JPH07201915A - Tab lead bonding method and bonding device - Google Patents

Abstract

PURPOSE:To achieve stable bonding between a TAB lead and an electrode of a semiconductor element or the wiring electrode of a circuit board, and to narrow a pitch. CONSTITUTION:A lamp housing 2 with a lamp 1 mounted on is fixed by a set screw in an arm fixed in the horn up and down moving mechanism 22 of an XY stage 21 bar. A supersonic wave horn 25 with a bonding tool fixed on its tip is moved up and down by the voice coil of the horn up and down moving mechanism. A semiconductor element is adsorbed by air in the heating stage 27 of an XYZtheta stage 26 bar. A TAB tape 12 is fixed by a tape stage 28 and a tape clamper 29.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a TAB (Tape Automated Bo) used for mounting a semiconductor element.
The present invention relates to a joining method and apparatus for joining the lead of a tape carrier for recording and the electrode of the semiconductor element.

[0002]

2. Description of the Related Art FIG. 5 shows a conventional single bonding method in which inner leads of a TAB tape and electrodes of a semiconductor element are sequentially bonded. In the figure, 13 is an inner lead, 16 is an Al electrode, 18 is a passivation film,
Reference numeral 14 is a semiconductor element, 31 is a flat bonding tool, and 32 is a bump. As shown in FIG. 5, the Al electrode 16 of the semiconductor element 15 or the inner lead 13 of the TAB is formed.
The Al electrode 16 and the Al electrode 16 are bonded to each other via the bump 32 by the bonding tool 31 by a method using both ultrasonic waves and heat. Generally, in order to form bumps, complicated steps such as lithography are required, and moreover expensive equipment is required. Therefore, TAB that requires bump formation
The inner lead joining method has a problem that the mounting cost is increased. Therefore, a direct single bonding method has been proposed in which bumps are unnecessary and the Al electrode of the semiconductor element and the TAB inner lead can be directly bonded (Japanese Patent Laid-Open No. 3-85895). FIG. 4 shows a conventional direct single bonding method. In the figure, 33 indicates ultrasonic vibration, 13 is an inner lead, 19 is a depression, 20 is a convex portion, 16 is an Al electrode, 18 is a passivation film, 15 is a semiconductor element, 11 is a bonding tool for direct bonding, It has a spherical tip.

First, as shown in FIG. 4, after the inner lead 13 and the Al electrode 16 of the semiconductor element 15 are aligned with each other, the bonding tool 11 is pushed into the inner lead 13 so that the inner lead 13 is bonded to the bonding tool 11. A protrusion 20 is formed on the back surface of the inner lead 13 at the same time as the recess 19 to which the tip shape of is transferred. Further, the tip of the bonding tool 11 and the inner lead 1
3 is closely attached, and at the same time, the inner lead 13 is connected to the Al electrode 1
Pressurize to 6. Next, while maintaining such a contact state, ultrasonic vibration 33 is applied to the bonding tool 11 to bond the convex portion 20 of the inner lead 13 and the Al electrode 16. At this time, the semiconductor element is heated by the heating stage to 2
It is heated to about 50 ° C.

[0004]

In order to obtain a stable bonding strength by the direct single bonding method by ultrasonic pressure bonding, ultrasonic vibration for destroying the oxide film of the Al electrode and mutual diffusion of the bonding metal are performed. It is important to supply this heat to the joint. Furthermore, the heat softens the inner leads (made of Cu material and is Au-plated) to facilitate plastic deformation and has an auxiliary role of breaking the oxide film of the Al electrode. However, the Cu material used for the TAB tape for narrow pitch has Sn and Co added to increase the rigidity in order to prevent bending of the inner leads during manufacturing.
This additive increases the softening temperature of Cu. Such an inner lead having a high softening temperature is difficult to join because the inner lead does not soften at the conventional joining temperature. When the temperature of the heating stage is raised to soften the inner leads, the polyimide film, which is the base material of the TAB tape, expands due to heat, which causes a pitch deviation of the inner leads, which makes it difficult to reduce the pitch. Also, in the connection between the circuit board and the outer lead of the TAB tape, the pitch deviation due to the same cause is a problem.

Furthermore, since pressure is applied to the semiconductor element through the hard inner leads during joining, Si cracks are generated due to an increase in chip damage, resulting in a problem of reduced reliability.

