Crystal element, crystal device, electronic device, and method for manufacturing crystal element

Abstract

The crystal element (10) includes a vibration portion (11), a holding portion (13), an electrode portion (14), and a recessed portion (18) serving as a recessed portion and / or a convex portion. The vibration portion (11) has a pair of vibration portion main surfaces (111, 112). The holding portion (13) is integrated with the vibration portion (11) at the outer edge of the vibration portion (11) and has a pair of holding portion main surfaces (131, 132) and holding portion side surfaces (133, 134, 135). The electrode portion (14) is provided on the vibration portion main surfaces (111, 112). The recessed portion (18) is located on the holding portion side surfaces (133, 135).

Description

Technical Field

[0001] The present disclosure relates to a crystal element, a crystal device including the crystal element, an electronic device including the crystal element, and a method for manufacturing the crystal element. Examples of the crystal element include a crystal vibrator and a crystal oscillator. Background Art

[0002] A thickness-shear quartz crystal element has excitation electrodes formed from a metal film pattern on both main surfaces of an AT-cut crystal. This device utilizes the piezoelectric and inverse piezoelectric effects to generate a specific oscillation frequency. A typical quartz crystal element is housed in a package and hermetically sealed with a lid (see, for example, Japanese Patent Application Publication No. 2016-139901). Summary of the Invention

[0003] The crystal element according to the present disclosure has:

[0004] a vibration portion having a pair of vibration portion main surfaces;

[0005] a holding portion integral with the vibrating portion at an outer edge of the vibrating portion and having a pair of holding portion main surfaces and holding portion side surfaces;

[0006] an electrode portion provided on the main surface of the vibration portion; and

[0007] The concave portion and / or convex portion is located on the side surface of the holding portion.

[0008] The crystal device according to the present disclosure includes the crystal element according to the present disclosure, and the electronic device according to the present disclosure includes the crystal device according to the present disclosure.

[0009] The method for manufacturing a crystal element according to the present disclosure is a method for manufacturing the crystal element according to the present disclosure by wet etching.

[0010] The orthogonal coordinate system XYZ consisting of the X-axis, Y-axis, and Z-axis, which are the crystal axes of the crystal, is rotated by 30° or more and 50° or less around the X-axis to define the orthogonal coordinate system XY'Z' consisting of the X-axis, Y'axis, and Z'axis. In this case, the following first to third steps are included.

[0011] In the first step, a crystal wafer having two wafer main surfaces parallel to the XZ' plane and in a front-back relationship is prepared, and masks composed of corrosion-resistant films are formed on the two wafer main surfaces.

[0012] In the second step, the crystal wafer having the mask formed thereon is immersed in an etching solution, thereby forming a crystal piece having the vibration portion, the holding portion, and the concave portion and / or convex portion on the crystal wafer.

[0013] In a third step, the mask is removed from the crystal wafer on which the crystal piece is formed.

[0014] Moreover, in the first step, the mask for protecting the portion of the main surface of the holding portion on the + side of the Y' axis is formed offset in the + direction of the Z' axis relative to the mask for protecting the portion of the main surface of the holding portion on the - side of the Y' axis. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 This is a top view of the crystal element according to the first embodiment.

[0016] Figure 2 It is perspective observation Figure 1 Top view of the back side of the crystal element.

[0017] Figure 3 yes Figure 1 Ic-Ic line cross-sectional view in.

[0018] Figure 4 This is a perspective view showing the crystal element according to the first embodiment.

[0019] Figure 5 It means equivalent to Figure 4 The cross-sectional view of the portion taken along line III-III in FIG. 1 is a first step of forming the recessed portion.

[0020] Figure 6 It means equivalent to Figure 4 The cross-sectional view of the portion taken along line III-III in FIG. 1 is a second step of forming the recessed portion.

[0021] Figure 7 It means equivalent to Figure 4 The cross-sectional view of the portion taken along line III-III in FIG. 1 is a third step of forming the recessed portion.

[0022] Figure 8 This is a perspective view showing another example of the crystal element according to the first embodiment.

[0023] Figure 9 This is a perspective view showing a crystal device according to the second embodiment.

[0024] Figure 10 yes Figure 9 Vb-Vb line cross-sectional view in.

[0025] Figure 11 This is a perspective view showing a portion of a crystal device according to the second embodiment.

[0026] Figure 12 This is a front view showing a first example of an electronic device according to a third embodiment.

[0027] Figure 13 This is a front view showing a second example of the electronic device according to the third embodiment.

[0028] Figure 14 This is a schematic plan view showing a first example of the holding portion in the first embodiment.

[0029] Figure 15 This is a schematic plan view showing a second example of the holding portion in the first embodiment.

[0030] Figure 16 This is a schematic plan view showing a third example of the holding portion in the first embodiment.

[0031] Figure 17 This is a schematic plan view showing a fourth example of the holding portion in the first embodiment. DETAILED DESCRIPTION

[0032] In a crystal element, when an alternating voltage is applied to the excitation electrodes, a portion of the crystal plate sandwiched between the excitation electrodes undergoes thickness shear vibration. In addition to the thickness shear vibration, bending vibration and contour vibration occur as secondary vibrations. These secondary vibrations occur not only in the portion sandwiched between the excitation electrodes but also throughout the crystal plate, and are prone to combining with the primary thickness shear vibration. The combination of thickness shear vibration and secondary vibrations alters the vibration state, potentially leading to an increase in the crystal element's equivalent series resistance, resulting in a decrease in electrical characteristics.

