JP3435868B2 - Edge reflection type surface acoustic wave device and method of manufacturing the same - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an end surface reflection type surface wave device using SH type surface waves such as BGS waves and Love waves, and more particularly to an end surface reflection type surface wave device having a resin exterior. The present invention relates to a surface acoustic wave device and a method for manufacturing the same.

The edge reflection type surface acoustic wave device of the present invention is used, for example, as a bandpass filter or an oscillator in various communication devices.

[0003]

2. Description of the Related Art The SH type surface wave is a surface wave whose displacement includes a component in a direction perpendicular to the surface wave propagation direction.
S waves and love waves are known. This type of SH-type surface wave is unlikely to change its components even if it is reflected by the end face. Therefore, as the surface acoustic wave device using the SH type surface wave, a so-called end face reflection type surface acoustic wave device has been proposed in which the surface wave is reflected between the two opposite end faces to obtain resonance characteristics. In the end surface reflection type surface acoustic wave device, since the surface wave is reflected between the two opposing end surfaces, no extra substrate portion is required outside the surface wave propagating portion.

That is, in the surface wave device using the ordinary Rayleigh wave, the end surface reflection type surface wave device cannot be constructed, and it is necessary to provide the reflector and the damping material outside the surface wave propagation region. In contrast to the problem that the size of the surface acoustic wave device becomes large, in the end surface reflection type surface acoustic wave device using the SH type surface wave, it is not necessary to provide the reflector and the damping material as described above. The surface acoustic wave device can be downsized.

On the other hand, in a normal surface wave device using Rayleigh waves, conventionally, a surface wave element chip is housed in a resin packaged leaded electronic part or in a ceramic package. Have been put to practical use. Of these, a conventional surface acoustic wave device having a resin dip applied will be described with reference to FIGS. 1 and 2.

The surface acoustic wave resonator 1 shown in FIG. 1 is a surface acoustic wave resonator utilizing Rayleigh waves. The surface acoustic wave resonator 1 has a structure in which an interdigital transducer (hereinafter, IDT) 3 including a pair of comb-teeth electrodes is formed on a rectangular piezoelectric substrate 2. Reflectors 4 and 5 are formed on both sides of the IDT 3 in the surface wave propagation direction.

When the surface acoustic wave resonator 1 is constructed as an electronic component coated with resin, the IDT 3 is connected to a lead terminal (not shown) by a bonding wire, and paraffin wax is applied to the upper surface of the surface acoustic wave substrate 2. To do. After that, the remaining portion of the lead terminal except for the pulled-out portion is covered with a thermosetting resin, the thermosetting resin is cured by heating, and the cavity 6 shown in FIG. 2 is formed.

FIG. 2 is a sectional view corresponding to a portion taken along the line II-II in FIG. 1. The cavity 6 is formed in the exterior resin layer 7 made of a thermosetting resin, and the cavity 6 of the surface wave substrate 2 is formed. The top surface is exposed. The cavity 6 has a function of exposing the surface wave propagating portion of the surface wave resonator 1 and thereby preventing deterioration of characteristics due to contact of the thermosetting resin on the surface wave propagation path.

As described above, in the conventional surface acoustic wave device, the surface wave is damped when the exterior resin adheres to the excitation surface, so that the cavity 6 is formed by using paraffin wax.

[0010]

By the way, in the same way as the surface wave device 1 using the Rayleigh wave described above, when the end face reflection type surface wave resonator using the SH type surface wave is provided with a resin sheath. Despite forming a cavity,
In some cases, desired resonance characteristics could not be obtained.

That is, in the end surface reflection type surface acoustic wave device,
Even if a series of steps such as application of paraffin wax, thermosetting resin dip, formation of a cavity by heating, and curing of a thermosetting resin are performed, the resonance characteristics are significantly deteriorated despite the formation of the cavity. There was an occasion.

