JPH09129645A - Bump electrode forming method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To electrically connect a bump electrode and a circuit substrate without performing a levelling process by a method wherein, after a ball part has been fixed to an electrode pad, an impressed part is formed on a metal wire by processing a capillary, and then the metal wire is cut at the impressed part. SOLUTION: When a bump electrode is formed on the electrode pad 2 formed on a semiconductor chip 1, the ball part 6 of a metal wire 5, on the tip part of which a ball part 6 is formed, is fixed to the electrode part 2 by a capillary 3. Then, after formation of an impressed part on the metal wire 5 by pressing the capillary 3 to the metal wire 5 from above the ball part 3, the metal wire 5 is pulled and the wire is cut at the impressed part. For example, after formation of a bump electrode main body 7, the capillary 3 is moved up, and the flat part 4 of its tip is moved to the point directly above the center part of the bump electrode main body 7. Then, the capillary 3 is brought down, and an impressed part is formed in such a manner that the Au wire 5 is crushed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the manufacture of semiconductor devices used in various electronic devices.

[0002]

2. Description of the Related Art With the recent miniaturization and thinning of semiconductor packages, as a method for electrically connecting an electrode pad of a semiconductor chip and an electronic circuit board, a conventional wire bonding method using a metal wire is used. The wireless bonding method using electrodes has been shifting.

Conventionally, a bump electrode has been mainly formed by a plating method. However, when the bump electrode is formed by this plating method, a troublesome operation such as formation and removal of a plating pattern is repeated. In addition, since it is difficult to adjust the plating thickness, there is a problem that it is difficult to secure the height of the obtained bump electrode at a predetermined height.

In order to deal with such a problem, a method of forming bump electrodes by a ball bonding method has been proposed. The method of forming bump electrodes by this ball bonding method is to form a ball portion at the tip of a metal wire by electrical discharge or the like, fix the formed ball portion to the electrode pad surface of the semiconductor chip, and then clamp the wire. Then, the bump electrode is formed by tearing it off. Japanese Patent Application Laid-Open No. 60-154540 discloses a bump electrode forming method by a ball bonding method and a specific example of the bump electrode obtained by the method. . FIG. 2 shows a specific example of the bump electrode shown in the publication. In FIG. 2, 1 is a semiconductor chip, 2 is an electrode pad, 7 is a bump electrode body, and 8 is a bump electrode top shape. It is shown.

Another method for forming bump electrodes using the ball bonding method is Japanese Patent Publication No. 6-95468.
As disclosed in the publication, a method is disclosed in which, after a capillary draws an arcuate trajectory on a bump electrode, a metal wire is cut out to form a bump electrode having an arcuate top.

[0006]

However, in these conventional bump electrode forming methods by the ball bonding method, the position of the cut portion varies when the metal wire is cut after the ball is fixed, and the resulting bump is formed. In addition to variations in the height of the electrode, the tip of the bump electrode top is sharp as shown in FIG. 2 or an arc-shaped convex as shown in JP-B-6-95468. Due to the partial shape, it is necessary to flatten the tops of the bump electrodes in order to make electrical connection with the circuit board.Therefore, the bump electrodes must be leveled before the connection process. It was necessary to add a so-called leveling step of flattening the top of the metal.

The present invention solves the above-mentioned problems in forming bump electrodes by the ball bonding method, and the bump electrodes and the circuit board can be electrically connected to the circuit board without adding a leveling step. It is an object of the present invention to provide a method for forming a bump electrode that can be electrically connected.

[0008]

SUMMARY OF THE INVENTION To achieve the above object, the present invention relates to a metal wire having a ball portion formed at its tip when forming a bump electrode on an electrode pad formed on a semiconductor chip. After the ball portion is fixed on the electrode pad by a capillary, the capillary is pressed against the metal wire portion from above the ball portion to form an indentation portion on the metal wire, and then the metal wire is pulled so that the indentation portion is formed. A method of forming a bump electrode is characterized in that the metal wire is cut.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The method of the present invention will be described with reference to FIG. Is placed on the electrode pad 2 of the semiconductor chip 1 (FIG. 1A), and then the ball portion 6 is bonded to the electrode pad 2 formed on the semiconductor chip 1 by the capillary 3 by thermocompression bonding or ultrasonic bonding. (FIG. 1 (b)), thereby forming the bump electrode body 7 on the electrode pad 2 (FIG. 1 (c)). Then, the bump electrode body 7 is attached to the bump electrode body 7 at the flat portion of the tip 4 of the capillary 3. An indentation is formed by pressurizing the connected metal wires 5 (FIG. 1D), and then the metal wires 5 are clamped by a clamp device (not shown), and then the metal wires 5 are pulled. This Tear in piezoelectric mark positions by, thereby having a mark tear the sides, top 8 can form a flat bump electrodes (FIG. 1
(E)).

