PATENT DOCUMENT

Publication Number: US-9664747-B2
Application Number: US-201313788541-A
Country: US
Kind Code: B2

Title: Electronic devices with magnetic sensors

Abstract:
Electronic devices may be provided with magnetic sensors for detecting the Earth&#39;s magnetic field. The magnetic sensors may include thin magnetic sensors located in magnetically quiet regions of the device. The magnetic sensors may be attached to a device housing or a component such as a battery or a cover structure for a battery. The device may include unidirectional magnetic sensors aligned in three orthogonal directions or sensors with two or three magnetic sensor elements aligned in orthogonal directions. Magnetic field data from the three orthogonally aligned sensors or sensor elements may be combined to form directional compass data for the device. Each magnetic sensor may include one or more magnetic sensor elements for detecting the magnetic field and one or more shielded reference sensor elements for detecting environmental changes that can affect the magnetic sensor element. Reference sensor elements may be shared elements for multiple magnetic sensors elements.

Claims:
What is claimed is: 
     
       1. A magnetic sensor, comprising:
 a silicon substrate; 
 a magnetic sensor element on the silicon substrate having a material that responds to a magnetic field; 
 a reference magnetic sensor element on the silicon substrate having a shield that prevents magnetic material in the reference magnetic sensor from being exposed to the magnetic field; and 
 a polyimide substrate that encapsulates the silicon substrate and the magnetic sensor element, wherein the polyimide substrate comprises a top layer and a bottom layer, and wherein the silicon substrate is interposed between the top layer and the bottom layer. 
 
     
     
       2. The magnetic sensor defined in  claim 1  wherein the magnetic sensor has a maximum height along a direction that is perpendicular to a surface of the silicon substrate and passes through the silicon substrate and the magnetic sensor element and wherein the maximum height is less than 150 microns. 
     
     
       3. The magnetic sensor defined in  claim 1  wherein the magnetic sensor element includes a portion that is interleaved with a portion of the reference magnetic sensor element on a surface of the silicon substrate. 
     
     
       4. The magnetic sensor defined in  claim 1 , wherein the silicon substrate is in direct contact with the top layer and the bottom layer. 
     
     
       5. The magnetic sensor defined in  claim 1 , further comprising:
 conductive traces formed between the top layer and the bottom layer such that the conductive traces are in direct contact with the top layer and the bottom layer. 
 
     
     
       6. The magnetic sensor defined in  claim 1 , wherein the silicon substrate comprises a back-thinned silicon substrate. 
     
     
       7. The magnetic sensor defined in  claim 1 , further comprising:
 circuitry on the silicon substrate that is configured to modify magnetic field signals from the magnetic sensor element using magnetic field signals from the reference magnetic sensor element. 
 
     
     
       8. The magnetic sensor defined in  claim 7 , further comprising:
 conductive traces formed between the top layer and the bottom layer; 
 additional conductive traces in the silicon substrate that couple the circuitry to the conductive traces. 
 
     
     
       9. The magnetic sensor defined in  claim 8 , wherein the conductive traces have a first portion that is interposed between and in direct contact with the top layer and the bottom layer of the polyimide substrate, and wherein the conductive traces have a second portion that is not in direct contact with the top layer and forms an exposed conductive contact. 
     
     
       10. The magnetic sensor defined in  claim 1 , further comprising:
 an additional magnetic sensor element on the silicon substrate, wherein the magnetic field has a first component that is oriented in a first direction and a second component that is oriented in a second direction that is orthogonal to the first direction, wherein the magnetic sensor element is configured to detect the first component of the magnetic field, and wherein the additional magnetic sensor element is configured to detect the orthogonal second component of the magnetic field. 
 
     
     
       11. The magnetic sensor defined in  claim 10 , further comprising:
 circuitry on the silicon substrate that is configured to modify magnetic field signals from the magnetic sensor element using magnetic field signals from the reference magnetic sensor element and to modify magnetic field signals from the additional magnetic sensor element using the magnetic field signals from the reference magnetic sensor element. 
 
     
     
       12. The magnetic sensor defined in  claim 10 , further comprising:
 an additional reference magnetic sensor element on the silicon substrate. 
 
     
     
       13. The magnetic sensor defined in  claim 1  wherein the magnetic sensor element and the reference magnetic sensor element are at least partially embedded in the silicon substrate. 
     
     
       14. The magnetic sensor defined in  claim 13  wherein the shield includes a first portion on a first surface of the silicon substrate, a second portion on an opposing second surface of the silicon substrate, and vertical portions that extend through the silicon substrate from the first surface to the opposing second surface. 
     
