PATENT DOCUMENT

Publication Number: US-9600112-B2
Application Number: US-201414511945-A
Country: US
Kind Code: B2

Title: Signal trace patterns for flexible substrates

Abstract:
A flexible substrate may have one or more bends. A bend in a flexible substrate may be made along a bend axis. Conductive traces in the flexible substrate may have elongated shapes. Each conductive trace may extend along a longitudinal axis that is perpendicular to the bend axis. Metal or other conductive materials may form the conductive traces. The traces may be formed from a chain of linked segments. Each segment may have patterned trace portions that surround one, two, or more than two openings. Traces may also be formed that have multiple layers of metal or other conductive material interconnected using vias. A polymer layer may cover the traces to align a neutral stress plane with the traces and to serve as a moisture barrier layer.

Claims:
What is claimed is: 
     
       1. Apparatus, comprising:
 a flexible substrate layer having a bend; 
 conductive traces on the flexible substrate layer that overlap the bend, wherein each conductive trace is formed from a chain of interconnected segments, each segment enclosing an opening having first and second opposing ends, wherein each conductive trace has a first portion formed in a first layer of metal and a second portion formed in a second layer of metal, wherein the first portion and the second portion have meandering shapes that intersect at the first and second opposing ends of each opening; and 
 a plurality of metal vias that interconnect the first portion and the second portion, wherein the plurality of metal vias includes first and second metal vias that couple the first portion and the second portion at the first and second opposing ends of each opening. 
 
     
     
       2. The apparatus defined in  claim 1  wherein the flexible substrate layer comprises a flexible polymer layer. 
     
     
       3. The apparatus defined in  claim 2  wherein the conductive traces each extend along a longitudinal axis, wherein the bend is formed around a bend axis, and wherein the longitudinal axis of each trace is perpendicular to the bend axis. 
     
     
       4. The apparatus defined in  claim 3  wherein the conductive traces comprise metal traces. 
     
     
       5. The apparatus defined in  claim 4  further comprising pixels that contain light-emitting diodes on the flexible substrate layer. 
     
     
       6. The apparatus defined in  claim 5  wherein the pixels are organized in an array of rows and columns forming an active area for a display in which images are produced and wherein the bend is formed in an inactive area of the display in which images are not produced. 
     
     
       7. The apparatus defined in  claim 4  further comprising:
 a dielectric coating over the metal traces. 
 
     
     
       8. The apparatus defined in  claim 7  wherein the dielectric coating has a thickness such that a neutral stress plane for the flexible substrate layer is aligned with the metal trace. 
     
     
       9. The apparatus defined in  claim 8  wherein the dielectric coating is a moisture barrier coating. 
     
     
       10. An apparatus, comprising:
 a flexible polymer substrate having a bend; and 
 conductive traces on the flexible polymer substrate that overlap the bend, wherein each conductive trace has a chain of interconnected sections, each section having a pattern of traces that encloses at least two openings, wherein each pattern of traces comprises first and second trace portions separated by a gap in which the at least two openings are enclosed, and a third trace portion that extends across the gap from the first trace portion to the second trace portion to separate the at least two openings from each other. 
 
     
     
       11. The apparatus defined in  claim 10  wherein the conductive traces each extend along a longitudinal axis, wherein the bend is formed around a bend axis, and wherein the longitudinal axis of each trace is perpendicular to the bend axis. 
     
     
       12. The apparatus defined in  claim 11  further comprising pixels that contain light-emitting diodes, wherein the conductive traces carry display signals. 
     
     
       13. The apparatus defined in  claim 12  wherein the pixels are organized in an array of rows and columns that forms an active area for a display in which images are produced and wherein the bend is formed in an inactive area of display in which images are not produced. 
     
     
       14. The apparatus defined in  claim 13  further comprising:
 a polymer coating over the conductive traces that serves as a moisture barrier. 
 
     
     
       15. A flexible structure that overlaps a bend axis, comprising:
 a flexible substrate layer that bends at the bend axis; 
 conductive traces on the flexible substrate layer that overlap the bend axis, wherein each conductive trace has a chain of linked metal trace segments, wherein each metal trace segment includes a first trace portion and a second trace portion that extends away from the first trace portion, wherein the first and second trace portions meet at opposing ends of the metal trace segment to form an opening that is enclosed by the first and second trace portions, and wherein each metal trace segment further includes a third trace portion that extends across the opening from the first trace portion to the second trace portion; and 
 a dielectric coating over the conductive traces. 
 