The object of the present invention is to solve these problems.
TAB that realizes highly reliable bonding and enables narrow pitch
It is to provide a method for joining leads.

[0007]

SUMMARY OF THE INVENTION The present invention provides a bonding method for directly bonding electrodes of a semiconductor element and leads of a TAB tape directly at a single point by heating a bonding portion of the leads with the electrode with a light beam, It is characterized by heating to the softening temperature of copper, which is a constituent material of the lead.

A horn moving mechanism for directly bonding the electrodes of the semiconductor element and the leads of the TAB tape, for moving an ultrasonic horn holding a bonding tool at the tip end vertically and horizontally, and a heating stage for heating the semiconductor element. In the bonding apparatus described above, the light beam heating device is fixed on the stage of the horn moving mechanism.

[0009]

In the method of joining TAB leads of the present invention, the copper material (leads) is softened by heating and annealing the copper, which is a constituent material of the leads, with the light beam to the softening temperature, so that the Au of the joined portion is Au.
And facilitates plastic deformation of Al. Due to this plastic deformation,
Stable bonding strength can be obtained by destroying the electrode oxide film and forming an Au / Al alloy layer on the entire bonding surface.

Further, since the leads are softened and the mechanical stress applied to the LSI chip is reduced, Si cracks can be prevented, and highly reliable bonding can be performed. Further, the local heating of the leads eliminates the influence of the elongation of the polyimide film, which is the base material of the TAB tape, due to the heat, so that the pitch deviation of the leads can be prevented and the pitch can be narrowed.

Further, in the TAB lead bonding apparatus of the present invention, the light beam heating apparatus is fixed on the XY stage of the horn moving mechanism to move in synchronization with the bonding tool fixed to the tip of the horn. At this time, by adjusting the irradiation position of the light beam to the bonding position of the lead in advance, the bonding position of the lead can be sequentially irradiated with the light beam. In this way, the light beam and the lead joint can be easily aligned with each other without providing a special drive mechanism in the light beam heating device.

[0012]

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

FIG. 1 is a vertical sectional view showing a joining method according to an embodiment of the present invention. FIG. 2 is a conceptual diagram showing the bonding apparatus of the present invention. FIG. 3 shows a joining method of the present invention, and is a vertical cross-sectional view of a joining portion. In the figure, 1 is a lamp, 2 is a lamp house, 3 is a reflection mirror, 4 is a light beam, 5 is a beam irradiation unit, 11 is a bonding tool, 1
2 is a TAB tape, 13 is an inner lead, 14 is a base film, 15 is a semiconductor element, 16 is an Al electrode, 17
Is an opening, 18 is a passivation film, 19 is a depression, 2
0 is a convex portion, 21 is an XY stage, 22 is a horn vertical movement mechanism, 23 is an arm, 24 is a set screw, 25 is an ultrasonic horn, 26 is an XYZθ stage, 27 is a heating stage,
28 is a tape stage, 29 is a tape clamper, and 33 is ultrasonic vibration. The TAB tape 12 is composed of an inner lead 13 and a base film 14 made of polyimide. A Cu lead having an inner lead width of 80 μm, an inner lead pitch of 180 μm and an inner lead thickness of 35 μm is plated with Au of 0.6 μm. The applied one was used.

The lamp 1 is a xenon short arc lamp of 150 W and is fixed and electrically connected by a socket (not shown) provided in the lamp house 2. In the lamp house 2, the reflection mirror 3 is formed by Au plating in order to focus the light beam 4 of the lamp 1 on the beam irradiation portion 5 of the inner lead 13. The semiconductor element 15 has electrodes formed on all four sides, and the opening 17 of the electrode 16 is formed to be larger than the width of the inner lead 11. The inner lead 13 of the TAB tape 12 is aligned above the Al electrode 16 with a gap of 100 μm, for example.
The TAB tape 12 used at this time had an inner lead width of 80 μm and an inner lead pitch of 180 μm.
0.6μ for Cu lead with inner lead thickness of 30μm
The connection was performed using a TAB tape plated with Au of m. The semiconductor element 15 has electrodes formed on all four sides, and the opening 17 of the electrode is formed to have a width larger than the width of the inner lead.

The bonding tool 11 has a conical tip, and a spherical protrusion having a radius smaller than the width of the inner lead 13 and having a radius R1 of 50 μm is provided at the tip of the cone.

In FIG. 2, a lamp house 2 on which the lamp 1 is mounted is fixed to an arm 23 fixed to a horn vertical moving mechanism 22 on an XY stage 21 with a set screw 24. The ultrasonic horn 25 having the bonding tool 11 fixed at its tip is moved up and down by a voice coil (not shown) of the horn up-and-down moving mechanism 22. The semiconductor element 14 is air-adsorbed on the heating stage 27 on the XYZθ stage 26. The TAB tape 12 is
It is fixed by a tape stage 28 and a tape clamper 29.

In the joining method of this embodiment, first of all,
After aligning the Al electrode 12 of the semiconductor element 14 and the inner lead 11 with the XYZθ stage 26 as shown in, the angle of the lamp house 2 is adjusted so that the light beam 4 is condensed near the junction, Fix with set screw 24.
The converging diameter of the light beam 4 at this time is adjusted to, for example, 3 to 5 mm so that the inner lead 11 is irradiated with several tens of beams. The beam irradiation unit 5 on the inner lead 13
Is the ultrasonic horn 25 because the ultrasonic horn 25 and the lamp house 2 are on the XY stage 21 via the arm 23.
XY of the bonding tool 11 fixed to the tip of the
It will be the same position in the plane. At this time, by adjusting the irradiation position of the light beam to the bonding position of the lead in advance, the bonding position of the lead can be sequentially irradiated with the light beam.

Next, as shown in FIG. 3, the inner lead 1
Bonding tool 11 to beam irradiator 5 of No. 3 under load F
= 100 gf, and the bonding tool 11 was pressed against the inner lead 13. At this time, the inner lead 1
A protrusion 20 is formed on the back surface of the inner lead 13 at the same time as the dent 19 in which the tip shape of the bonding tool 11 is transferred to 3. Next, ultrasonic vibration 33 was applied to the bonding tool 11 to bond the inner lead 13 and the Al electrode 16. At the time of bonding, although not shown in the drawing, the semiconductor element 14 was heated and held at 280 ° C. by a heating device. The temperature of the beam irradiation unit can be adjusted by changing the voltage applied to the lamp 1 and the focal length of the light beam 4. The temperature of the beam irradiation part 5 of this example was 500 ° C. when the applied voltage was 15 V and the focal length was 20 mm (spot diameter of about 5 mm). (Temperature measurement was performed with an infrared thermometer.

After repeating the above operation for all the inner leads 13, the bonding strength was measured and the presence or absence of cracks on the electrode surface 12 was observed. As a result, the average pull strength was 60 gf or more, and stable bonding was possible with practically sufficient strength. Moreover, it was confirmed that no cracks were generated on the electrode surface 16. Furthermore, as a result of similar joining using a TAB tape having a high softening temperature of the Cu material used for the inner lead, for example, a narrow pitch of 500 ° C., the average pull strength is 30 gf or more, which is practically sufficient. A strong and stable joining became possible.
Moreover, it was confirmed that no cracks were generated on the electrode surface 16. The TAB tape used at this time had an inner lead width of 40 μm, an inner lead pitch of 80 μm,
0.6μ for Cu lead with inner lead thickness of 20μm
The connection was performed using a TAB tape plated with Au of m. The semiconductor element used had electrodes formed on all four sides, and the openings of the electrodes were formed to be larger than the width of the inner leads. As the bonding tool 11, a bonding tool having the same shape as that shown in FIG. 1 is used,
For example, a spherical protrusion having a radius of 30 μm is provided.

Next, another embodiment of the present invention will be described. In the present embodiment, the inner lead 13 is previously connected to the light beam 4
The inner lead 13 is softened by heating the substrate and annealing the beam irradiation portion 5. In the beam irradiation method of this embodiment, the focal length is set to 40 mm and the spot diameter is set to about 15 in order to irradiate the beam to all the inner leads 13.
mm. At this time, the temperature of the beam irradiation unit 5 (on the inner lead 13) is 50 V when the applied voltage is 25 V and the irradiation is for 5 seconds.
It was 0 ° C. (temperature measurement was performed with an infrared thermometer).

The TAB tape (softening temperature of Cu material: 500 ° C.) used at this time had an inner lead width of 40 μm.
m, the inner lead pitch was 80 μm, the inner lead thickness was 20 μm, and the connection was performed using a narrow-pitch TAB tape in which a Cu lead of 0.6 μm was plated with Au. The semiconductor element used had electrodes formed on all four sides, and the openings of the electrodes were formed to be larger than the width of the inner leads. As the bonding tool 11, a bonding tool having the same shape as that shown in FIG. 1 is used, and for example, a spherical projection having a radius of 30 μm is provided.

Next, as shown in FIG. 3, the bonding tool 11 was applied with a load F = 100 gf to press the bonding tool 11 against the inner leads 13. At this time, the protrusions 20 are formed on the back surface of the inner leads 13 at the same time as the depressions 19 in which the tip shape of the bonding tool 11 is transferred to the inner leads 13. Next, ultrasonic vibration 33 was applied to the bonding tool 11 to bond the inner lead 13 and the Al electrode 16. At the time of bonding, although not shown in the drawing, the semiconductor element 14 was heated and held at 280 ° C. by a heating device.

After repeating the above operation for all the inner leads 13, the bonding strength was measured and the presence or absence of cracks on the electrode surface 12 was observed. As a result, the average pull strength was 30 gf or more, and stable bonding was possible with practically sufficient strength. Moreover, it was confirmed that no cracks were generated on the electrode surface 16.

Further, as another embodiment, although not shown, the same effect can be obtained by irradiating the bonding tool with a light beam and indirectly supplying the heat of the heated bonding tool to the inner lead. It was confirmed.

In this embodiment, the description has been made only for the inner leads, but the same can be said for the joining of the outer leads.

[0026]

As described above, in the method of joining TAB leads according to the present invention, the light beam is used as auxiliary heat at the time of joining to soften the lead material so that Au and Al at the joining portion are softened.
Plastic deformation, oxide film destruction, and alloy layer formation can be facilitated, and stable bonding strength can be obtained. Further, the softening of the leads reduces mechanical stress, prevents Si cracks, and enables highly reliable bonding. Further, there is an effect that the local heating of the leads eliminates the influence of the elongation of the TAB tape due to the heat, the pitch deviation of the leads can be prevented, and the TAB tape having a narrow pitch can be mounted.

Further, with the construction of the TAB lead joining apparatus of the present invention, there is an effect that the light beam and the lead joining portion can be easily aligned without providing a special driving mechanism in the light beam heating apparatus. is there.

[Brief description of drawings]

FIG. 1 is a vertical sectional view showing a joining method according to an embodiment of the present invention.

FIG. 2 is a conceptual diagram showing a bonding apparatus of the present invention.

FIG. 3 is a vertical cross-sectional view of a joining portion, showing the joining method of the present invention.

FIG. 4 is a vertical cross-sectional view of a joining portion showing a conventional joining method.

FIG. 5 is a cross-sectional view showing a conventional TAB inner lead bonding method using bumps.

[Explanation of symbols]

 1 Lamp 2 Lamp House 3 Reflection Mirror 4 Light Beam 5 Beam Irradiation Section 11 Bonding Tool 12 TAB Tape 13 Inner Lead 14 Base Film 15 Semiconductor Element 16 Al Electrode 17 Opening 18 Passivation Film 19 Recess 20 Convex 21 XY Stage 22 Horn Top and Bottom Moving mechanism 23 Arm 24 Set screw 25 Ultrasonic horn 26 XYZθ stage 27 Heating stage 28 Tape stage 29 Tape clamper 31 Bonding tool 32 Bump 33 Ultrasonic vibration

Claims (2)

[Claims] 1. A bonding method for directly bonding electrodes of a semiconductor element and leads of a TAB tape directly at a single point, wherein a bonding portion of the leads with the electrodes is heated by a light beam to soften the components of the leads. A joining method characterized by heating up to. 2. A horn moving mechanism for moving an ultrasonic horn up and down and left and right holding a bonding tool for directly bonding an electrode of a semiconductor element and a lead of a TAB tape at a tip portion, and a heating stage for heating the semiconductor element. In the bonding device provided, a light beam heating device is fixed on the stage of the horn moving mechanism.