JP2003318692A - Piezoelectric device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a piezoelectric device capable of preventing deterioration in electrical characteristics due to expansion of a conductive resin paste, in a holding portion of a quartz resonator and reducing its thickness. <P>SOLUTION: Electrode pads 5a, 5a having a slope surface inclined outward are formed in a cavity section 20 of a ceramic package 2. The quartz resonator 3 is bonded to the pads 5a, 5a via a conductive adhesive member 4 so as to be substantially parallel to the internal bottom surface of the section 20 (surface of a substrate 21). <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a piezoelectric device in which a piezoelectric vibrator is bonded to a substrate or the like via a conductive adhesive member. The piezoelectric vibrator includes a crystal plate, a piezoelectric ceramic substrate, and a vibrator using a single crystal piezoelectric substrate,
The piezoelectric device is an oscillator having only a piezoelectric vibrating element, or an oscillator having a predetermined circuit such as an IC chip, a capacitor, and a resistor mounted together with the piezoelectric vibrator.
Further, the substrate is an insulating substrate having a flat plate shape as a whole, a case-shaped container body having an electrode pad on the flat plate portion, and the like.

[0002]

2. Description of the Related Art A conventional piezoelectric device, for example, a crystal oscillator, has a crystal oscillator, which is a piezoelectric oscillator, and a ceramic, which is a substrate on which electrode pads are formed on the lower surface of the cavity, as shown in FIGS. It was placed in a container (hereinafter referred to as a ceramic package).

A crystal oscillator 51 shown in FIGS. 8 to 10 comprises a ceramic package 52, a crystal oscillator 53, and a conductive adhesive 54.

As shown in FIG. 8, the ceramic package 52 is a ceramic insulating substrate 521 or 522 made of alumina or the like.
And a cavity 520 for accommodating the crystal unit 53 is formed inside.

External terminal electrodes 526 are formed on the bottom surface of the ceramic package 52. As shown in FIG. 9, the ceramic package 52 has a planar electrode separated in the width direction at one end in the longitudinal direction. Pads 55, 55 are formed. The electrode pads 55, 55 have a substantially rectangular shape, and are connected to the external terminal electrodes 526 and the like via via hole conductors. Further, as shown in FIG. 10, bumps 551 extending in the width direction are formed on the surfaces of the electrode pads 55, 55 on the inner side of the ceramic package 52.

Further, the crystal unit 53 has excitation electrodes 531 and 533 facing each other on both main surfaces of a rectangular crystal substrate.
Further, extraction electrodes 532 and 534 are formed to extend from the excitation electrode to both main surfaces on one short side of the crystal substrate. Each of the electrode patterns is formed by using a method such as sputtering or vapor deposition.

In such a crystal oscillator 51, one end of a bump 55 is made of a conductive resin paste which becomes a conductive adhesive member 54.
1 and the other end is applied so as to be closer to the outside of the ceramic package, and mounted on this conductive resin paste so that the lower surfaces of the extraction electrodes 532 and 534 of the crystal unit 53 are positioned.

After that, the ceramic package 52 and the crystal unit 53 are cured by hardening the conductive resin paste.
And electrically connect and bond with the cavity 520.
In order to achieve airtight sealing, the ceramic package 52 is covered with a lid 56 and sealed by seam welding or the like (for example, JP-A-4-3610).

[0009]

However, according to the prior art, in FIGS. 8 to 10, the conductive resin paste is applied so as to cover the bumps 551 on the electrode pads 55, 55, and then applied. The extraction electrodes 532 and 534 of the crystal unit 53 are placed on the conductive resin paste so that they are located. At this time, the bumps 55 were intended to prevent the conductive resin paste from spreading particularly toward the excitation electrodes 531 on the lower surface of the crystal unit 53. 531
In some cases, the electrical characteristics of the crystal oscillator 51, especially the crystal impedance value (hereinafter,
This is called the CI value).

