JP2001298342A - Surface acoustic wave device and method of manufacturing the same - Google Patents

Abstract

(57) [Problem] To provide a surface acoustic wave device capable of preventing separation of a bump from a connection electrode due to thermal stress without increasing the size. SOLUTION: The package includes a package 16 having an external connection electrode 17 on an inner bottom surface, a surface acoustic wave element 10 housed in the package 16, and a lid 18 sealing an opening of the package 16. The device 10 and the external connection electrode 17 are electrically connected via first and second bumps 14 and 15.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a surface acoustic wave device used for wireless communication equipment and the like, and a method of manufacturing the same.

[0002]

2. Description of the Related Art A conventional surface acoustic wave device will be described with reference to FIG.

First, an interdigital transducer electrode 101 and a connection electrode 102 electrically connected to the interdigital transducer electrode 101 are formed on a piezoelectric substrate 100 to obtain a surface acoustic wave element 103.
Next, a bump 104 is formed on the connection electrode 102.

Next, the bump 104 is aligned with the external connection electrode 106 of the package 105, and the bump 104 and the connection electrode 102 are joined by applying pressure and applying ultrasonic waves from above the piezoelectric substrate 100, and the surface acoustic wave element 103 is removed. It is mounted on the package 105.

Thereafter, the opening of the package 105 is
07, the package was sealed with a lid 108 to form a surface acoustic wave device.

[0006]

In the above configuration, if the package 105 and the surface acoustic wave element 103 have significantly different coefficients of thermal expansion, the bumps 104 from the connection electrodes 102 may be displaced by the strain generated by thermal stress such as reflow. There was a problem that the possibility of peeling was large.

In order to prevent this, the height of the bump 104 is increased and the surface acoustic wave element 1
It is only necessary to reduce the thermal stress applied to the connection electrode 102. However, if the height of one bump 104 is to be increased, the height also increases in the width direction. It was difficult to form bumps 104 that could be alleviated.

Accordingly, the present invention provides a method for producing a bump from a connection electrode of a bump due to thermal stress without increasing the size of the connection electrode, that is, the surface acoustic wave device, even if the package and the surface acoustic wave element have different coefficients of thermal expansion. It is an object of the present invention to provide a surface acoustic wave device capable of preventing peeling.

[0009]

In order to achieve this object, a surface acoustic wave device according to the present invention comprises a package having an external connection electrode on an inner bottom surface, a surface acoustic wave element housed in the package, and A lid that seals an opening of the package, electrically connects the surface acoustic wave element and an external connection electrode via a bump, and the bump has at least a two-stage structure. Can be increased only in height, which is the same as in the prior art, so that the above object can be achieved.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The invention according to claim 1 of the present invention provides a package having an external connection electrode on an inner bottom surface,
A surface acoustic wave element housed in the package, and a lid sealing an opening of the package, and electrically connecting the surface acoustic wave element and an external connection electrode via a bump; The bump is a surface acoustic wave device having at least a two-stage structure, and can prevent the bump from peeling off from the connection electrode due to thermal stress such as reflow.

According to a second aspect of the present invention, there is provided the surface acoustic wave device according to the first aspect, wherein the bump on the surface acoustic wave element is softer than the bump on the package. Stress can be further reduced.

According to a third aspect of the present invention, a first step of forming at least an interdigital transducer electrode on a piezoelectric substrate and a connection electrode connected to the interdigital transducer electrode to obtain a surface acoustic wave element;
Next, a second step of forming a first bump on the connection electrode, a third step of forming a second bump on the first bump, and then a package having an external connection electrode on an inner bottom surface In the surface acoustic wave element, the second bump is aligned with the external connection electrode, and the external connection electrode and the second bump are pressed by applying ultrasonic waves from above the piezoelectric substrate. This is a method for manufacturing a surface acoustic wave device, comprising a fourth step of joining and a fifth step of sealing the package opening with a lid, and can prevent peeling of a bump from a connection electrode due to thermal stress. A surface acoustic wave device can be obtained.

According to a fourth aspect of the present invention, there is provided the method for manufacturing a surface acoustic wave device according to the third aspect, wherein the second bump is made smaller than the first bump. Even if the displacement occurs, the second bump can be reliably formed on the first bump.

According to a fifth aspect of the present invention, the third step is performed after the second step.
4. A method for manufacturing a surface acoustic wave device according to claim 3, wherein a step of flattening the surface of the first bump is provided before the step, and the second bump can be formed into a desired shape with high accuracy.

According to a sixth aspect of the present invention, a first step of forming at least an interdigital transducer electrode on a piezoelectric substrate and a connection electrode connected to the interdigital transducer electrode to obtain a surface acoustic wave element;
Next, a second step of forming a first bump on the connection electrode, and then forming the surface acoustic wave in a package having an external connection electrode on the inner bottom surface and a second bump provided on the external connection electrode A third step of aligning the element so that the first and second bumps are in contact with each other, applying pressure from above the piezoelectric substrate, and applying ultrasonic waves to join the first and second bumps; And a fourth step of sealing the package opening with a lid, the method comprising the steps of: (a) forming a surface acoustic wave device; and (b) removing a bump from a connection electrode due to thermal stress such as reflow. A wave device can be obtained.

According to a seventh aspect of the present invention, there is provided the method for manufacturing a surface acoustic wave device according to the sixth aspect, wherein the second bump is made larger than the first bump. Can be securely joined.

According to an eighth aspect of the present invention, there is provided the method for manufacturing a surface acoustic wave device according to the sixth aspect, wherein the surface of the second bump is a flat surface, and the first bump and the second bump are joined. Can be easily performed.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a cross-sectional view of a surface acoustic wave device according to Embodiment 1 of the present invention, FIG. 2 is an enlarged cross-sectional view of an essential part of FIG. 1, and FIGS. FIG. 4 is a cross-sectional view for explaining a forming process, and FIG.
FIG. 5 is a cross-sectional view of a surface acoustic wave device according to Embodiment 2 of the present invention, and FIG. 6 is an enlarged cross-sectional view of a main part of FIG. 7 (a) and 7 (b) are cross-sectional views for explaining a bump forming step in the second embodiment, and FIG.
10 is a cross-sectional view for explaining the bonding between the bumps and the external connection electrodes in FIG. 10, 10 is a surface acoustic wave element, 11 is a piezoelectric substrate, 12 is an interdigital transducer electrode,
13 is a connection electrode, 14 is a first bump, 15 is a second bump, 16 is a package, 17 is an external connection electrode, 18
Is a lid, 19 is solder, 20 is a bump leveler for flattening the bump surface, and 21 is a US (Ultrasonic) tool for applying ultrasonic waves and pressure.

(Embodiment 1) First, an interdigital transducer electrode 12 which is input and output on the surface of a piezoelectric substrate 11 using aluminum or an aluminum alloy.
Then, the connection electrode 13 electrically connected to the interdigital transducer electrode 12 is formed, and the surface acoustic wave device 10 is obtained.

Next, as shown in FIG. 3A, a surface acoustic wave device 1 is formed by using a bonding tool having a gold wire provided at the center.
The first bumps 14 are formed on the 0 connection electrodes 13. Next, as shown in FIG. 3B, the surface of the first bump 14 is made flat by a bump leveler 20.
As shown in (c), a second bump 15 is formed thereon. Here, both the first and second bumps 14 and 15 are formed using gold or a gold alloy. At this time, by forming the first bumps 14 larger than the second bumps 15 as shown in FIG. 2, even if the formation positions of the second bumps 15 are slightly displaced, they can be reliably and sufficiently formed. The second bump 1 is formed on the first bump 14 with a high bonding strength.
5 can be formed.

Next, alignment is performed so that the tip of the second bump 15 contacts the external connection electrode 17 provided on the inner bottom surface of the package 16. The external connection electrode 17 is also formed using gold or a gold alloy.

Next, after applying pressure from the back surface of the piezoelectric substrate 11 with the US tool 21, ultrasonic waves are applied and the pressing force is gradually increased. By doing so, the tip portion of the second bump 15 is softened to form an intermetallic compound with the external connection electrode 17, and the ultrasonic bonding is terminated when the bonding strength between the two is sufficiently ensured. I do.

Thereafter, the opening of the package 16 is
The surface acoustic wave device shown in FIG.

The surface acoustic wave device obtained in this way has a higher bump height without increasing the size as compared with the prior art. Therefore, the surface acoustic wave device is subject to thermal stress such as reflow when mounting the surface acoustic wave device. In addition, since the first bumps 14 can be prevented from peeling off from the connection electrodes 13, the long-term reliability is excellent.

Note that the surface acoustic wave element 10 is
6, the first and second bumps 14 and 15 and the surface acoustic wave element 10 are flexibly vibrated during ultrasonic bonding.
However, the reciprocating motion is performed in the horizontal direction with the joint between the second bump 15 and the external connection electrode 17 as a fulcrum. For this reason, stress is applied to the joint between the first bump 14 and the connection electrode 13. In the present invention, by increasing the overall height of the bump, this stress can be alleviated. The occurrence of cracks in the element 10 can also be prevented.

(Embodiment 2) First, in the same manner as in Embodiment 1, aluminum or an aluminum alloy is used to enter and output the interdigital transducer electrode 12 and the interdigital transducer electrode 12 on the surface of the piezoelectric substrate 11. Connection electrode 1 for electrical connection
3 is formed, and the surface acoustic wave device 10 is obtained.

Next, as shown in FIG. 7A, a first bump 14 is formed on the connection electrode 13 of the surface acoustic wave device 10. As shown in FIG. 7B, a second bump 15 is formed on an external connection electrode 17 provided on the inner bottom surface of the package 16.
The surface is made flat by the bump leveler 20. Thereafter, as shown in FIG. 8, the first bumps 14 are positioned on the second bumps 15 and pressurized by the US tool 21 from the back surface of the piezoelectric substrate 11, and then, while applying ultrasonic waves, the pressing force is gradually increased. To increase. By doing so, the contact portion between the first and second bumps 14 and 15 is softened, an intermetallic compound is formed between the two, and the ultrasonic wave is formed when the bonding strength between the two is sufficiently ensured. End the joining.

Here, both the first and second bumps 14 and 15 are formed using gold or a gold alloy. Also, as shown in FIG. 6, the second bump 15 is
By forming the first bump 14 larger than the first bump 14, the first bump 14 and the second bump 15 can be reliably and sufficiently bonded even if the first bump 14 is slightly misaligned on the second bump 15. And the bumps 15 can be bonded. The external connection electrode 17 is also formed using gold or a gold alloy.

Thereafter, the opening of the package 16 is
The surface acoustic wave device shown in FIG. 5 and FIG.

The surface acoustic wave device according to the second embodiment also has the same height as the surface acoustic wave device according to the first embodiment without increasing the size of the bump as compared with the prior art. Since the first bump 14 can be prevented from peeling off from the connection electrode 13 due to thermal stress such as reflow at the time of mounting or the like, long-term reliability is excellent.

Hereinafter, the points of the present invention will be described.

(1) Although the connection electrodes 13 are formed using aluminum in the above embodiment, the first bumps 14 are formed in order to make the connection with the first bumps 14 stronger. It is preferable that the first electrode 14 be covered with a metal that forms the first bump 14.

(2) The external connection electrode 17 is formed by using the same gold as the second bump 15. However, when the external connection electrode 17 is formed by using a metal different from the second bump 15, it is necessary to secure the bonding strength. It is desirable that the surface be covered with the same metal as the second bump 15.

(3) First bump 14 and second bump 1
5 is preferably formed of the same metal in order to obtain a sufficient bonding strength.

(4) In the first embodiment, the surface of the first bump is made flat, and then the second bump 15 is formed. In the second embodiment, the surface of the second bump 15 is made flat. After that, the first bumps 14 were bonded. By making the surface of one of the bumps flat before joining the two in this way, the second bump 15 can be easily formed into a desired shape in the first embodiment, and the first bump 15 in the second embodiment. Bonding between the second bump 15 and the second bump 15 becomes easier. However, it is not always necessary to make one bump surface flat.

[0037]

As described above, according to the present invention, even if the thermal expansion coefficient of the package differs from that of the surface acoustic wave element, the bumps can be connected by the thermal stress without increasing the size of the connection electrode, that is, the surface acoustic wave device. It is possible to provide a surface acoustic wave device capable of preventing separation from an electrode.

[Brief description of the drawings]

FIG. 1 is a sectional view of a surface acoustic wave device according to Embodiment 1 of the present invention.

FIG. 2 is an enlarged sectional view of a main part of FIG.

FIG. 3A is a cross-sectional view illustrating the formation of a bump according to the first embodiment of the present invention. FIG. 3B is a cross-sectional view illustrating the formation of a bump according to the first embodiment of the present invention. Sectional view for explaining bump formation in Embodiment 1.

FIG. 4 is a cross-sectional view for explaining bonding between the bump and the external connection electrode according to the first embodiment of the present invention.

FIG. 5 is a sectional view of the surface acoustic wave device according to the second embodiment of the present invention.

FIG. 6 is an enlarged sectional view of a main part of FIG. 5;

FIG. 7A is a cross-sectional view illustrating a bump forming step according to a second embodiment of the present invention. FIG. 7B is a cross-sectional view illustrating a bump forming step according to the second embodiment of the present invention.

FIG. 8 is a cross-sectional view for explaining bonding between a bump and an electrode for external connection according to a second embodiment of the present invention.

FIG. 9 is a sectional view of a conventional surface acoustic wave device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Surface acoustic wave element 11 Piezoelectric substrate 12 Interdigital transducer electrode 13 Connection electrode 14 First bump 15 Second bump 16 Package 17 External connection electrode 18 Lid 19 Solder 20 Bump leveler 21 US tool

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H01L 21/92 602G

Claims (8)

[Claims] 1. A package having an external connection electrode on an inner bottom surface, a surface acoustic wave element housed in the package, and a lid sealing an opening of the package. A surface acoustic wave device in which a connection electrode is electrically connected via a bump and the bump has at least a two-stage structure. 2. The surface acoustic wave device according to claim 1, wherein the bumps are softer on the package side than on the surface acoustic wave element side. 3. A first step of forming at least an interdigital transducer electrode on a piezoelectric substrate and a connection electrode connected to the interdigital transducer electrode to obtain a surface acoustic wave element, and then forming a first step on the connection electrode. A second step of forming a first bump, a third step of forming a second bump on the first bump, and then mounting the surface acoustic wave element in a package having an external connection electrode on an inner bottom surface. A fourth step of aligning the second bump with the external connection electrode, applying pressure and applying ultrasonic waves from above the piezoelectric substrate to join the external connection electrode and the second bump, and And a fifth step of sealing the package opening with a lid. 4. The method according to claim 3, wherein the second bump is smaller than the first bump. 5. The method for manufacturing a surface acoustic wave device according to claim 3, wherein a step of flattening the surface of the first bump is provided after the second step and before the third step. 6. A first step of forming at least an interdigital transducer electrode on a piezoelectric substrate and a connection electrode connected to the interdigital transducer electrode to obtain a surface acoustic wave element, and then forming a first step on the connection electrode. A second step of producing the first bump, and then mounting the surface acoustic wave element in a package having an external connection electrode on the inner bottom surface and a second bump provided on the external connection electrode. Align the bumps so that they touch,
A third step of applying pressure and applying ultrasonic waves from above the piezoelectric substrate to join the first bump and the second bump, and a fourth step of sealing the package opening with a lid.
And a method for manufacturing a surface acoustic wave device. 7. The method according to claim 6, wherein the second bump is larger than the first bump. 8. The method according to claim 6, wherein the surface of the second bump is a flat surface.