JPH04336440A - Wire bonding apparatus and wire bonding method - Google Patents

Abstract

PURPOSE:To form the appropriate loop of a wire between a first and a second bonding pad without the loop contacting with a counterpart pad which causes a short circuit, the disconnection of the wire on the first bonding pad, and the damage to the wire due to the clamping impact of a clamper. CONSTITUTION:At the initial stage prior to the bonding, a clamper 17 clamps a wire 6 with a smaller force until the arrival of a capillary 2 at a first bonding pad. Thereafter, the clamper 7 continues the clamping with a larger force. After the completion of the bonding of the first bonding pad, the clamper 17 and the capillary 2, both situated at a predetermined height above a second bonding pad, effect a second bonding, with a suitable length ensured for a loop 6b, by a timing delay in the completion of the fall between the capillary 2 and the clamper 17.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wire bonding apparatus and a wire bonding method for connecting a semiconductor chip and an object to be connected such as an external lead using a thin metal wire.

0002

[Prior Art] FIGS. 4 and 5 are, for example, Japanese Patent Laid-Open No. 61-11
3250 is a schematic side view of a conventional wire bonding device and an explanatory diagram showing a wire bonding method in order of operation. FIG. In FIG. 4, reference numeral 1 denotes a wire bonding device, which is configured as follows. A capillary 2, a clamping means 3 for clamping the wire 6 above the capillary 2, and a bobbin 7 disposed above the capillary 2 and feeding the wire 6.
It is equipped with 8 is a guide for the wire 6.

A wire 2 is passed through the capillary 2, and the capillary 2 is moved up and down by an up and down moving means (not shown). The clamping means 3 is moved up and down by a vertical moving means (not shown), and clamps and releases the wire 6 by an opening/closing means (not shown).

Next, a wire bonding method using this wire bonding apparatus 1 will be explained with reference to FIG. First, in Fig. A, the clamping means 3 clamps a wire 6, and the tip of the wire 6 is brought out from the lower part of the capillary 2 to form a sphere 6a. A lead frame 5 is fixed on a stage (not shown), and a semiconductor chip 4 is fixed on the lead frame. 4a is the electrode of chip 4;
5a is an external lead, and 5b is an electrode portion. An electrode 4a is located directly below the capillary 2.

Next, as shown in Figure B, the clamping means 3
After releasing the clamp, the capillary 2 is lowered and the electrode 4a
The tip of the wire 6 is pressed onto the electrode 4a by heating. Next, the capillary 2 is raised, and as shown in Figure C, the stage is moved to move the capillary 2 and the clamp means 3 parallel to the stage, and position them above the electrode section 5b of the external lead 5a. This movement allows the wire 6 to be paid out a predetermined length.

After that, the capillary 2 is lowered, and on the way down, the wire 6 is clamped by the clamping means 3 as shown in Fig. D.
This clamping means 3 is lowered together with the capillary 2, the capillary 2 is pressed against the electrode part 5b, and heated to press the middle of the wire 6 to the electrode part 5b.

Subsequently, as shown in Fig. E, the clamping means 3 is released and the capillary 2 begins to rise. As shown in Figure F, the wire 6 is clamped by the clamping means 3 while the capillary 2 is rising. Furthermore, as shown in Figure G, the clamping means 3 is raised together with the capillary 2. As a result, the wire 6 is cut from above the crimped portion to the electrode portion 5b, and the chip 4 and the external lead 5a are wire-bonded.

Finally, as shown in Figure H, the tip of the wire 6 is heated with a hydrogen torch 9, and as shown in Figure I, the tip of the wire 6 is formed into a sphere 6a, completing the process.

The timing of clamping the clamping means 3 is adjusted by a so-called combination cam using two cams, taking into consideration the length of the wire 6 and the height of the capillary 2.
The capillary 2 is clamped in the middle of its descent.

When the capillary 2 rises in the state shown in FIG. 5C, the wire 6 may be bent between it and the clamping means 3, causing slack 6d, as shown in FIG. This is because the wire 6 is extremely thin and soft, and is pushed up by the frictional resistance within the capillary 2. Therefore, compared to the proper loop 6b made by using the entire length H of the wire 6, a short and small loop 6c is formed, which is shorter by the slack 6d. When the short loop 6c is formed, the intermediate portion contacts the corner portion of the semiconductor chip 4, resulting in a short circuit. Further, as shown in FIG. 7, the wire 6 may be strongly pulled by the short loop 6c and may be bent and broken on the connection portion of the electrode 4a.

