JP5779354B2 - Piezoelectric vibrator - Google Patents

Description

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

  FIG. 17 shows a package 5 in which a piezoelectric vibrator 1 in a width-longitudinal / longitudinal coupled mode in which a conventional width-longitudinal vibration is main vibration is mounted. The piezoelectric vibrator 1 includes main vibration sides 2a and 2b in the width-longitudinal mode and sub-vibration sides 2c and 2d in the length-longitudinal mode, the surface of which the excitation electrode 7 is formed, the piezoelectric diaphragm 2 and the pair It has a pair of support arms 3 that support one end of the main vibration sides 2a and 2b and are formed with an electrode pattern (not shown) connected from the terminal electrode 6 to the excitation electrode 7. The support arm 3 has a structure having a loop-like projecting portion (simple beam) in order to give rigidity together with springiness. The piezoelectric vibrator 1 having such a structure has a favorable temperature characteristic by adjusting the degree of coupling (coupling) by limiting the sub-vibration in the longitudinal mode by the support arm 3 and controlling the frequency. Was getting.

  The resonance frequency of the main vibration due to the width longitudinal vibration has been put to practical use up to about 1 to 3.5 MHz. For example, when the resonance frequency of the main vibration is 2.1 MHz, the length of one side of the piezoelectric diaphragm 2 is about 1.5 mm. In such a large piezoelectric diaphragm 2, the excitation electrode 7 is also relatively wide, so that the vibration energy of the piezoelectric diaphragm 2 is sufficiently large. For this reason, in order to obtain a favorable temperature characteristic, the coupling state with the main vibration is controlled by limiting the secondary vibration by the support arm 3 having a shape as shown in FIG. 17 and adjusting the vibration frequency. It was relatively easy.

  Further, the piezoelectric vibrator 1 can change the frequency temperature characteristic by changing the coupling state between the frequency of the width longitudinal mode as the main vibration and the frequency of the length longitudinal mode as the sub vibration. It has become.

  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 method of changing the frequency of the secondary vibration mode is to adjust the spring property by changing the thickness and length of the loop-shaped support arm, and to limit the vibration of the secondary vibration mode (kill the vibration momentum). The other is a method of adjusting by decreasing 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 case of the width-length / length-length coupling mode, the value of the capacitance ratio γ does not depend on the size (frequency) of the piezoelectric diaphragm. The capacity ratio of a general conventional piezoelectric vibrator at 2.1 MHz that is reported is 400 to 600, which is larger than the value of the capacity ratio (200 to 400) with only the piezoelectric diaphragm ignoring the support arm. The influence on the deterioration of the capacity ratio due to the control arm controlling the secondary vibration is increased. In other words, the support arm having a conventional shape that greatly restricts the secondary vibration has a good frequency temperature characteristic while greatly losing the vibration energy of the piezoelectric diaphragm, and can obtain an electrical characteristic that has no problem in actual use. It can be said that it was designed in a range.

  In the piezoelectric vibrator 1, if the piezoelectric diaphragm 2 is downsized to increase the resonance frequency of the main vibration, the vibration energy itself is reduced. As described above, the support arm 3 having a conventional shape has a structure in which the secondary vibration is largely limited by the loop-shaped projecting portion. Therefore, the lower the vibration energy, the more difficult it is to control the secondary vibration. It was. Therefore, there is no practical problem in the resonance frequency band of 1 to 3.5 MHz where the size of the piezoelectric diaphragm 2 is relatively large, but the design becomes very difficult only by downsizing the conventional shape as it is.

  As the vibration energy of the piezoelectric diaphragm 2 becomes smaller, the supporting arm 3 must be made smaller, thinner, thinner, and lighter to reduce the limit amount of the secondary vibration. Since the support arm 3 also has a role of holding the piezoelectric diaphragm 2 in the package 5 in a hollow state, it is necessary to consider resistance to an impact that causes damage or the like. For this reason, the support arm 3 cannot be made unlimitedly small, thin, thin and light. Under such circumstances, the degree of freedom of design is narrowed, and it has been difficult to obtain satisfactory vibration characteristics and temperature characteristics. Further, even if various practical characteristics are obtained, there is a problem that the capacity ratio becomes a value of 400 to 600.

