JPH07249956A - Piezoelectric vibrator and its manufacture - Google Patents

Abstract

PURPOSE:To attain piezoelectric vibrator having excellent characteristics and high stability at a cost lower than that of a conventional product. CONSTITUTION:In the case of holding a piezoelectric substrate 1 between two holding substrates 5 by pressing projection parts 3 into contact with external electrodes 4 formed on the surfaces of the substrates 5, the projections 3 are pressed into contact with the electrodes 4 in a state leaving patterning resist masks 8 for forming the projection parts 3 on prescribed positions. After the press-contact processing, the regist films 8 are removed. Since the substrate 1 is prevented from being inclined due to the existence of the resist masks 8 at the time of pressing the projection parts 3 into contact with the electrodes 4, the stability of characteristics of the piezoelectric vibrator can be improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a piezoelectric vibrator using a piezoelectric material such as piezoelectric ceramic, crystal, niobium lithium and the like, and a method of manufacturing the same.

[0002]

2. Description of the Related Art An example of a piezoelectric vibrator using a piezoelectric material such as piezoelectric ceramics, crystal, niobium lithium and the like will be described below with reference to FIGS.

Piezoelectric vibrators used for mechanical filters, oscillators, etc. are made of materials such as piezoelectric ceramics, crystal, niobium lithium, and the like, and an appropriate vibration mode is excited by the piezoelectric effect according to the frequency range used. .

These piezoelectric vibrators are held near the nodes of the vibrator where the vibration amplitude becomes 0 so that the vibration of the vibrator is not suppressed, and are electrically connected at this holding portion. It is configured as a filter or oscillator.

Since these nodes (nodes) theoretically exist as points or lines having no area, it is ideally desirable to hold the piezoelectric vibrators at the nodes by points or lines in terms of characteristics.

However, as a practical problem, in order to stably hold the piezoelectric vibrator, it is necessary to give it a certain area and hold it in a planar shape.

FIG. 5 is a perspective view of a rectangular plate type piezoelectric vibrator made of a piezoelectric material such as piezoelectric ceramic. Driving electrodes 2a and 2b are formed on two main surfaces of the piezoelectric substrate 1 which face each other. When an electric field is applied between the electrodes, longitudinal vibration is excited in the longitudinal direction of the rectangular plate as indicated by arrow q in the figure. The nodes of vibration in the length vibration mode are linear in the center of the rectangle. Therefore, as shown in FIG.
The projections 3a and 3b made of a conductive material are formed by thermal spraying.

FIG. 6 is a schematic sectional view of a holding structure for a vibrator. The piezoelectric vibrator shown in FIG.
It is sandwiched and held between the external electrodes 4a and 4b provided on the holding substrates 5a and 5b via a and 3b. The holding substrates 5 a and 5 b are fixed via the holding frame 7. The external terminals 6a and 6b are in contact with and connected to the external electrodes 4a and 4b, respectively, as shown in the figure.

FIG. 7 shows the protrusion 3b (3
FIG. 7A is an enlarged view of the vicinity and the holding state of the piezoelectric vibrator will be described with reference to FIG. 7.

The bottom surface of the protrusion 3b is attached to the electrode 2b, while the top surface of the projection 3b is in contact with the external electrode 4b by being pressed into the external electrode 4b by external pressure as shown in the figure. As a result, the protrusion 3b (3a) and the external electrode 4
It is prevented from shifting from b (4a).

Such protrusions 3a and 3b are formed by the conventional lift-off method using a resist. To explain the outline of the lift-off method, first, a resist such as an organic substance (usually provided in a liquid form or a film form) is patterned by screen printing or photolithography to form an opening, and is formed as a resist mask on a piezoelectric substrate. . The opening is formed at the node of vibration in relation to FIG.

After that, a conductive projection is formed in the opening by thermal spraying, and the resist mask is removed by melting, peeling, or the like to form a node by the projection. Regarding the method of forming the protrusion, a patent (patent application number H)
05-207652).

[0013]

However, when the protrusions are formed by the lift-off method, the following problems occur.

That is, the shape of the projection 3 formed as shown in FIG. 7 is such that the surface in contact with the external electrode 4a is a substantially flat surface. Therefore, when placed on the floor, the piezoelectric substrate 1 itself is It is self-supporting only through the protrusion 3.

However, the piezoelectric substrate 1 is actually connected to the external electrode 4
When sandwiching and fixing from both sides with a and 4b, the external electrode 4a
8 is placed on the piezoelectric substrate 1 and the outer frame 7, almost all of FIG.
There is some deviation δ as in the part A of (a).

