JP2023119229A - Crystal oscillator, manufacturing method for the same, and intermediate wafer for crystal oscillator - Google Patents

Abstract

To provide a crystal oscillator with a novel structure having a through-hole that is preferable to conduct the front and back sides of a crystal piece.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, a through-hole 17, and electrodes (excitation electrode 11a and wiring electrode 11b) provided on one surface of the crystal piece, on an inner wall of the through-hole, and on the other surface of the crystal piece. The through-hole 17 is provided on a portion of a connecting and fixing area 11c of the crystal piece, penetrating the front and back sides of the crystal piece, and having on the inner wall a surface on which the crystallinity of the crystal is vanished. The through-hole 17 is formed using a picosecond laser or a femtosecond laser, which is a short pulse laser.SELECTED DRAWING: Figure 1

Description

The present invention relates to a crystal oscillator characterized by a structure in which a crystal piece is adhered and fixed to a container with a conductive adhesive, a manufacturing method thereof, and an intermediate wafer for the crystal oscillator.

Most modern crystal oscillators are of the SMD type. Therefore, when fixing the crystal blank to the container, one of the two main surfaces of the crystal blank faces the bonding pad side of the container, and a predetermined portion of the main surface is electrically and mechanically attached to the bonding pad by a conductive adhesive. properly connected and fixed.

On the other hand, since the crystal piece has excitation electrodes on its front and back sides, the excitation electrodes on the side opposite to the bonding pads must be routed toward the bonding pads. Generally, this routing is performed via the side surface of the crystal piece.
When the excitation electrodes are routed from one surface of the crystal piece to the other surface via the side surface of the crystal piece, disconnection of the electrode tends to occur at the edge of the crystal piece, which is the boundary between the main surface and the side surface of the crystal piece. .
As one measure for reducing this disconnection, for example, as shown in Patent Document 1, a through hole is provided from one surface of the crystal piece to the other surface, and the through hole is used to achieve conduction between the front and back surfaces. There is a structure (Patent Documents 1, 3, 5, paragraph 83, etc.).

JP 2020-191579 A

However, Patent Literature 1 does not describe the specific structure of the through-hole, especially the internal shape in the depth direction. Moreover, there is no description of a method for manufacturing through holes. A method using photolithography technology and wet etching technology can be considered as a method for manufacturing a through hole, but when this method is used to form a through hole in a crystal piece, the opening and inside of the through hole are caused by the crystallinity of the crystal. Due to the influence of the crystal planes, the inside of the through-hole has a complicated structure composed of multiple crystal planes. Therefore, it is difficult to form a through hole in which a conductive member such as an electrode film can be easily formed.
In other words, depending on the structure of the through-holes, the purpose of achieving conduction between the front and back surfaces of the crystal piece may not be satisfied, and there is room for improvement in the structure of the through-holes and the manufacturing method thereof.
The inventors of the present application have also made earnest studies on the structure of the through-holes for achieving conduction between the front and back surfaces of the crystal piece and the manufacturing method thereof.
This application has been made in view of the above points, and the object of this application is to provide a crystal resonator having a novel structure having through-holes suitable for conducting between the front and back surfaces of a crystal piece, and a crystal unit that simplifies this structure. and an intermediate wafer for forming the crystal oscillator.

In order to achieve this object, according to the crystal oscillator of this application, there are provided a crystal piece, a container for containing the crystal piece, a conductive adhesive for connecting and fixing the crystal piece to the container, and the crystal. a through hole provided in a part of the connecting and fixing region of the piece and penetrating the front and back of the crystal piece,
a through hole having, as the through hole, an inner wall surface in which crystallinity of crystal is eliminated;
and an electrode provided over one surface of the crystal piece, an inner wall of the through hole, and the other surface of the crystal piece.

Here, the surface from which the crystallinity of the crystal has disappeared is formed by a photolithography technique and a wet etching technique using a hydrofluoric acid-based etchant, and the crystal surface of the crystal remains on part or all of the inner wall and bottom surface of the recess. It is a side that is different from the normal side.
Specifically, the surface where the crystallinity of the crystal is lost means that linear traces extending in the depth direction from the surface of the crystal piece are arranged on the inner wall of the through hole in the circumferential direction of the inner wall. This is the surface on which fine unevenness is generated by linear traces (see the SEM photograph of FIG. 2(A)). Such a surface can be formed by a manufacturing method using a short pulse laser, such as a picosecond laser or a femtosecond laser, which is another invention of the present application.

