JPH03243008A - Method for fixing superthin plate crystal resonator - Google Patents

Abstract

PURPOSE:To reduce the dispersion of temperature/frequency characteristics at the time of massproducing superthin plate piezo-electric resonators by sticking a crystal block constituting the resonator to a prescribed case on a portion along the z axis of the edge of the circular surrounding part of the block. CONSTITUTION:The adhering portion of the resonator 9 is set up on the surface of one edge of the recessed part 2 side of the circular surrounding part 4 along the z axis of the AT cut crystal block 1. Consequently, the degree of dispersion in the temperature-frequency characteristics of the resonator is superior in the state fixing the block 1 to the case on one edge along the z axis of the block 1 as compared to a state fixing the block to the case on one edge of the x axis.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for fixing an ultra-thin plate piezoelectric resonator capable of exciting a high frequency of about several tens to several hundreds of MHz in a case storage part by fundamental wave vibration.

(Prior art) In recent years, demands for higher frequencies and higher frequency stability have become stricter in various electronic devices and communication devices, but AT, which has been widely used as piezoelectric devices (vibrators, filters), Although cut crystal resonators also have extremely excellent temperature-frequency characteristics, their resonant frequency is inversely proportional to the plate thickness, so from the viewpoint of manufacturing technology and mechanical strength, the frequency that can be obtained by fundamental wave vibration is limited to about 40 MHz. .

For this reason, so-called overtone oscillation means that extracts the harmonic components of an AT-cut crystal resonator to obtain a frequency that is an odd multiple of the fundamental resonance frequency is also widely used, but this method uses a coil such as an LC tuned circuit in the oscillation circuit. This is disadvantageous in that it is difficult to integrate the oscillation circuit, and the capacitance ratio is large and the impedance level becomes high, which may lead to difficulty in oscillation.

On the other hand, the surface acoustic wave resonator, whose oscillation frequency is determined by the electrode finger pitch of the interdigital transducer electrodes, has developed an IGH technology due to advances in photolithography technology.
Although it has become possible to oscillate up to about Z, there is a problem in that the temperature-frequency characteristics of piezoelectric substrates that can be used for this are significantly inferior to those of AT-cut products.

In order to solve the above-mentioned problems, the surface of the A-cut crystal block is made concave by etching or mechanical polishing, and the concave part is made into an ultra-thin vibrating part, and the annular surrounding part formed around it is made into a concave part. An ultra-thin piezoelectric resonator is provided which aims to obtain a frequency of several tens to several hundreds of megahertz in fundamental wave vibration while maintaining the mechanical strength of the vibrating part by using the supporting frame around the ultra-thin plate fitting part. proposed and researched.

However, such types of resonators have to date been limited to laboratory studies. Since the company had never gone bankrupt, virtually no consideration had been given to how to fix the resonator in a predetermined case without impairing its seven characteristics.

(Objective of the Invention) The present invention is based on the fact that when an ultra-thin AT-cut crystal resonator of the type described above is adhesively fixed to a predetermined case, the seven characteristics of the device can vary considerably depending on the selection of the adhesive site. The object of the present invention is to provide a method for fixing an ultra-thin crystal resonator that can reduce variations in the characteristics of the device, especially the temperature-frequency characteristics during mass production. The purpose is

(Summary of the Invention) In order to achieve the above object, a method for fixing a resonator according to the present invention involves bonding a crystal block constituting the resonator to a predetermined case at a portion along the Z-axis of the edge of the annular surrounding portion thereof. It is something to do.

(Embodiments of the Invention) The present invention will be described below in detail based on embodiments shown in the drawings and experimental data.

Prior to explaining the experimental data of the examples and the samples made based on the examples, in order to help understand the present invention,
This article provides a brief explanation of ultra-thin piezoelectric resonators, which have been studied in the past.

FIG. 3 (al and (bl) are respectively a perspective view showing the configuration of an ultra-thin piezoelectric resonator that has been generally studied in the past, and a sectional view showing the state in which it is housed and fixed in a case, in which piezoelectric resonators such as crystal A concave portion 2 is formed approximately in the center of one main plane of the block 1 by mechanical polishing or etching, and the bottom surface of the concave portion 2 is made into an extremely thin vibrating portion 3. As a result, the vibrating portion 3
The ultra-thin vibrating section 3 is supported by a thick annular surrounding section 4 formed integrally with the periphery of the vibrating section 3.

On the surface of the piezoelectric block l processed in this manner on the side where the concave portion 2 is formed, a conductive film is deposited on the entire surface of the annular surrounding portion 4, the inner wall surface of the concave body, and the surface of the vibrating portion 3, and a full-surface electrode 5 is formed.
On the other hand, a partial electrode 7 and an electrode lead portion 8 extending from the partial electrode 7 to the edge of the block are provided on the flat surface 6 facing this, thereby completing an ultra-thin plate piezoelectric resonator 9.

