Crystal Vibrator

Abstract

To provide a crystal vibrator having a new structure that can reduce thermal stress.SOLUTION: A crystal vibrator 10 comprises an AT-cut crystal vibrator piece 11, a container 13 having two adhesive pads 13a and 13b provided along a first direction (a), a pedestal 23 made of a crystal arranged between the crystal vibrator piece and the two adhesive pads, and conductive adhesives 21 and 25 connecting the crystal vibrator piece, the pedestal and the adhesive pads to one another. The crystal vibrator piece is made to adhere to the pedestal, at two positions along an X-axis of the crystal or at two positions along a Z'-axis of the crystal. The pedestal has the X-axis or the Z'-axis or a Z-axis of the crystal, in a direction parallel to the surface, depending on whether the crystal vibrator piece is made to adhere to the pedestal, at the two positions along the X-axis or the piece is made to adhere to the pedestal, at the two positions along the Z'-axis, and the crystal vibrator piece is made to adhere to the two adhesive pads in a positional relation in which the axis is in parallel to the first direction, where a relational expression of a thickness T to a thickness t of the crystal vibrator piece is represented by / is 0.9t≤T≤3.1t.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a quartz crystal resonator having a base. [Background technology]

[0002] AT-cut quartz crystal units are often used as reference signal sources for electronic devices. A typical example of an AT-cut quartz crystal unit has a container and a quartz crystal resonator piece glued inside the container. Higher precision is being demanded of AT-cut quartz crystal units. One method of achieving this is to provide a base between the quartz crystal element and the container. For example, Patent Document 1 describes the use of a pedestal having the same expansion coefficient as the quartz crystal resonator element (e.g., claim 1 of Patent Document 1). Furthermore, it describes the use of a quartz crystal plate having the same cutting angle as the quartz crystal resonator element (e.g., paragraph 4 of Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2010-135890 Summary of the Invention [Problem to be solved by the invention]

[0004] In a structure in which a pedestal is interposed between a quartz crystal resonator element and a container, using a quartz crystal plate with the same cutting angle as the quartz crystal resonator element as the pedestal is certainly effective in reducing thermal stress caused by the adhesive structure. However, the inventors of this application have found that further optimization is necessary to reduce thermal stress caused by the adhesive structure. This application has been made in consideration of the above points, and therefore, an object of this application is to provide a quartz crystal resonator having a base made of a quartz crystal piece between a quartz crystal resonator piece and a container, and having a novel structure that can further reduce thermal stress. [Means for solving the problem]

[0005] In order to achieve this object, according to the present invention, a quartz crystal resonator includes an AT-cut quartz crystal resonator element having a rectangular shape in a plan view, a container having two adhesive pads arranged along a first direction, a quartz crystal base arranged between the quartz crystal resonator element and the two adhesive pads, and a conductive adhesive connecting the quartz crystal resonator element, the base, and the adhesive pads. The quartz crystal vibrating piece is attached to the base at two points along the X-axis of the quartz crystal or at two points along the Z'-axis of the quartz crystal, The quartz crystal base has the quartz crystal's X-axis, Z'-axis, or Z-axis parallel to its surface, depending on whether the quartz crystal vibrating piece is bonded to the base at two points along the X-axis or two points along the Z'-axis, and has a thickness T, where t is the thickness of the quartz crystal vibrating piece, that is 0.9t≦T≦3.1t, and is bonded to the two bonding pads in a positional relationship such that the axes are parallel to the first direction (however, the Z'-axis is an axis that is offset from the true Z-axis of the quartz crystal due to the cutting angle of the AT-cut quartz crystal piece). [Effects of the Invention]

[0006] According to this invention, a quartz crystal resonator that makes extensive use of a cantilever support structure can be realized, in which a quartz crystal base is bonded to an adhesive pad in a cantilever support manner, and an AT-cut quartz crystal resonator piece is bonded to this quartz crystal base in a cantilever support manner. Furthermore, depending on whether the quartz crystal resonator blank is connected to the base at two points along the X-axis of the quartz crystal or at two points along the Z'-axis of the quartz crystal, a quartz crystal pedestal of a predetermined thickness with an axis corresponding to the axis parallel to the face can be used, and the quartz crystal resonator blank and the quartz crystal pedestal are bonded in a positional relationship such that the crystallographic axis of the quartz crystal resonator blank and the crystallographic axis of the pedestal are parallel to each other. Therefore, the quartz crystal resonator blank and the quartz crystal pedestal can be positioned so that the crystallographic conditions between the two bonding points, which are most susceptible to the effects of thermal stress, are similar to each other, thereby reducing the effects of thermal expansion coefficients and other factors compared to when this is not done. Furthermore, because the pedestal has a predetermined thickness, thermal stress reduction is further achieved, as can be seen from the experimental and analytical results described below, and the thickness of the quartz crystal resonator can be prevented from increasing. Therefore, it is possible to provide a quartz crystal resonator having a novel structure that can further reduce thermal stress. [Brief explanation of the drawings]

