JP3477707B2 - Crystal filter - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a piezoelectric vibrating device using a ceramic package, and particularly, considering the improvement of strength of a downsized ceramic package.

[0002]

2. Description of the Related Art Crystal oscillators, crystal filters, crystal oscillators and the like are examples of piezoelectric vibrating devices requiring hermetic sealing. In all of these, a metal thin film electrode is formed on the surface of a quartz diaphragm (piezoelectric diaphragm), and the metal thin film electrode is hermetically sealed in order to protect the metal thin film electrode from the outside air.

Due to the demand for surface mounting of components, these crystal-applied products are increasingly being hermetically housed in a ceramic package. By selecting an appropriate hermetic sealing method, good hermeticity is ensured. can do. An example of a piezoelectric vibrating device using such a ceramic package will be described with reference to FIGS. FIG. 5 is a plan view of a ceramic package showing a conventional example, and shows a state in which a crystal vibration plate (piezoelectric vibration plate) is mounted in a storage portion. FIG. 6 is an internal cross-sectional view of FIG. 5, and shows a state of hermetically sealing with a metal lid (not shown).

The ceramic package as a whole has a rectangular parallelepiped shape in which a concave storage portion 45 is formed in the central portion, and a metal seal portion 41 is provided on the upper surface of the bank 40 around the storage portion.
Are formed. The castellations 42a-4, which are processed into concave grooves, are formed on the peripheral side surface of the ceramic package.
2h is formed. Castellation conductors 43a to 43h are formed in the castellations. Electrode pads 46a, 4 are provided on the bottom of the storage portion 45.
6b, 46c, 46d are formed, and the quartz crystal diaphragm 5 is mounted on the electrode pad and electrically and mechanically connected. After that, the metal lid 6 and the ceramic package 4
The metal seal portion formed in the above is joined by seam welding using the welding roller R to hermetically seal.

Recently, due to further miniaturization and weight reduction of electronic equipment, it has been required to miniaturize the piezoelectric vibration device. When miniaturizing a piezoelectric vibration device, in addition to how to efficiently arrange the piezoelectric vibration plate in the storage space within the given external dimension range, consider the external size of the piezoelectric vibration plate or the wall of the package. The consideration of the thickness becomes important in the design of the piezoelectric vibration device. However, if the piezoelectric vibrating plate is made too small, it becomes impossible to secure a necessary vibrating region, and it becomes impossible to obtain predetermined electrical characteristics. In addition, if the wall thickness of the package is too thin, the package may be damaged due to thermal stress at the time of hermetic sealing. In particular, when seam welding the metal lid and the metal seal portion, as shown in FIG. 4, due to the pressing force of the welding roller R and the thermal strain that locally becomes high temperature during welding, or the heat of the metal lid, the metal seal portion and the ceramic is generated. The package may be damaged due to the difference in expansion coefficient. This damage is due to the castellation 42b at the center of each side of the package.
Many are found in the 42d, 42f, 42h forming regions, and it is considered that stress strain and thermal strain are concentrated in the regions.

[0006]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and a crystal filter which ensures good piezoelectric vibration characteristics even when it is made extremely small and has improved strength of a ceramic package. Is intended to provide.

[0007]

In order to solve the above-mentioned problems, the present invention, as set forth in claim 1, is a rectangular parallelepiped shape as a whole, and an accommodating portion having an upward opening for accommodating a crystal diaphragm, and the accommodating portion. A crystal vibrating device, which is hermetically sealed with a metal lid, using a ceramic package consisting of a bank portion formed around the wall portion and a metal seal portion formed on the upper portion of the bank portion, the periphery of the package. A castellation is formed at the center of each side of the side surface, and a shield wall made of ceramics that reinforces the pair of castellations formed on the opposite side surfaces is formed inside the storage portion. It is characterized in that a shield electrode is formed on the upper portion, and a crystal diaphragm is arranged on the shield electrode.

According to the above structure, the shield wall is formed on the side of the storage portion corresponding to the castellation forming region, and since the shield wall plays a reinforcing role, the strength of the package as a whole is improved. As a result, the damage of the package during or after the hermetic sealing which has conventionally occurred is reduced. In particular, it is possible to reinforce the central region of each side of the side surface where the package is often damaged, and it is possible to improve the package strength in the case of downsizing.

