PATENT DOCUMENT

Publication Number: US-9756733-B2
Application Number: US-201113252971-A
Country: US
Kind Code: B2

Title: Display and multi-layer printed circuit board with shared flexible substrate

Abstract:
An electronic device may be provided with a display and a multi-layer printed circuit. Integrated circuits and other components may be mounted to the multi-layer printed circuit. The display and multi-layer printed circuit may share a common layer formed from a flexible substrate. The flexible substrate may have portions that are integrated into the display and portions that are integrated into the multi-layer printed circuit board. The flexible substrate may contain patterned conductive traces that are used to route signals from components in the multi-layer printed circuit to display circuitry such as a display driver integrated circuit. An array of thin-film transistors may be used to control the emission of light from the display and may be formed on portions of the flexible substrate that are integrated into the display. The display may be a flexible display that includes an array of organic light-emitting diodes.

Claims:
What is claimed is: 
     
       1. An electronic device, comprising:
 a display having an array of display pixels; 
 a printed circuit having a substrate; and 
 a flexible substrate having a first portion that forms a layer in the display, a second portion that is attached to the printed circuit, and a bent portion interposed between the first and second portions, wherein the array of display pixels is disposed on the first portion of the flexible substrate. 
 
     
     
       2. The electronic device defined in  claim 1  wherein the display comprises an array of thin-film transistors formed on the first portion of the flexible substrate and wherein the array of thin-film transistors is configured to control emission of light from the display. 
     
     
       3. The electronic device defined in  claim 2  wherein the display further comprises a layer of organic light-emitting diodes formed over the array of thin-film transistors. 
     
     
       4. The electronic device defined in  claim 1  further comprising at least one integrated circuit mounted to the printed circuit. 
     
     
       5. The electronic device defined in  claim 4  wherein the flexible substrate contains signal lines that convey signals from the at least one integrated circuit to the display. 
     
     
       6. The electronic device defined in  claim 1  wherein the second portion of the flexible substrate is attached to the printed circuit using a board-to-board connector. 
     
     
       7. An electronic device, comprising:
 a printed circuit having a substrate; and 
 a display having a flexible substrate, wherein the flexible substrate comprises a first portion on which an array of display pixels are formed, a second portion that is connected to the printed circuit, and a bend between the first portion and the second portion. 
 
     
     
       8. The electronic device defined in  claim 7  wherein the array of display pixels comprises an array of organic light-emitting diode display pixels. 
     
     
       9. The electronic device defined in  claim 7  wherein the flexible substrate comprises polyimide. 
     
     
       10. The electronic device defined in  claim 7  further comprising at least one integrated circuit mounted to the printed circuit. 
     
     
       11. The electronic device defined in  claim 10  wherein the flexible substrate includes signal lines that convey signals from the at least one integrated circuit to the array of display pixels. 
     
     
       12. The electronic device defined in  claim 7  wherein the first portion of the flexible substrate overlaps the second portion of the flexible substrate. 
     
     
       13. The electronic device defined in  claim 7  wherein the array of display pixels comprises thin-film transistor circuitry formed on the first portion of the flexible substrate. 
     
     
       14. The electronic device defined in  claim 13  wherein the array of display pixels comprises light-emitting material formed over the thin-film transistor circuitry. 
     
     
       15. The electronic device defined in  claim 14  wherein the display comprises a layer of sealant formed over the light-emitting material. 
     
