Patent Publication Number: US-2023163097-A1

Title: Wire bonding device, wire cutting method and non-transitory computer-readable recording medium recording program

Description:
TECHNICAL FIELD 
     The disclosure relates to a wire bonding device, a wire cutting method and a program. 
     RELATED ART 
     Conventionally, known is a wire bonding device in which a first bonding point (for example, a pad of a semiconductor die) and a second bonding point (for example, a lead of a package) are electrically connected by a wire. Depending on the bonding conditions of the wire bonding device, the shape of the bonding end part, which is the connection part between the lower end of the wire tail and the electrode pad (which is the second bonding point), may not be thin. In this case, when the wire is gripped by the clamper and the wire tail is pulled up, a large tension is applied to the wire tail, whereby the wire tail is in a stretched state. Then, after the wire tail is further pulled up, the wire tail is cut at the bonding end part. At this time, the stretched wire tail jumps up due to the reaction force at the time of cutting. This causes the wire and the wire tail at the lower part of the clamper to bend in an S shape. The bent wire tail may cause poor ball formation by electric discharge or the like during the next bonding to the electrode pad. Therefore, a method for cutting a wire tail that does not cause bending of the wire tail has been proposed. 
     CITATION LIST 
     Patent Literature 
     [Patent Literature 1] Japanese Patent Lain-Open No. 2723277 
     SUMMARY 
     Technical Problem 
     The wire bonding method disclosed in Patent Literature 1 raises the capillary diagonally upward from the bonding position after bonding so that the wire tail led out to the tip end of the capillary does not bend. However, in the wire bonding method, if the bonding end part which is the connection part between the lower end of the tail wire and the electrode pad is not thin enough, a large tensile force is applied to the wire when the wire tail is cut. In this case, in the wire bonding method, the wire may jump up due to the reaction force at the time of cutting the wire tail, and the wire at the lower part of the clamper and the wire tail may bend in an S shape. 
     Therefore, the disclosure has been made in view of the above, and the disclosure cuts the wire tail without applying a large tensile force to prevent bending of the wire when the wire tail is cut. 
     Solution to Problem 
     A wire bonding device according to an embodiment of the disclosure is a wire bonding device for performing a wire bonding process. The wire bonding device includes: a bonding tool for inserting a wire; an ultrasonic vibrator for supplying ultrasonic vibration to the bonding tool via an ultrasonic horn; a drive mechanism for moving the bonding tool; and a control part for controlling the wire bonding process. The control part performs: a bonding step of bonding the wire to a bonding point which is a bonding target by pressing the wire with the bonding tool; a tail feeding out step of feeding out a wire tail from the wire bonded to the bonding point; a tension applying step of raising the bonding tool to apply tension to the wire while the wire is clamped; a tension release step of lowering the bonding tool to release the tension applied to the wire; and after performing a series of steps comprising the tension applying step and the tension release step at least once, a tail cutting step of raising the bonding tool to cut the wire tail from the wire bonded to the bonding point. 
     A wire cutting method according to an embodiment of the disclosure is a wire bonding method performed by using a wire bonding device for performing a wire bonding process. The wire bonding device includes: a bonding tool for inserting a wire; an ultrasonic vibrator for supplying ultrasonic vibration to the bonding tool via an ultrasonic horn; a drive mechanism for moving the bonding tool; and a control part for controlling the wire bonding process. The wire cutting method includes: a bonding step of bonding the wire to a bonding point which is a bonding target by pressing the wire with the bonding tool; a tail feeding out step of feeding out a wire tail from the wire bonded to the bonding point; a tension applying step of raising the bonding tool to apply tension to the wire while the wire is clamped; a tension release step of lowering the bonding tool to release the tension applied to the wire; and after performing a series of steps comprising the tension applying step and the tension release step at least once, a tail cutting step of raising the bonding tool to cut the wire tail from the wire bonded to the bonding point. 
     A program according to an embodiment of the disclosure is a program for causing a wire bonding device to perform a wire bonding process. The wire bonding device includes: a bonding tool for inserting a wire; an ultrasonic vibrator for supplying ultrasonic vibration to the bonding tool via an ultrasonic horn; a drive mechanism for moving the bonding tool; and a control part for controlling the wire bonding process. The program causes the wire bonding device to perform: a bonding step of bonding the wire to a bonding point which is a bonding target by pressing the wire with the bonding tool; a tail feeding out step of feeding out a wire tail from the wire bonded to the bonding point; a tension applying step of raising the bonding tool to apply tension to the wire while the wire is clamped; a tension release step of lowering the bonding tool to release the tension applied to the wire; and after performing a series of steps comprising the tension applying step and the tension release step at least once, a tail cutting step of raising the bonding tool to cut the wire tail from the wire bonded to the bonding point. 
