JPH09162219A - Method and device for wire bonding - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a wire bonding method with which the state of low loop can be accomplished without restriction on the length of a wire and also without giving damage to the neck part of a loop. SOLUTION: A capillary 5, with which the connection electrode 10a on a semiconductor chip 10 and a lead 15 are connected by a bonding wire 13, is connected to the connection electrode 10a on the tip of the bonding wire 13. Then, the capillary 5 is brought up to almost just above the connection electrode 10a and then it is brought down toward the connection electrode 10a. Then, the capillary 5 is moved to lateral direction, and the prescribed position of the bonding wire 13 is connected to the lead 15.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wire bonding method and apparatus, and more particularly to a technology effective when applied to wire bonding which can realize a low loop without damaging a neck portion in wire bonding.

[0002]

2. Description of the Related Art In recent years, packages such as VLSI logic devices have been increasing in number of pins and thinning. For example, in order to realize a thin plastic package, development of a technology / device for forming a low loop and wire material Development is required.

In order to realize a low loop of the bonding wire, the development of the wire material has been a big part at present. In the nail head bonding, the neck directly above the ball is affected by the thermal effect of the discharge current when the wire is melted to form the ball. Since the loop portion is recrystallized and the loop height is determined by the length of the neck portion, a wire is being developed to control the discharge current and at the same time add an additive element that is difficult to recrystallize to shorten the neck portion.

In the process of wire bonding, a loop forming technique for stabilizing the loop height has been developed. For example, in order to reduce the loop height, a clamper is controlled to pull out from a capillary (bonding tool). It is considered that the bonding is realized by reducing the loop to some extent by reducing the amount of bonding wire to be formed.

Here, in the wire bonding apparatus which has been studied by the present inventor, which is not publicly known, the capillary itself can be moved in the Z-axis direction, and the XY table on which this capillary is mounted can be used as the X-axis and the X-axis table. It is movable in the Y-axis direction, and the connection electrode on the semiconductor chip and the lead are connected by a bonding wire by controlling the operation of the capillary and the XY table.

As an example in which the technique relating to such wire bonding is described in detail, for example,
Published by Ohmsha, "LSI Handbook" (November 1984)
Issued on 30th), P406 ~ P411.

[0007]

Although it is possible to realize a low loop to some extent by controlling the discharge current, developing the wire material, and controlling the clamper, it is inevitable that the wire length becomes long. As a result, the loop height becomes high, and there is a limit to the reduction of the loop.

In the low loop, since the wire is bent from the ball portion toward the lead immediately, the neck portion of the loop is damaged, and the damage cannot be reduced, so that the tensile strength of the wire cannot be obtained. This is a factor that causes disconnection during molding after wire bonding.

Therefore, an object of the present invention is to provide a technique for wire bonding that can realize a low loop without being restricted by the wire length.

Another object of the present invention is to provide a technique for wire bonding which can realize a low loop without damaging the neck portion of the loop.

The above and other objects and novel features of the present invention will become apparent from the description of the present specification and the accompanying drawings.

[0012]

SUMMARY OF THE INVENTION Among the inventions disclosed in the present application, the outline of a representative one will be briefly described.
It is as follows.

That is, the wire bonding method according to the present invention uses a bonding tool for connecting the connection electrode on the semiconductor chip and the lead with a bonding wire.
A first operation of connecting the tip of the bonding wire to the connection electrode, a second operation of rising almost directly above the connection electrode, a third operation of descending toward the connection electrode, and a lateral movement to perform bonding. The fourth operation of connecting a predetermined position of the wire to the lead is performed in this order.

Third method in this wire bonding method
In the above operation, it is desirable to lower the tip of the bonding tool to a height of about 100 μm directly above the connection electrode, for example, from the surface of the semiconductor chip.

In the wire bonding apparatus according to the present invention, an electric torch that melts the tip of the bonding wire by an electric discharge current to form a ball, and a bonding wire that is pulled out is used to connect the ball to a connection electrode of a semiconductor chip. The operation trajectory of the bonding tool for electrically connecting the chip and the lead and the bonding tool when the bonding wire is connected to the connection electrode and the lead is elevated almost directly above the connection electrode and then directed toward the connection electrode. It moves down and then moves laterally to reach the lead.