     
       15. An electronic device, comprising:
 a housing; 
 a display in the housing; 
 first, second and third unidirectional magnetic sensors in the housing that are configured to detect respective first, second, and third orthogonal components of a magnetic field; 
 circuitry coupled to the first, second, and third unidirectional magnetic sensors that is configured to combine magnetic field data gathered using the first, second, and third unidirectional magnetic sensors to form compass data; and 
 a battery, wherein the battery has a top surface and a side surface that is perpendicular to the top surface, wherein the first and second unidirectional magnetic sensors are mounted directly to the top surface of the battery, and wherein the third unidirectional magnetic sensor is mounted directly to the side surface of the battery.

Description:
This application claims priority to U.S. provisional patent application No. 61/694,103 filed Aug. 28, 2012, which is hereby incorporated by reference herein in its entirety. 
    
    
     BACKGROUND 
     This relates generally to electronic devices and, more particularly, to electronic devices with magnetic sensors. 
     Electronic devices such as portable computers are often provided with compasses and other electronic components. Compasses may be used to gather magnetic field data for the electronic device. For example, a Global Positioning System (GPS) device or cellular telephone may have a compass for orienting maps displayed to a user on an associated device display. 
     Other electronic components in an electronic device with a compass often generate local magnetic fields during operation of the other electronic components. These local magnetic fields can interfere with the proper operation of the compass. 
     It can therefore be difficult to provide accurate compass data, particularly in compact electronic devices in which compasses must be placed in close proximity to other electronic components. 
     It would therefore be desirable to be able to provide electronic devices with improved magnetic sensors. 
     SUMMARY 
     Electronic devices may be provided with magnetic sensors. The magnetic sensors may be used by the device for sensing the Earth&#39;s magnetic field. The device may include one or more magnetic sensors that are each used to sense one or more components of the Earth&#39;s magnetic field. For example, a device may include three separate magnetic sensors that are each oriented along a particular direction or magnetic sensors with two or three magnetic sensor elements oriented along orthogonal directions to gather magnetic field data for a particular orthogonal component of the magnetic field. 
     Magnetic field data from each sensor or sensor element may be combined to form compass data for the device that indicates a direction in which the device is oriented. 
     Each magnetic sensor may be placed in a location within a housing for the device that is magnetically quiet along a particular direction or directions associated with that sensor. Electronic components in the housing may generate local magnetic fields having first, second, and third orthogonal components. A magnetic sensor may, for example, be located in a region within the housing at which a component of the local magnetic fields that is aligned with the particular direction associated with that sensor is smaller than the orthogonal second and third components of the local magnetic fields. 
     Each magnetic sensor may include a substrate having circuitry for processing magnetic field data and a magnetic sensing element that is used to gather the magnetic field data. 
     The substrate in each magnetic sensor may be back-thinned so that thin magnetic sensors may be provided. The substrate and the magnetic sensor element may be encapsulated in a substrate material with conductive traces that route magnetic field signals from the substrate to additional circuitry in the device. The substrate material may be a flexible substrate material such as polyimide, a more rigid substrate material such as a glass-infused epoxy, or other suitable materials for electronic circuit fabrication. 
     Each magnetic sensor may include one or more orthogonally aligned magnetic sensor elements and one or more shielded reference sensor elements. A shielded reference sensor element may be coupled to the substrate and the conductive traces in substantially the same way as a magnetic sensor element and may have an additional magnetic shielding layer. The magnetic shielding layer may include mu-metal or other magnetic shielding material that prevents magnetically sensitive material in the reference sensor element from being exposed to external magnetic fields. 
     Magnetic sensor elements and reference sensor elements may be formed separately on a surface of the substrate, may be interleaved on the surface of the substrate, or may be partially or completely embedded within the substrate. 
     Further features of the invention, its nature and various advantages will be more apparent from the accompanying drawings and the following detailed description. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective front view of an illustrative electronic device having magnetic sensors in accordance with an embodiment of the present invention. 
         FIG. 2  is a diagram of illustrative circuitry and components for an electronic device having magnetic sensors in accordance with an embodiment of the present invention. 
         FIG. 3  is a perspective view of an illustrative housing showing how magnetic sensors may be attached to the housing in various orientations in accordance with an embodiment of the present invention. 
