JP2000151343A - Piezoelectric oscillator and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide highly accurately thin a piezoelectric substrate and to provide a piezoelectric device which can practically be used to a higher frequency area by integrally forming an oscillation piezoelectric substrate and a metallic supporting body, without sandwiching an interposed object in-between. SOLUTION: A piezoelectric oscillator 1 is provided with a piezoelectric substrate 2, formed of a rectangular and thin crystal board and a metallic support body 3 for supporting a piezoelectric substrate. The piezoelectric substrate 2 and the metallic support body 3 face directly opposed each other and are formed integrally. A through-hole 3a along the thickness direction is formed almost in the center of the metallic support body 3. A vibration area α in the center of one side of the piezoelectric substrate 2 is exposed, and a vibration space β is secured in the area. The piezoelectric oscillator which is thus constituted is held by the metallic support body 3 to the effect that its whole periphery is solid. Thus, physical damages hardly occur, even if the thickness of the piezoelectric substrate 2 is set to be not more than 30 μm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a piezoelectric vibrator used for a high-frequency vibrator or a broadband filter element using a piezoelectric material, and a method of manufacturing the same.

[0002]

2. Description of the Related Art In recent years, miniaturization and digitization of mobile communication devices have been promoted, and with such technical trends, piezoelectric vibrators used as filters and the like in mobile communication devices have high frequencies and wide bands. The demand for conversion is increasing.

Therefore, conventionally, by improving the polishing precision and promoting the thinning, it has been possible to meet the demand for a higher frequency and wider band of the piezoelectric vibrator. An example of a quartz oscillator will be described below as a conventional piezoelectric oscillator with reference to the drawings, but it goes without saying that the same applies to other piezoelectric oscillators.

FIG. 7 shows a conventional crystal unit. Numeral 71 denotes a quartz crystal substrate for oscillation. The quartz crystal substrate 71 for oscillation is polished on both sides to a predetermined thickness by a method called AT-cut, and an excitation electrode 72 and a lead electrode 73 are provided on both main surfaces thereof. Normally, the extraction electrodes 73 are extended to the outer peripheral portions of both ends of the vibrating quartz substrate 71 and are held by holding members (not shown). In addition, the thus-configured crystal resonator is housed in an airtight container.

[0005] This crystal oscillator is a thickness-slip mode oscillator, and has a resonance frequency f (MH) depending on the thickness t (μm).
z) is determined, during which approximately f = 1670 / t
There is a relationship. Therefore, in this crystal resonator, the resonance frequency is controlled by adjusting the vibration crystal substrate 71 to a required thickness. When a high resonance frequency is obtained,
The thickness of the vibrating quartz substrate 71 is reduced, and as a thickness adjusting method, a method of adjusting the thickness of the vibrating quartz substrate 71 by double-side polishing has been adopted.

However, in the double-side polishing method, as the polishing proceeds and the thickness becomes thinner, the mechanical strength of the vibrating quartz substrate 71 decreases, and defects such as cracks and the like tend to occur during polishing. For this reason, it is not easy to reduce the thickness of the vibrating quartz substrate 71 to a desired thickness, and there is a disadvantage that the yield is significantly reduced.

As a method of solving such inconvenience,
Conventionally, as shown in FIG. 8, a method in which a reinforcing plate 74 is attached to one surface of a vibrating quartz substrate 71 and only the other surface on which the reinforcing plate 74 is not attached is polished on one side. it was thought. Hereinafter, this method will be referred to as a first conventional example, for example, a technique described in Japanese Patent Application Laid-Open No. 3-116882.

The details of the first conventional example are as follows. That is, first, a through hole 74a for forming a vibration space is formed in the center.
A reinforcing plate 74 having a concave portion (may be a concave portion) is prepared. After the excitation electrode 72 and the extraction electrode 73 are formed on one surface of the vibrating quartz substrate 71 in advance, a reinforcing plate 74 is adhered to the one surface. In this state, the vibrating quartz plate without the reinforcing plate 74 is provided. The other surface of the substrate 71 is polished to a desired thickness. Then, the remaining electrodes (the excitation electrode 72 and the extraction electrode 73) are formed on the polished other surface. According to this method, it is possible to assemble the crystal unit while the reinforcing plate 74 is adhered, and the step of removing the reinforcing plate 74 can be omitted.

Furthermore, there is a second conventional example shown in FIG. That is, a reinforcing quartz plate 74 'having no through hole is prepared as a reinforcing plate. And, taking advantage of the characteristic that the reinforcing quartz plate 74 ′ is made of the same material as the vibrating quartz substrate 71 and can be directly joined without using an adhesive, the reinforcing quartz plate 71 is provided on one surface of the vibrating quartz substrate 71. 74 'are directly joined without using an adhesive. Then, in this state, the other surface of the vibrating quartz substrate 71 is polished, and after the polishing is completed, a through hole 74a 'is formed in the reinforcing quartz plate 74' by etching. This method is described in, for example,
The technique described in JP-A-745569 is cited as an example.

According to the first and second conventional examples, the vibrating quartz substrate 71 is mechanically reinforced by the reinforcing plate 74 or the reinforcing quartz plate 74 '. It has been considered that the problem of chipping does not occur, and a piezoelectric vibrator having the vibrating quartz substrate 71 having a desired thickness can be produced with high yield.

[0011]

However, the first and second conventional examples configured as described above have the following problems.

First, the first conventional example has a problem that the thickness cannot be adjusted with high accuracy. The reinforcing plate 74 is adhered to the vibration crystal substrate 71 via an adhesive 75 made of wax or an epoxy resin. Specifically, the adhesive 75 is applied to the reinforcing plate 74 or the vibrating quartz substrate 7.
After application to No. 1, the reinforcing plate 75 and the vibrating quartz substrate 71 are adhered to each other by pressing and bonding, so that the two are bonded. On the other hand, the thickness of the adhesive 75 fluctuates easily depending on the degree of pressure bonding between the reinforcing plate 74 and the vibrating quartz substrate 71 performed after the application of the adhesive, since the adhesive at the time of application is liquid. It was difficult to control the degree of crimping with high accuracy in the process. For this reason, the thickness of the adhesive 75 varies (±) due to a change in the degree of pressure bonding between the reinforcing plate 74 and the quartz substrate 71 for vibration.
(Approximately 3 μm).

