PATENT DOCUMENT

Publication Number: US-9671889-B1
Application Number: US-201414340138-A
Country: US
Kind Code: B1

Title: Input member with capacitive sensor

Abstract:
Input members with capacitive sensors are disclosed. In one embodiment of an electronic button, a first circuit is configured to capture a fingerprint of a user&#39;s finger placed on the electronic button, and a second circuit is configured to sense a force applied to the electronic button by the user&#39;s finger. The first circuit is further configured to provide temperature information to compensate for temperature sensitivities of the second circuit, and the second circuit is further configured to provide force information to the first circuit.

Claims:
What is claimed is: 
     
       1. An electronic button, comprising:
 a first circuit configured to capture a fingerprint of a user&#39;s finger placed on the electronic button; and 
 a second circuit configured to sense a force applied to the electronic button by the user&#39;s finger; 
 wherein the first circuit is further configured to provide temperature information to compensate for temperature sensitivities of the second circuit, and the second circuit is further configured to provide force information to the first circuit. 
 
     
     
       2. The electronic button of  claim 1 , wherein the temperature information is provided to a third circuit, the third circuit being configured to correct the sensed force using the temperature information. 
     
     
       3. The electronic button of  claim 1 , wherein the first circuit is configured to determine when to sense a fingerprint based on the force information provided by the second circuit. 
     
     
       4. The electronic button of  claim 1 , wherein the electronic button is mechanically decoupled from a housing surrounding the electronic button. 
     
     
       5. The electronic button of  claim 1 , wherein the first circuit comprises a plurality of temperature sensors in a plurality of quadrants of the first circuit. 
     
     
       6. The electronic button of  claim 1 , wherein the first circuit is configured to correct the captured fingerprint responsive to the sensed force being greater than a predefined acceptable force for fingerprint capture. 
     
     
       7. The electronic button of  claim 1 , further comprising a third circuit configured to combine an orientation of the captured fingerprint and the sensed force to provide three dimensional control of an electronic device. 
     
     
       8. The electronic button of  claim 1 , wherein the second circuit is mounted directly on the first circuit. 
     
     
       9. The electronic button of  claim 1 , wherein the second circuit is integrally included within a semiconductor die that also includes the first circuit. 
     
     
       10. The electronic button of  claim 1 , wherein the first circuit comprises a capacitive fingerprint sensor and the second circuit comprises a strain gauge.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims the benefit under 35 U.S.C. §119(e) of U.S. Provisional Patent Application No. 61/858,606, filed Jul. 25, 2013, entitled “Input Member With Capacitive Sensor,” the entirety of which is incorporated herein by reference as if fully disclosed herein. 
    
