JP3519322B2 - Wire bonding apparatus and 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 apparatus and a wire bonding method, and more particularly to a wire bonding apparatus and a wire bonding method using laser irradiation.

[0002]

2. Description of the Related Art A conventional wire bonding method is shown in FIG.
0, shown in FIG.

FIG. 10 is a perspective view showing an outline of a conventional wire bonding method using gold as a wire material. In the conventional bonding method, as shown in FIG. 10, while vibrating the gold ball 1a drawn into the conical portion of the tool by ultrasonic waves, pressure is applied to the pad 2 of the device from above and heat is applied from the bottom of the device. Thus, the gold ball 1a and the pad 2 of the device are joined.

FIG. 11 is a sectional view showing a tool tip enlarged portion of the conventional bonding method of FIG. By applying heat as described above, the Ag paste 5 that joins the chip 4 and the lead frame island portion 6 is re-softened by heat, and the chip vibrates by ultrasonic waves during bonding, and the ultrasonic waves escape. I will end up. Furthermore, at this time,
If the size of the chip 4 is small, the bonding area with the lead frame island portion 6 is small, so that the escape of ultrasonic waves becomes significant and a defect due to non-adhesion occurs. Further, if the power of ultrasonic waves or pressure from above is increased to prevent defects due to adhesion, Al peeling, which is a defect that destroys the Al layer in the upper layer portion of the pad 2 by ultrasonic waves, and pressure from above. V crack, which is a defect that destroys the Si layer in the lower layer of the pad, is generated. Further, in the conventional bonding process, when the equipment is stopped due to an error, the lead frame island portion may be exposed to high temperature for a longer time than usual, and an oxide film may be formed on the surface. In such a case, the oxide film deteriorates the adhesion between the island portion and the sealing resin, and resin peeling occurs from this portion, which lowers the reliability of the package.

Further, in the wire bonding method disclosed in Japanese Patent Laid-Open No. 63-078543, a pad portion is irradiated with a laser and heated, and then a gold ball is bonded, or a laser is irradiated only during the bonding, and the pad portion is heated. Indicates that the gold wire or the gold ball is not irradiated with the laser, and is not heated by the laser.

[0006]

As described above,
The conventional bonding method has a problem that a defect occurs in the bonding process, as described with reference to FIGS.

There is also a problem that the reliability of the package itself is lowered.

In order to solve such a problem, it is impossible to solve it by the conventional equipment and method.

Therefore, an object of the present invention is to prevent the occurrence of defects in the bonding process in order to solve the above problems.

Another object of the present invention is to improve the reliability of the package itself.

[0011]

In order to achieve the above object, a wire bonding apparatus of the present invention comprises a bonding tool used for bonding a pad on a chip and a lead on a lead frame to a wire, and the bonding of the wire.
In a wire bonding device that includes a laser irradiator that irradiates a laser on the interface, and electrically connects the pad on the chip and the lead on the lead frame with a wire,
Be moved during the bonding interface is bonded, the bonding interface is to be heated locally, characterized by comprising means for controlling the laser irradiation position and the irradiation angle of the laser irradiator.

The means for controlling the irradiation position and the irradiation angle are preferably controlled by the height information of the bonding tool.

Further, the laser irradiator is preferably arranged so as to surround the bonding tool.

Further, the wire bonding method of the present invention comprises a bonding tool used for bonding a pad on a chip and a lead on a lead frame to a wire,
Laser irradiation for irradiating a laser on the bonding interface of the wire
With the vessels, the lead on the pad and the lead frame on the chip in the wire bonding method for electrically connecting a wire, even if the bonding interface moves during the bonding, can locally heat the bonding interface Thus, the irradiation position and the irradiation angle of the laser of the laser irradiator are controlled.

Further, the control is preferably controlled by the height information of the bonding tool.

Further, it is preferable to irradiate the laser from four sides of the bonding tool.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is applied to ball bonding in which gold is used as a wire material and a ball is formed at the tip of the wire will be described in detail with reference to the drawings.

First, an embodiment of the wire bonding apparatus of the present invention will be described with reference to FIGS.