On the other hand, the polishing amount of the vibration quartz substrate 71 is adjusted with reference to the reinforcing plate 74. Therefore, if the thickness of the adhesive 75 interposed between the reinforcing plate 74 and the vibrating quartz substrate 71 varies, the adhesive 7
In accordance with the thickness variation of No. 5, it is inevitable that the thickness variation of the polished oscillation quartz substrate 71 occurs.

Further, the thickness variation of the adhesive 75 occurs not only in each of the vibrating quartz substrates 71 to be polished, but also in each of the adhesive applied regions of the same vibrating quartz substrate 71. I was In other words, in order to perform even pressure bonding, the vibration crystal substrate 71 and the reinforcing plate 75 are arranged so that their bonding surfaces are parallel to each other. It is necessary to satisfy conditions such as applying a force along the perpendicular direction and applying an equal force at each point on the surface to be crimped.

[0015] However, it is not easy to maintain these crimping conditions with high accuracy, and it is inevitable that the crimping conditions vary. Therefore, the crimping force at each point to be crimped becomes uneven, whereby the thickness of the adhesive 75 at each point to be crimped becomes uneven, and the vibrating quartz substrate 71
And the reinforcing plate 74 are adhered in a non-parallel state, and it is inevitable that the thickness of the vibrating quartz substrate 71 becomes non-uniform even if polishing is performed in this state.

Furthermore, since the vibrating quartz substrate 71 and the reinforcing plate 74 are pressure-bonded after the adhesive 75 is interposed, a large amount of force is applied to the vibrating quartz substrate 71, which may cause scratches or distortion. There was also nature.

Furthermore, since the reinforcing plate 74 is polished after forming the through-hole 74a (recess), the through-hole 74a is formed.
In the region of the reinforcing plate 74 where the vibrating crystal substrate 71 is formed, the vibrating crystal substrate 71 is not supported during polishing, so that the excitation portion of the vibrating crystal substrate 71 is easily deformed, and it is difficult to perform highly parallel polishing. Met.

On the other hand, in the second conventional example, since the reinforcing quartz plate 74 'is bonded by direct connection without using an adhesive, the problem unlike the first conventional example does not occur. It is difficult to completely remove a part of the reinforcing quartz plate 74 without damaging the reinforcing quartz plate 74 ′ by etching performed when forming the through holes 74 a ′ in the reinforcing quartz plate 74 ′. Had limitations. That is, when a single crystal of quartz constituting the reinforcing quartz plate 74 ′ is deeply etched, if a crystal defect exists in the reinforcing quartz plate 74 ′,
That portion is etched quickly, so that a so-called etch tunnel occurs. When such an etch tunnel occurs, the etchant reaches the bonding interface of the vibrating quartz substrate 71 'through the etch tunnel earlier than the time when the etching of the entire through hole 74a' is completed, and erodes the vibrating quartz substrate 71. Had been damaged.

It is an object of the present invention to obtain a piezoelectric device which can be used up to a higher frequency range by thinning a piezoelectric substrate with high precision.

[0020]

In order to solve the above-mentioned problems, the present invention has a piezoelectric substrate for vibration and a metal support, and the metal support is interposed with respect to the piezoelectric substrate. It is characterized in that it is integrally molded without interposing any inclusions.

[0021]

The invention according to claim 1 of the present invention has a piezoelectric substrate for vibration and a metal support, and the metal support is interposed between the piezoelectric substrate and the metal substrate. It is characterized in that the piezoelectric vibrator is formed by being integrally molded without sandwiching an object, thereby having the following operation.
That is, since the metal support is formed integrally with the piezoelectric substrate without interposing any intervening body, the mounting accuracy of the metal support with respect to the piezoelectric substrate (including horizontal accuracy)
In addition, the accuracy of the thickness of the metal support after the attachment is increased. Therefore, when the piezoelectric substrate is polished on one side with the metal support as a backing, the polishing accuracy of the piezoelectric substrate is also improved. As a result, the piezoelectric substrate can be thinned (thinned) with high accuracy.

Further, the piezoelectric substrate is fixed by using the metal support as a supporting portion, and the supporting shape of the piezoelectric substrate is stabilized, and the supporting portion of the vibrator shifts mechanically or due to temperature change. Instead, the resonance frequency of the vibrator can be stabilized, and the characteristics of the vibrator can be stabilized. In addition, since the integrated metal support reinforces the piezoelectric substrate, the thickness of the piezoelectric substrate can be reduced, and the overall thickness of the piezoelectric vibrator is also relatively reduced, resulting in a low-profile, high-frequency piezoelectric vibrator. Can be

According to a second aspect of the present invention, there is provided the piezoelectric vibrator according to the first aspect, wherein the metal support is provided in a region other than a vibration region of the piezoelectric substrate. Which has the following effect.
That is, the above-described operation of claim 1 can be enjoyed in a state where the vibration space is securely secured.

According to a third aspect of the present invention, there is provided the piezoelectric vibrator according to the second aspect, wherein the metal support is provided all around a side edge of the piezoelectric substrate excluding the vibration region. This has the following effects. That is, in the piezoelectric vibrator of the all around holding type,
The above-described operation of the first aspect can be enjoyed.

According to a fourth aspect of the present invention, there is provided the piezoelectric vibrator according to the second aspect, wherein the metal supports are provided at both ends of the piezoelectric substrate excluding the vibration region. It has the following features. That is, the above-described operation of the first aspect can be enjoyed in the end-supporting type piezoelectric vibrator.

According to a fifth aspect of the present invention, there is provided the piezoelectric vibrator according to any one of the first to fourth aspects, wherein an exposed surface of the metal support is covered with an insulating film. This has the following effects. That is, it is possible to reliably electrically insulate the electrode provided on the piezoelectric substrate from the metal support.

