Patent Publication Number: US-2023157608-A1

Title: Electronic device

Description:
CROSS-REFERENCE TO RELATED APPLICATION(S) 
     This application is a continuation of International Application No. PCT/CN2021/097023, filed May 29, 2021, which claims priority to Chinese Patent Application No. 202021719904.7, filed Aug. 17, 2020, the entire disclosures of which are incorporated herein by reference. 
    
    
     TECHNICAL FIELD 
     The disclosure relates to the field of communication devices, in particular, to an electronic device. 
     BACKGROUND 
     A smart watch is usually provided with an electrocardiograph (ECG) electrode on the back thereof and a touch electrode on a side face thereof, and the ECG electrode is configured to contact a wrist of a user. A circuit conduction path connecting the ECG electrode and the touch electrode may be disposed inside the smart watch. The circuit conduction path is configured to make the ECG electrode and the touch electrode be in a conducting state, facilitating obtaining an electrocardiogram of the user. However, the circuit conduction path connecting the ECG electrode and the touch electrode has a complex structure, resulting in insensitive ECG detection and poor user experience. 
     SUMMARY 
     An electronic device is provided in the disclosure. The electronic device includes a housing, a first electrocardiograph (ECG) electrode, a second ECG electrode, an ECG circuit board, and a conductive resilient sheet. The housing includes a back cover and a middle frame fixed with the back cover. The first ECG electrode is disposed at the back cover. The second ECG electrode is disposed at the middle frame. The ECG circuit board is disposed inside the back cover and inside the middle frame, and provided with a first branch electrically connected with the first ECG electrode and a second branch disposed adjacent to and extending toward the second ECG electrode. The conductive resilient sheet is fixed inside the middle frame and configured to make the second ECG electrode and the second branch be in a conducting state. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       To describe the technical solutions in the implementations of the disclosure more clearly, the following briefly introduces the accompanying drawings required for describing the implementations. Apparently, the accompanying drawings in the following description illustrate some implementations of the disclosure. Those of ordinary skill in the art may also obtain other drawings based on these accompanying drawings without creative efforts. 
         FIG.  1    is a schematic partial cross-sectional view of an electronic device provided in an implementation of the disclosure. 
         FIG.  2    is a schematic top view of the electronic device provided in the implementation illustrated in  FIG.  1   . 
         FIG.  3    is a schematic partial cross-sectional view of an electronic device provided in an implementation of the disclosure. 
         FIG.  4    is a schematic top view of the electronic device provided in the implementation illustrated in  FIG.  3    of the disclosure. 
         FIG.  5    is a schematic partial cross-sectional view of an electronic device provided in another implementation of the disclosure. 
         FIG.  6    is a schematic internal structural view of the electronic device provided in the implementation illustrated in  FIG.  5    of the disclosure. 
         FIG.  7    is a schematic partial perspective view of an electronic device provided in an implementation of the disclosure. 
         FIG.  8    is a schematic partial cross-sectional view of an electronic device provided in another implementation of the disclosure. 
         FIG.  9    is a schematic partial exploded view of an electronic device provided in an implementation of the disclosure. 
         FIG.  10    is a schematic partial perspective view of electronic device provided in another implementation of the disclosure. 
         FIG.  11    is a schematic enlarged view of the electronic device at circle X in  FIG.  10   . 
         FIG.  12    is a schematic enlarged view of a branch base and a branch resilient arm in the implementation illustrated in  FIG.  10    of the disclosure. 
         FIG.  13    is a schematic enlarged view of the electronic device at circle VII in  FIG.  7   . 
         FIG.  14    is a schematic partial cross-sectional view of an electronic device provided in another implementation of the disclosure. 
         FIG.  15    is a schematic enlarged view of the electronic device at circle IX in  FIG.  9   . 
         FIG.  16    is a schematic partial cross-sectional view of an electronic device provided in another implementation of the disclosure. 
         FIG.  17    is a schematic partial cross-sectional view of an electronic device provided in another implementation of the disclosure. 
         FIG.  18    is a schematic partial cross-sectional view of an electronic device provided in an implementation of the disclosure. 
         FIG.  19    is a schematic partial view of an electronic device provided in an implementation of the disclosure. 
         FIG.  20    is a schematic partial perspective view of an electronic device provided in an implementation of the disclosure. 
         FIG.  21    is a schematic partial cross-sectional view of an electronic device provided in an implementation of the disclosure. 
         FIG.  22    is a schematic partial cross-sectional view of an electronic device provided in an implementation of the disclosure. 
         FIG.  23    is a schematic partial cross-sectional view of an electronic device provided in an implementation of the disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     The technical solutions in the implementations of the disclosure are clearly and completely described in the following with reference to the accompanying drawings in the implementations of the disclosure. 
     An electronic device is provided in implementations of the disclosure. The electronic device includes a housing, a first electrocardiograph (ECG) electrode, a second ECG electrode, an ECG circuit board, and a conductive resilient sheet. The housing includes a back cover and a middle frame fixed with the back cover. The first ECG electrode is disposed at the back cover. The second ECG electrode is disposed at the middle frame. The ECG circuit board is disposed inside the back cover and inside the middle frame, and provided with a first branch electrically connected with the first ECG electrode and a second branch disposed adjacent to and extending toward the second ECG electrode. The conductive resilient sheet is fixed inside the middle frame and configured to make the second ECG electrode and the second branch be in a conducting state. 
     In an implementation, the electronic device further includes a side-button circuit board fixed inside the middle frame, where the conductive resilient sheet is fixedly connected with the side-button circuit board. 
     In an implementation, the conductive resilient sheet is fixedly connected with the second branch. 
     In an implementation, the electronic device further includes a side button connected with the middle frame and being pressable, where the side-button circuit board is provided with a button switch corresponding to the side button. 
     In an implementation, the second ECG electrode is disposed in the side button. 
     In an implementation, the second ECG electrode and the side button are arranged side by side and spaced apart from each other. 
     In an implementation, the conductive resilient sheet is provided with a fixed base close to the button switch and attached to the side-button circuit board and a resilient arm extending from the fixed base in a bent way, and an end portion of the resilient arm faces the button switch and resiliently abuts against the side button. 
     In an implementation, the conductive resilient sheet is also provided with a branch base extending from the fixed base and a branch resilient arm extending from the branch base in a bent way, and the branch base is attached to the side-button circuit board, and the branch resilient arm resiliently abuts against the second branch. 
     In an implementation, the branch base is provided with two limit buckles opposite each other, an end portion of the branch resilient arm is limited between the two limit buckles and provided with a limit protrusion that is clamped by the two limit buckles, so that the branch resilient arm is prevented from generating plastic deformation. 
