Quartz crystal elements and crystal devices

Abstract

A crystal vibration element (1) comprises: a crystal piece (C) that has an oscillation frequency in a range of 50-100 MHz; and excitation electrodes (EU) that are respectively positioned on both surfaces of the crystal piece (C), and each have a rectangular shape smaller than the crystal piece (C) in a plan view. The excitation electrodes (EU) each have a length in a first direction along an electrical axis direction of the crystal piece (C) in a plan view that is 1.993 to 2.525 times the width in a second direction perpendicular to the first direction.

Description

[Technical field]

[0001] The present disclosure relates to a quartz crystal resonator element and a quartz crystal device. [Background technology]

[0002] In a quartz crystal vibration element that generates a clock signal by oscillating a quartz crystal piece, an oscillation frequency according to the thickness of the quartz crystal piece can be obtained. In recent years, as the frequency of the required clock signal increases, the number of quartz crystal vibration elements in the 50-100 MHz band, such as a nominal frequency of 76.8 MHz, has increased. JP 2020-99038 A discloses a technology for making the fixed portion of the quartz crystal piece thicker than the vibrating portion and appropriately determining the ratio of the long side dimension and the short side dimension of the vibrating portion in order to obtain better oscillation frequency characteristics at this frequency. Summary of the Invention

[0003] One aspect of the present disclosure is A crystal piece having an oscillation frequency in the range of 50 MHz to 100 MHz, Electrodes each having a rectangular shape in a plan view and smaller than the crystal piece, each electrode being located on both sides of the crystal piece; A lead conductor having one end connected to an outer edge extending along a second direction perpendicular to a first direction along the X-axis direction of the crystal piece in a plan view of the electrode; Equipped with The electrode has a length in the first direction that is 1.993 times or more and 2.525 times or less than its width in the second direction; The lead conductor is linear. the law of nature , The distances from both ends of the crystal piece to the ends of the electrodes in the second direction in a plan view are each 0.130 mm or more and 0.195 mm or less. It is a quartz crystal oscillator element. [Brief description of the drawings]

[0004] [Figure 1] 2 is a diagram showing the shape of a cross section of the crystal device of the present embodiment. FIG. [Figure 2A] 1 is a plan view showing a configuration of a quartz crystal vibrating element according to an embodiment of the present invention. [Figure 2B]FIG. 2 is a cross-sectional view of a quartz crystal vibration element. [Figure 2C] FIG. 2 is a side view of the quartz crystal vibration element. [Figure 3A] FIG. 13 is a diagram showing an example of an aspect ratio of an excitation electrode. [Figure 3B] FIG. 11 is a diagram showing experimental results of temperature characteristics of frequency deviation according to the aspect ratio of the excitation electrodes. [Figure 3C] FIG. 13 is a diagram showing experimental results of the temperature characteristics of ESR according to the aspect ratio of the excitation electrodes. [Figure 4A] FIG. 13 is a diagram showing an example of an aspect ratio of an excitation electrode. [Figure 4B] FIG. 11 is a diagram showing experimental results of temperature characteristics of frequency deviation according to the aspect ratio of the excitation electrodes. [Figure 4C] FIG. 13 is a diagram showing experimental results of the temperature characteristics of ESR according to the aspect ratio of the excitation electrodes. [Figure 5A] FIG. 13 is a diagram showing an example of an aspect ratio of an excitation electrode. [Figure 5B] FIG. 11 is a diagram showing experimental results of temperature characteristics of frequency deviation according to the aspect ratio of the excitation electrodes. [Figure 5C] FIG. 13 is a diagram showing experimental results of the temperature characteristics of ESR according to the aspect ratio of the excitation electrodes. [Figure 6A] FIG. 13 is a diagram showing an example of an aspect ratio of an excitation electrode. [Figure 6B] FIG. 11 is a diagram showing experimental results of temperature characteristics of frequency deviation according to the aspect ratio of the excitation electrodes. [Figure 6C] FIG. 13 is a diagram showing experimental results of the temperature characteristics of ESR according to the aspect ratio of the excitation electrodes. [Figure 7A] FIG. 13 is a diagram showing an example of an aspect ratio of an excitation electrode. [Figure 7B] FIG. 11 is a diagram showing experimental results of temperature characteristics of frequency deviation according to the aspect ratio of the excitation electrodes. [Figure 7C] FIG. 13 is a diagram showing experimental results of the temperature characteristics of ESR according to the aspect ratio of the excitation electrodes. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0005] Hereinafter, an embodiment will be described with reference to the drawings. FIG. 1 is a diagram showing the shape of a cross section of a crystal device 100 according to this embodiment. The quartz crystal device 100 includes a quartz crystal vibrating element 1, a base body 2, a cover body 3, a component 4, and the like.

