JPH0258804B2 - - Google Patents

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to an energy trapping type piezoelectric resonator and a manufacturing method thereof, and particularly an improved structure and manufacturing method for providing a cavity formed on a substrate. Regarding.

<Prior art> In general, internal lead wires, resonator electrodes, etc. of general electronic components such as hybrid microcircuit elements and resonators are subject to adverse effects such as distortion, disconnection, and vibration suppression due to direct exterior resin coating. A hybrid structure in which the fragile part is directly covered with a porous thermosetting insulating resin layer impregnated with wax such as paraffin through the air, and the outside of the porous thermosetting insulating resin layer is covered with a moisture-resistant insulating resin layer. General electronic components such as microcircuit elements exist, and the space allows them to be made smaller and more robust, improving their reliability.

Recently, so-called energy coupling methods have been developed in which partial electrodes are formed on piezoelectric substrates such as piezoelectric ceramics, and electrical input signals are used to excite mechanical vibrations in the pressure direction of the substrate, producing resonance or anti-resonance at specific frequencies. Embedded piezoelectric resonators have been proposed and realized.

In such a piezoelectric resonator, the substrate and electrodes are generally molded with a porous resin such as epoxy resin or phenol resin. Since the piezoelectric resonator has a structure in which the partial electrodes cause vibrations in the substrate, the surface area including the partial electrodes provided on the substrate is placed in a space or cavity so that the vibrations are not inhibited. It is necessary to do so. To this end, various structures and methods have been proposed in the past.

By the way, special patent application No. 100369 (1982)
12810), even if it is an energy trapping type piezoelectric resonator, the G/D/T of a piezoelectric filter is
A piezoelectric device in which a cavity is provided in only one of the opposing vibrating electrodes and no cavity is provided in the other electrode for the purpose of improving characteristics, etc. In other words, a piezoelectric device that has a cavity on one electrode and is entirely sealed with resin. A resonator exists.

<Problems to be Solved by the Invention> The present invention is an improvement of such conventional structures and methods.

That is, an object of the present invention is to enable the use of an exterior resin with excellent moisture resistance.

Another purpose of this invention is to improve productivity.

Another objective of this invention is cost reduction.

Another purpose of this invention is to improve quality.

Another purpose of this invention is to improve reliability.

<Means for Solving the Problems> To summarize, the present invention provides a piezoelectric resonator that has a cavity on a part of the substrate surface and is entirely sealed with resin, in which UV resin attached to the substrate surface This piezoelectric resonator is characterized in that the substrate is warped and a cavity is formed by shrinkage and hardening except for the area near the center of the surface contact portion.

Furthermore, in summary, in a piezoelectric resonator that has a cavity on a part of the substrate surface and is completely sealed with resin, UV resin is attached to the substrate surface where the cavity is to be formed, and the interior of the UV resin is This method of manufacturing a piezoelectric resonator is characterized in that the substrate is warped to form a cavity by shrinking and hardening the substrate except for the central inner portion of the substrate surface contact portion.

Embodiment FIG. 1 shows a two-terminal energy trapping piezoelectric resonator unit used in an embodiment of the present invention. In the figure, 1 is a piezoelectric ceramic substrate, 2 is a partial electrode (vibration electrode) provided on one side of the substrate 1,
3 is a partial electrode (vibrating electrode) provided on the other side of the substrate 1 facing the electrode 2; 4 and 5 are the electrodes 2 and 5, respectively;
3, the drawer type. 6 and 7 are terminal electrodes electrically connected to the extraction electrodes 4 and 5, respectively.

FIGS. 2 to 5 show steps of an embodiment of the manufacturing method of the present invention, and portions not directly related to the present invention, such as electrodes 4, 5, 6, and 7, are omitted from the figures.

In the energy trapping type piezoelectric resonator unit as shown in FIGS. 1 and 2, as shown in FIG. 3, UV resin 8 is adhered to the location where a cavity is to be formed.

As shown in Japanese Patent Application No. 54-100369, it is only necessary to provide a cavity in one of the opposing electrodes, so in this embodiment, electrode 2 of the opposing electrodes 2 and 3 is
The area around will be the planned location for cavity formation.

When the UV resin 8 is irradiated with ultraviolet rays, it is cured, and the depth of curing is determined by the amount of irradiation.

If the UV resin 8 is made to have a predetermined thickness, the UV resin inside the center of the contact area with the substrate surface, in this example, the electrode 2 and its surroundings (vibration area) and above, can remain in a gel state due to the relationship with the irradiation amount.

Depending on the thickness, material, etc. of the substrate 1, the substrate 1 may warp upward due to shrinkage and hardening of the UV resin 8, creating a cavity 10 in and above the electrode 2 and its surroundings (vibration area).
occurs.

If the substrate board 1 does not warp or is insufficiently warped by shrinkage hardening of the UV resin 8, as shown in Figs. The UV resin 8 shrinks due to the heat generated when the resin 9 is heated and cured, causing the substrate 1 to warp.

A resonator as used in the present invention is a concept that includes not only a simple resonator but also a filter, an FM discriminator, an oscillator, and a frequency-impedance variable element. The number of cavities provided on the substrate surface is arbitrary.

<Effects of the Invention> As is clear from the above embodiments, according to the present invention, the shrinkage and hardening of the UV resin causes the substrate to warp and form a cavity. The exterior resin is not limited to porous or inferior moisture resistance as in the invention of the present invention;
An exterior resin with excellent moisture resistance can be used.
Furthermore, since UV resin cures in about a few seconds, productivity is good. Furthermore, the conventional work of coating a porous exterior resin with a dense resin can be omitted, and a product with high quality and high reliability can be supplied at a low cost.

[Brief explanation of drawings]

FIG. 1 is a front view of a piezoelectric resonator unit used in an embodiment of the present invention, and FIGS. 2 to 5 are sectional views sequentially showing steps in an embodiment of the invention. DESCRIPTION OF SYMBOLS 1... Piezoelectric ceramic substrate, 2, 3... Partial electrode (vibration electrode), 8... UV resin, 9... Exterior resin, 10... Cavity.

Claims (1)

[Claims] 1. In a piezoelectric resonator that has a cavity on a part of the substrate surface and is entirely sealed with resin, the UV resin attached to the substrate surface contracts except for the inner part of the center of the part that contacts the substrate surface. A piezoelectric resonator characterized by a substrate warping and creating a cavity when cured. 2. In a piezoelectric resonator that has a cavity on a part of the substrate surface and is completely sealed with resin, UV resin is applied to the substrate surface where the cavity is to be formed, and the area near the center of the substrate surface contact area inside the UV resin is 1. A method of manufacturing a piezoelectric resonator, comprising: warping a substrate by shrinking and hardening the substrate to form a cavity.