PATENT DOCUMENT

Publication Number: US-9658648-B2
Application Number: US-201414224892-A
Country: US
Kind Code: B2

Title: Flexible printed circuit cables with service loops and overbending prevention

Abstract:
An electronic device may have a signal cable formed from a flexible printed circuit. A service loop may be formed in the signal cable. The bend may be formed in a desired location on the flexible printed circuit by contraction of an elastic member having ends attached to the flexible printed circuit. The elastic member may be conductive to carry signals and provide shielding. Structures may be attached to the flexible printed circuit to promote bending in a desired location and direction. A crease or other bending promotion feature may be applied to the flexible printed circuit at a desired bend location. Overbending prevention structures such as overmolded elastomeric structures may be applied to the flexible printed circuit at the bend. Integral strain relief features may prevent overbending of the flexible printed circuit upon exiting the elastomeric structures. Overmolded structures may serve as protective bumpers.

Claims:
What is claimed is: 
     
       1. A signal cable, comprising:
 a flexible printed circuit with metal traces for carrying signals, wherein the flexible printed circuit has a bend; 
 an elastic member coupled to the flexible printed circuit on opposing sides of the bend, wherein the bend is formed by contraction of the elastic member while the elastic member is coupled to the flexible printed circuit, wherein the bend comprises one of a plurality of bends in a service loop, and wherein the contraction of the elastic member forms the bends of the service loop; and 
 a spacer attached to the flexible printed circuit that prevents over bending of the flexible printed circuit at the bend. 
 
     
     
       2. The signal cable defined in  claim 1  wherein the elastic member is connected to the flexible printed circuit with fused plastic connections. 
     
     
       3. The signal cable defined in  claim 1  wherein the flexible printed circuit includes a bend promotion feature aligned with the bend. 
     
     
       4. The signal cable defined in  claim 3  wherein the bend promotion feature comprises a crease. 
     
     
       5. The signal cable defined in  claim 1  further comprising an overmolded elastomeric overbending prevention structure that is overmolded over the flexible printed circuit at the bend. 
     
     
       6. The signal cable defined in  claim 1  further comprising a structure attached to the flexible printed circuit that promotes formation of the bend in a desired direction. 
     
     
       7. An electronic device, comprising:
 a first electronic component; 
 a second electronic component; 
 a flexible printed circuit coupled between the first and second components, wherein the flexible printed circuit has a bend; and 
 an elastic member coupled to the flexible printed circuit on opposing sides of the bend, wherein the bend is formed by contraction of the elastic member, wherein the bend is part of a service loop in the flexible printed circuit, and wherein the electronic device further comprises an over bending prevention structure at the bend. 
 
     
     
       8. The electronic device defined in  claim 7  wherein the first component comprises a printed circuit board and wherein the second component is selected from the group consisting of: a touch sensor, a display, and an antenna. 
     
     
       9. Apparatus, comprising: a flexible printed circuit having a bend; and an overmolded elastomeric structure that is molded over the bend, wherein the bend forms part of a service loop and wherein the overmolded elastomeric structure covers the bend in the service loop. 
     
     
       10. The apparatus defined in  claim 9  wherein the overmolded elastomeric structure is configured to serve as an overbending prevention structure that prevents the flexible printed circuit from bending more than a desired amount in the bend. 
     
     
       11. The apparatus defined in  claim 10  wherein the overmolded elastomeric structure has strain relief features over portions of the flexible printed circuit. 
     
     
       12. The apparatus defined in  claim 11  wherein the strain relief features comprise tapered integral portions of the overmolded elastomer structure. 
     
     
       13. The apparatus defined in  claim 12  wherein the overmolded elastomeric structure comprises a recess that is configured to receive an edge of a printed circuit board. 
     
     
       14. The apparatus defined in  claim 9  further comprising an elastic member attached to the flexible printed circuit. 
     
     
       15. The apparatus defined in  claim 14  wherein the elastic member has opposing first and second ends that are attached to the flexible printed circuit at locations on opposing sides of the bend. 
     
     
       16. The apparatus defined in  claim 15  wherein the elastic member is conductive. 
     
     
       17. Apparatus, comprising:
 a flexible printed circuit having a bend; 
 a conductive elastomeric structure that holds the bend in the flexible printed circuit; and 
 an electronic component, wherein the conductive elastomeric structure covers and electromagnetically shields the electronic component. 
 
     
     
       18. The apparatus defined in  claim 17  wherein the electronic component is mounted on the flexible printed circuit. 
     
     
       19. The apparatus defined in  claim 17  further comprising:
 a printed circuit board; and 
 an electronic component mounted on the printed circuit board, wherein the conductive elastomeric structure covers and electromagnetically shields the electronic component. 
 
     
     
       20. A signal cable, comprising:
 a flexible printed circuit with metal traces for carrying signals, wherein the flexible printed circuit has a bend; and 
 a member coupled to the flexible printed circuit on opposing sides of the bend, wherein the bend is formed by contraction of the member while the member is coupled to the flexible printed circuit, and wherein the member comprises a shape memory alloy structure.

