Crystal devices, crystal oscillators, and crystal wafers

Abstract

To minimize age-related changes without complicating the configuration and control. [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 obtained by dividing the thickness of the quartz crystal plate by the thickness of the electrodes is greater than 7.4 and 23.9 or less.

Description

Technical Field

[0001] The present disclosure relates to a quartz device, a quartz resonator implemented in 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 for the 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 that can reduce the variation in the oscillation frequency due to ambient temperature changes by providing a temperature compensation circuit in the crystal oscillator. For example, Patent Document 1 discloses a temperature-compensated crystal oscillator equipped with a memory having reference data including deterioration transition data. In particular, in the temperature-compensated crystal oscillator disclosed in Patent Document 1, control is performed to search for at least one reference data in the memory in which various parameter data related to mass-produced products of the crystal oscillator and deterioration transition data of the output frequency of the mass-produced products from the time after burn-in to a second elapsed time shorter than the first elapsed time are similar, and correction data for canceling the deterioration transition data of the output frequency is derived.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, as in Patent Document 1, when the output frequency fluctuation due to aging is suppressed by a special correction using a special memory and the data stored therein as part of the crystal oscillator configuration, the number of components in the crystal oscillator increases, and its structure and control become more complex. This leads to increased manufacturing costs, and further complicates the manufacturing process, which also affects the yield of the crystal oscillator.

[0006] This disclosure has been made in view of the above issues, and its purpose is to provide a quartz device that can reduce aging without complicating its configuration and control, a quartz diaphragm used therein, and a quartz wafer consisting of a plurality of quartz diaphragms. [Means for solving the problem]

[0007] According to one aspect of the present disclosure, a crystal device is provided that comprises "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 element plate in plan view; and a fixing member for fixing the crystal vibrator to the adhesive pad, wherein the value obtained by dividing the thickness of the crystal element plate by the thickness of the electrodes is greater than 7.4 and 23.9 or less."

[0008] According to one aspect of this disclosure, a quartz crystal vibrator is provided, characterized in that electrodes are formed on the front and back surfaces of a rectangular quartz crystal plate in plan view, and the value obtained by dividing the thickness of the quartz crystal plate by the thickness of the electrodes is greater than 7.4 and 23.9 or less.

[0009] According to one aspect of the present disclosure, a quartz wafer is provided, comprising: 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 obtained by dividing the thickness of the quartz plate by the thickness of the electrodes is greater than 7.4 and less than or equal to 23.9; a frame portion to which the quartz resonators are connected; and a connecting portion connecting each of the quartz resonators to the frame portion. [Effects of the Invention]

[0010] According to this disclosure, it is possible to provide a quartz device that can reduce aging without complicating its configuration and control, a quartz diaphragm used therein, and a quartz wafer consisting of a plurality of quartz diaphragms.

[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 reflow test results for a sample of a crystal oscillator. [Figure 5] This graph summarizes the reflow test results for a sample of a crystal oscillator. [Figure 6] This graph shows the test results of the high-temperature storage characteristics of a sample crystal oscillator at 125°C. [Figure 7] This graph summarizes the test results of the high-temperature storage characteristics of a sample crystal oscillator at 125°C. [Figure 8] Figure 8(a) is a plan view of a quartz wafer according to the first embodiment, Figure 8(b) is an enlarged view of region R1 in Figure 8(a), and Figure 8(c) is a surface view of the quartz vibrator with electrodes formed on it, similar to Figure 8(b). [Figure 9] Figure 9(a) is an end view of a crystal oscillator according to a second embodiment, similar to Figure 2(a), and Figure 9(b) is an end view of a crystal resonator according to a 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, the basic structure of the crystal oscillator and crystal diaphragm according to this disclosure will be described with reference to Figures 1 to 3. Figure 1 is a perspective view of the crystal oscillator according to this embodiment. Figure 2(a) is an end view along the dashed line AA in Figure 1, and in particular is an end view of the long side of the crystal oscillator. Figure 2(b) is a top view of the crystal oscillator according to this embodiment, and in particular shows the internal structure with the crystal diaphragm mounted. Figure 2(c) is an end view along the dashed line BB in Figure 2(a), and in particular is an end view of the short side of the crystal oscillator. Figure 3(a) is a side view of the crystal diaphragm provided in the crystal oscillator according to this embodiment, and in particular shows the structure on the long side of the crystal diaphragm. Figure 3(b) is a front view of the crystal diaphragm provided in the crystal oscillator according to this embodiment, and in particular shows the structure on the short side of the crystal diaphragm.