     
     
       16. The flexible structure defined in  claim 15  wherein the dielectric coating comprises a moisture barrier, wherein each conductive trace is formed from overlapping meandering lines, and wherein the overlapping meandering lines are shorted together using metal vias.

Description:
BACKGROUND 
     This relates generally to electronic devices, and, more particularly, to flexible substrates in electronic devices. 
     Electronic devices such as cellular telephones, computers, and other electronic equipment often contain flexible substrates. The ability to bend a flexible substrate allows the substrate to be used in situations in which rigid substrates would be difficult or impossible to use. 
     Flexible substrates may be used for components such as displays and touch sensors. Flexible substrates may also be used in forming flexible printed circuits. Flexible printed circuits may be used to interconnect electrical components and can be used in forming signal bus cables. Signal traces may be formed on these flexible substrates to carry signals. 
     Challenges can arise when the traces on a flexible substrate are bent. If care is not taken, bending stress will give rise to trace cracks or other faults that can disrupt the ability of the traces to reliably carry signals. 
     It would therefore be desirable to be able to provide improved techniques for facilitating the bending of flexible substrates with signal traces. 
     SUMMARY 
     A flexible substrate may have one or more bends. A portion of the substrate may form a display with an array of pixels. Flexible substrates may also be used in forming touch sensors, displays with integrated touch sensor electrodes, and flexible printed circuits. 
     A bend in a flexible substrate may be made along a bend axis. The bend may be located in an inactive area of a display or in another region of the flexible substrate. 
     Conductive traces in the flexible substrate may have elongated shapes. Each conductive trace may extend along a longitudinal axis that is perpendicular to the bend axis. Metal or other conductive materials may form the conductive traces. 
     The traces may each be formed from a chain of linked segments. Each segment may have patterned trace portions that surround one, two, or more than two openings. Serpentine patterns, zigzag patterns, and other trace patterns may be used in forming the traces. A polymer layer may cover the traces to align a neutral stress plane with the traces and to serve as a moisture barrier layer. 
     Traces may be formed that have multiple layers of metal or other conductive material that are interconnected using vias. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of an illustrative electronic device in accordance with an embodiment. 
         FIG. 2  is a top view of an illustrative electronic device display with a flexible substrate in accordance with an embodiment. 
         FIG. 3  is a cross-sectional view of a conductive trace on a flexible substrate that has been coated with a layer of material such as polymer in accordance with an embodiment. 
         FIG. 4  is a cross-sectional side view of an illustrative flexible substrate with a bend in accordance with an embodiment. 
         FIG. 5  is a cross-sectional side view of an illustrative flexible substrate with a bend that has been made at less than a right angle in accordance with an embodiment. 
         FIG. 6  is a cross-sectional side view of an illustrative flexible substrate with two right-angle bends in accordance with an embodiment. 
         FIG. 7  is a cross-sectional side view of an illustrative flexible substrate with a curved bend in accordance with an embodiment. 
         FIG. 8  is a diagram of an illustrative double sine wave trace pattern that may be used in the bent region of a flexible substrate in accordance with an embodiment. 
         FIG. 9  is a diagram of an illustrative trace of the type shown in  FIG. 8  with an angled longitudinal redundant metal line feature in accordance with an embodiment. 
         FIG. 10  is a diagram of an illustrative trace of the type shown in  FIG. 8  with an angled lateral redundant metal line feature in accordance with an embodiment. 
         FIG. 11  is a diagram of an illustrative double sine wave trace with a pair of interior longitudinal redundant lines in accordance with an embodiment. 
         FIG. 12  is a diagram of an illustrative double sine wave trace with a single longitudinal serpentine redundant trace in accordance with an embodiment. 
         FIG. 13  is a diagram of a double zigzag trace that may be used in the bent region of a flexible substrate in accordance with an embodiment. 
         FIG. 14  is a diagram of a trace pattern of the type shown in  FIG. 13  with an angled longitudinal redundant line in accordance with an embodiment. 
