PATENT DOCUMENT

Publication Number: US-10877332-B2
Application Number: US-202016806526-A
Country: US
Kind Code: B2

Title: Displays with minimized border regions having an apertured TFT layer for signal conductors

Abstract:
An electronic device may be provided with a display having a thin-film transistor layer. One or more holes in the thin-film transistor layer may be used to form pathways from display circuitry to other circuitry underneath the display. One or more conductive bridges may pass through holes in the thin-film transistor layer and may have one end that couples to the display circuitry and a second end that couples to a printed circuit underneath the display. These conductive bridges may be formed from wire bonding. Wire bond connections may be encapsulated with potting material to improve the reliability of the wire bond and increase the resiliency of the display. Display signal lines may be routed through holes in a thin-film transistor layer to run along a backside of the display thereby reducing the need for space in the border region for display circuitry.

Claims:
What is claimed is: 
     
       1. An electronic device, comprising:
 a display having a display layer with an opening, wherein the display layer extends entirely around a perimeter of the opening; 
 a printed circuit substrate; and 
 a conductive structure that passes through the opening in the display layer, wherein the conductive structure couples circuitry in the display to circuitry on the printed circuit substrate. 
 
     
     
       2. The electronic device defined in  claim 1  wherein the conductive structure comprises conductive material that fills the opening in the display layer. 
     
     
       3. The electronic device defined in  claim 2  wherein the opening is one of an array of openings in the display layer and wherein the conductive material fills each of the openings of the array of openings. 
     
     
       4. The electronic device defined in  claim 3  wherein the conductive structure further comprises a wire bond that is coupled to the conductive material and to the circuitry on the display layer. 
     
     
       5. The electronic device defined in  claim 3  wherein the conductive structure further comprises a flex circuit that is coupled to the conductive material and to the circuitry on the display layer. 
     
     
       6. The electronic device defined in  claim 5  wherein the flex circuit is coupled to the conductive material through a conductive adhesive. 
     
     
       7. The electronic device defined in  claim 1  wherein the display layer is a thin-film transistor layer, wherein the thin-film transistor layer extends around an entire perimeter of the opening, and wherein the conductive structure passes through the opening in the thin-film transistor layer. 
     
     
       8. The electronic device defined in  claim 7  wherein the thin-film transistor layer comprises a flexible substrate that includes a material selected from the group consisting of: a glass substrate, a sheet of polymer, a polymer composite film, and a metal foil. 
     
     
       9. The electronic device defined in  claim 1  wherein the display layer is a first display layer and the opening is a first opening, wherein the display comprises a second display layer having a second opening that is aligned with the first opening, and wherein the conductive structure passes through the first and second openings. 
     
     
       10. The electronic device defined in  claim 9  wherein the conductive structure comprises conductive material that fills the first and second openings. 
     
     
       11. The electronic device defined in  claim 1  wherein the conductive structure has a first end that is coupled to a bond pad on the display layer and a second end that is coupled to a bond pad on the printed circuit substrate. 
     
     
       12. The electronic device defined in  claim 11  wherein the conductive structure comprises a wire bond that extends through the opening, the electronic device further comprising:
 potting material that fills the opening and encapsulates the wire bond that passes through the opening. 
 
     
     
       13. The electronic device defined in  claim 1  further comprising:
 a backlight layer interposed between the printed circuit substrate and the display layer. 
 
     
     
       14. An electronic device, comprising:
 a display layer having a substrate with opposing first and second surfaces, wherein the substrate has an opening that extends from the first surface to the second surface; 
 a printed circuit that comprises signal lines; and 
 conductive material in the opening that couples the signal lines to display circuitry. 
 
     
     
       15. The electronic device defined in  claim 14  wherein the display layer is a first display layer and the opening is a first opening, the electronic device further comprising:
 a second display layer having a second opening that is aligned with the first opening, wherein the conductive material fills the first and second openings. 
 
     
     
       16. The electronic device defined in  claim 14  wherein the opening in the display layer is one of a plurality of openings that extend from the first surface to the second surface and wherein the conductive material fills each of the plurality of openings. 
     
     
       17. The electronic device defined in  claim 14  wherein the display circuitry is formed on the display layer. 
     
     
       18. The electronic device defined in  claim 14  wherein the display layer completely surrounds a perimeter of the opening. 
     