[0033] According to the crystal element according to the present disclosure, since the side surfaces of the holding portion are provided with the concave portion and / or the convex portion, degradation of the electrical characteristics due to adverse vibrations can be suppressed.

[0034] Hereinafter, the method for implementing the present disclosure (hereinafter referred to as "embodiment") will be described with reference to the accompanying drawings. In addition, in this specification and the accompanying drawings, for substantially the same structural elements, the description thereof will be appropriately omitted by using the same reference numerals. The shapes depicted in the accompanying drawings are depicted to facilitate understanding by those skilled in the art, and therefore the actual dimensions and ratios may not necessarily be the same. For example, the etched surface of a crystal actually becomes a complex shape due to the unique anisotropic etching, but here, except for Figures 5 to 7 Other than that it is simply described.

[0035] <Implementation Method 1>

[0036] Figure 1 is a top view showing the crystal element of embodiment 1, Figure 2 It is perspective observation Figure 1 A top view of the back side of the crystal element, Figure 3 yes Figure 1 Ic-Ic line cross-sectional view in. Figure 4 This is a perspective view showing the crystal element according to the first embodiment. Figures 5 to 7 It means equivalent to Figure 4 The sectional view of the part along the III-III line is shown in FIG. Figure 5 (First process), Figure 6 (Second process), Figure 7 The step of forming the recessed portion is performed in the order of (third step).

[0037] This embodiment 1 relates to a crystal element. A pair of surfaces in a positive and negative relationship are referred to as "principal surfaces," a surface sandwiched between the pair of principal surfaces is referred to as a "side surface," and a dimension perpendicular to the principal surface is referred to as a "thickness." Furthermore, an orthogonal coordinate system XYZ consisting of the X-axis, Y-axis, and Z-axis, which are the crystal axes of the crystal, is rotated about the X-axis by 30° or more and 50° or less to define an orthogonal coordinate system XY'Z' consisting of the X-axis, Y'-axis, and Z'-axis. In each figure, the direction indicated by the arrows of the X-axis, Y'-axis, and Z'-axis is positive (+), and the opposite direction is negative (-).

[0038] The crystal element 10 of the first embodiment includes a vibrating portion 11, a holding portion 13, an electrode portion 14, and a recessed portion 18 serving as a recessed portion and / or a convex portion. The vibrating portion 11 has a pair of vibrating portion principal surfaces 111 and 112. The holding portion 13 is integral with the vibrating portion 11 at its outer edge and has a pair of holding portion principal surfaces 131 and 132 and holding portion side surfaces 133, 134, and 135. The electrode portion 14 is provided on the vibrating portion principal surfaces 111 and 112. The recessed portion 18 is located on the holding portion side surfaces 133 and 135.

[0039] More specifically, the vibrating portion 11 has a pair of planar vibrating portion main surfaces 111 and 112, and vibrating portion side surfaces 113, 114, and 115 sandwiched between the pair of vibrating portion main surfaces 111 and 112. The holding portion 13 has a pair of planar holding portion main surfaces 131 and 132, and holding portion side surfaces 133, 134, and 135 sandwiched between the pair of holding portion main surfaces 131 and 132, thereby holding the outer edge of the vibrating portion 11. The electrode portion 14 applies a voltage to the vibrating portion main surfaces 111 and 112, causing the vibrating portion 11 to generate primary vibrations. The recessed portion 18 is located on the holding portion side surfaces 133 and 135 and is absent on the vibrating portion side surfaces 113, 114, and 115, thereby suppressing secondary vibrations associated with the primary vibrations.

[0040] The above-mentioned structural elements may also be as follows. The thickness of the holding portion 13 is greater than the thickness of the vibration portion 11. The vibration portion 11 is substantially quadrilateral when viewed from above. The holding portion 13 is located on at least one side 116 of the vibration portion 11 when viewed from above. The holding portion 13 has a fixing portion 130 ( Figure 2Electrode portion 14 includes excitation electrodes 141 and 142 located on vibrating portion main surfaces 111 and 112, mounting electrodes 151 and 152 located in fixed portion 130, and wiring electrodes 161 and 162 electrically connecting excitation electrodes 141 and 142 to mounting electrodes 151 and 152. The recessed and / or convex portions are recessed portions 18 recessed into retaining portion side surfaces 133 and 135.

[0041] In other words, the crystal element 10 includes: a vibrating portion 11 having a substantially quadrilateral shape in a plan view and having vibrating portion principal surfaces 111, 112 and vibrating portion side surfaces 113, 114, 115; a holding portion 13 having holding portion principal surfaces 131, 132 and holding portion side surfaces 133, 134, 135 and being located on at least one side 116 of the vibrating portion 11 in a plan view; excitation electrodes 141, 142 located on the vibrating portion principal surfaces 111, 112; mounting electrodes 151, 152 located on at least one of the holding portion principal surfaces 131, 132; wiring electrodes 161, 162 electrically connecting the excitation electrodes 141, 142 and the mounting electrodes 151, 152; and a recess 18 serving as a recess and / or a protrusion located on the holding portion side surfaces 133, 135 and not on the vibrating portion side surfaces 113, 114, 115.

[0042] The planar shape of the vibration part 11 is not limited to a substantially quadrilateral, and may be a substantially circular or substantially elliptical shape, etc. “Substantially quadrilateral” also includes a square, a rectangle (rectangle), and a rectangle with rounded corners.