         FIG. 15  is a diagram of a trace pattern of the type shown in  FIG. 13  with a straight longitudinal redundant line in accordance with an embodiment. 
         FIG. 16  is a diagram of a trace pattern of the type shown in  FIG. 13  with laterally oriented angled redundant lines in accordance with an embodiment. 
         FIG. 17  is a diagram of a trace pattern of the type shown in  FIG. 13  with lateral redundant lines in accordance with an embodiment. 
         FIG. 18  is a diagram of a trace pattern of the type shown in  FIG. 13  with diagonal redundant lines in accordance with an embodiment. 
         FIG. 19  is a diagram of a trace pattern of the type shown in  FIG. 13  with diagonal cross-shaped redundant patterned traces in accordance with an embodiment. 
         FIG. 20  is a diagram of an illustrative serpentine trace that may be used in the bent region of a flexible substrate in accordance with an embodiment. 
         FIG. 21  is a diagram of an illustrative trace of the type shown in  FIG. 20  with longitudinal redundant lines in accordance with an embodiment. 
         FIG. 22  is a diagram of an illustrative trace of the type shown in  FIG. 20  with angled longitudinal redundant lines in accordance with an embodiment. 
         FIG. 23  is a diagram of an illustrative trace of the type shown in  FIG. 20  with serpentine redundant lines in accordance with an embodiment. 
         FIG. 24  is a diagram of an illustrative trace of the type shown in  FIG. 20  with a chain-shaped trace pattern having multiple joined circular traces in accordance with an embodiment. 
         FIG. 25  is a flow chart of illustrative steps involved in forming traces for bent regions of flexible substrates in accordance with an embodiment. 
         FIG. 26  is a diagram of an illustrative two-layer trace of “temple gate” traces that may be used in forming signal lines in bent portions of flexible substrates in accordance with an embodiment. 
         FIG. 27  is a diagram of a two layer trace pattern with interweaved sine wave traces in accordance with an embodiment. 
         FIG. 28  is a diagram of a two layer zigzag trace pattern in accordance with an embodiment. 
         FIG. 29  is a diagram of a two layer trace having oval-shaped segments in accordance with an embodiment. 
         FIG. 30  is a flow chart of illustrative steps involved in forming multilayer traces for a bent portion of a flexible substrate in accordance with an embodiment. 
         FIG. 31  is a cross-sectional side view of an illustrative plug via for interconnecting traces in a two-layer trace in accordance with an embodiment. 
         FIG. 32  is a cross-sectional side view of an illustrative contact via for interconnecting traces in a two-layer trace in accordance with an embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     An electronic device such as electronic device  10  of  FIG. 1  may contain flexible substrates. Conductive traces on the flexible substrates may be used to carry signals. The conductive traces may be bent when a portion of the flexible substrate is bent. The conductive traces may be provided with patterns that resist damage during bending. 
     Electronic device  10  may be a computing device such as a laptop computer, a computer monitor containing an embedded computer, a tablet computer, a cellular telephone, a media player, or other handheld or portable electronic device, a smaller device such as a wrist-watch device, a pendant device, a headphone or earpiece device, a device embedded in eyeglasses or other equipment worn on a user&#39;s head, or other wearable or miniature device, a television, a computer display that does not contain an embedded computer, a gaming device, a navigation device, an embedded system such as a system in which electronic equipment with a display is mounted in a kiosk or automobile, equipment that implements the functionality of two or more of these devices, or other electronic equipment. In the illustrative configuration of  FIG. 1 , device  10  is a portable device such as a cellular telephone, media player, tablet computer, or other portable computing device. Other configurations may be used for device  10  if desired. The example of  FIG. 1  is merely illustrative. 
     In the example of  FIG. 1 , device  10  includes a display such as display  14  mounted in housing  12 . Housing  12 , which may sometimes be referred to as an enclosure or case, may be formed of plastic, glass, ceramics, fiber composites, metal (e.g., stainless steel, aluminum, etc.), other suitable materials, or a combination of any two or more of these materials. Housing  12  may be formed using a unibody configuration in which some or all of housing  12  is machined or molded as a single structure or may be formed using multiple structures (e.g., an internal frame structure, one or more structures that form exterior housing surfaces, etc.). 