         FIG. 4  is a perspective view of an illustrative electronic component in a device housing showing how magnetic sensors may be attached to the electronic component in various orientations in accordance with an embodiment of the present invention. 
         FIG. 5  is a perspective view of an illustrative set of magnetic sensors that are attached to a cowling structure that covers an electronic component in accordance with an embodiment of the present invention. 
         FIG. 6  is a perspective view of an illustrative set of magnetic sensors that are attached to a cowling structure having folded portions in multiple orientations that cover an electronic component in accordance with an embodiment of the present invention. 
         FIG. 7  is a top view of an illustrative unidirectional magnetic sensor in accordance with an embodiment of the present invention. 
         FIG. 8  is a cross-sectional side view of an illustrative unidirectional magnetic sensor in accordance with an embodiment of the present invention. 
         FIG. 9  is a perspective view of an illustrative unidirectional magnetic sensor having a stepped edge for low-profile coupling to a flexible circuit in accordance with an embodiment of the present invention. 
         FIG. 10  is a cross-sectional side view of an illustrative magnetic sensor having a reference sensor element in accordance with an embodiment of the present invention. 
         FIG. 11  is a top view of an illustrative bidirectional magnetic sensor in accordance with an embodiment of the present invention. 
         FIG. 12  is a top view of an illustrative bidirectional magnetic sensor with a shared reference sensor element in accordance with an embodiment of the present invention. 
         FIG. 13  is a top view of an illustrative bidirectional magnetic sensor with multiple reference sensor elements in accordance with an embodiment of the present invention. 
         FIG. 14  is a cross-sectional side view of an illustrative magnetic sensor element showing how magnetic sensor layers in the magnetic sensor element may include passivation layers and a layer of magnetically sensitive material in accordance with an embodiment of the present invention. 
         FIG. 15  is a cross-sectional side view of an illustrative reference magnetic sensor element showing how magnetic sensor layers in the reference sensor may be covered by an additional shield layer in accordance with an embodiment of the present invention. 
         FIG. 16  is a top view of an illustrative magnetic sensor showing how a magnetic sensor element and a reference sensor element may be interleaved on the surface of a substrate in accordance with an embodiment of the present invention. 
         FIG. 17  is a cross-sectional perspective view of an illustrative magnetic sensor showing how a magnetic sensor element and a reference sensor element may be embedded in a substrate in accordance with an embodiment of the present invention. 
         FIG. 18  is a top view of an illustrative tri-directional magnetic sensor with an optional shared reference sensor element in accordance with an embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     Electronic devices may be provided with one or more magnetic sensors and other electronic components. The magnetic sensors may include one or more unidirectional, bidirectional, or tri-directional magnetic sensors that are coupled to compass interface circuitry. The compass interface circuitry may be configured to convert raw magnetic field data from the magnetic sensors into directional compass data (also called compass data). 
     Other electronic components may include cameras, speakers, auto-focus lens mechanisms, camera flashes, Light Emitting Diodes (LEDs), processing circuitry such as central processing units, memory or other integrated circuits, Global Positioning System (GPS) circuitry, display circuitry, light-emitting display circuitry, display backlights, headphones, batteries, vibrators, actuators or other components. 
     The magnetic sensors may be located within the electronic device at locations where local magnetic fields generated by the other components are relatively small. The magnetic sensors may be thin magnetic sensors that are able to be placed in relatively low magnetic field regions of the electronic device that are too small to place a conventional compass chip. In this way, the electronic device may be provided with improved magnetic sensors. 
     An illustrative electronic device of the type that may be provided with magnetic sensors is shown in  FIG. 1 . Electronic device  10  of  FIG. 1  may be a cellular telephone, media player, computer, handheld device, portable computer, tablet computer, Global Positioning System device, camera, gaming device, or other electronic equipment. 
     As shown in  FIG. 1 , device  10  may have a housing such as housing  12 . Housing  12  maybe formed from plastic, metal, aluminum, carbon fiber composite material, other composites, glass, ceramics, other materials, or combinations of these materials. Housing  12  may be formed using a unibody construction in which housing  12  is substantially formed from a single structure (e.g., machined or cast metal, plastic, etc.) or may be formed from multiple pieces of material. 
     For example, housing  12  may include front and rear planar housing structures. The front planar housing structure may be a display cover layer for a display such as display  14 . The display cover layer may be formed from glass and may sometimes be referred to as cover glass or display cover glass. The display cover layer may also be formed from other transparent materials such as plastic. 
