PATENT DOCUMENT

Publication Number: US-10470305-B2
Application Number: US-201916280920-A
Country: US
Kind Code: B2

Title: Conductive strands for fabric-based items

Abstract:
Strands of material may be intertwined using weaving techniques, knitting techniques, non-woven or entanglement techniques, or braiding techniques. Fabric that is formed from the strands of material may be used in forming a fabric-based item. The fabric based item may include electrical components. The strands may include conductive strands that form signal paths. The signal paths can carry electrical signals associated with operation of the electrical components. Each strand may have an elongated core and a coating. Strands may also include intermediate layers between the cores and coatings. The cores, intermediate layers, and coatings may be formed from polymer without conductive filler, polymer with conductive filler, and/or metal. A polymer core may be provided with recesses to help retain subsequently deposited layers such as a metal coating layer. The recesses may be grooves that extend along the longitudinal axis of the core.

Claims:
What is claimed is: 
     
       1. A conductive strand for carrying signals within a fabric, comprising:
 an elongated conductive core; 
 an intermediate layer that covers the elongated conductive core, wherein the intermediate layer has recesses that pass entirely through the intermediate layer; and 
 a conductive coating on the intermediate layer that extends through the recesses in the intermediate layer to directly contact the elongated conductive core. 
 
     
     
       2. The conductive strand defined in  claim 1 , wherein the intermediate layer comprises a polymer layer with conductive filler. 
     
     
       3. The conductive strand defined in  claim 2 , wherein the conductive filler shorts the conductive coating to the elongated conductive core. 
     
     
       4. A fabric-based item, comprising:
 a fabric formed from intertwined strands, wherein the intertwined strands include a conductive strand; and 
 electrical components that are interconnected using a signal path formed from the conductive strand, wherein the conductive strand comprises:
 a core; 
 a conductive coating layer; and 
 an intermediate layer between the core and the conductive coating layer, wherein the intermediate layer has a plurality of recesses, wherein the conductive coating has first portions in the recesses and second portions that are interposed between the recesses, wherein the first portions of the conductive coating have a first thickness, and wherein the second portions of the conductive coating have a second thickness that is less than the first thickness. 
 
 
     
     
       5. The fabric-based item defined in  claim 4 , wherein the core is a conductive core. 
     
     
       6. The fabric-based item defined in  claim 4 , wherein the core is a polymer core that includes a conductive filler. 
     
     
       7. The fabric-based item defined in  claim 6 , wherein the conductive filler comprises metal particles. 
     
     
       8. The fabric-based item defined in  claim 4 , wherein the plurality of recesses in the intermediate layer comprise longitudinal grooves. 
     
     
       9. A multi-filament strand for carrying signals within a fabric, the multi-filament strand comprising:
 a core strand; and 
 a plurality of conductive strands wrapped around the core strand, wherein each conductive strand of the plurality of conductive strands comprises:
 a polymer core; and 
 a conductive coating layer. 
 
 
     
     
       10. The multi-filament strand defined in  claim 9 , wherein the core strand is a polymer core strand. 
     
     
       11. The multi-filament strand defined in  claim 9 , further comprising:
 a conductive coating formed over the plurality of conductive strands.

Description:
This application is a continuation of patent application Ser. No. 15/942,159, filed Mar. 30, 2018, which is a continuation of patent application Ser. No. 15/146,601, filed May 4, 2016, which claims the benefit of provisional patent application No. 62/163,802, filed May 19, 2015, all of which are hereby incorporated by reference herein in their entireties. 
    