According to this, since the loop height of the wire loop can be substantially set to the lowered position in the third operation of the bonding tool, it is possible to realize an ultra-low loop without being restricted by the wire length. become.

Further, the bonding wire is formed in such a shape that it rises vertically from the surface of the semiconductor chip and then goes to the lead, and the neck portion of the loop is not damaged. Therefore, even if the loop is made low, the tensile strength of the wire is sufficient. Therefore, there is no risk of disconnection during molding.

[0018]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is an external perspective view showing an example of a wire bonding apparatus according to an embodiment of the present invention, and FIG. 2 is an explanatory view showing the operation of a capillary in the wire bonding apparatus according to the present embodiment in succession. 3 is an explanatory view showing an example of the movement locus of the capillary and the loop state of the wire, and FIG. 4 is a cross-sectional view showing the main part relationship between the capillary and the wire in the technique comparatively studied with this embodiment.

The wire bonding apparatus of this embodiment employs nail head bonding by a thermocompression bonding method using a bonding wire such as a gold (Au) wire. As shown in FIG. A loader unit 1 that supplies a die-bonded substrate, a feeder unit 2 that conveys this substrate and stops it at a predetermined position to perform wire bonding, and an unloader unit 3 that stores the wire-bonded substrate. , A bonding head portion 4 which is driven in the X-axis, Y-axis and Z-axis directions to perform wire bonding between the connection electrode on the semiconductor chip and a lead which is an external lead-out terminal on the substrate.

The bonding head unit 4 includes a capillary (bonding tool) 5 through which a bonding wire is passed, a tool holder 6 to which the capillary 5 is attached, an XY table 7 that moves in the X-axis and Y-axis directions, a position between a semiconductor chip and a substrate. Tool holder 6 which is composed of a camera 8 for detecting
Is moved up and down, and a bonding wire is connected between the bonds to form a loop by operation control of the XY table 7 on which the bonding head unit 4 is mounted. At this time, the camera 8 mounted on the bonding head unit 4 The relative position between the substrate and the semiconductor chip die-bonded on the substrate is detected, and the bonding wire is connected to a predetermined position.

Further, in order to control the movement locus of the capillary 5 by the relative movement control of the tool holder 6 to which the capillary 5 is attached to the bonding head portion 4 and the XY table 7 on which the bonding head portion 4 is mounted. Control unit (operation control means) 9 is connected, and the operation of the capillary 5 in which the tip of the bonding wire is connected to the connection electrode on the semiconductor chip is controlled as described later to execute a series of wire bonding operations. It has become.

Here, the bonding operation by the capillary 5 controlled by the controller 9 will be described with reference to FIG.

First, the substrate 11 on which the semiconductor chip 10 supplied from the loader unit 1 is die-bonded is carried by the feeder unit 2, stopped at a predetermined position on the feeder unit 2 and positioned at the wire bonding position. At the same time, the capillaries 5 of the bonding head unit 4 are also positioned on the semiconductor chip 10 at the positions of the predetermined connection electrodes 10a.

Next, the bonding wire 13 is supplied from the wire spool 12, and the tip of the bonding wire 13 passed through the capillary 5 is melted by a ball forming torch 14 such as an electric torch or a gas flame to form a ball ( FIG. 2A). Then, the capillaries 5 move the balls to the substrate 11
The connection electrode 10a on the semiconductor chip 10 die-bonded to the upper side is pressure-bonded and connected (FIG. 2B).

