JP2002026680A - Piezoelectric vibrator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent an area of the piezoelectric vibrating element from being narrower as the volume in a cave is small due to a thick wall thickness of a ceramic outer wall with respect to the conventional piezoelectric vibrator consisting of a package main body where the ceramic outer wall is stood upright and fixed along an upper face circumferential edge of a ceramic-made bottom plate, of the piezoelectric vibrating element contained in the cave of the package main body, and of a metallic cover fixed via a seal ring fixed on the outer wall upper face. SOLUTION: The package main body 22 of this invention is provided with a bottom plate 24 made of a ceramic material, a ceramic thin film 25 and a metallized film 26 that are sequentially layered along the circumferential edge of the bottom plate upper face, and a torus metallic seal ring 27 fixed on the metallized film, the piezoelectric vibrating element is fixed on an electrode pad 28a exposed on the inward end of the ceramic thin film, the electrode pad is communicatively connected to an external electrode 28b at the bottom plate outer bottom face via a connection conductor 28 imbedded in the thickness of the bottom plate and the metallic cover 35 is communicatively fixed to an upper face of the metallic seal ring.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in a package structure of a piezoelectric vibrator, and more particularly to a piezoelectric vibrator capable of solving various problems caused by forming an outer peripheral wall of a package with ceramic at a glance. It is about.

[0002]

2. Description of the Related Art A piezoelectric vibrating element such as a quartz vibrating element is used by being incorporated in a piezoelectric vibrator, a piezoelectric oscillator or the like. The piezoelectric vibrator has a configuration in which excitation electrodes, lead terminals, and the like are formed on a vibrating portion of a piezoelectric plate having a vibrating portion having a suitable thickness to obtain a target resonance frequency by vapor deposition or the like. FIG. 4A is a longitudinal sectional view (XX sectional view of FIG. 4B) for explaining a package structure of a crystal unit as an example of a conventional piezoelectric unit, and FIG. 4B is a perspective view of a package body. (C) is a plan view of the package body. This crystal resonator 1 is fixed to a package body 2 made of an insulating material such as ceramic, a crystal resonator element 11 arranged in a recess 3 formed on the upper surface of the package body 2, and to an upper surface of an outer wall of the package body 2. And a metal lid 15 for hermetically sealing the inside of the recess 3. The package body 2 includes a ceramic bottom plate 4.
A ceramic thin film 5 laminated at a required width along the periphery of the upper surface of the bottom plate 4, an annular outer wall (outer peripheral wall) 6 made of ceramic fixed to the upper surface of the ceramic thin film 5, and an outer wall 6.
And a conductor 8 extending along the side wall and bottom surface of the bottom plate 4 from the top surface of the ceramic thin film 5. The ceramic thin film 5 is obtained by coating a paste obtained by mixing powder containing alumina as a main material with a resin binder, that is, a ceramic paste containing alumina as a main material, on the upper surface of a bottom plate by screen printing or the like, and hardening the resin. The binder component volatilizes, and only the alumina remains on the bottom plate in a hardened state, forming a ceramic thin film. In practice, a ceramic paste is applied on the bottom plate 4 by screen printing,
The ceramic annular outer wall 6 is placed thereon and the electrode 8 is assembled and baked in a state where the electrode 8 is assembled.
The bottom plate 4 and the outer wall 6 are fixed by the ceramic thin film 5. The seal ring 7 is a rectangular metal body having a thickness smaller than the width (wall thickness) of the outer wall 6, and is fixed to the upper surface of the outer wall 6 via the metallized film 9. Metallized film 9
Is formed by screen-printing a paste obtained by mixing tungsten powder in an organic solvent on the upper surface of the outer wall 6 and then baking it. At this time, the solvent evaporates,
Only the tungsten film remains fixed. When fixing the seal ring 7 on the metallized film 9, a nickel film is plated on the metallized film 9, and then the seal ring bottom surface is fixed with silver solder. The inner end of the conductor 8 functions as an electrode pad 8 a that supports the crystal resonator element 10 by being exposed on the inner protrusion 5 a of the ceramic thin film 5, and the outer mold end is exposed at the outer bottom of the bottom plate 4. Thereby, it functions as the external electrode 8b. The crystal vibrating element 11
Excitation electrodes 13 are formed on both main surfaces of the quartz crystal plate 12, respectively. When a required alternating current is applied to the excitation electrode 13, a quartz crystal plate portion (main vibrating portion) sandwiched between the front and back excitation electrodes 12 is provided. ) Causes a thickness slip and an energy trapping phenomenon, so that the main vibration is excited at the portion where the excitation electrode is attached. The crystal vibrating element 11 is conductively fixed on the electrode pad 8a by a conductive adhesive.