On the contrary, if the amount of the conductive resin paste supplied in order to eliminate the conductive resin paste applied to the lower surface side of the crystal unit 53 is reduced, the damping of the fundamental wave is suppressed and the CI value is improved. However, the bonding strength between the ceramic package 52 and the crystal unit 53 is reduced.
As a result, the mechanical strength decreases, and when an impact is applied from the outside due to a drop or the like, peeling easily occurs at this joint portion, and the oscillation frequency largely changes or oscillation failure occurs.

The present invention has been devised in view of the above problems, and an object thereof is to prevent the conductive resin paste from spreading toward the excitation electrode of the crystal unit.
Good electrical characteristics are obtained, good oscillation is possible,
Further, the present invention provides a piezoelectric device having good bonding strength and a method for manufacturing the same.

[0012]

According to the present invention, an excitation electrode is formed on both main surfaces of a rectangular piezoelectric substrate, and the excitation electrode is connected to at least the lower surface on one short side of the piezoelectric substrate and has a width. Piezoelectric vibrator formed with a pair of extraction electrodes separated in the direction, a substrate having an electrode pad connected to the extraction electrode on the surface, in the piezoelectric device bonded via a conductive adhesive member, the electrode pad, The piezoelectric substrate has an inclined surface whose surface is inclined downward toward the outer side of the substrate, and the piezoelectric substrate is bonded substantially parallel to the substrate surface via the conductive adhesive member. Is a device.

Further, the connection pad is a piezoelectric device formed on the surface of the substrate on an inner surface of a concave portion inclined downward toward the outside of the substrate.

According to the present invention, the electrode pad is formed on the substrate so that the electrode pad has an inclined surface that descends outward.
In addition, a conductive resin paste is applied onto the electrode pad, a crystal oscillator is mounted, and the conductive resin paste is cured and bonded while the crystal oscillator is slightly pressed.

As a result, when the crystal unit is pressed against the electrode pad via the conductive paste, the conductive resin paste flows toward the outer side of the substrate along the inclined surface of the electrode pad, and the vibration is excited. It is possible to prevent the conductive resin paste from spreading in the central region near the electrodes.
Further, the conductive adhesive member does not contact the extraction electrode or the like on the upper surface beyond the end surface of the crystal unit near the extraction electrode.

Therefore, the extraction electrode on the lower surface side of the crystal unit is surely connected to the electrode pad, and at the same time, the conductive adhesive member spreads to the excitation electrode on the lower surface of the crystal unit which is the piezoelectric unit. Therefore, it is possible to prevent the CI value from deteriorating. Further, since the crystal unit is bonded to the substrate substantially in parallel, the height at the tip of the crystal unit can be reduced, and the thickness of the crystal unit can be reduced.

In addition, an inclined concave portion is formed on the substrate,
By forming the electrode pad on the concave portion so as to decrease outward, it becomes possible to further reduce the thickness of the crystal oscillator.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION The piezoelectric device of the present invention will be described below in detail with reference to the drawings. In the description, a piezoelectric device using a crystal oscillator as a piezoelectric oscillator, for example, a crystal oscillator will be described.

FIG. 1 is a side sectional view of a crystal oscillator, which is a piezoelectric device according to the present invention, and FIG. 2 is a top view of the crystal oscillator without a lid. FIG. 3 is a top view of a ceramic container body which is a substrate used for the crystal oscillator.

The crystal oscillator 1 of the piezoelectric device of the present invention is
It is mainly composed of a ceramic container body (ceramic package) 2, which is a substrate, a crystal resonator 3, a conductive adhesive member 4, and a metallic lid body 6.

The ceramic package 2 has a rectangular flat plate-shaped substrate 21, a frame-shaped substrate 22 provided around the flat-plate-shaped substrate 21, and a seal ring 24 mounted on the frame-shaped substrate 22. It consists of and.