According to a sixth aspect of the present invention, there is provided a piezoelectric original plate having a thickness greater than a desired thickness of a piezoelectric substrate for vibration, and a metal support on one surface of the piezoelectric original plate by plating. A step of forming a body, and a step of manufacturing an excitation piezoelectric substrate having a desired thickness by removing the other surface of the piezoelectric original plate and thinning the piezoelectric original plate. The method is characterized in that the method for manufacturing a child is constituted, and thereby has the following operation. That is, the mounting position accuracy (including the horizontal accuracy) of the metal support with respect to the piezoelectric substrate is improved, and the thickness accuracy of the metal support after the mounting is also improved. Then, since the other surface of the piezoelectric substrate is removed by backing such a metal support having high formation accuracy, the polishing accuracy of the piezoelectric substrate is enhanced, and the piezoelectric substrate can be thinned with high accuracy. .

According to a seventh aspect of the present invention, there is provided a piezoelectric original plate having a thickness larger than a desired thickness of a piezoelectric substrate for vibration, and then forming a base metal layer on one surface of the piezoelectric original plate. Forming a metal layer on the base metal layer by forming a metal layer on the base metal layer, and removing the other surface of the piezoelectric base plate by removing the other surface of the piezoelectric base plate. A step of manufacturing a piezoelectric substrate for vibration having a desired thickness by thinning the body original plate, and forming an opening in the metal support to open a vibration region of the piezoelectric substrate to the outside by etching. And a process, which has the following effects. That is, it is possible to manufacture an all-circumference holding type piezoelectric vibrator while enjoying the same operation as the above-described operation. Further, the metal support is a material having almost no crystal defects, and an etchant used for forming the openings can be selected so as to hardly etch the piezoelectric substrate (piezoelectric vibrator). When the openings are formed, the piezoelectric substrate is hardly damaged by the etching.

According to the present invention, a piezoelectric original plate having a thickness larger than a desired thickness of a piezoelectric substrate for vibration is prepared, and an electrode and a base metal layer are formed on one surface of the piezoelectric original plate. Forming a resist pattern having an opening selectively on at least one part of the electrode and the underlying metal layer on one surface of the piezoelectric original plate, and selectively plating metal on the opening. Forming a metal support by applying, and removing the other surface of the piezoelectric original plate to make the piezoelectric original plate thinner, thereby producing a piezoelectric substrate for vibration having a desired thickness, The method is characterized in that the method for manufacturing a piezoelectric vibrator includes the step of removing the resist pattern, and has the following effects. That is, it is possible to manufacture the end-supporting type piezoelectric vibrator while enjoying the same operation as the above-described operation of claim 6. Moreover,
Since the metal support is formed by metal plating, the piezoelectric substrate is hardly damaged during the process.

According to a ninth aspect of the present invention, a base metal layer having a thickness greater than a desired thickness of a piezoelectric substrate for vibration is prepared, and then a base metal layer is formed on one surface of the piezoelectric base plate. And a step of forming a resist pattern on one surface of the piezoelectric original plate to selectively cover the vibration region of the piezoelectric substrate, and selectively plating metal on one surface of the piezoelectric original plate excluding the resist pattern. To form a metal layer, thereby forming a metal support on the piezoelectric original plate, and by thinning the piezoelectric original plate by removing the other surface of the piezoelectric original plate, The method is characterized by including a step of manufacturing a piezoelectric substrate for vibration having a thickness and a step of removing the resist pattern, thereby having the following operation. In other words, it is possible to manufacture an all-periphery-supported piezoelectric vibrator that is most suitable for use as a piezoelectric filter while enjoying the same effect as the above-described claim 6. Further, since the metal support is formed by metal plating, the piezoelectric substrate is hardly damaged during the process.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

First Embodiment FIG. 1A is an external perspective view of a piezoelectric vibrator according to the present embodiment, and FIG. 1B is a cross-sectional view taken along the line AA ′ of FIG. 1A. . The piezoelectric vibrator 1 of the present embodiment includes a piezoelectric substrate 2 made of a rectangular and thin plate-like quartz plate and a metal support 3 for supporting the piezoelectric substrate. The piezoelectric substrate 2 and the metal support 3 are in direct contact with each other and are integrally formed, and a through hole 3 a is formed at a substantially central portion of the metal support 3 along the thickness direction. The through hole 3a exposes the vibration region α at the center on one surface side of the piezoelectric substrate 2, and a vibration space β is secured there.

The insulating film 4 is provided on the exposed surface of the metal support 3. The exposed surface of the metal support 3 is
Coated with Excitation electrodes 5A and 5B are formed on the front and back surfaces of the piezoelectric substrate 2, respectively. Excitation electrodes 5A, 5B
Are arranged to face each other with the piezoelectric substrate 2 interposed therebetween in the central portion (vibration region α) of the piezoelectric substrate 2. One end of the upper surface 1a of the piezoelectric vibrator 1 (the surface with the piezoelectric substrate 2 in the figure) 1a
An external electrode 6A is formed. Upper surface 1 of piezoelectric vibrator 1
The excitation electrode 5A and the external electrode 6A provided on the piezoelectric vibrator 1 are connected to the extraction electrode 7A provided on the upper surface 1a of the piezoelectric vibrator 1.
A is electrically connected.

On the other hand, an external electrode 6B is formed on the other end of the lower surface 1b of the piezoelectric vibrator 1 (the surface with the metal support 3 in the figure). The excitation electrode 5B and the external electrode 6B provided on the lower surface 1b of the piezoelectric vibrator 1
a, the inner peripheral surface of the through hole 3a, and the back surface of the piezoelectric substrate 2 are electrically connected by a lead electrode 7B that is routed.

Since the piezoelectric vibrator 1 thus configured is held by the solid metal support 3 on the entire circumference, the thickness of the piezoelectric substrate 2 is conventionally 30 μm or less during manufacturing or handling. Even if the thickness is set to be difficult to produce due to mechanical damage, physical damage such as cracking or chipping hardly occurs.

