Quartz crystal oscillator, its manufacturing method, and intermediate wafer for quartz crystal oscillator

Abstract

To provide a crystal oscillator with a novel structure suitable to increase the bite of a conductive adhesive when connecting and fixing a crystal piece to a container by the conductive adhesive.SOLUTION: A crystal oscillator 10 includes a crystal piece 11, a container 13 that accommodates the crystal piece, a conductive adhesive 15 that connects and fixes the crystal piece to the container, and a recess 17 provided in a connecting and fixing area 11c of the crystal piece to increase the conductive adhesive's bite to the crystal piece. The recess 17 has a surface 17a on which the crystallinity of the crystal is vanished. The recess 17 is formed by a picosecond laser or a femtosecond laser, which is a short pulse laser.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a quartz crystal resonator characterized by a structure in which a quartz crystal blank is adhesively fixed to a container with a conductive adhesive, a method for manufacturing the same, and an intermediate wafer for the quartz crystal resonator. [Background technology]

[0002] 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 surface of the crystal blank halfway through the thickness direction is provided in the area where the crystal blank connects to the container (for example, Abstract), and the through-hole or recess serves as a container for a conductive adhesive. This structure is said to increase the adhesive holding force and amount held (for example, Paragraph 15).

[0003] Furthermore, Patent Document 1 describes that the through-hole or recess is formed by photolithography (for example, paragraph 27). This method makes it possible to form a housing that utilizes the anisotropy of quartz crystal (for example, paragraph 26). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2009-171591 Summary of the Invention [Problem to be solved by the invention]

[0005] 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. [Means for solving the problem]

[0006] 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.

[0007] 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 in which the crystallinity of the quartz crystal has been eliminated is a surface in which linear traces extending in the depth direction from the surface of the quartz crystal blank are aligned in 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.

[0008] 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: [Effects of the Invention]

[0009] According to the crystal unit of this application, a recess is provided in the crystal blank to enhance the adhesion of the conductive adhesive to the crystal blank. The result Because the recess has a surface that has been devoid of crystallinity, an adhesive structure can be realized that utilizes a recess that has a stronger wedge effect on the conductive adhesive than a recess that does not have a crystal surface, i.e., a mirror surface, such as that of quartz. 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 by using a 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. [Brief explanation of the drawings]

[0010] [Figure 1]1A to 1C are explanatory diagrams of a quartz crystal resonator 10 according to an embodiment. [Figure 2] 1A and 1B are SEM photographs of a recess 17 formed in a quartz crystal resonator 10 according to an embodiment. [Figure 3] 1A and 1B are diagrams illustrating the main steps of an embodiment of a manufacturing method. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, embodiments of the inventions of this application will be described with reference to the drawings. Note that the drawings used for the description are merely schematic illustrations to the extent that the inventions can be understood. 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 the present invention. Therefore, the present invention is not limited to the following embodiments.

[0012] 1. Crystal unit embodiment A quartz crystal resonator 10 according to an embodiment will be described with reference to Fig. 1. Figs. 1A to 1C are explanatory diagrams of the quartz crystal resonator 10 according to an embodiment. In particular, Fig. 1A is a top view, Fig. 1B is a cross-sectional view taken along line PP in Fig. 1A, and Fig. 1C is an enlarged view of part Q in Fig. 1B. The quartz crystal resonator 10 of this embodiment is a quartz crystal resonator 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 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.

[0013] In this case, the crystal blank 11 is an AT-cut crystal blank. The crystal blank 11 includes 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 region on the front and back principal surfaces of the crystal blank 11, and is made of any suitable metal film. The extraction electrode 11b is extracted from each of the excitation electrodes 11a on both principal surfaces of the crystal blank 11, in this case, to the end regions of one side of the 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 extends into the recess 17.

[0014] In this example, the container 13 includes a recess 13a that accommodates 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) provided 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 bank portion 13b of container 13, sealing crystal blank 11 in container 13. Note that the bonding between container 13 and lid member is performed by any suitable method depending on the sealing method. Container 13 can be formed, for example, from 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.

[0015] 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 FIG. 2 in addition to FIG. 1. FIG. 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, FIG. 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 FIG. 2(B) is an enlarged SEM photograph of one recess 17 in FIG. 2(A). The recess 17 is for enhancing the adhesion of the conductive adhesive 15 to the crystal blank 11, and the side walls and bottom surface are made of the same material as the crystal blank 11. The result The recesses are surfaces 17a where crystallinity has been eliminated. 2(B), surface 17a in this example is a surface in which linear traces 17ax extending in the depth direction from the surface of quartz crystal blank 11 are aligned in the circumferential direction of the sidewall of recess 17, causing unevenness due to these aligned linear traces 17ax. Surface 17a like this can be easily formed by a manufacturing method using a short-pulse laser, which is another invention of the present application.