     Effects of Invention 
     According to the disclosure, the wire tail may be cut without a large tensile force being applied to prevent bending of the wire when the wire tail is cut. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a view showing an example of the wire bonding device according to the embodiment. 
         FIG.  2 A  is a top view of a bonding arm. 
         FIG.  2 B  is a bottom view of the bonding arm. 
         FIG.  3    is a view showing an example of an outline of a detection part. 
         FIG.  4    is a view showing another example of an outline of the detection part. 
         FIG.  5    is a flowchart showing an example of the wire bonding method. 
         FIG.  6 A  is a view showing an example of an operation of forming a ball part. 
         FIG.  6 B  is a view showing an example of an operation of bringing the ball part into contact with the electrode pad. 
         FIG.  6 C  is a view showing an example of a reverse operation. 
         FIG.  6 D  is a view showing an example of an operation of a wire loop step. 
         FIG.  6 E  is a view showing an example of an operation of pressing a part of a wire against an electrode pad. 
         FIG.  6 F  is a view showing an example of an operation of feeding out a wire. 
         FIG.  6 G  is a view showing an example of an operation of closing a clamper. 
         FIG.  6 H  is a view showing an example of an operation of a first tension applying step. 
         FIG.  6 I  is a view showing an example of an operation of a first tension release step. 
         FIG.  6 J  is a view showing an example of an operation of a second tension applying step. 
         FIG.  6 K  is a view showing an example of an operation of a second tension release step. 
         FIG.  6 L  is a view showing an example of a state in which a wire tail is cut. 
         FIG.  7    is an example of a timing chart showing each step. 
         FIG.  8    is an example of a detailed timing chart of the tension applying step and the tension release step. 
         FIG.  9    is another example of a detailed timing chart of the tension applying step and the tension release step. 
         FIG.  10    is a view showing another example of the wire bonding method. 
     
    
    
     DESCRIPTION OF THE EMBODIMENTS 
     Embodiments of the disclosure will be described below. In the description of the drawings below, the same or similar components are denoted by the same or similar reference numerals. The drawings are examples, and the dimensions and shapes of each part are schematic, and the technical scope of the disclosure should not be limited to the embodiments. 
     [Configuration of Wire Bonding Device  1 ] The wire bonding device  1  will be described with reference to  FIGS.  1  to  4   .  FIG.  1    is a view showing an example of the wire bonding device according  1  to the embodiment.  FIG.  2 A  is a top view of a bonding arm  20 .  FIG.  2 B  is a bottom view of the bonding arm  20 .  FIG.  3    is a view showing an example of an outline of a detection part  70 .  FIG.  4    is a view showing another example of an outline of the detection part  70 . 
     As shown in  FIG.  1   , the wire bonding device  1  includes, for example, an XY drive mechanism  10 , a Z drive mechanism  12 , the bonding arm  20 , an ultrasonic horn  30 , a bonding tool  40 , a load sensor  50 , an ultrasonic vibrator  60 , the detection part  70 , a control part  80 , and a bonding tool position detection part  90 . 
     The XY drive mechanism  10  is configured to be movable in the XY axis direction (direction parallel to the bonding surface), for example. The XY drive mechanism  10  is provided with, for example, the Z drive mechanism  12  capable of moving the bonding arm  20  in the Z-axis direction (direction perpendicular to the bonding surface). 
     The bonding arm  20  is supported by a support shaft  14  and is configured to be swingable with respect to the XY drive mechanism  10 . The bonding arm  20  is formed in a substantially rectangular parallelepiped to extend from the XY drive mechanism  10  toward a bonding stage  16  on which a semiconductor device  100  to be bonded is placed. The bonding arm  20  includes an arm base end part  22  attached to the XY drive mechanism  10 , an arm tip end part  24  located on the tip end side (−Y direction side) of the arm base end part  22  and to which the ultrasonic horn  30  is attached, and a flexible connection part  23  that connects the arm base end part  22  and the arm tip end part  24 . The connection part  23  is configured by, for example, slits  25   a  and  25   b  having a predetermined width extending from a top surface  21   a  toward a bottom surface  21   b  of the bonding arm  20 , and a slit  25   c  having a predetermined width extending from the bottom surface  21   b  toward the top surface  21   a  of the bonding arm  20 . In this way, the connection part  23  is locally configured as a thin-walled part by the slits  25   a ,  25   b , and  25   c , so that the arm tip end part  24  may be bent with respect to the arm base end part  22 . 
