PATENT DOCUMENT

Publication Number: US-9558875-B1
Application Number: US-201615284179-A
Country: US
Kind Code: B1

Title: Electronic device with signal line routing to minimize vibrations

Abstract:
An electronic device may have a source of magnetic field such as a magnet that produces a static magnetic field. A flexible printed circuit may have a flexible tail that surrounds a central portion. The central portion may overlap the magnet. Electrical components may be mounted to the central portion. To prevent undesired vibrations and noise due to interactions between magnetic fields induced by signals flowing in signal lines in the flexible printed circuit and the static magnetic field, the signal lines may be vertically stacked or may be routed along a curved path that does not overlap the magnet. The tail may serve as a service loop that allows a portion of a housing for the device and electrical components mounted to the central portion in alignment with windows in the housing to be detached for servicing.

Claims:
What is claimed is: 
     
       1. An electronic device, comprising:
 a housing; 
 a display mounted in the housing; 
 a permanent magnet mounted under the display that produces a static magnetic field; 
 a light-emitting diode; 
 a printed circuit on which the light-emitting diode is mounted, wherein the static magnetic field at least partially passes through the printed circuit and the light-emitting diode is mounted to the printed circuit in the vicinity of the permanent magnet; and 
 signal lines on the printed circuit that are coupled to the light-emitting diode, wherein the signal lines produce a second magnetic field and are configured to reduce vibrations in the printed circuit due to interactions between the static magnetic field and the second magnetic field. 
 
     
     
       2. The electronic device defined in  claim 1  wherein the signal lines are vertically stacked to minimize interactions between the static magnetic field and the second magnetic field. 
     
     
       3. The electronic device defined in  claim 1  wherein the signal lines are routed around the permanent magnet so that the signal lines do not overlap the permanent magnet to minimize interactions between the static magnetic field and the second magnetic field. 
     
     
       4. The electronic device defined in  claim 1  wherein the printed circuit comprises a flexible printed circuit that has a curved edge. 
     
     
       5. The electronic device defined in  claim 1  further comprising a light sensor. 
     
     
       6. The electronic defined in  claim 5  wherein the light-emitting diode and the light sensor detect a body characteristic associated with a user of the electronic device. 
     
     
       7. The electronic device defined in  claim 1  wherein the signal lines include first and second metal traces that are coupled to the light-emitting diode and that do not overlap the permanent magnet. 
     
     
       8. The electronic device defined in  claim 7  wherein the first and second metal traces spiral around the permanent magnet. 
     
     
       9. The electronic device defined in  claim 1  wherein the permanent magnet is configured to hold the electronic device to a docking station. 
     
     
       10. An electronic device, comprising:
 a housing; 
 a display mounted in the housing; 
 a source of a magnetic field mounted under the display; 
 a light-emitting diode; 
 a light sensor, wherein the light-emitting diode and the light sensor detect body characteristics associated with a user of the electronic device; 
 a printed circuit on which the light-emitting diode is mounted, wherein the magnetic field at least partially passes through the printed circuit and the light-emitting diode is mounted to the printed circuit in the vicinity of the source of the magnetic field; and 
 at least one signal line on the printed circuit that is coupled to the light-emitting diode, wherein the at least one signal line produces a second magnetic field and is configured to reduce vibrations in the printed circuit due to interactions between the magnetic field and the second magnetic field. 
 
     
     
       11. The electronic device defined in  claim 10  wherein the at least one signal line comprises first and second signal lines that are vertically stacked to minimize interactions between the magnetic field and the second magnetic field. 
     
     
       12. The electronic device defined in  claim 10  wherein the at least one signal line is routed around the source of the magnetic field so that the at least one signal line does not overlap the source of the magnetic field to minimize interactions between the magnetic field and the second magnetic field. 
     
     
       13. The electronic device defined in  claim 10  wherein the at least one signal line includes first and second metal traces that are coupled to the light-emitting diode and that do not overlap the source of the magnetic field. 
     
     
       14. The electronic device defined in  claim 10  wherein the source of the magnetic field is a permanent magnet. 
     
     
       15. An electronic device, comprising:
 a housing; 
 a display mounted in the housing; 
 a permanent magnet mounted under the display that produces a static magnetic field; 
 a light-emitting diode; and 
 signal lines that are coupled to the light-emitting diode, wherein the signal lines produce a second magnetic field and are configured to reduce magnetic-field-induced vibrations due to interactions between the static magnetic field and the second magnetic field. 
 
