JP2000165192A - Surface acoustic wave device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an extremely minimized device capable of being loaded on the surface by arranging an excited electrode to excite surface acoustic waves and a cover consisting of resin by which a vibration space of the excited electrode is secured on a piezoelectric substrate and providing an electrode for being loaded on the surface which is connected with the excited electrode at least the side of the piezoelectric substrate. SOLUTION: A surface acoustic wave filter F1 is provided with a piezoelectric substrate 5 on which an excitation electrode 1 consisting of a comb line IDT electrode and a reflector electrode, a wiring electrode 2, a side electrode 3 and an external takeout electrode 4 are formed. In addition, it is provided with an inner cover 6 and an outer cover 7 consisting of resin for securing the vibration space S of the excited electrode 1. The comb line excited electrode 1 is connected with the wiring electrode 2 and aluminum or an alloy primarily composed of aluminum is used for a first layer electrode 2a to constitute the excited electrode 1 and the wiring electrode 2. The dinner lid 6 is formed by performing surface bonding of its surroundings so that the excited electrode l is included in the recessed inner cover 6 for the purpose of securing the vibration space by the excited electrode 1 provided on the piezoelectric substrate 5.

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 using a surface acoustic wave such as a surface acoustic wave filter or a surface acoustic wave resonator used in a wireless communication circuit of a mobile communication device or the like.

[0002]

2. Description of the Related Art In recent years, many surface acoustic wave elements have been used as elements such as filters, delay lines, and transmitters of electronic devices utilizing radio waves. In particular, a surface acoustic wave filter device which is small and lightweight and has a high sharp cutoff performance as a filter is used in mobile communication devices in the field of mobile terminals.
It is often used as an F-stage and IF-stage filter.

[0003] As portable terminal devices have become smaller and lighter, the number of circuits incorporated therein for multi-band operation corresponding to a plurality of communication systems has been increasing. In order to increase the density, there is a strong demand for small components that can be surface-mounted. In a surface acoustic wave filter device which is a key part of a portable terminal device, a small surface acoustic wave filter device which can be surface-mounted with low loss and a cut-off characteristic outside a pass band is required.

Until now, ceramic package types have been put to practical use as surface acoustic wave filter devices rather than can package type devices. Among them, the ceramic package type is more surface mountable and smaller than the can package type. It has been widely used as a possible surface acoustic wave filter device.

In the first-generation ceramic package type surface acoustic wave filter device, the filter element bonded and fixed in the package and the internal electrode of the package are electrically connected by wire bonding. The outer shape has become larger, and the outer shape has an area occupying 5 to 6 times the built-in filter element.

In order to solve this problem and reduce the size, a second-generation ceramic package type surface acoustic wave filter device has been developed. For example, a surface acoustic wave device such as a surface acoustic wave device J shown in FIG. The element S is a ceramic base 5
3, a package formed of a frame 56, a lid 57, and the like, which is face-down bonded to an electrode 54, has been put to practical use.

That is, the surface acoustic wave element S is
1 on which an excitation electrode 52 is formed.
2 and an internal electrode 54a connected to the external electrodes 54b and 54c of the package via a metal bump 55. As a result, it is not necessary to use wire bonding, and the size is reduced to about one half of that of the first-generation ceramic package type surface acoustic wave device.

However, even in such a second-generation face-down mounting type ceramic package type surface acoustic wave filter device, the external size of the package is about three times as large as the built-in filter element, and is sufficiently small. At present, it has not been converted.

SUMMARY OF THE INVENTION The present invention has been made to address such a problem, and has an extremely small surface mountable device in which the area occupied by the outer shape is substantially equal to that of the built-in surface acoustic wave device. It is an object to provide a simple surface acoustic wave device.

[0010]

In order to solve the above-mentioned problems, a surface acoustic wave device of the present invention secures an excitation electrode for exciting a surface acoustic wave and a vibration space for the excitation electrode on a piezoelectric substrate. A lid made of resin is provided, and a surface mounting electrode connected to the excitation electrode is provided on at least a side surface of the piezoelectric substrate.