The flat plate-shaped substrate 21 and the frame-shaped substrate 22 are laminated, and the seal ring 24 is brazed and fixed to the upper part of the plate-shaped substrate 21 and the frame-shaped substrate 22 with the sealing conductor film 23 interposed therebetween. Then, as a whole, as shown in FIG. 1, a substantially rectangular cavity 20 having a substantially rectangular opening on the front surface side and accommodating the crystal resonator 3 is formed. Further, a holding portion 25a having an inclined portion that descends toward the outside is formed on the inner lower surface of the cavity portion 20, that is, on one short side (the left side in FIG. 1) of the upper surface of the substrate 21, The electrode pad 5a is formed on the inclined surface of the holding portion 25a. The holding portions 25a are formed separately in the width direction of the short sides (vertical direction in FIG. 2).

The electrode pads 5a and 5a are formed on the surface of the holding portion 25a. This holding part 25
The a and 25a are inclined so that at least the electrode pad 5a is lowered toward the outside of the ceramic package 2. As a result, the surface of the electrode pad 5a is inclined so as to decrease toward the outside of the ceramic package 2.

The flat substrate 21 and the frame substrate 22 are made of ceramic, and the seal ring 24 is made of Fe.
It is made of a metal such as —Ni or Fe—Ni—Co and is formed by brazing or the like on the sealing conductor film 23 formed on the upper surface of the frame-shaped substrate 22. This frame-shaped substrate 22,
The thickness of the cavity 20 is defined by the sealing conductor film 23 and the seal ring 24. For example, when the thickness of the seal ring 24 can provide the thickness of the cavity portion 20 that can accommodate the crystal unit 3, the frame-shaped substrate 22
Can be omitted.

On the mounting bottom surface of the ceramic package 2, external terminal electrodes 26 are formed which are electrically connected to the electrode pads 5a, 5a via via hole conductors, for example. The external terminal electrode 26 is connected to, for example, a predetermined wiring of a mother board or a terminal electrode of another container in which an IC chip forming an oscillation circuit by being connected to the crystal resonator 3 is housed. When the electrode pads 5a, 5a and the formation positions of the external terminal electrodes 26 do not correspond to each other, the substrate 21 which is the inner lower surface of the cavity 20 may be a laminated substrate and predetermined internal wiring may be formed therein.

The above electrode pads 5a, 5a and the sealing conductor film 23 are made of a metal such as molybdenum or tungsten. These conductors (electrode pads 5a, 5a, conductor film 23) are formed by baking a conductive paste on the surface of the flat substrate 21 and then plating the surface with Ni or Au.

These conductors (electrode pad 5a, conductor film 2)
The thickness of 4) is about 10 to 30 μm.

The crystal resonator 3 which is a piezoelectric vibrator is, for example, a rectangular crystal substrate 30 which is cut (AT cut) according to a predetermined crystal azimuth angle, and an excitation which is adhered and formed on both main surfaces of the crystal substrate 30. Electrodes 31 and 33 and a pair of excitation electrodes 3
1 and 33, and extraction electrodes 32 and 34 extending in the short side direction (left side in the drawing) of the quartz substrate 30, respectively. For example, the extraction electrode 32 extending from the upper surface side excitation electrode 31 extends to the vicinity of the short side of the upper surface, and extends to the lower surface side via the end surface (the lower end surface in the figure) of the piezoelectric substrate 30 near the short side. It has been extended. On the contrary, the extraction electrode 34 extending from the excitation electrode 33 on the lower surface side is extended to the upper surface side via the end surface (upper end surface in the drawing) near the short side of the piezoelectric substrate 30. As a result, the crystal unit 3 becomes a front and back target,
The main process of the crystal unit 3 becomes very simple.

For the excitation electrodes 31, 33 and the extraction electrodes 32, 34, a mask having a predetermined shape is arranged on the upper and lower surfaces of the quartz substrate 30, and Au, Ag, etc. are formed by means of sputtering or vapor deposition. It is formed of Cr or the like.