     
       19. An electronic device comprising:
 a printed circuit substrate; 
 a plurality of display layers having an opening that passes through the plurality of display layers; and 
 conductive material that fills the opening and that couples the printed circuit substrate to circuitry on a given one of the plurality of display layers. 
 
     
     
       20. The electronic device defined in  claim 19  further comprising:
 a driver integrated circuit mounted to the printed circuit substrate, wherein the driver integrated circuit provides control signals to the given one of the plurality of display layers through the conductive material that fills the opening and wherein the printed circuit substrate is interposed between the driver integrated circuit and the given one of the plurality of display layers.

Description:
This application is a continuation of patent application Ser. No. 16/355,569, filed Mar. 15, 2019, which is a continuation of patent application Ser. No. 13/253,844, filed Oct. 5, 2011, now U.S. Pat. No. 10,261,370, which are hereby incorporated by reference herein in their entireties. 
    
    
     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. Displays generally include multiple layers. For example, a display may include a layer of liquid crystal material sandwiched between two layers of glass. Other types of displays such as flexible displays may contain a layer of light-emitting material such as organic light-emitting diodes (OLEDs) formed on a layer of flexible material. A display may also include a display circuitry layer such as a thin-film transistor (TFT) layer that may be used to control the emission of light in the display. 
     A flexible printed circuit (“flex circuit”) is often mounted to the TFT layer in order to electrically connect the display circuitry to internal components within the electronic device. A conductive adhesive is often used to mount the flexible circuit board to the TFT layer. 
     Conductive structures within a display and conductive structures connected to the display do not emit light and may therefore be located in the inactive region of a display. Additional border area may be required for mounting a flex circuit to the TFT layer. Conductive structures in the display border region and flex circuits attached to the display border region may therefore reduce the amount of active display area that is available to display images and may create aesthetically unappealing border regions around the periphery of the display. 
     It would therefore be desirable to provide improved displays for electronic devices. 
     SUMMARY 
     A display may be provided for an electronic device such as a portable electronic device. A display may have an inner portion of active display area surrounded by a peripheral border of inactive display area. 
     A display may have a thin-film transistor (TFT) layer that contains display circuitry for operating the display. A display may be provided with one or more openings formed in the TFT layer in order to allow conductive bridges to pass through layers of the display. Conductive bridges may be formed from wire bonds or other conductive materials that pass through the openings in the thin-film transistor layer connecting the display circuitry with other device circuitry. 
     Wire bonds may form conductive bridges that pass down through the openings in the TFT layer. Wire bonds that pass through the openings may have one end coupled to an electrical contact on the surface of the TFT layer and another end coupled to an electrical contact on the surface of other device circuitry. 
     Potting may be formed over the wire bonds to improve the reliability of the wire bonds. 
     Openings in the TFT layer may be filled with a conductive material. The conductive material may have a portion that is electrically coupled to an electrical contact associated with the TFT layer and another portion that is electrically coupled to an electrical contact associated with other device circuitry. One or more wire bonds or flex circuits may be used to electrically connect the display circuitry with the conductive material in the opening. 
     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 conventional electronic device having display circuitry arrangements that result in undesirably large inactive display areas around the border of a display. 
         FIG. 3  is a cross-sectional side view of a portion of an illustrative electronic device having conductive bridges that pass through holes in the thin-film transistor layer of a display 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 wire bonds that pass through a gap between the display and an enclosure in accordance with an embodiment of the present invention. 
         FIG. 5  is a cross-sectional side view of a portion of an illustrative electronic device having potting that is used to improve the reliability of wire bonds in accordance with an embodiment of the present invention. 
         FIG. 6  is a cross-sectional side view of a portion of an illustrative electronic device having openings in the thin-film transistor layer of a display that are filled with a conductive material coupled to wire bonds in accordance with an embodiment of the present invention. 