Description:
This application claims priority to U.S. provisional patent application No. 61/874,802 filed Sep. 6, 2013, which is hereby incorporated by reference herein in its entirety. 
    
    
     BACKGROUND 
     This relates generally to printed circuits and, more particularly, to structures used within electronic devices for guiding and protecting printed circuits such as flexible printed circuits. 
     Electronic devices such as computers, cellular telephones, and other electronic devices often include printed circuits. Electrical components such as integrated circuits and other electronic devices can be interconnected using signal traces on printed circuits. Rigid printed circuit boards are planar. Flexible printed circuits can be bent and can serve as signal cables for interconnecting components in different portions of a device. 
     Challenges arise when routing flexible printed circuits within an electronic device. If a flexible printed circuit is bent too abruptly, the signal traces on the flexible printed circuit can become damaged. Flexible printed circuits may also be susceptible to damage from contact with sharp structures such as the exposed edges of rigid printed circuit boards. Service loops may need to be included in flexible printed circuits to facilitate device assembly and disassembly. If care is not taken, electronic devices with flexible printed circuits may be unreliable and difficult to manufacture. 
     It would therefore be desirable to be able to provide improved structures for controlling the bending and routing of flexible printed circuits in electronic devices. 
     SUMMARY 
     An electronic device may be provided with electrical components that are interconnected using printed circuits. The printed circuits may include rigid printed circuit boards and flexible printed circuits. The flexible printed circuits may include signal lines such as metal traces that carry signals such as power and data signals that allow the flexible printed circuits to serve as signal cables. When assembled in an electronic device, a signal cable may be coupled between electrical components such as touch sensors, displays, printed circuits, audio components, antennas, and other components. A service loop may be formed in the signal cable to facilitate assembly and disassembly operations. 
     The formation of the service loop in a flexible printed circuit cable may be controlled using bend promotion features and an elastic member. Structures such as plastic members may be attached to the surfaces of the flexible printed circuit to serve as bending promotion features that encourage bending at a desired location. Creases or other bending promotion features may also be formed within the polymer substrate of the flexible printed circuit. The elastic member may have ends attached to opposing sides of a bend in the flexible printed circuit. The bend may be formed by contraction of the elastic member. The elastic member may be conductive to carry signals and provide shielding. 
     Overbending prevention structures such as overmolded elastomeric structures may be applied to the flexible printed circuit at a bend. The overbending prevention structures may prevent the flexible printed circuit from being bent more abruptly than desired. Integral strain relief features may prevent overbending of the flexible printed circuit upon exiting the elastomeric structures. Metal structures and other structures may be included in the overbending prevention structures. Overmolded elastomeric structures may have recesses that receive sharp objects such as the edges of printed circuit boards so that the overmolded elastomeric structures can serve as protective bumpers for the flexible printed circuits. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of an illustrative electronic device such as a handheld computing device or other electronic device that may be provided with flexible printed circuits and flexible printed circuit guiding structures in accordance with an embodiment. 
         FIG. 2  is a cross-sectional side view of an electronic device of the type that may be provided with a flexible printed circuits and flexible printed circuit guiding structures in accordance with an embodiment. 
         FIG. 3  is a cross-sectional side view of a flexible printed circuit in accordance with an embodiment. 
         FIG. 4  is a cross-sectional side view of a flexible printed circuit with elastic structures for helping to form a service loop in the flexible printed circuit in an electronic device in accordance with an embodiment. 
         FIG. 5  is a cross-sectional side view of a flexible signal cable formed from a flexible printed circuit of the type shown in  FIG. 4  in which the elastic structures have contracted to form a service loop in the flexible printed circuit in accordance with an embodiment. 
         FIG. 6  is a cross-sectional side view of a tool such as a heated die that can be used to create a crease or other local feature that serves as a bending promotion feature defining a preferred bending location on a flexible printed circuit in an electronic device in accordance with an embodiment. 
         FIG. 7A  is a cross-sectional side view of a flexible printed circuit that has been locally deformed to form a crease at a desired bending location using a tool of the type shown in  FIG. 6  in accordance with an embodiment. 
         FIG. 7B  is a cross-sectional side view of the flexible printed circuit of  FIG. 7A  following attachment of a resilient biasing structure in accordance with an embodiment. 
         FIG. 8  is a cross-sectional side view of a flexible printed circuit with a service loop that has been formed in the flexible printed circuit of  FIG. 7B  at the desired bending location in accordance with an embodiment. 
         FIG. 9  is a cross-sectional side view of a flexible printed circuit that has been provided with an elastic member for bending the flexible printed circuit and structures that help define a desired service loop shape for the flexible printed circuit when the flexible printed circuit is bent in accordance with an embodiment. 
