JP2005039331A - Surface acoustic wave device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a surface acoustic wave device sealed by a resin, for suppressing flowing-in of an outer layer resin to a vibration space and particularly adhesion of the outer layer resin to electrode lands on a mount substrate and capable of promoting downsizing. <P>SOLUTION: In the surface acoustic wave device 1 sealed with the outer layer resin 32 wherein a surface acoustic wave element 6 is mounted on the mount substrate 2 on the upper side of which the electrode lands 3 to 5 are formed through flip-chip bonding by directing an electrode forming face downwardly, a square annular dam 25 made of a resin is formed to the surrounding of the electrode forming face of a surface acoustic wave substrate of the surface acoustic wave element and corners 3a, 4a, 4b, 5a of the electrode lands 3 to 5 close to corners of the dam 25 are formed rounded to extend the distance from the corners 3a, 4a, 4b, 5a to the corners of the dam. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a surface acoustic wave device having a structure in which a surface acoustic wave element is mounted on a mounting substrate by flip-chip bonding using bumps, and more specifically, to the surface acoustic wave element electrode side of an outer layer resin. The present invention relates to a surface acoustic wave device provided with a dam for preventing intrusion of water.
[0002]
[Prior art]
In a surface acoustic wave device in which a comb-shaped electrode made of a metal such as Al is formed on a piezoelectric substrate such as quartz, LiTaO ₃ or LiNbO ₃ , a vibration space is formed on the comb-shaped electrode or the surface acoustic wave propagation portion of the piezoelectric substrate. It is necessary to secure Further, it is necessary to protect the comb-shaped electrode portion from moisture and dust.
[0003]
Therefore, in the conventional surface acoustic wave device, the first package material having an opening opened upward and the second package material as a lid material for closing the opening of the first package material are elastic in the package. The surface wave element was sealed. That is, the die bonding material is applied to the inner bottom surface of the first package material, and the surface acoustic wave element is mounted inside the first package material by die bonding. And the terminal of a package and the electrode of a surface acoustic wave element are connected by wire bonding. After that, the second package material as the lid material was fixed to the first package material, and the internal surface acoustic wave element was sealed. The first and second package materials are made of, for example, insulating ceramics such as alumina or metals such as Kovar.
[0004]
In order to reduce the size, an electrode land is formed on the inner bottom surface of the first package material, and a surface acoustic wave element is mounted by die bonding using a flip chip bonding method.
[0005]
Surface acoustic wave devices using these first and second package materials are disclosed in, for example, Patent Document 1 and Patent Document 2 below.
However, the above-described package structure has a problem that even if the surface acoustic wave element is downsized, the surface acoustic wave device cannot be reduced in size and height unless the package is downsized. Further, when the miniaturization is advanced, there is a problem that the cost of the package structure is high.
[0006]
Therefore, in recent years, for example, as disclosed in Patent Document 3 below, a surface acoustic wave element is mounted on a mounting substrate by a flip chip bonding method, and the surface acoustic wave element is sealed with a resin. A surface acoustic wave device having a chip size package has been proposed. That is, instead of the package structure having the first and second package materials, the surface acoustic wave element is sealed with an outer layer resin to achieve downsizing. In this case, in order to prevent the uncured resin from flowing into the vibration space, at least one of the surface acoustic wave element and the mounting substrate is provided with a square annular dam made of a synthetic resin.
[0007]
[Patent Document 1]
Japanese Patent Laid-Open No. 7-283684 [Patent Document 2]
JP 2000-91880 A [Patent Document 3]
Japanese Patent Laid-Open No. 10-321666
[Problems to be solved by the invention]
As described in Patent Document 3, the structure that prevents the resin from flowing into the vibration space by forming a dam has the following problems.
[0009]
When the surface acoustic wave device is mounted on the mounting substrate by the flip chip bonding method and then sealed with the outer layer resin, the resin before curing is a hollow portion between the surface acoustic wave device and the mounting substrate, particularly the elastic surface. In order to suppress the intrusion into the hollow part facing the wave propagation part, the square annular dam has been formed as described above. However, depending on the case, the outer layer resin before curing may get over the dam and enter the vibration space side. In this case, as shown in FIG. 7, the resin 102 tends to accumulate inside the corner portion 101 a of the annular dam 101.
