PATENT DOCUMENT

Publication Number: US-10101857-B2
Application Number: US-201514838959-A
Country: US
Kind Code: B2

Title: Methods for integrating a compliant material with a substrate

Abstract:
A sensor module can include a sensor that is configured to detect any given input or environmental conditions, such as, for example, touch or force inputs. The sensor module can be included in an electronic device. Methods for producing the sensor module are disclosed.

Claims:
What is claimed is: 
     
       1. A method for forming a sensor module, comprising:
 providing a compliant structure that includes a compliant layer between a first protective layer and a second protective layer; 
 forming a first conductive layer on the first protective layer and forming a second conductive layer on the second protective layer; 
 patterning the first conductive layer to form a first conductive electrode and patterning the second conductive layer to form a second conductive electrode aligned with the first conductive electrode, the first conductive electrode and the second conductive electrode forming a capacitor; 
 forming a first adhesive layer that covers the first conductive electrode and a portion of the first protective layer; 
 patterning the first adhesive layer to form a first opening and a second opening in the first adhesive layer; 
 forming a first substrate layer on the first adhesive layer, wherein the first substrate layer includes a first third conductive layer, and the third conductive layer electrically connects to the first conductive layer through the first opening; and 
 producing a first flexible substrate tail from a portion of the first substrate layer, the first flexible substrate tail produced by removing a multi-layer portion of the compliant structure and a portion of the first conductive layer that are aligned with and to one side of the second opening. 
 
     
     
       2. The method of  claim 1 , further comprising:
 forming a second adhesive layer that covers the second conductive electrode and a portion of the second protective layer; 
 patterning the second adhesive layer to form a third opening and a fourth opening in the second adhesive layer; 
 forming a second substrate layer on the second adhesive layer, wherein the second substrate layer includes a fourth conductive layer, and the fourth conductive layer electrically connects to the second conductive layer through the third opening; and 
 producing a second flexible substrate tail from a portion of the second substrate layer, the second flexible substrate tail produced while removing the multi-layer portion of the compliant structure and a portion of the second conductive layer. 
 
     
     
       3. The method of  claim 2 , wherein producing the first and second flexible substrate tails from the portions of the first and second substrate layers further comprises:
 removing a portion of the first substrate layer and the second substrate layer. 
 
     
     
       4. The method of  claim 2 , wherein the first substrate layer comprises a first flexible printed circuit, the second substrate layer comprises a second flexible printed circuit, and the compliant layer comprises a silicone layer. 
     
     
       5. The method of  claim 4 , wherein the first conductive layer and the second conductive layer are each patterned to form a plurality of conductive electrodes, wherein each conductive electrode in the first conductive layer is aligned with a respective conductive electrode in the second conductive layer to form a plurality of capacitors. 
     
     
       6. The method of  claim 2 , wherein:
 forming the first substrate layer comprises forming a third protective layer over the first adhesive layer, the third protective layer having a fifth opening aligned with the first opening and the first conductive electrode; 
 forming the second substrate layer comprises forming a fourth protective layer over the second adhesive layer, the fourth protective layer having a sixth opening aligned with the third opening and the second conductive electrode; 
 wherein the third conductive layer extends through the first opening and the fifth opening and contacts the first conductive electrode, and the fourth conductive layer extends through the third opening and the sixth opening and contacts the second conductive electrode. 
 
     
     
       7. The method of  claim 2 , wherein producing the first flexible substrate tail and the second flexible substrate tail comprises:
 removing portions of the compliant layer, the first conductive layer, the second conductive layer, the first adhesive layer, and the second adhesive layer. 
 
     
     
       8. The method of  claim 2 , wherein the first substrate layer is formed on the first adhesive layer and the second substrate layer is formed on the second adhesive layer using a compressive molding process. 
     
     
       9. The method of  claim 2 , further comprising:
 attaching an interposer flexible circuit to the first flexible substrate tail and the second flexible substrate tail. 
 
     
     
       10. The method of  claim 1 , wherein forming the first substrate layer on the first adhesive layer comprises:
 forming a first layer in the first substrate layer on the first adhesive layer; and 
 forming a second layer in the first substrate layer on the first layer. 
 
     
     
       11. The method of  claim 1 , wherein removing the portion of the compliant structure comprises:
 removing portions of the compliant layer, the first protective layer, and the first conductive layer.

