JPH0884045A - Surface acoustic wave device and antenna branching filter using this device - Google Patents

Abstract

PURPOSE: To prevent characteristics degradation by making a dielectric substrate of an inductance element in a laminated structure, forming a microstrip line on an intermediate layer and covering the portion corresponding to the microstrip line with a conductor layer. CONSTITUTION: A surface acoustic wave resonator 1 is adhered/fixed with adhesive 8 on the conductor layer 16 for grounding formed on the bottom surface within the recessed part of the package 7 composed by laminating ceramics and metal on the rear surface of an inductance element 4. The conductor layer 13 on the upper surface of the element 4 is connected with the conductor layer 16 of the package 7 by a wiring wire 9. Therefore, the microstrip line 6 of the element 4 is formed between the upper and lower grounds with interposed dielectric layer. Because the line 6 of the element 4 is formed between the upper and lower ground surfaces with interposed dielectric layer, the influence of parasitic capacity is eliminated, and the dispersion and the degradation of the characteristics of a surface acoustic wave device can be prevented, even if the distance of the upper surface of the element 4 and the cover 11 of the package 7 is changed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface acoustic wave device including a surface acoustic wave resonator and an inductance element, and an antenna duplexer including the surface acoustic wave device.

[0002]

2. Description of the Related Art A surface acoustic wave device can be manufactured by applying a photolithography technique like an LSI (Large Scale Integrated Circuit) which is produced in a very large amount, and therefore it is excellent in mass productivity. Therefore, it is widely used in consumer equipment and communication equipment. In particular, in recent years, it is often used as a high frequency filter in mobile communication such as pagers and mobile phones as an application that makes use of the small size and light weight of the surface acoustic wave device.

The surface acoustic wave device used in the above-mentioned mobile communication is required to have a steep frequency characteristic with a particularly low loss. Therefore, the IDT (Interdigitated Interdigital Transducer) is used.
A device configured by using an (ers) type filter or a surface acoustic wave resonator is widely used.

As an example of a surface acoustic wave device constructed by using the surface acoustic wave resonator as described above, "Technical Research Report of Institute of Electronics, Information and Communication Engineers"; US92-52 (1992-0).
9), there are techniques described on pages 9 to 16. This prior art uses a surface acoustic wave resonator as a series / parallel element of a ladder filter to form a bandpass filter.

As another conventional technique, "Electronics Letter"; 1985, Volume 21, 25/26.
Issue, pp. 1211 to 1212 (ELECTRONICS LETTER
S 5thDecember 1985, Vol.21, No.25 / 26, pp.1211-1212
), There is a technique of forming a filter by using an inductance element as a series element of a ladder filter and a surface acoustic wave resonator as a parallel element.

Further, as described above, there is a strong demand for downsizing and weight reduction in application to mobile communication, so a surface mount type so-called SMD package (Surface Mounted Device) is used for the package of the surface acoustic wave device. Is being started.

As a conventional technique using such an SMD package, for example, there is a technique disclosed in Japanese Utility Model Laid-Open No. 4-131033. In the prior art shown in this prior application, a wiring pattern is formed on the inner bottom surface of a ceramic base having recesses, and a ground pattern is formed on the back surface of the ceramic base, and the ground pattern is used to connect between ground terminals. The wiring pattern is connected, and the wiring pattern and the metal lid are connected.

Another prior art is Japanese Patent Laid-Open No. 3-629.
No. 53, which discloses a glass bottom plate in which a side wall is provided along the peripheral edge of one side plate to form a concave cross section, a metal seal ring, an accommodated electronic component, and a metal. And a lid body made of metal, and a technique of forming the inside of the side wall into an inwardly inclined surface is disclosed.

Further, in Japanese Patent Laid-Open No. 3-284006, for the purpose of improving isolation between input and output and improving element characteristics of a surface acoustic wave device, a bonding pad for grounding and a bottom metallization layer are connected to each other by a connecting metal. The technique of connecting with a conductor is disclosed.

Further, Japanese Patent Laid-Open No. 3-62951 discloses that
As a technique related to the surface mount type container, in order to reduce the thermal stress and the residual stress at the time of sealing, the peripheral portion of the lid is positioned within the range of 5 to 30% of the width of the seal ring from the outer peripheral end of the seal ring to perform the welding. Techniques for doing so are disclosed.

[0011]

The structure of the surface acoustic wave device related to the present invention and the problems that the surface acoustic wave device has will be described with reference to the drawings.

