JP2003087092A - Base plate for surface acoustic wave device, and surface acoustic wave device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a base plate for an surface acoustic wave device which can obtain proper attenuation characteristic outside a passing band, without increasing the number of grounding conductive patterns. SOLUTION: There are provided a base composed of a ceramic plate; a first conductive pattern formed on a surface of the base; a second conductive pattern formed on a back of the base; a castellation formed on a side surface of the base, for connecting between the first and second conductive patterns; and an in-hole conductive substance embedded in a hole which passes through a both-side surface of the base, for connecting between the first and second conductive patterns.

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 base substrate and a surface acoustic wave device, and more particularly to a technique for improving out-of-band attenuation characteristics of a surface mount ceramic package.

[0002]

2. Description of the Related Art With the recent rapid spread of mobile phones, cordless phones, etc., and their miniaturization / weight reduction, there is an increasing demand for small filters with low loss and excellent attenuation characteristics. In addition, the surface acoustic wave device has come to be widely used as an electronic component (filter) of a mobile communication device that requires a particularly small size. The attenuation characteristic outside the pass band in the surface acoustic wave device is an important issue in filter characteristics.

The surface acoustic wave element has a metal pattern formed on a piezoelectric substrate. The metal pattern has an input / output electrode having a comb-tooth shape, a ground electrode arranged to face the input / output electrode, and an electrode pad connected to these electrodes. Further, as a mounting technique of a surface acoustic wave element, there is a face-down bonding method in which a ceramic base and a surface acoustic wave element are electrically joined via a bump made of Au or the like. In the face-down bonding method, the conductor pattern formed on the surface of the ceramic base and the signal extraction electrode pad (A, B, G) including the IDT electrode of the surface acoustic wave element are arranged to face each other with a gap. .

As shown in FIG. 6A, on the surface of the ceramic base 51, an input (52a) and an output (52a) are formed.
b) and a first conductor pattern for grounding (52c) are formed. As shown in FIG. 6B, the input (55a) and the output (55
b) and the second conductor pattern for grounding (55c) are formed. The first conductor pattern 52 and the second conductor pattern 55 are connected by a castellation 53 formed on the side surface of the ceramic base 51. As shown in FIG. 6C, the ceramic base 51
A surface acoustic wave element is mounted in the central portion of the surface of, and a cavity 56 is formed on the outer periphery thereof. Electrode pads (A, B, G) are bump-bonded to each first conductor pattern 52.

[0005]

Due to the miniaturization of surface acoustic wave devices, the number of conductor patterns (terminals) formed on the front and back surfaces of the ceramic base tends to be small, and in particular, the number of conductor patterns (terminals) for grounding is reduced. The decreasing tendency is remarkable. Therefore, if a surface acoustic wave device is created using a ceramic base substrate having only a conventional castellation structure, the potential of the ground electrode cannot be sufficiently lowered to the ground level (0 V), and the surface acoustic wave device is not produced. However, there is a problem in that the characteristics, especially the attenuation characteristics outside the pass band as a filter cannot be obtained sufficiently.

The present invention has been made in order to solve the above-mentioned problems of the prior art, and an object thereof is to provide good attenuation characteristics outside the pass band without increasing the number of grounding conductor patterns. A base substrate for a surface acoustic wave device,
Another object of the present invention is to provide a surface acoustic wave device using this base substrate.

[0007]

In order to achieve the above object, a base substrate for a surface acoustic wave device according to the present invention comprises a base made of a ceramic plate, a first conductor pattern formed on the surface of the base, The second conductor pattern formed on the back surface of the base and the first conductor pattern formed on the side surface of the base.
And a castellation that connects between the second conductor pattern and an in-hole conductor that connects between the first and second conductor patterns and is embedded in a hole that penetrates the front and back surfaces of the base.

According to the base substrate for a surface acoustic wave device of the present invention, the space between the first and second conductor patterns formed on the front and back surfaces of the base is not limited to the castellation, but is also electrically conductive by the conductor in the hole. Connected to each other,
The electrode resistance between the first and second conductor patterns is reduced. By supplying the ground potential to the surface acoustic wave device mounted on the base substrate for the surface acoustic wave device via the first and second conductor patterns, the potential of the ground electrode is sufficiently lowered to the ground level (0V). It is possible to obtain good characteristics as a surface acoustic wave device, and particularly sufficient attenuation characteristics outside the pass band as a filter.

