Piezoelectric vibrating piece, piezoelectric vibrator, and oscillator

Abstract

To provide a high-quality piezoelectric vibrating piece that suppresses frequency fluctuations after frequency adjustment and has excellent vibration characteristics.SOLUTION: A piezoelectric vibrating piece 3 includes a piezoelectric plate 30 having a pair of vibrating arms 31, electrode films 40 arranged on the front and back surfaces of the piezoelectric plate 30, and a weight metal film 50 for frequency adjustment arranged on the electrode film 40 on the front surface 64 side of the vibrating arm 31. The back surface 63 of the vibrating arm 31 has a back-side exposed portion 61 where the piezoelectric plate 30 is exposed. The front surface 64 of the vibrating arm 31 includes a front-side exposed portion 62 where the weight metal film 50 and the electrode film 40 have been removed to expose the piezoelectric plate 30. When viewed in the thickness direction of the piezoelectric plate 30, the entire front-side exposed portion 62 overlaps the back-side exposed portion 61 with a gap between it and the electrode film 40 on the back surface 63.SELECTED DRAWING: Figure 8

Description

[Technical Field]

[0001] The present invention relates to a piezoelectric vibrating piece, a piezoelectric vibrator, and an oscillator. [Background technology]

[0002] For example, in electronic devices such as mobile phones and personal digital assistants, piezoelectric vibrators using quartz crystals or the like are used as devices used as time sources, timing sources for control signals, reference signal sources, etc. A known type of piezoelectric vibrator is one in which a piezoelectric vibrating reed is hermetically sealed in a package with a cavity formed therein.

[0003] The piezoelectric vibrating reed described above includes a piezoelectric plate having a base and a pair of vibrating arms extending parallel to each other from the base, and excitation electrodes arranged on the outer surfaces of the vibrating arms. When a voltage is applied to the excitation electrodes, the piezoelectric vibrating reed vibrates at a predetermined resonant frequency in directions in which the vibrating arms approach or move away from each other, starting from their base ends (the portions connected to the base).

[0004] Here, one method for adjusting the frequency of a piezoelectric vibrating reed (vibrating arm) is to form a metal weight film on the tip of the vibrating arm in advance, and then partially remove (trim) this metal weight film to adjust the mass of the metal weight film so that the frequency of the vibrating arm reaches a target value. For example, Patent Document 1 below discloses a configuration in which a laser beam is irradiated onto the metal weight film to partially remove it and perform coarse adjustment of the resonant frequency, and then an ion beam is irradiated onto the metal weight film to perform fine adjustment of the resonant frequency. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2013-118652 Summary of the Invention [Problem to be solved by the invention]

[0006] However, in addition to the weight metal film, an electrode film having the same film structure as the excitation electrode is disposed on the outer surface of the vibrating arm. Therefore, when trimming the weight metal film using laser light as in the aforementioned Patent Document 1, the weight metal film is removed, and the laser light incident on the piezoelectric plate passes through the piezoelectric plate. As a result, the laser light is irradiated onto the electrode film disposed on the opposite side of the weight metal film, removing the irradiated portion of the electrode film and potentially generating burrs on the edges of the remaining portion of the electrode film. Furthermore, if the burrs come into contact with the package or become deformed, the frequency adjusted by trimming may fluctuate.

[0007] SUMMARY OF THE INVENTION The present invention provides a high-quality piezoelectric vibrating piece, a piezoelectric vibrator, and an oscillator that suppress frequency fluctuations after frequency adjustment and have excellent vibration characteristics. [Means for solving the problem]

[0008] The piezoelectric vibrating piece of the present invention comprises a base, a piezoelectric plate having a pair of vibrating arms extending longitudinally from the base, and an electrode film arranged on the front and back surfaces of the piezoelectric plate, wherein the vibrating arms have a main body extending from the base end of the vibrating arms toward the tip, and a weight portion located at the tip of the vibrating arms and wider than the main body, and a weight metal film for frequency adjustment arranged on the electrode film on the surface of the weight portion, the back surface of the weight portion having a back-side exposed portion where the piezoelectric plate is exposed, the surface of the weight portion having a front-side exposed portion where the weight metal film and the electrode film have been removed to expose the piezoelectric plate, the electrode film is further arranged on the tip surface facing the longitudinal direction of the vibrating arms, and the weight metal film is further formed on the electrode film formed on the tip surface, and the entire front-side exposed portion overlaps the back-side exposed portion with a gap relative to the electrode film on the back surface when viewed in the thickness direction of the piezoelectric plate.

[0009] According to the present invention, when a laser is used to remove the weight metal film together with the underlying electrode film for frequency adjustment to form a front-side exposed portion, the laser light transmitted through the piezoelectric plate passes through the rear-side exposed portion. Therefore, the laser light is not irradiated onto the electrode film on the rear surface of the piezoelectric plate, thereby preventing burrs from forming on the rear surface electrode film. This prevents frequency fluctuations due to burr shedding or deformation of the electrode film. This reduces frequency fluctuations after frequency adjustment, resulting in a high-quality piezoelectric vibrating reed with excellent vibration characteristics. Furthermore, while the weight metal film may wrap around to the end faces of the vibrating arms when the weight metal film is formed, the electrode film on the end faces of the vibrating arms acts as a base for the weight metal film, improving adhesion of the weight metal film compared to when the end faces of the vibrating arms are exposed. This prevents shedding of the weight metal film. This reduces frequency fluctuations due to shedding of the weight metal film. This reduces frequency fluctuations after frequency adjustment.

[0010] In the above-mentioned piezoelectric vibrating piece, the electrode film arranged on the surface of the weight portion may be formed from the base end of the weight portion to the tip end, and may be formed across the boundary of the weight portion between the back-side exposed portion and the electrode film arranged on the back surface of the weight portion.

[0011] In the above-described piezoelectric vibrating piece, the rear-side exposed portion may have a length in the longitudinal direction greater than that of the front-side exposed portion when viewed in the thickness direction of the piezoelectric plate.

[0012] In the above-described piezoelectric vibrating piece, the front-side exposed portion and the back-side exposed portion may be formed continuously from the tip end toward the base end of the vibrating arm portion.

