Crystal devices, crystal oscillators, and crystal wafers

Abstract

To reduce temperature hysteresis without complicating the package structure. [Solution] The package comprises a rectangular base plate in plan view, a wall portion provided along the edge of the base plate, and an adhesive pad provided on one end of the inner region enclosed by the wall portion in the direction of the long side; a quartz crystal vibrator having electrodes formed on the front and back surfaces of a rectangular quartz crystal plate in plan view; and a fixing member for fixing the quartz crystal vibrator to the adhesive pad, wherein the value calculated by the following formula is greater than -2.6. -(F1-F2) / (F0) 2 ×1000 However, F1 is the frequency of the quartz crystal plate, F2 is the frequency of the quartz crystal oscillator, and F0 is the nominal frequency.

Description

Technical Field

[0001] The present disclosure relates to a quartz device, a quartz resonator mounted on the quartz device, and a quartz wafer on which a plurality of quartz resonators are formed.

Background Art

[0002] Piezoelectric devices are widely used in various electronic devices such as mobile phones and personal computers mainly for frequency selection and control. Piezoelectric devices can be classified into piezoelectric vibrators, piezoelectric oscillators, SAW devices, optical devices, etc. according to their functions. Among them, quartz vibrators and quartz oscillators using quartz as a piezoelectric element are widely known and commonly used.

[0003] Since quartz has the characteristic that its oscillation frequency varies with temperature (frequency-temperature characteristic), a temperature-compensated crystal oscillator (TCXO) is known which can reduce the variation of the oscillation frequency due to the ambient temperature change by providing a temperature compensation circuit in the crystal oscillator. For example, Patent Document 1 discloses a temperature-compensated crystal oscillator provided with an intermediate substrate between a base and a vibrating element. In particular, it is disclosed that the intermediate substrate absorbs and relaxes the stress from the package, making it difficult for the stress to be transmitted to the vibrating element, and thus reducing the hysteresis of the temperature characteristics.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, when improving the hysteresis of temperature characteristics by using a special substrate as part of the package structure, as in Patent Document 1, the structure of the crystal oscillator becomes complex, increasing manufacturing costs and further complicating the manufacturing process, which also affects the yield of the crystal oscillator.

[0006] This disclosure has been made in view of these challenges, and its purpose is to provide a quartz device that can reduce the hysteresis of temperature characteristics without complicating the package structure, a quartz vibrator used therein, and a quartz wafer consisting of a plurality of quartz vibrators. [Means for solving the problem]

[0007] According to one aspect of the present disclosure, a crystal device comprising: a package having a rectangular base plate in plan view, a wall portion provided along the edge of the base plate, and an adhesive pad provided on one end in the long-side direction of an inner region enclosed by the wall portion; a crystal vibrator having electrodes formed on the front and back surfaces of a rectangular crystal plate in plan view; and a fixing member for fixing the crystal vibrator to the adhesive pad, wherein the value calculated by the following formula is greater than -2.6. -(F1-F2) / (F0) 2 ×1000 However, F1 is the frequency of the quartz crystal plate, F2 is the frequency of the quartz crystal oscillator, and F0 is the nominal frequency.

[0008] According to one aspect of this disclosure, a quartz crystal vibrator is characterized in that electrodes are formed on the front and back surfaces of a rectangular quartz crystal plate in plan view, and the value calculated by the following formula is greater than -2.6. -(F1-F2) / (F0) 2 ×1000 However, F1 is the frequency of the quartz plate, F2 is the frequency of the quartz oscillating element, and F0 is the nominal frequency.

[0009] According to one aspect of the present disclosure, a quartz wafer is characterized by having a plurality of quartz resonators having electrodes formed on the front and back surfaces of a rectangular quartz plate in plan view, wherein the value calculated by the following formula is greater than -2.6, a frame portion to which the quartz resonators are connected, and a connecting portion connecting each of the quartz resonators to the frame portion. -(F1-F2) / (F0) 2 ×1000 However, F1 is the frequency of the quartz plate, F2 is the frequency of the quartz oscillating element, and F0 is the nominal frequency. [Effects of the Invention]

[0010] According to this disclosure, it is possible to provide a quartz device that can reduce the hysteresis of temperature characteristics without complicating the package structure, a quartz vibrator used therein, and a quartz wafer consisting of a plurality of quartz vibrators.