Further, the insulating film 4 is formed on the surface of the metal support 3.
Is formed, the excitation electrodes 5A and 5B are separated from each other with a distance corresponding to the thickness of the metal support 3, and therefore, even in an actual use mode in which the excitation electrodes 5A and 5B are housed in a container (not shown), a short circuit between the excitation electrodes 5A and 5B. Has the advantage of preventing.

Next, a method of manufacturing the piezoelectric vibrator 1 will be described with reference to FIG.
This will be described with reference to FIG.

Here, an AT-cut quartz plate is used as the piezoelectric substrate 2, and the thickness of the piezoelectric substrate 2 is set to 30 μm.
m, the thickness of the metal support 3 was 100 μm.
In such an example, even if a material having relatively low mechanical strength such as quartz is used as the piezoelectric substrate 2, the mechanical strength is reinforced by the metal support 3. Even with a thickness of about 30 μm, which is conventionally highly likely to cause physical defects during handling,
It is as described above that the specification relating to the mechanical strength of a general piezoelectric vibrator is satisfied.

This piezoelectric vibrator 1 is realized by the following manufacturing steps.

That is, first, as shown in FIG. 2 (a), the piezoelectric original plate 10 (this is the base of the piezoelectric substrate 2 and is sufficiently thicker than the desired thickness (for example, 30 μm) of the piezoelectric substrate 2). In the example, a quartz plate that is horizontally polished to a thickness of 200 μm) is prepared, and a base metal layer 11 is formed on one surface of the piezoelectric original plate 10. The base metal layer 11 is a layer serving as a base layer for integrally forming the metal support 3 without interposing a support such as an adhesive layer on the piezoelectric original plate 10. The base metal layer 11 is preferably formed by a Ni electroless plating step, but a similar structure can be obtained by forming the base metal layer 11 by a technique such as sputtering or vapor deposition. In the present embodiment, the thickness of base metal layer 11 is 1 μm.

Next, as shown in FIG. 2B, a metal layer 12 made of a metal thick film is further formed on the base metal layer 11 by a thick film plating step (electrolytic plating). Metal layer 1
2 is preferably formed mainly of Ni by an electrolytic plating step, similarly to the base metal layer 11. In the step of forming the metal layer 12, the thickness of the metal layer 12 to be formed is constant.
Current control and temperature control are performed to obtain a metal layer 12 having a desired thickness. In this manufacturing method, the metal support 3 is composed of the metal layer 12 and the base metal layer 11. Also,
When the thickness of the metal layer 12 is 99 μm,
The total thickness of the metal support 3 (metal layer 12 + base metal layer 11) was adjusted to 100 μm in accordance with the thickness of (1 μm). The metal support 3 thus produced is
There is no interposition such as an adhesive (thickness control is difficult) between the metal support 3 and the piezoelectric original plate 10 by a manufacturing method capable of performing high-precision thickness control such as a plating method, a sputtering method, and a vapor deposition method. To form the metal support 3
Can be manufactured with high formation accuracy.

Next, as shown in FIG. 2C, the exposed surface (upper surface in the figure) of the piezoelectric original plate 10 is horizontally polished to a set thickness. In the present embodiment, a 200
Using a quartz plate polished parallel to μm, in this process, 30μ
m to obtain a piezoelectric substrate 2 having a desired thickness. At this time, the piezoelectric original plate 10 is horizontally polished while the metal support 3 is lined, so that the piezoelectric substrate 2 (thickness 3) is polished.
0 μm) and the metal support 3 (thickness: 100 μm) can be obtained without cracks. Moreover,
Since the precision of forming the metal support 3 as the backing is high, the polishing precision (thickness precision and horizontal precision) of the piezoelectric substrate 3 is also high.

Further, as shown in FIG. 2D, a through hole 3a is formed in the central portion of the metal support 3 corresponding to the vibration area α of the metal support 3 to secure a vibration space β. . In this step, first, the metal support 3 is masked with high accuracy by a photolithography technique in a region other than the region where the through hole 3a is formed, and then the region other than the masking region is selectively etched to form the through hole 3a. Form with high accuracy. At this time, the base metal layer 11 at the bottom of the through hole 3a
Is also removed.

At the time of performing such etching, it is conceivable that the piezoelectric substrate 2 may be damaged by the etchant.
However, since the metal support 3 to be etched hardly has a crystal defect such as a single crystal quartz plate, partial promotion of etching caused by the crystal defect (the problem to be solved by the present invention) (Detailed description in the column) does not occur, and therefore, the piezoelectric substrate 2 is hardly damaged by the etchant. Furthermore, if an etching solution that etches only metal is selected and performed, it is possible to remove only the metal portion without particular care.

Next, as shown in FIG. 2E, the whole substrate (piezoelectric substrate 2 and metal support 3) is heated
Then, the insulating film 4 made of an oxide film is formed on the exposed surface of the metal support 3 by carrying out heat treatment. At this time,
The atmosphere at the time of heating may be added with oxygen, water vapor, or the like so that oxidation proceeds effectively, but usually, treatment in the air is sufficient. By forming the insulating film 4, the piezoelectric substrate 2 and the metal support 3 (conductive portion) are insulated from each other, and there is almost no danger of electrode short-circuit in the next electrode forming step.

Next, the excitation electrodes 5A and 5B and the external electrodes 6
A, 6B and lead electrodes 7A, 7B are formed. That is, as shown in FIG. 2 (f), the electrodes 5A, 5B, 6A, and 6 of the surfaces of the piezoelectric substrate 2 and the metal support 3 are formed.
After covering the surface region where B, 7A, 7B is not formed with a mask 13 made of metal or the like, various electrodes 5A, 5B, 6A, 6B, 7A, 7B are formed vertically by a technique such as vapor deposition. Thus, the piezoelectric vibrator 1 is completed.

In the piezoelectric vibrator 1 thus manufactured, the vibration space β is formed at an accurate position, and the piezoelectric substrate 2 is thinned (about 30 μm thick) to form the vibration region α (metal The area of the piezoelectric substrate 2 facing the through hole 3a of the support 3 can also be made thinner, so that a high-precision high-frequency vibrator can be obtained.

