JP2002261548A - Piezoelectric device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a piezoelectric device exhibiting stable electrical characteristics by minimizing the electromagnetic influence on a board, carrying a piezoelectric vibrator and an oscillation circuit board of the piezoelectric device from the outside and the electromagnetic influence due to them to the outside. SOLUTION: The piezoelectric device is composed of a board, carrying the piezoelectric vibrator which has a rectangular container in one major surface of which a cavity is formed, several electrode pads which are formed on the bottom surface of the cavity, a piezoelectric vibrator in which a pair of excitation electrodes to be connected to the electrode pads, and a metal cover for sealing the cavity and an oscillation circuit board which has a rectangular case on one major surface of which a cavity is formed, inner wiring which is formed on the bottom surface of the cavity, and an electronic component which is connected to the inner wiring and drives the piezoelectric vibrator. The piezoelectric device electrically and mechanically connects one major surface of the board carrying the piezoelectric vibrator and one major surface of the oscillation circuit board each other, and makes the metal cover connect to the ground potential.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a piezoelectric device, and more particularly to a piezoelectric device such as a piezoelectric vibrator or an IC chip used for mobile communication equipment.

[0002]

2. Description of the Related Art A crystal oscillator, which is an example of a conventional piezoelectric device, has a structure as shown in FIGS. 6 and 7 (see Japanese Patent Application Laid-Open No. 2000-278047).

The crystal oscillator 51 includes a ceramic package 52 having cavities on both sides, a crystal oscillator 53,
Conductive adhesive member 54, flat substrate 57, IC chip 58
It is mainly composed of In the crystal unit 53, excitation electrodes 53b are attached to both main surfaces of a strip-shaped crystal substrate 53a. In addition, a lead electrode 53c extending from each excitation electrode is attached to one short side of the quartz substrate 53a.

[0004] The ceramic package 52 is formed by laminating dielectric substrates 521a and 521b of alumina or the like, and a seal ring 523 for forming a cavity 520a is formed on one main surface in the laminating direction. An electrode pad 524 formed on the bottom surface is provided in one cavity 520a.
Then, the quartz oscillator 5 is placed so that the extraction electrode 53c is placed thereon.
3, the cavity 520a is hermetically sealed by seam welding the metal lid 56 to the seal ring 523, which is fixed and connected by the conductive adhesive member 54.

On the opening end face of the other cavity 520b, an electrode pad derived from an electrode pad 524 to which the above-described crystal unit 53 is connected by a lead electrode 53c and an electrode pad connected to GND are formed. I have.

As described above, the ceramic package 5
2 is a substrate structure having an H-shaped cross section (hereinafter referred to as “H-shaped structure”).
).

Further, a wiring pattern is formed on the flat plate substrate 57, and electronic component elements 59 such as an IC chip 58 and a capacitor are mounted and connected. Also, IC
A filling resin 570 is filled on the chip 58 and the electronic component 59 so as to cover the whole.

The above-described quartz oscillator 53 and IC chip 58
And the electronic component elements 59 are connected by a predetermined wiring pattern (not shown) formed from the inside of one main surface of the ceramic package 52 to the opening end surface of the other main surface and a predetermined wiring pattern (not shown) formed on the flat board. An external terminal electrode 571 formed on the lower surface of the flat substrate 57
It is configured to extend.

[0009]

However, conventionally, there have been the following problems. That is, as shown in FIGS. 6 and 7, in the conventional crystal oscillator 51, the dielectric substrate 521 a on the bottom surface of the ceramic package 52 is not formed with a member having a shielding effect, and the internal crystal oscillator is not provided. Since the oscillation circuit 53 is susceptible to electromagnetic influences from the oscillation circuit via the ceramic package 52, and the oscillation circuit itself tends to exert electromagnetic influences to the outside, the characteristics may be unstable.

The present invention has been devised in view of the above-mentioned problems, and has as its object to stabilize electrical characteristics such as an oscillation frequency by individually increasing a shielding effect of a piezoelectric vibrator and an oscillation circuit of a piezoelectric device. Accordingly, it is an object of the present invention to provide a piezoelectric device that can improve reliability and improve mass productivity and improve yield.

[0011]

SUMMARY OF THE INVENTION The present invention provides a rectangular container having a cavity formed on one main surface, a plurality of electrode pads formed on the bottom surface of the cavity, and a pair of excitation pads connected to the electrode pads. A piezoelectric vibrator having electrodes formed thereon, a piezoelectric vibrator mounting substrate having a metal lid sealing the cavity, a rectangular container having a cavity formed on one main surface, and a An oscillation circuit board having the formed internal wiring and an electronic component connected to the internal wiring and driving the piezoelectric vibrator, wherein one main surface side of the piezoelectric vibrator mounting board and the oscillation circuit board Are electrically and mechanically connected to each other on one main surface side, and the metal lid is connected to a ground potential.