[0043] In the first embodiment, the mounting electrodes 151 and 152 are located on the main surface 132 of the holding portion serving as the fixing portion 130. The holding portion 13 may surround not only one side 116 of the vibration portion 11 but also two, three, or all sides of the vibration portion 11. Figures 14 to 17 Specific examples of these will be described. Figure 14 The holding portion 13 a of the first example shown has a substantially I-shaped planar shape similarly to the first embodiment, and is located on the first side 117 a side of the vibrating portion 11 . Figure 15 The holding portion 13 b of the second example shown has a substantially L-shaped planar shape and is located on the first side 117 a and the second side 117 b of the vibrating portion 11 . Figure 16 The holding portion 13 c of the third example shown has a substantially U-shaped planar shape and is located on the first side 117 a , the second side 117 b , and the third side 117 c of the vibrating portion 11 . Figure 17The retaining portion 13d of the fourth example shown has a roughly U-shaped plan view and is located on the first side 117a, second side 117b, third side 117c, and fourth side 117d of the vibrating portion 11. The thickness of the retaining portions 13a, 13b, 13c, and 13d can differ from the thickness of the vibrating portion 11. For example, they can be thicker than the vibrating portion 11 (a so-called inverted mesa type) or thinner than the vibrating portion 11 (a so-called mesa type). The fixing portions 130 of the retaining portions 13a, 13b, 13c, and 13d are all located at the same position, but can also be located at different positions. That is, the fixing portions 130 can be located at any position on each of the retaining portions 13a, 13b, 13c, and 13d.

[0044] The recess 18 is a groove-shaped portion recessed into the retaining portion side surfaces 133 and 135, extending along the longitudinal direction of the crystal element 10 on the retaining portion side surface 133. The dimension (depth of the groove) of the recess 18 in the Z'-axis direction may not be constant; for example, it may become deeper as it approaches the retaining portion side surface 135. Furthermore, the recess 18 may be provided on the retaining portion side surface 134. The "recesses and / or protrusions" may include, for example, protrusions or concave-convex portions other than the recess 18, and may be formed, for example, by wet etching, laser processing, or ion beam processing, and there is no limitation on the number, position, or shape of the recesses and / or protrusions.

[0045] The vibrating portion main surface 111 and the holding portion main surface 131 are coplanar, and the thickness of the holding portion 13 is greater than that of the vibrating portion 11. The holding portion 13 has two holding portion side surfaces 133 and 134 along the XY' plane and one holding portion side surface 135 along the Y'Z' plane. The recess 18 is arranged from the holding portion side surface 133 to the holding portion side surface 135. In this case, the recess 18 can be formed by wet etching as described later.

[0046] In the first embodiment, the inclined portion 12, which has inclined portion main surfaces 121 and 122 and inclined portion side surfaces 123 and 124, is located between the vibrating portion 11 and the retaining portion 13. The inclined portion main surface 121 is coplanar with the vibrating portion main surface 111 and the retaining portion main surface 131, while the inclined portion main surface 122 forms an inclined surface connecting the vibrating portion main surface 112 and the retaining portion main surface 132. A through hole 17 is formed in the inclined portion 12, penetrating the inclined portion main surfaces 121 and 122 in the thickness direction. If the crystal axis of the crystal plate 21 is set as shown, the inclined portion main surface 122 is formed by wet etching. Furthermore, recesses and / or protrusions (recesses 18) may also be located on the inclined portion side surface 123.

[0047] Next, a method of manufacturing the crystal element 10 by wet etching will be described in outline as a manufacturing method of Embodiment 1. The manufacturing method of Embodiment 1 includes the following first to third steps.

[0048] First step: prepare a crystal wafer 20 having two wafer main surfaces 201 and 202 parallel to the XZ' plane and in a front-back relationship, and form masks 31 and 32 composed of corrosion-resistant films on the two wafer main surfaces 201 and 202 ( Figure 5 ).

[0049] Second step: The crystal wafer 20 having the masks 31 and 32 formed thereon is immersed in an etching solution 33 to form a crystal plate 21 ( Figure 4 、 Figure 6 ).

[0050] The third step: removing the masks 31 and 32 from the crystal wafer 20 on which the crystal piece 21 is formed ( Figure 7 ).

[0051] Furthermore, in the first step, the mask 32 protecting the portion of the holding portion main surface 132 on the + side of the Y' axis is offset in the + direction of the Z' axis relative to the mask 31 protecting the portion of the holding portion main surface 131 on the - side of the Y' axis.

[0052] According to the manufacturing method of the first embodiment, recess 18 can be easily formed by offsetting one mask 32 of protective holding portion 13 relative to the other mask 31 in the Z'-axis direction during wet etching to form crystal plate 21. Therefore, in addition to being able to manufacture crystal element 10, which exhibits the functions and effects described below, recess 18 can also be formed simultaneously with the formation of crystal plate 21. This eliminates the need for a special step for forming recess 18, thereby simplifying the manufacturing process.

[0053] Furthermore, when the thickness t of the crystal wafer 20 in the Y'-axis direction is between 30 μm and 50 μm, in the first step, the mask 32 protecting the portion of the retaining portion main surface 132 on the + side of the Y'-axis may be offset by 10 μm to 20 μm in the + direction of the Z'-axis relative to the mask 31 protecting the portion of the retaining portion main surface 131 on the - side of the Y'-axis. In this case, if the thickness is less than 10 μm or exceeds 20 μm, adjacent retaining portions 13 are easily connected via the protrusions 18a, and thus separation of the retaining portions 13 takes time. Therefore, by setting the thickness to between 10 μm and 20 μm, separation of the thick retaining portions 13 can be facilitated.