It is to be noted that a piezoelectric substrate having a plate thickness of about 30 μm can be manufactured by the conventional manufacturing method. However, in this case, the yield is extremely deteriorated and the manufacturing cost is increased. On the other hand, according to the manufacturing method of the present embodiment, it is possible to realize a similar thinning (30 μm) without deteriorating the yield.

Second Embodiment In a second embodiment of the present invention, the present invention is applied to an end-supporting long rectangular piezoelectric vibrator 20 using a lithium niobate substrate. FIG. 3A is an external perspective view of the piezoelectric vibrator 20 of the present embodiment, and FIG. 3B is a cross-sectional view of the piezoelectric vibrator 20 of the present embodiment in a state where the piezoelectric vibrator 20 is housed in a container 21. It is. The piezoelectric vibrator 20 has a width (200 μm), a length (1200 μm), and a thickness (60 μm).
m), the size is reduced.

The piezoelectric vibrator 20 is the same as the first embodiment in that the piezoelectric substrate 22 and the metal supports 23A and 23B are laminated and integrated, but the first embodiment has the following points. Is different from the form. That is, the piezoelectric substrate 22 is formed of a strip (long rectangle) thin plate of a lithium niobate substrate,
An excitation electrode 2 is provided on each of the longitudinal central portions of the front and back surfaces.
4A and 24B are provided. Further, the excitation electrode 2
4A and 24B are opposed to each other with the piezoelectric substrate 22 interposed therebetween. One surface (upper surface in the figure) 2 of the piezoelectric substrate 22
An external electrode 25A is formed at one end of 2a. The excitation electrode 24A and the external electrode 25A provided on the upper surface 22a of the piezoelectric substrate 22
are electrically connected to each other by a lead electrode 26A provided at a.

Similarly, an external electrode 25B is formed at the other end (the end facing the one end of the above-mentioned one surface 22a) of the other surface (the lower surface in the figure) 22b of the piezoelectric substrate 22. The excitation electrode 24B and the external electrode 25B provided on the other surface 22b of the piezoelectric vibrator 22
Are electrically connected to each other by a lead electrode 26B provided at the bottom. On the other surface 22b of the piezoelectric substrate 22, a base metal layer 25C is provided at an end of the substrate facing the external electrode 25A. The base metal layer 25C is interposed between the metal support 23A and the piezoelectric substrate 22 as a base layer of the metal support 23A. Excitation electrodes 24A, 24B
The external electrodes 25 </ b> A and 25 </ b> B are arranged on the front and back surfaces of the piezoelectric substrate 22 from one end to the other in the width direction (direction orthogonal to the longitudinal direction) of the piezoelectric substrate 22.

The metal supports 23A and 23B are provided at both ends in the longitudinal direction of the other surface 22b of the piezoelectric substrate 22. Each metal support 23A, 23B and piezoelectric substrate 22
And are integrally formed in direct contact with each other. Metal support 2
Each of 3A and 23B is disposed from end to end of the piezoelectric substrate 22 along the width direction of the piezoelectric substrate 22,
The metal supports 23A and 23B are provided at both ends in the longitudinal direction of the piezoelectric substrate 22 and are spaced apart from each other. Between the two metal supports 23A and 23B, the vibration region α of the piezoelectric substrate 22 is exposed. To secure the vibration space β. In order to sufficiently reinforce the piezoelectric substrate 22, the thickness of the metal supports 23A and 23B is preferably set to about 200 μm.

The external electrode 25A is exposed on the upper surface of the piezoelectric substrate 22, and can be connected to the outside via this exposed portion. On the other hand, the external electrode 25B is on the lower surface of the piezoelectric substrate 22, is covered with the metal support 23B, and is not exposed. However, the external electrode 25
The end face of B is exposed at the side edge of the piezoelectric substrate 22,
It can be connected to the outside through this exposed part. Further, on the external electrode 25B, the metal support B is stacked and arranged in direct contact with the external electrode 25B, whereby the metal support 23B is electrically connected to the external electrode 25B. Since the metal support 23B is exposed to the outside, the metal support 23B functions as a mediating electrode in connection with the outside.

The piezoelectric vibrator 20 thus configured is
Usually, it is stored in the container 21. The container 21 includes a mounting board 21a and a lid 21b for sealing the upper side of the mounting board 21a.
And On the lower surface of the mounting substrate 21, terminal electrodes 27A and 27B are provided at both ends in the longitudinal direction. The terminal electrodes 27A, 27B are connected to the via holes 28A,
8B, it is pulled out to the upper surface of the mounting board 21.
The piezoelectric vibrator 20 is mounted on the upper surface of the mounting substrate 21, and the external electrodes 25 A and 25 B of the piezoelectric vibrator 20 are electrically connected to the via holes 28 A and 28 B and the terminal electrodes 27 A and 27 B by the conductive paste 29. It is connected to the. The lid 21b is mounted on the mounting substrate 21a in a state where the piezoelectric vibrator is mounted.
It covers and seals the upper surface. The piezoelectric vibrator 20 configured as described above is provided on the metal support 2.
3A and 23B are integrally formed by being in contact with each other at the longitudinal end of the piezoelectric substrate 22 having a rectangular shape. Further, the excitation electrodes 24A and 24B facing each other are arranged at substantially the center of the piezoelectric substrate 22 so as to excite.

The piezoelectric vibrator 20 whose ends are supported by the metal supports 23A and 23B is connected to the metal supports 23A and 23B.
The vibration space β can be easily secured simply by placing the device on a flat surface with. Therefore, as shown in FIG.
When housed in the container 21, it is not necessary to provide the vibration space β on the container side. In the container 21, the vibration space α is reliably formed only by mounting the piezoelectric vibrator 20 on the mounting substrate 21a (including the connection between the external electrodes 25A and 25B and the terminal electrodes 27A and 27B). Can be taken out.