In carrying out the invention of the crystal oscillator, the cross-sectional shape of the through hole cut along the thickness direction of the crystal piece is from the first surface side of the crystal piece to the opposite second surface side. It preferably has a funnel shape that tapers toward (see FIG. 1(C)).
Further, in carrying out the invention of the crystal oscillator, the cross-sectional shape of the through-hole cut along the thickness direction of the crystal piece is reduced in the middle of the thickness direction of the crystal piece and then enlarged. It may have a so-called hourglass shape (see FIG. 2(B)).
Such a funnel shape or hourglass shape makes it easy to cover the inside of the through hole with a film for forming an electrode.

According to another invention of this application, which is an invention of a method for manufacturing a crystal oscillator, in manufacturing a crystal oscillator having a structure in which a crystal piece is fixed to a container with a conductive adhesive,
a step of forming a through-hole penetrating through the crystal piece by means of a short-pulse laser in a part of the region of the crystal piece to be fixed by the conductive adhesive;
a step of forming a metal film for forming an electrode of a crystal oscillator on the crystal piece in which the through holes are formed so as to cover the inside of the through holes;
a step of forming a photoresist on the crystal piece on which the metal film is formed so as to cover the inside of the through hole;
exposing and developing the photoresist to form a resist pattern for forming an electrode; and selectively removing the metal film exposed from the resist pattern to cover the inside of the through hole as the electrode. and forming an electrode on the substrate.

According to the crystal oscillator of this application, a through hole penetrating through the crystal piece and having a surface in which the crystallinity of the crystal is eliminated is provided in a part of the region of the crystal piece connected to the container of the crystal piece; an electrode provided over one surface of the crystal piece, the inner wall of the through hole, and the other surface of the crystal piece. Therefore, a crystal oscillator having a crystal piece having a structure in which there is no crystal plane of the crystal piece in the through hole can be obtained. Moreover, the excitation electrodes on the side opposite to the container side are routed to the container side through the through holes to obtain a crystal oscillator connected to the bonding pads. Here, if there is a crystal plane of quartz crystal in the through-hole, the crystal plane is a plane resulting from the anisotropy of the crystal, and the opening degree of the through-hole tends to be lowered in many cases. This is a detriment to the purpose of routing the electrodes. On the other hand, in the present invention, since the through-holes have side surfaces in which crystallinity has disappeared, the aperture ratio of the through-holes can be increased compared to the case where the through-holes have crystal planes. Therefore, the electrodes provided on one surface of the crystal blank, on the inner wall of the through hole, and on the other surface of the crystal blank are also effectively formed in the through hole, so that the front and back of the crystal blank are electrically connected. I can do it for sure.
In addition, according to the method of manufacturing a crystal oscillator of this application, since the through-holes penetrating the front and back of the crystal piece are formed by a short-pulse laser, the through-holes having crystallinity-disappeared surfaces can be easily formed. can. In addition, a through-hole having a surface in which crystallinity is lost tends to have a higher opening ratio than a through-hole having a surface having crystallinity, and the inner wall is made of a metal film or a photoresist. It becomes a through-hole with a high coating property. Therefore, it is easy to cover the inside of the through hole with a metal film or a photoresist for forming the electrode of the crystal oscillator, so that a desired electrode can be formed inside the through hole.

(A) to (D) are explanatory diagrams of the crystal resonator 10 of the embodiment. (A) to (C) are diagrams for explaining some specific examples of through holes according to the present invention. (A) and (B) are process diagrams for explaining an embodiment of a manufacturing method. (A) and (B) are process diagrams following FIG. 3 for describing the embodiment of the manufacturing method.

Hereinafter, embodiments of each invention of this application will be described with reference to the drawings. It should be noted that each drawing used for explanation is only schematically shown to the extent that these inventions can be understood. In addition, in each drawing used for explanation, the same component may be denoted by the same number, and the explanation thereof may be omitted. Further, the shapes, materials, manufacturing method examples, etc. described in the following embodiments are merely preferred examples within the scope of the present invention. Therefore, the present invention is not limited only to the following embodiments.