A surface acoustic wave device according to the present invention includes a surface acoustic wave including a piezoelectric substrate and a metal pattern formed on the surface of the piezoelectric substrate including a comb electrode and an electrode pad connected to the comb electrode. An element, a bump formed on an electrode pad, a base made of a ceramic plate, and a first conductor pattern formed on the surface of the base and electrically and mechanically connected to the electrode pad via the bump , A second conductor pattern formed on the back surface of the base, a castellation formed on the side surface of the base for connecting between the first and second conductor patterns, and a hole penetrating the front and back surfaces of the base. And an in-hole conductor that connects the embedded first and second conductor patterns.

According to the surface acoustic wave device of the present invention, the first and second conductor patterns formed on the front and back surfaces of the base are electrically connected not only by the castellation but also by the conductor in the hole. Because it is done, the first and second
The electrode resistance between the conductor patterns is reduced. By supplying the ground potential to the surface acoustic wave element via the first and second conductor patterns, the potential of the ground electrode can be sufficiently lowered to the ground level (0 V), and good characteristics as a surface acoustic wave device can be obtained. In particular, a sufficient attenuation characteristic outside the pass band as a filter can be obtained.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. In the description of the drawings, the same or similar parts are denoted by the same or similar reference numerals. However, it should be noted that the drawings are schematic and the shapes of the patterns, the ratio between the patterns, and the like are different from the actual ones. Further, it is needless to say that the drawings include parts in which dimensional relationships and ratios are different from each other.

(First Embodiment) FIG. 1A is a plan view showing a surface structure of a base substrate for a surface acoustic wave device according to an embodiment of the present invention. As shown in FIG.
The base substrate is a base made of a ceramic plate (hereinafter,
1) and a first conductor pattern 2 formed on the surface of the ceramic base 1.
The first conductor pattern 2 includes a first conductor pattern (2a) for input connected to an input electrode of a surface acoustic wave element mounted on a base substrate and a first conductor pattern (2a) for output connected to an output electrode. One conductor pattern (2b) and the first conductor pattern (2c) for grounding connected to the ground electrode. Electrode pads of a surface acoustic wave element (chip) described later are connected to each of the first conductor patterns 2 via conductive bumps. That is, the chip is mounted on the surface of the ceramic base 1.

A part of each first conductor pattern is extended to a corner of the ceramic base 1 and is connected to a second conductor pattern described later by a castellation formed on the side surface of the ceramic base 1 at the corner. Has been done. In addition, holes (via holes, through holes, etc.) that penetrate the front and back surfaces of the ceramic base are formed,
The first conductor pattern 2c for grounding is connected to the second conductor pattern for grounding by the conductor 4 embedded in this hole.

FIG. 1B is a plan view showing the back surface structure of the surface acoustic wave device base substrate shown in FIG.
As shown in FIG. 1B, the base substrate further has a second conductor pattern 5 formed on the back surface of the ceramic base 1. The second conductor pattern 5 includes an input second conductor pattern (5a) and an output second conductor pattern (5a).
b) and a second conductor pattern (5c) for grounding. Each second conductor pattern 5 has a castellation 3
Are respectively connected to the first conductor pattern 2 via. Further, as described above, the grounding second conductor pattern 5c is connected to the grounding first conductor pattern 2c by the in-hole conductor 4. That is, the first conductor pattern 2c for grounding and the second conductor pattern 5c for grounding are connected not only by the castellation 3 but also by the conductor 4 in the hole.

FIG. 2 shows a first conductor pattern 2c for grounding.
It is sectional drawing which showed typically the connection state of the 2nd conductor pattern 5c for grounding. As shown in FIG. 2, the surface of the ceramic base 1 has a first conductor pattern 2c for grounding.
And a second conductor pattern 5c for grounding is formed on the back surface of the ceramic base 1. First for grounding
Conductor pattern 2c and second conductor pattern 5c for grounding
Are connected by the castellation 3 and, at the same time, by the in-hole conductor 4.
The first and second conductor patterns (2, 5) and the castellation 3 are composed of a tungsten (W) metallized layer, a nickel (Ni) layer formed by plating, and gold (Au) formed by electrolytic plating. ) 3 layers
Each has a layered structure.

FIG. 3A is a plan view showing a state where the cavity 6 is formed on the surface of the ceramic base 1.
The cavity 6 is formed outside a portion where a surface acoustic wave element described later is mounted, has a ring-shaped planar shape, and is exposed inside the ring by mounting the surface acoustic wave element inside the ring. Face down bonding can be performed on one conductor pattern 2.

