Tuning fork piezoelectric element and method for manufacturing tuning fork piezoelectric element

Abstract

To provide a tuning fork type piezoelectric element capable of achieving miniaturization or improvement of impact resistance required in a tuning fork type piezoelectric vibrator, and to provide a method of manufacturing the same.SOLUTION: The front principal surface excitation electrodes 5 and 6 and the back principal surface excitation electrodes 7 and 8 of the vibration arms 3132 and of the tuning-fork type piezoelectric element 1 are electrically connected via the through-holes 141142 and penetrating from the front surface to the back surface, and the wiring pattern 13 electrically connecting the front principal surface excitation electrode 5 and the bonding electrode 11 formed on the base 30 and the wiring pattern 18 electrically connecting the front principal surface excitation electrode 6 and the side surface excitation electrode 9 are provided on the front surface of the base 30. The bonding electrode 11 and the side-surface excitation electrode 10 are connected to each other on the side surface where the base 30 and the vibrating arm 32 are coupled to each other, the bonding electrode 12 and the side-surface excitation electrode 9 are connected to each other on the side surface where the base 30 and the vibrating arm 31 are coupled to each other, and no wiring pattern corresponding to the wiring pattern 13,18 is provided on the back surface on which the bonding electrode 11,12 is formed.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a tuning fork type piezoelectric element used in a tuning fork type piezoelectric vibrator and a method for manufacturing the tuning fork type piezoelectric element. [Background technology]

[0002] Tuning fork type piezoelectric vibrators, especially tuning fork type quartz crystal vibrators made from quartz crystal, are widely used as low-power clocks in electronic devices such as mobile phones, smart watches, smart rings, voice recorders, and action cameras. However, as these devices become smaller, there is a demand for miniaturization of the vibrators as well. A tuning fork type piezoelectric vibrator generally consists of a tuning fork-shaped piezoelectric element hermetically housed in a vacuum sealed container consisting of a ceramic base and a metal lid. The tuning fork type piezoelectric vibrator 100 is mounted on a mounting portion of a ceramic base with a conductive adhesive. Fig. 10 is a diagram for explaining the general structure of a tuning fork type piezoelectric vibrator, with Fig. 10(a) being a plan view of the tuning fork type piezoelectric vibrator with the metal lid removed, and Fig. 10(b) being a side cross-sectional view of the tuning fork type piezoelectric vibrator. The tuning fork type piezoelectric vibrator 100 has a structure in which a tuning fork type piezoelectric element 101 is bonded and mounted on a ceramic base 102 with a conductive adhesive 104, and the metal lid 103 is welded to the ceramic base 102 by a method such as seam welding to hermetically seal the tuning fork type piezoelectric element 101.

[0003] Fig. 7 shows the structure of a conventional tuning fork-type piezoelectric element 101. Fig. 7(a) is a perspective view of the tuning fork-type piezoelectric element 101 as seen from the front side, and Fig. 7(b) is a perspective view of the tuning fork-type piezoelectric element 101 as seen from the back side, which is the surface that is bonded to the ceramic base 102 (shown in Fig. 10). The tuning fork-type piezoelectric element 101 is composed of a base 130 and a pair of vibrating arms 131 and 132 that extend in the same direction from the base 130. The base 130 has bonding electrodes 111 and 112 that are fixed to the ceramic base 102 with a conductive adhesive 104 (shown in Fig. 10). Each of the pair of vibrating arms 131, 132 has rear principal surface excitation electrodes 107, 108 on the surface (rear surface) on the side where bonding electrodes 111, 112 that are bonded to the ceramic base 102 are located, and front principal surface excitation electrodes 105, 106 are provided on the opposite surface (front surface) that faces the rear surface. Side surface excitation electrodes 109, 110 are provided on the side surfaces of the respective vibrating arms 131, 132.