Description:
FIELD 
     The described embodiments relate generally to electronic devices. More particularly, the present embodiments relate to methods for integrating a compliant material with at least one substrate. 
     BACKGROUND 
     Electronic devices include many different electrical, mechanical, and structural components. One example of an electrical component is a sensor, such as a capacitive sensor that can be used to detect a touch or force input applied to a surface of the electronic device. A capacitive sensor typically includes two conductive plates, or electrodes, separated by a gap. In some instances, it is desirable to reduce the thickness or height of the sensor in the z-direction. For example, it can be beneficial to produce a sensor with a reduced height when the sensor is to be positioned in location that has limited space. Additionally or alternatively, the construction of the sensor should permit efficient manufacturing and mass production. 
     SUMMARY 
     A sensor module can include a sensor that is configured to detect any given input or environmental condition, such as, for example, touch or force inputs. The sensor module can be included in an electronic device. In one embodiment, the sensor can include a compliant layer positioned between two substrates. Each substrate can include one or more electrical components, such as conductive electrodes. Each conductive electrode of one substrate can be aligned with a respective electrode in the other substrate. Each pair of conductive electrodes forms a capacitor. In one embodiment, the first and second substrates are flexible printed circuits and the compliant material is a liquid silicone. The sensor module can include one or more substrate tails that extend out from the sensor. In one embodiment, the one or more substrate tails can extend into an opening that is surrounded by the sensor. A conductive structure, such as an interposer flexible circuit, is connected to the end of each substrate tail. 
     The sensor module can be produced using one of several methods. In one embodiment, a method for producing the sensor module includes providing a compliant structure that includes a compliant layer and forming a first substrate layer over a first surface of the compliant structure. A first substrate tail is produced from a portion of the first substrate layer. In one embodiment, the first substrate tail is produced by removing a portion of the compliant structure and at least one layer in the first substrate layer. In some embodiments, a second substrate layer may be positioned over a second surface of the compliant structure, and a second substrate tail can be produced from a portion of the second substrate layer. 
     In another embodiment, a method for producing the sensor module can include providing a first substrate layer and a second substrate layer, where the first and second substrate layers each include one or more electrical components. The first and second substrate layers are separated from each other by a gap. A spacer element can be positioned in the gap between the first and second substrate layers. The spacer element fills only a portion of the gap between the first and second substrate layers. A compliant material may then be injected into the portion of the gap that does not include the spacer element. The spacer element is then removed to produce a first substrate tail from a portion of the first substrate layer and a second substrate tail from a portion of the second substrate layer. 
     In another embodiment, a method for producing the sensor module can include providing a first substrate layer that includes one or more electrical components and providing a compliant structure that includes a compliant layer. The first substrate layer is attached to a first surface of the compliant structure, and a first substrate tail is produced from a portion of the first substrate layer. In some embodiments, the method may include providing a second substrate layer that includes one or more electrical components and attaching the second substrate layer to a second surface of the compliant structure. A second substrate tail can then be produced from a portion of the second substrate layer. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The disclosure will be readily understood by the following detailed description in conjunction with the accompanying drawings, wherein like reference numerals designate like structural elements, and in which: 
         FIG. 1  shows a plan view of one example of an electronic device that can include a sensor; 
         FIG. 2  shows a cross-sectional view of the electronic device taken along line  2 - 2  in  FIG. 1 ; 
         FIG. 3  shows one example of a sensor module; 
         FIG. 4  shows a flowchart of an example method that can be used to produce a sensor module; 
         FIG. 5  shows one example of a sheet of a sensor structure; 
         FIG. 6  shows a plan view of a bottom surface of a liner that is attached to a sensor; 
         FIG. 7  shows a first method for forming a sensor structure and the flexible circuit tails; 
         FIGS. 8A-8C  illustrate the method shown in  FIG. 7 ; 
         FIG. 9  shows a second method for forming a sensor structure and the flexible circuit tails; 
         FIGS. 10A-10C  illustrate the second method shown in  FIG. 9 ; 
         FIG. 11  shows a third method for forming a sensor structure and the flexible circuit tails; 
         FIGS. 12A-12C  illustrate the third method shown in  FIG. 11 ; 
         FIG. 13  shows a fourth method for forming a sensor structure; 
         FIGS. 14A-14F  illustrate one embodiment of the fourth method shown in  FIG. 13 ; and 
         FIGS. 15A-15B  depict another embodiment of the fourth method shown in  FIG. 13 . 
     
    
    
