Quartz crystal device, quartz crystal resonator element, and quartz crystal wafer

Abstract

To provide a crystal device having a low crystal impedance characteristic.SOLUTION: A package including a bottom plate having a rectangular shape in a plan view, a bank portion provided along an edge of the bottom plate, and an adhesive pad provided at one end side in a long side direction of an inner area surrounded by the bank portion; an AT-cut crystal vibrating piece having a rectangular shape in a plan view and having an excitation electrode, a pad electrode located at one end side in the long side direction, and an extraction electrode connected to the excitation electrode and the pad electrode formed on front and rear surfaces thereof; and, and a fixing member for fixing the crystal vibration piece to the bonding pad, wherein the ratio of the width of the extraction electrode to the dimension in the short side direction of the crystal vibration piece is 15% or more and less than 50%.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present disclosure relates to a quartz crystal device, a quartz crystal vibrating piece mounted on the quartz crystal device, and a quartz crystal wafer on which a plurality of quartz crystal vibrating pieces are formed. [Background technology]

[0002] Piezoelectric devices are widely used in various electronic devices such as mobile phones and personal computers, mainly for frequency selection and control. Piezoelectric devices can be classified into piezoelectric resonators, piezoelectric oscillators, SAW devices, optical devices, etc., depending on their function. Crystal devices, such as crystal resonators and crystal oscillators, which use quartz crystal as the piezoelectric element, are widely known and commonly used.

[0003] In recent years, there has been a growing demand for further miniaturization of such quartz crystal devices, and photolithography and wet etching techniques are being used. For example, Patent Document 1 discloses that a quartz crystal unit with a relatively low frequency is formed by adjusting the shape of the quartz crystal piece using photolithography and wet etching techniques. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 6613482 Summary of the Invention [Problem to be solved by the invention]

[0005] However, even for high-frequency crystal units with frequencies exceeding 100 MHz, although there is a demand for miniaturization, they cannot be designed in the same way as crystal units with frequencies of several tens of MHz. In particular, high-frequency crystal units require thinner electrode film thicknesses compared to low-frequency crystal units, and if the electrode film thickness is made thinner, there is a problem that the demand for low crystal impedance (hereinafter also referred to as low CI) cannot be fully met.

[0006] The present disclosure has been made in consideration of these problems, and its purpose is to provide a quartz crystal device with lower crystal impedance characteristics, a piezoelectric quartz crystal blank used therein, and a quartz crystal wafer consisting of multiple quartz crystal vibrating blanks. [Means for solving the problem]

[0007] According to one aspect of the present disclosure, there is provided a quartz crystal device comprising: a package including a bottom plate that is rectangular in plan view, a bank portion provided along the edge of the bottom plate, and an adhesive pad provided at one end of the long side of an inner area surrounded by the bank portion; an AT-cut quartz crystal vibrating piece that is rectangular in plan view and has an excitation electrode, a pad electrode located at one end of the long side, and extraction electrodes connecting the excitation electrode and the pad electrode formed on its front and back surfaces; and a fixing member that fixes the quartz crystal vibrating piece to the adhesive pad at a position where the pad electrode faces the adhesive pad, wherein the ratio of the width of the extraction electrode to the dimension of the short side of the quartz crystal vibrating piece is 15% or more and less than 50%.

[0008] According to one aspect of the present disclosure, there is provided a quartz crystal vibrating piece that is "rectangular in plan view, having excitation electrodes formed on the front and back surfaces, a pad electrode located on one end side of the long side of the quartz crystal vibrating piece, and an extraction electrode connecting to the excitation electrode and the pad electrode, wherein the ratio of the width of the extraction electrode to the dimension of the short side of the quartz crystal vibrating piece is 15% or more and less than 50%."

[0009] According to one aspect of the present disclosure, there is provided a quartz crystal wafer comprising: "a plurality of quartz crystal vibrating pieces that are rectangular in plan view, each having excitation electrodes formed on the front and back surfaces, a pad electrode located at one end of the quartz crystal vibrating piece in the long side direction, and an extraction electrode connected to the excitation electrode and the pad electrode, wherein the ratio of the width of the extraction electrode to the dimension in the short side direction of the quartz crystal vibrating piece is 15% or more and less than 50%, a frame portion to which the quartz crystal vibrating pieces are connected, and connection portions connecting each of the quartz crystal vibrating pieces to the frame portion." [Effects of the Invention]

[0010] According to the present disclosure, it is possible to provide a crystal device having low crystal impedance characteristics, a piezoelectric crystal blank used therein, and a crystal wafer made up of a plurality of crystal vibrating blanks.