[0013] In the above piezoelectric vibrating piece, the entire front-side exposed portion may overlap at least the rear-side exposed portion in the width direction of the piezoelectric plate, and the area of the rear-side exposed portion may be larger than the area of the front-side exposed portion.

[0014] In the above-described piezoelectric vibrating piece, the weight metal films may be formed on the tip and base end sides of the weight portion in the longitudinal direction, with the front-side exposed portion interposed therebetween, and may also be formed on the electrode film.

[0015] In the above-mentioned piezoelectric vibrating piece, the exposed back portion is formed continuously from the tip edge of the weight portion toward the base end side, the electrode film has a front portion formed on the surface side of the weight portion and a back portion formed on the back side of the weight portion, the back portion is formed continuously from the base end side toward the tip end side of the weight portion, and the weight metal film and the front portion may be formed across the boundary between the exposed back portion and the back portion at the tip end side.

[0016] In the above piezoelectric vibrating piece, the interval may be shorter than the length of the weight metal film.

[0017] A piezoelectric vibrator of the present invention includes the above-described piezoelectric vibrating piece and a package that hermetically seals the piezoelectric vibrating piece.

[0018] An oscillator of the present invention includes the above-described piezoelectric vibrator, which is electrically connected to an integrated circuit as an oscillator. [Effects of the Invention]

[0019] According to the present invention, it is possible to provide a high-quality piezoelectric vibrating piece, a piezoelectric vibrator, and an oscillator that suppress fluctuations in frequency after frequency adjustment and have excellent vibration characteristics. [Brief explanation of the drawings]

[0020] [Figure 1] FIG. 1 is a diagram illustrating an oscillator according to an embodiment. [Figure 2] 1 is a perspective view of the appearance of a piezoelectric vibrator according to an embodiment; [Figure 3] FIG. 2 is a plan view of the piezoelectric vibrator with the sealing plate removed. [Figure 4] FIG. 4 is a cross-sectional view corresponding to line IV-IV in FIG. [Figure 5] FIG. 2 is an exploded perspective view of the piezoelectric vibrator according to the embodiment. [Figure 6] FIG. 1 is a plan view of a piezoelectric vibrating reed according to a first embodiment. [Figure 7]FIG. 7 is a cross-sectional view taken along line VII-VII in FIG. [Figure 8] FIG. 7 is a cross-sectional view taken along line VIII-VIII in FIG. 6. [Figure 9] 4 is a flowchart showing a method for manufacturing the piezoelectric vibrating piece according to the first embodiment. [Figure 10] 9A to 9C are cross-sectional views illustrating a method for manufacturing the piezoelectric vibrating reed according to the first embodiment, which correspond to FIG. 8. [Figure 11] 9A to 9C are cross-sectional views illustrating a method for manufacturing the piezoelectric vibrating reed according to the first embodiment, which correspond to FIG. 8. [Figure 12] FIG. 10 is a plan view of a piezoelectric vibrating reed according to a second embodiment. [Figure 13] FIG. 13 is a cross-sectional view taken along line XIII-XIII in FIG. DETAILED DESCRIPTION OF THE INVENTION

[0021] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In the following description, components having the same or similar functions will be denoted by the same reference numerals. Duplicate descriptions of those components may be omitted.

[0022] (Oscillator of an embodiment) FIG. 1 is a diagram showing an oscillator according to an embodiment. As shown in FIG. 1, the oscillator 100 includes a substrate 101, an electronic component 102, an integrated circuit 103, and a piezoelectric vibrator 1. The electronic component 102 is, for example, a capacitor, and is mounted on the substrate 101. The integrated circuit 103 is for the oscillator, and is also mounted on the substrate 101. The integrated circuit 103 is electrically connected to the piezoelectric vibrator 1 and the electronic component 102 via wiring (not shown). The piezoelectric vibrator 1 is mounted, for example, on the substrate 101 near the integrated circuit 103. The piezoelectric vibrator 1 functions as an oscillator. The piezoelectric vibrator 1 will be described later. At least a portion of the oscillator 100 may be molded with a resin (not shown) as appropriate.

[0023] In the oscillator 100, when power is supplied to the piezoelectric vibrator 1, the piezoelectric vibrating piece 3 (see FIG. 5) of the piezoelectric vibrator 1 vibrates. The vibration of the piezoelectric vibrating piece 3 is converted into an electric signal by the piezoelectric characteristics of the piezoelectric vibrating piece 3. This electric signal is output from the piezoelectric vibrator 1 to the integrated circuit 103. The integrated circuit 103 performs various processes on the electric signal output from the piezoelectric vibrator 1 to generate a frequency signal.

[0024] The oscillator 100 can be used, for example, as a single-function oscillator for a clock, a timing control device that controls the operation timing of various devices such as a computer, or a device that provides time or a calendar. The integrated circuit 103 is configured according to the functions required of the oscillator 100, and may include a so-called RTC (real-time clock) module.

[0025] (Piezoelectric vibrator according to an embodiment) Fig. 2 is a perspective view of the appearance of a piezoelectric vibrator according to an embodiment. Fig. 3 is a plan view of the piezoelectric vibrator with a sealing plate removed. Fig. 4 is a cross-sectional view taken along line IV-IV in Fig. 3. Fig. 5 is an exploded perspective view of a piezoelectric vibrator according to an embodiment. As shown in Figures 2 to 5, the piezoelectric vibrator 1 is a so-called ceramic package type surface-mount vibrator. The piezoelectric vibrator 1 includes a package 2 having an airtightly sealed cavity C therein, and a piezoelectric vibrating piece 3 housed in the cavity C. The piezoelectric vibrator 1 has a rectangular parallelepiped shape. In this embodiment, the longitudinal direction of the piezoelectric vibrator 1 in a plan view is referred to as the longitudinal direction L, the lateral direction is referred to as the width direction W, and the direction perpendicular to the longitudinal direction L and the width direction W is referred to as the thickness direction T.

[0026] The package 2 includes a package body 5 and a sealing plate 6 that is joined to the package body 5 and forms a cavity C between the package body 5 and the sealing plate 6. The package body 5 includes a first base substrate 10 and a second base substrate 11 that are bonded together in a stacked state, and a seal ring 12 that is bonded onto the second base substrate 11.