An object of the present invention is to provide an end face reflection type surface acoustic wave device utilizing SH type surface acoustic waves, in which a cavity for preventing deterioration of resonance characteristics is formed and a resin coating is applied. Even so, it is an object of the present invention to provide an end surface reflection type surface acoustic wave device and a method for manufacturing the same, which can surely obtain desired characteristics.

[0013]

The present invention has been made in order to achieve the above-mentioned object, and is a surface acoustic wave device using SH type surface acoustic waves, in which inner surfaces are parallel to each other. Thus, the piezoelectric substrate having the first and second grooves formed from the one main surface side and at least one interdigital formed in the substrate portion sandwiched between the first and second grooves of the piezoelectric substrate. And a transducer,
The inner surface of the second groove forms two opposite end surfaces to form an end surface reflection type surface wave element between the two opposite end surfaces, and the outer surface of the first and second grooves of the piezoelectric substrate is formed. A part is a non-excitation part, and the excitation part of the surface acoustic wave element and the first and the first
The exterior resin layer covering the periphery of the piezoelectric substrate is electrically connected to the surface acoustic wave element, leaving a cavity for exposing the inner surface of the groove 2 and the exterior resin layer outside. The end face reflection type surface acoustic wave device further comprising:

The inventors of the present application have made various studies on the phenomenon in which the resonance characteristics are deteriorated when the end face reflection type surface acoustic wave device is provided with a resin coating while leaving the cavity. That is, for example, the end face reflection type surface wave resonator 11 shown in FIG. 3 was used, a resin coating was applied, and its resonance characteristics were evaluated.

The end face reflection type surface wave resonator 11 shown in FIG.
Uses BGS waves, and is configured by using a rectangular piezoelectric substrate 12 polarized in the P direction. On the upper surface 12a of the piezoelectric substrate 12, a pair of comb-teeth electrodes 13,
14 is formed, and thereby one IDT is formed. That is, the comb-tooth electrode 13 has a plurality of electrode fingers 13a to 13c, the comb-tooth electrode 14 has a plurality of electrode fingers 14a to 14c, and the electrode fingers 13a to 13c.
And the electrode fingers 14a to 14c are interleaved with each other.

Further, the width of the remaining electrode fingers excluding the electrode fingers 14a and 13c at both ends and the interval between the respective electrode fingers are λ / 4. However, (lambda) shows the wavelength of the excited BGS wave. The width of the electrode fingers 14a and 13c is set to λ / 8. Furthermore, the electrode fingers 14a and 13c are formed along the upper ends of the end faces 12b and 12c, respectively.

In the end surface reflection type surface acoustic wave resonator 11, by applying an AC voltage from the comb-teeth electrodes 13 and 14, the BG
The S wave is excited and propagates in the direction of the arrow X, and the end faces 12b, 1
It is reflected by 2c and resonates.

When forming the exterior resin layer by resin dip, first, lead terminals (not shown) are connected to the comb electrodes 13 and 14 by bonding wires, and then paraffin wax is applied on the upper surface 12a. Thereafter, an epoxy resin is used to cover the lead terminals except the pulled-out portions, and the paraffin wax is scattered by heating to form cavities and an exterior resin layer. That is, as shown in the cross-sectional view of FIG. 4, a cavity 15 is formed on the upper surface of the end surface reflection type surface acoustic wave resonator 11, and the cavity 15 is left so that the periphery is covered with the exterior resin layer 1.
By coating with 6, a surface acoustic wave device with a resin exterior is obtained. In addition, in FIG. 4, 18 and 19 show lead terminals.