    
     BACKGROUND 
     This relates generally to strands of material and, more particularly, to conductive strands for forming conductive pathways in fabric-based items. 
     It may be desirable to form electrical devices, enclosures, and other items from fabric. The fabric may contain insulating and conductive strands. In some situations, it may be desirable to form signal paths or other conductive structures from the conductive strands. 
     Challenges may arise when forming conductive structures from conductive strands in a fabric. Fabric is often bent back and forth during use. Solid wires may experience large amounts of stress when bent. Polymer strands covered with metal coatings can be used in place of solid wire strands. If care is not taken, however, fabric bending motions may cause a metal coating to be abraded from a polymer strand or may cause a metal coating to fail due to the difference between the modulus of elasticity of the metal coating and the modulus of elasticity of the underlying polymer strand material. Metal coating failures can lead to unexpected open circuits and other reliability issues. Defects such as unexpected open circuits may prevent an item from functioning properly. 
     It would therefore be desirable to be able to provide improved techniques for forming conductive strands for use in fabric-based items. 
     SUMMARY 
     Strands of material may be intertwined using weaving techniques, knitting techniques, non-woven or entanglement techniques, or braiding techniques. Fabric that is formed from the strands of material may be used in forming a fabric-based item. The fabric based item may include electrical components. The strands may include conductive strands that form signal paths. The signal paths can carry electrical signals associated with operation of the electrical components. 
     Conductive strands may be formed from elongated cores and associated coatings. Strands may also include intermediate layers between the cores and coatings and may include additional layers. The cores, intermediate layers, and coatings may be formed from materials such as polymer without conductive filler, polymer with conductive filler, and metal. 
     A polymer core may be provided with recesses to help retain subsequently deposited layers such as a metal coating layer. The recesses may be grooves that extend along the longitudinal axis of the core. When a coating is formed on the core, the metal of the coating may extend into the recesses. The recesses may therefore enhance the ability of a core to retain a metal coating. If desired, the bottoms of the recesses may be enlarged to form interlocking features that retain the metal coating. 
     Extrusion techniques or other fabrication techniques may be used to form elongated polymer cores with longitudinal grooves. Metal coatings may be deposited using electrochemical deposition techniques (e.g., electroless deposition). If desired, additional fabrication techniques may be used in forming layers of material in the conductive strands. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic diagram of an illustrative item that may include strands of material in accordance with an embodiment. 
         FIG. 2  is a diagram of a portion of a fabric with conductive strands in accordance with an embodiment. 
         FIG. 3  is a cross-sectional side view of an illustrative conductive strand in accordance with an embodiment. 
         FIG. 4  is a diagram of illustrative extrusion and coating equipment of the type that may be used in forming conductive strands in accordance with an embodiment. 
         FIG. 5  is a diagram showing equipment and operations involved in forming fabric-based items with conductive strands in accordance with an embodiment. 
         FIG. 6  is a cross-sectional side view of an illustrative conductive strand with a series of deep longitudinal grooves that are spaced evenly about the circumference of the strand and that are covered with a coating in accordance with an embodiment. 
         FIG. 7  is a cross-sectional side view of an illustrative conductive strand having an elongated core with grooves that are widened near the center of the core to form interlocking features to retain a coating in accordance with an embodiment. 
         FIG. 8  is a cross-sectional side view of an illustrative conductive strand having shallow longitudinal grooves that are spaced evenly about the circumference of the strand and that are covered with a coating in accordance with an embodiment. 
         FIG. 9  is a cross-sectional side view of an illustrative conductive strand having a pair of opposing grooves with profiles that form interlocking features to retain a coating in accordance with an embodiment. 
         FIG. 10  is a cross-sectional side view of an illustrative conductive strand having a conductive core, a polymer intermediate layer with conductive filler, and an outer conductive layer that is electrically shorted to the conductive core through the intermediate layer in accordance with an embodiment. 
