Vibration element, vibrator, and method for producing vibration element with a vibrating piece having a protruding part for improved vibration characteristics

A vibrator, a vibrating element and a method for producing the vibrating element may include vibrating piece having a central portion and a peripheral portion. The vibrator, the vibrating element and the method may further include a pair of excitation electrodes provided on a first side and a second side of a main surface of the central portion. The vibrator, the vibrating element and the method may further include a pair of connection electrodes provided on the peripheral portion and electrically connected to the pair of excitation electrodes. The vibrator, the vibrating element and the method may further include a substrate configured to be connected to the pair of connection electrodes via an electrically-conductive holding member interposed therebetween and configured to support the vibration element in an excitable manner.

TECHNICAL FIELD

Aspects of the present disclosure are directed to a vibration element, a vibrator, and a method for producing the vibration element.

BACKGROUND OF THE INVENTION

A recent reduction in the size of a crystal vibrator narrows a gap between a crystal vibration element and an inner surface of a case in which the crystal vibration element is contained. Accordingly, in a case where the crystal vibration element is inclined with respect to the inner surface of the case, a mesa part (central part) that holds excitation electrodes of the crystal vibration element tends to make contact with the inner surface of the case. This inhibits free vibration of the crystal vibration element caused by the excitation elements, thereby affecting vibration characteristics of the crystal vibrator. It therefore may be necessary to make the mesa part (central part) of the small-sized crystal vibrator and the inner surface of the case less likely to make contact with each other.

For example, Japanese Unexamined Patent Application Publication No. 2014-180050 (hereinafter “JP '050”) discloses a vibration element having a first region that vibrates mainly in a thickness-shear mode and has a constant thickness and a second region that is coupled to outer peripheral parts on both sides arranged along a vibration direction of the main vibration of the first region with a step interposed there between and has a thickness smaller than the first region, wherein in plan view, two first protruding parts are provided on a part of a main surface located on a second end portion side opposite to a first end portion side where a fixation part of the second region is disposed but excluding a central part of a width along a direction crossing the vibration direction so that the protruding parts are located apart from the first region and located inside an outer periphery of the vibration element, and a second protruding part is provided on a part of the main surface of the second region on the first end portion side. The vibration element disclosed JP '050 has protruding parts that are provided at a peripheral part of a crystal piece so as to be apart from a central part of the crystal vibrator so that the central part becomes less likely to make contact with an inner surface of a package.

However, according to the vibration element disclosed in JP '050, in a case where a crystal piece is provided with protruding parts, it may be necessary to reduce an area of a central part in order to secure an area for providing the protruding parts as compared with a case where a crystal piece is provided with no protruding part, even in a case where these crystal pieces have the same size. Since the area of the central part is reduced, an area of an excitation electrode that may be mounted on the central part is also reduced accordingly. This reduces an excitation region of the excitation electrode, thereby increasing an equivalent series resistance value of the vibration element. As a result, good vibration characteristics cannot be obtained in some cases.

SUMMARY OF THE INVENTION

According to an exemplary aspect of the disclosure, for addressing the problem described above, it may be to increase a size of a crystal piece so that even in a case where protruding parts are provided, a central part can keep an area obtained in a case where no protruding part is provided. However, a reduction in size of a vibration element cannot be realized due to the increase in size of a crystal piece.

The present disclosure has been accomplished in view of such circumstances, and an object of the present disclosure is to provide a vibration element, a vibrator, and a method for producing the vibration element that can achieve a reduction in size and obtain good vibration characteristics.

A vibrator according to an exemplary aspect of the present disclosure includes a vibration element including a vibrating piece having a central part and a peripheral part whose dimension in a thickness direction is smaller than the central part, a pair of excitation electrodes provided on central part main surfaces on both sides of the central part in the thickness direction, and a pair of connection electrodes electrically connected to the pair of excitation electrodes, respectively and provided on the peripheral part; a substrate connected to the connection electrodes of the vibration element with an electrically-conductive holding member interposed there between on one side in the thickness direction so as to support the vibration element in an excitable manner; and a lid part that covers the vibration element on the other side in the thickness direction, wherein the vibrating piece has at least one protruding part provided in contact with the central part when the central part main surfaces of the vibration element are viewed in plan view, and the at least one protruding part protrudes in the thickness direction in a position where the at least one protruding part makes contact with the substrate or the lid part in a case where the vibration element is inclined toward the substrate or the lid part while being supported on a side where the pair of connection electrodes are provided.

According to another aspect of the present disclosure, a vibration element, a vibrator, and a method for producing the vibration element make it possible to realize a reduction in size and obtain good vibration characteristics.

Additional advantages and novel features of the system of the present disclosure will be set forth in part in the description that follows, and in part will become more apparent to those skilled in the art upon examination of the following or upon learning by practice of the disclosure.

DETAILED DESCRIPTION

Aspects of the present disclosure is described below. In the drawings, identical or similar constituent elements are given identical or similar reference signs. The drawings are illustrative, and dimensions and shapes of parts are schematic illustration, and it should not be interpreted that the technical scope of the present disclosure is limited to specific aspects.

First, a crystal vibrator (Quartz Crystal Resonator Unit)1according to an exemplary aspect of the disclosure is described with reference toFIGS.1and2.FIG.1is an exploded perspective view of the crystal vibrator1, andFIG.2is a cross-sectional view taken along line II-II ofFIG.1. InFIG.2, illustration of electrodes of a crystal vibration element10is omitted.

Furthermore, the crystal vibrator1includes electrically-conductive holding members36aand36b, and a sealing frame37and a joining member40that serve as joining members. The crystal vibrator1is an example of a vibrator, and the crystal vibration element10is an example of a vibration element.

In an exemplary aspect, the crystal vibration element10is mounted on the substrate30with the electrically-conductive holding members36aand36binterposed therebetween, and then the lid part20is joined to the substrate30with the sealing frame37and the joining member40interposed therebetween so as to cover the crystal vibration element10. In this way, the crystal vibration element10is contained or sealed in an internal space26of a holder constituted by the lid part20and the substrate30. In accordance with an aspect of the disclosure, the crystal vibration element10, the lid part20, and the substrate30may each have a rectangular shape, and directions of long sides and directions of short sides of these members match one another, when the crystal vibrator1is viewed in plan view along a thickness direction of the crystal vibrator1.