[0054] Furthermore, the crystal wafer 20 having the crystal piece 21 formed thereon may further include a step of cutting a portion of the portion forming the concave portion and / or the convex portion (concave portion 18) using a plane 136 parallel to the XY' plane. In this case, the convex portion 18a can be removed, leaving only the concave portion 18.

[0055] Next, the case where the recessed portion 18 is formed by wet etching will be described in more detail.

[0056] First, if Figure 5 As shown, masks 31 and 32 are formed on quartz crystal wafer 20 to form the outer shape of crystal plate 21. Quartz crystal wafer 20 is an AT-cut wafer, and masks 31 and 32 are made of a corrosion-resistant film such as chromium (Cr). At this point, the crystal axis of quartz crystal wafer 20 is set as shown in the figure, and mask 32 on main surface 132 of the protective retaining portion is offset in the Z'-axis direction by an offset Δz relative to mask 31 on main surface 131 of the protective retaining portion. For example, when the thickness of retaining portion 13 is 30 to 50 μm, the offset Δz is 10 to 20 μm.

[0057] Next, if Figure 6 As shown, a crystal wafer 20 with masks 31 and 32 formed thereon is immersed in an etching solution 33 containing hydrofluoric acid or the like. As a result, portions of the crystal wafer 20 not covered by masks 31 and 32 are gradually removed, and recesses 18 with unique three-dimensional shapes appear in the crystal wafer 21. This is achieved by anisotropic etching of the crystal, where the etching rate increases in the order of the Y-axis, X-axis, and Z-axis.

[0058] Finally, if Figure 7 As shown, by removing the masks 31 and 32 , the recess 18 is obtained simultaneously with the outer shape of the crystal piece 21 . Figure 7 The recess 18 shown can be used directly, or the recess 18 can be cut with a surface 136 parallel to the XY' plane to obtain a retaining portion side surface 133 parallel to the XY' plane. Figure 7 In the case of the recessed portion 18 shown, the convex portion 18 a formed together with the recessed portion 18 is an example of a convex portion in the “recessed portion and / or convex portion”.

[0059] Next, each component of the crystal element 10 will be described in further detail.

[0060] The crystal element 10 operates in a thickness-shear vibration mode, with an oscillation frequency (fundamental wave) of, for example, 150 MHz or higher. The vibrating portion 11, the inclined portion 12, and the holding portion 13 are formed from a single crystal piece 21. The excitation electrodes 141, 142, the mounting electrodes 151, 152, and the wiring electrodes 161, 162 are formed from metal patterns made of the same material.

[0061] Crystal plate 21 is an AT-cut crystal plate. Specifically, when the orthogonal coordinate system XYZ, consisting of the X-axis (electrical axis), Y-axis (mechanical axis), and Z-axis (optical axis), is rotated about the X-axis by 30° to 50° (for example, 35°15') to define the orthogonal coordinate system XY'Z', the wafer cut parallel to the XZ' plane becomes the raw material for crystal plate 21. Furthermore, crystal plate 21 has its longitudinal direction parallel to the X-axis, its short side parallel to the Z' axis, and its thickness parallel to the Y' axis.

[0062] The following shows an example of the dimensions of the crystal plate 21 and other components. The length (X-axis direction) of the crystal plate 21 is 750 to 950 μm, and the width (Z'-axis direction) is 600 to 800 μm. The thickness (Y'-axis direction) of the holding portion 13 is 30 to 50 μm, the thickness (Y'-axis direction) of the vibrating portion 11 is approximately 6.8 μm, and the diameters of the excitation electrodes 141 and 142 are 250 to 400 μm. The oscillation frequency in this case is approximately 245 MHz.

[0063] The inclined portion main surface 121 is flush with the vibrating portion main surface 111 and the retaining portion main surface 131, but the inclined portion main surface 122 forms an inclined surface, connecting the vibrating portion main surface 112 and the retaining portion main surface 132. In other words, the thickness of the inclined portion 12 decreases as it moves away from the retaining portion 13. Therefore, the stress transmitted from the retaining portion 13 to the vibrating portion 11 is absorbed or dispersed by the inclined portion 12 (with its gentle height difference). Furthermore, the secondary vibration generated by the vibrating portion 11 gradually attenuates as it moves toward the retaining portion 13, thereby reducing the impact of the secondary vibration reflected by the retaining portion 13 on the vibrating portion 11. Consequently, the inclined portion 12 contributes to, for example, a reduction in the equivalent series resistance.

[0064] The through hole 17 passes through between the mounting electrodes 151 and 152 and the vibration portion 11 in the thickness direction. Therefore, the stress transmitted from the retaining portion 13 side to the vibration portion 11 side is absorbed or dispersed by the through hole 17. In other words, when the retaining portion 13 is connected to the package, the deformation generated in the vibration portion 11 can be reduced. In addition, the through hole 17 plays the role of sealing the vibration energy of the vibration portion 11. Therefore, the through hole 17 can achieve a reduction in the equivalent series resistance value. Furthermore, by forming the through hole 17 in the inclined portion 12, these effects interact with the effect of the inclined portion 12, and these effects are enhanced.