[0011] The effects described above are merely illustrative for the sake of explanation, and the effects relating to this disclosure are not limited to those described above. In addition to the effects described above, any other effects described herein may be achieved. [Brief explanation of the drawing]

[0012] [Figure 1] This is a perspective view of a crystal oscillator according to the first embodiment. [Figure 2] Figure 2(a) is an end view along the dashed line AA in Figure 1, Figure 2(b) is a top view of the crystal oscillator according to the first embodiment, and Figure 2(c) is an end view along the dashed line BB in Figure 2(a). [Figure 3] Figure 3(a) is a side view of the crystal oscillator included in the first embodiment, and Figure 3(b) is a front view of the crystal oscillator included in the first embodiment. [Figure 4] This graph shows the experimental results of hysteresis characteristics during frequency-temperature characteristic measurement of a crystal oscillator. [Figure 5]Figure 5(a) is a plan view of a quartz wafer according to the first embodiment, Figure 5(b) is an enlarged view of region R1 in Figure 5(a), and Figure 5(c) is a surface view of the quartz vibrator with electrodes formed on it, similar to Figure 5(b). [Figure 6] Figure 6(a) is an end view of a crystal oscillator according to the second embodiment, similar to Figure 2(a), and Figure 6(b) is an end view of a crystal resonator according to the third embodiment, similar to Figure 2(a). [Modes for carrying out the invention]

[0013] Hereinafter, with reference to the drawings, a crystal oscillator and crystal resonator, which are examples of piezoelectric devices of this disclosure; a crystal resonator, which is an example of a piezoelectric vibrator, and a crystal wafer, which is an example of a piezoelectric wafer, will be described in detail. Note that this disclosure is not limited to the contents described below, and can be modified and implemented as such without altering its essence. Furthermore, the drawings used in each embodiment schematically represent the crystal oscillator, crystal resonator, crystal resonator, and crystal wafer related to this disclosure, and have been partially emphasized, enlarged, reduced, or omitted to enhance understanding, and may not accurately represent the scale or shape of each component. In addition, some numerical values ​​used in each embodiment and its modifications are examples only and can be changed as needed. Common components in the drawings are denoted by the same reference numerals.

[0014] (First Embodiment) First, while referring to FIGS. 1 to 3, the basic structures of the crystal oscillator and the crystal vibrating piece according to the present disclosure will be described. FIG. 1 is a perspective view of the crystal oscillator according to the present embodiment. FIG. 2(a) is an end view taken along the dash-dotted line A-A in FIG. 1, particularly an end view of the long side of the crystal oscillator. FIG. 2(b) is a top view of the crystal oscillator according to the present embodiment, particularly showing the internal structure in a state where the crystal vibrating piece is mounted. FIG. 2(c) is an end view taken along the dash-dotted line B-B in FIG. 2(a), particularly an end view of the short side of the crystal oscillator. FIG. 3(a) is a side view of the crystal vibrating piece included in the crystal oscillator according to the present embodiment, particularly showing the structure on the long side of the crystal vibrating piece. FIG. 3(b) is a front view of the crystal vibrating piece included in the crystal oscillator according to the present embodiment, particularly showing the structure on the short side of the crystal vibrating piece.

[0015] As can be seen from FIGS. 1 and 2(a) to (c), the crystal oscillator 1, which is an example of a piezoelectric device, includes a crystal oscillator package 2 (hereinafter simply referred to as package 2), a crystal vibrating piece 3 and an IC chip 4 mounted in the concave mounting space 2a of the package 2, and a metal cover (lid) 5 for sealing the mounting space 2a. The crystal oscillator 1 is an electronic component that integrates a crystal vibrating piece 3, which is an example of a piezoelectric vibrating piece, and an IC chip 4, which is an oscillation circuit, and can generate a stable frequency and a regular reference signal.

