JPH02309807A - Piezoelectric resonator - Google Patents

Abstract

PURPOSE:To improve the solvent resistance by using a packaging resin containing a packing material such as filler with a high porosity so as to coat a vibration element from the upper part of an elastic rubber and filling the pore of the outer package with the pore closing resin. CONSTITUTION:After a lead terminal 6 is soldered to an external leadout electrode or the like of a vibration element 1, the vibration element 1 is coated with an elastic rubber 2 such as silicone rubber and the elastic rubber 2 is coated with a packaging resin such as an epoxy resin containing filler for restricting expansion and contraction to form the hard external package 3. The outer package 3 has a high porosity and contains lots of pores 4. Then the outer package 3 of the piezoelectric resonator A having lots of pores 4 is completely cured, the state of relaxing the stress is kept and the resonator A is immersed in a pore closing resin liquid 5a such as a pure epoxy resin or a resin with high epoxy resin purity, the pore closing resin 5 is immersed in the pore 4 and cured and the pore 4 is filled with the pore choking resin 5. Thus, the solvent resistance of the piezoelectric resonator A is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a piezoelectric resonator that utilizes a thickness shear vibration mode, such as a filter, a discriminator, or a trap.

[Background Art] In a piezoelectric resonator using a conventional thickness-shear vibration mode, a vibrating element 1 as shown in FIG. The rubber-like elastic body was covered with a pure epoxy resin to form an exterior part. Here, the reason why the vibrating element is covered with a rubber-like elastic body is to suppress the generation of spurious vibrations and damp the Q of the resonator. However, when the exterior part is formed of pure epoxy resin as in this conventional example, a tightening force F acts on the internal vibrating element 1 due to contraction of the epoxy resin during curing, which affects the characteristics of the piezoelectric resonator. There is a problem. That is, when a tightening force is applied to the vibrating element 1, the resonance frequency varies from the set value. Similarly, vibration element 1 may also be affected by thermal expansion and contraction of the exterior part.
Since a force F is applied during tightening, the resonance frequency also changes depending on the environmental temperature.

For this reason, in the improved conventional piezoelectric resonator, as shown in FIG. The exterior part 3 is formed by covering the exterior part 3, and a filler such as a feeler is used to prevent curing shrinkage and thermal expansion and contraction of the exterior part 3 to alleviate stress.

[Problems to be Solved by the Invention] However, when a filler such as a filler is mixed with the epoxy resin as described above, the porosity of the exterior resin increases, so it is difficult to form the exterior part 3 with such exterior resin. When formed, a large number of pores 4 are formed in the exterior portion 3 as shown in FIG.

For this reason, when such a piezoelectric resonator is mounted on a wiring board or the like and soldered and then cleaned with a solvent such as Freon in a cleaning process, the solvent penetrates into the exterior part 3 through the pores 4. As a result, the rubber-like elastic body 2 such as silicone rubber swells due to the solvent that has passed through the exterior part 3, resulting in deterioration of the characteristics of the piezoelectric resonator. There was a problem that cracks occurred.

The present invention was made in view of the technical background of soft earth, and is intended to improve the solvent resistance of a piezoelectric resonator sheathed with a relatively high porosity resin containing a filler such as a filler. The purpose is to improve.

[Means for Solving the Problems] The piezoelectric resonator of the present invention has a vibrating element that utilizes thickness-shear vibration covered with a rubber-like elastic body, and a relatively high porosity exterior containing a filler such as a filler. The vibrating element is covered with a rubber-like elastic body to form an exterior part, and then the pores of the exterior part are closed with a pore-sealing resin.

[Function] In the piezoelectric resonator of the present invention, since the vibrating element is covered with an exterior resin containing a filler such as a filler to form an exterior part, curing shrinkage and thermal expansion and contraction of the exterior part are prevented. Stress relaxation can be achieved by reducing the size, and a piezoelectric resonator with stable characteristics can be obtained.

In addition, since the pores of the exterior part, which has a relatively high porosity, are closed with a pore-sealing resin, the solvent does not penetrate into the exterior part even during the cleaning process with a solvent such as Freon, and the piezoelectric resonator is resistant to solvents. will improve.