For the electrical connection and mechanical joining between the ceramic package 2 and the crystal unit 3 described above, a conductive resin paste is prepared by adding Ag powder or the like to a resin such as silicon, epoxy, or polyimide. This is achieved by the cured conductive adhesive member 4. Specifically, the flat substrate 2
Electrode pad 5 formed on the surface of the holding portion 25a above
A conductive resin paste is supplied onto a and 5a by a dispenser or the like, and the crystal oscillator 3 is mounted so that the extraction electrodes 32 and 34 extended to the lower surface of one short side of the crystal oscillator 3 come into contact with each other. Then, the conductive resin paste is cured.

The conductive resin paste is preferably applied to the upper side of the electrode pads 5a, 5a on which the conductive adhesive member 4 has an inclined surface. Then, the ceramic package 2 is placed on the applied conductive resin paste.
The crystal resonator 3 is placed in a state where the crystal resonator 3 is maintained so as to be substantially parallel to the inner lower surface (surface of the substrate) of the cavity portion 20, and a slight load is applied and pressed.
The lower surface of the crystal unit 3 and the inner lower surface of the cavity 20 of the ceramic package 2 are arranged with a gap of 25 to 35 μm, for example. Specifically, the crystal unit 3
Is placed using a handling holding part or a suction pad that holds the surface of the cavity 20 substantially parallel to the surface of the inner lower surface, and pressure is applied at the same time. After that, the conductive resin paste is cured by heating or ultraviolet rays.

In practice, after the crystal unit 3 is electrically connected to the electrode pads 5a, 5a and mechanically joined, the oscillation frequency of the crystal unit 3 is measured using the external terminal electrodes 26 and the like. If necessary, the surface of the upper-side excitation electrode 31 of the crystal unit 3 is irradiated with Ar gas by an ion gun or the like to remove Au on the surface of the excitation electrode, vapor deposition of Ag or the like is performed, and the frequency is adjusted. Do it.

The metallic lid 6, which is a lid, is made of a substantially flat metal such as Fe-Ni alloy (42 alloy) or Fe.
-Ni-Co alloy (Kovar) or the like. The metal lid 6 as described above hermetically seals the cavity portion 20 which is the accommodation region of the crystal unit 3 with nitrogen gas or vacuum. Specifically, the metal lid 6 is placed on the seal ring 24 of the ceramic package 2 in a predetermined atmosphere, and the metal on the surface of the seal ring 24 and a part of the metal of the metal lid 6 are welded. Seam welding is performed by applying a predetermined current as described above.

According to the above structure, the electrode pads 5a, 5
The surface of a is a slanted surface so as to descend outward on the upper surface of the flat substrate 21 which is the lower surface of the ceramic package 2. The electrode pads 5a,
The lower surface side extraction electrodes 32 and 34 of the crystal unit 3 are electrically and mechanically joined to a by a conductive adhesive member.

Specifically, when a conductive resin paste is applied to the surface of the flat electrode pad 55 as in the conventional case, the applied conductive resin paste spreads in a substantially hemispherical shape due to the surface tension, and is applied to the upper portion thereof. When the crystal unit 3 is mounted, the conductive resin paste spreads on the excitation electrodes 531 and 533 side. Even if the bumps 551 that suppress the spread are provided,
It may spread beyond the bump 551.

However, according to the present invention, since the surface of the electrode pads 5a, 5a to which the conductive resin paste is supplied is an inclined surface which goes downward, the crystal oscillator 3 is placed on the conductive resin paste. Even when placed, the conductive resin paste will flow to the outside, and as a result, the cured conductive adhesive member 4 will not spread to the excitation electrode side of the crystal unit 3. This prevents the conductive adhesive member 4 from deteriorating the CI value of the crystal unit 3.

FIG. 4 is a top view of the ceramic package used in the second embodiment of the present invention. Although two holding portions 25a, 25a were formed in the cavity 20 of the ceramic package 2 of FIGS. 1 to 3, as shown in FIG. 4, it may be lowered from the center of the ceramic package 2 toward the corners of the ceramic package 2. Formed on an inclined surface
One holding portion 25b is formed, and two electrode pads 5b and 5b are formed on this surface position. The positions where the two electrode pads 5b, 5b are formed are formed near the corners of the holding portion, and the shape thereof is triangular. This also makes it possible to connect the crystal unit 3 to the electrode pads 5b, 5b at the extraction electrodes 32, 34 on the lower surface, and prevent the CI value from being deteriorated.

