JP7799503B2 - Quartz crystal oscillator, its manufacturing method, and intermediate wafer for quartz crystal oscillator - Google Patents

Description

The present invention relates to a quartz crystal unit characterized by a structure in which a quartz crystal blank is adhesively fixed to a container using a conductive adhesive, a method for manufacturing the same, and an intermediate wafer for the quartz crystal unit.

Most recent quartz crystal units have a structure in which a portion of the quartz crystal blank is electrically and mechanically connected to an adhesive pad on the case using a conductive adhesive. This fixing with a conductive adhesive affects the electrical characteristics and shock resistance of the quartz crystal unit, so a reliable structure is desirable.
For example, Patent Document 1 discloses a structure in which a through-hole that penetrates the crystal blank itself or a recess that is recessed from the crystal blank surface to the middle of the thickness direction is provided in the area where the crystal blank connects to the container, and the through-hole or recess serves as a container for a conductive adhesive (see, for example, the abstract). This structure is said to increase the adhesive holding force and amount held (see, for example, paragraph 15).

Patent Document 1 also describes forming the through-hole or recess using photolithography (see, for example, paragraph 27). It also states that this method makes it possible to form a housing that takes advantage of the anisotropy of quartz crystal (see, for example, paragraph 26).

JP 2009-171591 A

However, the conventional structure and manufacturing method leave room for improvement in terms of the holding power of the conductive adhesive by the housing portion and the method for manufacturing the housing portion.
The inventors of the present application have also conducted extensive research into the most suitable structure for the recesses to be provided in the crystal blank in order to improve the adhesion of the conductive adhesive, as well as into a method for easily manufacturing such suitable recesses in the crystal blank.
This application has been made in consideration of the above points, and therefore, the object of this application is to provide a quartz crystal unit having a novel structure for improving adhesive adhesion when connecting and fixing a quartz crystal blank to a container with a conductive adhesive, a manufacturing method that can easily form this structure, and an intermediate wafer for forming the quartz crystal unit.

In order to achieve this object, the quartz crystal resonator of this application comprises a quartz crystal piece, a container for accommodating the quartz crystal piece, a conductive adhesive for connecting and fixing the quartz crystal piece to the container, and a recess provided in the connection and fixing area of the quartz crystal piece to enhance adhesion of the conductive adhesive to the quartz crystal piece, wherein the recess is a recess having a surface in which the crystallinity of the quartz crystal has been eliminated.
In carrying out the present invention, it is preferable to provide a plurality of recesses in the connection and fixing region.

Here, the surface from which the crystallinity of the quartz crystal has been eliminated refers to a surface that is different from the surface formed by photolithography and wet etching using a hydrofluoric acid-based etchant, in which the quartz crystal surface remains on part or all of the inner wall and bottom surface of the recess.
Specifically, a surface that has lost the crystallinity of the quartz is a surface in which linear traces that extend from the surface of the quartz crystal piece in the depth direction are aligned along the circumferential direction of the sidewall of the recess, creating unevenness due to these aligned linear traces (see the SEM photograph in Figure 2). Such a surface can be formed by a manufacturing method using a short-pulse laser, which is another invention of this application.

Furthermore, according to the method for manufacturing a quartz crystal resonator of this application, when manufacturing a quartz crystal resonator having a structure in which a quartz crystal blank is fixed to a container with a conductive adhesive,
forming a plurality of recesses by a short pulse laser in an area of the crystal blank that is to be fixed with a conductive adhesive;
forming an excitation electrode for the quartz crystal unit on the quartz crystal piece in which the recess is formed, and an extraction electrode connected to the excitation electrode and covering the formed recess;
applying a conductive adhesive to the predetermined area on the container side or on the crystal blank side on which the recess is formed;
a step of adhering the crystal blank and the container after the application of the conductive adhesive;
The present invention is characterized by comprising:

According to the quartz crystal unit of this application, the recesses provided in the quartz crystal blank to improve adhesion of the conductive adhesive to the quartz crystal blank are recesses having a surface that eliminates the crystallinity of the quartz crystal. Therefore, an adhesive structure can be realized that utilizes recesses that have a stronger wedge effect on the conductive adhesive than recesses that do not have such a crystal surface, i.e., a mirror surface, for example.
Furthermore, according to the method for manufacturing a quartz crystal unit of this application, when forming a recess in the quartz crystal blank to improve adhesion of the conductive adhesive to the quartz crystal blank, the quartz crystal blank is processed with a short-pulse laser, making it possible to easily manufacture a recess with a surface that eliminates the crystallinity of the quartz crystal. In other words, forming a recess using photolithography requires multiple steps, such as forming a mask film, forming a photoresist, exposing and developing, and etching the quartz crystal, whereas the method of the present invention requires only laser irradiation. Furthermore, when forming a recess using photolithography and wet etching techniques, it is difficult to form the desired recess due to the anisotropy of the etching of the quartz crystal, but this problem can be avoided with the method using a short-pulse laser.
Therefore, it is possible to provide a quartz crystal resonator having a novel structure suitable for improving adhesive adhesion when connecting and fixing a quartz crystal blank to a container with a conductive adhesive, and a simple manufacturing method for forming the novel structure.

