JPS6051282B2 - Piezoelectric resonator and its manufacturing method - Google Patents

Description

[Detailed description of the invention] The present invention relates to a method for manufacturing a thickness-shear type piezoelectric resonator.

Piezoelectric resonators configured to operate at frequencies above 1MH2 generally operate in a thick-wall mode and are often circular in diameter, typically 8 to 14 wn. When an electrode is attached to the center of such a resonator, the mass of that part increases, which causes a phenomenon in which the vibration energy of the resonator is taken away. The way in which this vibrational energy is taken away is greatest in the area covered by the electrodes, and decreases to an exponential function curve as it goes to areas not covered by the electrodes. Such a resonator is supported at its periphery, and the resonator thickness, electrode thickness, density and diameter are taken into account to provide adequate support without lowering the Q. Minimum diameter can be determined. For planar resonators that operate at low frequencies, a large single-diameter design is necessary, which is not suitable for applications where ultra-miniaturization is important.

Alternatively, one is forced to use electrode diameters where the dynamic damage is insufficient to use the resonator assembly as an oscillator. To overcome these limitations, the surface of the resonator can be of spherical or conical shape, but then the resonator shape is similar to the well-known plano-convex, biconvex or umbrella resonator. becomes.

However, in such cases, machining becomes very difficult and the cost of the product becomes prohibitively high for many applications. Without considering the energy trap phenomenon,
In order to prevent Q degradation due to support, the resonator is coupled by a coupling member in the form of arms that are integral with the resonator, have a thickness smaller than that of the resonator, and preferably face each other at both ends of the resonator's diameter. It has been proposed to support (eg British Patent No. 447,665).

However, such a resonator is also very difficult to machine, and the tuning angle of the resonator arm (An?EOftllet)
Such a support structure is unsatisfactory in practice, since it also causes undesirable reflections. It is therefore an object of the present invention to obtain a small, thick, full-mode operating resonator which prevents Q degradation due to support and whose cost is kept within an acceptable range due to simple machining. That's true.

The resonator or resonator assembly of the present invention that operates in the thickness mode includes a part to which an electrode is attached and vibrates;
This is obtained by stamping out a single piece of AA arm which cantilevers this part and holds the lead connecting the electrode to the support area.

Preferably, this punching is carried out from a piezoelectric material plate of uniform thickness, so that several resonators or resonator assemblies can be obtained from the same piezoelectric plate. In a preferred embodiment of the method of the invention, the entire circumference of each resonator, except for the three free ends of the arms, is cut away from the piezoelectric material plate. The free end of the arm is connected to the piezoelectric material plate by a notch or strain concentration point, which notch is severed at the end of the manufacturing process. Electrical connections between the electrodes and the leads and the four external conductive regions of the arm, as well as several resonators, are obtained in a single metallization process, which allows the resonators to be vibration tested separately during manufacture. or all resonators can be tuned to several frequencies in close proximity. Hereinafter, the present invention will be described in detail with reference to the drawings.

The influence of thickness on the Q of support of the vertical mode is related to the distance between the support point and the electrode edge and the manner of energy reduction.

The manner of this energy reduction is a function of the electrode geometry. The distance between the electrode edge and the resonator edge is not important as long as the resonator edge has a large Q. The fact that the edges of the resonator have a large Q means that the structure of the piezoelectric material is not different from that of the resonator.
These aspects are taken into account in the realization of the resonator 1, as shown in FIG. 1a.

In the resonator 1, an arm 5 is punched out from a rectangular plate shown by a chain line. Figure 1 shows a square plate 2.
A conventional resonator 1'', punched out from ``resonator 1'' and having the same performance as resonator 1, is shown superimposed to the same scale. As can be readily seen from this figure, the area occupied by the resonator 1 of the invention and the amount of material required are significantly reduced compared to the conventional resonator 1''. The diameter of the electrode 3 shown can be arbitrarily selected as shown in Fig. 1b. Also, as is clear from Fig. 1, the circular resonator 1 and the arm 5 that cantilevers it are made of the same material. and have substantially the same thickness, resulting in a relatively large Q at the resonator edge compared to the prior art.