The crystal vibration element10can include a plate shape. Furthermore, the crystal vibration element10can include a crystal piece11and a plurality of electrodes provided on the crystal piece11. The plurality of electrodes include excitation electrodes14aand14b, extended electrodes15aand15b, and connection electrodes16aand16b.

In accordance with an aspect of the disclosure, the crystal piece11can be an AT cut crystal piece and is cut out from artificial crystal (Synthetic Quartz Crystal) so that a surface (hereinafter referred to as an “XZ′ surface”; surfaces specified by other axes are also referred to in similar manners) parallel with a plane specified by an X axis and a Z′ axis becomes a main surface assuming that crystal axes of the crystal are the X axis, a Y axis, and a Z axis and axes obtained by rotating the Y axis and the Z axis by 35 degrees 15 minutes±1 minute 30 seconds in a direction from the Y axis to the Z axis about the X axis are a Y′ axis and the Z′ axis, respectively. The crystal vibration element10that employs the AT cut crystal piece11mainly vibrates in a thickness-shear mode. In the crystal piece11according to as aspect of the disclosure, the thickness direction is parallel with a Y′-axis direction. When the crystal piece11is viewed in plan view along the Y′-axis direction, the XZ′ surface of the crystal piece11has a rectangular shape having long sides parallel with an X-axis direction and short sides parallel with a Z′-axis direction. Details of constituent elements of the crystal vibration element10are described below.

The constituent elements of the crystal vibrator1are described below on the basis of the X-axis direction, the Y′-axis direction, and the Z′-axis direction of AT cut. The wording “plan view” means that these constituent elements are viewed in plan view along the thickness direction (the Y′-axis direction) of the crystal vibrator1(the constituent elements) unless otherwise specified. In a case where these constituent elements are viewed in plan view along two or more axis directions, expressions “on the XZ′ plane,” “on the XY′ plane,” and “on the Y′Z′ plane” are used to distinguish the directions. The “XY′ plane” means a cross section in the thickness direction. Shapes of the crystal vibration element10, the lid part20, and the substrate30seen when the crystal vibration element10, the lid part20, and the substrate30are viewed in plan view are referred to as “planar shapes” of these constituent elements.

The lid part20has a box shape opened on a side joined to the substrate30, and a planar shape thereof is a rectangular shape larger than a planar shape of the crystal vibration element10. The lid part20has a ceiling part21and a side wall part22that is formed so as to protrude from an outer edge of the ceiling part21. Furthermore, the lid part20has an inner surface24having a concave shape constituted by a ceiling rear face21aof the ceiling part21and an inner surface of the side wall part22. Dimensions of the inner surface24in the X-axis direction, the Y′-axis direction, and the Z′-axis direction can be larger than those of the crystal vibration element10.

A material for the lid part20is not limited in particular, and the lid part20is, for example, made of an electrically-conductive material such as a metal. This can add a shield function to the lid part20by electrically connecting the lid part20to a ground potential. Alternatively, the lid part20may be made of an insulating material or a complex structure of an electrically-conductive material and an insulating material.

The substrate30has a flat plate shape, and a planar shape thereof is a rectangular shape larger than the planar shape of the lid part20. The substrate30supports the crystal vibration element10in an excitable manner and has a base31and a plurality of electrodes provided on the base31. The plurality of electrodes include connection electrodes33aand33b, via electrodes34aand34b, and outer electrode35ato35d.

The base31is a sintered body obtained by laminating a plurality of sheets made of insulating ceramic, for example, alumina and sintering the laminated sheets. Alternatively, the base31may be made of a glass material, a crystal material, a glass epoxy resin, or the like. The glass material can be, for example, silicate glass or a material whose main component is a material other than silicate and is a material having a glass-transition phenomenon occurring due to a rise in temperature. The crystal material can be, for example, an AT cut crystal. The base31is preferably made of a heat resistant material. Furthermore, the base31may be a single layer or may be plural layers. In a case where the base31is plural layers, the base31includes an insulating layer as a topmost layer.

The base31has a first main surface32aand a second main surface32b, which are XZ′ surfaces facing each other, and two via holes32cthat pass through the base31in the Y′-axis direction in the vicinity of a short side on a negative side in the X-axis direction. In an assembled state, the first main surface32afaces the inner surface24(ceiling rear surface21a) of the lid part20and constitutes the internal space26in which the crystal vibration element10is contained together with the inner surface24. The second main surface32bfaces a mount substrate (not illustrated) on which the crystal vibrator1is mounted.

The connection electrodes33aand33bare provided on the first main surface32ain the vicinity of the short side on the negative side in the X-axis direction. The outer electrodes35a,35b,35c, and35dare provided at four corners of the second main surface32b, respectively. The via electrodes34aand34bare provided in the two via holes32c, respectively. The outer electrode35ais electrically connected to the connection electrode33aby the via electrode34a, and the outer electrode35bis electrically connected to the connection electrode33bby the via electrode34b. To achieve such electric connection, the outer electrodes35aand35bare provided so as to face the connection electrodes33aand33bin the Y′ direction, respectively.

The connection electrodes33aand33band the outer electrodes35ato35dare metal films, and may be, for example, configured such that a molybdenum (Mo) layer, a nickel (Ni) layer, and a gold (Au) layer are laminated in this order from a lower layer to an upper layer. The via electrodes34aand34bare, for example, formed by filling the via holes32cwith a metal material such as molybdenum.

The connection electrode33ais a terminal for electric connection with the connection electrode16aof the crystal vibration element10, and the connection electrode33bis a terminal for electric connection with the connection electrode16bof the crystal vibration element10. The outer electrodes35ato35dare terminals for electric connection with the mount substrate (not illustrated). In an aspect of the disclosure, the outer electrodes35aand35bare input output electrodes to which an input/output signal of the crystal vibration element10is supplied, and the outer electrodes35cand35dare electrodes to which an input/output signal of the crystal vibration element10is not supplied. To the outer electrodes35cand35d, an input/output signal of other electronic elements on the mount substrate (not illustrated) is not supplied either. Alternatively, at least one of the outer electrodes35cand35dmay be an electrode for grounding to which a ground potential is supplied. The shield effect of the lid part20can be improved by connecting the lid part20to the outer electrode that is an electrode for grounding.