[0004] The excitation electrodes are connected so that the front principal surface excitation electrode 105, the rear principal surface excitation electrode 107 of one vibrating arm 131, and the side surface excitation electrode 110 of the other vibrating arm 132 are at the same potential. The excitation electrodes of the vibrating arm 132 are also connected in a similar relationship. Therefore, the front principal surface excitation electrode 105, the rear principal surface excitation electrode 107, and the side surface excitation electrode 110 are connected by wiring patterns 113 and 115, which are connected to a bonding electrode 111. Similarly, the front principal surface excitation electrode 106, the rear principal surface excitation electrode 108, and the side surface excitation electrode 109 are connected by wiring patterns 114 and 118, which are connected to a bonding electrode 112. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2006-217603 [Patent Document 2] Japanese Patent Application Laid-Open No. 2010-10734 Summary of the Invention [Problem to be solved by the invention]

[0006] To realize a small piezoelectric vibrator, it is first necessary to make the tuning fork piezoelectric element smaller, but considering the manufacturing variations in the manufacturing process, there is a limit to how small the vibrating arms can be. When the vibrating arms have been made as small as possible, further miniaturization of the piezoelectric vibrator requires making the base smaller.

[0007] 7(b), the conventional tuning fork-type piezoelectric element 101 has, on the back surface of the base 130, a wiring pattern 114 that connects the back principal surface excitation electrode 108 and the bonding electrode 112 to apply an electric field to the vibrating arms 131 and 132 to vibrate them, and a wiring pattern 115 that electrically connects the back principal surface excitation electrode 107 and the side surface excitation electrode 110. In addition, the other bonding electrode 111 and the side surface excitation electrode 110 are electrically connected on the side surface of the base 130.

[0008] There is a certain width between each of the wirings and bonding electrodes at different potentials; for example, there is a separation 117 between wiring pattern 114 and wiring pattern 115, and there is a separation 116 between bonding electrode 111 and wiring pattern 114. Each separation must have a minimum width to prevent conductive adhesive 104 from spreading and causing a short circuit between the wiring patterns when conductive adhesive 104 is applied and tuning fork type piezoelectric element 101 is bonded to ceramic base 102. Taking into account empirical variations in adhesive spreading, the width of each of separations 116 and 117 must be at least 40 μm.

[0009] Furthermore, the bonding electrodes 111 and 112 require a minimum bonding area to ensure impact resistance. Depending on the application, there may be cases where it is necessary to enhance impact resistance, and conversely, there may be cases where the bonding area needs to be large.

[0010] As technologies relating to the above-mentioned problem, Patent Documents 1 and 2 disclose a method of establishing electrical continuity between the front and back principal surface electrodes of a tuning fork-type piezoelectric element through through holes. In particular, Patent Document 2 describes that providing through holes simplifies the wiring pattern and is effective in preventing disconnections during the manufacturing process. However, Patent Document 2 does not describe a method for solving the above-mentioned problem, and there is no mention of reducing the base or increasing the bonding area to improve impact resistance, so the purpose is different.

[0011] An object of the present invention is to solve the above-mentioned problems and to provide a tuning-fork type piezoelectric element that can achieve the miniaturization or improved impact resistance required for tuning-fork type piezoelectric vibrators, and a method for manufacturing a tuning-fork type piezoelectric element. [Means for solving the problem]

[0012] a tuning fork-type piezoelectric element comprising a base, a pair of vibrating arms extending from the base, a first excitation electrode formed on the front and back surfaces of the vibrating arms, a second excitation electrode formed on the side of the vibrating arms, a pair of bonding electrodes formed on the back surface of the base, a first wiring pattern electrically connected to the first excitation electrode of one of the vibrating arms, the second excitation electrode of the other vibrating arm, and one bonding electrode, and a second wiring pattern electrically connected to the first excitation electrode of the other vibrating arm, the second excitation electrode of one of the vibrating arms, and the other bonding electrode; wherein the vibrating arms have through holes penetrating between the front and back surfaces of the vibrating arms, the first excitation electrode formed on the front surface of the vibrating arms and the first excitation electrode formed on the back surface are electrically connected via a conductive layer formed in the through holes, and the first wiring pattern and the second wiring pattern are formed only on the front surface or the back surface of the base.

[0013] Preferably, the bonding electrode formed on the rear surface of the base is a tuning-fork type piezoelectric element that is a mounting portion for mounting the tuning-fork type piezoelectric vibrator on a support member that supports the tuning-fork type piezoelectric vibrator.

[0014] More preferably, the tuning fork type piezoelectric element has a groove on at least one of the front and back surfaces of the vibrating arm, and at least one of the openings of the through hole opens into the groove.