  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 is composed of a piezoelectric diaphragm having at least one pair of excitation electrodes formed thereon, and a support arm that controls the longitudinal longitudinal mode that causes sub-vibration on the piezoelectric diaphragm. The support arm is provided so as to surround the piezoelectric vibration plate and the support main body portion extending outward from the outer peripheral portion of the piezoelectric vibration plate so as to maintain strength and prevent damage due to impact caused by dropping or the like. In some cases, each of the support main body portions may include a support frame (frame) to which one end of the support main body portion is connected.

  Further, in order to prevent the vibration energy of the piezoelectric diaphragm from leaking through the support arm, the support arm may be made thin, but the support arm is likely to be damaged during assembly in the manufacturing process. There is a drawback, and as described above, it is necessary to increase the strength by configuring the support arm with a support main body extending from the piezoelectric diaphragm and a frame connected to the support main body. However, if the piezoelectric diaphragm is completely surrounded by the support main body and the frame, the support strength increases, but the size of the entire 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 piezoelectric diaphragm very small. For example, in the case of a fundamental wave with a resonance frequency of 12 MHz, the width of the rectangular piezoelectric diaphragm is about 270 μm. If the supporting arm having the structure as in the conventional example is kept downsized and the frequency is increased, the vibration energy itself of the piezoelectric 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 unit is a coupled state that obtains good frequency-temperature characteristics when the weight of the support arm that adjusts the frequency of the length-length mode is too large compared to the weight of the piezoelectric diaphragm. Cannot be created. Therefore, when the resonance frequency is increased and the piezoelectric diaphragm is made smaller and lighter, the support arm is also made thinner, smaller, thinner, and lighter. As a result, there is a problem that even if the support arm can be manufactured in a shape and size that can provide satisfactory frequency-temperature characteristics, the strength becomes too weak to hold the piezoelectric diaphragm.

  Further, as shown in FIG. 17, when the conventional piezoelectric vibrator 1 is to be mounted in the package 5, only the pair of support arms 3 without a frame is bonded to the ends of the support arms 3 by conductive bonding. It is indispensable to directly support and fix the pair of terminal electrodes 6 with an agent or the like. However, many of the existing small ceramic packages, such as the 3.2mm x 2.5mm for AT-cut thickness-slip quartz crystal units standardized by the Quartz Device Industry Association, etc., have a structure in which the resonator is fixed only on one side inside the package. There are many. Therefore, a conventional piezoelectric vibrator having no frame cannot be mounted on such a relatively easily available ceramic package.

  Accordingly, an object of the present invention is to provide a support that can efficiently obtain vibration energy due to the main vibration of a piezoelectric diaphragm that is downsized in response to a high oscillation frequency, and can stably support the piezoelectric diaphragm. It is an object of the present invention to provide a piezoelectric vibrator having a width-longitudinal-longitudinal coupling mode having a structure.

In order to solve the above problems, the piezoelectric vibrator of the present invention rotates a Y-plate crystal perpendicular to the mechanical axis (Y axis) by an angle θx = + 40 ° to + 60 ° with the electric axis (X axis) as the rotation axis. Further, the piezoelectric vibrator of the longitudinal / longitudinal coupled mode is cut by rotating the angle θy = 40 ° to 50 ° with the new axis (Y ′ axis) after the rotation of the X axis as a rotational axis. And having a pair of main vibration sides with a main vibration in the width-longitudinal mode and a pair of sub-vibration sides perpendicular to the pair of main vibration sides and having a sub-vibration in the length-longitudinal mode, and an oscillation frequency of 4 MHz to 30 MHz. A square piezoelectric diaphragm having a capacitance ratio of 250 to 400, a pair of support arms having one end connected to the pair of main vibration sides and extending outward from the main vibration side, and the piezoelectric diaphragm And a frame to which the other ends of the pair of support arms are connected. Each support arm includes a first arm portion extending in a direction orthogonal to the main vibration side from a substantially intermediate position of the pair of main vibration sides, and a main vibration side from the first arm portion via a first bent portion. A second arm portion extending in parallel; a third arm portion extending in a direction perpendicular to the main vibration side from the second arm portion via the second bent portion; and a third bent portion from the third arm portion. A fourth arm portion that is folded back and extends parallel to the main vibration side, and a fifth arm portion that extends from the fourth arm portion through the fourth bent portion and extends outwardly perpendicular to the main vibration side, The ends of the pair of support arms are connected to the frame.

