JPH11102933A - Bonding method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a bonding method between a bump and connection electrode so as to improve bonding strength and productivity. SOLUTION: This method makes bonding bonds in plural steps, achieved by increasing both a load applied and an ultrasonic output. Also, the first step bonding, which is heavier than a load just required for leveling a bump height, is applied to contribute to a solid diffused junction between a bump 14 and electrodes 11a and 12a. This bonding creates junction strength larger than from prior methods and improves electronic device reliability.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing an electronic device in which electronic components such as surface acoustic wave devices and semiconductor devices are mounted on a substrate, and more particularly to an electronic device in which chip-type electronic components are mounted on a substrate by a flip-chip method. And a method for producing the same.

[0002]

2. Description of the Related Art A flip-chip method is one of the techniques for mounting electronic components having various chip shapes such as semiconductor elements on a substrate, a package, or the like. This is a mounting method in which connection terminals provided on an electronic component and connection terminals provided on a substrate or the like are connected by conductive bumps.

Conventionally, electronic components such as surface acoustic wave devices (SAW devices) such as surface acoustic wave filters and surface acoustic wave resonators have been mainly mounted by wire bonding. A flip-chip method using pressing has been introduced. For example, a “flip-chip type SAW filter in the GHz band” (IEICE Technical Report, published on May 7, 1995 by the Institute of Electronics, Information and Communication Engineers) includes a flip-chip type SA using face-down bonding.
A technique relating to W devices is described. here,
It describes effective conditions of ultrasonic waves and loads when performing face-down bonding. According to this method, a method of performing face-down bonding twice for one chip is used, and the first time, flattening of bumps (level adjustment) using weak ultrasonic waves with a constant load is performed, and the second time. In this method, the bumps and the connection terminals are joined by using the same constant load as the first time and using ultrasonic waves stronger than the first time. According to this method, face down bonding with a shear strength of about 40 gf / bump is possible.

[0004] The shear strength of the bump connection varies in various ways depending on the application and use conditions of the semiconductor device and the electronic device equipped with the surface acoustic wave device. The bonding strength obtained by the above-described method is considered to be a sufficient shear strength when sufficient bonding strength is not required and sufficient bonding reliability is not required.

However, the use conditions are severe,
When a high degree of reliability is required, it is necessary to secure a larger bonding strength. For example, when the difference between the coefficient of thermal expansion of a chip such as a semiconductor element or a surface acoustic wave element and the substrate on which the chip is mounted is large, the difference may be caused by a manufacturing process or a thermal load applied by an actual use environment. As a result, there is a high possibility that a connection failure such as bump peeling will occur. Also, when a chip that is face-down bonded on a substrate is sealed with a resin such as a mold resin,
That is, even when the curing shrinkage stress or the thermal expansion stress of the sealing resin directly acts on the chip, the above-mentioned shear strength is insufficient.

[0006] In addition, since such electronic components are often mounted in a large amount, how to reduce the cost and the tact time required for mounting is a major issue in improving productivity. Thus, there is a need to establish a technique for mounting electronic components with high productivity while securing sufficient bonding strength.

[0007]

SUMMARY OF THE INVENTION The present invention has been made to solve such a problem. That is, an object of the present invention is to provide a method for manufacturing a highly reliable electronic device which can increase the shear strength of bump connection. It is another object of the present invention to provide a method of manufacturing an electronic device that can improve connection reliability and improve productivity. Another object of the present invention is to provide a method of manufacturing an electronic device capable of improving the bonding strength between an electronic component and a substrate and reducing the contact resistance.

[0008]

In order to solve such a problem, the present invention employs the following configuration.

The present invention relates to a bonding method for bonding a bump provided on a first electrode and a second electrode, wherein the first electrode and the second electrode are connected to the bump. Pressing with a second load greater than the first load required for leveling at a height, and applying ultrasonic waves at a first output to join the bump and the second electrode. I do. The ratio between the first output and the second load may be adjusted to be greater than about 0.001 W / gf per bump.