[Example code] Embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

FIG. 2 is a sectional view of one embodiment of the present invention, and FIG.
Part of the manufacturing process is shown in a) and (bHc). The vibrating element 1 has electrode films such as vibrating electrodes and external lead-out electrodes formed on the surface of a piezoelectric substrate made of piezoelectric ceramic (see Figure 4), and when a signal voltage is applied to the vibrating electrode, thickness shear vibration occurs. The mode of piezoelectric vibration is excited. After soldering lead terminals 6 to external lead-out electrodes of the vibrating element 1, the vibrating element 1 is covered with a rubber-like elastic body 2 such as silicone rubber, and a rubber-like elastic body 2 is further covered with a rubber-like elastic body 2 for suppressing expansion and contraction. The hard exterior part 3 is formed by covering with an exterior resin such as an epoxy resin containing a filler.

As described above, the exterior part 3 molded from epoxy resin or the like containing filler has a high porosity and contains a large number of pores 4 (see Fig. 5). This is shown in Figure 1(a). After the exterior part 3 is completely cured and the stress-relaxed state is maintained, the piezoelectric resonator A containing a large number of pores 4 is made of pure epoxy resin or high-purity epoxy resin, as shown in FIG. 1(b). It is immersed in a pore-sealing resin liquid 5a such as a resin, and the pore-sealing resin 5 is impregnated into the pores 4 and hardened. As a result, Figure 1(c)
As shown in the figure, the pores 4 of the exterior part 3 of the piezoelectric resonator A are filled with a pore-sealing resin 5 such as pure epoxy resin.

A cross-sectional view of the piezoelectric resonator A manufactured in this manner is shown in FIG. 2, and an enlarged view of the X portion thereof is shown in FIG. As shown in FIG. 3, the pores 4 of the exterior part 3 are closed with a pore-sealing resin 5 such as pure epoxy resin that does not contain pores, so soldering is done in a subsequent cleaning process with a solvent such as Freon. Also, it is possible to prevent the solvent from penetrating into the exterior part 3 through the pores 4, and the solvent resistance is improved.

Note that it is not necessary to completely close the pores 4 with the pore-sealing resin 5, and it is sufficient to close the surface layer or a part of the pores 4 as shown in FIG.

Further, the type of the pore-sealing resin 5 is not particularly limited, and may be any solvent-resistant resin, but a resin of the same quality as the exterior resin is preferable.

[Effects of the Invention] According to the present invention, since the exterior resin is filled with a filler such as a filler, curing shrinkage and thermal expansion and contraction of the exterior part can be suppressed, and tightening by the exterior part reduces stress. It is possible to stabilize frequency characteristics and the like against temperature changes.

Moreover, although such an exterior part has a relatively high porosity, in the present invention, these pores are closed with a pore-sealing resin, so there is no risk of the solvent penetrating into the exterior part through the pores. When soldering to a board, even if it is cleaned with a solvent afterward, the internal rubber-like elastic body will not be swollen by the solvent, and the characteristics of the piezoelectric resonator will not deteriorate or the exterior part will be damaged due to the stress of the moistened rubber-like elastic body. It is possible to prevent cracks and the like, and it is possible to obtain a piezoelectric resonator with high solvent resistance. Furthermore, since moisture does not enter through the pores, moisture resistance is also improved.

[Brief explanation of drawings]

FIGS. 1(a), (b), and (c) are explanatory diagrams showing a manufacturing method according to an embodiment of the present invention, FIG. 2 is a cross-sectional view of a piezoelectric resonator manufactured by the same method, and FIG. Enlarged view of the X part in Figure 2,
FIG. 4 is a perspective view of the vibrating element, and FIG. 5 is a partially enlarged sectional view showing a conventional example. 1... Vibration element 2... Rubber-like elastic body 3.
... Exterior part 4... Pore 5... Pore sealing resin No. 2i! I Figure 4 Figure 5 Procedural amendment (method) 1. Display of the case 1999 Patent Application No. 133767 2 Name of the invention Piezoelectric resonator 3, Person making the amendment Relationship to the case Patent applicant Address 2-26-10 Tenjin, Nagaokakyo City, Kyoto Name (623) Stock Company Murata Manufacturing Representative Murata 1
) Akira

Claims (1)

[Claims] (1) A vibrating element that utilizes thickness-shear vibration is covered with a rubber-like elastic body, and the vibrating element is covered with a relatively high porosity exterior resin containing a filler such as a filler from above the rubber-like elastic body. A piezoelectric resonator characterized in that the piezoelectric resonator is coated to form an exterior part, and the pores of the exterior part are closed with a pore-sealing resin.