However, in the surface acoustic wave device 17, as shown in FIG.
As compared with the surface acoustic wave resonator 11 before the resin coating shown in (4), the deterioration of the resonance characteristics was remarkable. Then, as a result of diligent study of the above problems, the inventors of the present application have found that, unlike the surface wave device using Rayleigh waves, the surface wave device using SH type surface waves is not limited to the surface of the piezoelectric substrate to some extent. It has been found that the surface wave propagates even in the depth part of 1. Therefore, the resonance is damped only by exposing the upper surface 12a of the piezoelectric substrate 12 to the cavity 15. That is, in the cross-sectional view shown in FIG. 4, since the piezoelectric substrate portion above the position indicated by the alternate long and short dash line A contributes to the excitation,
In other words, since the excitation portion 17A is the entire portion above the dashed-dotted line A, the upper surface 1 of the piezoelectric substrate 12 is simply
It was found that only exposing 2a in the cavity 15 damps the resonance.

Therefore, in order to prevent the damping of the excitation part 17A by the exterior resin, it is exposed not only on the upper surface 12a of the piezoelectric substrate 12 but also on the upper part of the end faces 12b, 12c, that is, on the end faces 12b, 12c of the excitation part 17A. We also thought that it was necessary to prevent the exterior resin from adhering to the part where it was present.

Therefore, in the present invention, the first and second grooves are formed on the piezoelectric substrate, and the inner surfaces of the first and second grooves are the opposite two end surfaces. The exterior resin layer is formed so that at least the upper part of the is exposed in the cavity.

In the present invention, the first and second grooves are formed in the piezoelectric substrate in order to facilitate the formation of the cavity.
A non-excitation part is provided outside the first and second grooves,
By applying paraffin wax from the non-excited portion of the second groove to the excited portion, it is possible to surely expose the excited portion in the cavity.

Therefore, in the end surface reflection type surface acoustic wave device of the present invention, the paraffin wax applied at the time of forming the cavity can easily enter the first and second grooves, so that the portion where the IDT of the piezoelectric substrate is formed. Not only that, the upper part of the opposite two end faces is surely exposed to the cavity. Therefore, it is possible to provide an end face reflection type surface acoustic wave device having excellent resonance characteristics because damping is less likely to occur due to the exterior resin layer despite the end face reflection type surface acoustic wave device provided with a resin exterior. ing.

Further, the depth of the exciting portion is usually three times the wavelength of the surface wave because the vibration component of the SH type surface wave propagates in a depth portion up to about three times the wavelength of the surface wave. The depth is up to. Therefore, it is preferable that the portion exposed in the cavity has one main surface on which the IDT of the piezoelectric substrate portion between the first and second grooves is formed and the wavelength of the SH type surface wave from the one main surface. The end face portion reaches a depth up to 3 times, so that the exciting portion is surely exposed in the cavity.

Further, the manufacturing method of the present invention is a method for obtaining the above-mentioned end surface reflection type surface acoustic wave device of the present invention, in which at least one IDT is provided in a portion constituting the excitation portion on one main surface of the piezoelectric substrate. Forming a first groove and a second groove so that the inner surfaces of the piezoelectric substrate are parallel to each other, and the inner surface of the piezoelectric substrate is parallel to the at least one IDT. A step of disposing an electrical connection member, a step of applying wax to the piezoelectric substrate so as to cover at least the excitation part, and a step of applying the wax,
A step of covering the entire portion except a portion where the electrical connection member is drawn out with a thermosetting resin; and a step of heating to scatter the wax to cause the excitation portion and the first and second grooves.
While forming a cavity to expose the inner surface of
Curing the thermosetting resin to form an exterior resin layer.

In the manufacturing method of the present invention, either the step of forming the IDT or the step of forming the first and second grooves on the piezoelectric substrate may be performed first. In any case, a piezoelectric substrate is prepared in which at least one IDT is formed, and the first and second grooves are formed so as to sandwich the excitation part in which the IDT is formed.
An electrical connection member is connected to T. Then, wax is applied so as to cover at least the excitation portion, and the remaining portion of the electrical connecting member except the pulled-out portion is covered with the thermosetting resin, and the thermosetting resin is cured by heating. The exterior resin layer is formed and the wax is scattered to form a cavity.

