JPH1074767A - Fine ball bump forming method and device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable fine ball bumps to be quickly and surely formed. SOLUTION: Fine vibrations are applied to a case 6 where fine balls 5 are housed to make fine balls 5 start jumping, one of the jumping fine balls 5 is attracted by vacuum suction to a ball arranging board 1 where a ball suction hole is bored, fine balls 5a other than the fine ball 5 attracted to the ball suction hole 3 by vacuum suction are removed by vibrations of smaller amplitude, and then the ball arranging board 1 is moved over a ball bump forming target board 10 and aligned. Then, the fine ball 5 attracted to the ball suction hole 3 of the ball arranging board l is transferred onto the target board 10 at a bump forming position for the formation of a ball bump, thereby a fine ball bump of high bonding reliability can be easily formed through a simple device.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for forming a fine ball bump, and more particularly to a method and an apparatus suitable for forming a fine ball bump on a substrate or an electrode of a semiconductor chip.

[0002]

2. Description of the Related Art Conventionally, wafer bumps and stud bumps have been known as bumps formed on electrodes such as semiconductor chips. The wafer bump is used to form a bump on a semiconductor element at a wafer stage, and it is necessary to repeat a complicated process many times as a wafer process. In addition, there is a disadvantage that it cannot be applied to small-quantity multi-products due to high cost.

On the other hand, stud bumps are formed by performing ball bonding at the time of primary bonding of wire bonding on electrode pads of a semiconductor chip one by one, and cutting the neck portion of the wire after bonding.

Therefore, in the case of the stud bump, the rest of the wire at the cut portion becomes convex, and the height of the wire remains uneven. Also,
Since the ball diameter of the wire is used, the ball diameter becomes two to three times the wire diameter, and it is difficult to form a minute bump.

[0005] There is a method in which a bump formed by plating on a substrate is transferred to a bump forming position and joined. However, since the bumps formed by the plating are hemispherical bumps, the bump width becomes considerably large when the bumps are formed to have a bump height necessary for bonding. For this reason, for example, there is a problem that cannot be applied to a case where a narrow pitch bonding of 100 μm or less is performed.

Accordingly, as a technique for forming uniform and fine bumps, a bump forming technique using minute metal balls has been proposed, for example, in Japanese Patent Application Laid-Open No. 7-153765.

In the bump forming method proposed in the above publication, at least one metal ball group of a semiconductor chip is sucked and held. Then, in order to suck and hold the plurality of metal ball groups, using an array substrate in which suction holes are formed in all positions corresponding to the bump formation positions, and after sucking and holding the minute metal balls on the array substrate,
The arrangement substrate is transported to a joining stage and joined to a portion to be joined.

[0008] Therefore, in this case, the uniformly formed fine metal balls can be joined together at the bump formation position, so that ball bumps with high reliability can be easily and efficiently formed. .

However, the suction holes formed in the array substrate are uniquely determined according to the bump formation positions of the semiconductors forming the ball bumps. There was a problem that had to be created and prepared.

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

As a method of forming a ball bump suitable for producing a small number of semiconductor devices with a small number of pins, for example, Japanese Patent Application Laid-Open No. Sho 62
The "solder ball forming method" proposed in Japanese Patent Application Publication No. 166548 can be considered.

The "solder ball forming method" includes a solder bump tool provided with a suction hole penetrating from a tip end of a heat generating portion at a tool end to a connection portion with a suction means;
The suction balls are used to form the solder balls, so that a thick solder bump with little variation can be formed.

[0013]

In recent years, semiconductor devices have been increasingly miniaturized, and the wiring pitch of electrodes has become extremely small. For this reason, metal balls used for forming ball bumps on the electrodes have become extremely fine in accordance with the miniaturization of the wiring pitch of the electrodes.

The handling of such fine metal balls is very difficult. However, in the "solder ball forming method", no special measure has been taken when handling the fine metal balls. For this reason, when trying to form a fine ball bump using the "solder ball forming method", a plurality of metal balls may be attracted when one fine metal ball is attracted to the tool end. There was sex.

If an extra metal ball is adsorbed, not only the metal ball is wasted, but also the extra metal ball may fall on the semiconductor chip to cause a defective product, which is not preferable.

In the case of the "solder ball forming method", a solder ball is welded to a bump forming position. Therefore, the tip of the soldering tool must be set to a high temperature corresponding to the melting point of the solder ball.

