JPS6019843B2 - Thickness shear oscillator - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a thickness-shear vibrator with excellent electrical characteristics.

Recently, in communication equipment etc. that use thickness-shear resonators,
There is a trend toward miniaturization and higher frequency of such devices, and accordingly, it is desired to improve the characteristics of the vibrator.

Generally, the approximate frequency of such a thickness-shear oscillator is determined by its shape, particularly its thickness, but fine adjustment of the frequency is performed by adjusting the mass of the electrodes of the oscillator.

Fig. 1 a, b and Fig. 2 a, b are a front view and a plan view showing an example of such a vibrator, and Fig. 1 is a vibrator element piece 1.
This is a vibrator in which electrode films for fine frequency adjustment, that is, adjustment films 3, are formed on electrodes 2 on both side plate surfaces of the transducer. What is shown in FIG. 2 is a vibrator in which an adjustment film 3 is formed on the electrode 2 only on one electrode side. By the way, when forming an adjustment film on the electrode of a vibrator, it is an important condition to minimize the influence on the electrical characteristics and circuit constants of the vibrator before and after adding the adjustment film.

In order to satisfy this condition, it is necessary to form the adjustment film 3 with a uniform thickness over the entire surface of the opposing electrode surfaces of the electrodes 2 as shown in the front view and plan view shown in FIGS. 3a and 3b. It is considered ideal. However, it is impossible with the current technology to form such an adjustment film of a predetermined shape and uniform thickness using means such as vapor deposition. For this reason, due to manufacturing technology problems, vibrators as shown in FIGS. 1 and 2 have been produced. That is, in the vibrator shown in FIG. 1, an adjustment film 3 is added to the central part of the opposing electrodes to reduce the influence on the parallel capacitance Co, which will be described later.
As a result, the effective resistance increases and the secondary vibration characteristics deteriorate. In addition, in the vibrator shown in FIG. 2, an adjustment film 3 is added to the entire surface of the opposing surface of one electrode 2 in order to prevent the aforementioned deterioration of electrical characteristics. There was a problem in that the adjustment film 3 that came off from the part increased the area of the opposing electrodes, substantially increasing the parallel capacitance Co among the equivalent constants of the vibrator, and changing the predetermined design value.

In this way, the vibrators shown in Figures 1 and 2 not only have manufacturing problems, but also have an adjustment membrane added to prevent the deterioration of the electrical characteristics of the vibrator when making fine adjustments to the frequency. However, it has been impossible to prevent changes in the equivalent constants, especially the value of the parallel capacitance Co. In addition, in these vibrators, since the diameters of the electrodes formed on the plate surface are the same, high precision is required for positioning when forming the electrodes, and the adjustment film is attached to the electrodes by vapor deposition. There was also the problem that productivity was extremely low because a high degree of skill was required to add it to a predetermined relative position.

The present invention has been made in consideration of the above-mentioned circumstances, and prevents an increase in effective resistance and deterioration of secondary vibration characteristics without changing the equivalent constant of the vibrator, especially the parallel capacitance Co, and has excellent productivity. The purpose of this invention is to provide a thick-shear resonator with a high thickness.

Hereinafter, one embodiment of the present invention will be described in detail with reference to FIGS. 4 and 5.

By the way, as described above, when an adjustment film is added on the electrode, the characteristics of the vibrator are affected as follows.

In other words, the graphs shown in Figures 4a and 4b are graphs showing the results of experiments conducted by the present inventors, and Figure 4a shows the actual resistance value of the vibrator when the diameter of the adjustment film is constant and the film thickness is varied. Graph showing the rate of change. In addition, in FIG. 4b, the adjusted film thickness is constant,
It is a graph showing the rate of change in the effective resistance value of the vibrator when the membrane diameter is changed. As is clear from this graph, the smaller the adjustment membrane surface is with respect to the electrode surface formed opposite the vibrator plate surface, and the thicker the membrane thickness, the greater the vibration loss of the vibrator. It was also confirmed that this caused deterioration of secondary vibration characteristics.

The present invention was made with the focus on the fact that the larger the adjustment membrane surface is compared to the electrode surfaces formed facing each other without changing the parallel capacitance Co, the more advantageous the resonator will be. be.

FIGS. 5a and 5b are a front view and a plan view showing an embodiment of the present invention. This thickness-shear oscillator has a first electrode 4 having a diameter a formed on one side plate surface of the vibrator plate 1, and a second electrode 4 having a diameter b facing oppositely to the first electrode 4 on the side plate surface. 5 is formed. Note that the width b of the second electrode 5 is set to be smaller than the width a of the first electrode 4. and,
A transparent frequency adjustment film 6 is formed on the first electrode 4 . Note that the diameter c of this frequency adjustment film 6 is the same as the first
With respect to the values a and b of the second electrodes 4 and 5, a>c>b is satisfied. ．． That is, the vibrator configured as described above has the following effects.

