JP2002261569A - Piezoelectric device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a piezoelectric device having proper bonding strength in which CI of a piezoelectric oscillator can be stabilized. SOLUTION: The piezoelectric device comprises a container, having a rectangular cavity, a pair of electrode pads formed on the bottom face of the cavity, and a piezoelectric oscillator having rectangular excitation electrodes formed on the opposite major surfaces of a rectangular piezoelectric substrate and a pair of lead electrodes connected with the parts extended from one short side of the excitation electrodes to the lower surface on one short side of the piezoelectric substrate, wherein the lead electrode and the electrode pad are bonded electrically and mechanically via a conductive adhesive member. The conductive adhesive, member being bonded to the piezoelectric oscillator, is formed such that the outer circumference of the bonding region on the excitation electrode side is substantially parallel with one short side of the excitation electrode.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a piezoelectric device equipped with a piezoelectric vibrator. Note that the piezoelectric vibrator includes a vibrator using a quartz plate, a piezoelectric ceramic substrate, and a single crystal piezoelectric substrate, and a piezoelectric device includes an oscillator having only a piezoelectric vibrating element alone, and a piezoelectric vibrator together with the vibrator. It refers to an oscillator equipped with a predetermined circuit such as an IC chip, a capacitor, and a resistor.

[0002]

2. Description of the Related Art As shown in FIGS. 6 and 7, a conventional piezoelectric device, for example, a crystal oscillator 51, has a piezoelectric vibrating element 53.
Is disposed in the ceramic package 52 having the fixed step portion 522 on which the electrode pad 522a is formed.

[0006] A crystal oscillator 51 shown in FIGS. 6 to 8 comprises a ceramic package 52, a crystal oscillator 53, and a conductive adhesive member 54.

As shown in FIG. 8, a ceramic package 52 is formed by laminating ceramic insulating plates such as alumina.
A cavity 520 for accommodating the quartz oscillator 53 is formed inside. Also, the external terminal electrodes 526 of the ceramic package 52 are formed, and the ceramic package 5
Step portions 522 are formed in the inside of the device 2 at both ends in the longitudinal direction by an insulating substrate. The step portion has a substantially rectangular shape, and is formed as a pair separated in the width direction.
And bumps 515 are formed. One side of this step is a fixing step 523a. The other step part is a holding step part 523b for holding the tip part of the crystal unit 53.
It is.

[0005] Further, a quartz oscillator 53 is provided with excitation electrodes 531, opposing each other on both main surfaces of a rectangular piezoelectric substrate 530.
533 and the excitation electrodes 531 and 533 from the piezoelectric substrate 530
Extraction electrodes 532, 5 extending to both main surfaces on one short side of
34 are formed. Each of these electrode patterns is formed by means such as vapor deposition.

The crystal oscillator 51 using such a piezoelectric substrate 530 is manufactured through the following manufacturing steps.

First, the above-described crystal unit 53 and the ceramic package 52 having the above-described structure are prepared. next,
As shown in FIG. 8, a conductive paste is applied on electrode pads 522a formed on the steps 522, 522 of the ceramic package 52, and the lower surfaces of the extraction electrodes 532, 534 of the crystal unit 53 are formed thereon. Place so that it is positioned. Thereafter, the conductive paste is cured to form a conductive adhesive member 54, and the ceramic package 52 is formed.
And the piezoelectric vibrator 53 are fixed. Further, the quartz oscillator 5
In order to hermetically seal 3, a lid 56 was attached on the ceramic package 52.

[0008]

However, according to the above-mentioned conventional technique, in FIGS. 6 to 8, the bump 55 formed on the electrode pad 522a on the step 523a, 523a having a substantially rectangular shape is formed. A conductive paste is applied, and then the applied conductive paste is applied to the quartz oscillator 5.
When the third extraction electrodes 532 and 534 are placed so as to be positioned, as shown in FIG. 9, the conductive paste in contact with the extraction electrodes 532 and 534 on the lower surface of the crystal unit 53 is formed in a substantially circular shape. Excitation electrode 53 on the lower surface of element 53
It spread toward 1,533 (see w in FIG. 9).

Then, the conductive paste is hardened. From the outer periphery w on the excitation electrode 531, 533 side of the bonding area of the conductive adhesive member 54 bonded to the crystal unit 53, to one short side of the excitation electrodes 531, 533. Is, for example, L in FIG.
51, L52, and L53.