     In an implementation, the conductive resilient sheet is also provided with a branch conductive resilient sheet that is fixed to the side-button circuit board and spaced apart from the fixed base, and the branch conductive resilient sheet and the fixed base are in a conducting state via the side-button circuit board, and the branch conductive resilient sheet elastically resists against the second branch. 
     In an implementation, the second ECG electrode is disposed at a button cap of the side button, the side button is also provided with a button column fixedly connected with the second ECG electrode, the button column and the second ECG electrode are in a conducting state, and the button column resiliently abuts against the end portion of the resilient arm and is configured to trigger the button switch when the second ECG electrode is pressed. 
     In an implementation, the second ECG electrode is provided with a touch panel disposed outside the middle frame and a conductive column extending from the touch panel, the touch panel serves as the button cap of the side button, and the conductive column resiliently abuts against the end portion of the resilient arm and is configured to trigger the button switch when the touch panel is pressed. 
     In an implementation, the side-button circuit board and the middle frame cooperatively define a gap therebetween, and an end portion of the second branch away from a printed circuit board (PCB) substrate of the ECG circuit board is disposed within the gap between the side-button circuit board and an inner wall of the middle frame. 
     In an implementation, the side-button circuit board is attached to an inner wall of the middle frame, an end portion of the second branch away from a PCB substrate of the ECG circuit board is attached to a side surface of the side-button circuit board away from the middle frame, part of the conductive resilient sheet is disposed on the side surface of the side-button circuit board away from the middle frame and connected with the second branch, and another part of the conductive resilient sheet is disposed on a side surface of the side-button circuit board close to the middle frame and connected with the second ECG electrode. 
     In an implementation, the ECG circuit board is fixed inside the back cover, the first branch and the second branch extend out two opposite positions on a circumferential side of the ECG circuit board, respectively, and the first branch is bent relative to a PCB substrate of the ECG circuit board and stacked on the back cover. 
     In an implementation, the second ECG electrode is fixed to the middle frame and partially disposed on an inner wall of the middle frame. 
     In an implementation, the conductive resilient sheet is fixed to a portion of the second ECG electrode disposed on the inner wall of the middle frame and resiliently abuts against the second branch. 
     In an implementation, the electronic device includes an ECG chip electrically connected with the first ECG electrode and the second ECG electrode, where the ECG chip is configured to generate ECG data according to electrical signals of the first ECG electrode and the second ECG electrode. 
     In an implementation, the electronic device further includes a display screen fixed to the middle frame and opposite the back cover, where the display screen is electrically connected with the ECG circuit board and configured to receive the ECG data from the ECG chip via the ECG circuit board and generate a displayable ECG image according to the ECG data. 
     In an implementation, the back cover is provided with two first ECG electrodes, each of the two first ECG electrodes is in a semi-annular shape, and the two first ECG electrodes cooperatively form a substantially annular shape and disposed on a periphery of the back cover. 
     The technical solutions in the implementations of the disclosure are clearly and completely described in the following with reference to the accompanying drawings in the implementations of the disclosure to make those skilled in the art better understand the technical solutions of the disclosure. Apparently, the described implementations are merely part rather than all of the implementations of the disclosure. All other implementations obtained by those of ordinary skill in the art based on the implementations of the disclosure without creative efforts are within the scope of the disclosure. 
     In the implementations of the disclose, it may be understood that terms such as “thickness” referred to herein which indicate directional relationship or positional relationship are directional relationship or positional relationship based on accompanying drawings and are only for the convenience of description and simplicity, rather than explicitly or implicitly indicate that devices or components referred to herein must have a certain direction or be configured or operated in a certain direction and therefore shall not be understood as limitation on the disclosure. 
     Refer to  FIG.  1    and  FIG.  2   , an electronic device  100  is provided in the disclosure. The electronic device  100  includes a housing  10 , a first electrocardiograph (ECG) electrode  20 , a second ECG electrode  30 , an ECG circuit board  40 , and a conductive resilient sheet  50 . The housing  10  includes a back cover  11  and a middle frame  12  fixed with the back cover  11 . The first ECG electrode  20  is disposed at the back cover  11 . The second ECG electrode  30  is disposed at the middle frame  12 . The ECG circuit board  40  is disposed inside the back cover  11  and inside the middle frame  12 , and provided with a first branch  41  electrically connected with the first ECG electrode  20  and a second branch  42  disposed adjacent to and extending toward the second ECG electrode  30 . The conductive resilient sheet  50  is fixed inside the middle frame  12  and allows for a conduction between the second ECG electrode  30  and the second branch  42 . It is noted that, the first ECG electrode  20  and the second ECG electrode  30  are both configured to contact a user, so that the electronic device  100  can obtain ECG data of the user and thus obtain an electrocardiogram according to the ECG data. 
     The ECG circuit board  40  is provided with the first branch  41  electrically connected with the first ECG electrode  20  and the second branch  42  disposed adjacent to and extending toward the second ECG electrode  30 , and the conductive resilient sheet  50  is provided to make the second ECG electrode  30  and the second branch  42  be in a conducting state, so that a closed path between the first ECG electrode  20  and the second ECG electrode  30  can be shortened, thereby improving a sensitivity of obtaining ECG data and user experience. It is noted that, in the implementations of the disclosure, the conductive resilient sheet  50  is configured to make the second ECG electrode  30  and the second branch  42  be in electrical connection with each other. 
     It may be understood that, in the implementations of the disclosure, a smart watch is taken as an example for illustrating the electronic device  100 , but the electronic device  100  is not limited to a smart watch, and may also be other electronic devices. The electronic device  100  may be a wearable device such as a wristband, glasses, a head-mounted device, or goggles that includes the first ECG electrode  20 , the second ECG electrode  30 , and the ECG circuit board  40 , and may also be a terminal device such as a mobile phone, a tablet computer, or a notebook computer that includes the first ECG electrode  20 , the second ECG electrode  30 , and the ECG circuit board  40 . The electronic device  100  of the disclosure may detect the ECG data of the user with aid of the first ECG electrode  20 , the second ECG electrode  30 , and the ECG circuit board  40 , and may obtain the electrocardiogram of the user according to the ECG data. In other words, the first ECG electrode  20  and the second ECG electrode  30  may serve as ECG components. 
     In the implementations, the housing  10  serves as an external protective component of the electronic device  100  and is used to protect the ECG circuit board  40  and other components inside the electronic device  100 . The back cover  11  is disposed on the back of the electronic device  100 , and thus when the electronic device  100  is worn on the user, the back cover  11  of the electronic device  100  is at a position where the back cover  11  is readily to contact the skin of the user. If the electronic device  100  is a smart watch, the back cover  11  may be a rear cover of the smart watch. The middle frame  12  may be disposed at a peripheral side of the electronic device  100  for stabilizing and fixing peripheral structures of the electronic device  100 . If the electronic device  100  is a smart watch, the middle frame  12  may serve as a structure at a peripheral side of a dial. The middle frame  12  may be provided with control structures, such as a button, a knob, a touch key, and a crown. The middle frame  12  may be but not be limited to a rectangular frame, and may also be a circular frame, a triangular frame, a pentagonal frame, or other polygonal frames. The middle frame  12  has two first sides  121  opposite each other and two second sides  122  opposite each other, and the two second sides  122  are disposed between the two first sides  121 . The two first sides  122  of the electronic device  100  may be connected with a watchband, and may be provided with control structures for receiving touch operations of the user. 