Therefore, high melting point noble metal balls such as Au and Pt have a high melting point, and it is desirable to perform thermocompression bonding at a temperature as low as possible in order to prevent thermal damage to chips and the like.

SUMMARY OF THE INVENTION In view of the above-mentioned problems, it is a first object of the present invention to surely hold only one fine ball when sucking the fine ball and transferring it to the bump formation position. . It is a second object of the present invention to reliably form a fine ball bump at a low temperature.

[0019]

According to the present invention, there is provided a method for forming a fine ball bump, comprising: a fine ball jumping step in which a fine ball is jumped by applying a slight vibration to a container containing the fine ball; A fine ball sucking step of vacuum-sucking and holding one of the fine balls jumping by the process at the tip of the arrayed substrate having one suction hole, and sucking the fine ball at the tip of the arrayed substrate. An unnecessary ball removing step of removing extra fine balls other than the one fine ball by vibration with a minute amplitude, and an array substrate from which the extra fine balls have been removed in the unnecessary ball removing step is mounted on an electrode of a substrate or a semiconductor chip. An array for moving the ball bump forming object including the ball bump forming object and positioning the ball bump forming object and the fine ball adsorbed on the array substrate A plate moving step is characterized by performing the bump forming step of forming a ball bump is transferred to a predetermined position of the fine balls adsorbed on the tip of the array substrate the ball bump forming object.

Another feature of the present invention is that
The vibration due to the minute amplitude in the unnecessary ball removing step is an ultrasonic vibration generated by an ultrasonic vibrator.

Another feature of the present invention is that, in the bump forming step according to any one of claims 1 and 2, the fine ball and the ball bump forming object are applied while applying ultrasonic energy. And is joined.

Further, the fine ball bump forming apparatus of the present invention has an arrangement substrate having one end of a suction hole for adsorbing one of the jumping fine balls opened at a tip end thereof; A vacuum suction device for applying a negative pressure to the inside of the formed suction holes to vacuum-suck one of the jumping fine balls at the tip of the array substrate; And a vibrating means for vibrating the ball array substrate with a minute amplitude in order to remove extra fine balls other than the fine balls sucked in vacuum.

Another feature of the present invention is that
The vibration means for removing the extra fine ball is an ultrasonic vibrator.

Another feature of the present invention is that the tip of the ball array substrate has a small diameter corresponding to the size of the fine ball to be used, thereby forming the ball bump. It is characterized in that it is formed smaller than the pitch at which it is formed.

Another feature of the present invention resides in that, when a ball is formed by transferring a fine ball adsorbed to a tip portion of the array substrate to a predetermined position of the ball bump forming object. An ultrasonic transducer for applying ultrasonic energy to the fine ball is further provided. Further, the ultrasonic vibrator may also have a function of removing extra balls.

[0026]

Since the present invention has the above technical means, the ball bumps are formed by holding the fine balls one by one. Therefore, it is necessary to manufacture a ball array substrate for each type of the product on which the ball bumps are formed. And great versatility is obtained.

Further, since bumps can be formed using fine balls formed in a desired size in advance, the height and diameter of the bumps can be made uniform, and high bonding reliability can be obtained. A bump can be formed.

Further, by using an ultrasonic vibrator as the vibrator, extra balls often appearing when using fine balls can be satisfactorily removed. Can be prevented.

Further, according to another feature of the present invention, at the time of forming a bump, the fine ball and the ball bump forming object are bonded while applying ultrasonic energy to the fine ball. The joining time can be reduced, and the joining strength can be improved.

[0030]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the method and apparatus for forming a fine ball bump according to the present invention will be described with reference to the drawings. As shown in FIGS. 1 and 2, the fine ball bump forming apparatus of the present embodiment has a ball array substrate 1 as a main configuration.
And an ultrasonic transducer 2.

The ball array substrate 1 is formed to have a smaller diameter toward the tip, and the diameter L at the tip is smaller than the pitch for forming the bumps. Further, a ball suction hole 3 is formed at the center thereof. A vacuum suction device 20 (see FIG. 2) such as a vacuum pump is connected to the ball array substrate 1 through a hose 21.
As shown by an arrow 4 inside the ball suction hole 3,
The vacuum suction force is applied.

