Wire bonding device

Abstract

This wire bonding device comprises: a capillary; an ultrasonic vibrator; a clamper which moves in a vertical direction in conjunction with the capillary to grip and release a wire; and a control unit. The control unit starts ultrasonic bonding to a lead of the wire through the ultrasonic excitation of the capillary with the ultrasonic vibrator after a time t1 when the capillary is lowered in a state in which the clamper is closed and the tip of the capillary is grounded to the lead, opens the clamper (17) at a time (t2) after the lapse of a predetermined period (DL), and changes the predetermined period (DL) according to a period (ΔUS) of the ultrasonic bonding. As a result, in the wire bonding device, poor extension of the tail wire is suppressed.

Description

Wire Bonding Equipment

[0001] The present invention relates to the operation control of a clamper of a wire bonding apparatus.

[0002] A wire bonding apparatus is used to connect pads of a semiconductor chip and leads of a lead frame with a metal wire. In this wire bonding apparatus, a wire is extended from the tip of a capillary, and the wire is formed into an initial ball using a discharge torch or the like. The capillary is then bonded to a first bond point. The capillary is then raised while the wire is being paid out, looped toward a second bond point, and bonded to the second bond point. After bonding to the second bond point is complete, the capillary is raised to pay out the wire from its tip. The clamper is then closed and the capillary and clamper are further raised, cutting the wire with a predetermined length of tail wire extended from the tip of the capillary. The capillary is then moved above the next first bond point, and the tail wire is formed into an initial ball using sparks from the discharge torch. Bonding is then performed at the next first bond point. By repeating this bonding cycle, the pads and leads are successively connected (see, for example, Japanese Patent Application Laid-Open No. 2003-144998).

[0003] Patent No. 5117462 specification

[0004] When wire bonding is performed using the conventional technique described in Patent Document 1, the bonding of the wire to the second bonding point may be insufficient, preventing the tail wire from extending, and causing the bonding device to stop.

[0005] Therefore, an object of the present disclosure is to suppress poor extension of a tail wire in a wire bonding apparatus.

[0006] The wire bonding apparatus of the present disclosure is a wire bonding apparatus comprising: a capillary through which a wire is inserted and which bonds the wire extended from the tip to a bonding target; an ultrasonic vibrator which ultrasonically vibrates the capillary; a clamper which moves up and down in conjunction with the capillary to grip and release the wire; and a control unit which adjusts the movement of the capillary, the opening and closing of the clamper, and the operation of the ultrasonic vibrator. The control unit is characterized in that it lowers the capillary with the clamper closed to ground the tip of the capillary to the bonding target, then ultrasonically vibrates the capillary with the ultrasonic vibrator to start ultrasonic bonding of the wire to the bonding target, opens the clamper after a predetermined period has elapsed after the start of ultrasonic bonding, and stops ultrasonic bonding after the clamper is fully open, changing the predetermined period depending on the duration of ultrasonic bonding.

[0007] In this way, by making it possible to adjust the predetermined period from the start of ultrasonic bonding to the opening of the clamper, the wire can be reliably bonded to the second bonding point before the clamper is opened, thereby preventing poor extension of the tail wire.

[0008] In the wire bonding apparatus of the present disclosure, the predetermined period may be 10% to 90% of the ultrasonic bonding period.

[0009] This allows the clamper to be opened after the wire has been reliably bonded to the second bonding point, thereby preventing the tail wire from being improperly extended.

[0010] In the wire bonding apparatus of the present disclosure, if the period from the start of ultrasonic bonding until the clamper is fully opened is longer than the ultrasonic bonding period, the control unit may extend the ultrasonic bonding period until the clamper is fully opened.

[0011] This allows ultrasonic bonding to be stopped after the clamper is fully opened, so that the wire can be reliably bonded to the second bonding point before the clamper is opened, thereby preventing poor extension of the tail wire.

[0012] The present disclosure can suppress poor extension of a tail wire in a wire bonding apparatus.