     
       16. The electronic device defined in  claim 7  wherein the printed circuit comprises a rigid printed circuit board. 
     
     
       17. The electronic device defined in  claim 7  wherein the printed circuit comprises a flexible printed circuit.

Description:
BACKGROUND 
     This relates generally to electronic devices, and more particularly, to displays for electronic devices. 
     Electronic devices such as cellular telephones, computers, and media players are often provided with displays for displaying images to a user. In a typical display, an array of active image pixels is controlled by display driver circuitry using a pattern of orthogonal control lines. 
     The active image pixels form a rectangular active area in the center of the display. The active region in the center of the display is surrounded by an inactive border region. The inactive border region 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 may be a flexible printed circuit that is used to route 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 connect the opposing end of the signal cable to a printed circuit board. 
     Ensuring that there is sufficient area to reliably attach the signal cable and to fan out the control lines along the edges of the active area may require a significant amount of inactive border area. It is not uncommon for the width of the inactive border to be up to a centimeter wide or more. This type of wide inactive region tends to make displays bulky and requires the use of electronic device housings with wide bezels. Connecting structures such as board-to-board connectors used to connect the signal cable to the printed circuit board may also add undesirable bulk to an electronic device. 
     It would therefore be desirable to be able to provide improved electronic devices. 
     SUMMARY 
     Electronic devices may be provided with a display and a multi-layer printed circuit. The multi-layer printed circuit board may be a flexible printed circuit, a rigid printed circuit board (PCB), or may have a combination of rigid and flexible layers (sometimes referred to as a “rigid-flex” printed circuit board). Integrated circuits and other components may be mounted on the multi-layer printed circuit. 
     The display and the multi-layer PCB may be provided with a shared flexible substrate layer. The flexible substrate may have a first portion that forms a layer in the display and a second portion that forms a layer in the multi-layer PCB. An array of thin-film transistors may be mounted on the first portion of the flexible substrate and may be used to control the emission of light from the display. Patterned conductive traces in the flexible substrate may be used to convey signals from components and circuitry in the multi-layer PCB to display circuitry such as display driver circuitry. 
     Vertical conductive structures such as vias may be used to form an electrical connection between layers in the multi-layer printed circuit and the second portion of the flexible substrate or between layers of the multi-layer printed circuit that are formed on opposing sides of the second portion of the flexible substrate. 
     In some configurations, the first portion of the flexible substrate may form an integrated layer of the display and the second portion may be attached to a printed circuit using a connecting structure such as a board-to-board connector. In other configurations, the first portion of the flexible substrate may be attached to the display using a conductive material (e.g., conductive adhesive, solder, etc.) and the second portion may form an integrated layer of a printed circuit. 
     If desired, the flexible substrate layer may form an integrated layer of a main logic board or other rigid logic board. 
     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 handheld electronic device with a display in accordance with an embodiment of the present invention. 
         FIG. 2  is a cross-sectional side view of a portion of an illustrative electronic device having a shared flexible substrate layer that forms an integrated layer of a display and a printed circuit board in accordance with an embodiment of the present invention. 
         FIG. 3  is a cross-sectional side view of a portion of an illustrative electronic device having a flexible substrate layer that forms an integrated layer of a printed circuit board in accordance with an embodiment of the present invention. 
         FIG. 4  is a cross-sectional side view of a portion of an illustrative electronic device having a flexible substrate layer that forms an integrated layer of a display in accordance with an embodiment of the present invention. 
         FIG. 5  is a perspective view of a portion of an illustrative electronic device having a shared flexible substrate layer that forms an integrated layer of a display and a printed circuit board in accordance with an embodiment of the present invention. 
         FIG. 6  is a perspective view of a portion of an illustrative electronic device having a shared flexible substrate layer that forms an integrated layer of a display and a plurality of printed circuit boards in accordance with an embodiment of the present invention. 
         FIG. 7  is a cross-sectional view of a portion of an illustrative electronic device having a shared flexible substrate layer that is bonded to layers in a printed circuit board using a conductive material in accordance with an embodiment of the present invention. 
         FIG. 8  is a cross-sectional view of a portion of an illustrative electronic device having a shared flexible substrate layer and a printed circuit board with vias that interconnect components and printed circuit board layers in accordance with an embodiment of the present invention. 