FIG. 1 is a schematic diagram showing the construction of an embodiment of the wire bonding apparatus of the present invention. This figure particularly shows the bond head portion of a wire bonding apparatus. This apparatus includes a bonding tool 11, a bonding arm 13 that supports an ultrasonic horn and moves the bonding tool 11 up and down, a tool vertical drive device 14 that vertically moves the bonding tool 11, an ultrasonic wave generator 15, an ultrasonic horn 12, and a bonding wire. It is composed of a wire clamper 16 for gripping the laser and a laser irradiator 21. The position and angle of the laser irradiator 21 are controlled by the height information of the bonding tool 11, and the laser irradiator 21 is arranged so as to surround the bonding tool 11 in the direction in which the laser 31 irradiates the tip of the bonding tool 11. The number is composed of one or more.

2 and 3 are schematic views showing the operation of the embodiment of the wire bonding apparatus of the present invention. Figure 2
FIG. 4 is an enlarged view showing the bonding between the pad and the wire in the embodiment of the wire bonding apparatus of the present invention, and FIG.
It is an enlarged view showing joining of a wire and a lead.

First, as shown in FIG. 2, when the bonding tool 11 bonds the pad and the wire, the laser irradiator 21 irradiates the laser 31 to the bonding interface 2a between the pad 2 and the ball 1a to bond the bonding interface. By activating 2a, the bonding wire 1 and the pad 2 which is the bonding target are bonded.

Further, as shown in FIG. 3, when bonding the wire and the lead with the bonding tool 11, a laser 31 is irradiated from the laser irradiator 21 to the bonding interface 3a between the lead 3 and the ball 1a to bond the bonding interface. The bonding wire 1 and the lead 3 are joined by activating 3a.

Next, an embodiment of the wire bonding method of the present invention will be described with reference to FIGS. In the embodiment of the wire bonding method of the present invention,
Particularly, it includes a step of joining a pad, which is an electrode terminal on the chip, and a lead, which is an electrode of the lead frame, with a gold wire. 4 to 6 show a pad side joining method, and FIGS. 7 and 8 show a lead side joining method.

First, a method of connecting a pad and a wire in an embodiment of the wire bonding method of the present invention will be described with reference to FIGS. 4 is a flowchart showing a method of connecting the pad and the wire, and FIG. 5 is a perspective view showing an outline of the method of connecting the pad and the wire in FIGS. 4B and 4C. Is shown in FIG.
6 (b) and 6 (c) are enlarged views of FIG. 4 (b) and FIG. 4 (c), respectively.

First, with reference to FIG. 4, the pad side joining method in the wire bonding method of the present invention will be described in the order of steps. FIG. 4A shows a step of lowering the tool, FIG. 4B shows a step of detecting contact and starting bonding, FIG. 4C shows a bonding step, and FIG.
The process of raising the tool is shown in. First, in FIG. 4 (a), the ball 1a formed at the tip of the wire 1 descends together with the bonding tool 11, and the laser irradiator 21 is positioned and angled so that the laser 31 hits the lowest end of the ball 1a in conjunction with it. Adjust. Next, in FIG. 4B, when the contact of the ball 1 a with the bonding pad 2 is sensed, the laser 31 is directed toward the lowermost end of the ball 1 a, that is, the contact portion (bonding interface 2 a) between the ball 1 a and the bonding pad 2. Is irradiated. The bonding interface 2a is activated by the thermal energy generated by the irradiation of the laser 31, and the bonding interface 2a between the ball 1a and the bonding pad 2 is easily bonded. After that, in FIG. 4C, the ultrasonic wave is applied while applying a load to the bonding tool 11, so that the height of the bonding tool 11 is gradually reduced.
As a result, the ball 1a is crushed and the ball 1a
The bonding interface between the bonding pad 2 and the bonding pad 2 is shown in FIG.
Move as shown in (b). At this time, the position and the irradiation angle of the laser irradiator 21 are controlled in conjunction with the height of the bonding tool 11 so that the laser 31 is always irradiated onto the bonding boundary 2a between the ball 1a and the bonding pad 2. When the ball 1a has a sufficient deviation diameter for joining, the laser irradiation and the application of ultrasonic waves are stopped.
Raise the bonding tool 11 as shown in (d),
Joining is completed.

Next, referring to FIG. 5, (b) of FIG.
A method of joining the pad and the wire in the step (c) will be described. This method is characterized in that the bonding wire 1 and the pad 2 are bonded by irradiating the bonding interface 2a with the laser 31 from the laser irradiator 21 and activating the bonding interface 2a during bonding in the semiconductor assembly process. To do.

6 (b) and 6 (c) are enlarged views of the joints of FIGS. 4 (b) and 4 (c), respectively. In the embodiment of the wire bonding method of the present invention, the laser irradiator 2 is configured to irradiate the bonding interface 2a that moves during bonding with the laser 31 during bonding during the bonding process.
It is characterized by controlling the position and angle of 1.

Next, referring to FIG. 7, a lead side connecting method in the method of connecting the wire and the lead will be described in the order of steps. FIG. 7 is a diagram showing the operation of connecting the wire 1 and the lead 3 connected to the pad 2 in the order of steps. Figure 7
In (a), the wire 1 connected to the pad 2 passes through the bonding tool 11 and drops onto the lead 3 together with the wire 1, and in conjunction with this, the laser 31 is connected to the connection portion of the wire 1 with the lead 3. The laser irradiator 21 adjusts the position and angle so as to hit. When the contact of the wire 1 with the lead 3 is sensed in FIG. 7B, the laser 31 is emitted toward the contact portion (bonding interface 3 a) between the wire 1 and the lead 3. The bonding interface 3a is activated by the thermal energy generated by the irradiation of the laser 31, and the wire 1
Then, the bonding interface 3a with the lead 3 is easily bonded. After that, in FIG. 7C, by applying a load and ultrasonic waves to the bonding tool 11, the height of the bonding tool 11 is gradually reduced, and the wire 1 is crushed accordingly.
The bonding interface 3 a between the wire 1 and the lead 3 gradually moves from the center of the bonding tool 11. At this time, the position and irradiation angle of the laser irradiator 21 are adjusted so as to interlock with the height of the bonding tool 11, and the laser 31 is controlled so as to constantly irradiate the boundary between the wire 1 and the lead 3. When the wire 1 has a sufficient shape for bonding, the laser irradiation and the application of ultrasonic waves are stopped, the bonding tool 11 is raised as shown in FIG. 7 (d), and the wire 1 as shown in FIG. 7 (e). When the tail has become sufficiently long, the wire clamp is closed, the bonding tool 11 is lifted as it is, and the wire 1 is cut to complete the bonding. After the bonding is completed, the ball 1a for bonding on the pad 2 side is formed by electric spark or the like as shown in FIG. 7F, and the bonding cycle is completed.

Next, referring to FIG. 8, as shown in FIG.
A method of connecting the wire and the lead in the step (c) will be described. This method is characterized in that at the time of bonding in the semiconductor assembly process, the bonding wire 3 and the lead 3 are bonded by irradiating the bonding interface 3a with the laser 31 from the laser irradiator 21 and activating the bonding interface 3a. To do.

Next, FIG. 9 is a flow chart showing laser irradiation in the embodiment of the wire bonding apparatus of the present invention. As shown in FIG. 9, the laser Z control system includes position, velocity, and acceleration. These are processed by the laser control processing system, and the laser irradiator height Z, the laser irradiator angle θ,
Adjust the laser power.

Next, another embodiment of the present invention will be described.

The second embodiment of the bonding method of the present invention is an example applied to a thermocompression bonder which does not use ultrasonic waves, and operates in the same manner as the description of the operation described in the above embodiment. Connect by thermocompression without using sound waves. When the bonding interface is sufficiently activated by laser irradiation, bonding can be performed without using ultrasonic waves.

Further, the third embodiment of the present invention is an example applied to a wedge bonder. The wedge bonder has a function to rotate the device side because it cannot connect with a wire in only one predetermined direction. Therefore, in order to add the function of heating from below in order to use thermal energy in combination, the head itself, which has a complicated mechanism, has to be a rotary head type in which the movable table rotates together with the movable table. However, by applying the present invention, heating from above can be performed, and wedge bonding using thermal energy can be performed without using a rotary head having a complicated mechanism. As a result, it is possible to prevent the occurrence of defects such as Al peeling and V cracks by performing bonding with the ultrasonic power reduced.

[0034]

As described above, according to the bonding method of the present invention, the heat energy is more efficiently bonded to the bonding energy than the conventional method in which the laser is locally heated and the heater is heated from below the lead frame. As a result, it is possible to perform bonding without heating the Ag paste that joins the lead frame island portion and the chip.

Further, there is an effect that the power of ultrasonic waves can be lowered as compared with the conventional case to perform bonding.

Further, from the above, the damage to the pad (Al peeling, V crack), the loss of ultrasonic waves (when the joint is not fixed sufficiently), and other defective bonding (A peeling, E peeling). ), It is possible to suppress defects such as peeling of the mold after encapsulation due to oxidation of the lead frame.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a configuration of a bond head in an example of the present invention.

FIG. 2 is an enlarged view of a tool tip (at the time of pad side bonding) in the embodiment of the present invention.

FIG. 3 is an enlarged view of a tool tip (at the time of joining on the lead side) in the example of the present invention.

4A to 4D are cross-sectional views showing a pad-side connection method in the embodiment of the present invention in the order of steps (a) to (d).

FIG. 5 is a schematic view showing a pad side connection method of the present invention in the steps of (b) and (c) of FIG.

FIG. 6 is an enlarged cross-sectional view showing a pad-side connection method in the embodiment of the present invention. 6B and 6C are diagrams corresponding to FIGS. 4B and 4C, respectively.

FIG. 7 is a cross-sectional view showing a lead side connecting method in the embodiment of the present invention in the order of steps (a) to (f).

FIG. 8 is a perspective view showing a lead-side connection method of the present invention in steps (b) and (c) of FIG.

FIG. 9 is a flowchart showing laser irradiation control in the example of the present invention.

FIG. 10 is a diagram showing a pad side connection method in a conventional example.

FIG. 11 is an enlarged view of the tool tip in the conventional example (at the time of pad side bonding).

[Explanation of symbols]

1 wire 1a ball 2 Bonding pad 2a Ball-pad interface 3 leads 3a Wire / lead joint interface 4 chips 5 Ag paste 6 Lead frame island 11 Bonding tool 12 ultrasonic horn 13 Bonding arm 14 Tool vertical drive 15 Ultrasonic generator 16 wire clamper 21 Laser irradiator 31 laser light

Continuation of front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) H01L 21/60 301 B23K 1/005 B23K 26/00

Claims (6)

(57) [Claims] 1. A bonding tool used to bond a pad on a chip and a lead on a lead frame to a wire, and a laser for irradiating a bonding interface of the wire with a laser.
A wire irradiator for electrically connecting a pad on a chip and a lead on a lead frame with a wire, including a laser irradiator, even if the bonding interface moves during bonding.
A wire bonding apparatus comprising means for controlling the irradiation position and irradiation angle of the laser of the laser irradiation device so that the interface is locally heated. 2. The wire bonding apparatus according to claim 1, wherein the means for controlling the irradiation position and the irradiation angle is controlled by height information of the bonding tool. 3. The wire bonding apparatus according to claim 1, wherein the laser irradiator is arranged so as to surround the bonding tool. 4. A bonding tool used for bonding a wire on a pad on a chip and a lead on a lead frame, and a laser for irradiating a bonding interface of the wire with a laser.
In a wire bonding method in which a pad on a chip and a lead on a lead frame are electrically connected by a wire using a laser irradiator, even if the bonding interface moves during bonding,
A wire bonding method characterized in that the irradiation position and irradiation angle of the laser of the laser irradiation device are controlled so that the interface can be locally heated. 5. The wire bonding method according to claim 4, wherein the control is performed according to height information of the bonding tool. 6. The laser according to claim 4, wherein the laser is emitted from four sides of the bonding tool.
The wire bonding method described in.