         FIG. 11  is a cross-sectional side view of an illustrative conductive strand having a conductive core, a polymer intermediate layer with grooves that penetrate to the core, and a conductive coating that extends into the grooves to contact the conductive core in accordance with an embodiment. 
         FIG. 12  is a cross-sectional side view of an illustrative conductive strand with a grooved core, a grooved intermediate layer, and a coating layer in accordance with an embodiment. 
         FIG. 13  is a cross-sectional side view of a bundle of strands covered with a coating in accordance with an embodiment. 
         FIG. 14  is a cross-sectional side view of an illustrative conductive strand arrangement in which strands are wrapped around a core in accordance with an embodiment. 
         FIG. 15  is a cross-sectional side view of the wrapped core of  FIG. 14  following application of a coating layer in accordance with an embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     Conductive strands of material and insulating strands of material may be used in forming fabric with conductive paths. The conductive paths may be used in forming signal paths (e.g., signal busses, power lines, etc.), may be used in forming part of a capacitive touch sensor electrode, a resistive touch sensor electrode, or other input-output device, or may be used in forming other patterned conductive structures. The conductive structures may be used in carrying power signals, digital signals, analog signals, sensor signals, control signals, data, input signals, output signals, or other suitable electrical signals. 
     The fabric containing these conductive structures may be used in forming a fabric-based item such as illustrative fabric-based item  10  of  FIG. 1 . Item  10  may be an electronic device or an accessory for an electronic 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 fabric-based item  10  is mounted in a kiosk, in an automobile, airplane, or other vehicle, other electronic equipment, or equipment that implements the functionality of two or more of these devices. If desired, item  10  may be a removable external case for electronic equipment, may be a strap, may be a wrist band or head band, may be a removable cover for a device, may be a case or bag that has straps or that has other structures to receive and carry electronic equipment and other items, may be a necklace or arm band, may be a wallet, sleeve, pocket, or other structure into which electronic equipment or other items may be inserted, may be part of a chair, sofa, or other seating (e.g., cushions or other seating structures), may be part of an item of clothing or other wearable item (e.g., a hat, belt, wrist band, headband, etc.), or may be any other suitable fabric-based item. 
     Strands in item  10  may form all or part of a housing wall for an electronic device, may form internal structures in an electronic device, or may form other strand-based structures. Item  10  may be soft (e.g., item  10  may have a fabric surface that yields to a light touch), may have a rigid feel (e.g., the surface of item  10  may be formed from a stiff fabric), may be coarse, may be smooth, may have ribs or other patterned textures, and/or may be formed as part of a device that has portions formed from non-fabric structures of plastic, metal, glass, crystalline materials, ceramics, or other materials. 
     Item  10  may include intertwined strands  12 . The strands may be intertwined using strand intertwining equipment such as weaving equipment, knitting equipment, or braiding equipment. Intertwined strands  12  may, for example, form woven fabric, knitted fabric, braided cords, or other items with intertwined strands. Configurations in which item  10  is based on fabric formed from strands  12  are sometimes described herein as an example. This is, however, merely illustrative. Strands  12  may be incorporated into any suitable items. 
     Strands  12  may be single-filament strands (sometimes referred to as fibers) or may be threads, yarns, ply yarns, cords, ropes, or other strands that have been formed by intertwining multiple filaments of material together. Strands may be formed from polymer, metal, glass, graphite, ceramic, natural strands such as cotton or bamboo, or other organic and/or inorganic materials and combinations of these materials. Conductive coatings such as metal coatings may be formed on non-conductive strands (e.g., plastic cores) to make them conductive. Reflective coatings such as metal coatings may be applied to strands to make them reflective. Strands  12  may also be formed from single-filament metal wire (e.g., bare metal wire), multifilament wire, or combinations of different materials. Strands may be insulating or conductive. Conductive strands may have exposed conductive surfaces or may be insulated. 