[0007] [Figure 1] 1A and 1B are diagrams illustrating a crystal resonator 10 according to a first embodiment. [Figure 2] 10A and 10B are diagrams illustrating a crystal resonator 30 according to a second embodiment. [Figure 3] 1 is a diagram for explaining the relationship between the quartz crystal vibrating piece and the base in the present invention, and in particular, a diagram for explaining the relationship regarding the crystal axes of the quartz crystal. FIG. [Figure 4] 1 is a diagram for explaining an example of a temperature compensated crystal oscillator to which the present invention is applied; [Figure 5] 1A to 1C are diagrams for explaining experiments and analyses according to the present invention. [Figure 6] 10A and 10B are diagrams for explaining the thickness of a quartz crystal base and the degree of stress relaxation. [Figure 7] 1 is a diagram illustrating the relationship between the distance h between the quartz crystal vibrating piece and the quartz crystal base, the angle θ between the quartz crystal vibrating piece and the quartz crystal base, and the crystal impedance. [Figure 8]10A and 10B are diagrams for explaining the dimensions of a quartz crystal base relative to a quartz crystal vibrating piece and an excitation electrode, and for explaining modified examples of the base structure. [Figure 9] 1A and 1B are diagrams illustrating a preferred container and a preferred base. [Figure 10] 1A and 1B are diagrams for explaining specific examples of quartz crystal vibrating pieces; DETAILED DESCRIPTION OF THE INVENTION

[0008] Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that each drawing used in the description is merely a schematic illustration to enable understanding of the present invention. Furthermore, in each drawing used in the description, similar components are designated by the same numbers, and their description may be omitted. Furthermore, the structural examples, components used, etc. described in the following description are merely preferred examples within the scope of the present invention. Therefore, the present invention is not limited to the following embodiments.

[0009] 1. Crystal unit embodiment 1-1. First embodiment 1 and 2 are diagrams illustrating a quartz crystal resonator 10 according to a first embodiment. In particular, FIG. 1(A) is a top view of the quartz crystal resonator 10, FIG. 1(B) is a cross-sectional view taken along line PP in FIG. 1(A), and FIG. 1(C) is a bottom view. Note that FIG. 1(A) shows the quartz crystal resonator 10 with the cover member 19 removed. In addition, FIG. 2 is a diagram illustrating the relationship between the quartz crystal resonator piece 11 and the base 23.

[0010] This quartz crystal unit 10 includes an AT-cut quartz crystal vibrating piece 11 that is rectangular in plan view, a container 13 having two adhesive pads 13a, 13b spaced a predetermined distance apart along a first direction a, a quartz crystal base 23 disposed between the quartz crystal vibrating piece 11 and the two adhesive pads 13a, 13b, and conductive adhesives 21, 25 that connect the quartz crystal vibrating piece 11, the base 23, and the adhesive pads 13a, 13b. In this example, the first direction a is parallel to the short side of the container 13. The quartz crystal vibrating piece 11 is attached to the base 23 at two points along the X-axis of the quartz crystal or at two points along the Z'-axis of the quartz crystal, as will be described in detail later. The quartz crystal base 23, which will be described in detail later, has the quartz crystal's X-axis, Z'-axis, or Z-axis parallel to the surface, depending on whether the quartz crystal vibrating piece 11 is bonded to the base at two points along the quartz crystal's X-axis or Z'-axis, and is bonded to two bonding pads 13a, 13b in a positional relationship such that this axis is parallel to the first direction a, and has a thickness T, where t is the thickness of the quartz crystal vibrating piece, in the range 0.9t≦T≦3.1t. The Z'-axis is an axis that is offset from the true Z-axis of the quartz crystal due to the cutting angle of the AT-cut quartz crystal piece. The quartz crystal vibrating piece 11 is hermetically sealed, for example, vacuum sealed, by a lid member 19. Each of the components will now be described in detail.

[0011] As shown in FIG. 2, the AT-cut quartz crystal vibrating piece 11 has a square shape in plan view, in this example a rectangular shape, and has a predetermined thickness according to the oscillation frequency. The AT-cut quartz crystal vibrating piece 11 has excitation electrodes 11a on both the front and back main surfaces, and an extraction electrode 11b that is extracted from the excitation electrodes 11a to one of the short sides of the quartz crystal vibrating piece. The quartz crystal vibrating piece 11 is selected according to the design of the quartz crystal unit from among so-called X-long ones, in which the long sides are parallel to the X-axis, which is the crystal axis of the quartz crystal, and the short sides are parallel to the Z'-axis, which is the crystal axis of the quartz crystal, or so-called Z-long ones, in which the long sides are parallel to the Z'-axis of the quartz crystal and the short sides are parallel to the X-axis of the quartz crystal, or ones with a rectangular planar shape and one side parallel to either the X-axis or the Z'-axis of the quartz crystal.

[0012] In this case, the container 13 is a ceramic package with a square planar shape, specifically a rectangular shape. The container 13 has banks 13c along its edges. The crystal vibrating piece 11 is mounted on adhesive pads 13a and 13b using the space surrounded by the banks 13c. Furthermore, the four corners of the outer bottom surface of the container 13 are provided with external connection terminals 13d, 13e, 13f, and 13g for connecting the crystal unit 10 to an electronic device, such as an electronic board for a mobile phone (see FIG. 1(C)). Two of the four terminals are electrically connected to the bonding pads 13a and 13b inside the container by via wiring or castellation wiring (not shown). The remaining two of the four terminals can be used as desired depending on the purpose. The top surface of the bank portion 13c of the container 13 is treated according to the sealing method. In this example, a seam sealing method is used, and a seam ring (not shown) is provided on the top surface of the bank portion 13c. The sealing method may also be a soldering method using gold and tin. In this case, a metallized pattern for gold and tin sealing may be provided on the top surface of the bank portion 13c. The bank portion 13c is made of ceramic. As shown in FIG. 1B, a conductor 13m is embedded in a predetermined position on the bank portion 13c and the container 13 to electrically connect the lid member 19 to one terminal 13f of the external connection terminals for a temperature sensor. The external connection terminal 13f is connected to the ground of an electronic device (not shown) to which the crystal unit 10 is connected. This connection structure ensures an electromagnetic shielding structure for the crystal unit 10. The container 13 including the bonding pads 13a, 13b, the bank portion 13c, the conductor 13m, and the external connection terminals 13d, 13e, 13f, and 13g can be manufactured by, for example, a ceramic package manufacturing technique.