According to the bump electrode forming method of the present invention described above, in the process of forming the indentation on the metal wire 5 on the ball portion 6 by operating the capillary 3, the bump electrode top portion 8 is completely flattened and Since the height can be made constant and the indentation portion for tearing off the metal wire 5 can be formed on the side surface of the bump electrode top portion 8 by appropriately adjusting the tip shape of the capillary, the top portion is flat. It is possible to form bump electrodes having a uniform height, and when performing electrical connection with a circuit board thereafter, a bonding action can be smoothly performed without adding a leveling step.

[0011]

EXAMPLES Specific examples of the present invention will be described below in accordance with the bump electrode forming method of the present invention shown in FIG. It goes without saying that the present invention is not limited to this embodiment.

First, in the step shown in FIG. 1A, the tip portion has a flat portion and a notched inclined portion, and the outer diameter of the tip portion is 12
Ceramic capillary 3 with a hole diameter of 7 μm and 25 μm
The Au wire 5 having a diameter of 18 μm is passed through the hole, and a ball portion 6 having a diameter of 60 μm is formed at the tip of the wire 5 by electric discharge.

Next, in the step of FIG. 1B, the ball portion 6 is bonded to the electrode pad 2 formed on the semiconductor chip 1 through the capillary 3 by a thermocompression bonding method or a thermocompression bonding method. It is fixed by using the ultrasonic vibration method together. Here, the bump electrode body 7 having a diameter of about 80 μm and a thickness of about 25 μm is formed.

Subsequently, in the step of FIG. 1C, after forming the bump electrode body, the capillary 3 is raised to
The flat end portion 4 of the capillary 3 is moved in parallel to a position right above the central portion of the bump electrode body 7. The amount of movement of the capillary 3 at this time is preferably about 1/2 of the outer diameter of the tip of the capillary.

Thereafter, in the step shown in FIG. 1D, the capillary 3 is lowered again, and the Au wire 5 is crushed on the bump electrode body 7 by the flat end portion 4 of the capillary 3 to form an indentation. Depending on the shape of the tip of the capillary, the bump electrode body 7 has an indentation portion such that the top portion 8 is flat and a cut portion of the metal wire is formed on the side surface. At this time, it is important that the load applied to the capillary 3 be such that the bump electrode top portion 8 maintains a flat shape and is not deformed.

Next, in the step of FIG. 1 (e), the Au wire is clamped by a clamp device (not shown), and the wire is pulled upward, so that the Au wire has its indented portion with the capillary as a fulcrum. It is cut so that it can be torn off from.

According to the above-mentioned embodiment, the diameter of the electrode pad 2 formed on the semiconductor chip 1 is 79 to 83 μm.
m, the height from the upper surface of the electrode pad to the bump top 8 is 3
7 to 41 μm with little variation in height, and the top 8
It was possible to obtain a bump electrode having a flat shape.

In this embodiment, the wire diameter is 18 μm.
However, the material and size of the metal wire are not limited to the above, and any metal wire capable of ball bonding can be used, and its diameter depends on the size and use of the intended bump electrode. Can be appropriately selected.

[0019]

As described above, according to the present invention, a bump electrode having a flat top and less variation in height can be formed in forming the bump electrode by the ball bonding method. When performing electrical connection between the electronic circuit board and the electronic circuit board, it is not necessary to perform a leveling step for aligning the heights of the bump electrodes, and highly reliable connection can be performed.

[Brief description of the drawings]

FIG. 1 is a diagram showing a method for forming bump electrodes according to the present invention,
(A)-(e) is a schematic sectional drawing which showed the order of the process.

FIG. 2 is a schematic sectional view of a bump electrode formed by a conventional ball bonding method.

[Explanation of symbols]

 1 Semiconductor Chip 2 Electrode Pad 3 Capillary 4 Flat End of Capillary 5 Metal (Au) Wire 6 Ball Part 7 Bump Electrode Body 8 Bump Electrode Top

Claims (1)

[Claims] 1. When forming a bump electrode on an electrode pad formed on a semiconductor chip, after fixing the ball portion of a metal wire having a ball portion at its tip end onto the electrode pad by a capillary, A method of forming a bump electrode, comprising: pressing a capillary against the metal wire portion from above the ball portion to form an indentation portion on the metal wire, and then pulling the metal wire to cut at the indentation portion.