Furthermore, since the wire 6 is strongly clamped by the clamping means 3, the wire 6 made of thin gold wire, thin aluminum wire, etc.
In some cases, the impact of pinching can cause a constriction with a reduced cross section. A state in which this constriction is located in the loop of the wire 6 is shown in a plan view in FIG. 6e is this constriction.

0012

[Problems to be Solved by the Invention] In the conventional wire bonding apparatus 1 and wire bonding method as described above, the loop of the wire 6 formed by wire bonding between the first and second bonding points becomes a short and small loop 6c. There are problems in that the loop may come into contact with the corner of the semiconductor chip 4 and cause a short circuit, or the wire may bend and break on the connection portion of the electrode 4a. In addition, since the wire 6 is suddenly and strongly clamped by the clamping means 3, the constriction 6
There is a problem that e may occur.

Furthermore, when the wire 6 is clamped by the clamping means 3 in the state shown in FIG. There was a problem in that it was difficult to obtain a suitable loop shape.

[0014] The present invention was made in order to solve such problems, and the wire between the first bond point and the second bond point is formed into a proper loop, and one of the connected wires is connected in the middle of the loop. To provide a wire bonding device and a wire bonding method in which the wire does not come into contact with objects or break on the connection portion of the first bonding point, and the wire does not become constricted due to strong clamping by a clamper means. The purpose is to obtain.

[0015]

[Means for Solving the Problems] The wire bonding apparatus and wire bonding method according to the present invention perform the wire bonding cycle operation with the wire always being clamped between the clampers, and when lowering the capillary at the beginning of the process. In this case, the clamper is held at a predetermined height position, and the wire is pulled down by a weak clamp, and in the process after the connection at the first bond point, the clamper clamps the wire in place, and the wire is clamped in place in the raised cavity. and the clamper are moved above the second bond point, and the completion of the capillary's descent above the second bond point is delayed relative to the completion of the descent of the clamper. After connection at the second bond point, the capillary starts to rise, and after this, the clamper starts to rise.

[0016]

[Operation] In this invention, the wire is always clamped by the clamper, and damage caused by shocks applied to the wire is eliminated by repeating clamping and releasing. In addition, there is no variation in the time it takes to clamp the wire, there is no slack in the wire between the clampers due to the rise of the capillary after connection at the first bond point, and the wire below the cavity is made to a predetermined length. The wire loop formed by the connection at the second bond point can be formed into an appropriate shape, and the middle part of the loop may come into contact with one of the objects to be connected, or the wire may be pulled and cut on the connection point at the first bond point. disappears.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a schematic diagram of an embodiment of a wire bonding apparatus according to the present invention. The wire bonding apparatus 10 is configured as follows. 11 is a bonding head main body, which is fixed on an XY table 12. The X-Y table 12 is moved in the X-axis direction by an X-axis electric motor 13 via an X-axis drive transmission means (not shown), and is moved by a Y-axis electric motor 14 via a Y-axis drive transmission means (not shown). is moved in the Y-axis direction. The capillary 2 is attached to the tip of the ultrasonic horn 15,
The ultrasonic horn 15 is rotatably supported by the head body 11 via a support pin 16 at an intermediate portion. A clamper 17 for clamping the wire 6 is attached to the tip of a support arm 18, and the support arm 18 is rotatably supported by the head body 11 via a support pin 19 at an intermediate portion. Reference numeral 20 denotes a first Z-axis electric motor, which is connected to the rear end of the ultrasonic horn 15 via a first vertical movement transmission means 21 to move it up and down. As a result, the ultrasonic horn 15 is rotated about the support pin 16, causing the capillary 2 to move up and down. Reference numeral 22 denotes a second Z-axis electric motor, which is connected to the rear end of the support arm 18 via a second vertical movement transmission means 23 to move it up and down. As a result, the support arm 18 is rotated about the support pin 19, causing the clamper 17 to move up and down. First and second vertical motion transmission means 2
1 and 23 are each configured as follows, for example. A connecting body 24 fixed to the shaft ends of the electric motors 20 and 22
The lower end of the link 26 is connected to the link 26 via a connecting pin 25. The link 26 is connected to the rear end of the ultrasonic horn 15 and the support arm 18 via a roller 27 at the upper end.

