JP2716362B2 - Wire bonding apparatus and wire bonding method - Google Patents

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, and more particularly, to a wire bonding apparatus for electrically connecting electrodes of a semiconductor device (semiconductor chip) to electrode portions of a lead frame or a package by thin metal wires. And a wire bonding method.

[0002]

2. Description of the Related Art As shown in FIG. 8, a conventional wire bonding apparatus has a capillary 12, an arm 11 for holding and swinging the capillary 12, a bearing 38 for rotating and supporting the arm 11, and moving the capillary 12 up and down. For this purpose, a Z-axis drive motor 36 for swinging the arm 11 is provided.

In the wire bonding apparatus shown in FIG. 8, for example, when the bearing 38 is worn and the wire bonding is performed as it is, the variation in the ball pressure bonding diameter of the fine metal wire in the bonding portion and the cratering of the electrode portion (the surface of the silicon substrate under the electrode) (A phenomenon in which a crack enters a part and peels off from the part), resulting in a product defect. For this reason, the occurrence of defects and the outflow of defective products have been prevented by regularly exchanging bearings and regularly finding the inconvenience of product appearance. However, in reality, there is a problem in that the degree of abrasion is different due to differences in the wire bonding apparatus, so that complete stopping is not possible, and it is not possible to reduce the number of man-hours required for regular product appearance inspection.

As a countermeasure, a wire bonding apparatus as shown in FIG. 9 has been conventionally considered. In FIG. 9, an XY table 35 in which a Y-axis drive motor 34 is coupled is mounted on an X-axis drive unit 33 having an X-axis drive motor 32 mounted on a fixed base 31. A Z-axis drive unit 37, to which a Z-axis drive motor 36 is coupled, is mounted on an XY table 35, and the arm 11 is rotatably supported by a bearing 38. A thin metal wire ball is formed in contact with an electrode of the semiconductor device 13 mounted on the heater block 14. And a strain gauge 4 for sensing the vibration of the arm 11
0 and an amplifier 4 for amplifying the output from the strain gauge 40
1 and a comparison circuit 42 for comparing and judging the output waveform from the amplifier 41 with the reference waveform. If it is judged that the output waveform during wire bonding is different from the reference waveform, the wire bonding apparatus is stopped as an error. This is a technique for storing as an error or an error, and subsequently discriminating it as a defective product.

[0005]

However, in this prior art, since the strain gauge 40 is attached to the arm 11, all vibrations and deflections in the direction not directly applied to the semiconductor device 13 are detected, and the semiconductor device 13 It was not possible to detect an accurate impact load applied to the vehicle.

Further, when the strain gauge 40 is attached to the arm 11, the inertial mass of the arm 11 changes depending on the position where the strain gauge 40 is attached, so that the measured impact load changes. Was difficult to manage.

Further, since the strain gauge 40 is interlocked with the swing of the arm 11 and the movement of the XY table 35, disconnection due to repeated fatigue of the code 41a for sending a signal from the strain gauge 40 to the amplifier 41, and the code of the strain gauge 40 There has been a problem that disconnection due to repeated fatigue and deterioration of the strain gauge 40 itself occur.

Accordingly, an object of the present invention is to eliminate the above-mentioned disadvantages of the prior art, to accurately grasp the state of a wire bonding apparatus, and to appropriately perform maintenance and repair of the apparatus, and thereby to improve reliability. The object of the present invention is to provide a wire bonding method capable of efficiently obtaining a semiconductor device having high reliability.

