JP2015043483A - Piezoelectric vibrator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a piezoelectric vibrator in a width longitudinal/length longitudinal coupling mode which is excellent in frequency temperature characteristics by optimizing the design conditions of a vibration part or the like in association with a high oscillation frequency and miniaturization.SOLUTION: The piezoelectric vibrator includes: a piezoelectric diaphragm 21 having vibration parts 22a, 22b and 22c constituted of a main vibration side (M) in a width longitudinal mode and a sub-vibration side (S) in a length longitudinal mode; excitation electrodes formed on the front and rear surfaces of each vibration part; an arm 23 for supporting one end of the piezoelectric diaphragm 21; and a frame 24 to which the arm 23 is connected. In the piezoelectric diaphragm 21, the rate of the length of the main vibration side (M) to the length of the sub-vibration side (S) in each of the vibration parts 22, 22b and 22c is set such that when the length of the sub-vibration side (S) is 1, the length of the main vibration side (M) becomes 1.00 to 1.45, and the rate of the thickness of the piezoelectric diaphragm 21 to the length of the main vibration side (M) is set such that when the length of the main vibration side (M) is 1, thickness (T) of the piezoelectric diaphragm 21 becomes less than 0.1.

Description

  The present invention relates to a piezoelectric vibrator in a width-length / length-length coupled mode.

  In the conventional longitudinal and longitudinal longitudinal coupled mode piezoelectric vibrators with the main longitudinal vibration being the width longitudinal vibration, those whose resonance frequency of the main vibration due to the width longitudinal vibration is about 1 to 3.5 MHz have been put into practical use. ing. For example, when the resonance frequency of the main vibration is 2.1 MHz, the length of one side of the diaphragm is about 1.5 mm. In such a large diaphragm, since the excitation electrode can be relatively wide, the vibration energy of the diaphragm is sufficiently large. For this reason, in order to obtain good temperature characteristics, it is necessary to control the coupling state with the main vibration by limiting the secondary vibration by the arm-shaped support portion that supports the diaphragm and adjusting the vibration frequency. It was relatively easy.

  In addition, the piezoelectric vibrator can change the frequency temperature characteristic by changing the coupling state between the frequency in the width longitudinal mode as the main vibration and the frequency in the length longitudinal mode as the sub vibration. ing.

  Normally, the frequency of the main vibration mode cannot be changed because it is a nominal frequency, and it is necessary to oscillate at a certain set frequency. Further, in order to change the temperature characteristic, it is necessary to change the coupling state. For this purpose, it is necessary to change the frequency of the secondary vibration mode. One of the methods to change the frequency of this secondary vibration mode is to adjust the spring property by changing the thickness and length of the loop arm and limit the vibration of the secondary vibration mode (killing the vibration momentum) The other is a method of adjusting by reducing or increasing the frequency of the secondary vibration mode by adding or removing a weight.

  Further, the capacity ratio γ of the main vibration serves as a barometer of conversion efficiency when the vibration state is good or bad and given electromagnetic energy is converted into vibration energy. In the width-length / length-length coupling mode, the value of the capacity ratio γ does not depend on the size (frequency) of the diaphragm. The reported capacitance ratio of a conventional piezoelectric vibrator at 2.1 MHz is 400 to 600, which is larger than the value of the capacitance ratio (200 to 400) with only the diaphragm ignoring the arm. However, the effect of controlling the secondary vibration on the capacity ratio is increased. In other words, the arm of the conventional shape that greatly restricts the secondary vibration has a good frequency temperature characteristic while greatly losing the vibration energy of the diaphragm, and within a range where electrical characteristics that are not problematic in practical use can be obtained. It can be said that it was designed.

  In the piezoelectric vibrator, when the diaphragm is downsized to increase the resonance frequency of the main vibration, the vibration energy itself is reduced. For this reason, there is no practical problem in the resonance frequency band of 1 to 3.5 MHz where the size of the diaphragm is relatively large, but the design becomes very difficult just by downsizing the conventional shape as it is.