     Display  14  may be a touch screen display that incorporates a layer of conductive capacitive touch sensor electrodes or other touch sensor components (e.g., resistive touch sensor components, acoustic touch sensor components, force-based touch sensor components, light-based touch sensor components, etc.) or may be a display that is not touch-sensitive. Capacitive touch screen electrodes may be formed from an array of indium tin oxide pads or other transparent conductive structures. 
     Display  14  may be protected using a display cover layer such as a layer of transparent glass or clear plastic. Openings may be formed in the display cover layer. For example, an opening may be formed in the display cover layer to accommodate a button such as button  16 . An opening may also be formed in the display cover layer to accommodate ports such as speaker port  18 . Openings may be formed in housing  12  to form communications ports (e.g., an audio jack port, a digital data port, etc.), to form openings for buttons, etc. 
     Display  14  may include an array of display pixels formed from liquid crystal display (LCD) components, an array of electrophoretic pixels, an array of plasma pixels, an array of organic light-emitting diode pixels or other light-emitting diodes, an array of electrowetting pixels, or pixels based on other display technologies. The array of pixels of display  14  forms an active area AA. Active area AA is used to display images for a user of device  10 . Active area AA may be rectangular or may have other suitable shapes. Inactive border area IA may run along one or more edges of active area AA. Inactive border area IA may contain circuits, signal lines, and other structures that do not emit light for forming images. 
     It may sometimes be desirable to bend flexible substrates within device  10  to minimize inactive area IA for aesthetic reasons, to accommodate components within device  10 , or to satisfy other design constraints. A flexible substrate that forms part of display  14  may, for example, be bent along one or more of its edges to minimize inactive area IA (e.g., to make display  14  borderless or nearly borderless or to otherwise help accommodate display  14  within device  10 ). Touch sensor substrates, substrates that include integrated display and touch sensor components, flexible printed circuits, and other flexible substrates may be bent. 
     An illustrative display for device  10  is shown in  FIG. 2 . As shown in  FIG. 2 , display  14  may include layers such as flexible substrate layer  20 . Substrate layers such as layer  20  may be formed from one or more layers of flexible polymer or other flexible materials. Flexible substrate  20  may have left and right vertical edges and upper and lower horizontal edges. If desired, substrates such as substrate  20  may have non-rectangular shapes (e.g., shapes with curved edges, rectangular shapes and other shapes with protrusions that form flexible tails, etc.). 
     Display  14  may have an array of pixels  26  for displaying images for a user. Each pixel may, for example, have a light-emitting diode (e.g., an organic light-emitting diode). Pixels  26  may be arranged in rows and columns. There may be any suitable number of rows and columns in the array of pixels  26  (e.g., ten or more, one hundred or more, or one thousand or more). Display  14  may include pixels  26  of different colors. As an example, display  14  may include red pixels that emit red light, green pixels that emit green light, blue pixels that emit blue light, and white pixels that emit white light. Configurations for display  14  that include pixels of other colors may be used, if desired. 
     Display driver circuitry may be used to control the operation of pixels  26 . The display driver circuitry may be formed from integrated circuits, thin-film transistor circuits, or other suitable circuitry. As shown in  FIG. 2 , display  14  may have display driver circuitry such as circuitry  22  that that contains communications circuitry for communicating with system control circuitry over path  32 . Path  32  may be formed from traces on a flexible printed circuit or other cable. If desired, some or all of circuitry  22  may be mounted on a substrate that is from substrate  20 . The control circuitry with which circuitry  22  communicates may be located on one or more printed circuits in electronic device  10 . During operation, the control circuitry may supply display  14  with information on images to be displayed on display  14  by pixels  26 . 