     
     
       16. The electronic device defined in  claim 15  further comprising:
 a light sensor, wherein the light-emitting diode and the light sensor are configured to detect a body characteristic associated with a user of the electronic device. 
 
     
     
       17. The electronic device defined in  claim 15  wherein the signal lines are vertically stacked to minimize interactions between the static magnetic field and the second magnetic field. 
     
     
       18. The electronic device defined in  claim 15  wherein the signal lines are routed around the permanent magnet so that the signal lines do not overlap the permanent magnet to minimize interactions between the magnetic field and the second magnetic field. 
     
     
       19. The electronic device defined in  claim 15  wherein the signal lines include first and second metal traces that are coupled to the light-emitting diode and that do not overlap the permanent magnet. 
     
     
       20. The electronic device defined in  claim 15  wherein the permanent magnet is configured to hold the electronic device to a docking station.

Description:
This application is a continuation of patent application Ser. No. 14/831,109, filed Aug. 20, 2015, which claims the benefit of provisional patent application No. 62/044,527 filed Sep. 2, 2014, which are hereby incorporated by reference herein in their entireties. 
    
    
     BACKGROUND 
     This relates generally to electronic devices, and, more particularly, to electronic devices that include magnets and other sources of magnetic field. 
     Electronic devices sometimes include sources of magnetic field such as magnets. For example, a display cover glass layer or other device structure may be mounted to a device housing using magnets and ferromagnetic materials that are attracted to magnets. Magnets and ferromagnetic materials may also be used as parts of latches in device covers, may be used to hold a device to a docking station, may be used as parts of speakers and other electrical components, and may be incorporated into other portions of a device. In some devices, magnetic fields may be produced by flowing currents and can interact with magnets and ferromagnetic material. 
     An electronic device supplies control signals to electrical components during operation. For example, signals may be provided to light-producing components, sensors, displays, integrated circuits, and other components. 
     If care is not taken, vibrations can be inadvertently produced within an electronic device. These vibrations, which may create undesirable noise, may arise due to the interaction between the magnetic field produced by a magnet, currents flowing in a device, and/or ferromagnetic material and the magnetic fields produced by time-varying currents flowing within a device. 
     It would therefore be desirable to be able to provide ways in which to reduce undesired noise in electronic devices such as noise that is produced from vibrations due to the interaction of magnetic fields from signal currents and magnetic fields from magnets, ferromagnetic materials, and current sources within electronic devices. 
     SUMMARY 
     An electronic device may have a source of magnetic field such as a permanent magnet, a ferromagnetic material, or currents flowing within the device. Flexible printed circuits and other substrates may couple electrical components in the device together. A flexible printed circuit may have a flexible tail that surrounds a central portion. The central portion may overlap the magnet (or other source of magnetic field) so that the magnetic field from the magnet passes through the central portion. Electrical components may be mounted to the central portion. The tail may serve as a service loop that allows a detachable portion of a housing for the device and electrical components that are mounted to the central portion in alignment with windows in the detachable portion of the housing to be detached for servicing. 
     The flexible printed circuit may have signal lines that extend from the tail to the central portion. Signals flowing in the signal lines may produce magnetic fields. To prevent undesired vibrations and noise due to interactions between the magnetic fields induced by the signals and the static magnetic field, the signal lines may be vertically stacked or may be routed in a spiral pattern that does not overlap the magnet. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a diagram of an illustrative electronic device in accordance with an embodiment. 
         FIG. 2  is a diagram of an illustrative magnet and structures in an electronic device that may produce magnetic fields that interact with magnetic fields from the magnet in accordance with an embodiment. 
         FIG. 3  is a cross-sectional side view of an illustrative flexible printed circuit having signal lines arranged to minimize vibrations in accordance with an embodiment. 
         FIG. 4  is a top view of an illustrative flexible printed circuit having signal lines routed around a magnet to minimize vibrations in accordance with an embodiment. 
         FIG. 5  is a cross-sectional side view of illustrative electronic device with a magnet and a printed circuit that overlaps that magnet in accordance with an embodiment. 