The electrically-conductive holding member36aelectrically connects the connection electrode16aof the crystal vibration element10to the connection electrode33aof the substrate30. Similarly, the electrically-conductive holding member36belectrically connects the connection electrode16bof the crystal vibration element10to the connection electrode33bof the substrate30. The electrically-conductive holding members36aand36bmay be formed, for example, by thermally curing an electrically-conductive adhesive. In an aspect of the disclosure, the crystal vibration element10may be supported on the first main surface32aof the substrate30in an excitable manner by the electrically-conductive holding members36. A short-side end of the crystal piece11where the connection electrodes16aand16bare provided is a fixed end, and the other ends are free ends. In a case where the electrically-conductive holding members36aand36bare not distinguished from each other, the electrically-conductive holding members36aand36bare referred to as “electrically-conductive holding members36.”

The sealing frame37is an example of a joining member and joins the lid part20and the substrate30together with the joining member40. Furthermore, the sealing frame37is provided on the first main surface32aand has a rectangular frame shape provided outside the connection electrodes33aand33bso as to surround the connection electrodes33aand33bin plan view. This sealing frame37is made of a material such as an electrically conductive metal film, for example, a molybdenum (Mo) layer or a laminate of a molybdenum (Mo) layer, a nickel (Ni) layer, and a gold (Au) layer.

The joining member40is an example of a joining member and joins the lid part20and the substrate30together with the sealing frame37. The joining member40is provided on the sealing frame37. The joining member40is, for example, a brazing member and is made of a material such as a gold (Au)-tin (Sn) eutectic alloy. In this way, the lid part20and the substrate30are metal-joined. According to the metal joining, sealing performance between the lid part20and the substrate30can be improved. The joining member40is not limited to an electrically-conductive material and may be an insulating material such as a glass adhesive material (e.g., low-melting-point glass) or a resin adhesive. This reduces influence of oxidation as compared with a metal, keeps a heating temperature low, and simplifies a production process.

In the crystal vibrator1according to an aspect of the disclosure, when an alternating electric field is applied across the pair of excitation electrodes14aand14bof the crystal vibration element10through the outer electrodes35aand35bof the substrate30, the crystal piece11(a central part11a, which is described below) vibrates in a predetermined vibration mode such as a thickness-shear vibration mode, and resonance characteristics are obtained due to the vibration.

Next, the constituent elements of the crystal vibration element10according to an aspect of the disclosure are described in detail with reference toFIGS.1and2. The crystal vibration element10according to an aspect of the disclosure includes the AT cut crystal piece11, and the pair of excitation electrodes14aand14b, the pair of connection electrodes16aand16b, and the pair of extended electrodes15aand15bthat are provided on the crystal piece11.

The crystal piece11is an example of a plate-shaped vibrating piece and has a mesa-type structure. This crystal piece11has a central part11athat constitutes a mesa part, a peripheral part11bwhose dimension in the thickness direction is smaller than that of the central part11a, and a pair of protruding parts11cthat are in contact with side surfaces of the central part11aand protrude in the thickness direction. The central part11a, the peripheral part11b, and the pair of protruding parts11care integral with each other. Furthermore, the crystal piece11has a first main surface12aand a second main surface12bon respective sides in the thickness direction. The first main surface12aincludes a central part main surface111a, a peripheral part main surface112a, and a protruding part main surface113a, which is described below, and the second main surface12bincludes a central part main surface111b, a peripheral part main surface112b, and a protruding part main surface113b, which is described below. In a case where the first main surface12aand the second main surface12bare not distinguished from each other, the first main surface12aand the second main surface12bare referred to as “main surfaces12.”

In accordance with an aspect of the disclosure, the central part11aand the protruding parts11cform a convex shape protruding from both surfaces of the peripheral part11bin the thickness direction on the XY′ plane. The central part11a, the peripheral part11b, and the protruding parts11chave uniform thicknesses. The central part11aand the protruding parts11chave the same thickness, and a dimension of the peripheral part11bin the thickness direction is smaller than that of the central part11aand the protruding parts11c. On the XZ′ plane, the central part11aand the peripheral part11b(crystal piece11) each have a rectangular shape, and directions of long sides and directions of short sides of these rectangular shapes match each other. The central part11ais provided on a substantially central side relative to an outer edge of the crystal piece11, the peripheral part11bis provided around the central part11aso as to surround the central part11a, and the pair of protruding parts11care provided at corners of respective ends of a short side of the central part11aon a positive side in the X-axis direction.

Hereinafter, for convenience of description, on the XZ′ plane, a short side of the peripheral part11bon a side opposite to a side where the connection electrodes16aand16b(described below) are provided, that is, on a side opposite to the connection electrodes16aand16bis sometimes referred to as a “first side L1,” and a short side of the central part11aon this opposite side, that is, on a side close to the first side is sometimes referred to as a “second side L2.”

The central part11ahas a rectangular parallelepiped shape and has the central part main surfaces111aand111b, which are XZ′ surfaces facing each other, and a side surface13aperpendicular to the central part main surface111a. In a case where the central part main surfaces111aand111bare not distinguished from each other, the central part main surfaces111aand111bare referred to as “central part main surfaces111.” In an aspect of the disclosure, the central part main surface111is located on a central side of the crystal piece11closer to the first side L1of the peripheral part11bwhen the central part11ais viewed in plan view. The side surface13ahas a side surface131a, a side surface132a, a side surface133a, and a side surface134a.

The peripheral part11bhas a plate shape and has the peripheral part main surfaces112aand112b, which are XZ′ surfaces facing each other, and a side surface13bperpendicular to the peripheral part main surface112a. In a case where the peripheral part main surfaces112aand112bare not distinguished from each other, the peripheral part main surfaces112aand112bare referred to as “peripheral part main surfaces112.” When the peripheral part11bis viewed in plan view, an outer edge of the peripheral part main surface112is an outer edge of the crystal piece11, and an inner edge of the peripheral part main surface112matches an outer edge of the central part main surface111. That is, the inner edge of the peripheral part main surface112is connected to the side surface13aof the central part11a.