     To display the images on pixels  26 , display driver circuitry  22  may supply corresponding image data to data lines  28  while issuing clock signals and other control signals to supporting display driver circuitry such as gate driver circuitry  24  using signal lines  38 . Data lines  28  are associated with respective columns of display pixels  26 . Gate driver circuitry  24  (sometimes referred to as scan line driver circuitry) may be implemented as part of an integrated circuit and/or may be implemented using thin-film transistor circuitry on substrate  20 . Horizontal signal lines such as gate lines  30  (sometimes referred to as scan lines or horizontal control lines) run horizontally through display  14 . Each gate line  30  is associated with a respective row of pixels  26 . If desired, there may be multiple horizontal control lines such as gate lines  30  associated with each row of pixels  26 . Gate driver circuitry  24  may be located on the left side of display  14 , on the right side of display  14 , or on both the right and left sides of display  14 , as shown in  FIG. 2 . 
     To minimize the footprint of display  14 , it may be desirable to bend portions of substrate  20  along one or more bend axis  34 . It may also be desirable to bend a flexible substrate such as substrate  20  in situations in which substrate  20  forms part of other device structures (e.g., part of a touch sensor substrate that carries an array of capacitive touch sensor electrodes, part of a touch screen display that has both capacitive touch sensor electrodes and display pixel structures on a common substrate layer, part of a flexible printed circuit cable, part of a flexible printed circuit on which integrated circuits and other devices have been mounted, or part of other device structures). 
     The bending of flexible substrate  20  creates bends in the conductive traces on substrate  20 . To help prevent damage to the conductive traces on substrate  20  during bending, it may be desirable to cover these traces with a coating layer such as a layer of polymer. As shown in  FIG. 3 , for example, conductive trace  40  (e.g., traces  28 ,  38 ,  30  or other traces) on flexible substrate  20  may be covered with a dielectric layer such as polymer layer  42 . 
     Conductive traces such as trace  40  may be formed from metal (e.g., copper, aluminum, silver, gold, molybdenum, etc.) or conductive polymer. The traces can be passivated. The conductive traces may, if desired, be formed from multilayer stacks of metals or other materials (e.g., titanium/aluminum/titanium, etc.). Conductive traces  40  may also be formed from other types of coated or printed materials such as silver nanowires, conductive inks such as silver inks or other metal inks, carbon nanotubes, carbon inks, etc. 
     Substrate layer  20  may be a sheet of polyimide, polyester, polyethylene napthalate, or other polymer. Substrate layer  20  may also be formed from composite films, metal foils, thin glass, or combinations of these materials. Polymer coating layer  42  may be a high performance polymer barrier film that provides corrosion protection or other suitable flexible polymer layer. The thicknesses T 1  and T 2  of layers  42  and  20  may be selected so that the neutral stress plane of the stack of layers in  FIG. 3  is aligned with trace  40 , thereby helping to minimize stress when traces  40  are bent. 
       FIG. 4  is a cross-sectional side view of a flexible substrate on which traces such as trace  40  have been bent. In the example of  FIG. 4 , flexible substrate  20  is part of a display (display  14 ) that has active area components  44  (e.g., pixels  26 ). This is merely illustrative. Flexible substrate  20  may form part of any suitable structure in device  10 . 
     Substrate  20  may be planar (unbent) in main region  54  or may have a slight curve in region  54 . Bent edge region  52  of substrate  20  may be bent downwards about bend axis  34  to form bend  48  in substrate  20 . Conductive traces such as trace  40  and polymer coating  42  bend with substrate  20 . Traces  40  may be elongated traces that extend along a dimension that is perpendicular to bend axis  34 . Circuitry  50  (e.g., display driver circuitry, touch sensor circuity in a touch sensor, etc.) may be mounted on bent edge region  52  and/or a flexible printed circuit cable or other component may be attached to substrate  20  in bent edge region  52 . 
     Substrate  20  may be bent along one or more edges and/or along one or more bend axes. In the example of  FIG. 5 , substrate  20  has been bent sufficiently to ease the edge of substrate  20 , but the bend angle of bend  48  is less than a right angle. In  FIG. 6 , there are two bends  48  each formed by bending a portion of substrate  20  about a different respective bend axis  34 .  FIG. 7  shows how substrate  20  may be bent about bend axis  34  to form a 180° bend. The examples of  FIGS. 4, 5, 6, and 7  are merely illustrative. Any suitable type of bend may be formed in flexible substrate  20 , if desired. 
     To help accommodate bending without cracking the metal or other conductive material used in forming trace  40 , trace  40  may be provided with a shape that accommodates bends. Illustrative trace patterns that may help accommodate bending in traces such as trace  40  without damaging the bent traces are shown in  FIGS. 8-24 and 26-29 . Other trace patterns to minimize damage during bending may be used, if desired. 