After the connection, the capillary 5 is raised almost directly above the connection electrode 10a, for example, by about 150 μm (FIG. 2 (c)). As a result, the bonding wire 13 is not restricted to a shape in which the bonding wire 13 is immediately bent toward the lead 15 at the ball portion, but is restricted to a shape in which the bonding wire 13 rises perpendicularly to the surface of the semiconductor chip 10 from this portion. Then, it is lowered again directly above the connection electrode 10a, for example, to a height of about 100 μm from the surface of the semiconductor chip 10 (FIG. 2).
(D)). It should be noted that the descending position of the capillary 5 here determines the loop height. Therefore, in order to reduce the loop, it should be descended as close to the connection electrode 10a as in the present embodiment. However, if the loop is not particularly low, it may be lowered to a desired and appropriate height.

Then, the capillary 5 is moved laterally to guide the bonding wire 13 to the lead 15, and a predetermined position of the bonding wire 13 is pressure-bonded onto the lead 15 at the edge of the capillary 5 to connect (FIG. 2 (e)). ). Then, the clamper 16 sandwiches the bonding wire 13 and pulls it to cut it.

As a result, one-time bonding is completed, and thereafter, the basic operation described above is repeated for all the connection electrodes 10a and the leads 15 on the semiconductor chip 10 so that one substrate 11 is wire-bonded. Complete.

Then, the substrate 11 on which wire bonding has been completed is conveyed by the feeder unit 2, and the substrate 11 on which wire bonding has been performed is stored in the unloader unit 3. All the substrates 11 stored in the loader unit 1 are subjected to the above operation.
Repeat for.

Next, the operation locus of the capillary 5 during wire bonding, which is a feature of this embodiment, will be described with reference to FIG. Note that, in FIG. 3, the solid line indicates the operation locus of the tip of the capillary 5, and the numbers from 1 to 5 in this operation locus indicate the operation sequence. The broken line shows the loop shape of the bonding wire 13 that has been bonded.

First, in the first operation, the tip of the bonding wire 13 on which the ball has been lowered and formed is connected to the connection electrode 10a on the semiconductor chip 10 (), and then the second operation.
By the operation of, the connection position is raised almost directly above (). Then, in the third operation, it is lowered again toward the connection electrode 10a ().

Then, in the fourth operation, for example, an arc-shaped locus is drawn to move laterally to the position of the lead 15 (), and a positioning operation is performed to connect the bonding wire 13 to the lead 15 (-). This allows
A predetermined position of the bonding wire 13 is connected to the lead 15.

In this series of operations of the capillary 5, the loop height of the wire loop is substantially determined at the lowered position by the third operation. For example, in the case of the present embodiment, it is about 100 μm from the surface of the semiconductor chip 10. The height of the loop is about 100 μm. Note that, as described above, the descending position by the third operation is set to a higher position, and is shown by a dashed line.
It is also possible to operate on the locus.

As described above, according to the wire bonding apparatus of the present embodiment, the connection electrode 1 on the semiconductor chip 10 is
0a and the lead 15 are electrically connected to each other by the bonding wire 13, the operation locus of the capillary 5 is controlled to the above-described first to fourth operations, so that the loop height of the wire loop is almost equal to that of the capillary 5. Since it can be set to the lowered position in the third operation, by lowering the tip of the capillary 5 to just above the connection electrode 10a, a significant reduction in loop can be achieved regardless of the wire length, for example, about 100 μm. Such an ultra-low loop can be realized.

The bonding wire 13 rises vertically from the surface of the semiconductor chip 10 and then leads 15
Since the neck portion of the loop is not damaged by being formed in a shape that faces toward, the tensile strength of the wire is sufficiently secured and there is no fear of disconnection during molding.

For example, in the technique studied in comparison with the present embodiment, the reverse mode operation of returning the capillary 5 elevated from the position of the connection electrode 10a to the opposite direction of the lead 15 to be connected once is inserted to achieve a low loop. To be done.
However, in this technique, when the bonding wire 13 is ejected from the capillary 5 by the reverse operation, as shown in FIG.
As shown in FIG. 5, the neck portion is damaged by rubbing with the radius chamfer 17, but such damage does not occur in the wire bonding technique of the present embodiment.

Although the invention made by the present inventor has been specifically described based on the embodiments, the present invention is not limited to the above embodiments, and various modifications can be made without departing from the scope of the invention. Needless to say.