  According to the piezoelectric vibrator of the present invention, since the support arm is connected on the main vibration side orthogonal to the sub-vibration direction in the longitudinal mode, the stable state without affecting the main vibration in the width longitudinal mode Can support the piezoelectric diaphragm. In addition, since the support arm is connected between the main vibration side and the frame by a single continuous path, and has two or more bent portions therebetween, the piezoelectric diaphragm can be elastically supported. The sub-vibration with respect to the main vibration can be efficiently reduced.

  In addition, since the intermediate position that substantially bisects the main vibration side is a node that becomes the starting point of the main vibration, the influence on the main vibration is minimized by connecting a support arm to this intermediate position. be able to.

It is a top view of the piezoelectric vibrator in a 1st embodiment of the present invention. It is a top view which shows a state when the said piezoelectric vibrator is mounted in a package. It is a graph which shows the relationship between the side-to-side ratio and capacity ratio of a piezoelectric diaphragm. It is a top view of the piezoelectric vibrator in 2nd Embodiment of this invention. It is a top view which shows the 1st modification of the piezoelectric vibrator of the said 2nd Embodiment. It is a top view which shows the 2nd modification of the piezoelectric vibrator of the said 2nd Embodiment. It is a top view which shows the dimension shape of the piezoelectric vibrator of the said FIG. 6, and the conventional piezoelectric vibrator. It is a graph which shows the frequency difference of the main vibration and the sub vibration in the difference in a support arm shape. It is a graph which shows the primary temperature coefficient in the difference in a support arm shape. It is a top view which shows the 3rd modification of the piezoelectric vibrator of the said 2nd real form. It is a top view of the piezoelectric vibrator in 3rd Embodiment of this invention. It is a top view of the piezoelectric vibrator in 4th Embodiment of this invention. It is a top view of the piezoelectric vibrator in 5th Embodiment of this invention. It is a top view of the piezoelectric vibrator in 6th Embodiment of this invention. It is a top view of the piezoelectric vibrator in 7th Embodiment of this invention. It is a top view of the piezoelectric vibrator in 8th Embodiment of this invention. It is a top view of the conventional piezoelectric vibrator.

  1 and 2 show a planar shape of the piezoelectric vibrator 11 according to the first embodiment, which is a basic shape, and an example of a mounting form on the package 15. The piezoelectric vibrator 11 has a basic shape with contour vibration, and has a rectangular piezoelectric diaphragm 12 for generating a vibration in a width-longitudinal / length-longitudinal mode, and an outer side from one side of the piezoelectric diaphragm 12. A support arm 13 extending in the direction and a frame 14 for supporting the support 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 support 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 11 rotates a Y plate crystal perpendicular to the mechanical axis (Y axis) by an angle θx = + 40 ° to + 60 ° with the electric axis (X axis) as a rotation axis, and further, after the rotation of the X axis A thin plate-shaped quartz crystal substrate 19 having upper and lower surfaces and four side surfaces rotated by an angle θy = 40 ° to 50 ° with the new axis (Y ′ axis) as a rotation axis is formed into a predetermined shape. . Further, 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 12 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 12, the support arm 13, and the frame 14 are formed by punching the quartz substrate 19 into a predetermined shape.

  The piezoelectric diaphragm 12 is orthogonal to the main vibration sides 12a and 12b so as to cause a pair of main vibration sides 12a and 12b facing each other so as to generate a longitudinal main vibration and a lengthwise sub vibration. It is formed in a quadrangular shape by a pair of sub-vibration sides 12c and 12d that face each other. The side ratio between the main vibration sides 12a and 12b and the sub-vibration sides 12c and 12d varies depending on the oscillation frequency. Further, a first excitation electrode 17 is formed on the front surface of the piezoelectric diaphragm 12 and a second excitation electrode 18 is formed on the back surface, and a pair of terminal electrodes 16 provided in the package 15 with voltages having opposite phases with respect to the respective excitation electrodes. The main vibration sides 12a and 12b and the sub-vibration sides 12c and 12d are bent and deformed by applying them through the frame 14 and the support arm 13 to generate a vibration in the width-length / length-length coupled mode.

  The support arm 13 has a shape (cantilever) that is elastically connected by a single path between the one main vibration side 12b and the frame 14. In the support arm 13 having such a cantilever shape, the number of connection points C with the piezoelectric diaphragm 12 is preferably as small and narrow as possible so as not to affect the main longitudinal vibration in the width-longitudinal mode as much as possible. For this reason, in the piezoelectric vibrator 11 of the present embodiment, the connection point C of the support arm 13 is provided on one main vibration side 12 b of the piezoelectric diaphragm 12. The connection point C is preferably set at a substantially intermediate position of the main vibration side 12b serving as a sub vibration node, and the support arm 13 preferably has a portion bent in the sub vibration direction in order to absorb unnecessary vibration. .

