JPH11234079A - Chip-type piezoelectric component - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the reliability of a chip-type piezoelectric component where sealing plates are stacked on both faces of a piezoelectric element plate. SOLUTION: Conductor layers 61a, 61b, 62a and 62b are formed on terminal electrodes 51 and 52 which are the main faces of a piezoelectric element plate 10. Sealing plates 21 and 22 are stacked on both faces of the piezoelectric element plate, where the conductor layers are formed with insulating adhesive. Adhesive is inserted between the conductor layer and the sealing plates. The conductor layers and the terminal electrodes on the piezoelectric element plate are connected electrically to mounted electrodes 31a and 31b provided for the sealing plates. It is preferable that the thickness of the conductor layers be 3-100 μm, and the shortest distance between the conductor layers and the vibration clearance part of the sealing plates be not less than 100 μm. The conductor layers may be formed on the whole terminal electrodes. Thus, the reliability of electrical connections is improved while mechanical strength and sealing ability are held.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a chip-type piezoelectric component such as a piezoelectric resonator and a piezoelectric filter, and more particularly to a chip-type piezoelectric component capable of improving reliability.

[0002]

2. Description of the Related Art Conventionally, in piezoelectric components, sealing plates have been bonded to both main surfaces of a piezoelectric element plate on which vibrating electrodes are formed for the purpose of protecting the piezoelectric element plate or suppressing unnecessary vibration. A chip-type piezoelectric component having an external electrode for mounting formed on an outer peripheral portion of a sealing plate is used. Such a piezoelectric component can be reduced in size as compared with a piezoelectric component having a configuration in which a piezoelectric element is sealed in a container, so that the mounting space can be reduced. In order to manufacture such a chip-type piezoelectric component, a piezoelectric element plate and a sealing plate are laminated, and then a terminal electrode (ie, a lead electrode) on the piezoelectric element plate and a mounting electrode ( That is, it is necessary to electrically connect the external electrodes). This electrical connection is made using the cross section of the terminal electrode on the piezoelectric element plate. However, when the terminal electrode is formed by vapor deposition or the like, the cross-sectional area of the electrode is extremely small. The connection area is also reduced. Therefore, there is a problem that a problem such as a defective electrical connection occurs and reliability is reduced.

In order to solve such problems, the following chip-type piezoelectric components of Conventional Examples 1 and 2 have been proposed. Conventional example 1: As shown in FIG. 3, concave portions 8a and 8b are provided at the center portions of two end sides of the sealing plate 2 provided with the vibration gap portion 7.
(Or notches). The other sealing plate has a similar configuration. And the concave portion 8
In a and 8b, the terminal electrode on the piezoelectric element plate and the mounting electrode on the sealing plate 2 are electrically connected by a conductor. With such a configuration, the terminal electrodes on the piezoelectric element plate can be exposed to the concave portions 8a and 8b of the sealing plate, so that the connection area of the electrodes can be increased. Therefore, the reliability of the electrical connection can be improved. (See Japanese Utility Model Application Laid-Open No. 4-34017) Conventional Example 2: An adhesive for bonding the piezoelectric element plate and the sealing plate is a conductive adhesive in the vicinity of the terminal electrode, and the other is an insulating adhesive. Thereby, the reliability of the electrical connection is improved. (See JP-A-3-265207)

[0004]

However, in the above-described chip type piezoelectric component of the prior art example 1, the sealing plate is thin due to the concave portion or the notch portion for electrically connecting the terminal electrode and the external electrode. Or the piezoelectric element plate is exposed. Therefore, when the chip-type piezoelectric component is mounted or when it comes into contact with another component, an impact may be applied to the concave portion or the cutout portion to cause damage or breakage. When such damage or breakage occurs, the reliability of the electrical connection is impaired, and cracks progress from the damaged portion, thereby impairing the sealing property.
Further, in the chip-type piezoelectric component of Conventional Example 2 in which the electrical connection between the terminal electrode and the external electrode is made by the conductive adhesive, the conductive adhesive generally has a lower adhesive strength than the insulating adhesive. Therefore, there is a problem that the film is easily peeled off by an impact or the like, and the reliability of the electrical connection and the sealing property is not sufficiently satisfied. Further, since it is necessary to apply two types of adhesives, that is, conductive and insulating, with high precision, it is necessary to pay attention when applying the adhesive during manufacturing.

