JP3543310B2 - Surface mount type piezoelectric filter and method of manufacturing the same - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a surface mount type piezoelectric filter using a clock source of an electronic device or a quartz plate used for a communication device or the like.
[0002]
[Prior art]
2. Description of the Related Art Generally, a piezoelectric vibrating device such as a piezoelectric vibrator, a piezoelectric filter, and a piezoelectric oscillator adjusts electrical characteristics such as frequency by partially depositing a metal material on a part of an excitation electrode formed on a piezoelectric vibrating plate. Is being done. The same applies to these surface mount type piezoelectric vibrating devices.However, since these operations are performed after being housed in a surface mount case, it is difficult to bring the adjustment mask close to the piezoelectric vibrating plate. Had. FIG. 8 is a perspective view showing a manufacturing state of a conventional surface mount type monolithic crystal filter. A case 90 made of ceramics and having an opening at the top is mounted with a quartz vibrating plate 91 having common electrodes (excitation electrodes) 91a and 91b formed on the front surface and input electrodes and output electrodes (each not shown) formed on the back surface. In this state, the adjustment mask held by the holding arms 93a and 93b is brought as close as possible to the opening, and in this state, the metal material is evaporated from the evaporation source 95 via the shutter 94. The adjustment state controls the opening and closing of the window of the shutter 94 and the supply of the deposition material from the deposition source while monitoring the electrical characteristics of the surface-mounted monolithic crystal filter. When the electrical characteristics such as a predetermined frequency have been obtained, the adjustment operation is completed, and then the container is hermetically sealed with a cover plate (not shown).
[0003]
[Problems to be solved by the invention]
When adjusting the electrical characteristics, it is preferable that the adjustment mask be as close as possible to the quartz plate. However, in the above-described conventional example, as can be understood from FIG. 8, the adjustment mask held by the holding arms 93a and 93b is brought close to the crystal vibration plate 91 housed in the case 90, so that the crystal vibration is inevitable. The distance between the plate and the adjustment mask is increased. For this reason, the electrode pattern formed at the time of adjusting the electrical characteristics is in a state wider than a predetermined shape, and the adjusting ability is reduced. In some cases, the characteristics may change significantly, or the electrodes may be short-circuited to another electrode. Such a problem may occur not only in a crystal filter but also in a piezoelectric vibrating device such as a piezoelectric vibrator or a piezoelectric oscillator.
[0004]
Further, since the metal mask for partial vapor deposition is used repeatedly during the manufacturing process, a vapor deposition material (metal material) is deposited around the periphery of the adjustment window. Since such deposition of the deposition material distorts the metal mask or changes the size of the adjustment window, maintenance for cleaning or replacing in a short cycle is required.
[0005]
Further, in a monolithic piezoelectric filter, an electric signal input to an input electrode may become an electromagnetic wave and generate a direct wave directly propagating to an adjacent output electrode. In such a case, the attenuation characteristic of the electric filter may be reduced. Sometimes it was lost.
[0006]
In addition, harmful electromagnetic wave noise may be generated outside the piezoelectric vibrator and the piezoelectric oscillator during operation, and a mechanism for ensuring electromagnetic shielding has been required.
[0007]
The present invention has been made in order to solve the above-mentioned problems, and it is possible to reliably perform partial vapor deposition, which is a means for adjusting electrical characteristics such as frequency, and to eliminate the need for maintenance of a metal mask and to reduce the direct wave. It is an object of the present invention to provide a surface mount type piezoelectric filter for preventing and suppressing electromagnetic wave noise generated from a circuit element including a piezoelectric element (piezoelectric diaphragm) and a method for manufacturing the same.