[0013] Any material may be used for the lid member 19 depending on the sealing method. When the sealing method is seam sealing, the lid member 19 may be made of, for example, a Kovar material plated with nickel. Although not limited to this, it is preferable to use a silicone-based conductive adhesive for the first conductive adhesive 21 and the second conductive adhesive 25. The first conductive adhesive 21 and the second conductive adhesive 25 may be the same or different, but it is preferable to use the same adhesive.

[0014] Although not limited to this, it is preferable to use a pedestal 23 that is rectangular in plan view because this makes it easier to process the pedestal. However, the planar shape of the pedestal 23 may be other shapes, such as a triangle or a trapezoid with a narrower tip. The size of the base 23 is not limited to this, but in this example it is larger in plan view than the quartz crystal vibrating piece 11. There are cases where it is preferable for the size of the base to be smaller than the quartz crystal vibrating piece. This point will be discussed later. Furthermore, the inventors have found that there is a preferred value for the thickness of the base 23. This point will also be discussed later. The appropriate base 23 is used depending on whether the quartz crystal vibrating piece 11 is connected to the base at two points along the X-axis of the quartz crystal, or at two points along the Z'-axis of the quartz crystal. This will be explained in detail with reference to Figure 2. The coordinate axes indicated by X, Y', and Z' in Figure 2 are the crystal axes of the quartz crystal derived from the AT-cut. The Y' and Z' axes indicate that the axes are offset from the quartz crystal's original Y and Z axes according to the cutting angle of the AT-cut.

[0015] FIG. 2A illustrates a pedestal in which the quartz crystal vibrating piece 11 is connected to the pedestal 23 at two locations along the X-axis of the quartz crystal. In other words, the ends of the extraction electrodes 11b are located at two separate locations along the X-axis of the quartz crystal, and the quartz crystal vibrating piece 11 is bonded to the pedestal 23a or 23b at these locations. The pedestal 23 in this case includes the X-axis of the quartz crystal parallel to its surface, and the quartz crystal vibrating piece 11 can be connected to the pedestal at two locations along the X-axis. Specifically, the pedestal 23a shown in the lower left of FIG. 2A is made of an AT-cut quartz crystal piece and is provided with adhesive wires 23a1 and 23a2 at two locations along the X-axis of the quartz crystal. Alternatively, the pedestal 23b shown in the lower right of FIG. 2A may be made of a Z-cut quartz crystal piece and is provided with adhesive wires 23a1 and 23a2 at two locations along the X-axis of the quartz crystal. The quartz crystal vibrating piece 11 and the base 23a or 23b are bonded to the adhesive pad, and the quartz crystal vibrating piece 11 is bonded to the base so that the X axes of the respective crystals are parallel to the first direction a (see Figure 1(A)).

[0016] 2(B) is an explanatory diagram of a pedestal when the quartz crystal vibrating piece 11 is connected to the pedestal 23 at two points along the Z' axis of the quartz crystal. In this case, the pedestal 23c includes the Z axis or Z' axis of the quartz crystal within its plane, and the quartz crystal vibrating piece 11 can be connected to the pedestal at two points along the Z axis or Z' axis. Specifically, the pedestal 23c is made of an AT-cut quartz crystal piece, and is provided with adhesive wiring 23c1 and 23c2 along the Z' axis of the quartz crystal on the pedestal, corresponding to the extraction electrode 11b of the quartz crystal vibrating piece 11. The quartz crystal vibrating piece 11 and the pedestal 23c are bonded to the adhesive pad and the quartz crystal vibrating piece 11 is bonded to the pedestal so that the Z' axes of the respective quartz crystals are parallel to the first direction a (see Figure 1(A)). In each of the above-mentioned bases 23a, 23b, and 23c, the X-axis and Z'-axis of the base do not have to be exactly the same as the X-axis and Z'-axis of the quartz crystal vibrating piece. Within the scope of the object of the present invention, there may be a slight angular deviation between the two axes, or the two may not be parallel to each other.

[0017] 1A and 1B, in the quartz crystal resonator 10 of this embodiment, the quartz crystal pedestal 23 is connected and fixed to the container 13 at the bonding pads 13a and 13b of the container 13 on one short side in a cantilevered manner by the first conductive adhesive 21. The quartz crystal resonator element 11 is also connected and fixed to the quartz crystal pedestal 23 at the bonding wiring (23c1, 23c2) of the quartz crystal pedestal 23 in a cantilevered manner by the second conductive adhesive 25 on one short side. Therefore, the quartz crystal resonator 10 has a structure in which the bonding pads 13a, the first conductive adhesive 21, one end of the pedestal 23, the second conductive adhesive 25, and one end of the quartz crystal resonator element 11 overlap in the vertical direction, and the quartz crystal pedestal 23 and the quartz crystal resonator element 11 are cantilevered at the same end. The effects of this structure will be described in detail later with reference to experimental results and analysis results using the finite element method.

