JP2010011267A - Piezoelectric oscillator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a piezoelectric oscillator which has good hysteresis characteristics and does not vary in oscillation frequency. <P>SOLUTION: The piezoelectric oscillator includes: a container body comprising a substrate portion, a seal ring provided on one principal plane of the substrate portion, and a frame portion provided on the other principal plane of the substrate portion: a piezoelectric vibration element mounted on a piezoelectric vibration element mounting pad provided on the principal plane of the substrate portion exposed in a first recessed portion space formed of the substrate portion and seal ring; an integrated circuit element mounted on an integrated circuit element mounting pad provided on the principal plane of the substrate portion exposed in a second recessed portion space formed of the substrate portion and frame portion; and a lid body airtightly sealing the first recessed portion space, the seal ring having a thickness of 0.125T to 0.21T, where T represents the thickness of the container body. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a piezoelectric oscillator used in an electronic device or the like.

FIG. 5 is a cross-sectional view showing a conventional piezoelectric oscillator.
As shown in FIG. 5, the conventional piezoelectric oscillator 200 mainly includes a container body 201, a piezoelectric vibration element 207, an integrated circuit element 209, and a lid body 208 as an example.
The container body 201 includes a substrate part 201a, a seal ring 201b, and a frame part 201c.
In the container body 201, the first ring space 202 is formed by providing the seal ring 201b on one main surface of the substrate portion 201a, and the frame portion 201c is provided on the other main surface of the substrate portion 201a. Thus, the second recessed space 204 is formed.
A pair of piezoelectric vibration element mounting pads 203 are provided on one main surface of the substrate portion 201 a exposed in the first recess space 202.
An integrated circuit element mounting pad 205 is provided on the other main surface of the substrate portion 201 a exposed in the second recess space 204.
On the piezoelectric vibration element mounting pad 203, a piezoelectric vibration element 207 having a pair of excitation electrodes electrically connected via a conductive adhesive 206 on the front and back main surfaces is mounted. The top surface of the seal ring 201b of the container body 201 surrounding the piezoelectric vibration element 207 is covered with a metal lid 208 and joined. Thereby, the first recess space 202 is hermetically sealed.
On the integrated circuit element mounting pad 205, an integrated circuit element 209 connected via a conductive bonding material such as solder is mounted.
The integrated circuit element 209 applies a control voltage in accordance with the ambient temperature to the variable capacitance element to compensate for fluctuations in the oscillation frequency of the oscillation circuit due to temperature changes, so that the temperature compensation circuit unit includes a cubic function generation circuit and a storage element unit. And a temperature sensor is connected to the cubic function generating circuit. This temperature sensor is configured to output a temperature data signal (voltage value) generated based on the detected temperature and a voltage value applied to the temperature sensor to a cubic function generation circuit. Such a piezoelectric oscillator 200 is known (see, for example, Patent Document 1).

Japanese Patent No. 3406845

However, in the conventional piezoelectric oscillator 200, even when heat is applied, heat is radiated from the seal ring, and the heat conduction of the container body 201 may be deteriorated.
Further, since the capacity of the first recess space 202 of the container body 201 is large, the temperature sensed by the temperature sensor built in the integrated circuit element 209 and the temperature around the actual piezoelectric vibration element 207 may be different. is there. For these reasons, the conventional piezoelectric oscillator 200 has a problem that the hysteresis characteristic is deteriorated.
In addition, a space is required such that the piezoelectric vibration element 207 does not come into contact with the main surface of the substrate portion 201 a and the lid 208 exposed in the first recess space 202 of the container body 201. However, when the thickness of the seal ring 201b of the container body 201 is reduced so as to reduce the first recessed space 202, the piezoelectric vibration element 207 is exposed in the first recessed space 202 of the container body 201. There is also a problem that the oscillation frequency of the piezoelectric oscillator 200 fluctuates due to contact with the main surface of the substrate portion 201a and the lid 208.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a piezoelectric oscillator that has good hysteresis characteristics and does not vary in oscillation frequency.