         FIG. 9  is a cross-sectional perspective view of a portion of an illustrative electronic device having a shared flexible substrate layer that forms an integrated layer of a display and is partially inserted into a printed circuit board in accordance with an embodiment of the present invention. 
         FIG. 10  is a cross-sectional side view of a portion of an illustrative electronic device having a printed circuit board with heat sink layers in accordance with an embodiment of the present invention. 
         FIG. 11  is a cross-sectional side view of a portion of an illustrative electronic device having a printed circuit board with shielding layers in accordance with an embodiment of the present invention. 
         FIG. 12  is a cross-sectional side view of a portion of an illustrative organic light-emitting diode display having a shared flexible substrate layer in accordance with an embodiment of the present invention. 
         FIG. 13  is a cross-sectional side view of a portion of an illustrative organic light-emitting diode display in accordance with an embodiment of the present invention. 
         FIG. 14  is a top view of a portion of an illustrative electronic device having a shared flexible substrate layer that is directly integrated into a display and a main logic board in accordance with an embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     A display may be provided for an electronic device such as a portable electronic device. Displays may be used to display visual information such as text and images to users. 
     Displays may be coupled to circuitry within the electronic device such as circuitry on a printed circuit board. For example, a display may contain driver circuitry that receives image data, control signals or other signals from a printed circuit board in the device. A flexible substrate layer may be used to convey image data and other signals from the printed circuit board to the driver circuitry in a display. The flexible substrate layer may have one portion that is directly integrated into the display (e.g., the flexible substrate may form a layer in the display). The flexible substrate layer may have a second portion that is directly integrated into the printed circuit board (e.g., the flexible substrate may form a layer in the printed circuit board). 
     An illustrative electronic device of the type that may be provided with a flexible substrate layer that is directly integrated into a display, a printed circuit board, or both the display and the printed circuit board, is shown in  FIG. 1 . Electronic device  10  may be a portable electronic device or other suitable electronic device. For example, electronic device  10  may be a laptop computer, a tablet computer, a somewhat smaller device such as a wrist-watch device, pendant device, or other wearable or miniature device, a cellular telephone, media player, electronic books, etc. The electronic device might be a larger device as well, such as a television or digital sign. 
     Device  10  may include a housing such as housing  12 . Housing  12 , which may sometimes be referred to as a case, may be formed of plastic, glass, ceramics, fiber composites, metal (e.g., stainless steel, aluminum, etc.), other suitable materials, or a combination of these materials. In some situations, parts of housing  12  may be formed from dielectric or other low-conductivity material. In other situations, housing  12  or at least some of the structures that make up housing  12  may be formed from metal elements. 
     Device  10  may include components such as buttons, input-output port connectors, ports for removable media, sensors, microphones, speakers, status indicators, and other device components. As shown in  FIG. 1 , for example, device  10  may include buttons such as menu button  16 . Device  10  may also include a speaker port such as speaker port  18  (e.g., to serve as an ear speaker for device  10 ). 
     Device  10  may include one or more displays such as display  14 . Display  14  may be rigid or flexible or may have a combination of rigid and flexible layers. For example, a flexible display may include a flexible display layer (e.g., a flexible organic light-emitting diode array and a thin-film transistor layer formed on a flexible substrate). For the purpose of this invention, organic light-emitting diode displays are intended to encompass all types of light-emitting displays that comprise thin organic film layers, including displays comprising organic small molecules, polymers, dendrimers, and quantum dots. The thin film layers within the organic light emitting display may comprise a cathode layer, an anode layer, one or more emissive layers, one or more hole transport layers, one or more electronic transport layers, capping layers, hole injection layers, electron injection layers, exciton blocking layers, and blends and composites of these materials. Other types of flexible display technologies may be used to form a flexible display (e.g., electronic ink displays, electronic paper displays, flexible liquid crystal displays, flexible electrochromic displays, flexible electrowetting displays, etc.). 
     As another example, a liquid crystal display (LCD) may include a layer of liquid crystal material sandwiched between a color filter layer and a thin-film transistor layer. In general, display  14  may be based on any suitable display technology (liquid crystals, light-emitting diodes, organic light-emitting diodes, plasma cells, electronic ink arrays, electronic paper displays, etc). 