1A to 1C are explanatory diagrams of a quartz crystal resonator 10 according to an embodiment. 1A and 1B are SEM photographs of a recess 17 formed in a quartz crystal resonator 10 according to an embodiment of the present invention. 1A and 1B are diagrams illustrating the main steps of an embodiment of a manufacturing method.

Embodiments of the inventions of this application will be described below with reference to the drawings. Note that the drawings used for the description are merely schematic illustrations to enable understanding of the inventions. Furthermore, in the drawings used for the description, similar components are designated by the same numbers, and their description may be omitted. Furthermore, the shapes, materials, manufacturing methods, etc. described in the following embodiments are merely preferred examples within the scope of this invention. Therefore, the present invention is not limited to the following embodiments.

1. Embodiment of Quartz Crystal Resonator A quartz crystal resonator 10 according to an embodiment will be described with reference to Figure 1. Figures 1(A) to 1(C) are explanatory diagrams of the quartz crystal resonator 10 according to the embodiment. In particular, Figure 1(A) is a top view, Figure 1(B) is a cross-sectional view taken along line P-P in Figure 1(A), and Figure 1(C) is an enlarged view of part Q in Figure 1(B).
The quartz crystal unit 10 of the embodiment is a quartz crystal unit that includes a quartz crystal blank 11, a container 13 that houses the quartz crystal blank 11, a conductive adhesive 15 that connects and fixes the quartz crystal blank 11 to the container 13, and a recess 17 that is provided in the area of the quartz crystal blank 11 that connects and fixes the conductive adhesive 15 and that improves adhesion of the conductive adhesive 15 to the quartz crystal blank 11, where the recess 17 is a recess having a surface 17a where the crystallinity of the quartz crystal has been eliminated. Each of the components will be described in detail below.

In this case, the quartz crystal blank 11 is an AT-cut quartz crystal blank. The quartz crystal blank 11 is equipped with an excitation electrode 11a, an extraction electrode 11b, and a recess 17 (described in detail below), which is a feature of the present invention. The excitation electrode 11a is provided in a predetermined area on the front and back main surfaces of the quartz crystal blank 11, and is made of any suitable metal film. The extraction electrode 11b is extended from each of the excitation electrodes 11a on both main surfaces of the quartz crystal blank 11, in this case, to the end regions of one side of the quartz crystal blank 11. The extraction electrode 11b is formed integrally with the excitation electrode 11a using the same metal film. It is preferable that the extraction electrode 11b also extend into the recess 17.

In this example, the container 13 includes a recess 13a for accommodating the crystal blank 11, a bank portion 13b that defines the recess 13a, and an adhesive pad 13c. In this example, the adhesive pad 13c is provided on the bottom surface of the recess 13a in an area corresponding to the extraction electrode 11b of the crystal blank 11. The adhesive pad 13c is connected to an external connection terminal (not shown) on the back surface of the container 13 via via wiring or castellation wiring (neither is shown). The crystal blank 11 is electrically and mechanically connected and fixed to the adhesive pad 13c at the position of the extraction electrode 11b using a conductive adhesive 15.
A lid member (not shown) is bonded to the top surface of the bank portion 13b of the container 13, sealing the crystal blank 11 in the container 13. The container 13 and the lid member are bonded together by any suitable method depending on the sealing method. The container 13 can be made of, for example, a ceramic package.
The conductive adhesive 15 can be made of any suitable material, but in this example, it is a silicone-based conductive adhesive.

Next, a specific structural example of the recess 17, a feature of the present invention, will be described. This description will be made with reference to Figure 2 in addition to Figure 1. Figure 2 is an SEM (electron microscope) photograph of the recess 17 provided in the connection and fixing region 11c of the crystal blank 11. In particular, Figure 2(A) is an SEM photograph of multiple recesses 17 in the region of the crystal blank 11 that is fixed with a conductive adhesive, and Figure 2(B) is an enlarged SEM photograph of one recess 17 in Figure 2(A).
The recess 17 is intended to enhance the adhesion of the conductive adhesive 15 to the crystal blank 11, and the side walls and bottom surface of the recess are surfaces 17a in which the crystallinity of the crystal has been eliminated.
2B, the surface 17a in this example is a surface in which linear traces 17ax extending in the depth direction from the surface of the crystal blank 11 are aligned in the circumferential direction of the sidewall of the recess 17, and these aligned linear traces 17ax create unevenness. Such a surface 17a can be easily formed by a manufacturing method using a short-pulse laser, which is another invention of the present application.

