JPH09321078A - Wire bonding equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase transmission efficiency of ultrasonic vibration when a capillary is exchanged, obtain excellent reproducibility and improve the life of an attaching part of an ultrasonic horn. SOLUTION: A plurality of metal bushes 2 which are circularly protruded are uniformly arranged on a peripheral wall of a fixing hole 1 of a horn 3 in which a capillary 4 is inserted and fixed. The capillary 4 is clamped and retained with the horn 3 via the metal bushes 2. Even if the capillary 4 has unevenness on the surface and irregularity in the outer dimension, a large number of point contacts or line contacts with an ultrasonic horn can be obtained in response to the irregularity of dimension or the unevenness of the capillary 4.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of pressing a metal thin wire (hereinafter referred to as a wire) to a pad of a semiconductor pellet or an inner lead of a lead frame, which is an object to be connected, by a bonding tool to apply ultrasonic vibration energy to connect the wire The present invention relates to a wire bonding apparatus for bonding to an object, and particularly to a structure for mounting a bonding tool on a horn that transmits ultrasonic vibration.

[0002]

2. Description of the Related Art Recently, as the integration of ICs increases, that is, semiconductor pellets become finer and the number of pads increases, the number of pads becomes smaller and the pad pitch becomes smaller. The width and pitch of the inner leads are also miniaturized. On the other hand, in a wire bonding device that connects a pad of a semiconductor pellet and an inner lead of a lead frame with a fine metal wire (hereinafter referred to as a wire), in addition to high speed and high accuracy, bonding of the wire to the pad of the semiconductor pellet is performed. It is required that the ball crimping diameter, which is a part, be stably obtained, and that the ball and pad be bonded and the inner lead and wire be highly reliable.

FIG. 3 is a diagram showing a main part of a conventional wire bonding apparatus. Conventionally, this type of ultrasonic connection type wire bonding apparatus has been disclosed in, for example, FIG.
As shown in FIG. 3, a capillary 4 which is a bonding tool is attached to the tip of the horn 3 which extends in one direction from the main body and which moves ultrasonic waves from the vibrator 14 to the capillary 4 and moves up and down. The heater plate 10 fixed to 11 and mounting the lead frame 18 on which the semiconductor pellets 19 are mounted, the heater block 9 for heating the heater plate 10, and the tip of the wire passed through the capillary 4 are discharged to form a ball-shaped wire. And a clamper 12 for temporarily fixing the wire sent to the capillary 4.

FIGS. 4A and 4B are views showing a mounting portion of a capillary which is the bonding tool of FIG. In this ultrasonic bonding type wire bonding apparatus, how to efficiently and stably transmit ultrasonic vibration to the capillary 4 has been an important issue. Especially, the transmission efficiency and stability depended on the mounting structure of the capillary 4 to the horn 3.

The mounting structure of the capillaries on this horn is, for example, the most known mounting structure of capillaries, as shown in FIG.
Insert the capillary 4 having the fine hole 4a through which the wire passes, into the mounting hole 1a at the tip of the, and tighten with the screw 5 so as to narrow the slit 15, and the capillaries 4 at the inner wall of the mounting hole 1a.
It was a structure to fix the outer wall of the.

[0006]

In the mounting structure of the capillary to the horn in the above-mentioned conventional wire bonding apparatus, the mounting hole 1a shown in FIG. 4 (a) is such that the capillary 4 can be easily inserted when the screw 5 is not tightened. It is slightly larger than the outer diameter of the capillary 4. For this reason, although the screw 15 is tightened in the direction in which the slit 15 is narrowed, the entire circumference of the capillary 4 is not tightened by the inner wall of the mounting hole 1a, but in reality, it is a direction perpendicular to the extending direction of the slit 15. The capillary 4 is tightened at only two points P of the hole 4. Moreover, since the contact is not a surface contact but a line contact, there is no tightening portion in the direction in which the slit 15 extends, and the holding force in this direction becomes weak. As a result, vibrations with a short wavelength such as ultrasonic vibrations are transmitted and transmitted through the outer skin surface, so that there is a problem that the transmission efficiency is deteriorated.