     Display  14  may include touch-sensitive elements (i.e., display  14  may be a touch screen). The touch sensitive elements may include an acoustic touch sensor, a resistive touch sensor, a piezoelectric touch sensor, a capacitive touch sensor (e.g., a touch sensor based on an array of indium tin oxide capacitor electrodes), a photosensitive touch sensor, or a touch sensor based on other touch technologies. 
     Display  14  may include a rectangular center portion (as indicated by dashed line  20  in  FIG. 1 ) that includes an array of display pixels and is sometimes referred to as the active portion of display  14 . The peripheral outer portion of display  14  (i.e., rectangular peripheral ring  22  of  FIG. 1 ) may include circuitry that does not emit light and may therefore be referred to as the inactive portion of display  14 . 
     Display  14  may receive image data from a main logic board, other printed circuit board, or other circuitry in the electronic device. Display  14  may transmit signals (e.g., touch input from a user of device  10 ) to a main logic board, other printed circuit board or other circuitry. For example, display driver circuitry may be mounted on a display layer such as a thin-film transistor (TFT) layer. The display driver circuitry may receive image data from a printed circuit board or return touch input to a printed circuit board. Control lines such as gate lines may be used to distribute signals to the display from the display driver circuitry. 
     In a conventional electronic device, a signal cable formed from a flexible printed circuit is used to convey image data from a printed circuit board to the display driver circuitry. In a typical arrangement, a first end of the flexible printed circuit is electrically connected to the TFT layer in a display. A layer of anisotropic conductive film is often used to mount the first end of flexible printed circuit to the TFT layer. A second end of the flexible printed circuit is electrically connected to a printed circuit board (PCB) in the device. A board-to-board connector is often used to connect the second end of the flexible printed circuit to the PCB. 
     A flexible printed circuit does not emit light and is therefore typically mounted in the inactive portion of a display. This creates an undesirable amount of inactive display area around the border of a display. 
     Device  10  may be provided with a flexible substrate layer that includes conductive paths for conveying data signals from a printed circuit board to the display or from the display to the printed circuit board. The flexible substrate layer may have one or more portions that form a layer of the display. The flexible substrate layer may have one or more portions that form a layer of the printed circuit board. The flexible substrate layer may have some portions that form a layer of the display and other portions that form a layer of the printed circuit board. As an example, the flexible substrate layer may have opposing ends. One or both of the opposing ends may be directly integrated into the display and/or the printed circuit board. 
     A flexible substrate layer having some portions that form a layer of a display and/or some portions that form a layer of a printed circuit board may reduce inactive display area and may reduce or eliminate the need for connecting structures on the display and/or the printed circuit board that add undesirable bulk to an electronic device. 
     A cross-sectional side view of an illustrative arrangement in which a shared flexible substrate forms an integrated layer of both a display and a printed circuit board is shown in  FIG. 2 . As shown in  FIG. 2 , display  14  may have one or more display layers such as display layer  14 A. Display layer  14 A may contain an array of active display pixels and may therefore form the active portion of display  14 . Display layer  14 A may be formed from glass, ceramic, plastic, flexible sheets of material such as polymers (e.g., polyimide, polyethylene terephthalate, or other materials that are capable of being provided in thin flexible sheets), other suitable materials, or a combination of these materials. 
     Display layer  14 A may include multiple layers such as a touch-sensitive layer (e.g., a sheet of polymer with an array of transparent capacitor electrodes for a capacitive touch sensor), optical layers such as polarizing layers, shielding layers (e.g., for preventing electric fields from disrupting the operation of the display), heat sinking layers (e.g., for conducting heat away from the display), sealing layers (e.g., layers of sealant formed from thin films, polymers, inorganic materials, metal foils, composites, etc.), cover layers (e.g., a layer of cover glass), other suitable display layers, or a combination of these display layers. 
     Portions of a flexible substrate such as flexible substrate  24  may form a layer of display  14 . For example, portion  24 A of flexible substrate  24  may form a display substrate for display  14 . If desired, circuitry for operating display  14  may be mounted on portion  24 A of flexible substrate  24 . For example, an array of thin-film transistors may be formed on the surface of flexible substrate  24  in region  24 A and may be used to control emission of light from display  14 . Transistors that may be formed on portion  24 A of substrate  24  include polycrystalline silicon transistors, amorphous silicon transistors, organic thin-film transistors, metal oxide transistors, carbon nanotube or graphene transistors, other nanoparticle-based transistors, etc. 