[0009]

A feature of the present invention is that in a wire bonding apparatus for wire bonding a thin metal wire by contacting a capillary with an electrode of a semiconductor device, the capillary is moved to a position where it can contact the surface thereof. The wire bonding apparatus includes a bonding check stage disposed, a strain sensor disposed so as to be in contact with the back surface of the bonding check stage, and means for processing a signal from the strain sensor. Here, the shape of the bonding check stage is a disk shape, and may include a stage up-down mechanism for vertically moving the bonding check stage mounted on the heater block and a stage rotating mechanism for rotating the stage. Alternatively, the bonding check stage has a rectangular shape, and may include a stage vertical mechanism for vertically moving the bonding check stage placed on the heater block and a stage linear driving mechanism for linearly moving the stage. In addition, it is preferable that heat insulating means are provided between the heater block on which the semiconductor device is mounted and the strain sensor and between the heater block on which the bonding check stage is mounted and the strain sensor.

Another feature of the present invention is that in a wire bonding method in which a capillary is brought into contact with an electrode of a semiconductor device to wire-bond a thin metal wire, the capillary is moved to a position where it can be brought into contact with the surface thereof. A bonding check stage and a strain sensor positioned so as to be in contact with the back surface of the bonding check stage are provided, and the bonding check stage is mounted under the same conditions as wire bonding conditions to the electrodes of the semiconductor device. The present invention is directed to a wire bonding method in which a bonding is performed, and the impact load at this time is detected by the strain sensor to check the state of the wire bonding apparatus. Here, it is preferable that the bonding check stage has a surface similar to the surface of the electrode of the semiconductor device.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings.

FIG. 1 is a structural view showing a wire bonding apparatus according to an embodiment of the present invention. An X-Y table 35 in which a Y-axis driving motor 34 is connected is mounted on an X-axis driving unit 33 having an X-axis driving motor 32 mounted on a fixed base 31. A Z-axis drive motor 36 is provided on an XY table 35 which is capable of moving in the X-axis direction and the Y-axis direction orthogonal to each other on a horizontal plane by driving the X-axis drive motor 32 and the Y-axis drive motor 34. The coupled Z-axis drive unit 37 is placed, and the arm 11 is mounted on the bearing mechanism 3.
8, a capillary 12 which is held by the arm 11 by the drive of the Z-axis drive motor 36 and moves up and down.
Performs ball bonding of a thin metal wire in contact with an electrode of a semiconductor device (semiconductor chip) 13 mounted on the heater block 14.

Further, a bonding check stage 20 having an upper surface at the same height as the wire bonding surface of the semiconductor device 13 is provided on the heater block 22 between the heater block 14 and the XY table 35. A strain sensor (hereinafter, referred to as a dynamic strain sensor) 21 for detecting an impact load at the time of bonding is provided below the bonding check stage 20. Insulating plates 27 and 28 are provided between the heater blocks 14 and 22 and the dynamic strain sensor 21 to prevent the temperature of the dynamic strain sensor 21 from rising. For example, a heat insulating plate 2 made of a metal plate
Radiation heat from the heater blocks 14 and 22 is shielded by 7 and 28. Also, stage 2 for bonding check
A stage rotation mechanism 23 is mounted so as to be rotatable together with the heater block 22, and a bonding check stage 20 is mounted on a stage elevating mechanism 24 so as to be able to elevate and lower together with the heater block 22. Have been.

During the operation of the wire bonding apparatus, after bonding a predetermined number of operations, the XY stage 35 is moved to a position where the capillary 12 can bond to the bonding check stage 20. Then, the semiconductor device (semiconductor chip) in which the capillary 12 is a product
Check bonding is performed on the bonding check stage 20 under the same conditions as the wire bonding conditions for the lead frame 13 and the lead frame. At this time, the impact load that the capillary 12 check-bonds to the bonding check stage 20 is detected by the dynamic strain sensor 21,
The resulting signal voltage is sent to the amplifier 41 of the transistor amplifier circuit by the code (line) 21a and amplified.

FIG. 2A shows a state in which a gold ball at the tip of a fine gold wire (bonding wire) 15 penetrating the capillary 12 is connected to an electrode (bonding pad) 13 a of a semiconductor device (semiconductor chip) 13 on a heater block 14. The ball bonding 17 pressed at 12 is shown. Further, a state in which the capillary 12 is moved rightward in the figure and stitch-bonded (wedge-bonded) 18 to the inner lead 19 of the lead frame is shown by a two-dot chain line imaginary line. The electrode 13a is a gold electrode or an aluminum electrode formed on the silicon oxide film on the surface of the silicon substrate. The lead frame is made of a copper alloy, and the bonding surface of the inner lead 19 is partially plated with gold.