[0015] Preferably, the through-hole is a tuning fork type piezoelectric element provided by laser processing.

[0016] a tuning fork comprising: a base; a pair of vibrating arms extending from the base; first excitation electrodes formed on the front and back surfaces of the vibrating arms; second excitation electrodes formed on the side surfaces of the vibrating arms; a pair of bonding electrodes formed on the back surface of the base; a first wiring pattern electrically connected to the first excitation electrode of one of the vibrating arms, the second excitation electrode of the other of the vibrating arms, and one bonding electrode; and a second wiring pattern electrically connected to the first excitation electrode of the other of the vibrating arms, the second excitation electrode of one of the vibrating arms, and the other bonding electrode, wherein the first wiring pattern and the second wiring pattern are formed only on the front surface of the front surface or the back surface of the base. a tuning-fork-shaped piezoelectric element manufacturing method, comprising: a tuning-fork-shaped forming process for forming a piezoelectric substrate into the outer shape of the base and the vibrating arms; a through-hole forming process for forming through-holes that penetrate between the front and back surfaces of the tuning-fork-shaped vibrating arms; and an electrode forming process for forming the first excitation electrode, the second excitation electrode, the bonding electrode, the first wiring pattern, and the second wiring pattern, wherein the electrode forming process includes a step of forming a conductive layer in the through-hole and electrically connecting the first excitation electrode formed on the front surface of the vibrating arms and the first excitation electrode formed on the back surface via the conductive layer formed in the through-hole.

[0017] The method for manufacturing a tuning fork type piezoelectric element may be such that the through-hole forming step is performed by either wet etching or laser processing.

[0018] Furthermore, the method for manufacturing a tuning-fork type piezoelectric element may be such that the tuning-fork shape forming step is performed by wet etching, and the through-hole forming step is performed by laser processing. [Effects of the Invention]

[0019] It is possible to provide a tuning fork type piezoelectric element that can be made smaller or have improved impact resistance, and a method for manufacturing the same. [Brief explanation of the drawings]

[0020] [Figure 1] 1A and 1B are diagrams showing a tuning fork-type piezoelectric element according to a first embodiment of the present invention, where FIG. 1A is a perspective view of the tuning fork-type piezoelectric element seen from the front side, and FIG. 1B is a perspective view of the tuning fork-type piezoelectric element seen from the back side. [Figure 2] 2A and 2B are cross-sectional views of a tuning-fork type piezoelectric element according to a first embodiment of the present invention, where FIG. 2A is a cross-sectional view of part A in FIG. 1A and FIG. 2B is a cross-sectional view of part B in FIG. [Figure 3] 3A and 3B are diagrams showing a tuning fork-type piezoelectric element according to a second embodiment of the present invention, where FIG. 3A is a perspective view of the tuning fork-type piezoelectric element seen from the front side, and FIG. 3B is a perspective view of the tuning fork-type piezoelectric element seen from the back side. [Figure 4] 4A and 4B are perspective views of a tuning fork-type piezoelectric element according to a third embodiment of the present invention, where FIG. 4A is a perspective view of the tuning fork-type piezoelectric element seen from the front side, and FIG. 4B is a perspective view of the tuning fork-type piezoelectric element seen from the back side. [Figure 5] 5A and 5B are overall views of a tuning fork-type piezoelectric element according to a fourth embodiment of the present invention, where FIG. 5A is a perspective view of the tuning fork-type piezoelectric element seen from the front side, and FIG. 5B is a perspective view of the tuning fork-type piezoelectric element seen from the back side. [Figure 6] 6A and 6B are cross-sectional views of a tuning-fork type piezoelectric element according to a fourth embodiment of the present invention, where FIG. 6A is a cross-sectional view of part A in FIG. 5A and FIG. 6B is a cross-sectional view of part B in FIG. 5A. [Figure 7] These figures show the structure of a conventional tuning fork-type piezoelectric element, where Fig. 7(a) is a perspective view of the tuning fork-type piezoelectric element seen from the front side, and Fig. 7(b) is a perspective view of the tuning fork-type piezoelectric element seen from the back side, which is the surface that is bonded to the ceramic base. [Figure 8]8A and 8B are schematic diagrams showing tuning-fork type piezoelectric elements of a conventional example, Example 1, and Example 2 bonded to a ceramic base with a conductive adhesive, where FIG. 8A shows the conventional example, FIG. 8B shows Example 1, and FIG. 8C shows Example 2. [Figure 9] 9A and 9B are diagrams showing the positional relationship between the tuning fork-type piezoelectric element and the conductive adhesive when the tuning fork-type piezoelectric element of the conventional example, Example 1, and Example 2 is bonded to a ceramic base with the conductive adhesive; FIG. 9A shows the conventional example, FIG. 9B shows Example 1, and FIG. 9C shows Example 2. [Figure 10] 10A and 10B are diagrams for explaining the general structure of a tuning fork type piezoelectric vibrator, where FIG. 10A is a plan view of the tuning fork type piezoelectric vibrator with the metal lid removed, and FIG. 10B is a side cross-sectional view of the tuning fork type piezoelectric vibrator. DETAILED DESCRIPTION OF THE INVENTION