Next, 28 is a guide body that is attached to the head body 11 and guides the wire 6, and 29 is a wire spool from which the wire 6 is wound and drawn out. 30 is a hydrogen torch or the like for forming the sphere 6a of the wire 6 at the bottom of the capillary 2.

The clamper 17 is shown in FIG. 31 is a fixed piece, 32 is a movable piece rotatably supported by the fixed piece 31 via a support shaft 33, and the wire 6 is passed between them in the vertical direction. 34 is an exciting coil, and 35 is a yoke. When the excitation coil 34 is energized, the movable iron piece at the rear end of the movable piece 32 is attracted, and the movable piece 32 closes and pinches the wire 6. When the power is cut off, the movable piece 3 is moved by a return spring (not shown).
2 opens. By switching the current to the excitation coil 34 into two stages, weak and strong, the clamping force can be set to a weak clamping force in the first stage that allows the wire 6 to be pulled out smoothly, and a weak clamping force in the first stage that allows the wire 6 to be fixed (to the extent that it does not deform). A second stage of strong pinching is performed.

Returning to FIG. 1, reference numeral 40 denotes a stage, on which a lead frame 42 is attracted, and a semiconductor chip 41 is fixed onto the lead frame 42. As shown in FIG. Reference numeral 41a denotes an electrode of the chip 41, which forms a first bonding point. 42b is an electrode portion of the external lead 42a of the lead frame 42.

A wire bonding method using the wire bonding apparatus 10 will be explained with reference to FIG. The clamper 17 performs a clamping operation during the entire process, and in the processes shown in figures A and B, it performs a weak first stage clamping that allows the wire 6 to be pulled out, and in the processes shown in figures C to H, it clamps the wire 6. The wire 6 is held firmly and strongly clamped (however, the wire 6 is not deformed and is indicated by hatching). First, in FIG. A, the clamper 17 clamps the wire 6 in the first stage, and the tip of the wire 6 is brought out from the lower part of the capillary 2 to form a sphere 6a. Capillary 2 and clamper 17 are
It is located above the electrode 41a.

Next, as shown in Figure B, the capillary 2 is lowered and the clamper 17 is lowered to the height of the clamping force switching position h. When the capillary 2 descends onto the electrode 41a of the chip 41, the ultrasonic horn 15 generates ultrasonic waves to perform the first bonding. During this bonding, the clamping force of the clamper 17 is switched to the second stage. When bonding is completed, the capillary 2 is raised to a height h1, as shown in Figure C. This h1 is the length necessary for connecting the wire 6 with a proper loop. h becomes h1+h2.

Next, as shown in FIG. D, the capillary 2 and clamper 17 are moved upward in the Y-axis direction by the X-Y table 12 and simultaneously lowered. At this time, as shown in Figure E, the clamper 17 completes its descent to the predetermined position faster than the capillary 2. The height h2 of the clamper 17 in this state is the sum of the distances h3 and h4. The wire 6 is pushed out below the capillary 2, and the length of the wire curved portion 6f is equal to the length h4 added to the length h1 necessary for connection with a proper loop.

Next, as shown in Fig. F, the capillary 2 is lowered onto the electrode portion 42b of the external lead 42a, and the ultrasonic horn 15 generates ultrasonic waves to perform second bonding, thereby forming the loop 6b of the wire 6. The distance between the capillary 2 and the clamper 17 is h2, and there is no bend in the wire 6 between the two. In Fig. E, even if the wire 6 is slack between the clamper 17 and the capillary 2, the slack can be lengthened by lowering only the capillary 2 by a length h4.

Subsequently, as shown in Fig. G, after the capillary 2 is raised to a height where the wire 6 has a protruding length m, the clamper 17 is also started to rise. This protrusion length m is the length necessary to form the sphere 6a on the wire 6. In this way, the wire 6 is cut off on the second bonding part. Further, as shown in Figure H, the clamper 17 and the cavity 2 are raised while maintaining the same distance, and the torch 30 forms a sphere 6a on the wire 6.

In this manner, one cycle of wire bonding is performed through a series of operations.

Note that in the above embodiment, the semiconductor chip 41
Although wire bonding is performed between the external lead 42a and the external lead 42a, the present invention is not limited to this, and can be applied to wire bonding between other types of electronic components and other objects to be connected.

Further, in the above embodiment, a mechanism using an electric motor as a driving source is used as the means for vertically moving the capillary 2 and the clamper 17, but the mechanism is not limited to this, and a mechanism using an air cylinder as a driving source may also be used. good.