According to the structure of the present invention, the piezoelectric vibrator mounting substrate and the oscillation circuit substrate on which the piezoelectric vibrator is mounted are connected by connecting the cavity side openings of the containers of the piezoelectric mounting substrate and the oscillation circuit substrate so as to face each other. In between, a metal lid for hermetically sealing the piezoelectric vibrator is interposed, and since the metal lid is connected to the ground potential, the electronic component for driving the piezoelectric vibrator and The piezoelectric vibrator will be shielded. This makes it possible to prevent electromagnetic waves generated from electronic components for driving the piezoelectric vibrator from interfering with the piezoelectric vibrator with a simple configuration. Also,
Since the metal lid serves as a shield electrode, the entire cavity opening can be shielded, and a shielding effect can be obtained for each of the piezoelectric vibrator mounting board and the transmission circuit board.

The first connection electrode connected from the electrode pad is exposed on the upper surface of the side wall of the container of the piezoelectric vibrator mounting substrate, and the first connection electrode is connected to the upper surface of the side wall of the container of the oscillation circuit substrate from the internal wiring. The second connection electrode is formed, and the connection between the piezoelectric vibrator mounting board and the oscillation circuit board is preferably configured such that the first connection electrode and the second connection electrode face each other. . With this configuration, electrical connection can be achieved simply by connecting the cavity-side openings of the piezoelectric mounting substrate and the oscillation circuit substrate so as to face each other.
The mechanical connection and the shielding effect can be achieved at the same time, the mass productivity is increased, and the yield can be improved.

Further, in the present invention, since the cavity-side openings of the containers are connected to face each other, when the piezoelectric device is mounted on the main substrate, the surface thereof is easily affected by external electromagnetic influences. However, in the present invention, a plurality of terminal electrodes for surface mounting are formed on the other main surface side of the piezoelectric vibrator mounting board, and a ground electrode is formed substantially over the entire area on the other main surface side of the oscillation circuit board. Also, a plurality of terminal electrodes for surface mounting are formed on the other main surface side of the oscillation circuit substrate, and a ground electrode is formed on substantially the entire other main surface side of the piezoelectric vibrator mounting substrate. .

With such a configuration, the surface of the main substrate on which the piezoelectric device is mounted is always covered with the ground electrode, and the metal lid is connected to the ground potential to prevent electromagnetic interference from internal electronic components. And the above-mentioned external electric interference can be shielded by a ground electrode, so that a highly reliable piezoelectric device can be provided.

[0016]

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. FIG. 1 is a side sectional view of a piezoelectric device of the present invention. FIG. 2A is a side sectional view of only a quartz oscillator mounting substrate used for the piezoelectric device, and FIG. FIG. 3 is a top view and a bottom view of the crystal unit without a metal cover, and FIG. 4 is a top view and a bottom view of an oscillation circuit board used for a piezoelectric device. In the following description, a crystal oscillator is used as a piezoelectric device. Among them, an example in which a crystal oscillator is used for a temperature-compensated crystal oscillator will be described. Further, the piezoelectric device of the present invention includes a piezoelectric ceramic substrate other than a crystal oscillator, a piezoelectric vibrator using a single crystal piezoelectric substrate, and a piezoelectric device constituted by a piezoelectric vibrator.

The crystal oscillator 1 of the present invention mainly comprises a container-shaped crystal oscillator mounting substrate 2 on which a crystal oscillator is mounted, a container-shaped oscillation circuit substrate 7 for accommodating IC chips 8 and electronic components 9, and a metal-made oscillator. It is composed of a lid 6.

The quartz crystal resonator mounting substrate 2 has a flat dielectric substrate 21, a ring-shaped dielectric substrate 22 provided around the dielectric substrate 21, and a ring having a larger inner circumference and a narrower width than the dielectric substrate 22. A dielectric substrate 23 is formed by being laminated on the outer peripheral portion of the upper surface of the dielectric substrate 22, and a sealing conductor 221 is formed on the inner peripheral surface of the upper surface of the dielectric substrate 22.