An excitation electrode for generating a surface acoustic wave and a lid made of resin for securing a vibration space for the excitation electrode are provided on the piezoelectric substrate, and at least a side surface of the lid is It may be configured such that an electrode for surface mounting connected to the excitation electrode is provided.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a surface acoustic wave device according to the present invention will be described below in detail with reference to the drawings.

FIG. 1 schematically shows a sectional view of an essential part of a surface acoustic wave filter F1 as an example of a surface acoustic wave device. FIG. 2 is a plan view showing the surface acoustic wave filter F1 excluding a cover and the like covering the upper part of the excitation electrode 1, and shows a region A where the wiring electrode 2 and the inner cover 6 made of resin are formed. Things.

The surface acoustic wave filter F1 has a comb-shaped ID.
An excitation electrode 1 composed of a T electrode and a reflector electrode (note that the reflector electrode may not be provided), a wiring substrate 2, a piezoelectric substrate 5 on which a side electrode 3 and an external extraction electrode 4 are formed, and a vibration space S of the excitation electrode 1. And an outer lid 7 made of resin.

Here, as the piezoelectric substrate 5, a piezoelectric substrate such as a lithium niobate crystal substrate, a lithium tantalate crystal substrate, a quartz crystal substrate, a lithium tetraborate crystal substrate, a langasite crystal substrate, and a PZT substrate is used.

The comb-like excitation electrode 1 is connected to the wiring electrode 2 as shown in a plan view in FIG. 2, and the excitation electrode 1 and the first layer electrode 2a constituting the wiring electrode 2 are made of aluminum or aluminum. An alloy containing aluminum as a main component to which copper or the like is added is used. The excitation electrode 1 is for exciting and receiving a surface acoustic wave, and is a single layer in this embodiment, but may be a multilayer electrode for improving the power durability of the electrode.

The wiring electrode 2 includes a first layer electrode 2a, a second layer electrode 2b, and a third layer electrode 2c.
, Chromium, titanium or the like, and gold, platinum, copper or the like is used as the third layer electrode 2c.

The side electrode 3 and the external extraction electrode 4 are preferably multilayer electrodes such as a two-layer electrode of lower / upper layer of chromium / gold and a three-layer electrode of titanium / platinum / gold. In particular, the outer extraction electrode 4 may be made of a solder alloy in the uppermost layer for the purpose of convenience of mounting on the circuit board. Note that such a mounting electrode may be connected to the excitation electrode 1 and formed on at least the side surface of the piezoelectric substrate 5. Further, these mounting electrodes are arranged at least at four corners of the piezoelectric substrate 5.

The inner lid 6 is surface-joined so that the excitation electrode 1 is included in the concave inner lid 6 for the purpose of securing a vibration space by the excitation electrode 1 provided on the piezoelectric substrate 5. Formed. The inner lid 6 is formed, for example, by forming a frame-shaped side wall 6a of the inner lid 6 by, for example, patterning a photosensitive organic resin film, and then using a photosensitive organic resin film to form the inner lid 6b. Is formed.

The outer lid 7 is formed of a mold resin such as a thermosetting epoxy resin such as a CRP series (manufactured by Sumitomo Bakelite Co., Ltd.).

According to the surface acoustic wave filter F1, the external take-out electrode 4 is formed on the piezoelectric substrate 5, thereby eliminating the need for a housing for mounting the surface acoustic wave filter F1. The inner lid 6 is provided on the surface,
By sealing with the outer lid 7 from above, high reliability and downsizing can be realized.

Next, another embodiment of the present invention will be described.

In the surface acoustic wave filter F2 shown in FIG. 4, an auxiliary substrate 9 for stress relaxation is joined to the back surface of the piezoelectric substrate 5 via an adhesive (joining portion) 8 made of a resin or the like for die bonding. , Except for these components, the surface acoustic wave filter F
1 is configured in the same manner.

According to the surface acoustic wave filter F2, the stress during mounting can be reduced by the auxiliary substrate 9 or the joint 8 with the auxiliary substrate 9. Here, the auxiliary substrate 9
For example, a ceramic substrate such as alumina, an organic resin substrate such as polyimide, a semiconductor substrate such as silicon, or the like can be preferably used. In particular, it is more preferable to use an auxiliary substrate 9 whose coefficient of thermal expansion is similar to that of a circuit board to be mounted (not shown) and use an adhesive 8 such as resin or rubber that can absorb distortion during mounting as much as possible. Thereby, it is possible to minimize the occurrence of cracks or the like due to stress applied to the piezoelectric substrate 5 during mounting, and it is possible to provide an excellent surface acoustic wave filter that is highly reliable and can be miniaturized.

