JPH09326411A - Wire bonding device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a wire bonding device which increases the bonding strength between a pad and a wire, and which forms an appropriate ball at the tip of a bonding wire, while avoiding attachment of the tip of the bonding wire to the end surface of a capillary when connecting the bonding wire to a lead. SOLUTION: The wire bonding device moves a capillary 1, having a through hole 1a where a bonding wire W is passed on its axis and having a conic-shaped tip portion, upward/downward, so as to press the bonding wire W with the conic-shaped tip portion of the capillary 1, thus connecting the bonding wire W to a pad on a semiconductor chip and to a lead, with the bonding wire W. In the capillary 1, the end of the through hole 1a has an rounded portion with a predetermined curvature, and the slope angle θ of an end surface F of the conic-shaped tip portion is 6 to 10 deg..

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wire bonding apparatus for connecting a connection electrode on a semiconductor chip and an external lead terminal of a package with a bonding wire.

[0002]

2. Description of the Related Art When connecting a bond pad, which is a connection electrode on a semiconductor chip, and a lead, which is an external lead terminal of a package, with a bonding wire, the bonding pad surface and the lead surface are bonded to each other. For example, a capillary provided in a bonding head that moves up and down with respect to a semiconductor chip and having a through hole for passing a bonding wire is used. That is, the bonding pad surface and the bonding wire are bonded by pressing the ball formed by melting the tip of the bonding wire by the electric torch with the tip surface of the capillary. Further, the bonding of the lead surface and the bonding wire is carried out by pushing the bonding wire, whose tip is bonded to the bond pad surface, out of the above through hole by the movement of the capillary and pressing it against the lead frame surface by the capillary tip surface. To do.

After the bonding between the lead surface and the bonding wire is completed, when the bonding wire is clamped in the capillary and the capillary is moved up, the bonding wire is cut near the bonding portion between the lead surface and the bonding wire. By melting the tip of the cut bonding wire with an electric torch to form a ball, the bond pad surface and the bonding wire can be joined again. The wire bonding work is performed by repeating such an operation.

[0004]

Conventionally, in the above wire bonding, there has been a problem that the bonding strength between the bond pad surface and the ball formed at the tip of the bonding wire is not sufficient. On the other hand, the lead frame formed with the above-mentioned leads has been conventionally made of, for example, Ag (silver) plating.
(Paradium) Plated lead frames have also come into use. The lead frame plated with Pd has a surface hardness several times higher than that of the Ag plated product. When the lead frame is made of Ag plating and a gold wire is used for the bonding wire, when the lead and the gold wire are pressed and joined by the tip end surface of the capillary, Ag and the gold wire are easily eutectic, The wire does not easily adhere to the tip surface of the capillary, but when the lead frame is made of Pd plating, it is difficult for the Pd and the gold wire to eutectic so that the gold wire easily adheres to the capillary tip surface. Therefore, if the capillary rises with the gold wire attached to the tip surface of the capillary,
The tip of the gold wire cannot be melted by the electric torch described above, and an appropriate ball is not formed at the tip of the gold wire,
There is a problem that good wire bonding cannot be performed.

The present invention has been made in view of the above-mentioned conventional problems, and enhances the bonding strength between the bond pad and the bonding wire, and when the bonding wire is bonded to the lead, bonding is performed to the tip surface of the capillary. It is an object of the present invention to provide a wire bonding apparatus in which the tip of a wire does not adhere and an appropriate ball can be formed on the tip of the bonding wire.

[0006]

In a wire bonding apparatus according to the present invention, a capillary having a conical hole having a through hole for passing the bonding wire formed in the axis thereof is vertically moved to move the bonding wire. A wire that is joined to the connection electrode on the semiconductor chip and the external lead terminal of the package by pressing with the conical tip of the capillary, and connects the connection electrode and the external lead terminal with the bonding wire. In the bonding apparatus, the capillary has an R portion having a predetermined curvature formed at a peripheral edge of a tip of the passage hole, and a conical tip surface has an inclination angle of 6 ° to 10 °. It is in.

The wire bonding apparatus according to the present invention is
The external lead-out terminals of the package are plated with palladium.