         FIG. 7  is a cross-sectional side view of a portion of illustrative electronic device having openings in the thin-film transistor layer of a display that are filled with a conductive material coupled to a flex circuit in accordance with an embodiment of the present invention. 
         FIG. 8  is a top view of a conventional display having a display circuitry arrangement that results in undesirably large inactive display areas around the border of a display. 
         FIG. 9  is a top view of an illustrative display having holes formed in the thin-film transistor layer in accordance with an embodiment of the present invention. 
         FIG. 10  is a perspective view of an illustrative display having round holes formed throughout the thin-film transistor layer in accordance with an embodiment of the present invention. 
         FIG. 11  is a perspective view of an illustrative display having rectilinear holes formed throughout the thin-film transistor layer in accordance with an embodiment of the present invention. 
         FIG. 12  is a cross-sectional side view of a portion of illustrative electronic device having wire bonds that pass through openings in the thin-film transistor layer of a display in accordance with an embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     An electronic device may be provided with a display. Displays may be used to display visual information such as text and images to users. 
     An illustrative electronic device of the type that may be provided with a display is shown in  FIG. 1 . Electronic device  10  may be a 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 book, 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 have a display 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 an array of organic light-emitting diodes (OLEDs) 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, etc.). 
     As another example, a liquid crystal display (LCD) may include a layer of liquid crystal material sandwiched between two rigid substrates. 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, flexible liquid crystal displays, flexible electrochromic displays, flexible electrowetting displays, etc.). 
     In some configurations, portions of display  14  such as peripheral regions  201  may be inactive and portions of display  14  such as rectangular central portion  20 A (bounded by dashed line  20 ) may correspond to the active part of display  14 . In active display region  20 A, an array of image pixels may be used to present text and images to a user of device  10 . In active region  20 A, display  14  may include touch sensitive components for input and interaction with a user of device  10 . If desired, regions such as regions  201  and  20 A in  FIG. 1  may both be provided with display pixels (e.g., all or substantially all of the entire front planar surface of a device such as device  10  may be covered with display pixels). 
     The width of peripheral regions  201  (sometimes referred to as the “peripheral border”) may be dictated by the amount of space needed within the display on which to form display circuitry or on which to mount connecting structures that connect the display components to other device components. It may be desirable to minimize the width of peripheral regions  201  in order to increase the active region of the display and to create a more aesthetically appealing device. 
     Display  14  may be provided with openings in a display circuitry layer such as a thin-film transistor layer that allow electrical connections with other device components to pass through the openings. Forming electrical connections that pass through openings in a display layer may help reduce the amount of circuitry formed in peripheral regions  201  of display  14  thereby reducing the required width of peripheral regions  201 . Electrical connections that pass through openings in a display layer may include wire bonds or other conductive bridges through the openings. 
     It may be aesthetically unappealing to have asymmetric border regions in the display of an electronic device such as device  10 . Circuitry that increases the width of peripheral border  201  on one side of display  14  may therefore be matched by additional unused peripheral border  201  on another side of display  14  to preserve display symmetry. Reducing the width of peripheral region  201  on one side of display  14  (e.g., bottom portion  24 , sometimes referred to as the “bottom border”) may therefore reduce the width of peripheral regions  201  on another side of display (e.g., top portion  22 ). 
     A cross-sectional side view of a conventional electronic device in the vicinity of a bottom border of a display is shown in  FIG. 2 . Device  100  includes display  200  and enclosure  38 . Display  200  contains color filter layer  200 A and TFT layer  200 B. 
     A flexible circuit is often used to electrically connect display circuitry with other circuitry within the device. Anisotropic conductive film  35  is used to mount one end of flex circuit  34  to the upper surface of TFT layer  200 B. Conductive adhesive  35  forms an electrical connection between flex circuit  34  and contact pad  540 . Contact pad  540  is typically connected to one or more traces in the TFT layer such as trace  19 . 