     Strands  12  may be conductive along their entire length or may have conductive segments. Strands  12  may have metal portions or other conductive portions that are selectively exposed by locally removing insulation (e.g., to form connections with other conductive strand portions). Strands  12  may also be formed by selectively adding a conductive layer to a portion of a non-conductive strand.). Threads and other multifilament yarns that have been formed from intertwined filaments may contain mixtures of conductive strands and insulating strands (e.g., metal strands or metal coated strands with or without exterior insulating layers may be used in combination with solid plastic strands or natural strands that are insulating). 
     Conductive strands (complete conductive strands and/or conductive strand segments) that cross other conductive strands may be shorted to each other to form a portion of a signal path. Electrical connections of this type may be formed by virtue contacting a first conductive strand with a second conductive strand. 
     Item  10  may include additional mechanical structures  14  such as polymer binder to hold strands  12  together, support structures such as frame members, housing structures (e.g., an electronic device housing), and other mechanical structures. 
     To enhance mechanical robustness and electrical conductivity at strand-to-strand connections, additional structures and materials (e.g., solder, crimped metal connections, welds, conductive adhesive, non-conductive adhesive, fasteners, etc.) may be used to help form strand-to-strand connections at strand intersections where connections are desired. Insulating material can be interposed between intersecting conductive strands at locations in which it is not desired to form a strand-to-strand connection. The insulating material may be plastic or other dielectric, may include an insulating strand or a conductive strand with an insulating coating, and may provide continuous or discontinuous coverage. 
     Circuitry  16  may be included in item  10 . Circuitry  16  may include components that are coupled to strands  12 , components that are housed within an enclosure formed by strands  12 , components that are attached to strands  12  using welds, solder joints, adhesive bonds (e.g., conductive adhesive bonds), crimped connections, or other electrical and/or mechanical bonds. Circuitry  16  may include metal structures for carrying current, integrated circuits, discrete electrical components such as resistors, capacitors, and inductors, switches, connectors, light-emitting components such as light-emitting diodes, audio components such as microphones and speakers, vibrators, solenoids, piezoelectric devices, and other electromechanical devices, connectors, microelectromechanical systems (MEMs) devices, pressure sensors, light detectors, proximity sensors, force sensors, moisture sensors, temperature sensors, accelerometers, gyroscopes, compasses, magnetic sensors, touch sensors, and other sensors, components that form displays, touch sensors arrays (e.g., arrays of capacitive touch sensor electrodes to form a touch sensor that detects touch events in two dimensions), and other input-output devices. Circuitry  16  may also include control circuitry such as non-volatile and volatile memory, microprocessors, application-specific integrated circuits, system-on-chip devices, baseband processors, wired and wireless communications circuitry, and other integrated circuits. 
     Item  10  may interact with electronic equipment or other additional items  18 . Items  18  may be attached to item  10  or item  10  and item  18  may be separate items that are configured to operate with each other (e.g., when one item is a case and the other is a device that fits within the case, etc.). Circuitry  16  may include antennas and other structures for supporting wireless communications with item  18 . Item  18  may also interact with item  10  using a wired communications link or other connection that allows information to be exchanged. 
     In some situations, item  18  may be an electronic device such as a cellular telephone, computer, or other portable electronic device and item  10  may form a case or other structure that receives the electronic device in a pocket, an interior cavity, or other portion of item  10 . In other situations, item  18  may be a wrist-watch device or other electronic device and item  10  may be a strap or other fabric-based item that is attached to item  18 . In still other situations, item  10  may be an electronic device, strands  12  may be used in forming the electronic device, and additional items  18  may include accessories or other devices that interact with item  10 . Signal paths formed from conductive strands may be used to route signals in item  10  and/or item(s)  18 . 
