JP2012054796A - Mesa type at-cut crystal oscillating piece and crystal device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a mesa type AT-cut crystal oscillating piece in which the occurrence of unwanted oscillation is suppressed, degradation of characteristics is prevented and the rate of occurrence of defective products is reduced by setting the thickness of an oscillating part and the thickness of the peripheral part of oscillation to appropriate values.SOLUTION: A mesa type AT-cut crystal oscillating piece (30) has a rectangular excitation part (31), and a peripheral part of excitation (32) formed on the outer periphery of the excitation part and thinner than the excitation part. In the mesa type AT-cut crystal oscillating piece oscillating at 38.4 MHz, the formula (Tm-Ts)/Tm is 0.048 or more to less than 0.2, where Tm is the thickness of the excitation part and Ts is the thickness of the peripheral part of excitation.

Description

  The present invention relates to a mesa-type AT-cut quartz crystal resonator element and a crystal device including the mesa-type AT-cut crystal oscillator piece.

  An AT-cut quartz crystal vibrating piece is known as one of typical thickness-sliding vibrating pieces. A crystal device in which this AT-cut quartz crystal resonator element is housed in a package is widely used as a frequency reference source in various electronic devices. These quartz devices are becoming smaller in size, and in order to obtain a vibration energy confinement effect more efficiently, curved surface processing such as bevel processing or convex processing in which an inclined region is provided on the outer periphery of the main surface of the AT-cut crystal vibrating piece is performed. It has been subjected.

  In curved surface processing such as bevel processing or convex processing, as disclosed in Patent Document 1, an inclined region is formed on the outer periphery of a quartz crystal vibrating piece by a method generally called barrel polishing. However, recently, the production of AT-cut quartz crystal vibrating pieces by the wafer method has advanced, and it has become difficult to perform curvature processing. Therefore, mesa-shaped (step-shaped) processing is performed on the AT-cut quartz crystal vibrating piece to substitute for curvature processing.

Japanese Patent Laid-Open No. 2002-18698

  However, the mesa-shaped AT-cut quartz crystal resonator piece is in a state where the vibration energy of the main vibration generated in the vibration part and the vibration energy of unnecessary vibration generated around the vibration outer part formed around the vibration part are mixed. There was a problem of deteriorating the characteristics of the cut quartz crystal vibrating piece.

  The present invention is a mesa type in which the occurrence of unnecessary vibration is suppressed by suppressing the thickness of the vibration part and the thickness of the vibration outer peripheral part, the deterioration of characteristics is prevented, and the occurrence rate of defective products is reduced. It is an object of the present invention to provide an AT-cut quartz crystal resonator element.

  The mesa-type AT-cut quartz crystal resonator element according to the first aspect has a rectangular excitation part and an excitation outer peripheral part formed on the outer periphery of the excitation part and having a thickness smaller than that of the excitation part, and vibrates at 38.4 MHz. Type AT-cut quartz crystal resonator element, when the thickness of the vibration part is Tm (μm) and the thickness of the excitation outer peripheral part is Ts (μm), the formula (Tm−Ts) / Tm is 0.048 or more. Less than 0.2.

  In the first aspect, the mesa-type AT-cut quartz crystal resonator element according to the second aspect has an outer frame that surrounds and supports the excitation outer peripheral part.

  A quartz device according to a third aspect includes a mesa-type AT-cut quartz crystal resonator element according to the first aspect, a base in which a concave portion is formed and a mesa-type AT-cut quartz crystal vibrator piece is accommodated in the concave portion, and a lid that seals the concave portion. .

  A crystal device according to a fourth aspect includes a mesa-type AT-cut quartz crystal resonator element according to the second aspect having one main surface and another main surface, and a lid having a first surface bonded to one main surface of the outer frame. And a base having a second surface joined to the other main surface of the outer frame.

  The present invention can provide a mesa-type AT-cut crystal vibrating piece in which generation of unnecessary vibration is suppressed by setting the size of the vibration part to an appropriate value, and the defective product generation rate is reduced.

