JP4122512B2 - Piezoelectric vibration device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a piezoelectric vibration device using a ceramic package and holding a piezoelectric diaphragm by a conductive resin adhesive, and more particularly to a structure of a lead electrode of the piezoelectric diaphragm.
[0002]
[Prior art]
Examples of piezoelectric vibration devices that require hermetic sealing include a crystal resonator, a crystal filter, and a crystal oscillator. All of these are hermetically sealed in order to form a metal thin film electrode on the surface of a crystal diaphragm (piezoelectric diaphragm) and protect the metal thin film electrode from the outside air. Due to the demand for surface mounting of parts, these quartz application products have been increasingly housed in ceramic packages, and by selecting an appropriate hermetic sealing method, good airtightness can be secured. it can.
[0003]
For example, as disclosed in Patent Document 1, the ceramic package as a whole has a rectangular parallelepiped shape in which a storage portion is formed at the center portion, and a conductive pad is formed at the bottom of the storage portion. This conductive pad is led to an external terminal by a via or castellation. The quartz diaphragm is formed with an excitation electrode and a lead-out electrode for connecting the excitation electrode to the outside. The lead-out electrode of the piezoelectric diaphragm is mounted on the upper surface of the conductive pad of the package, and electrically connected with a conductive resin adhesive. Mechanically connected. Then, the lid is covered and hermetically sealed.
[0004]
[Patent Document 1]
JP-A-9-199972 [0005]
[Problems to be solved by the invention]
Recently, as electronic devices are further reduced in size and weight, piezoelectric vibration devices are also required to be miniaturized, and accordingly, the size of the piezoelectric vibration plate housed in the package is also reduced. However, when the package becomes smaller, the holding area also becomes smaller, and sufficient bonding strength between the package and the piezoelectric diaphragm cannot be secured, and the impact resistance is remarkably lowered. As a conventional method for this, it is conceivable to increase the bonding strength by increasing the amount of conductive resin adhesive applied. However, in recent miniaturized packages, the holding area is also small, and there is a risk of short circuit between terminals (electrodes). There was a problem that the property became extremely high.
[0006]
Therefore, in the above-mentioned Patent Document 1, it is proposed to improve the bonding strength by forming an electrodeless region in a part of the lead-out electrode. However, when the package becomes smaller, it is not possible to secure a region where the conductive resin adhesive is overcoated from the upper part of the piezoelectric diaphragm, and the area is held only by the undercoat conductive resin adhesive interposed between the piezoelectric diaphragm and the conductive pads of the package. In some cases, there was a problem that sufficient bonding strength could not be obtained.
[0007]
The present invention was made to solve the above problems, and even if the application region of the conductive resin adhesive is limited with the downsizing of the package, the holding strength of the crystal diaphragm can be improved, An object of the present invention is to provide a more reliable piezoelectric vibration device having better drop impact resistance.
[0008]
[Means for Solving the Problems]
In order to solve the above-mentioned problems, according to the present invention, a package having a conductive pad and a quartz diaphragm having an excitation electrode and a lead electrode for connecting the excitation electrode to the outside are provided. The quartz diaphragm is mounted on the upper surface of the conductive pad at an end portion of the quartz diaphragm on which the lead-out electrode is formed, and a conductive resin adhesive interposed between the quartz diaphragm and the conductive pad. A piezoelectric vibration device that is held, wherein the lead-out electrode has a conductive region that is electrically connected to the conductive pad, an electrodeless region where a surface of the surface of the crystal plate is exposed, and a crystal plane. An unpenetrated pinhole exposing the base material inside the quartz crystal plate is formed in the state, and one or a plurality of pinholes are formed in the electrodeless region, and the pin of the quartz crystal plate is formed Conductive inside the hall Characterized in partially intruding state of the resin adhesive, by the conductive resin adhesive, conductive region and the non-electrode region of the leading electrode of the quartz plate, the conductive pads of the package is joined to each other And
[0009]
According to a second aspect of the present invention, the pinhole is formed symmetrically on both the front and back surfaces of the crystal diaphragm.
[0010]
According to a third aspect of the present invention, the quartz diaphragm is composed of a tuning fork type quartz vibrating piece.
[0011]
【The invention's effect】
According to the present invention, the conductive region and the non-electrode region of the lead-out electrode of the crystal diaphragm and the conductive pad of the package are bonded to each other by the conductive resin adhesive. In addition to securing the surface tension of the quartz diaphragm, the interfacial tension (bonding force at the interface) with the conductive bonding material is increased, thereby improving the bonding strength. In addition, since a part of the conductive resin adhesive has entered the pinhole of the quartz diaphragm, an anchor effect is produced, and the mechanical holding strength of the quartz diaphragm is further improved.
