JP2002009100A - Apparatus for forming fine ball bump - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an apparatus for forming fine ball bumps which continuously supplies fine balls and can reliably form bumps. SOLUTION: A ball suction hole 2 is formed at the center in the longitudinal direction of a leading edge of a bump formation tool 1. A pushing rod 5 is set in the ball suction hole 2 so as to move back and forth. In the ball suction hole 2, a fine ball supplying section 4 which supplies fine balls 9 one after another from a fine ball supplying hopper 10, and a suction pipe 3 for holding by suction force the fine balls 9 supplied into the ball suction hole 2, are provided. With the fine balls 9 held by suction force, the bump formation tool 1 is positioned at a target place where the fine ball 9 is to be bonded, and then the fine ball 9 is pushed out by the pushing rod 5 to be bonded at the target place. Since the metal fine balls are supplied one after another to form ball bumps, it is not necessary to manufacture a ball alignment substrate for individual semiconductor chips or facilities, and thus a great versatility is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fine ball bump forming apparatus, and more particularly to a fine ball bump forming apparatus for forming a ball-shaped bump on an electrode pad of an electronic circuit element such as an inner lead of a film carrier or a semiconductor chip. Related to the device.

[0002]

2. Description of the Related Art Conventionally, there are a wafer bump and a stud bump as bumps formed on an electrode pad portion on a semiconductor chip.

[0003] Wafer bumps are used to form bumps on electrode pads during a wafer process at the wafer stage, and it is necessary to perform complicated steps many times as a wafer process. For this reason, the yield of the wafer bumps is low, and the cost is high for a small number of high-mix products.

Further, the stud bump is formed by bonding a ball-shaped metal formed by the technique to each electrode pad of a semiconductor chip by ultrasonic thermocompression bonding by using a wire bonding technique and cutting a neck portion of the wire. When the wire is cut, the capillary tool is pulled up in the vertical direction and cut, so that the wire remains in the cut portion in a convex shape and non-uniformly.

[0005] Since it is necessary to control the height variation of the bonding bumps to a very small range, for example, ± 5 μm or less, stud bumps using the wire bonding technique are required to have high precision due to the manufacturing method. There was a problem that it was very difficult to control.

[0006] Further, the stud bump using the wire bonding technique has a problem that the recrystallized region which is thermally affected has an adverse effect on the bonding property in the subsequent flip chip bonding, for example. .

Therefore, as a technique for forming uniform and fine bumps, a bump forming technique using a fine metal is disclosed in, for example, JP-A-7-153765 and JP-A-9-15.
3496 and Japanese Patent Application Laid-Open No. 10-74767.

In the bump forming method proposed in Japanese Patent Application Laid-Open No. 7-153765, at least one metal ball group of a semiconductor chip is sucked and held.
Then, in order to hold a plurality of metal ball groups by suction, an array substrate having suction holes formed at all positions corresponding to the bump formation position is used, and the array substrate is transported to a bonding stage to be bonded to the bonding portion. So that it can be joined.

Therefore, in this case, the uniformly formed minute metal balls can be joined together at the bump formation position, so that a ball bump with high reliability can be easily and efficiently formed.

However, the suction holes formed in the array substrate are
Since it is uniquely determined according to the bump forming position of the semiconductor chip on which the ball bump is formed, an array substrate must be prepared and prepared for each type of semiconductor device and for each semiconductor chip.

Therefore, a method of collectively forming a plurality of ball bumps using an array substrate having a plurality of suction holes is suitable for mass production of multi-pin semiconductor products. However, it is not suitable for producing a small number of semiconductor products with a small number of pins.

Japanese Patent Application Laid-Open No. 9-1534 discloses a ball bump forming method suitable for producing a small number of semiconductor products with a small number of pins.
No. 96 and Japanese Patent Application Laid-Open No. 10-74767. In the bump forming method described in Japanese Patent Application Laid-Open No. 9-153496, there is provided a ball supply unit having an extraction window which is opened so that only one ball is exposed upward at the tip of the tube, and the suction tool is moved from the extraction window by one.
Only the individual balls are picked up, conveyed onto an electrode on which a bump is to be formed, and subjected to ultrasonic thermocompression bonding.