[0011] It should be noted that the above effects are merely examples for the sake of convenience of explanation, and the effects of the present disclosure are not limited to these. In addition to the above effects, the present disclosure can achieve any of the effects described herein. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 1 is a perspective view of a quartz crystal resonator according to an embodiment. [Figure 2] 2(a) is an end view taken along dashed line AA in FIG. 1, FIG. 2(b) is a top view of the crystal resonator according to the embodiment, and FIG. 2(c) is an end view taken along dashed line BB in FIG. 2(a). [Figure 3] FIG. 3(a) is a side view of a quartz crystal vibrating piece included in the quartz crystal resonator according to the embodiment, and FIG. 3(b) is a surface view of the quartz crystal vibrating piece included in the quartz crystal resonator according to the embodiment. [Figure 4] FIG. 4(a) is a side view of the quartz crystal vibrating piece included in the quartz crystal resonator according to the embodiment, and FIG. 4(b) is a rear view of the quartz crystal vibrating piece included in the quartz crystal resonator according to the embodiment. [Figure 5]FIG. 5(a) is a graph showing the relationship between the lead wiring width and the prober CI in the quartz crystal unit used in the evaluation, and FIG. 5(b) is a graph showing the relationship between the lead wiring width and the wiring resistance in the quartz crystal unit used in the evaluation. [Figure 6] FIG. 6 is a graph showing the ratio of the lead wiring width to the Z direction dimension of the quartz crystal unit used in the evaluation. [Figure 7] FIG. 7 is a graph showing the ratio of the lead wiring width to the pad electrode width in the Z direction of the quartz crystal resonator used for evaluation. [Figure 8] FIG. 8(a) is a plan view of a quartz-crystal wafer according to the embodiment, and FIG. 8(b) is an enlarged view of region R1 in FIG. 8(a). [Figure 9] FIG. 9(a) is a back view of the state in which a mesa portion has been formed on each quartz crystal vibrating piece of the quartz crystal wafer according to the embodiment, and FIG. 9(b) is a plan view of the state in which an electrode has been formed on each quartz crystal vibrating piece of the quartz crystal wafer according to the embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0013] Below, with reference to the drawings, a quartz crystal resonator, a quartz crystal vibrating piece, and a quartz crystal wafer, which are examples of quartz crystal devices according to the present disclosure, will be described in detail. The present disclosure is not limited to the content described below and can be implemented with any modifications within the scope of the present disclosure. Furthermore, the drawings used in the embodiments are all schematic representations of the quartz crystal resonator, quartz crystal vibrating piece, and quartz crystal wafer according to the present disclosure. To facilitate understanding, some parts may be emphasized, enlarged, reduced, or omitted, and the scale or shape of each component may not be accurately represented. Furthermore, some numerical values ​​used in the embodiments are merely examples and may be subject to various modifications as necessary. The same reference symbols are used to designate common components throughout the drawings.

[0014] <Structure of a quartz crystal unit> First, the basic structure of a quartz crystal resonator and a quartz crystal vibrating piece according to the present disclosure will be described with reference to FIGS. 1 to 4. FIG. 1 is a perspective view of a quartz crystal resonator according to the present embodiment. FIG. 2(a) is an end view taken along dashed line AA in FIG. 1, FIG. 2(b) is a top view of the quartz crystal resonator according to the present embodiment, and FIG. 2(c) is an end view taken along dashed line BB in FIG. 2(a). FIG. 3(a) is a side view of a quartz crystal vibrating piece included in a quartz crystal resonator according to the present embodiment, particularly a side view in one direction showing the connection configuration related to the front electrodes of the quartz crystal vibrating piece. FIG. 3(b) is a front view of a quartz crystal vibrating piece included in a quartz crystal resonator according to the present embodiment. FIG. 4(a) is a side view of a quartz crystal vibrating piece included in a quartz crystal resonator according to the present embodiment, particularly a side view in another direction (opposite to the one direction) showing the connection configuration related to the back electrodes of the quartz crystal vibrating piece. FIG. 4(b) is a back view of a quartz crystal vibrating piece included in a quartz crystal resonator according to the present embodiment.

[0015] 1 and 2(a) to 2(c), a quartz crystal unit 1, which is an example of a quartz crystal device, has a quartz crystal unit package 2 (hereinafter simply referred to as package 2), a quartz crystal vibrating piece 3 mounted in a recessed mounting space 2a of the package 2, and a metal cover (lid) 4 for sealing the mounting space 2a. The quartz crystal unit 1 is an element that can generate a constant frequency due to the piezoelectric phenomenon when a voltage is applied to the quartz crystal vibrating piece 3, which is an example of a piezoelectric vibrating piece.

[0016] The package 2 is a ceramic package formed by stacking multiple ceramics with desired metal patterns formed on their surfaces. Specifically, the package 2 has a laminated structure in which an outer frame wall 11, which is a bank portion with an opening of a predetermined dimension, and a bottom plate 12 that is rectangular in plan view are stacked. In particular, the outer frame wall 11 is provided along the edge of the bottom plate 12. Due to this laminated structure, the package 2 has a mounting space 2a with a recess for mounting the quartz crystal vibrating piece 3. Furthermore, an area for mounting the quartz crystal vibrating piece 3 is formed on the surface of the bottom plate 12 in the mounting space 2a, and electrode pads, described below, are provided around this area.

