JP3182986B2 - Chip type piezoelectric resonator - Google Patents

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 resonator used as, for example, a filter, an oscillator, a discriminator and the like, and more particularly to an improvement in a structure for forming external electrodes.

[0002]

2. Description of the Related Art Conventionally, piezoelectric resonators used as, for example, filters, oscillators, discriminators and the like have generally been provided with leads.

However, in recent years, surface mount technology (SMD) has been adopted in order to reduce the size of electronic devices, and accordingly, piezoelectric resonators of this type are also of the chip type without lead wires. Is required.

[0004]

Related Applications A chip type piezoelectric resonator which has been proposed under such a demand and which is of interest to the present invention is disclosed by the present applicant in Japanese Patent Application No. Hei.
No. 08. A specific example of the chip-type piezoelectric resonator will be described with reference to FIGS.

[0005] As shown in FIG.
Is a piezoelectric substrate 2 made of a piezoelectric ceramic such as PZT.
Is provided. This piezoelectric substrate 2 is a mother substrate 3 shown in FIG.
Is obtained by cutting the A part of the mother substrate 3 is shown in FIG.

On one main surface of the mother substrate 3, divided vibration electrodes 4 and 5 are formed, and on the other main surface, a vibration electrode 6 facing these vibration electrodes 4 and 5 is formed. Terminal electrodes 7, 8 and 9 are connected to the vibrating electrodes 4, 5 and 6, respectively. A plurality of elements 10 each constituted by one set of the vibrating electrodes 4 to 6 and the terminal electrodes 7 to 9 are provided by one mother substrate 3. The mother substrate 3 is divided for each element 10 by being cut along cutting lines 11 and 12 indicated by a chain line in FIG. 8, and as a result of these divisions, a plurality of piezoelectric substrates 2 shown in FIG. Provided.

Each of the above-mentioned elements 10 constitutes an energy trapping type double mode piezoelectric resonator using the thickness longitudinal vibration mode, having the divided vibration electrodes 4 and 5 and the vibration electrode 6 opposed thereto. Therefore, in order to secure the vibration space, an adhesive layer 13a is formed so as to surround a vibration region on the mother substrate 3, as shown for one element 10 in FIG. The cover sheet 13b is arranged on 13a.
The adhesive layer 13a and the cover sheet 13b are applied to both main surfaces of the mother substrate 3 for all the elements 10.

As shown in FIG. 6, a thermosetting exterior resin layer 1 is provided so as to cover both main surfaces of the piezoelectric substrate 2 respectively.
4 and 15 are formed. External electrodes 17 and 18 are provided on the surface of the chip 16 having a sandwich structure including the piezoelectric substrate 2 and the exterior resin layers 14 and 15.
And 19 are each adapted to surround the chip 16. These external electrodes 17, 18 and 19 are electrically connected to the terminal electrodes 7, 8 and 9, respectively. The external electrodes 17, 18 and 19 are respectively provided with thick film portions 20, 21 and 2 formed on the main surface of the chip 16, that is, on the main surfaces of the exterior resin layers 14 and 15.
2 and a thin film portion 2 formed on the end face of the chip 16
3, 24 and 25. The thick film portions 20 to 22 enable soldering when the piezoelectric resonator 1 is mounted on the surface thereof. The thick film portions 20 to 22 are printed with a metal paste such as a copper paste containing a thermosetting resin, and are baked and hardened. It is formed. The thin film portions 23 to 25 are formed by sputtering or vapor deposition.

The cutting of the mother substrate 3 is preferably performed by cutting the outer resin layers 14 and 15 and the thick film portions 20 to 2.
2 is formed. That is, although not shown, the mother substrate 3 shown in FIG. 7 is disposed in a frame-shaped mold, and in that state, the thermosetting resin is formed on both main surfaces of the mother substrate 3 to become the exterior resin layers 14 and 15. The resin is poured and then heat cured. The sandwich structure thus obtained is polished if necessary, and then a conductive film to be the thick film portions 20 to 22 is formed in a predetermined pattern on both main surfaces thereof. Then, the cutting line 1 shown in FIG.
Cutting along 1 and 12 is performed to obtain the chip 16 shown in FIG. Next, the chip 16 is subjected to barrel polishing, and then the thin film portions 23 to 25 are formed.

In this manner, the surface-mountable piezoelectric resonator 1 is obtained. In the piezoelectric resonator 1, since the piezoelectric substrate 2 and the resin layers 14 and 15 are excellent in adhesion, the piezoelectric resin The layers 14 and 15 allow sufficient damping to be applied to the piezoelectric substrate 2 and therefore provide good electrical properties.

[0011]

However, in the piezoelectric resonator 1 shown in FIG.
If the stress applied to the piezoelectric substrate 2 from the substrate 5 is too strong, the electric characteristics of the piezoelectric resonator 1 may be distorted or cracks may be generated in the piezoelectric substrate 2. For this reason, a relatively large amount of filler is mixed into the exterior resin layers 14 and 15 for stress relaxation.

