JPH0428135B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a bonding method in a wire bonding apparatus that connects an element side electrode of a workpiece such as a semiconductor device and an external lead electrode using a thin metal wire.

Conventional technology As a conventional wire bonding device,
There is one shown in application No. 58-240211. Since the present invention is an improvement on the bonding method using this conventional device, the conventional device will first be explained based on FIGS. 2 and 3.

In FIG. 2, 1 is a slide block whose lifting position and speed are controlled by a control means 2, 3 is a bonding arm rotatably supported by the slide block via a pivot 4, and 5 is a bonding arm 3. The capillary attached to the tip of the
Reference numeral 6 denotes a biasing means for applying an elastic load to the bonding arm 3.

A semiconductor device a as a workpiece is set on the XY table 7, and the device is operated to connect its element side electrode 8a and external lead electrode 8b with a thin metal wire b supplied to the capillary 5. .

The slide block 1 is raised and lowered by the drive of a linear motor 9, and its raising/lowering position and speed are controlled by a control means 2 comprising a main control circuit 2a, a memory 2b, a drive circuit 2c, etc.

The biasing means 6 is a spring 6a which is always connected to the bonding arm 3 via a lever 10.
and a solenoid 6b that applies an elastic load (electromagnetic attraction force) to the bonding arm 3 via the lever 10 only when energized.

The bonding arm 3 consists of an ultrasonic horn, and transmits the vibrations of the ultrasonic vibrator 11 to the capillary 5.

Next, a method of controlling the vertical movement of the slide block 1 in the above device will be explained with reference to FIG.

FIG. 4 shows the ascending and descending positions of the slide block 1 over time. The left half shows the first bonding step (see FIG. 2) for bonding the element side electrode 8a of the semiconductor device a, and the right half shows the second bonding step (see FIG. 3) for bonding the external lead electrode 8b.
However, both are basically controlled in the same way.

In FIG. 4, H is the preset top dead center position, S is the preset search position, and C is the vertical position (contact) of the slide block 1 when the capillary 5 first contacts the bonding surface of the semiconductor device a. position), L is the bottom dead center position.

The contact position C is detected by the contact detection device 12 using the fact that the vibration waveform of ultrasonic vibration changes when the capillary 5 contacts the bonding surface (see FIG. 2). The bottom dead center position L is a certain distance (for example, 0.2 mm) ΔL from the contact position C.
It is defined below.

Thus, as shown in FIG. 4, the slide block 1 descends from the top dead center position H to the search position S at a high speed, and then switches to a low speed and gradually descends while searching for the contact position C, and detects the contact. When the contact position C is detected by the device 12, it further descends at a low speed by the predetermined distance ΔL and reaches the bottom dead center position L (the movement of the capillary 5 is shown by a broken line in FIG. 4). ).

Bonding is performed while the slide block 1 is from the contact position C to the bottom dead center position L, and in the first bonding step, the elastic load by the spring 6a is applied, and in the second bonding step, the elastic load is applied to the spring 6a and the Elastic loads are applied from the respective capillaries 5 to the bonding surfaces by the solenoids 6b.

Problems to be Solved by the Invention According to the conventional method described above, it is essential that the contact position C be accurately detected by the contact detection device 12. However, the contact detection device 12 may malfunction due to the influence of the material of the bonding surface, the vibration of the capillary 5, the bonding arm 3, etc.

For example, if the contact detection device 12 malfunctions before the capillary 5 comes into contact with the bonding surface, the slide block 1 will then descend only by the predetermined distance ΔL, so that the elastic load applied to the capillary 5 from the biasing means 6 will be insufficient. As a result, proper bonding cannot be performed, and in extreme cases, bonding cannot be performed. On the other hand, if the contact is not detected by the contact detection device 12, the elastic load becomes excessive, and bonding failure also occurs in this case.