     DETAILED DESCRIPTION 
     Reference will now be made in detail to representative embodiments illustrated in the accompanying drawings. It should be understood that the following descriptions are not intended to limit the embodiments to one preferred embodiment. To the contrary, it is intended to cover alternatives, modifications, and equivalents as can be included within the spirit and scope of the described embodiments as defined by the appended claims. 
     The following disclosure relates to sensor module that includes a sensor configured to detect any given input or environmental condition, such as, for example, touch or force inputs. As one example, the sensor can include a compliant layer positioned between two substrates. Each substrate can include one or more electrical components, such as conductive electrodes. Each conductive electrode of one substrate may be aligned with a respective electrode in the other substrate. Each pair of conductive electrodes forms a capacitor. In one embodiment, the first and second substrates are flexible printed circuits and the compliant material is a liquid silicone. 
     The sensor module can be included in an electronic device. In a particular embodiment the sensor of the sensor module is positioned around an internal periphery of the electronic device. One or more substrate tails extend out from the sensor into the interior of the electronic device. A conductive structure, such as an interposer flexible circuit, is connected to the end of each substrate tail. The conductive structure is used to connect the sensor to another electrical component in the electronic device. For example, the sensor can be operably connected to a processing device through the substrate tail(s). 
     The sensor module can be attached to a support structure in the electronic device with one or more adhesive layers. In one embodiment, the support structure can be a ledge that is attached to the enclosure of the electronic device or integrally formed as a part of the enclosure of the electronic device. Various techniques for producing the sensor module are disclosed herein. 
     These and other embodiments are discussed below with reference to  FIGS. 1-15 . However, those skilled in the art will readily appreciate that the detailed description given herein with respect to these Figures is for explanatory purposes only and should not be construed as limiting. 
     Directional terminology, such as “top”, “bottom”, “front”, “back”, “leading”, “trailing”, etc., is used with reference to the orientation of the Figure(s) being described. Because components of embodiments described herein can be positioned in a number of different orientations, the directional terminology is used for purposes of illustration only and is in no way limiting. When used in conjunction with layers of an electronic component (e.g., a sensor), the directional terminology is intended to be construed broadly, and therefore should not be interpreted to preclude the presence of one or more intervening layers or other intervening features or elements. Thus, a given layer that is described as being formed, positioned, disposed on or over another layer, or that is described as being formed, positioned, disposed below or under another layer may be separated from the latter layer by one or more additional layers or elements. 
       FIG. 1  illustrates a plan view of one example of an electronic device that can include a sensor. The illustrated electronic device  100  is depicted as a wearable electronic device that may provide information regarding time, health, fitness, wellness, messages, video, operating commands, and statuses of externally connected or communicating devices and/or software executing on such devices (and may receive any of the foregoing from an external device). Other embodiments are not limited to a wearable electronic device. For example, an electronic device can be a tablet computing device, a digital music player, a gaming device, a laptop computer, a remote control, a smart telephone, and any other suitable electronic device. 
     An enclosure  102  can form an outer surface or partial outer surface for the internal components of the electronic device  100 . The enclosure  102  at least partially surrounds a display  104  and one or more input/output devices (not shown). The enclosure  102  can be formed of one or more components operably connected together, such as a front piece and a back piece. Alternatively, the enclosure  102  can be formed of a single piece operably connected to the display  104 . The enclosure  102  can be formed of any suitable material, including, but not limited to, plastic and metal. In the illustrated embodiment, the enclosure  102  is formed into a substantially rectangular shape, although this configuration is not required. 
     The display  104  can provide a visual output to the user. The display  104  can be implemented with any suitable technology, including, but not limited to, a multi-touch sensing touchscreen that uses liquid crystal display (LCD) technology, light emitting diode (LED) technology, organic light-emitting display (OLED) technology, organic electroluminescence (OEL) technology, or another type of display technology. In some embodiments, the display  104  can function as an input device that allows the user to interact with the electronic device  100 . For example, the display can include a touch sensing device that allows the display to function as a multi-touch display. 
     In some embodiments, a cover glass  106  can be disposed over a top surface of the display  104  and the electronic device  100 . The cover glass can be a transparent cover glass when the cover glass is disposed over the display (or the portion of the cover glass overlying the display may be transparent). The cover glass  106  may be made of any suitable material, such as glass, plastic, or sapphire. 
     In some embodiments, the electronic device can include one or more sensors that is configured to detect any given input or environmental condition. In one embodiment, a sensor is positioned around an internal periphery of the electronic device. For example, a proximity sensor, a motion sensor, a touch sensor, and/or a force sensor may be included in the electronic device.  FIG. 2  shows a cross-sectional view of the electronic device taken along line  2 - 2  in  FIG. 1 . In the illustrated embodiment, a force sensor  200  is positioned between the enclosure  102  and the cover glass  106 . In particular, the force sensor  200  rests on a ledge  202  of the enclosure  102 . The ledge  202  extends into the interior of the electronic device. In some embodiments, the ledge  202  can be integrally formed as part of the enclosure  102 . Alternatively, in other embodiments the ledge  202  is connected or affixed to the enclosure  102  using any suitable attachment mechanism. For example, the ledge  202  can be affixed to the enclosure  102  using an adhesive, one or more mechanical attachments such as a screw, or by welding the ledge  202  to the enclosure  102 . 
     In the illustrated embodiment, the enclosure includes an opening  204  that corresponds to the shape of the cover glass  106 . The cover glass  106  is disposed in the opening  204 . As shown in  FIG. 2 , a top surface of the cover glass  106  can extend beyond the top surface of the enclosure  102 . In other embodiments, the top surface of the cover glass  106  may be co-planar with or below the top surface of the enclosure  102 . In some embodiments, the force sensor  200  can seal the space or the junction between the top surface of the ledge  202  and the bottom surface of the cover glass  106 . In one embodiment, the force sensor  200  is a continuous sensor that extends completely around the internal perimeter of the electronic device  100 . In another embodiment, the force sensor  200  can be one or more discrete sensors that are disposed at select locations around the internal periphery of the electronic device  100 . 
