JP3417520B2 - Wire bonding equipment - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor device assembling process in which a pad (electrode) on an IC chip, for example, is used as a first bonding point and is formed on a lead frame to which the IC chip is attached. Lead second
As a bonding point, the present invention relates to a wire bonding apparatus that connects both bonding points by using a wire having conductivity. More specifically, the present invention relates to a wire bonding device that performs crimp connection using ultrasonic vibrations in combination.

[0002]

2. Description of the Related Art FIG. 6 shows a main part of a conventional wire bonding apparatus.

As shown in the figure, it comprises a horn 1 and a vibrator 3 coupled to the rear end of the horn 1. The horn 1 has its nodal point (node position of ultrasonic vibration)
It is attached to a holding frame (not shown) by a flange portion 1a provided on the section, and constitutes a part of a bonding arm together with the holding frame. The bonding arm is driven up and down by a driving means (not shown).

A voltage of a predetermined frequency is applied to the vibrator 3 by an oscillator 5 to generate ultrasonic vibration of this frequency. The vibrator 3 and the oscillator 5 are collectively referred to as ultrasonic excitation means. The horn 1 serves to mechanically amplify the vibration generated by the vibrator 3. The direction of vibration is indicated by arrow U ₁ .

A capillary 7 as a bonding tool is attached to the tip of the horn 1. The capillary 7 is formed in a hollow shape, and a wire 8 is inserted from above, and a ball 8a formed by sparking the tip of the wire 8 with a high voltage is applied to a pad and a lead to be bonded. It is for crimping.

As indicated by the arrow U ₁ , the ultrasonic energy transmitted to the horn 1 is a longitudinal vibration in the axial direction of the horn 1, so that the lateral vibration necessary for joining the ball 8a and the bonding target is generated. For the purpose of conversion, the capillary 7 is mounted so that its axial center is perpendicular to the axial center of the horn 1.

A clamper 10 for holding the wire 8 is provided above the capillary 7.

In the wire bonding apparatus,
The lead frame L \ F to which a plurality of IC chips 12 are attached side by side in the longitudinal direction is treated as a component to be bonded, and the lead frame L \ F is placed on a bonding stage (not shown) heated by a heater at the start of work. F is carried in, and the earliest IC chip 12 is positioned at the bonding work position. In this state, the earliest IC chip 12 is bonded by the bonding means having the above structure
Bonding work is performed.

As is apparent from FIG. 7, the IC chip 1
The reference numeral 2 is, for example, a square, and a large number of pads 12a are arranged in parallel along the outer peripheral portion of the upper surface thereof, and are attached to the land portion 14 formed in the lead frame L \ F. The lead frame L \ F is provided with leads 15 corresponding to the pads. However, FIG. 7 shows each pad 12
This shows a state in which the connection between the a and each lead 15 by the wire 8 is almost completed.

Next, the bonding step will be described, but before that, a brief description will be given of self-teaching performed in advance before the bonding work. The self-teaching means the pad 12a of the IC chip 12 as the first bonding point and the lead 1 as the second bonding point.
Information such as the position on the coordinates such as 5 and various conditions are set. Here, the setting of the coordinate positions of both bonding points will be described.

This self-teaching is basically based on the manual alignment of the operator.

That is, above the capillary 7, the bonding point, that is, the pad 12a and the lead 15 is provided.
A camera (not shown) for picking up the image is installed, and this camera is mounted on an XY table (not shown) together with the above-mentioned bonding means including the capillary 7 and the horn 1. The operator manually operates the XY table while viewing the image from the camera on the monitor, and aligns the intersection of the cross lines provided on the screen of the monitor with the approximate center of the bonding point. The coordinates of this intersection are previously stored in the data table as the coordinates on the XY table, and when the alignment is completed, the coordinates are stored as the target bonding point in the data table.

In addition to the teaching by only the operator, the following is also performed for the purpose of preventing the displacement of the bonding point due to the operator's mistake.