  In order to satisfy the above various conditions, the support arm 13 of the present embodiment includes a first arm portion 20a extending in a direction orthogonal to the main vibration side 12b, and one side from the first arm portion 20a via the first bent portion 13a. The second arm portion 20b extending in parallel with the main vibration side 12b and the third arm portion 20c extending from the second arm portion 20b toward the frame 14 via the second bent portion 13b. The first arm portion 20a, the second arm portion 20b, and the third arm portion 20c constitute one path that is bent in an approximately L shape.

  By setting the bending angle of the two bent portions 13a and 13b to approximately 90 degrees, the entire length of the support arm 13 that connects the piezoelectric diaphragm 12 and the frame 14 is set short, but the bending portions 13a and 13b By setting the bending angle to be larger than 90 degrees, the length of the support arm 13 can be adjusted.

  As shown in FIG. 2, the frame 14 fixes the piezoelectric vibrator 11 to the package 15 and applies a voltage to the first excitation electrode 17 and the second excitation electrode 18 of the piezoelectric diaphragm 12 via the support arm 13. Is provided. Since the frame 14 also constitutes a part of the support arm 13, it is desirable that the frame 14 be as light as possible while maintaining the support strength. Therefore, in this embodiment, the piezoelectric diaphragm 12 is formed in a U shape so as to surround the three vibration sides 12b, 12c, and 12d excluding the upper main vibration side 12a. The frame 14 has a support arm 13 connected to one of the vertical sides 14c by soldering a vertical side 14a away from a portion to which the support arm 13 is connected to a terminal electrode 16 in the package 15; The piezoelectric diaphragm 12 can be supported in a floating state.

  Next, the best mode for reducing the strength and equivalent series resistance (R1) of the piezoelectric vibrator 11 and obtaining good frequency temperature characteristics will be described with reference to FIGS. FIG. 3 shows an FEM simulation of the change in the capacitance ratio γ at a predetermined cut angle θx based on the vertical / horizontal side ratio of the piezoelectric diaphragm 12. Here, as shown in FIG. 1, the side ratio (VW / VL) of the vertical (main vibration side VW) and the horizontal (sub vibration side VL) in the piezoelectric diaphragm 12, the weight (WV) of the piezoelectric diaphragm 12, and It is necessary to appropriately select the weight ratio (WE / WV) of the weight (WE) of the support arm 13 and the width and length (Ew1, El1) of the support arm 13 for controlling the longitudinal mode. In particular, when the oscillation frequency is 4 MHz or higher, VW decreases, and if Ew1 and El1 are increased to maintain the strength, WE / WV increases and satisfactory characteristics cannot be obtained. Therefore, Ew1 and El1 are set such that (WE / WV) <= 0.23 and vibration leakage is reduced, so that the support arm 13 has a spring property to bend. Further, the frame 14 is shaped so as not to surround the piezoelectric diaphragm 12 with a predetermined gap (a U-shape), and Fw1 and Fl1 are set to appropriate dimensions to maintain the strength of the entire piezoelectric vibrator 11. As described above, the frame 14 itself is also provided with a spring property to control the frequency in the longitudinal longitudinal mode, so that the conditions of strength, equivalent series resistance, and frequency-temperature characteristics can be in the most favorable state.

  According to this simulation result, it was confirmed that the capacity ratio γ = 250 to 400 was obtained in the range of (VW / VL) = 1.00 to 0.92 by adopting the support arm 13 having the above shape. . In particular, even when the resonance frequency of the main vibration is 4 MHz or more and the vibration energy is reduced by downsizing the piezoelectric diaphragm 12, the capacity ratio can be obtained while ensuring the necessary impact resistance. Became possible.