FIG. 3 (b) is a plan view showing the structure of the surface acoustic wave element mounted on the surface of the ceramic base 1 in the state shown in FIG. 3 (a). As shown in FIG. 3 (b),
The surface acoustic wave element is formed of LTA (lithium tantalate (Li
It has a piezoelectric substrate 7 such as a TaO ₃ )) substrate and a metal pattern formed on the piezoelectric substrate 7. The metal pattern includes comb-teeth electrodes 8 and electrode pads (A, B, G) connected to the respective comb-teeth electrodes. The comb-teeth electrode 8 is composed of an input electrode, an output electrode, and a ground electrode arranged to face the input / output electrode. The input electrode pad A is connected to the input electrode, the output electrode pad B is connected to the output electrode, and the ground electrode pad G is connected to the ground electrode.

FIG. 4A is a plan view showing a state in which the surface acoustic wave device shown in FIG. 3B is face-down bonded to the surface of the ceramic base 1 shown in FIG. 3A. As shown in FIG. 4A, the surface acoustic wave element is arranged inside the cavity 6. The input electrode pad A is arranged on the first conductor pattern 2a for input, the output electrode pad B is arranged on the first conductor pattern 2b for output, and the ground electrode pad G is for grounding. Is arranged on the first conductor pattern 2c. Each electrode pad (A, B, G) and each first conductor pattern 2 are
Electrically and mechanically connected by bumps.

FIG. 4B is a sectional view taken along the line II of FIG. 4A. As shown in FIG. 4B, the first conductor pattern 2 for grounding is provided on the surface of the ceramic base 1.
c is arranged, and the ground electrode G is connected via the bump 9 on the first conductor pattern 2c for grounding. At this time, the surface acoustic wave element is mounted on the surface of the ceramic base 1 by so-called flip chip connection in which the surface of the piezoelectric substrate 7 is opposed to the surface of the ceramic base 1. A cavity 6 is arranged around the surface acoustic wave element on the ceramic base. Although illustration is omitted, the surface acoustic wave element shown in FIGS. 4A and 4B is formed of a housing (cap) made of ceramic or resin.
The surface acoustic wave element can be sealed (packaged) by covering with.

As described above, according to the embodiment of the present invention, only the castellation 3 is provided between the first and second conductor patterns (2, 5) formed on the front and back surfaces of the ceramic base 1. However, since it is also electrically connected by the conductor 4 in the hole, the electrode resistance between the first and second conductor patterns (2, 5) is reduced. By supplying the ground potential to the surface acoustic wave element mounted on the surface acoustic wave device base substrate through the first and second conductor patterns (2, 5), the potential of the ground electrode is changed to the ground level ( It is possible to obtain a sufficient characteristic as a surface acoustic wave device, particularly a sufficient attenuation characteristic outside the pass band as a filter.

That is, in the face-down bonding type surface acoustic wave device, the conductor patterns (2, 5) formed on the front surface and the back surface of the ceramic base 1 are electrically connected by the castellation structure 3, and a single or By being electrically connected also by the conductors 4 embedded in the plurality of via holes, the grounding conductor patterns (2c, 5c) can be more uniformly dropped to the ground potential. Therefore, the surface acoustic wave element has an effect of improving the attenuation particularly with respect to the characteristics outside the band, and in turn, it is possible to reduce the electrical influence of the device performance particularly the characteristics outside the band.

In the embodiment of the present invention, the case where a single layer ceramic base 1 is used has been described, but a ceramic base composed of a plurality of layers of ceramic plates may be used.

Further, although FIGS. 1A and 1B show the case where two in-hole conductors 4 are formed for each second conductor pattern 5c, the present invention is not limited to this. However, the number of the in-hole conductors 4 may be one or three or more.

(Comparative Experiment Example) In order to confirm the effect of the above-described embodiment of the present invention, the inventors conducted the following comparative experiment. In order to confirm the effect of separating the ground electrode of the base substrate for the surface acoustic wave device, the base substrate according to the related art having only the castellation structure (FIG. 6), the castellation 3 and the two in-hole conductors 4 are provided. Base substrate according to an embodiment of the present invention (FIG. 1)
Prepared.

As a surface acoustic wave element, an A
A resonator type in which an l-alloy electrode was patterned was adopted. The designed LTA board has a chip size of 0.9 x
The size is 1.4 × 0.35 mm, and the electrode structure including the IDT electrode is as shown in FIG. In this experiment, surface acoustic wave devices made of the same LTA wafer were mounted on the base substrate according to the related art and the base substrate according to the example of the present invention. The conditions other than the base substrate were substantially the same. The package size after sealing with the cap is 2.5 × 2.0 × 1.
It is 0 mm.