[0015] As can be seen from FIGS. 1 and 2(a) to (c), a crystal oscillator 1, which is an example of a piezoelectric device, includes a package 2 for a crystal oscillator (hereinafter simply referred to as the package 2), a crystal vibrating piece 3 and an IC chip 4 mounted in a 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] The package 2 is a ceramic package in which a plurality of ceramics with a desired metal pattern formed on the surface are laminated. Specifically, the package 2 has a laminated structure in which an outer frame wall 11, which is a base portion having an opening with a predetermined dimension, an inner frame wall 12 having an opening smaller than 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, the package 2 has a concave and stepped mounting space 2a for mounting the crystal vibrating piece 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 the 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 the package 2 is defined as the vertical direction, and the direction orthogonal to the vertical direction is defined as the horizontal direction. Also, regarding 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 the 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 the 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 onto the conductor pattern 15 by a known metal joining method. Thereby, the mounting space 2a of the package 2 is sealed, and the mounting space 2a is sealed using a gas such as vacuum or nitrogen.

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

[0020] Four external connection terminals 20a, 20b, 20c, and 20d are formed at the four corners on the back surface of the bottom plate 13 of the package 2. Also, terminals 21 that are electrically connected to the respective electrodes of the IC chip 4 are formed on the respective surfaces of the pedestals 14 installed on the bottom plate 13. For example, when the number of electrodes of the IC chip 4 is six, six pedestals 14 and terminals 21 are provided, and each electrode and each terminal 21 are electrically connected by wire bonding. Here, by forming the pedestals 14, it becomes possible to align the heights of the electrode formation surface of the IC chip 4 and the terminals 21, and the accuracy of wire bonding can be improved. Note that the number of the electrodes is not limited to six, and the IC chip 4 may be a flip chip type element. In this case, the shapes and the number of the pedestals 14 and the terminals 21 are appropriately changed.

[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, the characteristics of the crystal diaphragm 3 mounted in the crystal oscillator 1 of this embodiment will be described with reference to Figures 4 to 7. Here, Figure 4 is a graph showing the reflow test results for a sample of the crystal oscillator. In particular, Figure 4 is a graph showing the frequency fluctuation values ​​(ΔF / F) before and after the reflow test for four types of samples with different ratios between the thickness of the crystal substrate 30 (described later) and the thickness of the surface electrode 40 and back electrode 50 (hereinafter, the two are collectively referred to simply as electrodes). Figure 5 is a graph that combines the reflow test results for a sample of the crystal oscillator. In particular, Figure 5 is a graph that combines the average values ​​of the frequency fluctuation values ​​(ΔF / F) before and after the reflow test for each sample in which the ratio between the thickness of the crystal substrate 30 and the electrode thickness is changed in steps. Furthermore, Figure 6 is a graph showing the test results of the high-temperature storage characteristics at 125°C for a sample of the crystal oscillator. In particular, Figure 6 is a graph showing the test results (aging characteristics) of frequency fluctuation values ​​(ΔF / F) after being left at a high temperature of 125°C for four types of samples with different ratios of the thickness of the quartz crystal plate 30 to the thickness of the electrodes. Then, Figure 7 is a single graph that summarizes the test results of the high temperature aging characteristics at 125°C for the quartz oscillator samples. Specifically, Figure 7 is a single graph that summarizes the average value of the frequency fluctuation value (ΔF / F) after 1000 hours at 125°C for each sample in which the ratio of the thickness of the quartz crystal plate 30 to the thickness of the electrodes was changed in steps.

[0026] First, in this embodiment, the quartz crystal oscillator 3 is set such that the thickness of the quartz crystal plate 30 divided by the thickness of the electrodes (front electrode 40 and back electrode 50) (hereinafter also referred to as the thickness ratio) is greater than "7.4" by adjusting the thickness of the quartz crystal plate 30, the front electrode 40, and the back electrode 50. In general quartz device design, from the viewpoint of vibration confinement in the quartz crystal oscillator 3, this thickness ratio is usually set to "7.4" or less. The inventors of this disclosure have found that by deliberately making this thickness ratio greater than "7.4," which is not a commonly practiced design, the effects described below can be obtained.