[0021] Various embodiments of the present invention will be described in detail below with reference to the accompanying drawings. However, it should be noted that the technical scope of the present invention is not limited to these embodiments, but extends to the inventions set forth in the claims and their equivalents. In addition, components with the same reference numerals in different drawings have the same functions. [Example]

[0022] Fig. 1 shows a tuning fork type piezoelectric element according to a first embodiment of the present invention, with Fig. 1(a) being a perspective view of the tuning fork type piezoelectric element seen from the front side and Fig. 1(b) being a perspective view of the tuning fork type piezoelectric element seen from the back side. Fig. 2 shows cross-sectional views of the tuning fork type piezoelectric element according to the first embodiment of the present invention, with Fig. 2(a) being a cross-sectional view of part A in Fig. 1(a) and Fig. 2(b) being a cross-sectional view of part B in Fig. 1(a). In the description of the present invention, the back side of the tuning fork type piezoelectric element is the mounting surface for mounting the tuning fork type piezoelectric element on a support member (for example, a vacuum-sealed container that houses the tuning fork type piezoelectric element), and the front side refers to the surface of the tuning fork type piezoelectric element that faces the back side.

[0023] The tuning-fork piezoelectric element 1 of the first embodiment includes a base 30 and a pair of vibrating arms 31 and 32 extending in the same direction from the base 30. The vibrating arms 31 and 32 each have through-holes 141 and 142 with a generally circular cross section near the end on the base 30 side, penetrating the front and back surfaces of the tuning-fork piezoelectric element 1. The tuning-fork piezoelectric element 1 also includes front principal surface excitation electrodes 5 and 6 formed on the front surfaces of the vibrating arms 31 and 32, back principal surface excitation electrodes 7 and 8 formed on the back surfaces of the vibrating arms 31 and 32, side surface excitation electrodes 9 and 10 formed on the side surfaces of the vibrating arms 31 and 32, a pair of bonding electrodes 11 and 12 formed on the back surface and side surfaces of the base 30, and wiring patterns 13 and 18 formed on the front surface of the base 30. In FIG. 1, the overall length of the tuning-fork piezoelectric element 1 is indicated as L1, and the length of the base 30 is indicated as K1.

[0024] The front main surface excitation electrodes 5, 6, the rear main surface excitation electrodes 7, 8, and the side surface excitation electrodes 9, 10 are electrically connected so that the front main surface excitation electrode 5, the rear main surface excitation electrode 7 of one vibrating arm 31, and the side surface excitation electrode 10 of the other vibrating arm 32 are at the same potential, and the front main surface excitation electrode 6, the rear main surface excitation electrode 8 of the other vibrating arm 32, and the side surface excitation electrode 9 of one vibrating arm 31 are electrically connected so that they are at the same potential. Here, the front principal surface excitation electrode 5 and the rear principal surface excitation electrode 7 of the vibrating arm 31 are electrically connected by a metal film formed on the inner surface of the through hole 141, and the front principal surface excitation electrode 6 and the rear principal surface excitation electrode 8 of the vibrating arm 32 are electrically connected by a metal film formed on the inner surface of the through hole 142. Furthermore, the front principal surface excitation electrode 5 and the rear principal surface excitation electrode 7 of the vibrating arm 31 are electrically connected to the wiring pattern 13, and the wiring pattern 13 is electrically connected to the bonding electrode 11. Furthermore, the side surface excitation electrode 10 is electrically connected to the bonding electrode 11 on the side surface of the tuning fork type piezoelectric element 1. The front principal surface excitation electrode 6 and the rear principal surface excitation electrode 8 of the vibrating arm 32 are electrically connected to the wiring pattern 18 and the side surface excitation electrode 9, and the side surface excitation electrode 9 is electrically connected to the bonding electrode 12 on the side surface of the tuning fork type piezoelectric element 1.