[0017] Here, the shape of the package 2 is a rectangular parallelepiped, and is rectangular when viewed from above (FIG. 2(b)). In the following, the thickness direction of the crystal unit 1 and the package 2 is referred to as the vertical direction, and the direction perpendicular to the vertical direction is referred to as the horizontal direction. The horizontal direction may also be distinguished as the long side direction (longitudinal direction) and the short side direction (transverse direction) of the crystal unit 1 and the package 2. Furthermore, the surface of each component located above in the vertical direction may also be referred to as the front surface, and the surface located below may also be referred to as the back surface.

[0018] A sealing conductor pattern 13 is formed on the exposed surface (the surface located on the upper vertical side) of the outer frame wall 11 of the package 2. The planar shape of the conductor pattern 13 is frame-like, just like the outer frame wall 11. A cover 4 is bonded onto the conductor pattern 13 by known metal bonding. This seals the mounting space 2a of the package, and the mounting space 2a is sealed using a vacuum or a gas such as nitrogen.

[0019] Two crystal resonator element mounting terminals 16 and 17, which are adhesive pads, are formed on the exposed surface (the surface located vertically above) of the bottom plate 12 of the package 2. In particular, the crystal resonator element mounting terminals 16 and 17 are provided on one end of the long side in the inner area surrounded by the outer frame wall 11. The crystal resonator element 3 is mounted on the crystal resonator element mounting terminals 16 and 17 via a conductive adhesive 18. Meanwhile, four external connection terminals 19a, 19b, 19c, and 19d are formed on the four corners of the back surface of the bottom plate 12 of the package 2. The crystal resonator element mounting terminals 16 and 17 are electrically connected to the external connection terminals 19a, 19b, 19c, and 19d via connection wiring (not shown) provided inside the package 2.

[0020] As can be seen from Figures 3(a), 3(b), 4(a), and 4(b), the quartz crystal vibrating piece 3 is composed of a flat excitation portion 3a on one end, a mesa portion 3b on the other end that is thicker than the excitation portion 3a, and an inclined portion 3c located between the excitation portion 3a and the mesa portion 3b. The quartz crystal vibrating piece 3 is rectangular in plan view. Furthermore, as shown in Figure 2(b), the quartz crystal vibrating piece 3 is mounted so that its long and short sides are aligned with the long and short sides of the quartz crystal unit 1. In other words, the long and short sides of the quartz crystal vibrating piece 3 coincide with the long and short sides of the quartz crystal unit 1, respectively.

[0021] The excitation portion 3a has a thickness corresponding to the frequency at which the crystal resonator 1 oscillates, and is the portion that generates the required vibrations. In contrast, the mesa portion 3b is provided to improve the adhesive strength and ease of bonding of the crystal resonator piece 3. The inclined portion 3c has a shape in which its thickness gradually increases from the excitation portion 3a toward the mesa portion 3b. This shape is formed due to the characteristics of the crystal structure of the crystal when the excitation portion 3a is made to a predetermined thickness by etching.

[0022] In addition, in this embodiment, the oscillation frequency of the crystal unit 1 is not particularly limited, but is preferably applied to high-frequency band elements. A specific frequency is 100 MHz or more and 160 MHz or less. That is, when oscillating at a fundamental wave (n=1), the thickness of the crystal unit 3 (more specifically, the thickness of the excitation portion 3a) is expected to be 8 μm or more and 16 μm or less. Crystal unit 1 with such a high oscillation frequency has a small electrode diameter relative to the chip size, making it easier to trap vibration energy compared to crystal unit with a low oscillation frequency of less than 100 MHz. Furthermore, by implementing the electrode design described below, it becomes easier to achieve low crystal impedance (low CI).

[0023] Electrodes are formed on the front and back surfaces of the quartz crystal vibrating piece 3, allowing a voltage to be applied to the quartz crystal vibrating piece 3. Specifically, as can be seen from FIGS. 3(a) and 3(b), a first surface electrode 20 and a second surface electrode 30 are formed on the surface of the quartz crystal vibrating piece 3. The first surface electrode 20 is composed of an excitation electrode 21 formed on the surface of the excitation portion 3a, a pad electrode 22 formed on the surface of the mesa portion 3b, and an extraction electrode 23 connecting the excitation electrode 21 and the pad electrode 22. Here, the extraction electrode 23 is composed of a rectangular portion 23a extending in the direction of the long sides of the quartz crystal vibrating piece 3, and an inclined portion 23b extending from the rectangular portion 23a toward the excitation electrode 21 and inclined with respect to the direction of the long sides of the quartz crystal vibrating piece 3.

[0024] The second surface electrode 30 is formed on the surface of the mesa portion 3b in parallel with the pad electrode 22, and has the same dimensions and shape as the pad electrode 22.

[0025] 4(a) and 4(b), a first back surface electrode 40 and a second back surface electrode 50 are formed on the back surface of the quartz crystal vibrating piece 3. The first back surface electrode 40 is composed of an excitation electrode 41 formed on the back surface of the excitation portion 3a, a pad electrode 42 formed on the back surface of the mesa portion 3b, and an extraction electrode 43 connecting the excitation electrode 41 and the pad electrode 42. Here, the extraction electrode 43 is composed of a rectangular portion 43a extending in the long side direction of the quartz crystal vibrating piece 3, and an inclined portion 43b extending from the rectangular portion 43a toward the excitation electrode 21 and inclined with respect to the long side direction of the quartz crystal vibrating piece 3.

