JP2003273690A - Piezoelectric vibration device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a high-reliable piezoelectric vibration device having no possibility of causing a short-circuit or the like even in the case of being miniaturized and capable of obtaining a required hold strength without increasing the coating quantity of a conductive bonding material for holding a piezoelectric diaphragm. <P>SOLUTION: In the piezoelectric vibration device in which a piezoelectric diaphragm 2 formed with an exciting electrode and a deriving electrode for connecting the relevant exciting electrode to the outside is packaged on the upper face of conductive pads 12 and 13 and held by the conductive bonds while using a ceramic package 1 formed with the relevant conductive pads, said conductive pads have base portions 121 and 131 connected with external terminals and protruding portions 122 and 132 for holding the piezoelectric diaphragm near its terminal parts, and said base portions are formed wider than the protruding portions. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a piezoelectric vibrating device using a ceramic package, and more particularly to a structure of a conductive pad that holds a piezoelectric vibrating plate with a conductive bonding material such as solder.

[0002]

2. Description of the Related Art Crystal oscillators, crystal filters, crystal oscillators and the like are examples of piezoelectric vibrating devices requiring hermetic sealing. In all of these, a metal thin film electrode is formed on the surface of a quartz diaphragm (piezoelectric diaphragm), and the metal thin film electrode is hermetically sealed in order to protect the metal thin film electrode from the outside air.

Due to the demand for surface mounting of components, these crystal-applied products are increasingly being hermetically housed in a ceramic package. By selecting an appropriate hermetic sealing method, good hermeticity is ensured. can do. An example of a piezoelectric vibrating device using such a ceramic package will be described with reference to FIGS. FIG. 5 is a perspective view of a ceramic package showing a conventional example, and shows a state in which a crystal vibration plate (piezoelectric vibration plate) is mounted in a housing portion. Figure 6
FIG. 6 is a plan view showing a state in which a crystal diaphragm is mounted in FIG. 5.

The ceramic package as a whole has a rectangular parallelepiped shape in which a concave storage portion 1a is formed in the central portion, and a metal seal portion 11 is provided on the upper surface of the bank 10 around the storage portion.
Are formed. A step portion and conductive pads 14 and 15 formed on the upper surface of the step portion are formed at the bottom of the storage portion 1a, and are guided to an external terminal (not shown) by the via V. The crystal diaphragm 2 is mounted on the conductive pad,
They are electrically and mechanically connected by a conductive bonding material D such as solder. The crystal diaphragm 2 has a tuning fork shape, and has excitation electrodes (not shown) formed on the legs and lead electrodes 21 and 22 from the excitation electrodes formed on the base. . Then, the metal lid (not shown) and the metal seal portion 11 formed on the ceramic package 1 are joined by welding and hermetically sealed.

[0005]

Recently, due to further miniaturization and weight saving of electronic equipment, miniaturization of piezoelectric vibrating device is also required, and accordingly, the size of the piezoelectric vibrating plate housed in the package is required. Is also miniaturized. However, as the package becomes smaller, the holding area also becomes smaller, which may reduce the impact resistance and risk of short circuit. In particular, in the case of using solder as the conductive bonding material, the solder spreads over the entire conductive pad of the package due to its wettability, and it is not possible to secure sufficient bonding strength between the package and the piezoelectric vibrating plate, resulting in shock resistance. Markedly reduced.

This also depends on the fact that the conductive pad is relatively large, the upper surface of the conductive pad is flat, and the solder is more likely to spread on the electrode upper surface than other conductive resin adhesives. As a conventional method against this, it is conceivable to increase the solder coating amount to improve the joint strength, but in recent miniaturized packages, the holding area is small, and there is a problem that the risk of short circuit becomes extremely high. .

The present invention has been made in order to solve the above-mentioned problems, and it is possible to obtain a required holding strength in holding a piezoelectric vibrating plate without increasing the coating amount of the conductive bonding material, and to make it compact. The object of the present invention is to provide a highly reliable piezoelectric vibrating device without the risk of short circuit.

[0008]

In order to solve the above-mentioned problems, the present invention uses a ceramic package having a conductive pad as described in claim 1, and connects the excitation electrode and the excitation electrode to the outside. A piezoelectric vibrating device in which a piezoelectric vibrating plate on which a lead electrode is formed is mounted on the upper surface of the conductive pad and held by a conductive bonding material, wherein the conductive pad includes a base portion connected to an external terminal and a piezoelectric vibrating plate. It is characterized in that it has a protruding portion that holds the vicinity of the end portion, and that the base portion is formed wider than the protruding portion.

According to a second aspect of the present invention, the projecting portion extends toward the center of the piezoelectric vibrating plate and in a direction in which the projecting portions approach each other.