Since the region of the conductive adhesive member 54 is formed so as to approach the excitation electrodes 531 and 533 in this manner, from the position where the conductive adhesive member 54 holds the crystal unit 53 to the excitation electrodes 531 and 533. Of the piezoelectric substrate 530 (see FIG. 3), the leakage when the vibration is caused by the excitation electrodes 531 and 533 is not uniformly transmitted to the position fixed by the conductive adhesive member 54. (Dimensions of the same dimension) exist in one piezoelectric substrate 530. When the L dimension of the piezoelectric substrate 530 changes, there is a problem that it is difficult to stabilize electrical characteristics such as a CI (crystal impedance) value due to spurious components such as contour vibration.

On the other hand, it is conceivable to reduce the amount of the conductive paste to be supplied so as not to approach the excitation electrodes 531 and 533 from the lower surface side of the crystal unit 53. However, in this case, although the damping of the fundamental wave is suppressed and the CI value is improved, the bonding strength between the ceramic package 52 and the crystal unit 52 is reduced, and as a result, the mechanical strength is reduced and For example, when an external impact is applied due to, for example, the peeling is likely to occur at the joint, the oscillation frequency is greatly changed, and there is a problem that the oscillation failure occurs.

The present invention has been devised in view of the above-mentioned problems, and has as its object to provide a piezoelectric device which can stabilize the CI and the like of a piezoelectric vibrator and has a good bonding strength and a method of manufacturing the same. To provide.

[0013]

According to the present invention, there is provided a container having a rectangular cavity,
A pair of electrode pads formed on the bottom surface of the cavity,
A rectangular excitation electrode is provided on both main surfaces of the rectangular piezoelectric substrate, and a pair of drawers connected to an extension extending from one short side of the excitation electrode on the lower surface on one short side of the piezoelectric substrate. A piezoelectric vibrator having an electrode formed thereon, wherein the extraction electrode and the electrode pad are each electrically and mechanically bonded via a conductive adhesive member, wherein the piezoelectric vibrator is A piezoelectric device is provided in which the conductive adhesive member to be joined is formed such that the outer periphery of the joining region on the excitation electrode side and one short side of the excitation electrode are substantially parallel.

According to the present invention, the conductive adhesive member to be joined to the piezoelectric vibrator is formed such that the outer periphery of the joining area on the excitation electrode side and one short side of the excitation electrode are substantially parallel. Therefore, the distance between the position fixed by the conductive adhesive member and the excitation electrode becomes constant, and the extra distance caused by the distance from the position where the quartz oscillator is held by the conductive adhesive member to the excitation electrode is partially different. It is possible to prevent the CI value of the crystal oscillator 1 from becoming worse without generating spurious components.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a piezoelectric device according to the present invention will be described in detail with reference to the drawings. In the description, a piezoelectric device using a quartz oscillator as the piezoelectric oscillator, for example, a quartz oscillator will be described.

FIG. 1 is a top view of a quartz oscillator, which is a piezoelectric device according to the present invention, in a state where a lid is omitted.
2 is a top view of the ceramic package used for the piezoelectric device. FIG. 3 is a sectional view of the crystal oscillator.

The crystal oscillator 1 of the present invention mainly comprises a crystal oscillator 3, a ceramic package 2 for accommodating the crystal oscillator 3, and a lid 6.

The crystal resonator 3 includes, for example, a rectangular crystal substrate 30 cut (AT cut) in accordance with a predetermined crystal azimuth angle, and excitation electrodes 31 and 33 formed on both main surfaces of the crystal substrate 30. , And extraction electrodes 32 and 34 extending from the pair of excitation electrodes 31 and 33 in the short side direction (left side in the figure) of the quartz substrate 30, respectively.

The excitation electrodes 31 and 33 are made of a rectangular quartz substrate 3.
0 is formed in a rectangular shape similar to that of the quartz substrate 30.
The short sides of the excitation electrodes 31 and 33 are formed to face the short sides of the electrodes.