     The strands that make up item  10  may be intertwined to form a fabric such as illustrative fabric  20  of  FIG. 2 . Fabric  20  may include strands  12 . Strands  12  may be formed from conductive and/or insulating materials. As an example, fabric may be formed from insulating strands interspersed with conductive strands  22 . In the illustrative configuration of  FIG. 2 , a first conductive strand  22  extends vertically and electrically connects node A and junction  24  and a second conductive strand  22  extends horizontally (i.e., perpendicular to the first conductive strand) and electrically connects node B and junction  24 . At the intersection of the first and second conductive strands at junction  24 , the first and second strands may be electrically connected using mechanical contact, solder, welds, conductive adhesive, a crimped metal connection or other metal connector, or other electrical connection structure. Using this type of technique, desired signal paths such as illustrative signal path  26  between nodes A and B may be formed within fabric  20  (e.g., to form signal busses, to form parts of sensors, to form other conductive structures, etc.). 
     Conductive strand  22  may be formed from one or more layered materials. For example, conductive strand  22  may have a core (e.g., an elongated member such as a monofilament) and an outer coating or conductive strand  22  may have a core, an intermediate layer, and an outer coating. The different portions of the conductive strand may be formed from different materials or, if desired, two or more of the portions of the conductive strand may be formed from the same material. As an example, a conductive strand may have a core and a coating that are formed from a common metal and that are separated by an intermediate layer formed from a different material. 
     In some configurations, conductive strand  22  may contain polymer. For example, conductive strand  22  may contain a polymer core to provide strand  22  with strength and flexibility. Examples of polymers that may be used in forming core  28  or other layers in strand  22  include polyamide (nylon—e.g., nylon6, nylon6,6, nylon 11), aromatic polyamide (i.e., para-aramids Kevlar® or other aramids), polyimide, polyester, polyolefin, acrylic, polyethylene, extruded cellulosic polymers such as rayon and Tencel® and polyurethane. Other polymers or mixtures of these polymers may be used, if desired. Core components may also be formed from non-polymer strands such as strands of cotton, wool, and other staple length yarns. 
     The polymer materials of strand  22  may be formed from conductive organic material, from insulating polymeric materials, from polymer that includes conductive filler such as particles of metal, particles of carbon nanotube material, graphene particles, fibrous carbon material, or other conductive particles. Conductive filler may be incorporated into the polymer in a concentration that renders a portion of strand  22  conductive or may be incorporated into the polymer in a lower concentration (e.g., to promote adhesion or otherwise enhance compatibility with other portions of strand  22  without necessarily increasing the conductivity of the polymer to a level that allows the material to serve as a conductive signal path in fabric  20 ). 
     In some situations, monofilaments may be formed of metal or polymer (i.e., polymer with conductive filler or without conductive filter). These monofilaments may be intertwined to form strands  22  or portions of strands  22 . In general, strands  22  may have one or more materials, two or more materials, three or more materials, four or more materials, or five or more materials. The structures of strands  22  may incorporate conductive materials such as metal, insulating materials such as polymer, conductive organic materials such as conductive polymer, polymer filled with metal particles and other conductive filler, other materials, and/or combinations of these materials. 
     To enhance the robustness of conductive strands, the core of strands  22  and/or other layers in strands  22  may be provided with textured surfaces. For example, strands  22  may have polymer cores with recesses such as longitudinal grooves that help adhere metal coatings onto strands  22 . A configuration of this type is shown in the cross-sectional side view of illustrative strand  22  of  FIG. 3 . As shown in  FIG. 3 , strand  22  may have a core such as core  28  and a coating such as coating  30 . Core  28  may be formed from polymer. Conductive filler such as conductive particles  34  may be incorporated into polymer core  28  or conductive particles  34  may be omitted. The incorporation of filler particles  34  into core  28  may enhance the strength of core  28 , may promote adhesion with adjacent layers, and may, at higher concentrations, render core  28  conductive. 
     Core  28  may be coated with a coating layer such as coating  30 . Coating  30  may be a conductive material such as metal. Examples of metals that may be used in forming coating  30  include gold, silver, copper, aluminum, nickel, palladium, molybdenum, platinum, titanium, and tungsten. Other metals may also be used in forming coating  30 . Coating  30  may be formed from an elemental metal or the metal that forms coating  30  may be part of a metal alloy. 