  Table 1 shows a comparison of the electrical characteristics of the piezoelectric vibrator according to the conventional support portion shape (conventional shapes 1 and 2) and the piezoelectric vibrator according to the above-described shape of the present invention (the present shape). Here, the data at the frequency F = 2.1 MHz of the conventional shape 1 is a general numerical value based on known literature materials, and the data of the conventional shape 2 is a prototype of a piezoelectric vibrator having the same shape as the conventional shape 1, It is a value when experimenting at F = 12 MHz. From this result, when the frequency is increased to 12 MHz as in the conventional shape 2, the equivalent series resistance R1 becomes particularly high. On the other hand, the present embodiment is a value when the prototype is made with (WE / WV) <= 0.23 in the piezoelectric diaphragm 12 shown in FIG. 1 and the experiment is performed at F = 12 MHz. From this experimental data, in this embodiment, the capacitance ratio γ and the equivalent series resistance R1 that most affect the characteristics of the piezoelectric vibrator are lower than those of the conventional shape 1 at 2.1 MHz and the conventional shape 2 at 12 MHz. It can be seen that good electrical characteristics can be obtained.

  As a result of the above simulation and electrical characteristic data, if the shape of the support arm 13 is the shape as shown in FIG. 1, the piezoelectric diaphragm 12 and the frame have the width and thickness of the support arm 13 that can maintain sufficient strength. 14 can be connected to easily change the vibration frequency of the length-longitudinal mode, which is a secondary vibration, to control the degree of coupling between the width-longitudinal mode and the length-longitudinal mode. When the piezoelectric diaphragm 12 can be vibrated in an optimal coupling state, that is, when the vibration efficiency is the best, the capacitance ratio is minimized and good electrical characteristics can be obtained. .

  FIG. 4 shows a planar shape of the piezoelectric vibrator 21 of the second embodiment. This piezoelectric vibrator 21 has a quadrangular piezoelectric diaphragm 22 for generating a vibration in the width-longitudinal length-coupled mode, and two bending directions outward from one main vibration side 22a of the piezoelectric diaphragm 22. A support arm 25 having a portion (25a, 25b) and constituting one path, and two bent portions (23a, 23b) outward from the other main vibration side 22b of the piezoelectric diaphragm 22 A support arm 23 that constitutes one path and a frame 24 that holds the pair of support arms 23 and 25 are integrally formed. The difference from the piezoelectric vibrator 11 of the first embodiment is that the piezoelectric diaphragm 22 is supported by two support arms 23 and 25 provided so as to have a mirror symmetry with the piezoelectric diaphragm 22 interposed therebetween. is there. Thus, since it is supported by the two support arms 23 and 25, the piezoelectric diaphragm 22 can be vibrated in a stable state. Further, each of the support arms 23 and 25 is connected to an intermediate position that bisects the main vibration sides 22a and 22b of the piezoelectric diaphragm 22, so that the sub vibration can be effectively suppressed without affecting the main vibration. it can.

  5, 6 and 10 show first to third modifications of the piezoelectric vibrator 21 of the second embodiment. The support arms 33 and 35 in the piezoelectric vibrator 31 of the first modified example shown in FIG. 5 pass through one path bent in a V shape from the pair of main vibration sides 32 a and 32 b of the piezoelectric diaphragm 32, respectively. It is connected to the. The support arms 33 and 35 are each formed with three bent portions (33a to 33c) and (35a to 35c).

  The support arms 43 and 45 in the piezoelectric vibrator 41 of the second modification shown in FIG. 6 are connected to the frame 44 through one path extending in a U-shape from the pair of main vibration sides 42a and 42b of the piezoelectric vibration plate 42, respectively. It is connected. On each of the paths, there are four bent portions (43a to 43d) and (45a to 45d).

  FIG. 7 shows the dimensions of the piezoelectric vibrator having the conventional support arm shape (simple beam model) and the piezoelectric vibrator 41 having the support arm shape (cantilever model) of the present invention shown in FIG. . Next, the difference in electrical characteristics between the simple beam model and the cantilever model will be described with reference to FIGS.

  FIG. 8 shows changes in the frequency difference δ between the main vibration and the sub-vibration due to the cut angle θ, and FIG. 9 shows changes in the primary temperature coefficient α due to the cut angle θ. The FEM analysis using this graph was performed under the conditions that the thickness of the crystal was 5 μm and the electrode thickness of Au was 500 mm in both the cantilever model and the simple beam model.

  As shown in FIG. 9, the conventional simple beam model cannot make α≈0 at any cut angle. However, with the cantilever model of the present invention, there is a cut angle satisfying α>, and α≈0 can be set. At this time, when the frequency difference between the main vibration and the sub vibration shown in FIG. 8 is seen, it can be seen that the frequency difference between the main vibration and the sub vibration is smaller in the cantilever model. As described above, the frequency difference between the main vibration and the sub-vibration is different depending on the shape of the support arm, resulting in a difference in temperature characteristics.