[0018] 1-2. Second embodiment Next, a crystal resonator 30 according to a second embodiment will be described with reference to Fig. 3. Fig. 3 is a cross-sectional view of the crystal resonator 30 corresponding to the view shown in Fig. 1(B). 1 and described above, the crystal unit 10 of the first embodiment has a structure in which the bonding pads 13a and 13b, the first conductive adhesive 21, one end of the base 23, the second conductive adhesive 25, and one end of the crystal resonator element 11 are vertically overlapped, and the crystal base 23 and the crystal resonator element 11 are cantilevered at the same end. In contrast, the crystal unit 30 of the second embodiment has a structure in which one end of the base 23d is connected to the bonding pads 13a and 13b with the first conductive adhesive 21, and one end of the crystal resonator element 11 is connected to the other longitudinal end of the base 23d with the second conductive adhesive 25, as shown in FIG. 3. In other words, the bonding points of the first conductive adhesive 21 and the bonding points of the second conductive adhesive 26 are located at opposite longitudinal ends of the base 23d. Therefore, in this case, the adhesive wiring (not shown) of the base 23 is elongated in the longitudinal direction of the base 23. In the case of this crystal unit 30, since the crystal unit 11 is adhered to the free end of the base 23, there is a concern about the tip of the base 23 shaking, but the same or greater effect as that of the crystal unit 10 can be obtained in reducing thermal stress.

[0019] 2. Application examples of the present invention FIG. 4 is a diagram for explaining an application example of the present invention, and is a cross-sectional view of a temperature-compensated crystal oscillator 40 to which the present invention is applied. That is, a temperature-compensating integrated circuit 41 is provided in the crystal resonator of the first embodiment described above with reference to FIGS. 1 and 2. By applying the present invention to a temperature-compensated crystal oscillator, the effect of the base 43 is added, and a temperature-compensated crystal oscillator with higher accuracy can be expected. Note that, because it is a temperature-compensated crystal oscillator, the wiring and the number of terminals have been changed accordingly, but a description of this will be omitted.

[0020] 3. Experimental results and finite element analysis results illustrating the features of the present invention 3-1. About the base One of the features of the present invention is that a predetermined pedestal made of quartz crystal is used as the pedestal, and the results of the investigation that led to this will be explained below. 3-1-1. Frequency hysteresis with and without base First, we investigated the presence or absence of a pedestal. To facilitate this investigation, we used a quartz crystal unit 10x (hereinafter sometimes referred to as the evaluation sample) with an integrated temperature sensor, as shown in the plan view, cross-sectional view, and bottom view of Figures 5(A), (B), and (C). This evaluation sample 10x has a recess 17 formed in the bottom portion of a container 13, and a thermistor 15 as a temperature sensor is built into the recess 17. Terminals 17a and 17b for the thermistor are provided on the bottom surface of the recess 17. These terminals 17a and 17b are connected to external connection terminals 13d and 13f on the outer bottom surface of the container via via wiring and castellation wiring (not shown).

[0021] The inventors of this application prepared multiple evaluation samples, each of which is an example evaluation sample having the pedestal structure of the quartz crystal resonator 10 described with reference to Figures 1 and 2, and a comparative example evaluation sample having a quartz crystal resonator without a pedestal, i.e., a structure in which the quartz crystal resonator piece 11 is directly bonded at one end to the bonding pads 13a and 13b with a silicone conductive adhesive. Both the examples and comparative examples were prototyped using a so-called 1612-size ceramic package. The AT-cut quartz crystal resonator element used in both the examples and comparative examples was an X-long quartz crystal resonator element, sized to fit into a 1612-size ceramic package, with an oscillation frequency of 76.8 MHz (the thickness of the quartz crystal resonator element was approximately 22 μm), and equipped with the specified excitation electrodes. The external dimensions of the quartz crystal resonator element used were, specifically, an X dimension of approximately 0.75 mm and a Z′ dimension of approximately 0.51 mm. The base used in the examples was an AT-cut quartz crystal resonator element with an X dimension of 1.0 mm, a Z′ dimension of 0.8 mm, and a thickness of 40 μm. The 1612-size ceramic package here has an external long side dimension of approximately 1.6 mm and a short side dimension of approximately 1.2 mm, and its internal structure is as described with reference to FIG. 1.