     The force sensor  200  can include any suitable circuitry or components that support the operations and functionality of the sensor. In a non-limiting example, a first set of conductive electrodes  206  can be formed over (e.g., included in or on) a surface of a substrate layer  208  and a second set of conductive electrodes  210  can be formed over a surface of a second substrate layer  212 . In one non-limiting example, the first and second substrate layers  208 ,  212  can each be a flexible printed circuit. Those skilled in the art will appreciate that different types of substrate layers can be used in other embodiments. 
     The first and second sets of conductive electrodes  206 ,  210  can each include one or more conductive electrodes. Each conductive electrode in the first set of conductive electrodes  206  is aligned and paired with a respective conductive electrode in the second set of conductive electrodes  210 . Each pair of conductive electrodes forms a capacitor. The force sensor  200  is configured to produce changes in capacitance based on a force applied to the cover glass  106 . The capacitance of one or more capacitors in the force sensor  200  may vary when a user applied a force to the cover glass  106 . A processing device (not shown) operably connected to the force sensor  200  can correlate the changes in capacitance to an amount of force (or to changes in force). The user can apply the force to the cover glass  106  with a body part (e.g., a finger) or with a device, such as a stylus. 
     A compliant layer  214  is disposed between the first and second flexible circuit layers  208 ,  212 . The compliant layer  214  can be formed with any suitable material. As one example, the compliant layer  214  is made of a polymer material, such as silicone, but other embodiments are not limited to this configuration. The compliant layer  214  is configured to provide elastic deformation to the sensor  200  based on a touch and/or a force applied to the cover glass  106 . Additionally, in the illustrated embodiment the compliant layer  214  is a dielectric for the one or more capacitors that are formed by the pairs of conductive electrodes in the first and second sets of conductive electrodes  206 ,  210 . 
     The force sensor  200  is attached to the cover glass  106  and to the enclosure  102  using adhesive layers  216 ,  218 , respectively. The first adhesive layer  216  is positioned between the second substrate layer  212  and the bottom surface of the cover glass  106 . The second adhesive layer  218  is positioned between the first substrate layer  208  and the top surface of the ledge  202 . Any suitable adhesive material can be used in the adhesive layers  216 ,  218 . In one embodiment, the first and second adhesive layers  216 ,  218  are pressure sensitive adhesive layers. 
     In other embodiments, the force sensor (as well as any other suitable sensor) can be constructed with different circuitry and/or components. As one example, a force sensor can be implemented as an optical force sensor, a strain gauge, or an ultrasonic force sensor. 
       FIG. 3  shows one example of a sensor module. The sensor module  300  includes the sensor  200  configured a continuous force sensor that extends completely around the internal periphery of the electronic device  100 . An opening  302  is formed in between the inside edges  304  of the sensor  200 . The first substrate layer  208  (not shown) and the second substrate layer  212  (not shown) extend away from an inside edge  304  of the sensor  200  and into the opening  302  to form first and second substrate tails  306 ,  308 , respectively. When the first and second substrate layers  208 ,  210  are flexible printed circuits, the first and second substrate tails  306 ,  308  are flexible circuit tails. The ends of the first and second substrate tails  306 ,  308  connect to an interposer flexible circuit  310 . Although not limited to this construction, the first substrate tail  306  can connect to a top surface of the interposer flexible circuit  310  and the second substrate tail  308  may connect to a bottom surface of the interposer flexible circuit  310 . A connector  312 , such as a board-to-board connector is connected to the interposer flexible circuit  310 . 
     In one embodiment, the second substrate tail  308  is used as a drive tail that is configured to transmit drive signals to the first set of conductive electrodes  206 . The first substrate tail  306  is used to as a sense tail that is configured to receive sense signals from the second set of conductive electrodes  210 . The connector  312  electrically connects the sensor  200  (through first and second substrate tails  306 ,  308 ) to another circuit or component in the electronic device, such as a processing device (not shown). The processing device is configured to receive the sense signals and correlate the changes in capacitance (represented by the sense signals) to an amount of force. 
       FIG. 4  shows a flowchart of an example method that can be used to produce a sensor module. Initially, a sensor structure is formed (e.g., sensor  200  in  FIG. 2 ). When formed, the sensor structure is an uninterrupted structure (e.g., a sheet) that includes multiple layers, such as the layers of the force sensor  200  shown in  FIG. 2 .  FIG. 5  illustrates one example of a sheet of a sensor structure. The sheet of the sensor structure  500  will be cut or singulated into individual sensor modules at a later time in the process. Although the sensor structure  500  is shown in a rectangular-like shape, in other embodiments the sensor structure  500  can have any given shape and/or dimensions. 
     Next, as shown in block  402 , the substrate tails are produced by removing the layers above or below each substrate tail. For example, as is described in more detail in conjunction with  FIGS. 9B and 9C , a spacer element may be positioned between the substrate tails during an injection molding process to form the compliant layer. The substrate tails are produced when the spacer element is removed. In another embodiment, portions of various layers can be cut out of the sensor structure to produce the first and second substrate tails (see e.g.,  FIGS. 7B and 7C ). 
     A conductive structure may then be attached to the ends of the substrate tails (block  404 ). The interposer flexible circuit  310  in  FIG. 3  is one example of a conductive structure. As described earlier, the conductive structure operably connects the sensor module to another circuit or component in an electronic device, such as a processing device (not shown). As one example, the first and second substrate tails (e.g., flexible circuit tails) can be connected to an interposer flexible circuit using surface-mount technology. 
     An adhesive layer can then be formed over a surface of the sensor structure, followed by the removal of portions of the sensor structure and adhesive layer (blocks  406  and  408 ). Removal of the portions of the sensor structure and the adhesive layer produces openings in each sensor (e.g., opening  302  in  FIG. 3 ). In one example, the adhesive layer can be laminated to the surface of the sensor structure, and the inner area of each sensor can be cut out of the sensor structure. In one embodiment, the adhesive layer can be a pressure sensitive adhesive. The adhesive layer aligns with each sensor in the sensor structure when the adhesive layer is formed over the sensor structure before the inner area of each sensor is removed. 