  Patent Documents 1 and 2 disclose a piezoelectric vibrator having a general shape and structure for generating vibration in a width-length / length-length coupled mode. This type of piezoelectric vibrator includes a diaphragm on which at least one pair of excitation electrodes are formed, and an arm that controls a longitudinal mode that is sub-vibration on the diaphragm. The arm is provided so as to surround the diaphragm and the support main body extending outward from the outer periphery of the diaphragm so that the strength is maintained and the arm is not damaged by an impact caused by dropping or the like. In some cases, a support frame (frame) to which one end of the support main body portion is connected is provided.

  Moreover, in order to prevent the vibration energy of the diaphragm from leaking through the arm, the arm may be configured to be thin, but there is a disadvantage that the arm is easily damaged when assembling in the manufacturing process, As described above, it is necessary to increase the strength by configuring the arm with the support main body extending from the diaphragm and the frame connected to the support main body. However, if the diaphragm is completely surrounded by the support main body and the frame, the support strength increases, but the overall size of the vibrator cannot be reduced. Further, if the support strength is increased more than necessary by the frame, there are cases where it becomes difficult to create an appropriate combined state with the longitudinal longitudinal vibration that becomes the main vibration by inhibiting the longitudinal longitudinal vibration that becomes the secondary vibration.

Japanese Patent Laid-Open No. 1-126009 JP-A-10-117120

  By the way, there are many examples in which the piezoelectric vibrators of the above-described conventional simple beam structure in the width-length / length-length coupling mode are practically used at a relatively low frequency of about 1.0 to 3.5 MHz. This is because if the resonance frequency is set to 4 MHz or more, it is necessary to make the diaphragm very small. For example, in the case of a fundamental wave at a resonance frequency of 12 MHz, the width of the rectangular diaphragm is about 270 μm. If the arm having the structure as in the conventional example is miniaturized and the frequency is increased, the vibration energy itself of the diaphragm is small, so that the vibration is inhibited and the equivalent series resistance (R1) is increased. In addition to R1, there is a drawback that satisfactory electrical characteristics such as capacity ratio γ and Q cannot be obtained.

  In addition, by adjusting the coupling degree between the width longitudinal vibration and the length longitudinal vibration, the frequency temperature characteristic better than that of the AT-cut piezoelectric vibrator which is generally best used and has the best frequency temperature characteristic. Can be obtained. However, the width-length / length-length coupled mode crystal resonator creates a coupled state that obtains good frequency temperature characteristics when the weight of the arm that adjusts the frequency of the length-length mode is too large compared to the weight of the diaphragm. I can't. Accordingly, when the resonance frequency is increased, the diaphragm is made smaller and the weight is reduced, the arm is also made thinner, smaller, thinner and lighter in weight. As a result, even if the arm can be manufactured in a shape and size that can provide satisfactory frequency-temperature characteristics, there is a problem that the strength becomes too weak to hold the diaphragm.

  Therefore, an object of the present invention is to provide a width-length / length-length coupled mode piezoelectric vibrator having excellent frequency temperature characteristics by optimizing design conditions such as a vibrating portion in response to a high oscillation frequency and downsizing. It is to provide.

  In order to solve the above-described problems, the piezoelectric vibrator of the present invention has a Y plate made of an XZ plane of a crystalline lens having a three-dimensional crystal orientation composed of an X axis, a Y axis, and a Z axis within a range of + 40 ° to + 50 °. The Y 'plate made of the XZ' plane obtained by rotating around the X axis is cut by a rotation angle obtained by rotating the plane in the range of 40 ° to 50 °, accompanied by the main vibration in the width-longitudinal mode. A piezoelectric diaphragm having a plurality of square-shaped vibrating portions each composed of a pair of main vibration sides and a pair of sub vibration sides orthogonal to the pair of main vibration sides and accompanied by a sub-vibration in a longitudinal mode; and Excitation electrodes formed on the front and back surfaces, a support part that supports one end of the piezoelectric diaphragm, and a base that is provided on the outer periphery of the piezoelectric diaphragm and to which the support part is connected, , The length of the main vibration side and the sub vibration side in each vibration part However, when the length of the main vibration side is 1, the length of the sub vibration side is set to 1.00 to 1.45, and the ratio between the thickness of the piezoelectric diaphragm and the length of the main vibration side is When the length of the main vibration side is 1, the thickness of the piezoelectric diaphragm is made smaller than 0.1, thereby reducing the equivalent series resistance R1 of the main vibration and the primary temperature coefficient α and the secondary temperature coefficient. β is matched in the vicinity of 0 to obtain a vibration frequency of 10 to 24 MHz.