This type of resonator takes advantage of the characteristics of its shape.
As shown in FIG.
A part of the surface to which the electrode is attached is fixed to the conductive film 11 provided on the bottom surface of the case 10 with a conductive adhesive 12, and extends from the partial electrode 7 on the flat surface facing the face. The electrode lead portion 8 is connected to the conductive film 13 provided on the stepped surface of the inner wall of the case 10 using a bonding wire 14, thereby minimizing the restraint of the resonator 9 to the case 10 and eliminating heat between the two. It is common practice to minimize the strain applied to the resonator due to differences in expansion coefficients.

In addition, the conductor film 11 on the bottom surface of the case and the stepped portion of the inner wall of the case
and 13 hermetically pass through the case wall and are electrically connected to external lead terminals 15 and 16 exposed on the outer wall of the case. Further, the opening of the case 10 is sealed with a suitable (generally metal) lid 17 after the resonator is housed and fixed as described above, thereby completing the piezoelectric device.

In the process of conducting mass production tests for the piezoelectric device as described above, the inventor of the present application discovered that if the resonator to be housed and fixed in the case was glued to the bottom of the case at different locations, there would be considerable variation in the temperature-frequency characteristics of the device. What I discovered that caused the difference is as mentioned above.

In order to pursue this problem, the inventor of the present application
As shown in the figure, the recessed part 2 of the annular surrounding part 4 has the adhesion part of the resonator 9 aligned with the Z-axis of the A-cut crystal block 1.
Ten samples each having side-to-edge surfaces and those having the Z axis as X were manufactured, and the degree of variation in temperature-frequency characteristics of these samples was investigated, and the results shown in FIG. 2 were obtained.

As is clear from the results of this experiment, the degree of variation in the temperature-frequency characteristics of this type of resonator is greater than that of the AT-cut crystal block l when it is fixed to the case at one edge along the Z-axis. It turned out to be better than fixing one edge.

Although data is omitted, no significant difference in Fi was observed between the two in terms of characteristics other than temperature-frequency characteristics.

It is currently unclear why such a result occurs, but in any case, at least as far as this type of resonator with an AT-cut crystal substrate is concerned, at one edge along the Z axis, It became clear that it should be fixed to the case with adhesive.

In the above, only the case where a rectangular parallelepiped crystal block is used as a substrate and is adhesively fixed to the case at one peripheral surface on the side of the concave portion has been described; however, the present invention is not necessarily limited to this only; for example, as shown in FIG. ) If the crystal block l is disk-shaped, apply adhesive 1 to the periphery along the Z axis.
2, or the effect is the same even if the resonator is fixed to the case 10 by adhesive bonding to one edge along the Z-axis of the flat surface 6 facing the concave portion 2 side of the crystal block l. .

Historically, the resonator to which the present invention is applied may include a resonator in which a partial electrode is attached to the surface on the side of the recessed part and a full electrode is attached to the flat surface opposite to the resonator, and the types of devices include a resonator, Any filter element (including so-called multi-moat filter elements having split electrodes) may be used.

Furthermore, in order to clearly indicate the adhesive fixing part of the resonator to the case, if an appropriate mark, such as a paint mark, is attached on both sides of the part where the adhesive should be applied, then the resonator can be attached to the case. This will be convenient because you will not have to make mistakes when attaching the parts.

(Effect of the invention) Since the present invention employs the method as explained above,
This method has a remarkable effect in reducing the variation in temperature-frequency characteristics during mass production of ultra-thin piezoelectric resonators without adding any special process, and providing devices of uniform quality to customers.

[Brief explanation of drawings]

FIGS. 1(a) and 1(b) are plan views showing different embodiments of ultra-thin crystal resonators to which the method according to the present invention is applied, respectively;
Figures 2 (a) and (b) are diagrams showing data from comparative experiments that confirmed the effectiveness of the method of the present invention, and Figures 3 (a) and (
b) is a sectional view showing the structure of a conventional ultra-thin piezoelectric resonator. ! ... AT cut crystal (piezoelectric) block, 2... recessed part, 3... vibrating part, 4... annular surrounding part, 9...
・Resonator, 10... Container (case), 12... Adhesive

Claims (1)

[Claims] (1) When an AT-cut crystal resonator, which is integrally composed of an ultra-thin vibrating part and a thick-walled annular surrounding part that supports the periphery of the vibrating part, is fixed to the storage part of a container with adhesive, A method for fixing an ultra-thin crystal resonator, characterized in that the adhesive is applied along an edge of the crystal resonator extending in the z-axis direction.