FIG. 5 is a graph showing wide band characteristics of the surface acoustic wave device (filter) assembled using the base substrate according to the prior art and the base substrate according to the embodiment of the present invention. As shown in FIG. 5, as compared with the base substrate according to the related art, the surface acoustic wave device assembled by the base substrate according to the embodiment of the present invention has a better attenuation amount in the unnecessary signal region outside the pass band. Was obtained. From the results of this comparative experiment, it was confirmed that the use of the base substrate according to the example of the present invention in producing the surface acoustic wave device is very effective in attenuating unnecessary signals outside the pass band. It was

[0027]

As described above, according to the present invention, it is possible to obtain a good attenuation characteristic outside the pass band without increasing the number of grounding conductor patterns, and a base substrate for this surface acoustic wave device. A surface acoustic wave device using a substrate can be provided.

[Brief description of drawings]

FIG. 1A is a plan view showing a surface configuration of a base substrate for a surface acoustic wave device according to an embodiment of the present invention. FIG. 1B is a plan view showing the back surface configuration of the base substrate for the surface acoustic wave device shown in FIG.

FIG. 2 is a cross-sectional view schematically showing a connection state of a first conductor pattern for grounding and a second conductor pattern for grounding.

FIG. 3A is a plan view showing a state in which a cavity is formed on the surface of a ceramic base. Figure 3
FIG. 3B is a plan view showing the structure of the surface acoustic wave element mounted on the surface of the ceramic base 1 in the state shown in FIG.

4 (a) is a plan view showing a state in which the surface acoustic wave device shown in FIG. 3 (b) is face-down bonded to the surface of the ceramic base 1 shown in FIG. 3 (a). . FIG. 4B is a sectional view taken along the line I-I of FIG. 4A.

FIG. 5 is a graph showing characteristics of a wide band of a surface acoustic wave device assembled by using a base substrate according to a conventional technique and a base substrate according to an embodiment of the present invention.

FIG. 6A is a plan view showing a surface configuration of a base substrate for a surface acoustic wave device according to a conventional technique. Figure 6
FIG. 6B is a plan view showing a back surface configuration of the base substrate for the surface acoustic wave device shown in FIG. FIG. 6C is a plan view showing a surface acoustic wave device according to a conventional technique.

[Explanation of symbols]

1 Ceramic base 2a, 2b, 2c First conductor pattern 3 castellations Conductor in 4 holes 5a, 5b, 5c Second conductor pattern 6 cavities 7 Piezoelectric substrate (LTA substrate) 8 Comb-shaped electrodes A input electrode pad B output electrode pad G Ground electrode pad

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Koji Kanazaki             8th Shinsugita Town, Isogo Ward, Yokohama City, Kanagawa Prefecture             Ceremony company Toshiba Yokohama office (72) Inventor Naoki Akahori             8th Shinsugita Town, Isogo Ward, Yokohama City, Kanagawa Prefecture             Ceremony company Toshiba Yokohama office (72) Inventor Rieko Nakajo             8th Shinsugita Town, Isogo Ward, Yokohama City, Kanagawa Prefecture             Ceremony company Toshiba Yokohama office (72) Minoru Kawase, inventor             8th Shinsugita Town, Isogo Ward, Yokohama City, Kanagawa Prefecture             Ceremony company Toshiba Yokohama office F term (reference) 5J097 AA16 HA04 JJ01 JJ07 KK04                       KK10

Claims (4)

[Claims] 1. A base made of a ceramic plate, a first conductor pattern formed on a front surface of the base, a second conductor pattern formed on a back surface of the base, and a side surface of the base. A castellation connecting between the first and second conductor patterns, and a hole connecting between the first and second conductor patterns embedded in a hole penetrating the front and back surfaces of the base. A base substrate for a surface acoustic wave device, comprising: a conductor. 2. The first and second conductor patterns are conductor patterns for supplying a ground potential to a surface acoustic wave element mounted on the surface acoustic wave device base substrate. The base substrate for a surface acoustic wave device according to claim 1. 3. A surface acoustic wave element comprising a piezoelectric substrate, a metal pattern formed on the surface of the piezoelectric substrate, including a comb-teeth electrode and an electrode pad connected to the comb-teeth electrode, and the electrode pad A bump formed on the base; a base made of a ceramic plate; a first conductor pattern formed on the surface of the base and electrically and mechanically connected to the electrode pad through the bump; A second conductor pattern formed on the back surface of the base, a castellation formed on the side surface of the base for connecting between the first and second conductor patterns, and a hole penetrating the front and back surfaces of the base. And a conductor in a hole that connects between the first and second conductor patterns embedded in the surface acoustic wave device. 4. The surface acoustic wave device according to claim 3, wherein the first and second conductor patterns are conductor patterns for supplying a ground potential to the surface acoustic wave element.