[0065] The pair of excitation electrodes 141 and 142 are generally circular in plan view and are provided approximately in the center of the vibrating portion main surfaces 111 and 112 of the vibrating portion 11, respectively. Wiring electrodes 161 and 162, which serve as connections but do not contribute to excitation, extend from the excitation electrodes 141 and 142 to the mounting electrodes 151 and 152. Specifically, the excitation electrode 141 is electrically connected to the mounting electrode 151 via the wiring electrode 161, and the excitation electrode 142 is electrically connected to the mounting electrode 152 via the wiring electrode 162.

[0066] Furthermore, the excitation electrodes 141 and 142 are not limited to being roughly circular; for example, they may also be roughly elliptical or rectangular. Wiring electrodes 161 and 162 may also be wider than the illustrated wiring electrodes to reduce the equivalent series resistance. While both mounting electrodes 151 and 152 are located on the retaining portion main surface 132, at least one may be located on the retaining portion main surface 131. In this case, mounting electrodes 151 and 152 may be electrically connected to a package, etc., via leads.

[0067] The metal pattern forming the excitation electrodes 141 and 142, for example, is formed as a laminate of a base layer containing chromium (Cr) and a conductor layer containing gold (Au). Specifically, the base layer is located on the crystal plate 21, and the conductor layer is located on top of the base layer. The base layer primarily serves to ensure close contact with the crystal plate 21, while the conductor layer primarily serves to ensure electrical continuity.

[0068] If forming a metal film is referred to as film formation, the metal pattern manufacturing process includes a method of forming a film on a quartz crystal, then forming a photoresist pattern, and then etching; a method of forming a photoresist pattern on a quartz crystal, then forming a film, and then peeling it off; or a method of covering the quartz crystal with a metal mask and then forming a film. Sputtering or vapor deposition is used for film formation.

[0069] The crystal element 10 can be manufactured as follows using, for example, photolithography and etching techniques.

[0070] First, a corrosion-resistant film is applied to the entire surface of an AT-cut crystal wafer, and a photoresist is applied thereon. Next, a mask depicting the outline of crystal plate 21 (including through-holes 17) and the pattern of vibrating portion 11 (on only one side) is overlaid on the photoresist. Exposure and development are performed to partially expose the corrosion-resistant film, which is then wet-etched. Then, using the remaining corrosion-resistant film as a mask, the crystal wafer is wet-etched to form the outline of crystal plate 21 and vibrating portion 11. The outline of crystal plate 21 is etched on both sides, while the vibrating portion 11 is etched on one side. This wet etching also forms the inclined portion main surface 122.

[0071] At this time, as described above, by shifting one of the masks on both sides relative to the other mask in the Z'-axis direction, it is possible to obtain both Figure 6 The recessed portion 18 is shown. In addition, since the vibration portion main surface 112 is not protected by the mask, the recessed portion 18 is not formed in the vibration portion 11 .

[0072] Next, the remaining corrosion-resistant film is removed from the crystal wafer, and a metal film, which will serve as the excitation electrodes 141, 142, etc., is deposited over the entire surface of the crystal wafer. Next, a photoresist mask, patterned after the excitation electrodes 141, 142, etc., is formed on the metal film. The unnecessary metal film is then removed by etching, thereby forming the excitation electrodes 141, 142, etc. The unnecessary photoresist is then removed, forming a plurality of crystal elements 10 on the crystal wafer. Finally, the crystal wafer is singulated into individual crystal elements 10, thereby obtaining individual crystal elements 10.

[0073] The crystal element 10 operates as follows. An alternating voltage is applied to the crystal plate 21 via the excitation electrodes 141 and 142. This causes the crystal plate 21 to generate thickness shear vibrations, causing the main surfaces 111 and 112 of the vibrating portion to offset relative to each other, generating a specific oscillation frequency. In this way, the crystal element 10 utilizes the piezoelectric effect and inverse piezoelectric effect of the crystal plate 21 to output a signal with a constant oscillation frequency. The thinner the thickness of the crystal plate 21 (i.e., the vibrating portion 11) between the excitation electrodes 141 and 142, the higher the oscillation frequency.

[0074] Next, the operation and effects of the crystal element 10 will be described.

[0075] (1) According to the crystal element 10 , by providing the recessed portion and / or convex portion (recessed portion 18 ) located on the holding portion side surfaces 133 and 135 and not located on the vibrating portion side surfaces 113 , 114 , and 115 , it is possible to suppress a degradation in electrical characteristics (such as an increase in equivalent series resistance) caused by adverse vibrations. The reason for this is as follows.

[0076] The vibrations of the crystal element 10 include thickness shear vibration as the primary vibration, and contour vibration and flexural vibration as secondary vibrations. Thickness shear vibration occurs when the portion sandwiched by the excitation electrodes 141 and 142 vibrates most strongly, while vibration also propagates from the outer edges of the excitation electrodes 141 and 142 toward the outer edges of the vibrating portion 11 in portions not sandwiched by the excitation electrodes 141 and 142. Contour vibration, one of the secondary vibrations, occurs when the shape of the crystal plate 21, for example, the contour of the vibrating portion 11, deforms and vibrates. Furthermore, flexural vibration, another secondary vibration, occurs when the shape of the crystal plate 21, for example, the vibrating portion 11, bends and vibrates in a direction parallel to the X-axis or the Z′-axis of the vibrating portion 11. This secondary vibration occurs not only in the portion sandwiched by the excitation electrodes 141 and 142 but also throughout the crystal plate 21, and is easily combined with the thickness shear vibration, the primary vibration. If the thickness shear vibration and the secondary vibration are combined, the vibration state changes, which may cause an increase in the equivalent series resistance value of the crystal element 10 and a deterioration in the electrical characteristics.