When this is corrected to a predetermined position and fixed, the external electrode 4 is moved while being in contact with the piezoelectric substrate 1 with some displacement. Therefore, as shown in FIG. 8B, the piezoelectric substrate 1 tilts like a seesaw in the displaced direction, and the vibrating portion such as the tip of the piezoelectric substrate 1 comes into contact with the external electrodes 4a, 4b, etc. There was a problem of deterioration.

For this reason, there have been problems that the characteristics are not sufficient and that the variations are large, and that assembly adjustment at the time of holding and fixing takes time and that productivity is improved.

In addition to the above, the following problems have occurred. FIG. 9 shows that on both surfaces of the piezoelectric substrate 1 having the width W1,
FIG. 6 is a perspective view showing a state in which drive electrode 2 is formed with a width W2 (<W1). The piezoelectric substrate 1 is further cut into the required dimensions to form the element shown in FIG.

For such a piezoelectric substrate 1, a drive electrode 2 is provided.
When a voltage is applied through the piezoelectric substrate to polarize the piezoelectric substrate, a large stress difference is generated inside the substrate due to the difference in strain between the portion where the drive electrode 2 is formed and the portion where the drive electrode 2 is not formed. Occurs.

Therefore, when cutting into each required size, the portion where the crack 11 is generated cannot be used and the yield is reduced, which has been a problem of improving productivity.

Naturally, the entire piezoelectric substrate 1 is not completely polarized, so that the characteristics are not sufficient.

As described above, with the conventional structure and method, it has not been possible to provide a piezoelectric vibrator with good characteristics, stability, ease, and productivity.

[0023]

The invention according to claim 1 of the present application provides a resist film having a required pattern opening in the vicinity of a node point of a piezoelectric substrate provided on a surface facing a driving electrode, It is formed on at least one surface provided with a driving electrode, and then a conductive material is sprayed in the opening to a required thickness to form a protrusion, and the piezoelectric substrate is connected to the external electrode via the protrusion. The method for manufacturing a piezoelectric vibrator is characterized in that the resist is removed after being sandwiched and held by a substrate having the same.

According to a fifth aspect of the present invention, the drive electrode is provided with a conductive resist film having a required pattern opening near a node point of a piezoelectric substrate partially provided on a surface facing the drive electrode. Is formed on the entire surface partially provided, and the piezoelectric substrate is polarized through the resist and the driving electrode.

According to a seventh aspect of the present invention, a piezoelectric substrate, a drive electrode provided on a surface of the piezoelectric substrate facing each other, and a drive electrode provided on at least one surface of the drive electrode are provided in the vicinity of a node point of the piezoelectric substrate. A resist film having a required pattern opening, a conductive protrusion formed by thermal spraying on the opening, and a piezoelectric substrate provided with a drive electrode in contact with the protrusion, the resist film, or the drive electrode. Removed by dissolving or peeling the resist film between the holding substrate formed with the external electrodes sandwiched and held from both sides, and the piezoelectric substrate sandwiched and held by the substrate via the protrusion and the resist film. A piezoelectric vibrator having a formed gap.

[0026]

According to the first aspect of the present invention, after the resist mask is formed and the projections are formed by thermal spraying, the resist mask is sandwiched by the external electrodes without removing the resist mask. Even if moved and fixed, the vibrating portion at the tip of the piezoelectric substrate does not come into contact with the external electrode or the like because of the resist mask. In this state, the resist mask is removed with a dedicated stripping solution or the like, so that the vibrating portion such as the tip of the piezoelectric substrate does not come into contact with the external electrode or the like and can be held completely free. Therefore, the productivity at the time of holding and adjusting can be improved.

According to the fifth aspect of the present invention, even when the piezoelectric substrate on which the drive electrodes are partially formed is used, the conductive resist mask is applied to the surface of the piezoelectric substrate on which the drive electrodes are formed, that is, polarization. By forming the entire surface of the voltage application surface at this time, patterning of the thermal spray node can be facilitated and the entire piezoelectric substrate can be easily polarized completely. Therefore, during polarization, an abnormal stress difference does not occur inside the piezoelectric substrate, cracks, etc. do not occur, and quality and yield can be improved.

According to the seventh aspect of the present invention, the resist mask previously provided on the piezoelectric substrate is sandwiched between the piezoelectric substrate held by the holding substrate and the holding substrate and then removed. This ensures that the necessary gap is provided between the piezoelectric substrate and the holding substrate. Therefore, since the vibrating portion such as the tip portion of the piezoelectric substrate does not come into contact with any part, it is possible to realize a piezoelectric vibrator having stable and excellent vibrator characteristics.