     Device  10  may have input-output devices such as input-output ports, speakers, microphones, displays, status indicator lights, touch screens, buttons, proximity sensors, wireless circuitry, accelerometers, ambient light sensors, touch pads, and other devices for accepting input from a user or the surrounding environment of device  10  and/or for providing output to a user of device  10 . 
     As shown in the illustrative configuration of  FIG. 1 , device  10  may, as an example, have one or more buttons  16  which may be used to gather user input. Buttons  16  may be based on dome switches or other switch circuitry. Buttons  16  may include button members that form push buttons (e.g., momentary buttons), slider switches, rocker switches, etc. Additional buttons such as buttons  16 , additional data ports such as port  26 , and additional input-output components such as speaker  18  may be provided in device  10  if desired. The example of  FIG. 1  is merely illustrative. 
     Device  10  may have a flexible or rigid display such as display  14 . Display  14  may be formed from multiple layers of material. These layers may include a touch sensor layer such as a layer on which a pattern of indium tin oxide (ITO) electrodes or other suitable transparent electrodes have been deposited to form a capacitive touch sensor array. These layers may also include a layer that contains an array of display pixels. 
     A rigid cover layer may have openings such as a circular openings for button  16  and a speaker port opening such as speaker port opening for speaker  18  (e.g., an ear speaker for a user). Device  10  may also have other openings (e.g., openings in display  14  and/or housing  12  for accommodating volume buttons, ringer buttons, sleep buttons, and other buttons, openings for an audio jack, data port connectors, removable media slots, etc.). 
     As shown in  FIG. 1 , device  10  may be provided with one or more internal magnetically sensitive devices such as magnetic sensor  20 . One or more magnetic sensors such as magnetic sensor  20  may be arranged in magnetically quiet regions of the electronic device and coupled to compass interface circuitry. 
     Compass interface circuitry may be configured to combine magnetic field data from multiple sensors  20 , generate directional compass data, and provide the compass data to other circuitry. Compass interface circuitry or other control circuitry in device  10  may be configured to store compass calibration data, may be configured to turn compass  30  on and off, may be configured to access information on the operational status of other electronic components, may be configured to apply corrections to compass data based on operational status information (also called status data, operational status data, etc.) associated with other electronic components, may be configured to combine these functions, or to perform any other compass related functions for device  10 . 
     As shown in  FIG. 2 , magnetic sensors  20  may be combined with circuitry such as compass interface circuitry  32  to form compass  30 . Compass interface circuitry  32  may be formed in part on magnetic sensors  20  and in part separately from sensors  20 , or may be formed entirely separately from sensors  20 . 
     Compass interface circuitry  32  may be configured to collect raw magnetic field data from sensors  20  and provide associated compass data to other control circuitry such as storage and processing circuitry  40  of device  10 . Storage and processing circuitry  40  may be configured to deliver compass data from compass  30  to other software applications running on circuitry  40 . 
     As shown in  FIG. 2 , device  10  may include other electronic components  22 . Components  22  may include one or more cameras (e.g., a front-facing camera, a rear-facing camera, etc.), one or more light sources (e.g., a camera flash, an LED camera light, a flashlight, etc.) or other components that generate magnetic fields that may interfere with detection of the Earth&#39;s magnetic field. Sensors  20  may be positioned within device  10  in relatively magnetically quiet regions of the device (e.g., away from components  22  or near a battery for the device). 
     Device  10  may include control circuitry such as storage and processing circuitry  40 . Storage and processing circuitry  40  may include storage such as hard disk drive storage, non-volatile 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 storage and processing circuitry  40  and other control circuits such as control circuits in compass  30  may be used to control the operation of device  10 . This processing circuitry may be based on one or more microprocessors, microcontrollers, digital signal processors, baseband processors, power management units, audio codec chips, application specific integrated circuits, etc. 
     Storage and processing circuitry  40  may be used to run software on device  10 , such as internet browsing applications, map applications, voice-over-internet-protocol (VoIP) telephone call applications, email applications, media playback applications, operating system functions, camera functions, camera based applications, light source functions, display functions, GPS operations, etc. 
     Some applications may use combined data from compass  30  and a positioning sensor such as inertial measurement unit (IMU)  44 . Inertial measurement unit  44  may include one or more accelerometers, one or more gyroscopes, GPS circuitry, etc. for determining the location and position of device  10 . Storage and processing circuitry  40  may be configured to operate IMU  44  in combination with compass  30  to provide position and location information to applications running on device  10 . 
