JP4186677B2 - Surface acoustic wave device and manufacturing method thereof - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a surface acoustic wave device, and more particularly to a surface acoustic wave device in which a surface acoustic wave element is mounted on a package.
[0002]
[Prior art]
In recent years, along with downsizing, weight reduction, and high frequency of mobile communication devices such as automobile phones and mobile phones, small and light surface acoustic wave devices are frequently used as filters mounted on these mobile communication devices. .
[0003]
The crystal or LiTaO _3, LiNbO ₃ or the like of the piezoelectric substrate made of a metal such as Al, comb in the electrode portion is formed by a surface acoustic wave device of the propagation of the surface acoustic wave interdigital transducer or a piezoelectric substrate It is necessary to secure a vibration space such as a portion and to protect the comb-shaped electrode portion from moisture and dust.
[0004]
Therefore, in the conventional surface acoustic wave device, a die bond agent is applied to the bottom surface of a package made of alumina or the like, the surface acoustic wave element is mounted on the package by die bonding, and the terminals inside the package and the electrode pads of the surface acoustic wave element are wired. After being connected by bonding, it was sealed with a lid (see Patent Document 1). In order to reduce the size, an electrode land is formed on the bottom surface of a package made of alumina or the like, a surface acoustic wave element is mounted on the package by flip chip bonding, and the package is sealed with a lid ( Patent Document 2).
[0005]
However, in the structure as described above, there is a problem that the surface acoustic wave device cannot be reduced in size and height unless the surface acoustic wave device is downsized and the package is downsized. There is also a problem that the cost for a small package is high.
[0006]
Therefore, in recent years, surface acoustic wave devices for chip size packages have been studied. For example, as shown in FIG. 7, in Patent Document 3, bumps 47 are formed on electrode pads 46 on a base substrate 48 having external terminals 51, electrode lands 49, and via holes 50 that connect the external terminals 51 and the electrode lands 49. A structure is disclosed in which the formed surface acoustic wave element 42 is mounted by flip chip bonding, and the mounted surface acoustic wave element 42 is covered with a sealing resin 53 to be sealed. At this time, at least one of the surface acoustic wave element 42 and the base substrate 48 is provided with a dam 70 made of resin, and the dam 70 is a surface acoustic wave made of a comb-shaped electrode portion 44 in the surface acoustic wave element 42. Prevents the sealing resin 53 from flowing into the part (function part) where the light propagates.
[0007]
As shown in FIG. 8, in Patent Document 4, as in the conventional example of FIG. 7, a base substrate 48 having an external terminal 51, an electrode land 49, and a via hole 50 that connects the external terminal 51 and the electrode land 49. Further, the surface acoustic wave element 42 having the bump 47 formed on the electrode pad 46 is mounted by flip chip bonding, and the surface acoustic wave element 42 mounted on the base substrate 48 is covered with a film 80 made of resin, metal, or the like. A structure that is further covered with a sealing resin 53 is disclosed.
[0008]
[Patent Document 1]
Japanese Patent Laid-Open No. 7-283684 [Patent Document 2]
JP 2000-91880 A [Patent Document 3]
JP-A-10-321666 [Patent Document 4]
Japanese translation of PCT publication No. 2002-504773
[Problems to be solved by the invention]
However, in the structure as shown in FIG. 7, the dam 70 must be formed on the surface acoustic wave element 42 and the base substrate 48, so the design freedom such as the arrangement of the comb-shaped electrode portion 44 in the surface acoustic wave element 42 is free. There is a problem that the degree is limited. Further, in order to reliably prevent the sealing resin 53 from flowing into the portion (functional portion) where the surface acoustic wave is propagated, which is composed of the comb-shaped electrode portion 44, the surface acoustic wave element 42 is flip-chiped on the base substrate 48. Prior to mounting by bonding, the dam 70 must be formed with high accuracy on at least one of the surface acoustic wave element 42 and the base substrate 48, so that a complicated dam formation process has to be used.
[0010]
Further, in the structure as shown in FIG. 8, the surface acoustic wave element 42 mounted on the base substrate 48 is completely covered with the film 80, so that stress is generated between the base substrate 48 and the film 80. Due to this stress, the base substrate 48 is deformed, the mechanical strength of the film 80 is deteriorated, or the surface acoustic wave element 42 is deformed, so that the distance between the comb-shaped electrode portions 44 and the distance between the electrode fingers of the comb-shaped electrode portions 44 are reduced. There has been a problem that the frequency fluctuates due to the change of.