Means for Solving the Problems In order to solve the above problems, the method of the present invention provides a method in which a bonding arm with a capillary attached is rotatably mounted on a slide block whose lifting position and speed are controlled by a control means. A wire bonding device comprising a biasing means for supporting the capillary and applying an elastic load to the capillary according to the rotation of the bonding arm when the capillary contacts the bonding surface of the workpiece and the bonding arm rotates. In the apparatus, a contact position is determined in advance as a lifting/lowering position of the slide block when the capillary contacts the bonding surface for the first time, and a position just before contact and a bottom dead center position are set above and below this contact position. Then, these are stored in the control means together with the top dead center position of the slide block, and the descending speed of the slide block from the top dead center position to the position immediately before contact and the descending speed of the slide block from the position immediately before contact to the bottom dead center position are controlled. The speed is stored in the control means, and based on these data, the slide block is lowered from the top dead center position to the position immediately before contact, and then lowered from the position immediately before contact to the bottom dead center position.

Function The present invention has the above configuration, and as shown in FIG. 1, the slide block descends at high speed from the top dead center position H to the position M just before contact, and then descends a certain distance ΔH at a predetermined low speed. Bonding can be performed while the bottom dead center position L is reached. Further, in the present invention, since the contact position is not detected as in the conventional example, there is no adverse effect due to malfunction of the contact detection device. Therefore, according to the present invention, there is no large difference in the descending distance of the slide block from when the capillary first contacts the bonding surface until it reaches the bottom dead center position L.
As a result of being able to maintain the elastic load at an appropriate value during bonding, the problem of poor bonding seen in the conventional example can be solved.

Embodiment A bonding method in a wire bonding apparatus according to an embodiment of the present invention will be described below with reference to the drawings.

The wire bonding apparatus shown in FIGS. 2 and 3 has basically the same structure as the conventional apparatus, but differs in that it does not include the contact detection device 12 shown by the phantom line.

The slide block 1 is guided by a guide rod 14 provided on a machine frame 13 to move up and down. This elevating movement is performed by driving a linear motor 9, which consists of a center pole 9a, a yoke 9b, a magnet 9c fixed to the machine frame 13 side, a bobbin 9d fixed to the slide block 1 side, and a coil 9e. It is composed of.

A bonding arm 3 composed of an ultrasonic horn is rotatably supported on the slide block 1 via a pivot 4. A capillary 5 is attached to the tip of this bonding arm 3, to which a thin metal wire b is supplied. Further, an ultrasonic vibrator 22 excited by an ultrasonic oscillator 18 is attached to the base end of the bonding arm 3.

A spring 6a biases the bonding arm 3 counterclockwise in FIG. 2 via the lever 10, and acts on the bonding arm 3 during the first bonding and the second bonding. At other times, the lever 10 is in contact with the stopper 15.

A solenoid 6b attracts the suction plate 16 when energized and uses its electromagnetic attraction force to bias the bonding arm 3 counterclockwise in FIG. 2 via the lever 10. From the main control circuit 2a of the control means 2,
During the second bonding, an energization command is issued, and the solenoid 6b energizes the bonding arm 3. Note that 17 is an auxiliary spring with a weak spring force.

The elevating position and elevating speed of the slide block 1 are controlled by a control means 2. This control means 2 includes a main control circuit 2a, a memory 2b, and a drive circuit 2c.
It is composed of etc. In addition, 19 is a position sensor that detects the vertical position of the slide block 1, and 20
is a speed sensor that detects the vertical speed of the slide block 1.

Fixedly support the semiconductor device a as a workpiece
The XY table 7 performs predetermined movements in two XY directions based on commands from the main control circuit 2a.

The memory 2b of the control means 2 stores a position immediately before contact, which is a position close to above the contact position, which is predetermined as the vertical position of the slide block 1 when the capillary 5 first contacts the bonding surface. M and the bottom dead center position L, which is located close to the bottom of the slide block 1, are stored together with the top dead center position H of the slide block 1. The speed of descent of the slide block 1 from the top dead center position H to the position M just before contact and the speed of descent of the slide block 1 from the position M just before contact to the bottom dead center position L are also stored in the memory 2b.