[0005] As described above, the conventional chip-type piezoelectric components are not always sufficiently satisfactory in electrical connection, sealing performance, reliability of mechanical strength, and easiness of manufacture. Did not. The present invention has been made in view of the problems of the conventional example, and has as its object to provide a chip-type piezoelectric component that has high reliability in electrical connection, sealing property, and mechanical strength, and that is easy to manufacture. It is to provide.

[0006]

In order to achieve the above-mentioned object, a chip-type piezoelectric component according to the present invention is characterized in that a conductive material is provided at least in the vicinity of a connection portion with a mounting electrode on a terminal electrode formed on a piezoelectric element plate. Forming a body layer so that the conductor layer and the terminal electrode are electrically connected to the mounting electrode, and wherein the conductor layer and the sealing plate are bonded with an insulating adhesive. I have. In the chip-type piezoelectric component of the present invention, the shortest distance between the conductor layer and the vibration gap of the sealing plate is preferably set to be larger than the thickness of the conductor layer, particularly,
It is preferable that the thickness of the conductor is 3 to 100 μm, and the shortest distance between the conductor layer and the vibration gap of the sealing plate is 100 μm or more.

[0007]

FIG. 1 shows a chip-type piezoelectric component according to an embodiment of the present invention. FIG. 1 (A) is an external perspective view of the component, and FIG. 1 (B) is a perspective view of the chip-type component. It is a perspective view of the piezoelectric element plate of FIG. In the figure, 10 is a piezoelectric element plate, 21 and 22 are sealing plates laminated with the piezoelectric element plate 10 interposed therebetween, 31a and 31
b denotes a mounting electrode, 41 and 42 denote vibration electrodes formed on the front and back of the piezoelectric element plate, and 51 and 52 denote terminal electrodes (lead electrodes). A terminal electrode 51 on the piezoelectric element plate 10,
52, a conductor layer 61a formed by applying a conductive material on the terminal electrode,
61b, 62a and 62b are provided. An insulating adhesive for laminating and bonding the piezoelectric element plate and the sealing plate is also interposed between these conductor layers and the sealing plates 21 and 22. As shown in FIG. 1B, the conductor layers are not formed at the two corners of each of the front and back surfaces of the piezoelectric element plate 10, but as shown in FIG.
2 may be formed in a rectangular shape so as to cover the entirety, and may be formed in an arbitrary shape.

The conductor layers 61a, 61b, 62a, 62b
(Or 61, 62) preferably has a thickness of about 3 to 100 μm. This is for the following reason. 4 to adhere the sealing plate and the piezoelectric element plate
Since an insulating adhesive having a thickness of about 0 to 50 μm is used, when the thickness of the conductive layer exceeds 100 μm, the insulating adhesive does not flow into the periphery of the conductive layer due to its flow characteristics. A portion is formed, thereby deteriorating the sealing property of the component. On the other hand, if the thickness of the conductor layer is less than 3 μm, the effect of the recoating is not sufficient, and sufficient reliability of the electrical connection cannot be obtained.

The piezoelectric element plate 10 and the sealing plates 21 and 22
It is preferable that the conductor layer is separated from the ends of the vibration gaps of the sealing plates 21 and 22 by 100 μm or more in a state where the layers are stacked. This is because even when a depletion portion where the adhesive does not flow around the conductor layer occurs, the thickness of the conductor layer is 100 μm.
m, the range of the depletion portion is at most 100 μm from the end of the conductor layer. Therefore, if the conductor layer is formed at a distance of 100 μm or more from the vibration gap, the gap between the vibration gap and the depletion portion This is because a portion closely contacted with the insulating adhesive is always formed, and the sealing property can be maintained. If the conductor layer is brought within 100 μm of the vibration gap, the sealing property will be deteriorated, and the reliability may be reduced. These conductor layers are formed by a silver paste, a conductive adhesive, or the like that cures at a low temperature.