[0025] Here, in this Example 1, as shown in Figure 2(a), the front principal surface excitation electrodes 5, 6 and the back principal surface excitation electrodes 7, 8 are electrically connected by a metal film formed on the inner surface of the through holes 141, 142, but instead of the metal film, a conductive material may be filled inside each of the through holes 141, 142. Furthermore, since the through holes 141, 142 are formed on the base 30 side of the vibrating arms 31, 32, the frequency can be changed without changing the width of the vibrating arms 31, 32 by changing the size of the through holes 141, 142, which is useful for miniaturizing the tuning fork-type piezoelectric element 1. [Example]

[0026] 3A and 3B show a tuning fork-type piezoelectric element according to a second embodiment of the present invention, with Fig. 3A being a perspective view of the tuning fork-type piezoelectric element as seen from the front side, and Fig. 3B being a perspective view of the tuning fork-type piezoelectric element as seen from the back side. The tuning fork-type piezoelectric element 1 in this second embodiment has the same basic configuration and function as the tuning fork-type piezoelectric element 1 in the first embodiment, and detailed descriptions of the components that have the same configuration will be omitted here, and only the different configurations will be described. In Fig. 3, the overall length of the tuning fork-type piezoelectric element 1 is indicated as L2, and the length of the base 30 is indicated as K2.

[0027] The tuning-fork type piezoelectric element 1 in Example 2 differs from the tuning-fork type piezoelectric element 1 in Example 1 in that the overall length L2 is shorter than the overall length L1 of the tuning-fork type piezoelectric element 1. This is because the length K2 of the base 30 in Example 2 is set to be shorter than the length K1 of the base 30 in Example 1, and the lengths of the bonding electrodes 11 and 12 provided on the base 30 are also set to be shorter. In this specification, the direction in which the vibrating arms extend from the base in a tuning-fork type piezoelectric element is defined as the length direction.

[0028] 8A, 8B, and 8C are schematic diagrams showing tuning-fork-type piezoelectric elements of the conventional example, Example 1, and Example 2 bonded to a ceramic base with a conductive adhesive, with FIG. 8A showing the conventional example, FIG. 8B showing Example 1, and FIG. 8C showing Example 2. Also, FIG. 9A, 9B, and 9C are schematic diagrams showing the positional relationship between the conductive adhesive and tuning-fork-type piezoelectric element 1 when tuning-fork-type piezoelectric elements of the conventional example, Example 1, and Example 2 are bonded to a ceramic base with a conductive adhesive, with FIG. 9A showing the conventional example, FIG. 9B showing Example 1, and FIG. 9C showing Example 2. The tuning-fork-type piezoelectric element 101 of the conventional example and the tuning-fork-type piezoelectric element 1 of Example 1 have the same overall length and base length, which are L1 and K1, respectively. The tuning fork-type piezoelectric element 1 of Example 2 has a total length L2 that is smaller than the total length L1 of the tuning fork-type piezoelectric element 101 of the conventional example and the tuning fork-type piezoelectric element 1 of Example 1, and the base length K2 is also smaller than the base length K1 of the tuning fork-type piezoelectric element 101 of the conventional example and the tuning fork-type piezoelectric element 1 of Example 1. 9, G1 indicates the lengthwise distance between the back principal surface excitation electrode and the conductive adhesive in the tuning fork type piezoelectric element 101 of the conventional example, and G2 indicates the lengthwise distance between the back principal surface excitation electrode and the conductive adhesive in the tuning fork type piezoelectric elements 1 of Examples 1 and 2, with distance G1 and distance G2 being G1>G2. Also, in FIGS. 8 and 9, M1 indicates the lengthwise dimension of the conductive adhesive 4 when the tuning fork type piezoelectric element 101 of the conventional example and the tuning fork type piezoelectric element 1 of Example 2 are bonded to the ceramic base 2 with the conductive adhesive 4, and M2 indicates the lengthwise dimension of the conductive adhesive 4 when the tuning fork type piezoelectric element 1 of Example 1 is bonded to the ceramic base 2 with the conductive adhesive 4. <M2である。