The distance ΔH between the position M immediately before contact and the bottom dead center position L is set to, for example, 0.5 mm. Furthermore, the speed of descent from the position M just before contact to the position L of bottom dead center is set to be low compared to the speed of descent from the position H just before contact to the position M just before contact.

As shown in FIG. 1, the vertical positions H, M, and L in the first bonding process and the second bonding process differ by the height difference between the electrodes 8a and 8b.

Thus, the control means 2 controls the vertical movement of the slide block 1 as shown in FIG. 1 based on the various data stored in the memory 2b.

First, in the first bonding step, the slide block 1 moves from the top dead center position H to the position M just before contact.
(at this time, for example, capillary 5
is approximately 0.3 mm above the bonding surface of the electrode 8a. ). Then, it descends at low speed from the position M immediately before contact to the bottom dead center position L by a certain distance ΔH (for example, 0.5 mm). During this time, the capillary 5 is in contact with the bonding surface as shown by the broken line in FIG. 1 and as shown in FIG. The first bonding action is performed using the elastic load of.

After the slide block 1 stops at the bottom dead center position L for a predetermined time, it rises at high speed and reaches the top dead center position H for the second bonding process.

While the slide block 1 is stopped at the top dead center position H, the XY table moves so that the electrode 8b is positioned directly below the capillary 5.
Next, the slide block 1 is raised and lowered in the same manner as in the first bonding step to perform the second bonding. However, in the second bonding process, the solenoid 6b is energized and bonding is performed under the condition that the elastic loads of both the spring 6a and the solenoid 6b are applied.

The present invention can be configured in various ways other than those shown in the above embodiments. For example, the motion characteristics regarding the vertical position and vertical speed of the slide block 1 are
Of course, it is not limited to what is shown in the figure.

Effects of the Invention The present invention has the above-mentioned configuration, in which the position immediately before the contact of the slide block and the bottom dead center position are accurately set in advance, and when the slide block descends at low speed between these positions, the capillary moves toward the bonding surface of the workpiece. Bonding is performed with the capillary in contact with the bonding surface and an elastic load is applied by the biasing means, and there is a large difference in the descending distance of the slide block from when the capillary first contacts the bonding surface to when it reaches the bottom dead center position. Since this does not occur, the elastic load during bonding can be maintained at an appropriate value.

Therefore, according to the present invention, it is possible to solve the problem of defective bonding caused by malfunction of the contact detection device in the conventional example.

[Brief explanation of drawings]

Fig. 1 is a motion characteristic diagram of a slide block in an embodiment of the present invention, and Fig. 2 is a partially longitudinal side view showing an example of a wire bonding device used in the present invention (however, the portion indicated by the imaginary line is a conventional one). 3 is a side view of the main parts showing its operation, and FIG. 4 is a diagram showing the movement characteristics of the slide block in the conventional example. 1...Slide block, 2...Control means, 3
...Bonding arm, 5...Capillary, 6
...Biasing means, a...Workpiece, H...Top dead center position, M...Position immediately before contact, L...Bottom dead center position.

Claims (1)

[Claims] 1. A bonding arm with a capillary attached is movably supported on a slide block whose lifting position and speed are controlled by a control means, and the bonding arm moves as the capillary comes into contact with the bonding surface of the workpiece. In the wire bonding apparatus, which is provided with a biasing means for applying an elastic load to the capillary in accordance with the movement of the bonding arm, the slide block is moved up and down when the capillary first contacts the bonding surface. A contact position is determined in advance, and a position immediately before contact and a bottom dead center position that approach above and below this contact position are set, and these are stored in the control means together with the top dead center position of the slide block, and the top dead center position is stored in the control means. The descending speed of the slide block from the position immediately before contact to the position immediately before contact and the descending speed of the slide block from the position immediately before contact to the position at bottom dead center are stored in the control means, and based on these data, the slide block is moved from the position at top dead center to contact. A method of bonding in a wire bonding apparatus, characterized in that the wire bonding device is lowered to a position immediately before contact, and then lowered from the position immediately before contact to a bottom dead center position.