JPH0527977B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a wire bonding device.

[Technical background of the invention and its problems]

Gold wire is used in fully automatic wire bonding for ICs, LSIs, etc. This wire material also becomes a factor in increasing costs as the cost of semiconductor devices decreases, and there is a demand for bonding using gold-substituting wires. Typical examples include attempts to use copper wire or aluminum wire, but these have not been put to practical use.

In particular, when base metal wire such as copper is used, it is necessary to heat the work stage and raise the temperature of the parts to be joined, such as IC pellets and lead frames, to about 200°C to 350°C. This oxidation causes bonding defects.

As a countermeasure against oxidation of wire
As described in No. 26246, it has been proposed to prevent oxidation by spraying an inert gas onto the tip of the wire and forming a ball at the tip of the wire while shielding with the inert gas.

However, even with this proposal, according to the research of the present applicant, the wires located close to each other above the heater stand are oxidized by the heat of the heater stand built into the work stage. In particular, since the capillary and wire clamper are also heated, thermal oxidation occurs at the wire clamper portion during the wire travel, and oxidation has already progressed by the time the wire travels near the members to be joined.

Therefore, even if an attempt is made to form a ball by an electric torch method or an oxyhydrogen torch method when the ball is run near a member to be welded, there is a problem in that the ball formation is often repeated.

[Object of the Invention] The present invention was made in view of the above points, and provides a wire bonding method that prevents oxidation of the wire during running, stabilizes ball formation, and provides high bonding strength. .

[Summary of the invention]

That is, in an apparatus that leads out a wire from a wire feeding part, inserts it into a capillary via a clamper, and presses it onto a member to be bonded for bonding.
The present invention provides a wire bonding device characterized in that a heat shielding plate configured to be able to be cooled is provided on a wire running path between the clamper and the capillary.

[Embodiments of the invention]

Next, an embodiment of the method of the present invention suitable for wire bonding using an electric torch method using copper wire will be described with reference to the drawings.

A fully automatic wire bonding apparatus using an electric torch method is well known to those skilled in the art, so a description thereof will be omitted.

That is, the bonding arm system of the wire bonding apparatus is shown in FIG. A bonding wire, such as a copper wire, is wound around a wire feeding portion, such as a wire spool 1, and installed in a bonding device. The copper wire 2 led out from the wire spool 1 passes through a wire guide 3 and runs through a clamper, for example, a first clamper 4 and a second clamper 5.
A capillary 6, which is a bonding tool, is inserted, and the tip of the copper wire 2 is guided so as to protrude from the capillary 6.

An electric torch rod 7 is installed near the protruding tip of the copper wire 2, and is set relative to the tip of the copper wire 2 so as to generate an electric discharge only when forming a ball at the tip of the copper wire 2. For example, the torch rod 7 is moved to form the ball 8. At this time, the area around the electric torch and wire is covered with an inert gas or a reducing gas such as nitrogen gas to prevent oxidation. Below this ball 8 is a lead frame 1 to which a member to be bonded, such as an integrated circuit (IC) 9, is attached.
A work stage 11 on which 0 is placed is provided. A heater 12 is built into the work stage 11, and generates a temperature of, for example, 200° C. to promote bonding of the copper wire 2. This heater 12 is heated before the start of bonding and continuously performs heating operation during bonding, and this heating may be performed by either direct current or alternating current.

The bonding arm described above is mounted on an X-Y drive table (not shown) separate from the work stage 11.
Although they are installed above, they are connected to a linear houlter (not shown) without directly engaging the cam mechanism, so that they can be driven in the Z-axis direction in the vertical direction as well.

Furthermore, a TV camera (not shown) for visually recognizing the bonding position is also installed on the table, and the output is input to a computer (not shown), which controls the bonding position.

In such an apparatus, the method of the present invention provides a heat shield plate in a region where the copper wire 2 is oxidized during running due to the heat generated by the heater 12.
This prevents hot air flow from rising to the clampers 4 and 5.

That is, after passing through the guide 3, a heat shield plate 1 is placed on the copper wire running path from the first clamper 4 to the capillary 6, for example, in the running path between the capillary 6 and the second clamper 5.
3 will be provided. This heat shielding plate 13 is provided with a through hole 14 through which the copper wire 2 runs, and each is characterized by the shape in which the copper wire 2 passes through one side of the heat shielding plate 13. .