[0029] As shown in Figures 8 and 9, the tuning fork-type piezoelectric element 101 of the conventional example and the tuning fork-type piezoelectric element 1 of Example 1 have the same base length K1, but the lengthwise dimension M2 of the conductive adhesive 4 in the tuning fork-type piezoelectric element 1 of Example 1 is larger than the lengthwise dimension M1 of the conductive adhesive 4 in the tuning fork-type piezoelectric element 101 of the conventional example. This is because the tuning fork-type piezoelectric element 101 of the conventional example has wiring patterns 114, 115 and spacing portions 116, 117 on the back surface of the base 130, and a distance G1 is required on the base 130 to arrange them, whereas the back surface of the base 30 of the tuning fork-type piezoelectric element 1 of Example 1 does not have a wiring pattern equivalent to the wiring patterns 114, 115 of the conventional example, which electrically connects either of the bonding electrodes 11, 12 to either of the rear principal surface excitation electrodes 7, 8, or a wiring pattern electrically connecting either of the rear principal surface excitation electrodes 7, 8 to either of the side electrodes 9, 10. Therefore, it is only necessary to provide a minimum length G2 on the base 30 between the rear principal surface excitation electrodes 7, 8 and the bonding electrodes 11, 12 to prevent a short circuit between the rear principal surface excitation electrodes 7, 8 and the conductive adhesive 4, and therefore a larger space can be secured for arranging the conductive adhesive 4 compared to the conventional example. As a result, the tuning fork-type piezoelectric element 1 of Example 1 has the same size as the tuning fork-type piezoelectric element 101 of the conventional example, but has a larger bonding area with the ceramic base 2, resulting in a tuning fork-type piezoelectric vibrator with high bonding strength and high impact resistance. It should be noted that, based on experience, the minimum length G2, taking into consideration the wet spread of the conductive adhesive 4, needs to be at least 40 μm.

[0030] Furthermore, the length K2 of the base 30 of the tuning fork-type piezoelectric element 1 in Example 2 is smaller than the length K2 of the base of the tuning fork-type piezoelectric element 101 of the conventional example and the tuning fork-type piezoelectric element 1 of Example 1, but the bonding length is the same as the bonding length M1 of the conventional example. Like the tuning fork-type piezoelectric element 1 of Example 1, the tuning fork-type piezoelectric element 1 of Example 2 does not require wiring patterns equivalent to the wiring patterns 114, 115 in the tuning fork-type piezoelectric element 101 of the conventional example. Therefore, while maintaining the same longitudinal dimension M1 of the conductive adhesive 4 as in the conventional example (while maintaining a predetermined adhesive strength), the length of the base 30 can be made shorter than the base 130 of the conventional example, and the tuning fork-type piezoelectric element can be made smaller than conventional ones. [Example]

[0031] 4A and 4B are perspective views of a tuning-fork-type piezoelectric element according to a third embodiment of the present invention, with Fig. 4A being a perspective view of the tuning-fork-type piezoelectric element as seen from the front side and Fig. 4B being a perspective view of the tuning-fork-type piezoelectric element as seen from the back side. The tuning-fork-type piezoelectric element 1 according to the third embodiment is a modified example of the tuning-fork-type piezoelectric element 1 according to the first embodiment. While the tuning-fork-type piezoelectric element 1 according to the first embodiment has through-holes 141 and 142 provided near the ends of the vibrating arms 31 and 32 on the base 30 side, the tuning-fork-type piezoelectric element 1 according to the third embodiment has through-holes 141 and 142 provided toward the tips of the vibrating arms 31 and 32. The shape of the through-holes 141 and 142 has also been changed from a substantially circular cross section to a rectangular cross section, but as in the first embodiment, they can function to electrically connect the front principal surface excitation electrodes 5 and 6 and the back principal surface excitation electrodes 7 and 8, respectively.

