JPH0897668A - Piezoelectric resonator incorporating load capacitor and its manufacture - Google Patents

Abstract

PURPOSE: To obtain a resonator with an excellent sealing performance in which short- circuiting to an electrode is surely prevented by forming a dielectric layer on a 1st capacitance electrode and on a board equivalent to a cap adhesion section. CONSTITUTION: A 1st capacitive electrode 11 is formed in the middle of an upper face of a board 10 and two outer electrodes 12, 13 are formed to an upper end face. Terminal sections 11a-13a of the electrodes 11-13 are led out up to a recessed throughhole 10a formed at both side ridges of the board 10 to be in continuity with the electrode formed on the inner face of the throughhole section 10a. A paste dielectric layer 15 corresponding to a part equivalent to the electrode 11 and the cap adhesion section. Second capacitive electrodes 16, 17 are formed on the layer 15 and part of them is in continuity with the electrodes 12, 13 via a window hole 15C. A resonance element 20 is adhered and fixed onto the electrodes 16, 17. The element 20 is provided with a photoelectric conversion element substrate 21, an electrode 22 is formed thereon and an electrode 23 is formed on its rear side. Both electrodes 22, 23 form a vibration section. The electrodes 22, 23 of the resonance element 20 are in continuity with the 2nd capacitive electrodes 16, 17. A cap 25 is adhered onto the element 20.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a piezoelectric resonator having a built-in load capacitance, and more particularly to a surface mount piezoelectric resonator.

[0002]

2. Description of the Related Art Conventionally, there is a piezoelectric resonator having a built-in load capacitance as shown in FIG. 1, which is used in a Colpitts oscillator circuit. This resonator is provided with an alumina substrate 1, on which a first capacitance electrode 2 and two external electrodes 3 on both sides thereof are formed. The first capacitor electrode 2 and the external electrode 3 are formed on the peripheral surface of the substrate 1 in a spiral shape. A paste-like dielectric 4 is applied on the first capacitance electrode 2, and two second capacitance electrodes 5 are formed on the dielectric 4.
The main part thereof is formed so as to face the dielectric 4, and a part of the main part is electrically connected to the external electrode 3. Two capacitors are composed of the upper and lower capacitance electrodes 2 and 5 with the dielectric 4 interposed therebetween. The resonator element 6 is attached on the second capacitance electrode 5 by a conductive adhesive or the like. After mounting the resonator element 6 on the substrate 1, an alumina cap 7 is bonded to the substrate 1 so as to cover the resonator element 6, and the inside is sealed. FIG. 2 shows the electric circuit.

[0003]

In the case of the surface mount type piezoelectric resonator, the product is required to be liquid-tight because a cleaning process is performed when the piezoelectric resonator is mounted on a printed circuit board. The liquid-tightness is secured by the adhesive 8 that bonds the substrate 1 and the cap 7, but since the electrodes 2 and 3 are formed with a predetermined thickness on the substrate 1 as shown in FIG. However, there is a problem in that unevenness due to the electrode thickness occurs, the adhesive 8 does not fully rotate, and a defective sealing portion 9 as shown in FIG. 4 occurs.

The electrode 3 formed on the substrate 1 by printing or the like has a thickness of about 5 to 20 μm, and the cap 7 itself has a warp of about 30 μm.
A step of about m can be made. A method of increasing the amount of the adhesive 8 applied to absorb this step difference may be considered. However, the extra adhesive 8 flows into the through-hole portion 1a of the substrate 1 and the vibrating portion of the resonator element 6, which causes another defect. There is a problem of becoming. There is also a method of forming a resin layer in advance on a portion of the substrate 1 where the cap 7 is bonded, but there is a drawback that the number of steps is increased and the material cost and the processing cost are increased.

As another method, there is an example of using a metal cap. In the case of the metal cap, the dimensional accuracy is improved as compared with the alumina cap, but it is necessary to prevent short circuit between the cap 7 and the electrode 3. Cap 7 and electrode 3
The adhesive 8 is interposed as an insulating layer between
In the case of a thermosetting adhesive that is generally used, the viscosity once decreases and fluidizes during curing, so that the film thickness of the adhesive 8 may decrease and the cap 7 and the electrode 3 may be short-circuited. .

Therefore, an object of the present invention is to provide a piezoelectric resonator having a built-in load capacitance, which has excellent sealing performance regardless of the material of the cap and which can surely prevent a short circuit with an electrode. Another object is to provide a manufacturing method capable of efficiently manufacturing the above piezoelectric resonator.