[0027] The first base substrate 10 is a ceramic substrate having a rectangular shape in a plan view seen in the thickness direction T. The upper surface of the first base substrate 10 forms the bottom of the cavity C. A pair of external electrodes 21A, 21B are formed on the lower surface of the first base substrate 10 with a gap between them in the longitudinal direction L. The external electrodes 21A, 21B are formed of a single-layer film made of a single metal formed by, for example, vapor deposition or sputtering, or a laminated film made of a laminate of different metals.

[0028] The second base substrate 11 is a ceramic substrate having the same outer shape as the first base substrate 10 in a plan view, and is integrally bonded to the first base substrate 10 by sintering or the like while being stacked on top of the first base substrate 10. Note that the ceramic material used for each of the base substrates 10, 11 can be, for example, HTCC (High Temperature Co-Fired Ceramic) made of alumina or LTCC (Low Temperature Co-Fired Ceramic) made of glass ceramic.

[0029] As shown in FIGS. 3 to 5, the second base substrate 11 has a through-hole 11a formed therein, penetrating the second base substrate 11 in the thickness direction T. The through-hole 11a has a rounded rectangular shape in a plan view. Mounting portions 14A and 14B protruding inward in the width direction W are formed on the inner surface of the through-hole 11a at portions located on both sides in the width direction W. The mounting portions 14A and 14B are located in the center of the second base substrate 11 in the longitudinal direction L.

[0030] A pair of electrode pads 20A, 20B are formed on the mounting portions 14A, 14B as connection electrodes with the piezoelectric vibrating reed 3. Like the external electrodes 21A, 21B described above, the electrode pads 20A, 20B are formed of a single-layer film made of a single metal, formed by, for example, vapor deposition or sputtering, or a laminated film made of laminated layers of different metals. The electrode pads 20A, 20B and the external electrodes 21A, 21B are electrically connected to each other via through-wiring (not shown) that penetrates each of the base substrates 10, 11 in the thickness direction T.

[0031] At the four corners of each of the base substrates 10, 11, cutout portions 15 having a quarter-circular arc shape in plan view are formed over the entire thickness direction T of both base substrates 10, 11. Each of the base substrates 10, 11 is fabricated, for example, by stacking and bonding two wafer-like ceramic substrates, forming a plurality of through-holes penetrating both ceramic substrates in a matrix pattern, and cutting both ceramic substrates in a grid pattern using each through-hole as a reference. At this time, the through-holes are divided into four to form the above-mentioned cutout portions 15.

[0032] The seal ring 12 is a conductive frame-shaped member that is slightly smaller than the outer shape of each of the base substrates 10, 11, and is joined to the upper surface of the second base substrate 11. Specifically, the seal ring 12 is joined to the second base substrate 11 by baking with a brazing material such as silver brazing or a solder material, or by welding to a metal joining layer formed on the second base substrate 11. The seal ring 12, together with the inner surface of the second base substrate 11 (through portion 11a), constitutes the side wall of the cavity C. In the illustrated example, the inner surface of the seal ring 12 is disposed flush with the inner surface of the second base substrate 11.

[0033] The material of the seal ring 12 may be, for example, a nickel-based alloy, and specifically may be selected from Kovar, Elinvar, Invar, 42-alloy, etc. In particular, it is preferable to select a material for the seal ring 12 that has a thermal expansion coefficient close to that of the base substrates 10 and 11, which are made of ceramics. For example, the base substrates 10 and 11 may have a thermal expansion coefficient of 6.8×10 -6 When alumina with a thermal expansion coefficient of 5.2×10 / °C is used, the seal ring 12 has a thermal expansion coefficient of 5.2×10 -6 / ℃ Kovar and thermal expansion coefficient 4.5~6.5×10 -6 It is preferable to use 42-alloy with a temperature of 1000 K / °C.

[0034] The sealing plate 6 is made of a conductive substrate and is joined onto the seal ring 12 to airtightly seal the inside of the package body 5. The space defined by the seal ring 12, the sealing plate 6, and each of the base substrates 10 and 11 constitutes a hermetically sealed cavity C.

[0035] The piezoelectric vibrating reed 3 is housed in a cavity C of a hermetically sealed package 2. The piezoelectric vibrating reed 3 includes a piezoelectric plate 30 made of a piezoelectric material such as quartz crystal, lithium tantalate, or lithium niobate. The piezoelectric plate 30 has a pair of vibrating arms 31 and 32 and a pair of support arms 33 and 34. The piezoelectric vibrating reed 3 is mounted in the package 2 by supporting the support arms 33 and 34 on the mounting sections 14A and 14B of the package 2 with a conductive adhesive within the cavity C. This allows the piezoelectric vibrating reed 3 to be supported in the cavity C with the vibrating arms 31 and 32 floating above the base substrates 10 and 11. Two excitation electrodes 41 and 42 (see FIG. 6) are arranged on the outer surfaces of the vibrating arms 31 and 32, causing the pair of vibrating arms 31 and 32 to vibrate when a predetermined voltage is applied.

[0036] To operate the piezoelectric vibrator 1, a predetermined voltage is applied to the external electrodes 21A and 21B (see FIG. 2). This causes a current to flow through the excitation electrodes 41 and 42, generating an electric field between the excitation electrodes 41 and 42. The vibrating arms 31 and 32 vibrate at a predetermined resonance frequency, for example, in directions in which they move toward or away from each other (width direction W), due to the inverse piezoelectric effect caused by the electric field generated between the excitation electrodes 41 and 42. The vibrations of the vibrating arms 31 and 32 are used as a time source, a timing source for control signals, a reference signal source, etc.

[0037] (Piezoelectric vibrating piece according to the first embodiment) The piezoelectric vibrating reed 3 of the first embodiment will be described in detail. FIG. 6 is a plan view of the piezoelectric vibrating reed according to the first embodiment. 6, the piezoelectric vibrating reed 3 includes a piezoelectric plate 30, an electrode film 40 disposed on the outer surface including the front and back surfaces of the piezoelectric plate 30, and a weight metal film 50 for frequency adjustment. In this embodiment, the longitudinal direction L, width direction W, and thickness direction T of the piezoelectric vibrator 1 coincide with the longitudinal direction, width direction, and thickness direction, respectively, of the piezoelectric vibrating reed 3. Therefore, in the following description of the piezoelectric vibrating reed 3, the longitudinal direction L, width direction W, and thickness direction T of the piezoelectric vibrator 1 will be used.

