JPH056917A - Manufacture of composite lead frame - Google Patents

Abstract

PURPOSE:To obtain a composite lead frame wherein its irregularity is eliminated, its reliability is high and it has been formed at high pin counts by a method wherein a bonding method used to thermocompression-bond an outer lead at a TAB tape to an inner lead at a lead frame is improved and their bonding strength is enhanced. CONSTITUTION:When an outer lead 8 at a TAB tape and an inner lead 7 at a lead frame are overlapped and thermocompression-bonded, the outer lead 8 is pushed into a U-shaped groove formed on the surface of the inner lead 7 while the outer lead is pastic-deformed. A bonded part which is not stripped and which is not irregular is formed. A composite lead frame whose bonding strength and reliability are high is formed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a composite lead frame having a high bonding strength, which is used for packaging semiconductor devices in the semiconductor electronics industry.

[0002]

2. Description of the Related Art In recent years, as semiconductor devices have become more highly integrated and have more functions, the number of pins in the package has become more and more, and further higher precision and fine pitch of the lead frame are required. Especially in the case of application specific integrated circuits (AISC) and the like, the demand is very strong. At present, there are a press working method and an etching method as a lead frame processing method. However, it is said that the limit of fine pitching in these processing methods is about 70 to 80% of the plate thickness by the lead width,
To reduce the lead width, it is necessary to reduce the plate thickness. However, as the plate thickness is made thinner, the strength becomes insufficient, and problems such as bending of leads due to handling or joining tend to occur. The limit is 0.1-0.15mm thickness
Therefore, the number of pins is about 200.
Although the etching method can achieve a finer pitch with higher precision than the pressing method, there is a problem that the manufacturing cost is several times higher than that of the pressing method.

On the other hand, the TAB technique is applied as one countermeasure against the increase in the number of pins. However, in the case of the TAB tape, since the leads are formed of Cu foil, the strength is low and problems such as alignment are likely to occur during external wiring, and the TAB tape cannot be used like the conventional lead frame.

On the other hand, as a measure for realizing a large number of pins, for example, as disclosed in Japanese Patent Laid-Open No. 232948/1987, an insulating film alone or a metal island portion formed on the insulating film is used. A composite lead frame in which an outer lead portion of a TAB tape having a pad portion is joined to a semiconductor lead frame, and Japanese Patent Laid-Open No. Hei 2
As described in Japanese Patent No. 2850, the outer lead portion of the TAB tape is joined to the inner lead portion of the semiconductor lead frame, and the TAB tape and the Si chip are connected to each other.
There has been proposed a composite lead frame that is collectively joined by AB joining.

In the production of these composite lead frames that have already been proposed, the inner lead of the lead frame and the outer lead of the TAB tape are joined by a soldering method, or a gold-plated TAB lead and a tin-plated lead frame. It is carried out by an alloy method or the like in which a gold-tin alloy is generated by heating and pressure bonding to form a gold-tin alloy on the bonding surface. Especially, in lead bonding of a multi-pin structure, it is not possible to uniformly and firmly bond each lead It is difficult, and problems such as yield loss due to defective bonding and reduction in productivity become problems.

That is, since the conventional thermocompression bonding is a bonding between flat surfaces, a new surface is formed on the lead surface which is normally oxidized by plastic deformation and creep deformation.
Furthermore, in order to cause sufficient diffusion to obtain a high bonding strength, a high bonding temperature, a long bonding time and a high bonding load are required. Moreover, due to variations in the thickness of the Cu foil of the lead frame and TAB tape, and deviations in the parallelism between the bonding tool and the stage, the pressure applied during thermocompression bonding tends to be uneven. Since the amount of plastic deformation is small, if the lead thickness varies, it is difficult to apply a load to a thin lead, and sufficient bonding strength may not be obtained. Therefore, a bonding failure occurs in the subsequent process, and the reliability is reduced.

[0007]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems of the prior art by improving the thermocompression bonding method of the inner lead of the lead frame and the outer lead of the TAB tape, which is high in a short time. An object of the present invention is to provide a manufacturing method of a composite lead frame having a high yield and having a large number of pins compared with the conventional number of pins by giving a bonding strength and performing a uniform bonding. It is what

[0008]

In order to achieve the above object, the gist of the present invention is as follows. That is, in manufacturing a composite lead frame, when the outer lead of the TAB tape and the inner lead of the lead frame are superposed and joined, the outer lead of the TAB tape is deformed by thermocompression bonding with a heating tool having a protrusion on the pressing surface. This is a method for manufacturing a composite lead frame having a high bonding strength, which is characterized by bonding. In the present invention, the projection provided on the lead pressing (pressing contact) surface of the heating tool may have any of a mountain shape, a wave shape, an arc shape, or the like,
Any material that plastically or creep-deforms the outer lead of the TAB tape by applying pressure may be used.

[0009]

The present invention will be described in detail below. FIG. 1 (a),
(B) is a schematic view of an example of a composite lead frame which is the object of the present invention. Composite lead frame 1
Is a TAB tape in which a lead frame 2 made of a thin plate of Fe-Ni alloy or Cu alloy by photo-etching or press punching, and leads 4 made of Cu foil on the surface of an insulating resin film 3 of polyimide or the like are formed. 5, the TAB tape 5 is provided with a chip window 6 at the center thereof. The combination of the lead frame 1 and the TAB tape 5 is made by the inner lead 7 of the lead frame 1.
Then, the outer leads 8 of the TAB tape are overlapped and joined by thermocompression bonding.

FIG. 2 schematically shows an example of a situation in which thermocompression bonding is attempted. That is, the lead frame 2 is placed on the stage 10, and the TAB is mounted on the inner lead 7.
The outer leads 8 of the tape 5 are aligned and stacked. Then, the overlapping portion is heated and pressure-bonded with a tool 9 having a built-in heater. That is, the inner lead 7
And the overlapping part of the outer lead 8 are approximately 200 to 600 ° C.
The pressurizing portion 12 of the tool 9 that has been heated to heat and press to join. At this time, the bondability can be improved by plating silver or gold on the respective bonding portions of the inner lead 7 and the outer lead 8.

Conventionally, as shown in the enlarged partial view of FIG.
Pressing surface 1 of tool 9 that contacts TAB outer lead 8
2 is a flat surface. However, as described above, the thermocompression bonding of the joint portion by such a flat surface is not always uniform. 3 to 5 show an embodiment of the method of the present invention, in which the outer lead 8 of the TAB tape and the inner lead 7 of the lead frame are superposed, and the superposed portion is pressed by the tool 9 heated to the above temperature. FIG. That is, FIG. 3 shows that the pressing portion 12 of the tool 9 has a shape 12a in which one side thereof is sharpened at an acute angle, FIG. 4 has a circular arc shape 12b having a convex shape, and FIG. There is. In the illustrated example, the projection-shaped tip does not have to be sharp, and an arc may be formed. Moreover, each example does not limit the present invention.

According to the present invention, the shape of the tool pressing portion 12 is formed in a different shape instead of a flat surface as described above, and the outer lead 8 of the TAB tape and the inner lead 7 of the lead frame are overlapped and thermocompression bonded by using this tool. By doing TA
Since a large plastic deformation is applied to the B outer lead 8, a new surface is generated over a wide range and a large thermocompression bonding strength is obtained. In addition, since the amount of movement of the tool in the lead thickness direction is large due to plastic deformation, uneven bonding due to variations in lead thickness is less likely to occur, and heat conduction is reduced because the lead thickness of the tool becomes thin at the plastically deformed part of the lead. It becomes favorable, and high bonding strength can be obtained in a short time.

[0013]

EXAMPLES Examples are shown in Table 1. The tip pressing portion of the tool is processed into the shape shown in FIGS. 3 to 5 (Examples 1 to 4),
The outer lead 8 of the TAB tape and the inner lead 7 of the lead frame were overlapped and the thermocompression bonding of the present invention was performed.
As a comparative example, thermocompression bonding was performed using the conventional tool shown in FIG.

The bonding strength of each example was measured by a push test, and the average bonding strength and the probability that a lead having a bonding strength of 50 g or less was generated as a variation of the bonding strength were obtained and are also shown in Table 1.

As is clear from Table 1, Examples 1, 3,
With respect to No. 4, the TAB lead portion broke because the bonding strength was large, and the bonding strength could not be obtained. However,
TA

[0016]

[Table 1]

Since the breaking strength of the B lead is about 200 g, it can be said that the bonding strength is 200 g or more. In Example 2, although the bonding temperature was low, the bonding strength was inferior, but the variation was very small, and all were 135 g or more, and there was no lead of 50 g or less. On the other hand, in the comparative example in which the bonding was performed under the same conditions as in Examples 1 and 4, not only the average bonding strength was low, but also 11% of the leads had a large variation and 50 g or less. As described above, the bonded product of the present invention exhibits very excellent characteristics such as a larger average bonding strength and a smaller variation as compared with the conventional method.

[0018]

As described above, according to the method of the present invention, since the thermocompression bonding of the lead overlapping portion is carried out by using the tool crimping portion having the deformed tip, the composite lead having high bonding strength and less variation. The frame can be obtained, the defective rate can be remarkably reduced, and the productivity can be remarkably improved.

[Brief description of drawings]

1A and 1B are schematic plan views of a composite lead frame of the present invention.

FIG. 2 is an explanatory diagram showing an example of a joining state of the present invention.

FIG. 3 is an enlarged cross-sectional explanatory view showing an example of the joining state of the present invention.

FIG. 4 is an enlarged cross-sectional explanatory view showing another example of the bonding state of the present invention.

FIG. 5 is an enlarged cross-sectional explanatory view showing another example of the joining condition of the present invention.

FIG. 6 is an enlarged cross-sectional explanatory view showing a conventional joining state.

[Explanation of symbols]

 1: Composite lead frame 2: Lead frame 3: Insulating resin film 4: Cu foil lead of TAB tape 5: TAB tape 6: Window for chip 7: Inner lead of lead frame 8: Outer lead of TBA tape 9: Tool 10: Stage 12: Pressurized surface

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[Procedure amendment]

[Submission date] February 6, 1992

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0016

[Correction method] Change

[Correction content]

[0016]

[Table 1]

Claims (1)

Claim: What is claimed is: 1. In manufacturing a composite lead frame,
When the outer lead of the AB tape and the inner lead of the lead frame are overlapped and joined, thermocompression bonding is performed while deforming the outer lead of the TAB tape with a heating tool having a protrusion on the pressing surface. A method of manufacturing a composite lead frame having high strength.