In each of the embodiment shown in FIGS. 1 to 3 and the embodiment shown in FIG. 4, at least the electrode pad 5a,
5a (5b, 5b) should be formed separately,
The holding portions 25a (25b) may be formed integrally or separately.

5 and 6 are a sectional view of a crystal oscillator and a top view of a ceramic package according to a third embodiment of the present invention. In this case, on the surface of the flat plate-shaped substrate 21 located on the lower surface of the ceramic package 2, concave portions 5c, 5c having an inclined inner bottom surface are formed. This recess 5
The inclination of the inner bottom surface of c
It is inclined so that it goes down toward the outside. And
Separation regions 25e are provided on the inner bottom surface of the recess 25c to form the electrode pads 5c and 5c. As a result, the surfaces of the electrode pads 5c, 5c can be inclined surfaces that are inclined downward toward the outside.

Then, a conductive resin paste is applied on the electrode pads 5c and 5c, and the extraction electrodes 32 and 34 on the lower surface side of the crystal unit 3 are bonded to the electrode pads 5c and 5c.

In the embodiment shown in FIGS. 1 to 4, the surfaces of the electrode pads 5a and 5a are inclined surfaces in the holding portions 25a and 25b protruding from the inner lower surface of the cavity portion 20, but in this embodiment, Since the concave portion 25c is formed on the surface of the substrate 21, the crystal oscillator 3 can be reduced from the surface of the substrate 21 by the height of the holding portion, so that the crystal oscillator 3 can be joined in a low-profile state. .

FIG. 7 is a top view of a ceramic package used in another embodiment of the present invention. Two recesses 25d having an inclined surface formed on the flat substrate 21 located on the lower surface of the ceramic package 2 are formed separately in the width direction, and the electrode pad 5 is formed on the surface.
d and 5d are formed.

In the figure, the inclined surface of the recess 25d is inclined toward the outer corner, and as a result, the surfaces of the electrode pads 5d and 5d are also inclined outward. It has an inclined surface.

Also in this embodiment, the cavity portion 20
Since it is not necessary to form the projecting holding portions 25a and 25b on the inner lower surface of the crystal resonator 3 and the cavity portion 20
It is possible to set a minimum distance required for vibration between the inner lower surface (substrate 21) of the.

As a result of the above-mentioned crystal oscillator 3 being arranged substantially parallel to the inner lower surface of the cavity portion 20 (the surface of the substrate 21), the cross-sectional shape of the conductive adhesive member 4 is that of the electrode pads 5a-5d. The thickness is set so as to face the inclined surface and increase toward the outside.

The outline of the manufacturing process of the above-mentioned crystal oscillator is shown in FIG.
˜ The crystal oscillator of FIG. 3 will be described as an example.

First, the excitation electrodes 3 are formed on both main surfaces of the crystal substrate 30.
1, 33, and the crystal resonator 3 having the extraction electrodes 32, 34 extended to both main surfaces on one short side is prepared. At the same time, the flat plate-like substrate 2 of the lowermost layer of the ceramic package 2
On the surface of No. 1, a holding portion 25a that is inclined so as to descend outward is formed, and the electrode pads 5a, 5
Further, the ceramic package 2 in which a is formed and the sealing conductor film 23 and the seal ring 24 are formed on the surface around the opening of the cavity 20 and the metal lid 6 are prepared.

Next, a conductive resin paste to be the conductive adhesive member 4 is supplied / applied to the electrode pads 5a, 5a by a dispenser or the like so as to be located near the upper part of the inclined portion. At this time, the supplied conductive resin paste has a substantially hemispherical shape and is entirely raised.