As shown in Figures 1(A) and (B), recesses 17 are provided within connection and fixing region 11c or in a specified region that is slightly narrower or slightly wider than connection and fixing region 11c. It is preferable to provide multiple recesses 17. For example, it is preferable to provide multiple recesses 17 arranged in a matrix. Considering the ongoing miniaturization of quartz crystal resonators 10, the size of connection and fixing region 11c itself is actually approximately 0.3 mm at most, and approximately 0.1 mm at most, in terms of dimensions a and b shown in Figure 1(B). Of course, these dimensions are merely examples.

The planar shape of the recess 17 can be any desired shape. In this embodiment, the recess 17 is ring-shaped in plan view (see FIG. 2). The inner wall and bottom surface of the ring-shaped recess are surfaces 17a where the crystallinity of the quartz crystal has been eliminated. A ring-shaped recess 17 is preferred because it is believed that the conductive adhesive 15 adheres more strongly to the recess 17 than if it were not ring-shaped. However, the recess may not be ring-shaped, but may be circular, elliptical, or rectangular in plan view. Furthermore, the depth of the recess 17 can be any desired depth depending on the design, as forming the recess requires additional man-hours if it is too deep, and the effect of the recess is limited if it is too shallow. While not limited thereto, the depth of the recess 17 is preferably 10 to 30 μm, more preferably 10 to 20 μm.

In the quartz crystal resonator 10 of this invention, the connection and fixing area 11c of the quartz crystal blank 11 with the conductive adhesive 15 is provided with a plurality of recesses 17 having surfaces 17a where the crystallinity of the quartz crystal has been eliminated, and the quartz crystal blank 11 and the bonding pads 13c of the container 13 are electrically and mechanically fixed together by the conductive adhesive 15, thereby increasing the adhesive strength compared to a case without recesses 17. This invention is particularly useful when quartz crystal resonators are miniaturized and the connection and fixing area 11c becomes increasingly narrow.
2. Manufacturing Method Embodiments and Intermediate Wafers

Next, an embodiment of the manufacturing method of the present invention will be described with reference to Fig. 3. Fig. 3 is a manufacturing process diagram showing the main parts of the manufacturing method of the embodiment. Note that since it is preferable to manufacture the quartz crystal resonator 10 of the present invention from a large quartz crystal wafer using a process that employs photolithography and film formation techniques, this embodiment will describe such an example.
First, an AT-cut quartz crystal wafer 110 of a predetermined thickness and size is prepared for manufacturing the quartz crystal unit 10 (FIG. 3A). The quartz crystal wafer 110 has a large number of intermediates 11x formed in a matrix pattern as intermediates 11x for the quartz crystal unit 10, in which the outer shape of the quartz crystal blank 11 has been processed but before the formation of the excitation electrodes (FIG. 3A).

The connection and fixing regions 11c of each intermediate 11x of the quartz crystal wafer 110, which are bonded with a conductive adhesive, are irradiated with short-pulse laser light 21a from a laser device, e.g., a short-pulse laser device 21. The laser device 21 is equipped with a galvanometer mirror (not shown) and can scan the laser light 21a in any desired shape on the connection and fixing regions 11c, thereby forming a desired number of recesses 17 of any desired planar shape. To form ring-shaped recesses in the plan view shown in Figures 2(A) and (B), the laser light 21a can be scanned in a ring shape. Furthermore, the depth of the recesses 17 can be adjusted by adjusting the power and/or number of scans of the laser light 21a under predetermined conditions (see Figure 3(A)). The recesses 17 thus formed by the laser have sidewalls and bottom surfaces that have lost the crystallinity of the quartz crystal, i.e., uneven surfaces with numerous linear traces.
The short pulse laser used may be any suitable laser selected from, for example, a picosecond laser or a femtosecond laser.