[0038] The piezoelectric plate 30 includes a base 35, a pair of vibrating arms 31, 32 (first vibrating arm 31 and second vibrating arm 32) extending from the base 35 in the longitudinal direction L, and a pair of supporting arms 33, 34 (first supporting arm 33 and second supporting arm 34) located on both sides of the base 35 in the width direction W. The piezoelectric plate 30 is formed so that its shape in a plan view, as viewed in the thickness direction T, is approximately symmetrical with respect to a central axis O along the longitudinal direction L. In this embodiment, quartz crystal will be used as an example of the piezoelectric material forming the piezoelectric plate 30.

[0039] The first vibrating arm 31 and the second vibrating arm 32 are arranged parallel to each other in the width direction W. Each vibrating arm 31, 32 has a base end on the base portion 35 side as a fixed end and a tip end as a free end, and vibrates in a direction in which they move toward and away from each other (the width direction W). Each vibrating arm 31, 32 has a main body 36 extending from the base end of each vibrating arm 31, 32 toward the tip, and a weight 38 located at the tip of each vibrating arm 31, 32.

[0040] FIG. 7 is a cross-sectional view taken along line VII-VII in FIG. 6 and 7, grooves 37 are formed in the main body 36. The grooves 37 are recessed in the thickness direction T on both main surfaces of the main body 36 and extend along the longitudinal direction L. The grooves 37 are formed from near the base ends of the vibrating arms 31 and 32 to near the tip ends of the main body 36.

[0041] 6, the weights 38 each extend in the longitudinal direction L from the tip of the main body 36. The weights 38 are rectangular in plan view and are formed to be wider in the width direction W than the main body 36. This increases the mass of the tip of each of the vibrating arms 31, 32 and the moment of inertia during vibration, and reduces the length of each of the vibrating arms 31, 32 compared to a piezoelectric vibrating piece 3 that does not have a weight 38.

[0042] Each of the support arms 33, 34 has an L-shape in plan view, and surrounds the base 35 and the vibrating arms 31, 32 (main body 36) from the outside in the width direction W. Specifically, each of the support arms 33, 34 protrudes outward in the width direction W from both end surfaces of the base 35 in the width direction W, and then extends parallel to the vibrating arms 31, 32 along the longitudinal direction L. The first support arm 33 is disposed on the same side of the central axis O as the first vibrating arm 31. The second support arm 34 is disposed on the same side of the central axis O as the second vibrating arm 32.

[0043] The electrode film 40 is, for example, a laminated film of chromium (Cr) and gold (Au), and is formed by depositing a chromium film, which has good adhesion to quartz crystal, as a base, and then laminating a thin film of gold on the chromium film. However, the film configuration of the electrode film 40 is not limited to this, and for example, a thin film of gold may be further laminated on a laminated film of chromium and nichrome (NiCr), or a single layer film of chromium, nickel, aluminum (Al), titanium (Ti), etc. may also be used.

[0044] The electrode film 40 includes excitation electrodes 41 and 42, mount electrodes 43 and 44, and a connection wiring 45. Two sets of excitation electrodes 41, 42 are provided on the outer surfaces of the main body 36 of the vibrating arms 31, 32. The excitation electrodes 41, 42 are patterned so as to be electrically insulated from each other. The excitation electrodes 41, 42 include a first excitation electrode 41 and a second excitation electrode 42. The first excitation electrode 41 is formed on both side surfaces of the main body 36 of the first vibrating arm 31 facing the width direction W and on the grooves 37 of the second vibrating arm 32. The second excitation electrodes 42 are formed on the grooves 37 of the first vibrating arm 31 and on both side surfaces of the main body 36 of the second vibrating arm 32. The excitation electrodes 41, 42 vibrate the vibrating arms 31, 32 in the width direction W when a predetermined drive voltage is applied between the excitation electrodes 41, 42.

[0045] The mount electrodes 43, 44 are provided as mount portions when the piezoelectric vibrating reed 3 is mounted in the package 2. The mount electrodes 43, 44 are provided on the main surfaces (rear surfaces) at the tip portions of the support arms 33, 34. Specifically, the mount electrodes 43, 44 include a first mount electrode 43 arranged on the first support arm 33 and a second mount electrode 44 arranged on the second support arm 34. The first mount electrode 43 is electrically connected to the first excitation electrode 41. The second mount electrode 44 is electrically connected to the second excitation electrode 42. The mount electrodes 43, 44 are electrically connected to the electrode pads 20A, 20B of the package 2 via a conductive adhesive.

[0046] The connection wiring 45A and 45B connect the excitation electrodes 41 and 42 to each other on the tip side of the vibrating arms 31 and 32. The connection wiring 45 has a first connection wiring 45A connected to the first excitation electrode 41 and a second connection wiring 45B connected to the second excitation electrode 42. The first connection wiring 45A electrically connects the first excitation electrodes 41 on both side surfaces of the first vibrating arm 31 to each other. The second connection wiring 45B electrically connects the second excitation electrodes 42 on both side surfaces of the second vibrating arm 32 to each other. The first connection wiring 45A and the second connection wiring 45B are formed in the same manner, and therefore, in the following description, when there is no need to distinguish between the first connection wiring 45A and the second connection wiring 45B, they will simply be referred to as connection wiring 45.

[0047] Each connection wiring 45 has a side portion 46, a front portion 47, and a back portion 48. The side portion 46 is disposed on the entire end surface of the vibrating arms 31, 32, closer to the tip than the groove portion 37 in the vibrating arms 31, 32. The end surface is a surface that connects the main surfaces to each other, and includes a front surface facing the longitudinal direction L and a side surface facing the width direction W. The front portion 47 is disposed on the surface 64 of the vibrating arms 31, 32, closer to the tip than the groove portion 37 in the vibrating arms 31, 32. The front portion 47 is disposed at an interval from the excitation electrodes 41, 42 in the longitudinal direction L. The front portion 47 extends so as to straddle the boundary between the main body portion 36 and the weight portion 38 in the vibrating arms 31, 32. The side edges of the front portion 47 are connected to the side portion 46. The back portion 48 is disposed on the back surface 63 of the vibrating arms 31, 32, closer to the tip end than the groove portion 37 of the vibrating arms 31, 32. The back portion 48 is disposed at an interval in the longitudinal direction L relative to the excitation electrodes 41, 42. The back portion 48 extends so as to straddle the boundary between the main body portion 36 and the weight portion 38 of the vibrating arms 31, 32. The side edges of the back portion 48 are connected to the side portions 46.