An internal wiring pattern (not shown) and a via-hole conductor penetrating the ceramic substrate in the thickness direction are formed between the dielectric substrate 21 and the dielectric substrates 22 and 23 to be laminated. The electrode pads 24, 24 are led out via via-hole conductors 236 to crystal oscillator lead-out electrodes 232, 232 formed on the upper end of the opening of the crystal oscillator mounting substrate 2 shown in FIG.

An oscillation circuit lead-out electrode 234 is formed at the corner of the opening end face on the upper surface of the container side wall of the crystal resonator mounting substrate 2 shown in FIG.
Are connected to the surface mounting terminal electrodes 26, 26, 26, 26 formed at the four corners of the back surface of the crystal resonator mounting substrate 2 via respective end faces. Reference numeral 233 denotes a ground electrode, which is connected to a sealing conductor 221 that is formed around the inner periphery of the upper surface of the dielectric substrate 22.

The sealing conductor film 221 is formed by depositing a metallized layer such as tungsten or molybdenum, and further, by plating the surface with Ni or Au. The electrode pads 233 and 234 such as the crystal oscillator lead-out electrodes 232 and 232 and the ground electrode are formed by baking a conductive resin paste, then Ni is formed by plating, and Au plating is further formed on the upper surface. .

The crystal unit 3 is cut at a predetermined crystal axis (AT
A cut-off rectangular crystal substrate 30 and a crystal substrate 30
And a lead electrode 32 extending from the excitation electrodes 31, 31 to one end of the quartz substrate 30. Such an excitation electrode 3
The 1 and the extraction electrode 32 are formed of Au, Ag, Cr, or the like using a means such as vapor deposition or sputtering by arranging a mask of a predetermined shape on the upper and lower surfaces of the quartz substrate 30. The metal lid 6 is a metal plate made of, for example, an Fe—Ni alloy (42 alloy) or an Fe—Ni—Co alloy (Kovar), and has a brazing material layer formed at least on the joint surface side. Examples of the layer include an Au alloy, Sn, solder, and aluminum alloy. Further, a plating layer of Ni, Au, or the like is formed on a surface on which the brazing material layer is not formed. The metal lid 6 is hermetically sealed by injecting nitrogen gas or the like into the cavity 20 or by seam welding with a sealing conductor film 221 in a vacuum.

The oscillation circuit substrate 7 is formed by laminating a dielectric substrate 71 and a dielectric substrate 72 provided around the dielectric substrate 71.

An internal wiring pattern 725 is formed between the dielectric substrate 71 and the dielectric substrate 72 to be laminated.
And the electronic component element 9 constitute a circuit of the oscillation circuit board 7,
The electrode pads 722 and 7 formed on the upper surface of the opening of the ring-shaped ceramic layer 72 by extracting a part of the internal wiring pattern
23 and 724. End electrodes 727 connected to the plurality of ground electrodes 724 are formed from the dielectric substrate 72 to the dielectric substrate 71.

A ground electrode 73 is formed on substantially the entire surface of the oscillation circuit board 7 on the side opposite to the opening, and is connected to a ground electrode 723 formed on the upper surface around the container.
Also, electrode pads 722, 724 formed in the openings,
The ground electrode 723 is a crystal resonator lead-out electrode 234 on the upper surface of the opening of the crystal resonator mounting substrate 2, and a crystal resonator lead-out electrode 232.
And the electrode pad 233.

The IC chip 8 is a circuit component on which a circuit for exciting the crystal unit 3 is integrated. For example, an Au bump is formed on an IC connection electrode (not shown) formed on the bottom surface of the cavity of the oscillation circuit board 7. It is connected by a construction method such as a flip chip through 7a. Specifically, IC
The connection of the chips 7 is performed by bonding an Ag paste to be the Au bumps 7a or fusing by an ultrasonic wave. Also,
As shown in FIG. 1, a thermosetting resin 74 covering the IC chip 8
Between the bottom surface of the cavity of the ceramic substrate 71 and the back surface of the IC chip.
4 may be filled. When the thermosetting resin 74 is cured by heating, the thermosetting resin 74 is reinforced in terms of the bonding strength between the IC chip 8 and the oscillation circuit board 7. As the thermosetting resin 74, for example, an epoxy resin is used.

Further, the quartz oscillator mounting board 2 and the oscillation circuit board 7 are arranged so that the openings face each other, and are connected by using a conductive resin paste or the like which is cured to form a conductive adhesive member. However, the crystal oscillator leading electrodes 232 and 232 and the electrode pads 722 and 722, and further, the electrode pads 233 and 234 and the electrode pads 723 and 724
Are arranged so as to correspond, and each is connected.