[0003] Incidentally, the dimensions of each part of the crystal unit are set as shown by the numerals indicating the dimensions shown in the figure.
The reason why the outer wall 6 has a large wall thickness of 0.4 to 0.45 mm is that it is necessary to secure a sufficient bonding strength between the outer wall 6 and the ceramic thin film 5 to improve the airtightness. . That is, the bonding strength and airtightness between the ceramic thin film 5 and the bottom plate 4 are set such that the width of the ceramic thin film 5 is widened as shown in the drawing and the inner edge thereof extends into the side recess 3. Can be secured. And, in order to sufficiently increase the bonding strength and airtightness with the bottom surface of the outer wall 6,
It is necessary to make the wall thickness of the outer wall 6 slightly larger to secure a large bonding area with the ceramic thin film 5. However, when the wall thickness of the outer wall 6 is increased, the following trouble occurs. That is, as shown in FIG.
If the vertical and horizontal dimensions are A x B mm, the outer wall thickness is 0.45 mm x
2, the vertical and horizontal dimensions of the recess 3 are (A-0.
9) × (B−0.9) mm. The vertical and horizontal dimensions of the quartz vibrating element 11 that can be mounted in the recess 3 are further reduced. As described above, the plane area (volume) of the recess 3 is reduced by the increase in the wall thickness of the outer wall 6, and the quartz vibrating element 11 is reduced.
When the size of the oscillator is reduced, the excitation electrode 13 (main electrode) on the quartz crystal plate 12 becomes smaller, and the crystal impedance rises, which makes it difficult to excite the oscillator. Similarly, when the plane area of the concave portion 3 is reduced, the main electrode of the crystal unit 11 and the quartz crystal plate 1 accommodated in the concave portion are reduced.
Since the distance from the periphery of the base plate 2 becomes short, the vibration of the main electrode is easily leaked to the periphery of the base plate, and the sub-vibration is excited at the periphery of the base plate,
The disadvantage that vibration reflected at the periphery of the base plate adversely affects the main vibration is likely to occur. In the future, when further miniaturization of the crystal unit is demanded, the above-mentioned problem is further amplified, and the adverse effect on the characteristics of the crystal unit becomes enormous.

[0004]

An object of the present invention is to provide a package body in which a ceramic outer wall is erected and fixed along a peripheral edge of an upper surface of a ceramic bottom plate, and a piezoelectric body accommodated in a concave portion of the package body. A disadvantage of the conventional piezoelectric vibrator comprising a vibration element and a metal lid fixed via a seal ring fixed to the upper surface of the outer wall, which is caused by a thick wall of the outer wall. An object of the present invention is to prevent a reduction in the area of the piezoelectric vibrating element due to a reduction in volume in the recessed portion. In other words, when the area of the piezoelectric vibrating element is reduced, the excitation electrode on the piezoelectric element plate becomes smaller and the impedance of the element plate increases, making it difficult to excite the oscillator when the oscillator is configured. It is easy for leakage to occur, and a sub-vibration is excited at the periphery of the base plate, or a problem that the vibration reflected at the periphery of the base plate adversely affects the main vibration is likely to occur, but the present invention solves this problem. Make it an issue.

[0005]