[0029]

As described above, according to the present invention, the wire is always clamped by the clamper during the bonding cycle operation, and the clamper is set to a weak clamping force before the first bonding at the beginning of the process. After that, a strong clamping force was applied, which eliminates the impact of clamping and eliminates abnormal deformation of the wire. In addition, when performing the second bonding, the timing of the completion of the capillary's descent was delayed relative to the completion of the descent of the clamper to the predetermined height position, so that a proper loop of the wire was formed and the connection was possible. This eliminates the possibility of the intermediate portion contacting one of the objects to be connected and short-circuiting, or cutting the wire on the first bonding portion. Furthermore, after the second bonding, the start of the clamper's rise is delayed relative to the start of the capillary's rise, so that the capillary's rise does not stop halfway, making it possible to create a wire protrusion of a stable length below the capillary. , one cycle time of wire bonding is shortened. In this way, the quality and productivity of wire bonding is improved.

[Brief explanation of drawings]

FIG. 1 is a schematic configuration diagram of an embodiment of a wire bonding apparatus according to the present invention.

FIG. 2 is a perspective view of the clamper of FIG. 1;

FIG. 3 is an explanatory diagram of the operation of the wire bonding method using the apparatus of FIG. 1;

FIG. 4 is a configuration diagram of main parts of a conventional wire bonding device.

FIG. 5 is an explanatory diagram of the operation of the wire bonding method using the apparatus of FIG. 4;

FIG. 6 is an explanatory diagram showing the formation of a wire loop between the first and second bonding parts by a conventional method.

7 is an explanatory diagram showing an accident of bending and cutting the wire on the first bonding portion in the case of the short and small loop of the wire in FIG. 6; FIG.

FIG. 8 is a plan view showing a constriction formed in the wire due to clamping using a conventional method.

[Explanation of symbols]

2 Capillary 6 Wire 6a Sphere 6b Proper loop 11 Bonding head body 12 X-Y table 15 Ultrasonic horn 17 Clamper 18 Support arm 20 1st Z-axis electric motor 21 First vertical motion transmission means 22 2nd Z-axis electric motor 23 Second vertical motion transmission means 29 Wire spool 41 Semiconductor chip 42 Lead frame 42a External lead

Claims (2)

[Claims] 1. The ultrasonic horn is fixed to the tip of an ultrasonic horn that is vertically movably supported by a bonding head body on an X-Y table, and is raised and lowered by a first vertical drive means, A capillary through which a wire passes from above is fixed to the tip of a support arm which is disposed above the capillary and supported by the bonding head body so as to be movable up and down, and is raised and lowered by a second vertical drive means. The wire pulled out from the upper wire spool is passed through and is equipped with a clamper that guides it to the capillary, and this clamper can be switched to two levels of clamping force, weak and strong, so that During the bonding cycle operation, the clamper clamps the wire with a weak clamping force until the initial capillary descends onto the first bonding point of the object to be connected. Now, there is a wire bonding device characterized in that the clamping force is switched to a strong clamping force to continue clamping the wire. 2. The wire is clamped with a weak clamping force by a clamper positioned at a predetermined height, a capillary is positioned below the clamper at a predetermined distance, a ball of wire is formed at the bottom of the capillary, and the wire is clamped with a weak clamping force. A first step of placing the capillary above the first bonding point of the object to be connected, lowering the clamper holding the wire with a weak clamping force to a predetermined position, lowering the capillary above the first bonding point, and lowering the capillary to the first bonding point. A second step of wire bonding, and a third step of switching the clamper to strong clamping force during the first wire bonding and raising the capillary after the first bonding to a height corresponding to the length required for the wire to form a proper loop. In the process, the capillary and clamper are moved horizontally to a position above the second bond point, and both are lowered at the same time, and the timing of completion of the capillary's descent to the second bond point is delayed relative to the completion of descent of the clamper to a predetermined height position. A fourth step, a fifth step of performing second bonding with the capillary lowered to the second bonding point, and a fifth step of starting to ascend the capillary after the second bonding, and when a predetermined length of wire has come out below the capillary, The sixth step is to start raising the clamper and cut the wire above the second bonding part, and the capillary and the clamper are raised to a predetermined height position while maintaining the distance in the sixth step, and a sphere is attached to the wire coming out from below the capillary. A wire bonding method according to a seventh step of forming.