  A piezoelectric oscillator according to the present invention includes a container body including a substrate portion, a seal ring provided on one main surface of the substrate portion, and a frame portion provided on the other main surface of the substrate portion, and the substrate portion and the seal ring. And a piezoelectric vibration element mounted on a piezoelectric vibration element mounting pad provided on the main surface of the substrate portion exposed in the first recess space formed by the second recess portion, and a second portion formed by the substrate portion and the frame portion. An integrated circuit element mounted on an integrated circuit element mounting pad provided on the main surface of the substrate portion exposed in the recessed space of the substrate, and a lid for hermetically sealing the first recessed space, When the thickness is T, the thickness of the seal ring is 0.125T to 0.21T.

According to the piezoelectric oscillator of the present invention, when the thickness of the container body is T, the thickness of the seal ring is 0.125T to 0.21T. And the heat conduction of the container body is improved. Further, since the capacity of the first recess space of the container body is also smaller than before, the temperature sensed by the temperature sensor built in the integrated circuit element and the temperature around the actual piezoelectric vibration element approach the same value. become. Therefore, the hysteresis characteristic of the piezoelectric oscillator can be improved.
In addition, since the thickness of the seal ring is 0.125T to 0.21T, the piezoelectric vibration element does not come into contact with the main surface of the substrate portion or the lid exposed in the first recessed space of the container body. It is possible to prevent the oscillation frequency of the piezoelectric oscillator from fluctuating.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings. A case where quartz is used for the piezoelectric vibration element will be described.
FIG. 1 is an exploded perspective view showing a piezoelectric oscillator according to an embodiment of the present invention. FIG. 2 is a cross-sectional view taken along the line AA of FIG. In addition, the illustrated dimensions are partially exaggerated.

  As shown in FIGS. 1 and 2, the piezoelectric oscillator 100 according to the embodiment of the present invention mainly includes a container body 10, a piezoelectric vibration element 20, a lid body 30, and an integrated circuit element 50. In the piezoelectric oscillator 100, the piezoelectric vibration element 20 is mounted in the first recess space 11 formed in the container body 10, and the integrated circuit element 50 is mounted in the second recess space 14. . The first recessed space 11 is hermetically sealed by the lid 30.

As shown in FIGS. 1 and 2, the piezoelectric vibration element 20 is formed by adhering and forming an excitation electrode 22 on a crystal base plate 21, and an alternating voltage from the outside passes through the excitation electrode 22 to form a crystal base plate. When applied to 21, excitation occurs in a predetermined vibration mode and frequency.
The quartz base plate 21 is a substantially flat plate shape that is cut from an artificial crystalline lens at a predetermined cut angle and is subjected to outer shape processing, and has a planar shape of, for example, a quadrangle.
The excitation electrode 22 is formed by depositing and forming metal in a predetermined pattern on both the front and back main surfaces of the quartz base plate 21.
Such a piezoelectric vibration element 20 includes a lead electrode extending from the excitation electrode 22 attached to both main surfaces of the piezoelectric vibration element 20 and a piezoelectric vibration element mounting pad 13 formed on the inner bottom surface of the first recess space 11. Are electrically and mechanically connected through the conductive adhesive 40 to be mounted in the first recessed space 11. At this time, an end side which is a free end opposite to the side on which the extraction electrode is provided is defined as a tip portion 23 of the piezoelectric vibration element 20.

As shown in FIGS. 1 and 2, the integrated circuit element 50 is provided with an oscillation circuit or the like for generating an oscillation output from the piezoelectric vibration element 20 on the circuit formation surface, and an output signal generated by the oscillation circuit. Is output to the outside of the piezoelectric oscillator 100 through the external connection electrode terminal 19, and is used as a reference signal such as a clock signal, for example.
In addition, the integrated circuit element 50 is applied with a control voltage according to the ambient temperature to the variable capacitance element to compensate for fluctuations in the oscillation frequency of the oscillation circuit due to temperature changes, by means of a cubic function generating circuit and a storage element unit. A compensation circuit unit is provided, and a temperature sensor is connected to the cubic function generation circuit.
This temperature sensor is configured to output a temperature data signal (voltage value) generated based on the detected temperature and a voltage value applied to the temperature sensor to a cubic function generation circuit.
The integrated circuit element 50 is mounted on the integrated circuit element mounting pad 15 formed on the substrate portion 10a exposed in the second recessed space 14 of the container body 10 via a conductive bonding material such as solder.

