JPH06104263A - Bump forming tool and bump forming method - Google Patents

Abstract

PURPOSE:To provide a bump forming tool capable of forming better a bump. CONSTITUTION:In a bump forming tool 10, a wire 2 is inserted into a lower end surface 10b in the vertical direction, and a ball 2a is formed at a tip part of this wire 2 on the lower end surface 10b and abutted against and connected with an electrode pad 5. Afterward, the ball 2a is slided slightly in the lateral direction to twist the wire 2 directly above the ball 2a to cut it off in this part, whereby a bump 12 is formed on the electrode pad 5. Flat parts (a), (b) which are abutted against the upper surface of the ball 2a when the tool is slightly slided in the lateral direction are provided in the lower end surface 10b.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bump forming tool and a bump forming method for forming bumps (projection electrodes) on electrodes of a semiconductor element.

[0002]

2. Description of the Related Art In the case of mounting a semiconductor element on a film carrier or a circuit board, bumps (projection electrodes) are formed on the electrode pads of the semiconductor element, and the electrode pads of the semiconductor element and the film carrier are connected via the bumps. The connection with external electrodes (leads) formed on the circuit board or the circuit board is performed.

As a method of forming such bumps,
There is a method of molding using a gold wire. This method uses the capillary indicated by 1 in FIG. A gold wire 2 is inserted into the capillary 1. A clamp device 3 that moves with the capillary 1 and that can clamp / unclamp the gold wire 2 is provided above the capillary 1.

The gold wire 2 is taken out from the lower end of the capillary 1 and is positioned above the electrode pad 5 of the semiconductor element 4 so as to face it. At the tip of the gold wire 2, a ball 2a is formed by an electric torch 6.

Next, as shown in FIG. 5 (b), the capillary 1 is driven downward, the ball 2a is pressed against the electrode pad 5, and the ball 2a is joined to the electrode pad 5.

Next, as shown in FIG. 5 (c), the capillary 1 is driven upward while feeding the gold wire 2, and slightly moves in the X direction. Then, as shown in FIG. 5D, the capillary 1 is again driven downward, and the lower end surface is pressed against the upper surface of the ball 2a. As a result, the capillary 1 causes the wire 2 immediately above the ball 2a to be constricted. When the wire 2 has a constriction, the clamp device 3 clamps the wire 2.

Then, as shown in FIG. 5 (e), the capillary 1 and the clamp device 3 are driven up, and the wire 2 is cut at the constricted portion. As a result, ball bumps 7 are formed on the electrode pads 5.

[0008]

The conventional bump forming method has the following problems to be solved.

That is, according to the above bump forming method, since the tip portion 1a (lower end portion) of the capillary 1 is a curved surface as shown in FIG. 4 (a), as shown in FIG. 5 (e), The upper surface of the formed bump 7 is not flat but inclined. Therefore, when the inner lead is bonded to the bump 7, the inner lead may slip and slide along the upper surface of the bump 7.

Further, as shown in FIG. 4B, when the molding interval of the bumps 7 becomes narrow, the tip of the capillary 1 may interfere with the bumps 7 already formed, and the bumps 7 may be damaged. .

The present invention has been made in view of such circumstances, and an object thereof is to provide a bump forming tool capable of forming bumps more favorably.

[0012]

According to a first means of the present invention, a wire is inserted in the vertical direction and a ball formed at the lower end surface of the tip of the wire is pressed against an electrode pad to join the wire. It is a bump forming tool for forming a bump on the electrode pad by cutting the wire right above the ball by slightly shifting in the lateral direction and cutting the wire at this portion. The lower end surface is provided with a flat portion that comes into contact with the upper surface of the ball when slightly displaced in the lateral direction.

A second means is, in the bump forming tool of the first means, a part of the lower end surface is escaped so that the lower end portion of the tool does not interfere with the already formed bumps. It is characterized in that a section is provided.

A third means is a lower end surface of a bump forming tool in which a wire is inserted, and a ball formed at a tip portion of the wire is pressed and bonded to a bonding surface of an electrode pad of a semiconductor element. In the first step, the bump forming tool is slightly displaced in the surface direction of the bonding surface so that the flat surface formed on the lower end surface of the bump forming tool forms the upper surface of the ball. The second step of making the wire substantially flat and constricting the wire immediately above the ball and cutting the wire at this portion.