         FIG. 6  is a cross-sectional side view of the illustrative electronic device of  FIG. 5  in a configuration in which a portion of a device housing is detached from the rest of the device housing in accordance with an embodiment. 
         FIG. 7  is a top view of an illustrative flexible printed circuit that has a service loop to accommodate detachment of a detachable portion of a device housing and that has signal lines routed to minimize noise in accordance with an embodiment. 
         FIG. 8  is a cross-sectional side view of flexible printed circuit structures of the type that may be associated with the flexible printed circuit of  FIG. 7  in accordance with an embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     An illustrative electronic device is shown in  FIG. 1 . As shown in  FIG. 1 , electronic device  10  may have control circuitry  16 . Control circuitry  16  may include storage and processing circuitry for supporting the operation of device  10 . The storage and processing circuitry may include storage such as hard disk drive storage, nonvolatile memory (e.g., flash memory or other electrically-programmable-read-only memory configured to form a solid state drive), volatile memory (e.g., static or dynamic random-access-memory), etc. Processing circuitry in control circuitry  16  may be used to control the operation of device  10 . The processing circuitry may be based on one or more microprocessors, microcontrollers, digital signal processors, baseband processors, power management units, audio chips, application specific integrated circuits, etc. 
     Input-output circuitry in device  10  such as input-output devices  18  may be used to allow data to be supplied to device  10  and to allow data to be provided from device  10  to external devices. Input-output devices  18  may include buttons, joysticks, scrolling wheels, touch pads, key pads, keyboards, microphones, speakers, tone generators, vibrators, cameras, sensors, light-emitting diodes and other status indicators, data ports, light-emitting diodes that form part of a sensor or communications device, light detectors that form part of a sensor or communications device, etc. A user can control the operation of device  10  by supplying commands through input-output devices  18  and may receive status information and other output from device  10  using the output resources of input-output devices  18 . 
     Input-output devices  18  may include one or more displays. Device  10  may, for example, include a touch screen display that includes a touch sensor for gathering touch input from a user or a display that is insensitive to touch. A touch sensor for a display in device  10  may be based on an array of capacitive touch sensor electrodes, acoustic touch sensor structures, resistive touch components, force-based touch sensor structures, a light-based touch sensor, or other suitable touch sensor arrangements. 
     Control circuitry  16  may be used to run software on device  10  such as operating system code and applications. During operation of device  10 , the software running on control circuitry  16  may display images for a user on one or more displays. Device  10  may use communications circuits to send and receive wireless and wired data. For example, device  10  may use light-emitting components to transmit data and may use light-receiving components to receive transmitted light signals. Device  10  may also use light-emitting components, light-receiving components, audio components, capacitive sensors, microelectromechanical systems devices, and other components as sensors and output devices. 
     Device  10  may include components that produce magnetic fields. For example, device  10  may include solenoids and other electromagnetic components that produce magnetic fields when driven with current. Device  10  may also include one or more magnets. Permanent magnets may produce static magnetic fields. Particularly in device configurations in which devices such as device  10  contain magnets that produce static magnetic fields, there is a potential for unwanted vibrations to develop within the devices during operation. 
     Consider, as an example, the components of device  10  of  FIG. 2 . In the example of  FIG. 2 , device  10  includes magnet  34 . Magnet  34  may be a permanent magnet that produces static magnetic field  56 . Device  10  may also include one or more substrates such as substrate  20  that include signal lines  50 . Substrate  20  may overlap a source of magnetic field such as magnet  34 , so that magnetic field  56  passes through substrate  20 . In some configurations, magnetic field  56  may be produced by currents flowing in device  10 , by a ferromagnetic material, and/or other sources of magnetic field. Configurations in which magnetic field is produced by magnet  34  are sometimes described herein as an example. This is, however, merely illustrative. Magnetic field  56  may, in general, be produced by any source. 
