JPH10116850A - Wire bonding device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To supply a sufficient joint energy to a ball and a bonding object by exciting a bonding tool axially so attached that on the tip of the horn that axis-centers are at almost right angle to each other. SOLUTION: The vibration in axis-center direction (arrow U1) applied to a horn 1 from a vibrator 3, in other word, longitudinal vibration is, based on the configuration wherein a capillary (bonding tool) 7 is attached with its axial orthogonal to the horn 1, converted into a deflection vibration in scrub direction of the capillary 7. With the output of a transmitter 23, or an oscillation frequency, set, for example, to maximum 1.5W, 30-60KHz, the horn 1 performs deflection vibration at this frequency. The deflection vibration is transferred as that in axial direction of the capillary 7 to the capillary 7, thus the capillary 7 is vibrated. With this vibration, the disturbance in the vibration in scrub direction caused by collapse of mass balance around the axis of the horn 1 is suppressed, so that a joint energy is sufficiently transferred.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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

[0002]

2. Description of the Related Art FIG. 5 shows a main part of a conventional wire bonding apparatus.

[0003] As shown in the figure, a horn 1 and a vibrator 3 connected to the rear end of the horn 1 are provided. The horn 1 has its nodal point (node position of ultrasonic vibration)
It is mounted on a holding frame (not shown) by a flange portion 1a provided in the portion, and forms a part of a bonding arm together with the holding frame. The bonding arm is driven up and down by driving means (not shown).

[0004] A voltage of a predetermined frequency is applied to the vibrator 3 by an oscillator 5 to generate ultrasonic vibration of this frequency. The horn 1 functions to mechanically amplify the vibration generated by the vibrator 3. The direction of vibration is indicated by arrow U1.

[0005] At the tip of the horn 1, a capillary 7 as a bonding tool is mounted. The capillary 7 is formed in a hollow shape, a wire 8 is inserted from above, and a ball 8a formed by, for example, sparking the tip of the wire 8 with a high voltage is used as a bonding target pad (described later) and a lead ( The same is for crimping.

As indicated by the arrow U1, the ultrasonic vibration from the vibrator 3 is transmitted to the horn 1 in the axial direction, that is, as a longitudinal vibration. The capillary 7, which joins the ball 8a and the object to be bonded, must be excited in a lateral direction necessary for joining, that is, in a scrub direction (indicated by an arrow S in FIG. 5). For conversion, the capillary 7 is mounted with its axis centered at right angles to the axis of the horn 1.

In the wire bonding apparatus,
A lead frame L # F (see FIG. 5) on which a plurality of IC chips 12 are stuck and arranged in the longitudinal direction is handled. The lead frame L＼F is loaded onto a heated bonding stage (not shown) at the start of the work, and
The C chip 12 is positioned at the bonding operation position. In this state, the bonding operation for the earliest IC chip 12 is performed by the bonding means (horn 1 or the like) having the above configuration.

The bonding means having the above-described configuration is mounted on an XY table (not shown), and is moved and positioned two-dimensionally by the operation of the XY table.

As shown in FIG. 6, the IC chip 12 is, for example, square and has a large number of pads 12 along its outer periphery.
a are juxtaposed and attached to the land portion 14 formed on the lead frame L # F. And the lead frame L
＼F includes leads 1 corresponding to each of these pads 12a.
5 are provided. However, FIG. 6 shows a state where the connection between each pad 12a and each lead 15 is almost completed.

Next, the bonding step will be described. The control of this operation is performed by a control unit including a microprocessor and the like.

First, when bonding to the pad 12a on the IC chip 12, the capillary 7 into which the wire 8 having the ball 8a formed at the tip is inserted is positioned just above the pad 12a by operating the XY table.

When the positioning is completed, the bonding arm composed of the horn 1 and the like is driven by a driving means (not shown) to lower the capillary 7, and crush the ball 8a on the pad 12a to perform thermocompression bonding.
At this time, the vibrator 3 is oscillated to excite the capillary 7.

When the connection to the first bonding point is completed, the raising and lowering operation of the bonding arm and the operation of the XY table are performed as appropriate, and the wire 8 is pulled out according to a predetermined loop control. Then, bonding to the second bonding point on the lead 15 is performed.

Thereafter, the wire is cut in the process of raising the bonding arm to a predetermined height, and the connection between the set of pads 12a and the leads 15 is completed.

Thereafter, the above-described series of operations is repeated for each pad 12a provided on the IC chip 12 and each lead 15 corresponding thereto.

[0016]

The above-mentioned conventional wire bonding apparatus has the following problems.

First, since the capillary 7 has a small mass, but is attached to the tip of the horn 1 in a hanging state, the balance of the mass with respect to the axis of the horn 1 is lost. Therefore, the vibration in the horn axis direction, that is, the longitudinal vibration is adversely affected, and as a result, the vibration in the scrub direction of the capillary 7 is disturbed,
There is a disadvantage that the bonding energy is not sufficiently transmitted.

The surface of the pad 12a and the surface of the lead 15 are in various states depending on the material added to these materials and the oxides thereof. Therefore, it may be difficult to stably supply the required bonding energy only by rubbing (scrubbing) the ball 8a formed at the tip of the capillary 7 on this surface, and this causes a bonding failure.

The present invention has been made in view of the above-mentioned drawbacks of the prior art, and has as its object to provide a wire bonding apparatus capable of sufficiently transmitting bonding energy between a ball and an object to be bonded. That is.

Further, the present invention provides a wire bonding apparatus capable of exhibiting still other effects.

[0021]

In order to solve the above-mentioned object, according to the present invention, a bonding tool is mounted on a tip of a horn so that their axes are substantially perpendicular to each other. In a wire bonding apparatus for performing bonding while exciting the bonding tool in the scrub direction by applying ultrasonic vibration in the direction, an ultrasonic excitation unit for exciting the bonding tool in the axial direction is provided.

In addition, the following configuration is employed in order to obtain still another effect.

That is, in the wire bonding apparatus, the ultrasonic excitation means has a vibrator for flexibly vibrating the horn.

In the wire bonding apparatus,
The vibrators are mounted on an end of the horn so as to be operated in substantially the same direction as each other and arranged side by side in a direction substantially orthogonal to the operation direction.

[0025]

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 is configured similarly to the conventional wire bonding apparatus shown in FIG. 5 except for the parts described below, and the description of the configuration and operation of the entire apparatus is duplicated. Omitted, and only the main part will be described.

In the following description and drawings, components that are the same as or correspond to the components of the above-described conventional example are denoted by the same reference numerals.

As shown in FIG. 1, the wire bonding apparatus has a vibrator 21 which should be called a second vibrator if the vibrator 3 is a first vibrator. The vibrator 21 is applied with a voltage of a predetermined frequency by another oscillator 23 without depending on the oscillator 5 for driving the vibrator 3, and emits ultrasonic vibration of the frequency. These vibrator 21 and oscillator 23 are collectively referred to as ultrasonic excitation means.

As will be described later, while the ultrasonic vibration generated by the vibrator 3 is a longitudinal vibration in the axial direction of the horn 1, the vibrator 21 causes the horn 1 to bend and vibrate. In FIG. 1, the direction of longitudinal vibration by vibrator 3 is indicated by arrow U1, and the direction of flexural vibration by vibrator 21 is indicated by arrow U2. As shown in the figure, the bending vibration is performed in the vertical direction, that is, in the axial direction of the capillary 7.

Here, the configurations of the vibrator 3 and the vibrator 21 will be described in detail.

First, as for the vibrator 3 which emits longitudinal vibration, as shown in FIG.
For example, two (2) ZT (piezoelectric) elements 25 are concentrically coupled (a single or three or more PZT elements may be formed). Specifically, the mutual coupling side has the same polarity.

In this configuration, if a current is applied to each PZT element 25, specifically, if the positive side of the voltage is applied, each PZT element 25
The element 25 undergoes elongation distortion as indicated by an arrow L in the figure, and is distorted so as to contract when a negative voltage is applied. This expansion and contraction operation is repeated at a predetermined frequency, thereby generating a longitudinal vibration (the direction of the vibration is indicated by an arrow U1 in FIG. 1).

On the other hand, the structure of the vibrator 21 for flexibly vibrating the horn 1 is as follows.

As shown in FIG. 2, the vibrator 21 is composed of half-cylindrical oscillators 27 and 28, each of which is formed by connecting two substantially semi-annular PZT elements 27a and 28a, respectively. They are arranged facing each other with a gap e therebetween, and have a substantially cylindrical shape as a whole. The halves 27 and 28 have the same operating direction and are arranged side by side in a direction perpendicular to the operating direction. Specifically, the PZT elements 27a and 28a of the halves 27 and 28 are each polarized in the axial direction, and the two coupled PZT elements 27a and two PZT elements 28a It is the same pole. The PZT element 27a and the PZT element 28a that face each other with the gap e therebetween are configured to have different polarities.

The vibrator 21 having such a structure is relatively easy to manufacture and is effective in reducing the manufacturing cost of the apparatus, and the vibrator 21 itself is small, so that the apparatus can be easily downsized.

With the above configuration, each of the PZT elements 27a, 28
When the positive side of the voltage is applied to the PZT element 27a, the PZT element 27a undergoes elongation strain as indicated by the arrow L, and the PZT element 28a
In a, it is distorted so as to contract as shown by the arrow S. When the applied voltage becomes negative, the PZT element 27a contracts,
The ZT element 28a extends. This expansion / contraction operation is repeated at a predetermined frequency, and a flexural vibration is generated in the direction indicated by arrow U2 in FIG.

In the wire bonding apparatus having the above-described configuration, when the ball 8a is thermocompression-bonded to the pad 12a (see FIG. 6) or the lead 15 (the same) as the bonding target, the oscillator 5 and the oscillator 23 shown in FIG. Activated. As a result, the horn 1 is given ultrasonic vibration in its axial direction by the vibrator 3 and the horn 1
This causes vertical vibration.

The axial vibration applied to the horn 1 from the vibrator 3, ie, the longitudinal vibration, appears as a compression wave of stress.
The amplitude is shown by a curve F in FIGS. 3 and 4A. This longitudinal vibration is converted into a flexural vibration in the scrub direction of the capillary 7 based on a configuration in which the capillary 7 is mounted with the axis orthogonal to the horn 1. The flexural vibration in the scrub direction is
a is a pad 12a to be bonded (see FIG. 6)
And lead 15 (same as above). 3 and 4A, the mode of the flexural vibration in the scrub direction is indicated by a curve A, and the vibration direction is indicated by a symbol S.

The oscillator 5 for generating the vibration in the scrub direction has an output and an oscillation frequency of, for example, 1.5 W at the maximum.
The frequency is set to 100 kHz to 150 kHz.

On the other hand, the output and the oscillation frequency of the oscillator 23 are set to, for example, 1.5 W at the maximum and 30 KHz to 60 KHz, and the horn 1 performs flexural vibration at this frequency.
The mode of this bending vibration is shown by a curve B in FIGS. This bending vibration is transmitted to the capillary 7 as vibration in the axial direction of the capillary, and excites the capillary 7. However, the vibration of the capillary 7 in the axial direction appears as a compression wave of stress, and its amplitude is shown by a curve E in FIGS. 3 and 4B.

As shown in FIGS. 3 and 4B, the capillary 7
In the vibration in the axial center direction, the joint between the tip of the capillary and the horn 1 has an antinode of vibration, that is, the amplitude is maximum and the stress is zero. By exciting the capillary 7 in the axial direction as described above, the following effects can be obtained.

First, since the capillary 7 is small but has a large mass, the mass balance around the axis of the horn 1 is broken by attaching the capillary 7 to the tip of the horn 1 in a hanging state, and this causes a vibration. The vibration in the scrub direction is disturbed by affecting the longitudinal vibration applied from step 3. When the capillary 7 is excited by the vibrator 21 in the axial direction, the vibration acts to press the capillary 7 toward the bonding object, and as a result, the disturbance of the vibration in the scrub direction is suppressed.

Since the oscillation frequency of the oscillator 23 is set relatively low as described above, the effect of pressing the capillary 7 against the bonding object is not so strong.
By this action, the bonding object, especially the pad 12
a, the IC chip 12 is not damaged.

Second, the pads 12a and the leads 15
Surface becomes various states due to the influence of the material added to these materials and the oxides thereof, and it becomes difficult to stably supply the bonding energy only by vibrating the tip of the capillary 7 in the scrubbing direction. There is. The above-described action of pressing the capillary 7 against the bonding object also avoids the adverse effects of the state of the bonding surface.

From the above effects, the wire bonding apparatus can sufficiently transmit the bonding energy.
Demonstrate good bonding properties.

In the wire bonding apparatus,
In order to excite the capillary 7 in the axial direction, a vibrator 21 is provided on the base end side of the horn 1 to cause the horn 1 to bend and vibrate. In this configuration, the vibrator 21 is arranged together with the other vibrator 3 behind the horn 1,
The vibrator itself does not affect the vibration of the horn 1, and the device can be made compact.

In this embodiment, the longitudinal vibration and the
The vibrators 3 and 21 that generate flexural vibration are driven by individual oscillators 5 and 23, respectively.
21 may be driven by the same oscillator. In this case, the vibrator 21 having a low drive frequency is driven through a frequency divider or the like.

[0047]

As described above, in the wire bonding apparatus according to the present invention, the bonding tool is excited in the axial direction. Therefore, the disturbance of the vibration in the scrub direction caused by the imbalance of the mass around the axis of the horn is suppressed by this excitation, and the adverse effect due to the condition of the bonding surface (the surface of the pad or the like) is also eliminated. Can transmit enough energy,
Demonstrate good bonding properties.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a part of a main part of a wire bonding apparatus as an embodiment of the present invention, which is partly blocked.

FIG. 2 is a perspective view including a partial cross section of a vibrator included in the wire bonding apparatus shown in FIG. 2;

FIG. 3 is a perspective view showing a vibration mode of a main part of the wire bonding apparatus shown in FIG. 1;

FIG. 4 is a perspective view showing a mode of vibration in the configuration shown in FIG. 3;

FIG. 5 is a perspective view showing a main part of a conventional wire bonding apparatus in a partially block diagram.

FIG. 6 is a plan view showing an IC chip and leads to be bonded;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Horn 3 Oscillator 5 Oscillator 7 Capillary (bonding tool) 8 Wire 8a (Wire) ball 12 IC chip 12a (IC chip) pad 15 Lead 21 Oscillator 23 Oscillator

Claims (3)

[Claims] 1. A bonding tool is mounted on the tip of a horn so that their axes are substantially perpendicular to each other, and ultrasonic vibration is applied to the horn in the axial direction so that the bonding tool is moved in a scrubbing direction. A wire bonding apparatus for performing bonding while exciting the wire bonding tool, comprising: an ultrasonic exciting means for exciting the bonding tool in an axial direction. 2. The wire bonding apparatus according to claim 1, wherein said ultrasonic exciting means has a vibrator for flexibly vibrating said horn. 3. The horn according to claim 2, wherein the vibrators are mounted on an end of the horn so as to operate in substantially the same direction as each other and to be arranged in a direction substantially orthogonal to the operating direction. The wire bonding apparatus as described in the above.