That is, after the information of the bonding point imaged by the camera is binarized by the binarization circuit,
The amount of deviation between the bonding point and the center in the X and Y directions is calculated with reference to the coordinate points on the XY table that have been calculated in advance, and the center coordinates of the bonding point are calculated and stored based on the calculated values. Is.

The above-mentioned self-teaching is described in detail, for example, in the specification of Japanese Patent Application No. 1-85647.

The bonding work performed based on the self-teaching will be described with reference to FIG.

The control of the operation described below is performed by a control unit including a microprocessor and the like.

First, the pad 12a on the IC chip 12
When wire bonding is to be performed (see FIG. 7), the capillary 7 through which the wire 8 having the ball 8a formed at the tip is inserted is moved to the XY position based on the information from the camera.
Positioning is performed just above the pad 12a by operating the table. More specifically, the target bonding point data stored in the data table by the self-teaching described above is illuminated with new information from this camera, and the XY table is activated. After that, by operating the above-mentioned driving means, the capillary 7 is lowered as shown in FIG. 8 to, and the ball 8a is crushed on the pad (the pad itself is not shown in FIG. 8) to perform thermocompression bonding. Perform bonding. At this time, the capillary 7 is excited by the ultrasonic excitation means described above.

In this step, → is a bonding arm (horn 1) to which the capillary 7 is attached.
, Etc.) at a high speed, and → at a low speed. At this time, the clamper 10 is open.

When the connection to the first bonding point is finished, the bonding arm is raised (indicated by the arrow Z) while the clamper 10 is in the open state as shown by → in FIG. 10
With the wire open, the wire 8 is pulled out and connected to the lead 15, which is a second bonding point shown in the same manner as for the first bonding point.

After this connection, the clamper 10 is closed in a state where the wire 8 is pulled out to the tip of the capillary 7 by a predetermined delivery amount f as shown by. In this state, the wire 8 is cut and the clamper 10 is returned to the open state as shown in the process of raising the bonding arm to a predetermined height. A set of pads 12a and leads 15 are connected by such a series of steps.

After that, a large number of pads provided on the earliest IC chip 12 and leads 1 arranged corresponding to these pads are provided.
The above series of operations is repeated for 5. Then, when the bonding of the earliest IC chip 12 is completed,
The lead frame L \ F (see FIG. 6) is moved by the pitch for arranging the IC chips 12, the bonding work for the next IC chip is performed, and the same is continued in sequence, and the bonding connection of all the IC chips is completed. To do.

[0023]

The conventional wire bonding apparatus described above has the following drawbacks.

That is, as shown in FIGS. 6 and 7, I
The C chip 12 has two sides X and Y which are perpendicular to each other, but the bonding state between each bonding point (pad 12a and lead 15) arranged along the X side and each bonding point arranged along the Y side. Specifically, a difference occurs in the pressure bonding diameter and shape of the ball 8a (of the wire 8), and stable bonding cannot be performed.

This is because the direction of vibration U ₁ transmitted to the capillary 7 through the horn 1 is constant, so that the bonding of the Y side acts to expand / contract the wire 8 and the bonding of the X side in the direction traversing the wire. It has been found to be based on the absence of this effect due to vibration. In particular, the lead 15 is thin and flexible, so that this influence is great.

The present invention has been made in view of the above-mentioned drawbacks of the prior art, and its main purpose is to always perform stable bonding regardless of the directionality of the wire connecting the bonding points. It is an object of the present invention to provide a bonding device, and also to provide a wire bonding device that can also exhibit other effects.

[0027]

The present invention is a wire bonding apparatus for bonding a component to be bonded by using a bonding tool at the tip of a horn, and ultrasonic excitation means for applying ultrasonic vibration to the bonding tool. And a switching means for switching the ultrasonic wave excitation means in different directions to excite the ultrasonic wave, and the ultrasonic wave excitation means includes a first vibrator that generates longitudinal vibration and a second vibrator that generates flexural vibration. And the first oscillator is formed of an annular ring polarized in the axial direction, and the second oscillator is formed by separating two substantially semi-cylindrical halves polarized in the axial direction. Are arranged in a generally cylindrical shape so as to face each other with different polarities, and the first oscillator and the second oscillator are coupled so that their respective vibration directions are substantially right angles. Is the first vibrator and the second vibrator, mounted coaxially at the rear end of the horn,
It is characterized in that the switching means switches the operation of the first vibrator and the second vibrator. Further, the second vibrator according to the present invention is arranged on the bonding tool side with respect to the first vibrator.

According to this structure, the vibration in the desired direction is transmitted to the bonding tool by the switching by the switching means.

[0029]

BEST MODE FOR CARRYING OUT THE INVENTION According to the present invention, ultrasonic vibration is applied by using each pad provided on a square or rectangular IC chip and an external lead arranged corresponding to the pad as a bonding point. In the case of bonding connection, it is used in order to eliminate the adverse effect caused by the ultrasonic vibration and to make uniform the pressure bonding diameter of the ball of the wire connecting the bonding points.

[0030]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, a wire bonding apparatus as an embodiment of the present invention will be described with reference to the accompanying drawings. However, this wire bonding apparatus according to the present invention has the same structure as the conventional wire bonding apparatus shown in FIG. 6 except for the part described below, and the description of the structure and operation of the entire apparatus is duplicated. It is omitted and only the main parts are explained.

Further, in the following description and drawings, the same reference numerals are attached to the same or corresponding components as those of the above-mentioned conventional example.

As shown in FIG. 1, in the wire bonding apparatus, if the vibrator 3 is the first vibrator,
It has a vibrator 21 which should be called a second vibrator. Similar to the vibrator 3, the vibrator 21 is applied with a voltage of a predetermined frequency by the oscillator 5, and emits ultrasonic vibration of the frequency. As will be described later, the ultrasonic vibration generated by the vibrator 3 is longitudinal vibration, whereas the vibrator 21 generates flexural vibration. These oscillators 3 and 21, and the oscillator 5,
Collectively referred to as ultrasonic excitation means.

The two oscillators 3 and 21 are combined so that their respective vibration directions are at right angles, and are attached to the rear end of the horn 1. In the figure, the direction of longitudinal vibration by the vibrator 3 is indicated by an arrow U ₁ , and the direction of flexural vibration by the vibrator 21 is indicated by an arrow U ₂ .

A switch 23 as switching means is interposed between the oscillators 3 and 21 and the oscillator 5.
The voltage from the oscillator 5 is selectively applied to the vibrators 3 and 21 by switching the changeover switch 23.

Here, the structures of the vibrators 3 and 21 will be described in detail.

First, as for the vibrator 3 which emits longitudinal vibration, as shown in FIG. 2, an annular P that is polarized in the axial direction is used.
For example, two ZT (piezoelectric: piezoelectric) elements 25 are concentrically coupled to each other (may be formed of a single or three or more PZT elements). In detail, the mutual coupling example has the same polarity.

In this structure, if both PZT elements 25 are energized, specifically, if the positive side of the voltage is applied, the PZT elements 25 are applied.
The T element 25 causes extension strain as shown by an arrow L in the figure,
When the negative side of the voltage is applied, it is distorted so as to contract. This expansion / contraction operation is repeated at a predetermined frequency, which causes longitudinal vibration (the direction of vibration is indicated by arrow U _{1 in} FIG. 1).

On the other hand, the vibrator 21 for generating flexural vibration is constructed as shown in FIG.

That is, a substantially semi-annular PZT element 27a,
Approximately semi-cylindrical half body 2 formed by joining two 28a each
7, 28 are arranged to face each other with a gap e therebetween, and have a substantially cylindrical shape as a whole. These PZT elements 27
a and 28a are polarized in the axial direction, respectively, and two PZT elements 27a are coupled to each other and P
The mutual coupling sides of the ZT elements 28a have the same polarity. Then, the PZT elements 2 facing each other with a gap e in between.
7a and the PZT element 28a have different polarities.