The protruding parts11chave a rectangular parallelepiped shape and have the protruding part main surfaces113aand113b, which are XZ′ surfaces facing each other, and a side surface13cperpendicular to the protruding part main surface113a. In a case where the protruding part main surfaces113aand113bare not distinguished from each other, the protruding part main surfaces113aand113bare referred to as “protruding part main surfaces113.” The pair of protruding parts11caccording to an aspect of the disclosure are provided at corners at both ends of the second side L2of the central part11aon a positive side in the X-axis direction, that is, on a side opposite to a side where the connection electrodes16are provided in plan view and forms a concave shape together with the rectangular central part11a. Specifically, each of the protruding parts11chas a side surface that is in contact with the side surface131aof the central part11awhere the second side L2is located and extends from the central part11atoward the first side L1of the peripheral part11b. In other words, the protruding parts11care provided between the first side L1and the second side L2. The protruding part main surface113of the protruding parts11cis a flat surface flush with the central part main surface111. That is, the protruding parts11chave the same thickness as the central part11ain the thickness direction.

The pair of excitation electrodes14aand14bare electrodes to which a voltage is applied to vibrate the central part11ain the thickness-shear mode, and the excitation electrodes14aand14bhave an identical configuration. The excitation electrodes14aand14bare provided on the central part main surfaces111aand111b, respectively so as to face each other with the central part11ainterposed there between. In other words, the excitation electrodes14aand14bare disposed so that the substantially whole excitation electrodes14aand14boverlap each other in plan view.

The connection electrodes16aand16bare terminals for electrically connecting the crystal vibration element10to the connection electrodes33aand33bof the substrate30. The connection electrode16aand the connection electrode16bare aligned along a short side, on a negative side in the X-axis direction, of the peripheral part main surface112bof the crystal piece11(peripheral part11b). Accordingly, in the crystal vibration element10, a short side end where the connection electrodes16aand16bof the crystal piece11are provided is a fixed end, and the other ends are free ends. That is, the crystal vibration element10(the crystal piece11) has a cantilever configuration. Hereinafter, in a case where the connection electrodes16aand16bare not distinguished from each other, the connection electrodes16aand16bare referred to as “connection electrodes16,” and a side where the connection electrodes16aand16bare provided is sometimes referred to as a “connection electrode side.”

The extended electrode15ais an electrode for electrically connecting the excitation electrode14ato the connection electrode16a, and the extended electrode15bis an electrode for electrically connecting the excitation electrode14bto the connection electrode16b. Specifically, the extended electrode15ais provided so as to connect the excitation electrode14aon the first main surface12aand the connection electrode16aon the second main surface12b, and the extended electrode15bis provided so as to connect the excitation electrode14band the connection electrode16bon the second main surface12b. In a case where the extended electrodes15aand15bare not distinguished from each other, the extended electrodes15aand15bare referred to as “extended electrodes15.”

A material for the excitation electrodes14, the extended electrodes15, and the connection electrodes16is not limited in particular, and, for example, the excitation electrodes14, the extended electrodes15, and the connection electrodes16may have a chromium (Cr) layer as a base and a gold (Au) layer on a surface of the chromium layer.

Next, an example of steps for producing the crystal vibration element10is described with reference toFIGS.3A to3C. This example of steps for producing the crystal vibration element10is an example in which the central part11a, the peripheral part11b, and the pair of protruding parts11care concurrently formed by etching.FIG.3Aillustrates a state where a resist has been applied to the crystal piece11,FIG.3Billustrates a state of the crystal piece11obtained after a first etching process and a second etching process, andFIG.3Cillustrates a state of the completed crystal piece11.FIGS.3A to3Cillustrate a processing method in the thickness direction of the crystal piece11. InFIGS.3A to3C, illustration of the excitation electrodes14, the extended electrodes15, and the connection electrodes16formed on the crystal piece11is omitted.

First, as illustrated inFIG.3A, a resist film50is formed on both main surfaces12of the crystal piece11cut out from a crystal wafer so as to be located in a part (seeFIG.1) where the central part11aand the pair of protruding parts11care to be formed. A part where the resist film50is not formed is a part where the peripheral part11b(seeFIG.1) is to be formed.

Next, as illustrated inFIG.3B, the part of the crystal piece11on both main surfaces12where the resist film50is not formed is removed by etching to form the peripheral part11b. Meanwhile, the part where the resist film50is formed, that is, the central part11aand the pair of protruding parts11cremains in a convex shape without being removed by the etching. The step for forming the peripheral part11bis an example of a first etching step, and the step for forming the central part11aand the pair of protruding parts11cis an example of a second etching step.

Such etching may make it possible to concurrently form the central part11a, the peripheral part11b, and the pair of protruding parts11c, thereby enabling efficient processing. Furthermore, the central part11aand the protruding parts11con both sides in the thickness direction may be processed by one etching processing, and therefore an accurate thickness of the crystal piece11can be obtained.

The etching according to an aspect of the present disclosure may be, for example, wet etching. In this case, hydrofluoric acid may be used or a mixed liquid, for example, made up of hydrofluoric acid and ammonium fluoride may be, for example, used. The crystal piece11that has been subjected to the etching processing is configured such that the central part11aand the protruding parts11ccovered with the resist film50are formed in a convex shape, as illustrated inFIG.3B.

After the etching, the remaining resist film50that covers the central part11aand the protruding parts11cof the crystal piece11is removed, as illustrated inFIG.3C. In this way, the crystal piece11is produced. Then, for example, metal films having a chromium (Cr) layer as a base and a gold (Au) layer on a surface of the chromium layer are formed on parts such as the central part main surface111of the central part11aof the crystal piece11. These metal films constitute the excitation electrodes14, the extended electrodes15, and the connection electrodes16. After the formation of the metal films, production of the crystal vibration element10is completed.