         FIG. 10  is a cross-sectional side view of the flexible printed circuit of  FIG. 9  following bending into a desired service loop shape by contraction of an elastic member that has ends coupled to the flexible printed circuit on opposing sides of a bend in accordance with an embodiment. 
         FIG. 11  is a cross-sectional side view of a flexible printed circuit showing equipment that may be used in attaching an elastic member to two or more locations along the length of the flexible printed circuit in accordance with an embodiment. 
         FIG. 12  is a cross-sectional side view of a flexible printed circuit that has been pulled into a desired service loop shape by an elastic member formed on an inner bend surface of the flexible printed circuit in accordance with an embodiment. 
         FIG. 13  is a cross-sectional side view of a flexible printed circuit service loop with a plurality of bends that has been formed using an elastic member that has pulled the flexible printed circuit inwardly at two points along the length of the flexible printed circuit in accordance with an embodiment. 
         FIG. 14  is a cross-sectional side view of a flexible printed circuit with overbending protection spacer structures to prevent over-bending of the flexible printed circuit when forming a service loop in the flexible printed circuit in accordance with an embodiment. 
         FIG. 15  is a cross-sectional side view of the flexible printed circuit and spacer structures of  FIG. 14  when formed into the shape of a service loop in accordance with an embodiment. 
         FIG. 16  is a cross-sectional side view of molding equipment being used to mold overbending prevention structures over a flexible printed circuit in accordance with an embodiment. 
         FIG. 17  is a cross-sectional side view of the flexible printed circuit of  FIG. 16  following removal of the molding equipment in accordance with an embodiment. 
         FIG. 18  is a cross-sectional side view of a flexible printed circuit with an overmolded guide structure having integral strain relief structures to prevent damage to the flexible printed circuit where the flexible printed circuit exits the overmolded guide structure in accordance with an embodiment. 
         FIG. 19  is a cross-sectional side view of a flexible printed circuit with an overmolded guide structure that serves as a protective bumper for a rigid printed circuit board and that has been attached to a housing structure in an electronic device in accordance with an embodiment. 
         FIG. 20  is a cross-sectional side view of a flexible printed circuit with an overmolded guide structure that has been press fit onto a rigid printed circuit board to serve as a protective bumper for the rigid printed circuit board in an electronic device in accordance with an embodiment. 
         FIG. 21  is a cross-sectional side view of a flexible printed circuit that has been bent into the shape of a desired service loop with the assistance of overmolded elastomeric guide structures having integral strain relief features in accordance with an embodiment. 
         FIG. 22  is a cross-sectional side view of elastomeric guide structures that have been used to secure a flexible printed circuit to a housing in an electronic device in accordance with an embodiment. 
         FIG. 23  is a cross-sectional side view of illustrative flexible printed circuit guide structures formed using molded elastomeric material on sheet metal support structures in accordance with an embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     An electronic device may be provided with electronic components that are interconnected by signal lines formed from conductive traces on printed circuits. The printed circuits may include rigid printed circuit boards formed from materials such as fiberglass-filled epoxy and flexible printed circuits formed from sheets of polyimide or other flexible polymer layers. The conductive traces may be formed from patterned metal layers. Signal buses and other signal paths may be formed from patterned metal lines on the printed circuits. For example, flexible printed circuit cables may include sets of parallel signal lines that form buses for conveying signals between components. 
     Overbending prevention structures may be used to prevent flexible printed circuits from bending more than a desired amount. Bumper structures may be used to prevent rubbing between flexible printed circuits and sharp objects such as the edges of printed circuit boards. An elastic member may be used to help bend a flexible printed circuit at a desired location to form a service loop. 
     An illustrative electronic device of the type that may be provided with printed circuits is shown in  FIG. 1 . 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, 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, a router, a set-top box, 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. 
     Device  10  may have one or more displays such as display  14  mounted in housing structures such as housing  12 . Housing  12  of device  10 , which is sometimes referred to as a case, may be formed of materials such as plastic, glass, ceramics, carbon-fiber composites and other fiber-based composites, metal (e.g., machined aluminum, stainless steel, or other metals), other materials, or a combination of these materials. Device  10  may be formed using a unibody construction in which most or all of housing  12  is formed from a single structural element (e.g., a piece of machined metal or a piece of molded plastic) or may be formed from multiple housing structures (e.g., outer housing structures that have been mounted to internal frame elements or other internal housing structures). 
     Display  14  may be a touch sensitive display that includes a touch sensor or may be insensitive to touch. Touch sensors for display  14  may be formed from an array of capacitive touch sensor electrodes, a resistive touch array, touch sensor structures based on acoustic touch, optical touch, or force-based touch technologies, or other suitable touch sensor components. 
