JP2000295073A - Piezoelectric filter and its manufacturing method - Google Patents

Abstract

(57) [Summary] To provide a means for reducing the size of a two-stage cascade-connected double mode piezoelectric filter. SOLUTION: In a state where a plurality of dual mode filter elements are arranged in a matrix on a wafer, a center frequency and a bandwidth are sequentially adjusted, and then separated into individual pieces including two sets of filter elements, and a package is formed. Multi-mode piezoelectric filter characterized in that it is housed in a package having a short-circuit electrode for cascade connection formed at the bottom of the filter, and the filter is constructed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multi-mode piezoelectric filter, and more particularly, to a multi-mode piezoelectric filter in which a center frequency and a bandwidth of a plurality of filter elements on a wafer are adjusted and then the package is mounted on a package.
The present invention relates to a multi-mode piezoelectric filter in which a set of dual-mode filter elements is provided with a short-circuit lead electrode at the bottom of a package so that the filters are connected in cascade, and the number of connection steps is improved, and a method of manufacturing the same.

[0002]

2. Description of the Related Art Multimode piezoelectric filters are widely used as IFs for mobile terminals because of their small size, high attenuation, and robustness. FIG. 4A is a plan view showing a configuration of a conventional surface mount type dual mode filter (hereinafter, referred to as a dual mode filter), and FIG. FIG. 4 is a plan view showing an electrode pattern on the back surface of a filter element F. As is well known, the conventional dual mode filter arranges the input / output electrodes 23 and 24 (split electrodes) with a predetermined gap on one surface of the piezoelectric substrate 22 and opposes them on the other surface. A common electrode 25 is provided to form a dual mode filter element F, and the element F is housed in, for example, a ceramic package 21 and each electrode 23, 2 of the filter element F
Lead electrodes 23L, 24L and 2 drawn from 4, 25
The 5L and the terminals 26 provided at the four corners of the package 21 are fixed with conductive adhesives 27, respectively, and are electrically connected. The opening of the package 21 is closed by a metal cover (not shown).

Generally, in the case of a dual mode filter, as shown in FIG. 4A, the common electrode 25 is located above the package 21 (opening side), and the input / output electrodes 23 and 24 are located below (bottom side). It is configured to be arranged. This is to prevent a short circuit between the electrodes 23 and 24 when adjusting the frequency of the filter. The input electrode 23 and the common electrode of this dual mode filter
When a high frequency voltage is applied between the input and output electrodes 23 and 24,
It is well known that acoustic coupling occurs between the common electrode 25 and the common electrode 25. As a result, the symmetric primary resonance mode and the antisymmetric primary resonance mode are strongly excited, and function as a double mode filter using these. is there.

In response to the rapid increase in demand for wireless communication devices such as portable telephones in recent years, increasing the number of channels by narrowing the intervals of communication channels, the use of IF filters for wireless communication devices There is a demand for improved selectivity. In order to realize this, there is a method of cascading two dual mode filters, but this method has a problem that the shape of the filter becomes too large. In order to solve this problem, a method of accommodating two sets of dual mode filter elements in one package to form a cascade connection type filter is generally used. That is, as shown in FIGS. 5A and 5B, two dual mode filter elements F1 and F2 are housed in a package 31, and the input / output electrodes, common electrodes and common electrodes of the filter elements F1 and F2 are connected to the package 31. Are electrically connected to the terminal electrodes 32 to 37 using a conductive adhesive 38, and the filter elements F1 and F2 are fixed.

The dual mode filter elements F1 and F2 have terminal electrodes 32-34 and 35-34 respectively connected to external terminals of the package.
37, the frequency of each of the filter elements F1 and F2 is individually adjusted after being housed in the package 31, so that a filter having substantially the same predetermined frequency and bandwidth can be obtained. Characteristics. Then, the terminal electrodes 34 and 35 are connected in the package 31 using a conductive adhesive or a bonding wire,
This constitutes a two-stage cascade connection type filter.

[0006]

However, in a conventional two-stage cascade filter, means such as vapor deposition is used to adjust the center frequency and the bandwidth to predetermined frequencies, so that two adjacent electrodes are used. In order to prevent a short circuit therebetween, it is common to house the dual mode filter elements F1 and F2 in a package with their respective common electrodes facing upward.
When adjusting to a predetermined center frequency and bandwidth, there is only an adjustment method for the common electrode, and it is difficult to adjust the bandwidth of the filter element as compared with a method of fine adjustment for the split electrode and the common electrode. There was a problem. Furthermore, after adjusting the predetermined frequency to the two dual mode filter elements F1 and F2, in order to connect the filter elements F1 and F2 in cascade, the terminal electrodes 34 and 35 are connected with a conductive adhesive or a bonding wire or the like. There is also a problem that it is necessary and it takes time. The present invention has been made in order to solve the above problems, and provides a cascade connection type filter which accurately adjusts a center frequency and a bandwidth of a dual mode filter element and does not require any connection man-hour between filter elements. The purpose is to do.

[0007]

In order to achieve the above object, a multi-mode piezoelectric filter according to the present invention and a method of manufacturing the same are characterized by providing first and second double-mode piezoelectric filter elements. In the cascade connection type piezoelectric filter in which the formed one piezoelectric substrate is housed in a package, the piezoelectric substrate is rectangular, and one side of the divided electrodes constituting the first double mode piezoelectric filter is connected to one side of the piezoelectric substrate. The first lead electrode extends from one of the divided electrodes constituting the second double mode piezoelectric filter toward the other side of the piezoelectric substrate, and the second lead electrode extends to the other side of the piezoelectric substrate. Two terminal electrodes corresponding to the first and second lead electrodes and an electrode pattern for connecting the terminal electrodes are provided, and the first and second lead electrodes and the second lead electrode are provided. And of the terminal electrodes electrically connected respectively, a piezoelectric filter, characterized in that to achieve a cascade. According to a second aspect of the present invention, the electrode pattern includes a band-shaped electrode formed on the inner bottom surface of the package, and has a band-shaped electrode and a non-conductive ground electrode on substantially the entire bottom surface of the package except for the band-shaped electrode. A piezoelectric filter characterized in that: The invention according to claim 3 is a cascade connection type piezoelectric filter in which a single piezoelectric substrate on which first and second dual-mode piezoelectric filter elements are formed is accommodated in a package, wherein the piezoelectric substrate has a rectangular shape. A first lead electrode from one of the divided electrodes forming one double mode piezoelectric filter toward one side of the piezoelectric substrate; and a piezoelectric substrate from one of the divided electrodes forming the second double mode piezoelectric filter. A second lead electrode extending toward the other side of the package, two terminal electrodes corresponding to the first and second lead electrodes on the package, and an electrode pattern for connecting the terminal electrodes. And a conductive connection between the first and second lead electrodes and the two terminal electrodes, respectively, to produce a piezoelectric filter that realizes a cascade connection. Forming a plurality of dual-mode piezoelectric filter elements in a matrix on the wafer; adjusting a center frequency and a bandwidth of each of the dual-mode piezoelectric filter elements; Separating a piezoelectric substrate having a mode piezoelectric filter element, and providing the package with two terminal electrodes corresponding to the first and second lead electrodes and an electrode pattern for connecting between the terminal electrodes. And housing the separated two sets of dual mode piezoelectric filter elements in the package;
And electrically connecting the first and second lead electrodes to two terminal electrodes corresponding to the first and second lead electrodes, respectively.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail based on an embodiment shown in the drawings. FIG. 1 is a plan view showing a configuration of a cascade connection type filter according to the present invention, and a metal cover of a package 1 is not shown. As shown in the right side of FIG. 2, the cascade connection type filter has a pair of input / output electrodes 3a and 4a arranged on one surface of a piezoelectric substrate 2 with a predetermined gap therebetween, and has a pair of input / output electrodes 3a and 4a facing the other side. Common electrode 5a
To form a so-called double mode filter element, a filter element having substantially the same shape as the double mode filter element,
That the input and output electrodes 3b, 4b, to form a filter element in which the common electrode 5b on the same piezoelectric substrate 2, to form a cascaded filter element F ₂ from the two sets of filter elements. Note that input and output electrodes 3a of the cascaded filter element F _2, 4a and the common electrode 5a
From the lead electrodes L1, L2 and L3 toward the end of the piezoelectric substrate 2.
Has been pulled out. Similarly, lead electrodes L4 to L6 are drawn from the input / output electrodes 3b and 4b and the common electrode 5b.

[0009] Then, to accommodate the cascaded filter element F ₂ in the package 1 as shown in FIG. 3, formed in the peripheral portion of the package, placing the stepped portion as shown in FIG. 3 (b), The six terminal electrodes 6 to 11 provided on the step portion and the lead electrodes L1 to L6 formed on the piezoelectric substrate 2 are fixed with the conductive adhesive 12. Since terminal electrodes 8 and 9 are connected by a short lead electrodes 13 formed in a substantially central portion of the bottom of the package, as shown in FIG. 3 (a), the cascaded filter element F ₂ as described above Housed in package 1,
By simply fixing each terminal electrode 6 to 11 with a conductive adhesive, the output of one dual mode filter and the input of the other dual mode filter are connected, so that a so-called cascade connection type filter can be configured. . An earth electrode 14 for shielding external noise is formed on the inner bottom surface of the package.This earth electrode is divided at substantially the center of the package, and the short-circuit lead electrode 13 is insulated from the divided earth electrode. Is formed. Further, each terminal electrode is electrically connected to an external terminal (not shown) provided on the outer bottom of the package.

The method of forming the cascade-connected filter element F ₂ (consisting of two sets of similar double-mode filter elements) which performs a filter function in the cascade-connected filter according to the present invention will be described in detail. Figure 2 is a plan view showing a backside overall electrode pattern when forming a cascaded filter element F ₂ to the wafer U in a matrix, has a portion surrounded by a broken line in the aspect in cascaded filter element F ₂ Yes, enlarged to the right. That is, two sets of input / output electrodes 3
a, 4a and 3b, 4b and common electrodes 5a, 5
b. Thus, cascaded filter element F ₂ has become a structure in which two sets of dual-mode filter element is independent, the lead electrode L1~L6 be each independently of the other drawn from each electrode of the element F ₂ ing. Cascaded filter element F ₂ is a wafer as described above
Since U is formed in a matrix on both the front and back surfaces using the photolithography technique, it is possible to measure the frequency of each dual mode filter element individually. Therefore, adjustment of the center frequency and the bandwidth of the cascaded filter element F ₂ is put wafer U vacuum device, in contact with the lead electrodes L1, L2 and L3 by using a plurality of probes, measuring a predetermined frequency Then, the center frequency and the bandwidth of the dual mode filter element are adjusted by adding the mass of the electrodes 3a, 4a and 5a as necessary, or by removing the mass with an electron beam device or the like. As described above, the center frequency and the bandwidth of the dual mode filter element are sequentially adjusted, and the entire dual mode filter element formed in a matrix on the wafer U is adjusted.

Since the wafer U is handled in a state formed on the wafer U, the reference of the position of the wafer U, for example, the positional relationship between the upper left corner and the electrode of each dual mode filter can be made very accurately, so that the electrodes 3a, 4a and 5a Even if a metal substance is vapor-deposited, or a thin film is removed from the electrode, the electrodes 3a, 4a and 5a can be accurately positioned at predetermined positions.
For example, the adjustment can be performed without protruding from the electrode. In addition, the frequency of the wafer U can be adjusted on both surfaces of the common electrode surface (5a) and the divided electrode surfaces (3a, 4a). Furthermore, there is an advantage that the frequency adjustment of the filter can be performed much more easily than the frequency adjustment of only the common electrode surface. For example, if the vapor deposition is performed simultaneously on the electrodes on the divided electrode surface, the bandwidth of the filter can be reduced, and if the vapor deposition is performed on the common electrode, the center frequency is reduced while the bandwidth of the filter is kept substantially constant. be able to.

As described above, after adjusting the center frequency and the bandwidth of the dual mode filter element on the wafer U to predetermined values, two blocks of the dual mode filter element are provided.
That cascaded filter element F ₂ is separated into pieces by dicing or the like. Then, the common electrode surfaces 5a of the cascaded filter element F _2, and the top 5b, accommodated in a package as shown in FIG. 3 (a). Then, after being housed in a package and applying the conductive adhesive, if the frequency of the filter slightly fluctuates due to distortion or the like when the conductive adhesive dries,
What is necessary is just to adjust the frequency with respect to the common electrode surfaces 5a and 5b. For example, while monitoring the characteristics of the filter in a vacuum device,
The center frequency of the filter will be adjusted by evaporating a substance such as a metal or removing the electrode material thinly with an electron beam, etc. It is sufficient to make only minimal fine adjustments as needed.

[0013]

According to the present invention, since it is configured as described above, the center frequency in the stage of wafer, after adjusting the bandwidth, because cutting into pieces a cascaded filter element F ₂ as a unit, the wafer In addition to the fact that the alignment between the mask and the mask can be performed easily and accurately, a filter having uniform filter characteristics can be obtained, and if this filter is used in a mobile phone or the like, an excellent effect of improving the performance of the IF stage can be obtained. .

[Brief description of the drawings]

FIG. 1 is a plan view showing a configuration of a cascade connection type filter according to the present invention.

FIG. 2 is an enlarged view of a wafer on which cascaded filter elements are arranged in a matrix and individual pieces thereof.

FIG. 3A is a plan view of a ceramic package provided with a lead electrode connecting an output terminal of one double mode filter and an input terminal of the other double mode filter to constitute a cascade connection type filter; (B) is a figure which shows the cross-section of a terminal electrode.

FIG. 4A is a plan view showing a configuration of a conventional SMD type dual mode filter, and FIG. 4B is a plan view showing an electrode configuration on a back surface of the dual mode filter element.

FIG. 5 is a plan view showing a configuration of a conventional SMD type two-stage cascade filter.

[Explanation of symbols]

1. Package 2 Piezoelectric substrate 3a, 3b, 4a, 4b, 5a, 5b Electrode 6, 7, 8, 9, 10, 11 Terminal electrode 12 Conductive adhesive 13 Package bottom earth electrode 14 lead electrodes ... package bottom U ... wafer F ₂ · cascaded filter elements L1, L2, L3 ... lead electrodes

Claims (3)

[Claims] 1. A cascade connection type piezoelectric filter in which a single piezoelectric substrate on which first and second dual-mode piezoelectric filter elements are formed is accommodated in a package. A first lead electrode from one of the divided electrodes forming the double mode piezoelectric filter toward one side of the piezoelectric substrate; and a first lead electrode from one of the divided electrodes forming the second double mode piezoelectric filter to the other of the piezoelectric substrate. Second lead electrodes are respectively extended toward one side, and two terminal electrodes corresponding to the first and second lead electrodes and an electrode pattern for connecting the terminal electrodes are provided on the package. And a cascade connection between the first and second lead electrodes and the two terminal electrodes, thereby realizing a cascade connection. 2. The method according to claim 1, wherein the electrode pattern includes a band-shaped electrode formed on the inner bottom surface of the package, and a ground electrode that is not electrically connected to the band-shaped electrode on substantially the entire bottom surface of the package except the band-shaped electrode. And a piezoelectric filter. 3. A cascade connection type piezoelectric filter in which a single piezoelectric substrate on which first and second dual mode piezoelectric filter elements are formed is accommodated in a package. A first lead electrode from one of the divided electrodes forming the double mode piezoelectric filter toward one side of the piezoelectric substrate; and a first lead electrode from one of the divided electrodes forming the second double mode piezoelectric filter to the other of the piezoelectric substrate. Second lead electrodes are respectively extended toward one side, and two terminal electrodes corresponding to the first and second lead electrodes and an electrode pattern for connecting the terminal electrodes are provided on the package. A method of manufacturing a piezoelectric filter in which the first and second lead electrodes and the two terminal electrodes are electrically connected to each other to realize a cascade connection. Forming a number of double-mode piezoelectric filter elements in a matrix; adjusting a center frequency and a bandwidth of each of the dual-mode piezoelectric filter elements; Separating the piezoelectric element into a piezoelectric substrate having a filter element, providing the package with two terminal electrodes corresponding to the first and second lead electrodes, and an electrode pattern for connecting the terminal electrodes; Housing the separated two sets of dual mode piezoelectric filter elements in the package;
A method of manufacturing a piezoelectric filter, comprising: electrically connecting two terminal electrodes corresponding to the first and second lead electrodes to the first and second lead electrodes, respectively.