JPS6214511A - Piezoelectric resonance parts and their production - Google Patents

Abstract

PURPOSE:To minimize the use quantity of an expensive silicone rubber to reduce the production cost of piezoelectric resonance parts by sticking the silicone rubber as a certain amount of elastic materials to only an oscillating part. CONSTITUTION:A pair of oscillating electrodes 2a and 3a are formed on the center part of one principal surface 1a of a piezoelectric substrate 1 constituting piezoelectric resonance parts, and electrodes 2a and 3a are connected to external connection electrodes 2b and 3b formed in corner parts of the substrate 1 by lead-out electrodes 3a and 3b. A common electrode 4a is formed on the position of the other principal surface 1b facing electrodes 2a and 3a, and the electrode 4a is connected to an external connection electrode 4b through a lead-out electrode 4c. The area where electrodes 2a and 4a are formed is defined as an oscillation part A, and the oscillation part A is oscillated in the thickness slip oscillation mode. A certain amount of a silicone rubber 6 is stuck to the oscillation part A as elastic materials, and the whole of them is molded with a sheath material 7 in this state. When the silicone rubber 6 is stuck,the silicone rubber 6 is dropped to only the oscillation part A by a dispenser.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a piezoelectric resonant component using a thickness shear vibration mode used in applications such as ceramic discriminators and filters, and a method for manufacturing the same.

There are various vibration modes of piezoelectric resonant components, such as vertical vibration, bending vibration, radial vibration, and thickness shear vibration.Among these, thickness shear vibration is achieved by partially providing an electrode on a piezoelectric substrate. It is based on the so-called energy confinement phenomenon in which vibrational energy is confined near the electrodes due to mass loading effects and piezoelectric reactions.

By the way, in a piezoelectric resonant component that utilizes this thickness-shear vibration mode, the vibrating electrode and the vibrating portion in its vicinity require a space sufficient to allow vibration. However, when used as a discriminator or filter, no space is provided and the device is covered with a soft elastic material. This is because by slightly suppressing vibrations using an elastic material, filters can suppress spurious signals, and discriminators can lower the mechanical Q and obtain good FM signal demodulation characteristics. be.

FIG. 4 shows a conventional ceramic discriminator covered with such a soft elastic material. In the figure, a is a piezoelectric substrate, b is a vibrating electrode, C is a lead frame, d is a soft elastic material, and e is an exterior material such as epoxy resin provided around the outer periphery of the elastic material d. Silicone rubber is generally used as the elastic material d. This silicone rubber is produced by immersing the piezoelectric substrate a to which the lead frame C is attached in a bath containing melted silicone rubber, as shown in FIG.
It is attached onto the piezoelectric substrate a by a so-called dip method). After drying the silicone rubber d, it is molded with an epoxy resin e, and the lead frame C is cut at a predetermined position to obtain a ceramic discriminator as a finished product.

However, in the conventional piezoelectric resonant products mentioned above, the silicone rubber as the elastic material is attached by a so-called dipping method, so it covers the entire piezoelectric substrate 1. There are problems like this.

■A large amount of silicone rubber, which is relatively expensive compared to other exterior resins, is used, and its partial pressure type resonance components are expensive.

(2) Since the entire piezoelectric substrate is covered with silicone rubber, unnecessary vibrations occurring in areas other than the vibrating electrode portion and its vicinity cannot be sufficiently suppressed. Since this unnecessary vibration also affects the characteristics of filters and discriminators, there is an urgent need to eliminate it.

In view of these points, the present invention uses a small amount of elastic material (silicon rubber), and furthermore, the vibrating electrode portion and its vicinity (hereinafter, this portion is referred to as the vibrating portion).

) It is an object of the present invention to provide a useful piezoelectric resonant component that can effectively prevent vibrations in parts other than those shown in FIG.

In order to achieve the above object, the piezoelectric resonant component of the present invention is characterized in that a certain amount of elastic material is attached only to the vibrating portion of the piezoelectric substrate that vibrates in the thickness shear vibration mode.

Further, the method for manufacturing a piezoelectric resonant component of the present invention is characterized in that the piezoelectric resonant component is manufactured by dropping a fixed amount of an elastic material onto a vibrating portion of a piezoelectric substrate that vibrates in a thickness-shear vibration mode.

