JPH10125713A - Wire bonding apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To surely connect flat parts formed by pressing balls over the entire surface by vibrating a bonding stage in a direction of the wire toward and away from a work. SOLUTION: The wire bonding apparatus comprises an oscillator 13, vibrating means 31 operative synchronously with the oscillator 13 being actuated such that when the ball 14a of a wire 14 is pressed flat by a capillary 9, the oscillator 13 is actuated for specified time to apply an ultrasonic vibration as shown by the arrow U while a motor of the vibrating means 31 is actuated for the same time at an amplitude set to a level not damaging an IC chip 20 as well as pads 20. This accelerates alloying the peripheral portion and central portion of the flat part, thereby ensuring a reliable connection over the entire surface.

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 a bonding point between the two 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.

In FIG. 1, a main body 1 is mounted on an XY table (not shown) movable in a two-dimensional direction, and a shaft 2 is rotatably mounted on the main body 1. A bonding arm 4 is attached to the shaft 2. A cut clamp 6 is attached to the bonding arm 4 via an arm 7.

[0004] At one end of the bonding arm 4,
A horn 11 on which a capillary 9 as a bonding tool is mounted is provided at a tip, and a vibrator 13 for generating ultrasonic vibration is attached to a base of the horn 11. The vibrator 13 operates when a high-frequency voltage is applied by a vibrator (not shown). These vibrators 1
3 and the vibrator are collectively referred to as ultrasonic excitation means. Horn 11
Has the function of mechanically amplifying the vibration generated by the vibrator 13. The direction of vibration is indicated by arrow U.

The capillary 9 is formed in a hollow shape, into which a wire 14 is inserted from above. A ball 14a formed by, for example, sparking the tip of the wire 14 with a high voltage is used as a bonding pad and lead. (To be described later).

As shown by the arrow U, the horn 1
1 is longitudinal vibration in the axial direction of the horn 11, so that the capillary energy is converted into lateral vibration necessary for bonding the ball 14a to the bonding object.
The horn 11 is mounted with its axis center perpendicular to the axis center of the horn 11.

On the other hand, a linear motor 15 is provided at the other end of the bonding arm 4 as driving means for swinging the bonding arm 4 together with the shaft 2. The linear motor 15 includes a flat coil 16 and
And a magnetic circuit 17 composed of a permanent magnet and a yoke. The flat coil 16 is attached to the bonding arm 4, and the magnetic circuit 17 is fixed to the main body 1.

Next, the bonding operation by the wire bonding apparatus having the above configuration will be described.

In the wire bonding apparatus,
A lead frame L # F in which a plurality of IC chips 20 are adhered side by side in a longitudinal direction (a direction perpendicular to the plane of FIG. 5) is treated as a part to be bonded, and is heated by a heater block 22 at the start of work. The lead frame L＼F is loaded onto the heater plate 24 as a bonding stage, and the first IC
The chip 20 is positioned at the bonding operation position.
In this state, bonding is performed on the earliest IC chip 20 by the bonding means having the above configuration.

First, when performing bonding to a pad (described later) as a first bonding point provided on the IC chip 20, the tip of the wire 14 protruding from the lower end of the capillary 9 and a discharge electrode (FIG. Not shown)
And discharge energy is generated between them, and the distal end of the wire 14 is melted by the discharge energy to form the ball 14a. Then, the above-described XY table is operated, and the capillary 9 and the ball 14a are moved to a certain pad 2 provided on the IC chip 20 as shown in FIG.
0a.

After the above, a driving current is supplied to the linear motor 15 to lower the capillary 9, and as shown in FIG. 6B, the ball 14a is pressed against the pad 20a to form a flat portion 14b. At the time of this pressure contact, the vibrator 1 shown in FIG.
3 is activated, and heat is generated between the flat portion 14b and the pad 20a due to mutual friction due to ultrasonic vibration. At this time, the heat from the heater block 22 shown in FIG. 5 is also applied, and the flat portion 14b and the pad 20a are thermocompression-bonded.

When the connection to the first bonding point is completed as described above, the linear motor 15 is operated to raise the capillary 9, and the XY table is driven while the wire 14 is extended from the tip of the capillary 9. To move the capillary 9 in the horizontal direction.
Is positioned immediately above a lead (not shown: formed on a lead frame L # F shown in FIG. 5) which is a second bonding point corresponding to. Then, a drive current is supplied to the linear motor 15 to lower the capillary 9 and the wire 1
4 is pressed against the lead. At this time, ultrasonic vibration is applied similarly to the first bonding point, and the thermocompression bonding is performed in combination with the heating by the heater block 22.

Thereafter, the linear motor 15 is operated to raise the capillary 9, and the cut clamp 6 is closed at a predetermined timing to cut the wire 14 from the second bonding point. Through such a series of steps, a set of pads 20a and leads are connected.

Hereinafter, the first I on the lead frame L # F
The above-described series of operations is repeated for each of the pads provided on the C chip 20 and the leads arranged corresponding to these pads. When the bonding of the earliest IC chip 20 is completed, the lead frame L # F (see FIG. 5) is transported by the arrangement pitch of the IC chips 20, and the bonding operation for the next IC chip is performed. The same process is sequentially continued to complete the bonding connection of all the IC chips.

[0015]

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

That is, with respect to the first bonding point, a flat portion 14b formed by pressing a ball 14a of the wire 14 (see FIG. 6A) to a pad 20a.
(Refer to (b) of FIG. 6) indicates that the entire surface is not connected to the pad 20a, but is connected in an annular shape as shown by cross-hatching 26 in FIG. It may be. One of the reasons is that, as is apparent from FIGS. 6A and 6B, the ball 14a is crushed because the capillary 9 has the wire insertion hole 9a through which the wire 14 is inserted. This is probably because the pressing surface is annular.

It is also presumed that the wire 14 following the ball 14a dissipates heat, thereby inhibiting the formation of alloy.

The present invention has been made in view of the above-mentioned drawbacks of the prior art, and a main object thereof is to provide a wire bonding apparatus in which a flat portion formed by pressing a ball is securely connected over the entire surface. To provide.

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

[0020]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides a method in which a bonding tool is excited by an ultrasonic exciting means while a wire inserted into the bonding tool is used to attach a component to be bonded on a bonding stage. In a wire bonding apparatus for performing bonding, the bonding stage is provided with a vibrating means for vibrating the wire in a direction in which the wire comes into contact with and separates from the component to be bonded. in addition,
In order to obtain various other effects, the following configurations are employed. That is, in the wire bonding apparatus of the present invention, the vibrating means is operated in synchronization with the ultrasonic exciting means. Further, in the wire bonding apparatus, the ultrasonic excitation unit excites in a direction substantially perpendicular to the contact / separation direction. Further, in the wire bonding apparatus, a taper portion gradually increasing in diameter from the wire receiving end to the wire sending end is formed at the wire sending end of the bonding tool so as to be continuous with the wire insertion hole. . Further, in the wire bonding apparatus, the vibrating means is configured to rotatively rotate the rotators around a parallel rotation axis and eccentrically rotatable in plane symmetry with respect to the rotation axis, and synchronize each of the rotators. And driving means for rotating. .

[0021]

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, the same or corresponding components as those of the above-described conventional example are denoted by the same reference numerals.

As shown in FIG. 1, in the wire bonding apparatus, a vibration means 31 is attached to a heater plate 24 as a bonding stage. FIGS. 2 and 3 show details of the vibration means 31. As is clear from these figures, the vibration means 31 is provided on the lower surface side of the heater block 22 for heating the heater plate 24. And a heat insulating material 32 (shown in FIG. 3).

As shown in FIG. 2 and FIG.
1 has a gear case 34. This gear case 34
Inside, two spindles 36 and 37 are arranged in parallel,
Further, each end is rotatably attached to the gear case 34 via a bearing 39. Weights 41, 42 as rotating bodies are attached to both spindles 36, 37.
Is fixed. These weights 41 and 42 are designed to rotate eccentrically in plane symmetry with each other. That is, when the spindles 36 and 37 rotate, one-way vibrations are generated based on the eccentric masses of the weights 41 and 42. The direction of the vibration is indicated by an arrow P in FIGS.

As shown in FIG. 2, a sub case 45 is attached to one side of the gear case 34. A motor 47 is fixed horizontally in the sub case 45. The spindle 47a of the motor 47 is
The drive gear 49 is inserted into the gear case 34 through an opening 34a formed at the front end thereof. The driven gears 51, 52 having the same diameter as the spindles 36, 37 and having a smaller diameter than the driving gear 49.
Is fitted and meshed with the drive gear 49. However, an idle gear 54 is interposed between one driven gear 52 and the driving gear 49, and both the driven gears 51,
52 are driven to rotate in opposite directions.

The above-described motor 47, drive gear 49,
The spindle 3 is driven by both driven gears 51 and 52.
Drive means for rotating the weights 6 and 37, and thus the weights 41 and 42 in synchronization with each other, are provided.

As shown in FIG. 1, the vibrating means 31 having the above-described structure has its vibration direction P coincident with the contact / separation direction Z of the wire 14 with respect to the IC chip 20 and the lead frame LF which are the parts to be bonded. It is attached to be.

In the wire bonding apparatus,
When the vibrator 13 shown in FIG. 1 is operated, the above-described vibrating means 31 is operated synchronously. That is, FIG.
As shown in (a) and (b) of FIG.
When the capillary 4 is pressed against the pad 20a by the capillary 9 to become the flat portion 14b, the vibrator 13 is operated for a predetermined time to perform ultrasonic vibration (indicated by an arrow U in FIG. 1).
At this time, as shown in the flowchart of FIG. 4, the motor 47 of the vibrating means 31 is simultaneously operated for the same time. However, the amplitude of the vibration is set to a value that does not damage the IC chip 20 including the pad 20 (see FIG. 6), for example, several μm. In view of the fact that the heater block 22 and the heater plate 24 which are almost in a mechanically fixed state are vibrated, the amplitude is determined based on the elasticity of the heater block 22, the heater plate 24 itself, and the entire supporting mechanism for supporting them. It is determined by adjusting the applied vibration energy.

Because of this configuration, melting of the interconnecting portion, that is, alloying is promoted not only in the outer peripheral portion but also in the vicinity of the central portion of the flat portion 14a, and the flat portion 14a is securely connected over the entire surface. It is inferred that such good effects are due to the following reasons.

First, the ultrasonic vibration U generated by the vibrator 13 is applied in a horizontal direction perpendicular to the vibrating direction P by the vibrating means 31, but since the tip pressing surface of the capillary 9 is annular. However, it has been described with reference to a conventional example that it is conceivable that alloying near the center of the flat portion 14b may be incomplete with only the ultrasonic vibration U.

On the other hand, considering how the vibration by the vibration means 31 affects alloying near the center of the flat portion 14b, that is, melting, it can be considered as follows.

That is, as shown in FIG.
A tapered portion 9b whose diameter gradually increases from the wire receiving end toward the wire sending end is formed at the wire sending end so as to be continuous with the wire insertion hole 9a. By providing the tapered portion 9b, the ultrasonic vibration U in the horizontal direction by the capillary 9 is effectively transmitted to the flat portion 14b, and the ball 14a of the wire 14 is smoothly moved to the flat portion 14b.
Further, when a wire loop is formed, effects such as avoiding stress concentration at the boundary between the loop and the flat portion 14b can be obtained.

In view of the provision of the tapered portion 9b, the energy of the vertical vibration applied by the vibrating means 31 is reduced by the energy traveling direction changing action of the tapered portion 9b. It is thought that it is directed and concentrated in the vicinity of the part and promotes alloying of the interconnected part in this part.

The structure of the vibrating means 31 shown in this embodiment is relatively simple, can be easily reduced in size, and is inexpensive, and may cause an increase in the size of the wire bonding apparatus, particularly, the size of the bonding stage. It can be avoided, and the cost does not increase much.

[0035]

As described above, the wire bonding apparatus according to the present invention is provided with the vibrating means for vibrating the bonding stage in the direction in which the wire comes into contact with and separates from the bonding component. Therefore, when a flat portion formed by pressing a ball with a bonding tool on a bonding component is applied with ultrasonic vibration in order to melt and alloy an interconnecting portion with the bonding component, the vibrating means is used. When activated, alloying is promoted not only in the outer peripheral portion of the flat portion but also in the vicinity of the central portion, and the entire surface is securely connected. Thereby, the bonding property is improved, for example, the compression diameter and the compression thickness of the flat portion are stabilized, and the shear strength is increased.

[Brief description of the drawings]

FIG. 1 is a front view including a partial cross section of a main part of a wire bonding apparatus according to the present invention.

FIG. 2 is a plan view including a partial cross section of a vibration unit provided in the wire bonding apparatus shown in FIG. 1;

FIG. 3 is a view on arrow BB in FIG. 2;

FIG. 4 is a flowchart showing a part of the operation of the wire bonding apparatus shown in FIG. 1;

FIG. 5 is a front view including a partial cross section of a main part of a conventional wire bonding apparatus.

FIG. 6 is a diagram illustrating a state in which bonding is performed by a capillary provided in the wire bonding apparatus illustrated in FIG. 5;

FIG. 7 is a view taken along the line AA of FIG. 6 (b).

[Explanation of symbols]

Reference Signs List 4 bonding arm 9 capillary (bonding tool) 9a wire insertion hole (of capillary 9) 9b taper portion (of capillary 9) 11 horn 13 vibrator 14 wire 14a ball (of wire 14) 14b flat portion (of wire 14) 15 linear Motor 20 IC chip 20a Pad (first bonding point) 22 Heater block 24 Heater plate (bonding stage) 31 Vibration means 32 Insulating material 36, 37 Spindle 41, 42 Weight (rotating body) 47 Motor 49 Drive gear 51, 52 Coated Drive gear 54 Idle gear

Claims (5)

[Claims] 1. A wire bonding apparatus for performing bonding to a part to be bonded on a bonding stage with a wire inserted into the bonding tool while exciting the bonding tool with an ultrasonic exciting unit, wherein the bonding stage is A wire bonding apparatus comprising: a vibrating unit configured to vibrate the wire in a direction in which the wire approaches and separates from the component to be bonded. 2. The wire bonding apparatus according to claim 1, wherein said exciting means is operated in synchronization with said ultrasonic exciting means. 3. The wire bonding apparatus according to claim 1, wherein said ultrasonic excitation means excites in a direction substantially perpendicular to the contact / separation direction. 4. A wire feeding end of the bonding tool is characterized in that a tapered portion gradually increasing in diameter from the wire receiving end toward the wire sending end is formed continuously with the wire insertion hole. The wire bonding apparatus according to any one of claims 1 to 3, wherein 5. The vibrating means comprises: a rotatable rotatable member rotatable about a parallel rotation axis and symmetrically symmetric with respect to the rotation shaft with respect to each other; and a drive for rotating each of the rotatable members in synchronization with each other. The wire bonding apparatus according to any one of claims 1 to 4, further comprising means.