    
     TECHNICAL FIELD 
     The present invention relates generally to electronic devices, and, more specifically, to input members with capacitive sensors for use in electronic devices. 
     BACKGROUND 
     Electronic devices in use today typically require input from a user in order to, for example, turn the electronic device on or complete some operation. A variety of different mechanisms are in place for receiving input from the user, such as a mechanical button. A mechanical button typically includes a body that is depressed by the user in order to complete an electrical circuit or otherwise trigger a reaction from the device. A restoring force then restores the button back to its original, non-depressed position, until the body is again depressed. Mechanical buttons such as these, however, typically consume a large amount of space in today&#39;s ever-slimming electronic devices. Furthermore, mechanical buttons such as these usually allow only for a binary output—indicating that the button is either depressed or is not depressed—and do not provide a smooth, continuous response. Such a smooth, continuous response is usually precluded by the structure of mechanical buttons as the depressed button either completes an electrical circuit or does not complete the circuit. 
     SUMMARY 
     In one aspect, an electronic button can include a first circuit configured to capture a fingerprint of a user&#39;s finger placed on the electronic button, and a second circuit configured to sense a force applied to the electronic button by the user&#39;s finger. In some embodiments, the first circuit is further configured to provide temperature information to compensate for temperature sensitivities of the second circuit, and the second circuit is further configured to provide force information to the first circuit. The first circuit may be configured to determine when to sense a fingerprint based on the force information provided by the second circuit. Additionally or alternatively, the first circuit can be configured to correct the captured fingerprint responsive to the sensed force being greater than a predefined acceptable force for fingerprint capture. 
     In other embodiments, the temperature information is provided to a third circuit, the third circuit being configured to correct the sensed force using the temperature information. 
     Additionally or alternatively, a third circuit configured to combine an orientation of the captured fingerprint and the sensed force to provide three dimensional control of an electronic device. 
     In another aspect, a method of operating an electronic button includes sensing a force applied to the electronic button using a force sensor, and correcting the sensed force using a temperature measurement. A fingerprint sensor is configured to trigger the force sensor to sense the force responsive to human skin being detected by the fingerprint sensor. The force sensor may be further configured to trigger capturing a fingerprint responsive to sensing a predefined level of force applied to the electronic button. In some embodiments, a user is notified when the sensed force exceeds a predefined level of force at which a fingerprint can be properly captured. 
     In yet another aspect, an electronic device includes an electronic button, where the electronic button includes a rigid body defining a beam and at least one opening adjacent the beam, and a strain gauge coupled to the rigid body. At least one portion of the strain gauge is mounted to the beam and sensitive to strain applied to a longitudinal axis of the beam. In some embodiments, the electronic device also includes a capacitive fingerprint sensor configured to provide a temperature measurement to correct measurements from the strain gauge. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1A  is a front view of an electronic device including an electronic button; 
         FIG. 1B  is a graph showing a continuous response that may be provided by the electronic button of the electronic device of  FIG. 1A ; 
         FIG. 2  is a simplified block diagram of the electronic button of the electronic device in  FIG. 1A ; 
         FIGS. 3A-3C  are simplified flow diagrams illustrating several uses of the electronic button of the electronic device in  FIG. 1A ; 
         FIG. 4  is an exploded view of one embodiment of the electronic button of the electronic device in  FIG. 1A ; 
         FIG. 5  is a bottom view of the electronic button of the electronic device in  FIG. 1A ; 
         FIG. 6A  is a cross-sectional view of the electronic button of the electronic device in  FIG. 1A , taken along line H-H of  FIG. 1A ; 
         FIG. 6B  is another cross-sectional view of the electronic button of the electronic device in  FIG. 1A , taken along line V-V of  FIG. 1A ; 
         FIG. 7  is a simplified schematic view of a strain gauge of the electronic button of the electronic device in  FIG. 1A ; 
         FIG. 8  is a simplified schematic view of a capacitive fingerprint sensor of the electronic button of the electronic device in  FIG. 1A ; 
         FIG. 9  is an exploded view of a second embodiment of the electronic button of the electronic device in  FIG. 1A ; 
         FIG. 10  is a cross-sectional view of the electronic button of the second embodiment of the electronic button shown in  FIG. 9 ; 
         FIG. 11  is an exploded view of a third embodiment of the electronic button of the electronic device in  FIG. 1A ; 
         FIG. 12  is a cross-sectional view of another embodiment of an electronic button; and 
         FIGS. 13A and 13B  are perspective and cross-sectional views of a button assembly. 
     
    
    