[0016] Package 2 is a ceramic package formed by laminating a plurality of ceramics with a desired metal pattern formed on the surface. Specifically, Package 2 has a laminated structure in which an outer frame wall 11, which is a base portion having an opening of a predetermined size, an inner frame wall 12 having an opening smaller than that of the outer frame wall 11 and a smaller thickness, and a bottom plate 13 having a rectangular shape in plan view are laminated. In particular, the outer frame wall 11 is provided along the edge of the bottom plate 13, and the inner frame wall 12 is provided in the inner region surrounded by the outer frame wall 11. With such a laminated structure, Package 2 has a mounting space 2a that is concave and has a step for mounting the crystal oscillator 3 and the IC chip 4. Further, on the surface of the bottom plate 13 in the mounting space 2a, a region for mounting the IC chip 4 is formed, and a plurality of pedestals 14 for installing electrode pads provided around the region are laminated.

[0017] Here, the shape of Package 2 is a rectangular parallelepiped shape and is rectangular in top view (Fig. 2(b)). In the following, the thickness direction of the crystal oscillator 1 and Package 2 is taken as the vertical direction, and the direction orthogonal to the vertical direction is taken as the horizontal direction. Further, with respect to the horizontal direction, it may be distinguished as the long side direction (longitudinal direction) and the short side direction (lateral direction) of the crystal oscillator 1 and Package 2. Further, in each member, the surface located on the upper side in the vertical direction may be referred to as the front surface, and the surface located on the lower side may be referred to as the back surface.

[0018] On the exposed surface (the surface located on the upper side in the vertical direction) of the outer frame wall 11 of Package 2, a conductor pattern 15 for sealing is formed. The planar shape of the conductor pattern 15 is a frame shape similar to that of the outer frame wall 11. And a cover 5 is joined on the conductor pattern 15 by a known metal joining method. Thereby, the mounting space 2a of the package is sealed, and the mounting space 2a is sealed using a gas such as vacuum or nitrogen.

[0019] Two quartz crystal mounting terminals 16 and 17, which are adhesive pads, are formed on the exposed surface (the upper surface in the vertical direction) of the inner frame wall 12 of package 2. In particular, the quartz crystal mounting terminals 16 and 17 are provided on one end in the long-side direction within the inner region enclosed by the outer frame wall 11. Here, the quartz crystal 3 is mounted on the quartz crystal mounting terminals 16 and 17 via conductive adhesive 18. Furthermore, the quartz crystal mounting terminals 16 and 17 are electrically connected to external connection terminals 20a, 20b, 20c, and 20d, which will be described later, via connection wiring (not shown) provided inside package 2.

[0020] Four external connection terminals 20a, 20b, 20c, and 20d are formed at the four corners of the underside of the bottom plate 13 of package 2. In addition, terminals 21 are formed on each surface of the base 14 installed on the bottom plate 13, which are electrically connected to each electrode of the IC chip 4. For example, if the IC chip 4 has six electrodes, six bases 14 and six terminals 21 are provided, and each electrode and each terminal 21 are electrically connected by wire bonding. Here, the formation of the base 14 makes it possible to align the height of the electrode formation surface of the IC chip 4 with that of the terminals 21, thereby improving the accuracy of wire bonding. Note that the number of electrodes is not limited to six, and the IC chip 4 may be a flip-chip type element. In this case, the shape and number of bases 14 and terminals 21 are changed as appropriate.

[0021] As can be seen from Figures 2(b), 3(a), and 3(b), the crystal oscillator 3 consists of a rectangular (i.e., flat) crystal plate 30 in plan view, a surface electrode 40 formed on the surface 30a of the crystal plate 30, and a back electrode 50 formed on the back surface 30b. In this way, since the surface electrode 40 and back electrode 50 are formed on the front and back surfaces of the crystal oscillator 3, it is possible to apply a voltage to the crystal oscillator 3. Here, as shown in Figure 2(b), the crystal oscillator 3 is mounted so that its long and short sides are aligned with the long and short sides of the crystal oscillator 1. In other words, the long side of the crystal oscillator 3 coincides with the long side of the crystal oscillator 1, and the short side of the crystal oscillator 3 also coincides with the short side of the crystal oscillator 1.

[0022] The surface electrode 40 consists of an excitation electrode 41 formed approximately in the center of the surface 30a of the quartz plate 30, pad electrodes 42 and 43 formed at one end of the long side of the surface 30a, and a connecting electrode 44 connecting the excitation electrode 41 and the pad electrode 42. Here, the surface-side lead electrode is formed from the pad electrode 42 and the connecting electrode 44. The pad electrode 43 is formed side by side with the pad electrode 42 and has the same dimensions and shape as the pad electrode 42.