Next, the protruding parts11cin a case where the crystal vibration element10is inclined toward the substrate30is described in detail with reference toFIGS.4A and4B.FIGS.4A and4Bare schematic views illustrating a state in a case where the crystal vibration element10is inclined toward the substrate30,FIG.4Aillustrates a state of the central part11ain a case where the protruding parts11cmake contact with the substrate30, andFIG.4Billustrates a state of the central part11ain a case where the protruding parts11care not employed. Since the same principle holds both in a case where the protruding parts11cmakes contact with the lid part20and a case where the protruding parts11cmakes contact with the substrate30, illustration of the central part11aand the protruding parts11cthat protrude from the peripheral part11btoward the lid part20, the lid part20, other members such as wires is omitted inFIGS.4A and4B. Hereinafter, on the XY′ plane, an end point of the crystal vibration element10on the connection electrode side on which the connection electrodes16are provided in a case where the crystal vibration element10is inclined is referred to as a “support point P4.”

Since the protruding parts11caccording to an aspect of the present disclosure may have the same thickness as the central part11aas described above, the protruding part main surface113bof the protruding parts11cand the central part main surface111bof the central part11aconstitute a straight line on the XY′ plane. Since the protruding parts11care provided on a side opposite to the support point P4relative to the central part11a, that is, on a side close to the free end of the crystal vibration element10, a straight line part corresponding to the protruding part main surface113bof the protruding parts11cis located closer to the free end side than a straight line part corresponding to the central part main surface111bof the central part11aon the XY′ plane. Furthermore, a distance from the support point P4to the substrate30is a constant distance determined by dimensions of the electrically-conductive holding members36and the connection electrodes33aand33bon the substrate30side in the thickness direction. Accordingly, on the XY′ plane, the central part11aon a support point P4side relative to the protruding parts11cdoes not make contact with the substrate30in a case where the crystal vibration element10is inclined toward the substrate30while being supported on the connection electrode side, for example, due to a variation in fixation state of the crystal vibration element10or deformation of the substrate30and the protruding parts11cmake contact with the substrate30, as illustrated inFIG.4A.

Meanwhile, if the protruding parts11care not employed, the central part11amakes contact with the substrate30in a case where the crystal vibration element10is inclined toward the substrate30while being supported on the connection electrode side, as illustrated inFIG.4B.

As described above, in a case where the crystal vibration element10is inclined toward the substrate30while being supported on the connection electrode side, the protruding parts11cmake contact with the substrate30, and as a result, it may be possible to prevent the central part11afrom making contact with the substrate30. This also makes it possible to prevent the excitation electrode14provided on the central part main surface111of the central part11afrom making contact with the substrate30. As a result, it may be possible to lessen inhibition of free vibration of the crystal vibration element10due to contact of the central part11aand the excitation electrodes14with the substrate30and influence of the inhibition on vibration characteristics of the crystal vibration element10.

Furthermore, since the protruding parts11caccording to an aspect of the present disclosure are provided at corners of the rectangular central part11aso as to be integral with the central part11a, it may be possible to provide the central part main surfaces111having a larger area and provide the excitation electrodes14having a larger area on the central part main surfaces111having such a large area, as compared with a case where the protruding parts11cof the crystal piece11having a similar area are provided separately from the central part11a. This may provide a wide excitation region of the excitation electrodes14even in a case where the crystal vibration element10has a small size, thereby suppressing an increase in equivalent series resistance value of the crystal vibration element10caused by a reduction in excitation region.

Since the protruding parts11caccording to an aspect of the present disclosure are provided at corners of the rectangular central part on the XZ′ plane, that is, at corners most remote from a maximum part of vibratory displacement energy that diffuses in an oval shape, it is possible to minimize a decrease in piezoelectric effect caused by contact of the protruding parts11cwith the substrate30.

Therefore, according to the protruding parts11caccording to an aspect of the present disclosure, it is possible to realize a reduction in size of the crystal vibration element10and obtain good vibration characteristics.

Although a case where the protruding parts11care provided symmetrically at two corners of the central part11ahas been described above, the protruding parts11ccan employ any configuration, any number, and any combination as long as the protruding parts11cmake contact with the substrate30or the lid part20and thereby prevent the central part11afrom making contact with the substrate30or the lid part20in a case where the crystal vibration element10is inclined toward the substrate30or the inner surface24of the lid part20while being supported on the connection electrode side. The following describes configuration conditions which may be necessary for the protruding parts11cto prevent the central part11afrom making contact with the substrate30or the lid part20with reference toFIGS.4A and4Band then describes specific modifications of the protruding parts11cwith reference toFIGS.5A to6B. Hereinafter, the “case where the crystal vibration element10is inclined toward the substrate30or the inner surface24of the lid part20while being supported on the connection electrode side” is referred to as a “case where the crystal vibration element10is inclined,” and “the protruding parts11cprevents the central part11afrom making contact with the substrate30or the lid part20” is referred to as “the central part11ais prevented from making contact with the substrate30or the like.”

First, a configuration condition is considered from a difference in positional relationship of the crystal vibration element10between a case where the protruding parts11care provided and a case where the protruding parts11care not provided. In a case where the crystal vibration element10is inclined, a first angle θ1illustrated inFIG.4Aformed between the central part main surface111and the substrate30in a case where the protruding parts11cmake contact with the substrate30is smaller than a second angle θ2illustrated inFIG.4Bformed between the central part main surface111and the substrate30in a case where the protruding parts11care not provided and the central part11amakes contact with the substrate or the lid part. Therefore, the crystal vibration element10having the protruding parts11cthat meet such a condition may prevent the central part11afrom making contact with the substrate30or the like in a case where the crystal vibration element10is inclined.

Furthermore, a configuration condition is considered from a difference in positional relationship of the free end of the crystal vibration element10between a case where the protruding parts11care provided and a case where the protruding parts11care not provided. In a case where the crystal vibration element10is inclined, a first distance H1illustrated inFIG.4Afrom a part of the peripheral part11bclosest to the substrate30to the substrate30in a case where the protruding parts11cmake contact with the substrate30is larger than a second distance H2illustrated inFIG.4Bfrom a part of the peripheral part11bclosest to the substrate30to the substrate30in a case where the protruding parts11care not provided and the central part11amakes contact with the substrate30. Therefore, the crystal vibration element10having the protruding parts11cthat meet such a condition may prevent the central part11afrom making contact with the substrate30or the like in a case where the crystal vibration element10is inclined.