[0027] First, as shown in Figure 4, the thicknesses of the quartz plate 30, the surface electrode 40, and the back electrode 50 were adjusted, and the frequency fluctuation values ​​(ΔF / F) before and after the reflow test were calculated for several samples with thickness ratios of "7.4", "9.6", "11.2", and "13.7", and the reflow characteristics were evaluated. More specifically, for each sample, the difference between the frequency measured before reflow (before the test) and the frequency measured after reflow (after the test) was divided by the nominal frequency (26 MHz in this embodiment) to obtain the frequency fluctuation value (ΔF / F) after the test. Therefore, the horizontal axis in Figure 4 shows the before and after of the test, and the vertical axis shows the frequency fluctuation value (ΔF / F).

[0028] As shown in Figure 4, it was found that increasing the film thickness ratio from "7.4" tended to decrease the frequency fluctuation value after the test. In particular, when the thickness ratio was "7.4", the frequency fluctuation value was around -0.6 ppm, but when the thickness ratio increased to "13.7", the frequency fluctuation value was found to be around -0.2 ppm.

[0029] Next, considering the above trends, we investigated how the frequency fluctuation value (ΔF / F) after testing changed when the thickness ratio was further increased. Specifically, as shown in Figure 5, it was found that as the thickness ratio was increased to "7.4", "9.6", "11.2", "13.7", "14.7", "15.9", "17.4", "19.1", "21.2", "23.9", "27.3", "31.9", "38.2", "47.8", "63.7", "95.6", and "191.2", the frequency fluctuation value (ΔF / F) after testing gradually increased from approximately -0.6 ppm. It was also found that when the thickness ratio exceeded 50, the increase in the frequency fluctuation value (ΔF / F) (the slope of the graph) tended to decrease. On the other hand, when the thickness ratio was "27.3" or higher, the frequency fluctuation value (ΔF / F) became approximately 0.6 ppm or higher, and it was found that the reflow characteristics worsened compared to the case where the thickness ratio was "7.4".

[0030] Considering the reflow characteristics based on these test results, it is important that the thickness ratio is greater than "7.4" and less than or equal to "23.9". In particular, to achieve exceptionally superior reflow characteristics, where the frequency fluctuation value (ΔF / F) is less than half compared to conventional designs (thickness ratio = 7.4 or less), it is important that the thickness ratio is between 13.7 and 19.1.

[0031] Next, as shown in Figure 6, the thicknesses of the quartz plate 30, the surface electrode 40, and the back electrode 50 were adjusted, and the frequency fluctuation values ​​(ΔF / F) due to high-temperature storage at 125°C were calculated for several samples with thickness ratios of "7.4", "9.6", "11.2", and "13.7", and the aging characteristics were evaluated. More specifically, for each sample, the frequency fluctuation value (ΔF / F) was calculated by dividing the difference between the frequency measured before being stored in a constant temperature bath at 125°C and the frequency measured after being stored in a constant temperature bath at 125°C for a predetermined time by the nominal frequency (26MHz in this embodiment). Here, the predetermined times are 22 hours, 44 hours, 66 hours, 160 hours, 350 hours, 516 hours, 874 hours, and 1016 hours for a thickness ratio of "7.4", and 23 hours, 93 hours, 259 hours, 497 hours, and 1021 hours for thickness ratios of "9.6", "11.2", and "13.7". Therefore, the horizontal axis of Figure 6 represents the time spent in a constant temperature bath at 125°C, and the vertical axis represents the frequency fluctuation value (ΔF / F). Note that measurements before leaving the samples in the constant temperature bath at 125°C, and measurements after the predetermined time have elapsed, were performed at 25°C.

[0032] As shown in Figure 6, the sample with a thickness ratio of "7.4" showed a tendency for the frequency fluctuation value to increase with the time spent at the high temperature of 125°C. In particular, the frequency fluctuation value after 22 hours was approximately 0.4 ppm, after 350 hours it exceeded 1.0 ppm, and after 1016 hours it exceeded 1.2 ppm. In contrast, the samples with thickness ratios of "9.6", "11.2", and "13.7" kept the frequency fluctuation value below 0.8 ppm even after being left at the high temperature of 125°C. Furthermore, it was found that increasing the thickness ratio tended to result in a smaller frequency fluctuation value. In particular, the sample with a thickness ratio of "13.7" showed a frequency fluctuation value of approximately 0.2 ppm at 23 hours, 93 hours, 259 hours, 497 hours, and 1021 hours, confirming that it possessed excellent aging characteristics.