[0023] Similarly, the back electrode 50 consists of an excitation electrode 51 formed approximately in the center of the back surface 30b of the quartz crystal plate 30, pad electrodes 52 and 53 formed at one end in the long-side direction of the back surface 30b, and a connecting electrode 54 connecting the excitation electrode 51 and the pad electrode 52. Here, the back side lead electrode is formed from the pad electrode 52 and the connecting electrode 54. The pad electrode 53 is formed side by side with the pad electrode 52 and has the same dimensions and shape as the pad electrode 52.

[0024] The surface electrode 40 and the back electrode 50 are formed to face each other via the quartz crystal plate 30. Furthermore, the surface electrode 40 and the back electrode 50 are formed to have similar dimensions. However, depending on the characteristics of the quartz crystal vibrator 3, their formation positions may be shifted or their dimensions may be different. For example, the excitation electrode 41 of the surface electrode 40 and the excitation electrode 51 of the back electrode 50 may be formed offset so that they do not completely overlap in the vertical direction, or the diameter or outer shape of one may be larger than the other.

[0025] Next, with reference to Figure 4, the characteristics of the crystal oscillator 3 implemented in the crystal oscillator 1 of this embodiment will be described. Here, Figure 4 is a graph showing the experimental results of the hysteresis characteristics when measuring the frequency-temperature characteristics of the crystal oscillator. In particular, Figure 4 is a graph showing the experimental results for samples in which the value calculated by formula (1), which will be described later, is changed in steps.

[0026] In this embodiment, the quartz crystal oscillator 3 is set such that the value calculated by the following formula (1) is greater than -2.6 by adjusting the thickness of the quartz crystal plate 30, the surface electrode 40, and the back electrode 50. Formula (1) -(F1-F2) / (F0) 2 ×1000 Here, F1 is the frequency of the quartz crystal plate 30, F2 is the frequency of the quartz crystal diaphragm 3, and F0 is the nominal frequency. In other words, F1 is the frequency calculated from the thickness of the quartz crystal plate 30 when the surface electrode 40 and back electrode 50 are not formed. Also, F2 is the frequency calculated from the thickness of the quartz crystal diaphragm 3 when the surface electrode 40 and back electrode 50 are formed. For example, when a nominal frequency of 26 MHz is achieved using a predetermined oscillation circuit (i.e., when a load capacitance exists), F0 becomes 26 MHz, F2 becomes a value that is shifted from 26 MHz by the amount of the load capacitance, and F1 becomes a value that is smaller than F2 by the amount of the electrode thickness. That is, the value calculated by formula (1) is a dimensionless (in other words, generalized) value of the ratio of the thickness of the quartz crystal plate 30 to the thickness of the surface electrode 40 and back electrode 50.

[0027] In the design of typical quartz devices, the value of equation (1) was usually set to -2.6 or less from the viewpoint of vibration confinement in the quartz oscillator 3. The inventors of this disclosure have found that by deliberately setting the value of equation (1) to a value greater than -2.6, as is not a common design practice, the following effects can be obtained.

[0028] Specifically, as shown in Figure 4, the thickness of the quartz plate 30, the surface electrode 40, and the back electrode 50 was adjusted, and the hysteresis characteristics during frequency-temperature characteristic measurement were evaluated for multiple samples whose values ​​calculated by formula (1) were "-2.6", "-1.7", and "-1.4". More specifically, for each sample, the ambient temperature was changed to "+25℃", "-10℃", "-40℃", "-10℃", "+25℃", "+85℃", and "+25℃". The oscillation frequency at the initial 25℃ was defined as f0, the oscillation frequency at the second +25℃ (+25℃ between -10℃ and +85℃) was defined as f1, and the oscillation frequency at the final 25℃ was defined as f2. The horizontal axis of each graph in Figure 4 was set to f1-f0 (ppm), and the vertical axis was set to f2-f1 (ppm) for evaluation.

