JPH0766661A - Piezoelectric oscillator - Google Patents

Abstract

PURPOSE:To improve reliability by further attaining an outline miniaturization by storing a piezoelectric oscillator with built-in capacitor within the recessed part pro vided on the upper surface of a package. CONSTITUTION:The electrode film 6 on the side of an upper surface is extended to a slightly left side from the right end of a ceramic piece 5 to a central part. The electrode film 7 on the side of a rear surface is extended up to the right side from a longitudinal direction central part from the left end of the rear surface of the ceramic piece 5. This point is the same as a conventional piezoelectric element 1. In this method, each film 6 and 7 formed on the upper surface and the rear surface of the ceramic piece 5 is extended to extension parts 6a and 7a going around from the end face of the ceramic piece 5 to the other surface side. By this method, the partial film having a main part on the surf ace side is made to creep to the side of the rear surface, and the both films 6 and 7 are enabled to be connected with films 16 and 17 formed on the bottom surface within the recessed part on the rear surface of the ceramic piece 5. The connection is performed by using a conductive adhesive 12, the upper surface side of one end part of the element 1 is covered by the part, large quantity of adhesive 12 is unnecessitated and the characteristic degradation due to the adhesive 12 is prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a piezoelectric oscillator suitable for forming an oscillator circuit using a C-MOS inverter.

[0002]

2. Description of the Related Art When an oscillating circuit is formed by using a piezoelectric ceramic element (hereinafter referred to as a piezoelectric element) 1, as shown in FIG.
Most commonly, it is formed using the OS inverter 2. In this case, as shown in FIG. 10, two capacitors 3 and 3 are required for phase inversion.

In order to facilitate the formation of such an oscillation circuit by a user, a piezoelectric oscillator 4 in which a piezoelectric element 1 and two capacitors 3 and 3 whose capacities are properly selected are integrated is provided. There is. Conventional piezoelectric oscillator 4
The structure of is shown in FIGS. 8 and 9.

In FIG. 8 and FIG. 9, reference numeral 1 denotes a piezoelectric element, and electrode coatings 6, 7 made of silver or the like are provided on the front and back surfaces of a strip-shaped piezoelectric ceramic piece 5 having a predetermined thickness in plan view. A thin film is formed by sputtering or the like. In FIG. 8, the electrode coating 6 on the front surface extends from the right end of the surface of the ceramic piece 5 to the left of the center in the longitudinal direction, while the electrode coating 7 on the back surface extends from the left end to the right of the center in the longitudinal direction. ing. Therefore,
Both electrode coatings 6, 7 formed on the front and back of the ceramic piece 5
Overlap each other over a predetermined area in plan view.
This overlapping area plays an important role in selecting the impedance of the piezoelectric element.

The piezoelectric element 1 as described above is integrally mounted on a base substrate 8 which itself has two capacitor functions. That is, the base substrate 8 includes a plate-shaped member made of a dielectric material, a first electrode coating 9 and a second electrode coating 1.
0 and the third electrode coating film 11 are formed in a loop shape on the front surface, the side surface, or the back surface of the base substrate 8, respectively. The positions of the first electrode coating film 9 and the second electrode coating film 10 in the longitudinal direction of the base substrate correspond to the positions of both ends of the piezoelectric element 1. The piezoelectric element 1 has electrode coatings 6, 7 formed on both front and back surfaces at both ends thereof.
However, while being electrically connected to the first electrode coating 9 and the second electrode coating 10 on the base substrate 8, they are mounted in a fixed manner by using a predetermined conductive adhesive 12, for example.

Since the base substrate 8 is made of a dielectric material, the first electrode coating 9 and the third electrode coating 1 on its surface are formed.
1 and between the third electrode coating 11 and the second electrode coating 1
Capacitors 3 and 3 are formed between 0 and 0, respectively.

On the base substrate 8, a cover body C shown by an imaginary line in FIG. 8 is attached so as to cover the piezoelectric element 1. The piezoelectric oscillator 4 thus formed is mounted on a predetermined rotating substrate by means of soldering or the like. At this time, as apparent from the circuit diagram of FIG. 10, the first electrode coating 9 and the second electrode coating 10 of the base substrate 8 are electrically connected to the C-MOS inverter 2, and the third electrode 11 is Will be connected to ground.