     In an implementation, the housing  10  further includes a rear housing  13  covering the middle frame  12 . The rear housing  13  defines a through hole  131 , and the back cover  11  covers the through hole  131 . The rear housing  13  may be but not be limited to a rectangular plate. The rear housing  13  may also be a circular plate, a triangular plate, a pentagonal plate, or other polygonal plates. The through hole  131  may be but not be limited to a circular opening, and may also be a square opening, a triangular opening, a polygonal opening, or the like. The rear housing  13  serves as a protective structure disposed at the back of the electronic device  100 , and is used to carry and protect internal components of the electronic device  100 . After the back cover  11  and the rear housing  13  are assembled together, the back cover  11  slightly exceeds the rear housing  13 , so that the back cover  11  may preferentially contact the skin of the user when the electronic device  100  is worn on the user, thereby facilitating contact between the first ECG electrode  20  and the skin of the user. The rear housing  13  and the middle frame  12  may be assembled by snap-fitting and bonded with each other via adhesive, or directly bonded with each other via adhesive. Alternatively, the rear housing  13  and the middle frame  12  may be stably connected via fixing members such as screws, pins, and rivets. The back cover  11  and the rear housing  13  may be connected by snap-fitting, which facilitates detachment of the back cover  11 , so that it is easy to maintain functional components inside the electronic device  100  without disassembling the whole machine. In other implementations, the rear housing  13  may also be integrally pre-formed with the middle frame  12 , and a space for plating electrodes is reserved in the rear housing  13 , such that the second ECG electrode  30  may be formed in the rear housing  13  through electroplating after the rear housing  13  and the middle frame  12  are integrally formed. 
     Optionally, the middle frame  12  may be made of metal, so that metal texture requirements of the electronic device  100  can be met. 
     Optionally, the rear housing  13  may be made of materials such as glass, pottery, sapphire, metal, and plastic, such that requirements of the rear housing  13  such as firmness, wear resistance, scratch resistance, fire prevention, explosion-proof, and dust-proof can be met. 
     Optionally, the back cover  11  may be made of glass, ceramics, sapphire, and other materials to meet the requirements of firmness, wear resistance, and scratch resistance, and may provide an insulating environment for the first ECG electrode  20  to facilitate a detection of the heart rate of the user by the first ECG electrode  20 . 
     In another implementation, as illustrated in  FIG.  3    and  FIG.  4   , a periphery of the back cover  11  is fixedly connected with the middle frame  12 , and the back cover  11  serves as a protective structure at the back of the electronic device  100 . The back cover  11  carries and protects functional components inside the electronic device  100 . The back cover  11  is directly engaged with the middle frame  12 , such that a structure of the housing  10  is simplified and an assembly of the housing  10  is easy. 
     In the implementations, in a case that the back cover  11  is made of sapphire or ceramic, the first ECG electrode  20  is attached to a surface of the back cover  11  and further extends from an edge of the back cover  11  to an inner surface of the back cover  11 , so that the first ECG electrode  20  is electrically connected with the first branch  41 . The first ECG electrode  20  and the back cover  11  are integrally formed to increase stability of the first ECG electrode  20  relative to the back cover  11 . For example, the first ECG electrode  20  may be formed on the back cover  11  through metal plating such as chrome plating, zinc plating, or aluminum plating. The first ECG electrode  20  may be implemented as two first ECG electrodes  20 . One of the two first ECG electrodes  20  may be used as a compensation electrode and configured to transmit a compensation signal to the user, so that interference generated by the user can be counteracted to ensure accuracy of the ECG data of the user obtained by the other one of the two first ECG electrodes  20  and the second ECG electrode  30 . The other one of the two first ECG electrodes  20  may be used as a detection electrode, and configured to cooperate with the second ECG electrode  30  to form a conductive path with the user, so that an ECG voltage under the skin tissue of the user can be obtained. The two first ECG electrodes  20  are arranged opposite to each other, and each of the two first ECG electrodes  20  is in a substantially semi-annular shape. The two first ECG electrodes  20  are arranged at the periphery of the back cover  11 . The two first ECG electrodes  20  cooperatively form a substantially annular electrode. A partition structure is arranged between the two first ECG electrodes  20  so that the two first ECG electrodes  20  are spaced apart from each other. In other implementations, the first ECG electrode  20  may also be a metal part embedded in the back cover  11 , or a metal part bonded to the back cover  11 . 
     In the implementations, refer to  FIG.  1   ,  FIG.  2   , and  FIG.  5   , the first branch  41  extends from an edge of a printed circuit board (PCB) substrate  43  close to the first ECG electrode  20 , so that the first branch  41  may be effectively shortened. The first branch  41  is attached to the back cover  11 , and the first branch  41  is provided with two soldering regions  411  at an end of the first branch  41  away from the PCB substrate  43 . The soldering region  411  is provided with but is not limited to an exposed copper structure, and may also be provided with a metal oxide pad structure, or a silver layer structure. The exposed copper structure of the soldering region  411  may be soldered with part of the first ECG electrode  20  extending to the inner surface of the back cover  11 , so that a conduction between the first branch  41  and the two first ECG electrode  20  can be achieved, that is, the first branch  41  is in electrical connection with the two first ECG electrode  20 . The first branch  41  is provided with conductive lines in conduction with the two first ECG electrodes  20 . The first branch  41  is used to conduct electrical signals of the first ECG electrode  20  to the PCB substrate  43  of the ECG circuit board  40 . The first branch  41  is attached to the back cover  11 , so that a thickness of a stacking of the first branch  41  and the back cover  11  can be reduced, thereby reducing a thickness of the electronic device  100 . The first branch  41  may be a flexible printed circuit board (FPCB), so that the first branch  41  can be bent relative to the PCB substrate  43 , thereby facilitating an electrical connection between the first branch  41  and the first ECG electrode  20 , and effectively reducing a space occupied by the first branch  41 . The first branch  41  and the PCB substrate  43  may be fixed by soldering, or by a rigid-flex way. The first branch  41  may be bent relative to and stacked on the PCB substrate  43 , so that an internal structure of the electronic device  100  can be relatively compact and an internal space arrangement of the electronic device  100  can be optimized. The first branch  41  is in a substantially annular shape, so that the first branch  41  may be disposed around electronic components on the ECG circuit board  40  to prevent signals of the first branch  41  from being interfered by the electronic components on the ECG circuit board  40 . In other implementations, the first branch  41  may also be bonded to the back cover  11  via conductive adhesive, and be in conduction with the first ECG electrode  20 . 