[0010]
On the other hand, a rectangular electrode land connected to the comb-shaped electrode of the surface acoustic wave element is arranged inside the square annular dam. That is, usually, the electrode land of the mounting substrate is arranged outside the comb-shaped electrode of the surface acoustic wave element at a position facing the electrode pad, and outside the region where the comb-shaped electrode and the electrode land are formed. The above dam is formed. Here, the electrode land and the corner portion of the dam are relatively close to each other. Therefore, the resin staying inside the corner portion of the dam may come into contact with the rectangular electrode land.
[0011]
In addition, since the low molecular component in the outer layer resin has relatively high wettability with respect to the electrode, the outer layer resin wets and spreads on the electrode land, and further passes on the bumps provided on the electrode land and on the comb electrode or piezoelectric substrate. It sometimes reaches the surface acoustic wave propagation part. Therefore, although the dam is provided, desired characteristics cannot be obtained, and the yield rate of the surface acoustic wave device tends to decrease.
[0012]
In order to solve the above problems, it is considered that the dam should be formed further away from the portion where the comb-type electrode and electrode land of the surface acoustic wave element are formed. However, when the dam and the electrode land are further away from each other, the surface acoustic wave element has to be enlarged.
[0013]
An object of the present invention is to eliminate the above-mentioned drawbacks of the prior art, and in a surface acoustic wave device having a structure in which a surface acoustic wave element is sealed with an outer layer resin, the outer layer resin is applied to the surface acoustic wave element electrodes and electrode lands. An object of the present invention is to provide a surface acoustic wave device that can more reliably suppress intrusion and that can be reduced in size.
[0014]
[Means for Solving the Problems]
According to a wide aspect of the present invention, a mounting substrate having a plurality of electrode lands formed on an upper surface, a piezoelectric substrate, a surface acoustic wave element forming electrode formed on one main surface of the piezoelectric substrate, and the elastic surface And an elastic pad mounted by flip-chip bonding so that the surface on which the surface acoustic wave element configuration electrode is formed is opposed to the upper surface of the mounting substrate. A square ring made of resin around the surface of the surface acoustic wave element on which the surface acoustic wave element constituting electrode is formed, and an outer layer resin that seals the periphery of the surface acoustic wave element In the surface acoustic wave device in which the dam is formed, a corner portion of the electrode land provided on the mounting substrate adjacent to the corner portion of the dam is rounded. Provided That.
[0015]
In a specific aspect of the surface acoustic wave device according to the present invention, the planar shape of the bump joining the electrode land of the mounting substrate and the electrode pad of the surface acoustic wave element is substantially circular.
[0016]
According to still another aspect of the surface acoustic wave device according to the present invention, the surface acoustic wave element constituting electrode of the surface acoustic wave element includes a comb electrode part and a reflector, and the comb electrode part and the reflection A second dam is formed inside the dam so as to surround the region where the vessel is provided.
[0017]
In still another specific aspect of the surface acoustic wave device according to the present invention, the inner line of the corner portion of the dam is rounded, the interval between the inner edge of the corner portion and the electrode land is l, and the corner portion of the dam is When the distance between the inner edge of the continuous side portion and the electrode land is L, L ≧ L.
[0018]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be clarified by describing specific embodiments of the present invention with reference to the drawings.
[0019]
1A and 1B are a front sectional view showing a surface acoustic wave device according to an embodiment of the present invention and a plan view of a mounting substrate used in the surface acoustic wave device.
A surface acoustic wave device 1 having a chip size package has a mounting substrate 2. The mounting substrate 2 is made of an appropriate insulating material such as insulating ceramics such as alumina or synthetic resin. In this embodiment, since the mechanical strength is excellent, the mounting substrate 2 is made of insulating ceramics such as alumina.
[0020]
As shown in FIG. 1B, electrode lands 3 to 5 are formed on the upper surface of the mounting substrate 2. The electrode lands 3 to 5 are electrically connected to an input electrode, an output electrode, and a ground electrode of a surface acoustic wave element to be described later. The electrode lands 3 to 5 are formed by printing W or the like on the upper surface of the mounting substrate 2 and baking it, and thereafter plating Ni, Au or the like.
[0021]
The feature of this embodiment is that some corners 3a, 4a, 4b and 5a of the electrode lands 3 to 5 are rounded. In the present embodiment, the corner portion is formed to have a shape along a fan-shaped arc having a central angle of about 90 degrees. But the roundness of a corner part may be made into other shapes. That is, for example, the corner portion 4a of the electrode land 4 may be rounded as shown in FIG. 2A, or may be cut into an oblique shape as shown in FIG. As shown in c), a plurality of straight lines may be connected at a certain angle.