[0032] As in Example 3, there is a degree of freedom in the design of the positions and shapes of the through holes 141, 142. However, there is an upper limit to the size because increasing the size of the holes (the size in the direction perpendicular to the axial direction of the holes) affects the vibration state of the vibrating arms 31, 32. Furthermore, although a smaller hole size is desirable, the lower limit of the size depends on the characteristics of the process for manufacturing the tuning fork-type piezoelectric element 1.

[0033] For example, as will be described later, when quartz crystal is used as the piezoelectric crystal and the shape is formed by wet etching with buffered hydrofluoric acid, the etching anisotropy and etching rate of the buffered hydrofluoric acid impose a lower limit on the size at which through-holes 141, 142 can be formed. Furthermore, since the manner in which the metal film is attached inside through-holes 141, 142 differs depending on whether sputtering deposition is used or vacuum deposition is used as the process for forming the metal film inside through-holes 141, 142, if the size is made smaller, the film will be formed too thin and will not be electrically connected, and therefore there is a lower limit on the size of through-holes 141, 142 for sufficient film formation.

[0034] Taking the above into consideration, when considering the opening size of the through holes 141, 142, if the length of the vibrating arms 31, 32 is between 800 μm and 1800 μm, an opening diameter or the size of one side of the opening of 10 to 30 μm will have little effect on the vibration state and will also be suitable for forming a metal film inside the hole. Furthermore, by providing the through holes 141, 142 at the tip end sides of the vibrating arms 31, 32, the influence of variations in the size and shape of the through holes 141, 142 on the CI value (crystal impedance) and frequency as characteristics of the tuning fork type piezoelectric element 1 can be suppressed. [Example]

[0035] FIG. 5 is an overall view of a tuning fork-type piezoelectric element according to Example 4 of the present invention, where FIG. 5(a) is a perspective view of the tuning fork-type piezoelectric element seen from the front side, and FIG. 5(b) is a perspective view of the tuning fork-type piezoelectric element seen from the back side. 6A and 6B are cross-sectional views of a tuning-fork type piezoelectric element 1 according to a fourth embodiment of the present invention, where FIG. 6A is a cross-sectional view of part A in FIG. 5A, and FIG. 6B is a cross-sectional view of part B in FIG. 5A. Example 4 is a modification of the tuning fork-type piezoelectric element 1 of Example 1, and grooves 405, 406, 407, and 408 are provided in the portions of the vibrating arms 31 and 32 where the front principal surface excitation electrodes 5 and 6 and the back principal surface excitation electrodes 7 and 8 are formed. It is widely known that providing the grooves 405, 406, 407, and 408 improves the CI (crystal impedance) value, which is a characteristic of the tuning fork-type piezoelectric element 1. Among the grooves 405, 406, 407, and 408, a through hole 141 is formed between the grooves 405 and 407 provided in one vibrating arm 31, and a through hole 142 is formed between the grooves 406 and 408 provided in the other vibrating arm 32. An opening of the through hole 141 or the through hole 142 arranged in the groove is present in each of the grooves 405, 406, 407, and 408.

[0036] Next, a method for manufacturing the tuning fork type piezoelectric elements 1 of Examples 1 to 4 will be described. First, a piezoelectric substrate is prepared, and a metal film is formed on the piezoelectric substrate. Next, a resist film corresponding to the external shape of the tuning fork piezoelectric element, consisting of the base 30 and vibrating arms 31 and 32 of the tuning fork piezoelectric element 1, is formed on the metal film. The resist film is used as a mask to etch the metal film and pattern it into the external shape of the tuning fork piezoelectric element. Then, using the patterned metal film as a mask, the piezoelectric substrate is wet-etched to form the external shape of the tuning fork piezoelectric element (tuning fork shape formation process). When the piezoelectric substrate is made of quartz, for example, buffered hydrofluoric acid can be used as an etchant for wet etching. Here, when grooves 405, 406, 407, and 408 are provided in the vibrating arms 31 and 32, as in the tuning fork-type piezoelectric element 1 described in Example 4, after the external shape of the tuning fork-type piezoelectric element is formed in the tuning fork shape forming process, a mask having openings corresponding to the grooves 405, 406, 407, and 408 is formed on the piezoelectric substrate, and the piezoelectric substrate is wet-etched to form the grooves 405, 406, 407, and 408 in the vibrating arms 31 and 32.