[0077] In conventional crystal elements, the side surfaces of the fixed portion and the vibrating portion have the same shape. This, in turn, generates secondary vibrations throughout the crystal element. Consequently, by making the secondary vibrations of the fixed portion and the vibrating portion similar, the secondary vibrations fall into a resonant state, making them difficult to attenuate.

[0078] In contrast, the crystal element 10 includes recessed and / or raised portions (recessed portions 18) on the holding portion side surfaces 133 and 135 but not on the vibrating portion side surfaces 113, 114, and 115. This allows the length of the holding portion 13 parallel to the Z' axis to be partially varied. Furthermore, by varying the depth of recessed portions 18 in the Z' axis direction, for example, the length of the holding portion 13 parallel to the X axis can be partially varied even at the edge of a side parallel to the X axis. Since bending vibration and contour vibration, which are secondary vibrations, depend on the length of the vibrating portion (e.g., the length parallel to the X axis or the length parallel to the Z' axis), partially varying this length can partially alter the vibrational states of these secondary vibrations. Consequently, the secondary vibrations of the holding portion 13 and the secondary vibrations of the vibrating portion 11 are in different states, which facilitates attenuation of the secondary vibrations. Consequently, degradation of electrical characteristics caused by the secondary vibrations can be suppressed.

[0079] (2) The "recess and / or protrusion" may be a recess 18 that is recessed into the side surfaces 133 and 135 of the retaining portion. In this case, as described later, when the crystal element 10 is mounted on the package using a conductive adhesive, the conductive adhesive enters the recess 18, thereby increasing the bonding area of ​​the conductive adhesive and thereby improving the bonding strength of the crystal element 10.

[0080] (3) Alternatively, the vibrating portion principal surface 111 and the holding portion principal surface 131 may be located on the same plane, and the holding portion 13 may be thicker than the vibrating portion 11. In this case, a structure in which the thick holding portion 13 supports the thin vibrating portion 11 can be achieved. Therefore, even if the vibrating portion 11 becomes thinner due to a higher oscillation frequency, the mechanical strength of the crystal element 10 can be maintained. Furthermore, since the thickness of the holding portion 13 can be sufficiently ensured, the recess 18 can be easily formed.

[0081] (4) The holding portion 13 may have two holding portion side surfaces 133 and 134 along the XY' plane and one holding portion side surface 135 along the Y'Z' plane, and the recess 18 may be arranged from the holding portion side surface 133 (or the holding portion side surface 134) to the holding portion side surface 135. In this case, during the wet etching for forming the crystal plate 21, the recess 18 can be easily formed by offsetting one mask for protecting the holding portion 13 relative to the other mask in the Z' axis direction. Therefore, the recess 18 can be formed simultaneously with the formation of the crystal plate 21, and a special process for forming the recess 18 is not required, thereby simplifying the manufacturing process.

[0082] <Another embodiment>

[0083] Figure 8 This is a perspective view showing another example of the crystal element according to Embodiment 1. The following description will be based on this drawing.

[0084] The "recesses and / or protrusions" in the crystal element 10a of this embodiment include a first recess 18 extending from the retaining portion side surface 133 to the retaining portion side surface 135, and a second recess 19 extending from the retaining portion side surface 134 to the retaining portion side surface 135. Recess 19, like recess 18, is a groove-shaped recessed portion extending into the retaining portion side surfaces 134 and 135 of the retaining portion 13, extending along the longitudinal direction of the crystal element 10. The Z'-axis dimension (groove depth) of recess 19 may not be constant; for example, it may become deeper as it approaches the retaining portion side surface 135. Furthermore, the recesses and / or protrusions (recesses 18 and 19) may be located on the inclined portion side surfaces 123 and 124, respectively.

[0085] According to crystal element 10a, by having recesses 18 and 19 on both retaining portion side surfaces 133 and 134, the difference between the secondary vibration of retaining portion 13 and the secondary vibration of vibrating portion 11 becomes larger, thereby further suppressing the degradation of electrical characteristics caused by the secondary vibration. In addition, by having recesses 18 and 19 on both retaining portion side surfaces 133 and 134, the bonding strength can be further improved when mounting to a package using a conductive adhesive. The remaining structure, function, and effects of this embodiment are the same as those of embodiment 1.

[0086] <Implementation Method 2>

[0087] Figure 9 1 is a perspective view showing a crystal device according to Embodiment 2. Figure 10 yes Figure 9 The Vb-Vb line cross-sectional view, Figure 11 It is a perspective view of a portion of a crystal device according to Embodiment 2. Hereinafter, a crystal device including the crystal element according to Embodiment 1 will be described as a crystal device 60 according to Embodiment 2 based on these drawings.

[0088] like Figure 9 as well as Figure 10 As shown, the crystal device 60 of the second embodiment includes: the crystal element 10 of the first embodiment; a base 61 on which the crystal element 10 is located; and a cover 62 that hermetically seals the crystal element 10 together with the base 61. Furthermore, the mounting electrodes 151 and 152 of the crystal element 10 are connected to the base 61 via a conductive adhesive 61e. Figure 11 As shown, the conductive adhesive 61 e is also filled in the recess 18 .