Next, the holder of the crystal oscillator 3 was used for the conductive resin paste supplied in the shape of a hemispherical crystal oscillator 3 with respect to the surface of the substrate 21 of the ceramic package 2. Place in parallel and apply some pressure.

Next, the conductive resin paste is hardened to bond and fix the ceramic package 2 and the crystal unit 3. Specifically, it is cured by application of heat.

Then, in a predetermined atmosphere, the seal ring 2
The metal lid 6 is placed on the plate 4, and both are seam welded.

In the above embodiments, the crystal oscillator is used as the piezoelectric oscillator, but the piezoelectric oscillator is not limited to the crystal oscillator. For example, a piezoelectric ceramic oscillator using a piezoelectric ceramic substrate or a piezoelectric single crystal substrate. It may be a piezoelectric single crystal oscillator using.

[0052]

According to the present invention, an electrode pad serving as an inclined surface is formed on the substrate on which the crystal unit is mounted so as to descend outward, and conductive adhesion is applied to the inclined surface of the electrode pad. The extraction electrode of the crystal unit is joined via the member.
In this mounting (pressing) step, it is possible to prevent the conductive resin paste from spreading toward the excitation electrode on the lower surface of the crystal resonator. This makes it possible to prevent deterioration of electrical characteristics, for example, the CI (crystal impedance) value of the crystal unit.

By forming this electrode pad in the concave portion formed on the surface of the substrate, the thickness of the crystal oscillator as a whole can be reduced and at the same time the structure of the present invention can be easily formed.

[Brief description of drawings]

FIG. 1 is a sectional view of a piezoelectric device of the present invention, for example, a crystal oscillator.

FIG. 2 is a top view of the piezoelectric device of the present invention, for example, a cover of a crystal oscillator is omitted.

FIG. 3 is a top view of a piezoelectric device of the present invention, for example, a ceramic package used for a crystal oscillator.

FIG. 4 is a top view of a piezoelectric device of the present invention, for example, a ceramic package used in a second embodiment of a crystal oscillator.

FIG. 5 is a sectional view of a piezoelectric device according to a third embodiment of the present invention, for example, a crystal oscillator.

FIG. 6 is a top view of a piezoelectric device of the present invention, for example, a ceramic package used in a third embodiment of a crystal oscillator.

FIG. 7 is a top view of a piezoelectric device of the present invention, for example, a ceramic package used in a fourth embodiment of a crystal oscillator.

FIG. 8 is a cross-sectional view of a conventional crystal oscillator.

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

FIG. 10 is a top view of a ceramic package used for a conventional crystal oscillator.

[Explanation of symbols]

1 ... Crystal oscillator 2 ... Ceramic package 20 ... Cavity 21 ... Flat substrate 22 ... Frame-shaped substrate 23..Sealing conductor 24 ... Seal ring 25a to 25b ... Holding unit 25c to 25d ... Recess 26 ... External terminal electrode 3 ... Crystal oscillator 30 ... Crystal substrate 4 ... Conductive adhesive member 5a to 5d ... Electrode pad 6 ... Metal lid

Claims (2)

[Claims] 1. A pair of extraction electrodes having excitation electrodes formed on both main surfaces of a rectangular piezoelectric substrate and connected to the excitation electrodes on at least the lower surface on one short side of the piezoelectric substrate and separated in the width direction. In the piezoelectric device formed by bonding the piezoelectric vibrator formed with, to a substrate having an electrode pad connected to the extraction electrode on the surface thereof via a conductive adhesive member, the electrode pad has a surface of the substrate. While having an inclined surface that slopes downward toward the outside,
The piezoelectric device is characterized in that the piezoelectric substrate is bonded to the surface of the substrate substantially in parallel with the conductive adhesive member. 2. The connection pad is provided on a surface of the substrate,
2. The piezoelectric device according to claim 1, wherein the piezoelectric device is formed on an inner surface of a concave portion that is inclined so as to decrease toward the outside of the substrate.