FIG. 3A is a perspective view of the quartz crystal device 100. FIG. FIG. 2B is a cross-sectional view of the crystal device 100. FIG. (C) is BB sectional drawing of FIG.1 (b). FIG. 4A is a plan view of an AT-cut quartz crystal vibrating piece 30. FIG. (B) is DD sectional drawing of Fig.2 (a). (A) is a graph showing the correlation between the CI value and the length Mx of the excitation unit 31 in the x-axis direction when (Tm−Ts) is 2 μm. (B) is a graph showing the correlation between the CI value and the length Mx of the excitation unit 31 in the x-axis direction when (Tm−Ts) is 4 μm. (C) is a graph showing the correlation between the CI value and the length Mx of the excitation unit 31 in the x-axis direction when (Tm−Ts) is 6 μm. (D) is a graph showing the correlation between the CI value and the length Mx of the excitation unit 31 in the x-axis direction when (Tm−Ts) is 8 μm. (E) is a graph showing the correlation between the CI value and the length Mx of the excitation unit 31 in the x-axis direction when (Tm−Ts) is 10 μm. (A) is a perspective view of the quartz crystal device 200. FIG. (B) is EE sectional drawing of Fig.4 (a). (A) is a top view of the lid 210. FIG. (B) is a plan view of the AT-cut quartz crystal vibrating piece 230. (C) is a plan view of the base 220.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. It should be noted that the scope of the present invention is not limited to these forms unless otherwise specified in the following description.

(First embodiment)
<Configuration of Crystal Device 100>
FIG. 1A is a perspective view of the quartz crystal device 100. The crystal device 100 includes a lid 10, a base 20, and an AT-cut crystal vibrating piece 30 (see FIG. 1B) placed in the base 20. The AT-cut quartz-crystal vibrating piece is inclined at 35 degrees 15 minutes from the Z-axis to the Y-axis around the X-axis with respect to the Y-axis of the crystal axis (XYZ) of the artificial quartz. For this reason, the long side direction of the crystal device 100 will be described as the x-axis direction, the short side direction of the crystal device 100 will be described as the z′-axis direction, and the vertical direction of the crystal device 100 will be described as the y′-axis direction. In the description of the present specification, the height in the y′-axis direction is expressed as the + direction being high and the − direction being low.

  The base 20 has a cavity 24 (see FIG. 1B) formed inside, and an AT-cut quartz crystal vibrating piece 30 is placed in the cavity 24. An external electrode 21 is formed on the bottom surface of the base 20. The lid 10 is disposed on the + y ′ axis side of the base 20 so as to seal the cavity 24. The lid 10 is formed of a material such as ceramic, glass, crystal, or metal. The base 20 is made of ceramics, glass, crystal, or the like.

  FIG. 1B is a cross-sectional view of the quartz crystal device 100. FIG. 1B is a cross-sectional view taken along line AA in FIG. 1A or CC in FIG. 1C described later. A cavity 24 is formed in the base 20 by forming a recess. A connection electrode 22 is formed below the cavity 24, and the connection electrode 22 is electrically connected to the external electrode 21 through a conduction portion (not shown). The AT cut quartz crystal vibrating piece 30 is formed with an excitation part 31 and an excitation outer peripheral part 32 formed on the outer periphery of the excitation part 31. The excitation outer peripheral portion 32 is formed thinner than the excitation portion 31. Excitation electrodes 33 are formed on the upper and lower main surfaces of the excitation unit 31. An extraction electrode 34 is formed on the excitation outer peripheral portion 32, and the extraction electrode 34 is electrically connected to the excitation electrode 33. The excitation electrode 33 and the extraction electrode 34 are made by forming a chromium (Cr) layer on the surface of quartz and forming a gold (Au) layer on the surface of the chromium layer. The extraction electrode 34 is electrically connected to the connection electrode 22 through the conductive adhesive 41. For this reason, the excitation electrode 33 is electrically connected to the external electrode 21.

  FIG.1 (c) is BB sectional drawing of FIG.1 (b). In the base 20, two connection electrodes 22 are formed in the cavity 24. One connection electrode 22 is electrically connected to the excitation electrode 33 formed on the upper surface of the excitation unit 31 of the AT-cut quartz crystal vibrating piece 30, and the other connection electrode 22 is formed on the lower surface of the excitation unit 31. The excitation electrode 33 is electrically connected.