According to a first aspect of the present invention, there is provided a package body having a concave portion on an upper surface, a piezoelectric vibrating element disposed in the concave portion of the package body, and In a piezoelectric vibrator having a metal lid for hermetically sealing the recess, the package body includes a bottom plate made of a ceramic material, and a ceramic thin film and a metallized film sequentially stacked along the periphery of the upper surface of the bottom plate. A seal ring having a bottom surface fixed on the metallized film, wherein the metal lid is conductively fixed to an upper surface of the metal seal ring. According to a second aspect of the present invention, there is provided a piezoelectric vibration device comprising: a package body having a concave portion on an upper surface; a piezoelectric vibrating element disposed in the concave portion of the package body; and a metal lid for hermetically sealing the concave portion. A package body comprising: a bottom plate made of a ceramic material;
A ceramic thin film and a metallized film sequentially laminated along the periphery of the upper surface of the bottom plate; and a seal ring having a bottom surface fixed on the metallized film, and on an electrode pad exposed on an inner end of the ceramic thin film. The piezoelectric vibrating element is fixed, the electrode pad is conductively connected to an external electrode on an outer bottom surface of the bottom plate via a connection conductor embedded inside the bottom plate, and the metal lid is conductively fixed to an upper surface of the metal seal ring. It is characterized by that. According to a third aspect of the present invention, there is provided a piezoelectric vibration device comprising: a package main body having a concave portion on an upper surface; a piezoelectric vibrating element disposed in the concave portion of the package main body; and a metal lid for hermetically sealing the concave portion. The package body includes a bottom plate made of a ceramic material, a metallized film laminated along a peripheral edge of an upper surface of the bottom plate, and a seal ring having a bottom surface fixed on the metallized film, and an upper surface of the bottom plate. The piezoelectric vibrating element is fixed on a thick electrode pad protruding from the base plate, and the electrode pad is conductively connected to an external electrode on an outer bottom surface of the bottom plate via a connection conductor embedded inside the bottom plate. It is characterized by being conductively fixed to the upper surface of the metal seal ring.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to embodiments shown in the drawings. FIGS. 1A and 1B are a longitudinal sectional view and a main part enlarged view of a quartz oscillator as a piezoelectric oscillator according to an embodiment of the present invention. This crystal oscillator 21
A package main body 22 made of an insulating material such as ceramics or other materials; a quartz vibrating element 31 disposed in a recess 23 formed on the upper surface of the package main body 22;
A metal lid 35 which is conductively fixed to the upper surface of the outer wall of the package body 22 and hermetically seals the inside of the recess 23. The package body 22 includes a ceramic bottom plate 24, a ceramic thin film 25 laminated with a required width along the periphery of the upper surface of the bottom plate 24, and a metal thin film 26 formed on the upper surface of the ceramic thin film 25 via a ceramic thin film. An annular seal ring (Kovar) 27 fixed to 25 and a conductor 28 that penetrates through the inside of the bottom plate 24 from the upper surface of the inner end of the ceramic thin film 25 and is exposed to the outside. The ceramic thin film 25 is obtained by coating a paste obtained by mixing a powder containing alumina as a main material with a resin binder, that is, a ceramic paste containing alumina as a main material, on a bottom plate upper surface by screen printing or the like, and sintering the resin. The binder component volatilizes, and only the alumina remains on the bottom plate 24 in a hardened state, forming a ceramic thin film. In practice, the conductor 28 and the ceramic thin film 25 are fixed to the bottom plate 24 by applying a ceramic paste on the bottom plate 24 by screen printing and baking at a predetermined temperature with the conductor 28 assembled. In this example, the bottom plate 24 is formed by laminating sheet-shaped ceramic plates 24a and 24b, and the conductor 28 has a via hole 24b 'formed in one ceramic plate 24b and the two ceramic plates 24a and 24b.
It is exposed to the outside through the interface between 24b. The inner end of the conductor 28 is connected to the inner protrusion 25a of the ceramic thin film 25.
And projecting to the upper surface to form an electrode pad 28a,
The outer end becomes the external electrode 28b. When fixing the seal ring 27 on the bottom plate 24 configured as described above, FIG.
As shown in the enlarged view of (b), a metallized film 26 of tungsten is formed on the ceramic thin film 25, and then the bottom surface of the seal ring 27 is fixed on the metallized film 26 using a silver solder 29.

The metallized film 26 is formed by mixing a tungsten powder into an organic solvent to form a paste, screen-printing the paste on the upper surface of the ceramic thin film 25, and baking it. At this time, the solvent volatilizes, and only the tungsten film remains fixed. When the seal ring 27 is fixed on the metallized film 26, a nickel film is plated on the metallized film 26, and
9, the seal ring 27 is fixed. Here, the seal ring 27 is a rectangular annular body made of Kovar having a width of about 0.25 to 0.3 mm. Crystal vibrating element 3
Reference numeral 1 denotes a configuration in which excitation electrodes 33 are formed on both main surfaces of a quartz crystal plate 32. When a required alternating current is applied to the excitation electrodes 33, a quartz crystal plate portion (main The vibrating portion) causes a thickness slip and an energy trapping phenomenon, so that the main vibration is excited at the portion where the excitation electrode is attached. This crystal vibrating element 31 has an electrode pad 28a
It is conductively fixed thereon by a conductive adhesive.

A feature of the crystal unit 21 according to this embodiment is that a seal ring 27 having a minimum necessary height is erected and fixed on the bottom plate 24 instead of the conventional ceramic outer wall (reference numeral 6 in FIG. 4). Thus, the wall thickness of the seal ring 27 is made thinner than the wall thickness of the conventional ceramic outer wall.
That is, since the conventional ceramic outer wall is configured to be fired and integrated on the ceramic thin film formed on the bottom plate, the bonding strength between the ceramic thin film and the bottom surface of the ceramic outer wall and the ceramic are required to be sufficiently secured. It was necessary to set the wall thickness of the outer wall to be relatively large (0.4 to 0.45 mm). On the other hand, when only the seal ring 27 is used,
After the metallized film 26 is formed on the ceramic thin film 25, the seal ring 27 is fixed by the silver solder 29, so that the metallized film 26 and the ceramic thin film 25 are fixed.
And the sealing strength between the sealing ring 27 and the sealing ring 27 can be sufficiently increased, and the joining strength and the airtightness can be sufficiently secured without making the wall thickness of the seal ring 27 so large. In this example, the wall thickness of the seal ring 27 is 0.25 to 0.3 mm
It is thin to the extent, which is much thinner than the wall thickness of the conventional ceramic outer wall. For this reason, as shown in FIG. 2, the vertical and horizontal dimensions (A−0.6) × (B−
0.6) mm is compared with the vertical and horizontal dimensions (A-0.9) × (B-0.9) mm of the inner circumference of the ceramic outer wall shown in FIG. Despite both A × B being constant, the inner flat area (volume) of the seal ring 2
7 is larger. For this reason, the vertical and horizontal dimensions of the crystal resonator element 31 can be increased by 0.2 to 0.3 mm. In recent years, the size of the short side of the quartz vibrating element 31 is about 2 to 3 mm in length along with miniaturization, but the present invention can increase the dimension by as much as 10%. As the area of the crystal resonator element 31 increases, the excitation electrode 33 (main electrode) on the crystal plate 32 increases, the crystal impedance decreases, and the excitation becomes easier when an oscillator is configured. Similarly, when the volume of the concave portion 3 is increased, the main electrode of the crystal unit 31 accommodated in the concave portion and the quartz crystal plate 3
Since the distance from the periphery of the base plate 2 is increased, the vibration of the main electrode hardly leaks to the periphery of the base plate, and the sub-vibration is excited at the periphery of the base plate. The problem of the occurrence of the problem no longer occurs. As described above, according to the present configuration, it is possible to sufficiently cope with a case where further reduction in the size of the crystal resonator is required. In the embodiment shown in FIG. 1 (b), since the inner end 25a of the ceramic thin film 25 is sufficiently extended, the height of the electrode pad 28a is sufficiently ensured and the height between the electrode pad 28a and the upper surface of the bottom plate is increased. In this case, a step having a sufficient height can be formed, and the crystal vibrating element 31 can be easily supported.

Next, FIG. 3A is an enlarged view showing a configuration of a main part of a modified embodiment of the present invention, in which a metallized film 26 is formed directly on the upper surface of a bottom plate 24 without providing a ceramic thin film 25. A characteristic feature is that the bottom of the seal ring 27 is fixed on the metallized film 26 using a silver solder 29. In this embodiment, the electrode pad 28a is made thicker by the amount that the ceramic thin film 25 is not provided to secure a sufficient step between the electrode pad 28a and the upper surface of the bottom plate 24, thereby making it easier to support the crystal resonator element 31. By configuring as in this embodiment, FIG.
In addition to the effects of the above-described embodiment, it is possible to improve the productivity by further omitting the step of forming the ceramic thin film 25, and to reduce the package height by the thickness of the ceramic thin film 25. Can demonstrate. Further, as shown in FIG. 3B, a step may be formed by providing a ceramic thin film between the electrode pad 28a and the bottom plate instead of increasing the thickness of the electrode pad 28a.

[0010]

As described above, according to the present invention, a package body in which a ceramic outer wall is erected and fixed along a peripheral edge of an upper surface of a ceramic bottom plate, a piezoelectric vibrating element housed in a concave portion of the package body, In a conventional piezoelectric vibrator consisting of a metal lid fixed via a seal ring fixed to the upper surface of the outer wall, the piezoelectric vibrator associated with the reduced volume in the recess due to the thick wall thickness of the ceramic outer wall. An object of the present invention is to prevent a reduction in the area of a vibration element. In other words, when the area of the piezoelectric vibrating element is reduced, the excitation electrode on the piezoelectric element plate becomes smaller and the impedance of the element plate increases, making it difficult to excite the oscillator when the oscillator is configured. It is easy for leakage to occur, so that a sub-vibration is excited at the periphery of the base plate, or a problem that the vibration reflected at the periphery of the base plate adversely affects the main vibration easily occurs. The present invention solves such a problem. . That is, conventionally, since the ceramic outer wall was erected via ceramic paste on the ceramic bottom plate and then fired and solidified, the bonding force between the bottom plate upper surface and the outer wall bottom surface, and the airtightness were sufficiently high. To maintain this, it was necessary to increase the wall thickness of the outer wall in order to increase the joint area between the two. For this reason, the volume of the recessed portion is reduced, and the size of the piezoelectric vibrating element to be accommodated is reduced, thus causing the above-described problem. In contrast, in the present invention,
Instead of the ceramic outer wall, a seal ring made of Kovar or the like was fixed on the bottom plate via a metallized film, and the seal ring was used as the outer wall of the package body. , Especially the plane area can be increased. For this reason, the area of the piezoelectric vibrating element accommodated in the recessed portion can be increased, and the above-mentioned problem can be solved at once.

[Brief description of the drawings]

FIGS. 1A and 1B are a longitudinal sectional view and a main part enlarged view of a quartz oscillator as a piezoelectric oscillator according to an embodiment of the present invention.

FIG. 2 is a plan view of a seal ring.

FIGS. 3A and 3B are main part configuration diagrams of another embodiment.

FIG. 4A is a longitudinal sectional view (XX sectional view of FIG. 4B) for explaining a package structure of a crystal resonator as an example of a conventional piezoelectric resonator, and FIG. FIG. 3C is a perspective view, and FIG.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 21 Quartz crystal oscillator, 22 Package main body, 23 Depressed part, 24 Bottom plate, 25 Ceramic thin film, 26 Metallized film, 27 Seal ring (Kovar), 28 conductor, 2
8a electrode pad, 28b external electrode, 29 silver solder,
31 crystal vibrating element, 32 crystal blank, 33 excitation electrode, 35 metal lid.

Claims (3)

[Claims] 1. A piezoelectric vibrator comprising: a package main body having a concave portion on an upper surface; a piezoelectric vibrating element disposed in the concave portion of the package main body; and a metal lid for hermetically sealing the concave portion. The package body includes a bottom plate made of a ceramic material, a ceramic thin film and a metallized film sequentially laminated along a peripheral edge of the upper surface of the bottom plate, and a seal ring having a bottom surface fixed on the metallized film; The lid is conductively fixed to an upper surface of the metal seal ring. 2. A piezoelectric vibrator comprising: a package main body having a concave portion on an upper surface; a piezoelectric vibrating element disposed in the concave portion of the package main body; and a metal lid for hermetically sealing the concave portion. The package body includes: a bottom plate made of a ceramic material; a ceramic thin film and a metallized film sequentially stacked along a periphery of an upper surface of the bottom plate; and a seal ring having a bottom surface fixed on the metalized film. The piezoelectric vibrating element is fixed on an electrode pad exposed on the inner end of the thin film, and the electrode pad is conductively connected to an external electrode on an outer bottom surface of the bottom plate via a connection conductor embedded inside the bottom plate; The lid is conductively fixed to an upper surface of the metal seal ring. 3. A piezoelectric vibrator comprising: a package main body having a concave portion on an upper surface; a piezoelectric vibrating element disposed in the concave portion of the package main body; and a metal lid for hermetically sealing the concave portion. The package body includes a bottom plate made of a ceramic material, a metallized film laminated along a peripheral edge of an upper surface of the bottom plate, and a seal ring having a bottom surface fixed on the metallized film. The piezoelectric vibrating element is fixed on the thick electrode pad provided, and the electrode pad is conductively connected to an external electrode on an outer bottom surface of the bottom plate via a connection conductor embedded in the bottom plate. A piezoelectric vibrator, which is conductively fixed to an upper surface of a metal seal ring.