[0010]

According to the present invention, in a structure using a ceramic package compatible with surface mounting, a conductive pad area on which a piezoelectric diaphragm is mounted is provided by providing a protruding portion that is narrower than the base portion as a conductive pad. The electrode area of only the (protrusion) is reduced to eliminate the spread of the conductive bonding material on the upper surface of the projection, and the conductive bonding material applied to the projection is covered by the boundary between the projection and the ceramic package. Since it rises due to the tension and wraps around the side wall of the piezoelectric diaphragm, the bonding strength is improved.

Further, since the unnecessary conductive bonding material that does not contribute to the bonding of the piezoelectric vibrating plate is caused to flow out from the protruding portion to the base portion, and the unnecessary conductive bonding material does not stay in the protruding portion, the unnecessary conductive bonding material spreads. In addition, it is possible to eliminate a problem such as a change in the characteristics of the piezoelectric vibrator due to an unnecessary rise of the conductive bonding material to the piezoelectric vibrating plate and a short circuit.

As described above, the conductive bonding material is applied to the protruding portion in a state in which it is optimally raised in order to improve the bonding strength of the piezoelectric vibration plate.

According to the second aspect, in addition to the above effect, since the respective projecting portions are formed so as to extend toward the center of the piezoelectric vibrating plate in the directions in which they are close to each other, piezoelectric elements having different dimension widths are provided. Even the vibrator can be mounted by shifting in the extending direction of the protrusion to the position of the distance between the protrusions that matches the distance between the lead-out electrodes of the piezoelectric vibrator. Therefore, since it is not necessary to change the width dimension of the conductive pad according to the width (short side) dimension of the piezoelectric vibrator, the package has high versatility. Moreover, by mounting the piezoelectric vibrating plate at the position closest to each of the protrusions in accordance with the distance between the lead-out electrodes of the piezoelectric vibrator, the piezoelectric vibrating plate is positioned so as to be arranged in the center of the accommodating portion of the ceramic package. The package has high mounting accuracy.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described with reference to FIGS. 1 and 2 by taking a surface mount type crystal resonator as an example. FIG. 1 is a perspective view showing the present embodiment, and shows a state in which a crystal vibration plate (piezoelectric vibration plate) is mounted in a storage portion. FIG. 2 is a plan view showing a state in which the crystal diaphragm is mounted in FIG. It should be noted that the same components as in the related art will be described using the same numbers.

The surface mount type crystal oscillator is a rectangular parallelepiped-shaped crystal package, and has a ceramic package 1 having a concave-shaped storage portion 1a having an opening at the top, and a crystal vibrating plate which is a piezoelectric vibration element accommodated in the package. 2 and a metal lid (not shown) joined to the opening of the package.

The crystal vibrating plate 2 housed in the ceramic package 1 has a tuning fork shape, and has excitation electrodes (not shown) formed on the legs and lead electrodes from the respective excitation electrodes formed on the base. 21 and 22 are formed. Each lead electrode 21, 22 is electrically and mechanically joined to a conductive pad 12, 13 described later.

The ceramic package 1 is concave in cross section and has a bottomed storage portion 1a and a bank (side wall) 10 around the storage portion. A circumferential metal seal portion 11 is formed on the upper surface of the bank 10. Metal seal part 11
Is composed of a metallized layer made of tungsten or the like and a metal film layer formed on the metallized layer. The metal film layer is composed of, for example, a nickel plating layer in contact with the metallization layer and an extremely thin gold plating layer formed on the nickel plating layer.

The storage portion 1a has step portions 1b and 1c at the bottom thereof, and conductive pads 12 and 13 are formed on the upper surfaces of the step portions. The conductive pad has a structure in which a metallized layer using a ceramic lamination technique is plated with nickel or the like, and has base portions 121 and 131 and rod-shaped protrusion portions 122 and 132 on which a crystal diaphragm is mounted. The base is formed wider than the protrusion, and a via V that leads to an external terminal is formed inside the base.

Further, the protrusion is set to have a width narrower than the width of the lead-out electrode formed on the crystal vibrating plate, so that the conductive bonding material applied to the protrusion can be applied to the protrusion and the ceramic package. With the boundary between and, the surface tension is likely to cause swelling, which is preferable in order to promote the wraparound to the side wall of the piezoelectric vibration plate. In particular, the holding strength was most improved when the width dimension of the protruding portion was set to about 70 to 90% of the width dimension of the lead electrode.

By the way, in this embodiment, the via V and the bases 121 and 131 formed to surround the via with a size larger than the via are closest to the corners of the ceramic package in the step. Inner wall angle 1 of the bank
The protrusions 122 and 132 are formed in the vicinity of the bases 1b and 11c and toward the center of the crystal diaphragm from the base (in this embodiment, the inner wall angle 11
It extends in the direction of the corners 12b and 12c of the step facing the b and 11c. As a result, even crystal oscillators having different widths can be mounted while being shifted in the extension direction of the protrusions up to the positions of the intervals of the protrusions that match the intervals of the lead-out electrodes of the crystal oscillator. Since it is not necessary to change the width of the conductive pad according to the width (short side) of the child, the package has high versatility. Moreover, when a crystal diaphragm is automatically mounted on the conductive pad by an image processing recognition device, etc., the crystal diaphragm should be mounted at the position closest to each protrusion according to the interval of the lead-out electrodes of the crystal resonator. Since the ceramic package is positioned so as to be arranged in the center of the storage portion of the ceramic package, the package has high mounting accuracy.