  According to the piezoelectric vibrator of the present invention, the frequency temperature is cut by the rotation angle that becomes the width-length / length-length coupling mode, and the piezoelectric diaphragm, the support portion, and the like are formed based on the design conditions based on a predetermined ratio. A piezoelectric vibrator having excellent characteristics can be obtained.

It is the top view (a) and AA sectional drawing (b) of the piezoelectric vibrator of 1st Embodiment. It is a top view of the piezoelectric vibrator of a 2nd embodiment. It is a top view when the said piezoelectric vibrator is accommodated in the package. It is a top view of the piezoelectric vibrator of a 3rd embodiment. It is a graph which shows the simulation analysis of the primary temperature coefficient (alpha) in the piezoelectric vibrator of the said 1st Embodiment. It is a graph which shows the simulation analysis of the secondary temperature coefficient (beta) in the piezoelectric vibrator of the said 1st Embodiment. It is a graph which shows the simulation analysis of the primary temperature coefficient (alpha) and secondary temperature coefficient (beta) in the piezoelectric vibrator of the said 2nd Embodiment. FIG. 8 is a graph plotting the side ratio (S / M) and cut angle (θ) at which the primary temperature coefficient α and the secondary temperature coefficient β are close to 0 based on the analysis result of FIG. 7. It is a graph which shows the simulation analysis of the primary temperature coefficient (alpha) and secondary temperature coefficient (beta) when the ratio of the thickness of a piezoelectric diaphragm and the thickness of an excitation electrode is set to 0.15. It is a graph which shows the simulation analysis of the primary temperature coefficient (alpha) and secondary temperature coefficient (beta) when the ratio of the thickness of a piezoelectric diaphragm and the thickness of an excitation electrode is set to 0.001. FIG. 10 is a graph in which the side ratio (S / M) and the cut angle (θ) at which the primary temperature coefficient α and the secondary temperature coefficient β are close to 0 are plotted based on the analysis result of FIG. 9. 11 is a graph in which the side ratio (S / M) and the cut angle (θ) at which the primary temperature coefficient α and the secondary temperature coefficient β are close to 0 are plotted based on the analysis result of FIG. 10. In the comparison between the piezoelectric vibrator of the second embodiment and the piezoelectric vibrator of the third embodiment, it is a graph showing the relationship between the primary temperature coefficient α and the secondary temperature coefficient β when the analysis frequency is 12 MHz. . In the comparison between the piezoelectric vibrator of the second embodiment and the piezoelectric vibrator of the third embodiment, it is a graph showing the relationship between the primary temperature coefficient α and the secondary temperature coefficient β when the analysis frequency is 16 MHz. . A graph showing the relationship between the primary temperature coefficient α and the secondary temperature coefficient β when the analysis frequency is 19.2 MHz in the comparison between the piezoelectric vibrator of the second embodiment and the piezoelectric vibrator of the third embodiment. It is. 6 is an experimental graph in which an equivalent series resistance R1 is measured with respect to a ratio of a thickness of a piezoelectric diaphragm and a main vibration side in the piezoelectric vibrator of the second embodiment. It is an experimental graph of C0 and R1 when the frequency is set to 12, 16, 19.2 MHz and the number of diaphragms and the crystal thickness are changed. It is a table | surface which shows the analysis result in each frequency when the primary temperature coefficient (alpha) and secondary temperature coefficient (beta) of a frequency temperature characteristic become zero.