     Next, as shown in block  410 , a liner layer may be attached to the sensor structure. The liner layer includes a liner for each sensor in the sensor structure. A liner can be used to position the sensor and the sensor module in an electronic device. In one embodiment, the liner layer can be laminated to the sensor.  FIG. 6  shows a plan view of a top surface of a liner that is attached to a sensor. The sensor is not visible in  FIG. 6  because the sensor is below the liner  600 . The liner  600  can include one or more optional alignment openings  602  that assist in aligning the sensor properly within the electronic device. For example, in the embodiment shown in  FIG. 2 , the sensor is positioned on the ledge  202 . The one or more optional alignment openings  602  can ensure the sensor is positioned properly on the ledge. 
     The liner  600  may also include an opening  604  that aligns with the connector  312  in  FIG. 3 . The opening  604  provides access to the connector  312  to operably connect the sensor to another circuit or component in the electronic device, such as a processing device (not shown). 
     Returning to block  412  in  FIG. 4 , the sensor structure is cut or singulated to form discrete sensor modules (e.g., sensor module  300  in  FIG. 3 ). Each discrete sensor module can then be positioned in an electronic device and/or connected to other structural elements or components. 
     The sensors and the flexible circuit tails (e.g.,  306 ,  308  in  FIG. 3 ) in a sensor structure (e.g.,  500  in  FIG. 5 ) can be formed or manufactured using one of a variety of techniques. The methods shown in  FIGS. 7-15  are described as including the first and second substrate layers and the patterned compliant layer. However, other embodiments can include additional, fewer, or different layers adjacent to (over or under) a compliant layer. 
       FIG. 7  shows a first method for forming a sensor structure and flexible circuit tails.  FIGS. 8A-8C  illustrate the method shown in  FIG. 7 . The process begins at block  700  by providing a compliant structure. The compliant structure  800  can include a compliant layer  802  positioned between two protective layers  804  (see  FIG. 8A ). A conductive layer  806  is positioned over each protective layer  804 . In some embodiments, the compliant structure  800  is formed in a manner similar to a flexible copper clad laminate process. Any suitable material can be used to form the compliant layer  802 , the protective layers  804 , and the conductive layers  806 . In one non-limiting example, the compliant layer  802  is formed with silicone, the protective layers  804  are formed with a polyimide material, and the conductive layers  806  are formed with copper. 
     Next, as shown in block  702 , each layer of the multiple layers that form a substrate  807  are assembled or formed over at least one surface of the compliant structure. The substrate is described as a flexible printed circuit in the embodiments shown in  FIGS. 7-15 , although other embodiments are not limited to this configuration. In the embodiment illustrated in  FIG. 8B , the layers of a flexible printed circuit are formed over two opposing surfaces of the compliant structure using a compressive molding process. Initially, the conductive layers  806  are each patterned to form one or more conductive electrodes  808 ,  810 . As described earlier, each conductive electrode (e.g.,  808 ) in one flexible printed circuit is aligned with a respective conductive electrode (e.g.,  810 ) in the other flexible printed circuit to form a capacitor. When a force is applied to the cover glass  106  ( FIG. 2 ), the compliant layer  802  deforms or compresses and the electrodes  808 ,  810  move closer together. When the force is reduced or removed from the cover glass  106 , the compliant layer  802  uncompresses (e.g., expands) and the electrodes  808 ,  810  move away from each other. The movement of the electrodes  808 ,  810  towards and away from each other causes the capacitance of the capacitor to change. These capacitance changes can be correlated to the amount of force applied to the cover glass  106 . 
     Next, an adhesive layer  812  is formed over the compliant structure  800 . The adhesive layers  812  cover the electrodes  808 ,  810  and portions of the protective layers  804 . Any suitable adhesive layer may be used. In the embodiment shown in  FIG. 8B , the adhesive layers  812  have been patterned to include a first opening  814 . A second opening  816  is also formed in the adhesive layers  812  to expose a portion of the electrodes  808 ,  810 . The first and second openings  814 ,  816  can be formed using any suitable technique. 
     A second protective layer  818  is then formed over the adhesive layers  812 . The second protective layers  818  can be formed with the same material or with a different material as the first protective layers  804 . An opening is formed in the second protective layers  818  that aligns with the openings  816  to expose the portion of the electrodes  808 ,  810 . In one embodiment, the first and second openings  814 ,  816  are formed by cutting the adhesive layers  812  and the second protective layers  818  prior to positioning the layers over the compliant structure  800 . In another embodiment, the first and second openings  814 ,  816  are formed by removing (e.g., cutting) the adhesive and second protective layers  812 ,  818  after the layers are positioned over the compliant structure  800 . 
     A second conductive layer  820  is then disposed over the second protective layers  818  and extends into the openings  816  to contact the electrodes  808 ,  810 . A third adhesive layer  822  is formed over the second conductive layers  820 . The third adhesive layers  822  cover the second conductive layers  820  and portions of the second protective layers  818 . An opening  824  is formed in the third adhesive layers  822  to expose a portion of the second conductive layers  820 . The exposed portions of the second conductive layers  820  can be used as contacts that electrically connect the flexible printed circuits to other circuits or components, such as the interposer flexible circuit  310  in  FIG. 3 . 
     A third protective layer  826  is then formed over the third adhesive layers  822 . The third protective layers  826  include an opening that aligns with the opening  824  to expose the portions of the second conductive layers  820 . At this point in the process the sensor structure has been formed (e.g., sensor structure  500  in  FIG. 5 ). 
     Returning to  FIG. 7 , the flexible circuit tails are then produced at block  704 . Portions of the compliant layer  802 , the first protective layers  804 , and the first adhesive layers  812  are removed to produce the first and second flexible circuit tails  306 ,  308  ( FIG. 8C ). As shown in  FIG. 8C , the left edges of the openings  814  correspond to the location where the flexible circuit tails  306 ,  308  begin. In some embodiments, one or more additional processing steps can be performed. For example, the processes associated with blocks  404 ,  406 ,  408 ,  410 , and/or  412  may be performed. 