[0029] As shown in Figure 4, it was found that as the value calculated using equation (1) was gradually increased from -2.6, the sample distribution gradually shifted from the fourth quadrant to the second quadrant of the graph. In other words, when the value calculated using equation (1) was -2.6, the hysteresis of the temperature characteristic tended to be large, but as the value calculated using equation (1) increased above -2.6, the hysteresis of the temperature characteristic tended to decrease. Furthermore, when the value calculated using equation (1) was -1.7, the sample distribution was located near the origin in the fourth quadrant, but when the value calculated using equation (1) was increased to -1.4, it was found that the sample distribution was located near the origin in the second quadrant. Here, having the sample distribution near the origin tends to result in the oscillation frequencies being the same at each +25°C, and the hysteresis of the temperature characteristic becomes particularly small. Therefore, based on the trend in Figure 4, it can be estimated that by setting the value calculated using formula (1) to between -1.6 and -1.5, the hysteresis of the temperature characteristics can be further reduced.

[0030] From the above, it is important to make the value obtained by equation (1) greater than -2.6, and preferably the value obtained by equation (1) is between -1.7 and -1.4. This makes it possible to reduce the hysteresis of the temperature characteristics. And, especially preferably the value obtained by equation (1) is between -1.6 and -1.5. This makes it possible to further reduce the difference between the oscillation frequency when the temperature is increased and the oscillation frequency when the temperature is decreased, even at the same temperature.

[0031] Furthermore, by adjusting the thickness of the quartz plate 30, the surface electrode 40, and the back electrode 50, equation (1) can be satisfied, thus reducing the hysteresis of the temperature characteristics without changing the structure of package 2. This makes it possible to realize a quartz oscillator 1 that can reduce the hysteresis of the temperature characteristics without complicating the structure of package 2.

[0032] Next, with reference to Figure 5, a method for manufacturing the piezoelectric wafer W, which is a quartz wafer, and the quartz vibrator 3 according to this disclosure will be described. Figure 5(a) is a plan view of a quartz wafer as an example of a piezoelectric wafer according to this embodiment. Figure 5(b) is an enlarged view of region R1 in Figure 5(a). Furthermore, Figure 5(c) is a surface view of the quartz vibrator with electrodes formed on it, similar to Figure 5(b).

[0033] First, a quartz wafer W with a roughly circular planar shape is prepared, as shown in Figure 5(a). For example, it is a wafer that has been cut from a quartz crystal using the AT cut method. However, the planar shape is not limited to a circle; it may also be square, and the cutting method is not limited to an AT cut; other cuts such as Z cut or SC cut (two-turn cut) may also be used.

[0034] Next, a metal film for forming an etching-resistant mask is formed on both the front and back surfaces of the quartz wafer W. Subsequently, the metal film is processed using a well-known photolithography technique to form an etching-resistant mask on both the front and back surfaces of the quartz wafer W to form the outline of the quartz diaphragm 3. In this embodiment, the etching-resistant mask has a structure that corresponds to a portion corresponding to the outline of the quartz diaphragm 3, a frame portion 61 (see Figure 5(b)) formed to surround the multiple quartz diaphragms 3, and a connecting portion 62 (see Figure 5(b)) that connects the frame portion 61 to each of the quartz diaphragms 3. After that, the quartz wafer W, with the etching-resistant mask formed, is immersed in an etching solution mainly composed of hydrofluoric acid for a predetermined time. Through this process, the portions of the quartz wafer W not covered by the etching-resistant mask are dissolved, and the rough outline of the quartz diaphragm 3 is obtained, as shown in Figure 5(b).

[0035] Next, the etching-resistant mask is removed from the quartz wafer W. At this time, only a portion of the etching-resistant mask corresponding to the quartz substrate 30 of the quartz oscillating element 3 is removed, leaving the portions corresponding to the frame 61 and connecting portion 62 of the quartz wafer W. This makes it possible to perform additional etching to make the quartz substrate 30 to a predetermined thickness while ensuring the strength of the frame 61 and connecting portion 62.

[0036] Next, the quartz wafer W, with a portion of the etching-resistant mask removed, is immersed again in an etching solution mainly composed of hydrofluoric acid for a predetermined time. Here, the predetermined time is the time it takes for the thickness of the quartz plate 30 of the quartz diaphragm 3 to reach a thickness that can meet the required oscillation frequency specifications.