  FIG. 2A is a plan view of the AT-cut quartz crystal vibrating piece 30. The x-axis direction of the AT-cut quartz crystal vibrating piece 30 coincides with the X-axis direction of the crystal axis of the quartz crystal. Further, the z′-axis direction of the AT-cut quartz crystal vibrating piece 30 coincides with a direction inclined by 35 degrees and 15 minutes from the Z-axis to the Y-axis direction with the X-axis direction of the crystal axis of the crystal as the center. The length Gx in the x-axis direction of the outer shape of the AT-cut crystal vibrating piece 30 is, for example, 990 μm, and the length Gz in the z′-axis direction of the outer shape of the AT-cut crystal vibrating piece 30 is, for example, 668 μm. The length of the excitation unit 31 in the x-axis direction is Mx, and the length in the z′-axis direction is Mz.

  FIG. 2B is a DD cross-sectional view of FIG. The thickness of the excitation outer peripheral portion 32 of the AT-cut crystal vibrating piece 30 is Ts, the thickness of the excitation portion 31 is Tm, and the height of the step between the excitation portion 31 and the excitation outer peripheral portion 32 is h. The step between the excitation portion 31 and the excitation outer peripheral portion 32 is formed on the surface on the + y′-axis side and the surface on the −y′-axis side of the AT-cut quartz crystal vibrating piece 30, and the heights of both steps are the same. Is formed. Further, the height h of the step is positive, and the thickness Tm of the excitation part 31 is larger than the thickness Ts of the excitation outer peripheral part 32. A thickness Tm of the excitation unit 31 is, for example, 41.8 μm.

<Regarding the thickness Tm of the excitation portion 31 and the thickness Ts of the excitation outer peripheral portion 32>
In the actual manufacturing process of the AT-cut quartz crystal vibrating piece 30, it is difficult to accurately form the length Mx of the excitation unit 31, and if the manufacturing error allowable range of the length Mx of the excitation unit 31 is narrow, the product defect rate Goes up. For this reason, it is desirable that the length Mx of the excitation unit 31 is designed so as to allow a wide manufacturing error allowable range. This allowable manufacturing range is determined so that unnecessary vibration generated in the AT-cut quartz crystal vibrating piece 30 can be suppressed by selecting a range in which the CI (crystal impedance) value is low. Hereinafter, with reference to FIG. 3A (a) to FIG. 3B (e), the thickness Ts of the excitation outer peripheral portion 32 and the thickness of the excitation portion 31 that can take a wide manufacturing error allowable range of the length Mx of the excitation portion 31. The relationship of Tm will be described.

  FIG. 3A (a) is a graph showing the correlation between the CI value and the length Mx of the excitation unit 31 in the x-axis direction when (Tm−Ts) is 2 μm. The case where (Tm−Ts) is 2 μm corresponds to the case where the height h of the step is 1 μm. Further, when the thickness Tm of the excitation part 31 is 41.8 μm, the thickness Ts of the excitation outer peripheral part 32 is 39.8 μm. The horizontal axis of FIG. 3A (a) shows the length Mx (micrometer) of the excitation part 31 in the x-axis direction, and the vertical axis | shaft has shown CI value.

  The black rhombus in FIG. 3A (a) has shown the experimental value in the conditions whose vibration frequency is 38.4 MHz and (Tm-Ts) is 2 micrometers. In the experiment, a plurality of AT cut quartz crystal vibrating pieces 30 are produced for one length Mx value, and a CI value is obtained for each AT cut quartz crystal vibrating piece 30. An alternate long and short dash line in the figure connects an intermediate value between the maximum value and the minimum value of the CI values at each length Mx with a line segment. Hereinafter, as a guide for considering the manufacturing error allowable range of the length Mx, a range of the length Mx in which an intermediate value between the maximum value and the minimum value of the CI value is 80Ω or less is estimated from the graph. In FIG. 3A (a), the intermediate value is lower than 80Ω when the length Mx is smaller than about 723 μm. From the graph, the width A1 of the length Mx where the intermediate value of the CI values is 80Ω or less cannot be obtained. At this time, the ratio (Tm−Ts) / Tm of (Tm−Ts) to Tm is 0.048.