     In a typical arrangement, flex circuit  34  wraps around one end of TFT layer  200 B by passing through gap  37  between TFT layer  200 B and enclosure  38  and then curving back under TFT layer  200 B. The end of flex circuit  34  that is not connected to the TFT layer is connected with printed circuit board  36 . 
     Flex circuit  34  and other circuitry on TFT layer  200 B does not emit light and may therefore create an inactive display region such as inactive border  40 . Inactive border  40  includes both the space needed on layer  200 B to mount flex circuit  34  as well as the width of gap  37  between TFT layer  200 B and enclosure  38  that is required to allow flex circuit  34  to wrap around the end of TFT layer  200 B. 
     The inactive portion of a display may be minimized by reducing the amount of space needed for display circuitry and by reducing the gap between the display and the enclosure.  FIG. 3  is a cross-sectional side view (i.e., a cross-section taken along axis  15  of  FIG. 1 ) of an electronic device of the type shown in  FIG. 1  illustrating how the inactive bottom border of a display may be minimized by providing openings in a display layer that allow conductive bridges through the openings. 
     As shown in  FIG. 3 , device  10  may include a display such as display  14 . Display  14  may have multiple layers such as display layer  14 A and thin-film transistor (TFT) layer  14 B. Display layer  14 A may be a color filter layer that includes an array of colored filter elements. A layer of liquid crystal material such as liquid crystal layer  13  may be interposed between color filter layer  14 A and TFT layer  14 B. This is merely illustrative. If desired, display  14  may be an organic light-emitting diode display that does not include a color filter layer or a liquid crystal layer. As another example, display  14  may be an organic light-emitting diode display that includes a color filter layer or other color changing material. Display  14  may, in general, be based on any suitable display technology (liquid crystals, organic light-emitting diodes, plasma cells, electronic ink arrays, flexible liquid crystal displays, electrochromic displays, electrowetting displays, etc.). Display  14  may be comprised of one or more glass substrates or substrates that include polymers or metal films. If desired, display  14  may be a flexible display. Examples that use liquid crystal technology are sometimes described herein as an example. 
     TFT layer  14 B may include circuitry for operating display  14  such as display driver circuitry and thin-film transistors. If desired, TFT layer  14 B may be a thin plastic film formed from polyimide, Polyethylene naphthalate (PEN), Polyethylene terephthalate (PET), other suitable polymers, a combination of these polymers, etc. Other suitable substrates that may be used to form TFT layer  14 B 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. For example, a layer of polyimide may be used to form the substrate for TFT layer  14 B. TFT layer  14 B may have a thickness of 10-25 microns, 25-50 microns, 50-75 microns, 75-100 microns, 100-125 microns, 125-150 microns, or more than 150 microns. In one particular example, TFT layer  14 B may be 100 microns thick. 
     Other layers or sublayers that may be included in display  14  include 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 shielding unwanted electric fields), 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. 
     TFT layer  14 B may include display circuitry such as display circuitry  53  for operating display  14 . Display circuitry  53  may include display image pixel structures such as display electrodes and display circuitry for controlling the display electrodes. Display circuitry  53  may form a portion of an array of thin-film transistors (TFTs) that corresponds with an array of display image pixels. Display circuitry  53  may include touch sensor electrodes, transistors (e.g., polycrystalline silicon transistors, amorphous silicon transistors, organic thin-film transistors, metal oxide transistors, carbon nanotube or graphene transistors, other nanoparticle-based transistors, etc.), interconnect lines associated with a thin-film transistor array or other image pixel array, integrated circuits, driver integrated circuits, other conductive structures, or a combination of these conductive structures. 
     Circuitry  53  in TFT layer  14 B may be interconnected using traces such as conductive trace  23 . Conductive traces such as trace  23  may be coupled to one or more contact pads such as contact pad  54 A. It may be desirable to connect display circuitry to other circuitry in the device (e.g., a main logic board or other printed circuit). One or more conductive paths such as conductive bridge  56  may be used to form an electrical connection between traces such as trace  23  and other circuitry within the device such as printed circuit substrate  58 . As shown in  FIG. 3 , conductive bridge  56  may pass through an opening in the display such as opening  50 A in TFT layer  14 B. 