     DETAILED DESCRIPTION 
     Embodiments of an input member with a capacitive sensor, such as an electronic button, are described herein.  FIG. 1A  is a front view of an electronic device  100  including one or more electronic buttons  110 . The electronic device  100  may be substantially any type of electronic or computing device, such as, but not limited to, a computer, a laptop, a tablet, a smart phone, a digital camera, a printer, a scanner, a copier, or the like. The electronic device  100  may also include one or more components typical of a computing or electronic device, such as, but not limited to, one or more processors, memory components, network interfaces, displays, cameras, and so on. 
     The electronic button  110  allows a user to interact with the electronic device  100 . For example, the electronic button  110  may turn the electronic device  100  on, allow a user to perform some action such as returning to a home screen, and the like. The electronic device  100  may include more than one electronic button  110  in some embodiments, or may include only a single electronic button  110 . The electronic device  100  may also include other input mechanisms, such as a mechanical button, multi-touch capacitive sensing display screen, one or more input/output ports, and so forth. 
     The electronic button  110  may in some embodiments be mechanically decoupled (e.g., isolated) from a housing  103  that surrounds the button  110  on one or more sides of the electronic button  110 , or be decoupled from another part of the body of the electronic device  100 . In other embodiments, the electronic button  110  may not be mechanically decoupled from the housing  103  or body (e.g., may be mechanically coupled to the housing  103 ), or may only be partially decoupled from the housing  103  or body. For example, in some embodiments, the housing  103  may be a glass plate, in which case one or more portions of the electronic button  110  may be integral with the glass plate. 
     As mentioned above, although not explicitly shown in  FIG. 1A , the electronic device  100  may include a number of internal components, such as one or more processors, a storage or memory component, an input/output interface, a power source, and one or more sensors. The one or more processors may control operation of the electronic device  100  (including the electronic button  110  as described herein), and may individually or collectively be in communication with substantially all of the components of the electronic device  100 . The processor may be any electronic device cable of processing, receiving, and/or transmitting instructions. As described herein, the term “processor” is meant to encompass a single processor or processing unit, multiple processors, or multiple processing units, or other suitably configured computing element. 
       FIG. 1B  illustrates a graph demonstrating the response of an electronic button, such as the electronic button  110  illustrated in  FIG. 1A , that has a continuous response to varying levels of force applied to the button. As used herein, continuous refers to a measurement that can take more than two values—for example, a measurement of force that can take one of five, ten, twenty, fifty, a hundred, a thousand, or tens of thousands of different values. The electronic button  110  in  FIG. 1A  may have a continuous response to applied forces, as compared with a mechanical button, which may only be on or off. 
       FIG. 2  is a simplified block diagram of one embodiment of the electronic button  110  of the electronic device  100  in  FIG. 1A . The electronic button  110  in  FIG. 2  includes a first circuit  130  and a second circuit  160 . The first circuit  130  may be configured to capture a fingerprint of a user&#39;s finger placed on the electronic button  110 . The first circuit  130  may include, for example, a capacitive fingerprint sensor. The first circuit  130  may also include one or more temperatures sensors embedded within or positioned external to the first circuit. 
     The second circuit  160  may be configured to sense a force applied to the electronic button  110  by the user&#39;s finger. The second circuit  160  may include, for example, a strain gauge, a capacitive gap sensor, and so forth. In some embodiments, such as when the second circuit  160  is a strain gauge, the second circuit  160  may be susceptible to temperature variations such that the force measurements provided by the second circuit  160  depend not only on the displacement of the electronic button  110 , but also on the ambient temperature around the second circuit  160  or on the temperature of the components of the second circuit  160  themselves. The temperature of the components of the second circuit  160  may change in some embodiments as a result of, for example, the heat from a user&#39;s finger and/or the heat from the first circuit  130  operating, if the first and second circuits  130 ,  160  are positioned in proximity to one another. 
     In some embodiments, and as illustrated in  FIG. 2 , the first circuit  130  may be configured to provide temperature information to compensate for temperature sensitivities of the second circuit  160 . This information may be used by the second circuit  160  to compensate for the temperature dependency of the force measurements. In some examples, the temperature information from the first circuit  130  may be provided to a third circuit (not illustrated in  FIG. 2 ). Such a third circuit may also receive the raw force measurement from the second circuit  160 , and may correct such raw force measurements using the temperature information. In other words, while the temperature information from the first circuit  130  may in some examples be provided directly to the second circuit  160  for the second circuit  160  itself to correct for the temperature dependency of the force measurements, in other examples, the temperature information from the first circuit  130  may be combined with the raw force information from the second circuit  160  in a separate, third circuit, such as a processor, to correct for the temperature distortions. 