Also, this cantilevered support structure facilitates attachment of this resonator to a utilization device. Furthermore, it can be easily understood that such a cantilever support structure allows the shape of the punched pattern to be reduced, making it suitable for mass production. The machining of such a shaped resonator 1 may not be carried out in the same manner as is commonly used for circular resonators.

Therefore, the present invention does not require resonance by optical engraving or ultrasonic punching. It is about obtaining. The method of the present invention begins by cutting out a thin 9) plate from the selected piezoelectric material by mass machining. Thickness of this thin plate Acid cutting performed after this cutting process
It is adjusted to correspond to the selected frequency, taking into account deformations caused by processes such as cutting (catching) and electrode attachment. Figure 2a shows one method of punching out several resonators from a piece of piezoelectric material 2, and Figure 2b
shows a method similar to that shown in FIG. 2a, which allows further material savings. Electrodes 3 and leads 4 can be deposited by known methods such as vacuum evaporation or cathode spacing, by using a mask or by covering the entire surface of the resonator and then applying a chemical that does not act on the piezoelectric material. By selectively removing undesirable portions by means of means, it can be deposited accurately in a predetermined position.1. Ru.

FIG. 3 shows details of the structure of the resonator of the invention.

The resonator 1 is coupled to the piezoelectric plate 2 at an arm 5 and a notch or strain concentration point 6. The punching is carried out around the entire circumference of the assembly comprising the resonator 1 and the arm 5, except for the notch 6, by photochemical machining, ultrasonic punching or similar processing methods, by removing material around one area 7. . The notch 6 that blocks the region 7 is the resonator 1 and its arm 5.
It is only necessary to cut it after the various processing steps in order to separate it from the rest of the piezoelectric plate 2. Electrode 3 is connected to the connection point between support 8 and lead 4. The lead 4 is pulled out along the edge of the arm 5. A counter electrode is provided on the back surface of the resonator 1, facing the electrode 3, and a lead 4'' (shown by a broken line) connected to the counter electrode is connected to an arm 5.
is pulled out along the other edge of the arm 5 in such a way as to avoid piezoelectric excitation of the arm 5. On the surface of the piezoelectric plate 2 , on the outer part of the arm 5 , a metallized region 9 is provided which is continuous with the lead 4 without being interrupted by the notch 6 . A metalized region 9″ similar to the region 9 is also provided on the back surface of the piezoelectric plate 2.
The metallized areas 9, 9'' are provided continuously with the lead 4'' in such a way as to avoid excitation of the piezoelectric plate 2.The metallized areas 9, 9'' allow the piezoelectric plate to be cut off at the notch 6 during the fabrication of the resonator 1. This is in order to be able to excite the resonator 1 in order to determine the characteristics of the resonator 1 and thus to correct the characteristics before separating the resonator 1 from the resonator 2. A typical manufacturing process for the resonator of the present invention can be summarized as follows.

a A thin piezoelectric plate 2 having uniform thickness is cut out from a square or rectangular piezoelectric plate by machining.

The thickness of the crystal plate that operates at a frequency of 10MHz is 0.166770F in the case of AT cut! It is.

b Place a positioning mark, such as a centering hole, on the piezoelectric plate 2.
Provided for. c. Apply a photosensitive material film to both sides of the piezoelectric plate 2.

d Exposure is performed from above a mask configured to reproduce the cut section 7. (e) Develop to remove the photoresist film adhering to the entire surface of all cut portions 7.

f Cut along the cutting section 7 with an acid or other solvent suitable for the given piezoelectric material.

g Remove the photosensitive material.

h Clean the surface of the piezoelectric plate 2 with a chemical substance that does not act on piezoelectric materials.

The electrode 3, the lead 4, and the conductive regions 8 and 9 are attached to the surface of the piezoelectric plate 2 by vacuum evaporation using an i mask.

j Connect the resonator 1 to a circuit while placed in a vacuum evaporation apparatus, and adjust the frequency of the resonator 1 by attaching metal to the electrode 3 using a removable mask.