     Substrate  20  may be a plastic carrier, a layer of glass, ceramic, or other dielectric, may be a printed circuit, or may be other dielectric structure that serves as a support for signal lines  50 . Signal lines  50  may be metal traces (e.g., metal traces that are deposited and patterned using photolithography) or other conductive signal lines. Printed circuit board substrates that may be used for forming substrate  20  include rigid printed circuit board substrates (e.g., printed circuits formed form fiberglass-filled epoxy or other rigid printed circuit board material) and flexible printed circuit substrates (e.g. printed circuits formed from flexible sheets of polyimide or other flexible layers of polymer). 
     Signal lines  50  may carry signals between circuits on different portions of printed circuit  20 . For example, signal lines  50  may carry digital signals, analog signals, power supply signals, etc. In the example of  FIG. 2 , signal lines  50  form a signal path that conveys signals between component  52  and component  54 . Components  52  and  54  may be integrated circuits, discrete components such as a inductors, capacitors, and resistors, may be switches, sensors, light-emitting components such as light-emitting diodes, light sensors, vibrators, speakers, microphones, displays, touch pads, keys, and other input-output devices  18 , control circuitry  16  and/or other components in device  10 . As an example, component  52  may be an integrated circuit that produces control signals and/or that processes sensor signals. Paths such as path  50  may be used to convey control signals between component  52  and component  54 . Components  54  may be a light-emitting diode(s) that is controlled by the control signals in path  50 , light sensor(s) that supply data to component  52  over path  50 , etc. 
     Device  10  may include a source of magnetic field such as component  34 . Component  34  may be a permanent magnet or other component that produces magnetic field  56  (e.g., a static magnetic field produced by a permanent magnet). Printed circuit  20  lies in the X-Y plane of  FIG. 2 . Magnetic field  56  in the example of  FIG. 2  is oriented vertically and crosses printed circuit  20  and signal path  50  at a right angle. Magnet  34  may be used to hold device  10  to a cradle, may be used as a clasp that holds a cover or case lid in a closed position, may be used as a detectable identifier (e.g., to produce magnetic fields that help identify device  10  to mating equipment), or may serve other functions within device  10 . 
     When signals are carried over path  50 , magnetic fields may be produced in the vicinity of magnet  34 . These induced magnetic fields may interact with static magnetic field  56 . In configurations in which path  50  carries time-varying signals, the magnetic fields that are induced by the signals will also be time varying. When the induced magnetic fields interact with static magnetic field  56 , forces may be impressed upon printed circuit  20  and magnet  34 . For example, forces may be produced that alternately cause magnet  34  and printed circuit  20  to be attracted towards each other and repelled apart from each other. These forces can cause printed circuit  20 , magnet  34 , and other structures in device  10  to vibrate and produce undesired noise. 
     Device  10  preferably includes signal path configurations for paths such as path  50  that help to reduce vibrations and thereby minimize or eliminated undesired noise.  FIG. 3  is a cross-sectional side view of an illustrative portion of a printed circuit in which signal path lines have been configured to help minimize interactions with magnetic field  56 . Printed circuit  92  of  FIG. 3  may be a rigid printed circuit board or a flexible printed circuit. As shown in  FIG. 3 , printed circuit  92  may have substrate  90 . Substrate  90  may be a flexible substrate formed from a flexible sheet of polyimide or other flexible polymer layer (as an example). Metal lines  50 A and  50 B may form signal path  50 . Metal lines  50 A and  50 B may be formed in two respective metal layers in printed circuit  92  (i.e., printed circuit  92  may be a multilayer printed circuit board in which line  50 B is stacked above line  50 A). 
     In the example of  FIG. 3 , magnetic field  56  is oriented vertically (parallel to vertical dimension Z), whereas printed circuit  92  lies in the X-Y plane (i.e., surface normal  94  of printed circuit  92  is parallel to magnetic field  56 ). Lines  50 B and  50 A run into and out of the page in the orientation of  FIG. 3  (i.e., lines  50 A and  50 B run parallel to each other along the Y dimension). Line  50 B overlaps line  50 A (i.e., lines  50 A and  50 B have the same footprint when viewed in direction −Z). When a current is being applied to a component such as component  54  (e.g., a light-emitting diode or other component), current will flow out of the page in line  50 B and will flow into the page in line  50 A. In this configuration, a current loop is established in the Y-Z plane that produces lateral magnetic field  60 . The magnitude of induced magnetic field  60  may vary as a function of time in scenarios in which the signal in path  50  is time varying, giving rise to a risk of unwanted vibrations due to the interaction between magnetic field  60  and magnetic field  56 . Nevertheless, because of the vertical alignment of line  50 B over  50 A, magnetic field  60  is oriented in the lateral X direction. The lateral orientation of magnetic field  60  relative to the vertical orientation of magnetic field  56  (i.e., the perpendicular orientation of field  60  relative to field  56 ) minimizes interaction between magnetic field  60  and magnetic field  56  and thereby helps to reduce magnetic-field-interaction-induced noise in device  10 . 
     In addition to or instead of vertically stacking signal lines to minimize magnetic field interactions, magnetic field interactions between field  60  and field  56  can be minimized by routing path  50  within the X-Y plane of printed circuit  92  so that overlap between path  50  and magnetic field  56  is minimized or avoided. This type of approach is illustrated in  FIG. 4 . As shown in  FIG. 4 , printed circuit  92  has a metal traces that form signal path  50  on substrate  90 . The metal traces may form signal lines  50 A and  50 B. During operation of device  10 , signals may be carried between components  52  and  54  over path  50 . Because signal lines  50 A and  50 B and the current loop these lines create are contained within the X-Y plane of substrate  90  (in the example of  FIG. 4 ), induced magnetic fields  60  will be oriented vertically along dimension Z (into and out of the page in the orientation of  FIG. 4 ). Magnetic field  56  from component  34  is also oriented vertically along dimension Z, which gives rise for a potential for magnetic field interactions. Nevertheless, magnetic field interactions and unwanted vibrations are minimized because path  50  is routed around component  34  and magnetic field  56  (i.e., path  50  does not overlap component  34  or magnetic field  56 ). 
     In some device configurations, signal lines may be aligned in a vertically overlapping (vertically stacked) configuration of the type shown in  FIG. 3  so that induced magnetic field  60  is oriented perpendicular to magnetic field  56  from component  34 . In other configurations, signal lines may be laterally routed around component  34  so that the signal lines do not overlap magnet  34 . Configurations with both multilayer vertically aligned signal lines and non-overlapping signal line patterns may also be used. 
       FIG. 5  is a diagram of an illustrative electronic device of the type that may include a source of magnetic field  56  such as component  34 . Component  34  may be, for example, a permanent magnet that produces a magnetic field such as magnetic field  56  that is oriented vertically (i.e., parallel to vertical dimension Z). Permanent magnet  34  may be used to help hold device  10  to a docking station, may be used as part of a clasp, may be used to help hold together structures in device  10 , etc. 
     Device  10  may include display  14 . Display  14  may overlap magnet  34 . Display  14  may have a display module such as display module  30 . Display module  30  may be an organic light-emitting diode display, a liquid crystal display module, etc. Display module  30  may be mounted under display cover layer  32 . Display cover layer  32  may include one or more transparent layers such as structures formed from glass, plastic, sapphire, ceramic, crystalline material, other materials, or combinations of these material. 
     Display  14  may be mounted in housing  12 . Housing  12  may be formed from plastic, glass, metal, carbon-fiber material or other fiber composites, or other suitable materials. 
     The interior of device  10  may include components  24 . Components  24  may include batteries, integrated circuits, sensors, buttons, and other input-output devices  18  and control circuitry  16 . As shown in  FIG. 5 , components  24  may include devices  28  that are mounted on one or more substrates  26  (e.g., printed circuits, etc.). For example, components  24  may include one or more electrical components  28  that are soldered to printed circuit  26 . 
     In the configuration of device  10  that is shown in  FIG. 5 , housing  12  has a rear wall such as rear housing wall  72 . Housing wall  72  may be formed from plastic, glass, metal, carbon-fiber material or other fiber composites, or other suitable materials. The material(s) used in forming housing wall  72  may be the same as the material used in forming housing sidewalls such as housing walls  12  of  FIG. 5  and/or may be different from the material used in forming housing walls  12 . 
     Rear housing wall  72  may include one or more windows such as windows  70 . Windows  70  may be formed from a different type of material than the remainder of the material used in forming rear housing wall  72 . For example, housing wall  72  may be formed from a material that is opaque, whereas windows  70  may be optical windows formed from optically transparent materials (e.g., materials that allow visible light, infrared light, or other light to pass into and out of the interior of the housing of device  10 ). As shown in  FIG. 5 , there may be one or more components in the interior of device  10  that are in alignment with openings  70 . For example, device  10  may include components such as components  36  and  38  that are attached to rear housing wall  72  and that are aligned with respective optically transparent windows  70  in rear housing wall  72 . There may be any suitable number of windows  70  in device  10  (e.g., one or more, two or more, three or more, four or more, less than five, more than 10, etc.). 