     Display  14  may include display pixels that are formed from liquid crystal display (LCD) components, organic light-emitting diode components, electrophoretic display components, or other suitable display pixel structures. 
     A display cover layer may cover the surface of display  14  or a display layer such as a color filter layer (e.g., a layer formed from a clear substrate covered with patterned color filter elements) or other portion of a display may be used as the outermost (or nearly outermost) layer in display  14 . The outermost display layer may be formed from a transparent glass sheet, a clear plastic layer, or other transparent member. If desired, openings may be formed in the outermost layer of display  14  to accommodate components such as button  16  and speaker port  18  of  FIG. 1  (as examples). Buttons, connector ports, and other structures may also be accommodated using openings in housing  12 . 
       FIG. 2  is a cross-sectional side view of electronic device  10  of  FIG. 1  taken along line  20  and viewed in direction  22  of  FIG. 1 . As shown in  FIG. 2 , display  14  may be mounted in electronic device housing  12 . Display  14  may include display cover layer  24  (e.g. a sheet of clear glass or plastic) and display layers  26 . Display layers  26  may be associated with a liquid crystal display and may include structures such as a thin-film transistor layer, color filter layer, a layer of liquid crystal material, polarizer layers, and backlight structures. Other types of display may be used in forming display  14  if desired. 
     One or more printed circuits such as printed circuit  28  and printed circuit  32  may be used to mount and interconnect electronic components in device  10 . Printed circuit  28  may be, for example, a rigid printed circuit board. Components  30  may be mounted to printed circuit  28  using solder or conductive adhesive. Components  30  may include integrated circuits, discrete components such as resistors, capacitors, and inductors, switches, sensors, connectors, audio components, etc. Printed circuit  32  may be a flexible printed circuit having one or more bends such as bend  34 . In the example of  FIG. 2 , flexible printed circuit  32  is being used to couple components  30  on printed circuit  28  to display  14  (e.g., to convey signals from components  30  to display driver circuitry on a thin-film transistor layer in a liquid crystal display or other display structure). This is merely illustrative. The components that are being coupled together using flexible printed circuit  32  may include any combination of: a display, a sensor, a touch sensor, a button, an antenna, a fingerprint sensor, a proximity sensor, an ambient light sensor, a capacitive touch sensor, integrated circuits on a printed circuit (i.e., a printed circuit board), a data port, a motherboard, audio components such as a speaker and/or microphone, light-emitting diodes for a status indicator component, or other electronic components. 
     A cross-sectional side view of a portion of a flexible printed circuit is shown in  FIG. 3 . As shown in  FIG. 3 , flexible printed circuit  32  may include layers of patterned metal traces  36  separated by respective layers of dielectric  44 . Dielectric  44  may be polyimide or other flexible polymer material. The layers of patterned metal traces and layers of dielectric may be sandwiched together to form flexible printed circuit  32 . Metal interconnect structures such as vias  38  may be used to interconnect horizontally extending metal traces  36 . The material that is used to form the conductive traces in printed circuit  32  (e.g., the patterned metal signal lines in layers  36  and vias  38 ) may be copper, gold, aluminum, molybdenum, other metals and metal alloys, non-metallic conductive materials, or other suitable conductors. As shown in  FIG. 3 , components such as component  30  may be mounted to flexible printed circuit  32  using conductive material  40 . Conductive material  40  may be solder, conductive adhesive, or other conductive material. Conductive material  40  may be used to electrically and mechanically connect contacts  42  of component  30  to metal traces such as contact pads  36 P in the uppermost metal layer on flexible printed circuit  32 . Component  30  may be a connector (e.g., a board-to-board connector or other connector), an integrated circuit, a sensor, a display structure, an antenna, a touch sensor, etc. 
     In the example of  FIG. 2 , printed circuit  32  has been provided with a single bend (bend  34 ). If desired, printed circuit  32  may have multiple bends that form a service loop. A service loop in a flexible printed circuit creates slack in the flexible printed circuit that helps accommodate movement of components  30  during assembly and disassembly operations. As an example, inclusion of a service loop in a portion of a flexible printed circuit that extends between a logic board and display allows the display to be moved relative to the logic board when mounting the display within the housing of a device during device assembly operations. The service loop also allows the display to be move relative to the device housing for rework or repair. A service loop generally includes two or more bends. For example, a service loop may include two outwardly extending bends separated by one inwardly protruding bend. 
       FIG. 4  is a cross-sectional side view of an illustrative flexible printed circuit that has been provided with an elastic structure to help form the flexible printed circuit into a desired service loop shape. As shown in  FIG. 4 , elastic member  46  may be stretched outwards before attachment to flexible printed circuit  32 . In particular, ends  50  of elastic member  46  may be stretched outwards in directions  48 . Once elastic member  46  has been stretched, ends  50  of elastic member may be attached to flexible printed circuit  32  using connections  52 . Connections  52  may be formed by fusing elastic member  46  to flexible printed circuit  32  using heat (e.g., heat applied using a radio-frequency welder, heat applied using a hot bar, heat applied using a laser, etc.), by coupling elastic member  46  to flexible printed circuit  32  using adhesive, or using other coupling structures. If desired, ends  50  may be attached to flexible printed circuit  32  at the locations shown in  FIG. 4  by bending flexible printed circuit  32  to bring desired portions of flexible printed circuit  32  under ends  50  instead of stretching member  46  (or while stretching member  46 ). The configuration of  FIG. 4  in which member  46  is stretched without bending flexible printed circuit  32  during formation of connections  52  is merely illustrative. 