     Printed circuit  58  and other printed circuits in device  10  may be formed from rigid printed circuit board material (e.g., fiberglass-filled epoxy), flexible sheets of material such as polymers, or a combination of rigid and flexible materials (sometimes referred to as “rigid-flex” printed circuit boards). Flexible printed circuits (“flex circuits”) may, for example, be formed from flexible sheets of polyimide. 
     Conductive paths such as conductive bridges  56  that connect display circuitry with other circuitry in electronic device  10  may have one end that bonds with a contact on the surface of the TFT layer and another end that bonds with a contact on the surface of a printed circuit within the device. In the example shown in  FIG. 3 , conductive bridge  56  may have one end that bonds with contact pad  54 A (on the surface of TFT layer  14 B) and another end that bonds with contact pad  54 B (on the surface of printed circuit  58 ). 
     Conductive bridge  56  may be formed from aluminum, copper, gold, other metals, other suitable conductive materials, a combination or composite of conductive materials, etc. Portions of conductive bridge  56  may include flex circuitry formed from flexible sheets of material such as polymers. Conductive bridge  56  may, in general, be formed using any suitable connector or mounting technology. In the example of  FIG. 3 , conductive bridge  56  is formed using one or more wire bonds that pass through openings in the display such as opening  50 A in TFT layer  14 B. Wire bond  56  electrically couples bond pad  54 A of TFT layer  14 B with bond pad  54 B of printed circuit  58 . This is merely illustrative. Conductive bridge  56  may be formed from other types of conductive connectors. Wire bonding to form conductive bridges  56 , as shown in  FIG. 3 , is sometimes described herein as an example. 
     Wire bonds  56  may be formed from wedge bonding, ribbon wedge bonding (e.g., to create a flat ribbon wire), ball bonding, other suitable wire bonding methods, etc. The welding process used to form wire bonds  56  may be facilitated with ultrasonic energy, thermal energy, pressure, or a combination of these forms of energy. Wire bonds  56  may have a diameter of 5-15 microns, 15-25 microns, 25-35 microns, 35-50 microns, or more than 50 microns. For illustrative purposes, the wires used for bonding may have a diameter of 25 microns, defining the minimum size of the contacting area. Alternatively, wires of 32 micron diameter may be used. Materials that may be used in forming wire bonds  56  include Tungsten Carbide, Titanium Carbide, composite materials (e.g., a composite material formed from ceramic and metal), other suitable materials, combinations of these materials, etc. 
     One or more openings such as opening  50 A (sometimes referred to as a hole) may be formed in TFT layer  14 B in order to allow conductive bridges such as conductive bridge  56  (sometimes referred to as a wire bond) to pass through TFT layer  14 B and couple to other device circuitry that is adjacent to the lower surface of TFT layer  14 B such as printed circuit  58  underneath display  14 . Openings  50 A may be designed to facilitate a wire bonding process that uses a bonding tool to attach wire bond  56  to bond pads  54 A and  54 B (sometimes referred to as landing pads). Openings  50 A may provide enough clearance around the edges of bond pad  54 B to allow the tool to connect to bond pad  54 B. Bond pads may be spaced sufficiently far apart to avoid shorting leads. Openings in the TFT layer such as opening  50 A may be formed using any suitable method (e.g., mechanical-drilling, laser-drilling, inserting a hot element, etc.) and may have any suitable shape (circular, rectilinear, other suitable shape, etc.). 
     Display  14  may be enclosed on one or more ends by an enclosure such as enclosure  62 . Enclosure  62  may be formed from part or all of one or more structures in device  10 . For example, enclosure  62  may be formed from part of device housing  12 . Providing openings  50 A in TFT layer  14 B that allow conductive bridges  56  to pass through TFT layer  14 B may allow a gap between TFT layer  14 B and enclosure  62  to be smaller than gaps between displays and device housings in conventional devices. Providing openings  50 A in TFT layer  14 B that allow conductive bridges  56  to pass through TFT layer  14 B may reduce the border regions around display  14  required for mounting connecting structures. Reducing the space needed in these areas may minimize the overall width of display border  601  (e.g., a bottom border of display  14 ), allowing for active display area such as active display region  60 A to extend closer to the edge of device  10  than in conventional devices. 