       FIG. 8  is a diagram of an illustrative double sine wave trace pattern that may be used for trace  40  in the bent region of flexible substrate  20 . In the illustrative configuration of  FIG. 8  and other illustrative configurations, trace  40  has a series of interconnected (and electrically shorted) loop-shaped segments  40 ′ each of which surrounds at least one opening  41  (or more than one opening  41 ). This forms a chain of electrically connected segments  40 ′. The shape of each section  40 ′ of trace  40  (i.e., a shape with one or more interior openings) provides redundancy due to parallelism between the portions of the trace in each section  40 ′. This parallelism helps ensure that trace  40  can continue to satisfactorily carry signals even in the presence of a bend. 
       FIG. 9  is a diagram of an illustrative trace of the type shown in  FIG. 8  with an angled longitudinal redundant metal line feature (redundant lines  60 , which are angled slightly away from longitudinal axis  62  of trace  40 ). In configurations of the type shown in  FIG. 9 , there are two openings  41  in each section (segment)  40 ′ of trace  40  (i.e., there are three parallel trace portions to provide redundancy). 
       FIG. 10  is a diagram of an illustrative trace of the type shown in  FIG. 8  with an angled lateral redundant metal line feature (redundant lines  64 , which are angled slightly away from lateral dimension  66 . 
     If desired, angles a of  FIGS. 9 and 10  may vary. The examples of  FIGS. 9 and 10  are illustrative. 
     In the example of  FIG. 11 , each segment of a double sine wave trace has been provided with a pair of interior longitudinal redundant lines  68  to form trace  40 . 
     In the example of  FIG. 12 , a double sine wave trace has been provided with longitudinal serpentine redundant trace portions  70  to form trace  40 . 
     In the example of  FIG. 13 , trace  40  has a double zigzag pattern. 
     In the examples of  FIGS. 14, 15, 16, and 17 , lines  72 ,  74 ,  76 , and  78  are respectively used to provide redundancy to trace  40 . Angle a of  FIGS. 14 and 16  may vary, if desired. 
       FIG. 18  is a diagram of trace  40  in a configuration in which segments  80  run diagonally across each section of trace  40 . 
       FIG. 19  shows how trace  40  may include cross-shaped redundant traces  82 . 
     As shown in  FIG. 20 , trace  40  may have a serpentine shape. 
     In the arrangement of  FIG. 21 , the serpentine portion of trace  40  has been provided with vertical redundant trace segments  84 . 
     In the arrangement of  FIG. 22 , redundant lines  86  run diagonally (at an angle with respect to the longitudinal axis of trace  40 ). 
       FIG. 23  is a diagram of trace  40  in an illustrative configuration in which a serpentine trace has been provided with redundant trace portions  88  that are themselves serpentine. 
       FIG. 24  is a diagram of trace  40  of a mirror imaged version of serpentine trace  40  of  FIG. 20 . In this type of arrangement, trace  40  forms a chain shape with circularly-shaped link segments. 
       FIG. 25  is a flow chart of illustrative steps involved in forming device  10  or other items with bent flexible substrates such as substrate  20 . 
     At step  90 , a glass carrier or other suitable support structure may be coated with a liquid polymer and cured. The cured polymer forms flexible substrate  20 . 
     At step  92 , photolithographic techniques, etching, and other techniques may be used in forming metal traces  40  with a desired pattern and other structures for flexible substrate  20  (e.g., pixel structures for pixels  26  in display  14 , touch electrodes on a touch sensor, etc.). 
     After forming traces  40  of desired shapes (see, e.g., the examples of  FIGS. 8-24  in which each elongated trace has a chain of segments each of which encloses one or two or more openings), a polymer coating such as coating  42  may be deposited on substrate  20  at step  94 . Coating  42  may be deposited to a thickness that helps move the neutral stress plane of substrate  20  into alignment with traces  40 , thereby minimizing stress on trace  40  during bending. Coating  42  may be formed form a moisture barrier polymer that helps prevent corrosion to metal and other materials of the type that may be used in forming traces  40 . 
     At step  96 , substrate  20  may be removed from the glass carrier. 
     At step  98 , substrate  20  may be bent around bend axis  34  to form bend  48  (or multiple bends  48  may be formed). Substrate  20  may then be assembled within device  10  with other device structures to form a completed device  10 . 