[0013] Fig. 1 is an elevational view showing the configuration of a wire bonding apparatus according to an embodiment; Fig. 2 is an explanatory diagram showing a process of bonding a wire between a semiconductor chip and a lead using the wire bonding apparatus according to an embodiment; Fig. 3 is a timing chart showing the timing of ultrasonic bonding and opening of a clamper; Fig. 4 is an explanatory diagram showing a process of extending a tail wire using the wire bonding apparatus according to an embodiment; Fig. 5 is a timing chart showing the case where the ultrasonic bonding period is extended;

[0014] A wire bonding apparatus 100 according to an embodiment will be described below with reference to the drawings. As shown in Fig. 1, the wire bonding apparatus 100 according to the embodiment includes a base 10, an XY table 11, a bonding head 12, a Z-direction motor 13, a horn holder 14, an ultrasonic horn 15, an ultrasonic vibrator 16, a capillary 20, a clamper 17, a clamper driver 17a, a discharge electrode 18, a bonding stage 19, and a controller 60. In the following description, the direction in which the horn holder 14 or the ultrasonic horn 15 extends is referred to as the X-direction, the direction perpendicular to the X-direction on a horizontal plane is referred to as the Y-direction, and the vertical direction is referred to as the Z-direction.

[0015] The XY table 11 is attached to the base 10 and moves an object mounted thereon in the X and Y directions.

[0016] The bonding head 12 is mounted on an XY table 11 and moved in the X and Y directions by the XY table 11. A Z-direction motor 13 and a horn holder 14 driven by the Z-direction motor 13 are housed inside the bonding head 12. The Z-direction motor 13 is equipped with a stator 13b. The horn holder 14 has a base portion 14a facing the stator 13b of the Z-direction motor 13, and serves as a rotor that is rotatably mounted around the shaft 13a of the Z-direction motor 13. An ultrasonic vibrator 16 is attached inside the tip of the horn holder 14.

[0017] An ultrasonic horn 15 is attached to the tip of the horn holder 14 in the X direction, and a capillary 20 is attached to the tip of the ultrasonic horn 15. The ultrasonic horn 15 ultrasonically vibrates the capillary 20 attached to the tip by the vibration of the ultrasonic vibrator 16. A through-hole is provided inside the capillary 20, penetrating it in the vertical direction, and a wire 41 is inserted through the through-hole.

[0018] A clamper 17 and a clamper driver 17a are provided above the ultrasonic horn 15. The clamper 17 moves up and down in conjunction with the capillary 20, and opens and closes with the operation of the clamper driver 17a to grip and release the wire 41.

[0019] A discharge electrode 18 is provided above the bonding stage 19. The discharge electrode 18 may be attached to a frame (not shown) provided on the base 10. The discharge electrode 18 generates a discharge between the discharge electrode 18 and a tail wire 46 (see FIG. 4 ) that is inserted into the capillary 20 and extends from the tip 25 of the capillary 20, melting the tail wire 46 to form the initial ball 42.

[0020] The bonding stage 19 fixes by suction the substrate 30 on which the semiconductor chip 35 is mounted, and heats the substrate 30 and the semiconductor chip 35 with a heater (not shown).

[0021] When the base 14a of the horn holder 14, which constitutes a rotor, rotates as shown by the arrow 91 in Figure 1 due to the electromagnetic force of the stator 13b of the Z-direction motor 13 of the bonding head 12, the capillary 20 attached to the tip of the ultrasonic horn 15 moves in the Z direction as shown by the arrow 92. Also, the bonding stage 19 moves in the X and Y directions by the XY table 11. Therefore, the capillary 20 moves in the X, Y and Z directions by the XY table 11 and the Z-direction motor 13.

[0022] The control unit 60 is a computer including a CPU 61, which is a processor that performs information processing therein, and a memory 62 that stores operation programs, operation data, etc. The operation of the control unit 60 is realized by the CPU 61 executing the operation programs stored in the memory 62.

[0023] The XY table 11 , the Z-direction motor 13 , the ultrasonic vibrator 16 , the clamper drive unit 17 a , the discharge electrode 18 , and the bonding stage 19 are connected to a control unit 60 and operate based on commands from the control unit 60 .

[0024] Next, the operation of the wire bonding apparatus 100 according to the embodiment will be described with reference to Figures 2 to 4. In the following explanation, the operation of bonding a wire 41 from a pad 36 of a semiconductor chip 35 to a lead 31 of a substrate 30 will be described. In this case, the pad 36 serves as a first bonding point, and the lead 31 serves as a second bonding point. The substrate 30 and the semiconductor chip 35 are also bonding targets to which the wire 41 is bonded.