[0011]
The surface acoustic wave device of the present invention has been made in view of the above-mentioned problems, and aims to solve these problems and provide a surface acoustic wave device that is small, low-profile and highly reliable. .
[0012]
[Means for Solving the Problems]
In order to achieve the above object, a surface acoustic wave device according to the present invention includes a surface acoustic wave element having a functional portion including a piezoelectric substrate and at least one comb-shaped electrode portion formed on the piezoelectric substrate, a bonding member, and a base. A surface acoustic wave device mounted on the base substrate via the bonding member in a state in which the surface on which the comb-shaped electrode portion is formed is opposed to the surface acoustic wave device. A resin inflow prevention member is formed on a base substrate around the surface acoustic wave element mounted on the substrate, and a gap between the surface acoustic wave element and the resin inflow prevention member is covered with a sealing member. In addition, the resin inflow prevention member is also formed on the surface acoustic wave element .
[0013]
It is preferable that the resin inflow prevention member is formed in a film shape, and a top surface thereof is at a position lower than a height of a space formed between the surface acoustic wave element and the base substrate.
[0014]
The base substrate preferably includes an external terminal, an electrode land, and a via hole that connects the external terminal and the electrode land.
[0015]
The method for manufacturing a surface acoustic wave device according to the present invention includes a step of preparing a plurality of surface acoustic wave elements formed by forming at least one comb electrode portion on a piezoelectric substrate, and an assembly of a plurality of base substrates. A state in which a step of preparing a certain aggregate substrate, a step of forming a bonding member on the plurality of surface acoustic wave elements or the aggregate substrate, and a surface on which the comb-shaped electrode portion is formed are opposed to the plurality of surface acoustic wave elements. Mounting on the collective substrate via the bonding member, forming a resin inflow blocking member around and on the surface acoustic wave element mounted on the collective substrate, and a sealing member And a step of covering the gap between the surface acoustic wave element and the resin inflow prevention member and a step of cutting out from the collective substrate.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings.
1 is a cross-sectional view of a surface acoustic wave device according to an embodiment of the present invention, FIG. 2 is a plan view of a surface acoustic wave element used in the embodiment of the present invention, and FIG. 3 is a production of the surface acoustic wave device according to the embodiment of the present invention. FIG. 4 is a plan view of a surface acoustic wave element mounted on a collective substrate (bonding substrate) in an embodiment of the present invention, and FIG. 5 is a cross-sectional view showing a modification of the embodiment of the present invention. 6 is a cross-sectional view showing a modification of the embodiment of the present invention.
[0017]
As shown in FIG. 1, the surface acoustic wave device 1 according to the present invention includes a surface acoustic wave element 2, a base substrate 8, bumps 7, a resin inflow blocking member 12, and a sealing resin 13 (sealing member). Yes.
[0018]
As shown in FIG. 2, the surface acoustic wave element 2 includes a piezoelectric substrate 3, a comb-shaped electrode portion 4 formed on the piezoelectric substrate 3, a reflector 5, and an electrode pad 6. The base substrate 8 has electrode lands 9, via holes 10, and external terminals 11. The surface acoustic wave element 2 is bonded to the base substrate 8 via the bumps 7 formed on the electrode pads 6 with the surface having the comb-shaped electrode portions 4 facing each other. The base substrate 8 may have a structure composed of a plurality of layers (multilayer structure).
[0019]
A film-like resin inflow prevention member 12 is formed on the base substrate 8 around the mounted surface acoustic wave element 2, and the surface acoustic wave element 2 and the resin inflow prevention member 12 are made of a sealing resin 13. Covered. Specifically, the gap between the surface acoustic wave element 2 and the resin inflow prevention member 12 is covered with the sealing resin 13. As a result, vibration spaces such as the comb-shaped electrode portion 4 and the surface acoustic wave propagation portion of the piezoelectric substrate 3 are sealed. That is, a vibration space such as a surface acoustic wave propagation portion of the comb-shaped electrode portion 4 and the piezoelectric substrate 3 is secured, and the comb-shaped electrode portion is protected from moisture and dust.
[0020]
At this time, since the top surface of the resin inflow blocking member 12 is at a position lower than the height of the space formed between the surface acoustic wave element 2 and the base substrate 8, the resin inflow blocking member 12 and the surface acoustic wave element 2. There is no contact. Therefore, the stress due to the resin inflow prevention member 12 is not applied to the surface acoustic wave element 2.
[0021]
Note that the size of the gap between the resin inflow prevention member 12 and the surface acoustic wave element 2 can be adjusted by changing the thickness of the resin inflow prevention member 12. Therefore, by appropriately adjusting the size of the gap between the resin inflow prevention member 12 and the surface acoustic wave element 2 according to the viscosity or the like of the sealing resin 13, the sealing resin 13 is made of an elastic material composed of the comb-shaped electrode portion 4 or the like. It is possible to prevent the surface wave from flowing into a portion (functional portion) through which the surface wave propagates.
[0022]
A method for manufacturing the surface acoustic wave device 1 according to the present invention will be described with reference to FIGS.
[0023]
First, a lift-off resist pattern (not shown) having a desired opening pattern is formed on the piezoelectric substrate 3 by using a photolithography technique in which a resist is applied and then exposed using a mask.
[0024]
Next, after forming a film of Al, which is an electrode material metal, by vapor deposition or the like, the resist pattern is peeled off (lifted off) by dipping and swinging in a resist stripping solution, thereby, as shown in FIG. The surface acoustic wave element 2 having the comb-shaped electrode portion 4, the reflector 5, the electrode pad 6, the lead wiring, and the like is manufactured.
[0025]
As the piezoelectric substrate 3, LiTaO ₃ , LiNbO ₃ , quartz, or the like is used according to the target characteristics. In addition to Al, a metal material such as Au, Cu, Ni, Ta, or W can be used as the electrode material.
[0026]
Subsequently, a bump 7 made of Au is formed on the electrode pad 6 of the surface acoustic wave element 2. In this embodiment, a bump made of Au is used as the bump 7. However, the present invention is not limited to this, and a bump made of solder may be used. However, when a bump made of Au—Sn or Sn—Ag solder is used, it is preferable to form a Ni layer on the electrode pad 6 as an adhesion layer of the bump made of solder.
[0027]
A collective substrate 20 made of alumina or the like and serving as the base substrate 8 is prepared. In the collective substrate 20 (base substrate 8), an electrode land 9 corresponding to the electrode pad 6 of the surface acoustic wave element 2, an external terminal 11, and a via hole 10 for electrically connecting the electrode land 9 and the external terminal 11 are formed. ing. The surface of the electrode land 9 is preferably plated with Au. Since the bumps 7 are also made of Au, the bonding strength can be increased when the surface acoustic wave element 2 and the base substrate 8 are bonded.
[0028]
Then, as shown in FIG. 3A, a plurality of surface acoustic wave elements 2 are mounted on the prepared aggregate substrate 20 by flip chip bonding. The electrode pads 6 of the surface acoustic wave element 2 and the electrode lands 9 of the collective substrate 20 (base substrate 8) are electrically and mechanically connected via the bumps 7. Although only one surface acoustic wave element 2 is shown in FIG. 3, a plurality of surface acoustic wave elements 2 are mounted on the collective substrate 20 (base substrate 8) as shown in FIG.
[0029]
As shown in FIG. 3B, a part of the resin substrate is prevented from flowing in from behind the collective substrate 20 (base substrate 8) on which the surface acoustic wave element 2 is mounted by a vacuum film formation method such as an evaporation method. A deposited film 14 to be the member 12 is formed. The deposited film 14 is formed not only on the collective substrate 20 (base substrate 8) but also on the surface acoustic wave element 2. At this time, the thickness of the deposited film 14 is set such that its top surface is at a position lower than the height of the space formed between the surface acoustic wave element 2 and the base substrate 8, and the deposited film 14 and the surface acoustic wave element 2. To the extent that it does not come into contact. The size of the gap between the deposited film 14 serving as the resin inflow blocking member 12 and the surface acoustic wave element 2 is adjusted by the thickness of the deposited film 14 in accordance with the viscosity of the sealing resin 13 used in the subsequent process.
[0030]
As shown in FIG. 3C, an epoxy-based resin is applied by a method such as screen printing on the aggregate substrate 20 (base substrate 8) on which the deposited film 14 is formed, and sealed by thermal curing. Resin 13 is formed. The sealing resin 13 is formed so as to cover at least a gap between the deposited film 14 serving as the resin inflow prevention member 12 and the surface acoustic wave element 2. At this time, as described above, since the size of the gap between the deposited film 14 serving as the resin inflow blocking member 12 and the surface acoustic wave element 2 is adjusted according to the viscosity of the sealing resin 13, It does not prevent the resin 13 from flowing into a portion (functional portion) where the surface acoustic wave including the comb-shaped electrode portion 4 propagates.
[0031]
Finally, as shown in FIG. 3D, the surface acoustic wave device 1 shown in FIG. 1 is obtained by dicing into pieces from the collective substrate 20 by dicing.
[0032]
In the present invention, examples of the material used for the deposited film 14 serving as the resin inflow blocking member 12 include metals such as Al, Cu, and ZnO, and insulators such as SiO ₂ , Si ₃ N ₄ , and Al ₂ O ₃ . When a metal is used as the deposited film 14, the laser beam is absorbed by the deposited film 14 formed on the surface acoustic wave element 2 when printing on the top surface of the surface acoustic wave device 1 with a laser. It is possible to prevent the comb-shaped electrode portion 4 from being broken through the transparent piezoelectric substrate 3 such as LiTaO ₃ , LiNbO ₃ , or quartz. In addition, when an insulator is used as the deposited film 14, even if the bump 7 and the deposited film 14 that join the base substrate 8 and the surface acoustic wave element 2 come into contact with each other, the deposited film 14 is an insulator, so that there is no short circuit.
[0033]
One modification of the embodiment of the present invention is shown in FIG. In FIG. 5, the gap between the resin inflow blocking member 12 and the surface acoustic wave element 2 is reduced. This is because the deposition direction of the deposited film 14 is not from the upper side of the collective substrate 20 (base substrate 8) on which the surface acoustic wave element 2 is mounted, but an oblique direction using an ECR sputtering apparatus or the like. The deposited film 14 is formed while the collective substrate 20 (base substrate 8) on which the surface acoustic wave element 2 is mounted is rotated in the horizontal direction. Since the deposition direction of the deposited film 14 is oblique, the resin inflow blocking member is slightly formed between the base substrate 8 and the surface acoustic wave element 2, but the resin inflow blocking member 12 can be raised. The gap between the resin inflow prevention member 12 and the surface acoustic wave element 2 can be reduced.
[0034]
One modification of the embodiment of the present invention is shown in FIG. In FIG. 6, the sealing resin 13 is formed only on the side surface of the surface acoustic wave element 2 so as to fill the gap between the resin inflow blocking member 12 and the surface acoustic wave element 2. The deposited film 14 formed on the top is exposed. In the present invention, as shown in FIG. 6, the sealing resin 13 is not necessarily formed so as to cover the entire surface acoustic wave element 2, and the gap between the resin inflow blocking member 12 and the surface acoustic wave element 2 is completely formed. A part of the surface acoustic wave element 2 may be exposed as long as it is covered. With such a structure, the surface acoustic wave device 1 can be reduced in height. Further, when a metal film is used for the deposited film 14 formed on the surface acoustic wave element 2, laser printing can be performed on the deposited film 14 formed on the surface acoustic wave element 2.
[0035]
【The invention's effect】
As described above, the surface acoustic wave device of the present invention includes a surface acoustic wave element having a functional portion including a piezoelectric substrate and at least one comb-shaped electrode portion formed on the piezoelectric substrate, a bonding member, and an electrode land. A surface acoustic wave device mounted on the base substrate via the bonding member in a state in which the surface on which the comb-shaped electrode portion is formed is opposed to the surface acoustic wave device, wherein the base substrate is mounted the circumference of the base substrate of the surface acoustic wave device, with the resin inflow preventing member is formed, the surface acoustic wave element and the resin inlet blocking member is covered with a sealing member And the said resin inflow prevention member is formed also on the said surface acoustic wave element.
In the present invention, since the dam is not provided in the surface acoustic wave element, the design of the arrangement of the comb-shaped electrode portion of the surface acoustic wave element can be made free.
[0036]
In particular, when the top surface of the resin inflow blocking member is at a position lower than the height of the space formed between the surface acoustic wave element and the base substrate, the resin inflow blocking member is in contact with the surface acoustic wave element. Therefore, almost no stress is applied to the surface acoustic wave device. Therefore, a highly reliable surface acoustic wave device can be obtained without causing frequency fluctuations due to deformation of the surface acoustic wave element and deformation of the base substrate.
[0037]
The method for manufacturing a surface acoustic wave device according to the present invention includes a step of preparing a plurality of surface acoustic wave elements formed by forming at least one comb electrode portion on a piezoelectric substrate, and an assembly of a plurality of base substrates. A state in which a step of preparing a certain aggregate substrate, a step of forming a bonding member on the plurality of surface acoustic wave elements or the aggregate substrate, and a surface on which the comb-shaped electrode portion is formed are opposed to the plurality of surface acoustic wave elements. Mounting on the collective substrate via the bonding member, forming a resin inflow blocking member around and on the surface acoustic wave element mounted on the collective substrate, and a sealing member The step of sealing the surface acoustic wave element and the resin inflow blocking member, and the step of cutting out from the aggregate substrate.
In the present invention, the resin inflow blocking member can be easily formed because the deposited film formed by a vacuum film forming method such as vapor deposition is used without patterning.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of a surface acoustic wave device according to an embodiment of the present invention.
FIG. 2 is a plan view of a surface acoustic wave element used in an embodiment of the present invention.
FIG. 3 is a process chart of a method for manufacturing a surface acoustic wave device according to an embodiment of the present invention.
FIG. 4 is a plan view of a surface acoustic wave element mounted on a collective substrate (bonding substrate) in an embodiment of the present invention.
FIG. 5 is a cross-sectional view showing a modification of the embodiment of the present invention.
FIG. 6 is a cross-sectional view showing a modification of the embodiment of the present invention.
FIG. 7 is a cross-sectional view of a conventional surface acoustic wave device.
FIG. 8 is a cross-sectional view of a conventional surface acoustic wave device.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1, 41, 61 Surface acoustic wave apparatus 2, 42 Surface acoustic wave element 3, 43 Piezoelectric substrate 4, 44 Comb-type electrode part 5 Reflector 6, 46 Electrode pad 7, 47 Bump 8, 48 Base substrate 9, 49 Electrode land 10 , 50 Via hole 11, 51 External terminal 12 Resin inflow blocking member 13, 53 Sealing resin 14 Deposition film 20 Collective substrate 70 Dam 80 Film

Claims (4)

A surface acoustic wave element having a functional part including a piezoelectric substrate and at least one comb-shaped electrode portion formed on the piezoelectric substrate, a bonding member, and a base substrate. The surface acoustic wave element includes a comb-shaped electrode portion. A surface acoustic wave device mounted on the base substrate via the bonding member in a state where the surfaces on which the surface is formed are opposed to each other,
A resin inflow prevention member is formed on the base substrate around the surface acoustic wave element mounted on the base substrate, and a gap between the surface acoustic wave element and the resin inflow prevention member is covered with a sealing member. We have you is, and wherein said resin inlet blocking member also on the surface acoustic wave element is formed, a surface acoustic wave device.   The resin inflow blocking member is formed in a film shape, and a top surface thereof is at a position lower than a height of a space formed between the surface acoustic wave element and the base substrate. A surface acoustic wave device according to claim 1.   3. The surface acoustic wave device according to claim 1, wherein the base substrate includes an external terminal, an electrode land, and a via hole that connects the external terminal and the electrode land. Preparing a plurality of surface acoustic wave elements formed by forming at least one comb-shaped electrode portion on a piezoelectric substrate;
Preparing an aggregate substrate that is an aggregate of a plurality of base substrates;
Forming a bonding member on the plurality of surface acoustic wave elements or the aggregate substrate;
Mounting the plurality of surface acoustic wave elements on the collective substrate via the bonding member in a state where the surfaces on which the comb-shaped electrode portions are formed are opposed to each other;
Forming a resin inflow blocking member around the surface acoustic wave element mounted on the collective substrate and on the surface acoustic wave element;
A step of covering a gap between the surface acoustic wave element and the resin inflow blocking member with a sealing member;
A method of manufacturing a surface acoustic wave device, comprising: cutting out from the aggregate substrate.

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