     Storage and processing circuitry  40  may be used to operate power management unit (PMU)  38  to supply electrical power to components  22  such as camera  34  and light source  36 . Storage and processing circuitry  40  may be used to operate input/output components such as input/output components  42  and to process and store data input to device  10  using input/output components  42 . 
     Input/output components  42  may include buttons or speakers such as button  16  and speaker  18  of  FIG. 1 . Input/output components  42  may include touch-sensitive portions of display  14 , may include a keyboard, wireless circuitry such as wireless local area network transceiver circuitry and cellular telephone network transceiver circuitry, and other components for receiving input and supplying output. Components  22  may be internal to device  10  or may have portions that are visible on a portion of an exterior surface of device  10 . 
     Control circuitry such as storage and processing circuitry  40  may include circuitry for interfacing with the resources of compass  30  (e.g., control circuitry of compass interface circuitry  32  may be considered to form part of storage and processing circuitry  40 ). For example, control circuitry  40  may be configured to run a compass interface software application that interfaces with compass  30 . 
     As shown in  FIG. 3 , device  10  may include magnetic sensors  20  that are attached to portions of housing  12 . In the example of  FIG. 3 , device  10  includes three unidirectional magnetic sensors  20  attached to housing sidewalls  12 S and rear housing portion  12 R. Each unidirectional magnetic sensor  20  may be aligned along a direction that is orthogonal to the other two sensors  20 . For example, one sensor may have an elongated dimension that is aligned along the x-direction of  FIG. 3 , one sensor may have an elongated dimension that is aligned along the y-direction, and one sensor may have an elongated dimension that is aligned along the z-direction. In this way, the magnetic sensors, in combination, may be positioned so that they sample all orthogonal components of the Earth&#39;s magnetic field. However, this is merely illustrative. If desired, device  10  may include multi-directional magnetic sensors (e.g., sensors  20  with sensor elements configured to detect magnetic field components in two or three orthogonal directions). 
     Magnetic field data gathered using three sensors  20  or multiple sensor elements on one or two sensors  20  may be combined (e.g., using compass interface circuitry  32 ) to form directional compass data that includes information associated with the direction in which device  10  is oriented with respect to the Earth&#39;s magnetic field. 
     Magnetic sensors  20  may be relatively thin compared with conventional magnetometers. These thin magnetic sensors may be placed in locations within device  10  that are too small to accommodate a conventional compass chip. Sensors  20  may therefore be located on portions of housing  12  that are relatively far from magnetic field generating electronic components within housing  12 . 
     As shown in  FIG. 4 , one or more sensors  20  may be mounted to a structure such as component  50  within device  10 . Component  50  may, for example, be a battery or other component in device  10  that generates relatively small magnetic fields (e.g., magnetic fields that minimally interfere with the detection of the Earth&#39;s magnetic field). The arrangements of  FIGS. 3 and 4  are merely illustrative. If desired, sensors  20  may be mounted on other components within device  10 , sensors  20  may include bidirectional magnetic sensors, sensors  20  may be mounted on a cover (cowling) structure for a component such as component  50 , or some of sensors  20  may be mounted on portions of housing  12  while other sensors  20  are mounted on a structure such as component  50 . 
       FIG. 5  is a perspective view of component  50  of device  10  showing how a mechanical cowling structure may be formed over at least part of component  50 . In the example in which component  50  is a battery for device  10 , component  50  may have some characteristics that make the surface of component  50  an undesirable location for mounting sensors  20 . For example, a battery may have a curved outer surface or a battery may grow throughout the operating lifetime of a device thereby moving the location of the outer surface of the battery over time. For this reason, a cover structure such as cowling  52  may used to at least partially surround battery  50 . In this way, a flat, stable surface may be provided on which sensors  20  can be mounted. 
     Cowling structure  52  may be formed from metal, plastic, glass, ceramic, composites or other suitable magnetically transparent rigid materials. If desired, structure  52  may include a top portion such as portion  52 T that covers an extended top surface of battery  50  and a side portion  52 S that is orthogonal to top portion  52 T. Side portion  52 S and top portion  52 T may be formed from a common structure that has been folded or bent, or side portion  52 S may be a separate structure that is attached to or mounted adjacent to top portion  52 T. 
     As shown in  FIG. 5 , two sensors  20  may be mounted in orthogonal directions (e.g., parallel to the x and y directions of  FIG. 5 ) on a top surface  52 T and a third sensor  20  may be attached to an orthogonal folded side portion  52 S of structure  52 . However, this is merely illustrative. 