  FIG. 3A (b) is a graph showing the correlation between the CI value and the length Mx of the excitation unit 31 in the x-axis direction when (Tm−Ts) is 4 μm. Black rhombuses in FIG. 3A (b) indicate experimental values under conditions where the vibration frequency is 38.4 MHz and (Tm−Ts) is 4 μm. The case where (Tm−Ts) is 4 μm corresponds to the case where the height h of the step is 2 μm. Further, the thickness Ts of the excitation outer peripheral portion 32 is 37.8 μm. Except for the height h of the step, it is the same as FIG. In FIG. 3A (b), it is considered that the intermediate value between the maximum value and the minimum value of the CI value of the AT-cut quartz-crystal vibrating piece 30 is 80Ω or less when the length Mx is between about 714 μm and about 731 μm. Therefore, the width A2 of the length Mx at which the intermediate value of the CI value is 80Ω or less is estimated to be about 17 μm. At this time, the ratio (Tm−Ts) / Tm of (Tm−Ts) to Tm is 0.096.

  FIG. 3B (c) is a graph showing the correlation between the CI value and the length Mx of the excitation unit 31 in the x-axis direction when (Tm−Ts) is 6 μm. Black diamonds in FIG. 3B (c) indicate experimental values under conditions where the vibration frequency is 38.4 MHz and (Tm−Ts) is 6 μm. The case where (Tm−Ts) is 6 μm corresponds to the case where the height h of the step is 3 μm. Further, the thickness Ts of the excitation outer peripheral portion 32 is 35.8 μm. Except for the height h of the step, the description is omitted because it is the same as FIG. 3A (a). In FIG. 3B (c), it is considered that the intermediate value between the maximum value and the minimum value of the CI value of the AT-cut quartz-crystal vibrating piece 30 is 80Ω or less when the length Mx is between about 723 μm and about 736 μm. Therefore, the width A3 of Mx at which the intermediate value of the CI value is 80Ω or less is estimated to be about 13 μm. At this time, the ratio (Tm−Ts) / Tm of (Tm−Ts) to Tm is 0.14.

  FIG. 3B (d) is a graph showing the correlation between the CI value and the length Mx of the excitation unit 31 in the x-axis direction when (Tm−Ts) is 8 μm. Black diamonds in FIG. 3B (d) indicate experimental values under conditions where the vibration frequency is 38.4 MHz and (Tm−Ts) is 8 μm. The case where (Tm−Ts) is 8 μm corresponds to the case where the height h of the step is 4 μm. Further, the thickness Ts of the excitation outer peripheral portion 32 is 33.8 μm. Except for the height h of the step, it is the same as FIG. In FIG. 3B (d), when the length Mx is between about 724 μm and about 735 μm, the intermediate value between the maximum value and the minimum value of the CI value of the AT-cut quartz crystal vibrating piece 30 seems to be 80Ω or less. For this reason, the width A4 of Mx at which the intermediate value of the CI value is 723Ω or less is estimated to be about 11 μm. At this time, the ratio (Tm−Ts) / Tm of (Tm−Ts) to Tm is 0.19.

  FIG. 3B (e) is a graph showing the correlation between the CI value and the length Mx of the excitation unit 31 in the x-axis direction when (Tm−Ts) is 10 μm. Black rhombuses in FIG. 3B (e) indicate experimental values under conditions where the vibration frequency is 38.4 MHz and (Tm−Ts) is 10 μm. The case where (Tm−Ts) is 10 μm corresponds to the case where the height h of the step is 5 μm. Further, the thickness Ts of the excitation outer peripheral portion 32 is 31.8 μm. Except for the height h of the step, the description is omitted because it is the same as FIG. 3A (a). In FIG. 3B (e), it is considered that the intermediate value between the maximum value and the minimum value of the CI value of the AT-cut quartz-crystal vibrating piece 30 is 80Ω or less when the length Mx is between about 729 μm and about 735 μm. Therefore, the width A5 of the length Mx at which the intermediate value of the CI value is 80Ω or less is estimated to be about 6 μm. At this time, the ratio (Tm−Ts) / Tm of (Tm−Ts) to Tm is 0.24.

  In order to reduce the defect occurrence rate of the product, it is preferable that the manufacturing tolerance range of the length Mx is 10 μm or more, so that the characteristics of the crystal oscillator on which the AT-cut crystal resonator element 30 is mounted are not affected. Preferably has a CI value of 80Ω or less. 3A (a) to 3B (e), the width A1 to the width A5 is 10 μm or more when (Tm−Ts) is 4 μm to 8 μm. At this time, the ratio (Tm−Ts) / Tm of (Tm−Ts) to Tm is 0.096 to 0.19. In FIG. 3A (a), although the width A1 is unknown, the value increases as (Tm−Ts) decreases from the width A2 to the width A5, and the width A1 is estimated to be 10 μm or more. The Therefore, it is considered that (Tm−Ts) / Tm may be 0.048 or more.

  Further, it is considered that the maximum value of (Tm−Ts) / Tm may be a value that is generally smaller than 0.2 in view of an error. That is, (Tm−Ts) / Tm is preferably 0.048 or more and smaller than 0.2. That is, in the AT-cut quartz crystal vibrating piece 30 with a vibration frequency of 38.4 MHz, when (Tm−Ts) / Tm is 0.048 or more and a value smaller than 0.2, a manufacturing error of length Mx is allowed. It is considered that the range can be widened and the defect rate of the product can be lowered. At this time, the CI value of the AT-cut crystal vibrating piece 30 is lowered, the occurrence of unnecessary vibration in the vibrating portion is suppressed, and the deterioration of characteristics can be prevented.

(Second Embodiment)
An outer frame may be formed on the AT cut quartz crystal vibrating piece 30. Hereinafter, a quartz crystal device 200 including an AT cut quartz crystal vibrating piece in which an outer frame is formed will be described.

<Configuration of crystal device 200>
FIG. 4A is a perspective view of the quartz crystal device 200. The quartz crystal device 200 includes a lid 210, an AT cut quartz crystal vibrating piece 230, and a base 220. In the crystal device 200, the lid 210 is disposed at the upper portion, the base 220 is disposed at the lower portion, and the AT-cut quartz crystal vibrating piece 230 is disposed at a position sandwiched between the lid 210 and the base 220. An external electrode 221 is formed on the lower surface of the base 220. The lid 210 and the base 220 are made of a material such as glass or quartz.

  FIG. 4B is an EE cross-sectional view of FIG. The AT cut quartz crystal vibrating piece 230 is formed with an excitation part 231 and an excitation outer peripheral part 232 formed on the outer periphery of the excitation part 231, and an outer frame 235 is formed so as to surround the periphery of the excitation outer peripheral part 232. ing. Excitation electrodes 233 are respectively formed on one main surface and the other main surface of the excitation portion 231, and the extraction electrode 234 is formed on the outer frame 235 from the excitation electrode 233 through the excitation outer peripheral portion 232. The AT cut vibrating piece 230 vibrates at a predetermined frequency when a voltage is applied by the pair of excitation electrodes 233. The lid 210 is joined to one main surface of the outer frame 235 and a first surface 211 formed on the surface of the lid 210 on the −y ′ axis side, and the base 220 is joined to the other main surface of the outer frame 235 and + y ′ of the base 220. It joins in the 2nd surface 223 currently formed in the surface by the side of a shaft. Further, a connection electrode 222 is formed on the surface of the base 220 on the + y′-axis side, and the connection electrode 222 is connected to the extraction electrode 234 when bonded to the AT-cut quartz crystal vibrating piece 230. The connection electrode 222 is electrically connected to the external electrode 221 through a conduction portion (not shown).

  The AT cut quartz crystal vibrating piece 230 is formed so that the thickness of the excitation part 231 is t and the thickness of the excitation outer peripheral part 232 is Gy. The step between the excitation portion 231 and the excitation outer peripheral portion 232 is formed on the surface on the + y′-axis side and the surface on the −y′-axis side, and the height is h. Similarly to the AT-cut quartz crystal vibrating piece 30, the AT-cut quartz crystal vibrating piece 230 is formed of an artificial crystal, and the axial direction of the AT-cut quartz crystal vibrating piece 230 is the same as the axial direction of the AT-cut quartz crystal vibrating piece 30.

  FIG. 5A is a plan view of the lid 210. The lid 210 has a rectangular main surface with a major axis in the x-axis direction and a minor axis in the z′-axis direction. Further, a first surface 211 connected to the outer frame 235 of the AT-cut quartz crystal vibrating piece 230 is formed on the outer peripheral portion of the surface on the −y ′ axis side, and the first portion 211 is surrounded by the central portion. A recess 212 is formed as described above.