     In the implementations, the ECG circuit board  40  is provided with the PCB substrate  43  and a photoplethysmograph (PPG)  44  disposed on the PCB substrate  43 . The PCB substrate  43  is fixed inside the middle frame  12  and spaced apart from the back cover  11 . The back cover  11  is provided with multiple light-transmitting portions  111  corresponding to the photoplethysmograph  44 . Part of the light-transmitting portions  111  is used for outgoing of light rays from the photoplethysmograph  44 , and the rest of the light-transmitting portions is used for incidence of light rays reflected by the skin tissue of the user. The first ECG electrode  20  is disposed around the multiple light-transmitting portions  111 , so that the back cover  11  can be sufficiently utilized. In the electronic device  100 , the first ECG electrode  20  and the second ECG electrode  30  may serve as the ECG components, and be used to obtain ECG data in combination with the photoplethysmograph  44 . It may be understood that other components are also provided on the ECG circuit board  40  to meet other functional requirements of the electronic device  100 . 
     In the implementations, the second branch  42  extends from an edge of the PCB substrate  43  close to one of the first sides  122 , and the second ECG electrode  30  is disposed on the one of the first sides  122 , so that the second branch  42  may be effectively shortened, thereby effectively shortening a closed conduction path between the ECG circuit board  40  and the second ECG electrode  30 , and in turn effectively shortening a closed conduction path between the first ECG electrode  20  and the second ECG electrode  30 . The second branch  42  may be a flexible circuit board (FPC), facilitating an electrical connection between the second branch  42  and the second ECG electrode  30  and reducing a space occupied by the second branch  42 . The second branch  42  and the PCB substrate  43  may be fixed by soldering, or by a rigid-flex way. The second branch  42  may be bent relative to the PCB substrate  43 , so that an end of the second branch  42  away from the PCB substrate  43  may be stacked with the second ECG electrode  30  in a direction substantially perpendicular to the PCB substrate  43 , thereby avoiding that the second branch  42  is stacked with the second ECG electrode  30  in a direction parallel to the PCB substrate  43 , and thus the thickness of the electronic device  100  is further optimized and reduced, internal structure arrangement of the electronic device  100  is relatively compact, and usage of internal space of the electronic device  100  is optimized. The end of the second branch  42  away from the PCB substrate  43  is provided with but is not limited to an exposed copper structure, and may also be provided with a metal oxide pad structure, or a silver layer structure. A conduction between the second branch  42  and the conductive resilient sheet  50  is achieved via the exposed copper structure, so that a conduction between the second ECG electrode  30  and the first ECG electrode  20  can be achieved via the conductive resilient sheet  50 , the second branch  42 , the PCB substrate  43 , and the first branch  41 . It may be understood that, since the first branch  41  and the second branch  42  directly extend from the PCB substrate  43  and have simple structures, the first branch  41  and the second branch  42  can be effectively shortened, and the closed conduction path between the first ECG electrode  20  and the second ECG electrode  30  are effectively shortened. As such, when the second ECG electrode  30  is touched by the user, electric signals from the user may be quickly transmitted to the first ECG electrode  20  via the second branch  42 , the PCB substrate  43 , and first branch  41 , and a sensitivity of obtaining the ECG data of the user by the electronic device  100  can be improved. 
     In the implementations, the conductive resilient sheet  50  is in contact with the second branch  42 , so that a conduction between the conductive resilient sheet  50  and the second branch  42  can be achieved. The conductive resilient sheet  50  may be in direct contact with the second ECG electrode  30 , or the conduction between the conductive resilient sheet  50  and the second ECG electrode  30  may be realized via a conductive member. The conduction between the second ECG electrode  30  and the second branch  42  is realized via the conductive resilient sheet  50 , so that it is convenient to assemble the ECG circuit board  40  and the second branch  42  with the middle frame  12  and the second ECG electrode  30 , simplifying a conductive structure between the second branch  42  and the second ECG electrode  30 , and avoiding an excessively complicated conduction structure between the second ECG electrode  30  and the second branch  42 . The conductive resilient sheet  50  may be fixed on the middle frame  12  or other fixing members inside the middle frame  12 , and resiliently contact the second branch  42  and the second ECG electrode  30 . The conductive resilient sheet  50  may also be fixed on the second branch  42  and resiliently contact the second ECG electrode  30 , or may be fixed on the second ECG electrode  30  and resiliently contact the second branch  42 . 
     In the implementations, as illustrated in  FIG.  5    and  FIG.  6   , the electronic device  100  further includes a pressing cover plate  49  fixed inside the rear housing  13  and covering the ECG circuit board  40 . The pressing cover plate  49  is fixed with the rear housing  13  by a pressing way, so that the ECG circuit board  40  is stably fixed between the pressing cover plate  49  and the rear housing  13 , facilitating a stable connection of the ECG circuit board  40  relative to the rear housing  13 , and an effective conduction among the ECG circuit board  40 , the first ECG electrode  20 , and the second ECG electrode  30 . 
     Specifically, the rear housing  13  defines a recess  132  on an inner side thereof, and the ECG circuit board  40  is fixed in the recess  132 . The first branch  41  is located between the PCB substrate  43  and the rear housing  13 , so that the first branch  41  may stably contact the first ECG electrode  20 . The pressing cover plate  49  may be engaged with the rear housing  13  at an opening end of the recess  132  by snap-fitting, so that the pressing cover plate  49  can be detachable, thereby facilitating detachment and maintenance of the ECG circuit board  40 . More specifically, the pressing cover plate  49  defines two through grooves  491 , and the two through grooves  491  match a portion of the first branch  41  connected with the PCB substrate  43  and a portion of the second branch  42  connected with the PCB substrate  43 , respectively, preventing the first branch  41  and the second branch  42  from being crushed by the pressing cover plate  49 . The through groove  491  matching the second branch  42  defines an opening on an edge of the pressing cover plate  49 , so that the second branch  42  can extend out of the opening of the through groove  491 , thereby facilitating the conduction between the second branch  42  and the conductive resilient sheet  50 . 
     Further, in the implementations, the rear housing  13  further defines a charging port  133  (see  FIG.  2   ). The ECG circuit board  40  is further provided with a conductive branch  48  communicating with the charging port  133 , and the charging port  133  is adjacent to the second side  122 . The conductive branch  48  is disposed around a peripheral side of the ECG circuit board  40 . The conductive branch  48  extends from an end of the second branch  42  connected with the ECG circuit board  40 . An end of the conductive branch  48  away from the charging port  133  may be connected with a main board of the electronic device  100  via a board-to-board connector, so that the main board of the electronic device  100  can control the charging port  133  to obtain power from an external power source, thereby facilitating charging a battery through the charging port  133  and the conductive branch  48 , and supplying power to the ECG circuit board  40 , the first branch  41 , and the second branch  42  by the battery. 