The chip-type piezoelectric component of the present invention is basically formed by the following steps a to f. a. Vibration electrodes 4 are provided on both main surfaces of the piezoelectric element plate 10, respectively.
An electrode pattern including the first and second electrodes 42 and the terminal electrodes 51 and 52 is formed. b. Conductor layers 61a, 61b on terminal electrodes 51, 52,
62a and 62b or 61 and 62 are formed. c. A sealing plate having a depression, that is, a vibration gap is formed at a position facing the vibration electrodes 41 and. d. The mounting electrodes 31a and 31b are formed on the sealing plates 21 and 22. e. The sealing plates 21 and 22 are laminated and bonded to both surfaces of the piezoelectric element plate 10. f. Terminal electrodes 51 and 52 of piezoelectric element plate 10 and sealing plate 2
The first and second mounting electrodes 31a and 31b are electrically connected. It will be clear that steps af need not necessarily be in that order. For example, steps c and d may be performed before steps a and b, or may be performed simultaneously. Further, step d may be performed before step c.

As the material of the piezoelectric element plate 10, a piezoelectric material such as lead titanate ceramics or lithium niobate single crystal is used, and it is appropriately selected according to the specifications such as the frequency of the piezoelectric component. As the material of the sealing plates 21 and 22, inorganic materials such as alumina, cordierite, and strontium titanate-based dielectric ceramics are preferable because of their high sealing properties. In addition, some inorganic materials can provide a capacitance, and using such a material makes it possible to provide a chip-type piezoelectric component with a built-in capacitance. An epoxy resin or the like, which is easy to process, can be used as the sealing plates 21 and 22. However, it is necessary to keep in mind that heat resistance is inferior to that of an inorganic material.

In step a, the electrode pattern formed of the vibrating electrodes 41 and 42 and the terminal electrodes 51 and 52 on the piezoelectric element plate 10 is etched by depositing or sputtering silver or the like, printing resist ink, and then etching. Formed by the method. In step b, the conductor layer 6
1a, 61b, 62a, 62b or 61, 62 are formed by printing and heat-treating a silver paste, a conductive adhesive or the like having a property of curing at a low temperature. The shape of the conductor layer may be any shape such as a semicircle, rectangle, trapezoid, etc., but the thickness and the distance from the vibration gap portion are not reduced by the formation of the conductor layer so that the sealing property of the piezoelectric component is not impaired. Must be set as follows.

In step d, the mounting electrodes 31a and 31b on the sealing plates 21 and 22 are formed by baking silver paste, applying a conductive adhesive, electroless plating, forming a metal film by sputtering or vapor deposition, or the like. It is formed. However, in general, it is difficult to say that the conductive adhesive has good solder wettability, and the electrode may be deteriorated only by electroless plating. It is desirable to form a tin film by electrolytic plating or the like. Note that such electrolytic plating can also be performed after connecting the external electrode and the internal electrode, that is, the mounting electrode and the terminal electrode. In step e, when the sealing plates 21 and 22 are laminated on both main surfaces of the piezoelectric element plate 10 by bonding, an epoxy-based adhesive or a polyimide-based adhesive is used from the viewpoint of sealing properties and heat resistance. Is preferred.

In step d, the terminal electrodes 51 and 52 on the piezoelectric element plate 10 and the conductor layers 61a, 61b and 62
a, 62b or 61, 62 and mounting electrode 3 on sealing plate 1
In order to electrically connect the conductors 1a and 31b, a silver paste or a conductive adhesive which is a conductor and can be cured at a low temperature is used, and the conductor is screen-printed or dipped to perform the electrical connection. In addition, techniques such as electroless plating, sputtering, and vapor deposition can also be employed. Further, in order to increase the mechanical strength of the conductor electrically connecting the terminal electrodes 51, 52 and the mounting electrodes 31a, 31b, it is preferable that the conductor is coated with a metal film by electrolytic plating.