     As also illustrated in  FIG. 2 , the second circuit  160  may be configured to provide force information to the first circuit  130  in some embodiments. The force information from the second circuit  160  may be fedback to the first circuit  130  in order to better understand a fingerprint captured by the first circuit  130 . For example, if a user applies a relatively large amount of force to the electronic button  110 , the fingerprint captured by the first circuit  130  may be distorted, or otherwise different than if the user had applied a normal amount of force. Similarly, if not enough force is used to press the electronic button  110 , the ridges and valleys of the fingerprint may not be properly captured by the fingerprint button  110 . The first and second circuits  130 ,  160 , optionally together with a third circuit (not shown), can thus work together to allow a shallower electronic button  110  to be used in an electronic device  100  in place of a conventional mechanical button. The feedback between the first and second circuits  130 ,  160  of the electronic button  110  enables the cooperation of the first and second circuits  130 ,  160 . 
     Turning now to  FIGS. 3A through 3C , flowcharts are shown illustrating a few examples of how the electronic button  110  may be used in operation. 
     With reference to  FIG. 3A , the electronic button  110  may in some examples be configured to estimate an actual force applied to the electronic button  110 . Specifically, the force measurement  302  from the second circuit  160  may be combined with the temperature measurement  304  from the first circuit  130  in order to provide an estimated force  308  with which the electronic button  110  was depressed. Using the estimated force  308 , the electronic button  110  may be able to correct a fingerprint captured using the first circuit  130  if, for example, the sensed force  302  is greater than a predefined acceptable force for fingerprint capture, as also explained in more detail below. 
     In some embodiments, and still with reference to  FIG. 3A , the electronic button  110  may be configured to trigger the second circuit  160  to sense the force applied to the electronic button  110  responsive to human skin (e.g., a finger, palm, etc.) being detected by the first sensor  130 . In order to conserve power, for example, the second circuit  160  may not continuously measure the force applied to the electronic button  110 , but instead may only activate the sensing circuitry of the second circuit  160  if human skin or a finger is detected on the electronic button. In another embodiment, the second circuit  160  may continuously measure the force applied to the electronic button  110 , but may signal a “click” to the electronic device  100  only in the event that a human finger or other portion of human skin is detected on the electronic button  110 . This may reduce accidental activation of the electronic button  110 , particularly when the electronic button  110  is not decoupled from one or more other portions of the electronic device  100 , but also when the electronic button is decoupled from one or more other portions of the electronic device  100 . This may reduce the likelihood that the electronic button  110  would signal a click activation if a pen in a user&#39;s pocket accidentally depresses the button. In still other embodiments, however, the second circuit  160  may continuously measure the force applied to the electronic button  110 , and provide the same to the electronic device  100 , regardless of whether human skin or a human finger is detected by the first circuit  130 . 
     With reference to  FIG. 3B , the electronic button  110  may in some examples be configured to determine when to sense a fingerprint based on the force information provided by the second circuit  160 . Specifically, the force measurement  312  from the second circuit  160  may be combined with a finger detection indication  316  from the first circuit  130  to provide an indication  318  that triggers the first circuit  130  to capture the fingerprint of the user. In some examples, a temperature measurement  314  from the first circuit  130  may optionally be used during this process in order to, for example, correct the force measurement  312  provided by the second circuit  160  for temperature distortions. 
     In one example, if the force measurement  312  from the second circuit  160 , as optionally corrected using the temperature measurement  314 , is within a range of forces at which a fingerprint can be properly captured, the indication  316  may be provided to the first circuit  130  in order to capture the fingerprint. If, on the other hand, the force measurement  312  from the second circuit  160 , as optionally corrected using the temperature measurement  314 , is below a predefined level of force, the electronic button  110  may cause the electronic device  100  to request that the user try again, pressing more firmly on the electronic button  110 . If, however, the sensed force  312  from the second circuit  160 , as optionally corrected using the temperature measurement  314 , exceeds a predefined level of force at which a fingerprint can be properly captured, the electronic button  110  may cause the electronic device  100  to request that the user try again, pressing less firmly on the electronic button  110 . 