However, on the exterior resin layers 14 and 15 containing such a relatively large amount of filler, as described above, a metal paste containing a thermosetting resin is applied with the thick film portions 20 of the external electrodes 17 to 19 as described above. ~ 22,
The resin component in the metal paste penetrates into the exterior resin layers 14 and 15 containing the filler, and the thick film portion 2
The strength of 0 to 22 may be significantly deteriorated as compared with the original strength. This causes a disadvantage that the thick film portions 20 to 22 are largely scraped off in the above-described barrel polishing step, and also causes a problem of solder cracking in subsequent soldering. After the piezoelectric resonator 1 is mounted on a printed circuit board, when the board is bent, peeling may occur in the thick film portions 20 to 22.

An object of the present invention is to provide a chip-type piezoelectric resonator that can solve the above-mentioned problems.

[0014]

According to the present invention, there is provided a piezoelectric substrate on which a vibration electrode and a terminal electrode connected to the same are formed, and a piezoelectric substrate which is formed so as to directly cover both main surfaces of the piezoelectric substrate, respectively . A thermosetting exterior resin layer containing a filler for stress relaxation, and at least one of the exterior resin layers electrically connected to the terminal electrode and formed on at least one of the exterior resin layers An external electrode made of a metal paste containing a thermosetting resin, which is directed to a chip-type piezoelectric resonator, in order to solve the above-described technical problem, in order to solve the above-described technical problem, the outer resin layer and the external electrode At the interface, the thermosetting resin contained in the external electrode
In order to prevent the permeation into the exterior resin layer, a permeation prevention film made of a thermosetting resin containing no filler is formed.

The above-described permeation prevention film is formed, for example, by printing a liquid thermosetting resin and thermally curing the same.

[0016]

According to the present invention, the thermosetting resin contained in the paste constituting the external electrode penetrates into the exterior resin layer even if the exterior resin layer contains a relatively large amount of filler due to the presence of the penetration preventing film. Is prevented.

[0017]

Therefore, the external electrode made of the metal paste maintains its original strength, and therefore is not largely scraped off by the barrel polishing or causes a problem of solder cracking, and a problem of peeling. Can also be prevented from occurring. Also, the variation in the strength of the external electrodes is reduced. Therefore, a highly reliable chip-type piezoelectric resonator can be obtained.

[0018]

FIG. 1 shows a piezoelectric resonator 1a according to an embodiment of the present invention. FIG. 1 is a diagram corresponding to FIG. 6 described above. The structure of the piezoelectric resonator 1a shown in FIG.
Corresponding elements have the same reference characters allotted for easy understanding in comparison with the structure of the piezoelectric resonator 1 shown in FIG. 6, and overlapping descriptions will be omitted.

In order to simultaneously obtain a plurality of chips 16 composed of the thermosetting exterior resin layers 14 and 15 formed so as to cover the piezoelectric substrate 2 shown in FIG. 1 and both main surfaces thereof, respectively, as shown in FIG. A simple sandwich structure 26 is prepared. The sandwich structure 26 is shown in FIGS.
And thermosetting resin layers 27 and 28 containing fillers formed so as to cover both main surfaces thereof, respectively. As previously mentioned,
The mother substrate 3 provides the piezoelectric substrate 2, and the thermosetting resin layers 27 and 28 provide the exterior resin layers 14 and 15, respectively. The method for manufacturing the sandwich structure 26 is as described above. Plane polishing is performed on the sandwich structure 26 as necessary.

Next, as shown in FIG. 3, on each main surface of the thermosetting resin layers 27 and 28 of the sandwich structure 26, thermosetting resin films 29 and 30 containing no filler are formed in a predetermined pattern. It is formed with These thermosetting resin films 29 and 30 are formed, for example, by printing a liquid thermosetting resin and then thermosetting. The thermosetting resin films 29 and 30 provide the penetration preventing films 31 and 32 shown in FIG.

Next, as shown in FIG. 4, conductive films 33 and 34 made of a metal paste such as a copper paste containing a thermosetting resin are formed on the thermosetting resin films 29 and 30, respectively. You. These conductive films 33 and 34
Is formed by printing a metal paste and thermally curing the metal paste. The conductive films 33 and 34 provide the thick film portions 20 to 22 of the external electrodes 17 to 19 shown in FIG.

Next, the sandwich structure 2 is cut along dashed lines 11 and 12 in FIG.
6 is the thermosetting resin films 29 and 30 and the conductive film 3
Cut with 3 and 34. These cutting lines 11 and 12 correspond to the cutting lines 11 and 12 shown in FIG. After this cutting, the obtained chips 16
Barrel polishing is applied to (FIG. 1). Note that the terminal electrodes 7 to 7 shown in FIG.
9 are each exposed. Next, as shown in FIG. 1, thin film portions 23 to 25 of the external electrodes 17 to 19 are formed on the end face of the chip 16 by sputtering or vapor deposition. Thereby, the external electrodes 17 to 19 are
Each is electrically connected to the terminal electrodes 7 to 9.