     The sensor structure and flexible circuit tails include a sensing portion  828  and a signal portion  830 . The sensing portion  828  includes the electrodes  808 ,  810  that form the one or more capacitors. The signal portion  830  includes the first and second flexible circuit tails  306 ,  308  and contacts  832 ,  834 . In one embodiment, the flexible circuit tail  308  transmits the drive signals to the bottom electrode of each capacitor and the flexible circuit tail  306  transmits the sense signals from the top electrode of each capacitor. A processing device (not shown) can cause the drive signals to be transmitted to the electrode(s) and may receive the sense signals from the electrode(s). The processing device is configured to correlate the sense signals into values representing the amounts of applied force. 
       FIG. 9  shows a second method for forming a sensor structure and flexible circuit tails.  FIGS. 10A-10C  illustrate the method shown in  FIG. 9 . Initially, as shown in block  900 , one or more flexible printed circuits are provided. In the embodiment illustrated in  FIG. 10A , two flexible printed circuits  1000  each include a sensing portion  1002  and a signal portion  1004 . Like the embodiment shown in  FIG. 8C , the sensing portion  1002  includes the electrodes  1006 ,  1008  that form the one or more capacitors. The signal portion  1004  includes the first and second flexible circuit tails  306 ,  308  and contacts  1010 ,  1012 . 
     Each sensing portion  1002  includes a first protective layer  1014 , a second protective layer  1016 , a first conductive layer  1018  (including contact  1012 ) and a first adhesive layer  1020  positioned between the first and second protective layers  1014 ,  1016 , a third protective layer  1022 , and a second conductive layer  1024  (including the electrodes  1006 ,  1008  and contact  1010 ) and a second adhesive layer  1026  positioned between the second and third protective layers  1016 ,  1022 . The first conductive layer  1018  extends into a first opening in the second protective layer  1016  to contact the electrodes  1006 ,  1008  (e.g., part of second conductive layer  1024 ). The first adhesive layers  1020  cover the first conductive layer  1018  and portions of the second protective layers  1016 . The second adhesive layers  1026  cover the third protective layers  1022 . 
     Each signal portion includes the first protective layer  1014 , the second protective layer  1016 , the first conductive layer  1018  and the first adhesive layer  1020  positioned between the first and second protective layers  1014 ,  1016 , and the second conductive layer  1024 . In the first flexible circuit tail  306 , the first conductive layer  1018  extends into a second opening in the second protective layer  1016  to contact the contact  1010  (e.g., part of second conductive layer  1024 ). 
     Returning to  FIG. 9 , a compliant layer is formed between the flexible printed circuit structures  1000  using injection molding (block  902 ). The flexible printed circuits  1000  are positioned in a mold (not shown) with a spacer element  1028  disposed between the signal portions  1004  (see  FIG. 10B ). The material that forms the compliant layer  1030  is then injected into the mold and fills the space between the sensing portions  1002  and the spacer element  1028 . A sensor structure is then removed from the mold (e.g., sensor structure  500  in  FIG. 5 ). 
     Next, as shown in block  904 , the flexible circuit tails  306 ,  308  are produced. In the embodiment shown in  FIG. 10C , the spacer element  1028  is removed to produce the first and second flexible circuit tails  306 ,  308 . Like the embodiment shown in  FIG. 8C , the sensor structure and flexible circuit tails include a sensing portion  1032  and a signal portion  1034 . The sensing portion  1032  includes the electrodes  1006 ,  1008  that form the one or more capacitors. The signal portion  1034  includes the first and second flexible circuit tails  306 ,  308  and the contacts  1010 ,  1012 . In some embodiments, one or more additional processes can be performed on the sensor structure. For example, the processes associated with blocks  404 ,  406 ,  408 ,  410 , and/or  412  may be performed. 
       FIG. 11  shows a third method for forming a sensor structure and flexible circuit tails.  FIGS. 12A-12C  illustrate the method shown in  FIG. 11 . Initially, as shown in block  1100 , one or more flexible printed circuits and a compliant structure are provided. In the embodiment illustrated in  FIG. 12A , each flexible printed circuit  1200  includes a first protective layer  1204 , a second protective layer  1206 , a first conductive layer  1208  and a first adhesive layer  1210  positioned between the first and second protective layers  1204 ,  1206 , and a second conductive layer  1212 . The first conductive layer  1208  includes the contact  1214  and the second conductive layers  1212  include the electrodes  1216 ,  1218  and contact  1220 . The first conductive layer  1208  extends into an opening in the second protective layer  1206  to contact the second conductive layer  1212 . The first adhesive layers  1210  cover the first conductive layer  1208  and portions of the second protective layers  1206 . The electrodes  1216 ,  1218  and the contact  1220  are exposed in that they are not covered by one or more additional layers. 
     The compliant structure  1202  includes a compliant layer  1222  positioned between third protective layers  1224 . In some embodiments, hairline cuts (as part of a die cutting process) can be formed in the flexible printed circuits  1200  and the compliant structure  1202  to define the locations where portions of the flexible printed circuits  1200  and the compliant structure  1202  will be removed to produce the flexible circuit tails. 
     Next, as shown in block  1102 , the flexible printed circuits are attached to the compliant structure to produce a sensor structure (e.g., sensor structure  500  in  FIG. 5 ). As shown in  FIG. 12B , a second adhesive layer  1226  bonds each flexible printed circuit structure  1200  to a surface of the compliant structure  1202 . In one embodiment, the flexible printed circuits  1200  can be attached to the compliant structure  1202  using a convention flexible printed circuit bonding adhesive, although other embodiments are not limited to this configuration. 
     In the illustrated embodiment, the second adhesive layers  1226  are positioned between the electrodes  1216 ,  1218  and the third protective layers  1224 . Openings  1228  are formed in the second adhesive layers  1226 . The openings  1228  can be formed in the second adhesive layers  1226  before or after the adhesive layers  1226  are formed over the third protective layers  1224 . 
     Next, as shown in block  1104 , the flexible circuit tails are produced. Portions of the compliant layer  1222 , the third protective layers  1224 , and the second adhesive layers  1226  are removed to produce the first and second flexible circuit tails  306 ,  308 . In some embodiments, one or more additional processing steps can be performed. For example, the processes associated with blocks  404 ,  406 ,  408 ,  410 , and/or  412  may be performed. 
     The sensor structure and flexible circuit tails include a sensing portion  1230  and a signal portion  1232 . The sensing portion  1230  includes the electrodes  1216 ,  1218  that form the one or more capacitors. The signal portion  1232  includes the contacts  1214 ,  1220  and the first and second flexible circuit tails  306 ,  308 . As shown in  FIG. 12C , the left edges of the openings  1228  correspond to the location where the flexible circuit tails  306 ,  308  extend out from the sensing portion  1230 . 