Therefore, as in the case of the conventional surface wave device using Rayleigh waves, it is possible to easily obtain a surface wave device having a resin sheath. Moreover, since the paraffin wax is applied so as to expose the excitation part, it is possible to provide the end surface reflection type surface acoustic wave device of the present invention in which the deterioration of the resonance characteristic hardly occurs.

In the manufacturing method of the present invention, preferably, the wax is applied so that one main surface on which the IDT of the piezoelectric substrate portion between the first and second grooves is formed and the one main surface. To the end face portion up to a depth of up to 3 times the wavelength of the SH type surface wave, thereby ensuring that the excitation portion is exposed in the cavity.

As the wax, an appropriate material such as paraffin wax can be used as long as it can be scattered to form a cavity when the exterior resin is cured by heating.

Also, as the thermosetting resin, a suitable thermosetting resin which is cured to have an appropriate hardness after the above wax is scattered to form a cavity can be used, and the thermosetting resin is not particularly limited. is not.

Further, regarding the above electrical connection member,
Appropriate lead wires and lead terminals used for electronic parts having a resin exterior can be used and are not particularly limited.

The step of forming the first and second grooves on the piezoelectric substrate can be performed by processing the groove from one main surface side of the piezoelectric substrate using, for example, a dicer or a cutting blade. In this case, The width of the groove to be formed needs to be larger than the surface wave energy can enter, and the width of such a groove is easily controlled by adjusting the thickness of the blade of the dicer, for example. be able to.

[0033]

As described above, in the end surface reflection type surface acoustic wave device of the present invention, the first and second grooves are formed in the piezoelectric substrate, and the first and second grooves of the piezoelectric substrate are formed. An end surface reflection type surface acoustic wave element is formed between them. And since the above-mentioned non-excitation part is constituted in the portion outside the 1st and 2nd grooves,
Wax or the like for forming the cavity is used as the excitation part and the first and the first parts .
The inner surface of the second groove can be provided so as to be surely exposed. Therefore, in the end surface reflection type surface acoustic wave device of the present invention, the excitation portion of the surface acoustic wave resonance element is surely exposed in the cavity.

Therefore, it is possible to surely provide the end face reflection type surface wave device utilizing the SH type surface wave and capable of realizing the desired characteristics. In the end-face reflection type surface acoustic wave device, since the exciting portion is formed between the two opposite end faces, it is possible to promote downsizing of the surface acoustic wave device.
In the end surface reflection type surface acoustic wave device of the present invention, the non-excited portion is provided outside the first and second grooves, and the size of the surface acoustic wave device is increased by the amount of the non-excited portion. However, the non-excitation part is merely provided so as to surely expose the excitation part to the cavity, that is, to expand the wax application area, and therefore the non-excitation part does not need to be so large. Therefore, even if the non-excitation section is provided,
Since it is not necessary to make the non-excitation part so large, the size of the surface acoustic wave device can be reduced as compared with the conventional surface acoustic wave device which is not the end face reflection type.

Further, in the method of manufacturing the surface acoustic wave device of the present invention, as described above, after obtaining the structure in which at least one IDT is formed in the piezoelectric substrate portion between the first and second grooves, at least the exciting portion is obtained. Wax is applied to cover the. In this case, since the non-exciting portion is provided outside the first and second grooves, the wax can be applied so as to surely cover the exciting portion when applying the wax. Therefore, it is possible to reliably form the cavity in which the excitation portion is exposed in the exterior resin layer. Therefore, as in the case of the conventional surface wave device using Rayleigh waves, it is possible to easily obtain a surface wave device provided with a resin sheath. Moreover, since the paraffin wax is applied so as to expose the above-mentioned excitation portion, the deterioration of the resonance characteristics is unlikely to occur in the same manner as in the above-described end surface reflection type surface acoustic wave device of the present invention, and the end surface provided with the resin coating. A reflective surface acoustic wave device can be provided.