     As shown in  FIGS.  1  and  2 B , a recess  26  in which the ultrasonic horn  30  is housed is formed on the bottom surface  21   b  side of the bonding arm  20 . The ultrasonic horn  30  is attached to the arm tip end part  24  by a horn fixing screw  32  in a state of being housed in the recess  26  of the bonding arm  20 . The ultrasonic horn  30  holds the bonding tool  40  at a tip end part protruding from the recess  26 , and the recess  26  is provided with the ultrasonic vibrator  60  that generates ultrasonic vibration. Ultrasonic vibration is generated by the ultrasonic vibrator  60 , and it is transmitted to the bonding tool  40  by the ultrasonic horn  30 . As a result, the ultrasonic vibrator  60  may apply ultrasonic vibration to the bonding target via the bonding tool  40 . The ultrasonic vibrator  60  is, for example, a piezo vibrator. 
     Further, as shown in  FIGS.  1  and  2 A , the slits  25   a  and  25   b  are formed in order from the top surface  21   a  toward the bottom surface  21   b  on the top surface  21   a  side of the bonding arm  20 . The upper slit  25   a  is formed wider than the lower slit  25   b . The load sensor  50  is provided in the upper slit  25   a  that is formed wider. The load sensor  50  is fixed to the arm tip end part  24  by a preload screw  52 . The load sensor  50  is disposed to be sandwiched between the arm base end part  22  and the arm tip end part  24 . That is, the load sensor  50  is mounted between the rotation center of the bonding arm  20  and the mounting surface of the ultrasonic horn  30  at the arm tip end part  24  (that is, the tip end surface of the arm tip end part  24  on the bonding tool  40  side) to be offset from the central axis in the longitudinal direction of the ultrasonic horn  30  in the contact/separation direction with respect to the bonding target. Then, as described above, since the ultrasonic horn  30  holding the bonding tool  40  is attached to the arm tip end part  24 , when a load is applied to the tip end of the bonding tool  40  by the reaction force from the bonding target, the arm tip end part  24  bends with respect to the arm tip end part  22 , and the load sensor  50  may detect the load. The load sensor  50  is, for example, a piezo load sensor. 
     The bonding tool  40  is for inserting a wire  42 , and is, for example, a capillary provided with an insertion hole  41 . The wire  42  used for bonding is inserted into the insertion hole  41  of the bonding tool  40 . The bonding tool  40  is configured so that a part of the wire  42  may be fed out from the tip end thereof. Hereinafter, for convenience of description, the wire  42  fed out from the tip end of the bonding tool  40  is referred to as a wire tail  42   a . Further, a pressing part  40   a  for pressing the wire  42  is provided at the tip end of the bonding tool  40 . The pressing part  40   a  has a rotationally symmetric shape around the insertion hole  41  of the bonding tool  40  in the axial direction, and has a pressing surface on the lower surface around the insertion hole  41 . The bonding tool  40  is attached to the ultrasonic horn  30  to be replaceable by a spring force or the like. 
     A clamper  44  is provided above the bonding tool  40 , for example, and operates together with the bonding tool  40 . The clamper  44  is configured to grip (constrain) or release the wire  42  at a predetermined timing based on, for example, a control signal output from a clamper control part  81 . A wire tensioner (not shown) may be provided above the clamper  44 . The wire tensioner is configured to, for example, insert the wire  42  and apply an appropriate tension to the wire  42  during bonding. 
     The material of the wire  42  is appropriately selected from the viewpoint of ease of processing, low electrical resistance, and the like, and for example, gold (Au), aluminum (Al), copper (Cu), silver (Ag), or the like is used. The wire  42  forms a ball part  43  extending from the tip end of the bonding tool  40 . The ball part  43  is bonded to a predetermined bonding point (for example, an electrode pad  112 , hereinafter referred to as a first bonding point). 
     The detection part  70  electrically detects, for example, whether the ball part  43  formed at the tip end of the wire  42  inserted into the bonding tool  40  is grounded to the semiconductor device  100  which is the bonding target. Further, the detection part  70  detects, for example, whether the wire tail  42   a  is cut from a predetermined bonding point of the semiconductor device  100  (for example, an electrode pad  122 , hereinafter referred to as a second bonding point) based on an output of an electric signal supplied to the wire  42 . 
