be formed on the surface of passivation layer  46  and buffer layer  50 . 
     Polymer layer  52 A may, for example, be a layer of polyimide, polyethylene naphthalate (PEN), polyethylene terephthalate (PET), other suitable polymers, a combination of these polymers, etc. Optional polymer layer  52 A may be used to adjust the location of the neutral plane in regions of polymer layer  32  that are bent. For example, in arrangements where polymer layer  32  bends around a bend axis, the presence of additional polymer layer  52 A may move the location of the neutral plane in the bent portion outward, thereby minimizing the risk of damage to the bent portion. 
     Transition region  81  (which includes region B of substrate layer  32 ) may include layers that are shared with polymer film  84  in region C and layers that are shared with display  14  in region A. For this reason, transition region  81  may be thicker than region  2 A of display  14  and may be thicker than polymer film  84 . 
     As shown in  FIG. 8 , transition region  81  includes metal layers such as metal layer  74 B, metal layer  72 B, metal layer  70 B, and metal layer  58 B. Metal layer  74 B may, for example, be a tie-coat layer (e.g., a nickel-chromium tie-coat). Metal layer  72 B may be a layer of copper seed, metal layer  70 B may be a layer of copper, and metal layer  58 B may be a layer of tin plating (as examples). A layer of adhesive such as adhesive  56 B may be formed over tin plating  58 B, and a layer of coverlay such as coverlay  54 B may be formed over adhesive  56 B. Metal layers  74 B,  72 B,  70 B, and  58 B, adhesive  56 B, and coverlay  54 B may be interposed between polymer substrate layer  32 B and optional polymer layer  52 B. 
     Some of the layers of transition region  81  are shared with polymer film  84  and some of the layers of transition region  81  are not shared with polymer film  84 . For example, as shown in  FIG. 8 , polymer film  84  also includes metal layers such as metal layer  74 C, metal layer  72 C, metal layer  70 C, and metal layer  58 C. Metal layer  74 C may, for example, be a tie-coat layer (e.g., a nickel-chromium tie-coat). Metal layer  72 C may be a layer of copper seed, metal layer  70 C may be a layer of copper, and metal layer  58 C may be a layer of tin plating (as examples). A layer of adhesive such as adhesive  56 C may be formed over tin plating  58 C, and a layer of coverlay such as coverlay  54 C may be formed over adhesive  56 C. Polymer film  84  does not necessarily include additional polymer layer  52 . 
     Transition region  83  (which includes region D of substrate layer  32 ) may include layers that are shared with polymer film  84  in region C and layers that are shared with flexible printed circuit  86  in region E. For this reason, transition region  83  may be thicker than polymer film  84  and may be thicker than flexible printed circuit  86 . 
     As shown in  FIG. 8 , transition region  83  includes layers coupled to a first surface of substrate  32 D and layers coupled to a second opposing surface of substrate  32 D. For example, metal layers such as metal layer  74 D, metal layer  72 D, metal layer  70 D, metal layer  60 D, and metal layer  58 D may be coupled to a first surface of substrate  32 D. Metal layer  74 D may, for example, be a tie-coat layer (e.g., a nickel-chromium tie-coat). Metal layer  72 D may be a layer of copper seed, metal layer  70 B may be a layer of copper, metal layer  60 D may be a layer of copper plating, and metal layer  58 D may be a layer of tin plating (as examples). A layer of adhesive such as adhesive  56 D may be formed over copper plating  60 D, and a layer of coverlay such as coverlay  54 D may be formed over adhesive  56 D. 
     Additional layers such as metal layer  76 D, adhesive layer  78 D, coverlay  80 D, and metal layer  82 D may be formed on an opposing surface of substrate layer  32 D (e.g., substrate layer  32 D may be interposed between metal layer  74 D and metal layer  76 D). Metal layer  76 D may, for example, be a layer of copper and metal layer  82 D may be a metal shield film (e.g., a shields film formed from silver or other suitable metals). 
     Some of the layers of transition region  83  are shared with flexible printed circuit  86  and some of the layers of transition region  83  are not shared with flexible printed circuit  86 . For example, as shown in  FIG. 8 , metal layer  70 E, metal layer  60 E, adhesive layer  56 E, and coverlay  54 E may be formed on a first surface of substrate  32 E. Metal layer  70 E may, for example, be a layer of copper and metal layer  60 E may be a layer of copper plating (as examples). Layers in transition region  83  such as tie-coat layer  74 D and copper seed layer  72 D need not be included in flexible printed circuit  86 . 