     Components  36  may be interconnected using signal paths such as paths  50  of  FIGS. 2, 3 , and  4  in a substrate such as flexible printed circuit  20 . A central portion of flexible printed circuit  20  may be attached to rear housing wall  72 . Flexible printed circuit  20  may have a tail portion such as tail  22  that couples flexible printed circuit  20  to components  24 . Tail  22  of flexible printed circuit  20  may be configured to form a flexible service loop for printed circuit  20 . The service loop may be used to facilitate assembly and disassembly of device  10 . As shown in  FIG. 6 , for example, tail  22  may be sufficiently long and flexible to flex so that a detachable portion of rear housing wall  72  can be removed from device housing  12  in direction  40  to facilitate rework or repair of device  10 . 
     To minimize magnetic field interactions that could produce undesirable vibrations and noise in device  10 , the signal paths in printed circuit  20  may be routed using vertically stacked signal line configurations of the type shown in  FIG. 2  and/or non-overlapping paths of the type shown in  FIG. 4 . 
     An illustrative configuration for printed circuit  20  of  FIGS. 5 and 6  is shown in  FIG. 7 . In the example of  FIG. 7 , flexible printed circuit  20  has a circular central portion on which two components  36  and two components  38  have been mounted in a rectangular two-by-two array (i.e., two rows of components and two columns of components). Components  36  may be diagonally opposed to each other in the array and components  38  may be diagonally opposed to each other in the array or other patterns may be used for mounting components  36  and  38  to printed circuit  20 . Flexible printed circuit tail  22  has a curved shape (e.g., a shape with curved edges) such as a spiral shape that runs around all or nearly all of the circular periphery of the circular central portion of flexible printed circuit  20  to which components  36  and  38  are mounted. 
     The outline of printed circuit  20  may be circular so that printed circuit  20  may be accommodated in a housing such as housing  12  that has a circular outline. In the  FIG. 7  example, housing  12  has a circular footprint (when viewed in direction −Z) and printed circuit  20  has a corresponding circular footprint. Configurations for device  10  and printed circuit  20  with other shapes (e.g., rectangles, ovals, etc.) may also be used. For example, housing  12  may have a rectangular footprint and some or all of wall  72  (e.g., the detachable portion of wall  72 ) may have a circular shape. Shapes with combinations of straight and curved edges may also be used for housing  12 . The configuration of  FIG. 7  is merely illustrative. 
     Magnet  34  may be located in the center of housing  12 , as shown in  FIG. 7 . Magnetic field  56  (e.g., a static magnetic field from magnet  34 ) may extend vertically through the center of printed circuit  20  in the vicinity of components  36  and  38  (i.e., along vertical dimension Z). Connector  200  may be used to couple signal paths  50 - 1 ,  50 - 2 ,  50 - 3 , and  50 - 4  to components  24 . Connector  200  may be, for example, a zero-insertion-force connector or other connector that couples traces on printed circuit  20  to printed circuit  26  on which components  28  have been mounted. 
     Signal path  50 - 1  may be coupled between the lower right component  36  and connector  200 . Signal path  50 - 2  may be coupled between the lower left component  38  and connector  200 . Signal path  50 - 3  may be coupled between the upper left component  36  and connector  200 . Signal path  50 - 4  may be coupled between the upper right component  38  and connector  200 . Components  36  and  38  may be any suitable components (see, e.g., input-output devices  18 , control circuitry  16 , etc.). With one illustrative configuration, components  36  are light-emitting diodes that emit light through a first pair of respective windows  70  in rear wall  72  and components  38  are light sensors that detect light that is received through a second pair of respective windows  70 . Components  36  and/or  38  may be used as light-based communications devices, as environmental sensors, as proximity sensors, as sensors that detect body characteristics associated with a user of device  10 , or other suitable devices. 
     To minimize vibrations that might result from interactions between induced magnetic fields from the signals running through the signal paths on printed circuit  20  and magnetic field  56 , signal paths  50 - 1 ,  50 - 2 ,  50 - 3 , and  50 - 4  may be routed around component  34  in a spiral pattern (e.g., a spiral path or other curved path), so that the signal paths do not overlap magnetic field  56 . Vertically stacked signal line configurations of the type described in connection with  FIG. 2  may also be used to minimize magnetic-field-induced vibrations. 