The characteristics of this vibrator will be explained below with reference to the results of measurement. First, the adjustment film 6 is placed on the surface of the first and second electrodes 4 and 5 because the adjustment film 6 has a ratio a>c>b with respect to the pots a and b of the first and second electrodes 4 and 5. It can be formed and added to have a uniform thickness over the entire surface of the projection plane of the second electrode 5 in the vertical direction. Therefore, even after applying force to the adjustment membrane 6, no increase in effective resistance or deterioration of secondary vibration characteristics occurs. FIG. 6 is a graph in which the horizontal axis represents the frequency change corresponding to the adjustment amount of the adjustment membrane 6, and the vertical axis represents the change in the effective resistance value of the vibrator after frequency fine adjustment with respect to the frequency change. In this graph, A indicates the characteristics of the conventional vibrator shown in FIG. 1, and B indicates the characteristics of the vibrator of the present invention. In addition, the outer diameter of the vibrator is 5.5, the frequency is 14 MH2, and the order is 7.
With harmonics, the first electrode flea a of the vibrator of the present invention has 2.6 ribs, the second electrode flea b has 1.9 ribs, and the adjustment membrane flea c has 2.6 ribs. I'm taking revenge. Further, the diameter of the electrodes of the conventional vibrator shown in FIG. 1 was 2.6 ribs, and the diameter of the adjustment membrane was 1.6 willow. As is clear from this graph, the conventional vibrator has a roughly linear curve that slopes upward to the right, and the effective resistance increases in proportion to the amount of adjustment, but the vibrator of the present invention has a quadratic curve that slopes downward to the right, and the effective resistance increases. There are also few. Further, as a result of comparative measurement of secondary vibration characteristics using the conventional vibrator described above and the vibrator of the present invention, the results shown in FIGS. 7a and 7b were obtained.

This graph shows the distribution of the level difference between the main vibration and the sub-vibration of a plurality of samples, and FIG. 7a shows the conventional vibrator, and FIG. 7b shows the vibrator of the present invention.

It is clear from this graph that the vibrator of the present invention exhibits good secondary vibration characteristics. Further, according to the present invention, the adjustment film 6
Even if it is added outside the maximum opposing area between the first and second electrodes 4 and 5, there is no change in the opposing area of the electrodes 4 and 5, so there is no change in the parallel capacitance Co, which is advantageous in terms of design. Become.

Furthermore, even if the adjustment film 6 protrudes from the outer periphery of the electrode 4,
No substantial increase in parallel capacitance Co occurs. Furthermore, since the first electrode 4 and the second electrode 5 have different sizes, alignment of the electrodes becomes easy. In addition, when adding the adjustment film 6 on the electrode 4, if the adjustment film 6 is formed within a range that changes the size of the second electrode 5, the main purpose of the present invention can be achieved and the work can be done easily. It is easy and has good productivity. As described in detail above, according to the present invention, the sizes of the electrodes of the vibrator element are made different, and the area of the electrode on the electrode side with a larger area is placed on the electrode side with a smaller area than the electrode with a smaller area facing this electrode. Since the adjustment film is added over a large area, it is possible to provide a thickness-shear oscillator with good increase in effective resistance and deterioration of secondary vibration characteristics without changing the equivalent constant of the oscillator, and with excellent productivity.

[Brief explanation of the drawing]

Fig. 1 a, b and Fig. 2 a, b are a front view and a plan view showing an example of a subordinate oscillator, Fig. 3 a, b are a front view and a plan view showing an example of an ideal oscillator. , FIGS. 4a and 4b are graphs showing the relationship between the electrode diameter and the adjustment film amount and the effective resistance, FIGS. 5a and 5b are front and plan views showing an embodiment of the present invention, and FIG. A graph showing the relationship between membrane and effective resistance,
FIGS. 7a and 7b are graphs showing spurious characteristics of the subordinate resonator and the resonator of the present application. DESCRIPTION OF SYMBOLS 1... Vibrator element piece, 4... First electrode, 5... Second electrode, 6... Frequency adjustment membrane. Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7

Claims (1)

[Claims] 1. A plate-shaped vibrator element, a first electrode having a predetermined diameter formed on one side plate surface of this vibrator element, and the first electrode formed on the other side plate surface of this vibrator element. A thickness shear vibrator comprising: a second electrode having a smaller diameter than the electrode; and a frequency adjustment film having a larger diameter than the second electrode and formed on the first electrode.