     In still other examples, the force measurements  312  may be used in other manners. For example, the force measurements  312  may be monitored such that when the force applied to the electronic button  110  is relatively stable (e.g., is not rapidly varying), the indication  318  is given to capture the fingerprint. Alternatively, the force measurement  312  may be used by the electronic button  110  to compensate for the effect of too much or too little force being used to press the button  110 —for example, if too much force is used, and the force measurement  312  reflects this excess, an algorithm may be applied to a fingerprint that is nonetheless captured by the first circuit  130  in order to compensate for the distortions in the captured fingerprint caused by the excess force. If, for example, the excess force causes the ridges of a fingerprint to be more spaced out and the valleys of the fingerprint to be wider, the force measurement  312  representative of the force applied to the electronic button  110  at that time may be used to adjust the width of the valleys and the spacing of the ridges. 
     In some embodiments, the force sensing accomplished by the second circuit  160  may consume less power and generate less heat than the fingerprint capturing of the first circuit  130 , and thus it may be more economical to measure the force applied to the electronic button  110  at a relatively high sample rate, and only capture a fingerprint when a sufficient, but not excessive, force is applied to the electronic button  110 . The first circuit  130  may nonetheless operate in a limited fashion, for example it may obtain and provide the temperature measurement  314  in order to adjust the force measurements  312  from the second circuit  160  during operation, without necessarily activating the components of the first circuit  130  that actually function to capture the fingerprint (e.g., the capacitive sensing aspects of the first circuit  130 ). 
     With reference to  FIG. 3C , the electronic button  110  may in some examples be configured to provide a 3-dimensional orientation of a user&#39;s finger that is used to depress the electronic button  110 . Specifically, the force measurement  322  from the second circuit  160  may be combined with a finger detection indication  326  from the first circuit  130  in order to provide the 3-dimensional orientation  328 —e.g., the first circuit  130  may provide vertical and horizontal orientation of the finger using the fingerprint ridges and valleys, while the second circuit  160  may provide the depth aspect of the 3-dimensional orientation. The 3-dimensional orientation  328  provided by the electronic button  110  may be used, for example, to control the electronic device  100 —such as controlling a character or other object in a game, or otherwise controlling the navigation within the electronic device  100 . 
     With reference now to  FIG. 4 , an exploded view of one embodiment of an electronic button  110  is shown. The electronic button  110  includes a first circuit  130  and a second circuit  160 , similar to those shown in  FIG. 2  and described above. 
     The first circuit  130  includes a cylindrical member  132 , which may include sapphire, glass, and so forth. The cylindrical member  132  may include a layer of ink  134  positioned on the bottom of the cylindrical member  132 . The first circuit  130  also includes a capacitive fingerprint sensor  138 , which may be embodied in a silicon die with circuitry for detecting and capturing a fingerprint, circuitry for sensing human skin, temperature sensors, and so forth. 
     The electronic button  110  also includes a second circuit  160 , which may include a strain gauge  162 . The strain gauge  162  may generally define a T-shape, and may in some embodiments include four gauge components  164 ,  165 ,  166 ,  167 , as explained in more detail below. The four gauge components  164 ,  165 ,  166 ,  167  may together form a full-bridge, in order to thermally and electrically match the strain gauge  162 . 
     The electronic button also includes trim  112 , which may generally have a ring shape, and may be coupled between the first and second circuits  130 ,  160 . The trim  112  may be a rigid body (comprised, for example, of stainless steel or another hard material), and may define a beam  116  and one or more openings  114 ,  115  adjacent the beam. As illustrated in  FIG. 4 , the capacitive fingerprint sensor  138  may be positioned on an opposite side of the trim  112  from the strain gauge  162 , as described in more detail below with reference to  FIG. 6A , in order to provide thermal insulation and/or electrical shielding between the strain gauge  162  and the capacitive fingerprint sensor  138 . 
     The electronic button  110  may also include a flex circuit  118  configured to be coupled to the first and second circuits  130 ,  160 , and to route signals from the first and second circuits  130 ,  160  to a processor or other portion of the electronic device  100 . 
     As illustrated in  FIG. 4 , the electronic button  110  may be mechanically decoupled from a housing  103  surrounding the electronic button  110 ; however in other embodiments, one or more components of the electronic button  110  (e.g., cylindrical member  132 ) may be integral with the housing  103  of the electronic device  100 . 