[0036]

Description of Embodiments An embodiment of a surface wave device applied to an end surface reflection type surface wave resonator utilizing BGS waves will be described below.

First, the piezoelectric substrate 22 shown in FIG. 5 is prepared. As the piezoelectric substrate 22, piezoelectric ceramics such as lead zirconate titanate, LiTaO ₃ or Li
A piezoelectric single crystal such as NbO ₃ or quartz can be used.

Next, an Al film is formed on the upper surface of the piezoelectric substrate 22 by sputtering a metal material such as Al. After that, A by photolithography
The I film is patterned to form the IDT 23. IDT
23 has a pair of comb electrodes 24 and 25. Each of the comb-teeth electrodes 24, 25 has a plurality of electrode fingers 24a to 24a.
24c, 25a to 25c. Multiple electrode fingers 24
The a to 24c and the plurality of electrode fingers 25a to 25c are arranged so as to be inserted into each other.

Next, the first and second grooves 26 and 27 having a predetermined width are formed from the upper surface of the piezoelectric substrate 22 by a dicing machine. The formation of the grooves 26 and 27 and the formation of the IDT 23 may be performed in reverse. That is, the IDT 23 may be formed after first forming the grooves 26 and 27.

Of course, the electrode fingers 24a to 24c and 25a to 2 of the comb-teeth electrodes 24 and 25 constituting the IDT 23 are formed.
The width of the electrode fingers 24c and 25a at both ends of 5c is half the width of the other electrode fingers, that is, λ / 8. The width of the remaining electrode fingers 24a, 24b, 25b, 25c is λ / 4. Therefore, when forming the grooves 26 and 27 after forming a pair of comb-shaped electrodes each having a plurality of electrode fingers each having a width of λ / 4, the width of the electrode fingers at both ends is divided into ½. By thus forming the grooves 26 and 27, the IDT 23 can be accurately formed. That is, the IDT 23 can be reliably formed so that the outer edges of the electrode fingers 24c and 25a at both ends accurately face the inner surfaces 26a and 27a of the grooves 26 and 27. Therefore, after the IDT 23 is first formed, the groove 26 is formed. , 27 are preferably formed.

The inner surfaces 26a and 27a of the grooves 26 and 27 are parallel to each other, and thus form the two opposite end surfaces of the end surface reflection type surface acoustic wave element. Groove 2 as above
By forming 6, 27, an end surface reflection type surface acoustic wave element portion is formed between the grooves 26, 27, and the grooves 26, 27
The non-excitation parts 28 and 29 are formed on the outer side of 27.

Next, the surface wave element chip 21 shown in FIG.
Is bonded to the first metal terminal 31 with an adhesive as shown in FIG. On the other hand, the first metal terminal 31 and one of the comb-teeth electrodes 24 are connected by a bonding wire 32. Further, the I-shaped second metal terminal 33 is arranged on the side of the metal terminal 31, and the metal terminal 33 and the other comb-shaped electrode 25 are connected by the bonding wire 34.

Although the metal terminals 31 and 33 constitute the electrical connecting member of the present invention, the electrical connecting material is not limited to the metal terminals 31 and 33 shown in FIG. You may comprise by. However, like the metal terminal 31, it is desirable to use a plate-shaped metal terminal in which the element mounting portion 31a having a size capable of mounting the surface acoustic wave element 21 is formed.

Next, paraffin wax is applied to the region shown by the one-dot chain line 30 in FIG. 5, and then the periphery is covered with a thermosetting resin such as an epoxy resin. In this case, the thermosetting resin is kept in a molten state, the surface wave element 21 coated with wax is immersed in the molten thermosetting resin, and the surface wave element 21 is further pulled up to form a coating made of the thermosetting resin. Can be formed.

Thereafter, by heating to a temperature at which the thermosetting resin is cured, for example, heat treatment is applied at a temperature of about 150 ° C. to cure the exterior resin layer made of the thermosetting resin. In this case, the applied paraffin wax is scattered by heating, and a cavity is formed inside.