This heat shield plate 13 is air-cooled. That is, it is cooled by being exposed to a flow path of air, inert gas, or reducing gas. These gases are e.g.
are provided parallel to the heat shield plate 13. This situation is as shown in FIG. 2, and the nozzle 15 is provided with a large number of gas outlet ports 21. Also the third
As shown in the figure, the nozzle 31 may be formed in an annular shape and arranged coaxially and parallel to the through hole 14 of the heat shielding plate 13. In this case as well, the annular nozzle 31 has a gas outlet 32.
All you have to do is arrange a large number of them in a ring.

Furthermore, although the flow rate of the gas may be constant, the flow rate may be varied over time, or may be made variable depending on the temperature of the heater.

Furthermore, the gas may not be continuously blown out, but may be operated intermittently in pulses at appropriate intervals.

When performing wire bonding with such a configuration, after setting the wire 2 to be led out prior to bonding, the power is turned on to the heater 12 and the nozzle 1 is turned on.
After controlling the N ₂ gas to flow in from the gas inlets 5 and 31, the computer performs program control to start the bonding work. As is well known, the bonding work is performed by forming a ball 8 on the tip of the copper wire 2 with a torch rod 7, pressing it to the bonding position with the capillary 6, and performing ball bonding by thermocompression bonding using ultrasonic waves in conjunction with heat from the heater 12. do.

By providing the cooling plate 13 between the clamper 5 and the capillary 6 on the running path of the copper wire 2, heating of the clampers 4 and 5 can be prevented, and thermal oxidation of the clampers 4 and 5 can be prevented during running. be. Particularly in wedge bonding after ball bonding, strong bonding could not be obtained with conventional gas shielding only at the tip, but this embodiment provides good bonding strength.

In the above example, an example was explained in which _N2 gas was used, but if the wire is an inert gas or reducing gas that has the effect of shielding the wire from thermal oxidation, such as argon gas or hydrogen mixed gas, the wire can be heated. Shielding from the atmosphere has a similar effect.

Furthermore, in the above embodiment, an example was explained in which copper wire was used as the base metal, but any base metal that can be used in wire bonding may be used, such as a copper alloy wire, an aluminum wire, or an aluminum alloy wire. Furthermore, in the above embodiment, the heat shield plate is connected to the capillary 6.
Although an example in which the clamper is provided between the first and second clampers 5 has been described, it may also be provided between the first and second clampers 4 and 5.

Furthermore, although wire bonding using an electric torch method has been described in the above embodiments, it is needless to say that similar effects can be obtained by bonding using a flame torch method or the like.

〔Effect of the invention〕

As explained above, according to the present invention, a heat shield plate is provided between the second clamper and the capillary of the bonding wire (base metal wire) running path, so that the wire is not oxidized when a ball is formed on the tip of the wire. This has the effect that a good ball can be formed and strong bonding can be performed. Furthermore, in wedge bonding after ball bonding, since the wire (base metal wire) is not oxidized, there are effects such as improved bonding strength between the wire and the surface to be bonded.

[Brief explanation of the drawing]

Figure 1 is a side view for explaining an embodiment of the method of the present invention, Figure 2 is a schematic diagram for explaining the structure of the heat shield plate in Figure 1, and Figure 3 is another embodiment of the method in Figure 2. It is an explanatory diagram. DESCRIPTION OF SYMBOLS 1... Spool, 2... Wire, 4, 5... First and second clampers, 6... Capillary, 13... Heat shielding plate, 15... Nozzle.

Claims (1)

[Scope of Claims] 1. In an apparatus for leading out a wire from a wire feeding portion, inserting it into a capillary via a clamper, and crimping it onto a member to be bonded for bonding, a wire running path between the clamper and the capillary is configured to be coolable. A wire bonding device characterized by being provided with a heat shield plate. 2. The wire bonding apparatus according to claim 1, wherein the wire is a base metal wire. 3. The wire bonding apparatus according to claim 1, wherein the heat shield plate is cooled by air, an inert gas, or a reducing gas. 4. The wire bonding apparatus according to claim 1, wherein the heat shield plate is provided with a through hole through which the wire runs.