     When fabric  20  is bent during use of item  10 , stresses can arise in strands  22  and the surface of strands  22  may rub against other strands. To help retain coating  30  on strand  22 , core  28  may be provided with recesses such as recesses  32 . Strand  22  may have a circular cross-sectional outline (as shown in  FIG. 3 ) or other cross-sectional outline and may have an elongated shape with a longitudinal axis such as axis  36  that extends into and out of the page of  FIG. 3 . The diameter of strand  22  may be 1-100 microns, more than 20 microns, less than 50 microns, less than 500 microns, or other suitable size. Recesses  32  may be pits in the outer surface of core  28  or may be elongated recesses such as grooves that run along the surface of core  28  parallel to the longitudinal axis (or that spiral around core  28  while running along the length of core  28 ). Other textured surfaces may be used, if desired. The use of groove-shaped recesses such as recesses  32  is merely illustrative. 
     Due to the presence of recesses  32 , coating  30  may have different thicknesses in different areas. In portions of coating  30  that do not overlap recesses  32 , coating  30  may overlap a protruding portion of core  28  and may have a relatively small thickness such as thickness T 2 . In portions of coating  30  that overlap recesses  32 , coating  30  may have a larger thickness such as thickness T 1  (T 1 &gt;T 2 ). The values of T 1  and T 2  may be less than 50 microns, less than 20 microns, 1-100 microns, more than 1 micron, or other suitable thicknesses. The depth of recesses  32  may be 1-100 microns, less than 20 microns, less than 4 microns, more than 5 microns, or other suitable depth. Recesses  32  enhance the surface area of core  28  and therefore help adhere coating  30  to core  28 . The presence of recesses  32  may also help shield some of layer  30  from direct contact from external objects (e.g., when strands are being rubbed against each other). As a result, strand  22  may retain conductive coating  30  even in environments in which strand  22  is exposed to wear. 
     Moreover, it has been observed that conductive coatings on fibers with cylindrical cross sections can fracture when exposed to excessive bending stresses. These bending stresses increase for locations at increasing distances from the neutral bending axis (distance from the center-of-mass of the fiber cross-section). By placing at least some of the conductive material of coating  30  in concave areas on the cross-section such as recesses  32 , bending stresses in the conductive material can be significantly reduced, thereby reducing or eliminating bend-induced fractures to coating  30 . 
     If desired, strands  22  may be based on polymer yarns containing multiple filaments. The yarn denier (gram weight of 9000 meters of yarn) for yarn strands may be between 15 and 250 denier or other suitable denier. Yarn elongation may be less than 20% (or other suitable value) during use to minimize failure of metal coating  30  (e.g., plated metal) due to strain elongation of the polymer filaments. Yarn tenacity may be between 6 and 9 denier per filament. To help prevent broken and loose filaments from breaking off of the yarn, the yarn may be provided with between 30-100 twists per meter or other suitable amount of twisting. 
       FIG. 4  is a diagram showing illustrative equipment that may be used in forming strand  22 . As shown in  FIG. 4 , core  28  of strand  22  may be extruded from polymer extruding tool  38  in direction  50 . Tool  38  may have one or more hoppers such as hoppers  42  that are filled with plastic pellets or other sources of polymer. Tool  38  may heat the plastic pellets until the polymer for core  28  has been melted. The molten polymer (e.g., molten thermoplastic) for core  28  may then be extruded through extrusion head  40 . If desired, grooves or other recesses such as recesses  32  may be formed by simultaneously extruding first and second plastic portions through a shared opening in head  40 . With this type of approach, the first plastic portion may have the shape of core  28  and the second plastic portion may fill recesses  32 . The second portion (which may, if desired, be formed from materials other than plastic) may be removed in chemical bath  44  (e.g., a liquid solvent bath or other chemical treatment) after extrusion to expose core  28 . 
     Pulley system  46  may, if desired, be used to stretch core  28  and thereby reduce the diameter of core  28 . Coating tool  48  may be used to apply coating  30  to core  28  and thereby form strand  22 . Tool  48  may, as an example, apply a metal coating to core  28  using electrochemical deposition (e.g., electroless plating or electroplating using an applied current). Coating  30  may also be deposited by physical vapor deposition, chemical vapor deposition, dipping and curing (e.g., when coating core  28  with a conductive liquid layer coating layer such as a conductive polymer or a polymer with a conductive filler), application from a brush, needle, liquid-infused pad, or other dispenser, or other coating technique. 