The chip-type piezoelectric resonator 1a thus obtained is composed of a piezoelectric substrate 2 on which vibration electrodes 4 to 6 and terminal electrodes 7 to 9 (FIG. 8) connected to them are formed.
Thermosetting external resin layers 14 and 1 formed to cover both main surfaces of piezoelectric substrate 2 and containing filler, respectively.
5 and the thickness of the external electrodes 17 to 19 electrically connected to the terminal electrodes 7 to 9 and formed on the main surfaces of the exterior resin layers 14 and 15 and made of a metal paste containing a thermosetting resin. Film portions 20 to 22, and the thick film portions 2 of the exterior resin layers 14 and 15 and the external electrodes 17 to 19.
At the interface with 0 to 22, penetration prevention films 31 and 32 made of a thermosetting resin containing no filler are formed.

FIG. 5 shows thick film portions 20 to 20 formed by barrel polishing.
The thickness reduction of No. 22 is shown by comparing the embodiment shown in FIG. 1 with the comparative example shown in FIG. In FIG. 5, the vertical axis indicates the residual thickness of the thick film portions 20 to 22, and the horizontal axis indicates the barrel polishing time.

Although barrel polishing requires a time of 10 to 15 minutes, in the embodiment of the present invention, even if barrel polishing is performed for 15 minutes, the thickness of the thick film portions 20 to 22 almost decreases. In contrast, in the comparative example, barrel polishing for 10 to 15 minutes resulted in a significant decrease in thickness. This indicates that in the comparative example, the strength of the thick film portions 20 to 22 is significantly deteriorated.

Although the present invention has been described with reference to the illustrated embodiment, the manufacturing method for obtaining the piezoelectric resonator according to the present invention is not limited to the method described above.

In the above-described embodiment, the external electrode 17
To 19 are thick film portions 20 to 22 and thin film portions 23 to 25, respectively.
However, the thin film portions 23 to 25 also have the thick film portions 20 to
As in the case of 22, a metal paste containing a thermosetting resin may be used. The external electrodes 17 to 19 are connected to the chip 1
6 is formed, but such a configuration is not essential. For example, if an external electrode is formed from a metal paste containing a thermosetting resin corresponding to the thick film portions 20 to 22 on at least the main surface of at least one of the exterior resin layers, it is within the scope of the present invention. The electrical connection between the external electrode and the terminal electrode may be made by a through hole or a via hole, in addition to the above-described thin film portions 23 to 25.

Further, the illustrated chip type piezoelectric resonator 1a
Is an energy confinement type piezoelectric resonator using a thickness longitudinal vibration mode, but the present invention can be applied to a piezoelectric resonator of another structure or type. For example,
The present invention can be applied to an energy trap type piezoelectric resonator utilizing a thickness shear vibration mode.

In the illustrated embodiment, the permeation prevention film 3 is used.
Although 1 and 32 are formed only in the region where the thick film portions 20 to 22 are formed, if it is not necessary to consider the waste of the material of the permeation prevention films 31 and 32, for example, if the exterior resin layer 14 and Permeation prevention films 31 and 32 may be formed so as to cover the entire main surface of each of the fifteen.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a chip-type piezoelectric resonator 1a according to an embodiment of the present invention.

FIG. 2 is a perspective view showing a sandwich structure 26 prepared for manufacturing the piezoelectric resonator 1a shown in FIG.

FIG. 3 is a perspective view showing a state where thermosetting resin films 29 and 30 are formed on the sandwich structure 26 shown in FIG.

FIG. 4 is a perspective view showing a state in which conductive films 33 and are formed on the thermosetting resin films 29 and 30 shown in FIG.

5 is a diagram showing a reduction in thickness of a thick film portion of an external electrode by barrel polishing in a comparison between the embodiment shown in FIG. 1 and a comparative example shown in FIG. 6;

FIG. 6 is a perspective view showing a chip type piezoelectric resonator 1 which is interesting for the present invention.

FIG. 7 is a perspective view showing a mother substrate 3 prepared for obtaining the piezoelectric substrate 2 shown in FIGS. 1 and 6, respectively.

8 is an enlarged perspective view showing a part of the mother board 3 shown in FIG. 7;

[Explanation of symbols]

 1a Piezoelectric resonator 2 Piezoelectric substrate 4-6 Vibration electrode 7-9 Terminal electrode 14,15 Outer resin layer 17-19 External electrode 20-22 Thick film part 23-25 Thin film part 31,32 Permeation prevention film

Claims (1)

(57) [Claims] A piezoelectric substrate on which a vibrating electrode and a terminal electrode connected to the vibrating electrode are formed; and a flange formed so as to directly cover both main surfaces of the piezoelectric substrate, and for relaxing stress from the exterior resin layer to the piezoelectric substrate. a thermosetting exterior resin layer containing a filler; and a metal including a thermosetting resin electrically connected to the terminal electrode and formed on at least a main surface of at least one of the exterior resin layers. and an external electrode formed of the paste, the chip-type piezoelectric resonator, the interface between the external electrode and the exterior resin layer, said external power
Infiltration of the thermosetting resin contained in the pole into the exterior resin layer
A chip type piezoelectric resonator characterized in that a permeation prevention film made of a thermosetting resin containing no filler is formed in order to prevent the penetration.