     As shown in  FIG. 6 , structure  52  may include an additional side portion  52 S′ that is orthogonal to both sidewall portion  52  and top portion  52 T. In this way, structure  52  may be provided with three orthogonal surfaces on which three unidirectional magnetic sensors  20  may be mounted. 
     As shown in the top view of magnetic sensor  20  of  FIG. 7 , each sensor  20  may include a magnetic sensing element such as element  58  on a sensor circuitry substrate such as substrate  56 . Sensing element  58  may be arranged so that magnetic fields that are aligned along the direction indicated by arrows  61  generate a response in sensing element  58  that can be detected by circuitry in substrate  56  or other circuitry in device  10 . In this way, sensor  20  may be configured as a unidirectional magnetic sensor. 
     Circuitry substrate  56  may be encapsulated by a substrate material such as substrate  54  that includes conductive lines (traces)  64  and electrical contacts  66 . Substrate  54  may be formed from a suitable flexible circuit material such as polyimide, a rigid substrate material such as a glass-infused epoxy, or other suitable materials or combinations of materials for electronic circuit fabrication. Substrate  56  may, for example, be a silicon substrate that includes circuitry for gathering magnetic field data based on magnetic field signals generated in magnetic sensing element  58 . 
     Sensor  20  may have a lateral width W that is less than 2 mm, less than 1 mm, between 1 mm and 2 mm, between 0.5 mm and 1.5 mm, greater than 0.1 mm, or less than 5 mm. Magnetic sensing element  58  may have a lateral width that is less than 20 microns, less than 10 microns, less than 8 microns, between 10 microns and 20 microns, between 5 microns and 20 microns, greater than 0.5 microns, or less than 12 microns. 
     Electrical contacts  66  may be attached to a printed circuit board, to another flexible printed circuit, or to other circuitry within device  10 . Traces  64  may be used to route magnetic field data from substrate  56  to other device circuitry such as compass interface circuitry  32  ( FIG. 2 ). 
     In some situations, environmental changes other than magnetic fields (e.g., temperature changes) around magnetic sensor  20  may cause changes in magnetically sensitive material in magnetic sensing element  58 . In order to help detect and remove noise signals due to these environmental changes, sensor  20  may be provided with a reference sensor element such as sensor element  60 . Sensor element  60  may be formed using magnetically sensitive material as in sensing element  58  that is shielded from external magnetic fields such as the Earth&#39;s magnetic field. Changes in magnetic field signals from reference sensing element  60  may be removed from magnetic field signals gathered using sensing element  58 . 
     As shown in the cross-sectional side view of magnetic sensor  20  of  FIG. 8 , magnetic sensing element  58  may be formed on top of (or partially or completely embedded within) circuitry substrate  54 . Substrate  56  may be mounted on a bottom layer of substrate  54 L and may be covered by additional substrate material  54 T. 
     Conductive traces  64  may be formed between top and bottom layers  54 T and  54 B of substrate material  54 . Each conductive trace  64  may include an exposed portion (i.e., a portion that is substantially free of s material) that serves as a conductive contact  66 . An opposing end of trace  64  may be coupled to conductive traces such as traces  55  in substrate  56 , thereby coupling magnetic sensing element  58  to contacts  66 . Conductive traces  64  may be formed from a magnetically transparent material such as copper so that traces  64  do not interfere with magnetic fields in the vicinity of sensor  20 . 
     Substrate  56  may include circuitry such as circuitry  57  for processing magnetic field signals received from magnetic sensing element  58 . For example, in configurations in which substrate  56  is provided with one or more magnetic sensing elements  58  and one or more reference sensing elements  60 , circuitry  57  may be used to modify magnetic field signals from element(s)  58  using magnetic field signals from element(s)  60  (e.g., by removing effects due to changes in the temperature of substrate  56  from magnetic field signals gathered by the element(s)  58 ). However, this is merely illustrative. If desired, magnetic field signals from elements  58  and  60  may be provided to additional circuitry such as processing circuitry  40  ( FIG. 2 ) without modifications. 
     Sensor  20  may be a relatively thin sensor having a characteristic maximum height H along a dimension that is perpendicular to a surface of sensor  20  and passes through substrate  56  and element  58 . As examples, height H may be less than 150 microns, less than 100 microns, less than 80 microns, between 80 and 150 microns, between 50 and 100 microns, or between 40 and 200 microns. 
     Sensors  20  may be provided with this type of thin height H by, for example, forming a magnetic sensor on a substrate, attaching a temporary carrier to the substrate, back-thinning the substrate (e.g., by etching a backside of the substrate that is opposite to the side on which the magnetic sensor is formed), removing the temporary carrier (e.g., by chemically detaching the carrier or releasing the carrier using ultraviolet radiation), and encapsulating the back-thinned substrate in flexible printed circuit material. However, this is merely illustrative. Sensor  20  may be formed using any suitable combination of these steps, or other suitable packaging techniques. 