Further, the capillaries are consumable items and must be replaced frequently. However, the accuracy of the outer diameter of the capillaries in which the ceramics are unglazed is lower than the accuracy of the mounting hole 1a that is machined in the steel horn, and the outer diameter is of course uneven, and the surface is uneven. As a result, the position of the contact point P fluctuates due to the variation in the outer diameter of the capillary, and the transmission efficiency of the vibration wave changes. For this reason, it has been necessary to make time-consuming adjustments such as trial striking each time the capillary is attached. This adjustment has a problem that not only the adjustment man-hours are wasted but also the operation rate of the apparatus is lowered.

Further, since the tip portion of the horn 3 is constantly subjected to heat and stress from the heater block, it causes creep and is deformed, and the tightening force by the mounting hole 1a is weakened and the horn itself has a life. There is. After exchanging this horn, it took longer adjustment time to get reproducibility of connection than that of the capillary.

Therefore, an object of the present invention is to provide a wire bonding apparatus having a bonding tool mounting structure which has high ultrasonic vibration transmission efficiency and good reproducibility even when the bonding tool is replaced, and has a long life. It is in.

[0010]

A feature of the present invention is that a bonding tool having a fine hole through which a fine metal wire is passed is fixedly held at the tip of an ultrasonic horn, and the ultrasonic wave is transmitted to the bonding tool, and the bonding tool is connected to the bonding object. In a wire bonding apparatus for pressing a thin metal wire to bond the thin metal wire to the connection object, the mounting hole is arranged at equal intervals from a peripheral wall of a circular mounting hole into which the bonding tool at the tip of the ultrasonic horn is inserted. Is a wire bonding apparatus having a plurality of protrusions that uniformly project along the depth of the above and uniformly press the cylindrical outer periphery of the bonding tool. Further, it is desirable that the protrusion can be inserted into and removed from the mounting hole.
Furthermore, whether the protrusion that can be inserted and removed is cylindrical,
Alternatively, a plurality of spherical members arranged in the depth direction of the mounting hole is preferable.

[0011]

Next, the present invention will be described with reference to the drawings.

FIGS. 1 (a) and 1 (b) are views showing a mounting portion of a capillary which is a bonding tool of a wire bonding apparatus according to an embodiment of the present invention. As shown in FIG. 1, the mounting portion of the capillaries in this wire bonding apparatus is arranged at equal depths from the peripheral wall of the circular mounting hole 1 into which the capillaries 4 at the tip of the horn are inserted, at a depth of the mounting hole 1. A plurality of metal bushes 2 are provided that uniformly project along the outer periphery of the cylindrical carrier 4.

The cylindrical metal bush 2 has a mounting hole 1
It is designed to be inserted into and removed from a groove formed in a substantially circular shape on the peripheral wall of the. Then, the capillary 4 is pressed against the outer surface of the metal bush 2 by tightening with the screw 5 in the direction in which the gap of the slit 15 disappears. If the metal bush 2 is provided as a tightening member in this way, even if the capillary 4 is as-fired and has a large variation in dimensions and unevenness on the surface, the capillary 4 is surely contacted by a plurality of points and line contact with the metal bush 2. As a result, the ultrasonic wave transmission efficiency is improved and the transmission efficiency is reproducible. Further, since there is no direct contact between the mounting hole 1 and the capillary 4, the mounting hole 1 is not worn and the necessity of replacing the horn is eliminated. further,
Even if the metal bush 2 wears after a long period of use, only the metal bush 2 needs to be replaced. It has the advantage that it can be easily replaced.