     Printed circuit  20  may be a single layer printed circuit in which signal traces are formed on only a single side of a printed circuit substrate or may be a multilayer printed circuit having two or more layers of signal lines, three or more layers of signal lines, or four or more layers of signal lines. Signal lines on different layers of printed circuit  20  may be coupled using vias (e.g., metal vias that couple adjacent metal layers by passing through an intervening dielectric substrate layer). 
     With one illustrative configuration, the service loop portion of printed circuit  20  (i.e., spiral tail  22 ) may be a two layer flexible printed circuit and circular central portion  21  of printed circuit  20  that overlaps magnet  34  may be a three layer flexible printed circuit. The use of three layers for the central portion of printed circuit  20  may allow printed circuit  20  to be provided with a grounded shielding layer that can help electromagnetically shield signal lines and components that are sensitive to electromagnetic noise. Other types of printed circuit may be used if desired. The use of a printed circuit that contains a tail portion with two metal layers and a central portion with three metal layers is merely illustrative. 
       FIG. 8  is a cross-sectional side view of structures of the type that may be included in a printed circuit having a two-layer tail and a three-layer central region. As shown in  FIG. 8 , printed circuit  20  may have a three layer central portion such as central portion  21  and may have a two-layer tail such as tail  22  that forms a service loop, as described in connection with  FIGS. 5 and 6 . Dielectric  300  (e.g., a flexible layer of polyimide or other flexible sheet of polymer material) may serve as a substrate for printed circuit  20 . Patterned metal traces (e.g., photolithographically patterned blanket layers of metal and vertical metal vias that couple signal lines in respective layers of printed circuit  20 ) may be used in forming signal paths  50 - 1 ,  50 - 2 ,  50 - 3 , and  50 - 4 . 
     In tail  22 , signal path  50 - 4  may be formed from sensor lines P 1  and P 2  on the lower surface of substrate  300 . Signal path  50 - 2  may be formed from sensor lines P 3  and P 4 . These lines may be routed to portion  21  and may be coupled to sensors  38 . Ground layer GND may form electromagnetic shielding for the sensor paths and sensors  38  in region  302 . 
     Path  50 - 1  may be formed from cathode line C 1  and anode A in tail  22 . Path  50 - 2  may be formed from cathode line C 2  and anode A in tail  22 . Anode A may be formed from separate lines or may be shared between paths  50 - 1  and  50 - 2 . 
     In region  21 , anode line A may be coupled to light-emitting diodes  36  using vias  304  and a third layer of metal traces (layer  306 ). Cathode C 1  may be routed to the lowermost metal layer in region  21  using via  308 . Cathode C 2  may remain on the lowermost layer in both tail region  22  and in central region  21 . 
     The cross-sectional side view of  FIG. 8  illustrates how a two-layer flexible printed circuit design allows tail  22  to be formed from relatively thin and flexible structures, whereas a three-layer flexible printed circuit design allows shielding layer GND to overlap and shield sensors  38 . Vias can be used to form paths between signal lines on different layers of printed circuit  20 . If desired, printed circuit  20  may be formed entirely as a three layer substrate, may include portions with four or more layers, may have only two layer portions, may be formed as a single layer printed circuit, or may have other combinations of flexible printed circuit layers. The arrangement of  FIG. 8  is described as an example. 
     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: 20161003
Publication Date: 20170131
Grant Date: 20170131
Priority Date: 20140902
Inventors: ENG MICHAEL
POULAIN KIERAN
MEAD CURTIS C.
DUKE CONNOR R.
Assignee: APPLE INC
CPC Classifications: [{"code": "H05K1/189", "inventive": true, "first": false, "tree": "[]"}, {"code": "H05B47/105", "inventive": true, "first": false, "tree": "[]"}, {"code": "H05K2201/10106", "inventive": false, "first": false, "tree": "[]"}, {"code": "H05K5/0017", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01F7/20", "inventive": false, "first": false, "tree": "[]"}, {"code": "H05B45/00", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01F7/0252", "inventive": true, "first": true, "tree": "[]"}, {"code": "H01F7/20", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01F7/0252", "inventive": true, "first": true, "tree": "[]"}, {"code": "H05B33/0842", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01F7/0252", "inventive": true, "first": true, "tree": "[]"}, {"code": "H05K1/189", "inventive": true, "first": false, "tree": "[]"}, {"code": "H05B37/0227", "inventive": true, "first": false, "tree": "[]"}, {"code": "H05K5/0017", "inventive": true, "first": false, "tree": "[]"}, {"code": "H05K2201/10106", "inventive": false, "first": false, "tree": "[]"}, {"code": "Y02B20/40", "inventive": false, "first": false, "tree": "[]"}, {"code": "H05B47/11", "inventive": true, "first": false, "tree": "[]"}, {"code": "H05B47/11", "inventive": true, "first": false, "tree": "[]"}, {"code": "H05B47/105", "inventive": true, "first": false, "tree": "[]"}, {"code": "H05B45/00", "inventive": true, "first": false, "tree": "[]"}]
Family ID: 55403270