[0008]
[Means for Solving the Problems]
In order to solve the above problem, the surface mount type piezoelectric filter according to claim 1 includes a piezoelectric vibrating plate in which at least one pair of an input electrode, an output electrode, and a corresponding common electrode is formed on the front and back surfaces, respectively. A metal mask having an adjustment window formed at a position corresponding to the input electrode, the output electrode or the common electrode, which is disposed above the piezoelectric vibrating plate, is housed in a case,
The case has a ceramic base, a plurality of external lead-out electrodes on the outer surface thereof, a lower mounting portion for mounting a piezoelectric vibrating plate therein, and an upper mounting portion for mounting the metal mask above the mounting portion. An electrode pad electrically connected to the external lead-out electrode is formed on each of the lower mounting portion and the upper mounting portion, and the electrode of the piezoelectric vibration plate is electrically conductively bonded to the electrode pad of the lower mounting portion. By connecting to a specific external lead-out electrode, the metal mask is electrically connected to the electrode pad to be electrically grounded via the specific external lead-out electrode. is there.
[0009]
Further, as described in claim 2, as a method of manufacturing the surface mount type piezoelectric filter according to claim 1, a lower mounting portion having a plurality of external lead-out electrodes on an outer surface and a piezoelectric vibrating plate inside is provided. A ceramic having an upper mounting portion for mounting the metal mask above the mounting portion, and an electrode pad electrically connected to the external lead-out electrode formed on each of the lower mounting portion and the upper mounting portion. A case having a base as a base is prepared, a piezoelectric vibration plate having an excitation electrode formed on at least the surface thereof is mounted on the electrode pad of the lower mounting portion, and means for conductive bonding is provided.
Means for capturing the mounted state of the mounted piezoelectric diaphragm into an image memory by image recognition technology, and calculating a planar inclination in the mounted state of the piezoelectric diaphragm from the image memory;
In accordance with the obtained inclination, the metal mask on which the adjustment window is formed is rotated and moved, the adjustment window is positioned corresponding to a predetermined position of the excitation electrode, and is installed on the upper mounting portion. Means,
Means for conductively bonding the positioned metal mask to the electrode pad of the upper mounting portion,
Means for partially depositing a metal material for electrical property adjustment using the metal mask,
Means for hermetically sealing by joining the sealing lid to the opening of the case.
[0010]
[Action]
According to the first aspect, since the metal mask is fixed in the case and partial vapor deposition is performed using the metal mask, the piezoelectric vibrating plate and the metal mask can be brought extremely close. Therefore, the partial vapor deposition is performed only within a predetermined limited range, so that electric characteristics such as a desired frequency can be adjusted, and a short circuit accident with another electrode can be prevented. Further, maintenance such as cleaning and replacement of the metal mask at the time of partial vapor deposition, which is conventionally required, becomes unnecessary.
[0011]
In addition, since this metal mask is electrically grounded via an external lead-out electrode, in the case of a piezoelectric filter, the direct wave is electromagnetically cut off to improve the damping characteristics of the electric filter or to reduce the piezoelectric vibration. In the case of the element and the piezoelectric oscillator, generation of electromagnetic waves can be suppressed.
[0012]
According to the second aspect, the metal mask is mounted by the image recognition means in accordance with the planar inclination of the mounted piezoelectric vibration plate and the excitation electrode, so that the piezoelectric vibration plate and the metal mask can be extremely close to each other. Since the relative positions of the adjustment window and the excitation electrode can be reliably matched, the adjustment of the electrical characteristics by the partial vapor deposition can be performed reliably.
[0013]
BEST MODE FOR CARRYING OUT THE INVENTION
An embodiment of the present invention will be described with reference to FIGS. 1, 2, 3, and 4, taking a surface-mounted monolithic crystal filter as an example. A method of manufacturing the monolithic crystal filter will be described with reference to FIGS.
FIG. 1 is an exploded perspective view of a surface-mount type monolithic quartz crystal filter according to the present invention, FIG. 2 is a perspective view showing a state in which a metal mask is incorporated in a case, and FIG. FIG. 4 is a plan view showing a state where the metal mask is rotated and installed in accordance with the planar inclination of the quartz vibrating plate (piezoelectric vibrating plate), and FIGS. FIG.