In this drawing, the metal bush 2 has 6
Although they are arranged in equal parts, it is desirable to arrange more parts, such as 8 parts or 10 parts, so as to increase the portion in line contact with the capillary 4. However, the metal bushes 2 must be provided so as to be paired with each other on the center line passing through the center of the capillaries 4 so that the capillaries 4 are evenly tightened.

2 (a) and 2 (b) are views showing a modified example of the mounting portion of the capillary of FIG. As shown in FIG. 2, the mounting portion of the capillary in this wire bonding apparatus has a plurality of metal balls 6 arranged in a row in the depth direction of the groove of the mounting hole 1 instead of the metal bush described in the above embodiment. It is arranged side by side. Other than that is the same as the above-mentioned embodiment.

Although the tightening member using the metal balls 6 is in point contact with the capillary 4, the same effect can be obtained by using multi-point contact. Further, if the groove in the depth direction of the mounting hole 1 is made slightly larger than the metal ball 6 in the width direction, the metal ball 6 can freely rotate and move in the groove, so that the outer surface of the capillary 4 is uneven. Even if there is, the metal ball 6 is rotated and moved according to the unevenness of the surface, and it is possible to make point contact without fail, so that the capillary 4 can be reliably held.

[0017]

As described above, according to the present invention, a plurality of circularly projecting protrusions are provided which are evenly arranged on the peripheral wall of the mounting hole of the ultrasonic horn into which the capillary as a bonding tool is inserted and mounted. By sandwiching and holding the capillaries with the ultrasonic horns through these protrusions, even if the capillaries have irregularities or external dimensions on the surface, there are many points with the ultrasonic horn depending on the irregularities and irregularities of the capillaries. Contact or line contact can be obtained evenly, the transmission efficiency of ultrasonic waves can be increased, and the transmission efficiency is good even if the capillary is replaced.Therefore, the output adjustment after replacement of the capillary is not necessary, and the wire connection is not required. There is an effect that the quality can be stably obtained.

Further, by allowing the protrusions to be inserted and removed, the mounting hole is not damaged and the life of the ultrasonic horn is long. Further, even if the protrusion is damaged, it is sufficient to replace only the protrusion, which leads to a low operating cost. Moreover, there is also an effect that the replacement of the protrusion can be completed in a short time.

[Brief description of drawings]

FIG. 1 is a diagram showing a mounting portion of a capillary which is a bonding tool of a wire bonding apparatus according to an embodiment of the present invention.

FIG. 2 is a view showing a modified example of a mounting portion of the capillary of FIG.

FIG. 3 is a diagram showing a main part of a wire bonding apparatus in a conventional example.

FIG. 4 is a view showing a mounting portion of a capillary which is a bonding tool on the horn of FIG.

[Explanation of symbols]

 1,1a Mounting hole 2 Metal bush 3 Horn 4 Capillary 4a Fine hole 5 Screw 6 Metal ball 8 Guide rail 9 Heater block 10 Heater plate 11 Work clamp 12 Torch 14 Vibrator 15 Slit 18 Lead frame 19 Semiconductor pellet

Claims (4)

[Claims] 1. A bonding tool having a fine hole through which a thin metal wire is passed is fixedly held at the tip of an ultrasonic horn, ultrasonic waves are transmitted to the bonding tool, and the thin metal wire is pressed against an object to be connected to the object. In a wire bonding device for joining thin metal wires, the tip of the ultrasonic horn is evenly arranged from a peripheral wall of a circular mounting hole into which the bonding tool is inserted, and protrudes uniformly along the depth of the mounting hole. A wire bonding apparatus having a plurality of protrusions that uniformly press the cylindrical outer periphery of the bonding tool. 2. The wire bonding apparatus according to claim 1, wherein the protrusion is insertable into and removable from the mounting hole. 3. The wire bonding apparatus according to claim 2, wherein the protrusion has a cylindrical shape. 4. The wire bonding apparatus according to claim 2, wherein the protrusion is a plurality of spherical members arranged in a depth direction of the mounting hole.