Although the chip-type piezoelectric component of the present invention shown in FIG. 1 can be manufactured independently for each element, a piezoelectric element wafer on which electrode patterns for multiple elements are formed and a vibration for multiple elements are formed. According to a method of laminating and bonding a sealing plate having a void portion formed therein and cutting it into one device using a dicing machine, mass production can be achieved, and device production costs can be reduced. The chip type piezoelectric component was experimentally manufactured based on the technical idea of the present invention, and its characteristics and the like were measured. The results will be described below.

EXPERIMENTAL EXAMPLE 1 A lead titanate-based piezoelectric material was 30 mm × 40 mm × 15 mm.
After sintering into a block shape and baking, it was sliced into a flat plate shape and polished with a lapping machine to a thickness of 0.22 mm to form a piezoelectric element plate. Then, silver electrodes were vapor-deposited and polarized on both surfaces of the piezoelectric element plate, electrode patterns for 50 elements were printed with a resist, unnecessary patterns were removed by etching, and then the resist was removed by washing. Note that the electrode pattern for one element is a pattern including a vibrating electrode and a terminal electrode connected to the vibrating electrode, as shown in FIG. Thereafter, a conductor layer of 50 elements having a thickness of 40 μm was formed on the terminal electrode of the electrode pattern on the piezoelectric element plate using an epoxy-silver paste. Conductor layers for one element are provided at two corners of the surface as shown in FIG.
/ 4 circular, 710 μm from the end of the vibrating gap in the laminated state
It was arranged to be separated. A conductor layer was similarly formed on the back surface of the piezoelectric element plate.

Next, alumina powder was mixed with an organic binder and granulated, and the resulting mixture was pressed into a plate shape so as to form a sealing plate for 50 elements and fired. At this time, in the press working, a concave portion having a depth of 0.15 mm was provided in a portion of the piezoelectric element plate facing the vibration electrode, so that a vibration gap portion was formed. Furthermore, in order to improve the adhesion to the piezoelectric element plate, the surface on which the vibration gap was formed was polished to a thickness of 0.5 mm. Then, two mounting electrodes were printed with a paste containing a silver-palladium alloy on the surface where the vibration gap was not provided and baked. Thus, two sealing plates for 50 elements were formed.

Then, one formed piezoelectric element plate is
Sandwiched between two sealing plates, bonded and laminated with an insulating epoxy-based adhesive, and
The device was divided into elements. The adhesive has an average thickness of 40
μm, and was also applied to the portion corresponding to the conductor layer of the piezoelectric element plate. The mounting electrodes on the two sealing plates of one divided element were electrically connected by applying a conductive paste by screen printing. At this time, the conductive paste was also applied to the cross-section where the conductive layer on the piezoelectric element plate was exposed on the side. Thereafter, barrel plating was performed to deposit a solder layer on the conductive paste and the mounting electrode made of silver / palladium, thereby producing 50 chip-type piezoelectric components having the configuration shown in FIG.

By repeating the above steps, 10
Make 0 chip-type piezoelectric components, and use a vector impedance analyzer to calculate 30M of 100 components.
The frequency-impedance characteristics near Hz and the impedance characteristics at the resonance frequency were measured. Then, as a result of the measurement, a part having a waveform observed was regarded as a good connection part, and a part having no waveform observed or extremely poor was regarded as a part having a disconnection as a poor connection part.

Further, in order to confirm the sealing property, the well-connected parts were exposed to steam at 130 ° C. and 2 atm for 24 hours.
Immediately thereafter, the impedance characteristics were measured. as a result,
Those whose resonance frequency increased by 20% or more compared to those before the exposure test were regarded as poor sealing parts, and the others were regarded as good sealing parts. This is due to the fact that, in a component having a low sealing property, the resonance frequency fluctuates due to the occurrence of poor oscillation as a result of water vapor penetrating into the vibrating gap from a pinhole or the like and condensing. Furthermore, the well-sealed parts were put into a pot mill together with distilled water and rotated for 2 hours to carry out a barrel test, and thereafter an appearance inspection was carried out. Barrel defective parts in which damages such as breakage of the sealing plate and the piezoelectric element plate and peeling of the sealing plate were found in the appearance inspection were determined.