[0022]
A surface acoustic wave element 6 is mounted on the mounting substrate 2. The surface acoustic wave element 6 has a piezoelectric substrate 7. As shown in a plan view in FIG. 3, comb electrodes 8 and 9 and reflectors 10 and 11, and comb electrodes 12 and 13 and a reflector 14 are formed on a piezoelectric substrate 7 to form a surface acoustic wave element. , 15 are formed. In the present embodiment, the first surface acoustic wave filter portion is constituted by the comb electrodes 8 and 9 and the reflectors 10 and 11, and the second elastic surface is constituted by the comb electrodes 12 and 13 and the reflectors 14 and 15. A wave filter unit is configured. The first and second surface acoustic wave filter portions are connected by a connection conductive portion 16. Therefore, a surface acoustic wave filter having a two-stage configuration is configured.
[0023]
The first surface acoustic wave filter section is connected to the electrode pads 21, 22, 22 '. The second surface acoustic wave filter section is connected to the electrode pads 23, 24, 24 '. The electrode pad 21 is electrically connected to the input end of the first surface acoustic wave filter unit, and the electrode pad 23 is electrically connected to the output end of the second surface acoustic wave filter unit. The electrode pads 22, 22 ', 24, 24' are electrically connected to electrodes connected to the ground potential of the first and second surface acoustic wave filter sections.
[0024]
In the surface acoustic wave element 6, on one surface 7 a of the piezoelectric substrate 7, the comb electrodes 8 and 9 and the reflectors 10 and 11 and the comb electrodes 12 and 13 and the reflector 14 that constitute the surface acoustic wave filter section. 15 and the first dam 25 is formed outside the region where the electrode pads 21 to 24 are formed. In addition, second dams 26 and 27 are formed so as to surround the first and second surface acoustic wave filter sections. In the present embodiment, the first dam 25 and the second dams 26 and 27 are formed by a photoresist method using a photosensitive photoresist resin mainly composed of polyimide. However, since the dams 25 to 27 are provided in order to prevent an inflow of an outer layer resin to be described later, the dams 25 to 27 may be made of a synthetic resin other than the photosensitive photoresist resin, and the formation method is not particularly limited.
[0025]
Each of the first dam 25 and the second dams 26 and 27 is configured to have a square annular planar shape.
The height h1 (see FIG. 1A) of the dams 25 to 27 is provided so as to be smaller than the gap between the two in a state where the surface acoustic wave element 6 is finally bonded to the mounting substrate 2. ing.
[0026]
As shown in FIG. 1A, the surface acoustic wave element 6 has a surface on which the surface acoustic wave filter section and dams 25 to 27 are formed, that is, one surface 7a of the piezoelectric substrate 7 is a lower surface. Then, it is bonded to the mounting substrate 2 by flip chip bonding. In FIG. 1, the electrode pads 21 to 24 are not shown. In this case, the bumps 31 shown in FIGS. 1A and 3 are previously formed on the electrode pads 21 to 24.
[0027]
The electrode lands 3 to 5 are bonded to the electrode pads 21 to 24 by flip chip bonding. More specifically, the electrode pads 21, 23 are bonded to the electrode lands 3, 5 by bumps, and the electrode pads 22, 24, 22 ′, 24 ′ are bonded to the electrode lands 4 by bumps. The bump 31 is made of, for example, Au, but may be made of another metal.
[0028]
As shown in FIG. 3, the bump 31 has a circular planar shape, and the bump 31 is formed so that the periphery is located inside the edge of the electrode pads 21 to 24.
[0029]
In the present embodiment, after the surface acoustic wave element 6 is bonded to the mounting substrate 2 by flip chip bonding as described above, the outer resin layer 32 is formed around the side surface of the surface acoustic wave element 6 and the surface acoustic wave element 6. It is given so as to seal the space between the mounting substrate 2. As the outer layer resin 32, an appropriate resin such as a photo-curing type or a thermosetting type epoxy resin is used. However, in this embodiment, a thermosetting type epoxy resin is used, and after the outer layer resin 32 is applied, heating is performed. By doing so, the outer layer resin 32 is cured. Therefore, the space between the surface acoustic wave element 6 and the mounting substrate 2 is sealed with the outer layer resin 32. Although the outer layer resin is not formed on the top surface of the surface acoustic wave element 6, it may be formed on the top surface.