     The detection part  70  includes, for example, a power supply part  71 , an output measurement part  72 , and a determination part  73 . The power supply part  71  applies a predetermined electric signal between the semiconductor device  100  and the wire  42 , for example. The output measurement part  72  measures, for example, the output of an electric signal supplied by the power supply part  71 . The determination part  73  determines whether the wire  42  has electrically contacted the semiconductor device  100 , for example, based on the measurement result of the output measurement part  72 . As shown in  FIG.  1   , in the detection part  70 , one terminal is electrically connected to the bonding stage  16 , and the other terminal is electrically connected to the clamper  44  (or a wire spool (omitted in  FIG.  1   )). 
     As shown in  FIG.  3   , the power supply part  71  of the detection part  70  may be configured by a DC voltage power supply. That is, when it is considered that the bonding point of the semiconductor device  100  and the bonding stage  16  are connected only by the resistance component (for example, when both are electrically conductive), the detection part  70  may use the DC voltage signal as a predetermined electric signal. In this case, when the ball part  43  of the wire  42  comes into contact with the bonding point of the semiconductor device  100 , an electrical short circuit occurs between the bonding stage  16  and the wire  42 . The detection part  70  may determine whether the ball part  43  has come into contact with the electrode pad  122 , which is the second bonding point of the semiconductor device  100 , based on the change in the presence or absence of this electrical short circuit (for example, the change in the output voltage v). In other words, the detection part  70  may detect whether the wire tail  42   a  is cut from the second bonding point of the semiconductor device  100 . 
     As shown in  FIG.  4   , the power supply part  71  of the detection part  70  may be configured by an AC voltage power supply. That is, when the bonding point of the semiconductor device  100  and the bonding stage  16  include a capacitive component (for example, when the two are not electrically conductive), an AC voltage signal may be used as a predetermined electric signal. In this case, when the ball part  43  of the wire  42  comes into contact with the bonding point of the semiconductor device  100 , the capacitance value of the semiconductor device  100  is further added to the capacitance value of the wire bonding device  1 . As a result, the capacitance value between the bonding stage  16  and the wire  42  changes. Therefore, the detection part  70  may determine whether the ball part  43  has come into contact with the electrode pad which is the second bonding point of the semiconductor device  100  based on the change in the capacitance value (for example, the change in the output voltage v). In other words, the detection part  70  may detect whether the wire tail  42   a  is cut from the second bonding point of the semiconductor device  100 . 
     With reference back to  FIG.  1   , the bonding tool position detection part  90  detects, for example, the position of the bonding tool  40  including the position of the bonding tool  40  in the Z-axis direction (for example, the position of the tip end of the bonding tool  40 ). The bonding tool position detection part  90  outputs information regarding the detection result (hereinafter referred to as detection result information) to the control part  80 . 
     The control part  80  includes, for example, a clamper control part  81  and an XYZ axis control part  82 . The clamper control part  81  controls the opening and closing operation of the clamper  44 . The XYZ axis control part  82  controls the operation in the X-axis direction, the Y-axis direction, and the Z-axis direction in the bonding tool  40 . 
     The control part  80  is connected to be able to transmit and receive signals to and from each configuration such as the XY drive mechanism  10 , the Z drive mechanism  12 , the ultrasonic horn  30  (ultrasonic vibrator  60 ), the clamper  44 , the load sensor  50 , the detection part  70 , the bonding tool position detection part  90 , and the like. By controlling the operation of these configurations, the control part  80  may perform a process of cutting the wire tail  42   a  so as not to cause bending of the wire tail  42   a  in the wire bonding. 
     The control part  80  raises and lowers the bonding tool  40  in the Z-axis direction based on the detection result information output from the bonding tool position detection part  90 . After bonding the wire  42  to the second bonding point, the control part  80  applies tension to the wire  42  by raising the bonding tool  40  in the Z-axis direction (hereinafter referred to as a tension applying step). That is, the control part  80  applies stress to the connection part between the wire tail  42   a  and the second bonding point. After that, the control part  80  releases the tension applied to the wire  42  by lowering the bonding tool  40  in the Z-axis direction (hereinafter referred to as a tension release step). That is, the control part  80  releases the stress at the connection part between the wire tail  42   a  and the second bonding point. 