FIG. 2B shows a state of the check bonding. The bonding check stage 20 is mounted on the heater block 22. A gold or aluminum metal film 20a having the same film configuration as the electrode 13a is formed on the entire surface of the bonding check stage 20. Then, under the same conditions as the ball bonding of FIG. 2A (the same weighting conditions and the like), the ball bonding 17 in which the gold ball at the tip of the fine gold wire 15 penetrating the capillary 12 is pressed against the metal film 20a by the capillary 12 is performed. Do
Thereafter, the capillary 12 is moved rightward in the figure to perform stitch bonding 18 (indicated by a two-dot chain line). Stage 2 for bonding check
The dynamic strain sensor 21 is in contact with the back surface below the position where the 0 ball bonding 17 is performed.

FIG. 3A shows the output waveform of the amplifier 41 at the time of normal wire bonding in the ball bonding of the check bonding, and FIG. 3B shows the rattling of the arm support due to wear of the bearing 38 and the like. 7 shows an output waveform of the amplifier 41 at the time of wire bonding in the case.

That is, at the time (period) when the wire bonding of the semiconductor device 13 is normally performed on the heater block 14 and no bonding failure occurs, the strain sensor 21 when the check bonding is performed on the boding check stage 20 under the same conditions. FIG. 3A shows a waveform obtained by amplifying the output voltage of the semiconductor device 13 by the amplifier 41. The wire bonding of the semiconductor device 13 is abnormally performed on the heater block 14 due to the above-described inconvenience of the bonding apparatus, and a bonding failure occurs. FIG. 3 shows a waveform at the time (period) when check bonding is performed to the bonding check stage 20 under the same conditions.
(B).

Therefore, when the waveform shown in FIG. 3B is obtained, it is recognized that the wire bonding to the semiconductor device at that time (period) is abnormal.

[0020] In FIG. 3 (B), the abnormality is an initial peak value V _P of the shock voltage due to the impact load higher than a predetermined setting value, the convergence time T is long. From this feature,
The initial peak value V _P only convergence time T _S (5 to 10 ms) can be measured and determined to be abnormal if the value of the set value or more.

Therefore, in the comparison circuit 42, a predetermined set value of the shock voltage is used as a reference voltage, and this voltage is compared with the input voltage of the shock voltage from the dynamic strain sensor due to the shock load. If it is determined, the operation stop signal is sent to the wire bonding apparatus control unit (not shown) to stop the operation and prompt the maintenance. Further, a Schmitt trigger circuit can be used as the comparison circuit 42.

For example, every time the bonding of the electrode connection of the semiconductor device is performed 100 to 1000 times, check bonding is performed on the bonding check stage 20, and FIG.
When the waveform is as shown in (B), the bonding work of the electrode connection is interrupted, and maintenance repair of the wire bonding apparatus such as replacement of the bearing mechanism 19 is performed.

FIG. 4 is a perspective view showing a boding check stage mechanism of the first embodiment. A shaft 25 is provided on the stage elevating mechanism 24 and the stage rotating mechanism 23.
The heater block 22 is placed via the heater block 22, and a disc-shaped bonding check stage 2 is mounted on the heater block 22.
0 is placed. Further, a dynamic strain sensor 21 is mounted below the outer periphery of the bonding check stage 20. The illustration of the heat insulating plate is omitted.