     Elastic member  46  may be formed from an elastomeric polymer, elastomeric polymer fibers, a strip of elastomeric material (e.g., a strip of elastomeric tape), conductive fibers interwoven with elastomeric fibers, elastomeric fibers coated with metal or other conductive materials, corrugated sheet metal springs or corrugated plastic springs, metal or plastic springs with other shapes, or other resilient structures that tend to return to an initial shorter length after being stretched outward to a longer length. In configurations in which flexible printed circuit  32  is provided with an elastic structures such as elastic member  46  formed from conductive materials, the elastic structure may serve as a grounding structure, a signal path for analog and/or digital signals, radio-frequency shielding, or other electromagnetic shielding or signal paths. 
     When flexible printed circuit  32  of  FIG. 4  is assembled into an electronic device, elastic member  46  can stretch, allowing full use of the slack provided by the service loop in flexible printed circuit  32 . When the components being assembled are in their final position, elastic member  46  can contract towards its original unstretched length. 
     When elastic member  46  contracts, a service loop is created with a predefined shape at a predefined location along the length of flexible printed circuit  32 .  FIG. 5  is a cross-sectional side view of a signal cable formed from flexible printed circuit  32  of  FIG. 4  following mounting of flexible printed circuit  32  within electronic device  10 . Elastic member  46  is resilient and therefore tends to contract once released from its stretched configuration. This causes ends  50  to be pulled inwardly towards each other in directions  54 , as shown in  FIG. 5 . Flexible printed circuit  32  is coupled to ends  50  of elastic member by connections  52  at ends  50 . As a result of the contraction of ends  50  in directions  54 , central portion  32 C of flexible printed circuit  32  is forced inwardly in direction  56 , forming inwardly protruding bend  34 - 3  between respective outwardly protruding bends  34 - 1  and  34 - 2 . Ends  50  are located on opposing sides of bend  34 - 3 . Because the direction in which bend  34 - 3  is formed is defined by the location of elastic member  46 , it is not necessary for a technician or machine to press inwardly on flexible printed circuit  32  to ensure correct service loop formation. Rather, the restoring force produced by stretched elastic member  46  as stretched elastic member  46  relaxes from its stretched configuration helps to move flexible printed circuit  32  into a satisfactory service loop shape such as the shape of the service loop of  FIG. 5 . 
     To help promote formation of flexible printed circuit bends at desired locations, flexible printed circuit  32  may be locally processed to form a crease (e.g., an indentation or otherwise locally weakened line across printed circuit  32 ) or other bending promotion feature at a particular position on flexible printed circuit. Local processing of flexible printed circuit  32  in this way may be accomplished using a laser, a heated die, a cutting tool, a hot bar, a lamp, or other equipment. As shown in  FIG. 6 , for example, flexible printed circuit  32  may be compressed between mating heated die. During localized processing, upper die  58  may be moved downwards towards flexible printed circuit  32  in direction  60  and lower die  62  may be moved upwards towards flexible printed circuit  32  in direction  64 . Die  58  may have a protrusion such as protrusion  66 . Die  62  may have a recess such as recess  68  that receives protrusion  66 . Following compression between upper die  58  and lower die  62 , flexible printed circuit  32  may have a crease or other locally weakened and/or processed feature such as illustrative bend promotion feature (crease)  70  of  FIG. 7A . 
       FIG. 7B  shows how flexible printed circuit  32  may appear following attachment of stretched elastic member  46  to flexible printed circuit  32 . Ends  50  of stretched elastic member  46  may be attached to flexible printed circuit  32  using connections  52 . Elastic member  46  may overlap bend promotion feature  70 . Because elastic member  46  covers localized bend promotion feature  70 , feature  70  may define a particular location along the length of flexible printed circuit  32  at which service loop bend  34 - 3  will be formed when elastic member  46  contracts and the service loop is formed in flexible printed circuit  32  as shown in  FIG. 8 . 
     If desired, structures may be attached to flexible printed circuit  32  to help ensure that flexible printed circuit  32  bends into a desired service loop shape. This type of arrangement is shown the cross-sectional side view of flexible printed circuit  32  of  FIG. 9 . As shown in  FIG. 9 , structures such as structures  78  and  80  may be attached to flexible printed circuit  32  using connections  76 . Structures  78  and  80  may have the shape of rods (e.g., cylindrical rods having circular cross sections as shown in the example of  FIG. 9 ), may have the shape of strips of material, or may have other suitable shapes. Materials such as plastic, metal, glass, and other materials may be used in forming structures  78  and  80 . Connections  76  may be formed by fusing structures  78  and/or  80  to flexible printed circuit  32  using heat, may be based on adhesive that attaches structures  78  and  80  to flexible printed circuit  32 , may be formed from interlocking features, or may be formed from other structures that attach members  78  and  80  to flexible printed circuit  32 . 