     If desired, the height of sensor  20  may be further reduced, for example, by providing substrate  56  with a recessed portion for receiving printed circuit  54 , as shown in  FIG. 9 . In the example of  FIG. 9 , a portion of substrate  56  has been removed so that extended portion  74  of substrate  56  can interface with an extended portion such as portion  75  of substrate  54 . In this way, substrate  56  may be provided without any top layer of printed circuit material. 
     In a configuration of the type shown in  FIG. 9 , substrate  56  may be provided with conductive traces (e.g., copper traces)  76  that extend from magnetically sensitive element  58  onto extended portion  74  and connect to electrical contacts  78  on extended portion  74 . Electrical contacts  78  may be coupled to traces  64  in substrate  54 . However, this is merely illustrative. If desired, conductive traces within substrate  56  may couple sensor element  58  to circuitry within substrate  56  and/or to contacts  78 . 
     By providing substrate  54  and substrate  56  of sensor  20  with interfacing extended portions of the type shown in  FIG. 9 , the height of sensor  20  may be reduced to a height H′ that is less than 80 microns, less than 60 microns, less than 50 microns, between 50 and 100 microns, between 50 and 150 microns, or between 30 and 150 microns. 
       FIG. 10  is a cross-sectional side view of a magnetic sensor such as sensor  20  showing how magnetic sensor element  58  and reference sensor element  60  may be formed on a common surface of substrate  56 . Substrate  56  may include electrical contacts  84  (e.g., exposed portions of a conductive metal layer in substrate  56 ) that are coupled to elements  58  and  60  and circuitry  57 . Conductive lines  55  may be used to provide magnetic field data from elements  58  and  60  to circuitry  57  and/or to conductive traces  64  of printed circuit  54 . 
     As shown in  FIG. 10 , both magnetic sensor element  58  and reference sensor element  60  may include magnetic sensor layers  80 . Magnetic sensor layers  80  may include a layer of magnetically sensitive material such as magneto-resistive materials or materials in which voltage differences may be induced by magnetic fields. Magnetic sensor layers may include other layers such as passivation layers, shielding layers, conductive layers, etc. 
     Reference sensor  60  may include one or more additional shielding layers  82  that cover magnetic sensor layers  80  and prevent external magnetic fields from reaching sensor layer  80  in the reference sensor. Shield layer  82  may be formed from magnetically shielding materials such as mu-metals, nickel, or other suitable magnetic field shielding materials or combinations of materials. As shown in  FIG. 10 , if desire, shielding layers  82  may extend under a portion of sensor layers in substrate  56 . 
     In the example of  FIG. 10 , sensor  20  includes one magnetic sensor element  58  and one reference sensor element  60 . However, this is merely illustrative. If desired, sensor  20  may be provided without any reference sensors, or sensor  20  may be provided with more than one magnetic sensor element and/or more than one reference sensor element. 
     As shown in  FIG. 11 , sensor  20  may be provided with two magnetic sensor elements. Sensor  20  may include a first sensor element  58  that is configured to detect magnetic field components along a direction parallel to arrows  61  and a second sensor element  58  that is configured to detect magnetic field components along an orthogonal direction that is parallel to arrows  61 ′. In this way, sensor  20  may be configured as bidirectional magnetic field sensor (i.e., a sensor that can detect magnetic field components in two orthogonal directions). 
     As shown in  FIG. 12 , a bidirectional magnetic field sensor  20  may also include a shared reference sensor  60 . Signals from a first sensor element  58  and element  60  may be combined (e.g., subtracted) and digitized (e.g., using circuitry  57  in substrate  56  or other circuitry in device  10 ). Signals from a second sensor element  58  and element  60  may be combined (e.g., subtracted) and digitized (e.g., using circuitry  57  in substrate  56  or other circuitry in device  10 ). If desired, combined signals from each sensor  58  and the shared reference sensor element  60  may be digitized using a common, shared analog-to-digital converter circuit. However, the example of  FIG. 12  in which sensor  20  is implemented as a bidirectional magnetic sensor having a shared reference sensor is merely illustrative. 
     As shown in  FIG. 13 , sensor  20  may be implemented as a bidirectional magnetic sensor with multiple reference magnetic sensor elements  60 . If desired, magnetic field signals from each magnetic sensor element  58  may be modified (corrected) using magnetic field signals from an associated reference sensor element  60  on substrate  56 . 
       FIG. 14  is a cross-sectional side view of a portion of magnetic sensor  20  showing various layers that may be used to form sensor layers  80  of magnetic sensor element  58 . As shown in  FIG. 14 , sensor layers  80  may include shield layer  90  formed on a surface of substrate  56 . Shield layer  90  may be formed from a magnetically shielding material such as mu-metal or nickel. If desired, shield layer  90  may be electrically isolated from contacts  84  (e.g., by including an insulating layer or an insulating coating between layer  90  and contacts  84 ). Passivation layer  92  may be formed over shield layer  90 . Passivation layer  92  may be formed from any suitable dielectric material such as a vapor deposited dielectric or other dielectric material. 