Further, in the bump forming method described in Japanese Patent Application Laid-Open No. H10-74767, a container for storing minute balls made of a metal material is vibrated by a vibration generator such as a parts feeder to cause the minute balls to jump, thereby causing the minute balls to jump. Vacuum suction is applied to the array substrate with suction holes, and ultrasonic vibration is applied to remove anything other than the necessary minute balls.
Only one minute ball can be transported. Then, the transported micro-balls are subjected to ultrasonic thermocompression bonding to each of the electrode pads of the semiconductor chip on the heated stage via the array substrate.

Therefore, the bump forming methods described in these publications do not need to fabricate an array substrate for each semiconductor device, and do not require an array substrate for each semiconductor chip. For small production,
It can be produced at low cost.

[0015]

However, even though it is suitable for small-scale production of semiconductor products with few pins,
In any of the bump forming methods, each time one bump is formed, it is necessary to move the suction tool or the array substrate to the take-out window of the ball supply unit or the container for the small balls. The traveling time cannot be ignored, and there is a problem that the efficiency in production is reduced.

Further, in the bump forming method described in Japanese Patent Application Laid-Open No. H10-74767, it takes a long time to vacuum-suck a jumping minute ball into a minute suction hole of an arrayed substrate. The decline is unavoidable, and furthermore, an ultrasonic transducer for ultrasonic thermocompression bonding is provided at the tip of the array substrate, but the ultrasonic transducer attached to the tip becomes small. In addition, since the mounting position is at the distal end, there is a problem that the ultrasonic vibration required for connecting the ball may not be sufficiently transmitted to the minute ball.

The present invention has been made in view of the above points, and has as its object to provide a minute ball bump forming apparatus capable of continuously supplying minute balls and reliably forming bumps. I do.

[0018]

According to the present invention, there is provided a minute ball bump forming apparatus including a bump forming tool for forming a bump by bonding a minute ball to an electrode pad of a semiconductor chip, wherein the bump forming tool comprises: A ball suction hole provided at the center of the semiconductor chip in the longitudinal direction at the tip end thereof and for sending out minute balls one by one to the electrode pad of the semiconductor chip;
A minute ball supply unit that communicates with the ball suction hole so as to be open to the ball suction hole and sequentially supplies the minute ball into the ball suction hole from a supply hopper that stores the minute ball; and the minute ball supplied into the ball suction hole. A suction pipe for holding the vacuum in the ball suction hole, and a micro-ball which is inserted and disposed in the ball suction hole so as to be able to advance and retreat, and is supplied to the ball suction hole and held in vacuum from the ball suction hole. And an extruding rod for extruding toward the electrode pad of the chip.

According to the above arrangement, the minute balls are supplied to the bump forming tool one by one and held in vacuum, and after positioning the bump forming tool on the predetermined electrode pad, the pushing rod is held in vacuum in the ball suction hole. The minute balls are extruded onto the electrode pads to form ball bumps on the electrode pads. Since the minute balls are formed one by one on the predetermined electrode pads, it is not necessary to manufacture a ball array substrate for each semiconductor chip on which ball bumps are formed and for each semiconductor manufacturing apparatus, and large versatility can be obtained. In addition, since the bumps can be formed with the extrusion rod by using the micro balls formed in a desired size in advance, the height and diameter of the bumps can be made uniform,
It is possible to form a bump with high reliability.

Further, in the present invention, the first ultrasonic vibrator is provided in the micro-ball supply section so as to prevent clogging of the micro-ball supplied to the bump forming tool. Thereby, the minute balls can be supplied one by one continuously, and the ball bumps can be efficiently formed in a short time.

Further, in the present invention, the bump forming tool is held at the tip of the horn having the second ultrasonic vibrator, and the minute ball is applied to the electrode pad of the semiconductor chip while applying ultrasonic energy at the time of forming the ball bump. Was subjected to ultrasonic thermocompression bonding. As a result, the bonding time can be shortened, the temperature at the time of forming the bumps can be reduced, the recrystallization of the metal material can be minimized, and the bonding strength can be improved.