That is, as shown in the sectional view of FIG. 7, a leaded electronic component in which a cavity 35 is formed above the surface acoustic wave device chip 21 and which is entirely covered with the exterior resin layer 36 is obtained.

By the way, in this embodiment, the cavity 35 is formed so as to surely expose the exciting portion 37 of the surface wave element portion sandwiched between the first and second grooves 26, 27. That is, as is apparent from FIG. 5, the paraffin wax is applied so as to reach the upper surfaces of the non-excited portions 28 and 29. Therefore, not only the upper surface of the piezoelectric substrate portion 22a between the first and second grooves 26 and 27 but also the inner surfaces 26a and 27a of the first and second grooves 26 and 27 forming the two opposite end surfaces are cavities 35. Will definitely be exposed. Therefore, in the end surface reflection type surface acoustic wave device 38 of the present embodiment shown in FIG.
The excitation portion 37 arranged above the portion indicated by the alternate long and short dash line A is reliably exposed in the cavity 35.

Therefore, even if it is configured as an electronic component with a lead provided with the exterior resin 36, it is possible to provide an end-face reflection type surface acoustic wave device in which deterioration of resonance characteristics hardly occurs.

Next, the effect of the present invention will be clarified based on a concrete experimental example. As the piezoelectric substrate, a piezoelectric substrate made of PZT and having a thickness of 500 μm was prepared. Next, an Al electrode having a thickness of 1 μm was formed on the entire upper surface by sputtering. After that, A by photolithography
The l electrode was patterned to form the IDT 23.
The excited BGS wave has a wavelength of 82 μm, the electrode finger cross width is 228 μm, and the number of electrode finger pairs is 2.
The IDT 23 was formed so as to be 0.

Then, using a dicing machine, 3
First and second grooves 26, 27 having a depth of 00 μm and a width of 100 μm were formed. First and second grooves 26, 2
7, the piezoelectric substrate is cut so as to leave the non-excited portions 28 and 29 having a dimension of about 200 μm in the width direction, that is, along the surface wave propagation direction, and the surface wave element chip shown in FIG. I got 21.

Next, paraffin wax is applied to the area shown by the alternate long and short dash line 30 in FIG. 5 to a thickness of 1/2 of the piezoelectric substrate, and then the whole is covered with a thermosetting resin and heated to heat the resin. The exterior and the cavity were formed.

For comparison, the non-excited portion 2 is cut by cutting along the inner surfaces 26a and 27a of the surface acoustic wave element chip 21 described above.
An end surface reflection type surface acoustic wave element chip having no components 8 and 29 was obtained, and the metal terminals were joined and the resin sheathing was formed in the same manner as in the above-described example. However, in this comparative example,
The paraffin wax was applied only to the upper surface of the piezoelectric substrate portion on which the IDT 23 was formed.

The surface acoustic wave devices of the above-mentioned examples and comparative examples are 50
The impedance characteristics and the phase characteristics were measured by pulling out one by one. FIG. 8 shows impedance characteristics and phase characteristics of the surface acoustic wave devices of Examples and Comparative Examples.

All of the above 50 surface acoustic wave devices exhibited the impedance characteristics and phase characteristics shown by the solid lines B and C in FIG. On the other hand, in the surface acoustic wave device of the comparative example, there are 5 to 6 impedance characteristics and phase characteristics shown by solid lines B and C, and in most surface acoustic wave devices, the impedance characteristics shown by broken lines D and E. It was confirmed that the phase characteristics were shown. That is, in the surface acoustic wave device of the embodiment, the peak-to-valley ratio (that is, the ratio of the impedance value at the anti-resonance point to the impedance value at the resonance point) is large and the phase rotation angle is large compared to the surface acoustic wave device of the comparative example. Recognize.

Table 1 below shows the peak-valley ratio and the maximum phase rotation angle of the above Examples and Comparative Examples together with the mechanical quality factor Qm.