For example, the extraction electrode 32 extending from the excitation electrode 31 on the upper surface side is extended by an extension portion 31 a extending from one short side of the excitation electrode 31 and formed to one short side of the quartz substrate 30. The lower surface of the quartz substrate 30 extends through one end of one longer side (the lower end in the drawing). Conversely, the extraction electrode 34 extending from the lower surface of the excitation electrode 33 is extended by the extension 33 a extending from one short side of the excitation electrode 33 to form up to one short side of the crystal substrate 30, One short side of the substrate 30 extends to the other long side (upper end face in the drawing).

The extraction electrodes 32 and 34 are not formed on one short side end face of the quartz substrate 30, but are formed on the long side end face in contact with the one short side. The extraction electrodes 32 and 34 are formed at positions opposing each other on both main surfaces of the quartz substrate 30, and have a shape, when arranged at a predetermined position, of a second bottom surface 22 a, 22 a described later.
It is a shape that can conduct electricity to.

The excitation electrodes 31, 33 and the extraction electrodes 32, 34 are provided on the upper and lower surfaces of the quartz substrate 30,
It is formed by depositing a mask of a predetermined shape and depositing Au, Ag, Cr, or the like using means such as evaporation or sputtering.

The ceramic package 2 is a single-plate rectangular ceramic substrate 21, ring-shaped ceramic substrates 22, 23 provided around the ceramic substrate 21, and a seal mounted on the ring-shaped ceramic substrate 23. Ring 2
And 5. In addition, this seal ring 25
Are brazed and fixed via a sealing conductor film 24. As a whole, as shown in FIG. 3, a rectangular cavity 20 having an opening on the front surface side and a short side corresponding to one short side of the crystal resonator 3 is formed, and substantially The vibrator 3 is accommodated.

Further, a second bottom surface 22a which is one step higher than the bottom surface 20a of the cavity 20 is formed on the ring-on ceramic substrate 22 formed on one short side (left side in FIG. 1) of the cavity 20. The electrode pads 22 are formed on the second bottom surface 22a so as to be electrically connected to the crystal resonator 3.
b is formed. The bottom surfaces 22a, 22a are formed separately in the width direction of the short side (the vertical direction in FIG. 1).

The bottom surface 22 of the ring-shaped ceramic substrate 22
a, the excitation electrode 33 on the lower surface side of the region where the
The side surface 22c facing one short side of the cavity is formed in a concave shape toward the one short side of the cavity 20, and the entire space formed in the concave shape is filled with a conductive paste to be a conductive adhesive member 4 described later. Is done.

The shape of the side surface 22c may be formed in an arc shape as shown in FIG. 2, and as shown in FIG.
Only the central part in the width direction of 22c may be omitted in a substantially rectangular shape.

The above-mentioned seal ring 25 is made of Fe—Ni,
It is made of a metal such as Fe-Ni-Co and is formed by brazing or the like on the sealing conductor film 24 formed on the upper surface of the ring-shaped ceramic substrate 23, thereby defining the thickness of the cavity 20.

On the bottom surface of the ceramic package 2 are electrically connected to the electrode pads 22b, 22b.
External terminal electrode 2 for bonding to an external printed wiring board
6 are formed. The electrode pads 22b, 22b and the external terminal electrodes 26 are connected by via-hole conductors (not shown) penetrating a part of the ceramic package 2.

On the surface of the electrode pads 22b, 22b, near the center of the cavity 20 on the surface,
The bump 5 is formed. The bumps 5 are formed by baking a conductive metal paste, printing a conductive paste, and printing and curing the conductive paste. For example, as shown in FIG. It may be formed in a band shape over the entire width in the width direction of 22b.

The above-mentioned electrode pads 22b, 22b, the conductor film 24 for sealing, and the bumps 5 are made of a metal such as molybdenum or tungsten. These conductors (electrode pad 2
2b, 22b, conductive film 24, and bump member 5)
1 is formed by baking a conductive paste on the surface, and then the surface is plated with Ni or Au. For example, when the bumps 5 are formed by baking a conductive metal paste, a conductor serving as a base conductor of the electrode pads 22b, 22b is formed by printing with the above-mentioned metal paste, and after drying, using the above-mentioned metal paste on the surface. In this way, printing is performed in accordance with the shape of the bump 5 and then both are fired.

These conductors (electrode pads 22b, 22b)
b, the thickness of the conductive film 24 and the bump 5) is about 10 to 30 μm.
m, whereby the height from the surface of the substrate 21 to the top of the bump 5 is 20 to 60 μm.

The electrical connection and mechanical connection between the ceramic package 2 and the crystal unit 3 are performed by adding an Ag powder or the like to a resin such as a silicon-based, epoxy-based, or polyimide-based resin to cure the conductive paste. This is achieved by the conductive adhesive member 4 described above. Specifically, the electrode pad 22
The conductive paste described above is supplied onto the b, 22b by a dispenser or the like, and the extraction electrodes 32, 34 extending to the lower surface on one short side of the crystal unit 3 are brought into contact with each other.
When the crystal resonator 3 is placed, the supplied conductive paste spreads concentrically, reaches the above-described side surface 22c, and then flows into the concave portion. However, although the conductive paste spreads toward the excitation electrode 33 on the lower surface of the crystal resonator 3, the conductive paste spreads concentrically because it is formed to flow to the cavity bottom surface 20a in the recess formed by the side surface 22c. It is possible to prevent the central portion from expanding toward the excitation electrode 33 of the crystal resonator 3. As a result, as shown in FIG. 4, the entirety of the recess formed on the side surface 22 c is filled with the conductive paste, and the outer periphery P on the excitation electrode side in the bonding region of the conductive bonding member 4 bonded to the lower surface of the crystal unit 3. One short side of the excitation electrode 33 is substantially parallel. Therefore, the amount of the conductive paste is also adjusted so as to be substantially parallel.

In practice, after the crystal resonator 3 is electrically connected and mechanically connected to the electrode pads 22b, 22b, the oscillation frequency of the crystal resonator 3 is measured using the external terminal electrodes 26 and the like. If necessary, Ag or the like is deposited on the surface of the upper excitation electrode 31 of the crystal unit 3 to adjust the frequency.

The metal lid 6 is made of substantially flat metal,
For example, Fe-Ni alloy (42 alloy) or Fe-Ni-C
o Alloy (Kovar) or the like. Such a metal lid 6 has a housing area (cavity) 20 for the crystal unit 3.
Is hermetically sealed with nitrogen gas, vacuum or the like. Specifically, the metal cover 6 is placed on the seal ring 25 of the ceramic package 2 in a predetermined atmosphere,
A predetermined current is applied so that the metal on the surface of the metal 5 and a part of the metal of the metal lid 6 are welded to perform seam welding.
In order to perform this welding reliably, it is preferable to form an Ag brazing layer or the like on the joining surface side of the metal lid 6 in advance. A Ni plating layer may be formed on the surface side of the metal lid 6 so that the brazing material contributing to the joining does not decrease around the surface side.

The above-described crystal oscillator is manufactured as follows. First, the excitation electrodes 31, on both main surfaces of the quartz substrate 30,
33, a crystal resonator 3 having extraction electrodes 32 and 34 extended to both main surfaces on one short side is prepared. At the same time, a pair of electrode pads 22 b, 2 b on the bottom surface 22 a of the ceramic package 2, that is, the surface of the ceramic substrate 21.
The ceramic package 2 in which the sealing conductor film 24 and the seal ring 25 are formed on the surface around the opening of the cavity 20 and the metal lid 6 are prepared.

Next, a conductive paste to be the conductive adhesive member 4 is supplied and applied to the upper surfaces of the electrode pads 22b and 22b by a dispenser or the like. At this time, the supplied conductive paste has a substantially hemispherical shape in which the whole is raised.

Next, the quartz oscillator 3 is placed on the conductive paste supplied in a substantially hemispherically raised shape. Specifically, the crystal resonator 3 is placed so that the pair of extraction electrodes 32 and 34 abut on the portion where the conductive paste is supplied. At the same time, as shown in FIG. 4, the relationship between the supplied conductive paste that becomes the conductive adhesive member 4 and the bonding area on the lower surface of the crystal unit 3 is controlled. That is, the amount of the conductive paste is controlled such that the outer periphery P on the excitation electrode side in the bonding area of the conductive adhesive member 4 bonded to the lower surface of the crystal unit 3 and one short side of the excitation electrode 33 are substantially parallel. .

Next, the conductive paste is cured, and the ceramic package 2 and the quartz oscillator 3 are cured and fixed by applying heat.

Then, in a predetermined atmosphere, the seal ring 2
A metal lid 6 is placed on 5 and both are seam-welded.

In the above-described embodiment, a quartz oscillator is used as the piezoelectric oscillator. However, the present invention is not limited to the quartz oscillator. For example, a piezoelectric ceramic oscillator using a piezoelectric ceramic substrate, a piezoelectric single crystal substrate May be used as the piezoelectric single crystal vibrator.

[0041]

As described above, according to the present invention, in the conductive adhesive member to be joined to the piezoelectric vibrator, the outer periphery of the joining area on the excitation electrode side and one short side of the excitation electrode are substantially parallel. As a result, the distance between the position fixed by the conductive adhesive member and the excitation electrode becomes constant, and the distance from the position where the quartz oscillator is held by the conductive adhesive member to the excitation electrode is partially reduced. It is possible to suppress the deterioration of the CI value of the crystal oscillator 1 without generating an extra spurious component caused by the difference.

The bottom surface of the cavity has a first bottom surface and a second bottom surface raised by an insulating substrate at an arbitrary position on the first bottom surface. The electrode pad is formed on the second bottom surface. A side surface of the insulating substrate facing the one short side of the excitation electrode is formed in a concave shape toward the one short side of the container cavity, and the conductive adhesive member is formed over substantially the entire area of the concave portion. With this arrangement, it is possible to effectively suppress the conductive paste from spreading toward the excitation electrode on the lower surface of the crystal unit 3, and it is possible to effectively prevent the conductive paste from being bonded to the bonding region between the piezoelectric unit and the conductive adhesive member as described above. The outer periphery on the excitation electrode side and one short side of the excitation electrode can be easily made substantially parallel. As a result, it is possible to prevent damping from occurring and prevent the CI value from deteriorating.

[Brief description of the drawings]

FIG. 1 is a top view of a crystal oscillator according to the present invention in which a lid is omitted.

FIG. 2 is a top view of a ceramic package used for the crystal oscillator of the present invention.

FIG. 3 is a sectional view taken along line AA of the crystal oscillator according to the present invention.

FIG. 4 is a top view of the crystal oscillator according to the present invention, in which a lid is omitted and a crystal oscillator is transmitted.

FIG. 5 is a top view showing another embodiment of the crystal oscillator of the present invention.

FIG. 6 is a top view of a conventional crystal oscillator with a lid omitted.

FIG. 7 is a sectional view of a conventional crystal oscillator.

FIG. 8 is a top view of a ceramic package used for a conventional crystal oscillator.

FIG. 9 is a top view in which a lid of a conventional crystal oscillator is omitted and a crystal resonator is transmitted.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Crystal oscillator 2 ... Ceramic package 20 ... Cavity 21 ... Ceramic substrate 22, 23 ... Ring-shaped ceramic substrate 22a ... 2nd bottom surface 24 ... Sealing conductor 25 ... ..Seal ring 26 ... External terminal electrode 3 ... Crystal vibrator 30 ... Crystal substrate 4 ... Conductive adhesive member 5 ... Bump 6 ... Metal cover

Claims (2)

[Claims] A container having a rectangular cavity; a pair of electrode pads formed on a bottom surface of the cavity; and a rectangular excitation electrode provided on both main surfaces of the rectangular piezoelectric substrate. A piezoelectric vibrator having a pair of extraction electrodes connected to an extension extending from one short side of the excitation electrode on one lower side of the lower surface; and electrically connecting the extraction electrodes and the electrode pads to each other. ,And,
A piezoelectric device mechanically bonded via a conductive bonding member, wherein the conductive bonding member bonded to the piezoelectric vibrator includes an outer periphery of the bonding region on the excitation electrode side and one short side of the excitation electrode. Are formed to be substantially parallel to each other. 2. The bottom surface of the cavity has a first bottom surface and a second bottom surface raised by an insulating substrate at an arbitrary position on the first bottom surface, and the electrode pad is formed on the second bottom surface. And a side surface of the insulating substrate facing one short side of the excitation electrode is formed in a concave shape toward one short side of the container cavity, and the conductive adhesive member is formed in the concave portion. 2. The piezoelectric device according to claim 1, wherein the piezoelectric device is formed over substantially the entire area of the piezoelectric device.