A fourth means is, in the bump forming method of the third means, sequentially using the relief portions provided on the lower end surfaces of the bump forming tools while avoiding the bumps already formed. It is characterized in that bumps are formed.

[0016]

According to the first means and the third means, the shape of the upper surface of the bump can be made substantially flat by bringing the flat portion into contact with the upper surface of the bump.

According to the second means and the fourth means, the lower end portion of the tool is less likely to interfere with the bumps already formed.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. The same components as those described in the conventional example are designated by the same reference numerals, and the description thereof will be omitted.

The bump forming tool 10 (hereinafter abbreviated as "tool") of the present invention has a shape that gradually becomes thinner toward the tip (lower end) as shown in FIG. 1 (a). The gold wire 2 is formed in the center of the capillary 10.
A through hole 10a is formed in the up-down direction, through which is inserted in the up-down direction.

The tip of the tool 10 is provided with a step 9 as an escape portion for preventing the tip from interfering with the bumps already formed, and the tip surface 10b is a fan having a central angle of 45 °. It is formed to have a shape. The tip surface 10b is formed to be substantially flat.

The upper end of the tool 10 is held by an ultrasonic horn (not shown). At the time of bonding, the ultrasonic horn vibrates the tip portion in the ultrasonic range to generate ultrasonic energy on the tip surface 10b.

On the other hand, as shown in FIG.
Above the tool 10, there is provided a clamp device 11 that moves with the tool 10 and can clamp / unclamp the wire 2.

Next, the operation of forming a bump using the tool 10 will be described. Reference numeral 4 in FIG. 2 denotes a semiconductor element, and electrode pads 5 ... Are formed at predetermined intervals on the upper surface of the four sides of the semiconductor element 4. It is assumed that bumps 12 (shown in FIG. 1B) are sequentially formed on each of the electrode pads 5 by using the tool 10 along the X and Y directions indicated by arrows in the drawing. Hereinafter, the case of forming the bumps 12 in the Y direction will be described with reference to FIGS. 1 to 3.

As shown in FIG. 3 (a), the tool 10 described above is used.
Is positioned opposite to the electrode pad 5, a ball 2a is formed at the tip of the wire 2 by an electric torch 6. Then, as shown in FIG. 3 (b), the tool 10 is driven downward, and the ball 2a is pressed onto the electrode pad 5 of the semiconductor element 4 to join them.

Then, as shown in FIG. 3 (c), the tool 10 is driven upward while feeding out the wire 2 and slightly driven in the -X direction, and then shown in FIG. 3 (d). Is driven downward again. This makes the tool 10
Presses the upper surface of the ball 2a with the lower end surface 10a and forms a constriction in the wire immediately above the ball.
At this time, the lower end surface 10b of the tool 10 shown in FIG.
The ball 2a is pressed by the flat part shown in (a) to (a).

Next, the clamp device 11 clamps the wire 2. Then, as shown in FIG. 3 (e), when the tool 10 and the clamp device 11 are driven to rise, the wire 2 is broken at the constricted portion and pulled up. As a result, the bump 12 is formed on the electrode pad 5 of the semiconductor element 4.

In this way, the tool 10 repeats the vertical movement and the movement in the -X direction for one electrode pad 5, and sequentially forms the bumps 12 on the electrode pads 5 arranged in the Y direction. I will do it.

Similarly, for each of the electrode pads 5 arranged in the X direction, the tool 10 is repeatedly moved up and down and moved in the Y direction to sequentially form bumps 12.
In this case, in order to press the upper surface of the ball 2a, the flat portion of the lower end surface 10b of the tool 10 shown in (b) of FIG. 1 (a) is used.

According to this structure, first of all,
Since the lower end surface of the tool 10 is made substantially flat, this tool 1
The shape of the upper surface of the bump 12 formed by 0 can be formed to be substantially flat. As a result, lateral displacement of the lead during bonding can be effectively prevented, and better bump formation can be performed.

Second, since the step 9 is provided at the tip of the tool 10 as an escape portion so as not to interfere with the bump 12 already formed, the already formed bump 12 is less likely to be broken. As a result, high-quality bumps can be formed even when the bumps 12 are formed with a narrow pitch.

The present invention is not limited to the above-mentioned embodiment, but can be variously modified without departing from the spirit of the invention.

For example, in the above embodiment, the tool 1 is
Although the shape of the lower end surface of 0 is a fan shape, the shape is not limited to this. Of the lower end surface, the outer shape may be any shape as long as the peripheral portion of the insertion hole used for bonding the bump to the electrode pad and the flat portions (a) and (b) shown in the figure can be secured. . In addition, the flat portion (a),
It is sufficient that (b) has a diameter that is at least larger than the outer diameter of the wire 2.

[0033]

As described above, in the first structure of the present invention, the wire is inserted in the vertical direction, and the ball formed at the lower end surface of the tip of the wire is pressed against the electrode pad to be joined. After that, a slight lateral displacement causes the wire directly above the ball to be constricted, and the wire is cut at this portion to form a bump on the electrode pad. The lower end surface is provided with a flat portion that comes into contact with the upper surface of the ball when the tool is slightly displaced laterally.

According to the first structure, by using the flat portion, the upper surface of the bump to be formed can be made substantially flat, so that the lateral displacement of the lead bonded to the upper surface of the bump is effective. It is possible to prevent the bumps from being formed, and the bumps can be formed more favorably.

The second structure is such that, in the bump forming tool of the first structure, a part of the lower end surface is escaped so that the lower end portion of the tool does not interfere with the already formed bumps. It is characterized in that a section is provided.

According to the second structure, the bumps already formed are less likely to be destroyed, so that high quality bumps can be formed even when the bumps are formed with a narrow pitch.

In the third structure, the lower end surface of the bump forming tool in which the wire is inserted, the ball formed at the tip end of the wire is pressed and bonded to the bonding surface of the electrode pad of the semiconductor element. In the first step, the bump forming tool is slightly displaced in the surface direction of the bonding surface so that the flat surface formed on the lower end surface of the bump forming tool forms the upper surface of the ball. The second step of making the wire substantially flat and constricting the wire immediately above the ball and cutting the wire at this portion.

According to the third structure, since the upper surface of the bump to be formed can be made substantially flat, lateral displacement of the lead bonded to the upper surface of the bump can be effectively prevented, and a better bump can be formed. It can be performed.

The fourth means is, in the bump forming method of the third means, sequentially using the relief portions provided on the lower end surfaces of the bump forming tools while avoiding the bumps already formed. It is characterized in that bumps are formed.

According to the fourth structure, the bumps already formed are less likely to be destroyed, so that high quality bumps can be formed even when the bumps are successively formed at a narrow pitch.

[Brief description of drawings]

FIG. 1A is a vertical cross-sectional view and a bottom view showing an embodiment of the present invention, and FIG. 1B is a vertical cross-sectional view showing the same bump formation.

FIG. 2 is a plan view showing a semiconductor element.

FIG. 3A to FIG. 3E are process diagrams similarly showing bump formation.

FIG. 4A is a vertical cross-sectional view and a bottom view showing a conventional example, and FIG. 4B is a vertical cross-sectional view showing the same bump formation.

FIG. 5A to FIG. 5E are process diagrams showing the bump formation similarly.

[Explanation of symbols]

2 ... Wire, 2a ... Ball, 4 ... Semiconductor element, 5 ... Electrode pad, 10 ... Bump forming tool, 9 ... Stepped portion (escaping portion), 10b ... Tip surface (lower end surface), (A) … Flat part,
(B) ... Flat part.

Claims (4)

[Claims] 1. A wire is inserted, and a ball formed at the lower end face of the wire at the tip thereof is pressed against the bonding surface of the electrode pad of the semiconductor element to bond it, and then slightly displaced in the surface direction of the bonding surface. This is a bump forming tool for forming a bump on the electrode pad by causing a constriction in the wire directly above the ball and cutting the wire at this portion. A bump forming tool, characterized in that a flat portion is provided so as to come into contact with the upper surface of the ball when the tool is slightly displaced in the surface direction of the bonding surface. 2. The bump forming tool according to claim 1, wherein a relief portion is provided on the lower end surface so as not to interfere with an already formed bump. 3. A first step of pressing and bonding a ball formed at the tip of the wire at the lower end surface of the bump forming tool having the wire inserted therethrough to the bonding surface of the electrode pad of the semiconductor element. By slightly shifting the bump forming tool in the surface direction of the bonding surface, the upper surface of the ball is made substantially flat by the flat portion formed on the lower end surface of the bump forming tool. And a second step of causing the wire just above the ball to be constricted and cutting the wire at this portion. 4. The bump forming method according to claim 3, wherein bumps are sequentially formed while avoiding bumps already formed by using a relief portion provided on a lower end surface of the bump forming tool. And a bump forming method.