For example, the wire bonding apparatus of the present embodiment is a nail head bonding wire bonding apparatus for connecting the bonding wires 13 by thermocompression bonding, but the present invention is not limited to this, and ultrasonic waves are used together. It can be widely applied to a nail head bonding by a thermocompression bonding method and a wire bonding device by a wedge bonding by an ultrasonic method.

Here, in the wedge bonding by the ultrasonic method, the bonding wire 13 is pressure-bonded to the connection electrodes 10a and the leads 15 on the semiconductor chip 10 while applying ultrasonic waves, using a bonding tool called a wedge. The feature is that they can be joined and that they are suitable for a finer pitch of electrodes as compared with nail head bonding.

When an aluminum wire is used as the bonding wire 13 in wedge bonding, the tensile strength of the aluminum wire is weak and it is easily corroded.
It is desirable to apply it to a hermetically sealed ceramic package.

[0041]

Advantageous effects obtained by typical ones of the inventions disclosed in the present application will be briefly described.
It is as follows.

(1). According to the wire bonding technique of the present invention, the movement locus of the bonding tool is determined by
By controlling to the fourth operation, the loop height of the wire loop can be almost set to the lowered position in the third operation of the bonding tool, so that the loop height is not restricted by, for example, the loop height of about 100 μm. It becomes possible to realize an ultra low loop such as.

(2) Further, since the bonding wire is formed in a shape that rises vertically from the surface of the semiconductor chip and then goes to the lead, the neck portion of the loop is not damaged. Sufficient tensile strength is ensured and there is no risk of disconnection during molding.

[Brief description of the drawings]

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

2A to 2E are explanatory views successively showing the operation of the capillaries in the wire bonding apparatus of the present embodiment.

FIG. 3 is an explanatory diagram showing an example of an operation trajectory of a capillary and a loop state of a wire.

FIG. 4 is a cross-sectional view showing a main part relationship between a capillary and a wire in a technique comparatively studied with the present embodiment.

[Explanation of symbols]

 1 loader part 2 feeder part 3 unloader part 4 bonding head part 5 capillary (bonding tool) 6 tool holder 7 XY table 8 camera 9 control part (operation control means) 10 semiconductor chip 10a connection electrode 11 substrate 12 wire spool 13 bonding wire 14 Ball forming torch 15 Lead 16 Clamper 17 Radius chamfer

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Nobuo Sakata 3-3, Fujibashi, Ome, Tokyo 2 3 Hitachi Hitachi Electronics Co., Ltd. No. Incorporated company Hitachi Ltd. Semiconductor Division (72) Inventor Junpei Konno 5-20-1 Kamimizuhonmachi, Kodaira-shi, Tokyo Incorporated Hitachi Ltd. Semiconductor Division

Claims (4)

[Claims] 1. A wire bonding method for connecting a connection electrode on a semiconductor chip and a lead with a bonding wire pulled out from a bonding tool, wherein the bonding tool connects the tip of the bonding wire to the connection electrode. A first operation to perform, a second operation to rise almost directly above the connection electrode, a third operation to descend toward the connection electrode, and a lateral movement to move a predetermined position of the bonding wire to the lead. A wire bonding method, which comprises operating in the order of a fourth operation of connecting. 2. The wire bonding method according to claim 1, wherein in the third operation, a tip of the bonding tool descends to a position right above the connection electrode. 3. The wire bonding method according to claim 2, wherein the tip of the bonding tool is lowered to a height of about 100 μm from the surface of the semiconductor chip. 4. An electric torch for melting a tip of a bonding wire by a discharge current to form a ball, and connecting the ball to a connection electrode of the semiconductor chip by a drawn bonding wire to electrically connect the semiconductor chip and a lead. And a bonding tool that is electrically connected to each other, and an operation locus of the bonding tool when the bonding wire is connected to the connection electrode and the lead is increased substantially straight above the connection electrode and then directed toward the connection electrode. A wire bonding apparatus comprising: an operation control unit that controls to descend and then move laterally to reach a lead.