     Additional layers such as metal layer  76 E, adhesive layer  78 E, coverlay  80 E, and metal layer  82 E may be formed on an opposing surface of substrate layer  32 E (e.g., substrate layer  32 E may be interposed between metal layer  70 E and metal layer  76 E). Metal layer  76 E may, for example, be a layer of copper and metal layer  82 E may be a metal shield film (e.g., a shields film formed from silver or other suitable metals). 
     Metal layers in flexible printed circuit  86  may be electrically connected to other metal layers in flexible printed circuit  86  using vertical conductive structures such as conductive vias  89 . 
     If desired, layers that are shared between any two or more of flexible printed circuit  86 , transition region  83 , polymer film  84 , transition region  81 , and display  14  may be contiguous layers that are formed in a single processing step or may be non-contiguous layers that are formed in separate processing steps. 
     Some portions of polymer substrate layer  32  may be flat and other portions of polymer substrate layer  32  may be bent or curved. For example, as shown in  FIG. 9 , polymer film  84  may form a 180 degree bend about bend axis P. Because substrate layer  32  forms a layer in polymer film  84 , substrate layer  32  may also form a 180 degree bend about bend axis P. 
     For simplicity,  FIG. 9  does not show the individual layers that make up display  14 , transition region  81 , polymer film  84 , transition region  83 , and flexible printed circuit  86 . However, it should be understood that display  14  includes additional layers and structures coupled to region A of substrate layer  32 ; transition region  81  includes additional layers and structures coupled to region B of substrate layer; polymer film includes additional layers and structures coupled to region C of substrate layer  32 ; transition region  83  includes additional layers and structures coupled to region D of substrate layer  32 ; and flexible printed circuit includes additional layers and structures coupled to region E of substrate layer  32 . The individual layers that make up display  14 , transition region  81 , polymer film  84 , transition region  83 , and flexible printed circuit  86  are described in the illustrative configurations of  FIGS. 6 and 8 . 
     The use of a shared substrate layer in display  14 , transition region  81 , polymer film  84 , transition region  83 , and flexible printed circuit  86  offers flexibility in the location in which display driver integrated circuit  88  is mounted. In one suitable embodiment, display driver integrated circuit  88  may be mounted in region  2 A of display  14 , as indicated by display driver integrated circuit  88 P. Display driver integrated circuit  88 P may be mounted to traces that are electrically coupled to traces on polymer film  84  (e.g., photolithographically patterned traces  90  of  FIG. 7 ). Traces  90  on polymer film  84  may be electrically coupled to traces on flexible printed circuit  86  such as traces  96  of  FIG. 7 . Traces  96  on flexible printed circuit  86  may in turn be electrically coupled to traces  104  on printed circuit  106  (e.g., a main logic board or other suitable printed circuit) via solder  100  (e.g., a hot bar solder connection). 
     Printed circuit  106  may, for example, be a rigid printed circuit board formed from a material such as fiberglass-filled epoxy (e.g., FR4), may be a flexible printed circuit formed from materials such as polyimide (sometimes referred to as a “flex circuit”), or may be formed from other suitable materials or combinations of these materials. If desired, printed circuit  106  may be a “rigid-flex” printed circuit that includes both rigid and flexible layers. Integrated circuits, discrete components such as resistors, capacitors, and inductors, and other electronic components  102  may be mounted to PCB  106 . Traces  104  may be used to convey electrical signals between components  102  and traces  96  on flexible printed circuit  86  via hot bar solder connection  100 . 
     In another suitable embodiment, display driver integrated circuit  88  may be mounted in transition region  81 , as indicated by display driver integrated circuit  88 Q. Display driver integrated circuit  88 Q may be mounted to traces on transition region  81  (e.g., traces  90  on polymer film  84  that extend into transition region  81 ). Signals may be conveyed between circuit  88 Q and components such as component  102  on PCB  106  via traces  90  on polymer film  84 , traces  96  on flexible printed circuit  86 , hot bar solder connection  100 , and traces  104  in PCB  106 . 