[0048] FIG. 8 is a cross-sectional view taken along line VIII-VIII in FIG. 6 and 8, the back portion 48 of the connection wiring 45 is arranged so as to expose a portion of the back surface 63 of the vibrating arm portions 31, 32. As a result, the back surface 63 of the vibrating arm portions 31, 32 has a back-side exposed portion 61 where the piezoelectric plate 30 is exposed. The back-side exposed portion 61 is provided only on the back surface of the weight portion 38. The back-side exposed portion 61 is formed so as to include a tip edge 63t of the back surface 63 of the vibrating arm portions 31, 32. Furthermore, the back-side exposed portion 61 is formed so as to include a pair of side edges 63s extending from the tip edge 63t on the back surface 63 of the vibrating arm portions 31, 32 to the base end side of the vibrating arm portions 31, 32. The back-side exposed portion 61 is formed in a rectangular shape.

[0049] The weight metal film 50 is disposed on the electrode film 40 on the surface 64 side of the vibrating arms 31, 32. The weight metal film 50 increases the mass at the tip of each vibrating arm 31, 32, and suppresses an increase in frequency that accompanies a shortening of the length of each vibrating arm 31, 32. The weight metal film 50 is made of, for example, Au or Ag, and has a thickness of approximately 1 to 10 μm. The weight metal film 50 is disposed on the front portion 47 of the connection wiring 45 of the electrode film 40. The weight metal film 50 is formed so that its side edges on both sides in the width direction W coincide with the side edges of the front portion 47 of the connection wiring 45. The base-end side edges of the weight metal film 50 of the vibrating arms 31, 32 extend in the width direction W and are located closer to the tip side than the base-end side edges of the vibrating arms 31, 32 on the front portion 47 of the connection wiring 45. The rear portion 48 of the connection wiring 45 straddles the edge of the base end side of the weight metal film 50 in plan view.

[0050] The front portion 47 of the connection wiring 45 and the weight metal film 50 are arranged to expose a portion of the surface 64 of the vibrating arms 31 and 32. As a result, the surfaces 64 of the vibrating arms 31 and 32 have a front-side exposed portion 62 where the piezoelectric plate 30 is exposed. The edges of the front portion 47 of the connection wiring 45 and the weight metal film 50 coincide with each other on the outline of the front-side exposed portion 62 in a planar view. The front-side exposed portion 62 is formed to include a tip edge 64t of the surface 64 of the vibrating arms 31 and 32. Furthermore, the front-side exposed portion 62 is formed to include a pair of side edges 64s extending from the tip edge 64t of the surface 64 of the vibrating arms 31 and 32 toward the base ends of the vibrating arms 31 and 32. The entire front-side exposed portion 62 overlaps the back-side exposed portion 61 in a planar view. The entire front-side exposed portion 62 is disposed at a distance from the electrode film 40 (the back portion 48 of the connection wiring 45) on the back surface 63 of the vibrating arm portions 31, 32 in plan view.

[0051] (Method for manufacturing the piezoelectric vibrating piece according to the first embodiment) A method for manufacturing the piezoelectric vibrating reed 3 of the first embodiment will be described. FIG. 9 is a flowchart showing a method for manufacturing the piezoelectric vibrating reed according to the first embodiment. As shown in FIG. 9, the method for manufacturing the piezoelectric vibrating reed 3 of the first embodiment includes an outer shape forming step S10, an electrode film forming step S20, a metal film forming step S30, and a trimming step S40.

[0052] First, the outer shape forming step S10 is performed. In the outer shape forming step S10, the piezoelectric plate 30 is formed on a wafer of piezoelectric material. First, a mask having a shape corresponding to the shape of the piezoelectric plate 30 in a planar view is formed on both sides of the wafer using photolithography technology. Next, the wafer is wet-etched. As a result, the unmasked areas of the wafer are selectively removed, and the wafer is shaped into the shape of the piezoelectric plate 30 in a planar view.

[0053] Next, grooves 37 are formed on both main surfaces (front and back) of each vibrating arm 31, 32. Specifically, a mask having a shape corresponding to the shape of the grooves 37 is formed on both main surfaces of the wafer using photolithography. Next, the wafer is half-etched using wet etching to the extent that the grooves 37 do not penetrate the wafer. As a result, a piezoelectric plate 30 having the grooves 37 is formed on the wafer.

[0054] Next, an electrode film forming process S20 is performed. In the electrode film forming process S20, electrode films 40 are arranged on the front and back surfaces of the piezoelectric plate 30, and back-side exposed portions 61 are formed on the back surfaces of the vibrating arm portions 31, 32 of the piezoelectric plate 30. In this embodiment, the electrode film forming process S20 includes an electrode film forming process S21 in which the electrode film 40 is formed, and a patterning process S22 in which the electrode film 40 is patterned to form the excitation electrodes 41, 42 and the back-side exposed portions 61.

[0055] In the electrode film forming step S21, an electrode film 40 is formed on the front and rear surfaces and end surfaces of the wafer by sputtering, vapor deposition, or the like.

[0056] In the patterning process S22, the electrode film 40 is patterned to form two systems of electrodes 41-44 and connection wiring 45A, 45B on the piezoelectric plate 30. First, a mask made of a resist material having a shape corresponding to the outer shapes of the electrodes 41-44 and connection wiring 45A, 45B is formed on the outer surface of the electrode film 40 using photolithography. The mask is formed so as to cover the portion corresponding to the front-side exposed portion 62. Next, the electrode film 40 is etched to selectively remove the electrode film 40 in the unmasked region. This results in the formation of the excitation electrodes 41, 42, the mount electrodes 43, 44, and the connection wiring 45A, 45B on the piezoelectric plate 30. Furthermore, as shown in FIG. 10 , a back-side exposed portion 61 is formed on the back surface 63 of the vibrating arm portions 31, 32 of the piezoelectric plate 30. In this process, the electrode film 40 is disposed on the portion corresponding to the front-side exposed portion 62 of the vibrating arm portions 31, 32 of the piezoelectric plate 30.