  If limited to this analysis condition, at least δ should be about 8.8%, but this is not possible with the conventional simple beam model. If the dimensional design is performed on the assumption of the simple beam model shown in FIG. 7A, the support arm must be made very thin in order to make it light. In general, in the case of a longitudinal / longitudinal coupled oscillator, the value of α becomes negative as the ratio of the electrode film thickness to the crystal thickness (Au / X′tal) increases. Usually, in order to widen the frequency adjustment range, the Au film thickness is often about 1000 mm, but the ratio (Au / X'tal) increases, so it is necessary to further reduce δ, and the support arm is also made thinner. There is a need to.

The maximum deflection δ1 in the conventional simple beam model shown in FIG. 7A is generally expressed by the following equation.
δ1 = P1 * L1 ^ 3 / (48 * E1 * I1)
here,
P1: Stress L1: Beam length E1: Young's modulus I1: Cross section secondary moment

On the other hand, the maximum deflection δ2 in the cantilever model of the present invention shown in FIG. 7B is expressed by the following equation.
δ2 = P2 * L2 ^ 3 / (3 * E2 * I2)
here,
P2: Stress L2: Beam length E2: Young's modulus I2: Sectional moment of inertia

  Considering the beam portion of the support arm when trying to obtain optimum temperature characteristics by suppressing the secondary vibration mode of a certain frequency, the following can be said.

  In order to obtain the same amount of deflection when the width and cross-sectional shape (E1 = E2, I1 = I2) of the beam portion of the support arm are the same, P1 = P2, and therefore L1 ^ 3 = 16 * L2 ^ 3 It becomes. That is, the beam length L1 in the simple beam model is required to be approximately 2.5198 (16 cube root) times the beam length L2 in the cantilever beam model. In other words, to obtain the same amount of deflection, the cantilever model is about 2.5 times lighter than the simple beam model. As described above, the factor that reduces the secondary vibration frequency is the effect of the weight. The effect of the weight is determined by the weight ratio between the diaphragm and the weight (support arm).

  Next, the case where the frequency of the width-longitudinal mode is high is considered from the viewpoint of vibration energy. As the frequency increases, the diaphragm becomes smaller and lighter. This reduces the vibration energy and the amplitude. In this way, the longitudinal longitudinal mode in which the vibration energy is small because the vibration plate is small and the frequency is high is compared with the width longitudinal mode compared to the case where the vibration plate is large and the vibration energy is large because the frequency is low. The connection becomes severe. Therefore, in order to obtain a sufficient coupling state, it is necessary to bring the frequency in the lengthwise longitudinal mode closer to the frequency in the widthwise longitudinal mode. That is, when the frequency in the width-longitudinal mode increases, the frequency in the length-longitudinal mode to be combined needs to be close to the frequency in the width-longitudinal mode.

  If a support arm consisting of heavy (thick and long) beams is constructed against a light diaphragm (high frequency diaphragm) as in the conventional simple beam model, the sub-vibration length will be increased by the effect of the weight. The frequency of the longitudinal mode is too low to be brought close to the frequency of the longitudinal mode of the main vibration width, and the frequency temperature characteristic of the main vibration cannot be adjusted to be optimum. The same can be said in terms of miniaturization, and the simple beam model is approximately 2.5 times longer than the cantilever beam model, which is disadvantageous in terms of miniaturization.

  From the above points, the cantilever model of the present embodiment is more advantageous than the simple beam model in terms of weight and size in configuring the support arm of the diaphragm having a high frequency.

  The support arms 53 and 55 in the piezoelectric vibrator 51 shown in FIG. 10 have six bent portions (53a to 53f) and (55a to 55f) from the pair of main vibration sides 52a and 52b of the piezoelectric diaphragm 52, respectively. However, it is connected to the frame 54 through a single S-shaped path.

  If the piezoelectric vibrators 21, 31, 41, 51 shown in FIGS. 4 to 6 and FIG. 10 have the same shape and size of the piezoelectric diaphragm, the spring property increases as the number of bent portions of the support arm increases. Since it becomes high, the effect of diffusing the secondary vibration due to the longitudinal mode becomes large.

  FIG. 11 shows a piezoelectric vibrator 71 provided with a piezoelectric diaphragm 72 in a higher-order width longitudinal / length longitudinal mode. The piezoelectric diaphragm 72 has a plurality of small excitation electrode surfaces 77a and 77b arranged in a matrix, and is arranged so that the small excitation electrode surfaces 77a and 77b having different polarities are adjacent in the vertical and horizontal directions. Has been. The piezoelectric diaphragm 72 shown in FIG. 11 is configured by a 5 × 5 small vibration section. Even in the piezoelectric diaphragm 72 having such a high-order width longitudinal / longitudinal longitudinal mode, one path that bends in a U-shape from a connection point located between the pair of main vibration sides 72a and 72b. By connecting to the frame 74 via a pair of support arms 73 and 75 that extend with a vertical axis, it is possible to suppress the secondary vibration caused by the high-order longitudinal length.

  12 and 13 show a structure in which the piezoelectric diaphragm is supported by three or more support arms. FIG. 12 shows a piezoelectric diaphragm 82 having two excitation electrodes 87a and 87b in the width-longitudinal direction, a pair of support arms 73 and 75 that support both main vibration sides of the vibration region where the excitation electrode 87a is formed, and A support arm 76 that supports one main vibration side of the vibration region in which the excitation electrode 87b is formed, and a frame 74 to which the three support arms 73, 75, and 76 are connected are configured. FIG. 13 shows a piezoelectric vibration plate 92 having three excitation electrodes 97a, 97b, and 97c in the vibration direction of the width-longitudinal mode and both main vibration sides of the vibration region in which the excitation electrode 97a is formed as one path. A pair of support arms 93 and 95 that support the main vibration sides of the vibration region in which the excitation electrode 97c is formed, and a pair of support arms 96 and 99 that support the main vibration sides. A frame 94 to which these four support arms 93, 95, 96, 99 are connected is configured. In this way, in the piezoelectric diaphragm 92 in which a plurality of vibrating portions by a plurality of excitation electrodes are formed, the piezoelectric diaphragm 92 is elastically supported via three or more support arms each having a single path, whereby While suppressing the sub-vibration due to the vertical mode, the main vibration in the width-longitudinal mode can be stabilized.

  The support arm shown in FIGS. 11 to 14 has a U shape with four bent portions, but an L shape having two bent portions, a V shape having three bent portions, It can also be S-shaped with six bends.

  FIG. 14 and FIG. 15 show an example of the structure of a frame that supports the piezoelectric diaphragm 102 in which the vibration part formed by the three excitation electrodes 107a, 107b, and 107c is formed in the vibration direction of the width-longitudinal mode. The support arms 103 and 105 are common and are each formed in a U shape having four bent portions on one path. The frame 104 shown in FIG. 14 includes a pair of legs 104a and 104b extending linearly from the pair of support arms 103 and 105 along the main vibration sides 102a and 102b of the piezoelectric diaphragm 102, and the pair of legs 104a. , 104b are connected to a base 104c. The leg portions 104a and 104b are formed with a narrower width than the support arms 103 and 105 and the base portion 104c.

  The frame 114 shown in FIG. 15 has a pair of leg portions 114a and 114b extending from the pair of support arms 103 and 105, respectively, and the leg portions 114a and 114b meander in a V shape with three bent portions. Is formed. The frame 114 is placed on both ends of the base portion 114c on a pair of terminal electrodes 117 disposed in the package 115, and electrically joined by a conductive bonding member 116 such as a conductive adhesive or a solder bump. A predetermined voltage can be supplied to the excitation electrode, and the piezoelectric diaphragm 102 can be held in a floating state.

  The leg portions 104a and 104b shown in FIG. 14 and the leg portions 114a and 114b shown in FIG. 15 have sufficient spring properties because they are meandering in a narrow or U shape. This spring property can effectively absorb the longitudinal vibration of the longitudinal longitudinal mode generated in the piezoelectric diaphragm 102. Therefore, also in the frame, the effect of suppressing the secondary vibration can be obtained by changing the width dimension and shape in the same manner as the support arm.

  The piezoelectric vibrator of each of the above embodiments is cantilevered by electrically connecting one end of a frame to a terminal electrode in a package such as ceramic, and is subjected to electron beam sealing, vacuum seam welding, glass sealing, AuSn sealing. The lid is closed with a stopper, and hermetically sealed at a vacuum degree of 1.0 × 10 Pa or less.