[0026] 3(b) and 4(a), the pad electrode 42 is formed to face the second surface electrode 30 formed on the surface side of the quartz-crystal vibrating piece 3. Furthermore, the second back surface electrode 50 is formed juxtaposed to the pad electrode 42 on the back surface of the mesa portion 3b, and has the same dimensions and shape as the pad electrode 42. Furthermore, as can be seen from FIGS. 3(a), 3(b), and 4(b), the second back surface electrode 50 is formed to face the pad electrode 22 formed on the surface side of the quartz-crystal vibrating piece 3.

[0027] 3(a), the first surface electrode 20 formed on the surface side of the quartz crystal vibrating piece 3 is electrically connected to the second back surface electrode 50 via a side electrode 60 formed on a side surface of the quartz crystal vibrating piece 3. Meanwhile, as shown in FIG. 4(a), the first back surface electrode 40 formed on the back surface side of the quartz crystal vibrating piece 3 is electrically connected to the second surface electrode 30 via a side electrode 70 formed on a side surface of the quartz crystal vibrating piece 3.

[0028] 4(b), a conductive adhesive 18 is positioned on the pad electrode 42 of the first back electrode 40 and the second back electrode 50, and the quartz-crystal vibrating piece 3 is fixed to the quartz-crystal vibrating piece mounting terminals 16, 17 by the conductive adhesive 18. That is, the mesa portion 3b is bonded to the quartz-crystal vibrating piece mounting terminals 16, 17 by the conductive adhesive 18 at a position where the mesa portion 3b faces the quartz-crystal vibrating piece mounting terminals 16, 17.

[0029] In this embodiment, based on the evaluation results of the quartz crystal resonator 1 described later, the following electrode design is adopted to achieve a low CI for the quartz crystal resonator 1. Specifically, in FIG. 3(b), the ratio of the width (L2) of the rectangular portion 23a of the extraction electrode 23 to the dimension (L1) in the short-side direction of the quartz crystal resonator piece 3 is preferably 15% or more and less than 50%. More preferably, the ratio of the width (L2) of the rectangular portion 23a of the extraction electrode 23 to the dimension (L1) in the short-side direction of the quartz crystal resonator piece 3 is 18% or more and 30% or less. Furthermore, in addition to the above conditions, the ratio of the width (L2) of the rectangular portion 23a of the extraction electrode 23 to the dimension (L3) of the pad electrode 22 in the short-side direction of the quartz crystal resonator piece 3 is preferably 32% or more and 70% or less.

[0030] 3(b), the angle θ formed between the excitation electrode 21 and the inclined portion 23b of the extraction electrode 23 is preferably 60 degrees or more and 70 degrees or less, and particularly preferably 61 degrees or more and 65 degrees or less. Here, the angle θ is the angle at which one side of the inclined portion 23b (a straight line along the inclined portion 23b) intersects with one side in the long side direction of the excitation electrode 21. In other words, when the inclination angle of the inclined portion 23b is defined as the angle θ of the crystal axis of the quartz with respect to the X-axis, it is preferably 60 degrees or more and 70 degrees or less, and particularly preferably 61 degrees or more and 65 degrees or less.

[0031] Naturally, since the electrodes on the front and back surfaces of the quartz crystal vibrating piece 3 have the same dimensions, the ratio of the width of the rectangular portion 43a of the extraction electrode 43 to the dimension (L1) in the short-side direction of the quartz crystal vibrating piece 3 is also the same as the design on the front surface side. In addition, the ratio of the width of the rectangular portion 43a of the extraction electrode 23 to the width of the pad electrode 42 in the short-side direction of the quartz crystal vibrating piece 3 is also the same as the design on the front surface side. Furthermore, the angle between the excitation electrode 41 and the inclined portion 43b of the extraction electrode 43 is also the same as the design on the front surface side.

[0032] <Evaluation of electrodes on quartz crystal units> Next, with reference to Figures 5(a), 5(b), 6, and 7, we will explain the electrode evaluation of a quartz crystal unit that was carried out to derive the above-mentioned electrode design. Here, Figure 5(a) is a graph showing the relationship between the lead line width and prober CI in the quartz crystal unit used in the evaluation. Also, Figure 5(b) is a graph showing the relationship between the lead wiring width and wiring resistance in the quartz crystal unit used in the evaluation. Furthermore, Figure 6 is a graph showing the ratio of the lead wiring width to the Z-direction dimension in the quartz crystal unit used in the evaluation. Finally, Figure 7 is a graph showing the ratio of the lead wiring width to the electrode pad width in the Z-direction dimension in the quartz crystal unit used in the evaluation.

[0033] First, three types of crystal resonators (samples) were prepared as shown in Table 1 below.