[0022]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a cross-sectional view showing a configuration of a main part of a micro-ball-bump forming apparatus of the present invention, and FIG. 2 is a perspective view showing an entire configuration of a micro-ball-bump forming apparatus of the present invention.

The micro-ball bump forming apparatus according to the present invention includes a bump forming tool 1 as shown in FIG. This bump forming tool 1 has a ball suction hole 2 formed at the center in the longitudinal direction. The ball suction hole 2 is formed so that a suction pipe 3 and a minute ball supply unit 4 communicate with each other. A push rod 5 is inserted and disposed inside the ball suction hole 2 so as to be able to advance and retreat, and a packing 6 for sealing a gap between the push rod 5 and the inner wall of the ball suction hole 2 is provided around the push rod 5. ing. Also,
The end surface of the push rod 5 inside the ball suction hole 2 is formed flat so that the surface of the bump to be formed is flat.

A vacuum generator 8 such as a vacuum pump is connected to the suction pipe 3 of the bump forming tool 1 via a hose 7. The minute ball supply unit 4 includes a minute ball 9 made of metal.
At the tip of the passage, the micro-ball supply unit 4 feeds the micro-balls 9 one by one to the ball suction holes 2 of the bump forming tool 1 through the micro-ball supply unit 4. A hopper 10 is provided. The minute ball 9 sent out to the ball suction hole 2 is sucked and held by the suction pipe 3 opened at the opposed position where the ball 9 is sent out. The suction pipe 3 is formed so as to have an inner diameter smaller than the diameter of the minute ball 9, so that the sent minute ball 9 is sucked and held by the tip of the rod 5 in the ball suction hole 2. ing.

An ultrasonic vibrator 11 for preventing clogging is fixed to the minute ball supply section 4. The clogging preventing ultrasonic vibrator 11 is driven and controlled by a frequency control device (not shown) to vibrate the microballs 9 passing through the passage, thereby eliminating clogging of the microballs 9 in the microball supply unit 4. Thus, the micro-ball supply hopper 10 functions to sequentially send the micro-balls 9 to the ball suction holes 2 efficiently. The vibration frequency of the ultrasonic transducer 11 for preventing clogging is
The frequency can be appropriately changed depending on the size of the minute ball, and the frequency is not particularly limited.

Further, an extruding device 12 is provided at the top end of the extruding rod 5. As the pushing device 12, an electromagnetic solenoid, an air cylinder, a linear motor, or the like can be used.

As shown in FIG. 2, the bump forming tool 1 having the above-described configuration is held at the tip of a horn 14 provided with an ultrasonic transducer 13 for ball bump bonding. The ultrasonic transducer 13 for bonding the ball bumps transmits ultrasonic energy when the micro-balls 9 supplied by the bump forming tool 1 are pressed and bonded to the electrode pads 17 of the semiconductor chip 16 placed on the heating stage 15. The ultrasonic vibration having a frequency of 30 to 200 KHz can be applied to the minute ball 9 so that the minute ball 9 can be deformed by a very small force.

Next, the operation of the minute ball bump forming apparatus will be described with reference to FIG. FIGS. 3A and 3B are diagrams for explaining a bonding procedure of micro balls, wherein FIG. 3A shows a micro ball supply state, FIG. 3B shows a micro ball bonding state, and FIG. 3C shows a ball bump formation state. .

First, the minute ball 9 formed in a desired size in advance is supplied to the bump forming tool 1 from the minute ball supply hopper 10 via the minute ball supply unit 4. When the micro-balls 9 supplied to the bump forming tool 1 are discharged to the ball suction holes 2, as shown in (A), the extruded rods 5 in the bump forming tool 1 are sucked by vacuum suction from the suction pipe 3. Is held by suction at the tip end.