[0025] 2, the control unit 60 generates a discharge between the discharge electrode 18 and the tail wire 46 (see FIG. 4) extending from the tip 25 of the capillary 20, melting the tail wire 46 to form the initial ball 42. Then, the control unit 60 aligns the central axis of the capillary 20 with the center of the pad 36 using the XY table 11.

[0026] The control unit 60 closes the clamper 17 using the clamper drive unit 17a, and drives the Z-direction motor 13 to lower the capillary 20 as shown by the arrow 93 in Figure 2, thereby pressing the initial ball 42 onto the pad 36 and forming a disk-shaped compressed ball 43. At this time, the control unit 60 ultrasonically vibrates the capillary 20 using the ultrasonic vibrator 16. This ultrasonically bonds the compressed ball 43 to the pad 36.

[0027] Next, the control unit 60 drives the clamper drive unit 17a to open the clamper 17, and drives the XY table 11 and the Z-direction motor 13 to raise the capillary 20 as shown by the arrow 94 in Fig. 2, and then loops the capillary 20 toward the center of the lead 31 as shown by the arrow 95a in Fig. 2. At this time, since the clamper 17 is open, the wire 41 is paid out from the tip 25 of the capillary 20.

[0028] When the center of the capillary 20 is directly above the center position of the lead 31, the control unit 60 drives the clamper driving unit 17a to close the clamper 17, and drives the Z-direction motor 13 as shown by the arrow 95b in Figure 2 to lower the capillary 20, ground the tip 25 to the lead 31, and press the wire 41 against the lead 31 with the capillary 20. This forms the loop portion 45.

[0029] When the tip 25 of the capillary 20 contacts the lead 31 at time t1 shown in FIG. 3 , the control unit 60 starts driving the ultrasonic vibrator 16 at time t1. The control unit 60 then drives the ultrasonic vibrator 16 while pressing the wire 41 against the lead 31 with the tip 25 of the capillary 20, causing the capillary 20 to ultrasonically vibrate, thereby ultrasonically bonding the wire 41 to the lead 31. The control unit 60 then stops driving the ultrasonic vibrator 16 at time t4 shown in FIG. 3 , thereby completing the ultrasonic bonding. As shown in FIG. 3 , the ultrasonic bonding period ΔUS is ΔUS = [t4 - t1]. When the ultrasonic bonding is completed, a stitch bond portion 44 is formed on the lead 31, as shown in FIG. 2 .

[0030] The control unit 60 drives the clamper drive unit 17a to change the clamper 17 from the closed state to the open state at time t2, which is delayed by a predetermined period DL from time t1 when ultrasonic bonding begins. The clamper 17 begins to open from the fully closed state at time t2 and is fully open at time t3. This predetermined period DL is set to 10% to 90% of the ultrasonic bonding period ΔUS. Therefore, as the ultrasonic bonding period ΔUS becomes longer, the predetermined period DL also becomes longer, and as the ultrasonic bonding period ΔUS becomes shorter, the predetermined period DL also becomes shorter. In this way, the wire bonding apparatus 100 can change the predetermined period DL in accordance with the ultrasonic bonding period ΔUS.

[0031] When the ultrasonic bonding is completed, the control unit 60 opens the clamper 17 as shown by an arrow 96 in Fig. 4, raises the capillary 20, and pays out the tail wire 46 to the tip 25 of the capillary 20. Thereafter, the control unit 60 drives the clamper driving unit 17a to close the clamper 17, and raises the capillary 20 and the clamper 17 as shown by an arrow 97 in Fig. 4. This causes the tail wire 46 extended from the tip 25 of the capillary 20 to be cut from the stitch bond portion 44.

[0032] Thereafter, the control unit 60 moves the capillary 20 onto the next pad 36, while forming the tail wire 46 into an initial ball 42 by sparks from the discharge electrode 18. Then, the control unit 60 performs bonding on the next pad 36 in the same manner as described with reference to FIG.