[0057] Next, a metal film forming step S30 is performed. As shown in Fig. 11, in the metal film forming step S30, a weight metal film 50 for frequency adjustment is formed on the electrode film 40 on the surface 64 side of each vibrating arm portion 31, 32. At this time, the weight metal film 50 is formed so that at least a portion of the weight metal film 50 overlaps the exposed back side portion 61 in a plan view. The weight metal film 50 can be formed by, for example, vapor deposition using a metal mask.

[0058] Next, a trimming process S40 is performed. In the trimming process S40, the resonance frequency of each piezoelectric vibrating piece 3 is roughly adjusted. In the trimming process S40, the weight metal film 50 is partially removed (trimmed) from the surface 64 of the vibrating arm portions 31, 32 together with the underlying electrode film 40 (surface portion 47 of the connection wiring 45) according to the adjustment amount of the resonance frequency. In the trimming process S40, the weight metal film 50 and the electrode film 40 are removed using a pulsed laser. As the pulsed laser, a picosecond laser or a femtosecond laser is suitable, with a picosecond laser being optimal.

[0059] In the trimming process S40, the weight metal film 50 is irradiated with laser light from the front side, thereby melting and removing the irradiated portion of the weight metal film 50 together with the electrode film 40 directly below it. At this time, the weight metal film 50 and the electrode film 40 are removed by the laser on the front surface 64 side of the vibrating arms 31, 32 within a range that overlaps with the exposed backside portion 61 in a plan view and is spaced apart from the electrode film 40 on the back surface 63. The exposed backside portion 61 described above is formed by adjusting the irradiation range of the laser light according to the adjustment amount of the resonant frequency. Then, the weight metal film 50 is trimmed, changing the moment of inertia of the vibrating arms 31, 32, thereby changing the frequency of the vibrating arms 31, 32.

[0060] As described above, the piezoelectric vibrating reed 3 of this embodiment includes electrode films 40 disposed on the front and back surfaces of the piezoelectric plate 30, and weight metal films 50 for frequency adjustment disposed on the electrode films 40 on the front surfaces 64 of the vibrating arms 31 and 32. The back surfaces 63 of the vibrating arms 31 and 32 have exposed back-side portions 61 where the piezoelectric plate 30 is exposed. The front surfaces 64 of the vibrating arms 31 and 32 have exposed front-side portions 62 where the weight metal films 50 and the electrode films 40 have been removed to expose the piezoelectric plate 30. The entire exposed front-side portions 62 overlap the exposed back-side portions 61 in a plan view, with a gap between them and the electrode films 40 (rear portions 48 of the connection wiring 45) on the back surfaces 63 of the vibrating arms 31 and 32. With this configuration, when the exposed front-side portions 62 are formed in the process of removing the weight metal films 50 together with the underlying electrode films 40 using a laser for frequency adjustment, laser light transmitted through the piezoelectric plate 30 passes through the exposed back-side portions 61. Therefore, the laser light is not irradiated onto the electrode film 40 on the rear surface 63 of the piezoelectric plate 30, which can prevent burrs from being formed on the electrode film 40 on the rear surface 63 side. This can prevent frequency fluctuations caused by burr falling off or deformation of the electrode film 40. This can prevent frequency fluctuations after frequency adjustment, and can provide a high-quality piezoelectric vibrating piece 3 with excellent vibration characteristics.

[0061] Furthermore, the electrode film 40 has side portions 46 of the connection wiring 45 arranged on the end faces of the vibrating arms 31, 32 around the front-side exposed portion 62. With this configuration, when the weight metal film 50 is formed, the weight metal film 50 may wrap around the end faces of the vibrating arms 31, 32. However, compared to when the end faces of the vibrating arms 31, 32 are exposed, the side portions 46 of the connection wiring 45 serve as a base for the weight metal film 50, improving the adhesion of the weight metal film 50. This makes it possible to prevent the weight metal film 50 from falling off. This makes it possible to prevent frequency fluctuations caused by the weight metal film 50 falling off. This makes it possible to prevent frequency fluctuations after frequency adjustment.

[0062] Furthermore, the back-side exposed portion 61 includes the tip edge 63t and the side edge 63s on the back surface 63 of the vibrating arm portions 31 and 32. If the back-side exposed portion 61 did not include the tip edge 63t and the side edge 63s of the back surface 63, the entire outline of the back-side exposed portion 61 would coincide with the edge of the electrode film 40 on the back surface 63. In this case, the weight metal film 50 on the front surface 64 side, inside the outline of the back-side exposed portion 61 in a plan view, must be removed. In this embodiment, the edge of the electrode film 40 on the back surface 63 does not exist in the part of the outline of the back-side exposed portion 61 that coincides with the tip edge 63t and the side edge 63s of the back surface 63. Therefore, even if the weight metal film 50 on the tip edge 64t and the side edge 64s of the front surface 64 is removed, it is possible to prevent the transmitted laser light from irradiating the electrode film 40 on the back surface 63. Therefore, compared to when the back-side exposed portion 61 does not include the tip edge 63t and the side edge 63s of the back surface 63, it is possible to increase the ratio of the area of the front-side exposed portion 62 to the area of the back-side exposed portion 61. Therefore, it is possible to set a wide frequency adjustment range. Furthermore, since the weight metal film 50 can be removed in order from the tip end toward the base end of the vibrating arm portions 31, 32, frequency adjustment can be performed efficiently.

[0063] Furthermore, the back portion 48 of the connection wiring 45 straddles the base-end side edge of the vibrating arm portions 31, 32 in the weight metal film 50 in plan view. According to this configuration, in a piezoelectric vibrating piece 3 in which the excitation electrodes 41, 42 are provided closer to the base end than the weight metal film 50, the connection wiring 45 connected to the excitation electrodes 41, 42 can be formed in the electrode film 40 so as to overlap with the weight metal film 50 in plan view. Therefore, even if the proportion of the area occupied by the weight metal film 50 increases as the piezoelectric vibrating piece 3 is made smaller, the connection wiring 45 can be reliably formed to ensure reliability.

[0064] In the manufacturing method of the piezoelectric vibrating reed 3 of this embodiment, in the trimming step S40, the weight metal film 50 and the electrode film 40 are removed with a laser on the front surface 64 side of the vibrating arm portions 31, 32 within a range that overlaps the exposed backside portion 61 in a plan view and is spaced apart from the electrode film 40 on the back surface 63. As a result, the laser light that has passed through the piezoelectric plate 30 in the trimming step passes through the exposed backside portion 61, preventing the electrode film 40 on the back surface 63 from being irradiated with the laser light and forming burrs. This makes it possible to suppress frequency fluctuations caused by burr shedding and deformation of the electrode film 40. Therefore, it is possible to suppress frequency fluctuations after frequency adjustment and manufacture a high-quality piezoelectric vibrating reed 3 with excellent vibration characteristics.

[0065] In the trimming step S40, a picosecond laser or a femtosecond laser is used, which, unlike the case where a nanosecond laser is used, can suppress the formation of burrs on the electrode film 40 and the weight metal film 50 on the front surface 64 side.

[0066] The electrode film forming process S20 includes an electrode film forming process S21 for forming the electrode film 40, and a patterning process S22 for patterning the electrode film 40 to form the excitation electrodes 41, 42 and the back-side exposed portion 61. This allows the back-side exposed portion 61 to be formed with the same processing accuracy as the excitation electrodes 41, 42. Furthermore, since no additional process for forming the back-side exposed portion 61 is required compared to conventional manufacturing methods, an increase in manufacturing costs can be suppressed.

[0067] Furthermore, since the piezoelectric vibrator 1 and oscillator 100 of this embodiment have the above-described piezoelectric vibrating piece 3, it is possible to provide a high-quality piezoelectric vibrator 1 and oscillator 100 with excellent operational reliability.

[0068] In the above embodiment, the exposed backside portion 61 is formed in the patterning step S22, but the method for forming the exposed backside portion 61 is not limited to this. In the electrode film forming step, the electrode film 40 may be formed with part of the back surface 63 of the vibrating arm portions 31, 32 masked, and the masked part may be used as the exposed backside portion 61. According to this method, the exposed backside portion 61 can be formed when the electrode film 40 is formed. Therefore, since no additional step for forming the exposed backside portion 61 is required compared to the conventional manufacturing method, an increase in manufacturing costs can be suppressed.

[0069] [Second embodiment] Next, a second embodiment will be described with reference to Figures 12 and 13. In the first embodiment, the front-side exposed portion 62 is formed to include the tip edge 64t of the surface 64 of the vibrating arm portions 31 and 32. In contrast, the second embodiment differs from the first embodiment in that the front-side exposed portion 62A is formed closer to the base end than the tip edge 64t of the surface 64 of the vibrating arm portions 31 and 32. Note that the configuration other than that described below is the same as that of the first embodiment.

[0070] Fig. 12 is a plan view of the piezoelectric vibrating reed according to the second embodiment, and Fig. 13 is a cross-sectional view taken along line XIII-XIII in Fig. 12. As shown in FIGS. 12 and 13 , the front-side exposed portion 62A is formed to include only the middle portions of a pair of side edges 64s on the surfaces 64 of the vibrating arms 31 and 32. As a result, the front portions 47A of the connection wiring 45 cover the leading edges 64t of the surfaces 64 of the vibrating arms 31 and 32 and are connected to the side portions 46 on the leading edges 64t of the surfaces 64. The weight metal film 50A is disposed on the front portion 47A of the connection wiring 45 on both sides of the front-side exposed portion 62A in the longitudinal direction L. The edges of the front portion 47A of the connection wiring 45 and the weight metal film 50A coincide with each other on the outline of the front-side exposed portion 62A in a plan view. In this embodiment, the entire front-side exposed portion 62A overlaps the back-side exposed portion 61 at a distance from the electrode film 40 on the back surfaces 63 of the vibrating arms 31 and 32 in a plan view.

[0071] As described above, in this embodiment, the entire front-side exposed portion 62A overlaps the back-side exposed portion 61 in plan view with a gap between them and the electrode film 40 on the back surface 63 of the vibrating arm portions 31, 32. Therefore, the piezoelectric vibrating piece 3A of this embodiment can achieve the same effects as those of the first embodiment.

[0072] The present invention is not limited to the above-described embodiment explained with reference to the drawings, and various modifications are possible within the technical scope of the present invention. For example, in the above embodiment, the piezoelectric vibrating reed 3 is a so-called side arm type vibrating reed in which the support arms 33, 34 are arranged outside the vibrating arms 31, 32. However, without being limited to this, the piezoelectric vibrating reed may be, for example, a so-called center arm type vibrating reed in which one support arm is arranged between a pair of vibrating arms, or a vibrating reed that does not have a support arm. Also, a configuration in which no grooves are formed in each vibrating arm may be used. Also, a configuration in which no weights are formed in each vibrating arm may be used.

[0073] 6 and 12, the edges of the weight metal films 50, 50A along the front-side exposed portions 62, 62A extend linearly in the width direction W, but the shape of the edges is not limited to this. For example, the edges of the weight metal films along the front-side exposed portions may extend concavely so as to be recessed inward of the weight metal film.

[0074] In the above embodiment, the back portion 48 of the connection wiring 45 straddles the base-end side edge of the weight metal film 50 in a plan view. However, the entire back portion of the connection wiring may be disposed closer to the base end than the weight metal film 50 in a plan view.

[0075] In addition, the components in the above-described embodiments can be replaced with well-known components as appropriate, without departing from the spirit of the present invention.