Next, after positioning the micro-balls 9 thus sucked and held on predetermined electrode pads 17 of the semiconductor chip 16 mounted on the heating stage 15,
As shown in FIG. 2B, the push rod 5 pushes the minute ball 9 held in the ball suction hole 2 of the bump forming tool 1 onto the electrode pad 17. Then, ultrasonic energy is applied to the extruded micro ball 9 while applying a load to the electrode pad 17. The application of ultrasonic energy to the micro-ball 9 is performed by the ultrasonic transducer 1 for bonding the ball bump.
The operation is performed by transmitting ultrasonic energy to the bump forming tool 1 through the horn 14 by operating the horn 3.

The minute balls 9 are minutely deformed by receiving ultrasonic vibration in the longitudinal direction of the horn 14 by the ultrasonic transducer 13 for bonding the ball bumps. This deformation causes a new surface to appear at the joint with the electrode pad 17, an alloy is generated by mutual diffusion of the metal, and the minute ball 9 is pressure-bonded to the electrode pad 17.

Accordingly, the pressure bonding of the micro-balls 9 to the electrode pads 17 by the ball bump bonding ultrasonic transducer 13 can be performed at a relatively low temperature, so that the time required for bonding can be shortened and the bonding strength can be reduced. Can be improved.

At this time, the extruding rod 5 having a flat end face is moved to the tip of the bump forming tool 1 by the minute ball 9.
, The bump is shaped so that the upper surface after the formation of the ball bump is flat.

After the minute balls 9 have been joined to the predetermined positions of the electrode pads 17 in this manner, the vacuum suction is released. Then, as shown in (C), the pushing rod 5 is pulled in, and at the same time, the bump forming tool 1 is raised to complete the joining.

During the pressure bonding, the micro-ball 9 is deformed by applying a load to the end surface of the tip portion by the push rod 5 having a flat end surface, so that the upper surface of the ball bump is deformed to a flat surface, and the ball is subjected to a subsequent flip-chip bonding. The resulting ball bump 18 has an ideal shape with high reliability. By deforming the upper surface of the ball bump 18 into a flat surface, a bonding area in a process after the formation of the ball bump, for example, flip chip bonding can be increased, and bonding strength can be increased.

Thereafter, the supply of the minute balls 9 is performed again.
Positioning is performed so that the bump forming tool 1 is positioned on the electrode pad 17 on which the next bump is to be formed. After the bonding of the minute balls 9, the next minute balls 9 are supplied to the tip of the bump forming tool 1 while moving to the next electrode pad 17, and are held by vacuum suction so that the minute balls 9 do not drop. ing. Then, ball bump formation is performed in the same procedure as described above. By repeating such a process, the minute balls 9 are bonded to predetermined positions of the semiconductor chip 16 to continuously form ball bumps.

In the above-described embodiment, the clogging preventing ultrasonic vibrator 11 is provided in the micro-ball supply unit 4 and the ball bump bonding ultrasonic vibrator 13 is provided in the horn 14 holding the bump forming tool 1. However, the ultrasonic vibration generated from the ultrasonic transducer 13 for bonding the ball bumps may be used for preventing clogging. In this case, the ultrasonic frequency applied at the time of joining and the ultrasonic frequency used to prevent clogging can be appropriately changed, and the ultrasonic frequency for joining is used during joining, and the ultrasonic frequency for preventing clogging at the time of supplying minute balls. Try to generate a sound wave frequency.

In any case, the frequency of the ultrasonic vibration is
Although it is necessary to change according to the size, type, and electrode pad state of the minute ball, the structure is controlled by a control device (not shown) so as to generate ultrasonic vibration according to each condition.

[0039]

As described above, according to the present invention, in the bump forming tool, the minute ball supply unit supplies the minute balls one by one and holds the minute balls in the ball suction holes by vacuum suction by the suction pipe. In addition, the extruding rod is configured to extrude to the tip of the bump forming tool at the time of bonding the minute ball onto the electrode pad. Thereby, since the metal micro-balls can be supplied one by one continuously to form the ball bumps, it is not necessary to manufacture a ball array substrate for each semiconductor chip or equipment, and large versatility can be obtained. Therefore, it is particularly effective, for example, when a small number of products of various varieties are produced.

Further, since a ball bump can be formed using a metal ball shaped in advance to a desired size, the height, diameter and shape of the bump can be made uniform, and high bonding reliability can be obtained. Ball bumps can be easily formed.