As shown in FIG.1 and FIG.2, the container body 10 is mainly comprised by the board | substrate part 10a, the seal ring 10b, and the frame part 10c.
The container body 10 is provided with a seal ring 10b on one main surface of the substrate portion 10a to form a first recessed space 11. In addition, a frame portion 10 c is provided on the other main surface of the container body 10 to form a second recessed space 14.
In addition, the board | substrate part 10a and the frame part 10c which comprise this container body 10 are formed by laminating | stacking multiple ceramic materials, such as an alumina ceramic and a glass-ceramic, for example.
The seal ring 10b is made of a metal such as 42 alloy or Kovar, and has a frame shape with a punched center.
The seal ring 10b is connected to the sealing conductor film 12 provided so as to surround the outer periphery of one main surface of the substrate portion 10a by brazing or the like.
Two pairs of piezoelectric vibration element mounting pads 13 a and 13 b are provided on one main surface of the substrate portion 10 a exposed in the first recess space 11.
Moreover, as shown in FIG.1 and FIG.2, the container body 10 has the 2nd recessed space 14 formed of the other main surface of the board | substrate part 10a, and the frame part 10c.
An integrated circuit element mounting pad 15 is provided on the other main surface of the substrate portion 10 a exposed in the second recess space 14.

External connection electrode terminals 19 are provided at the four corners of the main surface opposite to the surface on which the piezoelectric vibration element mounting pad 13 of the frame 10c of the container body 10 is provided.
The integrated circuit element mounting pad 15 and the external connection electrode terminal 19 include a wiring pattern (not shown) having a portion formed in the substrate portion 10a in the second recessed space 14 of the container body 10 and the frame portion 10c. They are connected by via conductors (not shown) formed inside.

The two pairs of piezoelectric vibration element measurement pads 16a and 16b are provided on the exposed substrate portion 10a in the second recessed space 14 of the container body 10, and are provided substantially at the center of the substrate portion 10a.
The piezoelectric vibration element measuring pads 16a and 16b are used for measuring characteristics such as an oscillation frequency and crystal impedance of the piezoelectric vibration element 20 mounted in the first recessed space 11 of the container body 10.

  The lid 30 is made of, for example, an Fe—Ni alloy (42 alloy), an Fe—Ni—Co alloy (Kovar), or the like. Such a lid 30 hermetically seals the first recessed space 11 with nitrogen gas or vacuum. Specifically, the lid 30 is placed on the seal ring 10b of the container body 10 in a predetermined atmosphere so that the metal on the surface of the seal ring 10b and a part of the metal of the lid 30 are welded. The seam welding is performed by applying a predetermined current to join the seal ring 10b.

The conductive adhesive 40 contains conductive powder as a conductive filler in a binder such as a silicone resin. As the conductive powder, aluminum (Al), molybdenum (Mo), tungsten (W ), Platinum (Pt), palladium (Pd), silver (Ag), titanium (Ti), nickel (Ni), nickel iron (NiFe), or a combination thereof is used. .

  When the container body 10 is made of alumina ceramic, a sealing conductor film 12, a piezoelectric vibration element is formed on the surface of a ceramic green sheet obtained by adding and mixing a suitable organic solvent to a predetermined ceramic material powder. Conventionally known screens include a conductive paste that becomes the mounting pad 13, the electrode terminal for external connection 14 and the like, and a conductive paste that becomes a via conductor in a through hole that has been punched in advance in the ceramic green sheet. It is manufactured by applying by printing, laminating a plurality of these and press-molding them, followed by firing at a high temperature.

As shown in FIG. 2, the thickness T of the container body 10 is the length in the height direction of the substrate portion 10 a, the seal ring 10 b, and the frame portion 10 c constituting the container body 10.
Further, when the thickness of the container body 10 is T, the thickness S of the seal ring 10b of the container body 10 is 0.125T to 0.21T.
If the thickness S of the seal ring 10b is larger than 0.21T, the heat conduction of the container body 10 is deteriorated due to heat dissipation from the seal ring, and the capacity of the first recessed space 11 of the container body 10 is reduced. Therefore, the temperature sensed by the temperature sensor built in the integrated circuit element 50 is different from the temperature around the piezoelectric vibration element 20. As a result, the hysteresis characteristics of the piezoelectric oscillator are deteriorated.
When the thickness S of the seal ring 10b is less than 0.125T, the interval in the first recess space 11 of the container body 10 is narrowed, and the tip portion 23 of the piezoelectric vibration element 20 is the first portion of the container body 10. The oscillation frequency of the piezoelectric oscillator 100 fluctuates due to contact with the exposed main surface or the lid 30 in the recessed space 11.
That is, when the thickness S of the seal ring 10b of the container body 10 is set to 0.125T to 0.21T, the distal end portion 23 of the piezoelectric vibration element 20 is exposed in the first recessed space 11 of the container body 10. Since the capacity of the first recess space of the container body 10 can be reduced to the extent that it does not contact the main surface or the lid body 30 and the heat conduction of the container body can be improved, the hysteresis characteristic is good and the oscillation frequency of the piezoelectric oscillator 100 is improved. It is possible to prevent fluctuations in the range.

(Example)
Examples of the piezoelectric oscillator of the present invention and the conventional piezoelectric oscillator are shown below.
FIG. 3 is a probability distribution diagram showing hysteresis values of the piezoelectric oscillator of the present invention and the conventional piezoelectric oscillator. FIG. 4 is a diagram showing hysteresis characteristics of the piezoelectric oscillator of the present invention. FIG. 6 is a diagram showing hysteresis characteristics of a conventional piezoelectric oscillator.
As an example, according to the structure of the piezoelectric oscillator 100 of the present invention shown in FIGS. 1 and 2, the thickness T of the container body 10 of the piezoelectric oscillator 100 was 0.7 mm, and the thickness S of the seal ring 10b was 0.125 mm. That is, when the thickness of the container 10 of the piezoelectric oscillator 100 is T, the thickness S of the seal ring 10b is 0.178T.

  As a comparative example, according to the structure of the conventional piezoelectric oscillator 200 shown in FIG. 5, the thickness T of the container body 201 of the piezoelectric oscillator 200 was 0.7 mm, and the thickness S of the seal ring 201b was 0.155 mm. That is, when the thickness of the container body 201 is T, the thickness S of the seal ring 201b is 0.221T.

  The reference oscillation frequency of the piezoelectric oscillator 100 of the present invention and the conventional piezoelectric oscillator 200 manufactured this time was 19.2 MHz.

First, the piezoelectric oscillator 100 of the present invention and the conventional piezoelectric oscillator 200 were placed on a ceramic heater and measured with an infrared thermo heater.
As a result, the conventional piezoelectric oscillator 200 showed about 109 ° C., and the piezoelectric oscillator 100 of the present invention showed about 112 ° C. Therefore, it was confirmed that the piezoelectric oscillator 100 of the present invention has good heat conduction by about 3 ° C.

Next, the oscillation frequencies of the piezoelectric oscillator 100 of the present invention and the conventional piezoelectric oscillator 200 were measured.
In the measurement method, first, the oscillation frequency fs is measured in steps of 1 ° C. in the interval from −25 ° C. to 85 ° C. of the piezoelectric oscillator 100 of the present invention and the conventional piezoelectric oscillator 200, and then from 85 ° C. to −25 ° C. In the interval, the oscillation frequency fs is measured in 1 ° C. steps. The measured oscillation frequency fs and the reference oscillation frequency f ₀ of the piezoelectric oscillator were substituted into the calculation formula (1), and the frequency deviation (df / f) was calculated.
df / f = (fs−f ₀ ) / f ₀ (1)
Thereafter, a frequency deviation of 25 ° C. when the temperature is raised from −25 ° C. and a frequency deviation (df / f) of 25 ° C. when the temperature is lowered from 85 ° C., which is a high temperature, are calculated, and the difference between the frequency deviations is calculated. It was calculated as a hysteresis value.
Next, 30 piezoelectric oscillators 100 of the present invention and 30 conventional piezoelectric oscillators 200 were produced, and a hysteresis value of 25 ° C. was calculated.

As a result, as shown in FIG. 4, in the piezoelectric oscillator 100 of the present invention, the hysteresis value was −0.1 ppm.
Moreover, as shown in FIG. 6, in the conventional piezoelectric oscillator 200, the hysteresis value was -0.8 ppm.
Further, as shown in FIG. 3, it can be seen that the hysteresis value of the piezoelectric oscillator 100 of the present invention is improved even when the probability distribution diagram of the hysteresis value of the piezoelectric oscillator 100 of the present invention and the conventional piezoelectric oscillator 200 is seen.
That is, it can be seen that when the thickness S of the seal ring 10b of the container body 10 of the piezoelectric oscillator 100 of the present invention is smaller than 0.21T, the hysteresis characteristics are improved. Therefore, in the piezoelectric oscillator 100 of the present invention, when the thickness S of the seal ring 10b of the container body 10 is 0.125T to 0.21T, the hysteresis characteristic is good and the fluctuation of the oscillation frequency can be prevented. Become.

In addition, this invention is not limited to the said embodiment, A various change, improvement, etc. are possible in the range which does not deviate from the summary of this invention.
For example, in the above-described embodiment, the case where quartz is used as the piezoelectric material constituting the piezoelectric vibration element 20 has been described. However, as other piezoelectric materials, lithium niobate, lithium tantalate, or piezoelectric ceramics is used as the piezoelectric material. The piezoelectric vibration element used may be used.

1 is an exploded perspective view showing a piezoelectric oscillator according to an embodiment of the present invention. It is AA sectional drawing of FIG. It is a probability distribution diagram which shows the hysteresis value of the piezoelectric oscillator which concerns on embodiment of this invention, and the conventional piezoelectric oscillator. It is a figure which shows the hysteresis characteristic of the piezoelectric oscillator which concerns on embodiment of this invention. It is sectional drawing of the conventional piezoelectric oscillator. It is a figure which shows the hysteresis characteristic of the conventional piezoelectric oscillator.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Container body 10a, ... Board | substrate part 10b ... Seal ring 10c ... Frame part 11 ... 1st recessed space 12 ... Conductive film 13a for sealing, 13b ... Piezoelectric Vibration element mounting pad 14... Second recess space 15. Integrated circuit element mounting pad 16 a, 16 b. Piezoelectric vibration element measuring pad 19. External connection electrode terminal 20. DESCRIPTION OF SYMBOLS 21 ... Crystal base plate 22 ... Excitation electrode 30 ... Cover body 31 ... Sealing member 40 ... Conductive adhesive 50 ... Integrated circuit element 100 ... Piezoelectric oscillator

Claims (1)

A container body comprising a substrate portion, a seal ring provided on one main surface of the substrate portion, and a frame portion provided on the other main surface of the substrate portion;
A piezoelectric vibration element mounted on a piezoelectric vibration element mounting pad provided on a main surface of the substrate part exposed in a first recess space formed by the substrate part and the seal ring;
An integrated circuit element mounted on an integrated circuit element mounting pad provided on a main surface of the substrate part exposed in a second recess space formed by the substrate part and the frame part;
A lid for hermetically sealing the first recess space;
The thickness of the said container body is set to T, The thickness of the said seal ring is 0.125T-0.21T, The piezoelectric oscillator characterized by the above-mentioned.

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