The surface acoustic wave filter F3 shown in FIG.
In this configuration, the mounting electrodes 10 and 11 are not disposed on the side surface of the piezoelectric substrate 5 but are disposed on at least the side surface of an outer lid 7 made of resin. It is the same as the filter F1. According to the surface acoustic wave filter F3, since the electrodes 10 and 11 are provided on the surface of the outer lid 7 made of the mold resin, the stress at the time of mounting on the circuit board can be reduced by the resin. A highly reliable surface acoustic wave filter can be obtained.

The surface acoustic wave filter F3 is formed by first resin-molding a wafer and then applying an external electrode 1
Then, the wafer is cut into strips, side electrodes 11 are selectively formed on each side of the strip, and the strip substrate is cut into individual chips to form a surface acoustic wave filter. Was produced.

The surface acoustic wave filters F4 and F5 shown in FIGS. 6 and 7 are different from the surface acoustic wave filters F1 and F3 in that the electrode 13 is located between the back surface of the piezoelectric substrate 5 and the electrode 15 having a similar shape. An electrode 13 having a U-shaped cross section plated with, for example, nickel based on copper is formed so that a gap is formed between the electrode 13 and the surface of the lid 14. By the action of elasticity, the stress at the time of mounting on a circuit board can be reduced as much as possible, whereby a highly reliable surface acoustic wave filter can be provided.

These surface acoustic wave filters F4 and F5 are:
First, after forming the inner lid 6, the wafer is cut into strips,
The electrodes 13 and 15 are connected to the wiring electrodes 2 by soldering or the like, and then the outer lids 12 and 14 are formed by resin molding.
The strip-shaped piezoelectric substrate is cut into individual chips, the frames of the electrodes 13 and 15 are cut, and the electrodes are bent and shaped to produce a surface acoustic wave filter.

Next, the surface acoustic wave filter F3 shown in FIG.
A preferred manufacturing method will be described with reference to FIG.
As shown in FIG. 8, at the time of resin molding or after resin molding, a through hole 16 reaching the wiring electrode 2 is formed in the molded portion by laser processing or mechanical drilling using a thin pin. By forming a film or plating in the hole 16, the external extraction electrodes 10 and 11 are processed and formed in a wafer state, whereby simple manufacturing can be realized.

In the above embodiment, the surface acoustic wave filter has been described. However, the present invention is not limited to this. The present invention can be suitably applied to a device using a so-called surface acoustic wave such as a surface acoustic wave resonator.

[0031]

Next, a specific embodiment of the surface acoustic wave filter device will be described.

FIGS. 3A to 3E are cross-sectional views showing the steps of manufacturing the surface acoustic wave filter F1.

First, as shown in FIG. 3A, the mounting electrodes 4 were formed on the piezoelectric substrate 5. As the piezoelectric substrate 5, a substrate made of a single crystal of 36 ° Y-cut lithium tantalate having a thickness of 350 μm is used. After forming a two-layer electrode having a lower layer / upper layer of chromium / gold on one side of the substrate by sputtering, Patterning was performed by lithography, and the electrode 4 was formed by gold plating.

Next, as shown in FIG.
An excitation electrode 1 and a wiring electrode 2 serving as filter elements were formed on the other surface of the substrate. Aluminum alloy (copper content 1%) for the first layer electrode 2a of the excitation electrode 1 and the wiring electrode 2
Chromium and gold were used for the second-layer electrode 2b and the third-layer electrode 2c of the wiring electrode 2, respectively. In addition, the thickness of the excitation electrode 1 was set to 2000 to 4000 °.

Next, as shown in FIG. 3C, the inner lid 6 was formed. That is, after the photosensitive organic resin film is attached to the piezoelectric substrate 5, the inner lid 6 is patterned in a frame shape to form the side wall 6a, and then the photosensitive organic resin film is further formed thereon. The lid 6b was formed by pasting and patterning. The thickness of the photosensitive organic resin film used was 50 μm. The side wall 6
The thickness of a is 80 μm.