     It may be desirable to provide signal trace redundancy by forming conductive trace  40  from multiple patterned layers of metal or other conductive material.  FIG. 26  is a diagram of trace  40  in an illustrative configuration involving a first “temple gate” trace portion  40 - 1  (a first serpentine trace formed from a first layer of metal or other patterned conductive material on substrate  20 ) and a second “temple gate” trace portion  40 - 2  (a second serpentine trace formed from a second layer of metal or other patterned conductive material that is deposited and patterned after the first layer). A layer of polymer or other dielectric (sometimes referred to as interlayer dielectric) may be interposed between the layers that form traces  40 - 1  and  40 - 2  and may be interconnected by vias  100 . Vias  100  may, for example, couple traces  40 - 1  and  40 - 2  at overlapping portions between traces  40 - 1  and  40 - 2  (e.g., at each intersection between traces  40 - 1  and  40 - 2 ). 
     In the example of  FIG. 27 , traces  40 - 1  and  40 - 2  are narrower than traces  40 - 1  and  40 - 2  of  FIG. 26  and have a sinusoidal shape. Vias  100  may couple trace  40 - 1  (which lies in a first conductive layer) to trace  40 - 2  (which lies in a second conductive layer that is separated from the first layer by a layer of interposed dielectric). 
     In the example of  FIG. 28 , traces  40 - 1  and  40 - 2  have zigzag shapes. 
       FIG. 29  shows how multiple vias  100  may be used at each overlapping portion between traces  40 - 1  and  40 - 2 . 
     The two-conductive-layer arrangements of  FIGS. 26, 27, 28, and 29  are merely illustrative. If desired, additional layers of metal traces may be used in forming trace  40  (e.g., additional layers may be coupled together by additional conductive vias  100 ). 
       FIG. 30  is a flow chart of illustrative steps involved in forming a multi-layer conductive trace  40 . 
     At step  102 , a glass carrier or other suitable support structure may be coated with a liquid polymer and cured. The cured polymer forms flexible substrate  20 . 
     At step  104 , photolithographic techniques, etching, and other fabrication processes may be used in patterning a first layer of conductive trace  40  (e.g., traces such as trace  40 - 1 ). Additional structures on substrate  20  may also be formed (e.g., pixel structures for pixels  26  in display  14 , touch electrodes on a touch sensor, etc.). 
     After forming a first layer of traces  40 - 1  at step  104 , a layer of polymer or other dielectric may be deposited on traces  40 - 1  and via holes for vias  100  may be formed through the polymer in alignment with traces  40 - 1  (step  106 ). 
     At step  108 , the via holes may be filled with metal or other conductive material to form conductive vias  100 . 
     At step  110 , photolithographic techniques, etching, and other fabrication processes may be used in forming a second patterned layer of conductive trace  40  (e.g. trace  40 - 2 ). Trace  40 - 2  may be aligned with vias  100 , so that vias  100  electrically connect layers  40 - 1  and  40 - 2  together, thereby forming conductive trace  40 . 
     At step  112 , polymer coating  42  may be deposited. The thickness of layer  42  may be adjusted so that the neutral stress plane of substrate  20  is aligned with conductive traces  40 . If desired, layer  42  may be a moisture barrier layer that helps prevent moisture from reaching traces  40 . 
     At step  114 , substrate  20  may be removed from the glass carrier. 
     At step  116 , substrate  20  may be bent around bend axis  34  to form bend  48  (or multiple bends  48  may be formed). Substrate  20  may then be assembled within device  10  with other device structures to form a completed device  10 . 
     Vias  100  for interconnecting multilayer traces may be formed using any suitable via structures.  FIG. 31  is a cross-sectional side view of an illustrative plug via for interconnecting traces in a two-layer trace. As shown in  FIG. 31 , dielectric layer  122  may separate upper trace  40 - 2  from lower trace  40 - 1 . Plug via  100  may be formed from metal plug structure  120 . Plug  120  may fill a via hole in dielectric  122 . Plug via  100  of  FIG. 31  may short traces  40 - 2  and  40 - 1  together as described in connection with traces  40  of  FIGS. 26, 27, 28, and 29 .  FIG. 32  is a cross-sectional side view of an illustrative contact via. In the arrangement of  FIG. 32 , via  100  is formed from portions of upper trace  40 - 2  that fill a via hole in dielectric layer  122  and thereby electrically connect trace  40 - 2  to trace  40 - 1 . 
     The foregoing is merely illustrative and various modifications can be made by those skilled in the art without departing from the scope and spirit of the described embodiments. The foregoing embodiments may be implemented individually or in any combination.

Metadata:
Filing Date: 20141010
Publication Date: 20170321
Grant Date: 20170321
Priority Date: 20141010
Inventors: ZHANG ZHEN
DRZAIC PAUL S.
TAO YI
Assignee: APPLE INC
CPC Classifications: [{"code": "H05K2201/09672", "inventive": false, "first": false, "tree": "[]"}, {"code": "H05K1/028", "inventive": true, "first": false, "tree": "[]"}, {"code": "H05K2201/09663", "inventive": false, "first": false, "tree": "[]"}, {"code": "G06F1/169", "inventive": true, "first": false, "tree": "[]"}, {"code": "H05K2201/10106", "inventive": false, "first": false, "tree": "[]"}, {"code": "H05K2201/09672", "inventive": false, "first": false, "tree": "[]"}, {"code": "H05K1/028", "inventive": true, "first": true, "tree": "[]"}, {"code": "G06F2203/04102", "inventive": false, "first": false, "tree": "[]"}, {"code": "H05K2201/09663", "inventive": false, "first": false, "tree": "[]"}, {"code": "H05K2201/10106", "inventive": false, "first": false, "tree": "[]"}, {"code": "H05K2201/10106", "inventive": false, "first": false, "tree": "[]"}, {"code": "H05K2201/09663", "inventive": false, "first": false, "tree": "[]"}, {"code": "H05K2201/09263", "inventive": false, "first": false, "tree": "[]"}, {"code": "H05K1/0393", "inventive": true, "first": false, "tree": "[]"}, {"code": "H05K2201/0979", "inventive": false, "first": false, "tree": "[]"}, {"code": "H05K2201/09672", "inventive": false, "first": false, "tree": "[]"}, {"code": "H05K1/0296", "inventive": true, "first": false, "tree": "[]"}, {"code": "H05K2201/09263", "inventive": false, "first": false, "tree": "[]"}, {"code": "H05K2201/09263", "inventive": false, "first": false, "tree": "[]"}, {"code": "G06F3/0412", "inventive": true, "first": true, "tree": "[]"}, {"code": "H05K2201/0979", "inventive": false, "first": false, "tree": "[]"}, {"code": "H05K1/0281", "inventive": false, "first": false, "tree": "[]"}, {"code": "H05K2201/0979", "inventive": false, "first": false, "tree": "[]"}, {"code": "H05K1/0393", "inventive": true, "first": false, "tree": "[]"}, {"code": "H05K2201/09672", "inventive": false, "first": false, "tree": "[]"}, {"code": "G06F1/169", "inventive": true, "first": false, "tree": "[]"}, {"code": "H05K2201/09263", "inventive": false, "first": false, "tree": "[]"}, {"code": "H05K2201/10106", "inventive": false, "first": false, "tree": "[]"}, {"code": "H05K2201/0979", "inventive": false, "first": false, "tree": "[]"}, {"code": "G06F2203/04102", "inventive": false, "first": false, "tree": "[]"}, {"code": "H05K1/0296", "inventive": true, "first": false, "tree": "[]"}, {"code": "H05K1/028", "inventive": true, "first": false, "tree": "[]"}, {"code": "H05K2201/09663", "inventive": false, "first": false, "tree": "[]"}, {"code": "G06F3/0412", "inventive": true, "first": true, "tree": "[]"}, {"code": "H05K1/0281", "inventive": false, "first": false, "tree": "[]"}, {"code": "H05K2201/09672", "inventive": false, "first": false, "tree": "[]"}, {"code": "H05K1/028", "inventive": true, "first": true, "tree": "[]"}, {"code": "H05K1/0296", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F3/0412", "inventive": true, "first": false, "tree": "[]"}, {"code": "H05K1/028", "inventive": true, "first": true, "tree": "[]"}, {"code": "H05K1/0393", "inventive": true, "first": false, "tree": "[]"}, {"code": "H05K2201/09263", "inventive": false, "first": false, "tree": "[]"}, {"code": "G06F1/169", "inventive": true, "first": false, "tree": "[]"}, {"code": "H05K2201/0979", "inventive": false, "first": false, "tree": "[]"}, {"code": "G06F2203/04102", "inventive": false, "first": false, "tree": "[]"}, {"code": "H05K2201/10106", "inventive": false, "first": false, "tree": "[]"}, {"code": "H05K2201/09663", "inventive": false, "first": false, "tree": "[]"}]
Family ID: 54261119