[0006] The base 2 is not particularly limited, and may be, for example, a ceramic material, a semiconductor material, a glass material, or a combination of these. The base 2 has a recess 2a in the center of the upper surface. An electrode pad 21 is located on the bottom surface of the recess 2a, and the electrode pad 21 has a flat upper surface and may be formed, for example, by screen printing. The uppermost surface of the electrode pad 21 may be gold-plated. The crystal vibration element 1 is bonded to the electrode pad 21 by a conductive adhesive 22. The conductive adhesive 22 may be, for example, a resin-based adhesive (such as an epoxy resin) containing a silver filler. The vibration (oscillation) part of the crystal vibration element 1 is fixed in a floating state without contacting the inner wall surface of the recess 2a.

[0007] The upper surface side of the recess of the base 2, i.e., the upper end of the frame portion surrounding the recess 2a, is joined to the lid 3 via a conductive sealing member such as gold-tin or silver solder. This seals the recess 2a. A conductive frame-shaped metallized layer may be located between the base 2 and the lid 3.

[0008] The electrode pads 21 can be electrically connected to the outside via a signal line (not shown) that penetrates the base 2 (for example, can be connected to an external wiring or a substrate from an external connection pad located on the bottom surface of the base 2). The component 4 is located on the bottom surface side of the base 2. The component 4 may be an electronic component such as an IC chip, or a sensor such as a temperature measuring element (such as a thermistor). The component 4 may also be a combination of a plurality of these. These output supplementary information related to the adjustment of the oscillation frequency of the crystal vibration element 1, or perform adjustment according to the supplementary information, that is, the crystal device 100 may be, for example, a temperature compensated crystal oscillator (TCXO). The position of the component 4 may not be near the center of the bottom surface in a plan view, but may be offset.

[0009] Fig. 2A is a plan view showing the configuration of the quartz crystal vibrating element 1 of this embodiment, Fig. 2B is a cross-sectional view taken along the cross-sectional line AA in Fig. 2A, and Fig. 2C is a side view of the quartz crystal vibrating element 1.

[0010] The quartz crystal vibrating element 1 includes a quartz crystal piece C, excitation electrodes EU and EL (electrodes) located on both sides of the quartz crystal piece C, lead wires Ex (lead conductors), and connection electrodes Ep.

[0011] The crystal blank C is obtained by AT-cutting, and the thickness is determined according to the oscillation frequency range of 50 MHz to 100 MHz, particularly in the range of 74 MHz to 78 MHz so that the nominal frequency is 76.8 MHz. As shown in FIG. 2A and FIG. 2C, the direction (first direction) along the crystal axis (electrical axis) of the crystal is generally defined as the X-axis. The direction along the optical axis of the crystal is defined as the Z-axis, and as shown in FIG. 2A, the direction (second direction) intersecting the X-axis within the plane of the crystal blank C is defined as the Za-axis (often written as the Z'-axis). The direction intersecting the X-axis and Za-axis (thickness direction of the crystal blank C) is the Ya-axis. Here, the X-axis direction is the long axis direction of the crystal blank C, and the Za-axis direction is the short axis direction of the crystal blank C.

[0012] The excitation electrodes EU, EL are respectively joined to the upper surface (+Ya side) and the lower surface (-Ya side) of the crystal blank C at the same position in plan view. The crystal blank C deforms and vibrates in response to the voltage applied between the excitation electrodes EU, EL. The vibration mode of the crystal blank C here is thickness shear vibration, in which the upper surface side and the lower surface side are displaced in opposite phases in the X-axis direction. The excitation electrodes EU, EL are rectangular in plan view, and their size is smaller than the size of the crystal blank C. Note that the rectangular shape in plan view referred to here is not limited to a perfect rectangular shape. For example, the corners of the excitation electrodes EU, EL may be slightly chamfered or rounded.