Further, by forming the shield electrode on the upper part of the shield wall, it is possible to block the direct wave generated in the crystal filter.

Further, as described in claim 2, in the crystal filter according to claim 1, the metal seal portion and the metal lid may be joined by seam welding or beam welding to hermetically seal.

According to the above construction, it is possible to obtain a crystal filter with less accidental damage to the package even when it is hermetically sealed by seam welding or beam welding, which has a particularly large thermal strain.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment according to the present invention will be described with reference to FIGS. 1 and 2 by taking a surface mount type crystal resonator as an example. FIG. 1 is a plan view showing the present embodiment, and FIG. 2 is an internal cross-sectional view in a state of being hermetically sealed with a metal lid. The surface mount type crystal resonator is a rectangular parallelepiped as a whole, and has a ceramic package 1 having a concave portion with an opening at the top, and a rectangular crystal vibrating plate 2 (indicated by a dotted line) which is a piezoelectric vibrating element housed in the package. ) And a metal lid 3 joined to the opening of the package.

The ceramic package 1 is concave in cross section, and has a bank portion (side wall) 10 around the recess and a circumferential metal seal portion 11 formed on the upper surface of the bank portion. The metal seal portion 11 includes a metallized layer made of tungsten or the like and a metal film layer formed on the metallized layer. The metal film layer is composed of, for example, a nickel plating layer in contact with the metallization layer and an extremely thin gold plating layer formed on the nickel plating layer. A metal ring for welding such as Kovar may be attached.

A plurality of castellations 12a, 12b, 12 are provided on the outer side wall of the ceramic package.
c, 12d, 12e, 12f, 12g, 12h are formed. The castellation is formed in the vertical direction in the shape of a concave groove, and the castellation conductors 13a, 13b, 13c, 13 are provided inside each castellation.
d, 13e, 13f, 13g, and 13h are formed and internally wired as appropriate. The castellation conductor has a structure in which, for example, a metallized layer made of tungsten is plated with nickel or gold.

In the interior of the ceramic package 1, castellations 12b, 12d, 12 formed in the central portions of the respective sides of the castellations.
Corresponding to f and 12h, the protrusions 16a, 16b, 16
c, 16d are formed. Each protrusion is made of ceramic, and electrode pads 17a and 17b are formed on the upper surfaces of the protrusions 16a and 16c, respectively. These electrode pads are led out to the outside by metal vias or the like, and are electrically connected to a part of the castellation conductor.

A rectangular AT-cut quartz crystal diaphragm 2, which is a piezoelectric vibrating element, is mounted on the electrode pads 17a and 17b, and is configured to support both ends in the long side direction. Although not shown, a pair of excitation electrodes are formed on the front and back surfaces of the crystal diaphragm 2 and are led out to the electrode pads 13 and 14, respectively, and are conductively bonded by the conductive bonding material S1.

The metal lid 3 has a flat plate-shaped Kovar as a base material, and its surface is plated with nickel. The metal lid 3 is mounted on the metal seal portion 11, and in this state, the metal lid and the metal seal portion are melted by seam welding or beam welding such as laser to hermetically seal.

The second embodiment of the present invention will be described with reference to FIGS. 3 and 4 by taking a surface mount type crystal filter as an example. FIG. 3 is a plan view showing the present embodiment, and FIG. 4 is an internal cross-sectional view in a state of being hermetically sealed with a metal lid. The same components as those in the above-described embodiment will be described using the same numbers, and a partial description will be omitted. The surface mount type crystal filter is a rectangular parallelepiped shape as a whole, and has a ceramic package 1 having a concave portion with an upper opening, and a rectangular crystal vibrating plate 2 (indicated by a dotted line) which is a piezoelectric vibrating element housed in the package. And a metal lid 3 joined to the opening of the package.