Furthermore, a configuration condition is considered from a relationship among the free end of the crystal vibration element10, the protruding parts11c, and the central part11a. For convenience of description, an end point of the peripheral part11bon a side opposite to the connection electrode side is referred to as a “first end point P1,” an end point of the central part11aon the side opposite to the connection electrode side is referred to as a “second end point P2,” and an end point of the protruding parts11con the side opposite to the connection electrode side is referred to as a “third end point P3.”

In this case, as illustrated inFIG.4A, on the XZ′ plane, a first virtual angle θ10formed between a first virtual line L10connecting the first end point P1and the third end point P3of the crystal vibration element10and the peripheral part main surface112of the peripheral part11bis larger than a second virtual angle θ20formed between a second virtual line L20connecting the first end point P1and the second end point P2and the peripheral part main surface112of the peripheral part11b. Therefore, the crystal vibration element10having the protruding parts11cthat meet such a condition can prevent the central part11afrom making contact with the substrate30or the like in a case where the crystal vibration element10is inclined.

Next, modifications of the protruding parts11care described with reference toFIGS.5A to6B.FIGS.5A to6Bare views for explaining a configuration of protruding parts11cof a crystal vibration element10according to another aspect of the disclosure. In the description of the protruding parts11caccording to other aspects of the disclosure, description of constituent elements identical to those in the above disclosure is omitted, and only different constituent elements are described. InFIGS.5A to6B, illustration of excitation electrodes14, extended electrodes15, and connection electrodes16formed on the crystal vibration element10is omitted.

Although a configuration in which the pair of protruding parts11cmake contact with the side surface131a(seeFIGS.1and2) of the central part11aopposite to the connection electrodes16, are isolated from each other, and have the same thickness as the central part1lain the thickness direction has been described in the above disclosure, this configuration is not restrictive. For example, it is possible to employ a protruding part11cthat has a rectangular planar shape larger than a dimension of the central part11ain the Z′-axis direction, as illustrated inFIG.5A. In this case, the rectangular protruding part11cmakes contact with the side surface131a(seeFIGS.1and2) of the central part11a. Such a protruding part11ccan improve strength of the protruding part11citself and increase an area of the central part11a.

Furthermore, for example, a pair of protruding parts11cillustrated inFIG.5Bhave a first part that extends from a corner of the central part11atoward the first side L1of the peripheral part11balong a direction opposite to a side where the connection electrodes16(seeFIGS.1and2) are provided and a second part that extends from the corner of the central part11atoward a side L3crossing the first side L1of the peripheral part11balong a direction crossing the direction opposite to the side where the connection electrodes16are provided, unlike the protruding parts11caccording to an aspect of the present disclosure. The configuration in which the protruding parts11care provided at corners encompasses not only the configuration in which the protruding parts11cextend from the corners of the central part11atoward the first side L1of the peripheral part11baccording to an aspect of the present disclosure, but also a configuration in which the protruding parts11cextend from the corners of the central part11atoward the side L3crossing the first side L1of the peripheral part11b, a configuration in which the protruding parts11chave both a part that extends from the corners of the central part11atoward the first side L1of the peripheral part11band a part that extends from the corners of the central part11atoward the side L3crossing the first side L1of the peripheral part11bso as to surround the corners as illustrated inFIG.5B, and a configuration in which the protruding parts11care provided close to the corners of the central part11a. Such protruding parts11ccan prevent the central part11afrom making contact with the substrate30or the like in a case where the crystal vibration element10is inclined in various directions.

Furthermore, for example, a pair of protruding parts11cillustrated inFIG.5Ceach has a protrusion body and a connecting part111cconnecting the protrusion body and the central part11ain plan view, unlike the protruding parts11caccording to an aspect of the present disclosure. Such protruding parts11ccan make parts where the protruding parts11cand the central part11aare connected thin, thereby lessening influence on a decrease in piezoelectric effect caused by contact of the protruding parts11cwith the substrate30or the like.

Furthermore, for example, a connecting part111cof each of a pair of protruding parts11cillustrated inFIG.6Ahas a groove, unlike the protruding parts11caccording to an aspect of the present disclosure. Such protruding parts11cmake parts where the protruding parts11cand the central part11aare connected narrow, thereby lessening influence on a decrease in piezoelectric effect caused by contact of the protruding parts11cwith the substrate30or the like.

Furthermore, for example, a pair of protruding parts11cillustrated inFIG.6Bare provided so as to be in contact with corners, specifically, side surface132aand134aclose to the corners, unlike the protruding parts11caccording to an aspect of the present disclosure. Such protruding parts11callows the central part11ato have a sufficient dimension in a direction along a direction opposite to a side where the connection electrodes16are provided, thereby suppressing an increase in equivalent series resistance value of the crystal vibration element10.

Although a pair of protruding parts11cis used in the above disclosure and modifications, any number of protruding parts11cmay be provided according to need. In a case where two or more protruding parts11care employed, the protruding parts11cmay have different heights, positions, combinations, and the like. In a case where the plurality of protruding parts11care provided, it may only be necessary that at least one protruding part can prevent the central part11afrom making contact with the substrate30or the like in a case where the crystal vibration element10is inclined.

The crystal vibrator1according to an aspect of the present disclosure includes the crystal vibration element10, which includes the crystal piece11having the central part11aand the peripheral part11bwhose dimension in a thickness direction may be smaller than the central part11a, the pair of excitation electrodes14provided on the central part main surfaces111on both sides of the central part11ain the thickness direction, and the pair of connection electrodes16electrically connected to the pair of excitation electrodes14, respectively and provided on the peripheral part; the substrate30connected to the connection electrodes16of the crystal vibration element10with the electrically-conductive holding member36interposed there between on one side in the thickness direction so as to support the crystal vibration element10in an excitable manner; and the lid part20that covers the crystal vibration element10on the other side in the thickness direction, wherein the crystal piece11has at least one protruding part11cprovided in contact with the central part11awhen the central part main surfaces111of the crystal vibration element10are viewed in plan view, and the at least one protruding part11cprotrudes in the thickness direction in a position where the at least one protruding part11cmakes contact with the substrate30or the lid part20in a case where the crystal vibration element10is inclined toward the substrate30or the lid part20while being supported on a side where the pair of connection electrodes16are provided.