[0013] The lead wires Ex are linear wiring that electrically connect the excitation electrodes EU, EL and the connection electrodes Ep. One lead wire Ex is located for each of the excitation electrodes EU, EL, on the top and bottom surfaces of the crystal piece C, respectively.

[0014] The connection electrode Ep is connected to the electrode pad 21 of the base 2, and a predetermined potential difference is applied from the outside when the quartz crystal vibration element 1 is in operation. This causes the quartz crystal vibration element 1 to resonate, and a clock signal of a determined frequency (approximately 76.8 MHz) is obtained from the quartz crystal oscillation circuit to which the quartz crystal vibration element 1 is connected.

[0015] As described above, the excitation electrodes EU, EL are smaller than the size of the crystal blank C in plan view. In the range of 50-100 MHz, which includes the oscillation frequency of the present crystal vibration element 1, the vibration range of the crystal blank C in plan view is conventionally designed to almost overlap the range of the excitation electrodes EU, EL. However, since the temperature characteristics of the crystal and the metal of the electrodes are significantly different, when the crystal is operated at a temperature that is different from the reference temperature, the distortion of the electrodes affects the vibration of the crystal, deteriorating (increasing) the temperature characteristics related to resonance, particularly ESR (equivalent series resistance, also called CI (Crystal Impedance)). In the crystal vibration element 1 of this embodiment, the excitation electrodes EU, EL are made smaller, thereby relatively reducing the influence of these on the crystal blank C.

[0016] On the other hand, if the range of the excitation electrodes EU, EL is made smaller than the vibration range in the X-axis direction, the voltage (power) required to obtain the required resonant wave increases, and power consumption efficiency decreases. In the quartz crystal vibrating element 1 of this embodiment, the length of the excitation electrodes EU, EL in the X-axis direction is not significantly changed (minor design changes (e.g., a few percent) are acceptable), and the excitation electrodes EU, EL are made smaller than the vibration range only in the Za-axis direction, thereby suppressing both the effect on the generation of the resonant wave and the effect on the resonance of the difference in temperature characteristics between the excitation electrodes EU, EL and the quartz crystal piece C.

[0017] Here, the ratio (aspect ratio Le / We) of the length (vertical length Le) in the X-axis direction of the excitation electrodes EU, EL to the width (horizontal width We) in the Za-axis direction is 1.993 or more and 2.525 or less, and is particularly set to 2.33. As described above, the aspect ratio Le / We of the excitation electrodes EU, EL that is matched to the vibration range of the crystal blank C is about 1.25, and the crystal vibrating element 1 is significantly longer in length than this. Note that, since the length Le of the excitation electrodes EU, EL is not significantly different from the length of the crystal blank C in the vertical direction (X direction), it is not conceivable here to increase the length Le of the excitation electrodes EU, EL, which are smaller than the crystal blank C, to increase the aspect ratio Le / We. In addition, since the aspect ratio Le / We is changed to reduce the size of the excitation electrodes EU, EL, it is not desirable to increase the length Le in the first place.

[0018] As described above, only the shape of the excitation electrodes EU, EL is reduced, and the vibration range of the crystal blank C is not reduced. Therefore, the width Wc of the crystal blank C is maintained at the conventional size, and the intervals dW1, dW2 between the long sides of the excitation electrodes EU, EL and the long sides of the crystal blank C (the distances from both ends of the crystal blank C extending in the X direction to the excitation electrodes EU, EL) are larger than before. The excitation electrodes EU, EL are preferably located near the center position (midpoint) of the crystal blank C in the Za axis direction, and therefore the intervals dW1, dW2 are approximately the same size (i.e., half the difference between the width Wc and the width We), but may be slightly offset from the center position of the crystal blank C in the Za axis direction within a range that does not adversely affect resonance. Here, for example, the intervals dW1, dW2 are equal values ​​between 0.130 mm or more and 0.195 mm or less.