Compared with the first embodiment, the present embodiment is different from the first embodiment in the arrangement and shape of the protruding portions, and has a configuration in which a shield wall 71 is vertically cut in the central portion, and a shield electrode 72 is formed on the upper surface thereof. The point is different. Direct waves generated in the crystal filter are blocked by the shield electrode. And the castellations 12a, 12
b, 12c, 12e, 12f, 12g, the protrusions 18a, 18b,
18c, 18d, 18e and 18f are formed correspondingly. The castellations 12d and 12h are reinforced by the shield wall. The shield wall is made of ceramics, and the shield electrode is formed by a method such as metallization or plating. In addition, the protruding portion 18
Electrode pads 19 are formed on the upper surfaces of a, 18c, 18d and 18f.
a, 19b, 19c and 19d are formed and electrically connected to a plurality of excitation electrodes (not shown) formed on the crystal diaphragm 2. Each of the electrode pads is appropriately wired by internal wiring made of laminated ceramics, is led out of the ceramic package, and is electrically connected to a part of the castellation conductor.

According to the present embodiment, the protruding portion plays a reinforcing role, and the shield wall and the shield electrode also have the same function, so that the strength of the package as a whole is improved and the airtightness which has been conventionally generated. Damage to the package at rest or thereafter is reduced.

In the above description, a crystal oscillator is illustrated as an example of the piezoelectric vibrating device, but in the above embodiment, for example, an IC that constitutes an oscillation circuit is attached to the lower space of the crystal vibrating plate, and necessary wiring is performed. A crystal oscillator may be configured, or the present invention can be applied to other piezoelectric vibrating devices such as a crystal filter having one element or multiple elements.
Further, electrode pads may be formed on the protrusions in the same number as the excitation electrodes formed on the crystal diaphragm (piezoelectric diaphragm).

[0022]

According to the first aspect of the present invention, the shield wall is formed on the housing portion side in correspondence with the castellation forming region, and since the shield wall plays a reinforcing role, the package as a whole is packaged. The strength of the package is improved, and the damage to the package during or after the hermetic sealing which has conventionally occurred is reduced. In particular, it is possible to reinforce the central region of each side of the side surface where the package is often damaged, and it is possible to improve the package strength in the case of downsizing. Therefore, it is possible to provide a crystal filter in which good piezoelectric vibration characteristics are ensured even when the size is reduced, and the strength of the ceramic package is improved.

According to the second aspect, it is possible to obtain the crystal filter with less accidental damage to the package even when airtightly sealed by seam welding or beam welding having a large thermal strain.

[Brief description of drawings]

FIG. 1 is a plan view according to a first embodiment.

FIG. 2 is an internal sectional view according to the first embodiment.

FIG. 3 is a plan view according to the second embodiment.

FIG. 4 is an internal sectional view according to a second embodiment.

FIG. 5 is a diagram showing a conventional example.

FIG. 6 is a diagram showing a conventional example.

[Explanation of symbols]

1, 4 Ceramic package 10, 40 Bank 11, 41 Metal seal 2, 5 Crystal diaphragm (piezoelectric diaphragm) 3, 6 Metal lid 12a, 12b, 12c, 12d, 12e, 12f, 1
2g, 12h Castellations 16a, 16b, 16c, 16d, 18a, 18b, 1
8c, 18d, 18e, 18f Projection part

─────────────────────────────────────────────────── ─── Continuation of front page (56) Reference JP-A-11-312748 (JP, A) JP-A-8-46075 (JP, A) JP-A-6-140866 (JP, A) JP-A-11- 214950 (JP, A) JP-A-8-195567 (JP, A) Actual opening 5-48427 (JP, U) Actual opening 5-46115 (JP, U) Actual public Sho-40-4506 (JP, Y1) (58) Fields surveyed (Int.Cl. ⁷ , DB name) H03H 9/02 H01L 23/02 H01L 23/04 H01L 41/09 H03H 9/10

Claims (2)

(57) [Claims] 1. A storage unit having a rectangular parallelepiped shape as a whole, which is opened upward to store a crystal diaphragm, a bank section formed around the storage section, and a metal seal section formed on the upper section of the bank section. A crystal filter that is air-tightly sealed with a metal lid using a ceramic package consisting of a castellation is formed at the center of each side of the peripheral side surface of the package and is formed on the opposite side surface.
Ceramics to reinforce a pair of castellations
Is formed inside the storage part.
, A shield electrode is formed on the upper part of the shield wall,
And the crystal diaphragm is placed above the shield electrode
A crystal filter characterized by that. 2. The crystal filter according to claim 1 , wherein the metal seal portion and the metal lid are joined and hermetically sealed by seam welding or beam welding .