[0034] [Table 1]

[0035] Here, the crystal unit size refers to the external dimensions of the package. The X dimension refers to the dimension along the long side of the crystal resonator element, and the Z dimension (L1) refers to the dimension along the short side of the crystal resonator element. The pad electrode width (L3) refers to the dimension of the pad electrode along the short side of the crystal resonator element (i.e., the Z direction).

[0036] For the first type of sample, a quartz crystal unit (sample C1) with a frequency of 125 MHz, the width of the extraction electrode was adjusted by adjusting the width (L2) of the rectangular portion of the extraction electrode, and 30 to 32 pieces of each of five types were prepared: 69 μm, 89 μm, 109 μm, 129 μm, and 149 μm, as shown in Table 2 below.

[0037] [Table 2]

[0038] Here, L2 / L1 (%) is the ratio of the width of the rectangular portion of the extraction electrode to the dimension in the short side direction of the quartz crystal resonator element. Also, L2 / L3 (%) is the ratio of the width of the extraction electrode to the width of the pad electrode. Furthermore, CI (Ω) is the value measured using an impedance analyzer in the photo wafer state before assembly and adjustment into a quartz crystal resonator, and is the median value of multiple samples.

[0039] For the second type of sample, a quartz crystal unit (sample C2) with a frequency of 153.6 MHz, the width of the extraction electrode was adjusted by adjusting the width (L2) of the rectangular portion of the extraction electrode, and 500 to 600 pieces of each of ten types were prepared: 56 μm, 66 μm, 76 μm, 86 μm, 96 μm, 106 μm, 116 μm, 126 μm, 136 μm, and 146 μm, as shown in Table 3 below.

[0040] [Table 3]

[0041] For the third sample, a quartz crystal unit (sample C3) with a frequency of 156.25 MHz, the width of the extraction electrode was adjusted by adjusting the width (L2) of the rectangular portion of the extraction electrode, and 30 to 32 pieces of each of five types were prepared: 69 μm, 89 μm, 109 μm, 129 μm, and 149 μm, as shown in Table 4 below.

[0042] [Table 4]

[0043] Next, as shown in Figure 5(a), for sample C2 (153.6 MHz), we investigated the influence of the interconnect width on the prober CI, with the interconnect width (μm) on the horizontal axis and the prober CI (Ω) on the vertical axis. Note that in Figure 5(a), four samples for each interconnect width are plotted.

[0044] As can be seen from Figure 5(a), the prober CI decreases as the interconnect width increases. In particular, when the interconnect width is 96 μm or more, the change in prober CI becomes small and remains constant at around 25 Ω.

[0045] Next, as shown in Figure 5(b), for sample C2 (153.6 MHz), we investigated the effect of the lead wire width on the wiring resistance, with the lead wire width (μm) on the horizontal axis and the wiring resistance (Ω) on the vertical axis. Here, since the value of the wiring resistance is very small, we measured the wiring resistance using the four-terminal measurement method. To measure the wiring resistance more specifically, we used a semiconductor analyzer to measure the resistance between the pad electrode and the tip of the excitation electrode (a position farther away from the pad electrode in the long side direction of the quartz crystal resonator element). Note that Figure 5(b) plots three samples for each lead wire width: 56 μm, 76 μm, 96 μm, 116 μm, and 136 μm.

[0046] As can be seen from Figure 5(b), the wiring resistance decreases as the wiring width increases. In particular, when the wiring width is 96 μm or more, the change in wiring resistance becomes smaller, and it is expected to tend to remain constant at around 10 Ω. This is presumably because the volume resistivity of the gold thin film, which is an example of an electrode material, decreases as the wiring area increases.

[0047] 5(a) and 5(b), it can be seen that by making the wiring width larger than a certain size, the CI value of the quartz crystal unit can be reduced and the value can be made to have small fluctuations. In other words, by making the wiring width larger than a certain size, it is possible to reduce the variation in the CI value due to the variation in electrode dimensions during the manufacturing of the quartz crystal unit.

[0048] Next, based on the results of Figures 5(a) and 5(b), we investigated how to adjust the lead electrode width to reduce the CI value of the crystal unit, regardless of the dimensions of the crystal unit and crystal blank, and regardless of the frequency (i.e., thickness) of the crystal unit. Specifically, we evaluated the relationship between the lead electrode width and the Z dimension (short side dimension) of the crystal blank, and the relationship between the lead electrode width and the pad electrode width, based on samples of the three frequencies mentioned above.

[0049] First, as shown in Figure 6, for each sample (C1, C2, C3), the horizontal axis represents the value obtained by dividing the lead wiring width (L2) by the Z dimension of the quartz crystal vibrating blank, and the vertical axis represents the prober CI (Ω) to examine the effect of the ratio of the lead electrode width to the Z dimension of the quartz crystal vibrating blank on the prober CI. Note that Figure 6 plots the L2 / L1 (%) values ​​from Tables 2 to 4 for each sample. Figure 6 also displays approximate curves (shown by dashed lines) based on the plots for each sample (C1, C2, C3).