1. Embodiment of Crystal Oscillator A crystal oscillator 10 of an embodiment will be described with reference to FIG. 1A to 1D are explanatory diagrams of a crystal oscillator 10 according to an embodiment. In particular, (A) is a top view thereof, (B) is a top view focusing on the crystal piece 11, (C) is a cross-sectional view taken along line PP in (B), and (D) is a (C) is a top view of the portion Q in the drawing viewed from above the crystal piece 11 (in the direction indicated by R in the drawing).
The crystal resonator 10 of the embodiment includes a crystal piece 11, a container 13 for accommodating the crystal piece 11, a conductive adhesive 15 connecting and fixing the crystal piece 11 to the container 13, and a conductive adhesive for the crystal piece 11. A through hole 17 is provided in a part of the connection fixing region 11c (see FIG. 1(B)) with the agent 15 and has a crystal-free crystal surface on the inner wall. Each component will be specifically described below.

In this case, the crystal blank 11 is an AT-cut crystal blank. The crystal piece 11 includes an excitation electrode 11a, an extraction electrode 11b, and a through hole 17 (details will be described later), which is a feature of the present invention. The excitation electrodes 11a are provided in predetermined regions on the front and back main surfaces of the crystal piece 11, and are made of any suitable metal film. The extraction electrodes 11b are routed from the excitation electrodes 11a on both main surfaces of the crystal piece 11 to one end side of the crystal piece 11 on the other side of the crystal piece 11 through the through holes 17 in this example. There is. That is, a structure is realized in which the excitation electrodes on the opposite side to the container side are routed to the container side surface via the electrodes in the through holes 17 . In order to route the excitation electrodes on the front and back sides of the crystal piece, a structure for routing through the side walls of the crystal piece may be used together.

In this example, the container 13 includes a recess 13a for accommodating the crystal piece 11, a bank portion 13b forming the recess 13a, and an adhesive pad 13c. In this example, the bonding pad 13c is provided on the bottom surface of the recess 13a and in a region corresponding to the extraction electrode 11b of the crystal piece 11. As shown in FIG. The bonding pads 13c are connected to external connection terminals (not shown) provided on the rear surface of the container 13 via via wiring or castellation wiring (both not shown). The crystal piece 11 is electrically and mechanically connected and fixed to the adhesive pad 13c at the position of the extraction electrode 11b by a conductive adhesive 15. As shown in FIG. That is, the crystal piece 11 is cantilevered by the container 13 .
A lid member (not shown) is joined to the top surface of the bank portion 13 b of the container 13 to seal the crystal piece 11 in the container 13 . Incidentally, the joining of the container 13 and the lid member is performed by any suitable method according to the sealing method. The container 13 can be composed of, for example, a ceramic package.
The conductive adhesive 15 can be composed of any suitable material, but in this example, a silicone-based conductive adhesive is used.

Next, a specific structural example of the through-hole 17, which is a feature of the present invention, will be described. This description is made with reference to FIG. 2 in addition to FIG. FIG. 2A is an SEM (electron microscope) photograph of a cross section of the crystal piece 11 near the connection fixing region 11C cut in the thickness direction of the crystal piece 11. FIG. 2(B) and 2(C) are diagrams showing other examples of through holes, and are cross-sectional views at the same position as FIG. 2(A). Note that the dimensions shown in the SEM photograph of FIG. 2(A) are examples of the dimensions at the time of prototype processing using a short-pulse laser.
The through-hole 17 is a through-hole for providing an electrode that electrically connects the front and back surfaces of the crystal blank 11, and the inner wall of the through-hole 17 is a surface 17a in which the crystallinity of the crystal is eliminated.
In this example, the surface 17a has linear traces extending in the depth direction from the surface of the crystal piece 11 on the inner wall of the through hole 17 and arranged in the circumferential direction of the inner wall. This is the surface 17a having irregularities. Such a surface can be easily formed by a manufacturing method using a short-pulse laser, which is another invention of the present application (details will be described later).

Further, as shown in FIGS. 1(C) and 2(A), the through-hole 17 of this embodiment has a cross-sectional shape along the thickness direction of the crystal piece. It has a funnel shape that tapers from the first surface toward the second surface, which is the opposite surface. With such a shape, it is easy to coat the metal film for electrode formation on the inner wall of the through-hole by, for example, a sputtering method, and to coat the inner wall of the through-hole with a photoresist. so preferred. The size of the through-hole 17 is determined in consideration of the ease of coating with a metal film or a resist film. Although not limited to this, the diameter of the large opening side of the through-hole 17 (upper opening in FIG. 2A) is, for example, 20 to 50 μm, and the small opening side of the through-hole 17 (lower side in FIG. 2A) It is preferable that the diameter of the opening is, for example, 10 to 30 μm.

The shape of the through-hole when viewed in cross section along the thickness direction of the crystal piece is a so-called hourglass-shaped through-hole 17x, in which the degree of opening decreases in the middle of the thickness direction of the crystal piece and then expands. (See FIG. 2B). In the case of this example as well, when a metal film for electrode formation is formed on the inner wall of the through-hole by, for example, sputtering, the metal particles are likely to enter the through-hole from both sides of the crystal piece. It is preferable because it is easy to coat, and it is easy to coat the inner wall of the through-hole with the photoresist. When the cross-sectional shape of the through hole 17x is hourglass-shaped, the depths d1 and d2 (see FIG. 2(B)) to the narrowed portion of the through hole 17x when viewed from the front and back of the crystal piece are preferably about the same. That is, a structure in which the thickness of the crystal piece 11 is thin near the center is preferable. However, there may be cases where d1>d2 or d1<d2.
Further, as shown in FIG. 2(C), through holes 17y having substantially the same thickness may be formed on the front and back sides of the crystal piece 11. As shown in FIG. However, in the case of this through-hole 17y, it is difficult to coat the inner wall of the through-hole with a metal film or a resist in the case of FIGS. 2A and 2B.
In each example of FIG. 2, one through-hole is provided for each of the two excitation electrodes having opposite potentials, but two or more through-holes may be provided for each.

Although the planar shape of the through-hole 17 can be arbitrary, considering the coverage of the electrode film at the opening of the through-hole, the opening of the through-hole is preferably circular or elliptical.
In the crystal oscillator 10 of the present invention, the front and back surfaces of the crystal blank can be electrically connected by the predetermined through holes and the electrodes in the through holes. The reliability of electrode routing is improved compared to the case of routing.

2. Embodiment of Manufacturing Method Next, an embodiment of the manufacturing method of the present application will be described with reference to FIGS. 3 and 4. FIG. 3 and 4 are manufacturing process diagrams showing essential parts of the manufacturing method of the embodiment. The crystal oscillator 10 of the present invention is preferably manufactured from a large crystal wafer by a construction method using photolithography technology and film formation technology, so such an example will be described in this embodiment.
First, an AT-cut crystal wafer 110 having a predetermined thickness and size for manufacturing the crystal resonator 10 is prepared (FIG. 3A). Then, on the crystal wafer 110, by a well-known method, a large number of intermediate bodies 11x for which the crystal blank 11 has been processed and before the excitation electrodes are formed are arranged in a matrix as the intermediate bodies 11x of the crystal oscillator 10. formed (FIG. 3(A)).
Next, a short pulse from a laser device, for example, a short pulse laser device 21 is applied to a part of the connection fixing region 11c of the intermediate body 11x of the individual oscillators of the crystal wafer 110, which is adhered with a conductive adhesive. A through-hole 17 is formed by irradiating the laser beam 21a. The laser device 21 has a galvanomirror (not shown) and can scan the connecting and fixing region 11c with the laser beam 21a in any shape, so that the through hole 17 can be formed in any planar shape. Further, the size of the through-hole 17 can be adjusted by setting the power of the laser beam 21a and/or the number of times of scanning to predetermined conditions (see FIG. 3A). The through-hole 17 formed by laser in this way has an inner wall and a bottom surface in which crystal tangency of crystal is lost, that is, a micro uneven surface in which a large number of linear traces are lined up.
Note that when the through hole 17x having an hourglass-shaped cross section shown in FIG.

A metal film 11m for forming the excitation electrodes 11a and the extraction electrodes 11b is formed on the entire surface of the crystal wafer 110 on which the through holes 17 have been formed by a well-known film forming technique such as sputtering. to obtain a crystal wafer 112 on which a metal film has been formed (FIG. 3(B)). At this time, as shown in FIG. 4A, not only both surfaces of the crystal wafer 112 but also the inner walls of the through holes 17 are covered with the metal film 11m. With the through-hole 17 of the present embodiment, the through-hole 17 can be coated with the metal film 11m as desired due to the effect of the micro-unevenness state in which the crystallinity of the quartz has disappeared and the funnel-shaped cross section.
Next, the entire surface of the crystal wafer 112 and the through holes 17 are covered with a photoresist 23 (FIG. 4A). With the through-hole 17 of the present embodiment, the through-hole 17 can be coated with the photoresist 23 as desired due to the effect of the above-described side surface state and funnel shape of the cross section.
Next, the photoresist 23 is exposed and developed to form a resist pattern (not shown) for forming an electrode, and then the metal film 11m exposed from the resist pattern is selectively removed to form the electrode. Electrodes covering the inside of the through-hole, that is, the excitation electrode 11a and the extraction electrode 11b are formed. The crystal wafer 112 shown in FIG. 4B corresponds to an intermediate wafer for crystal oscillators.
After that, the crystal wafer 112 is singulated into intermediate bodies 11y of crystal oscillators by a well-known method, and these are bonded and fixed to the container 13 (see FIG. 1) with a conductive adhesive.
The crystal oscillator 10 shown in FIG. 1A is formed by adjusting the frequency of the crystal piece 11 whose conductive adhesive has been cured and sealing the container 13 with a lid member (not shown). can.
According to this manufacturing method, the through hole 17 is formed by a short-pulse laser. It is possible to easily form a through-hole having a shape that facilitates covering the inside of the through-hole.

In the above-described embodiment, an example of using an AT-cut crystal piece as the crystal piece was shown, but the crystal piece may be a crystal piece other than the AT-cut crystal piece, such as a tuning-fork type crystal piece or an SC-cut crystal piece. It may be a so-called two-turn crystal piece, such as a piece. In addition, the lead-out electrodes 11b are led from the excitation electrodes 11a on both main surfaces of the crystal piece 11 to the both end regions of one side of the crystal piece 11, i.e., cantilever holding. However, the present invention can also be applied to a two-point fixation structure supporting both ends and a four-point fixation structure supporting both ends. In addition, although an example of a structure having a concave portion 13a as the container 13 has been shown, the container may be flat plate-shaped, and the lid member may be a cap-shaped cap having a concave portion for accommodating the crystal piece. The present invention is applicable.

10: crystal oscillator of the embodiment, 11: crystal piece,
11a: excitation electrode, 11b: extraction electrode,
11c: connection fixing area, 13: container,
13a: concave portion, 13b: embankment portion,
13c: adhesive pad, 15: conductive adhesive,
17: Through-hole 17a: Crystal tangency-free surface 21: Laser device 21a: Laser light
23: Photoresist 110: Crystal wafer 112: Crystal wafer (intermediate wafer for crystal oscillator),
11x, 11y: crystal oscillator intermediate 11m: metal film for electrode formation

1. Embodiment of Manufacturing Method Next, an embodiment of the manufacturing method of the present application will be described with reference to FIGS. 3 and 4. FIG. 3 and 4 are manufacturing process diagrams showing essential parts of the manufacturing method of the embodiment. The crystal oscillator 10 of the present invention is preferably manufactured from a large crystal wafer by a construction method using photolithography technology and film formation technology, so such an example will be described in this embodiment.
First, an AT-cut crystal wafer 110 having a predetermined thickness and size for manufacturing the crystal resonator 10 is prepared (FIG. 3A). Then, on the crystal wafer 110, by a well-known method, a large number of intermediate bodies 11x for which the crystal blank 11 has been processed and before the excitation electrodes are formed are arranged in a matrix as the intermediate bodies 11x of the crystal oscillator 10. formed (FIG. 3(A)).
Next, a short pulse from a laser device, for example, a short pulse laser device 21 is applied to a part of the connection fixing region 11c of the intermediate body 11x of the individual oscillators of the crystal wafer 110, which is adhered with a conductive adhesive. A through-hole 17 is formed by irradiating the laser beam 21a. The laser device 21 has a galvanomirror (not shown) and can scan the connecting and fixing region 11c with the laser beam 21a in any shape, so that the through hole 17 can be formed in any planar shape. Further, the size of the through-hole 17 can be adjusted by setting the power of the laser beam 21a and/or the number of times of scanning to predetermined conditions (see FIG. 3A). The through-hole 17 formed by laser in this manner has an inner wall and a bottom surface in which the crystallinity of the crystal has disappeared, that is, a micro uneven surface in which a large number of linear traces are lined up.
Note that when the through hole 17x having an hourglass-shaped cross section shown in FIG.

10: crystal oscillator of the embodiment, 11: crystal piece,
11a: excitation electrode, 11b: extraction electrode,
11c: connection fixing area, 13: container,
13a: concave portion, 13b: embankment portion,
13c: adhesive pad, 15: conductive adhesive,
17: through-hole 17a: surface where the crystallinity of crystal is eliminated 21: laser device 21a: laser beam
23: Photoresist 110: Crystal wafer 112: Crystal wafer (intermediate wafer for crystal oscillator),
11x, 11y: crystal oscillator intermediate 11m: metal film for electrode formation

Claims (7)

A crystal piece, a container for housing the crystal piece, a conductive adhesive that connects and fixes the crystal piece to the container, and a portion of the connection and fixing region of the crystal piece that is provided on the front and back of the crystal piece. A crystal oscillator comprising a through-hole that penetrates,
a through hole having, as the through hole, an inner wall surface in which crystallinity of crystal is eliminated;
A crystal oscillator, comprising: an electrode provided over one surface of the crystal piece, an inner wall of the through hole, and the other surface of the crystal piece. A cross-sectional shape of the through hole cut along the thickness direction of the crystal piece is a funnel shape that tapers from the first surface side of the crystal piece toward the second surface side opposite thereto. The crystal oscillator according to claim 1. 2. A surface shape of said through-hole cut along the thickness direction of the crystal piece is an hourglass shape in which the degree of opening decreases in the middle of the thickness direction of the crystal piece and then expands. Crystal oscillator described in . In manufacturing a crystal oscillator having a structure in which a crystal piece is fixed to a container with a conductive adhesive,
a step of forming a through-hole penetrating through the crystal piece by means of a short-pulse laser in a part of the region of the crystal piece to be fixed by the conductive adhesive;
a step of forming a metal film for forming an electrode of a crystal oscillator on the crystal piece in which the through holes are formed so as to cover the inside of the through holes;
a step of forming a photoresist on the crystal piece on which the metal film is formed so as to cover the inside of the through hole;
exposing and developing the photoresist to form a resist pattern for forming an electrode; and selectively removing the metal film exposed from the resist pattern to cover the inside of the through hole as the electrode. A method of manufacturing a crystal oscillator, comprising: In an intermediate wafer for crystal oscillators, which includes a large number of crystal pieces arranged in a matrix as intermediates for forming crystal oscillators,
A through hole penetrating through the front and back of the crystal blank in a part of the area of the crystal blank that is the intermediate body to be connected and fixed to the container by the conductive adhesive, and the crystallinity of the crystal is lost. a through hole having a surface on the inner wall;
An intermediate wafer for a crystal oscillator, comprising: an electrode provided on one surface of the crystal piece, an inner wall of the through hole, and the other surface of the crystal piece. A cross-sectional shape of the through hole cut along the thickness direction of the crystal piece is a funnel shape that tapers from the first surface side of the crystal piece toward the second surface side opposite thereto. 6. The intermediate wafer for crystal oscillators according to claim 5.
crystal oscillator. 6. A cross-sectional shape of the through-hole cut along the thickness direction of the crystal piece is an hourglass shape in which the degree of opening decreases in the middle of the thickness direction of the crystal piece and then expands. An intermediate wafer for the crystal resonator according to .

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