     A layer of magnetically sensitive material such as ferromagnetic material, magneto-resistive material, Hall-effect material, or other magnetically sensitive material may be formed over shield layer  90  and passivation layer  92 . Shield layer  90  and passivation layer  92  may be provided with openings that allow magnetic material  94  to be formed in contact with electrical contacts  84  on substrate  56 . Magnetic fields may be detected by, for example, detecting changes in current that flows through material  94  from a first contact  84  to a second contact  84 . 
     A second (upper) passivation layer  96  may be formed over magnetic material  94  that substantially covers material  94 . 
     As shown in  FIG. 15 , a reference magnetic field sensor element  60  may be formed by forming an additional layer of magnetically shielding material such as shield layer  98  over passivation layer  96 . In this way, magnetic material  94  of element  60  may be surrounded by magnetically shielding material and thereby prevented from being affected by external magnetic fields. 
     The examples in the preceding figures in which one or more magnetic sensor elements  58  and one or more reference sensor elements  60  are formed separately on a surface of substrate  56  are merely illustrative. If desired, elements  58  and elements  60  may be formed having other configurations on the surface of substrate  56  or may be partially or completely embedded within substrate  56 . 
     In the example of  FIG. 16 , sensor  20  includes a magnetic sensor element  58  and a reference sensor element  60  that are interleaved on the surface of substrate  56 . An interleaved pair of sensor elements  58  and  60  of this type may be formed by forming an interleaved pattern of magnetic material  94  on substrate  56  (or on a passivation layer on substrate  56 ) and forming shielding material  98  over a portion of the interleaved magnetic material  94 . 
     In the example of  FIG. 17 , magnetic sensor element  58  and reference sensor element  60  are embedded within substrate  56 . In this type of configuration, sensor element  58  and sensor element  60  may be formed from a patterned layer of magnetically sensitive material that forms a portion of a layer within substrate  56 . Reference sensor element  60  may be partially or completely surrounded by shielding material  98 . Shielding material  98  may include a top shielding layer  98 T formed on a top surface of substrate  56 , a bottom shielding layer formed on an opposing bottom surface of substrate  56  and embedded vertical shielding layers  98 V that extend from the top surface to the opposing bottom surface of substrate  56 . 
     Vertical shielding layers  98 V may be formed by forming openings in substrate  56  (e.g., by laser drilling or mechanical drilling) and filling the openings with magnetically shielding material (e.g., mu-metal). Vertical shielding layer  98 V may be formed in contact with top shield layer  98 T and bottom shield layer  98 B so that magnetically sensitive material in reference sensor element  60  is surrounded by shielding material so that the magnetically sensitive material is blocked from exposure to external magnetic fields. 
     As shown in  FIG. 18 , sensor  20  may be provided with three magnetic sensor elements. Sensor  20  may include a first sensor element  58  that is configured to detect magnetic field components along a direction parallel to arrows  61 , a second sensor element  58  that is configured to detect magnetic field components along an orthogonal direction that is parallel to arrows  61 ′, and a third sensor element  58  that is configured to detect magnetic field components along another orthogonal direction that is parallel to arrow  61 ″. In this way, sensor  20  may be configured as tri-directional (three-axis) magnetic field sensor (i.e., a sensor that can detect all components of a magnetic field in three orthogonal directions). 
     If desired, a tri-directional magnetic field sensor of the type shown in  FIG. 18  may include one or more reference magnetic sensor elements such as reference sensor element  60 . Reference sensor element  60  may be a shared reference sensor  60  for two or more of sensor elements  58  (i.e., reference signals from sensor element  60  may be used to correct magnetic field signals from more than one of sensor elements  58 ) or sensor  20  may include three reference sensor elements  60  each of which is used to correct magnetic field signals from an associated one of sensor elements  58 . If desired, combined signals from each sensor  58  and a shared reference sensor element  60  may be digitized using a common, shared analog-to-digital converter circuit. 
     The foregoing is merely illustrative of the principles of this invention and various modifications can be made by those skilled in the art without departing from the scope and spirit of the invention.

Metadata:
Filing Date: 20130307
Publication Date: 20170530
Grant Date: 20170530
Priority Date: 20120828
Inventors: YANG HENRY H.
LEE CHIAJEN
ARNOLD SHAWN XAVIER
Assignee: APPLE INC
CPC Classifications: [{"code": "G01R33/02", "inventive": true, "first": true, "tree": "[]"}, {"code": "G01R33/0206", "inventive": true, "first": false, "tree": "[]"}, {"code": "G01C17/28", "inventive": true, "first": false, "tree": "[]"}, {"code": "G01R33/02", "inventive": true, "first": true, "tree": "[]"}, {"code": "G01C17/28", "inventive": true, "first": false, "tree": "[]"}, {"code": "G01C17/28", "inventive": true, "first": false, "tree": "[]"}, {"code": "G01R33/0206", "inventive": true, "first": true, "tree": "[]"}, {"code": "G01R33/0206", "inventive": true, "first": false, "tree": "[]"}]
Family ID: 50186637