Next, the operation of FIG. 4 will be described with reference to FIG. After performing check bonding on the outer peripheral portion of the surface of the bonding check stage 20 to confirm and determine the operation state of the bonding apparatus, the stage elevating mechanism 24
By raising the shaft 25, the heater block 22 and the bonding check stage 20 are raised (FIG. 5A), and by rotating the shaft 25 by the stage rotating mechanism 23, the heater block 22 and the bonding check stage 20 are moved. Rotate (Fig. 5
(B)), the shaft 2 is moved by the stage raising / lowering mechanism 24.
5, the heater block 22 and the bonding check stage 20 are lowered to bring the back surface of the outer peripheral portion of the bonding check stage 20 into contact with the dynamic strain sensor 21 (FIG. 5C), and the next check bonding is performed. I do. In this embodiment, the impact load can be measured 360 times, for example, by rotating the bonding check stage 20 at a rotation angle of 1 ° (degree).

FIG. 6 is a perspective view showing a boding check stage mechanism according to the second embodiment. Linear drive mechanism 26
A stage raising / lowering mechanism 24 is mounted on the upper side, and the heater block 2 is mounted on the stage raising / lowering mechanism 24 via a shaft.
2, and a rectangular bonding check stage 20 is mounted on the heater block 22.

Next, the operation of FIG. 6 will be described with reference to FIG. Check bonding is performed on the surface portion near one long side of the bonding check stage 20 to check and determine the operating state of the bonding apparatus. Then, the shaft 25 is raised by the stage raising / lowering mechanism 24 to check the bonding between the heater block 22 and the heater block 22. Stage 20
Is raised (FIG. 7A), and the heater block 22 and the bonding check stage 2 are moved by the linear drive mechanism 26.
0 by a predetermined distance in the long side extending direction (FIG. 7)
(B)) The shaft 25 is lowered by the stage raising / lowering mechanism 24 to lower the heater block 22 and the bonding check stage 20, and the back surface near one long side of the bonding check stage 20 is moved to the dynamic strain sensor 21. (FIG. 7 (C)), and the next check bonding is performed. Then, after the check bonding along one long side, the bonding check stage 21 is turned 180 ° and mounted, so that the check bonding along the other long side can be performed.

The first embodiment has the advantage of using a rotating mechanism that can simplify the mechanism structure without using a linear drive mechanism. On the other hand, in the second embodiment, since check bonding can be performed along two long sides, there is an advantage that running cost is low.

In the embodiment, the electrode 1 of the semiconductor device 13 is used.
A metal film 20a having the same configuration as that of 3a was formed on the surface of the bonding check stage 20, and a check was performed by ball bonding. This is to bring the state closer to the actual ball bonding state to the electrode of the semiconductor device.

However, as described with reference to FIG. 3, the present invention compares the shock voltage when the bonding apparatus is in a normal state and the shock voltage when the bonding apparatus is in an abnormal state.
There is no strict restriction on the material, shape and surface treatment of No. 0. Since the comparison between the normal state and the abnormal state is made as described above, the dynamic strain sensor 21 can also be selected from general commercially available ones.

Then, the bonding check stage 2
0 is the required assembly temperature (200 ° C.) by the heater block 22.
To 400 ° C.), the semiconductor device 13
Check bonding can be performed under the same conditions as wire bonding to the semiconductor device, and the impact load (impact voltage) can be measured.

Since the absolute value of the impact load in ball bonding is larger than stitch bonding,
In check bonding, it is preferable to determine whether the device is normal or abnormal using the impact load (impact voltage) in ball bonding.

When the check is performed using stitch bonding, it is conceivable that the metal film 20a on the surface of the bonding check stage 20 is a gold plating film in the same manner as the surface of the lead frame or the surface of the electrode layer of the package. .

[0033]

As described above, in the present invention, the bonding check stage is arranged at a position where the capillary moves and can abut on the surface thereof, and the dynamic strain sensor is arranged so as to be able to abut on the back surface of the bonding check stage. I have. Therefore, the signal from the dynamic strain sensor can accurately indicate the influence of the state of the bonding apparatus on the wire bonding.