     The transistors of the array may be controlled by control signals from driver circuitry such as display driver circuitry  26  (e.g., a driver integrated circuit). Display driver circuitry  26  may, if desired, be mounted on flexible substrate layer  24  and may be used to supply control signals to the array of transistors. This is, however, merely illustrative. If desired, driver circuitry  26  may be formed as an integral portion of flexible substrate  24 . If desired, circuitry such as thin-film transistors and display driver integrated circuits may be formed entirely within flexible substrate  24 , between flexible substrate  24  and display layer  14 A, partially within display layer  14 A, entirely within display layer  14 A or partially within both display layer  14 A and flexible substrate  24 . 
     Portion  24 B of flexible substrate  24  may form an integrated layer of printed circuit  30 . Printed circuit  30  and other printed circuits in device  10  may contain a stack of multiple layers such as layers  31 . For example, a printed circuit may contain a combination of both rigid and flexible layers (sometimes referred to as a “rigid-flex” PCB). A multi-layer printed circuit such as printed circuit  30  may sometimes be referred to as a PCB stack or PCB stack-up. Layers  31  of PCB  30  may be formed from dielectrics such as fiberglass-filled epoxy (e.g., as a rigid layer in a PCB stack) and polyimide (e.g., as a flexible layer in a PCB stack), FR-2 (phenolic cotton paper), FR-3 (cotton paper and epoxy), FR-4 (woven glass and epoxy), FR-5 (woven glass and epoxy), FR-6 (matte glass and polyester), G-10 (woven glass and epoxy), CEM-1 (cotton paper and epoxy), CEM-2 (cotton paper and epoxy), CEM-3 (woven glass and epoxy), CEM-4 (woven glass and epoxy), CEM-5 (woven glass and polyester), paper impregnated with phenolic resin, polystyrene, polyimide, polytetrafluoroethylene (PTFE), plastic, other polymers, ceramics, or other suitable dielectrics. 
     Layers  31  may include attachment layers such as layers of prepreg (i.e., pre-impregnated layers of fiber and resin). Layers of copper or other conductive materials may be formed on the surfaces of layers  31 . For example, one or more of layers  31  may have upper and lower surfaces that are covered with a layer of metal such as copper. 
     Integrated circuits, discrete components such as resistors, capacitors, and inductors, and other electronic components  32  may be mounted to PCB  30 . Display driver circuitry  26  may receive image data from processing circuitry in PCB  30  (e.g., from integrated circuits such as components  32 ) and produce corresponding control signals for display  14 . Flexible substrate  24  may be used to route signals to display driver integrated circuit  26  from components  32  or other circuitry in PCB  30 . Flexible substrate  24  may contain patterned conductive traces  102  (e.g., conductive traces on flexible sheets of substrate such as polyimide sheets). Patterned conductive traces  102  may form signal lines that convey signals from PCB  30  (e.g., from integrated circuits such as components  32 ) to display circuitry such as display driver circuitry  26 . Driver circuitry  26  may distribute signals to the display pixels via traces such as traces  17 . 
     In the example of  FIG. 2 , portion  24 A of flexible substrate  24  may form an integrated layer of display  14 . Portion  24 B of flexible substrate  24  may form an integrated layer of PCB  30  (e.g., substrate  24  may form one of the layer  31  in PCB stack  30 ). In configurations in which flexible substrate  24  forms a portion of both display  14  and PCB  30 , the need for a connecting structure such as a board-to-board connector to attach flexible substrate  24  to PCB  30  and the need for surface area for mounting a separate structure to the display may be reduced or eliminated. Inactive borders around a display may therefore by reduced or eliminated. This arrangement may also simplify the interconnects between display  14  and PCB  30  and thus reduce power consumption and increase efficiency of the display. 
     If desired, portion  24 A of flexible substrate  24  may be electrically coupled to display  14  using a conductive material and the portion  24 B may form an integrated layer of PCB  30 , as shown in  FIG. 3 . 
     In the example of  FIG. 3 , display  14  may contain multiple layers such as display layer  14 A and display layer  14 B. Display layer  14 B may contain circuitry for operating display  14 . For example, an array of thin-film transistors (TFTs) may be formed on the surface of display layer  14 B and may be used to control the emission of light from display  14 . Transistors in layer  14 B may include polycrystalline silicon transistors, amorphous silicon transistors, organic thin-film transistors, metal oxide transistors, carbon nanotube or graphene transistors, other nanoparticle-based transistors, etc. The transistors of the array may be controlled by control signals from driver circuitry  26  (e.g., a driver integrated circuit). If desired, driver circuitry  26  may be mounted on layer  14 B. 
     Display layers  14 A and  14 B may be formed from glass, ceramic, plastic, flexible sheets of material such as polymers (e.g., polyimide, polyethylene terephthalate, or other materials that are capable of being provided in thin flexible sheets), other suitable materials, or a combination of these materials. 
     Flexible substrate  24  may be used to convey data signals between display  14  and PCB  30 . Portion  24 B of flexible substrate  24  may form an integrated layer of printed circuit  30 . Data signals from circuitry in PCB  30  (e.g., data signals from processing circuitry or other components such as components  32 ) may be routed to display layer  14 B via patterned traces  102  (sometimes referred to as signal lines) on flexible substrate  24 . 