[0029]

Embodiments of the present invention will now be described in detail with reference to the drawings FIGS. 1 to 4, taking a rectangular plate type piezoelectric vibrator as an example.
It should be noted that components having the same or equivalent functions as those of the conventional example are designated by the same reference numerals, and detailed description thereof will be omitted.

First, a first embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a sectional view of the piezoelectric vibrator. 2 and 3 are cross-sectional views near the protrusion.

In FIG. 1, reference numeral 1 is a piezoelectric substrate made of a piezoelectric material such as piezoelectric ceramic, quartz, niobium lithium, and the like. Reference numeral 2 is Ag, Au provided on the piezoelectric substrate 1 by vapor deposition, CVD, plating or printing. , Cu, Ni, C
drive electrodes made of metal such as r or alloys thereof, 8
Reference numerals a and 8b are resist masks of an organic material, which are provided on the drive electrode 2 and have openings at the nodes of the piezoelectric substrate 1.

Reference numeral 3 denotes a protrusion provided on the drive electrode 2 in the opening of the resist mask 8 by a thermal spraying method and made of a metal such as Mo, Ni or Cr, an alloy thereof, or a composite material.

As shown in FIG. 1A, the piezoelectric substrate 1 is incorporated in the holding substrates 5a and 5b, the holding frame 7 and the like with the resist film 8 having substantially the same height as the protrusions 3a and 3b attached. .

The steps up to FIG. 1A are performed as follows. First, on the surface of the piezoelectric substrate 1 on which the drive electrode 2 is formed,
A resist mask 8 for patterning the protrusions is formed.
The resist mask 8 has patterned openings at the nodes of the piezoelectric substrate 1. Then, a projection is formed in the opening by thermal spraying.

After that, the piezoelectric substrate 1 is placed at a predetermined position on the holding substrate 5b on which the holding frame 7 is placed and the external electrode 4b is formed, via the resist mask 8b and the protrusion 3b, and the external electrode 4a is further formed. The holding substrate 5a thus prepared is placed from above.

Thus, while holding the piezoelectric substrate 1 from both sides by holding substrates 5a and 5b at predetermined positions, the holding substrates 5a and 5b are fixed to the holding frame 7 with an adhesive or the like. This state is shown in FIG.

In this state, since the resist mask 8 is formed, even if the holding substrates 5a and 5b are slightly displaced when fixed, the piezoelectric substrate 1 is tilted as shown in FIG. There is no direct contact with the electrode 4.

After assembling the piezoelectric substrate 1 and the holding frame and the like in this manner, the resist mask 8 is removed, so that the piezoelectric substrate 1 is held by the holding substrate 5 and the frame 7 as shown in FIG. 1B. It is correctly positioned and fixed in a regular position with respect to the like.

Next, the thickness of the resist mask 8 and the thickness of the protrusion 3 will be described with reference to FIG.

Here, the thickness Tr of the resist mask 8 is
The relation of the thickness Tn of the protrusion is Tr <Tn. Specifically, the difference between Tn and Tr is about 5 μm to about 30 μm.
m.

The reason for this is that by having such a thickness relationship, a slight gap is formed between the external electrode 4 and the resist mask 8 in the state of FIG. 1A, and the resist mask 8 is removed. The stripping solution for this purpose easily penetrates through this gap, and the resist mask 8 is easily removed.

Further, in the state of FIG. 1A, the protrusion 3 and the external electrode 4 are surely brought into contact with each other, and the piezoelectric substrate 1 is prevented from being displaced when the resist mask 8 is removed.

Here, Cu is used for the external electrode 4 and Mo, which is harder than Cu, is used for the protrusion 3. Also, the protrusion 3
Is formed by the thermal spraying method because the surface of the thermal spray coating is rough and fine irregularities are easily formed. This allows
When sandwiched between the holding substrates 5a and 5b, the fine irregularities due to the roughness of the surface of the protrusion 3 shown in FIG. 7 come into contact with the external electrode 4 so as to bite into the external electrode 4, and the external electrode 4 and the piezoelectric substrate 1 are not easily displaced. The substrate 1 is reliably held.

The resist mask 8 used was of a type that could be patterned by photolithography and was dissolved or softened and peeled by a dedicated peeling liquid. For example,
A dry film photoresist manufactured by Tokyo Ohka Kogyo Co., Ltd., which is an Audil α, AF00, BF type. Three
There was no problem in using.