       FIG. 5  is a diagram of illustrative operations and equipment involved in forming strands such as strand  22 . Initially, extrusion tool  38  may extrude core  28  with removable material  52  filling recesses  32 . Removable material  52  may be a polymer or other material that can be removed by chemical treatment in chemical treatment equipment  44  to produce core  28  with unfilled recesses  32 . Coating tool  48  may then be used to form coating  30  on the exterior of core  28 . Coating  30  may, for example, be a metal coating that is deposited on core  28  using electroless deposition. Core  28  may include metal filler particles or other conductive filler  34  to promote metal deposition and adhesion. After strands  22  have been formed in this way, strand intertwining equipment (e.g., weaving equipment, knitting equipment, or braiding equipment) may be used to form an item with intertwined strands  22  such as fabric  20 . Item  10  may be assembled using fabric  20  and other component. 
     If desired, recesses  32  may be provided with relatively deep groove shapes to help enhance the ability of recesses  32  to retain coating  30 . This type of arrangement is shown in  FIG. 6 . In the example of  FIG. 6 , depth D of each recess  32  is greater than width W. Width W may be, for example, the full-width-half-maximum width of recess  32 . In general, D may be 0.1-10 times W, 0.1-1 times W, 1-10 times W, 2-4 times W, etc. The example of  FIG. 6  in which D is greater than W is merely an example. 
     In the illustrative configuration of  FIG. 7 , each recess  32  has an interlocking portion with a locally expanded width W 1 . Because width W 1  at the bottom of recess  32  of  FIG. 7  is greater than width W 2  in the middle of recess  32 , metal or other coating  30  that has been deposited within recess  32  will be secured into place. Coating retention features such as interlocking recess shapes of the type shown in  FIG. 7  in which recess  32  widens near the center of strand  22  may be used to help retain coating  30  when strand  22  is subjected to wear in fabric  20 . 
     As shown in  FIG. 8 , recesses  32  may be relatively shallow (e.g., D may be 0.1-1 times W). Shallow grooves or other shallow recesses  32  may help enhance the exposed surface area of core  28  and thereby enhance adhesion between coating  30  and core  28 . Recesses  32  may be spread evenly about the circumference of strand  30  as shown in  FIG. 8  or may be distributed in other patterns. 
     The illustrative arrangement of  FIG. 9  shows how each recess  32  may be provided with a portion that has straight sidewalls such as portion  32 - 1  and a flared interlocking portion such as portion  32 - 2  that has selectively widened sidewalls to lock coating  30  in place. There are a pair of recesses  32  on opposing sides of strand  22  in the configuration of  FIG. 9  which may help balance the compressive and tensile strains that are imparted to coating  30  in recesses  32  when strand  22  is bent. More than two recesses of the type shown in  FIG. 9  or a single recess may be used if desired. 
     In some arrangements, it may be desirable to form conductive strands  22  from three or more layers. In the example of  FIG. 10 , core  28  is covered with recessed intermediate layer  30 - 1  and outer coating  30 - 2 . Core  28  may be a conductive material such as metal. Intermediate layer  30 - 1  may be a polymer that has a conductive filler such as illustrative filler particles  34 . Particles  34  may be provided with a sufficient density to form conductive paths between metal core  28  and outer coating layer  30 - 2 . 
     Outer coating layer  30 - 2  may be a metal coating or other conductive layer. Because coating layer  30 - 2  is shorted to metal core  28  through layer  30 - 1 , the conductivity of strand  22  of  FIG. 10  may be minimized. If desired, core  28  may be formed from a first polymer and intermediate layer  30 - 1  may be formed from a second polymer (each of which may optionally include conductive filler  34 ). The use of a conductive metal core, conductive intermediate polymer layer, and conductive metal outer layer is merely illustrative. 
     In the example of  FIG. 11 , outer coating layer  30 - 2  is able to penetrate to core  28  using recesses  32  (openings) that pass entirely through intermediate layer  30 - 1 . Outer layer  30 - 2  may be a metal layer and core  28  may be formed from metal. Intermediate layer  30 - 1  may be a polymer layer and may or may not include conductive filler  34 . With this type of configuration, it is not necessary for conductive filler  34  to be incorporated into intermediate layer  30 - 1  in order for outer layer  30 - 2  to be electrically connected to metal core  28 , because electrical connections are formed between layer  30 - 2  and core  28  through the openings in intermediate layer  30 - 1 . 