In a bonding method according to the present invention, in the bonding method for bonding a bump disposed on a first electrode and a second electrode, the first electrode and the second electrode may be bonded to the bump. And a second load larger than the first load required for leveling at the same height, and applying an ultrasonic wave at a first output to join the bump and the second electrode.
And pressing the first electrode and the second electrode with a third load greater than the second load, and pressing the first electrode and the second electrode with a second output greater than the first output. A second connection step of applying a sound wave to join the conductive bump and the second connection terminal.

The ratio between the first output and the second load and the ratio between the second output and the third load are set to be greater than about 0.001 W / gf per bump. It may be adjusted. Further, the second joining step may be performed in multiple stages while increasing the second output and the third load.

That is, according to the bonding method of the present invention, when electronic components such as surface acoustic wave devices and semiconductor devices are mounted on a host side (simply called a substrate) such as a package substrate and a mother substrate by so-called face-down bonding, the heating is performed. ,
The solid-phase diffusion connection between the bump and the electrode (connection terminal) is performed by bonding in a plurality of stages in which pressing and application of ultrasonic waves are combined. Ultrasonic waves are applied from the first stage while applying a load larger than the load required for level adjustment and substantially contributing to the solid phase diffusion connection between the bump and the electrode. By performing such bonding, higher bonding strength than before can be obtained, and connection reliability can be improved. Further, according to the present invention, not only the joining strength can be improved, but also the time required for joining can be greatly reduced. Therefore, the productivity of the electronic component mounting process can be greatly improved, and the product cost can be reduced.

Furthermore, by optimizing the ratio between the load applied in each bonding step and the ultrasonic output, the incidence of defective bonding can be greatly reduced without increasing the overall tact time. .

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in more detail.

(Embodiment 1) FIG. 1 is a time chart showing an example of bonding conditions in the ultrasonic thermocompression bonding method according to the present invention. For comparison, an example of a time chart showing bonding conditions in the conventional ultrasonic thermocompression bonding method is shown in FIG. As shown in FIG. 2, in the conventional ultrasonic thermocompression bonding method, the first stage bonding is performed by applying a weak ultrasonic output while applying a load necessary to make the bump height uniform. In order to perform ultrasonic thermocompression bonding of the electrodes and the electrodes, the second stage bonding is performed by applying an ultrasonic output stronger than the first stage while applying the same load as the first stage. In other words, two-stage bonding is performed by changing the ultrasonic output while applying substantially the same load.

On the other hand, the bonding method according to the present invention performs bonding in a plurality of stages while increasing both the applied load and the ultrasonic output in multiple steps. Also one
The load applied at the time of the step of bonding is larger than the load required for leveling the bump height, but is a load that contributes to the solid-phase diffusion connection between the bump and the electrode.

By performing such bonding, a higher bonding strength can be obtained than in the conventional bonding method, and the reliability of the electronic device can be improved.

FIG. 3 is a view for explaining a state of a bonding portion when performing flip chip bonding according to the present invention. By performing the bonding while increasing the load and the ultrasonic output in multiple stages, as shown in FIG. 3, the contact portion 1 between the connection terminal 11a on the surface acoustic wave element and the bump 14 is formed.
1x, and the bonding strength between the bump 14 and the contact portion 12x with the connection terminal 11a disposed on the substrate 11 is shown in FIG.
(A), FIG. 3 (b), FIG. 3 (c), and FIG. Therefore, not only the joining strength is improved, but also a strong joining can be obtained with a lower ultrasonic output. Therefore, the bonding strength after bonding can be stabilized and improved as a whole.

FIG. 4 is a diagram schematically showing an example of the structure of an electronic device manufactured by applying the present invention. This electronic device
This is a semiconductor package in which a semiconductor element 12 is mounted face-down on a substrate 11 and further sealed with a mold resin 13. A connection terminal 12a made of, for example, Al is provided on a surface of the semiconductor element 12 facing the substrate 11. On the other hand, a connection terminal 11a made of, for example, Au, Ni, Cr, Cu, or an alloy thereof is provided on a surface of the substrate 11 on which the semiconductor element 12 is mounted. The semiconductor element 12 and the substrate 11 are connected to the connection terminals 12 of the semiconductor element 12.
and a bump 14 made of, for example, Au, sandwiched between a. The bumps 14 may be provided on the semiconductor element 12 or on the substrate 11. Such a bump 14 may be formed, for example, by bringing an Au bonding wire into contact with a connection terminal with a bonding tool and applying a voltage. According to the bonding method of the present invention, the bonding strength can be improved as compared with the conventional bonding method.
Therefore, for example, when the mold resin 13 cures and contracts, the stress acting between the substrate 11 and the semiconductor element 12 due to the difference in the thermal expansion coefficient between the substrate 11 and the semiconductor element 12 or the semiconductor package Due to the thermal load applied cyclically to the actual use of electronic components such as
The bonding between the substrate 11 and the semiconductor element 12 can be performed with sufficient strength to resist stress, and the bonding state can be stably maintained. Therefore, a highly reliable electronic device can be provided by applying the present invention. (Embodiment 2) Next, the results of experiments performed to confirm the effects of the bonding method of the present invention will be described. Au bumps were formed on connection terminals mainly made of Al, such as semiconductor elements and surface acoustic wave elements, using, for example, a bonding tool. On the other hand, connection terminals made of Au were formed on a wiring board on which this element was mounted. Then, the connection terminals of the wiring board and the bumps of the element are arranged so as to face each other, and while the whole is heated to about 200 ° C., the back surface of the element is pressed by a bonding head, and ultrasonic waves are applied to the bumps. And the connection terminal were connected by solid phase diffusion.

In this example, the first-stage bonding is performed with a load of about 150 gf / bump and the ultrasonic output of about 0.07 W / bump, and the second-stage bonding is performed with a load of about 250 gf / bump.
Bump and ultrasonic output were set at about 0.29 W / bump. As a result, a shear strength of about 150 gf / bump corresponding to about three times or more of the bonding strength obtained by the conventional bonding method could be obtained.

In the conventional example, an ultrasonic thermocompression bonding method in which the ultrasonic output is increased in two stages is adopted. However, the ultrasonic output applied in the first bonding step is only used for leveling in which the height of the bumps is adjusted. In this case, the ultrasonic waves are weak against the applied load, so that the effect of increasing the bonding area between the bump and the electrode and improving the shear strength cannot be obtained. On the other hand, in the present invention, by applying ultrasonic waves in multiple stages with an output optimized for the load, the bonding strength can be remarkably improved, and highly reliable mounting can be performed.

(Embodiment 3) Bonding was performed by an ultrasonic thermocompression bonding method under conditions different from those of the example described in Embodiment 2, and the effect of the bonding method of the present invention was confirmed.

In this example, the first-stage bonding is set to a load of about 50 gf / bump, the ultrasonic output is set to about 0.03 W / bump, and the second-stage bonding is set to a load of about 150 gf / bump.
Bump, ultrasonic output set to about 0.07W / bump, 3
Ultrasonic thermocompression bonding between the electrode and the bump was performed by setting the bonding at the stage to a load of about 250 gf / bump and an ultrasonic output of about 0.29 W / bump. By such a three-stage bonding process, a shear strength of about 150 gf / bump equivalent to the two-stage bonding process described above was obtained. Further, the processing time required for ultrasonic oscillation and load application can be reduced to about あ た り per one-stage bonding. Therefore, the time required for the process can be reduced to about ／ compared to the conventional bonding method and the bonding method of the second embodiment. As described above, according to the present invention, not only can the bonding strength between the electrode and the bump be improved, but also the productivity can be greatly improved.

(Embodiment 4) As described above, the bonding method of the present invention performs bonding while increasing both the load and the ultrasonic output in multiple steps, and applies a load larger than the load required for leveling the bumps. It is added from the beginning. Furthermore, by appropriately adjusting the value of the ultrasonic output with respect to the load applied throughout the entire bonding process, the diffusion bonding can always proceed.

The present inventors adjusted the load applied to the electrode and the bump in each stage of bonding and the value of the ultrasonic output so as to be larger than about 0.001 W / gf per bump. It was found that a better bonding state could be obtained. Another experimental result performed to confirm the effect of the present invention will be described.
First, a description will be given of a case where connection is performed in a single-stage bonding process. Load applied at the time of bonding is 250 gf
/ Bump and ultrasonic power were set to 0.29W. At this time, (ultrasonic output / load) is about 0.0012 W / gf. In the conventional bonding method, the ultrasonic power applied in the first stage is much weaker than that for the purpose of leveling, and contributes to the formation of a solid-state diffusion bond between the electrode and the bump. Not. In the conventional bonding method, the load applied in the first stage is about 40 gf / bump because the purpose is to level a plurality of bumps.
On the other hand, in the present invention, a load and an ultrasonic output which substantially contribute to the formation of the solid-phase diffusion bonding between the electrode and the bump are applied from the first bonding step. According to such a bonding method of the present invention, a shear strength of 150 gf / bump, which is three times or more, compared to a shear strength of 40 gf / bump obtained in a bonding step of two steps in the conventional example, could be obtained. The process time for this experiment was 0.5
Seconds, which was reduced to 1/3 or less of 1.6 seconds in the conventional example. However, when a peeling portion was examined at the time of a shear test performed by extracting a part of the sample, a bonding failure was found in about 30% of the whole bumps.

(Embodiment 5) An example in which two-stage bonding is performed will be described. The load applied at the time of the first-stage bonding was about 121 gf / bump, and the ultrasonic output was 0.1 gf.
14 W, the load to be applied at the time of the second stage bonding is about 250 gf / bump, and the ultrasonic output is about 0.29 W
Set to. At this time, the value of (ultrasonic output W / load gf) is about 0.0012 W / gf in both the first and second stages.

When the bonding state of the sample was examined after the completion of the bonding, the obtained shear strength was about 150 gf / bump equivalent to the strength obtained by the one-stage bonding. It could be reduced to 10%. The process time in this bonding was 0.25 seconds for each stage, and the total was 0.5 seconds. As described above, the ratio between the ultrasonic output W and the load gf is set to about 0.0012 W.
By performing the bonding at each stage while setting the ratio to / gf or more, the bonding strength can be improved and the productivity can be improved.

(Embodiment 6) An example in which three-stage bonding is performed will be described. The load applied during the first stage bonding was set to about 64 gf / bump and the ultrasonic output was set to 0.07 W. The load applied during the second stage bonding was set to about 121 gf / bump and the ultrasonic output was set to 0.1.
Bonding was performed continuously with the load set to 4 W, the load applied during the third stage bonding set to about 250 gf / bump, and the ultrasonic output set to 0.29 W. The value of (ultrasonic output W / load gf) at this time is about 0.001 in the first stage.
1 W / gf, the second stage is about 0.0012 W / g, and the third stage is about 0.0012 W / gf.

After the three stages of joining, the samples were taken out and examined for the joining condition. The shear strength obtained was about 150%, which is equivalent to the case of joining in one stage and the case of joining in two stages.
gf / bump, but the incidence of bonding failure could be reduced to about 3% of the total bumps. The process time in this experiment was 0.17 seconds for each stage, and the total time was 0.5 seconds.

(Embodiment 7) An example in which four-stage bonding is performed will be described. The load applied during the first stage bonding was set to about 64 gf / bump and the ultrasonic output was set to 0.07 W. The load applied during the second stage bonding was set to about 121 gf / bump and the ultrasonic output was set to 0.1.
4 W, the load applied during the third stage bonding was set to about 188 gf / bump, the ultrasonic output was set to 0.21 W, and the load applied during the fourth stage bonding was about 25.
Bonding was performed continuously at 0 gf / bump and an ultrasonic output of 0.29 W. At this time, the value of (ultrasonic output W / load gf) is about 0.0011 W / g in the first stage.
f, the second stage is about 0.0012 W / g, the third stage is about 0.0011 W / gf, and the fourth stage is about 0.012 W / g.
012 W / gf.

When the joining state at the time of completion of the four-stage joining was examined, the obtained shear strength was about the same as when joining in one stage, joining in two stages, and joining in three stages. Although it was 150 gf / bump, the incidence of defective bonding could be reduced to 1% of all bumps. The process time in this experiment was 0.13 seconds for each stage,
This was performed for a total of 0.5 seconds.

As can be seen from the above experiments, optimization of the load and the ultrasonic output is effective in greatly improving the shear strength. Furthermore, by performing the multi-stage bonding by appropriately adjusting the load and the ultrasonic output as described above, it is possible to dramatically improve the bondability between the bump and the electrode without extending the process time. . In addition, the present invention could be applied to the materials of the electrodes and the bumps other than the above examples.

[0033]

As described above, according to the present invention,
The joining strength between the bump and the electrode can be improved. Therefore, the reliability of an electronic device on which electronic components such as a surface acoustic wave element and a semiconductor element are mounted can be greatly improved. Further, according to the present invention, not only the joining strength can be improved, but also the time required for joining can be greatly reduced. Therefore, the productivity of the electronic component mounting process can be greatly improved, and the product cost can be reduced.

Further, by optimizing the ratio between the load applied in each bonding step and the ultrasonic output, the incidence of defective bonding can be greatly reduced without increasing the overall tact time. . As described above, according to the present invention, the bonding strength between the bump and the electrode can be improved, the tact time can be reduced, and the yield can be improved.

[Brief description of the drawings]

FIG. 1 is a time chart showing conditions for applying a load and an ultrasonic output in a bonding method of the present invention.

FIG. 2 is a time chart showing conditions for applying a load and an ultrasonic output in a conventional joining method.

FIG. 3 is a view for explaining a joining operation of the present invention;
The figure which shows the structure of a joining part typically.

FIG. 4 is a diagram schematically showing an example of the structure of a semiconductor package mounted according to the present invention.

[Explanation of symbols]

 11 Electronic component 11a Connection terminal (first electrode) 12 Substrate 12a Connection terminal (second electrode) 13 Mold resin 14 Bump

 ──────────────────────────────────────────────────の Continued on the front page (72) Inventor Tadashi Watanabe 7-1 Nisshincho, Kawasaki-ku, Kawasaki-shi, Kanagawa Prefecture Toshiba Electronic Engineering Co., Ltd.

Claims (5)

[Claims] A first electrode disposed on the first electrode and a second electrode disposed on the first electrode;
In the bonding method for bonding the first electrode and the second electrode, the first electrode and the second electrode are pressed with a second load larger than a first load required for leveling the height of the bump, and Bonding the bump and the second electrode by applying an ultrasonic wave with the output of (1). 2. The method of claim 1, wherein the ratio of the first output to the second load is adjusted to be greater than about 0.001 W / gf per bump. Joining method. 3. The method according to claim 1, wherein the bump disposed on the first electrode and the second
In the bonding method for bonding the first electrode and the second electrode, the first electrode and the second electrode are pressed with a second load larger than a first load required for leveling the height of the bump, and A first bonding step of bonding the bump and the second electrode by applying an ultrasonic wave at the output of the first step; and setting the first electrode and the second electrode to be larger than the second load. And a second output for applying the ultrasonic wave at a second output larger than the first output to join the conductive bump and the second connection terminal.
And a connecting step. 4. The ratio of the first output to the second load and the ratio of the second output to the third load are greater than about 0.001 W / gf per bump. The joining method according to claim 3, wherein the adjustment is performed in such a manner. 5. The bonding according to claim 3, wherein the second bonding step is performed in multiple stages while increasing the second output and the third load. Method.