The ball array substrate 1 configured as described above
When the ball bump is formed by using the above, first, the ball array substrate 1 is moved onto the container 6 in which the fine metal balls 5 are stored. As shown in FIG. 3, the container 6 is fixed on a vibration generator 7 such as a parts feeder, and the fine metal balls 5 jump when the vibration generator 7 vibrates.

The frequency of the vibration generated by the vibration generator 7 is, for example, 0 in accordance with the size of the fine metal ball 5 or the like.
The frequency is variable up to 1 kHz, and the container 6 can be detached from the vibration generator 7.

Next, in order to attract the fine metal balls 5 to the ball array substrate 1, the ball array substrate 1 is lowered to the vicinity of the container 6 and amplitude is applied, and the jumping fine metal balls 5 are moved to the ball array substrate 1. Is vacuum-sucked into the ball suction hole 3 of FIG. Here, the descending distance and the amplitude distance of the ball array substrate 1 can be controlled, for example, in units of 0.1 mm, and the number of amplitudes can be controlled.

As described above, when the fine metal balls 5 are vacuum-sucked into the ball suction holes 3 of the ball array substrate 1, as shown in FIG.
a may adhere.

In this embodiment, the ultrasonic vibrator 2 is operated in order to remove the extra fine metal balls 5a, and as shown by reference numeral 8 in FIG. Is subjected to ultrasonic vibration. Thereby, as shown by the arrow 9, the extra fine metal ball 5a attached to the fine metal ball 5 can be dropped downward,
Only one fine metal ball 5 can be reliably sucked to the tip of the ball array substrate 1 by vacuum.

After one fine metal ball 5 is vacuum-adsorbed to the tip of the ball array substrate 1 as described above, the ball array substrate 1 is then placed on the semiconductor chip 10 as shown in FIG. To a predetermined position.

A plurality of electrodes 11 are formed on the semiconductor chip 10 at a predetermined pitch, and when the ball array substrate 1 is moved onto the electrodes 11 on which bumps are to be formed, FIG. The ball array substrate 1 is lowered as shown.

Then, after positioning the fine metal balls 5 at predetermined positions on the electrodes 11 of the semiconductor chip 10 on the heated stage 12, the fine metal balls 5 are thermocompression bonded to the electrodes 11. At this time, in the present embodiment, the ultrasonic vibrator 2 is operated to apply ultrasonic energy. For example, 20 to 150 KHz (preferably 30 to
Ultrasonic vibration of a frequency of 120 KHz is applied, whereby the fine metal ball 5 is brought into a state in which it can be deformed with a very small force.

Since the new surface is exposed at the bonding portion by the deformation, solid phase bonding can be performed at a relatively low temperature, that is, an alloy can be formed by mutual diffusion of metals. Therefore, in this embodiment, since bonding can be performed at a low temperature, the bonding time can be shortened and the bonding strength can be improved.

When the fine metal ball 5 is thermocompression bonded to the electrode 11, it may be heated on the stage 12 side.
Heating may be performed on the ball array substrate 1 side. Alternatively, heating may be performed from both the stage 12 side and the ball array substrate 1 side.

After the fine metal balls 5 have been bonded to the predetermined positions of the electrodes 11 as described above, the vacuum suction is released and the ball array substrate 1 is raised to complete one bonding. By repeating such processing, the fine metal balls 5 are bonded to predetermined positions of the semiconductor chip 10 to form ball bumps one after another.

When operating the ultrasonic vibrator 2, the operation timing is synchronized with the suction of the fine metal balls 5, that is, the fine metal balls 5 are transferred to the ball array substrate 1.
May be activated at the time of adsorption. In this case, the fine metal balls 5 are adsorbed to the ball suction holes 3 and, at the same time, the extra fine metal balls 5a can be prevented from being attached.

In the above description, an example in which the ultrasonic transducer 2 is fixed on the ball array substrate 1 has been described. Should be fixed to. Further, an appropriate adhesive, rubber, high-viscosity grease, or the like may be interposed between the ball array substrates 1 and fixed. Further, instead of being fixed on the ball array substrate 1, it may be embedded in the ball array substrate 1 in a buried form.

Further, in the above-described embodiment, one ultrasonic vibrator 2 is provided to remove an extra fine ball or to join a fine metal ball 5. However, an ultrasonic vibrator for removing extra fine balls and an ultrasonic vibrator for joining the fine metal balls 5 at predetermined positions of the semiconductor chip 10 may be separately provided.