[0022] Next, the hysteresis characteristics of the frequency-temperature characteristics of each of the evaluation samples of the examples and comparative examples were measured. The measurements were performed using a temperature control device (not shown) that had a substrate with a Peltier element and a temperature control unit that controlled the temperature of the Peltier element, a frequency measurement device, and a temperature measurement device. Specifically, the evaluation samples of the examples and comparative examples are connected to a substrate having a Peltier element. Of the external connection terminals (13d to 13g in FIG. 5C) of the evaluation samples, terminals 13e and 13g connected to quartz crystal vibrating piece 11 are connected to a frequency measuring device, and terminals 13d and 13f connected to temperature sensor 15 are connected to a temperature measuring device. Next, the temperature of the Peltier element is raised from t1 to tn (tn>t1) degrees using a temperature control device at predetermined temperature intervals and under predetermined temperature rise conditions, and then immediately lowered to t1 under the same temperature change conditions as during the temperature rise. The actual temperatures of the evaluation sample 10x during this temperature rise and temperature fall were measured using a temperature sensor 15 and a temperature measurement device, and the frequency of the quartz crystal vibrating piece 11 was measured using a frequency measurement device. Based on these measurement results, the frequency-temperature characteristics during temperature rise and temperature fall were extracted. Next, the frequency difference between the frequency-temperature characteristics during temperature rise and the frequency-temperature characteristics during temperature fall at the same temperature, that is, frequency hysteresis information, was determined, and the average value of the frequency difference was calculated for each evaluation sample. These average values ​​were then used to determine the average, maximum, and minimum values ​​of the frequency difference for the sample group of the example and the sample group of the comparative example. These results are shown in Table 1. The frequency difference is shown in ppm, which is the ratio of the frequency difference divided by the oscillation frequency. From Table 1, it can be seen that when comparing the average values ​​of the frequency difference during temperature rise and fall defined above, the example has a value of 0.06 / 0.026 ≒ 0.23, which is approximately one-fifth of the comparative example. The maximum value of the example also has a value of 0.09 / 0.96 ≒ 0.09, which is approximately one-eleventh of the comparative example. TIFF0007780679000001.tif36140

[0023] 3-1-2. Base material and crystal axis of the base Additionally, as another evaluation, the following evaluation was performed using the finite element method. Four types of analytical models were created using the finite element method, imitating the quartz crystal resonator 10 described with reference to Figure 1. The crystal axis conditions for the quartz crystal in the direction in which the two bonding points of the AT-cut quartz crystal resonator element are aligned, as well as the base material and crystal axis conditions, were set as shown in Table 2 below. The von Mises stress generated at the center point of the quartz crystal resonator element in each analytical model was then determined when the temperature of each analytical model was changed from 25°C to 105°C. The results are shown in Table 2. TIFF0007780679000002.tif76154

[0024] Table 2 shows that the stress generated at the center of the quartz crystal vibrating piece due to the above temperature changes is approximately 366 to 386 kPa in analytical models 1 and 2, but is approximately 10 kPa in analytical models 3 and 4, which is about 1 / 37th of the normal value. It can be seen that stress can be reduced by using a quartz crystal base with an appropriate axial relationship between the crystal axis corresponding to the line segment connecting the two bonding points of the quartz crystal vibrating piece and a quartz crystal base with a crystal axis that matches this crystal axis. Therefore, from the results in Tables 1 and 2, it can be seen that taking into consideration the bonding direction of the two points of the AT-cut quartz crystal piece, and appropriately selecting and using an AT-cut quartz crystal base or a Z-cut quartz crystal base as the base is effective in reducing thermal stress in the bonding structure of the quartz crystal unit.

[0025] 3-1-3. Base thickness and stress on the crystal element In another evaluation using the finite element method, we investigated how the thickness of the quartz crystal pedestal affects stress in the quartz crystal resonator blank. Specifically, we created eight analytical models, each of which is analytical model 4 in Table 2, with the thickness T of the AT-cut quartz crystal pedestal varying in 10-μm increments between 10 μm and 80 μm. We then measured the von Mises stress generated at the center of each analytical model's quartz crystal resonator blank when the temperature was changed from 25°C to 105°C. Figure 6(A) shows the results, with the horizontal axis representing the pedestal thickness and the vertical axis representing the stress value (relative value). Figure 6(B) also shows the definitions of the thickness T of the pedestal 23 and the thickness t of the quartz crystal resonator blank 11. From Figure 6(A), it can be seen that, if we consider the stress when the base thickness T is 10 μm as the standard, the stress is about one-third when the base thickness T is 20 μm, and about one-sixth when the base thickness T is 30 μm. Up to a base thickness T of 60 μm, the stress rises to about one-fifth of the standard, and as the base thickness T increases further, the stress tends to decrease. Therefore, it can be said that a thicker base thickness T is better, but if it is too thick, the base will not fit inside the crystal unit's container, so there is a limit. Taking this into consideration, when considering the optimum value for the base thickness, the following can be said.

[0026] In this analysis model, the thickness of the quartz crystal blank is approximately 22 μm (derived from an oscillation frequency of 76.8 MHz), so if we take the quartz crystal blank thickness of 22 μm as the standard, the base thickness T should be 20 μm≦T, or greater than the thickness of the quartz crystal blank, and considering that it can be stored in a container, 20 μm≦T≦70 μm or (quartz crystal blank thickness≦T≦70 μm is preferable. Furthermore, stress is smaller when the base thickness T is in the range from approximately 20 μm, slightly thinner than the quartz crystal blank, to 60 μm, so the base thickness T should be 20 μm≦T≦60 μm, and even better 30 μm≦T≦60 μm. Generalizing the above results, the following can also be said. When the thickness of the crystal vibrating piece is t and the thickness of the base is T, T≧0.9t is preferable. 0.9t≦T≦3.1t or t≦T≦3.1t is preferable, 0.9t≦T≦2.7t or t≦T≦2.7t is more preferable, and 1.3t≦T≦2.7t is even more preferable. Here, the value 0.9 is based on the above lower values, 20 / 22≒0.9. The value 3.1 is based on 70 / 22≒3.18. The value 2.7 is based on 60 / 22≒2.7. The value 1.3 is based on 30 / 22≒1.36.