In the wire bonding apparatus according to the present invention, the conical tip surface of the capillary has an inclination angle of 6 ° to 1 °.
At any angle between 0 °, when the bonding wire is pressure-bonded to the connection electrode, the force tends to be concentrated on the R portion of the distal end peripheral portion of the passage hole of the capillary, and the bonding wire is bonded to the connection electrode. The strength will increase. Further, since the force is likely to be concentrated on the R portion at the peripheral portion of the tip of the passage hole of the capillary, the tip of the bonding wire is unlikely to adhere to the tip surface of the capillary.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of a wire bonding apparatus according to the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a perspective explanatory view showing an example of the outer shape of a capillary 1 provided in a bonding head of a wire bonding apparatus according to the present invention. Capillary 1
A through hole 1a for passing a bonding wire made of, for example, a gold wire or the like is formed in the axis center of.

FIG. 2 shows an enlarged cross-sectional view of the tip of the capillary 1 shown within the dotted circle in FIG. As shown in FIG. 2, an R portion having a predetermined curvature is formed at the tip peripheral edge portion of the passage hole 1a, and the tip surface F is formed in a conical shape.

The capillary 1 shown in the figure is for a small pad IC, and can be made of, for example, ceramic, and the diameter of the passage hole 1a of the capillary 1 is, for example, 33 μm.
And the outer diameter of the tip face F is 140 μm. The curvature of the R portion of the passage hole 1a of the capillary 1 is, for example, 5 μm.
Alternatively, it is set to 10 μm. In the present embodiment, the inclination angle θ of the tip surface F is any angle between 6 ° and 10 °. The diameter of the bonding wire W inserted into the passage hole 1a of the capillary 1 is, for example, about 25 μm.

The operation near the tip of the capillary 1 when performing the wire bonding work using the above-described capillary will be described below with reference to FIGS. As shown in FIG. 3, the tip of the bonding wire W is melted by an electric discharge from an electric torch (not shown) to form a ball B. Ball diameter is, for example, 75
It is controlled so that it becomes μm ± 10 μm.

Next, as shown in FIG. 4, a bonding head (not shown) holding the capillary 1 is driven to form a predetermined bonding pad P as a connecting electrode of a semiconductor chip installed vertically below the capillary 1. The capillary 1 is moved toward. The bonding pad P is made of, for example, Al. By the vertical downward movement of the capillary 1, the ball B formed at the tip of the bonding wire W is sandwiched between the tip surfaces F and R of the capillary 1 and the bonding pad P, and the tip surface of the capillary 1 It is pressed by the F and R parts.
In addition, a load is applied to the capillary 1, and
In order to improve the bondability between the ball B formed at the tip of the bonding wire W and the bonding pad P, it is possible to apply ultrasonic vibration, for example. At this time,
The ball B formed at the tip of the bonding wire W is crushed and the surface of the bonding pad P and the ball B formed at the tip of the bonding wire W are joined together.

When the bonding between the surface of the bonding pad P and the ball B formed at the tip of the bonding wire W is completed, the capillary 1 is formed on the lead frame arranged so as to surround the semiconductor chip by the above bonding head. Move above a given lead. At this time, the bonding wire W is paid out from the passage hole 1a of the capillary 1 as it moves. In the present embodiment, the length of the extended bonding wire W is, for example, 2.68 mm at the longest and 2.01 mm at the shortest. The lead frame may be made of Ag plating or Pd.

As shown in FIG. 5, the capillary 1 moved above the predetermined lead L is moved toward the lead L. At this time, the bonding wire W is pressed and crushed by the tip surfaces F and R of the capillary 1. As a result, the bonding wire W and the lead L
Is joined to the surface of.

When the bonding of the bonding wire W and the surface of the lead L is completed, the capillary 1 is moved upward. At this time, the bonding wire W is clamped by the capillary 1 and the capillary 1 is moved. Movement in the passage hole 1a direction is restricted. Capillary 1 mentioned above
In the bonding wire W crushed by the tip surfaces F and R of the above, the portion crushed by the R part of the capillary 1 is the thinnest. Therefore, when the bonding wire W is pulled along with the upward movement of the capillary 1, as shown in FIG.
The bonding wire W is cut from the portion crushed by the R portion of the capillary 1 described above.

The bonding wire W in the state shown in FIG.
Then, release the clamp described above, and as shown in FIG.
The tip portion is extended for a predetermined length. The extended portion of the bonding wire W is discharged by, for example, an electric torch from the direction shown by the arrow in FIG. 7, and the extended portion of the bonding wire W is melted to form the ball B shown in FIG.
To be formed again. When the formation of the ball B is completed, the capillary 1 is moved to bond the new bonding pad P and the ball B.