Further, in this embodiment, by forming the via in the vicinity of the inner wall angle of the bank in the step, the weakness of mechanical strength in the vicinity of the via is formed between the banks of two adjacent sides. Can be supplemented with. Furthermore, since the base portion of the conductive pad is formed larger than the via, it is possible to eliminate the influence of the positional shift when forming the via, and to secure the reliable electrical connection with the external terminal.

As described above, the lead-out electrode 2 of the crystal diaphragm 2
1, 22 and the protrusions 122, 132 of the conductive pads are electro-mechanically joined by the solder D. Although not shown, the metal lid (not shown) is mounted on the metal seal portion 11, and in this state, the metal lid and the metal seal portion are melted by electron beam welding or beam welding such as laser to hermetically seal. To do.

A second embodiment according to the present invention will be described with reference to FIG. 3 by taking a surface mount type crystal resonator as an example. FIG. 3 is a perspective view showing the present embodiment. Since the basic configuration is the same as that of the above-described embodiment, the same components will be described using the same numbers, and a partial description will be omitted.

The surface mount type crystal unit is a rectangular parallelepiped as a whole, and has a ceramic package 1 having a recessed upper portion, a tuning fork type crystal vibrating plate 2 which is a piezoelectric vibrating element housed in the package. Although not shown,
A metal lid joined to the opening of the package.
The present embodiment is different from the first embodiment in the configuration of the protruding portion that holds the crystal diaphragm. In the projecting portions 123 and 133, the metallized layers are laminated to increase the thickness with respect to the base portion and form the joint surface high. These shapes can be easily created by a screen printing method or the like. By forming only the protrusions high, the amount of solder applied is adjusted according to the area of the protrusions, and the holding contact of the crystal diaphragm becomes small, so vibration from the crystal diaphragm to the ceramic package is reduced. It has a configuration that suppresses leakage and contributes to further improvement of electrical characteristics.

A third embodiment according to the present invention will be described with reference to FIG. 4 by taking a surface mount type crystal resonator as an example. FIG. 4 is a plan view showing the present embodiment in a state where the crystal diaphragm is not mounted. Since the basic configuration is the same as that of the above-described embodiment, the same components will be described using the same numbers, and a partial description will be omitted. In the present embodiment, a modified example of the conductive pad portion is shown. 12
Reference numerals 1a, 131a, 121b, and 131b denote base portions, and 122a, 132a, 122b, and 132b.
Each indicate a protrusion.

In the above description, a crystal oscillator is illustrated as an example of the piezoelectric vibrating device, but in the above embodiment, for example, an IC that constitutes an oscillation circuit is attached to the lower space of the crystal vibrating plate, and necessary wiring is provided. Then, the crystal oscillator may be configured, or the present invention can be applied to other piezoelectric vibrating devices such as a crystal filter including one element or multiple elements. Further, the ceramic package is not limited to the concave shape, but can be applied to a plate shape having a reverse concave lid.

[Brief description of drawings]

FIG. 1 is a perspective view according to a first embodiment.

FIG. 2 is a plan view showing a state in which a crystal diaphragm is mounted in FIG.

FIG. 3 is a perspective view according to a second embodiment.

FIG. 4 is a plan view according to a third embodiment.

FIG. 5 is a diagram showing a conventional example.

FIG. 6 is a diagram showing a conventional example.

[Explanation of symbols]

1 Ceramic package 10 bank 11 Metal seal part 2 Crystal diaphragm (piezoelectric diaphragm) 12, 13 Conductive pad

─────────────────────────────────────────────────── ─── Continued Front Page (51) Int.Cl. ⁷ Identification Code FI Theme Coat (Reference) H03H 9/02 H01L 41/18 101A

Claims (2)

[Claims] 1. A ceramic package having a conductive pad formed thereon is used, and a piezoelectric vibration plate having an excitation electrode and a lead-out electrode for connecting the excitation electrode to the outside is mounted on the upper surface of the conductive pad and held by a conductive bonding material. In the piezoelectric vibrating device, the conductive pad has a base portion that is connected to an external terminal and a protruding portion that holds a vicinity of an end portion of the piezoelectric vibrating plate, and the base portion is formed wider than the protruding portion. Piezoelectric vibration device characterized by being 2. The piezoelectric vibrating device according to claim 1, wherein the protruding portion extends toward the center of the piezoelectric vibrating plate and in a direction in which the protruding portions approach each other.