       FIG. 4  is a cross-sectional side view of a portion of device  10  illustrating another example of how the inactive portion of a display may be minimized. In this example, conductive bridges may couple display circuitry with other device circuitry by passing through the gap between the display and the display enclosure. As shown in  FIG. 4 , a gap such as gap  50 B may be formed between TFT layer  14 B and enclosure  62 . Conductive bridges such as wire bond  56  may pass through opening  50 B to couple to circuitry underneath the display such as printed circuit  58 . 
     Conductive bridge  56  may be a wire, a flat ribbon, a bundle of wires, or a bundle of flat ribbons formed using the method of wire bonding. Using a wire bond such as wire bond  56  to couple display circuitry with other device circuitry may allow a gap between TFT layer  14 B and enclosure  62  to be smaller than gaps between displays and device housings in conventional devices. Wire bond  56  may also reduce the peripheral area around display  14  required for mounting connecting circuitry. Reducing the space needed in these areas may minimize the overall width of display border  641  (e.g., a bottom border of display  14 ), allowing for active display area such as active display region  64 A to extend closer to the edge of device  10  than in conventional devices. 
     It may be desirable to cover or encapsulate conductive bridge  56 .  FIG. 5  is a cross-sectional side view of a portion of device  10  illustrating how potting may be used to encapsulate wire bond  56 . After forming wire bond  56 , an encapsulant such as potting material  66  may be used to fill opening  50 A and surround wire bond  56 . Potting material  66  may also surround the junction between wire bond  56  and contact pad  54 A, as well as the junction between wire bond  56  and contact pad  54 B. Examples of materials that may be used in forming potting  66  include epoxy, silicone, urethane, acrylic, polyester, other types of potting material, a combination of these potting materials, etc. 
     Potting or encapsulating conductive bridge  56  may provide several benefits to both the conductive path itself and the electronic device. For example, in some configurations TFT layer  14 B may be formed from glass. A glass surface with multiple holes in it such as hole  50 A may be prone to failure if exposed to excess pressure or force. Filling openings in TFT layer  14 B such as opening  50 A with potting material may increase the resiliency of the display around the openings. Other benefits of using potting material  66  may include protection against moisture, contaminants, and corrosion, electrical insulation, heat dissipation, and other benefits. Potting material  66  may also help divert unwanted pressure away from the display and improve the reliability and robustness of wire bonds  56 . 
     Other features may optionally be added to improve the resiliency of the display and the reliability of conductive bridges  56 . For example, a layer of adhesive such as adhesive  68  may be formed between TFT layer  14 B and printed circuit  58 . If desired, adhesive  68  may surround openings in TFT layer  14 B such as opening  50 A. Adhesive  68  may be configured to attach printed circuit substrate  58  to the underside of TFT layer  14 B. Adhesive  68  may increase the robustness of the display around these openings and may also provide protection against moisture, contaminants, and corrosion. Adhesive  68  may be formed from pressure sensitive adhesive (PSA), epoxy, or other suitable adhesives. 
     The space-saving benefits of using one or more holes in the TFT layer for connections between display circuitry and other device circuitry may be obtained with other configurations. One example of an alternative configuration is shown in  FIG. 6 . In this example, opening  50 A is filled with a conductive material, such as conductive material  25 . Conductive material  25  may be formed from conductive paste, conductive adhesive, conductive foam, or other suitable conductive material. An electrical contact such as contact pad  54 C may be situated over opening  50 A on the surface of conductive material  25 . Contact pad  54 C may be a separate component from conductive material  25  or may be formed from an integrated portion of conductive material  25 . An additional electrical contact such as contact pad  54 D may be situated under opening  50 A on the surface of other device circuitry such as printed circuit substrate  58 . Conductive material  25  may form an electrical connection between electrical contacts  54 C and  54 D. 
     Conductive bridges such as wire bond  59  may be used to connect bond pad  54 A with conductive material  25 . Wire bond  59  may have one end that bonds with contact pad  54 A (on the surface of TFT layer  14 B) and another end that bonds with contact pad  54 C (on the surface of conductive material  25 ). Signals may travel from display circuitry  53  to other device circuitry  58  via wire bond  59  and conductive material  25 . 
     If desired, other materials may be used to connect bond pad  54 A with conductive material  25  inside opening  50 A. For example, as shown in  FIG. 7 , a layer of conductive adhesive such as conductive adhesive  49  may be used to mount a portion of a flexible circuit such as flex circuit  63  over electrical contacts  54 A and  54 C. Conductive adhesive  49  may be formed from anisotropic conductive film (ACF) or other suitable conductive adhesive. Signals may travel from display circuitry  53  to other device circuitry  58  via flex circuit  63  and conductive material  25 . 