However, in order to prevent the peeled resist mask from being caught on the external electrode 4, the holding substrate 5, the holding frame 7, etc., it is necessary to provide a sufficient gap or passage through which the peeling liquid and the peeled resist mask can come in and out. .

Therefore, basically, it is preferable to use the type in which the resist mask 8 is dissolved in the stripping solution. For example, PMER, P-A manufactured by Tokyo Ohka Kogyo Co., Ltd.
R9000.

The resist mask 8 may be formed by patterning by a screen printing method. In this case, for example,
Soluble etching resist inks X-87 and M-85 type manufactured by Taiyo Ink Mfg. Co., Ltd. may be used.

Although there was no problem in using these as a resist mask, it is necessary to consider the following in selecting a resist material.

That is, the piezoelectric substrate 1, the drive electrode 2, the external electrode 4, the holding substrate 5, the holding frame 7, etc. are not corroded or corroded by the resist mask developing solution or stripping solution, and the necessary film is formed. Whether or not the thickness can be easily obtained.

However, the resist material is not limited to the same kind of resist material, and any material satisfying the above and basically composed of an organic substance can be used as a resist mask for forming the projection 3 by thermal spraying, and therefore the above-mentioned types can be used. It is not limited to ones.

It should be noted that, in general, 30 which corresponds to the thickness of the protrusion.
In order to obtain a resist mask having a thick film of μm or more, the film type is easier to obtain than the ink type, but even in the case of the ink type, a thick film can be obtained by forming the resist in multiple layers.

When this multi-layer resist film is formed, FIG.
It is also possible to form the protrusion 23 as shown in FIG. In the case of multiple layers, especially when the uppermost layers 21A and 22A are formed of a dissolution type resist material, when the uppermost layers 21A and 22A are first dissolved, a gap corresponding to that layer is formed, so that the peeling liquid can pass through easily. 21B, 22B,
The 22C resist mask can be easily peeled off. In the case of multiple layers, the same effect can be obtained by using a dissolution type resist in at least a part of the upper, middle and lower layers.

According to the structure described with reference to FIGS. 1 to 3 above, even if the resist mask 8 is removed, the piezoelectric substrate 1 is held by the holding substrates 5a and 5b in the state before removal. The piezoelectric substrate 1 includes an external electrode 4, a holding substrate 5 and a holding frame 7.
There is no contact with etc. As a result, the characteristics and stability of the piezoelectric vibrator can be improved, and the efficiency of assembly and adjustment, and thus the productivity can be significantly improved.

Next, a second embodiment of the present invention will be described with reference to FIG. This can solve the problem that occurs when the piezoelectric substrate 1 is polarized.

In FIG. 4, reference numeral 1 is a piezoelectric substrate, 2a and 2b.
Are drive electrodes 3a, which are partially formed on the piezoelectric substrate 1,
Reference numeral 3b is a protrusion formed by a thermal spraying method, and 8a and 8b are conductive resist masks.

By using the conductive resist mask 8, polarization is performed in the state of FIG.
It is possible to completely polarize even the portion of the piezoelectric substrate 1 in which the holes are not formed.

Therefore, it is possible to prevent cracks in the piezoelectric substrate due to generation of internal stress as in the conventional case, and to improve the characteristics and stability of the piezoelectric vibrator as compared with the conventional case.
The yield improvement, that is, the productivity improvement can be realized.

Needless to say, this resist mask 8 is used for patterning the protrusions 3, and can be used for the same purpose as that of the embodiment of FIG. 1, for example.

Although the polarization is performed after the projection is formed here, it is naturally possible to form the projection after polarization.

However, since it is necessary to pay attention to the temperature and the like of the piezoelectric substrate so as not to exceed the Curie point when forming the protrusions after polarization, it is advantageous for manufacturing to perform polarization after formation. Is.

For the resist mask 8 here, a certain amount of Ag was added as a conductive material to a liquid resist material to impart conductivity. Basically, the piezoelectric substrate 1 is an insulator and has a large specific resistance.

Furthermore, since the resist mask 8 is thinner than the piezoelectric substrate 1, its specific resistance may be smaller than that of the piezoelectric substrate by, for example, three digits. Therefore, the addition amount of the conductive material may be controlled so that the specific resistance becomes smaller than this.

However, if the amount of the conductive material added is too large, the characteristics such as patternability and elasticity required for the resist mask deteriorate.

In such a case, the resist mask may be added with a specific resistance of about 1 mΩ · m as a guide. The conductive material to be added may be a material having appropriate conductivity such as a metal such as Au, Ni or Mo or an alloy thereof, or a compound such as a carbide, boride or oxide.