The connection failure rate, the sealing failure rate, and the barrel failure rate were defined as follows, and the respective failure rates were calculated. Connection failure rate (%) = connection failure parts / total parts (10
0) × 100 defective sealing rate (%) = number of defective sealing parts / number of good connection parts × 100 barrel defective rate (%) = number of defective barrel parts / number of good sealing parts × 100

EXPERIMENTAL EXAMPLE 2 100 chip-type piezoelectric components were manufactured in substantially the same manner as in Experimental Example 1 above, except that the conductor layer on the piezoelectric element plate was rectangular as shown in FIG. , Its thickness is 8
0 μm and the shortest distance from the vibration gap is 120
μm. The disconnection test, the sealing test, and the barrel test were performed on the manufactured 100 parts in the same manner as in Experimental Example 1, and the respective defective rates were calculated.

In order to verify the function and effect of the chip-type piezoelectric component of the present invention, the following comparative examples were prepared and the defect rates were calculated in the same manner. In Comparative Examples 1 and 2, the thickness of the conductor layer and the shortest distance between the vibrating gap and the conductor layer were set to be equal, though they were substantially in line with the technical idea of the present invention. Comparative Examples 3 and 4 correspond to Conventional Examples 1 and 2 described above.
Was manufactured using the same material and size as in the above-described Experimental Example 1. Comparative Example 1 100 chip-type piezoelectric components were produced in substantially the same manner as in Experimental Example 1 described above, except that the conductor layer on the piezoelectric element plate had a thickness of 120 μm, a rectangular shape, and The minimum distance from the vibration gap was 120 μm. A disconnection test, a sealing test, and a barrel test were performed on the manufactured 100 parts in the same manner as in Experimental Example 1, and the respective defective rates were calculated.

COMPARATIVE EXAMPLE 2 100 chip-type piezoelectric components were manufactured in substantially the same manner as in the above-described Experimental Example 1, except that the thickness of the conductor layer on the piezoelectric element plate was 80 μm and the shape was rectangular. And the distance from the vibration gap portion was set to 80 μm at the shortest. A disconnection test, a sealing test, and a barrel test were performed on the manufactured 100 parts in the same manner as in Experimental Example 1, and the respective defective rates were calculated.

COMPARATIVE EXAMPLE 3 100 chip-type piezoelectric components were produced in substantially the same manner as in the above-described Experimental Example 1, except that the conductor plate was not provided, and the conventional example shown in FIG. 0.6mm as in 1
After forming a semicircular concave portion and laminating, a silver paste was applied to the entire end face of the portion where the concave portion was formed, thereby making electrical connection. A disconnection test, a sealing test, and a barrel test were performed on the manufactured 100 parts in the same manner as in Experimental Example 1, and the respective defective rates were calculated.

Comparative Example 4 100 chip-type piezoelectric components were produced in substantially the same manner as in the above-mentioned Experimental Example 1, except that no conductive layer was provided.
As the adhesive used for lamination, an epoxy-based conductive adhesive containing silver is used for the part overlapping the terminal electrodes on the piezoelectric element plate, and a normal epoxy-based insulating adhesive is used for the other parts. Was. At that time, in order to prevent the two kinds of adhesives from being mixed, a conductive adhesive was applied on the piezoelectric element by screen printing, and an insulating adhesive was applied on the sealing plate by screen printing. A disconnection test, a sealing test, and a barrel test were performed on the manufactured 100 parts in the same manner as in Experimental Example 1, and the respective defective rates were calculated.