[0007]

In order to achieve the above object, the invention described in claim 1 is a substrate made of an insulating material, a first capacitor electrode and two external electrodes formed on the substrate. And a paste-like dielectric layer formed on the first capacitance electrode to a certain thickness, and a main portion of the dielectric layer on the dielectric layer is opposed to the first capacitance electrode with the dielectric layer in between, and a part of each is A second capacitance electrode formed so as to be electrically connected to the external electrode, a resonator element mounted on the second capacitance electrode so that each electrode is electrically connected to the second capacitance electrode, and a resonator element. In a load capacitance built-in piezoelectric resonator including a cap adhered to cover the substrate, the dielectric layer is formed not only on the first capacitance electrode but also on a portion corresponding to the cap adhesion portion on the substrate. It is characterized by

According to a fourth aspect of the present invention, there is provided a method of manufacturing the above-described load capacitance built-in piezoelectric resonator, wherein a first capacitance electrode and two external electrodes are provided on a substrate made of an insulating material. And a step of simultaneously applying a pace-like dielectric layer on the first capacitance electrode and a substrate corresponding to the cap adhesion portion, and two second capacitance electrodes on the dielectric layer. A step of forming a resonator element on the second capacitor electrode so that a main part thereof faces the first capacitor electrode with a dielectric layer in between and a part thereof is electrically connected to the external electrode, and The method includes a step of attaching the two capacitance electrodes so that they are electrically connected to each other, and a step of adhering a cap covering the resonator element such that its opening is in close contact with the cap adhering portion of the dielectric layer.

[0009]

In the case of the invention described in claim 1, the dielectric layer is the first
Since it is formed not only on the capacitor electrode but also on the substrate corresponding to the cap adhesion part, the dielectric layer can absorb the unevenness due to the electrode on the substrate upper surface and the step due to the warp of the cap, and the upper surface of the dielectric layer is Almost flattened. Therefore, if the cap is adhered on the dielectric layer, the adhesive sufficiently wraps between the cap and the substrate even with a relatively small amount of the adhesive, and the sealing failure can be eliminated.

Further, when the cap is made of a metal material, it is necessary to prevent a short circuit with the electrode on the substrate, but as described above, a dielectric layer which is an insulating material is formed on the electrode. Therefore, even if the adhesive film is thin, there is no fear of a short circuit. When the dielectric layer is composed of a glass base, it has an insulation resistance of the order of 10 ¹¹ Ω and has excellent adhesion strength, heat resistance, moisture resistance, airtightness, etc., and thus has excellent long-term reliability.

In the case of the manufacturing method according to the fourth aspect, the dielectric layer is formed not only on the first capacitance electrode but also on the substrate corresponding to the cap bonding portion, so that the number of manufacturing steps is not increased. In particular, when the paste-like dielectric layer is applied on the substrate by pattern printing, the desired dielectric layer can be easily formed only by changing the print pattern so as to include a portion corresponding to the first capacitor electrode and the cap adhesive portion. Can be formed.

[0012]

FIG. 5 shows an example of a piezoelectric resonator with a built-in load capacitance according to the present invention. This resonator is provided with one resonator element and two capacitors used in a Colpitts type oscillation circuit, and its electric circuit is the same as that of FIG.

The substrate 10 is formed of alumina ceramics by sheet molding or tablet molding, and has a thickness of 0.3 to 0.7 m.
m, which is 0.5 mm in this embodiment. The first capacitor electrode 1 is provided at the center of the upper surface of the substrate 10.
1 is formed, and two external electrodes 12 and 1 are provided on both ends of the upper surface.
3 is formed. These electrodes 11 to 13 are formed by a known method such as sputtering, vapor deposition, printing and thermal spraying. In this embodiment, in consideration of fixing strength and solderability, Ag / Pd-based baking type conductive paste is used. ~ 2
It was printed to a thickness of 0 μm and baked at 850 ° C./1 hour.
The terminals 11a to 13a of the electrodes 11 to 13 are the substrate 1
0-shaped concave through-holes 10a formed on both side edges
To the electrode formed on the inner surface of the through hole portion 10a. Although not shown in FIG. 5, strip-shaped electrodes that are electrically connected to the electrodes 11 to 13 are also formed on the lower surface of the substrate 10 in a spiral shape.