Further, the piezoelectric vibrator 2 configured as described above
0 is held by hard metal supports 23A and 23B at both ends in the longitudinal direction as in the first embodiment.
In the case of a piezoelectric vibrator using a lithium niobate substrate as a piezoelectric substrate, the thickness of the piezoelectric substrate 22 is 60 μm or less, which is conventionally difficult to produce due to physical damage during production and handling. Even if it is set to, hardly any physical damage such as chipping occurs. In this case, the thickness of the metal supports 23A and 23B is about 60 μm as described above.

The manufacturing process of the piezoelectric vibrator 20 of the present embodiment will be described below with reference to the drawings.

The manufacturing method shown here is a mass production method on the premise that a large number of vibrators are formed using a large-sized wafer-shaped piezoelectric original plate 30.

First, as shown in FIG. 4A, the piezoelectric substrate 22 is made of lithium niobate, has a size that allows a plurality of desired piezoelectric substrates 22, and has a thickness of the piezoelectric substrate 22 (in the above example, A piezoelectric original plate 30 having a thickness sufficiently larger than 60 μm) is prepared, and electrode patterns 31A and 31B are formed on one surface 30a of the piezoelectric original plate 30. Electrode pattern 3
1A is configured by combining a pattern 31A ₁ and pattern 31A ₂ and the pattern 31A _3. Pattern 3
1A ₁ is piezoelectric original plate 30 in a later step is part of the excitation electrode 24B by being divided. Pattern 31A ₂
Is a portion that becomes the external electrode 25B by dividing the piezoelectric original plate 30 in a later step. Pattern 31A ₃ is,
This is a portion that becomes the extraction electrode 26B by dividing the piezoelectric original plate 30 in a later step. The electrode pattern 31B is
An electrode pattern to be the base metal layer 25C of one of the metal supports 23A by dividing the piezoelectric original plate 30 in a later step, and is provided at a position where the metal support 23A is formed.

In the first embodiment, these electrodes are manufactured by a technique such as vapor deposition. However, when the size of the piezoelectric vibrator is reduced and its electrode size is reduced, it is necessary to form the electrode by a more precise method. Therefore, it is difficult to cope with the vapor deposition method described in the first embodiment. Therefore, in the present embodiment, the electrode patterns 31A, 3A
1B. In the present embodiment, the electrode patterns 31A and 31B are made of Ni, and the thickness of the electrodes is 1 μm.

Next, as shown in FIG. 4B, a resist pattern 32 is formed on one surface 30a of the piezoelectric original plate 30. Resist pattern 32, by forming an opening 32a upwardly above, and the patterns 31A ₂ of the pattern electrode 31B, the electrode pattern 31B and pattern 31A
₂ has an exposed shape. Also, resist pattern 3
As the resist constituting 2B, a high-viscosity resist or a film-like resist is used to increase the thickness.

Next, as shown in FIG. 4C, the piezoelectric original plate 30 is plated with a metal, for example, Ni. This step is
An electroplating method (hereinafter, such a method is referred to as an electroforming method) which can make the thickness uniform by performing thick film plating on a region regulated by a resist (the resist pattern 32B in the above-described example) is preferable. It is also possible by electrolytic plating. Thus when electroplating piezoelectric original plate 30 is the resist pattern 32B metal part (electrode pattern 32B, pattern 31A ₂₎ by an opening 32a of are selectively plated only the exposed portion. At this time,
The plating thickness depends on the depth of the opening 32a (resist pattern 3
2 thickness). Therefore, the plating layers 33A, 33 that eventually become the metal supports 23A, 23B are formed.
The thickness of B can be controlled with high accuracy by adjusting the thickness of the resist pattern 32. The plating layers 33A and 33B formed in this manner are provided on the metal support 23A,
23B are connected to the original pattern.

Next, as shown in FIG. 4D, the other surface 30b of the original piezoelectric body plate 30 is horizontally polished to a set thickness. In the present embodiment, in this step, the piezoelectric original plate 30 'having a desired thickness is formed by reducing the thickness to 60 μm. At this time, since the piezoelectric original plate 30 is horizontally polished while the piezoelectric original plate 30 is backed by the plating layers 33A and 33B and the resist pattern 32, the polished piezoelectric original plate 3 is polished.
0 (thickness 60 μm) can be obtained without cracks. Further, the metal supports 23A and 23B as the backing
Since the precision of the formation is high, the polishing precision (thickness precision and horizontal precision) of the piezoelectric body plate 30 also increases.

Thereafter, as shown in FIG. 4E, the resist pattern 32 is removed. In this state, the electrode patterns 31A and 31B are provided on one surface 30a of the piezoelectric original plate 30 '.
Is formed, but no electrode pattern is formed on the other surface 30b of the piezoelectric body original plate 30 '. Therefore, FIG.
As shown in (f), the other surface 30b of the piezoelectric original plate 30 '
Then, an electrode pattern 31C similar to the above-described electrode pattern 31A is formed. The electrode pattern 31C includes a portion that becomes the excitation electrode 24A by dividing the piezoelectric original plate 30 in a later step, a portion that becomes the external electrode 25A, and a portion that becomes the extraction electrode 26A.

By completing the step shown in FIG.
The assembly 34 of the piezoelectric vibrator 20 is completed.
As shown in (g), by cutting the assembly 34 along the vertical and horizontal cutting lines 35 along the periphery of each piezoelectric vibrator 20, the piezoelectric vibrator 20 as shown in FIG. 3 is completed. .

In this manufacturing method, the electrode pattern 31B serving as a base layer for plating is connected to each electrode (the excitation electrodes 24A and 24A).
B, external electrodes 25A, 25B, lead electrodes 26A, 2
6B) can be formed together with the electrode pattern 31A, and the number of steps can be reduced accordingly.

Further, in the first embodiment, after the metal support 3 is formed, the metal support 3 having a desired shape is obtained by forming the through hole 3a in the metal support 3. On the other hand, in the present embodiment, the plating layers 33A, 3A
By patterning 3B, metal supports 23A and 23B having desired shapes are obtained, and in that respect, the manufacturing methods of the two embodiments are slightly different. However, both manufacturing methods are applicable to either structure of the piezoelectric vibrator (the entire circumference support structure or the end support structure), and the present invention is not limited to the combination of the structure and the manufacturing method in each of the above-described embodiments. Absent.