     The locations at which structures  78  and  80  are attached to flexible printed circuit  32  may be selected to encourage the formation of bends that protrude in desired directions. For example, structure  78  may be mounted to the upper (outer) surface of flexible printed circuit  32  and structures  80  may be mounted on opposite sides of structure  78  on the opposing lower (inner) surface of flexible printed circuit  32 . Ends  50  of stretched elastic member  46  may be attached to flexible printed circuit  32  with connections  52  so that member  46  overlaps structure  78  on the outer surface of flexible printed circuit  32 . Member  46  is under tension and will therefore press downwards in directions  72  on structure  78 . This, in turn, will press structure  78  downward in direction  74 . As shown in  FIG. 10 , this will cause bend  34 - 3  to bow inwardly on the side of flexible printed circuit  32  opposing structure  78 . The presence of structure  78  serves to promote bending of flexible printed circuit  32  in a known direction (i.e. inwardly) at a desired location to form bend  34 - 3  for a service loop (i.e., structures such as structure  78  may serve as bending promotion structures). 
     If desired, one or more layers of material that change shape when signals are applied may be used in compressing the service loop to assist in assembly. For example, a layer of material such as layer  47  of  FIG. 10  (e.g., an electroactive polymer structure or a shape memory alloy structure) may be formed on top of layer  46  or may be used instead of layer  46 . A signal source such as a current or voltage source (e.g. source  49  of  FIG. 10 ) may apply a signal (e.g., a current or voltage signal) to layer  47  during assembly to change the shape of layer  47  (e.g., to shrink layer  47  and thereby help press structure  78  downwards to form bend  34 - 3 . After the desired shape change has been activated by application of the signal to layer  47  (e.g., a signal that causes a member attached to flexible printed circuit  32  such as layer  47  to contract), flexible printed circuit  32  may remain nested in its desired position (e.g., the position of  FIG. 10 ) by structures  78  and  80  or by other supporting structures in device  10 . 
       FIG. 11  is a cross-sectional side view of an illustrative system for forming connections  52  between stretched elastic member  46  and flexible printed circuit  32 . In the example of  FIG. 11 , computer-controlled positioner  84  is being used to position tool head  82  at a desired location relative to elastic member  46  and flexible printed circuit  32 . Tool head  82  may be a radio-frequency welding head, a hot bar for applying heat, an ultrasonic welding head, a riveting head, an adhesive application head such as a needle dispenser or spray dispenser, or other equipment for forming connections  52 . During operation, elastic member  46  may be stretched outward and/or flexible printed circuit  32  may be bent while the equipment of  FIG. 11  is used to form connections  52  at locations along the length of flexible printed circuit  32  that are separated by a desired distance D. For example, heat may be applied to form fused plastic connections between the polymer of member  46  and the polymer of flexible printed circuit  32  or adhesive may be used in joining member  46  and flexible printed circuit  32 . Flexible printed circuit  32  can then be installed in a system. When installed, elastic member  46  will contract to help place flexible printed circuit  32  in a desired service loop configuration. 
     If desired, elastic member  46  may be attached to the inner bend surface of flexible printed circuit  32 , as shown in  FIG. 12 . Elastic member  46  may be attached to flexible printed circuit  32  using connections  52  at respective ends of elastic member  46 . Elastic member  46  may also be attached to flexible printed circuit  32  using a connection  52  at an intermediate location along the length of flexible printed circuit  32  such as location  50 M (i.e., a location that is midway between ends  50 ). When elastic member  46  contracts in directions  86 , portions  90  on the outer surface of flexible printed circuit  32  will tend to bow outward in directions  88 , thereby forming outward service loop bends  34 - 1  and  34 - 2 . Portion  92  of flexible printed circuit  32  will tend to bow inwardly to form inward service loop bend  34 - 3 . 
     In the illustrative example of  FIG. 13 , elastic member  46  has been attached to flexible printed circuit  32  using connections  52  that are located at opposing ends  50  of elastic member  46 . Elastic member  46  has also been attached to flexible printed circuit  32  using connections  52  at two intermediate locations between ends  50  (i.e. intermediate locations  50 M- 1  and  50 M- 2 ). When elastic member  46  contracts in directions  86 , flexible printed circuit  32  will move outwardly in direction  96  at three locations along the length of flexible printed circuit  32 , thereby forming a service loop with three outward bends. This type of arrangement may, in general, be used in forming service loops with any suitable number of flexible printed circuit bends. The formation of three outwardly protruding bends in the illustrative service loop of  FIG. 13  is merely an example. 