[0027] 3-1-4. Distance between the crystal element and the base, and the angle between them In addition, the following evaluation was performed as another evaluation. FIG. 7 is an explanatory diagram. The crystal impedance (CI) of each of the samples of the example fabricated in Section 3-1-1 above was measured. Then, for each sample, the distance h between the tip of the quartz crystal vibrating piece 11 and the base 23, and the angle θ between the quartz crystal vibrating piece 11 and the base 23 were measured, as shown in FIG. 7(A). 7B is a diagram showing the relationship between CI and the distance h between the tip of quartz crystal vibrating piece 11 and base 23, based on the above measurement results. From FIG. 7B, it can be said that CI improves when distance h is relatively large. Furthermore, if distance h is small, there is a risk that the tip of quartz crystal vibrating piece 11 may come into contact with base 23 when the quartz crystal unit is subjected to an impact, resulting in damage or other problems. Therefore, from this perspective, it is better to set distance h relatively large. In this example, from Figure 7(B), it can be said that it is best to set the distance h to a reasonable value of 20 μm or more, taking into consideration the restrictions on the container height direction, etc. Considering this point in light of the thickness of the quartz crystal resonator blank prototyped this time being 22 μm, it can also be said that it is best to set the distance h to a reasonable value of 20 / 22 ≒ 0.9t or more, where t is the thickness of the quartz crystal resonator blank. FIG. 7C is a diagram showing the relationship between CI and the angle θ between the quartz crystal vibrating piece 11 and the base 23, based on the above measurement results. From FIG. 7C, it can be said that the CI improves when the angle θ is set to a certain degree. Furthermore, as mentioned above, it can be said that a certain degree of angle θ is better from the perspective of improving impact resistance. In this example, from FIG. 7C, it can be said that it is best to set the angle θ to a reasonable angle of 0.5 degrees or more. It is believed that if the distance h or angle θ is increased to a certain extent, the conductive adhesive 25 will be less likely to flow toward the center of the quartz vibrating piece 11, which will reduce the impact of the conductive adhesive on the vibrating part and prevent deterioration of the CI. Furthermore, if the distance h is small, the stray capacitance from the base to the excitation electrode may have an adverse effect, so taking this into consideration, it is better to make the distance h somewhat large.

[0028] 3-1-5. Size and shape of base In the above-described embodiment, an example was described in which the base was larger than the quartz crystal vibrating piece. However, the base does not need to be so large as long as it can reduce the effects of thermal stress on the quartz crystal vibrating piece and does not pose any problems in terms of adhesive strength, and also for reasons such as avoiding contact between the quartz crystal vibrating piece and the base. Even when taking into account the effects of the distance h and angle θ described above, the base does not need to be so large. Consideration regarding the size of the base will be explained with reference to FIG. 8(A). 8A is a diagram showing a cross-sectional view of the quartz crystal resonator 10 corresponding to FIG. 1B, a plan view of the base 23, and a plan view of the quartz crystal resonator piece 11. The long side dimension of the quartz crystal resonator piece 11 is designated as Lb, and various examples of the long side dimensions of the base are shown. In FIG. 8A, the longitudinal dimension La of the base, designated as La, is greater than the longitudinal dimension Lb of the quartz crystal resonator piece. As mentioned above, when considering the reduction of the effects of thermal stress on the quartz crystal vibrating piece, shock resistance, and stray capacitance, it is considered that the base does not need to be very large as long as there are no problems with the adhesive strength. In the example of Figure 8(A), four examples are shown in which the tip position of the base 23 differs from the tip position of the quartz crystal vibrating piece 11 and the tip position of the excitation electrode 11a.

[0029] In the first example, the long side dimension of the base is set to La1 so that the tip position of the base 23 is located between the tip position of the quartz crystal vibrating piece and the tip position of the excitation electrode. In the second example, the long side dimension of the pedestal is set to Lx so that the tip position of the pedestal 23 is located between the tip position of the excitation electrode and the center position of the excitation electrode. In the third example, the long side dimension of the base 23 is set to Ly so that the tip position of the base 23 is located between the center position of the excitation electrode and the end position of the excitation electrode on the conductive adhesive 25 side. In the fourth example, the long side dimension of the base is set to Lz so that the tip position of the base 23 is located between the conductive adhesive 25 and the end of the excitation electrode on the conductive adhesive 25 side. Whether the long side dimension of the pedestal is La1, Lx, Ly, or Lz can be determined depending on the design of the quartz crystal unit 10. However, considering that the pedestal can reduce the effects of thermal stress on the quartz crystal unit and is good enough in terms of adhesive strength, it is considered best to set the long side dimension of the pedestal to Lz. In other words, it is considered best to position the tip of the pedestal between the conductive adhesive 25 and the end of the excitation electrode 11a on the conductive adhesive 25 side so that the pedestal does not face the excitation electrode 11a.

[0030] As for the three-dimensional structure of the base, as shown in Figures 8(B) and 8(C), the base may be a base 23x (Figure 8(B)) in which the thickness of the base is thinned from the middle of the longitudinal direction to the other end, for example, from just before the area facing the excitation electrode to the other end, or a base 23y (Figure 8(C)) in which the thickness of the base is thinned in the central region in the longitudinal direction, for example, in an area slightly wider than the area facing the excitation electrode.

[0031] Although the above-described embodiment shows an example in which the oscillation frequency is 76.8 MHz, the present invention can be applied to other frequencies. For example, the present invention is useful for various frequency bands that have proven successful as reference signal sources. Furthermore, the present invention is increasingly useful for even higher frequencies that will be used in the future, such as the 152 MHz band. Furthermore, while the above-described embodiment has been described as an example of a 1612 type package in terms of external dimensions, the present invention can also be applied to other sizes. It can also be applied to package external dimensions of 1210, 1008, even smaller ones, and ones larger than the 1612 size. In particular, in the case of small packages, the crystal resonator element becomes even smaller, so the effect of thermal stress becomes greater. Therefore, it is believed that applying the present invention makes it easier to reduce thermal stress.

[0032] 4. Other preferred containers and other preferred pedestals In the above embodiment, the container 13 described with reference to Figures 1(A) and 1(B), etc., is exemplified as an example of a container. That is, the container 13 is exemplified as having a quadrangular, specifically rectangular, planar shape, a ceramic bank portion 13c along the edge, and a seam ring (not shown) on the top surface of the bank portion 13c. Also, the pedestal 23 described with reference to Figures 2, 8, etc. is exemplified as an example of a pedestal. That is, the pedestal 23 is exemplified as having a rectangular shape in a plan view, and has wiring 23a1 and the like routed along the side surface of the container 13 on the bank portion 13c side. However, when further improving the characteristics and miniaturizing the piezoelectric device, a container and base having the following structure are preferable. These will be described below with reference to Figures 9(A) and 9(B). Here, Figure 9(A) is a cross-sectional view corresponding to Figure 1(B) to explain a preferable container 70. Figure 9(B) is a side view, top view, and rear view (perspective view) to explain a preferable base 80.

[0033] A preferred container 70 includes a ceramic main body 70a and a metal ring-shaped member 70c connected to the main body 70a and serving as the sidewall of a recess 70b that is rectangular in plan view and accommodates the crystal vibrating piece. Specifically, the main body 70a has a square, or more specifically, rectangular, planar shape. The metal ring-shaped member 70c is connected to the main body 70a, for example, with brazing material, along the edge of the surface of the main body 70a where the adhesive pads 13a and the like are formed. The metal ring-shaped member 70c thus forms the sidewall of the recess 70b. The planar shape of the metal ring-shaped member 70c is similar to the bank portion 13c shown in FIG. 1(A). The metal ring-shaped member 70c is typically made of Kovar material. 9(A), a conductor 13m is embedded in a predetermined position of the ceramic body 70a to electrically connect the metal ring-shaped member 70c to one of the external connection terminals, terminal 13f. The external connection terminal 13f is connected to the earth of the electronic device (not shown) to which the crystal unit 10 is connected, and this connection structure ensures an electromagnetic shielding structure for the crystal unit 10. Two adhesive pads 13a, 13b (see FIG. 1) are provided along a portion of the main body 70a on the first side wall 70ca side, which corresponds to the first side of the ring-shaped member 70c. In the case of this preferred container 70, the recess in which the quartz crystal vibrating piece 11 is mounted is surrounded by a metal ring-shaped member 70c, which, in combination with the metal lid member 19, provides advantages such as stronger electromagnetic shielding. This increases the electromagnetic shielding resistance of the quartz crystal unit. Furthermore, since the recess (cavity) area in which the quartz crystal vibrating piece 11 is mounted can be defined by a metal ring, the desired recess can be easily formed. Furthermore, while the quartz crystal unit 10 of the embodiment uses the bank portion 13c and a seal ring (not shown) as shown in FIG. 1A, the container 70 uses a metal ring-shaped member instead of the bank portion 13c, making it easier to reduce the height of the quartz crystal unit.

[0034] On the other hand, a preferred base 80 has a first wiring pattern 80a on a first surface for connecting to a quartz vibrating piece, a second wiring pattern 80b on a second surface opposite the first surface for connecting to a container, specifically for connecting to two adhesive pads 13a, 13b, and a third wiring pattern 80c connecting the first wiring pattern 80a and the second wiring pattern 80b to the side wall, and the third wiring pattern 80c is provided on the side wall of the base 80 opposite the side wall facing the first side wall 70ca. A preferred pedestal 80 further includes cutouts 80x at both ends of the side wall facing the first side wall 70ca. The cutouts 80x are preferably configured as C-chamfered portions. The size of the cutouts 80x is not limited to this, but is preferably 20 to 70 μm, and more preferably 30 to 50 μm, in terms of the C dimension.

[0035] Furthermore, each of the first wiring pattern 80a and the second wiring pattern 80b has a recessed portion 80d, recessed from the edge of the pedestal 80 toward the center, at least on the side of the first sidewall 70ca of the pedestal 80. The recessed dimension S1 of the recessed portion 80d may be a dimension that prevents the first wiring pattern 80a from contacting (short-circuiting with) the metal ring-shaped member 70c even when the pedestal 80 comes into contact with the metal ring-shaped member 70c. If the recessed dimension S1 is too large, the area of ​​the wiring pattern becomes small, which is undesirable. Although not limited to this, the recessed dimension S1 is preferably, for example, about 30 to 50 μm. Each of the first wiring pattern 80a and the second wiring pattern 80b further includes recessed portions 80e on the two side walls of the base 80 that intersect with the side wall opposite the first side wall 70ca of the container. The recessed dimension S2 of the recessed portion 80e may be determined similarly to the dimension S1. S1 and S2 may be the same or different. In addition to the recessed portion 80d, the second wiring pattern 80b includes a recessed portion 80f, which has a recessed dimension S3 larger than the recessed dimension of the recessed portion 80d, located near the center of the side of the base 80 where the recessed portion 80d is provided, extending from the edge of the base 80 toward the center of the base 80. This recessed portion 80f is designed to prevent damage to the second wiring pattern 80b by a breaking jig used to break off each base from the wafer after a large number of bases 80 are manufactured in wafer form. The width of the recessed portion 80f and the recessed dimension S3 are determined taking into account the size of the breaking jig. However, if the width of the recessed portion 80f or the recessed dimension S3 is too large, the area of ​​the second wiring pattern 80b will become small, which is undesirable in terms of electrical continuity, and therefore, it is advisable to take this into consideration when determining these dimensions.