  FIG. 5B is a plan view of the AT-cut quartz crystal vibrating piece 230. The AT cut vibrating piece 230 and the outer frame 235 are connected by a connecting arm 236. The outer frame 235 supports the excitation outer peripheral portion 232 with a connection arm 236. The extraction electrode 234 extracted from the excitation electrode 233 formed in the excitation portion 231 passes through the excitation outer peripheral portion 232 and the connection arm 236 and is formed to the corner of the outer frame 235. The extraction electrode 234 is connected to a connection electrode 222 formed on the base 220 at a corner connection point 237 of the outer frame 235. The connection point 237 is formed on the surface on the −y′-axis side of the corner of the outer frame 235 indicated by a dotted ellipse in FIG. The length Gx in the x-axis direction of the excitation outer peripheral portion 234 of the AT-cut crystal vibrating piece 230 is, for example, 990 μm, and the length Gz in the z′-axis direction of the excitation outer peripheral portion 234 of the AT-cut crystal vibrating piece 230 is, for example, 700 μm. . The length of the excitation unit 231 in the x-axis direction is Mx, and the length in the z′-axis direction is Mz.

  FIG. 5C is a plan view of the base 220. A second surface 223 that is a surface to be joined to the outer frame 235 of the AT-cut crystal vibrating piece 230 is formed on the outer peripheral portion of the surface on the + y′-axis side of the base 220, and a concave portion is formed on the inner side of the second surface 223. 225 is formed. A connection electrode 222 that is electrically connected to the connection point 237 of the extraction electrode 234 of the AT-cut quartz crystal vibrating piece 230 is formed on a part of the second surface 223 on the + y′-axis side surface of the base 220.

  Even if the outer frame is formed on the AT-cut crystal vibrating piece, the excitation outer peripheral portion and the outer frame are only connected by the connecting arm, and the vibration energy of unnecessary vibration generated in the excitation outer peripheral portion is not greatly changed. Therefore, the fact that (Tm−Ts) / Tm is 0.048 or more and smaller than 0.2 can also be applied to the AT-cut quartz crystal vibrating piece 230.

  As described above, the optimal embodiment of the present invention has been described in detail. However, as will be apparent to those skilled in the art, the present invention can be implemented with various modifications and variations within the technical scope thereof.

10, 210 ... Lid 20, 220 ... Base 21, 221 ... External electrode 22, 222 ... Connection electrode 24, 224 ... Cavity 30, 230 ... AT cut crystal vibrating piece 31, 231 ... Excitation part 32, 232 ... Excitation outer peripheral part 33 233 ... Excitation electrode 34, 234 ... Lead electrode 40 ... Sealing material 41 ... Conductive adhesive 100, 200 ... Quartz device 211 ... First surface 212, 225 ... Recess 223 ... Second surface 235 ... Outer frame 236 ... Connection Arm 237… Connection point

Claims (4)

In a mesa-type AT-cut quartz crystal vibrating piece having a rectangular excitation part and an excitation outer peripheral part formed on the outer periphery of the excitation part and having a thickness smaller than the excitation part, and vibrating at 38.4 MHz,
When the thickness of the vibrating part is Tm (μm) and the thickness of the excitation outer peripheral part is Ts (μm), the formula (Tm−Ts) / Tm is 0.048 or more and is a mesa type smaller than 0.2 AT-cut crystal vibrating piece.   The mesa-type AT-cut quartz-crystal vibrating piece according to claim 1, further comprising an outer frame that surrounds the periphery of the excitation outer peripheral portion and supports the excitation outer peripheral portion. The mesa-type AT-cut quartz crystal resonator element according to claim 1,
A base in which a concave portion is formed and the mesa-type AT-cut quartz crystal vibrating piece is accommodated in the concave portion;
A lid for sealing the recess;
Quartz device with. The mesa-type AT-cut quartz crystal resonator element according to claim 2, having one main surface and another main surface;
A lid having a first surface joined to one main surface of the outer frame;
A base having a second surface joined to the other main surface of the outer frame;
Quartz device with.