     Structures  94  of  FIG. 13  may be provided on flexible printed circuit  32  to help maintain a minimum desired bend radius for flexible printed circuit  32  at one or more of the bends in flexible printed circuit  32 . Structures  94  may be formed from overmolded elastomeric material or other suitable material (e.g., plastic metal, etc.). The overmolded elastomeric material of each structure  94  may be molded onto flexible printed circuit  32  when flexible printed circuit  32  is bent (i.e., each structure  94  may be overmolded over a bend in flexible printed circuit  32  so that the overmolded structure covers the bend). Further bending (i.e. additional bending that might reduce the bend radius of the flexible printed circuit at each bend) may be prevented by the presence of the structure  94  overlapping the bend. Structures such as optional elastomeric structures  94  of  FIG. 13  may sometimes be referred to as flexible printed circuit guiding structures or overbending prevention structures. If desired, overbending prevention structures may be configured to serve as printed circuit bumpers or other protective bumper structures, may include metal, or may be formed in other shapes and/or using other materials. 
       FIG. 14  is a side view of flexible printed circuit  32  showing how an overbending prevention structure may be formed from spacers that are attached to flexible printed circuit  32 . Spacers  98  may be formed from plastic, metal, glass, magnetic material or other structures. Spacers  98  may be attached to flexible printed circuit  32  using adhesive, welds, or other suitable connections. When flexible printed circuit  32  is bent into a service loop shape of the type shown in  FIG. 15 , the presence of spacers  98  may prevent the bends in the flexible printed circuit material from being more abrupt than a desired amount (i.e., spacers  98  may ensure that the bends in flexible printed circuit  32  are characterized by a bend radius that is more than a minimum bend radius). Any suitable number of spacers  98  may be provided on flexible printed circuit  32 . For example, a minimum bend radius may be ensured for a single bend in a flexible printed circuit using a single pair of mating spacers  98 . In the example of  FIG. 15 , two pairs of spacers  98  are being used to ensure that each of two bends is provided with a desired minimum bend radius. An additional pair of spacers  98  may be provided where shown by dashed lines  98 ′ in arrangements in which it is desired to ensure a minimum bend radius for each of the three bends in the service loop. More or fewer spacers may be used in different usage scenarios. 
     If desired, spacers  98  may be magnetic (i.e. spacers  98  may be formed from magnets and/or ferromagnetic material such as iron). In this situation, opposite magnetic poles may be provided to spacers that are intended to attract each other whereas common magnetic poles may be arranged to face each other in scenarios in which it is desired for the magnets to repel each other and thereby ensure that a desired minimum bend radius is maintained. Optional elastic member  46  may be attached to flexible printed circuit  32  to help form the service loop of  FIG. 15 . 
     Overbending prevention structures may be formed from overmolded plastic material. As an example, a heated plastic injection molding die may be used to overmold elastomeric material around a portion of flexible printed circuit  32  as shown in  FIG. 16 . In the example of  FIG. 16 , elastomeric structure  94  may be formed using a mold formed from die  100  and die  102 . The elastomer using in forming structure  94  may be a unitary injection molded structure or multiple parts may be joined using fasteners or other attachment mechanisms. Following removal of the plastic injection molding die, overbending prevention structure  94  may be used to prevent flexible printed circuit  32  from being bent more abruptly than would be associated with a predetermined minimum bend radius R, as shown in  FIG. 17 . The elastomeric material used for forming an injection molded overbending prevention structure may be a thermoplastic material, a thermoset material or other suitable polymer. As an example, the elastomeric material used in forming the overbending prevention structure may be a thermoplastic elastomer such as thermoplastic silicone. 
       FIG. 18  shows how overbending prevention structure  94  may be overmolded over flexible printed circuit  32  in a shape that includes integral strain relief structures  104 . Strain relief structures  104  may be narrower than the rest of structure  94  (i.e. structures  104  may be tapered so that they have smaller lateral dimensions perpendicular to the surface of flexible printed circuit  32  than other portions of overbending prevention structure  94 ). The local narrowing of strain relief structures  104  allows strain relief structures  104  to bend when stressed by flexible printed circuit  32 . Because strain relief structures  104  tend to bend when pulled by flexible printed circuit  32 , structures  104  are less likely to cause flexible printed circuit  32  to bend sharply when exiting overbending prevention structure  94  than overbending prevention structure  94  without integral strain relief structures  104 . 
     Overbending prevention structures  94  may be provided with screw holes and other features for facilitating mounting within device  10 . As shown in  FIG. 19 , a fastener such as screw  106  may be used to attach overbending prevention structure  94  to screw boss  109  on housing structure  12 ′ (e.g., an internal housing structure in electronic device  10 ). Overbending prevention structures  94  may also be provided with recesses such as recess  108 . Components that are sharp or that may otherwise present an abrasive and potentially damaging contact point with flexible printed circuit  32  may be covered with an elastomeric structure such as overbending prevention structure  94  to prevent flexible printed circuit  32  from being damaged by contact with these components. In the example of  FIG. 19 , elastomeric structure  94  is using recess  108  to receive the edge of printed circuit board  28  (e.g., a rigid printed circuit board). In this configuration, elastomeric structure  94  serves as an elastomeric bumper that protects flexible printed circuit  32  from damage due to contact with printed circuit board  28 . Bumper structures of this type may be used to protect flexible printed circuit  32  from damage due to contact between flexible printed circuit  32  with other printed circuits, with internal housing structures, from packaged integrated circuits and other electronic devices in housing  12  of device  10 , or other structures. The bumper structures may be formed from the same overmolded elastomeric structure that is being used to prevent flexible printed circuit  32  from being bent too much (i.e., overmolded elastomeric structures  94  or other structures may serve both as protective bumper structures and as overbending prevention structures. 