     In an implementation, refer to  FIG.  7   ,  FIG.  8   , and  FIG.  9   , an example that the conductive resilient sheet  50  is disposed on a side-button circuit board  60  that is stably fixed inside the middle frame  12  is taken for illustration. In the implementation, the electronic device  100  further includes the side-button circuit board  60  fixed inside the middle frame  12 , and the conductive resilient sheet  50  is fixedly connected with the side-button circuit board  60 . The side-button circuit board  60  has a first portion  61  spaced apart from an inner wall of the first side  121  and a second portion  62  bent relative to the first portion  61  and connected to the ECG circuit board  40 . An end of the second portion  62  away from the first portion  61  may be connected to the main board of the electronic device  100  via a board-to-board connector, so that a signal of a button switch  63  can be transmitted to the main board of the electronic device  100 . A strength of the first portion  61  is greater than that of the second portion  62 , so that the conductive resilient sheet  50  can be fixed on the first portion  61 , and the first portion  61  can be provided with the button switch  63  that can be readily triggered by a side button  70 . A gap is defined between the first portion  61  and the inner wall of the middle frame  12 , and the end of the second branch  42  away from the PCB substrate  43  is stacked in the gap between the first portion  61  and the inner wall of the middle frame  12 , so that an assembly of the side-button circuit board  60  and the middle frame  12  can be relatively compact in structure, the internal space arrangement of the electronic device  100  can be optimized, and the conductive resilient sheet  50  can be closer to the second ECG electrode  30  in the middle frame  12 . It may be understood that, the first portion  61  may be provided with a reinforcing layer, so that the strength of the first portion  61  may be greater than that of the second portion  62 . The side-button circuit board  60  may also be configured as a rigid-flex circuit board, so that the strength of the first portion  61  is greater than that of the second portion  62 . The second portion  62  may be freely bent, facilitating a connection between the second portion  62  and the main board of the electronic device  100 , and thus facilitating transmission of the signal of the button switch  63  on the side-button circuit board  60  to the main board of the electronic device  100 . 
     In the implementations, the electronic device  100  further includes a side button  70  connected with the middle frame  12 , where the side button  70  can be pressed. The side-button circuit board  60  is provided with the button switch  63  corresponding to the side button  70 . The button switch  63  is disposed on a side surface of the first portion  61  close to the inner wall of the middle frame  12 , so that the side button  70  can trigger the button switch  63 . The second ECG electrode  30  is disposed at the side button  70 , so that an electrical signal can be transmitted to the first ECG electrode  20  via the second ECG electrode  30  when the side button  70  is touched by the user, and the ECG data can be obtained by the electronic device  100 . The side button  70  may also be pressed by the user to realize a control of the electronic device  100 , thereby optimizing an arrangement of components on the middle frame  12 . 
     Specifically, the electronic device  100  is provided with two side buttons  70  arranged side by side on the first side  121 . The second ECG electrode  30  is disposed at one of the two side buttons  70 . The side-button circuit board  60  is provided with two button switches  63  respectively corresponding to the side buttons  70  on both sides of the side-button circuit board  60 , and the two side buttons  70  may respectively trigger the two button switches  63  to send signals. The conductive resilient sheet  50  is adjacent to one of the two button switches  63  that faces the side button  70   where the second ECG electrode  30  is located. It may be understood that, with aid of the side button  70  provided with the second ECG electrode  30 , it is possible to realize a control function of the electronic device  100 , and furthermore, when the side button  70  is touched by the user, the second ECG electrode  30  can also be touched, and thus the electronic device  100  can obtain the ECG data of the user. The other one of the two side buttons  70  can be used to realize a control function of the electronic device  100  different from the control function of the electronic device realized with aid of the side button  70  provided with the second ECG electrode  30 , so that the electronic device  100  has various control functions. 
     Further, in an implementation, refer to  FIG.  10   , the conductive resilient sheet  50  is provided with a fixed base  51  and a resilient arm  52 , where the fixed base  51  is close to the button switch  63  and attached to the side-button circuit board  60 , and the resilient arm  52  extends from the fixed base  51  in a bent way. An end portion of the resilient arm  52  faces the button switch  63  and resiliently abuts against the side button  70 . The fixed base  51  is provided with a U-shaped ring at a peripheral side of the button switch  63 , and the resilient arm  52  extends from two free ends of the U-shaped ring and is bent relative to the U-shaped ring. The resilient arm  52  is also in the shape of a U-shaped ring. The resilient arm  52  is provided with a resilient tab  53  at a closed end of the resilient arm  52 , and the resilient tab  53  extends toward an open end of the U-shaped ring. An end of the resilient tab  53  faces the button switch  63 , and the resilient tab  53  resiliently abuts against the side button  70 , so that a conduction between the resilient arm  52  and the second ECG electrode  30  can be achieved. The fixed base  51  is located at the peripheral side of the button switch  63 , so that the resilient arm  52  can resiliently resist against the side button  70  effectively, and an effective conduction between the second ECG electrode  30  and the conductive resilient sheet  50  can be achieved. The fixed base  51  is spaced apart from the button switch  63 , avoiding a short circuit between the conductive resilient sheet  50  and the button switch  63 , and preventing a trigger signal of the button switch  63  from interfering with conduction of an electrical signal of the second ECG electrode  30  by the conductive resilient sheet  50 . 
     Optionally, the fixed base  51  may be fixedly connected with the side-button circuit board  60  via insulating adhesive, to avoid a short circuit between the side-button circuit board  60  and the conductive resilient sheet  50 . 
     Optionally, the conductive resilient sheet  50  may be a metal piece containing silver, magnesium, aluminum, copper, or the like. 
     It may be appreciated that, a conductive line connected to the button switch  63  on the side-button circuit board  60  is routed between the two free ends of the U-shaped ring of the fixed base  51 , so that the conductive line connected to the button switch  63  can be kept away from the fixed base  51 , the conduction of the electrical signal of the second ECG electrode  30  via the conductive resilient sheet  50  can be independent of a conduction of an electrical signal of the button switch  63 , and thus the accuracy of the ECG data obtained and a control accuracy of the side button  70  can be ensured. 
     During obtaining of the ECG data of the user by the second ECG electrode  30 , the first ECG electrode  20  is in contact with the skin of the wrist of the user, and when the side button  70  provided with the second ECG electrode  30  is touched and pressed by the user or is merely touched by the user, a closed conduction path is formed among the second ECG electrode  30 , the conductive resilient sheet  50 , the second branch  42 , the PCB substrate  43 , the first branch  41 , the first ECG electrode  20 , and the user. Further, the first ECG electrode  20  and the second ECG electrode  30  contacts two non-equipotential portions of the user, respectively, so that a potential difference is formed between the second ECG electrode  30  and the first ECG electrode  20 , and thus the ECG data of the user can be obtained by the electronic device  100  with aid of the components on the ECG circuit board  40 . 
     During triggering of the button switch  63  by the side button  70 , the side button  70  is pressed by the user, and then the side button  70  drives the resilient tab  53  and the resilient arm  52  to deform to make the resilient tab  53  abut against the button switch  63 , and thus the button switch  63  sends signal, that is, the button switch  63  is eventually triggered. 
     In an implementation, refer to  FIG.  10    and  FIG.  11   , the conductive resilient sheet  50  is further provided with a branch base  54  extending from the fixed base  51  and a branch resilient arm  55  extending from the branch base  54  in a bent way, the branch base  54  is attached to the side-button circuit board  60 , and the branch resilient arm  55  resiliently abuts against the second branch  42 . The branch base  54  extends from an closed end of the U-shaped ring of the fixed base  51 , so that a stability of the branch base  54  relative to the fixed base  51  can be increased. The branch base  54  is located on the side-button circuit board  60  at a position close to the back cover  11 , so that the branch base  54  is close to the second branch  42 , and thus a path from the first ECG electrode  20  to the conductive resilient sheet  50  is shortened. An extension arm  56  is connected between the branch base  54  and the fixed base  51 , and the extension arm  56  is attached to the side-button circuit board  60 , so that the conductive resilient sheet  50  as a whole is stably fixed with the side-button circuit board  60 . The branch resilient arm  55  extends from an edge of the branch base  54  away from the extension arm  56 , so that the branch resilient arm  55  is inclined relative to the side-button circuit board  60 , facilitating a resilient abutting of the branch resilient arm  55  against the second branch  42 . 
     During assembly of the second branch  42  with the side-button circuit board  60 , the second branch  42  may first contact the branch resilient arm  55  and eventually resiliently contact an end of the branch resilient arm  55 , so that the end of the branch resilient arm  55  can be prevented from puncturing by the second branch  42 . The branch base  54  extends from the fixed base  51 , and the branch resilient arm  55  extends from the branch base  54 , so that the branch resilient arm  55 , the branch base  54 , the fixed base  51 , and the resilient arm  52  are integrally formed, facilitating an effective conduction between the second branch  42  and the second ECG electrode  30  via the conductive resilient sheet  50 , and the sensitivity of obtaining the ECG data of the user by the electronic device  100  can be improved. 
     In order to increase a resilient resistance force of the branch resilient arm  55  against the second branch  42  and prevent the branch resilient arm  55  from puncturing the second branch  42 , the branch resilient arm  55  is bent. After the branch resilient arm  55  is bent, the end of the branch resilient arm  55  is bent inwardly toward the branch base  54 , so that a resilient stress of the branch resilient arm  55  increases. The branch resilient arm  55  is provided with a bending resistance portion  552  that abuts against the second branch  42 . A surface of the bending resistance portion  552  that contacts the second branch  42  is curved, so that stress concentration on the second branch  42  can be reduced, and the second branch  42  can be prevented from being punctured. 
     In order to facilitate an effective resilient abutment between the branch resilient arm  55  and the second branch  42  and ensure an effective resilience of the branch resilient arm  55 , the branch base  54  is provided with two limit buckles  541  opposite each other, and the two limit buckles  541  may effectively limit an end of the branch resilient arm  55 . Specifically, the two limit buckles  541  respectively extend from the branch base  54  at both sides of the branch resilient arm  55  in a curl and bent way. The two limit buckles  541  are bent relative to the branch base  54 , and a limit guide groove is defined between ends of the two limit buckles  541  and the branch base  54 . 
     It is understood that, when being pressed, the branch resilient arm  55  is easy to generate resilient deformation. However, due to that a thickness of the branch resilient arm  55  is generally small, the branch resilient arm  55  is also prone to generate plastic deformation under a force and cannot generate a resilience force to restore to an original state of the branch resilient arm  55 . The branch resilient arm  55  is provided with a limit protrusion  551  at an end of the branch resilient arm  55 , and the limit protrusion  551  extends into the limit guide groove defined by the two limit buckles  541  and the branch base  54 , so that the limit protrusion  551  may be hooked by the two limit buckles  541 , and thus the limit protrusion  551  can be effectively limited. When the bending resistance portion  552  is pulled to deform to a large extent, the bending resistance portion  552  drives the limit protrusion  551  to move, and the limit protrusion  551  may then be hooked by the two limit buckles  541 , such that the plastic deformation of the branch resilient arm  55  caused by a further pulling and deformation of the bending resistance portion  552  can be avoided. For example, the bending resistance portion  552  can be pulled to increase a distance between the limit protrusion  551  and the branch base  54 , and when the distance increases to a certain extent, the limit protrusion  551  will abut against the limit buckles  541  to avoid further increment of the distance, thereby preventing the bending resistance portion  552  from being further pulled. 
     In an implementation, refer to  FIGS.  11 - 14   , the second ECG electrode  30  is disposed at a button cap of the side button  70 , the side button  70  is further provided with a button column  71  fixedly connected with the second ECG electrode  30 , the button column  71  and the second ECG electrode  30  are in a conducting state, and the button column  71  resiliently abuts against the end portion of the resilient arm  52  and is configured to trigger the button switch  63  when the second ECG electrode  30  is pressed. 
     It may be understood that the second ECG electrode  30  may be a metal plate, so that the entire button cap of the side button  70  may serve as the second ECG electrode  30 . The second ECG electrode  30  may also be a metal layer or a metal sheet formed on a surface of the button cap of the side button  70 , that is, part of the surface of the button cap of the side button  70  serves as the second ECG electrode  30 . When the entire button cap of the side button  70  serves as the second ECG electrode  30 , the side button  70  is also provided with an insulating sleeve  72  sleeved on a periphery side of the second ECG electrode  30 . The insulating sleeve  72  is made from an insulating material, so that the insulating sleeve  72  is insulated from the second ECG electrode  30 . The second ECG electrode  30  is insulated from the middle frame  12  via the insulating sleeve  72 , preventing the middle frame  12  from interfering with reception of electrical signals by the second ECG electrode  30 . The button column  71  is a conductive metal member. The button column  71   may be bonded to the second ECG electrode  30  via conductive adhesive. The conductive adhesive can make the second ECG electrode  30  and the button column  71  be in a conducting state. An end of the button column  71  away from the second ECG electrode  30  elastically resists against the resilient tab  53  to achieve a conduction between the conductive resilient sheet  50  and the second ECG electrode  30  via the button column  71 . The conductive adhesive has a certain elastic deformation property, so that when the side button  70  tilts up, the conductive adhesive deforms to make the button column  71  not incline, ensuring that the button column  71  can effectively trigger the button switch  63 . In order to ensure a waterproof performance of the electronic device  100 , a sealing ring is sleeved on a peripheral side of the button column  71 , and the sealing ring is sealed against the inner wall of the button hole of the middle frame  12 , so that the button hole of the middle frame  12  is sealed to ensure the water resistance of the electronic device  100 . 
     Further, refer to  FIG.  15    and  FIG.  16   , in order to ensure a stability of the second branch  42  relative to the side-button circuit board  60 , the electronic device  100  further includes a circuit board support  80 . The circuit board support  80  is fixed inside the middle frame  12  and spaced apart from the inner wall of the first side  121 . The circuit board support  80  can effectively support the side-button circuit board  60 . Specifically, the circuit board support  80  is provided with a plate member spaced apart from the inner wall of the first side  121 . The first portion  61  of the side-button circuit board  60  is attached to a side surface of the plate member of the circuit board support  80  close to the second side  122 . The second portion  62  of the side-button circuit board  60  is bent relative to the first portion  61  and then attached to a side surface of the plate member of the circuit board support  80  away from the first side  121 . In order to facilitate contact between the conductive resilient sheet  50  and the side button  70  and triggering of the button switch  63  by the side button  70 , both the conductive resilient sheet  50  and the button switch  63  are disposed on a side surface of the first portion  61  away from the second portion  62  of the side-button circuit board  60 , so that the conductive resilient sheet  50  and the button switch  63  may be adjacent to the inner wall of the middle frame  12  and may easily contact the side button  70 . In order to facilitate effective contact between the second branch  42  and the conductive resilient sheet  50 , the branch base  54  of the conductive resilient sheet  50  is located at an edge of the first portion  61  close to the back cover  11 . The end of the second branch  42  away from the PCB substrate  43  is stacked on a side surface of the first portion  61  close to the middle frame  12 . The end of the second branch  42  is located within the gap between the side-button circuit board  60  and the middle frame  12 , so that the internal space of the electronic device  100  is fully utilized and a structure arrangement is effectively optimized. A part of the second branch  42  connected with the PCB substrate  43  is bent relative to a part of the second branch  42  stacked on the side-button circuit board  60 , and the part of the second branch  42  connected with the PCB substrate  43  extends from an edge of the PCB substrate  43  close to the side-button circuit board  60 , so that the second branch  42  can be shortened and the conduction path between the first ECG electrode  20  and the second ECG electrode  30  can be effectively shortened. 
     Further, refer to  FIG.  17   , in order to obtain the ECG data of the user, the electronic device  100  includes a main board and an ECG chip disposed on the main board. The main board may be electrically connected with the ECG circuit board via a flexible circuit board and a board-to-board connector, so that the ECG chip is electrically connected with the first ECG electrode  20  via the main board and the ECG circuit board  40 , and also electrically connected with the second ECG electrode  30  via the second branch  42  and the conductive resilient sheet  50 , thereby generating the ECG data according to the electrical signals of the first ECG electrode  20  and the second ECG electrode  30 . It is understood that, when the first ECG electrode  20  and the second ECG electrode  30  contact two non-equipotential portions of the user, for example, when the first ECG electrode  20  is touched by the left wrist of the user and the second ECG electrode  30  is touched by the right hand, a voltage difference signal is generated between the first ECG electrode  20  and the second ECG electrode  30 , and the ECG chip obtains the voltage difference signal and processes the voltage difference signal into the ECG data. 
     Further, in order to facilitate the user to view his/her own electrocardiogram, the electronic device  100  further includes a display screen  110  fixed to the middle frame  12  and opposite the back cover  11 . The display screen  110  is electrically connected with the main board and configured to receive the ECG data from the ECG chip via the main board and generate a displayable ECG image according to the ECG data. The user may know his own electrocardiogram by observing the ECG image on the display screen  110 . Of course, in other implementations, the electronic device  100  may transmit the ECG image to other electronic devices  100  with a display function through communication networks such as Bluetooth, wireless fidelity (Wi-Fi), fifth-generation (5G) wireless communication, and fourth-generation (4G) wireless communication, so that the ECG image may be displayed by an external electronic device with a display function. 
     In another implementation, refer to  FIG.  18   , the implementation illustrated in  FIG.  18    is substantially the same as the implementation illustrated in  FIG.  16   , except that the conductive resilient sheet  50  is fixedly connected with the second branch  42 . Specifically, the end of the second branch  42  away from the PCB substrate  43  is attached to a side surface of the circuit board support  80  close to the middle frame  12 . The conductive resilient sheet  50  may be bonded to a side surface of an end of the second branch  42  away from the circuit board support  80  via conductive adhesive. The conductive resilient sheet  50  may be connected with a conductive line in the second branch  42  via the conductive adhesive. The fixed base  51  of the conductive resilient sheet  50  is attached to an end of the second branch  42 , and the resilient arm  52  extends relative to the second branch  42  and resiliently resists the button column  71  of the side button  70  or the second ECG electrode  30 , so that the conductive resilient sheet  50  can make the second branch  42  and the second ECG electrode  30  be in a conducting state. More specifically, in order to increase a structural strength of an end of the second branch  42 , the second branch  42  is provided with a reinforcing layer on a side surface of the second branch  42  away from the conductive resilient sheet  50 , so that the second branch  42  may effectively support the conductive resilient sheet  50 , thereby preventing the second branch  42  from being deformed under a resilient resistance force of the conductive resilient sheet  50 , and ensuring safety of the second branch  42 . In other implementations, the conductive resilient sheet  50  may also be soldered on the second branch  42 . 
     In another implementation, refer to  FIG.  19   , the implementation illustrated in  FIG.  19    is substantially the same as the implementation illustrated in  FIG.  16   , except that the second ECG electrode  30  is spaced apart from the side button  70 , and the second ECG electrode  30  is a metal member embedded in the middle frame  12 . The side button  70  and the second ECG electrode  30  are arranged on the middle frame  12  side by side. Specifically, the electronic device  100  is provided with two side buttons  70  at the first side  121 , where the two side buttons  70  can be pressed. Two button switches  63  corresponding to the two side buttons  70  are provided on the side-button circuit board  60  . The second ECG electrode  30  is disposed between the two side buttons  70 . The second ECG electrode  30  is fixedly connected with the first side  121 . The second ECG electrode  30  cannot be pressed. The second ECG electrode  30  extends through the middle frame  12 , so that the resilient arm  52  of the conductive resilient sheet  50  can resiliently abut against the second ECG electrode  30 , that is, the conductive resilient sheet  50  is fixed to the side button  70  at a position between the two button switches  63 . The second branch  42  is stacked on the side-button circuit board  60  at a position close to the second ECG electrode  30 , so that the conductive resilient sheet  50  can also resiliently abut against the second branch  42 . The conductive resilient sheet  50  is separated from the two button switches  63 , so that the electrical signals of the button switches  63  will not interfere with the conduction between the second ECG electrode  30  and the first ECG electrode  20 . 