  FIG. 1 shows a planar form (a) of the piezoelectric vibrator 10 of the first embodiment and a cross-sectional form (b) of the vibration part. The piezoelectric vibrator 10 has a basic shape with contour vibration, and has a rectangular piezoelectric vibration plate 11 for generating vibration in a width-longitudinal length-longitudinal mode and an outer surface from one side surface of the piezoelectric vibration plate 11. A support portion (arm) 13 extending in the direction and a base portion (frame) 14 that supports the arm 13 are integrally formed.

  In the width-length / length-length coupling mode, normally, vibrations in the length-length mode are adjusted and the width-length mode is coupled to obtain favorable vibrator characteristics such as temperature characteristics. The arm 13 functions as a weight with respect to the vibration in the longitudinal mode and has a spring property, and thus has a role of adjusting the frequency by suppressing the vibration.

  The piezoelectric vibrator 10 rotates a Y plate crystal perpendicular to the mechanical axis (Y-axis) by an angle θx = + 40 ° to + 50 ° with the electric axis (X-axis) as a rotation axis, and further after the rotation of the X-axis. A thin plate-like quartz substrate 19 cut out at a rotation angle (cut angle) θ rotated at an angle θy = 40 ° to 50 ° with the new axis (Y ′ axis) as a rotation axis, and having upper and lower surfaces and four side surfaces. It is formed by processing into a predetermined shape. In addition, at least a pair of excitation electrodes 17 and 18 (the back side of 17) having different polarities are provided on the front and back surfaces of the piezoelectric diaphragm 11 which are surfaces perpendicular to the Y ′ axis, which is the new axis after the rotation of the Y axis. Opposed to each other. The piezoelectric diaphragm 11, the arm 13, and the frame 14 are formed by processing the crystal substrate into a predetermined shape.

  The piezoelectric diaphragm 11 has a pair of main vibration sides 12a and 12b (M) facing each other so as to generate a longitudinal main vibration, and the main vibration side (M) so as to generate a longitudinal vibration. Is formed by a quadrangular vibrating portion 12 composed of a pair of sub-vibrating sides 12c and 12d (S) facing each other in a direction orthogonal to. In the present invention, in the piezoelectric vibrator 10 having the above-described configuration, the equivalent series resistance R1 is reduced, and the primary temperature coefficient α and the secondary temperature coefficient β coincide with each other near 0, and the vibration frequency becomes 10 to 24 MHz. The optimum design conditions are defined based on the analysis data.

  The side ratio between the main vibration side (M) and the sub vibration side (S) varies depending on the frequency to be oscillated, but in the present embodiment, the length of the main vibration side (M) and the sub vibration side (S) is When the ratio (S / M) was set to 1 for the main vibration side (M), the sub vibration side (S) was set to a value of 1-1.45. Further, when the ratio (T / M) between the thickness (T) of the piezoelectric diaphragm 11 and the length of the main vibration side (M) is set to 1, the length of the main vibration side (M) is 1. The thickness (T) was set to be smaller than 0.1.

  A first excitation electrode 17 is formed on the front surface and a second excitation electrode 18 is formed on the rear surface of the vibration part 12. The thickness (T) of the piezoelectric diaphragm 11 and the thicknesses of the first and second excitation electrodes 17 and 18 are formed on the vibration part 12. The ratio (T2 / T) to (T2) is such that the thickness (T2) of the first and second excitation electrodes 17 and 18 is 0.001 or more when the thickness (T) of the piezoelectric diaphragm 11 is 1. It was set to be less than 0.15. By applying a reverse phase voltage to the first and second excitation electrodes 17 and 18 via the frame 14 and the arm 13, the main vibration side (M) and the sub vibration side (S) are bent and deformed. As a result, vibration in the width / length combination mode occurs.

  The arm 13 has a shape in which the one main vibration side (M) and the frame 14 are connected with elasticity through one continuous path. In the arm 13 having such a beam shape, in order to minimize the influence on the main vibration in the width-longitudinal mode, it is better that the number of connecting portions with the vibrating portion 12 is small and narrow. For this reason, in the piezoelectric vibrator 10 of the present embodiment, the connection portion of the arm 13 is provided on both main vibration sides (M) of the vibration portion 12.

  Therefore, the connection width (D1) between the arm 13 and the vibration part 12 is 0.1 to 0.3 when the length of the main vibration side (M) is 1, and the thickness (T3) of the arm 13 is When the thickness (T) of the piezoelectric diaphragm 11 is 1, it is preferably set to at least 1 or more. Further, the connection width (D2) between the other end of the arm 13 and the frame 14 is preferably 0.1 to 0.3 when the length of the main vibration side (M) is 1.

  FIG. 2 shows the piezoelectric vibrator 20 of the second embodiment. In this piezoelectric vibrator 20, a piezoelectric diaphragm 21 is constituted by three vibrating portions 22 a to 22 c, and a pair of arms 23 extend from the main vibration side of the vibrating portion 22 b located at the center, and a common frame 24. It is connected to the. The three vibration parts 22a to 22c have the same shape and the same size, and the ratio of the length (S / M) of the main vibration side (M) and the sub vibration side (S) in each vibration part, piezoelectric The ratio (T / M) between the thickness (T) of the diaphragm 11 and the length of the main vibration side (M), and as shown in FIG. 1, the thickness (T) of the piezoelectric diaphragm 11 and the first and The ratio (T2 / T) between the second excitation electrodes 17 and 18 and the thickness (T2) is the same as that of the piezoelectric vibrator 10 of the first embodiment. Further, the same applies to the connecting portion between the arm 23 and the vibrating portion 22.

  The excitation electrodes 17 and 18 formed on the vibrating portions 22 a to 22 c of the piezoelectric vibrator 20 are arranged so that the polarities are alternately reversed on the front surface and the back surface of the piezoelectric vibration plate 21. Thus, by arranging a plurality of vibration parts, a higher-order vibration mode can be obtained, and an effect of improving the frequency temperature characteristic can be obtained as compared with the configuration of the single vibration part 12 as shown in FIG.

  FIG. 3 shows a state in which the piezoelectric vibrator 20 is housed in the package 15. The frame 24 is provided to fix the piezoelectric vibrator 20 to the package and to apply a voltage to the first excitation electrode 17 and the second excitation electrode 18 of the vibration part 22 b via the arm 23. The frame 24 can support the piezoelectric diaphragm 21 in a floating state by connecting both base ends to the terminal electrodes 16 in the package 15 via solder members 19.

  FIG. 4 shows the piezoelectric vibrator 30 according to the third embodiment in which the vibration portions are configured in five rows in order to further improve the frequency temperature characteristics and the equivalent series resistance. Similarly to the second embodiment, the piezoelectric vibrator 30 can further improve the frequency-temperature characteristics by making the ratios of the shapes and sizes of the vibrating portions and arms the same.

  Next, analysis results by FEM simulation when the design conditions shown in FIG. 1 are applied to the piezoelectric vibrators 20 and 30 having the shapes shown in FIGS. 2 and 4 will be described. Here, the ratio (S / M) of the main vibration side (M) to the sub-vibration side (S) in each vibration part, and the ratio of the thickness (T) of the piezoelectric diaphragm to the length of the main vibration side (M) ( T / M) and the ratio (T2 / T) of the thickness (T) of the piezoelectric diaphragm and the thickness of the excitation electrode (T2) were selected from the design conditions.

  First, FIG. 5 and FIG. 6 show the analysis results in the piezoelectric vibrator 10 having one vibration part as shown in FIG. 5 and 6, as common settings, the analysis frequency is changed to 12 MHz, the side ratio (S / M) is changed from 1.00 to 1.11, and the cut angle is changed from 46 ° to 52 °. In FIG. 5A, (T2 / T) is 0.01, and in FIG. 5B, (T2 / T) is set to 0.001, and the primary temperature coefficient α is analyzed by simulation. Yes, in FIG. 6A, (T2 / T) is set to 0.01, and in FIG. 6B, (T2 / T) is set to 0.001, and the secondary temperature coefficient β is analyzed by simulation. It is. From this analysis result, the side ratio and the cut angle are such that the primary temperature coefficient α and the secondary temperature coefficient β are close to 0 even if the side ratio (S / M) and the cut angle are varied in the case of a single vibration part. It turns out that does not exist.

  Next, FIG. 7 shows an analysis result in the piezoelectric vibrator 20 having three vibration parts as shown in FIG. In FIG. 7, as common settings, the analysis frequency is 12 MHz, (T2 / T) is 0.01, the side ratio (S / M) is 1.00 to 1.09, and the cut angle is 46 ° to 52 °. The primary temperature coefficient α (FIG. 7 (a)) and the secondary temperature coefficient β (FIG. 7 (b)) when changed in the range are respectively analyzed by simulation. From this analysis result, in the case of a three-vibration configuration, when the side ratio (S / M) and the cut angle are varied, the side ratio is such that the primary temperature coefficient α and the secondary temperature coefficient β are close to zero. It can be seen that there is a cut angle.

  FIG. 8 is a plot of side ratio (S / M) and cut angle (θ) at which the primary temperature coefficient α and the secondary temperature coefficient β are close to 0 based on the analysis result of FIG. This intersection is the side ratio (S / M) and the cut angle (θ) at which both the primary temperature coefficient α and the secondary temperature coefficient β are 0. Looking at where the primary temperature coefficient α and the secondary temperature coefficient β intersect, the side ratio (S / M) = 1.04 and the cut angle θ = 46 °.

  FIG. 9 shows that in the piezoelectric vibrator 20, the ratio (T2 / T) between the thickness (T) of the piezoelectric diaphragm 21 and the first and second excitation electrodes 17, 18 and the thickness (T2) is set to 0.15. It is a simulation analysis result of the primary temperature coefficient (alpha) (FIG. 9 (a)) and secondary temperature coefficient (beta) (FIG.9 (b)) at the time of doing. FIG. 10 shows the primary when the ratio (T2 / T) between the thickness (T) of the piezoelectric diaphragm 21 and the thickness (T2) of the first and second excitation electrodes 17 and 18 is set to 0.001. It is a simulation analysis result of temperature coefficient alpha (Drawing 10 (a)) and secondary temperature coefficient beta (Drawing 10 (b)). In addition, Au was used for the excitation electrode, and conditions other than (T2 / T) were the same as in the case of FIG. Thus, even when the setting of (T2 / T) is changed, there are side ratios and cut angles at which the primary temperature coefficient α and the secondary temperature coefficient β are close to 0, but (T2 It can be seen that increasing the / T) reduces the number of points where the secondary temperature coefficient becomes zero.

  FIG. 11 is a plot of side ratio (S / M) and cut angle (θ) at which the primary temperature coefficient α and the secondary temperature coefficient β are close to 0 based on the analysis result of FIG. Although there are side ratios (S / M) and cut angles (θ) such that the primary temperature coefficient α and the secondary temperature coefficient β are close to 0, the primary temperature coefficient α and the secondary temperature coefficient β There are no side ratios and cut angles such that both are near zero. Thus, by increasing the ratio of (T2 / T), it is affected by the temperature characteristics of the excitation electrode. Therefore, in order to obtain the optimum temperature characteristics, (T2 / T) is smaller than 0.15. There is a need to.

  FIG. 12 is a plot of side ratio (S / M) and cut angle (θ) at which the primary temperature coefficient α and the secondary temperature coefficient β are close to 0 based on the analysis result of FIG. . Thus, even when the ratio between the thickness of the piezoelectric diaphragm and the thickness of the excitation electrode is 0.001, the side ratio (S / S) where the primary temperature coefficient α and the secondary temperature coefficient β are both 0. It can be seen that there are M) and a cut angle (θ). Here, when the place where the primary temperature coefficient α and the secondary temperature coefficient β intersect is seen, the side ratio (S / M) = 1.06 and the cut angle θ = 49 °. Therefore, in order to obtain optimum temperature characteristics, it is necessary to set (T2 / T) to a range that is not less than 0.001 and less than 0.15. At this time, T is fixed at 10 μm, and T2 is analyzed in the range of 0.01 to 1.5 μm. In order to make the frequency up to 10 to 24 MHz, M is about 130 to 350 μm. Therefore, T2 / M is set larger than 0 and smaller than 0.004.

  13 to 15 show an analysis in the piezoelectric vibrator 20 (a) according to the second embodiment having three vibration parts and the piezoelectric vibrator 30 (b) according to the third embodiment having five vibration parts. This shows the relationship between the primary temperature coefficient α and the secondary temperature coefficient β when the frequency is changed in three stages of 12 MHz (FIG. 13), 16 MHz (FIG. 14), and 19.2 MHz (FIG. 15). The point at which the primary temperature coefficient α and the secondary temperature coefficient β intersect in each figure is the optimum point of the side ratio (S / M) and cut angle (θ). As a result, the side ratio (S / M) = 1.04 in the three-vibration configuration, the cut angle (θ) = around 46.5 ° to 47 °, and the side ratio (S / M) = in the 5-vibration configuration. 1.11, cut angle (θ) = around 46.5 °.

  FIG. 16 shows the experimental results of measuring the equivalent series resistance R1 in the ratio (T / M) of the thickness (T) of the piezoelectric diaphragm and the main vibration side (M) in the piezoelectric vibrator having the three vibrating sections. It is. The analysis frequency at this time is set to 12 MHz. From this result, when (T / M) is 0.1 or more, R1 is as extremely high as 800Ω or more. Since it is generally recommended that R1 be 300Ω or less, to realize this, it is necessary to set the (T / M) smaller than 0.1.

  FIG. 17 shows the relationship between the parallel capacitances C0 and R1 obtained by experiments when the frequency is 12, 16, 19.2 MHz, and the thickness (T) of the vibrating plate is changed. is there. From this result, in order to set R1 to 300Ω or less, it is necessary to adjust the thickness (T) of the piezoelectric diaphragm and the number of vibrating portions so that C0 becomes 0.4 pF or more.

  FIG. 18 shows the analysis results at each frequency when the primary temperature coefficient α and the secondary temperature coefficient β of the frequency temperature characteristic are zero. The frequencies and equivalent constants of the main vibration and the sub vibration are analysis values obtained by FEM simulation. From this analysis result, the equivalent series inductance L1 of the main vibration is 30 to 80 mH, and the equivalent series capacitance C1 is 0.5 to 5 fF. The equivalent series inductance L2 of the secondary vibration is 200 to 700 mH, and the equivalent series capacitance C2 is 0.1 to 1 fF. Furthermore, the capacity ratio of the secondary vibration in the coupling with the main vibration is 1000 to 3000. At this time, as shown in FIG. 2 and FIG. 4, the arms 23 and 33 that greatly influence the vibration of the secondary vibration do not limit the secondary vibration and are coupled with the main vibrations in order to couple with the main vibration. Is set to 0.1 to 0.3 when the length of the main vibration side (M) is 1, and the thickness of the arms 23 and 33 is 1 to the thickness of the piezoelectric diaphragms 21 and 31. Is set to at least 1 and the connection width (D2) between the other ends of the arms 23 and 33 and the frames 24 and 34 is 0.1 when the length of the main vibration side (M) is 1. Must be set to 0.3.

  On the other hand, with respect to the frame 14, as shown in FIG. 3, when the holding width (D3) with the terminal electrode 16 provided in the package 15 is set to 0.5 or more when the length of the main vibration side (M) is 1. By setting, the piezoelectric diaphragm 21 can be held in a stable state against an external impact or the like. For this reason, the optimal frequency temperature characteristic as set can be obtained by the vibration part and the arm formed based on various design conditions without being influenced by external factors.

  As described above, in the piezoelectric vibrator of the present invention, when the piezoelectric diaphragm is reduced in size, the side ratio and thickness of the vibration part, the thickness of the excitation electrode, and the like are set as the primary temperature coefficient α and the secondary temperature coefficient β. By limiting the numerical value to an optimum value at which the equivalent series resistance decreases within a range where the values coincide with each other in the vicinity of 0, it becomes possible to obtain a vibration mode with good frequency temperature characteristics. Further, with respect to the arm (support part) and the frame (base part) that hold the piezoelectric diaphragm, the side ratio, the thickness, etc. are limited numerically with the portion connected to the piezoelectric diaphragm as the center, and the impact on the piezoelectric diaphragm, etc. The influence on external factors can be reduced.

M Main vibration side S Sub vibration side D1 Connection width D2 Connection width D3 Holding width T Piezoelectric vibration plate thickness T2 Excitation electrode thickness T3 Arm thickness 10, 20, 30 Piezoelectric vibrator 11, 21, 31 Piezoelectric vibration plate 12, 22a to 22c, 32a to 32e Vibration parts 12a and 12b Main vibration sides 12c and 12d Sub vibration sides 13, 23 and 33 Arms 14, 24 and 34 Frame 15 Package 16 Terminal electrode 17 First excitation electrode 18 Second excitation electrode 19 Solder Element

Claims (8)

A Y plate made of an XZ plane of a crystalline lens having a three-dimensional crystal orientation composed of an X axis, a Y axis, and a Z axis is rotated around the X axis in a range of + 40 ° to + 50 °, and XZ obtained by this rotation It is cut by the rotation angle obtained by rotating the plane “Y” plate in the range of 40 ° -50 °.
Piezoelectric vibration having a pair of main vibration sides with a main vibration in the width-longitudinal mode and a plurality of quadrangular vibration parts that are orthogonal to the pair of main vibration sides and have a pair of sub-vibration sides with a sub-vibration in the length-longitudinal mode The board,
Excitation electrodes formed on the front and back surfaces of each vibration part;
A support portion for supporting one end of the piezoelectric diaphragm;
A base provided on the outer periphery of the piezoelectric diaphragm and connected to the support;
In the piezoelectric diaphragm, the length ratio of the main vibration side to the sub vibration side in each vibration part is such that the length of the sub vibration side is 1.00 to 1 when the length of the main vibration side is 1. .45, and
When the ratio of the thickness of the piezoelectric diaphragm and the length of the main vibration side is set to 1, when the length of the main vibration side is 1, the thickness of the piezoelectric diaphragm is made smaller than 0.1, so that the equivalent series resistance of the main vibration is reduced. A piezoelectric vibrator characterized in that R1 is lowered and the primary temperature coefficient α and the secondary temperature coefficient β are made to coincide in the vicinity of 0 to obtain a vibration frequency of 10 to 24 MHz.   2. The piezoelectric vibration according to claim 1, wherein the piezoelectric diaphragm is adjusted to have a parallel capacitance C0 of 0.4 pF or more and an equivalent series inductance L1 of a main vibration of 30 to 80 mH by adjusting a thickness and the number of vibration parts. Child.   The piezoelectric vibrator according to claim 1, wherein a capacity ratio of the secondary vibration when coupled with the main vibration is set to 1000 to 3000.   In the vibrating portion, the ratio of the thickness of the piezoelectric diaphragm and the thickness of the excitation electrode is set such that the thickness of the excitation electrode is 0.001 or more and less than 0.15 when the thickness of the piezoelectric diaphragm is 1. The piezoelectric vibrator according to claim 1, wherein the thickness of the excitation electrode with respect to the length of the main vibration side is set to be larger than 0 and smaller than 0.004. The support portion includes an arm that supports a substantially central portion of a main vibration side of at least one vibration portion that constitutes the piezoelectric diaphragm, and a connection width to the vibration portion is set to a length of the main vibration side of 1. 0.1 to 0.3, and the thickness of the arm is set to at least 1 or more when the thickness of the piezoelectric diaphragm is 1.
The piezoelectric vibrator according to claim 1, wherein a connection width between the other end of the arm and the base is set to 0.1 to 0.3 when the length of the main vibration side is 1.   2. The piezoelectric vibrator according to claim 1, wherein the base portion is set to 0.5 or more when a holding width is set to a length 1 of the main vibration side.   2. The piezoelectric vibrator according to claim 1, wherein the piezoelectric diaphragm is formed by arranging a plurality of vibration portions in a main vibration direction or a sub vibration direction.   The piezoelectric vibrator according to claim 1, wherein the piezoelectric vibration plate, the support portion, and the base portion are integrally formed by a quartz substrate.

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