[0037] Next, the etching-resistant mask is removed from the quartz wafer W after the etching process is complete, exposing the entire surface of the quartz wafer W. Subsequently, metal films for each electrode of the quartz vibrator 3 are formed on the entire surface (front and back) of the quartz wafer W using a well-known film deposition method. Subsequently, these metal films are patterned into electrode shapes using well-known photolithography and metal etching techniques, and the electrodes are formed on the front and back surfaces of the quartz wafer W as shown in Figures 2(b), 3(a), 3(b), and 5(c).

[0038] Then, when mounting the crystal oscillator 3, the crystal oscillator 3 is separated into individual pieces by etching the crystal wafer W to remove the connection portion 62, or by physically cutting the connection portion 62. After that, the crystal oscillator 1 is manufactured by mounting the separated crystal oscillator 3 onto the package 2.

[0039] (Second Embodiment) In the first embodiment, the crystal oscillator 3 and the IC chip 4 were mounted in the mounting space 2a of the package 2, but the crystal oscillator 3 and the IC chip 4 may be mounted in different mounting spaces. This case will be described as the second embodiment with reference to Figure 6(a). Here, Figure 6(a) is an end view of the crystal oscillator 101 according to the second embodiment, shown in the same way as Figure 2(a).

[0040] As can be seen from Figure 6(a), the crystal oscillator 101 has a package 102, a crystal diaphragm 103 mounted in the concave first mounting space 102a of the package 102, an IC chip 104 mounted in the second mounting space 102b of the package 102, and a metal cover (lid) 105 for sealing the first mounting space 102a. Similar to the crystal oscillator 1 of the first embodiment, the crystal oscillator 101 is an electronic component that integrates a crystal diaphragm 103, which is an example of a piezoelectric diaphragm, and an IC chip 104, which is an oscillation circuit, into a single package, and can generate a stable frequency and produce a regular reference signal.

[0041] Package 102 is a ceramic package formed by laminating multiple ceramics on which a desired metal pattern is formed on the surface. Specifically, package 102 has a laminated structure in which a first outer frame wall 111, which is a bank portion with an opening of a predetermined size, a second outer frame wall 112, which has a smaller opening than the first outer frame wall 111, and a rectangular bottom plate 113 are laminated. Package 102 has a so-called H-shaped structure in which the first outer frame wall 111 is laminated on the surface 113a of the bottom plate 113, and the second outer frame wall 112 is laminated on the back surface 113b of the bottom plate 113. With this laminated structure, package 102 realizes a structure in which the quartz crystal oscillator 103 and the IC chip 104 can be mounted in separate mounting spaces.

[0042] A sealing conductor pattern 115 is formed on the exposed surface (the upper surface in the vertical direction) of the first outer frame wall 111 of the package 102. The planar shape of the conductor pattern 115 is frame-shaped, similar to the first outer frame wall 111. A cover 105 is then joined to the conductor pattern 115 by known metal bonding. This seals the first mounting space 102a of the package, and the first mounting space 102a is sealed using a vacuum or a gas such as nitrogen.

[0043] Two crystal diaphragm mounting terminals (only crystal diaphragm mounting terminal 116 is shown in Figure 6(a)) are formed on the surface 113a of the bottom plate 113 of the package 102. A crystal diaphragm 103 is mounted to each of these crystal diaphragm mounting terminals via conductive adhesive 118. Each of these crystal diaphragm mounting terminals is electrically connected to an external connection terminal via connecting wiring (not shown) provided inside the package 102.

[0044] Multiple IC terminals 141 are formed on the back surface 113b of the bottom plate 113 of the package 102. Each of the IC terminals 141 is provided with a bonding member 151, and the IC chip 104 is mounted via these bonding members 151. For example, the bonding members 151 may be made of materials such as gold bumps, solder, or conductive adhesive. In other words, in the crystal oscillator 101, a flip-chip type IC chip 104 is mounted by flip-chip bonding. Each of the IC terminals 141 is electrically connected to an external connection terminal via connection wiring (not shown) provided inside the package 102.

[0045] Four external connection terminals (only external connection terminals 120c and 120d are shown in Figure 6(a)) are formed on the back surface of the second outer frame wall 112 of package 102. Each of these external connection terminals is connected to either the crystal oscillator mounting terminal or the IC terminal 141 via connection wiring (not shown) provided inside package 102.