[0050] As can be seen from Figure 6, for all samples, the prober CI decreases as the L2 / L1 value increases from 10% or more. In particular, for sample C2, the fluctuation in prober CI becomes smaller and becomes approximately 30Ω or less when the L2 / L1 value becomes 15% or more, and the prober CI becomes a constant value (approximately 26Ω) when the L2 / L1 value becomes 18% or more. It can also be said that the fluctuation in prober CI becomes smaller for samples C1 and C3 when the L2 / L1 value becomes 15% or more.

[0051] On the other hand, according to the approximation curve for sample C2, when the L2 / L1 value exceeds 25%, the prober CI value tends to increase. In particular, when the L2 / L1 value exceeds 30%, the prober CI value becomes 30Ω or more, and its fluctuation also becomes large. Similarly, according to the approximation curves for samples C1 and C3, when the L2 / L1 value exceeds 30%, the prober CI value tends to increase. However, for samples C1 and C3, even when the L2 / L1 value exceeds 30%, there is no tendency for the fluctuation of the prober CI to become large, as with sample C2.

[0052] Based on these results, we set the preferable lower limit of L2 / L1 at L2 / L1 = 15%, which minimizes fluctuations in the prober CI value. Furthermore, taking into account the leakage of vibration energy, we estimated that the limit for the extraction electrode dimensions is approximately half the dimension in the short side direction of the quartz crystal vibrating blank, and set the preferable upper limit of L2 / L1 at L2 / L1 = 50%. Furthermore, we estimated that a range in which the prober CI value remains constant is more preferable, and set the preferable range for L2 / L1 to be between 18% and 30%.

[0053] Next, as shown in Fig. 7, for each sample (C1, C2, C3), the horizontal axis represents the value obtained by dividing the lead wiring width (L2) by the pad electrode width (L3), and the vertical axis represents the prober CI (Ω), to study the effect of the ratio of the lead electrode width to the pad electrode width on the prober CI. Note that Fig. 7 plots the L2 / L3 (%) values ​​from Tables 2 to 4 for each sample. Also shown in Fig. 7 are approximate curves (shown by dashed lines) based on the plots for each sample (C1, C2, C3).

[0054] As can be seen from Figure 7, for all samples, the prober CI decreases as the L2 / L3 value increases from 25% or higher. In particular, for sample C2, the fluctuation in prober CI decreases when the L2 / L3 value is 34% or higher, reaching approximately 30Ω or less, and the prober CI becomes a constant value (approximately 26Ω) when the L2 / L3 value is 43% or higher. Also, for samples C1 and C3, the fluctuation in prober CI decreases when the L2 / L3 value is 25% or higher, and decreases when the L2 / L3 value is 32% or higher.

[0055] On the other hand, according to the approximation curve for sample C2, when the L2 / L3 value exceeds 60%, the prober CI value tends to increase. In particular, when the L2 / L3 value exceeds 70%, the prober CI value becomes 28 Ω or more, and its fluctuation also becomes larger. Furthermore, according to each approximation curve for sample C1 and sample C3, the prober CI value tends to decrease until the L2 / L3 value reaches 70%.

[0056] From these results, we inferred that the range in which the prober CI value is constant is the preferable range, and set the L2 / L3 range to be 32% or more and 70% or less. Furthermore, we found that the range in which the prober CI value is more stable is more preferable when the L2 / L3 range is 40% or more and 60% or less.

[0057] <Manufacturing method> Next, a method for manufacturing a quartz crystal wafer W and quartz crystal vibrating pieces 3 according to the present disclosure will be described with reference to Figures 8 and 9. Figure 8(a) is a plan view of the quartz crystal wafer W according to the present embodiment. Figure 8(b) is an enlarged view of region R1 in Figure 8(a). Figure 9(a) is a rear view of the quartz crystal wafer W according to the present embodiment, with mesas 3b formed on each quartz crystal vibrating piece 3. Figure 9(b) is a plan view of the quartz crystal wafer W according to the present embodiment, with electrodes formed on each quartz crystal vibrating piece 3.

[0058] First, prepare a quartz crystal wafer W with a roughly circular planar shape, as shown in Figure 8(a). For example, it may be an AT-cut quartz crystal cut from a rough quartz crystal. However, the planar shape is not limited to a circular shape and may be rectangular, and the cut is not limited to an AT-cut but may be other cuts such as a Z-cut or SC-cut, which are two-turn cuts.

[0059] Next, a metal film for forming an etching-resistant mask is formed on the front and back surfaces of the quartz-crystal wafer W. Subsequently, the metal film is processed using well-known photolithography techniques to form etching-resistant masks for defining the outline of the quartz-crystal vibrating pieces 3 on both the front and back surfaces of the quartz-crystal wafer W. In this embodiment, the etching-resistant mask has a structure corresponding to the outline of the quartz-crystal vibrating pieces 3, a frame portion 91 (see FIG. 8(b)) formed to surround the multiple quartz-crystal vibrating pieces 3, and multiple connection portions 92 (see FIG. 8(b)) connecting the frame portion 91 to each of the quartz-crystal vibrating pieces 3. After that, the quartz-crystal wafer W with the etching-resistant mask formed thereon is immersed for a predetermined period of time in an etching solution primarily composed of hydrofluoric acid. This process dissolves the portions of the quartz-crystal wafer W not covered by the etching-resistant mask, resulting in the rough outline of the quartz-crystal vibrating pieces 3, as shown in FIG. 8(b). The number of connecting portions 92 for each quartz-crystal vibrating piece 3 is not limited to four as shown in FIG. 8(b), but may be two, three, five or more, or even one.