     The control part  80  determines, for example, the moving direction and the height of raising the tip end of the bonding tool  40  in the tension applying step based on preset information on raising (hereinafter referred to as raising information). Similarly, the control part  80  determines, for example, the moving direction and the height of lowering the tip end of the bonding tool  40  in the tension release step based on preset information on lowering (hereinafter referred to as lowering information). Here, the height of the tip end of the bonding tool  40  means a distance from a predetermined reference point, and the predetermined reference point is not particularly limited and may be, for example, the second bonding point. In the above description, it has been described that the control part  80  determines the height of the tip end of the bonding tool  40  based on the raising information or the lowering information, but the disclosure is not limited thereto. For example, the control part  80  may determine the moving distance of the tip end of the bonding tool  40  based on the raising information or the lowering information. Specifically, as an example, the control part  80  may determine in the tension applying step the moving distance that is raised in the Z-axis direction from the second bonding point, or may determine in the tension release step the moving distance that is lowered in the Z-axis direction from the end point that has been raised in the tension applying step. Hereinafter, for convenience of description, the raising height or moving distance of the tip end of the bonding tool  40  may be referred to as the “raising moving amount,” and the lowering height or moving distance may be referred to as the “lowering moving amount.” 
     Here, the raising moving direction is, for example, a direction away from the second bonding point, and is preferably the Z-axis direction. The lowering moving direction is, for example, a direction approaching the second bonding point, and is preferably a direction along the raising moving direction. However, when the raising moving direction and the lowering moving direction are angled with respect to the Z-axis direction, stress in the X-axis direction or the Y-axis direction may be applied to the lower end of the wire tail  42   a . As a result, the wire tail  42   a  may be cut with a small tensile force as described later. Here, the start point in the raising moving direction may be, for example, the second bonding point or a point deviated from the second bonding point in the XY plane. As a result, stress in the X-axis direction or the Y-axis direction may be applied to the lower end of the wire tail  42   a , so that the wire tail  42   a  may be cut with a small tensile force as described later. Further, the start point in the lowering moving direction may be, for example, the end point of the tension applying step. Hereinafter, for convenience of description, in the control part  80 , the raising moving direction and the lowering moving direction are set in the Z-axis direction; the start point of the starting raising moving direction is set as the second bonding point; and the start point of the starting lowering moving direction is set as the end point of the tension applying step. 
     Further, the control part  80  may automatically set the height or the moving distance (moving amount) in the tension applying step and the tension release step based on the thickness of the wire  42 , for example. Specifically, the control part  80  may set, for example, a predetermined ratio (for example, 60%) to the thickness of the wire  42  as the raising moving amount. The control part  80  may set a predetermined ratio (for example, 30%) to the thickness of the wire  42  as the lowering moving amount. Further, the control part  80  may automatically set the lowering moving amount in the tension release step based on, for example, the raising information. Specifically, the control part  80  may set a predetermined ratio (for example, 50%) to the raising moving amount as the lowering moving amount. Furthermore, the control part  80  may automatically set, for example, the raising moving amount of the tension applying step and the lowering moving amount of the tension release step based on the material of the wire  42  in addition to the thickness of the wire  42 . Specifically, for example, the control part  80  may set the raising moving amount to be larger and the lowering moving amount to be smaller when the material of the wire  42  is harder. This is because the stronger the strength of the wire  42 , the less bending deformation occurs even if a large tension is applied. As a result, the amount of work required for setting of the operator may be reduced. 
     Further, the control part  80  sets so that, for example, the raising moving amount in the tension applying step is larger than the lowering moving amount in the tension release step. Then, it is preferable that the control part  80  repeats, for example, the tension applying step and the tension release step multiple times. That is, in the control part  80  sets so that, for example, the height of the tip end of the bonding tool  40  in the current tension applying step (the second tension applying step described later) is higher than the height of the tip end of the bonding tool  40  in the previous tension applying step (the first tension applying step described later). In this way, the control part  80  repeats the tension applying step and the tension release step, so that metal fatigue is gradually caused in the part between the lower end of the wire tail  42   a  (the end in the −Z axis direction) and the end of the wire  42  connected to the second bonding point in a thinly crushed shape (hereinafter referred to as a bonding end part  42   c ). That is, the tensile strength at the part between the lower end of the wire tail  42   a  and the bonding end part  42   c  is reduced. As a result, the wire tail  42   a  may be cut from the second bonding point without applying a large tensile force to the part. In other words, the connection part between the wire tail  42   a  and the second bonding point is gradually thinned, and the wire tail  42   a  may be cut with a small pulling force at the time of cutting. As a result, the wire tail  42   a  is not bent and deformed, and the bonding quality may be improved. 
     Further, the control part  80 , for example, stops a series of steps including the tension applying step and the tension release step when the detection part  70  detects that the wire tail  42   a  is cut from the second bonding point of the semiconductor device  100 . As a result, the tension applying step and the tension release step may be performed a minimum number of times, so the time of the cutting step of the wire tail  42   a  may be shortened. Further, since it is not necessary to set the number of times of the tension applying step and the tension release step, the amount of work of the operator may be reduced. 