As shown in FIG. 6 on the first capacitance electrode 11 of the substrate 10 and on a portion corresponding to a cap bonding portion described later.
As shown in, the paste-like dielectric layer 15 is formed to have a constant thickness and at the same time. As the material of the dielectric layer 15, there are a resin base and a glass base, but in this embodiment, the glass base is used in consideration of insulation properties, moisture resistance and the like.
The method of forming the dielectric layer 15 includes printing, transfer, dispensing, etc., but a pattern printing method capable of accurately controlling the layer thickness was used. Although the thickness of the dielectric layer 15 varies depending on the target load capacitance value,
The cap 25 described later that alleviates unevenness due to
The thickness is, for example, about 40 μm so that sufficient insulation between the electrodes and the electrodes 11 to 13 is secured. After printing, a drying process was performed, and baking was performed at 850 ° C./1 hour to perform a curing process. The dielectric layer 15 of this embodiment is the first capacitor electrode 11
And a frame-shaped adhesive portion 15b corresponding to the cap adhesive portion are continuously formed, and two window holes 15c for exposing a part of the external electrodes 12 and 13 are formed near both ends. However, as shown in FIG. 7, the capacitance portion 15a and the adhesive portion 15b may be separated. In this case, the amount of dielectric paste used can be saved.

Two second capacitance electrodes 16 and 17 are formed on the dielectric layer 15 by a known method such as sputtering, vapor deposition, printing or thermal spraying. In this example, the electrode 1
Pattern print conductive paste in the same manner as 1 to 13
It was baked at 0 ° C./1 hour. These capacitance electrodes 16 and 17
Has a main portion facing the first capacitance electrode 11 with the capacitance portion 15a in between, and a part of the external electrodes 12, 1 respectively.
3 and 3 through the window hole 15c.

On the second capacitance electrodes 16 and 17, a resonator element 20 is adhesively fixed by a material such as a conductive adhesive 18 which has both conductive and adhesive functions. The resonator element 20 of this embodiment is a known thickness-shear vibration mode resonator, and includes a piezoelectric substrate 21 made of piezoelectric ceramics or piezoelectric single crystal. The electrode 22 is formed from one end side of the surface of the piezoelectric substrate 21 to a region of about ⅔,
The electrode 23 is formed over the area of about ⅔ from the other end side of the back surface. One end of both electrodes 22, 23 is the piezoelectric substrate 2
The vibrating portion is formed so as to face each other with the intermediate portion 1 in between, and the vibrating portion is provided with a certain space by the thickness of the conductive adhesive 18 so as not to contact the second capacitance electrodes 16 and 17. ing. The other ends 22a of the electrodes 22, 23,
Reference numeral 23a extends from the end surface of the piezoelectric substrate 21 to the other surface side. By bonding with the conductive adhesive 18 as described above, the electrodes 22 and 23 of the resonator element 20 are electrically connected to the second capacitance electrodes 16 and 17, respectively.

The cap 25 is adhered onto the substrate 10 with an adhesive 26 so as to cover the resonator element 20.
As the material of the cap 25, there are ceramics such as alumina, resin, and metal, but in this embodiment, a metal material was used in order to ensure downsizing of the product and dimensional accuracy. The selection of the metal material is arbitrary as long as product strength and adhesiveness are obtained, but this time, 0.2 mm thick Al alloy (A-5000
System) was used. An epoxy-based adhesive is used as the adhesive 26, which is transferred and applied to the bottom surface of the opening of the cap 25, and then the adhesive 15 of the dielectric layer 15 is applied.
Bonded on b and cured.

The test results of the piezoelectric resonator manufactured by the above method and its sealing property and withstand voltage property compared with the conventional product are shown below. The conventional product is a piezoelectric resonator having the structure shown in FIG. 1, and its material and shape are the same as those of the product of the present invention. Table 1 shows the test results regarding the sealing property, and the number of bubbles generated from the adhesive portion was measured in 30 seconds by immersing it in Fluorinert (trade name). Among these, those which were repeated twice for 30 seconds at 260 ° C. and then immersed in Fluorinert, those which were repeatedly repeated 100 times from −55 ° C. to 85 ° C. and then immersed in Fluorinert, were the pressure cooker This is a test, in which pressure is applied at 121 ° C. and 2 atm for 20 hours, and then the product is immersed in Fluorinert.

[0019]

[Table 1]

Table 2 shows the test results regarding withstand voltage,
A pressure load of 3 kg was applied to the cap, a voltage of 200 V was applied, and when the insulation resistance between the cap and the electrode was 10 ⁸ Ω or less, it was determined to be defective.

[Table 2]

As is clear from the above test results, both the conventional product and the product of the present invention are excellent in heat resistance and thermal shock, but in the pressure cooker test, the product of the present invention has superior performance to the conventional product. I understand. Also,
Regarding the withstand voltage property, about half of the conventional products were defective, whereas the defective rate was 0 in the product of the present invention, and the performance is remarkably excellent. In addition, when a pressing load of 3 kg was applied to the cap 25 for 60 seconds, in 50 of the products of the present invention, the dielectric layer 15 had cracked paste.