[0056]

[Table 1]

The values shown in Table 1 are average values of 50 surface acoustic wave devices of Examples and Comparative Examples. As is clear from Table 1, the surface acoustic wave device of the example has a peak-to-valley ratio of about 10 dB and a phase rotation angle of about 10 compared to the surface acoustic wave device of the comparative example.
It can be seen that the mechanical quality factor Qm can be increased more than twice.

Further, when the surface acoustic wave device of the embodiment having the characteristics shown by the solid lines B and C in FIG. 8 was taken out and cut along the surface wave propagation direction and the inside was observed, the cavity surely exposed the excitation part. It was recognized that it was configured to. On the other hand, in the surface acoustic wave device of the comparative example having the characteristics shown by the broken lines D and E, the cavity is not sufficiently formed, and the thermosetting resin contacts the vicinity of both ends of the comb-teeth electrode and the upper part of the opposite two end faces. Was confirmed.

Further, the surface acoustic wave device of the example having the characteristics shown by the solid lines B and C was incorporated into a transmission circuit as an oscillator having an oscillation frequency of 30 MHz and evaluated. As a result, the call was never stopped. On the other hand, when the surface acoustic wave device of the comparative example showing the characteristics of the broken lines D and E was similarly incorporated in the oscillation circuit, the oscillation stop occurred in more than half of the surface acoustic wave devices.

FIG. 9 is a perspective view for explaining an end surface reflection type surface acoustic wave device according to the second embodiment of the present invention. In the first embodiment, the embodiment applied to the end surface reflection type surface acoustic wave resonator having one IDT has been described, but the present invention is the end surface reflection type surface acoustic wave in which two or more IDTs are formed. It can also be applied to a device.

The second embodiment shown in FIG. 9 has two IDTs.
It is an end-face reflection type transversal type surface acoustic wave filter having 42 and 43. In the surface wave element chip 41, ID
T42 and T43 are formed at a predetermined distance along the surface wave propagation direction. In the piezoelectric substrate 44, the first
Second grooves 45 and 46 are formed, and the IDTs 42 and 43 are formed between the first and second grooves 45 and 46. That is, a transversal type surface acoustic wave filter element is formed between the first and second grooves 45 and 46. The inner surface 45 of the first and second grooves 45, 46
a and 46a are parallel to each other and therefore face each other 2
It constitutes the end face.

The piezoelectric substrate 44 is polarized in the direction of the arrow P shown in the figure, that is, parallel to the extending direction of the electrode fingers. The other points are similar to those of the first embodiment.

Further, the surface wave device chip 41 applied to the above-mentioned transversal type surface wave filter is used to construct a surface wave device having an exterior resin layer in which a cavity is formed as in the case of the first embodiment. Was measured. Further, for comparison, a surface acoustic wave device with leads was similarly constructed using element chips cut at the inner surfaces 45a and 46a of the grooves 45 and 46, and the characteristics were measured. As a result, in the surface acoustic wave device of the comparative example, the propagation loss was 10 dB,
It was confirmed that the propagation loss was significantly reduced to 5 dB in the surface acoustic wave device of the second embodiment.

[Brief description of drawings]

FIG. 1 is a plan view for explaining a conventional surface wave resonator using Rayleigh waves.

FIG. 2 is a cross-sectional view of a surface acoustic wave device provided with a resin sheath using the surface acoustic wave resonator shown in FIG.

FIG. 3 is a perspective view showing a conventional end surface reflection type surface acoustic wave resonator.

FIG. 4 is a transverse cross-sectional view of a surface acoustic wave device having a resin sheath formed by using the end face reflection type surface acoustic wave resonator shown in FIG.

FIG. 5 is a perspective view showing a surface acoustic wave element chip prepared in the first embodiment.

FIG. 6 is a perspective view showing a state where the surface acoustic wave element chip is mounted on a metal terminal in the first embodiment.