FIG. 1 shows a piezoelectric resonant component as an embodiment of the present invention. 1 is a piezoelectric substrate made of, for example, PZT, and as shown in FIG. Vibrating electrodes 2a and 3a are formed. Each vibrating electrode 2a, 3a is an external connection electrode 2b formed at a corner of the piezoelectric substrate 1, as shown in FIG.

3b through extraction electrodes 2c and 3c. The vibrating electrodes 2a, 3 are provided on the other main surface 1b of the piezoelectric substrate 1.
A common electrode 4a is formed at a position opposite to a. This electrode 4a is also connected to an external connection electrode 4b formed at the end of the piezoelectric substrate 1 through an extraction electrode 4C. The external connection electrodes 2b, 3b, 4b are connected to the lead terminals 5a, 5b, 5c of the lead frame 5 via solder or the like, and the vibrating electrodes 2a, 3a and their vicinity A (corresponding to the other main surface 1b) ) is a part that vibrates in the thickness shear vibration mode, and a fixed amount of silicone rubber 6 is attached to this part A as an example of an elastic material. In this state, the entire piezoelectric substrate 1 is molded with an exterior material 7 such as epoxy resin. However, the method of packaging is not limited to the resin mold described above, and various methods used as mounting techniques can be used.

In order to manufacture the above piezoelectric resonant component, as shown in FIG. Using a dispenser 10, a dispenser 10 is used to drop molten silicone rubber 6 at a constant rate onto the vibrating portion A of the central part of the lb, and after the silicone rubber dries, an exterior material 7 is molded. Then, a part of the tie bar of the lead frame 5 is cut,
A piezoelectric resonant component is obtained as a finished product.

According to the piezoelectric resonant component manufactured as described above, since silicone rubber is attached only to the vibrating part A, moderate damping is applied to the vibrating part A based on the elasticity of the silicone rubber, and the parts other than the vibrating part A are Vibration is effectively suppressed by the molding of the exterior material 7. Therefore, when used as a filter, spurious emission can be suppressed to an extremely low level, and when used as a discriminator, the mechanical Q is suitably low and excellent demodulation characteristics can be exhibited.

As described above, according to the present invention, the amount of elastic materials such as silicone rubber, which are relatively expensive, can be reduced to the necessary minimum, resulting in lower product costs. Since unnecessary vibrations can be efficiently suppressed in areas other than the vibrating portion A by directly molding the substrate surface with an exterior resin, it is possible to obtain a piezoelectric resonant component with excellent characteristics.

In addition, in the present invention, it is only necessary to drop a fixed amount of the elastic material onto the vibrating part, so there is no need for the dissociation process in which the entire piezoelectric substrate is immersed in a bath of molten silicone rubber, which is required in the past. After connecting the frame, the work of attaching the elastic material can be done in the same line, which increases productivity.Also, since parts other than the vibrating parts are usually molded directly with the exterior resin, the thickness of the exterior resin increases accordingly. , the impact resistance of the parts themselves increases.

[Brief explanation of the drawing]

FIG. 1(a) is a front cross-sectional view of a piezoelectric resonant component as an embodiment of the present invention, FIG. 1(b) is a side cross-sectional view, FIG. 2 is a diagram showing a piezoelectric substrate, and FIG. 4 is a front sectional view showing a conventional piezoelectric resonant component, and FIG. 5 is a diagram illustrating a procedure for manufacturing a conventional piezoelectric resonant component. 1...Piezoelectric substrate, A...Vibration part Patent applicant Murata Manufacturing Co., Ltd.) Figure 1 Figure 2 Figure 3

Claims (4)

[Claims] (1) A piezoelectric resonant component characterized in that a fixed amount of elastic material is attached only to the vibrating portion of a piezoelectric substrate that vibrates in a thickness-shear vibration mode. (2) The piezoelectric resonant component according to claim (1), wherein the elastic material is silicone rubber. (3) A method for manufacturing a piezoelectric resonant component, characterized in that it is manufactured by dropping a fixed amount of an elastic material onto a vibrating portion of a piezoelectric substrate that vibrates in a thickness-shear vibration mode. (4) The method for manufacturing a piezoelectric resonant component according to claim (3), wherein the elastic material is silicone rubber, and the elastic material is dispensed only onto the vibrating portion by a dispenser.