     In another implementation, refer to  FIG.  20   , the implementation illustrated in  FIG.  20    are substantially the same as the implementation illustrated in  FIG.  10   , except that the conductive resilient sheet  50  has a split-type structure. The conductive resilient sheet  50  is further provided with a branch conductive resilient sheet  500  that is fixed to the side-button circuit board  60  and spaced apart from the fixed base  51 , and the branch conductive resilient sheet  500  and the fixed base  51  are in a conducting state via the side-button circuit board  60 , and the branch conductive resilient sheet  500  elastically resists against the second branch  42 . Specifically, a structure of the branch conductive resilient sheet  500  is similar to that of the branch base  54  and the branch resilient arm  55  of the conductive resilient sheet  50  in the implementation illustrated in  FIG.  10   , except that the branch conductive resilient sheet  500  is spaced apart from the fixed base  51 . The fixed base  51  is bonded to the side-button circuit board  60  via conductive adhesive, and is connected with a circuit of the side-button circuit board  60 . The branch conductive resilient sheet  500  is bonded with a circuit of the side button  70  via conductive adhesive, and is connected with the circuit of the side-button circuit board  60 , thereby realizing a conduction between the branch conductive resilient sheet  500  and the fixed base  51 , and thus when the second branch  42  resiliently abuts against the branch conductive resilient sheet  500 , the second branch  42  and the second ECG electrode  30  are in the conducting state. The conductive resilient sheet  50  has a split-type structure, so that a volume of the conductive resilient sheet  50  is effectively reduced, facilitating optimization in an arrangement of internal structural components of the electronic device  100 . In other implementations, the branch conductive resilient sheet  500  may also be soldered on the side-button circuit board  60 , and the fixed base  51  may also be soldered on the side-button circuit board  60 . 
     In another implementation, refer to  FIG.  21   , the implementation illustrated in  FIG.  21    are substantially the same as the implementation illustrated in  FIG.  16   , except that the second ECG electrode  30  is provided with a touch panel  31  disposed outside the middle frame  12  and a conductive column  32  extending from the touch panel  31 , the touch panel  31  serves as the button cap of the side button  70 , the conductive column  32  serves as the button column  71  of the side button  70 , and the conductive column  32  resiliently abuts against the end portion of the resilient arm  52  and is configured to trigger the button switch  63  when the touch panel  31  is pressed. It is understood that, with aid of the conductive column  32  of the second ECG electrode  30 , the side button  70  can trigger the button switch  63 , so that the conductive resilient sheet  50  directly contacts the second ECG electrode  30 , thereby reducing a resistance between the second ECG electrode  30  and the first ECG electrode  20 , and improving a conduction sensitivity between the first ECG electrode  20  and the second ECG electrode  30 . The insulating cover  72  of the side button  70  is arranged around a peripheral side of the touch panel  31  to isolate the second ECG electrode  30  from the middle frame  12 , ensuring that the second ECG electrode  30  may effectively receive touch signals of the user. 
     In another implementation, refer to  FIG.  22   , the implementation illustrated in  FIG.  22    are substantially the same as the implementation illustrated in  FIG.  16   , except that the side-button circuit board  60  is attached to an inner wall of the middle frame  12 , an end portion of the second branch  42  away from the PCB substrate  43  is attached to a side surface of the side-button circuit board  60  away from the middle frame  12 , part of the conductive resilient sheet  50  is disposed on the side surface of the side-button circuit board  60  away from the middle frame  12  and connected with the second branch  42 , and another part of the conductive resilient sheet  50  is disposed on a side surface of the side-button circuit board  60  close to the middle frame  12  and connected with the second ECG electrode  30 . In order to shorten the second branch  42 , the second branch  42  as a whole is disposed on a side surface of the circuit board support  80  away from the middle frame  12 . An end of the second branch  42  is stacked with and spaced apart from the second portion  62  of the side-button circuit board  60 , so that the branch base  54  and the branch resilient arm  55  of the conductive resilient sheet  50  can be disposed on the second portion  62  and resiliently resist against the second branch  42 . It may be understood that, the fixed base  51  of the conductive resilient sheet  50  is disposed on the first portion  61 , and the branch base  54  of the conductive resilient sheet  50  is disposed on the second portion  62 , so that the conductive resilient sheet  50  forms a bent resilient piece, that is, the conductive resilient sheet  50  can clamp the first portion  61  and the second portion  62  on the circuit board support  80 , so that an effective conduction between the conductive resilient sheet  50  and the second branch  42  can be realized, and structures of the side-button circuit board  60  and the circuit board support  80  can be further stable. 
     In another implementation, refer to  FIG.  23   , the implementation illustrated in  FIG.  23    are substantially the same as the implementation illustrated in  FIG.  16   , except that the second ECG electrode  30  is fixed to the middle frame  12  and partially disposed on the inner wall of the middle frame  12 , Specifically, the second ECG electrode  30  is a coating layer plated on a surface of the middle frame  12 . Another part of the second ECG electrode  30  is plated on an inner surface of the middle frame  12 , facilitating the conduction between the second ECG electrode  30  and the conductive resilient sheet  50 . When part of the second ECG electrode  30  plated on an outer surface of the middle frame  12  is touched by the user, the second ECG electrode  30  and the user are in a conducting state. 
     More specifically, the conductive resilient sheet  50  is fixed on the inner wall of the middle frame  12 , and is connected with the part of the second ECG electrode  30  disposed on the inner wall of the middle frame  12 . Optionally, the conductive resilient sheet  50  may be soldered to the part of the second ECG electrode  30  disposed on the inner wall of the middle frame  12 . The conductive resilient sheet  50  may also be bonded to the part of the second ECG electrode  30  disposed on the inner wall of the middle frame  12  via conductive adhesive. The conductive resilient sheet  50  is provided with the resilient arm  52  that may resiliently deform relative to the middle frame  12 , and the resilient arm  52  resiliently abuts against the second branch  42 , so that the second ECG electrode  30  and the second branch  42  are in a conducting state via the conductive resilient sheet  50 , and the closed conduction path between the second ECG electrode  30  and the first ECG electrode  20  can be effectively shortened. The conductive resilient sheet  50  is stably fixed on the inner wall of the middle frame  12 , so that the stability of the conductive resilient sheet  50  is improved, the conductive resilient sheet 5 can effectively contact the second branch  42 , and conduction between the second ECG electrode  30  and the first ECG electrode  20  is improved. 
     The above implementations are exemplary implementations of the disclosure, and it is noted that various improvements and modifications may be made without departing from the principle of the disclosure to those of ordinary skill in the art, and the improvements and the modifications are also considered as the protection scope of the disclosure.