     In some embodiments, the sensor can be formed using additive manufacturing or three-dimensional printing techniques.  FIG. 13  shows an additive manufacturing method for forming a sensor structure. The method of  FIG. 13  is described in conjunction with  FIGS. 14 and 15 .  FIGS. 14A-14F  illustrate one embodiment of the fourth method shown in  FIG. 13 , while  FIGS. 15A-15B  depict another embodiment of the fourth method shown in  FIG. 13 . 
     Initially, as shown in block  1300 , a first substrate is formed by melting a substrate material. This process is shown in  FIG. 14A . In one embodiment, the melted substrate material  1400  can be jetted from one or more thermal print heads  1402  to form successive layers  1404  of the first substrate  1406 . The substrate material can be any suitable material, such as, for example, a polymer (e.g., a polyimide), a thermoplastic polyester (e.g., a polyethylene terephthalate), and a thermoplastic polymer (e.g., a polypropylene). The rate of output of the substrate material  1400  (as well as the other materials in  FIGS. 14B-14E ) from the one or more print heads  1402  may be controlled by a processing device  1408 . 
     Next, as shown in block  1302 , a first set of conductive electrodes is formed over the substrate. The first set of conductive electrodes  1410  can include one or more electrodes (see  FIG. 14B ). The first set of electrodes  1410  can be formed by jetting a melted conductive material  1412  from one or more thermal print heads  1414 . Any suitable conductive material may be used. For example, in one embodiment the conductive material can be a metal such as copper or indium tin oxide. In other embodiments, the conductive material may be conductive or conductive-coated nanoparticles that are included in an insulating material. 
     A compliant layer is then formed over the substrate and the first set of electrodes (block  1304 ). This process is shown in  FIG. 14C . The compliant layer  1416  can be formed by jetting a melted compliant material  1418  from one or more thermal print heads  1420 . Any suitable compliant material may be used. For example, in one embodiment the compliant material can be silicone. 
     In some embodiments, the compliant material may be an ultra-violet (UV) curable compliant material. In such embodiments, the compliant layer  1416  can be patterned at block  1306 .  FIG. 15A  illustrates a patterned compliant layer  1500 . In the illustrated embodiment, the compliant layer is patterned to have areas that include the compliant material and areas that do not include the compliant material. In some embodiments, the patterned compliant layer  1500  can provide the sensor with a higher degree of compressibility. The compliant material that forms the patterned compliant layer can squeeze into the areas that do not include the compliant material when a force is applied to the sensor. 
     The pattern in the UV curable compliant material can be formed using any suitable technique. For example, in one embodiment a mask having openings that define the pattern can be positioned over the compliant material. An ultraviolet light may be directed toward the mask, where the openings allow portions of the ultraviolet light to impinge on the compliant material and create a photo-chemical reaction that sets or hardens portions of the liquid or semi-liquid compliant material. In another embodiment, the pattern can be formed using a nanoimprint lithography process. A processing device (e.g., processing device  1408 ) can control the process of forming the pattern in the compliant layer. 
     Next, as shown in block  1308 , a second set of conductive electrodes is formed over the compliant layer. In some embodiments, the compliant layer is patterned as shown in  FIG. 15A . The second set of conductive electrodes  1422  can include one or more electrodes (see  FIG. 14D ). The second set of electrodes  1422  can be formed by jetting a melted conductive material  1424  from one or more thermal print heads  1426 . Any suitable conductive material may be used, and the conductive material in the second set of electrodes can be the same material or a different material from the material in the first set of electrodes  1410 . 
     A second substrate may then be formed over the second set of electrodes and the compliant layer (block  1310 ). This process is shown in  FIG. 14E . Melted substrate material  1430  can be jetted from one or more thermal print heads  1432  to form the second substrate  1428 . Like the first substrate  1406 , the second substrate  1428  can be formed with any suitable material or combination of materials, such as, for example, a polymer, a thermoplastic polyester, and a thermoplastic polymer. 
     A completed sensor structure  1434 ,  1502  is shown in  FIG. 14F  and  FIG. 15B , respectively. One or more of the processes associated with blocks  404 ,  406 ,  408 ,  410 , and/or  412  may be performed with the sensor structure  1434 ,  1502 . 
     The conductive layers and the protective layers can be formed using a variety of techniques. As one example, the conductive layers and/or the protective layers may be formed using conventional methods used to fabricate flexible printed circuits. Alternatively, in some embodiments, the conductive layers and/or the protective layers may be formed by deposition, coating and patterning techniques. In other embodiments, the conductive layers and/or the protective layers may be formed by screen-printing the layer or layers. And in some embodiments, the conductive layers and/or the protective layers may be formed by stamping, embossing, and thermal compression methods. 
     Additionally or alternatively, an interconnection between the first and second conductive layers may be formed using one of a variety of techniques. For example, the interconnection can be formed using a through via that is filled with a conductive material (e.g., copper). Alternatively, the interconnection may be implemented with conductive dot dispensing. In this technique, conductive particles make an electrical connection between the first and second conductive layers. In another embodiment, the interconnection can be formed with a conductive nanowire coating or through wire bonding. 
     Additionally or alternatively, the connection between a substrate tail (e.g., flexible printed circuit tails  306 ,  308  in  FIG. 3 ) and the conductive structure (e.g., interposer flexible circuit  310  in  FIG. 3 ) can be implemented in a variety of ways. For example, the connection can be formed with surface mount technology. Alternatively, in some embodiments the connection may be formed through metal thermos-compression bonding. Like the interconnection between the first and second conductive layers, the connection between the substrate tail and the conductive structure can be implemented with conductive dot dispensing, conductive nanowire coating, or wire bonding. 
     The foregoing description, for purposes of explanation, used specific nomenclature to provide a thorough understanding of the described embodiments. However, it will be apparent to one skilled in the art that the specific details are not required in order to practice the described embodiments. Thus, the foregoing descriptions of the specific embodiments described herein are presented for purposes of illustration and description. They are not targeted to be exhaustive or to limit the embodiments to the precise forms disclosed. It will be apparent to one of ordinary skill in the art that many modifications and variations are possible in view of the above teachings.