After the recesses 17 have been formed on the quartz crystal wafer 110, excitation electrodes 11a and extraction electrodes 11b are formed using well-known film formation and photolithography techniques, forming an intermediate 11y of a quartz crystal resonator having the excitation electrodes 11a and extraction electrodes 11b on the quartz crystal wafer 110 (FIG. 3(B)). The quartz crystal wafer 112 shown in FIG. 3(B) corresponds to the intermediate wafer for the quartz crystal resonator.
Thereafter, the crystal wafer 110 is cut into individual crystal unit intermediates 11y by a known method, and each individual crystal unit is bonded and fixed to the container 13 (see FIG. 1) with a conductive adhesive. The conductive adhesive 15 is typically applied to the bonding pads 13c of the container 13, the crystal unit intermediate 11y is placed on top of the adhesive, and the conductive adhesive is allowed to harden, but the conductive adhesive may also be applied to the crystal unit intermediate 11y side and then mounted in the container.
After the conductive adhesive has hardened, the frequency of the crystal blank 11 is adjusted, and the container 13 is sealed with a lid (not shown), thereby completing the crystal resonator 10 shown in FIG. 1A.
According to this manufacturing method, the recess 17 is formed using a short pulse laser, so that it is possible to easily form a minute recess 17 of any planar shape and depth, and recesses whose inner walls and bottom surfaces are surfaces where the crystallinity of the quartz has been removed.

While the above embodiment illustrates an example in which an AT-cut crystal blank is used as the crystal blank, the crystal blank may be a crystal blank other than an AT-cut crystal blank, such as a tuning fork-shaped crystal blank or an SC-cut crystal blank, which is a so-called two-rotation crystal blank. Furthermore, while the example illustrates an example in which the extraction electrodes 11b are extended from the excitation electrodes 11a on both main surfaces of the crystal blank 11 to the end regions of one edge of the crystal blank 11, i.e., a shape corresponding to cantilever support, the present invention can also be applied to adhesive structures with two-point fixation and four-point fixation for both-side support. Furthermore, while the example illustrates a structure in which the container 13 has a recess 13a, the present invention can also be applied to crystal resonators in which the container is flat and the lid member is cap-shaped with a recess that accommodates the crystal blank.

10: Crystal resonator of the embodiment; 11: Crystal blank;
11a: Excitation electrode, 11b: Extraction electrode,
11c: connection and fixing region; 13: container;
13a: recessed portion, 13b: bank portion,
13c: adhesive pad; 15: conductive adhesive;
17: recess, 17a: surface where the crystallinity of the quartz crystal has disappeared, 17ax: linear trace,
21: laser device; 21a: laser light;
110, 112: quartz crystal wafer (intermediate wafer for quartz crystal oscillator),
11x, 11y: Intermediate of quartz crystal oscillator

Claims (7)

A quartz crystal unit comprising: a quartz crystal blank; a container for accommodating the quartz crystal blank; a conductive adhesive for connecting and fixing a connection and fixing region of the quartz crystal blank to the container; and a recess provided in the connection and fixing region of the quartz crystal blank to enhance adhesion of the conductive adhesive to the quartz crystal blank,
A quartz crystal unit characterized in that the recess is a recess having a surface on the side wall where the crystallinity of the quartz crystal has been eliminated, and linear traces progressing in the depth direction from the surface of the quartz crystal piece are lined up in the circumferential direction of the side wall, causing unevenness due to these lined up linear traces . The quartz crystal unit according to claim 1, characterized in that the connection and fixing area has multiple recesses. A quartz crystal unit as described in claim 1 or 2, characterized in that the planar shape of the recess is circular, elliptical, or ring-shaped. When manufacturing a quartz crystal unit having a structure in which a quartz crystal blank is fixed to a container with a conductive adhesive,
A process of forming a plurality of recesses by a short pulse laser in an area of the quartz element to be fixed with a conductive adhesive , the recesses having a surface where the crystallinity of the quartz has been eliminated, and linear traces extending in the depth direction from the surface of the quartz element are aligned in the circumferential direction of the side wall, causing unevenness due to these aligned linear traces ;
forming an excitation electrode for the quartz crystal unit and an extraction electrode connected to the excitation electrode and covering the recess on the quartz crystal piece in which the recess is formed;
applying a conductive adhesive to an area of the container where the crystal piece is to be fixed, or to an area of the crystal piece with the recess formed therein that is to be connected to the container;
a step of adhering the crystal blank and the container after the application of the conductive adhesive;
A method for manufacturing a quartz crystal resonator, comprising: In an intermediate wafer for crystal resonators, which has a large number of crystal pieces arranged in a matrix, the intermediate wafer is used to form crystal resonators.
An intermediate wafer for a quartz oscillator, characterized in that the intermediate quartz piece has a recess in the area where it is connected and fixed to a container with a conductive adhesive, which improves the adhesion of the conductive adhesive to the quartz piece, and the side wall has a recess having a surface where the crystallinity of the quartz has been eliminated, and linear traces that progress in the depth direction from the surface of the quartz piece are lined up circumferentially around the side wall, creating unevenness due to these lined up linear traces . An intermediate wafer for a quartz crystal oscillator as described in claim 5, characterized in that it has multiple recesses in the area to be connected and fixed. An intermediate wafer for a quartz crystal unit according to claim 5 or 6, characterized in that the planar shape of the recess is circular, elliptical, or ring-shaped.