[0046] Furthermore, the crystal oscillator 103 according to this embodiment has the same structure as the crystal oscillator 3 according to the first embodiment, and the mounting method using the conductive adhesive 118 is also the same. For this reason, the structure and mounting method of the crystal oscillator 103 will not be explained.

[0047] In this embodiment as well, it is important to make the value calculated by formula (1) greater than -2.6, and preferably, the value calculated by formula (1) is between -1.7 and -1.4. This makes it possible to reduce the hysteresis of the temperature characteristics. Particularly preferably, the value calculated by formula (1) is between -1.6 and -1.5. This makes it possible to further reduce the difference between the oscillation frequency when the temperature is increased and the oscillation frequency when the temperature is decreased, even at the same temperature.

[0048] (Third embodiment) In the first embodiment, a crystal oscillator 1 having an IC chip 4 was described as an example of a piezoelectric device. However, a crystal resonator without an IC chip 4 may also be applied to the piezoelectric device according to this disclosure. Such a case will be described as a third embodiment with reference to Figure 6(b). Here, Figure 6(b) is an end view of the crystal resonator 201 according to the third embodiment, shown in the same way as Figure 2(a).

[0049] As can be seen in Figure 6(b), a quartz crystal oscillator 201, an example of a piezoelectric device, comprises a quartz crystal oscillator package 202 (hereinafter simply referred to as package 202), a quartz crystal oscillator 203 mounted in a concave mounting space 202a of package 202, and a metal cover (lid) 205 for sealing the mounting space 202a. Package 202 is a ceramic package formed by laminating multiple ceramics on which a desired metal pattern is formed on the surface. Specifically, package 202 has a laminated structure in which a frame wall 211, which is a bank portion with an opening of a predetermined size, and a rectangular bottom plate 213 are laminated.

[0050] A sealing conductor pattern 215 is formed on the upper surface of the frame wall 211 of the package 202. The planar shape of the conductor pattern 215 is frame-like, similar to the frame wall 211. A cover 205 is then joined to the conductor pattern 215 by known metal bonding. This seals the mounting space 202a of the package, and the mounting space 202a is sealed using a vacuum or a gas such as nitrogen.

[0051] Two crystal oscillator mounting terminals (only crystal oscillator mounting terminal 216 is shown in Figure 6(b)) are formed on the surface of the bottom plate 213 of package 202. A crystal oscillator 203 is mounted to each of these crystal oscillator mounting terminals via conductive adhesive 218. Each of these crystal oscillator mounting terminals is electrically connected to an external connection terminal via connecting wiring (not shown) provided inside package 202. On the other hand, four external connection terminals 219c, 219d are formed on the back surface of the bottom plate 213 of package 202.

[0052] Furthermore, the crystal oscillator 203 according to this embodiment has the same structure as the crystal oscillator 3 according to the first embodiment, and the mounting method using the conductive adhesive 218 is also the same. For this reason, the structure and mounting method of the crystal oscillator 203 will not be explained.

[0053] In this embodiment as well, it is important to make the value calculated by formula (1) greater than -2.6, and preferably, the value calculated by formula (1) is between -1.7 and -1.4. This makes it possible to reduce the hysteresis of the temperature characteristics. Particularly preferably, the value calculated by formula (1) is between -1.6 and -1.5. This makes it possible to further reduce the difference between the oscillation frequency when the temperature is increased and the oscillation frequency when the temperature is decreased, even at the same temperature.

[0054] (Embodiments of this disclosure) A first embodiment of the present disclosure is a quartz device having a package comprising a rectangular base plate in plan view, a wall portion provided along the edge of the base plate, and an adhesive pad provided on one end in the long-side direction of the inner region enclosed by the wall portion; a quartz resonator having electrodes formed on the front and back surfaces of a rectangular quartz element plate in plan view; and a fixing member for fixing the quartz resonator to the adhesive pad, wherein the value calculated by the following formula is greater than -2.6. -(F1-F2) / (F0) 2 ×1000 However, F1 is the frequency of the quartz crystal plate, F2 is the frequency of the quartz crystal oscillator, and F0 is the nominal frequency.