[0033] Next, taking the above trends into consideration, we investigated how the frequency fluctuation value (ΔF / F) changes after a predetermined time (after 1000 hours) when the thickness ratio is further increased. Specifically, as shown in Figure 7, it was found that as the thickness ratio was increased to "7.4", "9.6", "11.2", "13.7", "14.7", "15.9", "17.4", "19.1", "21.2", "23.9", "27.3", "31.9", "38.2", "47.8", "63.7", "95.6", and "191.2", the frequency fluctuation value (ΔF / F) gradually decreased from approximately 1.4 ppm. It was also found that when the thickness ratio exceeds "27.3", the amount of decrease in the frequency fluctuation value (ΔF / F) (the slope of the graph) tends to increase. On the other hand, when the thickness ratio exceeds "27.3", the frequency fluctuation value (ΔF / F) becomes approximately -1.77 ppm or less, indicating that the aging characteristics worsen compared to the case with a thickness ratio of "7.4".

[0034] Considering the aging characteristics based on these test results, it is important that the thickness ratio be greater than "7.4" and less than or equal to "23.9". In particular, to achieve exceptionally superior aging characteristics with a frequency fluctuation value (ΔF / F) of less than 1 / 3 compared to conventional designs (thickness ratio = 7.4 or less), it is important that the thickness ratio be between 13.7 and 19.1.

[0035] From the above, it is important to set the thickness ratio, determined by the thicknesses of the quartz substrate 30, the surface electrode 40, and the back electrode 50, to be greater than "7.4" and less than or equal to "23.9". In particular, considering the reflow characteristics and aging characteristics, it is preferable to set the lower limit of the thickness ratio to "13.7" or more and the upper limit to "19.1" or less. This makes the frequency fluctuation value (ΔF / F) of each characteristic significantly smaller compared to the case of conventional designs.

[0036] Furthermore, by adjusting the thickness of the crystal plate 30, the surface electrode 40, and the back electrode 50, the above thickness ratio can be satisfied, thus improving the reflow characteristics and aging characteristics without changing the structure of the package 2 or preparing special parts. In other words, it becomes possible to reduce the aging changes expressed as reflow characteristics and aging characteristics without complicating the configuration and control of the crystal oscillator 1.

[0037] As mentioned above, from the viewpoint of confining vibrations in the crystal oscillator 3, the thickness ratio is preferably 7.4 or less, and such a design makes it possible to reduce the crystal impedance (CI). Therefore, if the thickness ratio is greater than 7.4, the crystal impedance increases, and depending on the conditions of the circuit board on which the crystal oscillator 1 is mounted, it may become difficult to satisfy the operating conditions. For this reason, when the thickness ratio is greater than 7.4, it becomes even more important to design the circuit board in a way that reduces the crystal impedance.

[0038] For example, to reduce crystal impedance, the dimensions of the crystal plate 30 can be optimized. Specifically, it is possible to reduce crystal impedance by making the dimensions of the crystal plate 30 as large as possible, or by adjusting the dimensions considering the temperature characteristics of the crystal plate 30. In such cases, it is possible to make the long and short sides of the crystal plate 30 as large as possible without contacting the outer frame wall 11 of the package 2. However, it is also necessary to consider the mounting accuracy of the crystal plate 30 and the package 2. For example, in a 1.6 mm x 1.2 mm crystal oscillator 1, it is preferable that the gap (clearance) between the outer frame wall 11 of the package 2 and the crystal plate 30 be 100 μm or more.

[0039] Next, with reference to Figure 8, 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 8(a) is a plan view of a quartz wafer as an example of a piezoelectric wafer according to this embodiment. Figure 8(b) is an enlarged view of region R1 in Figure 8(a). Furthermore, Figure 8(c) is a surface view of the quartz vibrator with electrodes formed on it, similar to Figure 8(b).

[0040] First, a quartz wafer W with a roughly circular planar shape is prepared, as shown in Figure 8(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 be square, and the cutting method is not limited to an AT cut; it may be a Z cut or a two-turn cut such as an SC cut, etc.

[0041] 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 8(b)) formed to surround the multiple quartz diaphragms 3, and a connecting portion 62 (see Figure 8(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 8(b).

[0042] 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.

[0043] 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.

[0044] 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 diaphragm 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 8(c).

[0045] 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.

[0046] (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 9(a). Here, Figure 9(a) is an end view of the crystal oscillator 101 according to the second embodiment, shown in the same way as Figure 2(a).