[0060] Next, the etching-resistant mask is removed from the quartz-crystal wafer W. At this time, only the portions of the etching-resistant mask corresponding to the excitation portion 3a and inclined portion 3c of the quartz-crystal vibrating piece 3 are removed, leaving behind the mesa portion 3b of the quartz-crystal vibrating piece 3 and the portions corresponding to the frame portion 91 and connecting portion 92 of the quartz-crystal wafer W. This makes it possible to form the inclined portion 3c located between the excitation portion 3a and the mesa portion 3b, and to ensure the strength of the frame portion 91 and connecting portion 92.

[0061] Next, the quartz-crystal wafer W with the etching-resistant mask partially removed is immersed again in an etching solution primarily composed of hydrofluoric acid for a predetermined time. The predetermined time is the time required for the thickness of the region where the excitation portion 3a of the quartz-crystal vibrating piece 3 is to be formed to a thickness that satisfies the required oscillation frequency specifications. Furthermore, due to the crystalline structure of the quartz-crystal wafer W, the amount of etching between the excitation portion 3a and the mesa portion 3b gradually increases toward the excitation portion 3a, resulting in the formation of a sloped portion 3c (see FIG. 9(a)).

[0062] Next, the etching-resistant mask is removed from the quartz crystal wafer W after the above etching is completed, exposing the entire surface of the quartz crystal wafer W. Then, a metal film for each electrode of the quartz crystal vibrating piece 3 is formed on the entire surface (front and back surfaces) of the quartz crystal wafer W using a well-known film-forming method. Next, the metal film is patterned into the shape of the electrodes using well-known photolithography and metal etching techniques, forming each electrode on the front and back surfaces of the quartz crystal wafer W, as shown in FIGS. 3(b), 4(b), and 9(b). Then, the connecting portions 92 are cut or removed to separate each quartz crystal vibrating piece 3 from the frame portion 91, thereby completing the formation of the quartz crystal vibrating piece 3 with the electrodes formed thereon.

[0063] The cutting and removal of the connecting portion 92 may be performed by etching or mechanically. If the cutting and removal is performed mechanically, finishing such as etching may be performed to remove unnecessary portions of the quartz crystal vibrating piece 3.

[0064] (Modification of the embodiment) In the above embodiment, a crystal resonator has been described as an example of a crystal device, but this is not limiting. That is, the crystal device of the present disclosure may also be a crystal oscillator in which the crystal resonator element 3 of the present embodiment is mounted. In this case, the crystal oscillator may have a structure in which the crystal resonator element 3 is mounted in the same space as the IC chip, or may have an H-shaped structure in which the crystal resonator element 3 faces the IC chip via a bottom plate.

[0065] In the above embodiment, the frequency of the crystal unit 1 is set to a high frequency of 100 MHz or more, but this is not limited to this and may be a low frequency of several tens of MHz. Even in such a case, it is expected that low crystal impedance can be achieved by adopting the above electrode design.

[0066] Furthermore, in the above embodiment, the mesa portion 3b and the inclined portion 3c are provided at one end of the quartz-crystal vibrating piece 3, but these may be omitted. That is, the shape of the quartz-crystal vibrating piece 3 may be a flat plate having the thickness of the excitation portion 3a. Furthermore, when the frequency of the quartz-crystal resonator 1 is several tens of MHz, the quartz-crystal vibrating piece 3 may have a shape in which both ends are tapered.

[0067] (Embodiments of the present disclosure) A first embodiment of the present disclosure is a quartz crystal device comprising: a package including a rectangular bottom plate in plan view, a bank along the edge of the bottom plate, and an adhesive pad at one end of a long side of an inner region enclosed by the bank; an AT-cut quartz crystal element having a rectangular shape in plan view and including excitation electrodes, pad electrodes at one end of the long side, and extraction electrodes connecting the excitation electrodes and the pad electrodes on both surfaces; and a fixing member for fixing the quartz crystal element to the adhesive pad at a position where the pad electrodes face the adhesive pad, wherein the ratio of the width of the extraction electrode to the short side dimension of the quartz crystal element is 15% or more but less than 50%. This ratio of the width of the extraction electrode to the short side dimension of the quartz crystal element reduces the wiring resistance of the electrodes and reduces the crystal impedance of the quartz crystal unit.

[0068] In a second embodiment of the present disclosure, the ratio of the width of the extraction electrode to the dimension of the short side of the quartz crystal resonator element in the first embodiment is 18% to 30%, which further reduces and stabilizes the wiring resistance of the electrodes, thereby reducing the crystal impedance of the quartz crystal resonator and reducing its variation.