[0055] By satisfying this equation, the difference between the oscillation frequency when the temperature is increased and the oscillation frequency when the temperature is decreased can be reduced for the same temperature. In other words, the temperature characteristic hysteresis is reduced in such a quartz device. Furthermore, since this equation can be satisfied by adjusting the thickness of the quartz plate and electrodes, there is no need to complicate the package structure.

[0056] A second embodiment of this disclosure is that, in the first embodiment, the value calculated by the formula is between -1.7 and -1.4. This makes it possible to further reduce the hysteresis of the temperature characteristics without complicating the package structure.

[0057] A third embodiment of this disclosure is that, in either the first or second embodiment, the value calculated by the formula is between -1.6 and -1.5. This makes it possible to further reduce the difference between the oscillation frequency when the temperature is increased and the oscillation frequency when the temperature is decreased, even at the same temperature.

[0058] A fourth embodiment of this disclosure is that, in any of the first to third embodiments, the package has an IC chip mounted on it. This enables control of the oscillation frequency and provides a stable frequency.

[0059] A fifth embodiment of this disclosure is a quartz crystal vibrator having electrodes formed on the front and back surfaces of a rectangular quartz crystal plate in plan view, wherein the value calculated by the following formula is greater than -2.6. -(F1-F2) / (F0) 2 ×1000 However, F1 is the frequency of the quartz crystal plate, F2 is the frequency of the quartz crystal oscillator, and F0 is the nominal frequency.

[0060] By satisfying this equation, the difference between the oscillation frequency when the temperature is increased and the oscillation frequency when the temperature is decreased can be reduced for the same temperature. In other words, the temperature characteristic hysteresis is reduced in such a quartz crystal.

[0061] A sixth embodiment of this disclosure is a quartz wafer characterized by having a plurality of quartz diaphragms as in the fifth embodiment, a frame to which the quartz diaphragms are connected, and connecting portions connecting each of the quartz diaphragms to the frame. This makes it possible to form and supply a plurality of quartz diaphragms simultaneously. [Explanation of Symbols]

[0062] 1. Crystal Oscillator 2. Packages for crystal oscillators (packages) 2a Implementation space 3 Crystal vibrating piece 4 IC chips 5 Cover (Lid) 11. Outer frame wall (embankment section) 12 Inner frame wall 13 Bottom plate 16,17 Terminals (adhesive pads) for mounting crystal oscillators 18 Conductive adhesive 30 Crystal base plate 30a surface 30b back side 40 surface electrode 41 Excitation electrode 42,43 Pad electrodes 44 connecting electrodes 50 Backside electrodes 51 Excitation electrode 52, 53 Pad electrodes 54 Connecting electrodes

Claims

1. A package comprising a rectangular base plate in plan view, a wall portion provided along the edge of the base plate, and an adhesive pad provided on one end in the long-side direction of the inner region enclosed by the wall portion, A quartz vibrator with electrodes formed on the front and back surfaces of a rectangular quartz plate in plan view, The system includes a fixing member for fixing the quartz crystal vibrator to the adhesive pad, A crystal device characterized by a value greater than -2.6 calculated by the following formula. -(F1-F2) / (F0) ２ ×1000 However, F1 is the frequency of the quartz plate, F2 is the frequency of the quartz oscillating element, and F0 is the nominal frequency.

2. The crystal device according to claim 1, characterized in that the value calculated by the above formula is between -1.7 and -1.

4.

3. The crystal device according to claim 1, characterized in that the value calculated by the above formula is between -1.6 and -1.

5.

4. The crystal device according to claim 1, characterized in that it has an IC chip mounted in the aforementioned package.

5. A quartz vibrator in which electrodes are formed on the front and back surfaces of a rectangular quartz plate in plan view, A quartz crystal oscillator characterized by a value greater than -2.6 calculated by the following formula. -(F1-F2) / (F0) ２ ×1000 However, F1 is the frequency of the quartz plate, F2 is the frequency of the quartz oscillating element, and F0 is the nominal frequency.

6. A plurality of crystal oscillators according to claim 5, The frame portion to which the crystal vibrator is connected, A quartz wafer characterized by having a connecting portion that connects each of the quartz vibrating elements to the frame portion.

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