JP3198489B2 - Filter package - Google Patents

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 filter using a surface acoustic wave propagating on a piezoelectric substrate, and more particularly to a filter such as a monolithic crystal filter, and more particularly to a package structure.

[0002]

2. Description of the Related Art The prior art will be described with reference to FIGS. 7 and 8, taking a resonator type surface acoustic wave filter as an example. FIG. 7 is a plan view of a conventional multi-stage connected resonator type surface acoustic wave filter, and FIG. 8 is a sectional view taken along line YY of FIG. The piezoelectric substrate 9 is made of a thin plate of LiNbO ₃ and is processed into a rectangular shape. On the surface of the piezoelectric substrate 9, interdigital electrodes 91a, 92a and reflector electrodes 91b, 91c, 92b, 92c are formed, and two pairs of surface acoustic wave resonators are provided in parallel. Type surface acoustic wave filters 91 and 92 are constituted. The ceramic package 8 has a generally four-layer structure of a lower layer, an intermediate layer, an upper layer, and a metal layer, and has electrode pads 81, 82, 83, 84, which lead electrodes to the outside.
85 and 86 are provided. The piezoelectric substrate 9 on which electrodes are formed is housed in this package, and is electrically connected to the electrode pads by bonding wires. The interdigital electrodes inside the resonator type surface acoustic wave filters 91 and 92 are commonly connected, and are led out to two opposite corners of the piezoelectric substrate by a bus electrode 93. The electrode pads 83 and 86 are led out to the outside as input / output electrodes, respectively.
Reference numerals 1 and 84 lead outside as a first ground electrode, and electrode pads 82 and 85 lead outside as a second ground electrode via a circuit element such as an inductance. Finally, the metal lid 80 and the metal layer are hermetically sealed by seam welding.

[0003]

In such a surface acoustic wave resonator type filter, since a plurality of filters are formed on a single wafer, an input signal supplied from an input electrode is applied to the resonator type elastic resonator type filter. Pass through the surface acoustic wave filters 91 and 92,
An electromagnetic wave (generally referred to as a direct wave) directly propagating between the input / output electrodes 86-83 or between the input electrode 86 and the resonator-type surface acoustic wave filter 92 instead of the normal flow of output from the output electrode. In some cases, a desired guaranteed attenuation cannot be obtained due to the influence of another elastic wave such as a bulk wave. Further, a bus electrode extended to connect a circuit element such as an inductor connected for adjusting the pass band characteristic of the filter and an electrode derived from between the resonator type surface acoustic wave filters 91 and 92. When 93 is present, this makes it easier to receive direct waves, further deteriorating the attenuation characteristics.

In addition, the above-mentioned adverse effects due to the direct wave also occur in other filters such as a quartz crystal monolithic filter (hereinafter referred to as MCF). Although not shown, for example, a filter in which a plurality of MCFs are housed in one package is also used. ,
In some cases, a desired guaranteed attenuation was not obtained.

The present invention has been made to solve the above-mentioned problems. For example, in a surface acoustic wave filter such as a resonator type connected in multiple stages, a direct wave or another elastic wave propagating between input and output electrodes is provided. It is an object of the present invention to provide a filter package which is not adversely affected by the above, and whose electric characteristics can be easily adjusted.

[0006]

In order to solve the above-mentioned problems, a filter package according to the present invention is composed of a laminated ceramic and is divided into a plurality of chambers separated by a separation band portion. At least a plurality of filter elements each having an excitation electrode for exciting an elastic wave are separately housed, and the package is hermetically sealed. A bonding pad surface electrically connected to the element and an air-tight sealing surface, and an electromagnetic shield electrode is formed between the plurality of filter elements, and the electromagnetic shield electrode is grounded. Features.

In addition to the above structure, a line electrode which is electrically connected between the filter elements is formed on the surface on which the filter elements are provided, and is led out to the outside. A configuration in which at least two electromagnetic shield electrodes are formed may be employed.

[0008]

The package accommodating the filter element has a plurality of chambers separated by a separation band, and the filter element is accommodated in each chamber, so that the acoustic elements are not adversely affected by each other.
Further, since an electromagnetic shield electrode is formed on each of the ceramic layers constituting the separation band portion, each filter element is not affected by a direct wave transmitted directly to each other.

A line electrode electrically connected between the filter elements is formed and led out to the outside, and at least two electromagnetic shield electrodes are formed with the line electrode interposed therebetween. According to the configuration described above, while having an electromagnetic shielding effect, by connecting a circuit element such as an inductor to a terminal from which the line electrode is led out, it is possible to adjust electric characteristics such as a pass band characteristic.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described with reference to the drawings, taking a surface acoustic wave filter as an example. FIG. 1 is a plan view of a surface acoustic wave filter using a filter package according to the present invention, FIG. 2 is a sectional view taken along line XX of FIG. 1 (however, a sectional view with a metal frame 4 added), and FIG. FIG. 4 is a plan view of a second ceramic layer forming the package, and FIG. 5 is a plan view of a third ceramic layer forming the package. Package 1 made of ceramic such as alumina is 2
It has a chamber separation structure, and includes a first chamber C1, a second chamber C2, and a separation band B separating these chambers. An external lead-out electrode and an electromagnetic shield electrode are provided around the bottom of the package. At the inner peripheral portion of the package and at the widthwise end of the separation band portion B, there is provided a step portion in which a part of a second ceramic layer 2 to be described later is exposed. 22 and electrode pads 23, 24, 25, 2
6, 27, 28 and 29 are provided. On the upper part of the package, there is provided a third ceramic layer 3 on which an electromagnetic shield electrode 31 and an electrode 32 for circumferential connection with a metal frame 4 described later are formed by metallizing. A metal frame 4 made of Kovar is bonded to the upper surface of the circumferential bonding electrode 32, that is, the opening of the package, with a metal brazing material. The resonator type surface acoustic wave filter elements 5a and 5b
An electrode for exciting a surface acoustic wave is formed on the upper surface of each of the piezoelectric substrates 51 and 52. The piezoelectric substrates 51 and 52 are made of, for example, a thin plate of LiNbO ₃ , and are each processed into a rectangular shape. Interdigital electrodes 51a and 52a are formed at the center of the surfaces of the piezoelectric substrates 51 and 52, respectively, and reflector electrodes 51b and 52b are formed at both ends in the longitudinal direction.
51c, 52b and 52c are formed. Each electrode on each piezoelectric substrate constitutes a resonator type surface acoustic wave filter in which two surface acoustic wave resonators are provided in parallel. These piezoelectric substrates 51 and 52 are installed in the respective storage chambers of the package, and the bottom of the package and the lower surface of the piezoelectric substrate are joined by a conductive joining material S. Then, the electrode pad 28 and the interdigital electrode 5
1a, the other end of the interdigital electrode 51a and the electrode pad 2
9, one end of the electrode pad 29 and one end of the interdigital electrode 52a,
The other end of the interdigital electrode 52a, the electrode pad 25, the reflector electrode 51b (commonly connected to the reflector electrode 51c), the electrode pad 23, and the reflector electrode 52c (commonly connected to the reflector electrode 52b). Each of the electrode pads 26 is electrically connected by a bonding wire W. Then, the electrode pads 28 and 25 are led out as input / output electrodes,
The electrode pads 23 and 26 are respectively led out as ground electrodes. The metallic lid 6 is hermetically joined to the metallic frame 4 by seam welding or the like. The respective electromagnetic shield electrodes are commonly connected by through holes 31a, 31b and the like.
It is led outside as a ground terminal.

The stacking order of such a ceramic package will be described with reference to FIGS. Notches 12a, 13a, and 14 are opposed to both ends in the short direction of the plate-shaped first ceramic layer 1 constituting the bottom surface of the package.
a, 15a, 16a, and 17a are provided. A wide electromagnetic shield electrode 11 is provided on the surface of the first ceramic layer 1 and extends along the longitudinal direction at the central portion in the lateral direction, and this electrode is connected to the extraction electrodes 12, 13, 15, 16. The extraction electrodes 14 and 17 are formed near the notches 14a and 17a. Each of these electrodes also extends to the back surface through the notch. A frame-shaped second ceramic layer 2 that surrounds the first ceramic layer 1 and overlaps the electromagnetic shield electrode 11 is provided. In the frame-shaped ceramic layer 2, the width of the central portion 2 a constituting a part of the separation band portion B is equal to the width of the electromagnetic shield electrode 11.
And the notches 21a, 22a, 25a and 28a are provided at the centers of the four sides, respectively. An electromagnetic shield electrode 2 is provided at the center 2a.
Numerals 1 and 22 extend from both ends in the width direction to the vicinity of the center, and an electrode pad 29 that is not electrically connected to these electromagnetic shield electrodes is formed at the center. The electromagnetic shield electrode 21 is connected to the extraction electrodes 23 and 24, and the electromagnetic shield electrode 22 is connected to the extraction electrodes 26 and 27, respectively.
An electrode pad 25 is provided around the notch 25a, and an electrode pad 28 is provided around the notch 28a to form an input / output electrode pad. Electrodes are formed on the side surfaces of the notches, and the electrodes are drawn out on the back surface. The electromagnetic shield electrodes 21 and 22 are connected to the electromagnetic shield electrode 11, the electrode pad 25 is connected to the electrode pad 14,
The electrode pads 28 are electrically connected to the electrode pads 17, respectively. A third ceramic layer is provided on the second ceramic layer. Although this layer has the same outer dimensions as the second ceramic layer, it has a similar shape with a narrow width as a whole, and has an electromagnetic shield electrode 31 and a circumferential bonding electrode 32 formed on the upper surface. Through holes 31a and 31b are formed in the vicinity of both ends in the longitudinal direction of the central portion 3a, electrodes are provided on the inner surfaces by suction, and the electrodes are drawn out on the back surface. The electrode led out to the back surface is connected to the electromagnetic shield electrodes 21 and 22. In addition, since the overall shape of the frame is smaller than that of the second ceramic layer, a part of each electrode pad formed on the second ceramic layer is exposed. A peripheral metal frame 4 having no central portion is joined to the upper portion of the third ceramic layer by brazing. With the above-described laminated configuration, the electromagnetic shield electrodes provided in the respective layers are commonly connected and led out.

A second embodiment will be described with reference to FIG. 6 which is a plan view of a first ceramic layer. Note that the same reference numerals are used for the same structural parts as in the first embodiment, and the description is partially omitted. In this embodiment, the first ceramics layer 7 has notches 71a, 72a, 74 around its periphery.
a, 75a, 76a, 77a, 78a, 79a are provided. Leading electrodes 75 and 78 for connection to an external element are formed around each of the cutouts 75a and 78a, and are commonly connected by a line electrode 73 extending in the longitudinal direction at the center in the short direction. 75a, 78
An electrode is drawn out to the back surface through a. The electromagnetic shield electrodes 71 and 72 are sandwiched between the line electrodes 73.
Are provided, each extending to the longitudinal end,
The cutouts 71a and 72a are respectively drawn to the back surface. Electrode pads 74, 76, 77, 79 are provided around the cutouts 74a, 76a, 77a, 79a, and are respectively drawn to the back surface through the cutouts. Second and third ceramic layers and a metal frame having substantially the same configuration as those of the first embodiment are laminated on the first ceramic layer 7, but a through hole is formed in the electrode pad 29 at the center of the second ceramic layer. By providing, for example, this electrode is electrically connected to the lower line electrode 73. Thus, the electrode between the two resonator-type surface acoustic wave filter elements can be electrically connected to an external element such as an inductor, and the electric characteristics such as the pass band characteristics can be adjusted.

In the package used in the above embodiment, the electromagnetic shield electrode is provided on the upper surface of each layer, but the electromagnetic shield electrode may be provided on the side surface. In this case, an electrode may be formed by a vacuum evaporation method or the like using a mask provided with a through hole only in a necessary portion of the electromagnetic shield electrode. Although a surface acoustic wave filter is used as a filter element, the present invention can be applied to a monolithic crystal filter (MCF) or the like. Further, the electrode patterns formed on the filter element and the wiring electrode patterns formed on the package are not limited to those in the above embodiment, and may be appropriately selected and designed according to desired electrical characteristics.

[0014]

The package for accommodating the filter element is:
It has a plurality of chambers separated by a separation band, and the filter element is separately housed in each chamber, so that it is not adversely affected by other elastic waves, and each ceramic layer constituting the separation band has electromagnetic waves. Since the shield electrode is formed, even if a direct wave is generated, it is absorbed by these electromagnetic shield electrodes, and the filter elements are not affected by the direct wave transmitted directly to each other. Therefore, a desired guaranteed attenuation can be obtained.

Further, a line electrode electrically connected between the filter elements is formed and led to the outside, and at least two electromagnetic shield electrodes are formed with the line electrode interposed therebetween. With the configuration described above, while having the above-mentioned electromagnetic shielding action, by connecting a circuit element such as an inductor to a terminal from which the line electrode is led out, it is possible to adjust electrical characteristics such as a pass band characteristic, A filter package having electrical characteristics according to needs can be obtained.

[Brief description of the drawings]

FIG. 1 is a plan view showing a first embodiment.

FIG. 2 is a sectional view taken along line XX of FIG.

FIG. 3 is a plan view showing a first ceramic layer.

FIG. 4 is a plan view showing a second ceramic layer.

FIG. 5 is a plan view showing a third ceramic layer.

FIG. 6 is a plan view showing another embodiment.

FIG. 7 is a plan view showing a conventional example.

FIG. 8 is a sectional view taken along line YY of FIG. 7;

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 1st ceramics layer 2 2nd ceramics layer 3 3rd ceramics layer 5a, 5b Resonator type surface acoustic wave filter element 51, 52, 9 Piezoelectric substrate 11, 21, 22, 31, 71, 72 Electromagnetic shield electrode B separator

Claims (2)

(57) [Claims] 1. A plurality of filter elements having excitation electrodes for exciting at least elastic waves on a surface of a piezoelectric substrate are separately housed in a package made of a laminated ceramic and divided into a plurality of chambers by a separator. In the filter package in which the filter band is hermetically sealed, at least a surface on which the filter element is provided, a bonding pad surface electrically connected to the filter element, and each of a hermetic sealing surface are provided in the separation band portion. An electromagnetic shield electrode is formed between the plurality of filter elements, and the electromagnetic shield electrode is grounded. 2. A package made of a laminated ceramic and divided into a plurality of chambers by a separation band portion, a plurality of filter elements having excitation electrodes for exciting at least an elastic wave on the surface of a piezoelectric substrate are separately housed, and the package is provided. The separation band portion is a surface on which at least a filter element is installed, a bonding pad surface electrically connected to the filter element, and each surface of a hermetic sealing surface, An electromagnetic shield electrode is formed between the filter elements, and the electromagnetic shield electrode is a grounded filter package, and a surface on which the filter element is installed is a line electrically connected between the filter elements. An electrode is formed and led to the outside, and at least two electromagnetic shield electrodes are formed with the line electrode interposed therebetween. A filter package characterized by the above-mentioned.