[0047] As can be seen from Figure 9(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.

[0048] 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.

[0049] 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.

[0050] Two crystal diaphragm mounting terminals (only crystal diaphragm mounting terminal 116 is shown in Figure 9(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.

[0051] Multiple IC terminals 141 are formed on the back surface 113b of the bottom plate 113 of the package 102. A bonding member 151 is applied to each of the IC terminals 141, and an IC chip 104 is mounted via these bonding members 151. For example, the bonding member 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.

[0052] Four external connection terminals (only external connection terminals 120c and 120d are shown in Figure 9(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.

[0053] 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.

[0054] In this embodiment as well, it is important that the thickness ratio determined by the thicknesses of the quartz plate 30, the surface electrode 40, and the back electrode 50 be greater than "7.4" and less than or equal to "23.9". Preferably, the lower limit of the thickness ratio is "13.7" or more, and the upper limit is "19.1" or less. This makes the frequency fluctuation value (ΔF / F) of each characteristic much smaller compared to the case of conventional designs.

[0055] (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 9(b). Here, Figure 9(b) is an end view of the crystal resonator 201 according to the third embodiment, shown in the same way as Figure 2(a).

[0056] As can be seen in Figure 9(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.

[0057] 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.

[0058] Two crystal oscillator mounting terminals (only crystal oscillator mounting terminal 216 is shown in Figure 9(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 (only external connection terminals 219c and 219d are shown in Figure 9(b)) are formed on the back surface of the bottom plate 213 of package 202.

[0059] 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.

[0060] In this embodiment as well, it is important that the thickness ratio determined by the thicknesses of the quartz plate 30, the surface electrode 40, and the back electrode 50 be greater than "7.4" and less than or equal to "23.9". Preferably, the lower limit of the thickness ratio is "13.7" or more, and the upper limit is "19.1" or less. This makes the frequency fluctuation value (ΔF / F) of each characteristic much smaller compared to the case of conventional designs.

[0061] (Embodiments of this disclosure) A first embodiment of the present disclosure is a quartz 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 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 obtained by dividing the thickness of the quartz element plate by the thickness of the electrodes is greater than 7.4 and less than or equal to 23.9.

[0062] By satisfying these conditions, frequency fluctuations before and after reflow testing, and frequency fluctuations before and after high-temperature storage, can be reduced. In other words, such a quartz device exhibits reduced aging characteristics, as shown by the reflow and aging properties. Furthermore, since these conditions can be met by adjusting the thickness of the quartz plate and electrodes, there is no need to complicate the configuration and control of the quartz device.

[0063] A second embodiment of this disclosure is that, in the first embodiment, the value obtained by dividing the thickness of the quartz plate by the thickness of the electrode is 19.1 or less. This makes it possible to reduce aging without complicating the configuration and control of the quartz device.

[0064] A third embodiment of this disclosure is that, in the first or second embodiment, the value obtained by dividing the thickness of the quartz plate by the thickness of the electrode is 13.7 or greater. This makes it possible to reduce aging without complicating the configuration and control of the quartz device.

[0065] A fourth embodiment of this disclosure includes an IC chip mounted on the package in any of the first to third embodiments. This enables control of the oscillation frequency and provides a stable frequency.

[0066] A fifth embodiment of the present disclosure is a quartz crystal vibrator having electrodes formed on the front and back surfaces of a rectangular quartz crystal plate in plan view, characterized in that the value obtained by dividing the thickness of the quartz crystal plate by the thickness of the electrodes is greater than 7.4 and 23.9 or less.

[0067] By satisfying these conditions, the frequency fluctuations before and after the reflow test, and the frequency fluctuations before and after high-temperature storage, can be reduced. In other words, such a quartz crystal vibrator exhibits reduced aging characteristics, as shown by its reflow and aging properties.

[0068] 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]

[0069] 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 quartz device characterized in that the value obtained by dividing the thickness of the quartz plate by the thickness of the electrode is greater than 7.4 and less than or equal to 23.

9.

2. The quartz device according to claim 1, characterized in that the value obtained by dividing the thickness of the quartz plate by the thickness of the electrode is 19.1 or less.

3. The quartz device according to claim 2, characterized in that the value obtained by dividing the thickness of the quartz plate by the thickness of the electrode is 13.7 or more.

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 vibrator characterized in that the value obtained by dividing the thickness of the quartz plate by the thickness of the electrode is greater than 7.4 and less than or equal to 23.

9.

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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