     With reference to  FIG. 5 , which is a bottom view of the embodiment of an electronic button  110  shown in  FIG. 4 , the strain gauge  162  of the second circuit  160  may be coupled to the rigid body of the trim  112 . More specifically, in one example, an elongated trunk of the T-shaped strain gauge  162  including NE and SE gauge components  164 ,  165  may be mounted to the beam  116  of the trim  112 . One or more of the NE, SE gauge components  164 ,  165  may be sensitive to strain applied to a longitudinal axis of the beam. In this example, NE gauge component  164  may be sensitive to strain applied to the longitudinal axis of the beam, whereas SE gauge component  165  may be sensitive to strain applied to the vertical axis of the beam. Due to their proximity to one another and their common location on the beam  116 , the NE gauge component  164  and the SE gauge component  165  may both be subject to similar temperature variations. Thus, the NE gauge component  164  is sensitive to strain applied along the horizontal axis of the beam  116  and also to temperature variations, while the SE gauge component  165  is not sensitive to strain applied along the horizontal axis of the beam  116  but is sensitive to temperature variations. Signals generated by the SE and NE gauge components  164 ,  165  can thus be combined in order to provide a first level of temperature correction, however the temperature sensors in the first circuit  130  can further be used to compensate for the temperature sensitivities of the strain gauge  162 . 
     Still with reference to  FIG. 5 , NW and SW gauge components  166 ,  167  of the strain gauge  162  may also be coupled to the rigid body of the trim  112 , but they may not be sensitive to displacement of the electronic button  110 . Instead, the NW, SW gauge components  166 ,  167  may be used to electrically match the NE, SE gauge components  164 ,  165 . 
     As mentioned above, the trim  112  may include one or more openings  114 ,  115 , which may facilitate communication of signals between the strain gauge  162  and the capacitive fingerprint sensor  138 , and also may allow a single flex circuit  118  to be used to route signals from both the strain gauge  162  and the capacitive fingerprint sensor  138  to another location of the electronic device  100 , such as a processor. As illustrated for example in  FIG. 5 , a plurality of through silicon vias (TSVs)  120  of the capacitive fingerprint sensor  138  may be positioned near one of the openings  115  in the trim  112 , such that signals E, N, S, W from the strain gauge  162  may be provided to the capacitive fingerprint sensor  138  and also to the flex circuit  118 . Signals from the capacitive fingerprint sensor  138  may also be provided to the strain gauge  162  and/or to the flex circuit  118  through the one or more openings  114 ,  115 , as shown in  FIG. 5 . In other words, the flex circuit  118  may be coupled to the capacitive fingerprint sensor  138  through the opening  115  of the trim  112  and also coupled to the strain gauge  162 . 
     As illustrated in  FIG. 5 , one or more components of the strain gauge  162  may be adjusted. For example, region  158  in  FIG. 5  illustrates a region  158  where one or more strain gauge  162  components can be laser trimmed in order to provide electrical matching between two or more portions of the strain gauge, in order for the strain gauge to properly function as a full bridge with good cancellation. The region  158  may be trimmed after the strain gauge  162  is mounted to the trim  112  in some examples. 
     As also illustrated in  FIG. 5 , in some examples, the NW, SW gauge components  166 ,  167  may be interdigitated in order to increase the thermal and strain matching. 
       FIG. 6A  illustrates a cross-sectional view of the electronic button  110  shown in  FIGS. 4 and 5 , taken along line H-H of  FIG. 1A , and  FIG. 6B  illustrates a cross-sectional view of the electronic button  110  shown in  FIGS. 4 and 5 , taken along line V-V of  FIG. 1A . With reference to both  FIGS. 6A and 6B , the cylindrical member  132  and ink layer  134  are coupled to the trim  112  via adhesive  136 . The ink layer  134  is also coupled to the capacitive fingerprint sensor  138  through adhesive  140 , and the capacitive fingerprint sensor  138  is coupled to the trim  112  through adhesive  142 . The strain gauge  162  is coupled to the beam  116  of the trim  112  through adhesive  161 . Also, flex circuit  118  is coupled to one or more TSVs of the capacitive fingerprint sensor  138  through adhesive  144 , and trim  112  is moveable within housing  103  via shim member  104 . 
     As can be seen in  FIGS. 6A and 6B , the trim  112  allows some separation between the capacitive fingerprint sensor  138  and the strain gauge  162 . Such separation may provide a thermal buffer and/or an electrostatic shield between the capacitive fingerprint sensor  138  and the strain gauge  162 . The trim  112 , however, provides stiffness, with the beam  116  dissipating some of the pressure applied to the electronic button  110 , and the openings  114 ,  115  in the trim facilitating communication of signals and measurements between the first and second circuits  130 ,  160 . 
       FIG. 7  illustrates a full bridge, including all of the NE, SE, SW, NW components  164 ,  165 ,  166 ,  167  of the strain gauge  162 . The full bridge strain gauge  162  provides many benefits, including helping eliminate errors due to the flex circuit  118  and wire or trace bond connection resistances. In other embodiments, however, a quarter or half bridge could be used with a single or only two components of a strain gauge  162 , in which case the first circuit can still provide temperature correction information in order to correct the temperature dependency of the measurements of force by the strain gauge  162 . 
       FIG. 8  illustrates a top view of a capacitive fingerprint sensor  138  of the first circuit  130 , with a plurality of different quadrants  139 -A,  139 -B,  139 -C,  139 -D,  139 -E,  139 -F,  139 -G,  139 -H,  139 -I. In some embodiments, each of the plurality of quadrants  139 -A,  139 -B,  139 -C,  139 -D,  139 -E,  139 -F,  139 -G,  139 -H,  139 -I includes one or more temperatures sensors. 