Further, since the minute balls can be continuously supplied by using the ultrasonic vibrator, the supply time of the minute balls can be reduced. Further, since ultrasonic energy can be applied when joining the micro-balls, the temperature at the time of joining the micro-balls and the electrode pads can be reduced, and the joining time can be shortened. The joining strength can be improved. In addition, since the ultrasonic vibrator for applying ultrasonic energy can be attached to the horn itself, a relatively large ultrasonic vibrator can be installed, and high-output ultrasonic energy can be applied. Can be joined, and the working time can be reduced.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a main configuration of a minute ball bump forming apparatus according to the present invention.

FIG. 2 is a perspective view showing the entire configuration of the minute ball bump forming apparatus of the present invention.

FIG. 3 is a view for explaining a joining procedure of a minute ball;
(A) shows a state of supplying minute balls, (B) shows a state of bonding minute balls, and (C) shows a state of forming ball bumps.

[Explanation of symbols]

1 ... Bump forming tool, 2 ... Ball suction hole, 3 ...
Suction pipe, 4 ... minute ball supply section, 5 ... push rod, 6 ... packing, 7 ... hose, 8 ... vacuum generator, 9 ... minute ball, 10 ... minute ball supply hopper, 11 ... ... an ultrasonic oscillator for preventing clogging, 12 ... an extruder, 13 ... an ultrasonic oscillator for ball bump bonding,
14 horn, 15 heating stage, 16 semiconductor chip, 17 electrode pad, 18 ball bump

Claims (7)

[Claims] 1. A micro-ball bump forming apparatus comprising a bump forming tool for forming a bump by bonding a micro ball to an electrode pad of a semiconductor chip, wherein the bump forming tool is provided at a front end portion in a longitudinal central portion. And a ball suction hole for sending the micro balls one by one to the electrode pad of the semiconductor chip, and a small ball is supplied into the ball suction hole from a supply hopper that communicates with the ball suction hole and is open to the ball suction hole. A micro-ball supply unit for sequentially supplying the micro-balls, a suction pipe for vacuum-holding the micro-balls supplied into the ball suction holes in the ball suction holes; Micro balls supplied into the holes and held in a vacuum are pushed out from the ball suction holes toward the electrode pads of the semiconductor chip. Micro ball bump forming apparatus characterized by comprising a rod out to. 2. The minute ball supplied from the minute ball supply unit, wherein the suction pipe is opened in the ball adsorption hole so as to face an opening of the minute ball supply unit to the ball adsorption hole. 2. An apparatus for forming a minute ball bump according to claim 1, wherein the tip of the push rod is held by vacuum suction. 3. The minute ball bump forming device according to claim 1, wherein the minute ball supply unit includes a first ultrasonic vibrator for preventing the supplied minute balls from being clogged. apparatus. 4. The bump forming tool is held at a tip of a horn having a second ultrasonic vibrator, and applies the ultrasonic energy to the electrode pad of the semiconductor chip while forming a ball bump. The micro-ball bump forming apparatus according to claim 1, wherein the micro-balls are joined. 5. The bump forming tool is held at a tip of a horn having an ultrasonic vibrator, and the ultrasonic vibrator is provided with a micro ball supplied by the micro ball supply section when supplying the micro ball. 2. The micro-ball-bump forming apparatus according to claim 1, wherein clogging is prevented and ultrasonic energy for bonding is applied to said micro-balls during ball-bump formation. 6. The vibration frequency of the ultrasonic vibrator is changed according to the size, type, and condition of an electrode pad state of the micro ball in accordance with prevention of clogging of the micro ball or bonding of the micro ball. 6. The method according to claim 5, wherein
The micro ball bump forming apparatus as described in the above. 7. An extruding rod according to claim 1, wherein said extruding rod is configured to flatten an end surface of a tip portion abutting on said micro-ball when extruding, and to shape a top surface of a ball bump formed on an electrode pad of said semiconductor chip into a flat surface. The apparatus for forming a minute ball bump according to claim 1, wherein: