JP2531099B2 - Wire-bonding method - Google Patents

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 more particularly to a wire bonding method applied to the manufacture of semiconductor devices.

[0002]

2. Description of the Related Art In the process of assembling a semiconductor device, an electrode pad formed on the main surface of a semiconductor chip and an external lead terminal for transmitting and receiving a signal to and from the electrode pad are wire-bonded to Au or It is connected by a metal thin wire such as Cu.

3 (a) to 3 (d) show a conventional wire bonding method. In the figure, the semiconductor chip 3 is
The electrode pad 4 mounted and fixed on the die pad 6 and formed on the main surface thereof is connected to the external lead terminal 5 by the capillary 1. Capillary 1 is 18-50 μm
A metal thin wire 2 having a diameter of about a certain extent is held so that it can be drawn out from its tip, and it can move freely in the vertical and horizontal directions, a load in the vertical direction is applied to the metal thin wire 2, and ultrasonic vibration is applied. Can be applied.

The capillary 1 first moves to the upper part of the electrode pad 4 and bonds the tip of the thin metal wire 2 to the electrode pad 4. For the bonding, the electrode pad 4 is previously attached to 2
After heating to around 00 ° C, using the capillary 1, 30 to 6
It is performed by applying a load of about 0 gf to press the thin metal wire 2 against the electrode pad 4 and applying ultrasonic vibration.

Next, the capillary 1 moves to the upper part of the external lead terminal 5 while leading out the thin metal wire 2, and connects the thin metal wire 2 to the outer lead terminal 5 heated to about 200 ° C. The connection in this case is similarly performed by using the capillary 1 while applying a load of about 80 to 120 gf and ultrasonic vibration to the thin metal wire. After that, the clamper 7 is operated to raise the capillary 1 in a state where the lead-out of the metal fine wire 2 is stopped, and the metal fine wire 2 is broken at the end of the connection point with the external lead terminal 5. By repeating the above-described series of operations, a large number of electrode pads 4 and external lead terminals 5 corresponding to the respective electrode pads 4 are sequentially wired.

[0006]

According to the above-mentioned conventional wire bonding method, there is a problem that curls are generated in the fine metal wires due to the application of ultrasonic vibration. That is, FIG.
As shown in FIG. 1, when the metal thin wire 2 is connected to the external lead terminal 5 while applying ultrasonic vibration, the capillary 1
There is a problem in that the rotational force due to ultrasonic vibration is transmitted to the portion of the metal thin wire 2 that is in contact with the tip of the metal thin wire 2 and the metal thin wire 2 after connection is bent in the horizontal direction.

When horizontal bending occurs in a thin metal wire,
The thin metal wires that are adjacent to each other may come into contact with each other to cause an electrical short circuit or the like, which reduces the reliability of the semiconductor device. In particular, the development of semiconductor products has been promoted in response to the recent miniaturization of semiconductor products.
m or less and the distance between the tips of the external lead terminals is 18
In a semiconductor device having a high-density wiring of 0 μm or less, or a semiconductor device in which the wiring length of the thin metal wire exceeds 5 mm, many such problems may occur.

In order to prevent the above-mentioned problems, a method of connecting the thin metal wire to the external lead terminal by simply thermocompression bonding without using ultrasonic vibration can be considered. However, if the temperature conditions during connection are the same, However, the strength required for bonding, for example, the wire tensile strength of 4 gf or more cannot be obtained. Further, it is possible to obtain the necessary strength by increasing the temperature condition at the time of connection to, for example, about 280 ° C. However, the oxidation of the external lead terminals due to the high temperature is accelerated or the external lead terminals are accelerated. In particular, in the high-density wiring, since the bending of the thin metal wire due to the repeated thermal expansion and the thermal contraction of the metal wire and the decrease in the movement position accuracy due to the thermal expansion of each part of the wire bonding apparatus are newly generated,
It is difficult to adopt the temperature condition exceeding 0 ° C.

Further, in the conventional wire bonding method, there is a problem of short circuit between the metal fine wire and the external lead terminal as shown in FIG. Generally, in a semiconductor device, there is a wiring portion where an angle is formed between the wiring direction of the thin metal wire 2 and the longitudinal direction of the external lead terminal. In particular, in the case of a semiconductor device with high-density wiring in which the distance between the tips of the external lead terminals 5 is 180 μm or less, it is unavoidable that each external lead terminal has a tapered shape in terms of manufacturing technology. Therefore, in order to obtain a sufficient bonding strength at the connecting portion, the thin metal wire is connected at a position apart from the tip of the external lead terminal by about 300 μm.

In FIG. 5, for example, the thin metal wire 2 at the right end
And the external lead terminal 5b adjacent to the external lead terminal 5a connected thereto, even if curling does not occur in the thin metal wire, and when curling occurs, a necessary separation distance is secured. It can be understood that it is difficult and that an electrical short circuit tends to occur between them. In order to prevent such a short circuit, the degree of freedom in the layout design of the semiconductor device is limited.

In view of the above-mentioned problems of the conventional wire bonding method, the present invention makes it easy to secure a necessary separation distance between the metal thin wires and between the metal thin wires and the external lead terminal, so that a short circuit accident occurs between them. An object of the present invention is to provide a difficult wire bonding method and to manufacture a highly reliable semiconductor device.

[0012]

In order to achieve the above object, a wire bonding method of the present invention is a wire bonding method for a semiconductor device, in which an electrode pad formed on a semiconductor chip and an external lead terminal are connected by a fine metal wire. A step of connecting the first portion of the thin metal wire to the electrode pad, a step of connecting the second portion of the thin metal wire to the first position of the external lead terminal without applying ultrasonic vibration, and the first portion The third part of the thin metal wire, which is on the side farther than the second part when viewed from above, is connected in this order while applying ultrasonic vibration to the second position of the external lead terminal. To do.

Both of the connection for applying ultrasonic vibration and the connection for not applying ultrasonic vibration are preferably connected under a low temperature condition of about 250 ° C. or less. The separation distance between the first position and the second position is, for example, about 50 μm or more, which is about the same distance as the diameter of the thin metal wire, and is about 300 μm in consideration of the arrangement efficiency of the semiconductor device. The following is preferable.

[0014]

The second portion of the fine metal wire is connected to the first position of the external lead terminal without being applied with ultrasonic vibration, and the third portion of the fine metal wire is subjected to ultrasonic vibration to cause external lead terminal. Since the curl caused by the ultrasonic vibration is prevented between the first portion and the second portion of the metal thin wires by being connected to the second position of the metal thin wires, the metal thin wires are connected to each other or to the metal thin wires. The space between the external lead terminal and the external lead terminal adjacent to the external lead terminal can be easily ensured, while the connection strength between the thin metal wire and the external lead terminal can be sufficiently ensured, resulting in electrical and mechanical reliability. Higher connection is possible.

[0015]

The present invention will be described in more detail with reference to the drawings. 1A to 1D are schematic side views showing, in the order of steps, a wire bonding method for a semiconductor device according to an embodiment of the present invention. First, after bonding the semiconductor element (chip) 3 to the die pad 6, one end forming the first portion of the thin metal wire 2 is thermocompression bonded to the electrode pad 4 formed on the main surface of the semiconductor chip 3 together with ultrasonic vibration. Connect by technology. The thin metal wire 2 is made of, for example, Au or Cu, and its diameter is about 18 to 50 μm. The electrode pad is preheated to about 200 ° C., and the load applied from the capillary 1 to the thin metal wire at this time is about 30 to 60 gf.

Then, as shown in FIG. 1A, the capillary 1 is connected to the external lead terminal 5 while the thin metal wire 2 is being drawn out.
Move it above the tip of the. The second portion of the thin metal wire 2 is pressed against the external lead terminal 5 with a load of about 100 to 150 gf at point A, which is a position (first position) about 150 μm away from the tip of the external lead terminal 5. Since the external lead terminals 5 are preheated to about 200 ° C., the metal thin wires 2
Is thermocompression-bonded to the external lead terminal 5 ((b) of the same figure). Since this thermocompression bonding is performed at a relatively low temperature of 200 ° C,
As the wire tensile strength, a low bonding strength of about 2 to 3 gf is possible. In this thermocompression bonding, since the ultrasonic vibration is not used together, the metal thin wire 2 is not bent.

Next, while deriving the thin metal wire 2 again,
Approximately 400μ of the capillary 1 from the tip of the external lead terminal 5
It is slightly moved to a position B (second position) at a distance of m, and at this position, the third portion of the thin metal wire 2 is loaded with a load of 80 to 120 g.
f and ultrasonic vibration are applied to connect (FIG. 1 (c)).
In this thermocompression bonding joint use with ultrasonic vibration, the fixing action at the previously connected point A prevents the metal thin wire 2 from rotating due to ultrasonic vibration. For this reason, in the metal thin wires 2 after connection, sufficient bonding strength of about 8 gf of wire tensile strength can be obtained without causing deformation such that adjacent metal thin wires 2 approach each other.

The amplitude of vibration due to ultrasonic vibration is generally 2 μm.
m or less, therefore, the connection with ultrasonic vibration combined,
There is no risk of peeling at the point A due to the thermocompression bonding. The separation distance between points A and B is generally 50
Approximately 300 μm is adopted. If this separation distance is set too large, the overall layout efficiency of the semiconductor device is impaired.

After that, the wire clamper 7 is closed to stop the lead-out of the thin metal wire 2, and then the capillary 1 is raised to bring the thin metal wire 2 at the end of the connection point (point B) with the external lead terminal 5. It breaks (FIG. 1 (d)). By repeating such a series of steps, a large number of electrode pads 4 are formed.
And the corresponding external lead terminal 5 are connected. In this case, between the electrode pad 4 and the external lead terminal 5, unlike the conventional case, the metal thin wire 2 is not bent in the horizontal direction. Therefore, a necessary separation distance is secured between the adjacent metal thin wires 2.

For example, according to the method of the above embodiment, 16
In the 0-pin semiconductor device, the amount of bending of the thin metal wire in the horizontal direction is reduced to about 1/3 of the conventional amount. Further, the length of the metal thin wire that enables connection with a predetermined horizontal bending amount or less can be increased by, for example, about 10%.

2A to 2D are schematic plan views showing a wire bonding method for a semiconductor device according to a second embodiment of the present invention. In the wire bonding method of this embodiment, as shown in the figure, there is a relatively large angle between the extending direction of the thin metal wire 2 and the longitudinal direction of each external lead terminal 5.

First, the metal fine wire 2 is connected to the electrode pad 4 formed on the main surface of the semiconductor chip 3 by the thermocompression bonding technique using the capillary 1 together with ultrasonic vibration. Next, while pulling out the thin metal wire 2, the capillary 1 is moved to a position A about 150 μm away from the tip of the preheated external lead terminal 5a.
Move to a point. At this position, the capillary 1 is used to apply a load of about 100 to 120 gf, and the thin metal wire 2 is pressed against the external lead terminal 5 for connection.

The connection at the point A shows a relatively low joining strength of about 1 to 2 gf for the wire pulling strength because the terminal width of the external lead terminal 5 at that position is as narrow as about 90 μm. However, by making the connection at this position,
A large separation distance can be secured between the thin metal wire 2 and the external lead terminal 5b adjacent to the external lead terminal 5a connected thereto. In addition, since the thermocompression bonding is used, unlike the connection using ultrasonic vibration, the bending of the thin metal wires due to the vibration does not occur, so that the separation distance between the thin metal wires adjacent to each other is not narrowed. .

Next, the capillary 1 is moved from the point A toward the position B, which is about 400 μm from the tip of the external lead terminal 5a, while leading out the thin metal wire 2. in this case,
At point A, the thin metal wire 2 is bent so as to face the longitudinal direction of the external lead terminal 5. When the capillary 1 reaches the point B, the third portion of the thin metal wire 2 is connected to the point B by the thermocompression bonding technique combined with ultrasonic vibration (FIG. 2B). At this time, the load applied from the capillary 1 is about 80 to 120 gf.

The connection at the point B is performed by a thermocompression bonding technique which also uses ultrasonic vibration. However, the fixing action by the connection at the point A prevents the metal thin wire 2 from rotating due to the ultrasonic vibration. It Therefore, the bent metal wire 2 does not remain in the horizontal direction after connection, and the wire tensile strength of about 8 gf can be obtained. In this embodiment, A
The distance between the point and the point B is preferably about 100 μm or more, for example.

When the connection at the point B is completed, the wire clamp is actuated to stop the lead-out of the thin metal wire 2, and then the capillary 1 is raised. As a result, the thin metal wire 2 is broken at the end of the point B. By repeating the above-described series of steps, the arrangement of the thin metal wires shown in FIG. 2C can be obtained. In this case, each electrode pad 4 and external lead terminal 5
Even when a relatively large angle is unavoidable between the extension direction of the thin metal wire 2 between the first connection points a and 5b and the longitudinal direction of the external lead terminal, as shown in FIG.
The metal thin wire 2 and the external lead terminal 5b adjacent to the external lead terminal 5a connected to the thin wire 2 are sufficiently separated from each other, so that there is no fear of electrical short circuit.

The wire bonding method of the present invention is highly advantageous and highly reliable in the case of a semiconductor device in which the wiring length of the thin metal wire is 5 mm or more between the electrode pad and the external lead terminal. Is possible. Further, conventionally, in a semiconductor device that requires high-density wiring, the width of the external lead terminal is narrow, so in order to obtain the necessary bonding strength, the connection position between the metal thin wire is
It was necessary to adopt a position separated from the tip of the external lead terminal by, for example, about 300 μm. Therefore, in the case of a semiconductor device in which there is a relatively large angle between the extension direction of the thin metal wire and the longitudinal direction of the external lead terminal, the necessary separation distance should be secured between the thin metal wire and the external lead terminal. However, by adopting the configuration of the above-described embodiment, it becomes easy to secure a necessary separation distance.

Although the wire bonding method according to the embodiments of the present invention has been described above, the configurations of the respective embodiments are merely examples, and it goes without saying that various modifications and changes can be made from these embodiments. Absent. Therefore, the present invention is not limited to the configuration of the above embodiment.

[0029]

As described above, according to the wire bonding method of the present invention, while ensuring the required bonding strength, the necessary separation distance can be secured between the metal thin wires or between the metal thin wires and the external lead terminals. Therefore, the remarkable effect is achieved that highly reliable wire bonding becomes possible.

[Brief description of drawings]

1A to 1D are schematic side views showing a wire bonding method according to an embodiment of the present invention in the order of steps.

2A to 2C are schematic plan views showing the wire bonding method of the second embodiment of the present invention in the order of steps.

3A to 3D are schematic side views showing a conventional wire bonding method in the order of steps.

FIG. 4 is a schematic plan view showing a problem in the conventional wire bonding method of FIG.

FIG. 5 is a schematic plan view showing another problem in conventional wire bonding.

[Explanation of symbols]

 1 Capillary 2 Metal Wire 3 Semiconductor Chip 4 Electrode Pad 5, 5a, 5b External Lead Terminal 6 Die Pad 7 Clamper

Claims (4)

(57) [Claims] 1. A wire bonding method for a semiconductor device, wherein an electrode pad formed on a semiconductor chip and an external lead terminal are connected to each other by a fine metal wire, comprising a step of connecting a first portion of the fine metal wire to the electrode pad. A procedure of connecting the second portion of the thin wire to the first position of the external lead terminal without applying ultrasonic vibration, and a third of the thin metal wire on the side farther from the second portion when viewed from the first portion. And a step of connecting the portion to the second position of the external lead terminal while applying ultrasonic vibration in this order. 2. The connection in each of the steps is about 250.
The method is performed under a temperature condition of ℃ or less.
The wire bonding method described in. 3. The wire bonding method according to claim 1, wherein the distance between the first position and the second position is about 50 to 300 μm. 4. The first position is a position within about 150 μm from the tip of the external lead terminal, and the second position is a position separated by about 250 μm or more from the tip of the external lead terminal. The wire bonding method according to any one of claims 1 to 3.