[0069] In a third embodiment of the present disclosure, in the first or second embodiment, the ratio of the width of the extraction electrode to the width of the pad electrode in the short side direction of the quartz crystal vibrating piece is 32% to 70%, which further reduces and stabilizes the wiring resistance of the electrodes, thereby reducing the crystal impedance of the quartz crystal vibrator and reducing its variation.

[0070] In a fourth embodiment of the present disclosure, in any one of the first to third embodiments, the thickness of the quartz crystal resonator element is 8 μm or more and 16 μm or less, thereby enabling the frequency of the quartz crystal resonator to be 100 MHz or more, and providing a high-frequency quartz crystal resonator with low crystal impedance characteristics.

[0071] In a fifth embodiment of the present disclosure, in any of the first to fourth embodiments, the extraction electrode includes a rectangular portion extending from the pad electrode toward the long side of the quartz crystal resonator element, and an inclined portion extending from the rectangular portion toward the excitation electrode and inclined with respect to the long side of the quartz crystal resonator element. This reduces and stabilizes the wiring resistance of the electrode, thereby reducing the crystal impedance of the quartz crystal resonator and reducing its variation.

[0072] A sixth embodiment of the present disclosure is a quartz crystal vibrating piece that is rectangular in plan view, and includes excitation electrodes formed on both surfaces, pad electrodes located at one end of the long side of the quartz crystal vibrating piece, and extraction electrodes connected to the excitation electrodes and the pad electrodes, wherein the ratio of the width of the extraction electrodes to the short side dimension of the quartz crystal vibrating piece is 15% or more but less than 50%. This ratio of the width of the extraction electrodes to the short side dimension of the quartz crystal vibrating piece reduces the wiring resistance of the electrodes and reduces the crystal impedance of the quartz crystal unit.

[0073] A seventh embodiment of the present disclosure is a quartz crystal wafer including a plurality of quartz crystal vibrating pieces according to the sixth embodiment, a frame to which the plurality of quartz crystal vibrating pieces are connected, and a connecting portion connecting each of the quartz crystal vibrating pieces to the frame, thereby enabling the simultaneous formation and supply of a plurality of piezoelectric vibrating pieces. [Explanation of symbols]

[0074] 1 crystal oscillator 2 Crystal oscillator package (package) 2a Mounting space 3 Crystal vibrating piece 3a Excitation part 3b Mesa section 3c Slope 4 Cover (Lid) 11 Outer frame wall (bank section) 12 Bottom plate 16,17 Crystal unit mounting terminals (adhesive pads) 18 Conductive adhesive 20 1st surface electrode 21 Excitation electrode 22 Pad electrode 23 Extraction electrode 23a Rectangular part 23b Slope 30 2nd surface electrode 40 First rear surface electrode 41 Excitation electrode 42 Pad electrode 43 Extraction electrode 43a Rectangular part 43b Slope 50 Second rear electrode 60,70 side electrode 91 Frame 92 Connection W quartz crystal wafer

Claims

1. a package including a bottom plate having a rectangular shape in a plan view, a bank portion provided along an edge of the bottom plate, and an adhesive pad provided on one end side in a long side direction of an inner region surrounded by the bank portion; an AT-cut quartz crystal vibrating piece having a rectangular shape in a plan view, the quartz crystal vibrating piece having an excitation electrode, a pad electrode located at one end of a long side direction, and extraction electrodes connected to the excitation electrode and the pad electrode formed on its front and back surfaces; a fixing member that fixes the crystal vibrating piece to the bonding pad at a position where the pad electrode faces the bonding pad, A quartz crystal device, wherein the ratio of the width of the extraction electrode to the dimension of the short side of the quartz crystal vibrating piece is 15% or more and less than 50%.

2. 2. The quartz crystal device according to claim 1, wherein a ratio of the width of the extraction electrode to the dimension of the quartz crystal vibrating piece in the short side direction is 18% or more and 30% or less.

3. 2. The quartz crystal device according to claim 1, wherein a ratio of the width of the extraction electrode to the width of the pad electrode in the short side direction of the quartz crystal vibrating piece is 32% or more and 70% or less.

4. 2. The quartz crystal device according to claim 1, wherein the thickness of the quartz crystal resonator element is 8 μm or more and 16 μm or less.

5. 2. The quartz crystal device according to claim 1, wherein the extraction electrode includes a rectangular portion extending from the pad electrode toward the long side of the quartz crystal vibrating piece, and an inclined portion extending from the rectangular portion toward the excitation electrode and inclined with respect to the long side of the quartz crystal vibrating piece.

6. A quartz crystal resonator element having a rectangular shape in a plan view, excitation electrodes formed on the front and back surfaces; a pad electrode located on one end side of the crystal vibrating piece in the long side direction; a lead electrode connected to the excitation electrode and the pad electrode; A quartz crystal vibrating piece, wherein the ratio of the width of the extraction electrode to the dimension of the short side of the quartz crystal vibrating piece is 15% or more and less than 50%.

7. A plurality of quartz crystal vibrating pieces according to claim 6; a frame portion to which the crystal vibrating piece is connected; and connecting portions that connect each of the crystal vibrating pieces to the frame portion.

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