Piezoelectric oscillator 4 shown in FIGS. 8 and 9.
In particular, since the base substrate 8 has a capacitor function, it is made compact as a whole. However, even the piezoelectric oscillator 4 has the following problems.

First, since the side surface or the back surface of the base substrate 8 is exposed in the mounted state, the dielectric constant of the dielectric material constituting the base substrate itself may change depending on the use environment. Therefore, the capacities of the two capacitors 3 and 3 to be formed by the base substrate 8 are not stable, and the oscillation characteristics of the piezoelectric oscillator may fluctuate over time.

Second, since the base substrate 8 serves both as a capacitor type member and an external terminal forming member, it is a problem that the capacitance of the capacitor can be freely set by limiting the size and shape of the base substrate 8.

Thirdly, since the piezoelectric element 1 is mounted on the base substrate 8 by a dip of the conductive adhesive 12, and the cover body C is further attached, there is a limit to the reduction of a particularly planar space of the piezoelectric oscillator as a whole. There is.

The present invention has been devised under the circumstances as described above, and it is possible to achieve further miniaturization, the degree of freedom in setting the capacitor capacity is increased, and the reliability is excellent. It is an object to provide a piezoelectric oscillator with a built-in capacitor.

[0013]

In order to solve the above problems, the present invention takes the following technical means. That is, the invention described in claim 1 of the present application is a piezoelectric oscillator including a package that houses a piezoelectric element, the package including a top surface, a bottom surface, and a side surface, and the piezoelectric element on the top surface. Is formed, and the inner surface of the recess is electrically connected to both ends of the piezoelectric element, and is provided with two element electrode coatings on the upper surface, the side surface or the bottom surface, and the package Is characterized in that a lid having two capacitor functions is provided on the upper surface of the so as to close the recess.

Further, the invention described in claim 2 of the present application is a piezoelectric oscillator provided with a package for accommodating a piezoelectric element, wherein the package has a top surface, a bottom surface and a side surface, and the top surface has a top surface. A recess for accommodating the piezoelectric element is formed, and the upper surface is electrically connected to both ends of the piezoelectric element on the inner surface of the recess.
Two element electrode coatings that reach the side surface or the bottom surface, and between the two element electrode coatings, the upper surface, the side surface or the bottom surface is provided with a ground electrode coating film,
In addition, on the upper surface of the package, a first electrode coating and a second electrode coating which contact the electrode coatings for the respective elements and a third electrode coating which contacts the electrode coating for the ground are dielectric on the upper surface of the package. The lid body formed on the body material is provided so as to close the recess.

Further, in the invention described in claim 3 of the present application, in the piezoelectric element according to claim 2, the first electrode coating, the second electrode coating and the third electrode coating formed on the lid body are lid bodies. It is characterized in that it is formed only on the back surface of.

[0016]

According to the piezoelectric oscillator of the present invention, the piezoelectric element is housed in the recess provided on the upper surface of the package. In the recess, two element electrode coatings that are electrically connected to the top, side, and bottom of the package are formed. At the bottom of the recess, for example, a conductive adhesive is used for the element electrode coating. Mounted.
In this case, even when the conductive adhesive is applied by dip coating from above, the size of the recess may be set to the minimum size corresponding to the piezoelectric element. For example, when the piezoelectric element is mounted on the base substrate by dip coating with a conductive adhesive as in the conventional structure shown in FIGS. 8 and 9, the flow range of the conductive adhesive to be dip coated is taken into consideration. Therefore, it is necessary to secure a sufficient size in the base substrate, and accordingly, the size of the cover body tends to increase in plan view. Due to the mounting of the element, the flow range of the conductive adhesive is also limited within this recess, so that the planar size of the package can be minimized. As a result, the piezoelectric element according to the present invention as a whole can be made smaller than the conventional one.