     In another suitable embodiment, display driver integrated circuit  88  may be mounted on polymer film  84 . As shown in  FIG. 9 , circuit  88  may be mounted on polymer film  84  before polymer film  84  bends around bend axis P (as shown by circuit  88 R), may be mounted on polymer film  84  in the bent region of polymer film  84  (e.g., in the portion of film  84  that runs perpendicular or nearly perpendicular to display  14 , as indicated by circuit  88 S), or may be mounted on polymer film  84  after polymer film  84  wraps around bend axis P (e.g., in the portion of film  84  that extends underneath display  14 , as indicated by circuit  88 T). Display driver integrated circuit  88  (e.g., circuit  88 R,  88 S, or  88 T) may be mounted to traces  90  on polymer film  84 . Signals may be conveyed between circuit  88  and components such as component  102  on PCB  106  via traces  90  on polymer film  84 , traces  96  on flexible printed circuit  86 , hot bar solder connection  100 , and traces  104  in PCB  106 . 
     A diagram illustrating how flexible printed circuit  86  may be electrically connected to PCB  106  is shown in  FIG. 10 . As shown in  FIG. 10 , patterned solder paste may be formed on the surface of PCB  106  and may be interposed between PCB  106  and flexible printed circuit  86 . A heated tool such as thermode  108  may be brought into proximity of patterned solder paste  100 . If desired, a protection structure such as polymer-based protection structure  100  may optionally be interposed between thermode  108  and flexible printed circuit  86  to avoid contamination of thermode  108 . The proximity of heated tool  108  may heat and reflow solder paste  100 . As the solder paste is heated and reflows, hot bar solder joints may be formed to electrically and mechanically couple printed circuit  86  to PCB  106 . Hot bar solder joints  100  may be used in forming electrical connections between traces on PCB  106  (e.g., traces  104  of  FIG. 9 ) and traces on flexible printed circuit  86  (e.g., traces  96  of  FIG. 7 ). 
     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.

Metadata:
Filing Date: 20160311
Publication Date: 20190723
Grant Date: 20190723
Priority Date: 20130226
Inventors: LIN, WEY-JIUN
YOUN, SANG
KIM, SANG HA
Assignee: APPLE INC
CPC Classifications: [{"code": "H05K1/189", "inventive": false, "first": false, "tree": "[]"}, {"code": "H05K2201/10128", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01L27/3244", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01L2251/5338", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01L2227/32", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01L27/3262", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01L51/0097", "inventive": true, "first": true, "tree": "[]"}, {"code": "H05K1/0281", "inventive": true, "first": false, "tree": "[]"}, {"code": "Y02E10/549", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01L51/5237", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01L51/5246", "inventive": true, "first": false, "tree": "[]"}, {"code": "H05K2201/10128", "inventive": false, "first": false, "tree": "[]"}, {"code": "Y02E10/549", "inventive": false, "first": false, "tree": "[]"}, {"code": "H05K1/189", "inventive": false, "first": false, "tree": "[]"}, {"code": "H10K2102/311", "inventive": false, "first": false, "tree": "[]"}, {"code": "H05K1/0281", "inventive": true, "first": true, "tree": "[]"}, {"code": "H10K59/10", "inventive": false, "first": false, "tree": "[]"}, {"code": "H05K2201/10128", "inventive": false, "first": false, "tree": "[]"}, {"code": "H10K77/111", "inventive": true, "first": true, "tree": "[]"}, {"code": "H10K2102/311", "inventive": false, "first": false, "tree": "[]"}, {"code": "H05K1/189", "inventive": false, "first": false, "tree": "[]"}, {"code": "H10K50/84", "inventive": true, "first": false, "tree": "[]"}, {"code": "H05K1/0281", "inventive": true, "first": false, "tree": "[]"}, {"code": "H10K59/12", "inventive": true, "first": false, "tree": "[]"}, {"code": "H10K59/1213", "inventive": true, "first": false, "tree": "[]"}, {"code": "H10K50/8426", "inventive": true, "first": false, "tree": "[]"}, {"code": "Y02E10/549", "inventive": false, "first": false, "tree": "[]"}, {"code": "H10K77/111", "inventive": true, "first": false, "tree": "[]"}, {"code": "H10K59/12", "inventive": true, "first": false, "tree": "[]"}, {"code": "H10K59/87", "inventive": true, "first": false, "tree": "[]"}]
Family ID: 51387227