     The layout of the capacitive fingerprint sensor  138  may be such that its various components are arranged in order to provide a substantially uniform temperature gradient of the capacitive fingerprint sensor adjacent the beam  116  of the trim  112 . So, for example, relatively “cool” digital components of the capacitive fingerprint sensor  138  may be positioned in quadrants  139 -F,  139 -G,  139 -H, and  139 -I so that the temperature gradient along those quadrants is minimized. In another example, the “warm” analog components of the capacitive fingerprint sensor  138  may be evenly distributed among quadrants  139 -F,  139 -G,  139 -H, and  139 -I in order to reduce the temperature gradient therealong. 
     Minimizing the temperature gradient along the NE and SE components  164 ,  165  of the strain gauge  162  may allow the SE component  165  to better cancel out the thermal dependency of the NE component  164 , because both SE, NE components  164 ,  165  will be subjected to similar thermal conditions. If, on the other hand, quadrants  139 -F and  139 -G were much warmer or much cooler than quadrants  139 -H,  139 -I, the effectiveness of the thermal cancellation between the NE and SE components  164 ,  165  of the strain gauge  162  may be reduced. 
     As mentioned above, and with reference still to the quadrants  139 -A,  139 -B,  139 -C,  139 -D,  139 -E,  139 -F,  139 -G,  139 -H,  139 -I illustrated in  FIG. 8 , one or more temperature sensors may be included in each of the quadrants quadrants  139 -A,  139 -B,  139 -C,  139 -D,  139 -E,  139 -F,  139 -G,  139 -H,  139 -I in order to, for example, measure and correct for any temperature gradient that nonetheless exists in the capacitive fingerprint sensor  138 . 
     With reference to  FIGS. 9 and 10 , another embodiment of an electronic button  910  is shown. The electronic button  910  illustrated in  FIGS. 9 and 10  is similar to the electronic button  110  shown and described above, except that the strain gauge  962  is mounted directly to the capacitive fingerprint sensor  938 . 
     With reference to  FIG. 11 , another embodiment of an electronic button  1110  is shown. The electronic button  1110  illustrated in  FIG. 11  is similar to the electronic button  110  shown and described above, except that the second circuit  1160  (including the strain gauge, for example) is integrally included within a semiconductor die that also includes capacitive fingerprint sensor  1139 . In this manner, a single semiconductor die can include circuitry for performing the functions of both the first and second circuits  130 ,  160  described above. 
       FIG. 12  illustrates another embodiment of an electronic button, with a stacked die configuration. It should be appreciated that the embodiment shown in  FIG. 12  is oriented such that the exterior surface of the button (or other input element) is at the bottom of the figure. 
     The sensor circuit  1201  is shown bonded to a control circuit  1203  via bond  1202 , which may be an adhesive. The sensor circuit  1201  may likewise be bonded to flex circuit  1208  by an adhesive or the like. As also shown, the sensor circuit may be positioned adjacent the button, which may be generally cylindrical in shape (although this shape is not necessary). 
     Wire bonding  1206  connects the flex circuit  1208  to the control circuit  1203 , and the wire bonding  1206  is encapsulated by rigid encapsulant  1210  and secondary compliant encapsulant  1212  to protect the wire bonding  1206 . The wire bonding  1206  is seated underneath locally thinned stiffener  1214  (with respect to the orientation shown in  FIG. 12 ), and a second flex circuit  1218  is positioned between stiffener  1214  and switch  1226 . A complaint encapsulant may fill at least a portion of the space between the stiffener  1214  and one or more of the flex  1208 , encapsulant  1210 , and control circuit  1203 . The stiffener may be locally thinned to form a cavity or depression in which the wire bond and/or rigid encapsulant may be at least partially located. 
       FIG. 13A  illustrates a button assembly embodiment, with switch  1326  and trim  1330 , and  FIG. 13B  is a corresponding cross-sectional representation taken along plane P 13 B in  FIG. 13A .  FIG. 13B  illustrates sensor circuit to flex circuit wire bonds at  1340  and further sensor circuit to control circuit  1303  wire bonds at  1345 . The sensor circuit to flex circuit wire bonds  1340  as disclosed in this embodiment carry signals to the underside of the die, where the wires are bonded to the flex circuit  1308  inset from the die perimeter. 
     The foregoing description has broad application. For example, while examples disclosed herein may focus on a strain gauge type of force sensing circuit, it should be appreciated that the concepts disclosed herein may equally apply to substantially any other type of force sensing circuit with or without appropriate modifications as would be appreciated by one skilled in the art of input members for electronic devices. Moreover, although certain examples have been described with reference to particular figures, it will be understood that other embodiments are also within the scope of this disclosure and the appended claims. 
     As another example of an alternate embodiment, in some examples a force concentrator may be coupled between the capacitive fingerprint sensor and the strain gauge, and may translate motion of the fingerprint sensor into deflection of the strain gauge, thereby indirectly causing strain. In this manner, strain can be applied in a localized area, which can allow for a very small strain gauge to be used, which may be more accurate and sensitive than a relatively larger strain gauge. This also may allow for thermal separation (e.g., air) between the capacitive fingerprint sensor and the strain gauge. 
     Accordingly, the discussion of any embodiment is meant only to be exemplary and is not intended to suggest that the scope of the disclosure, including the claims, is limited to these examples.