Thus, the impact load at the time of wire bonding is measured for each predetermined number of operations (the number of wire bonding operations). If the impact load is equal to or greater than a set value, the operation is stopped and maintenance is promoted. Can be accurately detected, and continuous defects can be eliminated.

Further, the frequency of regular product appearance inspection can be reduced, and labor can be saved.

When the embodiment shown in FIGS. 1 to 5 of the present invention is applied to an actual product, wire bonding failure which has conventionally occurred by 0.5% can be reduced to 0.01% or less.

[Brief description of the drawings]

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

FIG. 2A is a diagram illustrating wire bonding of a semiconductor device and FIG. 2B is a diagram illustrating check bonding of a bonding check stage in the example of the present invention.

3A and 3B are diagrams showing output waveforms of an amplifier in check bonding according to an embodiment of the present invention, wherein FIG. 3A shows an output waveform when the bonding apparatus is normal, and FIG. 3B shows an output waveform when the bonding apparatus is abnormal. It is.

FIG. 4 is a diagram showing a bonding check stage and a structure in the vicinity thereof according to the first embodiment of the present invention;

FIG. 5 is a diagram showing a bonding check stage of FIG. 4 and check bonding using the same.

FIG. 6 is a diagram showing a bonding check stage and a structure in the vicinity thereof according to a second embodiment of the present invention.

7 is a diagram showing the bonding check stage of FIG. 6 and check bonding using the same.

FIG. 8 is a diagram showing a conventional wire bonding apparatus.

FIG. 9 is a diagram showing another conventional wire bonding apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Arm 12 Capillary 13 Semiconductor device (semiconductor chip) 13a Electrode 14 Heater block 15 Gold wire 17 Ball bonding 18 Stitch bonding 19 Inner lead 20 Bonding check stage 20a Metal film 21 Dynamic strain sensor 21a Code 22 Heater block 23 Stage rotation mechanism 24 Stage up / down mechanism 25 Shaft 26 Linear drive mechanism 27, 28 Heat insulating plate 31 Fixed base 32 X-axis drive motor 33 X-axis drive unit 34 Y-axis drive motor 35 XY table 36 Z-axis drive motor 37 Z-axis Drive unit 38 Bearing 40 Strain gauge 40a Code 41 Amplifier 42 Comparison circuit

Claims (6)

(57) [Claims] 1. A wire bonding apparatus for contacting a capillary to an electrode of a semiconductor device to wire-bond a thin metal wire, wherein a bonding check stage arranged at a position where the capillary moves and can contact the surface thereof; A wire bonding apparatus, comprising: a strain sensor disposed so as to be able to abut on a back surface of a bonding check stage; and means for processing a signal from the strain sensor. 2. The bonding check stage has a disk shape, and includes a stage up-down mechanism for vertically moving the bonding check stage placed on a heater block and a stage rotating mechanism for rotating the stage. The wire bonding apparatus according to claim 1, wherein 3. The bonding check stage has a rectangular shape, and has a stage vertical mechanism for vertically moving the bonding check stage mounted on a heater block and a stage linear drive mechanism for linearly moving the stage. The wire bonding apparatus according to claim 1, wherein 4. A heat insulating means is provided between a heater block on which the semiconductor device is mounted and the strain sensor, and between the heater block on which the bonding check stage is mounted and the strain sensor. The wire bonding apparatus according to claim 1, wherein: 5. A wire bonding method in which a capillary is brought into contact with an electrode of a semiconductor device to wire-bond a thin metal wire, a bonding check stage which is located at a position where the capillary moves and can come into contact with the surface thereof. A strain sensor positioned so as to be in contact with the back surface of the bonding check stage is provided, and bonding is performed on the bonding check stage under the same conditions as those for wire bonding to the electrodes of the semiconductor device. A wire bonding method, wherein the state of a wire bonding apparatus is checked by detecting the impact load at the time by the strain sensor. 6. The wire bonding method according to claim 5, wherein the bonding check stage has a surface similar to a surface of an electrode of the semiconductor device.