However, the end support structure described in the second embodiment does not necessarily include a step of forming an insulating film on the surfaces of the metal supports 23A and 23B. This is because, in this structure, since the metal supports 23A and 23B are disposed separately from each other, the excitation electrodes 24
This is because A and 24B (external electrodes 25A and 25B) do not come close to each other, and even if the surfaces of the metal supports 23A and 23B have conductivity, there is almost no risk of short-circuiting to each other. However, it goes without saying that an insulating film may be formed to ensure insulation.

Similarly, in the case of the first embodiment, it is not always necessary to form an insulating film. However, in the first embodiment, since the metal support 3 is formed integrally and the respective electrodes are arranged very close to the metal support 3, it is better to have the insulating film 4. Only preferred.

Third Embodiment FIG. 5A is an external perspective view of an MCF (monolithic crystal filter) according to this embodiment, and FIG.
FIG. 6 is a sectional view taken along the line BB ′ of FIG. The piezoelectric filter 40 of the present embodiment includes a rectangular and thin plate-shaped piezoelectric substrate 41 made of lithium tantalate and a metal support 42 for supporting the piezoelectric substrate. The piezoelectric substrate 41 and the metal support 42 are integrally formed, and the metal support 42
A through hole 42a is formed substantially in the center along the thickness direction. The vibration region α at the center on one surface side of the piezoelectric substrate 41 is opened to the outside by the through hole 42a, and the vibration space β is secured. An insulating film 43 is provided on the exposed surface of the metal support 42, and the exposed surface of the metal support 42 is covered with the insulating film 43.

One surface (upper surface in the figure) 41 of the piezoelectric substrate 41
Excitation electrodes 44A and 44B are provided at a. The excitation electrodes 44A and 44B are provided on one surface 41a of the piezoelectric substrate 41.
Are arranged facing each other at predetermined intervals along the longitudinal direction of the piezoelectric substrate 41. Both ends in the longitudinal direction of one surface 41a of the piezoelectric substrate 41 (excitation electrodes 44A,
External electrodes 45A, 45B
Are formed, and the excitation electrode 44A and the external electrode 45A and the excitation electrode 44B and the external electrode 45B which are close to each other are formed.
Are electrically connected by lead electrodes 46A and 46B similarly provided on one surface 41a of the piezoelectric substrate 41. On the other surface (lower surface in the figure) 41b of the piezoelectric substrate 41,
A metal underlayer 47 is formed on the entire surface of the piezoelectric substrate 4.
1 is formed integrally with the other surface 41b. A through hole 42a is formed in the metal layer 48. The metal support 42 described above includes a metal base layer 47 and a metal layer 48.

The piezoelectric filter 40 of the present embodiment uses lithium tantalate as the piezoelectric substrate 41.
Although this material is more brittle than quartz, it can be easily thinned by employing the structure of the present invention.
Hereinafter, the manufacturing method of the present embodiment will be described with reference to the drawings. Here, the piezoelectric substrate 4 having a thickness of 40 μm
1 is formed by disposing a metal support 42 having a thickness of 100 μm.

First, as shown in FIG. 6A, the piezoelectric substrate 41 is made of lithium tantalate, which is a source and is sufficiently thicker than the desired thickness of the piezoelectric substrate 41 (40 μm in the above example). A piezoelectric original plate 50 is prepared, and a base metal layer 47 is formed on one surface of the piezoelectric original plate 50. The base metal layer 47 is a layer serving as a base layer for integrally forming the metal layer 48 without interposing a carrier such as an adhesive layer on the piezoelectric original plate 50. The base metal layer 47 is preferably formed by a Ni electroless plating step.
A similar structure can be obtained by forming by a method such as vapor deposition. The ground metal layer 47 also serves as a ground electrode of the piezoelectric filter 40.

Next, as shown in FIG. 6B, a resist pattern 51 is formed on a portion of the metal base layer 47 which is to be a vibration space β (through hole 42a). As shown in the first embodiment, this resist pattern 51 is formed by applying a thick coating using a high-viscosity one and patterning it using a photolithography technique.

Next, as shown in FIG. 6C, a metal layer 48 is formed by electroforming.

Next, as shown in FIG. 6D, with the metal support 42 and the resist pattern 51 as the backing, the other surface of the piezoelectric original plate 50 is horizontally polished to make it thinner (40 μm).
m) to form the piezoelectric substrate 41. At this time, since the periphery of the piezoelectric original plate 50 is always reinforced by the metal support 42, it is easier to handle as compared with a case where it is handled alone, and the piezoelectric original plate 5 is not physically damaged.
It is possible to manufacture the piezoelectric substrate 41 by reducing the thickness of 0.

Then, as shown in FIG. 6 (e), after removing the resist pattern 51 to form a through hole 42 a in the metal support 42, the excitation electrodes 44 A, 44 B, External electrodes 45A and 45B and lead electrodes 46A and 46B are formed.

Next, as shown in FIG. 6F, excitation electrodes 44A and 44B, external electrodes 45A and 45B, and lead electrodes 46A and 46B are formed on the upper surface 41a of the piezoelectric substrate 41. Note that this electrode is divided to form the MCF. In addition, since the filter requires precise dimensional control of the electrode size and the electrode interval, it is difficult to cope with electrode pattern deposition using a metal mask as described in the first embodiment. Here, in this embodiment mode, various electrodes are formed using a photolithography technique. Note that the MCF requires a back electrode (ground electrode). In the above configuration, since the back surface of the piezoelectric filter has a recess (metal support 47), it is difficult to apply a uniform resist, and it is difficult to form a back electrode by applying photolithography technology. Since 47 also serves as a ground electrode (backside electrode), there is no need to separately form a backside electrode.

