JPH0744198B2 - Wedge for wire bonding - Google Patents

Description

TECHNICAL FIELD The present invention relates to a wedge used for wire bonding of a semiconductor device such as an LSI or an IC.

[Conventional technology]

In the semiconductor device, a thin conductive wire made of gold or aluminum and having a diameter of about 0.015 to 0.1 mm is used to connect the electrode of the semiconductor chip and the lead electrode of the package, and a capillary or a wire is used for this connecting step (wire bonding). Wedges are used. Of these, wedge 1 is
As shown in FIGS. 2 (a) and 2 (b), the conductor is sent out through the oblique pore 1a provided at the tip, and the conductor is crimped by the pressing portion 1b. Since the crimping portion can be made thin, there is an advantage that it can be used for higher density wire bonding.

Further, since the pressing portion 1b at the tip end of the wedge 1 is thin and the ceramic is easily broken, it is formed entirely by cemented carbide, and an aluminum wire mainly used at a low cost is used as a conductive wire.

[Problems of conventional technology]

However, in the case of the wedge 1 formed of carbide, since the metal has a large adhesive property, the powder of the conductor or electrode is likely to adhere to the tip portion. There was a connection failure such as an abnormality.

In addition, since the wedge 1 is struck on the electrode surface when the conductor wire is crimped onto the electrode at a high speed of about 8 times per second, the pressing portion 1b at the tip is likely to be worn or broken. If the wire was severely broken or broken, the conductor wire could not be securely crimped, causing wire deviation.

Due to these poor connections, the wedge 1 made of carbide has a relatively short life.

[Means for solving problems]

In view of the above, the present invention provides a wedge for wire bonding by depositing a hard thin film made of TiC, TiN, diamond or the like on the surface of at least the tip portion of a wedge base body made of cemented carbide.

〔Example〕

The wedge 1 according to the present invention is made of a super hard material and is provided with pores 1a for sending out a conductor wire and a pressing portion 1b for crimping the conductor wire as shown in the tip portion of FIG. I'm wearing it. The hard thin film 2 is formed up to the inner surface of the pore 1a,
Since the surface is smooth, the conductor wire can be delivered smoothly, and the chemical reaction between the wedge 1 and the conductor wire can be prevented, so that the conductor wire and the electrode powder can be prevented from adhering.

Further, since the hard thin film 2 is adhered to the surface of the pressing portion 1b, the strength of the pressing portion 1b, especially the wear resistance can be increased.

Such a wedge 1 substrate is made of tungsten carbide (WC)
And a hard thin film of the kind shown in Table 1 was applied for trial production, and a wire bonding test was performed with a wedge on which the hard thin film was not applied. Each wedge
Ten pieces were prepared, and under the same conditions, wire bonding was performed using aluminum wires, and the relationship between the number of times of bonding and the connection state of the conducting wire was examined. As a result, each average value was as shown in Table 1. . The thickness of the hard thin film deposited on the wedge was 14 μm.

From Table 1, the number of wedges that do not adhere to No. 1 hard thin film is 30
After bonding about 10,000 times, the connection was defective due to wear of the tip and adhesion of conductive wire powder, and it became unnecessary to use. Further, the wedge coated with No. 2 SiC and the wedge coated with No. 3 Si ₃ N ₄ were hard to peel off the hard thin film and had a life of about 400,000 cycles, which was not so effective.

On the other hand, wedges and N coated with No. 4 diamond
The wedges coated with TiN of No. 5 and the wedges of No. 6 with TiC have been kept in a usable state with little wear of the tip and adhesion of conductive wire powder even after about 600,000 times of bonding. It was

From the above results, diamond, TiN, TiC, etc. were good as the hard thin film adhered to the wedge base made of cemented carbide, and among them, TiC had the best connection state.

In the above examples, a hard thin film having an average film thickness of 14 μm was used. However, as a result of various experiments, if the average film thickness is less than 0.5 μm, wear resistance and strength are weak, and if the film thickness is more than 50 μm, Not only is peeling due to cracking more likely, but there is also the disadvantage that the pores are made smaller.
That is, the average thickness of the hard thin film deposited on the tip of the wedge base is preferably 0.5 to 50 μm.

There are various methods of depositing such a hard thin film. For example, when depositing a diamond thin film, active molecules in plasma, radicals, ions, electrons, etc. are used.
The plasma CVD method of depositing a diamond layer on a substrate is suitable. In addition, a thin film may be deposited by PVD method, ion plating method, sputtering method or the like depending on the difference in material and the like. Further, the pores of the wedge may be formed wide in advance, and may be appropriately sized by polishing after depositing the thin film. By forming a hard thin film by the plasma CVD method in this way, a fine grain size and a smooth surface without voids can be obtained, but if the surface is polished as necessary, a smoother surface can be obtained. You can

〔The invention's effect〕

According to the present invention as described above, by attaching a hard thin film to the surface of at least the tip portion of the wire bonding wedge formed by cemented carbide, the wear resistance of the wedge tip portion, hardness, corrosion resistance is large. In addition to reducing the occurrence of cracks and breaks, the inner surface of the pores becomes smooth and the friction coefficient is reduced, so that the wire can be delivered smoothly.
Less contact failure. Furthermore, since these hard thin films have high thermal conductivity, they improve the heat dissipation properties of the wedge, and because they have high conductivity, they have many features such as being able to prevent electrostatic charge and other electrification. Can be provided.

[Brief description of drawings]

FIG. 1 is an enlarged sectional view showing a tip portion of a wire bonding wedge according to the present invention. 2 (a) and 2 (b) respectively show a conventional wire bonding wedge. FIG. 2 (a) is a side view, and FIG. 2 (b) is an enlarged view of part A in FIG. 2 (a). FIG. 1: Wedge for wire bonding 1a: Pore 1b: Pressing part 2: Hard thin film

Claims (1)

[Claims] 1. A wedge for wire bonding, characterized in that a hard thin film made of TiC, TiN, diamond or the like is deposited on the surface of at least the tip portion of a wedge base body formed by cemented carbide.