Further, any material having conductivity and a property that a sprayed film is unlikely to adhere and patterning can be easily performed can be basically used as a resist mask, and the resist mask material is not limited to the above.

In each of the above embodiments, the case where the protrusions are provided on both surfaces of the piezoelectric substrate has been described, but it is also possible to form only one protrusion on the piezoelectric substrate.

For example, in FIG. 1, the protrusion 3b on the lower surface may be formed as in the above embodiment, and one protrusion 3a may be formed as a part of the external electrode 4a on the holding substrate 5a. In this case, the characteristics are slightly lower than those of the structure in which the protrusions are formed on both sides, but the productivity is markedly increased due to the formation of the protrusions on only one side. There is an effect against.

[0068]

According to the present invention, it is possible to easily hold the piezoelectric substrate in a stable manner and to easily polarize the entire piezoelectric substrate regardless of whether the drive electrode is the entire surface or a partial area. It is possible to realize a piezoelectric vibrator with excellent stability, reduce its cost, and improve its productivity.

[Brief description of drawings]

FIG. 1 is a sectional view of a main part of a piezoelectric vibrator according to a first embodiment of the present invention.

FIG. 2 is a sectional view of a protrusion in the embodiment.

FIG. 3 is a cross-sectional view showing another form of the protrusion in the embodiment.

FIG. 4 is a perspective view of a main part according to a second embodiment of the present invention.

FIG. 5 is a perspective view showing a schematic configuration of a conventional piezoelectric vibrator.

FIG. 6 is a schematic cross-sectional view showing a holding configuration of the piezoelectric vibrator of the conventional example.

FIG. 7 is a sectional view of a holding portion of the conventional piezoelectric vibrator.

FIG. 8 is a sectional view of a piezoelectric vibrator of the conventional example.

FIG. 9 is a schematic perspective view of a piezoelectric substrate portion of the conventional example.

[Explanation of symbols]

 1 Piezoelectric Substrate 2 Drive Electrode 3 Projection 4 External Electrode 5 Holding Substrate 6 External Terminal 7 Holding Frame 8 Resist Mask

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hiroshi Fukushima 1006 Kadoma, Kadoma, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (72) Hirofumi Taka, 1006 Kadoma, Kadoma City, Osaka Matsushita Electric Industrial Co., Ltd.

Claims (7)

[Claims] 1. A resist film having a required pattern opening near a node point of a piezoelectric substrate provided on a surface facing a driving electrode is formed on at least one surface provided with a driving electrode, After that, a conductive material is sprayed to the required thickness in the opening to form a protrusion, and the piezoelectric substrate is sandwiched and held by a substrate having an external electrode through the protrusion, and then the resist is removed. A method for manufacturing a piezoelectric vibrator, comprising: 2. The method of manufacturing a piezoelectric vibrator according to claim 1, wherein the thickness of the resist is smaller than the thickness of the projection formed by thermal spraying. 3. The method of manufacturing a piezoelectric vibrator according to claim 1, wherein the resist is formed of a plurality of layers. 4. The method for manufacturing a piezoelectric vibrator according to claim 1, 2 or 3, wherein at least a part of the resist is dissolved and removed. 5. A drive electrode is partially provided with a conductive resist film having a required pattern opening in the vicinity of a node point of a piezoelectric substrate which is partially provided on a surface opposed to the drive electrode. A method of manufacturing a piezoelectric vibrator, comprising: forming the entire surface of the piezoelectric substrate, and polarizing the piezoelectric substrate through the resist film and the driving electrode. 6. After forming a conductive resist film, a projection having conductivity is formed in the opening of the resist film by thermal spraying, and then the resist film, the projection or the driving electrode is used to form a piezoelectric substrate. The method for manufacturing a piezoelectric vibrator according to claim 5, wherein polarization is performed. 7. A piezoelectric substrate, a drive electrode provided on an opposing surface of the piezoelectric substrate, and a required pattern opening portion provided on at least one surface of the drive electrode in the vicinity of a node point of the piezoelectric substrate. A resist film having, a conductive protrusion formed by thermal spraying on the opening, and contact between the protrusion, the resist film, or the drive electrode to sandwich and hold the piezoelectric substrate from both sides on which the drive electrode is provided. A holding substrate having an external electrode formed thereon and a gap formed by removing or peeling the resist film by melting or peeling the resist film between the protrusion and the piezoelectric substrate sandwiched and held by the substrate via the resist film. A piezoelectric vibrator having.