  The piezoelectric vibrator 121 shown in FIG. 16 is formed by adjusting the width or thickness of a part of each component based on the piezoelectric vibrator 101 shown in FIG. The piezoelectric vibrator 121 reduces the area ratio in the thickness direction of a part (123a, 125a) of the support arms 123, 125, and reduces the area ratio in the width direction and the thickness direction of the legs 124a, 124b of the frame 124. And formed. As described above, the frequency temperature characteristic can be further improved by reducing one or both of the width direction and the thickness direction. Further, with respect to the piezoelectric diaphragm 122, the edge of the piezoelectric diaphragm 122 excluding the three-surface vibrating section is formed by forming a thick edge and recessing the surface on which the excitation electrodes 127a, 127b, and 127c are formed. It itself serves as a weight. Thereby, the secondary vibration due to the longitudinal mode can be suppressed. Further, since the excitation electrodes 127a, 127b, and 127c can be formed along the inner wall surface and the bottom surface where the piezoelectric diaphragm 122 is recessed, the effect that the effective area of the excitation electrode is increased and the vibration characteristics can be improved. Is obtained.

C Connection point 11 Piezoelectric vibrator 12 Piezoelectric diaphragm 12a, 12b Main vibration side 12c, 12d Sub vibration side 13 Support arm 13a, 13b Bending part 14 Frame 15 Package 16 Terminal electrode 17 First excitation electrode 18 Second excitation electrode 19 Crystal Substrate 20a First arm portion 20b Second arm portion 20c Third arm portion

Claims (10)

A Y-plate crystal perpendicular to the mechanical axis (Y axis) is rotated by an angle θx = + 40 ° to + 60 ° with the electric axis (X axis) as the rotation axis, and a new axis (Y ′ axis) after the rotation of the X axis. ) As a rotation axis, and a piezoelectric vibrator in a width-longitudinal-longitudinal coupling mode cut by rotating at an angle θy = 40 ° to 50 °,
It has a pair of main vibration sides with a main vibration side in the width-longitudinal mode and a pair of sub-vibration sides with a sub-vibration in the length-longitudinal mode, and generates an oscillation frequency of 4 MHz to 30 MHz. A rectangular piezoelectric diaphragm having a capacitance ratio of 250 to 400 ;
A pair of support arms having one end connected to the pair of main vibration sides and extending outward of the main vibration sides;
A frame provided on the outer periphery of the piezoelectric diaphragm, and connected to the other ends of the pair of support arms;
Each of the support arms includes a first arm portion extending in a direction orthogonal to the main vibration side from a substantially intermediate position of the pair of main vibration sides, and a main vibration side from the first arm portion via a first bent portion. A second arm portion extending in parallel; a third arm portion extending in a direction perpendicular to the main vibration side from the second arm portion via the second bent portion; and a third bent portion from the third arm portion. A fourth arm portion that is folded back and extends parallel to the main vibration side, and a fifth arm portion that extends from the fourth arm portion through the fourth bent portion and extends outwardly perpendicular to the main vibration side,
The piezoelectric vibrator characterized in that the ends of the pair of support arms are connected to the frame. The frame includes a base portion that is electrically secured via a conductive bonding member, claim has a pair of legs extending meander comprises at least two or more bent portions from both ends of the base portion 1 The piezoelectric vibrator described in 1 . The piezoelectric vibrator according to claim 1 , wherein the support arm is set to a weight ratio of 0.23 or less with respect to the piezoelectric diaphragm. 2. The piezoelectric vibrator according to claim 1 , wherein the support arm is bent and extends in a substantially U-shape from a substantially middle position of the main vibration side toward the frame. The piezoelectric vibrator according to claim 1 , wherein the frame is formed in a substantially U shape so as to follow an outer periphery of the piezoelectric diaphragm. The piezoelectric vibrator according to claim 1 , wherein the piezoelectric diaphragm has a plurality of vibration surfaces with respect to a main vibration direction or a sub vibration direction. The piezoelectric vibrator according to claim 1 , wherein the piezoelectric diaphragm, the support arm, and the frame are integrally formed by a quartz substrate. Main vibration width longitudinal mode by the main vibration side, the secondary vibration sides by higher resonance frequency than the secondary vibration of the length longitudinal mode, and the piezoelectric vibrator according to the equivalent series resistance is small claim 1. 2. The piezoelectric vibrator according to claim 1 , wherein the support arm or the frame is formed so as to partially include a portion having a small area ratio in at least one of the width direction and the thickness direction. The piezoelectric vibrator according to claim 1 , wherein the piezoelectric diaphragm is provided with a concave portion on a surface thereof, and an excitation electrode is formed along an inner surface of the concave portion.

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