[0089] Base 61, also known as a component mounting member or package, is composed of a substrate 61a and a frame 61b. The space enclosed by the upper surface of substrate 61a, the inner surface of frame 61b, and the lower surface of lid 62 serves as a housing 63 for crystal element 10. Crystal element 10 outputs a reference signal used in, for example, electronic devices.

[0090] In other words, the crystal device 60 comprises: a substrate 61a having a pair of electrode pads 61d on the upper surface and four external terminals 61c on the lower surface; a frame 61b arranged along the outer periphery of the upper surface of the substrate 61a; a crystal element 10 mounted on the pair of electrode pads 61d via a conductive adhesive 61e; and a cover 62 that hermetically seals the crystal element 10 and the frame 61b.

[0091] The substrate 61a and the frame 61b are made of a ceramic material such as alumina ceramic or glass ceramic and are integrally formed to form the base 61. The base 61 and the cover 62 are generally rectangular in shape when viewed from above. The external terminals 61c, the electrode pads 61d, and the cover 62 are electrically connected via conductors formed inside or on the side of the base 61. Specifically, the external terminals 61c are located at the four corners of the lower surface of the substrate 61a. Two of the external terminals 61c are electrically connected to the crystal element 10, and the remaining two external terminals 61c are electrically connected to the cover 62. The external terminals 61c are used for mounting on a printed wiring board, etc., of an electronic device, etc.

[0092] As described above, the crystal element 10 includes the crystal plate 21, the excitation electrode 141 formed on the upper surface of the crystal plate 21, and the excitation electrode 142 formed on the lower surface of the crystal plate 21. Furthermore, the crystal element 10 is bonded to the electrode pad 61d via the conductive adhesive 61e, and functions to oscillate a reference signal for electronic devices, etc., through stable mechanical vibration and the piezoelectric effect.

[0093] Electrode pads 61d are used to mount the crystal element 10 on the base 61. A pair of electrode pads 61d are arranged adjacent to each other along one side of the substrate 61a. The pair of electrode pads 61d connects the mounting electrodes 151 and 152, respectively. With one end of the crystal element 10 serving as a fixed end and the other end of the crystal element 10 serving as a free end separated from the upper surface of the substrate 61a, the crystal element 10 is fixed to the substrate 61a using a cantilever support structure.

[0094] The conductive adhesive 61e is, for example, a silicone resin containing conductive powder as a conductive filler. The cover 62 is made of, for example, an alloy containing at least one of iron, nickel, or cobalt, and is joined to the frame 61b by seam welding, thereby hermetically sealing the housing 63, which is vacuumed or filled with nitrogen, for example.

[0095] According to the crystal device 60, by including the crystal element 10, stable electrical characteristics can be achieved. Furthermore, by the conductive adhesive 61e entering the recess 18, the bonding area of ​​the conductive adhesive 61e is increased, thereby improving the bonding strength of the crystal element 10. Furthermore, the crystal device 60 is not limited to the crystal element 10 of the first embodiment, and may also include the crystal element 10a of another embodiment.

[0096] <Implementation Method 3>

[0097] like Figure 12 as well as Figure 13 As shown, electronic devices 71 and 72 according to the third embodiment each include a crystal device 60 . Figure 12 The electronic device 71 is a smartphone. Figure 13 The illustrated electronic device 72 is a personal computer.

[0098] like Figures 9 to 11 The crystal device 60 configured as shown is mounted on the surface of printed circuit boards constituting electronic devices 71 and 72 by attaching the bottom surface of the external terminal 61c to the printed circuit board using soldering, gold (Au) bumps, or a conductive adhesive. Furthermore, the crystal device 60 is used as an oscillation source in various electronic devices, including smartphones, personal computers, clocks, game consoles, communication devices, and in-vehicle devices such as car navigation systems.

[0099] According to the electronic devices 71 and 72 , by including the crystal device 60 , it is possible to achieve high-performance and high-reliability operation based on stable electrical characteristics.

[0100] <Other>

[0101] While the present disclosure has been described above with reference to the above-described embodiments, the present disclosure is not limited thereto, and various modifications that can be understood by those skilled in the art can be added to the configuration and details of the present disclosure.

[0102] This application claims the benefit of priority based on Japanese patent application No. 2019-212985, filed on November 26, 2019, the disclosure of which is incorporated herein in its entirety.

[0103] -Explanation of Symbols-

[0104] 10, 10a crystal element

[0105] 11. Vibration unit

[0106] 111, 112 main surface of vibration part

[0107] 113, 114, 115 Vibration part side

[0108] 116 One side

[0109] 117a First side

[0110] 117b Second side

[0111] 117c Third Side

[0112] 117d Fourth Side

[0113] 12 Inclined portion

[0114] 121, 122 inclined portion main surface

[0115] 123, 124 Side of the inclined portion

[0116] 13, 13a, 13b, 13c, 13d: holding portion

[0117] 130 fixed parts

[0118] 131, 132 Main surface of holding portion

[0119] 133, 134, 135 side of the retaining part

[0120] 136 Surface parallel to XY' plane

[0121] 14 Electrode

[0122] 141, 142 Excitation electrodes

[0123] 151, 152 equipped with electrodes

[0124] 161, 162 wiring electrodes

[0125] 17 through holes

[0126] 18, 19 Recessed parts (concave and / or convex parts)

[0127] 18a Concave (concave and / or convex)

[0128] 20 crystal wafers

[0129] 201, 202 wafer main surface

[0130] 21 crystal pieces

[0131] 31, 32 Mask

[0132] 33 Etching solution

[0133] 60 crystal devices

[0134] 61 Base (component mounting member)

[0135] 61a base plate

[0136] 61b frame

[0137] 61c external terminal

[0138] 61d electrode pad

[0139] 61e conductive adhesive

[0140] 62 cover

[0141] 63 Containment Department

[0142] 71, 72 electronic equipment.