     Portion  24 A of flexible substrate  24  may be electrically coupled to display layer  14 B. In the example of  FIG. 3 , conductive adhesive  38  and solder pad  35  electrically couple conductive traces  102  on flexible substrate  24  with conductive traces on display layer  14 B such as conductive trace  33 . Traces  33  may interconnect signal lines  102  from flexible substrate  24  to display driver circuitry  26 . Display driver circuitry  26  may distribute signals to display  14  via conductive traces  17 . 
     If desired, portion  24 B of flexible substrate  24  may be attached to PCB  30  using a connecting structure and the portion  24 A may form an integrated layer of display  14 , as shown in  FIG. 4 . 
     In the example of  FIG. 4 , portion  24 B of flexible substrate layer  24  is connected to PCB  30  using a connecting structure such as connecting structure  34  (e.g., a board-to-board connector, zero insertion force connector, etc.). 
     Portion  24 A of flexible substrate  24  may form an integrated layer of display  14 . For example, portion  24 A of flexible substrate  24  may form a display substrate for the display. If desired, circuitry for operating display  14  may be mounted on portion  24 A of flexible substrate  24 . For example, an array of thin-film transistors may be formed on the surface of flexible substrate  24  in region  24 A and may be used to control emission of light from display  14 . Transistors that may be mounted on portion  24 A of substrate  24  include polycrystalline silicon transistors, amorphous silicon transistors, organic thin-film transistors, etc. Display driver circuitry  26  may, if desired, be mounted on flexible substrate layer  24  and may be used to supply control signals to the array of transistors. This is, however, merely illustrative. If desired, driver circuitry  26  may be formed as an integral portion of flexible substrate  24 . If desired, circuitry such as thin-film transistors and display driver integrated circuits may be formed entirely within flexible substrate  24 , between flexible substrate  24  and display layer  14 A, partially within display layer  14 A, entirely within display layer  14 A or partially within both display layer  14 A and flexible substrate  24 . 
     As described above in connection with  FIGS. 2 and 3 , patterned traces  102  on flexible substrate layer  24  may be used to form signal lines that convey data signals between circuitry on PCB  30  and display circuitry such as display driver circuitry  26 . Because flexible substrate layer  24  forms an integrated layer of display  14 , no surface area is required for mounting a separate structure to the display. This may reduce the amount of inactive display area around the border of a display and allow signals to be conveyed directly from traces on flexible substrate  24  to display driver circuitry  26 . Simplifying the interconnects between display  14  and PCB  30  in this way may help reduce power consumption, increase efficiency, and improve reliability of the display. 
     Flexible substrate layer  24  may have some portions that form a layer of display  14  and some portions that form a layer of PCB  30  that protrudes from multiple edges (sides) of PCB  30  as shown in  FIG. 5 . In the example of  FIG. 5 , flexible substrate layer  24  protrudes from two edges (sides) of PCB  30 . This is merely illustrative. Flexible substrate layer  24  may protrude from one side, from two sides, from three sides, or from all four sides of PCB  30 . 
     If desired, a flexible substrate layer such as flexible substrate layer  24  may form a layer of one or more PCB stacks and/or one or more displays as shown in  FIG. 6 . In the example of  FIG. 6 , flexible substrate layer  24  is integrated into a plurality of PBC stacks such as PCB stack  30 A and PCB stack  30 B. Some portions  24 B′ of flexible substrate layer  24  may form a layer of PCB stack  30 A while other portions  24 B″ may form a layer of PCB stack  30 B. Portion  24 A of flexible substrate layer  24  that is integrated into display  14  may contain circuitry such as circuitry for operating display  14 . Signals may be routed between PCB  30 A, PCB  30 B, and display  14  via conductive traces  102  in flexible substrate layer  24 . 
     As shown in  FIGS. 2, 5, and 6 , a single flexible substrate such as flexible substrate  24  may have at least one portion that forms a layer in a multi-layer PCB and at least one portion that forms a layer in a display. Other configurations in which a shared flexible substrate layer is directly integrated into both a display and a PCB may be used. The examples shown in  FIGS. 2, 5, and 6  are merely illustrative. If desired, flexible substrate  24  may be formed as an integral portion of a PCB stack-up. If desired, one or more PCB stack-ups may be prefabricated and mounted on opposing sides of flexible substrate  24  as shown in  FIG. 6 . 
       FIG. 7  is a side view of an illustrative configuration that may be used to attach portion  24 B of flexible substrate layer  24  to PCB stack  30 . A layer of conductive material such as conductive adhesive  44  may be interposed between flexible substrate layer  24  and adjacent layers  31 A and  31 B of PCB  30 . Conductive adhesive  44  may be formed from anisotropic conductive film (ACF) or other suitable conductive adhesives that will form an electrical bond between contacts or conductive traces in PCB  30  and contacts or conductive traces in flexible substrate layer  24 . Adhesives, conductive foam, conductive springs, welds (e.g., laser welds), solder joints, or other types of bonds may be used in connecting the conductive and/or dielectric materials in flexible substrate layer  24  and PCB  30 . The use of conductive adhesive as shown in  FIG. 7  is merely illustrative. 
