JP2010035078A - Piezoelectric oscillator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a piezoelectric oscillator which has good frequency drift characteristics. <P>SOLUTION: The piezoelectric oscillator comprises a container body provided with a first recess space formed on one principal surface of a substrate portion and a second recess space formed on the other principal surface of the substrate portion, a piezoelectric vibrating element mounted on a pair of two piezoelectric vibrating element mounting pads provided in the first recess space, an integrated circuit element mounted on integrated circuit element mounting pads provided in the second recess space, and a cover body for airtightly sealing the first recess space, wherein a pillow member is provided to the substrate portion opposed to a tip portion of the piezoelectric vibrating element mounted on the piezoelectric vibrating element mounting pads, and the pillow member and one of the integrated circuit element mounting pads are connected by a via conductor. <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. FIG. 6A is a perspective plan view showing one main surface of a substrate portion of a container body constituting a conventional piezoelectric oscillator, and FIG. 6B is a substrate of the container body constituting the conventional piezoelectric oscillator. FIG. 6C is a perspective plan view showing the other main surface of the substrate portion of the container body constituting the conventional piezoelectric oscillator.
As shown in FIGS. 5 to 6, a 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 and two frame parts 201b and 201c.
The container body 201 is provided with a frame portion 201b on one main surface of the substrate portion 201a to form a first recessed space 202, and a frame portion 201c is provided on the other main surface of the substrate portion 201a to form a second portion. A recessed space 204 is formed.
A pair of piezoelectric vibration element mounting pads 203 a and 203 b 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.
The substrate portion 201a has a laminated structure, and as shown in FIG. 6B, the first wiring pattern 212a, the second wiring pattern 212b, and the like are provided in the inner layer of the substrate portion 201a. Yes.
On the piezoelectric vibration element mounting pads 203a and 203b, 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 frame portion 201b of the container body 201 that surrounds the piezoelectric vibration element 207 is covered with and joined to a metal lid 208. Thereby, the first recess space 202 is hermetically sealed.
Further, the integrated circuit element 209 is electrically and mechanically bonded to the integrated circuit element mounting pad 205 via a conductive bonding material such as solder. This state is called loading.

  In addition, the integrated circuit element 209 compensates for a variation in the oscillation frequency of the oscillation circuit due to a temperature change by applying a control voltage according to the ambient temperature to the variable capacitance element, so that the temperature compensation is performed by the cubic function generation circuit and the storage element unit. A 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.

Further, as shown in FIGS. 6A to 6C, two pairs of piezoelectric vibration element measurement pads 210 a are formed on the other main surface of the substrate portion 201 a exposed in the second recess space 204. 210b.
The one piezoelectric vibration element mounting pad 203a is connected to one piezoelectric vibration element measurement pad 210a through a via conductor 211 and a first wiring pattern 212a provided in the inner layer of the substrate portion 201a of the container body 201. ing.
The other piezoelectric vibration element mounting pad 203b is connected to the other piezoelectric vibration element measurement pad 210b via the via conductor 211 and the second wiring pattern 212b provided in the inner layer of the substrate portion 201a of the container body 201. A connected structure is known (for example, see Patent Document 1).

Further, such a crystal resonator element 207 is formed by fixing a lead-out electrode extending on one side from an excitation electrode provided on each of the front and back main surfaces to the crystal resonator element mounting pad 203 with a conductive adhesive 204. It is fixed. At this time, an end side which is a free end opposite to the one side where the extraction electrode is provided is defined as a tip end portion 207a of the crystal resonator element 207.
When the tip 207a comes into contact with the bottom surface in the first recess space 202 of the container body 201, the frequency fluctuates. Therefore, in the conventional piezoelectric device, the quartz crystal in the bottom surface in the first recess space 202 of the container body 201 is used. There has been proposed a structure in which a pillow member 213 is formed on a surface of the vibration element 207 facing the tip 207a (see, for example, Patent Document 2).