Next, as shown in FIG. 3D, sealing with a resin mold was performed. That is, the outer cover 7 was formed by filling the piezoelectric substrate 5 with the mold resin using a frame-shaped jig so that the thickness of the mold resin was constant. The thickness of the outer lid 7 was 300 to 400 μm.

Next, a rectangular substrate including a plurality of elements was cut out from the piezoelectric substrate 5 by dicing so that both side surfaces of the filter element were cut.

Next, as shown in FIG. 3E, side electrodes 3 were formed. A wiring mask 2 was formed on one side of the piezoelectric substrate 5 and an electrode 4 formed on the other side of the piezoelectric substrate 5 using a metal mask on the side surface of the cut-out strip-shaped filter element assembly. . This electrode was a chromium / gold two-layer electrode.

Finally, the assembly of the strip-shaped surface acoustic wave filter devices was individually separated by dicing to produce a surface acoustic wave filter.

In the manufactured surface acoustic wave filter, the comb-shaped electrodes are protected by the inner lid 6 and the outer lid 7, so that they have extremely high reliability and a filter element (1 mm × 1.5 mm). A height reduction of about 0.8 mm with almost the same occupation area was realized.

[0041]

As described above in detail, according to the surface acoustic wave device of the present invention, since the substrate of the filter element has the electrode capable of surface mounting, the conventional ceramic package and the like are unnecessary. In addition, the present invention provides an excellent surface acoustic wave filter device which is extremely miniaturized and can be mounted on the surface, in which the size and weight can be significantly reduced, and the area occupied by the outer shape is substantially equal to the built-in surface acoustic wave element. be able to.

In particular, since the mounting electrodes are provided on at least the side surface of the piezoelectric substrate in a state where the auxiliary substrate is bonded to the piezoelectric substrate, or on at least the side surface of the lid made of resin, the surface acoustic wave device can be used. Even when the thermal expansion coefficient difference between the circuit board to be mounted and the piezoelectric substrate is large, the stress after mounting can be reduced as much as possible, and a highly reliable and excellent surface acoustic wave device can be provided.

[Brief description of the drawings]

FIG. 1 is a sectional view of a principal part schematically illustrating a surface acoustic wave filter according to the present invention.

FIG. 2 is a plan view schematically illustrating a state in which a lid of the surface acoustic wave filter is removed.

FIGS. 3 (a) to 3 (e) are cross-sectional views illustrating steps of manufacturing the surface acoustic wave filter shown in FIG.

FIG. 4 is a cross-sectional view of a principal part schematically illustrating another surface acoustic wave filter according to the present invention.

FIG. 5 is a cross-sectional view of a principal part schematically illustrating another surface acoustic wave filter according to the present invention.

FIG. 6 is a cross-sectional view of a principal part schematically illustrating another surface acoustic wave filter according to the present invention.

FIG. 7 is a sectional view of a principal part schematically illustrating another surface acoustic wave filter according to the present invention.

FIG. 8 is a cross-sectional view of a principal part schematically illustrating the manufacture of the surface acoustic wave filter shown in FIG.

FIG. 9 is a cross-sectional view of a main part schematically illustrating a conventional surface acoustic wave filter.

[Explanation of symbols]

 1: Excitation electrode 2: Wiring electrode 3: Side electrode 4: External extraction electrode 5: Piezoelectric substrate 6: Inner lid 7: Outer lid 8: Adhesive 9: Auxiliary substrate F1, F2, F3, F4, F5: Elasticity Surface wave filter

Claims (2)

[Claims] An excitation electrode for exciting a surface acoustic wave and a lid made of a resin for securing a vibration space of the excitation electrode are provided on a piezoelectric substrate, and at least a side surface of the piezoelectric substrate is provided on the piezoelectric substrate. A surface acoustic wave device comprising a surface mounting electrode connected to the excitation electrode. 2. An excitation electrode for generating a surface acoustic wave and a lid made of resin for securing a vibration space of the excitation electrode are disposed on a piezoelectric substrate, and at least a side surface of the lid is A surface acoustic wave device comprising a surface mounting electrode connected to the excitation electrode.