[0012]
In particular, in addition to the above effects, the formation of the non-electrode region exposed green body of the plane of the quartz plate, and a pin hole to expose the interior of the matrix of the quartz plate in the same area, the machine from conductive region Electrodeless region with strong mechanical bonding strength and pinhole with the strongest mechanical bonding strength are formed in stages, and the synergistic effect due to the interfacial tension (bonding force of the interface) of the exposed part of the quartz diaphragm and the anchor effect As a result, the mechanical holding strength of the quartz diaphragm is dramatically improved. In particular, the effect is improved by forming a plurality of pinholes in one electrodeless region. In addition, the conduction region can be easily designed and formed with the lead-out electrode having a limited area, and the conduction region can be secured, so that deterioration of the electrical characteristics of the piezoelectric vibrating device due to an increase in contact resistance can be suppressed. In addition, since a non-penetrating pinhole that exposes the inner surface of the crystal diaphragm is formed with the crystal plane of the crystal appearing, the etching proceeds even if it is continuously immersed in the crystal etching solution. It is possible to use an etching stop action that never happens. For this reason, since pinholes can be formed without depending on the etching processing time, manufacturing can be simplified.
[0013]
Therefore, even if the application area of the conductive resin adhesive is limited due to the downsizing of the package, the holding strength of the quartz diaphragm can be improved, and more reliable piezoelectric vibration with better anti-drop impact characteristics. A device can be provided.
[0014]
According to claim 2, in addition to the above effects, the recess, because it is formed symmetrically on both the front and back surfaces of the quartz plate, eliminating the front and back direction when mounting the quartz plate to a package, productivity Can be increased.
[0015]
According to the third aspect, the present invention can also be applied to a piezoelectric vibration device using a tuning fork type crystal vibrating piece.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
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 diaphragm (piezoelectric diaphragm) is mounted on a storage unit. FIG. 2 is a cross-sectional view taken along the line AA in a state where the crystal diaphragm of FIG. 1 is mounted. FIG. 3 is a bottom view of the crystal diaphragm showing the first embodiment. FIG. 4 is a bottom view showing a part of a crystal diaphragm showing a modification of the first embodiment.
[0017]
The surface-mount type crystal resonator has a rectangular parallelepiped shape as a whole, and has a ceramic package 1 having a concave storage portion 1a having an open top, a crystal vibration plate 2 that is a piezoelectric vibration element housed in the package, Although not shown in the drawing, it comprises a metal lid joined to the opening of the package.
[0018]
The ceramic package 1 has a concave shape when viewed in cross section, and has a bottomed storage portion 1a and a bank portion (side wall) 10 around the storage portion. A circumferential metal seal 11 is formed on the top surface of the bank 10. The metal seal portion 11 includes 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 metallized layer and an ultrathin gold plating layer formed on the nickel plating layer.
[0019]
The bottom portion of the storage portion 1a has step portions 1b and 1c, and conductive pads 12 and 13 are formed on the upper surface of the step portion. The conductive pad has a structure in which a metallized layer using a ceramic lamination technique is plated with nickel or the like, and is led to an external terminal by a via or a castellation (not shown).
[0020]
The crystal diaphragm 2 housed in the ceramic package 1 has a tuning fork shape, and an excitation electrode (not shown) formed on the leg portion and a lead electrode 21 from each excitation electrode formed on one end of the base portion. , 22 are formed. In these electrodes, for example, a gold electrode is formed on top of a chromium base electrode. The lead-out electrodes 21 and 22 include conductive regions 211 and 221 in which electrodes are formed, and a plurality of non-electrode regions 212 and 222 in which the surface of the surface of the quartz crystal plate having a rectangular shape is exposed, Further, a plurality of non-penetrating pinholes 213 and 223 are formed in the non-electrode region so as to expose the substrate inside the crystal diaphragm. These are formed symmetrically on both the front and back surfaces of the crystal diaphragm.
[0021]
The pinhole is formed by reducing the number of pinholes toward the vibration node (or the vicinity of the leg) of the tuning-fork type crystal diaphragm (in FIG. 2, the vicinity of the crystal diaphragm). 2 locations, 3 locations in the center and 3 locations in the vicinity of both ends in the short side), reducing the adverse effects of vibration leakage from the quartz diaphragm to the ceramic package, contributing to further improved electrical characteristics. ing.