FIG. 7 is a cross-sectional view of the surface acoustic wave device according to the first embodiment.

FIG. 8 is a diagram for explaining impedance characteristics and phase characteristics of the example and the comparative example.

FIG. 9 is a perspective view showing an edge reflection type surface acoustic wave element chip used in the surface acoustic wave device of the second embodiment.

[Explanation of symbols]

21 ... Surface wave element chip 22 ... Piezoelectric substrate 23 ... IDT 24,25 ... Comb tooth electrode 26, 27 ... First and second grooves 28, 29 ... Non-excitation part 30 ... Area where paraffin wax is applied 31, 33 ... Metal terminals as electrical connection members 35 ... Cavity 36 ... Exterior resin layer 37 ... Excitation section 41 ... Surface wave element chip 42, 43 ... IDT 44 ... Piezoelectric substrate 45, 46 ... First and second grooves

Front page continuation (72) Inventor Michio Kadota 2-10-10 Tenjin, Nagaokakyo, Kyoto Prefecture Murata Manufacturing Co., Ltd. (56) References JP-A-5-183369 (JP, A) JP-A-4-239210 (JP, A) JP 4-82315 (JP, A) JP 6-21748 (JP, A) JP 1-293708 (JP, A) JP 64-5219 (JP, A) Kai 55-135410 (JP, A) JP 51-11393 (JP, A) JP 51-15987 (JP, A) JP 54-108551 (JP, A) (58) Fields investigated (58) Int.Cl. ⁷ , DB name) H03H 9/25 H03H 3/08

Claims (4)

(57) [Claims] 1. A surface acoustic wave device using an SH type surface acoustic wave, comprising: a piezoelectric substrate having first and second grooves formed from one main surface side so that inner surfaces are parallel to each other. And at least one interdigital transducer formed in a substrate portion sandwiched between the first and second grooves of the piezoelectric substrate, wherein inner surfaces of the first and second grooves are opposite two end surfaces. An end facet reflection type surface acoustic wave element is formed between the two opposing end faces, and portions outside the first and second grooves of the piezoelectric substrate are non-excited portions, An exterior resin layer covering the periphery of the piezoelectric substrate, leaving a cavity for exposing the excitation part of the element and the inner surfaces of the first and second grooves, and the surface wave element. An electrical connection member that is electrically connected and is drawn out of the exterior resin layer Further comprising, edge reflection type surface acoustic wave device. 2. A portion exposed to the cavity is one main surface of the piezoelectric substrate portion between the first and second grooves, on which the interdigital transducer is formed, and the SH type from the one main surface. 2. The end surface reflection type surface acoustic wave device according to claim 1, wherein the end surface portion reaches a depth of up to 3 times the wavelength of the surface wave. 3. A step of forming at least one interdigital transducer in a portion that constitutes an excitation section on one main surface of the piezoelectric substrate, and a step of sandwiching the excitation section from the one main surface of the piezoelectric substrate, and the inner surfaces of the piezoelectric substrate. Forming the first and second grooves in parallel with each other, arranging an electrical connection member connected to the at least one interdigital transducer, and the piezoelectric substrate so as to cover at least the excitation part. A step of applying a wax to the wax, and a step of coating the entire portion except a portion where the electrical connection member is pulled out with a thermosetting resin after applying the wax, and a step of scattering the wax by heating and exciting the portion. The above
The end surface reflection type according to claim 1, further comprising: forming a cavity for exposing the inner surfaces of the first and second grooves and curing the thermosetting resin to form an exterior resin layer. Method of manufacturing surface acoustic wave device. 4. The portion to which the wax is applied is the first,
One main surface of the piezoelectric substrate portion between the second grooves in which the interdigital transducer is formed, and an end surface portion reaching a depth of up to three times the wavelength of the SH-type surface wave excited from the one main surface. The manufacturing method of the end surface reflection type surface acoustic wave device according to claim 3, wherein