As shown in the cross-sectional view of FIG. 10, the conventional structure of the surface acoustic wave device related to the present invention has a single-aperture surface acoustic wave resonator (hereinafter referred to as a surface acoustic wave resonator) 1 and an inductance element. 4 and the package 7, and a wiring wire 9 for electrically connecting them. The surface acoustic wave resonator 1 is composed of a piezoelectric substrate 2 made of LiNbO ₃ , LiTaO ₃ or the like on which a comb-shaped electrode 3 is formed, and the inductance element 4 is made of a dielectric material such as ceramic, glass or an organic material. The microstrip line 6 is formed by plating on the substrate 5. In FIG. 10, reference numeral 11 is a metal lid that covers the opening of the package 7.

The surface acoustic wave resonator 1 and the inductance element 4 described above are arbitrarily combined in series and in parallel with a ladder structure according to the required frequency characteristics, and are configured to operate as a filter. An example of this combination is shown in FIG. FIG. 12 shows an example of frequency characteristics of the surface acoustic wave device of the combination shown in FIG. 11, and is used as a filter device for high frequency signals.

As one of the applications of the surface acoustic wave device,
There is a mobile phone antenna duplexer. Antenna duplexer
The surface acoustic wave device on the transmitting side and the surface acoustic wave device on the receiving side are arranged side by side, and transmit the transmission signal from the transmitter to the antenna and the reception signal from the antenna to the receiver, respectively. Work.

Neither the technique relating to the surface acoustic wave device as described above nor the technique for constructing an antenna demultiplexer using the surface acoustic wave device has been practically used so far, and it is technically clear. There are many points that are not. Therefore, the following problems addressed by the present invention have not been revealed so far.

That is, in the surface acoustic wave device or the antenna duplexer constructed by using the surface acoustic wave device, there is a problem that there is a large variation in the characteristics after the lid 11 of the package 7 is sealed. The remarkable characteristic variation is as shown by the broken line in the frequency characteristic of FIG.
This is the deterioration of the suppression degree in the high frequency range. When such characteristic deterioration occurs, the unnecessary signal 2 having a frequency twice that of the transmission signal T
The inconvenience occurs that T is not suppressed.

[0017]

As a result of studying the deterioration of the suppression degree in the high frequency range, which is a problem of the surface acoustic wave device described above, the characteristic variation after sealing the lid 11 of the package 7 is larger than that before sealing. Is large,
The sealing process of the lid 11 is related to the variation, and as a result of an experimental examination, it is found that when the distance between the inductance element substrate (dielectric substrate 5) and the lid 11 becomes shorter, the characteristic deterioration in the high frequency range occurs. It was Since the lid 11 is grounded and the microstrip line 6 of the inductance element 4 is formed on the surface of the dielectric substrate 4, the parasitic capacitance between the microstrip line 6 and the lid 11 deteriorates in characteristics. Is considered to be the cause. That is, it is considered that the lid 11 is distorted at the time of sealing, the distance between the lid 11 and the microstrip line 6 is changed, and the magnitude of the parasitic capacitance is changed to cause characteristic variations or deterioration.

As described above, since the mobile phone is required to be small and lightweight, the surface acoustic wave device to be used is replaced with the can package which has been generally used in the past, and is thin and has a small volume. Type SMD package is used, and the height dimension from the surface of the surface-mounted device chip to the lid is smaller than before in the space dimension inside the package, and thinner packages will be used in the future. May be done. Therefore, in the surface acoustic wave device of this type, the above problems are more serious.

In the surface acoustic wave device according to the present invention, in order to solve the above problems, the dielectric substrate of the inductance element used in the surface acoustic wave device is a substrate having a laminated structure, and a microstrip line is provided in the intermediate layer of the substrate. , At least in the part corresponding to the microstrip line on the upper surface of the substrate,
The conductor layer was formed.

[0020]

As described above, in the case of a structure in which a laminated substrate is used as the dielectric substrate of the inductance element, a microstrip line is provided in the intermediate layer of the substrate, and a conductor layer is formed on the upper surface of the substrate, the substrate is packaged. By mounting and grounding the conductor layer on the top surface of the board, the microstrip line is located between the ground plane of the package and the ground plane of the top conductor layer with a dielectric layer of a predetermined thickness sandwiched between them. Even if the distance is changed, it is not affected and it is possible to prevent the characteristics of the surface acoustic wave device from varying or deteriorating.