     As shown in  FIG. 20 , overmolded elastomeric overbending prevention structure  94  may have a recess or other feature that allows structure  94  to be press fit onto edge  110  of printed circuit board  28  or other structure in device  10 . In the  FIG. 20  configuration, structure  94  serves both as an overbending prevention component that prevents overbending of flexible printed circuit  32  and as a protective bumper that prevents damage due to rubbing between flexible printed circuit  32  and internal device structures such as printed circuit board  28 . 
     If desired, structure  94  may be formed from a conductive elastomer (e.g. an elastomeric material that contains metal particles or other suitable conductive material). When formed from a conductive elastomeric material, structures such as structure  94  may be shaped to serve as an electromagnetic interference shield. As shown in  FIG. 20 , for example, structure  94  may be configured to cover and electromagnetically shield components on printed circuit  28  such as component  30 - 1  and/or may be configured to cover and electromagnetically shield components on flexible printed circuit  32  such as component  30 - 2 . 
     Structure  94  or other elastomeric structures in device  10  may also be formed form a conductive elastomeric material that is patterned to provide electrical paths for signals such as power signals and data signals (see, e.g., illustrative electrical path  115  between node  1  on the upper surface of printed circuit  28  and node  113  on the opposing lower surface of printed circuit  28 ). Signal paths formed from elastomeric structure  94  may be used to route power and data signals between printed circuits such as printed circuits  28  and  32 , between electrical components  30 , or between other circuitry in device  10 . 
     Components such as illustrative component  30 - 3  may also be mounted to a conductive elastomeric material such as structure  94 . For example, structure  94  may be patterned to form signal lines for power and/or data signals. Components such as component  30 - 3  of  FIG. 20  may be attached to the signal paths formed from structure  94  using conductive adhesive or other conductive coupling material. 
       FIG. 21  shows how overmolded elastomeric structures  94  may be provided at multiple locations along the length of flexible printed circuit  32 . The shapes of the bends that are defined by structures  94  and the shapes of strain relief structures  104  helps ensure that flexible printed circuit  32  will form a service loop of a desired shape (e.g., a service loop with two outward bends and one inward bend in the example of  FIG. 21 ). Other service loop arrangements can be created using overmolded elastomeric structures if desired. 
     In the illustrative configuration of  FIG. 22 , overbending prevention structures have been formed from mating inner elastomeric structure  94 A and outer elastomeric structure  94 B. Fasteners such as fastener  106  may be used to attach flexible printed circuit overbending prevention structures such as the illustrative overbending prevention structures of  FIG. 22  to device structures such as housing  12 . If desired, structures  94 A and  94 B may be joined using connections  112  (e.g. fused plastic regions formed by applying heat to structures  94 A and  94 B, regions joined by adhesive, etc.). 
     More than one material may be used in forming overbending prevention structures (and bumper structures). In the example of  FIG. 23 , members  120  and  124  may be formed from stamped sheet metal or rigid plastic (as examples). Elastomeric material  122  may be molded or otherwise attached to member  120  to form overbending prevention structure  94 A. Elastomeric material  126  may be molded or otherwise attached to member  124  to form overbending prevention structure  94 B. A fastener such as screw  106  or other attachment mechanisms may be used to join structures  94 A and  94 B together over flexible printed circuit  32  to form an overbending prevention structure that prevents flexible printed circuit  32  from being overbent. The structure of  FIG. 23  may be configured to serve as a bumper by shaping member  120  to receive the edge of a printed circuit board or other potentially sharp object in device  10 . 
     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: 20140325
Publication Date: 20170523
Grant Date: 20170523
Priority Date: 20130906
Inventors: RAPPOPORT BENJAMIN M.
WODRICH JUSTIN R.
BALAJI SANTHANA
MALEK SHAYAN
Assignee: APPLE INC
CPC Classifications: [{"code": "H05K2201/2009", "inventive": false, "first": false, "tree": "[]"}, {"code": "H05K1/0281", "inventive": true, "first": false, "tree": "[]"}, {"code": "H05K2201/09109", "inventive": false, "first": false, "tree": "[]"}, {"code": "H05K3/0064", "inventive": false, "first": false, "tree": "[]"}, {"code": "G06F1/1633", "inventive": true, "first": true, "tree": "[]"}, {"code": "H05K1/0281", "inventive": true, "first": true, "tree": "[]"}, {"code": "H05K2201/09109", "inventive": false, "first": false, "tree": "[]"}, {"code": "H05K2201/2009", "inventive": false, "first": false, "tree": "[]"}, {"code": "H05K2201/2009", "inventive": false, "first": false, "tree": "[]"}, {"code": "H05K1/0281", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F1/1656", "inventive": true, "first": false, "tree": "[]"}, {"code": "H05K3/0064", "inventive": false, "first": false, "tree": "[]"}, {"code": "H05K3/0064", "inventive": false, "first": false, "tree": "[]"}, {"code": "G06F1/1633", "inventive": true, "first": true, "tree": "[]"}, {"code": "G06F1/1656", "inventive": true, "first": false, "tree": "[]"}, {"code": "H05K2201/09109", "inventive": false, "first": false, "tree": "[]"}]
Family ID: 52625380