Japanese Patent No. 3406845 Japanese Patent No. 396585

  However, in the conventional piezoelectric oscillator 200, when the piezoelectric vibration element 207 is mounted, the front end 207 a of the piezoelectric vibration element 207 is provided on the substrate portion 201 a exposed in the recessed space 204 of the container body 201. The heat generated in the integrated circuit element is transmitted to the piezoelectric vibration element 207 via the via conductor, and the heat transmitted to the piezoelectric vibration element is transmitted from the pillow portion 213 to the container body 201, so that it is built in the integrated circuit element 209. The temperature sensed by the temperature sensor being used may be different from the actual temperature around the piezoelectric vibration element 207. As a result, the conventional piezoelectric oscillator 200 is corrected by an erroneous temperature data signal (voltage value), and therefore, the oscillation frequency at the time when the voltage is applied to the piezoelectric oscillator and a certain time has elapsed since the voltage was applied. There has been a problem that the frequency drift characteristic indicating the frequency fluctuation difference from the oscillation frequency at the time becomes worse.

  This invention is made | formed in view of the said subject, and makes it a subject to provide the piezoelectric oscillator with a favorable frequency drift characteristic.

  The piezoelectric oscillator of the present invention includes a first recessed space formed on one main surface of the substrate portion by the substrate portion and the frame portion, and a second recess formed on the other main surface of the substrate portion by the substrate portion and the frame portion. Are mounted on a pair of piezoelectric vibration element mounting pads provided on one main surface of the substrate portion exposed in the first recess space, and provided with excitation electrodes. The piezoelectric resonator element, the integrated circuit element mounted on the integrated circuit element mounting pad provided on the other main surface of the substrate portion exposed in the second recessed space, and the first recessed space are hermetically sealed. A pillow member is provided on a substrate portion facing the tip of the piezoelectric vibration element mounted on the piezoelectric vibration element mounting pad, and one of the pillow member and the integrated circuit element mounting pad is They are connected by via conductors.

According to the piezoelectric oscillator of the present invention, a pillow member is provided on the surface of the one main surface of the substrate portion exposed in the first recess space, which faces the tip portion of the piezoelectric vibration element, and the pillow member and the Since one of the integrated circuit element mounting pads is connected by the via conductor, even if the tip of the piezoelectric vibration element contacts the pillow member, the pillow member is connected to the integrated circuit element mounting pad via the via conductor. Since heat is conducted, heat conduction between the first recessed space and the second recessed space of the container body is improved.
Therefore, 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. Therefore, since the correction is made with the correct temperature data signal (voltage value), the frequency drift characteristic of the piezoelectric oscillator can be improved.

  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 a first embodiment of the present invention. FIG. 2 is a cross-sectional view taken along the line AA of FIG. FIG. 3A is a perspective plan view showing one main surface of the substrate portion of the container body constituting the piezoelectric oscillator according to the first embodiment of the present invention, and FIG. FIG. 3 is a perspective plan view showing an inner layer surface of a substrate portion of a container body constituting the piezoelectric oscillator according to the first embodiment, and FIG. 3C constitutes the piezoelectric oscillator according to the first embodiment of the present invention. It is a perspective top view which shows the other main surface of the board | substrate part of a container body. In addition, the illustrated dimensions are partially exaggerated.

  As shown in FIGS. 1 and 2, the piezoelectric oscillator 100 according to the first embodiment of the present invention is mainly configured by 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 FIGS. 1-3, the container body 10 is mainly comprised by the board | substrate part 10a and the frame parts 10b and 10c.
The container body 10 is provided with a frame portion 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 substrate portion 10a has a structure in which ceramic materials are stacked.
The frame portion 10b is, for example, a seal ring. In this case, the frame portion 10b is made of a metal such as 42 alloy or Kovar, and has a frame shape with a punched center.
The frame portion 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, a pillow member P is provided on one main surface of the substrate portion 10a exposed in the first recessed 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.
As shown in FIG. 3B, wiring patterns 17a, 17b and the like are provided in the inner layer of the substrate portion 10a.
As shown in FIG. 3C, a plurality of integrated circuit element mounting pads 15 and two pairs of piezoelectric vibration element measurement pads are provided on the other main surface of the substrate portion 10a exposed in the second recess space 14. 16a and 16b are formed.