       FIG. 12  shows how conductive strand  22  may have core and intermediate layers with recesses  32  (e.g., deep recesses, shallow recesses of the type shown in  FIG. 12 , longitudinal recesses such as grooves, recesses with other shapes, recesses with a combination of different shapes and sizes, etc.). If desired, recesses  32  may be omitted from core  28  and/or intermediate layer  30 - 1 . Core  28 , intermediate layer  30 - 1 , and outer coating layer  30 - 2  may be formed from polymer without conductive filler, metal, polymer filled with conductive filler, and/or other suitable materials. 
     With one suitable arrangement, core  28  of  FIG. 12  is formed from a polymer to provide strand  22  with strength and flexibility and intermediate layer  30 - 1  is a polymer layer that includes conductive filler  34  to enhance the conductivity of strand  22  and to enhance adhesion to outer layer  30 - 2 . Outer layer  30 - 2  may be metal coating to enhance the conductivity of strand  22  and to facilitate electrical connections with other conductive fibers, electrical components, etc. If desired, outer layer  30 - 2  may be formed from a polymer that has a large amount of conductive filler  34  so that the conductivity of layer  30 - 2  is sufficiently large to serve as signal path in fabric  20  while exhibiting satisfactory flexibility and abrasion resistance. 
     Conductive strands and/or insulating strands may, if desired, by intertwined to form multi-filament strands. This type of arrangement is shown in  FIG. 13 . In the example of  FIG. 13 , multifilament strand  58  has been formed by intertwining multiple strands  54 . Strands  54  may be insulating strands, conductive strands, and/or strands such as the multilayer conductive strands described in connection with strands  22 . An optional coating such as coating  56  may cover strands  54 . Coating  56  may be polymer (with or without conductive filler  34 ), may be metal, or may be other suitable material. 
       FIG. 14  shows and arrangement in which core strand  62  has been wrapped with outer strands  60  to form multi-filament strand  64 . Strand  62  may be, for example, a polymer core (with or without conductive filler) or may be a core such as conductive core  22 . Wrapping strands  60  may be conductive strands  22  and/or may include other conducting and/or insulating strands. 
     As shown in  FIG. 15 , strands  62  and  60  may be covered with coating  66  to form multifilament strand  68 . Coating  66  may be an insulating polymer, a conducting polymer, a polymer layer that is conductive due to the incorporation of conductive filler  34 , and/or a metal layer. Strand  68  may be formed by wrapping strands  60  around strand  62  and depositing layer  66  by dipping, electrochemical deposition, or other deposition techniques or may be formed by wrapping a strip of material such as layer  66  that includes embedded strands  60  around core  62  (using longitudinal wrapping and/or spiral wrapping techniques). 
     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: 20190220
Publication Date: 20191105
Grant Date: 20191105
Priority Date: 20150519
Inventors: SUNSHINE, Daniel D.
PODHAJNY, DANIEL A.
CREWS, KATHRYN P.
MAYER, KIRK M.
MAASBERG, JOHN ARTHUR
Assignee: APPLE INC
CPC Classifications: [{"code": "H05K3/103", "inventive": false, "first": false, "tree": "[]"}, {"code": "H05K1/038", "inventive": true, "first": true, "tree": "[]"}, {"code": "C23C18/1633", "inventive": true, "first": false, "tree": "[]"}, {"code": "H05K1/038", "inventive": true, "first": true, "tree": "[]"}, {"code": "C23C18/1633", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01B13/0026", "inventive": true, "first": false, "tree": "[]"}, {"code": "C23C18/16", "inventive": true, "first": false, "tree": "[]"}, {"code": "H05K2201/0281", "inventive": false, "first": false, "tree": "[]"}, {"code": "C25D7/0607", "inventive": true, "first": false, "tree": "[]"}, {"code": "C25D7/0607", "inventive": true, "first": false, "tree": "[]"}, {"code": "H05K2201/0281", "inventive": false, "first": false, "tree": "[]"}, {"code": "H05K3/103", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01B13/0036", "inventive": true, "first": false, "tree": "[]"}, {"code": "C25D7/0607", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01B13/0036", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01B13/0026", "inventive": true, "first": false, "tree": "[]"}, {"code": "C23C18/16", "inventive": true, "first": false, "tree": "[]"}, {"code": "C23C18/1633", "inventive": true, "first": false, "tree": "[]"}, {"code": "H05K3/103", "inventive": false, "first": false, "tree": "[]"}, {"code": "H05K2201/0281", "inventive": false, "first": false, "tree": "[]"}, {"code": "H05K1/038", "inventive": true, "first": true, "tree": "[]"}]
Family ID: 62091405