[0030]
Here, the outer layer resin 32 has fluidity before curing, and may enter the space A between the surface acoustic wave element 6 and the mounting substrate 2 until curing. However, in this embodiment, since the first dam 25 is provided, the first dam 25 first suppresses the inflow of the outer layer resin 32 to the inside.
[0031]
However, as shown in the description of the prior art, the outer layer resin 32 tends to get over the first dam 25 at the corner 25a of the first annular dam 25 and accumulate inside the corner portion.
[0032]
However, in this embodiment, the corner portions 3a, 4a, 4b, and 5a of the electrode lands 3 to 5 are rounded as described above. In other words, the corner portions of the electrode lands 3 to 5 adjacent to the corner portion of the first dam 25 are rounded. It has been.
[0033]
Therefore, even if the outer layer resin 32 enters the inside of the corner portion of the dam 25, the contact between the electrode lands 3 to 5 and the outer layer resin 32 can be reliably prevented.
That is, the feature of this embodiment is that the corner portion of the first annular dam 25 and the corner portions of the electrode lands 3 to 5 adjacent to the corner portion are formed to be rounded, thereby forming the outer layer. This is because the adhesion of the resin 32 to the electrode lands 3 to 5 is suppressed.
[0034]
In the present embodiment, the comb electrodes 8 and 9 and the reflectors 10 and 11 and the comb electrodes 12 and 13 and the reflectors 14 and 15 constituting the first and second surface acoustic wave filter units are further provided. Second dams 26 and 27 are formed so as to cover the respective regions where the Therefore, for example, even if the outer layer resin gets over the center of the long sides 25b and 25c of the dam 25 in FIG. 3, the second dams 26 and 27 apply the outer layer resin to the first and second surface acoustic wave filter portions. Inflow is suppressed. Therefore, the desired filter characteristics can be obtained with certainty.
[0035]
In the present embodiment, the corner portions 3a, 4a, 4b, 5a of the electrode lands 3-5 are formed so as to be rounded, thereby suppressing the adhesion of the outer layer resin 32 to the electrode lands 3-5. Therefore, the adhesion of the outer layer resin 32 to the electrode lands 3 to 5 can be suppressed without increasing the area of the opening of the dam 25. Therefore, the outer layer resin 32 can be prevented from adhering to the electrode lands 3 to 5 without causing an increase in size.
[0036]
In the above embodiment, the second dams 26 and 27 are provided. However, as shown in FIG. 4, only the first dam 25 may be provided on the one surface 7 a of the piezoelectric substrate 7. Further, the comb electrodes 8 and 9 and the reflectors 10 and 11 and the comb electrodes 12 and 13 and the reflectors 14 and 15 which are inside the first dam and constitute the surface acoustic wave filter unit, and the electrodes A third dam may be provided outside the region where the pads 21 to 24 are formed.
[0037]
Moreover, in the said embodiment, although the electrode lands 3-5 were formed in the upper surface of the mounting substrate 2 according to one surface acoustic wave element, as shown in FIG. In order to mount the surface acoustic wave element, a plurality of sets of electrode lands 3 to 5 may be arranged.
[0038]
FIG. 6 is a partially cutaway plan view showing a modification of the shape of the dam and electrode land used in the present invention. A description will be given by taking the electrode land 4b shown in FIG. 1 as an example. In this modification, a first dam 25A is provided outside the electrode land 4b. The first dam 25A has a substantially rectangular ring shape, but has a rounded corner portion. Thus, in the present invention, the corner portion of the annular ring dam may be rounded. In this case, when the distance between the corner portion 25Aa of the dam 25A and the electrode land 4b is l, and the distance between the inner edge 25Ab of the side portion of the dam 25A and the electrode land 4b is L, l is L or more. And it is sufficient. That is, by setting l to L or more, it is possible to suppress the adhesion of the outer layer resin to the electrode land as in the above embodiment.
[0039]
In the above-described embodiment, a resonator type surface acoustic wave filter having a two-stage configuration is used as the surface acoustic wave element 6. However, the surface acoustic wave filter of another configuration or a surface acoustic wave other than the surface acoustic wave filter element is used. The present invention can also be applied to a resonator or the like.
[0040]
【The invention's effect】
In the surface acoustic wave device according to the present invention, an angular dam made of resin is formed around the surface of the surface of the surface acoustic wave element on which the electrodes of the piezoelectric substrate are formed, and close to the corner of the dam. The corner portions of the electrode lands provided on the mounting substrate side are formed to be rounded. Therefore, since the distance between the corner portion of the dam and the rounded corner portion of the electrode land becomes large, even if the outer layer resin flows into the corner portion of the dam, the outer layer resin does not move to the electrode land. It is hard to adhere to. Therefore, conventionally, in this type of surface acoustic wave device, the outer layer resin flows in from the inside of the corner portion of the dam, adheres to the electrode land, spreads the surface of the electrode land, and causes deterioration of the characteristics. In the surface acoustic wave device, the adhesion of the outer layer resin to the electrode lands can be reliably suppressed, and the characteristics of the surface acoustic wave device can be stabilized and the yield rate can be improved.
[0041]
When the planar shape of the bump that joins the electrode land of the mounting substrate and the electrode pad of the surface acoustic wave element is circular, the distance between the electrode lands from the end of the bump can be made constant and the arrangement can be made efficient. be able to.
[0042]
When the electrode of the surface acoustic wave element has a comb-shaped electrode and a reflector, and a second dam is formed inside the dam so as to surround a region where the comb-shaped electrode and the reflector are provided The second dam can more reliably suppress the deterioration of characteristics due to the undesired inflow of the outer layer resin.
[0043]
When the inner edge of the corner of the dam is rounded, the distance between the inner edge of the corner and the electrode land is l, and the distance between the inner edge of the side portion connected to the corner of the dam and the electrode land is L, When l ≧ L, adhesion of the outer layer resin flowing from the corner portion to the electrode land can be more reliably suppressed.
[Brief description of the drawings]
1A and 1B are a front sectional view of a surface acoustic wave device according to an embodiment of the present invention and a plan view of a mounting substrate used in the surface acoustic wave device.
FIGS. 2A to 2C are partial cutaway plan views showing modifications of the shape of electrode lands in the surface acoustic wave device of the invention.
3 is a schematic plan view showing an electrode forming surface of a surface acoustic wave element used in the surface acoustic wave device shown in FIG. 1. FIG.
FIG. 4 is a schematic plan view for explaining another example of the surface acoustic wave element used in the present invention.
FIG. 5 is a plan view showing a modified example of the mounting board used in the surface acoustic wave device of the invention.
FIG. 6 is a schematic partially cutaway plan view showing a modification of the surface acoustic wave device of the present invention.
FIG. 7 is a partially cutaway plan view for explaining problems of a conventional surface acoustic wave device.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Surface acoustic wave apparatus 2 ... Mounting substrate 3-5 ... Electrode land 3a, 4a, 4b, 5a ... Corner part 6 ... Surface acoustic wave element 7 ... Piezoelectric substrate 7a ... One surface 8, 9 ... Comb-type electrode 10, 11 ... reflectors 12 and 13 ... comb electrodes 14 and 15 ... reflector 16 ... connection conductive parts 21 to 24 ... electrode pads 25 and 25A ... dams 26 and 27 ... second dam 31 ... bump 32 ... outer layer resin

Claims (4)

A mounting substrate having a plurality of electrode lands formed on the upper surface;
A piezoelectric substrate; a surface acoustic wave element constituting electrode formed on one main surface of the piezoelectric substrate; and an electrode pad connected to the surface acoustic wave element constituting electrode; A surface acoustic wave element mounted by flip chip bonding so that the surface on which the surface wave element constituting electrode is formed is opposed,
An outer layer resin that seals the periphery of the surface acoustic wave element;
In the surface acoustic wave device in which an angular dam made of a resin is formed around the surface of the surface acoustic wave element on which the surface acoustic wave element constituting electrode is formed,
The surface acoustic wave device according to claim 1, wherein a corner portion of the electrode land provided on the mounting substrate is rounded near a corner portion of the dam. The surface acoustic wave device according to claim 1, wherein a planar shape of a bump joining the electrode land of the mounting substrate and the electrode pad of the surface acoustic wave element is substantially circular. The surface acoustic wave element constituting electrode of the surface acoustic wave element has a comb-shaped electrode part and a reflector, and is disposed inside the dam so as to surround a region where the comb-shaped electrode part and the reflector are provided. The surface acoustic wave device according to claim 1 or 2, wherein a second dam is formed. When the inner line of the corner of the dam is rounded, the distance between the inner edge of the corner and the electrode land is l, and the distance between the inner edge of the side part connected to the corner of the dam and the electrode land is L Furthermore, it is l> = L, The surface acoustic wave apparatus in any one of Claims 1-3 characterized by the above-mentioned.

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