[0076] The present invention includes the following aspects. <1> a piezoelectric plate having a pair of vibrating arms; Electrode films disposed on the front and back surfaces of the piezoelectric plate; a weight metal film for adjusting a frequency, which is disposed on the electrode film on the surface side of the vibrating arm; Equipped with a rear surface of the vibrating arm portion having a rear-side exposed portion where the piezoelectric plate is exposed; the surface of the vibrating arm has a front-side exposed portion where the weight metal film and the electrode film are removed to expose the piezoelectric plate, the entirety of the front-side exposed portion overlaps the back-side exposed portion with a gap between it and the electrode film on the back surface when viewed in the thickness direction of the piezoelectric plate; Piezoelectric vibrating reed. <2> the electrode film is disposed on the end surface of the vibrating arm portion around the front-side exposed portion; <1> The piezoelectric vibrating piece according to claim 1. <3> the rear surface of the vibrating arm portion includes a tip edge on the tip side of the vibrating arm portion and a pair of side edges extending from the tip edge to the base end side of the vibrating arm portion, the rear-side exposed portion includes the tip edge and the side edge on the rear surface of the vibrating arm portion, <1> or <2> The piezoelectric vibrating piece according to claim 1. <4> a portion of the electrode film disposed on the rear surface of the vibrating arm portion straddling an edge of the weight metal film on the base end side of the vibrating arm portion when viewed from the thickness direction; <1> from <3> 10. The piezoelectric vibrating piece according to claim 1, wherein <5> <1> from <4> The piezoelectric vibrating piece according to any one of the above items, a package that hermetically seals the piezoelectric vibrating piece; A piezoelectric vibrator comprising: <6> <5> The piezoelectric vibrator according to claim 1, The piezoelectric vibrator is electrically connected to an integrated circuit as an oscillator. Oscillator. <7> an electrode film forming process of arranging electrode films on the front and rear surfaces of a piezoelectric plate having a pair of vibrating arm portions and forming a rear-side exposed portion where the piezoelectric plate is exposed on the rear surface of the vibrating arm portions; a metal film forming step of forming a weight metal film on the electrode film on the surface side of the vibrating arm portion so that at least a portion of the weight metal film overlaps with the rear-side exposed portion when viewed in a thickness direction of the piezoelectric plate; a trimming process of removing the weight metal film and the electrode film by a laser on the surface side of the vibrating arm portion within a range that overlaps the rear-side exposed portion when viewed from the thickness direction and is spaced apart from the electrode film on the rear surface; A method for manufacturing a piezoelectric vibrating piece comprising: <8> In the trimming step, a picosecond laser or a femtosecond laser is used. <7> 2. A method for manufacturing the piezoelectric vibrating piece according to claim 1 . <9> The electrode film forming step includes: an electrode film forming step of forming the electrode film; a patterning step of patterning the electrode film to form an excitation electrode and the rear side exposed portion; Equipped with <7> or <8> 2. A method for manufacturing the piezoelectric vibrating piece according to claim 1 . <10> The electrode film forming step includes forming the electrode film in a state where a part of the back surface of the vibrating arm portion is masked, and the part is made the back-side exposed portion. <7> or <8> 2. A method for manufacturing the piezoelectric vibrating piece according to claim 1 . [Explanation of symbols]

[0077] REFERENCE SIGNS LIST 1...piezoelectric vibrator 2...package 3,3A...piezoelectric vibrating piece 30...piezoelectric plate 31...first vibrating arm (vibrating arm) 32...second vibrating arm (vibrating arm) 40...electrode film 41,42...excitation electrode 50,50A...weight metal film 61...exposed back side portion 62,62A...exposed front side portion 63...back surface 63s...side edge 63t...tip edge 64...surface 100...oscillator 103...integrated circuit S20...electrode film forming process S21...electrode film deposition process S22...patterning process S30...metal film forming process S40...trimming process

Claims

1. a piezoelectric plate having a base and a pair of vibrating arms extending longitudinally from the base; Electrode films disposed on the front and rear surfaces of the piezoelectric plate; Equipped with The vibrating arm portion is a main body portion extending from a base end of the vibrating arm portion toward a tip end thereof; a weight portion located at a tip of the vibrating arm portion and wider than the main body portion; and a weight metal film for adjusting a frequency, which is disposed on the electrode film on the surface of the weight portion; a back surface of the weight portion, a back surface exposed portion where the piezoelectric plate is exposed; the surface of the weight portion has a front-side exposed portion where the weight metal film and the electrode film are removed to expose the piezoelectric plate; The electrode film is further disposed on a tip surface facing the longitudinal direction of the vibrating arm portion, the weight metal film is further formed on the electrode film formed on the tip surface, the entirety of the front-side exposed portion overlaps the back-side exposed portion with a gap between it and the electrode film on the back surface when viewed in the thickness direction of the piezoelectric plate; Piezoelectric vibrating reed

2. The electrode film disposed on the surface of the weight portion is the electrode film is formed from the base end of the weight portion toward the tip end thereof, and is formed across the boundary of the weight portion between the back-side exposed portion and the electrode film disposed on the back surface of the weight portion. The piezoelectric vibrating piece according to claim 1 .

3. When viewed in the thickness direction of the piezoelectric plate, the rear-side exposed portion has a length in the longitudinal direction that is greater than the length of the front-side exposed portion. The piezoelectric vibrating piece according to claim 2 .

4. the front-side exposed portion and the back-side exposed portion are formed continuously from the tip end to the base end of the vibrating arm portion. The piezoelectric vibrating piece according to claim 3 .

5. In the width direction of the piezoelectric plate, the entire front-side exposed portion overlaps at least the back-side exposed portion, The area of the rear-side exposed portion is larger than the area of the front-side exposed portion. The piezoelectric vibrating piece according to claim 4 .

6. the weight metal film is formed on the tip end side and the base end side of the weight portion in the longitudinal direction, with the front side exposed portion interposed therebetween, and is also formed on the electrode film; The piezoelectric vibrating piece according to claim 2 .

7. the exposed backside portion is formed continuously from the tip edge of the weight portion toward the base end side, The electrode film is a surface portion formed on a surface side of the weight portion; a back portion formed on a back side of the weight portion; and the back portion is formed continuously from the base end side to the tip end side of the weight portion, the weight metal film and the front portion are formed across the boundary between the rear-side exposed portion and the rear portion on the tip side; The piezoelectric vibrating piece according to claim 1 .

8. the interval is shorter than the length of the weight metal film; The piezoelectric vibrating piece according to claim 1 .

9. The piezoelectric vibrating piece according to any one of claims 1 to 8, a package that hermetically seals the piezoelectric vibrating piece; A piezoelectric vibrator comprising:

10. A piezoelectric vibrator according to claim 9, The piezoelectric vibrator is electrically connected to an integrated circuit as an oscillator. Oscillator.

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