[0021]

The details of the present invention will be described below with reference to the illustrated embodiments. 1 is a sectional view showing the structure of a surface acoustic wave device according to a first embodiment of the present invention. In the figure,
Reference numeral 1 is a surface acoustic wave resonator, 2 is a piezoelectric substrate, 3 is a comb-shaped electrode formed on the piezoelectric substrate 2, 4 is an inductance element, 5 is a dielectric substrate having a laminated structure, and 6 is a dielectric substrate 5. A microstrip line formed in the intermediate layer, 7 is a package, 8 is an adhesive, 9 is a wiring wire, 10 is a conductor terminal portion formed in the package 7, 11 is a metal lid of the package 7, and 12 is the package 7 Seal ring, 13 is a ground conductor layer formed on the upper surface of the dielectric substrate 5, and 14
Is a bonding pad (conductor terminal portion) for wiring formed on the upper surface of the dielectric substrate 5, 15 is a via hole (through hole) provided in the dielectric substrate 5, and 16 is a package 7.
Is a grounding conductor layer formed on the.

The surface acoustic wave resonator 1 is made of LiNbO ₃ , L
The piezoelectric substrate 2 made of iTaO ₃ or the like is formed with a large number of pairs of interdigital electrodes 3 made of an aluminum thin film or an aluminum alloy thin film on the surface thereof, and is configured as a publicly known single-aperture surface acoustic wave resonator. Inductance element 4
Is formed by forming a microstrip line 6 of a plated copper film on an intermediate layer of a dielectric substrate 5 having a laminated structure, and further forming a conductor layer 13 and a bonding pad 14 of a plated copper film on the upper surface of the substrate 5. The bonding pad 14 is connected to the microstrip line 6 through the via hole 15. The dielectric substrate 5 of the inductance element 4 may be made of ceramic, glass, resin, resin and fiber material, or the like.

The back surfaces of the surface acoustic wave resonator 1 (surface acoustic wave resonator chip) and the inductance element 4 (inductance element chip) are grounded on the inner surface of the concave portion of the package 7 formed by laminating ceramic and metal. Conductor layer 1
It is adhered and fixed onto the surface 6 by an adhesive 8. The conductor layer 13 on the upper surface of the inductance element 4 is connected to the ground conductor layer 16 of the package 7 by the wiring wire 9. Therefore, the microstrip line 6 of the inductance element 4 is formed between the upper and lower ground planes with the dielectric layer in between.

The respective element chips are connected to each other or to the conductor terminal portion 10 of the package 7 and the conductor layer 16 for grounding by a wiring wire 9 made of aluminum or gold. The lid 11 of the package 7 is welded to the seal ring 12 of the package 7 in order to maintain airtightness.

As described above, according to this embodiment, since the microstrip line 6 of the inductance element 4 is formed between the upper and lower ground planes with the dielectric layer sandwiched between them, the upper surface of the inductance element 4 and the package 7 are separated. Even if the distance to the lid 11 changes, it is not affected by the parasitic capacitance, and it is possible to prevent the characteristics of the surface acoustic wave device from varying or deteriorating.

Here, in the present embodiment, a plated copper film is used for the microstrip line 6, but in addition to this, it is also possible to use copper as a thin film or thin plate material. Further, as the piezoelectric substrate 2, quartz, Li ₂ B ₄ O ₇ or the like can be used other than the above. Furthermore, although the package 7 is formed by laminating ceramic and metal, it goes without saying that the same effect can be obtained by using a package made of metal.

FIG. 2 is a perspective view of the surface acoustic wave device of the first embodiment shown in FIG. In the figure, the lid 11 is omitted to clarify the internal state of the package 7. As shown in FIG. 2, most of the upper surface of the dielectric substrate 5 of the inductance element 4 is covered with the conductor layer 13,
The conductor layer 13 is electrically connected to the ground conductor layer 16 of the package 7 by the wiring wire 9. The conductor layer 1
3 does not need to be formed on substantially the entire upper surface of the dielectric substrate 5, and the effect of the present invention can be obtained if the upper surface of the dielectric substrate 5 corresponds to the portion where the microstrip line 6 is formed. Is enough.

FIG. 3 is a sectional view showing the structure of a surface acoustic wave device according to a second embodiment of the present invention. In the figure, the same components as those in the previous embodiment are designated by the same reference numerals, and the description thereof will be omitted to avoid duplication (this also applies to the following embodiments).