     The control part  80  is connected to, for example, an operation part  132  for inputting information for control (hereinafter referred to as control information) and a display part  134  for outputting the control information. The operator confirms the screen on the display part  134 , and inputs control information (raising information, lowering information, and the like) by the operation part  132 . The control part  80  is a computer device including a CPU, a memory, and the like, and the memory stores a program and the like for executing processing necessary for wire bonding in advance. The control part  80  is configured to perform each step for controlling the operation of the bonding tool  40  described in the wire bonding method described later (for example, includes a program for causing a computer to execute each step). 
     [Wire Bonding Method] 
     Next, the wire bonding method will be described with reference to  FIGS.  5  to  8   . The wire bonding method is a method using a wire bonding method using the wire bonding device  1 .  FIG.  5    is a flowchart showing an example of the wire bonding method.  FIGS.  6 A to  6 L  are views showing an example of the operation of each step.  FIG.  7    is a timing chart showing each step. The times t 1  to t 9  in  FIGS.  6 A to  6 L  correspond to the times t 1  to t 9  in  FIG.  7   .  FIG.  8    is a timing chart showing a detailed example of the tension applying step and the tension release step. 
     In step S 10  (time t 1 ), as shown in  FIG.  6 A , the wire bonding device  1  forms the ball part  43  at the tip end of the wire  42  extending from the tip end of the bonding tool  40 . In step S 10 , the clamper  44  is, for example, in an open state. 
     In step S 11  (time t 1 ), the wire bonding device  1  lowers the bonding tool  40  toward the electrode pad  112  of a semiconductor die  110 . In step S 11 , the clamper  44  is, for example, in a closed state. 
     In step S 12  (time t 2 ), as shown in  FIG.  6 B , the wire bonding device  1  brings the ball part  43  into contact with the electrode pad  112 . Then, the wire bonding device  1  keeps the clamper  44  open and turns on the ultrasonic vibration (first bonding step). As a result, the ball part  43  is bonded to the electrode pad  112 . The wire bonding device  1  feeds out the wire  42  from the tip end of the bonding tool  40  while raising the tip end of the bonding tool  40  in the Z-axis direction. In step S 12 , the detection part  70  detects an electric signal. At this time, the clamper  44  is in an open state. 
     In step S 13  (time t 3 ), as shown in  FIG.  6 C , the wire bonding device  1  operates the wire  42  on the side opposite to the second bonding point (here, the electrode pad  122 ) (in the direction of the “arrow” in  FIG.  6 C ) (reverse operation). As a result, the wire  42  exhibits a bent shape. 
     In step S 14  (time t 4 ), as shown in  FIG.  6 D , the wire bonding device  1  forms a wire loop of the wire  42  while bending the wire  42  toward the second bonding point (wire loop step). Then, the wire bonding device  1  brings a part of the wire  42  into contact with the upper surface of the electrode pad  122 . As a result, a wire loop (not shown) that electrically connects the electrode pad  112 , which is the first bonding point, and the electrode pad  122 , which is the second bonding point, is formed. In step S 14 , the clamper  44  is in the closed state. 
     In step S 15  (time t 5 ), as shown in  FIG.  6 E , the wire bonding device  1  presses a part of the wire  42  against the electrode pad  122  by the pressing part  40   a  of the bonding tool  40 . The wire bonding device  1  turns on the ultrasonic vibration and bonds a part of the wire  42  to the electrode pad  122  (second bonding step). At this time, the bonding end part  42   c  in a thinly crushed shape is formed at the end part of the wire  42  connected to the electrode pad  122 . 
     At time t 6 , as shown in  FIG.  6 F , the wire bonding device  1  raises the tip end of the bonding tool  40  in the Z-axis direction and feeds out the wire tail  42   a  from the tip (tail feeding step). At this time, the clamper  44  is in the open state. The bonding tool position detection part  90  detects the height of the tip end of the bonding tool  40 , and outputs information indicating the height (hereinafter referred to as height information) to the control part  80 . 
     Further, at time t 6 , when the control part  80  acquires the height information indicating that the height of the bonding tool  40  is the height H 1 , it controls the Z drive mechanism  12  by the XYZ axis control part  82  to stop the operation of the bonding tool  40 . At this time, as shown in  FIG.  6 F , the height of the tip end of the bonding tool  40  is the height H 1 , and the wire tail  42   a  is led out from the tip end of the bonding tool  40 . 
     At time t 7 , as shown in  FIG.  6 G , the wire bonding device  1  closes the clamper  44  and grips the wire  42 . With the clamper  44  closed, at time t 8 , the wire bonding device  1  performs the tension applying step and the tension release step. As shown in  FIG.  7   , the wire bonding device  1  turns on the ultrasonic vibration in, for example, the tension applying step and the tension release step. Hereinafter, the tension applying step and the tension release step at time t 8  will be described with reference to  FIG.  8    as well. 
     In step S 16  (time t 81  in  FIG.  8   ), as shown in  FIG.  6 H , the wire bonding device  1  raises the tip end of the bonding tool  40  together with the clamper  44  to a predetermined height (here, height H 1 +D 1 ) in the Z-axis direction while gripping the wire  42  with the clamper  44  (hereinafter referred to as the first tension applying step). In other words, the tip end of the bonding tool  40  is raised by a predetermined moving distance (here, the moving distance D 1 ). As a result, the wire bonding device  1  may apply tension to the bonding end part  42   c  in the Z-axis direction. At this time, for example, when the control part  80  acquires the height information indicating that the height of the tip end of the bonding tool  40  is the height H 1 +D 1 , it controls the Z drive mechanism  12  by the XYZ axis control part  82  to stop the operation of the bonding tool  40  (clamper  44 ). 
     In step S 17  (time t 82  in  FIG.  8   ), as shown in  FIG.  6 I , the wire bonding device  1  lowers the wire tail  42   a  to a predetermined height (here, height H 1 +D 1 −D 2 ) in the Z-axis direction (hereinafter referred to as the first tension release step). In other words, the tip end of the bonding tool  40  is lowered by a predetermined moving distance (here, the moving distance D 2 ). As a result, the wire bonding device  1  may release the tension applied to the bonding end part  42   c . At this time, for example, when the control part  80  acquires the height information indicating that the height of the tip end of the bonding tool  40  is the height H 1 +D 1 −D 2 , it controls the Z drive mechanism  12  by the XYZ axis control part  82  to stop the operation of the bonding tool  40  (clamper  44 ). 
     In step S 18 , the wire bonding device  1 , for example, sets a moving amount indicating the height or moving distance of the bonding tool  40  for each of the next tension applying step (hereinafter referred to as the second tension applying step) and tension release step (hereinafter referred to as the second tension release step) with respect to the first tension applying step and the first tension release step. The wire bonding device  1  sets the moving amount of each step based on, for example, information (raising information, lowering information, and the like) regarding the moving amount stored in a predetermined storage part. 
     Here, the wire bonding device  1  sets, for example, the height of the second tension applying step to be higher than the height of the first tension applying step. Similarly, the wire bonding device  1  sets, for example, the height of the second tension release step to be higher than the height of the first tension release step. Further, the wire bonding device  1  may set the moving distance of the second tension applying step and the moving distance of the second tension release step to be equal to the moving distance of the first tension applying step and the moving distance of the first tension release step. Here, the “equal moving distance” means, for example, a moving distance that allows a mechanical error of the wire bonding device  1  in two moving distances. 
     In step S 19  (time t 83  in  FIG.  8   ), as shown in  FIG.  6 J , the wire bonding device  1  raises the tip end of the bonding tool  40  together with the clamper  44  to a predetermined height (here, height H 1 +2D 1 −D 2 ) in the Z-axis direction while gripping the wire  42  with the clamper  44  in the second tension applying step. In other words, the tip end of the bonding tool  40  is raised by a predetermined moving distance (here, moving distance D 1 ) starting from the end point (here, height H 1 +D 1 −D 2 ) of the first tension release step. As a result, the wire bonding device  1  may apply tension to the bonding end part  42   c  in the Z-axis direction. At this time, for example, when the control part  80  acquires the height information indicating that the height of the tip end of the bonding tool  40  is the height H 1 +2D 1 −D 2 , it controls the Z drive mechanism  12  by the XYZ axis control part  82  to stop the operation of the bonding tool  40  (clamper  44 ). 
     In step S 20  (time t 84  in  FIG.  8   ), as shown in  FIG.  6 K , the wire bonding device  1  lowers the wire tail  42   a  to a predetermined height (here, height H 1 +2D 1 −2D 2 ) in the Z-axis direction in the second tension release step. In other words, the tip end of the bonding tool  40  is lowered by a predetermined moving distance (here, moving distance D 2 ) starting from the end point (here, height H 1 +2D 1 −D 2 ) of the second tension applying step. As a result, the wire bonding device  1  may release the tension applied to the bonding end part  42   c . At this time, for example, when the control part  80  acquires the height information indicating that the height of the tip end of the bonding tool  40  is the height H 1 +2D 1 −2D 2 , it controls the Z drive mechanism  12  by the XYZ axis control part  82  to stop the operation of the bonding tool  40  (clamper  44 ). 