[0019] In this structure, the lead wire Ex is drawn out (one end is connected) from the short side (outer edge extending in the Za direction) of the excitation electrodes EU, EL, and the other end is connected to the connection electrode Ep so as to reduce the effect on the vibration of the crystal blank C. Here, the lead wire Ex is linear. A shorter lead wire Ex can reduce the effect on the vibration of the crystal blank C. Here, the lead wire Ex extends at a predetermined angle with respect to the short side of the excitation electrodes EU, EL, but is not limited to the angle shown in the figure. The angle of inclination may be small, and may be perpendicular to the short side, as long as it does not cause problems such as short circuits with other conductor parts during manufacturing.

[0020] By adopting such a structure, the oscillation efficiency and temperature characteristics of the crystal vibration element 1 of this embodiment are stabilized.

[0021] Figures 3A to 3C, 4A to 4C, 5A to 5C, 6A to 6C, and 7A to 7C show experimental results of the temperature characteristics of frequency deviation (df / f) [ppm] (Figures 3B to 7B) and the temperature characteristics of ESR [Ω] (Figures 3C to 7C) when the aspect ratios Le / We of the excitation electrodes EU and EL are changed (Figures 3A to 7A). Here, the results were obtained three times for each ratio Le / We and are shown overlapping each other.

[0022] In the case of Le / We=2.150 to 1.993 shown in FIG. 4A and FIG. 5A, the temperature characteristic of the frequency deviation is generally expressed by a neat cubic function as shown in FIG. 4B and FIG. 5B, and the ESR is approximately 25Ω almost regardless of the temperature as shown in FIG. 4C and FIG. 5C. below Therefore, it can be seen that the quartz crystal resonator element 1 can properly resonate within the temperature range required for practical use. As shown in FIG. 3A, when the aspect ratio Le / We increases, the column resistance value fluctuates and exceeds 25 Ω as shown in FIG. 3B and FIG. 3C, but when the aspect ratio Le / We is in the range of 2.525 or less, the value is maintained below 30 Ω, which is the standard value for general products.

[0023] On the other hand, as shown in Figures 6A and 7A, when the aspect ratio Le / We becomes smaller, the column resistance value increases, especially at the low temperature side, and reaches 30Ω, as shown in Figures 6B, 6C, 7B, and 7C. That is, in a range where the aspect ratio of the excitation electrodes EU, EL is significantly larger than in the past (1.993≦Le / We≦2.525), the quartz crystal resonator element 1 has good temperature characteristics, and when the aspect ratio Le / We deviates from this range, the temperature characteristics deteriorate, especially due to an increase in ESR.

[0024] As described above, the quartz crystal vibrating element 1 of this embodiment includes the quartz crystal piece C having an oscillation frequency in the range of 50 MHz to 100 MHz, and the excitation electrodes EU, EL, which are located on both sides of the quartz crystal piece C and have a rectangular shape in a planar view that is smaller than the quartz crystal piece C. The excitation electrodes EU, EL have a length Le in a first direction along the X-axis (electrical axis) direction of the quartz crystal piece C in a planar view that is 1.993 to 2.525 times their width (horizontal width We) in a second direction (Za-axis direction) perpendicular to the first direction. In a quartz crystal element with an oscillation frequency of 50-100MHz, the following is usually used: Le / We is about 1.25, and the excitation electrodes EU, EL are determined so as to almost coincide with the vibration range of the quartz crystal piece C. In contrast, in the quartz crystal vibrating element 1 of this embodiment, the width We is intentionally made shorter than the length Le. Le / We By setting the size of the excitation electrodes EU, EL to be large and reducing the size of the excitation electrodes EU, EL, it is possible to suppress a decrease in the excitation level while reducing the effect of the difference in thermal expansion coefficient between the excitation electrodes EU, EL and the quartz crystal piece C, thereby suppressing deterioration of the temperature characteristics related to the oscillation of the quartz crystal vibration element 1 and enabling more stable oscillation.

[0025] In particular, the oscillation frequency is preferably in the range of 74 MHz to 78 MHz inclusive. That is, the configuration of the present disclosure is preferably used for a quartz crystal resonator element 1 with a nominal frequency of 76.8 MHz or the like.

[0026] In addition, in the quartz crystal vibrating element 1, the distances from both ends of the quartz crystal blank C in the second direction (Za axis direction) in a plan view to the ends of the excitation electrodes EU, EL are each 0.130 mm or more and 0.195 mm or less. In other words, by having the excitation electrodes EU, EL both positioned approximately in the center of the quartz crystal blank C in the Za axis direction, the vibration range of the quartz crystal blank C that protrudes (leaks) from the range of the excitation electrodes EU, EL in the Za axis direction is prevented from reaching both ends of the quartz crystal blank C, so that the oscillation of the quartz crystal blank C is not hindered and the quartz crystal vibrating element 1 can oscillate efficiently.

[0027] Furthermore, the quartz crystal vibrating element 1 includes a lead wire Ex, one end of which is connected to the outer edge (short side) of the excitation electrodes EU, EL that extends along the second direction (Za axis direction). In this way, the vibration range of the quartz crystal blank C extends beyond the long side of the excitation electrodes EU, EL, whereas the vibration range hardly extends beyond the short side. Therefore, by drawing out the lead wire Ex from this short side, it is possible to reduce the adverse effect of the lead wire Ex on vibration.

[0028] The lead wire Ex has a straight shape. A short lead wire Ex has less effect on the vibration of the crystal blank C and can also reduce the intrusion of external noise, so a straight shape is preferable.

[0029] Moreover, the crystal device 100 of this embodiment includes the above-mentioned crystal vibration element 1. According to this crystal device 100, it is possible to obtain an appropriate signal by oscillating the crystal vibration element 1 with more stable and better temperature characteristics than before.

[0030] The above-described embodiment is merely an example, and various modifications are possible. For example, in the above embodiment, the crystal device 100 is described as including the component 4, but it does not necessarily have to include the component 4. It may simply be a crystal package that is contained in a base and a lid, oscillates, and outputs a signal. Furthermore, the crystal vibration element 1 does not have to be bonded to the base 2 as the crystal device 100. The crystal vibration element 1 may be sold separately.

[0031] The shapes of the base 2 and the cover 3 (including the shape of the recess 2a) may be appropriately changed so as to properly store and seal the quartz crystal vibrating element 1 and properly position the signal lines and electrode pads 21. The shape of the quartz crystal piece C may also be finely adjusted in thickness at its ends, etc. Although the quartz crystal piece C has been described as having the same thickness (flat shape) in the vibrating portion where the excitation electrodes EU, EL are located and in the fixed portion where the connection electrode Ep is located, the thickness of the fixed portion may be set to be greater than the thickness of the vibrating portion (step shape) to more stably support the quartz crystal piece C.

[0032] The shape of the lead wire Ex is not limited to the shape shown in the above embodiment. It may have a bent portion or a curved portion, and may not be led out from the short side of the excitation electrodes EU and EL.

[0033] In addition, in the above embodiment, the nominal frequency is 76.8 MHz as an example. However, if the oscillation frequency is in the range of 50-100 MHz, the features related to the shapes of the excitation electrodes EU, EL are effective, so the quartz vibration element 1 may oscillate other frequency signals within that range. In addition, the specific configurations, structures, materials, and the like shown in the above embodiments can be appropriately modified without departing from the spirit of the present disclosure. The scope of the present invention includes the scope described in the claims and their equivalents. [Industrial Applicability]

[0034] The present disclosure can be applied to quartz crystal resonator elements and quartz crystal devices.

Claims

1. A quartz crystal piece having an oscillation frequency in the range of 50 MHz to 100 MHz, Electrodes each having a rectangular shape in a plan view and smaller than the crystal piece, each electrode being located on both sides of the crystal piece; A lead conductor having one end connected to an outer edge of the electrode extending along a second direction perpendicular to a first direction along the X-axis direction of the crystal piece in a plan view; Equipped with The electrode has a length in the first direction that is 1.993 times or more and 2.525 times or less than its width in the second direction; The lead conductor has a linear shape, The distances from both ends of the crystal piece to the ends of the electrodes in the second direction in a plan view are each 0.130 mm or more and 0.195 mm or less. Quartz crystal element.

2. 2. The quartz crystal resonator element according to claim 1, wherein the oscillation frequency is in the range of 74 MHz to 78 MHz.

3. A quartz crystal device comprising the quartz crystal resonator element according to claim 1 or 2.

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