     Forming conductive bridges (e.g., wire bonds, conductive pastes, etc.) through holes in the TFT layer may provide a robust electrical bridge between display circuitry and other device circuitry while minimizing inactive display border regions. 
     It may be desirable to reduce the width of inactive display area around the entire periphery of a display. In a conventional display such as display  140  shown in  FIG. 8 , width  140 W of inactive display border  1401  is typically dictated by display driver circuitry located in border region  201 . Each row and column in a pixel array may have an associated conductive trace (sometimes referred to as an interconnect, driver line, or control line). Typically, these traces will run alongside each other in a common plane, parallel to side border  720  (i.e., parallel to the y-axis shown in  FIG. 8 ). This method requires an added amount of width in region  201  of inactive display border  1401  for each trace coming out of active display region  140 A. Since each row and column of a pixel array may have a control line associated with it, each added row or column of pixels in a conventional display may increase the width (such as width  140 W) of inactive display border  1401 . 
       FIG. 9  is a top view of display  14  illustrating how the width of inactive display borders may be reduced by routing display control lines through openings in a TFT layer. As shown in  FIG. 9 , display  14  may contain display circuitry such as driver integrated circuit  51  driver circuitry  55 . Driver integrated circuit  51  and driver circuitry  55  may be used to drive signals to an array of pixels in display  14 . Signal lines such as signal lines  99  may be used to distribute signals from the display driver circuitry to control lines such as control lines  41 . As shown in  FIG. 9 , control lines  41  may include data lines (D) and gate lines (G). 
     A plurality of holes such as holes  50 C may be formed in one or more layers of display  14  such as TFT layer  14 B. Signal lines  99  may pass through holes  50 C in display (parallel with the z-axis as marked in  FIG. 9 ) to run along a back side of the display. If desired, signal lines  99  coming from driver integrated circuit  51  may pass down through holes  50 C (in region  81 A) to a printed circuit adjacent to the back side of display  14  and may pass up through holes  50 C (in region  81 B) to reach control lines  41 . This may reduce the need for space in the border region for display circuitry. 
     As shown in  FIG. 10 , a plurality of holes such as holes  50 C may be formed throughout TFT layer  14 B. If desired, holes such as holes  50 C may be formed on one side, on two sides, on three sides, or on all four sides of display  14 . Holes  50 C may be located in regions of TFT layer  14 B that protrude out from under display layer  14 A such as regions  81 A and  81 B. Holes  50 C may also be located in regions of TFT layer  14 B that are covered by display layer  14 A. In general, holes may be located anywhere in TFT layer  14 B. 
     Holes in the TFT layer may be of any suitable size or shape. For example, holes such as holes  50 C of  FIG. 11  may have a rectilinear shape. 
     Holes  50 C of  FIGS. 9-11  may be used to form a connection path from display circuitry to other device circuitry. Signal lines from display circuitry may be routed through openings  50 C in the TFT layer to run along a back side of the display. This may help reduce the width of inactive display area around the border of a display.  FIG. 12  is a cross-sectional side view (cross-section taken along axis  85  of  FIG. 1 ) of device  10  in the vicinity of display  14  illustrating how holes such as hole  50 C (sometimes referred to as an opening) may help reduce width  14 W of inactive display border regions. 
     In the example shown in  FIG. 12 , display  14  may be a liquid crystal display (LCD). Display  14  may have multiple layers such as color filter layer  14 A, TFT layer  14 B, and light source layer  14 C. A layer of liquid crystal material such as liquid crystal  13  may be interposed between color filter layer  14 A and TFT layer  14 B. Light source layer  14 C may be a backlight layer that illuminates the liquid crystal material from the back of display  14 . 
     Components on TFT layer  14 B such as pixels  98  may be interconnected using traces such as conductive traces  41  (sometimes referred to as control lines). Control lines  41  may be configured to control the array of pixels and may be connected to one or more electrical contacts on TFT layer  14 B such as contact pad  84 A. 