     If desired, layers  31  of PCB  30  may be electrically connected to other layers  31  through flexible substrate  24  as shown in  FIG. 8 . As shown in  FIG. 8 , vertical conductive structures such as conductive vias  46  may be used to electrically connect interconnects in different layers of PCB  30 . As shown in  FIG. 8 , vias  46  may be plated or hollowed vias that line vertical openings  39  in the PCB stack. If desired, other types of vias may be used (e.g., vias may be filled or partially filled with conductive material). 
     Vias such as vias  46  may be contained entirely within the interior of PCB  30  (sometimes referred to as buried vias), may connect an exterior surface of PCB  30  to an interior surface of PCB  30  (sometimes referred to as blind vias), or may pass through the entire thickness of PCB (sometimes referred to as through vias). Vias  46  may be formed using laser drilling, mechanical drilling (i.e., with a drill bit) or other mechanical machining techniques. Openings  39  may be filled or coated using metal (e.g., copper) plating techniques, by filling openings  39  with conductive paste, by filling openings  39  with conductive adhesive, or by filling openings  39  with other conductive material. Materials that may be used in forming vias  46  include copper, silver, gold, copper-tungsten, other suitable metals, carbon-based or organic conductors, or a combination of these materials. Other methods or structures may be used to electrically connect different layers of PCB stack  30  that includes shared flexible substrate layer  24 . The use of conductive vias  46  as shown in  FIG. 8  is merely illustrative. 
     If desired, the flexible substrate layer may form a partial layer of a PCB stack as shown in  FIG. 9 . For example, flexible substrate layer  24  may only be partially inserted into the stack of PCB layers. In the example of  FIG. 9 , a portion such as portion  30 - 1  of PCB stack  30  includes layers  31  on opposing sides of a portion of flexible substrate layer  24 . Flexible substrate  24  may therefore be integrated as a layer of portion  30 - 1  of PCB stack  30 . Flexible substrate layer  24  may not be included in a portion of the PCB such as portion  30 - 2  of PCB  30 . 
     Layers  31  of PCB stack  30  may have conductive layers such as conductive PCB layers  30 C and dielectric layers such as dielectric PCB layers  30 D. Conductive layers  30 C may be patterned metal layers for forming interconnects. Dielectric layers  30 D may be alternating layers of prepreg and core material (e.g., FR-4) or other suitable dielectric layers. Electrical contacts such as contacts  21  may be used to connect traces  102  on flexible substrate layer  24  with traces in PCB stack  30 . Electrical contacts in PCB  30  such as contacts  21  may be contact pads, solder pads, or interconnect structures, or may be formed from patterned conductive layers in PCB  30  (e.g. layers such as PCB layers  30 C), or other suitable conductive structures. Contacts  21  may, for example, be formed from copper or copper plated with gold or other materials. Contacts  21  may be electrically connected to the interconnects of PCB  30  (e.g., using vias such as vertical vias  46  of  FIG. 8 , using parts of horizontal interconnects in layers  30 C, etc.). 
     Components such as components  32  may be mounted on PCB  30 . Components  32  or other circuitry associated with PCB  30  may generate heat that may damage components  32  or PCB  30 . PCB  30  may be provided with heat sink structures such as heat sink layer  31 H of  FIG. 10 . As shown in  FIG. 10  PCB stack  30  may include a heat sink structure such as heat sink layer  31 H that is formed over shared substrate layer  24 . Heat sink layer  31 H may help dissipate heat that is generated by components in PCB stack  30 . Heat sink layer  31 H may also help conduct heat away from display  14 . 
     If desired, PCB  30  may be provided with one or more shielding layers as shown in  FIG. 11 . High frequency signals may be communicated between display  14  and PCB  30  during operation of display  14 . Shielding layers such as shielding layers  31 S may help block emission from these high frequency signals that may cause electromagnetic interference (EMI) with circuitry in PCB  30  or other components of device  10 . Shielding layers  31 S may also reduce the amount of unwanted electromagnetic energy radiated by device  10 . Shielding layers  31 S may shield separate circuits in PCB  30  from interfering with each other. Shielding layers  31 S may be interposed between substrate layer  24  and adjacent PCB layers  31 A and  31 B. This is merely illustrative. PCB  30  may be provided with one shielding layer, two shielding layers, three shielding layers, or more than three shielding layers. Shielding layers such as shielding layers  31 S may be formed on one side of substrate  24  or on opposing sides of substrate  24 . If desired, PCB  30  may be provided without any shielding layers. 
     If desired, display  14  may be a flexible display that uses flexible display technology such as an organic-light emitting diode (OLED) pixel array formed on a flexible substrate. As shown in  FIG. 12 , display layer  14 A may include multiple layers formed on flexible substrate layer  24 . Display layer  14 A may include a circuitry layer such as thin-film transistor (TFT) circuitry layer  14 - 3  that includes an array of thin-film transistors. Layer  14 - 3  may be formed on shared substrate layer  24 , may be formed as a separate circuitry layer, or may have portions formed in substrate layer  24  and portions formed in display layer  14 A. TFT circuitry layer  14 - 3  may contain circuitry such as display driver integrated circuits, gate line drivers formed from low-temperature polysilicon transistors, transistors formed from amorphous silicon, metal oxide transistors, carbon nanotube or graphene transistors, other nanoparticle-based transistors, etc. Circuitry and electronic components in TFT circuitry layer  14 - 3  may be mounted on flexible substrate layer  24 . 
