JPH08115938A - Wire bonder - Google Patents

Abstract

PURPOSE: To provide a wire bonder in which the spark of a torch electrode can be stabilized. CONSTITUTION: The wire bonder comprises a capillary tool 12 inserted with a wire 11, an arm for moving the capillary tool 12 up and down, and a torch electrode 14 having a potential difference with respect to the wire 11 and approaches the lower end of the wire 11 to generate a spark G thus forming a ball. A magnet 16 for converging the spark G, generated between the torch electrode 14 and the wire 11, toward the lower end part 11a of the wire 11 is disposed between the torch electrode 14 and the lower end part 11a of the wire 11.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wire bonding device capable of stabilizing the shape of a ball.

[0002]

2. Description of the Related Art In wire bonding for connecting an electrode of a substrate and an electrode of a chip mounted on this substrate with a wire, a ball is formed at the lower end of the wire, so that there is a potential difference between the torch electrode and the wire, The process of generating a spark is performed.

3 and 4 are enlarged views showing a spark generation process in a conventional wire bonding apparatus. In FIG. 3, A is a substrate such as a lead frame, B is a chip mounted on the substrate A, C is a capillary tool into which a wire D is inserted, and E is between a tip portion E1 thereof and a lower end portion D1 of the wire D. , A torch electrode for generating a spark G. Here, a positive potential is applied to the torch electrode E, and a negative potential is applied to the wire D.

Now, as shown in FIGS. 3 and 4, in this step, the lower end portion D1 of the wire D and the torch electrode E are brought close to each other,
Originally, the tip E1 of the torch electrode E and the lower end D1 of the wire D
It is intended to cause a spark by a path that connects directly with.

[0005]

However, in the conventional wire bonding apparatus, the lower end portion D1 of the wire D should be originally discharged, and the lower end portion D1 should be melted to form a ball. The locations where the occurrences of V were not constant, and as shown in FIG. 3, discharge could occur at any position of the wire D exposed from the capillary tool C. Further, the shape of the formed ball differs depending on the discharge location on the wire D. Therefore, the conventional wire bonding apparatus has a problem that the shape of the ball is not stable and the bonding quality is likely to deteriorate.

Further, in the normal wire bonding apparatus, several tens to several hundreds of wires are bonded to one chip B, and as shown in FIG. 4, the bonded wires F are formed near the torch electrode E. May exist. In such a case, the wire F that has already been bonded may be erroneously discharged, instead of the lower end D1 of the wire D that is originally intended to be discharged. If such an accident occurs, a bonding failure will occur, such as a break in the bonded wire F.

As described above, the conventional wire bonding apparatus has a problem that the spark is unstable and the bonding quality is apt to deteriorate.

Therefore, an object of the present invention is to provide a wire bonding apparatus which can stabilize the spark of the torch electrode.

[0009]

A wire bonding apparatus according to the present invention comprises a capillary tool having a wire inserted therethrough,
An arm for raising and lowering the capillary tool and a torch electrode having a potential difference with respect to the wire and forming a ball by approaching the lower end of the wire to generate a spark are provided, and the space between the torch electrode and the lower end of the wire is provided. Further, a magnet for converging the spark generated between the torch electrode and the wire toward the lower end of the wire is provided.

[0010]

With the above construction, in the step of generating a spark between the lower end of the wire and the torch electrode, the spark discharged from the tip of the torch electrode is controlled in its course by the magnet and converges at the lower end of the wire. To do. Therefore, the sparks are always concentrated on the lower end of the wire, and the electric discharge occurs at a fixed position on the wire. As a result, the shape of the ball formed on the wire becomes constant, and good bonding quality can be obtained.

[0011]

Embodiments of the present invention will now be described with reference to the drawings. FIG. 1 is a perspective view of a wire bonding apparatus in one embodiment of the present invention, and FIG. 2 is an enlarged view of the vicinity of a torch electrode in one embodiment of the present invention.

In FIG. 1, reference numeral 1 is a transport rail for transporting or positioning a substrate 2 such as a lead frame or a thick film ceramic substrate in the X direction, and 3 is formed on the substrate 2 so as to surround a chip 4 mounted on the substrate 2. It is the formed electrode. Reference numeral 5 denotes a pressing member that presses the substrate 2 on the transport rail 1 from above, and the pressing member 5 has an opening 5a for exposing the chip 4 and the electrode 3.