Experimental Examples 1 and 2 and Comparative Example 1
Table 4 shows the connection failure rate (%), sealing failure rate (%), and barrel failure rate (%) obtained in Tables 1 to 4. Table 1 also shows the shortest distance (μm) between the vibration gap and the conductor layer and the thickness (μm) of the conductor layer in Experimental Examples 1 and 2 and Comparative Examples 1 and 2. .

[Table 1]Table 1  Connection failure rate Sealing failure rate Barrel failure rate Shortest length Thickness Experimental Example 1 0 0 1 710 40 Experimental Example 2 0 4 0 120 80 Comparative Example 1 0 22 1 120 120 Comparative Example 2 0 34 2 80 80 Comparative Example 3 40 14 ―― ―― Comparative Example 4 0 20 42 ―― ――

As is clear from Table 1, Experimental Examples 1 and 2
In Comparative Examples 1, 2 and 4, no disconnection occurred, but in Comparative Example 1 (the structure in which the terminal electrode and the mounting electrode were connected by the recess provided in the sealing plate), the connection was incomplete. Was 4%. In Comparative Examples 1 and 2, the sealing property was poor. However, this was because the thickness of the conductor layer and the shortest distance between the conductor layer and the vibration gap were equal to each other. This is because the adhesive layer was not formed around the conductor layer due to the body layer being too thick or the conductor layer being too close to the vibration gap, resulting in a depleted portion. is there. The poor sealing property of Comparative Example 4
This is because the conductive adhesive has a lower adhesive strength than a normal epoxy-based insulating adhesive, and as a result, the sealing property of the portion using the conductive adhesive is deteriorated. further,
In Comparative Examples 3 and 4, barrel failure has occurred.
In the barrel failure, in the comparative example 3, damage occurs to the concave portion due to contact between components during the barrel test, and
In Comparative Example 4, the sealing plate was peeled off during the barrel test due to the low adhesive strength of the conductive adhesive.

As described above, by providing the conductor layer on the terminal electrode of the piezoelectric element plate, the cross-sectional area of the electrical connection between the terminal electrode and the mounting electrode on the sealing plate can be increased. If the layer is set to an appropriate thickness and size so that an insulating adhesive is also interposed between the conductor layer and the sealing plate, the electrical connectivity, sealing property, and barrel resistance of the chip-type piezoelectric component are improved. It is clear from the results of the above experiments that the (mechanical strength) is improved. Therefore, according to the chip type piezoelectric component of the present invention, the reliability of the product is remarkably improved as compared with the conventional example.

[Brief description of the drawings]

FIG. 1 is a perspective view of a chip-type piezoelectric component according to an embodiment of the present invention and a piezoelectric element plate on which a conductive layer is formed.

FIG. 2 is a perspective view of a piezoelectric element plate on which a conductor layer of another form is formed in the chip-type piezoelectric component of the present invention.

FIG. 3 is a perspective view for explaining a conventional example of a chip type piezoelectric component.

Claims (3)

[Claims] 1. A piezoelectric element plate having an electrode pattern formed of a vibrating electrode and a terminal electrode connected to the vibrating electrode formed on both main surfaces, and bonded to both surfaces of the piezoelectric element plate so as to sandwich the piezoelectric element plate. A chip-type piezoelectric component comprising: two sealing plates provided with a vibration gap at a position facing the vibration electrode; and a mounting electrode provided to surround the sealing plate. A conductive layer is formed at least in the vicinity of a connection portion with the mounting electrode, and the conductive layer and the terminal electrode are both electrically connected to the mounting electrode. A chip-type piezoelectric component, wherein the plate and the plate are bonded with an insulating adhesive. 2. The chip-type piezoelectric component according to claim 1, wherein the shortest distance between the conductor layer and the vibration gap of the sealing plate is set to be larger than the thickness of the conductor layer. Chip type piezoelectric parts. 3. The chip-type piezoelectric component according to claim 2, wherein the thickness of the conductor is 3 to 100 μm, and the shortest distance between the conductor layer and the vibration gap of the sealing plate is 100 μm.
A chip-type piezoelectric component characterized by the above.