Claims

1. A crystal element comprising: a vibration portion having a pair of vibration portion main surfaces; a holding portion, which is integral with the vibrating portion and has a pair of holding portion main surfaces and holding portion side surfaces, at an outer edge of the vibrating portion; an inclined portion having a pair of inclined portion main surfaces and a pair of inclined portion side surfaces between the vibrating portion and the holding portion; an electrode portion provided on the main surface of the vibration portion; and A recessed portion located on a side of the retaining portion, The holding portion includes a fixing portion including a portion in contact with the component mounting member. The electrode portion includes a mounting electrode located at the fixed portion. The main surface of the inclined portion on one side is located on the same plane as the main surface of the vibrating portion on one side and the main surface of the holding portion on one side, and the main surface of the inclined portion on the other side is connected to the main surface of the vibrating portion on the other side and the main surface of the holding portion on the other side to form an inclined surface, whereby the thickness of the inclined portion becomes thinner as it moves away from the holding portion. The inclined portion has a through hole formed therein that penetrates through the main surfaces of the pair of inclined portions in the thickness direction. The through hole penetrates between the mounting electrode and the vibration portion in the thickness direction. When the orthogonal coordinate system XYZ consisting of the X-axis, Y-axis, and Z-axis, which are the crystal axes of the crystal, is rotated by 30° or more and 50° or less around the X-axis to define the orthogonal coordinate system XY'Z' consisting of the X-axis, Y'-axis, and Z'-axis, When the same plane is defined as the XZ' plane and the thickness direction is defined as the Y' axis direction, The recessed portion is provided on a side surface of the holding portion in the XY' plane, and the recessed portion extends in the X-axis direction when viewed from above in the XY' plane.

2. The crystal element according to claim 1, wherein The holding portion has a thickness greater than that of the vibrating portion.

3. The crystal element according to claim 2, wherein The vibration portion has a substantially quadrilateral shape in a plan view.

4. The crystal element according to claim 3, wherein The holding portion is located on at least one side of the vibration portion in a plan view.

5. The crystal element according to claim 4, wherein The electrode portion further includes an excitation electrode located on the main surface of the vibration portion, and a wiring electrode electrically connecting the excitation electrode and the mounting electrode. The crystal element according to claim 1 , wherein: The holding portion has two holding portion side surfaces along an XY′ plane and one holding portion side surface along a Y′Z′ plane.

7. The crystal element according to claim 6, wherein The recess includes: a first recess, configured from one of the two retaining portion side surfaces along the XY' plane to one of the retaining portion side surfaces along the Y'Z' plane; and a second recess, configured from the other of the two retaining portion side surfaces along the XY' plane to one of the retaining portion side surfaces along the Y'Z' plane.

8. A crystal device comprising: The crystal element according to any one of claims 1 to 7; an element mounting member for arranging the crystal element; and The cover hermetically seals the crystal element and the element mounting member.

9. The crystal device according to claim 8, wherein: The mounting electrode of the electrode portion of the crystal element is connected to the element mounting member via a conductive adhesive. The conductive adhesive is also filled in the recess.

10. An electronic device, A crystal device according to claim 8 or 9.

11. A method for manufacturing a crystal element, comprising manufacturing the crystal element according to any one of claims 1 to 7 by wet etching. The orthogonal coordinate system XYZ consisting of the X-axis, Y-axis, and Z-axis, which are the crystal axes of the crystal, is rotated by 30° or more and 50° or less around the X-axis to define the orthogonal coordinate system XY'Z' consisting of the X-axis, Y'axis, and Z'axis. In this case, The method of the crystal element comprises: In the first step, a crystal wafer having two main surfaces parallel to the XZ' plane and in a front-back relationship is prepared, and a mask composed of a corrosion-resistant film is formed on the two main surfaces of the wafer. In a second step, the crystal wafer having the mask formed thereon is immersed in an etching solution, thereby forming a crystal piece having the vibration portion, the holding portion, and the concave portion and / or convex portion on the crystal wafer; as well as In the third step, the mask is removed from the crystal wafer on which the crystal piece is formed. In the first step, the mask protecting the portion of the main surface of the holding portion on the + side of the Y' axis is formed offset in the + direction of the Z' axis relative to the mask protecting the portion of the main surface of the holding portion on the - side of the Y' axis.

12. The method for manufacturing a crystal element according to claim 11, wherein: When the thickness of the crystal wafer in the Y'-axis direction is 30 μm or more and 50 μm or less, In the first step, the mask protecting the main surface of the holding portion on the + side of the Y' axis is formed so as to be offset by 10 μm or more and 20 μm or less in the + direction of the Z' axis relative to the mask protecting the main surface of the holding portion on the - side of the Y' axis.

13. The method for manufacturing a crystal element according to claim 11 or 12, wherein: The method further includes cutting the crystal wafer on which the crystal piece is formed, using a surface parallel to the XY' plane to form a portion of the concave portion and / or convex portion.

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