In this manner, the shielded containers of the crystal oscillator mounting substrate 2 and the oscillation circuit substrate 7 are connected,
By forming a crystal oscillator, a crystal oscillator with an enhanced shielding effect has been achieved.

As another example, as shown in FIG. 5, a ground electrode 125 is formed on substantially the entire surface of the quartz resonator mounting substrate 2 on the side opposite to the cavity 120, while the oscillation circuit substrate container 17 is formed. The electrode pad 176 may be formed on the surface on the side opposite to the cavity, and may be formed so that the upper and lower main surfaces are located opposite to the example shown in FIGS.
The above-described electrical and mechanical connection between the quartz oscillator mounting substrate 2 and the opening end face of the oscillation circuit substrate 7 is made by using a conductive resin paste (not shown) which is cured and becomes a conductive adhesive member.

The above-described crystal oscillator 1 is manufactured as follows. First, a strip-shaped crystal substrate 3 is prepared. Next, the excitation electrodes 31 are formed on both main surfaces of the crystal substrate 30, and the extraction electrodes 32 derived from the excitation electrodes 31 are formed on both surfaces of the crystal substrate 30, thereby manufacturing the crystal resonator 3.

Next, a quartz resonator mounting substrate 2 is prepared in which a cavity 20 is formed on one main surface, and a pair of electrode pads 24, 24 are formed by plating on the bottom surface, that is, on one main surface of the dielectric substrate 21. I do. The quartz oscillator container is provided with a dielectric substrate 22, 2 in one main surface of the dielectric substrate 21.
3, a sealing conductor film 221 is formed on the upper surface near the inner periphery of the dielectric substrate 22, and the other dielectric substrate 2
3 has electrode pads such as 232, 233 and 234 formed on the upper surface.

Next, for example, the electrode pads 24
A conductive resin paste which becomes the conductive adhesive member 4 upon curing is supplied and applied by a dispenser or the like. At this time, the supplied conductive resin paste has a substantially spheroidal shape as a whole.

The extraction electrode 3 of the crystal unit 3
2 and 32 are placed on the conductive resin paste so that they come into contact with each other. Next, the conductive resin paste is hardened, and the ceramic package 2 and the quartz oscillator 3 are hardened by heat and fixedly joined.

Next, the frequency of the crystal resonator 3 is adjusted.
Specifically, an electrode pad (not shown) for measuring the oscillation frequency is formed on the electrode pads 232 and 232 formed on the opening end surface of the quartz crystal resonator mounting substrate 2 so that the probe for measuring the power supply voltage, ground, and frequency can be formed. Is connected, and while the crystal resonator 3 is oscillated, the oscillation frequency is adjusted by increasing or decreasing the mass of the excitation electrode on the excitation electrode of the crystal resonator 3 by means of Ag vapor deposition or an ion gun. Next, N
The metal lid 6 is placed on the sealing conductor film 221 so that the bonding surface faces downward in a predetermined atmosphere such as 2 or He, and both are sealed by seam welding. Next, the IC chip 8 is mounted on one main surface of the oscillation circuit board 7. Specifically, first, Au bumps (not shown) formed on the IC chip 8 and electrode pads (not shown) formed on the main surface of the ceramic substrate 71 are positioned and mounted at corresponding positions.
Thereafter, the IC chips 8 are bonded to each other by bonding using an Ag paste or fusion using an ultrasonic wave. Next, IC
Epoxy-based thermosetting resin 74 so as to cover chip 8
And heat and cure.

Finally, the crystal resonator mounting substrate 2 and the oscillation circuit substrate 7 are arranged so that their respective openings face each other, and the electrode pads 232, 232 and the electrode pads 722, 722, and the electrode pads 233, 234 and 723, In a state where 724 is located at the corresponding position, the crystal oscillator mounting substrate 2 and the oscillation circuit substrate 7 are connected and heated by using a conductive resin paste or the like which is hardened to become a conductive adhesive member. To cure.

[0036]

According to the structure of the present invention, by connecting the cavity-side openings of the containers of the piezoelectric mounting substrate and the oscillation circuit substrate so as to face each other, the piezoelectric vibrator mounting substrate on which the piezoelectric vibrator is mounted is connected to the oscillation circuit. A metal lid for hermetically sealing the piezoelectric vibrator is interposed between the circuit boards, and since the metal lid is connected to the ground potential, an electronic device for driving the piezoelectric vibrator is provided. The component and the piezoelectric vibrator will be shielded. Accordingly, it is possible to prevent an electromagnetic wave generated from an electronic component for driving the piezoelectric vibrator with a simple configuration from interfering with the piezoelectric vibrator, thereby providing a piezoelectric device with increased reliability.