According to the above configuration, a reduction in size of the vibrator can be obtained with good vibration characteristics.

In the above configuration, the protruding part11cdoes not contact the substrate30nor the lid part20in a case where the central part main surfaces111of the crystal vibration element10are parallel with at least a part of the substrate30or the lid part20.

According to the above configuration, it may be possible to lessen inhibition of free vibration of the crystal vibration element and influence of the inhibition on vibration of the crystal vibration element.

In the above configuration, on a cross section in the thickness direction, the peripheral part11bhas a first end point P1on a side opposite to the side where the pair of connection electrodes16are provided, the central part11ahas a second end point P2on the side opposite to the side where the pair of connection electrodes16are provided, and the at least one protruding part11chas a third end point P3on the side opposite to the side where the pair of connection electrodes16are provided; and a first virtual angle formed between a first virtual line L1connecting the first end point P1and the third end point P3and the peripheral part11bis larger than a second virtual angle formed between a second virtual line L2connecting the first end point P1and the second end point P2and the peripheral part11b.

According to the above configuration, it may be possible to suppress inhibition of vibration caused by the excitation electrodes.

In the above configuration, the at least one protruding part11cis provided on a periphery of the central part11aon a side different from the side where the pair of connection electrodes16are provided when the central part main surfaces111of the crystal vibration element10are viewed in plan view.

According to the above configuration, it may be possible to realize a reduction in size of the vibrator and suppression of inhibition of vibration caused by the excitation electrodes.

In the above configuration, the at least one protruding part11cis provided on the periphery of the central part11aon a side opposite to the side where the pair of connection electrodes16are provided when the central part main surfaces111of the crystal vibration element10are viewed in plan view.

According to the above configuration, it may possible to realize a reduction in size of the vibrator and suppress inhibition of vibration caused by the excitation electrodes.

In the above configuration, the at least one protruding part11cis two or more protruding parts11c; and the two or more protruding parts11care provided apart from each other when the central part main surfaces111of the crystal vibration element10are viewed in plan view.

According to the above configuration, it may possible to suppress inhibition of vibration caused by the excitation electrodes with certainty.

Furthermore, the at least one protruding part11cprotrudes so as to have a thickness equal to or larger than a thickness of the central part11ain the thickness direction.

According to the above configuration, it may be possible to lessen inhibition of free vibration of the crystal vibration element and influence of the inhibition on vibration of the crystal vibration element.

In the above configuration, when the central part main surfaces111of the crystal vibration element10are viewed in plan view, at least a part of the at least one protruding part11cis located on the periphery of the central part11aon a side opposite to the side where the pair of connection electrodes16are provided, and the at least the part protrudes so as to have a thickness equal to or larger than a thickness of the central part11ain the thickness direction.

According to the above configuration, it may be possible to realize a reduction in size of the vibrator and suppress inhibition of vibration caused by the excitation electrodes.

In the above configuration, when the central part main surfaces111of the crystal vibration element10are viewed in plan view, at least one protruding part11cis provided at a corner on a periphery of the central part11ain a direction opposite to the side where the pair of connection electrodes16are provided, and the at least one protruding part11cincludes a first part that extends from the corner toward a periphery of the peripheral part11balong the opposite direction and has at least a part having a same thickness as the central part11aand/or a second part that extends from the corner toward the periphery of the peripheral part11balong a direction crossing the opposite direction and has at least a part thicker than the central part11a.

In the above configuration, when the central part main surfaces111of the crystal vibration element10are viewed in plan view, the central part11ahas a rectangular shape, and the at least one protruding part11cis provided at a corner of the rectangular shape.

According to the above configuration, a decrease in piezoelectric effect can be minimized. In the above configuration, the at least one protruding part11cis provided at least on a side of the crystal piece11that faces the substrate30.

According to the above configuration, it may be possible to suppress inhibition of vibration of the excitation electrodes due to contact with the substrate. In the above configuration, the crystal piece11is made of crystal. According to the above configuration, it is possible to realize a reduction in size of the crystal vibrator and obtain good vibration characteristics.

A method for producing the crystal vibration element10according to an aspect of the present disclosure is a method for producing the crystal vibration element10including the crystal piece11having the central part11aand the peripheral part11bwhose dimension in a thickness direction is smaller than the central part11a, the pair of excitation electrodes14provided on the central part main surfaces111on both sides of the central part11ain the thickness direction, and the pair of connection electrodes16electrically connected to the pair of excitation electrodes14, respectively and provided on the peripheral part11b, the method including: a first etching step of etching the substrate30to form a first part having the central part11aand the peripheral part11b; and a second etching step of etching the first part to form at least one protruding part11cthat is in contact with the central part11awhen the central part main surfaces111of the crystal vibration element10are viewed in plan view.

According to the above method, it may be possible to realize a reduction in size of the crystal vibrator and obtain good vibration characteristics.

In the above method, in the first etching step, the central part11ais formed so as to have a rectangular shape when the central part main surfaces111of the crystal vibration element10are viewed in plan view; and in the second etching step, the at least one protruding part11cis formed at a corner of the rectangular central part11a.

According to the above method, the vibration element can be processed by a simple method. In the above method, the first etching step and the second etching step are concurrently performed.

According to the above method, the vibration element may be processed efficiently.