As described above, the Pd-plated lead frame has a surface hardness of several times that of the Ag-plated product, and when a gold wire is used as the bonding wire W, the lead K and the gold wire are capillaries. When the lead wire is made of Pd plating, it is difficult for the gold wire to adhere to the tip surface F of the capillary 1 because Ag and the gold wire are easily eutectic when they are pressed and joined by the tip surface F of 1. , Pd and the gold wire are less likely to be eutectic, the gold wire is likely to adhere to the tip surface F of the capillary 1.

Therefore, after the bonding wire W and the surface of the lead L shown in FIG. 5 are bonded, the gold wire as the bonding wire W is clamped in the capillary 1 and the capillary 1 is moved upward. When the gold wire is cut, as shown in FIG. 8, the tip E of the gold wire may be attached to the tip surfaces F and R of the capillary 1. In the state shown in FIG. 8, even if the bonding wire W is to be fed out from the passage hole 1a of the capillary 1 by a predetermined length, the tip E of the gold wire is attached to the tip end surfaces F and R of the capillary 1 and is fed out. I can't.
Therefore, there is a problem that the ball B cannot be formed at the tip of the gold wire as the bonding wire W.

In this embodiment, the tip surface F of the capillary 1 is
The above problem is solved by setting the inclination angle θ of 1 to any angle between 6 ° and 10 °. That is,
Conventionally, the tilt angle θ of the tip surface F of the capillary 1
The wire bonding work was done at 4 °,
In this case, as shown in FIG. 8, the gold wire was frequently attached to the tip surface F of the capillary 1. When the inclination angle θ of the tip surface F of the capillary 1 is set to any angle between 6 ° and 10 °, the tip of the bonding wire W has a cutting shape as shown in FIG. The adhesion of gold wire is eliminated. This is the tip surface F of the capillary 1.
Of the bonding wire W by applying a load to the capillary 1 by making the inclination angle θ of 6 ° to 10 ° to make the inclination angle θ of the tip surface F steeper than in the conventional case. When pressing the wire, R of the capillary 1
Since the load is concentrated on the portion, the adhesiveness between the gold wire as the bonding wire W and the lead L becomes stronger, and the adhesiveness between the gold wire as the bonding wire W and the tip surface F is superior, so the tip of the capillary 1 is It is considered that the gold wire is prevented from adhering to the surface F.

When the tilt angle θ of the tip surface F of the capillary 1 was changed to 4 °, 6 °, 8 °, and 10 °, respectively, and experiments were conducted, when the tilt angle θ was 6 °, 8 °, and 10 °, In addition, the tip shape of the gold wire does not jump up as shown in FIG. 6, but when the inclination angle θ is 4 °,
The tip of the gold wire adhered to the tip surface F of the capillary 1.

On the other hand, when the inclination angle θ of the tip surface F of the capillary 1 is set to any angle between 6 ° and 10 °, the bonding strength between the ball W formed on the bonding wire W and the bonding pad P is shown. The ball shear strength is also improved at the same time. Here, the ball shear strength is the strength when a ball bonded to the bonding pad P is pushed in a direction away from the bonding pad P. Also in this case, similarly to the above, the inclination angle θ of the tip surface F of the capillary 1 is set to any angle between 6 ° and 10 °, and the inclination angle θ of the tip surface F is made steeper than in the conventional case. As a result, when a load is applied to the capillary 1 and a gold wire as the bonding wire W is pressed against the bonding pad P, the load is concentrated on the R portion of the capillary 1, so that the ball W formed on the bonding wire W and the bonding pad It is considered that the bonding strength with P is increased.

The tilt angle θ of the tip surface F of the capillary 1 is set to 1
Up to 0 ° means that the inclination angle θ of the tip surface F is further increased.
This is because when the angle becomes a steep angle, the load concentrated on the R portion of the capillary 1 becomes too large and the bonding pad P is damaged.

Here, in FIG. 9, the front end face F of the capillary 1 is shown.
The inclination angle θ of 8 ° and the conventional capillary 1
An example of the comparison result of the ball shear strength when the inclination angle θ of the tip surface F of 4 is set to 4 ° is shown. 9, in Example 1, the inclination angle θ was 8 ° and the radius of curvature of the R portion was 10 μ.
m. In Comparative Example 1, the inclination angle θ is 4 ° and the radius of curvature of the R portion is 5 μm. In Example 2, the inclination angle θ was set to 8 ° as in Example 1, but R
The radius of curvature of the portion is 10 μm. Comparative Example 2
In the same manner as in Comparative Example 1, the inclination angle θ was 4 °, but the radius of curvature of the R portion was 10 μm.