When the resonator shown in FIG. 5 is actually manufactured, for example, the electrodes 11 to 13, the dielectric layer 15, the electrodes 16 and 17, etc. are simultaneously formed for a plurality of elements on the mother substrate,
After mounting the plurality of resonator elements 20 and the cap 25 on the mother substrate, the mother substrate may be cut into a substrate 10 one element at a time. Also, after forming electrodes 11 to 13, dielectric layer 15, electrodes 16 and 17 for multiple elements on the mother substrate at the same time, the mother substrate is cut one element at a time, and the resonator elements 20 and The caps 25 may be attached one by one. Either method can be mass-produced with high productivity.

[0023]

As is apparent from the above description, according to the present invention, since the dielectric layer is formed not only on the first capacitor electrode but also on the substrate corresponding to the cap bonding portion, the dielectric layer is formed. The body layer can absorb the unevenness due to the electrodes on the upper surface of the substrate and the step due to the warp of the cap, and the upper surface of the dielectric layer is substantially flattened. Therefore, if the cap is adhered on the dielectric layer, the adhesive sufficiently wraps between the cap and the substrate even with a relatively small amount of the adhesive, and the sealing failure can be eliminated. Further, even if the cap is made of a metal material, the dielectric layer, which is an insulating material, is formed on the electrode, so that there is no fear of short circuit even if the adhesive has a small film thickness. Also,
In the case of the manufacturing method of the present invention, since the dielectric layer is formed not only on the first capacitor electrode but also on the substrate corresponding to the cap adhesion portion, the sealing property and the withstand voltage can be increased without increasing the number of steps. It is possible to manufacture a piezoelectric resonator with a built-in load capacitance that has excellent properties.

[Brief description of drawings]

FIG. 1 is an exploded perspective view of a conventional piezoelectric resonator with a built-in load capacitance.

FIG. 2 is an electric circuit diagram of the piezoelectric resonator shown in FIG.

3 is a cross-sectional view of a bonded portion of the piezoelectric resonator shown in FIG.

FIG. 4 is an enlarged view of part A of FIG.

FIG. 5 is an exploded perspective view of an example of a piezoelectric resonator with a built-in load capacitance according to the present invention.

6 is a plan view of a substrate on which a dielectric layer in FIG. 5 is formed.

FIG. 7 is another example of a pattern of a dielectric layer.

[Explanation of symbols]

 10 Substrate 11 First Capacitance Electrode 12 and 13 External Electrode 15 Dielectric Layer 16 and 17 Second Capacitance Electrode 20 Resonator Element 25 Cap 26 Adhesive

Claims (5)

[Claims] 1. A substrate made of an insulating material, a first capacitor electrode and two external electrodes formed on the substrate, and a paste-like dielectric layer formed on the first capacitor electrode with a constant thickness. Two second capacitance electrodes formed on the dielectric layer such that a main part faces the first capacitance electrode with the dielectric layer in between and a part of the second capacitance electrode is electrically connected to the external electrode; Piezoelectric resonator with built-in load capacitance, which includes a resonator element mounted on the capacitance electrode so that each electrode is electrically connected to the second capacitance electrode, and a cap bonded to the substrate so as to cover the resonator element. In the load capacitance built-in type piezoelectric resonator, the dielectric layer is formed not only on the first capacitance electrode but also on a portion of the substrate corresponding to the cap bonding portion. 2. The piezoelectric resonator with a built-in load capacitance according to claim 1, wherein the dielectric layer is made of a glass base. 3. The piezoelectric resonator with a built-in load capacitance according to claim 1, wherein the cap is made of a metal material. 4. A step of forming a first capacitance electrode and two external electrodes on a substrate made of an insulating material, and a pace-like dielectric on the first capacitance electrode and on the substrate corresponding to the cap adhesion portion. A step of forming a layer at the same time, and two second capacitance electrodes on the dielectric layer, the main part of which faces the first capacitance electrode with the dielectric layer in between, and a part of the second capacitance electrode and the external electrode. A step of forming a conductive element; a step of mounting a resonator element on the second capacitor electrode so that the electrode and the second capacitor electrode are in a conductive state; And a step of adhering so as to be in intimate contact with the cap adhesive portion of the dielectric layer. 5. The method for manufacturing a piezoelectric resonator with a built-in load capacitance according to claim 4, wherein the dielectric layer is formed by pattern printing.