[0022]
As a method for forming the pinhole, for example, a tuning fork-shaped outer shape is formed on the quartz diaphragm by etching or the like, and at the same time, the pinholes 213 and 223 are formed. In other words, when a tuning fork type metal pattern is formed on a crystal diaphragm, a tuning fork type outer shape is formed when the crystal diaphragm is etched by not providing a metal resist at the position where the pinhole is to be formed. At the same time, a pinhole is formed in the region of the lead-out electrode of the crystal diaphragm. With regard to this pinhole etching process, by appropriately setting the area of the region where the metal resist is not applied (for example, φ30 as the diameter of the pinhole), a crystal plane appears on the etched surface when the etching proceeds to some extent. Since the etching stop action (e.g., 40 μm as the pinhole depth with respect to the thickness of the crystal diaphragm, eg, 120 μm), the etching does not proceed even if immersed in the crystal etching solution continuously, can be used. Since the pinhole can be formed without depending on the etching processing time for forming the tuning fork type outer shape, the manufacturing can be simplified.
[0023]
Thereafter, all the metal resist for forming the tuning fork type outer shape is removed, electrodes are formed on the entire surface of the quartz plate having the tuning fork type outer shape and the pinholes, and the resist is formed in a predetermined shape. By providing and performing metal etching, excitation electrodes and lead-out electrodes (conduction regions and non-electrode regions) can be formed.
[0024]
At this time, in the first embodiment of the present invention, the pinhole exposing the substrate inside the piezoelectric diaphragm is formed in the vicinity of the center of the electrodeless region where the planar substrate of the piezoelectric diaphragm is exposed. The electrode film (conduction region) is not in contact with the opening end of the pinhole, and there is no problem of electrode peeling or the like in the vicinity of the opening end of the pinhole when metal etching is performed.
[0025]
As shown in FIG. 2, the lead electrodes 21 and 22 of the crystal diaphragm formed in this way are part of the conductive resin adhesive D inside the pinholes 213 and 223 (only 223 is shown in FIG. 2). With the conductive resin adhesive D in a state of entering, conductive regions 211 and 221 (only 221 is shown in FIG. 2) and non-electrode regions 212 and 222 (only 222 are shown in FIG. 2) of the piezoelectric diaphragm. ), The conductive pads 12 and 13 (only 13 is shown in FIG. 2) of the package are bonded to each other. As a result, the quartz diaphragm is more firmly held on one side only by the undercoat conductive resin adhesive interposed between the quartz diaphragm and the conductive pad of the package.
[0026]
As the conductive resin adhesive, for example, a silicon-based or urethane-based one is used, and the interface tension (bonding force at the interface) is influenced by the material of the lead electrode. When a gold electrode is employed on the uppermost surface as in the present invention, the interfacial tension with these conductive resin adhesives (interface bonding force) decreases and the holding strength of the quartz diaphragm decreases. By adopting the configuration, the quartz diaphragm has been dramatically improved.
[0027]
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 and hermetically sealed by beam welding or seam welding.
[0028]
In the lead-out electrode according to the first embodiment, a plurality of electrode bodies in which the substrate on the surface of the quartz crystal plate having a rectangular shape is exposed are exposed to a plurality of electrodeless regions in which the substrate on the surface of the quartz crystal plate is exposed. Although a non-penetrating pinhole is formed, it may be as shown in FIG. That is, in FIG. 4A and FIG. 4B, one pinhole is formed in correspondence with one electrodeless region. In FIG. 4C to FIG. 4G, the conduction region and the non-electrode region are formed in parallel, and a pinhole is formed corresponding to the non-electrode region. In FIG. 4 (h) and FIG. 4 (i), an electrodeless region is formed on the outer periphery of the conduction region, and a pinhole is formed corresponding to the electrodeless region. These configurations may be appropriately combined and formed.
[0029]
Next, a second embodiment according to the present invention will be described with reference to FIG. FIG. 5 is a bottom view of the crystal diaphragm showing the second embodiment. Since the basic configuration is the same as that in the above embodiment, the same components will be described using the same numbers, and a part of the description will be omitted.
[0030]
The present embodiment is different from the first embodiment in that the electrodeless region and the pinhole forming position in the lead-out electrode are separated. That is, the lead-out electrodes 23 and 24 are composed of conductive regions 231 and 241 in which electrodes are formed, and electrodeless regions 232 and 242 in which the surface of the surface of the quartz crystal plate having a rectangular shape is exposed, Further, a plurality of non-penetrating pinholes 233 and 243 are formed in the position surrounding the non-electrode region, exposing the base material inside the crystal diaphragm. These are formed symmetrically on both the front and back surfaces of the crystal diaphragm. In addition to the second embodiment, an electrodeless region may be formed at a position surrounding the pinhole, or the conductive region, the electrodeless region, and the pinhole may be alternately arranged.