[0016] As shown in Figures 1(A) and 1(B), the recess 17 is provided within the connection and fixing region 11c or in a predetermined region that is slightly narrower or slightly wider than the 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 the crystal unit 10, the size of the connection and fixing region 11c itself is actually about 0.3 mm at most, and about 0.1 mm at most, in terms of the dimensions a and b shown in Figure 1(B). Of course, these dimensions are merely examples.

[0017] The planar shape of the recess 17 can be any shape. In the 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 made of quartz crystal. The result The recess 17 has a surface 17a that has lost its crystallinity. A ring-shaped recess 17 is preferable because it is believed that the conductive adhesive 15 will adhere more strongly to the recess 17 than if it were not. However, the recess does not have to be ring-shaped, and may have a circular, elliptical, or rectangular shape in plan view. Furthermore, the depth of the recess 17 can be set to any depth depending on the design, since if it is too deep, the number of steps required to form the recess is increased, and if it is too shallow, the effect of the recess is reduced. While not limited to this, the depth of the recess 17 is preferably 10 to 30 μm, and more preferably 10 to 20 μm.

[0018] In the crystal unit 10 of the present invention, the crystal blank 11 is fixed to the connection fixing area 11c with the conductive adhesive 15. The result The device has a plurality of recesses 17 with surfaces 17a that have been decrystallized, and the crystal blank 11 and the bonding pads 13c of the case 13 are electrically and mechanically fixed together with the conductive adhesive 15, resulting in a stronger bond strength than would be possible without the recesses 17. This invention is particularly useful when crystal units are made smaller and the connection and fixing area 11c becomes increasingly narrow. 2. Manufacturing Method and Intermediate Wafer

[0019] 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. 3(A)). On the quartz crystal wafer 110, a large number of intermediates 11x for the quartz crystal unit 10 are formed in a matrix pattern (FIG. 3(A)). These intermediates 11x are quartz crystal blanks 11 that have been processed to their outer shape but have not yet had excitation electrodes formed on them.

[0020] The connection and fixing regions 11c of each intermediate 11x of the quartz wafer 110, which are bonded with a conductive adhesive, are irradiated with short-pulse laser light 21a from a laser device, for example, 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 shape on the connection and fixing regions 11c, thereby forming a desired number of recesses 17 of any 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. The depth of the recesses 17 can be adjusted by setting the power of the laser light 21a and / or the number of scans to predetermined conditions (see Figure 3(A)). The recesses 17 formed by the laser in this way have sidewalls and bottom surfaces made of quartz. The resultThe surface becomes one in which the crystallinity has been eliminated, that is, an uneven surface with many linear traces lined up. The short pulse laser used may be any suitable laser selected from, for example, a picosecond laser or a femtosecond laser.

[0021] After the recesses 17 have been formed, excitation electrodes 11a and extraction electrodes 11b are formed on the quartz crystal wafer 110 using well-known film formation and photolithography techniques, and an intermediate 11y of a quartz crystal resonator having the excitation electrodes 11a and extraction electrodes 11b is formed 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 well-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 member (not shown), thereby forming the crystal resonator 10 shown in FIG. 1(A). According to this manufacturing method, the recesses 17 are formed using a short-pulse laser, so that it is easy to form minute recesses 17 of any planar shape and depth, with the inner walls and bottom surfaces being surfaces where the crystallinity of the quartz has been removed.

[0022] 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 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 both end regions of one side 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 at both ends. Furthermore, while the example illustrates a structure in which the container 13 has a recess 13a, the present invention can also be applied to a crystal resonator in which the container is flat and the lid member is cap-shaped with a recess for accommodating the crystal blank. [Explanation of symbols]

[0023] 10: Crystal resonator of an embodiment; 11: Crystal blank; 11a: Excitation electrode, 11b: Extraction electrode, 11c: connection fixing area; 13: container; 13a: recessed portion, 13b: bank portion, 13c: adhesive pad; 15: conductive adhesive; 17: recess, 17a: crystal The result Surface with no crystallinity 17ax: linear trace, 21: laser device; 21a: laser light; 110, 112: quartz crystal wafer (intermediate wafer for quartz crystal oscillator), 11x, 11y: Intermediate crystal oscillator

Claims

1. 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.

2. 2. The crystal unit according to claim 1, wherein a plurality of the recesses are provided in the connection and fixing region.

3. 3. The quartz crystal resonator according to claim 1, wherein the planar shape of the recess is circular, elliptical or ring-shaped.

4. 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:

5. 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.

6. 6. The intermediate wafer for a quartz crystal resonator according to claim 5, wherein a plurality of said recesses are provided in said region to be connected and fixed.

7. 7. The intermediate wafer for a quartz crystal resonator according to claim 5, wherein the planar shape of the recess is circular, elliptical or ring-shaped.

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