[0033] The wire bonding apparatus 100 described above can change the predetermined period DL from the start of ultrasonic bonding until the clamper 17 is opened in accordance with the ultrasonic bonding period ΔUS. This allows the clamper 17 to be opened after the wire 41 has been reliably bonded to the lead 31, thereby preventing poor extension of the tail wire 46. Furthermore, since the predetermined period DL is set to 10% to 90% of the ultrasonic bonding period ΔUS, the clamper 17 will not be opened immediately before the end of the ultrasonic bonding period ΔUS, and the clamper 17 can be opened after the wire 41 has been reliably bonded to the lead 31, preventing poor extension of the tail wire 46.

[0034] Next, another operation of the wire bonding apparatus 100 will be described with reference to FIG. 5 . As shown in FIG. 5 , the control unit 60 drives the clamper drive unit 17a to change the clamper 17 from the closed state to the open state at time t5, which is a predetermined period DL after time t1 when ultrasonic bonding begins. The clamper 17 begins to open from the fully closed state at time t5. The clamper 17 is not yet fully open at time t4 when ultrasonic bonding ends. The clamper 17 then fully opens at time t6, after time t4. In this way, if the period DA from the start of ultrasonic bonding until the clamper 17 is fully opened is longer than the ultrasonic bonding period ΔUS, the control unit 60 extends the ultrasonic bonding period ΔUS by an extension period ΔTA until the clamper 17 is fully opened at time t6. As a result, ultrasonic bonding ends at time t6 when the clamper 17 is fully opened.

[0035] This prevents the ultrasonic vibration from being stopped before the clamper 17 is fully opened, resulting in insufficient bonding of the wire 41 to the lead 31 and the occurrence of poor extension of the tail wire 46.

[0036] The above has described the operation of bonding the wire 41 from the pad 36 of the semiconductor chip 35 to the lead 31 of the substrate 30, but the wire 41 may also be bonded in the reverse order, from the lead 31 to the pad 36. In this case, the lead 31 serves as the first bonding point, and the pad 36 serves as the second bonding point. Then, the initial ball 42 is bonded to the lead 31, and as shown in Figure 3, the ultrasonic vibrator 16 is driven to open the clamper 17 to bond the wire 41 to the pad 36, and then the capillary 20 is raised to extend the tail wire 46.

[0037] 10 base, 11 XY table, 12 bonding head, 13 Z direction motor, 13a shaft, 13b stator, 14 horn holder, 14a base portion, 15 ultrasonic horn, 16 ultrasonic vibrator, 17 clamper, 17a clamper drive portion, 18 discharge electrode, 19 bonding stage, 20 capillary, 25 tip, 30 substrate, 31 lead, 35 semiconductor chip, 36 pad, 41 wire, 42 initial ball, 43 pressure-bonded ball, 44 stitch bond portion, 45 loop portion, 46 tail wire, 60 control portion, 61 CPU, 62 memory, 100 wire bonding apparatus, DA period from start of ultrasonic bonding to fully opening of clamper, DL predetermined period, ΔUS ultrasonic bonding period, ΔTA extension period.

Claims

1. A wire bonding apparatus comprising: a capillary through which a wire is inserted and which bonds the wire extended from its tip to a bonding target; an ultrasonic vibrator which ultrasonically vibrates the capillary; a clamper which moves up and down in conjunction with the capillary to grip and release the wire; and a control unit which adjusts the movement of the capillary, the opening and closing of the clamper, and the operation of the ultrasonic vibrator, wherein the control unit: with the clamper closed, lowers the capillary to ground the tip of the capillary to the bonding target, and then ultrasonically vibrates the capillary with the ultrasonic vibrator to start ultrasonic bonding of the wire to the bonding target; opens the clamper after a predetermined period has elapsed after the start of ultrasonic bonding; stops the ultrasonic bonding after the clamper is fully opened; and changes the predetermined period according to a duration of the ultrasonic bonding.

2. A wire bonding apparatus according to claim 1, wherein the predetermined period is 10% to 90% of the ultrasonic bonding period.

3. A wire bonding apparatus as described in claim 2, characterized in that, when the period from the start of the ultrasonic bonding until the clamper is fully opened is longer than the ultrasonic bonding period, the control unit extends the ultrasonic bonding period until the clamper is fully opened.

Images