With this configuration, each PZT element 27a, 28a
When the positive side of the voltage is applied to the PZT element 27a, extension strain occurs in the PZT element 27a as indicated by an arrow L, and the PZT element 28a
Then, it is distorted so as to contract as shown by an arrow S. Then, when the applied voltage becomes negative, the PZT element 27a contracts, and the PZT element 27a contracts.
The T element 28a extends. This expansion / contraction operation is repeated at a predetermined frequency, and a flexural vibration whose direction is indicated by an arrow U ₂ in FIG. 1 is generated.

FIG. 4 is a block diagram showing an operation control system of the wire bonding apparatus. In the figure, the keyboard execution switch 31 is operated when the wire bonding apparatus is activated, and information such as coordinates of each target bonding point obtained based on the image from the camera 33 during the self-teaching described above. Used to enter. This keyboard execution switch 31
The information input by the operation of is stored in the data table 35 through the control unit 34.

The control unit 34 illuminates the new information obtained from the camera 33 or the like with the stored information in the data table 35, and sends a command signal to the table drive circuit 37, the ultrasonic wave control circuit 38, etc., and thereby the XY table 40 and the switching. The switch 23 and the like are activated.

Next, the operation of the wire bonding apparatus, particularly the operation relating to the application of ultrasonic vibration will be described with reference to FIG.
The description will be made with reference to the flowchart of FIG.

When the keyboard execution switch 31 is operated to activate the device, the bonding work is performed for each bonding point in the same manner as described above based on the information from the camera 33. At the time of bonding to each of the bonding points, the bonding point is the IC chip 12
The direction of the applied vibration is switched depending on which of the X side and the Y side (see FIG. 7) it belongs to.

That is, as shown in FIG. 7, it is assumed that the bonding to the lead 15 corresponding to the pad 12a belonging to the X side of the IC chip 12 is performed. Whether the lead 15 belongs to the X side or the Y side is determined by the data table 35 based on the self-teaching described above.
It can be derived from the contents stored in (see FIG. 4). Therefore, the coordinates of the lead 15 based on the image from the camera 33 (see FIG. 4) are illuminated to the stored content to confirm which side, the X side or the Y side, is (step S1 in FIG. 5).

When it is confirmed that it is on the X side, it is confirmed whether the vibrator 21 is to be operated (step S
2) If YES, then the bonding work is performed based on the operation of the vibrator 21 (step S3), and NO.
If so, it is switched to the vibrator 3 (step S4),
A bonding operation is performed based on the operation of the vibrator 3.

On the other hand, if it is on the Y side, the vibrator 3
Check if is supposed to work (step S5)
If YES, bonding is performed by the operation of the vibrator 3, and if NO, the vibrator is switched and then bonding is performed.

As described above, when connecting the bonding points belonging to either the X side or the Y side, the ultrasonic vibration in the direction of expanding and contracting the wire 8 is always applied.

As described above, since the ultrasonic vibration applied is switched according to the directionality of the wire connecting the bonding points, the pressure bonding diameter and shape of the ball 8a (see FIG. 7) are made uniform at all bonding points. Therefore, a stable bonding state can always be obtained.

By the way, in the wire bonding apparatus, by adding the vibrator 21 that generates flexural vibration to the vibrator 3 that generates longitudinal vibration, vibrations in two different directions are generated. With this structure, it is possible to reduce the width dimension of the vibration generating portion including both vibrators, that is, to reduce the size.

That is, in order to generate the vibrations in the two directions as described above, it is possible to combine, for example, the vibrators that respectively generate the longitudinal vibrations in a form orthogonal to each other. However, with this configuration, the vibration direction of one of the vibrators greatly projects in the width direction of the vibration generating portion, and it is difficult to make the vibration generating portion thinner. In the configuration in which the flexural vibration is combined with the longitudinal vibration as described above, both the vibrators 3 and 21 are coaxial, that is, arranged in series, and the vibration generating portion can be made thin.

Further, in the wire bonding apparatus according to the present invention, the vibrator 21 that emits flexural vibration is
It is arranged on the side of the capillary 7 with respect to the vibrator 3 that generates longitudinal vibration. With this configuration, the amplitude of the capillary 7 in the direction of the flexural vibration (indicated by the arrow U ₂ in FIG. 1) can be suppressed to be small, and therefore, the bonding can be performed with high accuracy. If the position of the vibrator 21 is replaced with that of the vibrator 3, the distance from the vibrator 21 to the capillary 7 increases, and the swing width via the horn 1 and the like increases. Therefore, it is difficult to suppress the amplitude of the capillary 7 due to the flexural vibration of the vibrator 21 to be small.

It should be noted that the amplitude of the capillary 7 is not affected whether the vibrator 3 which emits longitudinal vibration in the axial direction of the horn 1 is arranged before or after the vibrator 21.

[0054]

As described above, in the wire bonding apparatus according to the present invention, the ultrasonic vibration means can generate ultrasonic vibrations in different directions, and the switching means switches the ultrasonic vibrations in the respective directions. Exciting the bonding tool. Therefore, the ultrasonic vibration applied depending on the directionality of the wire connecting between the bonding points can be switched, whereby the pressure bonding diameter and shape of the ball can be made uniform at all bonding points, and stable bonding is always performed. The state is obtained.

[Brief description of drawings]

FIG. 1 is a perspective view showing a part of a main portion of a wire bonding apparatus as an embodiment of the present invention in a block form.

FIG. 2 is a perspective view of a vibrator for vertical vibration included in the wire bonding apparatus shown in FIG.

3 is a perspective view including a partial cross section of a flexural vibration vibrator included in the wire bonding apparatus shown in FIG.

FIG. 4 is a block diagram showing an operation control system of the wire bonding apparatus according to the present invention.

FIG. 5 is a flowchart showing an operation flow of the wire bonding apparatus according to the present invention.

FIG. 6 is a perspective view showing a part of a main part of a conventional wire bonding apparatus in a block form.

FIG. 7 is a plan view showing an IC chip and leads to be bonded.

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

[Explanation of symbols]

1 horn 3 (first) oscillator 5 oscillators 7 Capillary (bonding tool) 8 wires 8a ball (of wire 8) 10 clamper 12 IC chip 12a pad 15 leads 21 (Second) oscillator 23 Changeover switch (changeover means) 25, 27a, 28a PZT element 31 Keyboard execution switch 33 cameras 34 Control unit 35 data table 37 Table drive circuit 38 Ultrasonic control circuit 40 XY table

─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-5-74874 (JP, A) JP-A-3-124039 (JP, A) JP-A-55-128841 (JP, A) JP-A-58- 161334 (JP, A) JP-A-6-29357 (JP, A) Jikken 53-4185 (JP, Y2) (58) Fields investigated (Int.Cl. ⁷ , DB name) H01L 21/60 H01L 21 / 607

Claims (2)

(57) [Claims] 1. A wire bonding apparatus for bonding a component to be bonded by using a bonding tool at the tip of a horn, and ultrasonic excitation means for applying ultrasonic vibration to the bonding tool.
Switching means for switching the ultrasonic excitation means in different directions to excite the ultrasonic excitation means, and the ultrasonic excitation means includes a first vibrator that generates longitudinal vibration and a second vibrator that generates flexural vibration. The first vibrator comprises an annular ring polarized in the axial direction, and the second vibrator has two substantially semi-cylindrical halves polarized in the axial direction with a gap therebetween. Are arranged to face each other in a substantially cylindrical shape so that different poles correspond to each other, and the first vibrator and the second vibrator are coupled so that the respective vibration directions thereof are substantially right angles, and the first vibrator The oscillator and the second oscillator are coaxially attached at the rear end of the horn, and the switching means switches the operation of the first oscillator and the second oscillator. Bonding equipment. 2. The wire bonding apparatus according to claim 1, wherein the second vibrator is arranged on the bonding tool side with respect to the first vibrator.