Common to the first, second and third embodiments, LiNbO ₃ , LiTaO ₃ , or KNbO ₃ crystal, quartz, or langasite-based crystal can be used for the piezoelectric substrate. The thickness of the piezoelectric substrate constituting the vibrator is 5
A range of from 150 to 150 μm is preferred. On one side of these piezoelectric substrates, a metal support is formed by pressure. The metal support can employ a metal plating layer, preferably Ni, Co,
Metals such as Cr and Fe are effective because of their high elastic modulus and high toughness. Also, Cu, A is used on the metal support.
g, Au, etc. can also be used.

Further, the manufacturing method of the present invention can include a step of thinning to a set thickness with a metal support as a backing.

[0081]

As described above, since the piezoelectric substrate can be accurately supported without using an adhesive or the like, the thickness of the substrate can be reduced with high precision, and a high frequency can be achieved.
Further, since the thin piezoelectric substrate is no longer handled alone, breakage of the substrate can be prevented, and the yield can be improved. As a result, it is possible to increase the frequency without deteriorating the yield. In addition, since the vibration space is accurately secured by the metal support, the mounting method can be simplified even when the element is downsized. Further, by forming an insulating film on the surface of the metal support, short-circuiting of the electrodes provided on the front and back surfaces of the piezoelectric substrate can be reliably prevented, so that the production yield is improved accordingly.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a configuration of a piezoelectric vibrator according to a first embodiment of the present invention and a sectional view thereof.

FIGS. 2A to 2C are cross-sectional views illustrating respective states of the piezoelectric vibrator according to the first embodiment during manufacture.

FIG. 3 is a perspective view and a cross-sectional view illustrating a configuration of a piezoelectric vibrator according to a second embodiment of the present invention.

FIGS. 4A to 4C are cross-sectional views illustrating respective states of the piezoelectric vibrator according to the second embodiment in the course of manufacturing.

FIG. 5 is a perspective view and a cross-sectional view illustrating a configuration of a piezoelectric filter according to a third embodiment of the present invention.

FIGS. 6A and 6B are cross-sectional views illustrating respective states during the manufacture of the third embodiment.

FIG. 7 is a perspective view showing a configuration of a conventional piezoelectric vibrator.

FIG. 8 is a sectional view of a first conventional example.

FIG. 9 is a sectional view of a second conventional example.

[Explanation of symbols]

Reference Signs List 2 piezoelectric substrate 3 metal support 3a through hole 4 insulating film α vibrating region β vibrating space 10 piezoelectric original plate 11 base metal layer 12 metal layer 13 mask 20 piezoelectric vibrator 22 piezoelectric substrate 23A metal support 23B metal support 30 Piezoelectric original plate 40 piezoelectric filter 41 piezoelectric substrate 42 metal support 42a through hole 43 insulating film 47 metal base layer 48 metal layer

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H03H 9/56 H01L 41/22 Z (72) Inventor Yoshihiro Tomita 1006 Kazuma Kadoma, Kadoma City, Osaka Matsushita Electric Industrial F term in the company (reference) 5J108 BB01 BB02 BB04 CC04 DD02 EE03 EE04 EE07 EE14 GG03 KK01 KK03

Claims (9)

[Claims] 1. A piezoelectric substrate for vibration and a metal support, wherein the metal support is formed integrally with the piezoelectric substrate without interposing any intervening body therebetween. Piezoelectric vibrator. 2. The piezoelectric vibrator according to claim 1, wherein the metal support is provided in a region excluding a vibration region of the piezoelectric substrate. 3. The piezoelectric vibrator according to claim 2, wherein said metal support is provided on the entire periphery of a side edge of said piezoelectric substrate excluding said vibration region. 4. The piezoelectric vibrator according to claim 2, wherein said metal supports are provided at both ends of said piezoelectric substrate excluding said vibration region. 5. The piezoelectric vibrator according to claim 1, wherein an exposed surface of said metal support is covered with an insulating film. 6. A step of preparing a piezoelectric original plate having a thickness larger than a desired thickness of a piezoelectric substrate for vibration, and forming a metal support on one surface of the piezoelectric original plate by a plating method; Producing a piezoelectric substrate for excitation having a desired thickness by removing the other surface of the original plate to make the piezoelectric original plate thinner, thereby producing a piezoelectric vibrator. 7. A piezoelectric base plate having a thickness greater than a desired thickness of a piezoelectric substrate for vibration is prepared, a base metal layer is formed on one surface of the piezoelectric base plate, and a metal layer is formed on the base metal layer. Forming a metal layer by plating to form a metal support on the piezoelectric original plate, and removing the other surface of the piezoelectric original plate to reduce the thickness of the piezoelectric original plate. A step of producing a piezoelectric substrate for vibration having a thickness of: and a step of forming an opening in the metal support to open a vibration region of the piezoelectric substrate to the outside. Child manufacturing method. 8. A step of preparing a piezoelectric original plate having a thickness larger than a desired thickness of a piezoelectric substrate for vibration, and forming an electrode and a base metal layer on one surface of the piezoelectric original plate; Forming a resist pattern having an opening selectively over at least a part of the electrode and the underlying metal layer on one surface; and forming a metal support by selectively applying metal plating to the opening. A step of producing a piezoelectric substrate for vibration having a desired thickness by removing the other surface of the piezoelectric original plate and thinning the piezoelectric original plate, and a step of removing the resist pattern. A method for manufacturing a piezoelectric vibrator, comprising: 9. A step of preparing a piezoelectric original plate having a thickness larger than a desired thickness of the piezoelectric substrate for vibration, and forming a base metal layer on one surface of the piezoelectric original plate; Forming a resist pattern that selectively covers the vibration region of the piezoelectric substrate; and selectively applying metal plating to one surface of the piezoelectric original plate excluding the resist pattern to form a metal layer. Forming a metal support on the piezoelectric base plate, and removing the other surface of the piezoelectric base plate to reduce the thickness of the piezoelectric base plate, thereby forming a piezoelectric substrate for vibration having a desired thickness. A method for manufacturing a piezoelectric vibrator, comprising: a step of manufacturing; and a step of removing the resist pattern.