A unit box 7 is disposed so as to face the transport rail 1 and is placed on the X table 9 and the Y table 8. The unit box 7 is known in the unit box 7 (for example, Japanese Patent Laid-Open No. 4-291735). The drive mechanism described in Japanese Patent Laid-Open Publication No. 2003-242242 is housed, and the drive mechanism causes the arm 10 that holds the capillary tool 12 at the tip end to swing, whereby the capillary tool 12 is moved up and down. Reference numeral 13 is a torch electrode portion fixed to the unit box 7 so as to be positioned on the side of the capillary tool 12, and a spark is blown to the lower end portion of the wire 11 inserted into the capillary tool 12 to form a ball.

Next, the structure of the torch electrode portion 13 will be described with reference to FIG. Reference numeral 14 is a torch electrode forming the core of the torch electrode portion 13, and a spark G is generated from the tip portion 14a thereof. The surface of the torch electrode 14 is covered with an insulating coat in order to prevent unnecessary sparks. Note that the tip portion 14a is formed in a conical shape using pure tungsten as a base material, and is naturally not provided with an insulating coat in order to permit discharge.

Reference numeral 15 is a cylindrical insulating tube that surrounds the torch electrode 14, and 16 is a ring-shaped permanent magnet fitted onto the tip of the insulating tube 15. Of course, an electromagnetic coil may be used instead of the permanent magnet 16 to excite it. The permanent magnet 16 is arranged such that its S pole faces the lower end 11 a of the wire 11 and its N pole faces the tip 14 a of the torch electrode 14.

Therefore, a magnetic field as shown in FIG. 2 is formed in the space between the tip portion 14a of the torch electrode 14 and the lower end portion 11a of the wire 11.

Here, a spark G generated between the tip portion 14a of the torch electrode 14 and the lower end portion 11a of the wire 11.
Is the movement of electrons, but controls the spark G by the magnetic field formed by the permanent magnet 16. That is, the permanent magnet 16 acts as an electromagnetic lens that concentrates the trajectory of electrons on the lower end 11 a of the wire 11.

Further, the energy of the spark G does not hit the wire 11 due to a diffused state like the discharge in the conventional wire bonding apparatus, but the wire 11 does not.
Since the lower end 11a of the wire 11 is intensively irradiated, most of its energy is spent on melting the lower end 11a of the wire 11.

That is, the ratio of effective energy per discharged energy is high, and sufficient ball formation can be realized even if the energy applied to the torch electrode 14 is reduced. This not only saves energy, but also suppresses wear of the torch electrode 14 and extends the life of the torch electrode portion 13.

[0020]

The wire bonding apparatus of the present invention has a capillary tool through which a wire is inserted, an arm for moving the capillary tool up and down, and a potential difference with respect to the wire, which causes a spark to approach the lower end of the wire. And a torch electrode forming a ball, and a magnet provided between the torch electrode and the lower end of the wire for converging the spark generated between the torch electrode and the wire toward the lower end of the wire. The sparks can be concentrated on the lower end portion of the wire, the shape of the ball formed on the wire can be made constant, and the bonding quality can be improved.

[Brief description of drawings]

FIG. 1 is a perspective view of a wire bonding apparatus according to an embodiment of the present invention.

FIG. 2 is an enlarged view of the vicinity of a torch electrode according to an embodiment of the present invention.

FIG. 3 is an enlarged view showing a spark generation process in a conventional wire bonding apparatus.

FIG. 4 is an enlarged view showing a spark generation process in a conventional wire bonding apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Arm 11 Wire 11a Lower end 12 Capillary tool 13 Torch electrode part 14 Torch electrode 14a Tip part 16 Permanent magnet

Claims (3)

[Claims] 1. A capillary tool having a wire inserted therethrough,
A wire bonding apparatus comprising: an arm for raising and lowering the capillary tool; and a torch electrode having a potential difference with respect to the wire and forming a ball by approaching a lower end portion of the wire to generate a spark. A wire bonding device is provided between the torch electrode and a lower end of the wire, and a magnet is provided to converge a spark generated between the torch electrode and the wire toward a lower end of the wire. . 2. The wire bonding apparatus according to claim 1, wherein the magnet is a permanent magnet. 3. The wire bonding apparatus according to claim 1, wherein the magnet is an electromagnetic coil.