[0031]
Next, a third embodiment of the present invention will be described with reference to FIGS. 6 and 7 by taking a surface-mount type crystal resonator as an example. FIG. 6 is a bottom view of the crystal diaphragm showing the third embodiment, and FIG. 7 is a cross-sectional view taken along the line BB of FIG. Since the basic configuration is the same as that of the above-described embodiment, the same reference numerals are assigned to the same components, and a part of the description is omitted.
[0032]
In the present embodiment, the shape of the crystal diaphragm is different from that of the first embodiment. That is, the crystal diaphragm 3 has a tuning fork shape, and has wide portions 31 and 32 and notches 33 and 34 at the base, and groove portions 41 and 42 are formed on the front and back main surfaces of the respective leg portions. Yes. Having these configurations has the following advantages. By forming the wide portions 31 and 32 in the tuning fork base, the area of the lead-out electrodes 23 and 24 can be made larger, and the holding to the package can be performed more firmly. Further, by forming the notches 33 and 34 at the boundary between the tuning fork base and the tuning fork leg, it is possible to reduce the adverse effects of vibration leakage to the package of the quartz crystal plate firmly held by the wide portion. Furthermore, by forming the groove portions 41 and 42 on the front and back main surfaces of each leg portion of the tuning fork, it is possible to provide a crystal resonator with improved CI value characteristics and better electrical characteristics. Each of these components (wide part, notch part, groove) may be formed independently according to the desired characteristics of the crystal resonator.
[0033]
In the first to third embodiments, as the concave portion of the lead-out electrode, an unpenetrated pinhole in which the mechanical strength of the crystal diaphragm is unlikely to be reduced as the size is reduced is exemplified. Can achieve the same effect. Moreover, if it is a large sized crystal diaphragm, a through-hole, a notch, etc. are also employable. In the above description, a tuning fork type crystal resonator is illustrated as an example of the piezoelectric vibration device, but a rectangular vibration piece including a thickness shear vibration such as an AT cut may be used. Further, for example, in the above-described embodiment, an IC constituting an oscillation circuit may be attached to the lower space of the crystal diaphragm, and necessary wiring may be performed to constitute a crystal oscillator, or a crystal composed of one element or multiple elements. It can also be applied to other piezoelectric vibration devices such as filters. In addition, the ceramic package is not limited to a concave shape, and may be applied to a plate shape having a reverse concave lid.
[Brief description of the drawings]
FIG. 1 is a perspective view according to a first embodiment.
2 is a cross-sectional view taken along line AA in a state where the crystal diaphragm of FIG. 1 is mounted.
FIG. 3 is a bottom view of the crystal diaphragm according to the first embodiment.
FIG. 4 is a bottom view showing a part of a crystal diaphragm showing a modification of the first embodiment.
FIG. 5 is a bottom view of a crystal diaphragm according to a second embodiment.
FIG. 6 is a bottom view of a crystal diaphragm according to a third embodiment.
7 is a cross-sectional view taken along line BB in FIG.
[Explanation of symbols]
1 Ceramic package 2, 3 Quartz diaphragm (piezoelectric diaphragm)
12, 13 Conductive pads 21, 22, 23, 24 Derived electrodes

Claims (3)

A package in which a conductive pad is formed; an excitation electrode; and a quartz diaphragm on which a lead-out electrode for connecting the excitation electrode to the outside is formed, and at an end portion of the quartz diaphragm on which the lead-out electrode is formed, The crystal vibration plate is mounted on the upper surface of the conductive pad, and is a piezoelectric vibration device that is held by a conductive resin adhesive interposed between the crystal vibration plate and the conductive pad,
In the lead-out electrode, a conductive region that is electrically connected to the conductive pad, an electrodeless region where the surface of the surface of the crystal plate is exposed, and a base inside the crystal plate with the crystal plane appearing are exposed. Unpenetrated pinholes are formed,
One or more pinholes are formed in the electrodeless region,
In a state where a part of the conductive resin adhesive enters the pinhole of the crystal diaphragm, the conductive resin adhesive allows the conduction region and the non-electrode region of the lead-out electrode of the crystal diaphragm, A piezoelectric vibration device comprising conductive pads bonded to each other. The piezoelectric vibration device according to claim 1, wherein the pinhole is formed symmetrically on both the front and back surfaces of the crystal diaphragm. 3. The piezoelectric vibrating device according to claim 1, wherein the quartz vibrating plate is a tuning fork type quartz vibrating piece.

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