JP3087890B2 - Bonding apparatus and 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 TAB (Tape Automated) used for mounting a semiconductor device.
The present invention relates to a bonding apparatus and a bonding method for bonding an inner lead of a bonding tape carrier to an electrode of a semiconductor chip.

[0002]

2. Description of the Related Art A bonding tool used in a conventional TAB mounting method and a bonding method using the same will be described with reference to the drawings. 5A and 5B show a film carrier type semiconductor device based on the TAB method, wherein FIG.
(B) is a sectional view.

As shown in FIGS. 5A and 5B, a film carrier tape used for mounting in a TAB system is an insulating base film 10 made of polyimide or the like.
After forming a sprocket hole 107 used for transport and positioning, and forming a square device hole 103 and an outer lead hole 109, which are openings for receiving the semiconductor chip 104, the base film 1
No. 01, a metal foil such as a copper foil is bonded to the surface of the lead 102 by photolithography.
Or by patterning a test pad 108 for electrical sorting. The lead 102 has an inner lead 102A protruding into the device hole 103 and an outer lead 102 that straddles the outer lead hole 109.
B, and a required portion of the surface is plated with metal such as gold, tin, or solder.

The outer lead holes 109 have a trapezoidal shape and are formed at four locations so as to surround the device holes 103.
A suspender 110 holding the lead 102 is provided between the device hole 103 and the device hole 103.

On the other hand, the semiconductor chip 104 mounted by this film carrier tape has a rectangular planar shape, and has a large number of electrodes on its main surface along each side. A pump 105 that is a metal protrusion is provided.

When bonding the leads 102 of the film carrier tape and the semiconductor chip 104 configured as described above, the corresponding bumps 105 of the semiconductor chip 104 are positioned immediately below the inner leads 102A, and the bonding is performed. ing. This bonding is performed by inner lead bonding (inner lead bonding).
d Bonding).

[0007] After the inner lead bonding, electrical screening is performed using the test pad 108. Thereafter, the base film 101 and the like are removed together with the test pad 108. The number of bumps 105 on each side is larger than that shown in the figure, and some leads 102 may be missing and arranged.

The above-mentioned inner lead bonding includes a method in which the inner leads 102A and the bumps 105 are joined together by a bonding tool (gang bonding method) and a method in which the inner leads 102A and the bumps 105 are joined one by one (single bonding). (Point bonding method). In the former method,
The size of the semiconductor chip 104 is increased and the lead 1
When the number 02 increases, it becomes difficult to maintain the parallelism between the bonding tool and the semiconductor chip 104. Further, in order to adjust the parallelism, each time the size of the semiconductor chip 104 changes, a long time setting and jig / tool (parts corresponding to the type) are performed.
Replacement is required, and the versatility required for high-mix low-volume production is poor. On the other hand, according to the latter method, since the inner leads 102A are securely bonded one by one with a bonding tool, fine adjustment as in the former is not necessary, and there is an opportunity to be adopted as the semiconductor chip 104 becomes larger. More and more.

FIGS. 6A and 6B show a single point bonding method of the inner lead, in which FIG. 6A is a sectional view and FIG. 6B is a perspective view. In the single point bonding method, as shown in FIGS.
Of the ultrasonic tool 114 and the vibration of the ultrasonic transducer 114 via the ultrasonic (US) transmitting means 112.
Then, the inner leads 102A are bonded one by one to the bumps 105 on the semiconductor chip 104 by the bonding tool 111.

However, forming the bumps 105 requires many man-hours such as a lithography step and a plating step, and the equipment for the steps is expensive. Therefore, the bonding cost of the TAB inner lead increases the mounting cost. There was a problem. Therefore, a direct single point bonding method has been proposed in which an aluminum electrode of a semiconductor chip and a TAB inner lead are directly bonded without using bumps (Japanese Patent Application Laid-Open No. 4-355940).

FIG. 7 is a perspective view showing a direct single point bonding method. FIG. 8A shows a direct single point bonding method in a case where the direction of the ultrasonic vibration 11 of the bonding tool 111A is orthogonal to the longitudinal direction of the inner lead 102A. FIG. 8B is a diagram illustrating a state of bonding, and FIG. 8B is a diagram illustrating a state of direct single-point bonding when the direction of the ultrasonic vibration 11 of the bonding tool 111A is parallel to the longitudinal direction of the inner lead 102A. . Here, the configuration of the bonding apparatus for executing the direct single-point bonding method is basically the same as that shown in FIG.

As shown in FIGS. 7 and 8, in the direct single point bonding method, first, the inner lead 102A is aligned with the aluminum electrode 12 of the semiconductor chip 104, and then the bonding tool 1
11A is pushed into the inner lead 102A. Thereby, the bonding tool 11 is attached to the inner lead 102A.
Simultaneously with the formation of the depression 15 to which the tip shape of 1A is transferred, the projection 16 is formed on the back surface of the inner lead 102A. Further, the tip of the bonding tool 111A is brought into close contact with the inner lead 102A, and at the same time, the inner lead 102A is pressed against the aluminum electrode 12. Next, while maintaining such a contact state, the bonding tool 1
11A, an ultrasonic vibration 11 is applied to the inner lead 10
The 2A projection 16 and the aluminum electrode 12 are joined. At this time, the semiconductor chip is placed on a heating stage (heating means 11 in FIG.
5) is maintained at about 280 ° C.

[0013]

In order to obtain a stable bonding strength by the direct single point bonding method using thermocompression combined with ultrasonic waves as described above, a natural oxide film of aluminum existing on the aluminum electrode surface is formed by ultrasonic vibration. The condition is that the layer is sufficiently broken and a sufficient alloy layer of gold on the inner lead surface and aluminum on the aluminum electrode surface is formed by the heat energy from the heating stage.

As shown in FIG. 5, the leads extend from four directions with respect to the device holes of the semiconductor chip, while the ultrasonic transmission means 112 is oriented in a certain direction as shown in FIG. . Therefore, the square semiconductor chip 1
Assuming that the four sides of the semiconductor chip 104 are referred to as first to fourth sides as shown in FIG. 9, the inner leads 10 provided corresponding to the first and third sides of the semiconductor chip 104 opposed to each other.
Assuming that the longitudinal direction of 2A is parallel to the direction of the ultrasonic vibration 11 of the bonding tool 111A as shown in FIG. 8B, the second direction of the semiconductor chip 104 as shown in FIG.
Inner lead 1 provided corresponding to the side and the fourth side
02A in the longitudinal direction of the bonding tool 111A
The directions of the ultrasonic vibration 11 are orthogonal.

As shown in FIG. 8B, the ultrasonic vibration 11
The inner lead 102A parallel to the direction of the inner lead 10A is close to the held state.
Stable ultrasonic energy transmission is possible to the joint interface between 2A and the aluminum electrode 12. However, FIG.
As shown in (a), when the ultrasonic vibration 11 is applied in a direction orthogonal to the longitudinal direction of the inner lead 102A, the inner lead 102A is close to a free state with respect to the vibration direction of the bonding tool 111A. As a result, it is blurred and energy transmission becomes unstable. Therefore, the energy of the ultrasonic vibration 11 is transferred to the inner lead 10.
The aluminum oxide film could not be sufficiently transmitted to the bonding interface between 2A and the aluminum electrode 12, and the aluminum oxide film could not be sufficiently destroyed. Therefore, there is a problem that the bonding strength between the inner leads 102A on the second and fourth sides of the semiconductor chip 104 and the aluminum electrode 12 is lower than that on the first and third sides.

Further, when the ultrasonic output is increased to reduce the variation in the bonding strength, the leads are repelled and cannot be bonded, or the deformation of the lower surface of the leads becomes large, stress is concentrated and damages such as cracks are caused. This may cause the inner leads to be misaligned, and may cause contact with the adjacent inner leads or aluminum electrodes. This has been an obstacle to narrowing the pitch of the TAB mounting method.

An object of the present invention is to solve the above-mentioned problems of the conventional example, and an object of the present invention is to make it possible to perform stable bonding to inner leads in both directions, and to realize TAB inner leads. It is an object of the present invention to provide a bonding apparatus and a bonding method capable of reducing a pitch.

[0018]

SUMMARY OF THE INVENTION An object of the present invention is to provide a bonding tool for directly bonding an electrode of a semiconductor chip and an inner lead of a TAB tape by a single point bonding method. This can be solved by forming the spherical surface so that the radius of curvature in a cross section parallel to the direction of ultrasonic vibration is different from the radius of curvature in a cross section orthogonal to the direction of the ultrasonic vibration. Preferably, the spherical shape of the tool tip has a radius of curvature in a cross section parallel to the direction of ultrasonic vibration larger than a radius of curvature in a cross section orthogonal to the direction of the ultrasonic vibration.

[Operation] In the bonding tool according to the present invention, the spherical shape of the tip portion is set so that the radius of curvature in the direction parallel to the ultrasonic vibration direction is larger than that in the direction orthogonal to the ultrasonic vibration. Even when the ultrasonic vibration is applied in a direction perpendicular to the longitudinal direction of the inner lead, the lead is close to a held state, and the lead is not blurred. Therefore, stable transmission of ultrasonic energy is possible even for the inner lead whose longitudinal direction is orthogonal to the direction of ultrasonic vibration.

Therefore, it is not necessary to increase the ultrasonic output with respect to the inner lead whose longitudinal direction is perpendicular to the direction of the ultrasonic vibration, so that the lead is repelled and cannot be joined, or the deformation of the lower surface of the lead is large. As a result, stress concentrates and damages such as cracks occur, and the displacement of the inner leads increases, so that there is no fear of contact with the adjacent inner leads or aluminum electrodes. On the other hand, by maintaining a small radius of curvature in a cross section perpendicular to the ultrasonic vibration direction, a convex portion can be effectively formed on the back surface of the inner lead, thereby destroying the oxide film on the electrode surface. Highly reliable bonding can be performed in both directions.

[0021]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a sectional view showing the configuration of a bonding apparatus according to the present invention. here,
6 are denoted by the same reference numerals as those used in FIG.

As shown in FIG. 1, in the bonding apparatus according to the present invention, an ultrasonic transmission means 112 is fixed to an ultrasonic vibrator 114. The bonding tool 11 is attached downward at the longitudinal end of the ultrasonic transmission means 112.
1B is attached. Also, by the load means 113,
The ultrasonic transmission unit 112 and the bonding tool 111B attached thereto are configured to be able to apply a downward load F thereto. Ultrasonic transducer 114
Vibrates in the longitudinal direction of the ultrasonic transmission means 112. The ultrasonic vibration 11 is transmitted in the longitudinal direction of the ultrasonic transmission means 112 and gives the ultrasonic vibration 11 in a direction orthogonal to the longitudinal direction to the bonding tool 111B attached to the tip end. Further, a heating unit 115 for heating the semiconductor chip 104 is provided. The configuration of this bonding apparatus is the same as the conventional bonding apparatus shown in FIG. 6 except for the structure of the bonding tool 111B.

FIG. 2 shows the bonding tool 1 shown in FIG.
11B shows a configuration example of 11B. FIG. 2A is a perspective view of the entirety, and FIGS. 2B and 2C are enlarged views of the circles in FIG. Here, (b) is a side view as viewed from a direction orthogonal to the direction of the ultrasonic vibration 11, and (c) is a side view as viewed from a direction parallel to the direction of the ultrasonic vibration 11.

As shown in FIG. 2, in the bonding tool 111B according to the present invention, the tip thereof is
The radius of curvature R1 in the cross section parallel to the direction 1 is larger than the radius of curvature R2 in the cross section orthogonal to the direction of ultrasonic vibration. By doing so, during bonding,
Even when ultrasonic vibration is applied in a direction perpendicular to the longitudinal direction of the inner lead, the lead does not blur.
As a result, stable transmission of ultrasonic energy is possible for the inner lead whose longitudinal direction is orthogonal to the direction of ultrasonic vibration, and the inner lead is perpendicular to the direction of ultrasonic vibration. Since it is no longer necessary to increase the ultrasonic output, the leads are repelled and cannot be joined, the deformation of the lower surface of the leads increases, stress concentrates and damages such as cracks occur, and the displacement of the inner leads increases, There is no danger of contact with the adjacent inner lead or aluminum electrode.

FIGS. 3 to 5 show a single point inner lead bonding method in the TAB method mounting according to the present invention. Here, FIG. 3 is a perspective view showing a bonding state, and FIG. 4A shows a bonding method on the second side and the fourth side of the semiconductor chip in which the ultrasonic vibration direction is orthogonal to the longitudinal direction of the inner lead. FIG. 4B is a cross-sectional view showing a bonding method at the first side and the third side of the semiconductor chip in which the vibration direction of the ultrasonic wave is parallel to the longitudinal direction of the inner lead.

As shown in FIGS. 3 and 4, first, the vibration direction of the ultrasonic wave is perpendicular to the longitudinal direction of the inner lead.
After the positioning of the bonding tool 111B with the inner lead 102A (see FIG. 9), a load F is applied to the bonding tool 111B by the load means 113.
1B is pressed against the inner lead 102A. At this time, at the same time when the recess 15 in which the tip shape of the bonding tool 111B is transferred is formed in the inner lead 102A,
The protrusion 16 is formed on the back surface of the inner lead 102A.

Next, the ultrasonic vibration 11 is applied to the bonding tool 111B to join the inner lead 102A and the aluminum electrode 12. Subsequently, inner lead bonding is sequentially performed on the aluminum electrode on the second side by the same method. At the time of joining, the semiconductor chip 104 is heated by the heating means 115 in a manner similar to the conventional method shown in FIGS.
Heat to 0 ° C. and hold.

After the bonding of the electrodes on the second side of the semiconductor chip is completed, subsequently, the ultrasonic vibration is performed on the fourth side, which is a direction orthogonal to the longitudinal direction of the inner lead (FIG. 4). (A)) and then
Bonding is sequentially performed on the first side of the semiconductor chip 104 in which the ultrasonic vibration direction is parallel to the longitudinal direction of the inner lead, and on the third side which is the same direction as this (FIG. 4B). As described above, it is more preferable that the TAB tape is thermally expanded due to the heating, and bonding is performed in a direction in which bonding becomes difficult when the lead is displaced due to the thermal expansion.

After the inner lead bonding for all the aluminum electrodes of the semiconductor chip was completed in this way, the bonding strength was measured, and the occurrence of cracks under the aluminum electrode 12 was observed. As a result, the ultrasonic vibration 1
The average pull strength of the connection portion where the direction of 1 acted perpendicularly and parallel to the longitudinal direction of the inner lead 102A was not less than a certain value, and it was possible to join with sufficient strength for practical use. Moreover, it was confirmed that no crack was generated under the aluminum electrode surface 12.

[0030]

As described above in detail, in the method and the apparatus for bonding the TAB inner lead using the bonding tool of the present invention, the roundness of the tip of the tool varies depending on the application direction of the ultrasonic wave. The natural oxide film can be sufficiently destroyed irrespective of the longitudinal direction of the inner lead, and the displacement of the inner lead can be prevented, so that the pitch can be reduced. In addition, the aluminum electrode of the semiconductor chip and the inner lead can be joined with a sufficient degree of heat without causing damage such as cracks under the aluminum electrode of the semiconductor chip.
That is, according to the present invention, highly reliable bonding can be obtained, and the pitch of the inner leads can be reduced.

[Brief description of the drawings]

FIG. 1 is a diagram showing an example of a bonding apparatus according to the present invention.

FIG. 2 is a view showing an example of a bonding tool in FIG. 1;

FIG. 3 is a perspective view showing a bonding method using the bonding tool of FIG. 2;

FIG. 4 is a view showing a state of a bonding method using the bonding tool of FIG. 2;

FIG. 5 is a diagram showing a film carrier type semiconductor device using a TAB method.

FIG. 6 is a diagram showing a single-point bonding method for inner leads.

FIG. 7 is a diagram showing a conventional direct single point bonding method.

FIG. 8 is a diagram showing a state of conventional direct single point bonding.

FIG. 9 is a diagram showing a relationship between names of four sides of a semiconductor chip and inner leads.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Ultrasonic vibration 12 Aluminum electrode 15 Depression 16 Convex part 101 Base film 102 Lead 102A Inner lead 102B Outer lead 103 Device hole 104 Semiconductor chip (semiconductor element) 105 Bump 111 Bonding tool 111A Conventional bonding tool 111B Bonding tool according to the present invention 112 Ultrasonic transmission means 113 Loading means 114 Ultrasonic transducer 115 Heating means

Claims (6)

(57) [Claims] An electrode pad of a semiconductor chip and an inner lead of a film carrier tape are connected by a single point.
A bonding apparatus for directly bonding by a bonding method, wherein (1) a tip portion has a spherical shape, and a radius of curvature of the tip portion is:
(2) means for pressing the bonding tool against the inner lead; (3) means for pressing the bonding tool against the inner lead; And a means for applying sonic vibration. 2. The method according to claim 1, wherein a radius of curvature at a cross section parallel to a vibration direction of the ultrasonic vibration is larger than a radius of curvature at a cross section orthogonal to the vibration direction of the ultrasonic vibration at a tip portion of the bonding tool. The bonding apparatus according to claim 1, wherein 3. A single-point electrode pad of a semiconductor chip and an inner lead of a film carrier tape.
A bonding method of directly bonding by a bonding method, wherein a tip portion in contact with the inner lead has a spherical shape,
In addition, a bonding tool having a different radius of curvature at the tip portion between a cross section parallel to the vibration direction of the ultrasonic vibration and a cross section orthogonal thereto is pressed against the inner lead to form a depression in the inner lead. Thereafter, ultrasonic waves are applied to the bonding tool. 4. A tip portion of the bonding tool, wherein a radius of curvature in a cross section parallel to the vibration direction of the ultrasonic vibration is larger than a radius of curvature in a cross section orthogonal to the vibration direction of the ultrasonic vibration. The bonding method according to claim 3, wherein 5. Joining two sides of the four sides of the semiconductor chip in a direction in which the vibration direction of the ultrasonic vibration is orthogonal to a longitudinal direction of the inner lead, and then joining two sides in a parallel direction. 5. The bonding method according to claim 4, wherein: 6. The bonding method according to claim 4, wherein the electrode pads of the semiconductor chip are formed of aluminum or an alloy thereof.