The crystal vibration element10according to an aspect of the present disclosure includes the crystal piece11having the central part11aand the peripheral part11bwhose dimension in a thickness direction is smaller than the central part11a; the pair of excitation electrodes14provided on the central part main surfaces111on both sides of the central part11ain the thickness direction; and the pair of connection electrodes16electrically connected to the pair of excitation electrodes14, respectively and provided on the peripheral part, wherein the crystal piece11has at least one protruding part11cprovided in contact with the central part11awhen the central part main surfaces111of the crystal vibration element10are viewed in plan view, on a cross section in the thickness direction, the peripheral part11bhas a first end point P1on a side opposite to a side where the pair of connection electrodes16are provided, the central part11ahas a second end point P2on the side opposite to the side where the pair of connection electrodes16are provided, and the at least one protruding part11chas a third end point P3on the side opposite to the side where the pair of connection electrodes16are provided, and a first virtual angle formed between a first virtual line L1connecting the first end point P1and the third end point P3and the peripheral part11bis larger than a second virtual angle formed between a second virtual line L2connecting the first end point P1and the second end point P2and the peripheral part11b.

According to the above configuration, a reduction in size of the crystal vibrator can be provided with good vibration characteristics.

In the above configuration, the at least one protruding part11cis provided on the side opposite to the side where the pair of connection electrodes16are provided and protrudes so as to have a thickness equal to or larger than a thickness of the central part1lain the thickness direction.

According to the above configuration, it may be possible to realize a reduction in size of the vibrator and suppress inhibition of vibration caused by the excitation electrodes.

In the above configuration, the at least one protruding part11cis two or more protruding parts11c; and the two or more protruding parts11care provided apart from each other when the central part main surfaces111of the crystal vibration element10are viewed in plan view.

According to the above configuration, it may be possible to suppress inhibition of vibration caused by the excitation electrodes with certainty. It is also noted that=the present disclosure is not limited to the above aspects and can be modified in various ways. Modifications according to the present disclosure are described below.

Although the crystal piece11, which is an example of a vibrating piece, is an AT cut crystal piece whose long side is parallel with the X axis and whose short side is parallel with the Z′ axis in the above disclosure, the above configuration is not restrictive. For example, the crystal piece11may be an AT cut crystal piece whose long side is parallel with the Z′ axis and whose short side is parallel with the X axis. Alternatively, the crystal piece11may be a crystal piece cut in a way (for example, BT cut) different from AT cut, as long as the crystal piece11vibrates mainly in a thickness-shear mode. Note, however, that AT cut crystal piece, which can obtain extremely high frequency stability in a wide temperature range, is most preferable. The vibrating piece may be any of other materials whose main vibration is thickness-shear vibration instead of the crystal piece11.

Although the crystal piece11, the central part main surface111, and the excitation electrodes14each have a rectangular shape having long sides and short sides when the crystal vibration element10is viewed in plan view in the above disclosure, the crystal piece11, the central part main surface111, and the excitation electrodes14may each have a rectangular shape whose four sides have equal lengths, that is, a square shape. The crystal piece11, the central part main surface111, and the excitation electrodes14may each have a substantially rectangular shape. The substantially rectangular shape encompasses a shape obtained, for example, by rounding or chamfering four corners (not right angles), a shape obtained by curving one or some sides, or a shape obtained by curving all sides of the outer edge of the crystal piece11and the planar shapes of the central part main surface111and the excitation electrodes14. Furthermore, the crystal piece11, the central part main surface111, and the excitation electrodes14may each have a shape such as a substantially circular shape or a substantially oval shape.

Although the planar shape of the excitation electrodes14is smaller than the planar shape of the central part main surface111when the crystal vibration element10is viewed in plan view in the above disclosure, the planar shape of the excitation electrodes14may be identical to the planar shape of the central part main surface111or may be larger than the planar shape of the central part main surface111.

Although the side surface13aof the central part11aof the crystal piece11is a surface that forms a right angle with respect to the XZ′ plane in the above disclosure, this angle is not limited in particular. For example, the angle between the side surface13and the XZ′ plane may be inclined to a predetermined angle depending on crystal orientation of the crystal. Such an inclined angle can be formed, for example, by wet etching. Note that the thickness of the peripheral part11bin the Y′-axis direction may be identical.

Although the peripheral part11bhas a uniform thickness in the above disclosure, the thickness of the peripheral part11bmay be non-uniform. For example, the peripheral part11bmay have a step-like configuration, an inclination configuration, or the like in which a thickness dimension gradually becomes smaller from a central part to an outer edge part.

Although an example of the connection electrodes33aand33b, the via electrodes34aand34b, and the outer electrode35atodof the substrate30has been described in the above disclosure, the configurations of the connection electrodes33aand33b, the via electrodes34aand34b, and the outer electrode35atodof the substrate30are not limited to the above example and can be modified in various ways. For example, the number of outer electrodes is not limited to four. For example, two outer electrodes may be disposed diagonally. Furthermore, the outer electrodes need not be disposed at corners, and may be provided on any side surface of the substrate30excluding the corners. In this case, as has been described above, a cutout side surface may be formed by cutting a part of a side surface in a cylindrical curved surface, and the outer electrodes may be formed on this side surface excluding the corners. Furthermore, other outer electrodes35cand35d, which are dummy electrodes, need not be formed. Furthermore, the substrate30may be provided with an extended electrode formed from the first main surface32ato the second main surface32bso that electric conduction there between is achieved.

Although the substrate30is a flat plate and the lid part20has a concave shape in the above disclosure, the shapes of the substrate30and the lid part20are not limited in particular, provided that the crystal vibration element10can be contained in an internal space. For example, the substrate30may have a concave shape, and the lid part20may have a flat plate shape. The substrate30and the lid part20may hold the crystal vibration element10by sandwiching the crystal vibration element10between the substrate30and the lid part20instead of containing the crystal vibration element10in the internal space.

Although the etching according to the production method is wet etching in the above disclosure, the etching may be dry etching. Furthermore, for example, the production method may use both dry etching and wet etching, for example, use dry etching in the first etching step and use wet etching in the second etching step.

In general, the description of the aspects disclosed should be considered as being illustrative in all respects and not being restrictive. The scope of the present invention is shown by the claims rather than by the above description, and is intended to include meanings equivalent to the claims and all changes in the scope. While preferred aspects of the invention have been described above, it is to be understood that variations and modifications will be apparent to those skilled in the art without departing from the scope and spirit of the invention.

DESCRIPTION OF REFERENCE SYMBOLS