The capacitor to be incorporated in the piezoelectric oscillator of the present invention is in the form of a lid that closes the recess of the package. This lid has three electrode coatings on the surface of the dielectric material plate, namely,
The first, second and third electrode coatings are formed separately from each other. Since the other electrode with which each electrode coating should come into contact faces the upper surface of the package, the three electrode coatings to be formed on this lid can be formed only on the back surface of the lid. .

Then, when the lid body is mounted on the upper surface of the package, the back surface of the lid body which should have a capacitor function is hidden in the package and is not exposed to the outside. Therefore, the piezoelectric oscillator of the present invention is
It is possible to obtain constant characteristics for a long period of time without the capacitance of the capacitor changing with time due to the environment of use.

Inside the package, the electrode film which is electrically connected to the piezoelectric element or the electrode film which is electrically connected to the electrode of the lid having the above-mentioned capacitor function is entirely on the bottom side through the surface of the package. The piezoelectric oscillator can be mounted on a predetermined circuit board by soldering or the like with its bottom face down without any problem.

Further, a member for forming a capacitor (lid) and a member for forming an external electrode (package)
Since and are basically separate bodies, the capacitance of the capacitor can be relatively easily changed by freely setting the size of each electrode coating formed on the lid.

As described above, the piezoelectric oscillator according to the present invention is further miniaturized and the reliability is further improved.

[0022]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The preferred embodiments of the present invention will be described below.
A detailed description will be given with reference to FIGS. 1 to 7. In these figures, members or portions equivalent to those of the conventional example shown in FIGS. 8 to 9 are designated by the same reference numerals.

The piezoelectric oscillator 4 of the present invention is basically a package 1 in which the piezoelectric element 1 is housed in a recess provided on the upper surface.
3 and a lid 1 having two capacitor functions for phase inversion
It is composed of 4 and.

The package 13 is, for example, LCP,
As shown in FIG. 2 and FIG. 3, obtained by molding using a resin material such as PBT, PES, PPS, etc., a block shape having a substantially rectangular shape in plan view and a certain thickness is formed. Mochi, the piezoelectric element 1 on the upper surface
Is formed with an elongated rectangular recess 15 capable of accommodating.

Element inner electrode coatings 16 and 17 are formed on the inner surfaces of both ends of the recess 15, respectively. The electrode coatings 16 and 17 are respectively the upper surface portions 16a and 17a and the side surface portions 16b and 16b of the package. It is extended to bottom face parts 16c and 17c via 17b.

At the center of the package 13 in the longitudinal direction, the electrode coating 1 for taking the ground electrode in relation to the lid 14 having a capacitor function, which will be described later, is formed.
8 passes through the package upper surface portion 18a and the side surface portion 18b,
It is formed to have a bottom surface 18c. However, it is not necessary to form the ground electrode coating film 18 in the upper recess 15 of the package 13.

The electrode coatings 16, 17 and 18 to be formed on the package 13 can be formed by plating, for example. Also, formation and printing by plating
The formation by firing can also be combined. In the case of forming by plating, a material that is easy to plate and a material that cannot be plated are combined, and the package 13 is exposed so that the material that is easy to plate is exposed to the outside in a pattern so as to form the electrode coating as described above. It is convenient to mold it and then subject it to plating.

The piezoelectric element 1 mounted in the recess 15 of the package 13 has a strip-shaped piezoelectric ceramic piece 5 on which the electrode coatings 6 and 7 are formed as thin films using silver or the like, respectively. Is used.

As shown in FIG. 3, the electrode coating 6 on the upper surface extends from the right end of the ceramic piece 5 to the left of the center, and the electrode coating 7 on the back surface side of the ceramic piece 5. It extends from the left end of the back surface to the right side of the central portion in the longitudinal direction. This point is similar to the piezoelectric element in the conventional piezoelectric oscillator shown in FIG. 8, but in the piezoelectric element 1 in the embodiment shown in FIG. 3, the electrode coating film 6 formed on the upper surface and the back surface of the ceramic piece 5 is used. , 7 are respectively formed so as to have extension portions 6a, 7a that wrap around from the end surface of the ceramic piece 5 to the other surface side. This allows
A part of the electrode coating 6 having a main part on the front side wraps around to the back side, and both electrode coatings 6 and 7 are formed on the bottom surface inside the recess only on the back side of the ceramic piece 5 to form the element electrode coating 16. , 17 can be connected. Such connection is performed using the conductive adhesive 12. In the case of the piezoelectric element 1 used in the present embodiment, the conductive adhesive is applied on the electrode film in the recess and the piezoelectric element 1 is applied thereon. By the mounting method, it is possible to establish conduction between each package side electrode coating and the electrode coating of the piezoelectric element. In other words, unlike the conventional example shown in FIG. 8, it is not necessary to use a large amount of conductive adhesive and apply dip coating so that a part of the conductive adhesive covers the upper surface of one end of the piezoelectric element. It is possible to prevent characteristic deterioration due to vibration damping due to the use of a large amount of conductive adhesive, and to save the conductive adhesive and to omit the coating process by dipping.

This means that the size of the concave portion 15 provided on the upper surface of the package 13 for accommodating the piezoelectric element 1 can be set to the minimum necessary size, which greatly reduces the size of the package 13. Contribute.

Of course, similar to the method according to the conventional example shown in FIG. 8, when the piezoelectric element having the same form as before is mounted in the recess of the package by the dip coating of the conductive adhesive 12, the dip coating is performed. There is no need to consider the size of the recess in consideration of the flow range of the conductive adhesive to be used, and the size of the recess can be set to the minimum necessary. The effect is great.

On the other hand, as shown in FIG. 1, FIG. 3 and FIG. 7, the lid 14 is in the form of a plate having a predetermined thickness and a planar shape corresponding to the planar shape of the package 13. This lid is basically obtained by forming predetermined electrode coatings 19, 20, 21 on a dielectric ceramic plate such as a barium titanate-based ceramic. As shown in FIG. 7, the lid 14 has a first electrode coating 19 and a second electrode coating 20 located in the vicinity of both ends thereof, and an intermediate portion between these first and second electrode coatings. The third electrode coatings 21 are formed so as to be isolated from each other.
Preferably, these first, second, and third electrode coatings 1
9, 20, and 21 are formed only on the back surface of the lid body 14.

As shown by the phantom line in FIG. 3, the lid 14 having the above-described structure has its back surface facing downward, and on the upper surface of the package 13 in which the piezoelectric element 1 is loaded in the upper surface recess 15 as described above. Mounted on. On the upper surface surrounding the recess 15 of the package 13, as described above, the element electrode coatings 16 and 17 located at both ends, and the ground electrode coating 18 located in the middle of these two element electrode coatings. Therefore, when the lid 14 is mounted on the package 13 as described above, the first and second electrode coatings 19 and 20 on the lid 14 side are replaced by the element electrode coatings 16 and 17 on the package 13 side. The third electrode coating 21 on the lid 14 side comes into contact with the ground electrode coating 18 on the package 13 side. After maintaining contact between such electrodes,
The lid 14 is airtightly attached to the upper surface of the package 13 using an adhesive or the like.

As a method of attaching the lid 14 to the upper surface of the package 13, in addition to the above, a conductive adhesive is used for the electrodes on the upper surface of the package 13 and the lower surface of the lid 14, and the electrodes other than the electrodes are insulated. Using body adhesive,
It is possible to adopt a method of mutually adhering at the same time, or a method of applying solder to the contact portions between the electrodes and simultaneously sealing the portions other than the electrode portions with an insulating adhesive by simultaneous heating.

Since the lid 14 is itself made of a dielectric material, it is provided between the first electrode coating 19 and the third electrode coating 21 and the third electrode coating 21 which are provided separately from each other. Capacitors 3 having a predetermined capacity are formed between the second electrode film 20 and the second electrode film 20. The capacities of the capacitors 3 and 3 can be appropriately adjusted with a relatively large degree of freedom by adjusting the size of each electrode coating and the interval between the electrode coatings. The electrode coatings 19, 20, and 21 may be formed on the lid 14 by a suitable means such as plating, printing, firing, or the like.

In this way, the piezoelectric oscillator of the present invention can form the piezoelectric oscillator indicated by reference numeral 4 in the oscillation circuit shown in FIG.

The piezoelectric oscillator 4 of the present invention has two electrode portions 16 and 1 to be electrically connected to both electrodes of the C-MOS inverter.
Since 7 and the ground electrode 18 are both exposed on the bottom surface of the package 13, on a suitable circuit board,
By using a solder or the like, the electronic component can be mounted by the same method as that for mounting an ordinary electronic component.

If the first, second and third electrode coatings 19, 20, 21 of the lid 14 are formed only on the back surface,
Lid 1 that should have a capacitor function in the assembled state
The back surface of No. 4 is not exposed to the outside, so that the capacity of the capacitor function of the lid 14 changes with time depending on the usage environment, and the characteristics of the piezoelectric oscillator 4 change with time due to this. Such problems will disappear and reliability will be significantly improved.

In this way, the piezoelectric oscillator 4 according to the present invention is
According to the above, it is possible to further reduce the size of the outer shape, and at the same time, the reliability is remarkably improved.

Of course, the scope of the present invention is not limited to the above embodiments. In the embodiment, the lid 14
Although the first, second, and third electrode coatings 19, 20, and 21 were formed only on the back surface of the lid, each electrode coating may be formed in a loop shape over the side surface or the upper surface of the lid body. Of course, this case is also included in the scope of the present invention.

As the member for forming the main body of the package 13, in addition to the resin as described above, any material such as ceramic having an insulating property may be used.

[Brief description of drawings]

FIG. 1 is an external perspective view of an example of a piezoelectric oscillator according to the present invention.

FIG. 2 is a plan view of a package of the piezoelectric oscillator shown in FIG.

FIG. 3 is a sectional view taken along line III-III in FIG.

FIG. 4 is a sectional view taken along line IV-IV in FIG.

5 is a cross-sectional view taken along the line VV of FIG.

FIG. 6 is a bottom view of the piezoelectric oscillator shown in FIG.

7 is a bottom view of the lid of the piezoelectric oscillator shown in FIG.

FIG. 8 is a partial cross-sectional view of a conventional example.

FIG. 9 is a plan view of a conventional example.

FIG. 10 is a circuit diagram showing an example of an oscillation circuit using the piezoelectric oscillator of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Piezoelectric element 4 Piezoelectric oscillator 13 Package 14 Lid body 15 Recess 16 Electrode coating for element 17 Electrode coating for element 18 Electrode coating for ground 19 First electrode coating 20 Second electrode coating 21 Third electrode coating

Claims (3)

[Claims] 1. A piezoelectric oscillator comprising a package for accommodating a piezoelectric element, wherein the package has a top surface, a bottom surface and a side surface, and a recess for accommodating the piezoelectric element is formed on the top surface. And is electrically connected to both ends of the piezoelectric element on the inner surface of the recess, and is provided with two element electrode coatings on the top surface, side surface or bottom surface, and two capacitors are provided on the top surface of the package. A piezoelectric oscillator, wherein a lid having a function is provided so as to close the recess. 2. A piezoelectric oscillator including a package for housing a piezoelectric element, wherein the package has a top surface, a bottom surface, and a side surface, and a recess for housing the piezoelectric element is formed on the top surface. And the two upper surface, side surface or bottom surface of the two element electrode coatings electrically connected to both ends of the piezoelectric element on the inner surface of the recess, and between the two element electrode coatings, the upper surface. A ground electrode film extending from the side surface to the bottom surface, and on the upper surface of the package, on the upper surface of the package, a first electrode film and a second electrode film in contact with the electrode film for each element, Further, a lid body having a third electrode coating film in contact with the ground electrode coating film formed on a dielectric material is provided so as to close the concave portion. To, the piezoelectric oscillator. 3. The piezoelectric oscillator according to claim 2, wherein the first electrode coating, the second electrode coating, and the third electrode coating are formed only on the back surface of the lid.