     Display layer  14 A may include a layer of light-emitting material such as light-emitting layer  14 - 2 . Light-emitting layer  14 - 2  may be formed over TFT circuitry layer  14 - 3 . Light-emitting layer  14 - 2  may be formed from an array of organic-light emitting diodes (OLEDs) or other light-emitting material, such as quantum dots. If desired, OLED material  14 - 2  may be formed from a thin film that is deposited or integrated into TFT layer  14 - 1 . 
     OLED layer  14 - 2  may be covered with a sealant such as sealant layer  14 - 1 . Sealant  14 - 1  may be formed from polymers (e.g., a layer of polymer that is deposited over OLED layer  14 - 2 ), metal foil (e.g., a layer of metal foil that is laminated, sputtered, evaporated, or otherwise applied onto OLED layer  14 - 2 ), or other suitable coating or conformal covering. If desired, sealant  14 - 1  may be formed from multiple layers. As shown in  FIG. 13 , sealant  14 - 1  may be formed from alternating layers of polymer  17  and inorganic material  19 . 
     A shared flexible substrate layer that forms a layer of a display and a multi-layer PCB may also help directly connect a high density of conductive traces in a PCB such as a main logic board to a low density of conductive traces in a flexible substrate as shown in  FIG. 14 . 
     In the example of  FIG. 14 , main logic board  30  includes components such as components  32 . Components  32  may include integrated circuits such as a microprocessor, a microcontroller, an audio chip, an application-specific integrated circuit, or other integrated circuit. If desired, discrete electrical components (e.g., resistors, inductors, capacitors, and transistors) may be mounted in internal cavities in printed circuit board  30  or multiple integrated circuits may be mounted in internal cavities in printed circuit board  30 . If desired, different types of stand-alone components may also be embedded in printed circuit board  30 , such as antennas, sensors, power sources such as batteries and supercapacitors, etc. The example of  FIG. 14  is merely illustrative. 
     Some portions of flexible substrate layer  24  may form a layer in main logic board  30 . Other portions of flexible substrate layer  24  may form a layer in display  14 . Substrate  24  may contain patterned conductive traces such as traces  102  that convey data signals from components  32  on board  30  to display circuitry in display  14  (e.g., a driver integrated circuit). 
     Traces on board  30  such as conductive traces  104  may be used to distribute data signals to signal lines  102  in substrate layer  24 . Signals may travel from components  32  on the outermost layers of board  30  to substrate layer  24  using vertical conductive structures such as conductive vias  46 . Conductive traces  104  in board  30  may have a relatively high pitch (e.g., a high density of conductive traces) compared to signal lines  102  in substrate layer  24 , which may have a relatively low pitch. Signal lines  102  may be form a pattern that fans high pitch traces  104  out from region  106  to low pitch traces  102  of substrate  24 . 
     Because shared substrate layer  24  forms an integrated layer in display  14 , signals from traces  102  may be routed directly to display circuitry without requiring any mounting surface area on display  14 . Because shared substrate layer  24  forms an integrated layer in board  30 , the need for a connecting structure such as a board-to-board connector may be eliminated. By simplifying interconnects between board  30  and display  14 , device  10  may be more efficient, may consume less power, may be more reliable, and may enable desirable design features. 
     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: 20111004
Publication Date: 20170905
Grant Date: 20170905
Priority Date: 20111004
Inventors: DRZAIC PAUL S.
FRANKLIN JEREMY C.
LYNCH STEPHEN BRIAN
MYERS SCOTT A.
RAPPOPORT BENJAMIN M.
ROTHKOPF FLETCHER R.
TERNUS JOHN P.
Assignee: APPLE INC
CPC Classifications: [{"code": "G02F1/13452", "inventive": false, "first": false, "tree": "[]"}, {"code": "H05K2201/10128", "inventive": false, "first": false, "tree": "[]"}, {"code": "H05K1/189", "inventive": true, "first": true, "tree": "[]"}, {"code": "G09G3/20", "inventive": true, "first": false, "tree": "[]"}, {"code": "G09G2300/0426", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G2300/0408", "inventive": false, "first": false, "tree": "[]"}, {"code": "H05K2201/10128", "inventive": false, "first": false, "tree": "[]"}, {"code": "H05K1/189", "inventive": true, "first": true, "tree": "[]"}, {"code": "G09G2330/06", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G2300/0426", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G2300/0408", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G3/20", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02F1/13452", "inventive": false, "first": false, "tree": "[]"}, {"code": "H05K1/189", "inventive": true, "first": true, "tree": "[]"}, {"code": "H05K2201/10128", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G3/20", "inventive": true, "first": false, "tree": "[]"}, {"code": "G09G2300/0426", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G2300/0408", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02F1/13452", "inventive": false, "first": false, "tree": "[]"}]
Family ID: 47992107