As shown in FIG. 9, the ball shear strength in Comparative Example 1 is about 0.55 [N] on average, and the ball shear strength in Example 1 is about 0.6 on average.
It is [N], and it can be seen that the ball shear strength is improved by changing the inclination angle θ from 4 ° to 8 °.

The ball shear strength in Comparative Example 2 is about 0.50 [N] on average, and the ball shear strength in Example 2 is about 0.65 [N] on average.
It can be seen that the ball shear strength is improved by changing the inclination angle θ from 4 ° to 8 °. In this case, the radius of curvature of the R portion was changed from 5 μm to 10 μm. In comparison between Example 1 and Example 2, the ball shear strength was improved when the radius of curvature of the R portion was 10 μm. You can see that Therefore, in this example, the example 2 has the most preferable result.

As described above, according to the wire bonding apparatus of the present embodiment, the adhesion between the gold wire as the bonding wire W and the lead L becomes stronger, and the gold wire as the bonding wire W and the tip face F. The adhesion of the gold wire to the tip surface F of the capillary 1 is prevented, and the problem that the ball B cannot be formed at the tip of the gold wire as the bonding wire W is solved.

Further, according to the wire bonding apparatus of this embodiment, the inclination angle θ of the tip surface F of the capillary 1 is set.
Is set to any angle between 6 ° and 10 °, and the inclination angle θ of the tip face F is made steeper than in the conventional case, so that the load is concentrated on the R portion of the capillary 1, so that the ball shear strength is improved. To do.

[0030]

As described above, according to the wire bonding apparatus of the present invention, it is possible to increase the bonding strength between the bond pad as the connection electrode on the semiconductor chip and the bonding wire, and to improve the reliability of the semiconductor. Can be increased.

Further, according to the wire bonding apparatus of the present invention, it is possible to prevent the tip of the bonding wire from adhering to the tip surface of the capillary when the bonding wire is joined to the lead serving as the external lead-out terminal of the package. You can Therefore, the bonding wire can be fed out from the tip of the capillary, and an appropriate ball can be formed at the tip of the bonding wire.

Further, according to the wire bonding apparatus of the present invention, good wire bonding can be performed even if the lead as the external lead-out terminal of the package is plated with palladium.

[Brief description of drawings]

FIG. 1 is a perspective explanatory view showing an example of the outer shape of a capillary provided in a bonding head of a wire bonding apparatus according to the present invention.

FIG. 2 is an enlarged explanatory diagram within a circle of FIG.

FIG. 3 is an explanatory cross-sectional view showing a state in which a ball is formed at the tip of a bonding wire.

FIG. 4 is a cross-sectional explanatory view showing a state in which a ball formed at a tip of a bonding wire is pressure-bonded to a bond pad by a tip surface of a capillary.

FIG. 5 is a cross-sectional explanatory view showing a state in which a bonding wire is pressure-bonded to a lead by the tip surface of a capillary.

FIG. 6 is a cross-sectional explanatory view showing a state in which a bonding wire is clamped and cut.

FIG. 7 is an explanatory cross-sectional view showing a state in which a bonding wire is paid out from the tip of a capillary to form a ball at the tip of the bonding wire.

FIG. 8 is a cross-sectional explanatory view showing a state in which the tip portion of the bonding wire adheres to the tip surface of the capillary when the bonding wire is clamped and cut.

FIG. 9 is an explanatory diagram showing a comparison between an example of ball shear strength and a conventional example when wire bonding is performed by the wire bonding apparatus according to the present invention.

[Explanation of symbols]

1 ... Capillary, 1a ... Passage hole, R ... R part, F ...
Tip surface, W ... Bonding wire, P ... Bond pad, L ... Lead, θ ... Inclination angle of tip surface F.

Claims (2)

[Claims] 1. A capillary having a conical tip formed with a through hole for allowing a bonding wire to pass therethrough is moved up and down, and the bonding wire is pressed by the conical tip of the capillary. A wire bonding device that is joined to a connection electrode on a semiconductor chip and an external lead terminal of a package, and connects the connection electrode and the external lead terminal with the bonding wire, wherein the capillary is the through hole. A wire bonding apparatus in which an R portion having a predetermined curvature is formed at the peripheral edge of the tip of the, and the inclination angle of the conical tip surface is any angle between 6 ° and 10 °. 2. The wire bonding device according to claim 1, wherein the external lead-out terminal of the package is plated with palladium.