[0036] The above-described preferable pedestal 80 can be positioned close to the wall of the container 70, even when using a container 70 in which the sidewall of the first recess 70b is formed of a metal ring-shaped member 70c. This is because the above-described predetermined recessed portion 80d and / or cutout portion 80x are provided, so even if the pedestal is positioned close to the wall of the container 70, the first wiring pattern 80a, the second wiring pattern 80b, and the third wiring pattern 80c of the pedestal 80 do not short-circuit with the metal ring-shaped member 70c. Therefore, even if crystal resonators are becoming increasingly smaller and the mounting margin for the pedestal 80 in the container 70 becomes narrower, mounting is easy.

[0037] It should be noted that the preferred container 70 and the preferred base 80 may of course be used in place of the container 13 and base 23 of the various crystal resonators described with reference to FIGS. In the above description, the quartz crystal vibrating piece 11 has a uniform thickness and a rectangular planar shape, but the shape of the quartz crystal vibrator is not limited to the above example. For example, as shown in FIG. 10(A), the crystal vibrating piece may have a so-called one-sided frame structure, which includes a vibrating portion 11c having a thickness corresponding to the frequency and a supporting portion 11d that is thicker than the vibrating portion 11c. Alternatively, as shown in FIG. 10(B), the crystal vibrating piece may have a notch 11e between the vibrating portion and the supporting portion. Alternatively, as shown in FIG. 10(C), the crystal vibrating piece may have a through-hole 11f between the vibrating portion and the supporting portion. The notch 11e or the through-hole 17f may be provided in a crystal vibrating piece with a uniform thickness, or may be provided in the crystal vibrating piece with the one-sided frame structure shown in FIG. 10(A). [Explanation of symbols]

[0038] 10, 30, 40: Crystal resonator of the embodiment, 11: AT-cut crystal element 13: Container 13a, 13b: two adhesive pads arranged along a first direction 15: Temperature sensor 17: Recessed portion for mounting the temperature sensor 19: Lid member 21: Conductive adhesive (first conductive adhesive) 23: Crystal base 25: Conductive adhesive (second conductive adhesive) 70: Preferred container 70a: Ceramic body 70b: Recessed portion for mounting the crystal vibrating piece 70c: Metal ring-shaped member 70ca: First side wall 80: Preferred base 80a: First wiring pattern 80b: Second wiring pattern 80c: Third wiring pattern 80d, 80e, 80f: Retracted section 80x: Notched section

Claims

1. a container having an AT-cut quartz crystal resonator element having a rectangular planar shape, two adhesive pads arranged along a first direction, a quartz crystal base arranged between the quartz crystal resonator element and the two adhesive pads, and a silicone-based conductive adhesive connecting the quartz crystal resonator element, the base, and the adhesive pads; The quartz crystal vibrating piece is attached to the base at two points along the X-axis of the quartz crystal or at two points along the Z'-axis of the quartz crystal, The quartz crystal base has an X-axis or a Z'-axis of the quartz crystal parallel to the surface, depending on whether the quartz crystal vibrating piece is bonded to the base at two points along the X-axis or at two points along the Z'-axis, and is bonded to the two bonding pads in a positional relationship in which the X-axis or the Z'-axis is parallel to the first direction; In a quartz crystal unit, the adhesive pad, the base, and one end of the quartz crystal resonator piece are overlapped in the vertical direction via the silicone-based conductive adhesive, The crystal vibrating piece has a dimension of approximately 0.75 mm along the X-axis and approximately 0.51 mm along the Z'-axis, and an oscillation frequency of 76.8 MHz, The thickness of the base is selected from the range of 30 to 60 μm, A quartz crystal resonator characterized in that the angle formed between the quartz crystal resonator piece and the base is 0.5 degrees or more, and increases in size as the angle increases away from the point where the base and the quartz crystal resonator piece are bonded with the conductive adhesive (wherein the Z' axis is an axis that is offset from the true Z axis of the quartz crystal due to the cutting angle of the AT-cut quartz crystal piece).

2. 2. The quartz crystal unit according to claim 1, wherein the base is an AT-cut quartz crystal piece and is bonded to the two bonding pads at two points along the X-axis of the quartz crystal.

3. 2. The quartz crystal unit according to claim 1, wherein the base is an AT-cut quartz crystal piece and is bonded to the two bonding pads at two points along the Z' axis of the quartz crystal.

4. 2. The quartz crystal unit according to claim 1, wherein the base is a Z-cut quartz crystal piece and is bonded to the two bonding pads at two points along the X-axis of the quartz crystal.

5. 5. A quartz crystal resonator according to claim 1, wherein the base is sized so that its tip is positioned closer to the bonding pad than the excitation electrode provided on the quartz crystal resonator piece.

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