The present embodiment is different from the first embodiment in that the conductor layer 13 for grounding is formed not only on the upper surface of the dielectric substrate (inductance element substrate) 5 but also on the rear surface. . A conductive or insulating adhesive 8 is used to bond the element chip to the package. However, in some cases, the adhesive 8 on the back surface of the element chip may contain bubbles or the thickness of the adhesive 8 is uneven. Inconvenience may occur. In such a case, in the configuration of the present embodiment in which the conductor layer 13 is also formed on the back surface of the dielectric substrate 5, variations in parasitic capacitance generated between the ground conductor layer 16 of the package 7 and the microstrip line 6 are provided. Is eliminated, and the characteristic deterioration of the surface acoustic wave device can be prevented. Although not shown in FIG. 3, the inductance element 4
As shown in FIG. 2, the conductor layer 13 on the chip upper surface side of
The wiring wire 9 is connected to the ground plane on the package 7 side.

In each of the following embodiments, the conductor layer 1 for grounding is also provided on both sides of the inductance element chip.
3 is formed, and the conductor layer 13 on the upper surface side of the inductance element chip is connected to the ground surface on the package 7 side by the wiring wire 9.

FIG. 4 is a sectional view showing the structure of a surface acoustic wave device according to a third embodiment of the present invention. The present embodiment is an application example to a surface acoustic wave device using a mounting method of a face-down structure.

In this embodiment, the conductor terminal portion 10 and the ground conductor layer 16 are formed on the inner bottom surface of the recess of the package 7. Further, wire bumps 17 are formed on the bonding pads (for wiring connection and grounding) of the surface acoustic wave resonator 1, the bonding pads 14 of the inductance element 4 and the grounding conductor layer 13 on the face-down side. Then, the connection portions of the respective element chips (the surface acoustic wave resonator 1 and the inductance element 4) are aligned with the corresponding connection portions of the package 7, and face-down mounting is performed to connect and fix them. As the bumps, solder bumps can be used instead of wire bumps.

In the conventional mounting method having such a face-down structure, the inductance element chip surface and the ground plane of the package are closer to each other as compared with the mounting method using the wiring wire, so that the parasitic capacitance is more problematic. . However, the structure of the surface acoustic wave device according to the present embodiment has the conductor layers 13 and 13 with the dielectric layer sandwiched between the microstrip line 6 of the inductance element 4 and does not relate to the ground plane of the package. Therefore, it is possible to prevent characteristic variation and characteristic deterioration, and is suitable for a face-down structure mounting method.

FIG. 5 is a sectional view showing the structure of a surface acoustic wave device according to a fourth embodiment of the present invention. In this embodiment, the surface acoustic wave resonator 1 is wire-bonded by normal mounting, and only the inductance element 4 is face-down mounted. It goes without saying that the same effect as in the third embodiment can be obtained in this case as well.

FIG. 6 is a sectional view showing the structure of the surface acoustic wave device according to the fifth embodiment of the present invention. In this embodiment, like the fourth embodiment, only the inductance element 4 is face-down mounted, but the bonding pad 14 for connecting to the surface acoustic wave resonator 1 in the inductance element 4 is replaced with a dielectric substrate. 5 is provided on the upper surface (opposite side of the face-down surface), and the bonding pad 14 is connected to the microstrip line 6 via the via hole 15.

In the inductance element 4 according to the present invention,
Since the dielectric substrate 5 having a laminated structure is adopted, there is an advantage that the above structure can be easily made. Also,
By adopting the structure of this embodiment, a flexible element chip layout can be achieved within a limited package area, so that there is an effect of miniaturization and improvement of assembling workability.

FIG. 7 is a perspective view showing the structure of a surface acoustic wave device according to a sixth embodiment of the present invention. In FIG.
The lid 11 is omitted to clarify the internal state of the package 7. In this embodiment, not only the conductor layer 13 for grounding and the bonding pad 14 for wiring connection but also the wiring line 18 in which the microstrip line 6 and the via hole 15 are connected to the bonding pad 14 are formed on the upper surface of the inductance element 4. I am doing it. With such a structure, the bonding pad 14 can be provided at an arbitrary position on the upper surface of the substrate, so that the degree of freedom of the element chip layout can be increased. Furthermore, the effect that the wiring wire 9 can be shortened can be obtained.

FIG. 8 is a sectional view showing the structure of the surface acoustic wave device according to the seventh embodiment of the present invention. In this embodiment, a stepped surface is provided in the formation layer of the microstrip line 6 of the dielectric substrate 5 in the inductance element 4, and the bonding pad 14 is provided on this stepped surface. With such a structure, the length of the wiring wire 9 can be shortened, and further, the wiring pattern of the inductance element 4 does not need to be laid around for a long time, so that the adverse effect due to the increased wiring line length can be reduced.