Metadata:
Filing Date: 20150828
Publication Date: 20181016
Grant Date: 20181016
Priority Date: 20150828
Inventors: CHEN, PO-JUI
SUNG, KUO-HUA
CHEN, HUI
Assignee: APPLE INC
CPC Classifications: [{"code": "G06F3/0414", "inventive": true, "first": false, "tree": "[]"}, {"code": "H03K17/962", "inventive": true, "first": false, "tree": "[]"}, {"code": "H03K2217/960755", "inventive": false, "first": false, "tree": "[]"}, {"code": "H03K2217/960765", "inventive": false, "first": false, "tree": "[]"}, {"code": "G06F3/044", "inventive": true, "first": true, "tree": "[]"}, {"code": "G06F2203/04103", "inventive": false, "first": false, "tree": "[]"}, {"code": "H05K3/361", "inventive": true, "first": false, "tree": "[]"}, {"code": "H03K17/962", "inventive": true, "first": true, "tree": "[]"}, {"code": "G06F3/0447", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F3/0445", "inventive": true, "first": false, "tree": "[]"}, {"code": "H03K17/962", "inventive": true, "first": true, "tree": "[]"}, {"code": "G06F3/0447", "inventive": true, "first": false, "tree": "[]"}, {"code": "H05K3/361", "inventive": true, "first": false, "tree": "[]"}, {"code": "H03K2217/960755", "inventive": false, "first": false, "tree": "[]"}, {"code": "H03K2217/960765", "inventive": false, "first": false, "tree": "[]"}, {"code": "G06F2203/04103", "inventive": false, "first": false, "tree": "[]"}, {"code": "G06F3/0445", "inventive": true, "first": false, "tree": "[]"}, {"code": "H03K2217/960755", "inventive": false, "first": false, "tree": "[]"}, {"code": "H03K2217/960765", "inventive": false, "first": false, "tree": "[]"}, {"code": "G06F2203/04103", "inventive": false, "first": false, "tree": "[]"}]
Family ID: 58104034