By bending the k-arm 5, the arm 5 is separated at the notch 6, and the resonator 1 having the arm 5 is separated from the piezoelectric plate 2.

Attachment of the resonator 1 to the circuit can be easily performed by operating a lamp.

However, in order to maximize the mounting strength, one of the conductive areas 8 of the resonator 1 may be soldered to the support 10 and the other conductive area 8 to the wire 12. A wire 11 is connected to the support 10, and wires 11 and 1
2 is connected to the circuit. The several embodiments described in this specification represent only a few of the many resonators made in accordance with the present invention.

As in the case of resonators made by methods other than the present invention,
A resonator made with the method of the invention must meet the desired parameters. The dynamic capacitance of these resonators is adjusted by the diameter of the electrode 3, which covers the entire surface of the resonator or only part of the surface. Parasitic frequencies due to non-harmonic modes can be eliminated by appropriate selection of the diameter, thickness and density values of the electrodes 3. The arm 5 is designed to eliminate parasitic vibrations caused by motion along the edge, surface vertical vibration mode, bending vibration mode, or longitudinal vibration mode.
It can be made into various shapes as shown in FIGS. 5A, b, and c. An application of the invention which appears to be of particular interest is one in which several resonators 1, for example filters, are assembled into a single sheet, with the various electrical connections necessary during the metal film deposition process completed. It can be manufactured directly from a small-area piezoelectric material plate.

The difference between this method of directly manufacturing an assembly using many resonators and the method described above is that in the former, there is no notch 6, so the resonator 1 with the arm 5 remains attached to the piezoelectric plate 2. It is a certain thing. Compared to monolithic filters, a significant advantage is obtained that there is no mechanical coupling between the resonators since the coupling element is external. Furthermore, by using the method described above, it is possible to work with the resonator and resonator support arm attached to one plate until the resonator or resonator assembly is completed, which also simplifies the manufacturing process and lowers the manufacturing quality. You can also do that.

Furthermore, according to the present invention, since the conductor connected to the electrode on the resonator is extended to the outer plate portion 9 of the resonator support arm through the portion where the cross section of the resonator support arm is reduced, piezoelectric resonance can be achieved. The performance of the resonator can be tested during the manufacturing process and, if necessary, adjusted before being disconnected.

FIG. 6 shows the circuit of a Jaumlann assembly with four corresponding resonator plates and their terminals.

[Brief explanation of drawings]

FIG. 1a is a plan view showing a separated resonator obtained by the method of the invention superimposed on a resonator according to the prior art;
FIG. 1b is a plan view showing an example of a resonator with a reduced electrode diameter, and FIGS. 2A and b are plan views showing different examples of manufacturing methods for resonators punched from the same piezoelectric plate. Third
4 is a plan view showing the resonator still attached to the piezoelectric plate to show the state of metal film attachment; FIG. 4 is a perspective view showing an example of bonding the resonator of the present invention in a separated state; FIG. 5A, b, and c are plan views showing various examples of shapes of the resonator of the present invention, and FIG. 6 is a circuit diagram showing the connection of the resonator of the present invention to an electric circuit and its actual connection mode. FIG.

Claims (1)

[Claims] 1 In a method for manufacturing a flat plate piezoelectric resonator that operates in a thickness-shear mode, a plurality of resonators 1 and one end of each resonator corresponding to each resonator are formed from a single plate 2 of a uniform thickness made of a piezoelectric material. By removing the periphery of the resonator support arm 5 provided at A large part of the plate is separated from other parts in the plate, and only a part 6 of each resonator support arm has a reduced cross-section than the other part, and only through this reduced part can the plate be separated. attaching electrodes to both sides of each resonator, and reducing the cross-section of each resonator support arm from each electrode attached to both sides to each side of each resonator support arm; 6 to the outer plate portion 9 of each resonator support arm; after depositing the electrodes and conductors described above, the outer plate portion 9 of each resonator support arm is used to conduct each resonator. A step of testing and adjusting the performance of the resonator 1; and a step of separating each resonator and each resonator support arm from the plate at a portion where the cross section of each resonator support arm is reduced. A method for manufacturing a piezoelectric resonator.