FIG. 9 is a diagram showing an antenna duplexer using the surface acoustic wave device of the present invention. As shown in the figure,
The antenna duplexer 21 is configured by combining a transmission filter (transmission-side surface acoustic wave device) 22A and a reception filter (reception-side surface acoustic wave device) 22B,
It functions to perform demultiplexing transmission of the transmission signal S _T from the transmitter to the antenna 23 and the reception signal S _R from the antenna 23 to the receiver.

By using the surface acoustic wave device shown in each of the embodiments of the present invention for such an antenna duplexer, it becomes possible to provide a compact and high-performance antenna duplexer.

[0041]

As described above, according to the present invention, the influence of the parasitic capacitance, which is a problem when miniaturizing the surface acoustic wave device, is reduced. Therefore, the surface acoustic wave constituted by the surface acoustic wave resonator and the inductance element is reduced. The wave device and the antenna demultiplexer configured by using this surface acoustic wave device have great effects in reducing the characteristic variation and preventing the characteristic deterioration, and their value is enormous.

[Brief description of drawings]

FIG. 1 is a sectional view showing the structure of a surface acoustic wave device according to a first embodiment of the present invention.

FIG. 2 is a perspective view of the surface acoustic wave device of FIG. 1 with a lid removed.

FIG. 3 is a sectional view showing the configuration of a surface acoustic wave device according to a second embodiment of the present invention.

FIG. 4 is a sectional view showing the structure of a surface acoustic wave device according to a third embodiment of the present invention.

FIG. 5 is a sectional view showing the structure of a surface acoustic wave device according to a fourth embodiment of the present invention.

FIG. 6 is a sectional view showing the structure of a surface acoustic wave device according to a fifth embodiment of the present invention.

FIG. 7 is a perspective view of a surface acoustic wave device according to a sixth embodiment of the present invention with a lid removed.

FIG. 8 is a sectional view showing the structure of a surface acoustic wave device according to a seventh embodiment of the present invention.

FIG. 9 is an explanatory view schematically showing a configuration of an antenna demultiplexer using the surface acoustic wave device according to the present invention.

FIG. 10 is a cross-sectional view showing a configuration of a conventional surface acoustic wave device.

FIG. 11 is an equivalent circuit diagram showing an example of a filter configuration of a surface acoustic wave device.

FIG. 12 is an explanatory diagram showing a frequency characteristic of the surface acoustic wave device and a problem in the frequency characteristic.

[Explanation of symbols]

 1 Surface Acoustic Wave Resonator 2 Piezoelectric Substrate 3 Interdigital Electrode 4 Inductance Element 5 Dielectric Substrate 6 Microstrip Line 7 Package 8 Adhesive 9 Wiring Wire 10 Conductor Terminal 11 Cover 12 Seal Ring 13 Conductor Layer 14 Bonding Pad 15 Via Hole 16 Grounding Conductor Layer 17 Wire Bump 18 Wiring Line 21 Antenna Divider 22A Transmission Filter (Transmission Surface Acoustic Wave Device) 22B Reception Filter (Reception Side Surface Acoustic Wave Device) 23 Antenna

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shozo Yubara, 292 Yoshida-cho, Totsuka-ku, Yokohama, Kanagawa Prefecture

Claims (4)

[Claims] 1. A surface acoustic wave resonator having a comb-shaped electrode formed on a piezoelectric substrate, and an inductance element having a microstrip line formed on a dielectric substrate.
In a surface acoustic wave device electrically connected to each other and arranged in a single package, the dielectric substrate of the inductance element has a laminated structure, and the microstrip line is provided in an intermediate layer of the dielectric substrate. A surface acoustic wave device which is formed, and at least a portion of the upper surface of the dielectric substrate corresponding to the microstrip line is covered with a conductor layer. 2. The device according to claim 1, wherein a portion of the back surface of the dielectric substrate of the inductance element, which corresponds to at least the microstrip line,
A surface acoustic wave device characterized by being covered with a conductor layer. 3. The wiring line according to claim 1, wherein a wiring line is formed on an upper surface of the dielectric substrate of the inductance element, and the wiring line is electrically connected to the microstrip line of the intermediate layer of the inductance element. A surface acoustic wave device characterized by being connected. 4. The surface acoustic wave device according to claim 1, wherein at least one of the surface acoustic wave device on the transmitting side and the surface acoustic wave device on the receiving side is used. Antenna duplexer.