In any case, the apparatus is configured to be controlled by a control device (not shown) so as to generate ultrasonic vibrations according to conditions such as the size and type of the fine metal balls 5. As means for removing extra fine balls, other vibration means such as a vibrator may be used in addition to the ultrasonic vibrator.

According to the present invention, as described above, the fine metal balls 5 are transferred one by one to the predetermined positions of the ball bump forming object and joined, so that the semiconductor chip on which a plurality of ball bumps are already formed is formed. A ball bump can be formed well at a predetermined position. Therefore, the fine ball bump forming apparatus of the present invention can be used favorably to recover bumping leakage.

[0048]

As described above, according to the present invention,
Since the ball bumps are formed by holding the fine balls jumped by the vibration one by one, it is not necessary to create a ball array substrate for each type of the product on which the ball bumps are formed, and great versatility can be obtained. . Therefore, it is particularly effective, for example, when producing a small number of semiconductor devices with a small number of pins.

Further, since bumps can be formed by using fine balls formed in a desired size in advance, the height and diameter of the bumps can be made uniform, and high bonding reliability can be obtained. The bump can be easily formed with a simple device.

Further, by applying ultrasonic vibration with an ultrasonic vibrator, an extra ball often appearing when a fine ball is used can be satisfactorily removed. Inconvenience can be reliably prevented.

Also, by applying ultrasonic energy when joining the fine balls, the joining temperature between the minute balls and the ball bump forming object can be lowered to shorten the joining time, and the joining strength can be reduced. Can be improved.

[Brief description of the drawings]

FIG. 1 is a diagram showing a joining procedure in an embodiment of the present invention.

FIG. 2 is a diagram for explaining dimensions and a schematic configuration of a ball array substrate according to the embodiment of the present invention.

FIG. 3 is a view showing an apparatus for floating fine metal balls.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Ball arrangement board 2 Ultrasonic transducer 3 Ball suction hole 4 Arrow 5 Fine metal ball 6 Container 7 Vibration generator 10 Semiconductor chip 11 Electrode

Claims (7)

[Claims] 1. A fine ball jumping step in which a fine ball is jumped by applying a slight vibration to a container containing the fine ball, and one of the fine balls jumping by the processing of the fine ball jumping step is: A fine ball suction step of vacuum-sucking and holding the tip of the arrayed substrate having one suction hole formed therein, and an extra fine ball other than the one fine ball sucked at the tip of the arrayed substrate is minutely removed. Unnecessary ball removing step of removing by vibration due to amplitude, and moving the array substrate from which extra fine balls have been removed in the unnecessary ball removing step, onto a ball bump forming object including electrodes of a substrate or a semiconductor chip, An array substrate moving step for aligning the ball bump forming object and the fine ball adsorbed on the array substrate; and adsorbing the tip of the array substrate. Fine ball bump forming method characterized by fine balls is transferred to a predetermined position of the ball bump forming object performing the bump forming step of forming a ball bump. 2. The method according to claim 1, wherein the vibration with the minute amplitude in the unnecessary ball removing step is an ultrasonic vibration generated by an ultrasonic vibrator. 3. The bump forming step according to claim 1, wherein the fine ball and the ball bump forming object are joined while applying ultrasonic energy. Method for forming fine ball bumps. 4. An array substrate having one end of a suction hole for sucking one of the jumping fine balls opened at a tip end thereof, and the inside of the suction hole formed in the array substrate being negative. A vacuum suction device for causing one of the jumping fine balls to be vacuum-sucked to the tip of the array substrate by applying pressure, and an extra part other than the fine balls vacuum-sucked to the tip of the array substrate. Vibrating means for vibrating the ball array substrate with a minute amplitude to remove fine balls. 5. The fine ball bump forming apparatus according to claim 4, wherein the vibrating means for removing the extra fine balls is an ultrasonic vibrator. 6. The method according to claim 6, wherein the tip of the ball array substrate is formed to have a small diameter corresponding to the size of the fine ball to be used, so that the tip is formed smaller than the pitch for forming the ball bumps. The apparatus for forming a fine ball bump according to claim 4, wherein: 7. A method for applying ultrasonic energy to the fine ball when transferring the fine ball adsorbed to the tip of the array substrate to a predetermined position of the ball bump forming object to form a ball bump. The fine ball bump forming apparatus according to any one of claims 4 to 6, further comprising: