JP2004304722A - Surface acoustic wave device and its fabricating method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a surface acoustic wave device with a small size, a low profile and high reliability. <P>SOLUTION: The surface acoustic wave element 2 comprises a piezoelectric substrate 3, a comb-shaped electrode 4 formed on the piezoelectric substrate 3, a reflector 5, and electrode pad 6. A base substrate 8 includes an electrode land 9, a via hole 10, and an external terminal 11. The surface acoustic wave element 2 is joined to the substrate 8 via a bump 7 formed on the electrode pad 6 with its comb-shaped electrode 4 including surface being opposed to the substrate 8. On the base substrate 8 around the surface acoustic wave element 2 mounted, a resin inflow preventing member 12 is formed, while the surface acoustic wave element 2 and the resin inflow preventing member 12 are covered with a sealing resin 13. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a surface acoustic wave device, and more particularly to a surface acoustic wave device having a surface acoustic wave element mounted on a package.
[0002]
[Prior art]
2. Description of the Related Art In recent years, as mobile communication devices such as mobile phones and mobile phones have become smaller, lighter, and higher in frequency, small and lightweight surface acoustic wave devices have been 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 bonding 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, the 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, the above structure has a problem that the surface acoustic wave device cannot be reduced in size and height unless the package is reduced in size even when the surface acoustic wave element is reduced in size. Another problem is that the cost of a small package is high.
[0006]
Therefore, in recent years, a surface acoustic wave device of a chip size package has been studied. For example, as shown in FIG. 7, in Patent Document 3, a bump 47 is formed on an electrode pad 46 on a base substrate 48 having an external terminal 51, an electrode land 49, and a via hole 50 connecting the external terminal 51 and the electrode land 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, a dam 70 made of resin is provided on at least one of the surface acoustic wave element 42 and the base substrate 48, and the dam 70 is formed by the surface acoustic wave To prevent the sealing resin 53 from flowing into a portion (functional portion) where the noise 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 connecting the external terminal 51 and the electrode land 49. Then, the surface acoustic wave element 42 having the bumps 47 formed on the electrode pads 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 in which the sealing resin 53 is further stopped and then covered with a sealing resin 53 is disclosed.
[0008]
[Patent Document 1]
JP-A-7-283684 [Patent Document 2]
Japanese Patent Application Laid-Open No. 2000-91880 [Patent Document 3]
JP-A-10-321666 [Patent Document 4]
JP 2002-504773 A
[Problems to be solved by the invention]
However, in the structure as shown in FIG. 7, since the dam 70 must be formed on the surface acoustic wave element 42 and the base substrate 48, the design of the surface acoustic wave element 42, such as the arrangement of the comb-shaped electrode portions 44, is free. There is a problem that the degree is limited. Further, in order to reliably prevent the sealing resin 53 from flowing into a portion (functional portion) of the comb-shaped electrode portion 44 where the surface acoustic wave propagates, the surface acoustic wave element 42 is flip-chip mounted on the base substrate 48. Before mounting by bonding, the dam 70 must be formed on at least one of the surface acoustic wave element 42 and the base substrate 48 with high accuracy, and thus there is a problem that a complicated dam forming process needs to be used.
[0010]
In the structure as shown in FIG. 8, since the surface acoustic wave element 42 mounted on the base substrate 48 is completely covered with the film 80, 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, and the deformation of the surface acoustic wave element 42 causes the space between the comb-shaped electrode portions 44 and the space between the electrode fingers of the comb-shaped electrode portion 44. There is a problem that the frequency fluctuates due to the change of the frequency.
[0011]
The surface acoustic wave device of the present invention has been made in view of the above problems, and has as its object to solve these problems and to provide a small, low-profile, and highly reliable surface acoustic wave device. .
[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 piezoelectric substrate and a functional portion including at least one interdigital electrode formed on the piezoelectric substrate, a joining member, and a base. A surface acoustic wave device, wherein the surface acoustic wave element is mounted on the base substrate via the joining member in a state where the surfaces on which the comb-shaped electrode portions are formed face each other. On the base substrate around the surface acoustic wave element mounted on the substrate, a resin inflow prevention member is formed, and a gap between the surface acoustic wave element and the resin inflow prevention member is covered with a sealing member. It is characterized by having.
[0013]
It is preferable that the resin inflow prevention member is formed in a film shape, and a top surface thereof is located at a position lower than a height of a space formed between the surface acoustic wave element and the base substrate.
[0014]
Preferably, the base substrate has an external terminal, an electrode land, and a via hole connecting the external terminal and the electrode land.
[0015]
Further, a method of manufacturing a surface acoustic wave device according to the present invention includes a step of preparing a plurality of surface acoustic wave elements each having at least one comb-shaped electrode portion formed on a piezoelectric substrate, and an assembly of a plurality of base substrates. 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 state in which the surfaces of the plurality of surface acoustic wave elements on which the comb electrode portions are formed face each other. At the step of mounting on the collective board via the joining member, the step of forming a resin inflow prevention member around the surface acoustic wave element mounted on the collective board, and the surface acoustic wave element by a sealing member The method includes a step of covering a gap with the resin inflow prevention member and a step of cutting out from the collective substrate.
[0016]
BEST MODE FOR CARRYING OUT THE INVENTION
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 an embodiment of the present invention, FIG. 2 is a plan view of a surface acoustic wave device used in the embodiment of the present invention, and FIG. FIG. 4 is a plan view of a surface acoustic wave device mounted on a collective substrate (joined substrate) according to an embodiment of the present invention. FIG. 5 is a cross-sectional view illustrating a modification of the embodiment of the present invention. FIG. 6 is a sectional view showing a modification of the embodiment of the present invention.
[0017]
As shown in FIG. 1, the surface acoustic wave device 1 of the present invention includes a surface acoustic wave element 2, a base substrate 8, a bump 7, a resin inflow prevention member 12, and a sealing resin 13 (sealing member). I have.
[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 an electrode land 9, a via hole 10, and an external terminal 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 portion 4 facing the base substrate 8. Note that the base substrate 8 may have a structure including 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 sealed with 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, a vibration space such as a portion where the surface acoustic wave of the piezoelectric substrate 3 propagates is sealed. That is, a vibration space such as a portion where the surface acoustic wave of the piezoelectric substrate 3 is propagated is secured, and the comb electrode portion is protected from moisture and dust.
[0020]
At this time, since the top surface of the resin inflow prevention member 12 is located 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 prevention member 12 and the surface acoustic wave element 2 Not in contact with Therefore, no stress is applied to the surface acoustic wave element 2 by the resin inflow prevention member 12.
[0021]
In addition, 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 blocking member 12 and the surface acoustic wave element 2 according to the viscosity of the sealing resin 13, the elasticity of the sealing resin 13 including the comb-shaped electrode portion 4 and the like can be improved. It is possible to prevent the surface wave from flowing into a portion (functional portion) where 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 resist pattern for lift-off (not shown) having a desired opening pattern is formed by using a photolithography technique in which a resist is applied on the piezoelectric substrate 3 and then exposed using a mask.
[0024]
Next, after forming a film of Al, which is an electrode material metal, by a vapor deposition method or the like, the resist pattern is peeled off (lifted off) by dipping and rocking in a resist peeling solution, 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 target characteristics. Further, as the electrode material, metal materials such as Au, Cu, Ni, Ta, and W can be used in addition to Al.
[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, but 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-based or Sn-Ag-based 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]
An aggregate substrate 20 made of alumina or the like and serving as the base substrate 8 is prepared. 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 in the collective substrate 20 (base substrate 8). ing. The surface of the electrode land 9 is preferably plated with Au. Since the bumps 7 are also made of Au, bonding strength between the surface acoustic wave element 2 and the base substrate 8 can be increased.
[0028]
Then, as shown in FIG. 3A, a plurality of surface acoustic wave devices 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 FIG. 3 shows only one surface acoustic wave element 2, 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 surface of the collective substrate 20 (base substrate 8) on which the surface acoustic wave element 2 is mounted is stopped by a vacuum film forming method such as a vapor deposition 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 (the base substrate 8) but also on the surface acoustic wave device 2. At this time, the thickness of the deposited film 14 is set so 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. So that it does not come into contact with The size of the gap between the deposited film 14 serving as the resin inflow prevention 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 a later step.
[0030]
As shown in FIG. 3C, an epoxy-based resin is applied on the collective substrate 20 (base substrate 8) on which the deposited film 14 is formed by a method such as screen printing, and is sealed by heat curing. A 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, the size of the gap between the deposited film 14 serving as the resin inflow prevention member 12 and the surface acoustic wave element 2 is adjusted according to the viscosity of the sealing resin 13 and the like. It does not prevent the resin 13 from flowing into the portion (functional portion) of the comb-shaped electrode portion 4 where the surface acoustic wave propagates.
[0031]
Finally, as shown in FIG. 3D, the surface acoustic wave device 1 shown in FIG. 1 is obtained by dicing the chip 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 prevention 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 light is absorbed by the deposited film 14 formed on the surface acoustic wave element 2 when printing is performed 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 by transmitting through the transparent piezoelectric substrate 3 such as LiTaO ₃ , LiNbO ₃ , and quartz. When an insulator is used as the deposited film 14, even if the bump 7 that joins the base substrate 8 and the surface acoustic wave element 2 and the deposited film 14 are in contact with each other, no short circuit occurs because the deposited film 14 is an insulator.
[0033]
FIG. 5 shows a modification of the embodiment of the present invention. In FIG. 5, the gap between the resin inflow prevention member 12 and the surface acoustic wave element 2 is reduced. This is because, using an ECR sputtering device or the like, the deposition direction of the deposited film 14 is not from above the collective substrate 20 (base substrate 8) on which the surface acoustic wave element 2 is mounted, but is oblique. The deposition film 14 is formed while rotating the collective substrate 20 (base substrate 8) on which the surface acoustic wave element 2 is mounted in the horizontal direction. Since the deposition direction of the deposited film 14 is oblique, the resin inflow prevention member is slightly formed between the base substrate 8 and the surface acoustic wave element 2, but the resin inflow prevention member 12 can swell up. The gap between the resin inflow prevention member 12 and the surface acoustic wave element 2 can be reduced.
[0034]
FIG. 6 shows a modification of the embodiment of the present invention. 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 prevention member 12 and the surface acoustic wave element 2. The deposited film 14 formed thereon is exposed. According to the present invention, as shown in FIG. 6, the sealing resin 13 does not necessarily need to be formed so as to cover the entire surface acoustic wave element 2, and the gap between the resin inflow prevention member 12 and the surface acoustic wave element 2 is completely reduced. If it is covered, a part of the surface acoustic wave element 2 may be exposed. With such a structure, the height of the surface acoustic wave device 1 can be reduced. Further, when a metal film is used as 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, a surface acoustic wave device according to the present invention includes a surface acoustic wave element having a piezoelectric substrate and a functional portion including at least one interdigital electrode formed on the piezoelectric substrate, a bonding member, and an electrode land. A surface acoustic wave device having a base substrate, wherein the surface acoustic wave element is mounted on the base substrate via the bonding member in a state where the surfaces on which the comb electrode portions are formed face each other, On the base substrate around the surface acoustic wave element mounted on the base substrate, a resin inflow prevention member is formed, and the surface acoustic wave element and the resin inflow prevention member are covered with a sealing member. . In the present invention, since no dam is provided on the surface acoustic wave element, the layout of the comb-shaped electrode portion of the surface acoustic wave element can be freely designed.
[0036]
In particular, when the top surface of the resin inflow prevention 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 prevention member contacts the surface acoustic wave element. Therefore, almost no stress is applied to the surface acoustic wave element. Therefore, it is possible to obtain a highly reliable surface acoustic wave device without causing a frequency change due to the deformation of the surface acoustic wave element and the deformation of the base substrate.
[0037]
The method of manufacturing a male surface acoustic wave device according to the present invention includes a step of preparing a plurality of surface acoustic wave elements each having at least one comb-shaped electrode portion formed on a piezoelectric substrate, and an assembly of a plurality of base substrates. 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 state in which the surfaces on which the plurality of surface acoustic wave elements are formed with comb-shaped electrode portions are opposed to each other. A step of mounting on the collective substrate via the joining member, a step of forming a resin inflow prevention member around the surface acoustic wave element mounted on the collective substrate, and the surface acoustic wave element by a sealing member The method includes a step of sealing the resin inflow prevention member and a step of cutting out from the collective substrate. In the present invention, since the resin inflow prevention member is used without patterning a deposited film formed by a vacuum film forming method such as vapor deposition, it can be easily formed.
[Brief description of the drawings]
FIG. 1 is a 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 device used in an embodiment of the present invention.
FIG. 3 is a diagram illustrating each process 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 device mounted on a collective board (joined board) according to an embodiment of the present invention.
FIG. 5 is a sectional view showing a modification of the embodiment of the present invention.
FIG. 6 is a sectional view showing a modification of the embodiment of the present invention.
FIG. 7 is a sectional view of a conventional surface acoustic wave device.
FIG. 8 is a sectional view of a conventional surface acoustic wave device.
[Explanation of symbols]
1, 41, 61 Surface acoustic wave device 2, 42 Surface acoustic wave element 3, 43 Piezoelectric substrate 4, 44 Comb-shaped electrode portion 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 prevention member 13, 53 sealing resin 14 deposited film 20 aggregate substrate 70 dam 80 film

Claims (4)

A surface acoustic wave element including a piezoelectric substrate and a functional portion including at least one comb-shaped electrode formed on the piezoelectric substrate; a bonding member; and a base substrate, wherein the surface acoustic wave element includes a comb-shaped electrode. A surface acoustic wave device mounted on the base substrate via the joining member in a state where the surfaces on which are 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. A surface acoustic wave device, comprising: 2. The resin inflow prevention member is formed in a film shape, and a top surface thereof is located 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. The surface acoustic wave device according to claim 1, wherein the base substrate has an external terminal, an electrode land, and a via hole connecting the external terminal and the electrode land. Preparing a plurality of surface acoustic wave elements each having at least one interdigital electrode formed on a piezoelectric substrate;
A step of preparing an aggregate substrate, which is an aggregate of a plurality of base substrates,
Forming a bonding member on the plurality of surface acoustic wave elements or the collective substrate,
A step of 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 face each other,
Forming a resin inflow prevention member around the surface acoustic wave element mounted on the collective substrate,
A step of covering a gap between the surface acoustic wave element and the resin inflow prevention member with a sealing member,
Cutting out from the collective substrate. A method for manufacturing a surface acoustic wave device.

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