In the present invention, since the openings on the cavity side of each container are connected to face each other, the boundary between the cavities can be structured such that the exposed electrode is not disposed because the metal lid as the shield electrode is not disposed. No capacity is generated.

The first connection electrode connected to the electrode pad is exposed on the upper surface of the side wall of the container of the piezoelectric vibrator mounting substrate, and the first connection electrode is connected to the upper surface of the side wall of the container of the oscillation circuit substrate from the internal wiring. The second connection electrode is formed, and the connection between the piezoelectric vibrator mounting board and the oscillation circuit board is performed by adopting a configuration in which the first connection electrode and the second connection electrode face each other and are in contact with each other. By simply connecting the cavities side openings of the piezoelectric mounting substrate and the oscillation circuit substrate so as to face each other, electrical and mechanical connection and a shielding effect can be achieved at the same time, increasing mass productivity and improving the yield. be able to.

Further, in the present invention, since the openings on the cavity side of each container are connected to face each other, when the piezoelectric device is mounted on the main substrate, the surface thereof is easily affected by external electromagnetic influences. In the present invention,
Since the surface of the main board on which the piezoelectric device is mounted is always covered with a ground electrode, the metal lid is connected to ground potential to prevent electromagnetic interference from internal electronic components, Can be shielded by the ground electrode, and a highly reliable piezoelectric device can be provided.

[Brief description of the drawings]

FIG. 1 is a side sectional view of a piezoelectric device of the present invention.

FIG. 2A is a side sectional view of only a quartz oscillator mounting substrate used for a piezoelectric device, and FIG. 2B is a side view of only a transmitting circuit board.

FIG. 3A is a top view of the quartz crystal device used in the piezoelectric device of the present invention, in which a lid is omitted, and FIG. 3B is a bottom view of the quartz crystal device used in the piezoelectric device of the present invention. .

4A is a top view of an oscillation circuit board used in the piezoelectric device of the present invention, and FIG. 4B is a bottom view of the oscillation circuit board used in the piezoelectric device of the present invention.

FIG. 5 is a side sectional view showing another example of the piezoelectric device of the present invention.

FIG. 6 is an exploded side sectional view of a conventional piezoelectric device.

FIG. 7 is a top view of a conventional piezoelectric device with a lid omitted.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Crystal oscillator 2 ... Crystal oscillator mounting board 20 ... Cavity 21 ... Dielectric substrate 221 ... Sealing conductor film 24 ... External terminal electrode 3 ... Crystal oscillator Reference numeral 30: quartz substrate 4: conductive adhesive member 6: metal lid 7: oscillation circuit board 73: ground electrode 8: IC chip

Claims (4)

[Claims] 1. A piezoelectric vibrator comprising: a rectangular container having a cavity formed on one main surface; a plurality of electrode pads formed on the bottom surface of the cavity; and a pair of excitation electrodes connected to the electrode pads. A piezoelectric vibrator mounting substrate having a metal lid for sealing the cavity, a rectangular container having a cavity formed on one main surface,
An oscillation circuit board having an internal wiring formed on the bottom surface of the cavity and an electronic component connected to the internal wiring and driving the piezoelectric vibrator; and one main surface side of the piezoelectric vibrator mounting board. A piezoelectric device, wherein one main surfaces of the oscillation circuit board are electrically and mechanically connected to each other, and the metal cover is connected to a ground potential. 2. A first connection electrode connected from the electrode pad is exposed on an upper surface of a side wall of a container of the piezoelectric vibrator mounting substrate, and a first connection electrode connected to the inner wiring is connected to an upper surface of a side wall of the container of the oscillation circuit substrate. Wherein the second connection electrode is formed, and the connection between the piezoelectric vibrator mounting board and the oscillation circuit board is made such that the first connection electrode and the second connection electrode face each other. The piezoelectric device according to claim 1, wherein 3. A plurality of terminal electrodes for surface mounting are formed on the other main surface side of the piezoelectric vibrator mounting substrate, and a ground electrode is formed on substantially the whole area on the other main surface side of the oscillation circuit substrate. The piezoelectric device according to claim 1, wherein: 4. A plurality of terminal electrodes for surface mounting are formed on the other main surface side of the oscillation circuit board, and a ground electrode is formed on substantially the whole area on the other main surface side of the piezoelectric vibrator mounting board. The piezoelectric device according to claim 1, wherein: