JP3243764B2 - Surface wave device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an SH for which a displacement such as a BGS wave is mainly a displacement in a direction perpendicular to a surface wave propagation direction.
More particularly, the present invention relates to a surface acoustic wave device having a structure in which a polymer resin material layer is provided on a substrate surface on which an interdigital transducer is provided.

[0002]

2. Description of the Related Art Conventionally, in a surface acoustic wave device, attaching an elastic body on a propagation path of a surface acoustic wave and on an interdigital transducer has been a taboo. This is because the surface acoustic wave is absorbed by the elastic body, and the output is attenuated. Therefore, when the surface acoustic wave device is configured as a component, a cavity is provided on the propagation path of the surface acoustic wave and on the interdigital transducer so as not to hinder the propagation of the surface acoustic wave. As a result, the package structure of the surface wave is complicated and expensive.

On the other hand, JP-A-54-108551 discloses that
A structure in which the cavity is omitted in a surface acoustic wave filter using a BGS wave is disclosed. Here, a structure in which insulating rubber which is a viscous liquid at normal temperature and normal pressure in the air and is cured by a heating or moisture absorbing action is arranged on the interdigital transducer and the surface wave propagation path, thereby eliminating the cavity is disclosed. Have been. Further, it is shown that the output of the BGS wave is not attenuated even when the insulating rubber as described above, specifically, the silicone rubber is arranged on the interdigital transducer and on the surface wave propagation path.

[0004]

SUMMARY OF THE INVENTION However, BGS
In a surface acoustic wave resonator utilizing a wave, if the interdigital transducer and the surface wave propagation path are covered with silicone rubber, there is a problem that the resonance resistance and the propagation loss become considerably high, so that the resonance characteristics and the filter characteristics change. Was. In order to solve the above-mentioned problem, the applicant of the present application disclosed in Japanese Patent Application No. Hei 3-2034 a gel or resin layer having a Shore hardness of 30 or less on the interdigital transducer and the surface wave propagation path. We have proposed a surface acoustic wave device that can simplify the package structure by coating without deteriorating the characteristics of the surface acoustic wave device.

FIG. 6 is a cross-sectional view of a surface acoustic wave device described in the above-mentioned prior art which is not yet known. The surface acoustic wave device 1 utilizing the BGS wave has a surface acoustic wave element 6 formed by forming interdigital electrodes 3 and 4 interposed on the upper surface of a piezoelectric substrate 2.
And a resin layer 5 formed on the surface acoustic wave element 6. The piezoelectric substrate 2 is polarized in the plane of the drawing-back direction of the drawing. The surface acoustic wave device 1 is configured such that a BGS wave is propagated in the direction of arrow X by applying an AC electric field between the comb electrodes 3 and 4. And this BG
Although the resin layer 5 having a gel or Shore hardness of 30 or less is provided on the S-wave propagation path, the resonance characteristics hardly deteriorate.

Accordingly, it is not necessary to provide a cavity in connecting the terminal to the surface acoustic wave device 1 and packaging it, so that the package structure can be simplified. In addition, as such a package structure, a method of forming a resin sheath around the surface acoustic wave device 1 shown in FIG. 6, or a method of housing the surface acoustic wave device 1 shown in FIG. 6 in a metal case is exemplified. . However, the gel or resin layer having a Shore hardness of 30 or less has considerably high fluidity, and therefore,
In practice, it has been found that it is difficult to reliably provide a resin exterior or package the package with a metal case. This will be described with reference to FIGS.

[0007] In the case of constituting as a part with a resin exterior, as shown in FIG. 7, lead terminals 8a and 8b formed integrally with a metal hoop 7 are prepared. Then, the surface acoustic wave element 6 is fixed on the element mounting portion 8c having a relatively large area at the tip of the lead terminal 8a, and the surface acoustic wave element 6 is electrically connected to the lead terminals 8a and 8b by bonding wires 9a and 9b. I do.

Next, the above-mentioned gel or shore hardness 3
A resin material of 0 or less, for example, silicone rubber is applied to the upper surface of the surface acoustic wave element 6. However, since the resin layer 5 made of silicone rubber as described above has a very high fluidity,
As shown in FIG. 8, the adhesive tends to adhere not only to the surface acoustic wave element 6 and the element mounting portion 8c but also to the middle of the lead terminals 8a and 8b. As a result, even if the resin exterior is applied in the state shown in FIG.
a, 8b tended to be present with the resin layer 5. Since the silicone rubber forming the resin layer 5 exhibits high water absorption, the resulting surface acoustic wave device absorbs moisture from the silicone rubber at the boundary between the lead terminals 8a and 8b and the exterior resin, and causes deterioration of characteristics and There was a risk of disconnection or the like. Also, in the case where the surface acoustic wave device 1 shown in FIG. 5 is packaged in a metal case, since the gel layer or the resin layer having a Shore hardness of 30 or less has high fluidity, the surface wave device 1 may The silicone rubber invades,
Poor welding tended to occur.

It is an object of the present invention to provide a surface acoustic wave device utilizing an SH type surface acoustic wave, in which not only the package structure can be simplified by coating an elastic body on an interdigital transducer, but also the reliability is excellent. Another object of the present invention is to provide a surface acoustic wave device which can be constructed with a simplified package structure, and is therefore less likely to have characteristic fluctuations.

[0010]

According to the present invention, there is provided a surface acoustic wave device comprising an SH type surface wave mainly consisting of a displacement in a direction perpendicular to the direction of propagation of a surface wave among surface waves propagating through a piezoelectric substrate. A surface acoustic wave device, comprising: a piezoelectric substrate; at least one interdigital transducer formed on the piezoelectric substrate; and a gel or shore hardness of at least 30 covering the interdigital transducer. And a polymer resin material layer in which an insulating powder is dispersed in the following resin.

In other words, the inventors of the present invention have found that in a surface acoustic wave device using an SH type surface acoustic wave, when a gel or resin having a Shore hardness of 30 or less is coated on the surface acoustic wave propagation path and on the interdigital transducer, Degradation of the resin can be prevented, but in view of the fact that the high fluidity of the resin makes it impossible to obtain a package structure having excellent reliability, as a result of various investigations on materials alternative to the resin, a gel or Shore hardness of 30 was obtained. It has been found that if the insulating fine powder is dispersed in the following resin, the fluidity can be reduced and the characteristics of the surface acoustic wave device do not deteriorate, and the present invention has been accomplished.

In the present invention, the SH type surface wave includes a surface wave mainly displaced in a direction perpendicular to the direction of propagation of the surface wave, such as a BGS wave or a Love wave. . Further, the term surface acoustic wave device in the present invention is used to include a general device using a surface wave such as a surface acoustic wave resonator, a surface acoustic wave filter, and a surface acoustic wave delay line. Any number of one or more interdigital transducers is provided on the piezoelectric substrate.

In the present invention, a polymer resin material layer is provided so as to cover at least the interdigital transducer, as described above, by dispersing an insulating powder in a gel or resin having a Shore hardness of 30 or less. The gel state refers to a state having flexibility that cannot be measured by the Shore hardness measurement method, and specifically, JIS K 2
Penetration measured based on 220 penetration measurement method is 1
Points out of the range of about 00 to 20. On the other hand, Shore hardness indicates hardness measured according to or according to ASTM D676. It is necessary to use a resin having a Shore hardness of 30 or less. When a resin having a Shore hardness of more than 30 is used, the resonance resistance of the surface acoustic wave device is greatly increased, and deterioration of characteristics cannot be ignored. Because.

The reason why the synthetic resin material layer is formed by dispersing an insulating powder in the resin having a gel or shore hardness of 30 or less is that the fluidity of the resin having a gel or shore hardness of 30 or less is reduced. It is to make it. Therefore, as the insulating powder, a material having an appropriate material and particle size can be used as long as the fluidity of the resin can be reduced. Examples of the insulating fine powder that can be used include, for example, fine powder silica, niobate powder, polishing powder, and the like.
Those having a size of about 10 μm are used. Surface wave according to the present invention
In certain aspects of the device, the gel or shore hardness of 3
With respect to 100% by weight of resin of 0 or less, the specific gravity of the insulating powder
x, when the mixing ratio of the insulating powder is y (% by weight),
The insulating powder is arranged so as to satisfy y ≦ 5.7x + 15.
Have been combined.

[0015]

According to the present invention, a gel or shore hardness of at least 30 covers the interdigital transducer.
Since a polymer resin material layer in which insulating powder is dispersed in the following resin is provided, it is not necessary to provide a cavity when packaging the surface acoustic wave device. Therefore, the package structure can be simplified. Moreover, since the insulating powder is dispersed in the polymer resin material layer, the fluidity is suppressed, thereby preventing the polymer resin material layer from adhering to an undesired portion in packaging. Thus, a package structure having excellent reliability can be formed.

[0016]

FIG. 2 shows a surface acoustic wave resonance element used in an embodiment of the present invention. The surface acoustic wave resonance element 11 is configured using a piezoelectric substrate 12 that has been polarized in the direction of arrow P. A pair of interdigital electrodes 13 and 14 are formed on the upper surface of the piezoelectric substrate 12, thereby forming one interdigital transducer. Each of the comb electrodes 13 and 14 has a plurality of electrode fingers interposed therebetween. By applying an AC electric field between the comb electrodes 13 and 14, a BGS wave is excited in the arrow X direction. The BGS wave is configured to be reflected by the end faces 12a and 12b of the piezoelectric substrate 12, and thus constitutes an end face reflection type surface acoustic wave resonance element. The step of obtaining the surface acoustic wave device of the present embodiment using the surface acoustic wave resonance element 11 includes:
This will be described with reference to FIGS. 1, 3 and 4.

First, as shown in FIG.
Prepare The metal hoop 17 has terminals 18a, 18b
Are integrated, and an element mounting portion 18c having a large area is connected to the distal end side of the terminal 18a. Then, the surface acoustic wave resonance element 11 is fixed on the element mounting portion 18c using an adhesive as shown by a broken line. Next, the surface acoustic wave resonance element 11 is connected with the bonding wires 19a and 19b.
And the terminals 18a and 18b. The bonding wires 19a and 19b are connected to the comb electrode 1 shown in FIG.
3 and 14, respectively.

Next, as shown in FIG. 3, a polymer resin material is applied on the surface acoustic wave resonance element 11, and a polymer resin material layer 20 is formed. The polymer resin material layer 20 is
Insulating powder is mixed with a gel or resin having a Shore hardness of 30 or less, and the insulating powder is uniformly dispersed by kneading. As the gel-like resin, for example, an epoxy resin such as TSJ3185 manufactured by Toshiba Silicone Co., Ltd. is used. As the resin having a shore hardness of 30 or less, for example, TSE32 manufactured by Toshiba Silicone Co., Ltd.
Silicone rubber such as 51, 3155 can be used. And, as the insulating powder, a particle size of 1 μm to 5 μm
What consists of a niobate powder is used. The insulating powder is mixed in a proportion of 50 parts by weight with respect to 100 parts by weight of a resin having a gel or Shore hardness of 30 or less.

As described above, the polymer resin material layer 20
Is a gel or shore hardness of 3 in which insulating powder is dispersed
Since it is made of a resin of 0 or less, the fluidity of the polymer resin material layer 20 is reduced, and as a result, the polymer resin material layer 20 spreads significantly outside the surface acoustic wave resonance element 11 as shown in the figure. Adhered without. Next, in the state shown in FIG. 3, the exterior resin 21 is covered as shown in FIG. 4, except for the portions of the terminals 18a and 18b on the metal hoop 17 side. As the exterior resin 21, an appropriate resin material conventionally used as an exterior resin of an electronic component, such as a thermosetting resin such as an epoxy resin, is used. In this manner, a surface acoustic wave device packaged with the exterior resin 21 can be obtained, as shown in FIG. 1 in a cross-sectional view along the line II in FIG.

[0020] Other embodiments Figure 5 is a sectional view showing an embodiment applied to a surface acoustic wave device having a packaging structure using a metal case. In the surface acoustic wave device 30, a packaging structure is configured using the metal case 31. The metal case 31
It is composed of a metal base 34 having a metal plate flange 32 on the periphery and a metal lid member 33 having a storage space 33a opened downward. The metal collar 32 and the lid member 33 are welded and joined at the peripheral portion, whereby the storage space 33a in the metal case 31 is sealed. In this embodiment, the surface acoustic wave resonance element 11 shown in FIG. 2 is fixed to the upper surface of the base 34 in the storage space 33a. Reference numerals 19a and 19b denote bonding wires, which connect the surface acoustic wave resonator 11 and the terminals 35 and 36, respectively. The terminals 35 and 36 are connected to the element mounting plate 3.
4 and is drawn out of the metal case 31 through the base 34 while being insulated from the base 34.

Also in this embodiment, a polymer resin material layer 20 is provided so as to cover the upper surface of the surface acoustic wave resonance element 11. The polymer resin material layer 20 is made of the same material as that of the above-described embodiment, and therefore has a low fluidity as apparent from FIG. It is provided in a widened range, and is provided in a range that does not reach the junction between the lid member 33 and the metal collar 32. Therefore, the metal brim 32 and the lid 3
Since poor welding with the metal case 3 hardly occurs, the metal case 31 having excellent reliability can be formed. Further, even if the polymer resin material layer 20 as described above is provided, the surface acoustic wave
Since the deterioration of the characteristics of the surface acoustic wave resonance element 1 hardly occurs,
A surface acoustic wave device having stable characteristics can be obtained without controlling the distance between the first member 1 and the lid member 33 with high accuracy.

Blending Ratio of Insulating Powder The blending ratio of the resin having a gel or shore hardness of 30 or less and the insulating powder in the present invention is determined so as to obtain a desired fluidity. However, since the effect of suppressing the fluidity of the resin is inversely proportional to the weight of the insulating powder, in the case of a heavy insulating powder, the volumetric compounding amount may be small, and the light insulating powder may be used. In such a case, it is necessary to increase the final blending amount, but the weight is reversed.

FIG. 9 is a diagram for explaining a preferable range of the mixing ratio of the insulating powder. In FIG. 9, the vertical axis represents the resin 100 having a gel or Shore hardness of 30 or less.
The mixing ratio (% by weight) of the added insulating powder to the weight% is shown, and the horizontal axis shows the specific gravity of the added insulating powder. In FIG. 9, for example, fine powder silica (specific gravity = 2.3)
This shows the results of the resonance characteristics in the case where a resin layer formed by mixing insulating powders having various specific gravities in various ratios is formed on the surface acoustic wave resonance element. In FIG. 9, a mark indicates that good resonance characteristics were exhibited, and a cross indicates that the resonance characteristics were deteriorated. That is, as is clear from FIG. 9, the mixing ratio (% by weight) of the insulating powder is y,
When the specific gravity of the insulating powder is x, y = 5.7x + 15
It can be seen that the resonance characteristics are not impaired in a region below the straight line A indicated by. Therefore, the mixing ratio y
Is preferably y ≦ 5.8x + 13.7. The lower limit of the compounding ratio y of the insulating powder is not particularly limited as long as the effect of suppressing the fluidity of the resin is obtained.

[0024]

According to the present invention, in a surface acoustic wave device utilizing an SH type surface acoustic wave, a gel or Shore hardness of 30 is used.
Since the polymer resin material layer containing the following resin is disposed on the interdigital transducer, the packaging structure can be simplified without deteriorating the characteristics of the surface acoustic wave device. Moreover, since the polymer resin material layer has a configuration in which the insulating powder is uniformly dispersed, the fluidity is suppressed, whereby the adhesion portion of the polymer resin material layer spreads to an undesired range. It is possible to prevent. Therefore, when packaging with a resin exterior or using a metal case, it is possible to configure a highly reliable package structure having excellent moisture resistance and sealing properties.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing a state in which a resin sheath is applied to a surface acoustic wave device according to an embodiment of the present invention, and is a cross-sectional view taken along line II of FIG.

FIG. 2 is a perspective view showing a surface acoustic wave resonance element used in one embodiment of the present invention.

FIG. 3 is a partially cutaway perspective view for explaining a state in which a polymer resin material layer is formed on a surface acoustic wave resonance element in one embodiment of the present invention.

FIG. 4 is a partially cutaway perspective view showing a state in which a polymer resin material layer is formed and then a resin sheath is applied in one embodiment of the present invention.

FIG. 5 is a sectional view of an embodiment applied to a packaging structure using a metal case.

FIG. 6 is a cross-sectional view showing a surface acoustic wave device that is still publicly known and disclosed in the prior application.

FIG. 7 is a partially cutaway perspective view showing a state where the surface acoustic wave device is joined to a terminal.

8 is a partially cutaway plan view showing a state where a gel or a resin having a Shore hardness of 30 or less is applied to the upper surface of the surface acoustic wave resonator shown in FIG. 7;

FIG. 9 is a diagram showing resonance characteristics of the surface acoustic wave resonator when the mixing ratio of the insulating powder and the specific gravity of the insulating powder are changed.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 11 ... Surface acoustic wave resonance element 12 ... Piezoelectric substrate 13, 14 ... Comb electrode which comprises an interdigital transducer 16 ... Surface acoustic wave device 20 ... Polymer resin material layer 21 ... Exterior resin

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-54-108551 (JP, A) JP-A-62-257211 (JP, A) JP-A-61-117913 (JP, A) (58) Field (Int.Cl. ⁷ , DB name) H03H 9/145

Claims (2)

(57) [Claims] 1. A surface wave propagating in a piezoelectric substrate, wherein the displacement is mainly a displacement in a direction perpendicular to the surface wave propagation direction.
A surface acoustic wave device using a surface acoustic wave of a type comprising: a piezoelectric substrate; at least one interdigital transducer formed on the piezoelectric substrate; and a gel provided so as to cover at least the interdigital transducer. A polymer resin material layer obtained by dispersing an insulating powder in a resin having a shape or Shore hardness of 30 or less. 2. The gel or Shore hardness of 30 or less.
With respect to 100% by weight of the resin, the specific gravity of the insulating powder is x,
When the compounding ratio of the insulating powder is y (% by weight), y ≦
The insulating powder is blended so as to satisfy 5.7x + 15.
The surface wave device according to claim 1, wherein the surface wave device is provided.
Place.