     It may be desirable to route signal lines from display circuitry through openings in the display. In some configurations, display circuitry such as driver integrated circuit  51  may be located on the TFT layer as shown in the example of  FIG. 9 . In the example shown in  FIG. 12 , driver integrated circuit  51  may optionally be located on a printed circuit under the display such as printed circuit  88  adjacent to light source layer  14 C. Control signals from driver integrated circuit  51  may be conveyed to control lines  41  through conductive bridges such as conductive bridge  82  that pass through openings  50 C in TFT layer  14 B. 
     Signal lines  99  may be used to distribute control signals from driver integrated circuit  51  to conductive bridge  82 . Conductive bridge  82  may be used to convey these control signals from signal lines  99  to control lines  41 . Printed circuit  88  may be formed from rigid printed circuit board material (e.g., fiberglass-filled epoxy) or flexible sheets of material such as polymers. 
     Conductive paths that pass through openings in the TFT layer may have one end that bonds with a contact on the surface of the TFT layer and another end that bonds with a contact on the surface of a printed circuit within the device. In the example shown in  FIG. 12 , a conductive bridge such as conductive bridge  82  may have one end that bonds with contact pad  84 A (on the surface of TFT layer  14 B) and another end that bonds with contact pad  84 B (on the surface of printed circuit  88 ). 
     Conductive bridge  82  may be formed from aluminum, copper, gold, other metals, other suitable conductive materials, a combination or composite of conductive materials, etc. Portions of conductive bridge  82  may include flex circuitry formed from flexible sheets of material such as polymers. Conductive bridge  82  may, in general, be formed using any suitable connector or mounting technology. In the example of  FIG. 12 , conductive bridge  82  is formed using one or more wire bonds that pass through openings in the display such as opening  50 C in TFT layer  14 B. Wire bond  82  electrically couples bond pad  84 A of TFT layer  14 B with bond pad  84 B of printed circuit  88 . Wire bond  82  passes through openings  50 C in TFT layer  14 B. This is merely illustrative. Conductive bridge  82  may be formed from other types of conductive connectors. Wire bonding to form conductive bridges  82 , as shown in  FIG. 12 , are sometimes described as an example. 
     Wire bonds  82  may be formed from wedge bonding, ribbon wedge bonding (e.g., to create a flat ribbon wire), ball bonding, other suitable wire bonding methods, etc. The welding process used to form wire bonds  82  may be facilitated with ultrasonic energy, thermal energy, pressure, or a combination of these forms of energy. Wire bonds  82  may have a diameter of 5-15 microns, 15-25 microns, 25-35 microns, 35-50 microns, or more than 50 microns. For illustrative purposes, the wires used for bonding may have a diameter of 25 microns, defining the minimum size of the contacting area. Alternatively, wires of 32 micron diameter may be used. Materials that may be used in forming wire bonds  82  include Tungsten Carbide, Titanium Carbide, composite materials (e.g., a composite material formed from ceramic and metal), other suitable materials, combinations of these materials, etc. 
     To improve the reliability of wire bonds  82 , potting material  66  may be formed around wire bond  82  in opening  50 C. Potting material  66  may also surround the junction between wire bond  82  and contact pad  84 A, as well as the junction between wire bond  82  and contact pad  84 B. 
     One or more openings such as opening  50 C (sometimes referred to as a hole) may be formed in TFT layer  14 B in order to allow conductive bridges such as conductive bridge  82  (sometimes referred to as a wire bond) to pass through TFT layer  14 B and couple to printed circuit  88  underneath display  14 . Openings in the TFT layer such as opening  50 C may be formed using any suitable method (e.g., mechanical-drilling, laser-drilling, inserting a hot element, etc.) and may have any suitable shape (circular, rectilinear, other suitable shape, etc.). 
     By having conductive bridges such as wire bond  82  pass down through holes in the display layers (parallel to the z-axis marked in  FIG. 12 ) instead of running alongside each other in a single layer (parallel to the y-axis marked in  FIG. 12 ), the width of inactive display area (such as width  14 W) around the border of the display may be significantly smaller than that of a conventional display. By positioning printed circuit  88  underneath light source layer  14 C, signal lines such as signal lines  99  that distribute signals to control lines  41  may be located under an active portion of a display. 
     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: 20200302
Publication Date: 20201229
Grant Date: 20201229
Priority Date: 20111005
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": "G02F2201/42", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02F1/13452", "inventive": true, "first": true, "tree": "[]"}, {"code": "G02F1/13452", "inventive": true, "first": true, "tree": "[]"}, {"code": "G02F2201/42", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02F1/13452", "inventive": true, "first": true, "tree": "[]"}, {"code": "G02F2201/42", "inventive": false, "first": false, "tree": "[]"}]
Family ID: 47003267