Metadata:
Filing Date: 20140724
Publication Date: 20170606
Grant Date: 20170606
Priority Date: 20130725
Inventors: MILLER THAYNE M.
BUSSAT JEAN-MARIE
HOTELLING STEVEN P.
COHEN SAWYER I.
CATER TYLER B.
Assignee: APPLE INC
CPC Classifications: [{"code": "G06F3/0414", "inventive": true, "first": true, "tree": "[]"}, {"code": "G06F2203/04106", "inventive": false, "first": false, "tree": "[]"}, {"code": "G06F2203/04105", "inventive": false, "first": false, "tree": "[]"}, {"code": "G06F3/044", "inventive": true, "first": false, "tree": "[]"}, {"code": "H03K17/962", "inventive": true, "first": true, "tree": "[]"}, {"code": "G06V40/1306", "inventive": true, "first": true, "tree": "[]"}, {"code": "H03K2217/960755", "inventive": false, "first": false, "tree": "[]"}, {"code": "H03K17/975", "inventive": true, "first": false, "tree": "[]"}, {"code": "H03K17/962", "inventive": true, "first": false, "tree": "[]"}, {"code": "H03K17/975", "inventive": true, "first": false, "tree": "[]"}, {"code": "H03K2217/960755", "inventive": false, "first": false, "tree": "[]"}]
Family ID: 58778644