As shown in FIG. 3A to FIG. 3C, one piezoelectric vibration element mounting pad 13 a is a via pattern 18 a formed on the inner layer of the substrate portion 10 a of the container body 10 by one via conductor 18 a. And connected. The wiring pattern 17a is connected to the other piezoelectric vibration element measurement pad 16b by a via conductor 18c. Thus, the one piezoelectric vibration element mounting pad 13a is connected to the other piezoelectric vibration element measurement pad 16b.
The other piezoelectric vibration element mounting pad 13b is connected to the wiring pattern 17b provided in the inner layer of the substrate portion 10a of the container body 10 by one via conductor 18a.
The wiring pattern 17b is connected to one piezoelectric vibration element measurement pad 16a by a via conductor 18c. As a result, the other piezoelectric vibration element mounting pad 13b is connected to the one piezoelectric vibration element measurement pad 16a.
External connection electrode terminals 19 are provided at the four corners of the main surface of the frame portion 10c which is parallel to the main surface of the container body 10 on which the integrated circuit element mounting pads 15 are 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.

As shown in FIG. 3A to FIG. 3C, the pillow member P is a surface on which the front end portion 23 of the piezoelectric vibrating element 20 of the substrate portion 10 a exposed to the first recessed space 11 of the container body 10 is opposed. Is provided. That is, the pillow member P is provided on the opposite side in the long side direction with respect to the position where the piezoelectric vibration element mounting pads 13a and 13b are provided.
The pillow member P is connected to the wiring pattern 17c provided in the inner layer of the substrate portion 10a of the container body 10 by the via conductor 18b.
The wiring pattern 17c is connected to one of the integrated circuit element mounting pads 15 by a via conductor 18d. As a result, the pillow member P is connected to the integrated circuit element mounting pad 15.
At this time, the integrated circuit element mounting pad 15 connected to the pillow member P is connected to the external connection electrode terminal 19 serving as a ground terminal.
Moreover, the pillow member P is formed by metallization, such as tungsten, for example.

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.

As shown in FIG. 3B, the wiring pattern 17a is drawn near the center of the container body 10 when viewed from the opening side of the first recessed space 11 of the container body 10, and the other via the via conductor 18c. The piezoelectric vibration element measurement pad 16b is connected.
Further, as shown in FIG. 3B, the wiring pattern 17b is drawn toward the vicinity of the center of the container body 10 when viewed from the opening side of the first recessed space 11 of the container body 10, and the via conductor 18c is connected to the via conductor 18c. And is connected to one piezoelectric vibration element measurement pad 16a.

  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 19 for external connection, 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.

According to the piezoelectric oscillator according to the first embodiment of the present invention, the front end portion 23 of the piezoelectric vibration element 20 on one main surface of the substrate portion 10a exposed in the first recessed space 11 of the container body 10 is opposed. A pillow member P is provided on the surface, and one of the pillow member P and the integrated circuit element mounting pad 15 is connected by via conductors 18b and 18d.
Thereby, even if the tip 23 of the piezoelectric vibration element 20 contacts the pillow member P, heat is conducted from the pillow member P to the integrated circuit element mounting pad 15 via the via conductors 18b and 18d. The heat conduction between the first concave space 10 and the second concave space 10 is improved.
The temperature sensed by the temperature sensor built in the integrated circuit element 50 is the same as the temperature around the piezoelectric vibration element 20. As a result, the frequency drift characteristic of the piezoelectric oscillator 100 can be improved because it is corrected by a correct temperature data signal (voltage value).
The good frequency drift characteristic means that there is little difference in fluctuation between the oscillation frequency when a voltage is applied to the piezoelectric oscillator 100 and the oscillation frequency when a certain time has elapsed after the voltage is applied. For example, when the elapsed time is on the horizontal axis and the frequency fluctuation difference is on the vertical axis, the closer the frequency fluctuation difference is to 0, the better the frequency drift characteristic is.

(Example)
Examples of the piezoelectric oscillator according to the embodiment of the present invention and the conventional piezoelectric oscillator will be described below.
FIG. 4 is a diagram showing frequency drift characteristics of the piezoelectric oscillator according to the embodiment of the present invention and the 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 tip portion 23 of the piezoelectric vibration element 20 which is one main surface of the substrate portion 10a exposed in the first recess space 11 is used. A pillow member P is provided on the opposing surface, one of the pillow member P and the integrated circuit element mounting pad 15 is connected by via conductors 18b and 18d, and the tip 23 of the piezoelectric vibration element 20 is connected to the pillow member P. To come into contact.

  Further, as a comparative example, according to the structure of the conventional piezoelectric oscillator 200 shown in FIGS. 6 and 7, the pillow is formed on the surface of the exposed piezoelectric substrate 20 on the opposite side of the piezoelectric vibration element 20 in the recessed space of the container body. A member 213 is provided, and the pillow member 213 is not connected anywhere, and the tip portion 207 a of the piezoelectric vibration element 207 is in contact with the pillow member 213.

The reference oscillation frequency f ₀ of the piezoelectric oscillator 100 of the present invention and the conventional piezoelectric oscillator 200 manufactured this time was set to 27.456 MHz.

First, the oscillation frequencies of the piezoelectric oscillator 100 of the present invention and the conventional piezoelectric oscillator 200 were measured.
The measurement method is to first measure 0.15 seconds after applying power to the piezoelectric oscillator 100 of the present invention and the conventional piezoelectric oscillator 200, and measure the oscillation frequency fs in 0.1 second steps after 0.15 seconds. To do. At this time, the oscillation frequency measured after 0.15 seconds was substituted with f ₁ , and the oscillation frequency after 0.15 seconds after was substituted with fs into the calculation formula (1) to calculate the frequency variation difference (df / f).
df / f = (fs−f ₁ ) / f ₁ (1)
The frequency fluctuation difference (df / f) at this time was calculated as a frequency drift value.

As a result, as shown in FIG. 4, in the piezoelectric oscillator 100 of the present invention, the maximum value of the calculated frequency drift value was 14.87 ppb. Moreover, as shown in FIG. 4, in the conventional piezoelectric oscillator 200, the maximum value of the calculated frequency drift value was 21.18 ppb.
Accordingly, it can be seen that the piezoelectric oscillator 100 of the present invention has better frequency drift characteristics because the frequency fluctuation difference is closer to zero. That is, it can be seen that the frequency drift characteristic is improved by connecting one of the pillow member P and the integrated circuit element mounting pad 15 of the piezoelectric oscillator 100 of the present invention by the via conductors 18b and 18d.

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. (A) is a see-through plan view showing one main surface of the substrate portion of the container body constituting the piezoelectric oscillator according to the embodiment of the present invention, and (b) shows the piezoelectric oscillator according to the embodiment of the present invention. It is a perspective top view which shows the inner layer surface of the board | substrate part of the container body to comprise, (c) is a perspective top view which shows the other main surface of the board | substrate part of the container body which comprises the piezoelectric oscillator which concerns on embodiment of this invention. It is. It is a figure which shows the frequency drift characteristic of the piezoelectric oscillator which concerns on embodiment of this invention, and the conventional piezoelectric oscillator. It is sectional drawing which shows the conventional piezoelectric oscillator. (A) is a see-through | perspective top view which shows one main surface of the board | substrate part of the container body which comprises the conventional piezoelectric oscillator, (b) is the inner-layer surface of the board | substrate part of the container body which comprises the conventional piezoelectric oscillator. FIG. 7C is a perspective plan view showing the other main surface of the substrate portion of the container body constituting the conventional piezoelectric oscillator.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Container body 10a ... 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 16a, 16b ... Piezoelectric vibration element measurement pad 17a, 17b ... Wiring pattern 18a, 18b, 18c, 18d ..Via conductor 19 ... External connection electrode terminal P ... Pillow member 20 ... Piezoelectric vibration element 21 ... Quartz element plate 22 ... Excitation electrode 23 ... Tip 30 ... Lid 40 ... Conductive adhesive 50 ... Integrated circuit element 100 ... Piezoelectric oscillator

Claims (1)

A first recessed space formed on one main surface of the substrate portion by the substrate portion and the frame portion, and a second recessed space formed on the other main surface of the substrate portion by the substrate portion and the frame portion. A provided container body;
A piezoelectric vibration element mounted on two pairs of piezoelectric vibration element mounting pads provided on one main surface of the substrate portion exposed in the first recess space and provided with an excitation electrode;
An integrated circuit element mounted on an integrated circuit element mounting pad provided on the other main surface of the substrate portion exposed in the second recess space;
A lid for hermetically sealing the first recess space;
A pillow member is provided on the substrate portion facing the tip portion of the piezoelectric vibration element mounted on the piezoelectric vibration element mounting pad,
One of the pillow member and the integrated circuit element mounting pad is connected by a via conductor.

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