     In step S 21 , the wire bonding device  1  determines whether the wire tail  42   a  has been cut. Specifically, the wire bonding device  1  determines that the wire tail  42   a  has been cut when the electric signal is not detected by the detection part  70  (step  521 : YES). In this case, the wire bonding device  1  ends the process for cutting the wire tail  42   a . On the other hand, the wire bonding device  1  determines that the wire tail  42   a  is not cut when the electric signal is detected by the detection part  70  (step  521 : NO). In this case, the wire bonding device  1  proceeds the process to step S 18 . 
     Further, in the above description, only the first and second tension applying steps and the first and second tension release steps have been described as shown at time t 81  to time t 84 , but as shown at times t 85  and t 86  in  FIG.  8   , the tension applying step and the tension release step are repeated until the electric signal is no longer detected by the detection part  70 . 
     By repeating the tension applying step and the tension release step in this way, as shown in  FIG.  8   , tension is applied to the wire tail  42   a  stepwise by multiple tension applying steps, and the bonding tool  40  can be operated without applying excessive tension to the wire tail  42   a . As a result, the connection part between the wire tail  42   a  and the bonding point (here, the bonding end part  42   c ) is gradually thinned, and the wire tail  42   a  may be cut with a small pulling force at the time of cutting. 
     As shown in  FIG.  6 L , in the wire bonding device  1 , when the wire tail  42   a  is cut, as shown in the graph (OFF) of the “electric signal” shown in  FIG.  7   , it is determined that the electric signal is not detected by the detection part  70 , and the tension applying step and the tension release step are ended. 
     Modified Example 
     In the above, as shown in  FIG.  8   , the operation of the wire bonding device  1  has been described in which the moving distance of the first tension applying step and the moving distance of the first tension release step are set to be equal, but the disclosure is not limited thereto.  FIG.  9    is a timing chart showing another example of the tension applying step and the tension release step. As shown in  FIG.  9   , in the wire bonding device  1 , for example, the setting may be adopted as long as the height of the second tension applying step (height H+D in  FIG.  9   ) is higher than the height of the first tension applying step (height H in  FIG.  9   ). That is, the height of the second tension release step may be equal to the height of the first tension release step. Furthermore, the height of the second tension release step and the height of the first tension release step may be substantially equal to the height of the second bonding point. This simplifies the processing for the lowering moving amount in the tension release step, and thus improves the processing speed of the system. 
     In the above, as an example of the wire bonding method, wire bonding for connecting two points of the bonding target by a wire has been described, but the disclosure is not limited thereto. For example, the above embodiment may be applied to a method of forming the bump  140  on the electrode  212  which is the bonding point of the semiconductor device  200  in the bump bonding shown in  FIG.  10   . In this case, the steps S 10  to S 14  may be omitted from the flowchart of  FIG.  5   . Further, for example, the above embodiment may be applied to wedge bonding. In this case, the step S 10  may be omitted from the flowchart of  FIG.  5   . 
     In the above, it has been described that the wire bonding device  1  determines whether the wire tail  42   a  has been cut after the second tension release step (step S 20 ), but the disclosure is not limited thereto. The wire bonding device  1  may determine whether the wire tail  42   a  has been cut after the second tension applying step (step S 19 ), or may constantly determine whether the wire tail  42   a  has been cut. As a result, it may be determined whether the wire tail  42   a  has been cut without delay, so that the operation related to the cutting of the wire tail  42   a  of the wire bonding device  1  may be reduced. 
     In the above, it has been described that in the wire bonding device  1 , the clamper  44  is closed in the tension release step, but the disclosure is not limited to this. In the tension release step, the clamper  44  may be open. This facilitates the operation of releasing the tension of the wire  42 . 
     The embodiments described through the embodiments of the disclosure may be appropriately combined, modified or changed according to the intended use, and the disclosure is not limited to the description of the above-described embodiments. It is clear from the description of the claims that such combinations or modifications or changes may also be included in the technical scope of the disclosure. 
     REFERENCE SIGNS LIST 
     
         
           1 : Wire bonding device;  12 : Z drive mechanism;  40 : Bonding tool;  42 : Wire;  42   a : Wire tail;  44 : Clamper;  60 : Ultrasonic vibrator;  80 : Control part.