[0014]
The case 1 having an opening has a structure in which a ceramic base is used, electrodes are formed inside using a lamination technique, and a plurality of external lead-out electrodes are formed on the bottom surface. Inside the opening, a lower mounting portion 11 and an upper mounting portion 12 are formed above the lower mounting portion 11, and a plurality of steps are formed. Particularly, the upper mounting portion 12 is formed in a circumferential shape. Electrode pads 11a and 12a are formed on the upper surface of each mounting portion, and these electrodes are electrically connected to external lead-out electrodes described later by a lamination technique. A metal ring 10b such as Kovar is attached to the opening. The quartz vibrating plate (piezoelectric vibrating plate) 2 is an AT-cut quartz plate having an input electrode 21 and an output electrode 22 formed on a front surface, and common electrodes 23 and 24 formed on the back surface corresponding to the input / output electrodes. I have. Extraction electrodes 21a, 22a, 23a and 24a are formed from each electrode to the end of the quartz plate. The metal mask 3 is made of a metal material such as SUS (stainless steel), and has adjustment windows 31 and 32 corresponding to the input electrodes 21 and the output electrodes 22 and an adjustment window 33 corresponding to the input / output electrodes. . The cover plate 4 is made of a metal material such as Kovar.
[0015]
The crystal vibrating plate 2 is mounted on the lower mounting portion 11 of the case, and the electrode pads and the extraction electrodes are conductively bonded by a conductive bonding material or the like, and the metal mask 3 is mounted on the upper mounting portion 12 by resistance welding or conductive bonding. Conductive bonding with a conductive bonding material. In this state, partial vapor deposition is performed to adjust electrical characteristics such as frequency. Thereafter, the cover plate 4 is closed, and the cover plate 4 and the metal ring 10b are joined by joining means such as seam welding. The metal mask is grounded via an external lead-out electrode. Note that the hermetic sealing with the lid plate may be performed with solder sealing, or may be performed with low melting point glass or the like. Also, due to the presence of the metal mask, an insulating material can be used for the lid plate.
[0016]
With the above configuration, each electrode formed on the quartz plate is connected to a specific external lead-out electrode via an electrode pad, and a metal mask provided on the upper portion of the quartz plate is also stored in the case. The metal mask is conductively connected to a specific external lead-out electrode by an electrode pad. Therefore, the direct wave E generated between the input and output electrodes is electromagnetically shielded by the metal mask.
[0017]
With the above-described configuration, when the metal mask is provided close to the piezoelectric vibrating plate of the present invention (see FIG. 9 (B)), compared to the attenuation characteristics (shown in FIG. 9 (A)) when the conventional metal mask is not provided. ))) Show good properties.
[0019]
Next, a method of manufacturing the surface-mounted monolithic crystal filter and adjusting electric characteristics such as frequency will be described.
As shown in FIG. 5 (a), a case where a crystal vibration plate having electrodes formed thereon is mounted on the lower mounting portion of the case 1 and bonded by a conductive bonding material is taken by a camera C from an upper surface (opening surface). Photographing is performed, and the obtained image data is A / D converted and written into an image memory. Based on this image data, the mounting state (up, down, left, right, rotation, etc.) of the crystal diaphragm is calculated. It should be noted that a known image processing means such as converting the image data into a binary signal as necessary may be employed.
[0020]
Then, as shown in FIG. 5 (b), the metal mask 3 is moved up and down, left and right or rotated by the suction arm A in accordance with the mounting state of the quartz vibrating plate. And mounted on the upper mounting portion. FIG. 4 shows that the metal mask 3 is also rotated with the right shoulder lowered with respect to the quartz plate 2 mounted on the lower mounting part with the right shoulder lowered, so that the adjustment window and the electrode portion are aligned. It shows a state in which it is mounted. The metal mask 3 is conductively fixed by resistance welding such as spot welding or a conductive bonding material. Basically, it is only necessary that the adjustment window and the electrode part coincide with each other. If the excitation electrode (input / output electrode, etc.) itself is not formed at a predetermined position, the quartz vibrating plate and the metal mask are installed. The states may not match.
[0021]
Thereafter, as shown in FIG. 5C, partial evaporation is performed from the evaporation source 5 to the electrode exposed from the adjustment window via the shutter 4 while monitoring the electrical characteristics of the monolithic quartz crystal filter. In the monolithic crystal filter, two vibration modes called a symmetric mode and an oblique symmetric mode are adjusted, so that the windows S1, S2, and S3 of the shutter S are independently opened and closed, and the evaporation material from the evaporation source is used. The partial vapor deposition is performed by controlling in relation to the supply of the gas. When the electrical characteristics such as a predetermined frequency have been obtained, the adjustment operation is completed, and then the container is hermetically sealed with a cover plate (not shown).
[0022]
In the above embodiment, one set of monolithic quartz filters is formed on one quartz vibrating plate. However, a multistage connection type in which a plurality of sets of monolithic filters are formed may be used. In this case, it is necessary to provide an adjustment window in which the metal mask corresponds to the set.
[0023]
Further, by forming a metal film on the bottom of the opening or on the bottom and the side of the opening, and connecting this metal film to the ground, the electromagnetic shield can be made more reliable.
[0024]
Another embodiment of the present invention will be described with reference to FIG. 6, taking a surface-mount type crystal resonator as an example. The description of the lid plate used for hermetic sealing is omitted.
Since the basic configuration of the case 6 is the same as that of the above-described embodiment, detailed description is omitted. However, since the configuration is such that the quartz diaphragm 25 is cantilevered, only one lower mounting portion 61 is formed. The electrode pad 61a formed on the lower mounting portion 61 and the extraction electrode 251a extracted from the excitation electrode 251 of the quartz vibrating plate are joined by a conductive joining material. After that, the metal mask 34 is positioned and mounted on the electrode pad 62a of the upper mounting portion 62, and conductively bonded. Of course, the relative position between the adjustment window 341 and the excitation electrode 251 is adjusted. With this configuration, electric characteristics such as frequency can be accurately adjusted, and an electromagnetic shielding effect can be obtained due to the presence of the metal mask.
[0025]
Another embodiment of the present invention will be described with reference to FIG. 7, taking a surface mount type crystal oscillator as an example. The description of the lid plate used for hermetic sealing is omitted.
The case 7 is divided into a chamber 7a for storing a crystal diaphragm and a chamber 7b for storing circuit components such as ICs. In the chamber 7a, a lower mounting portion 71 for supporting the crystal vibration plate 26 in a cantilever manner is formed, and the electrode pad 71a formed on the lower mounting portion 71 and the excitation electrode 261 of the crystal vibration plate are drawn out. The extraction electrode 261a is joined by a conductive joining material. An IC 25 is housed in the chamber 7b and is electrically connected by a bonding wire (not shown). The metal mask 34 mounted on the upper mounting portion 72 has an adjustment window corresponding to the excitation electrode portion of the crystal plate housed in the chamber 7a and has a size covering the chamber 7b. Have been. Metal films 74 and 75 are formed on the bottom surfaces of these chambers, respectively, and these metal films are grounded. With this configuration, it is possible to accurately adjust the electrical characteristics such as the frequency, and it has an effect of shielding electromagnetic noise generated from the quartz plate 26 and the IC 27.
[0026]
【The invention's effect】
According to the first aspect, since the metal mask is fixed in the case and partial vapor deposition is performed using the metal mask, the piezoelectric vibrating plate and the metal mask can be brought extremely close. Therefore, the partial vapor deposition is performed only within a predetermined limited range, so that electric characteristics such as a desired frequency can be adjusted, and a short circuit accident with another electrode can be prevented.
[0027]
In addition, since the metal mask is housed in the case, maintenance such as cleaning and replacement of the metal mask at the time of partial vapor deposition, which has been conventionally performed, becomes unnecessary.
[0028]
In addition, since this metal mask is electrically grounded via an external lead-out electrode, a direct wave is electromagnetically shielded in the case of a piezoelectric filter, and an electromagnetic wave is generated in the case of a piezoelectric vibrator or a piezoelectric oscillator. Can be suppressed. Therefore, desired good attenuation characteristics can be obtained.
[0029]
According to the second aspect, the metal mask is mounted by the image recognition means in accordance with the planar inclination of the mounted piezoelectric vibration plate and the excitation electrode, so that the piezoelectric vibration plate and the metal mask can be extremely close to each other. Since the relative positions of the adjustment window and the excitation electrode can be reliably matched, the adjustment of the electrical characteristics by the partial vapor deposition can be performed reliably.
[Brief description of the drawings]
FIG. 1 is an exploded perspective view showing an embodiment.
FIG. 2 is a perspective view showing the embodiment when the lid is opened.
FIG. 3 is a sectional view taken along line LL of FIG. 2;
FIG. 4 is a plan view illustrating an embodiment.
FIG. 5 is a diagram showing a manufacturing method.
FIG. 6 is an exploded perspective view showing another embodiment. FIG. 7 is an exploded perspective view showing another embodiment. FIG. 8 is a view showing a conventional example.
FIG. 9 shows a comparative example.
[Explanation of symbols]
1, 6, 7, 90 Case 11, 61, 71 Lower mounting part 12, 62, 72 Upper mounting part 2, 25, 26, 91 Quartz diaphragm (piezoelectric diaphragm)
3, 34, 35, 92 Metal mask 31, 32, 33, 341, 351 Adjustment window 4 Cover plate S Shutter

Claims (2)

At least one set of an input electrode, an output electrode, and a corresponding common electrode is disposed on the front and back surfaces of a piezoelectric vibrating plate, respectively, and is disposed above the piezoelectric vibrating plate. A surface mounted piezoelectric filter containing a metal mask having an adjustment window formed in a portion to be accommodated in a case,
  The case has a ceramic base, a plurality of external lead-out electrodes on the outer surface thereof, a lower mounting portion for mounting a piezoelectric vibrating plate therein, and an upper mounting portion for mounting the metal mask above the mounting portion. An electrode pad electrically connected to the external lead-out electrode is formed on each of the lower mounting portion and the upper mounting portion, and the electrode of the piezoelectric vibration plate is electrically conductively bonded to the electrode pad of the lower mounting portion. A surface mounting wherein the metal mask is electrically connected to the electrode pad and is electrically grounded through the specific external lead-out electrode by connecting the metal mask to the electrode pad. Type piezoelectric filter. While having a plurality of external lead-out electrodes on the outer surface, the inside has a lower mounting portion for mounting a piezoelectric vibration plate, and an upper mounting portion for mounting the metal mask above the mounting portion, these lower mounting portions, In the upper mounting part, a ceramic-based case is prepared, in each of which an electrode pad electrically connected to the external lead-out electrode is formed, and an excitation electrode is formed on at least the surface of the electrode pad of the lower mounting part. Means for mounting a piezoelectric vibrating plate and conducting conductive bonding,
  Means for capturing the mounted state of the mounted piezoelectric diaphragm into an image memory by image recognition technology, and calculating a planar inclination in the mounted state of the piezoelectric diaphragm from the image memory;
  In accordance with the obtained inclination, the metal mask on which the adjustment window is formed is rotated and moved, the adjustment window is positioned corresponding to a predetermined position of the excitation electrode, and is installed on the upper mounting portion. Means,
  Means for conductively bonding the positioned metal mask to the electrode pad of the upper mounting portion,
  Means for partially depositing a metal material for electric property adjustment using the metal mask,
  Means for hermetically sealing by joining a sealing lid to an opening of a case.

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