[0037] Next, the through holes 141 and 142 are formed (through hole forming process). The through holes 141 and 142 can be formed by forming a mask having openings corresponding to the through holes 141 and 142 on the piezoelectric substrate and wet etching the piezoelectric substrate. Alternatively, the tuning fork shape forming process and the through hole forming process may be performed simultaneously using wet etching. In this case, the formation of each film and mask can be performed simultaneously, allowing for more efficient processing than separate processes.

[0038] Next, an electrode film is formed on the piezoelectric substrate by sputtering or vacuum deposition, and the front principal surface excitation electrodes 5 and 6, the rear principal surface excitation electrodes 7 and 8, the side excitation electrodes 9 and 10, and the bonding electrodes 11 and 12 of the tuning fork type piezoelectric element 1 are formed (electrode formation process). In this way, the tuning fork type piezoelectric element 1 is completed.

[0039] In the through-hole forming process, the through-holes 141 and 142 can be formed by laser processing instead of wet etching. Wet etching is efficient because it allows multiple tuning-fork-type piezoelectric elements 1 to be processed in a single process. However, if the diameters of the through-holes 141 and 142 are small, the etching rate slows, requiring a long etching time, which can reduce productivity. Furthermore, if the etching time is long, areas other than the through-holes 141 and 142 may be affected by the etching, potentially resulting in excessive processing of areas other than the processed area. Therefore, performing the through-hole forming process using laser processing can avoid these issues and even drill extremely small holes. More specifically, laser processing is suitable for forming small through-holes 141 and 142 with diameters of approximately 10 to 30 μm. Laser processing is advantageous because it minimizes the impact on the design flexibility and characteristics of the tuning-fork-type piezoelectric element 1. When the piezoelectric substrate is made of quartz, an IR laser or a UV laser can be selected as the laser to be used for laser processing, and the most suitable laser can also be selected depending on the piezoelectric material used.

[0040] By performing the tuning fork shape formation step by wet etching and the through hole formation step by laser processing, it is possible to perform high-precision processing with high productivity even when the diameters of the through holes 141, 142 are small. Furthermore, by performing the through hole formation step by laser processing, the axial cross-sectional shape of the through holes 141, 142 can easily be processed into shapes such as a mortar shape, an hourglass shape, or a sloping shape, and this ensures that a metal film will adhere to the inside of the through holes 141, 142 in the electrode formation step.

[0041] The tuning fork-type piezoelectric element 1 and its manufacturing method of the present invention have been described above based on each embodiment, but tuning fork-type piezoelectric element 1 is generally constructed by forming various electrodes such as excitation electrodes and bonding electrodes on a tuning fork-shaped quartz substrate, which is a piezoelectric material. However, tuning fork-type piezoelectric element 1 is not limited to being constructed from quartz, and various piezoelectric crystal piezoelectric materials such as langasite crystal and langatate crystal may also be used.

[0042] Although the through holes 141, 142 are located on the side closer to the base 30 or the side closer to the tip of the vibrating arms 31, 32, they are not limited to this and may be located at any position within the longitudinal range of the front principal surface excitation electrodes 5, 6 and the back principal surface excitation electrodes 7, 8.

[0043] Furthermore, the conductive materials of the wiring patterns 13 and 18, the excitation electrodes 5, 6, 7, 8, 9, and 10, and the bonding electrodes 11 and 12 in the portions overlapping the front surface and side surface, the back surface and side surface, the side surfaces of the grooves 405, 406, 407, and 408 and the bottom surfaces of the grooves 405, 406, 407, and 408, the inner surfaces of the through holes 141 and 142 and the front surface, and the inner surfaces of the through holes 141 and 142 and the back surface are not present only on a single surface but are present across the respective surfaces. By being present across the surfaces, there is an effect that breakage due to peeling is less likely to occur when the conductive materials of the wiring patterns 13 and 18, the excitation electrodes 5, 6, 7, and 8, and the bonding electrodes 11 and 12 are mounted in each portion. [Industrial Applicability]

[0044] As described above, a tuning fork type piezoelectric vibrator incorporating the tuning fork type piezoelectric element 1 of the present invention is advantageous for miniaturization and is suitable as a timing device for portable electronic devices such as mobile phones and electronic devices with a high degree of integration of circuit components. Furthermore, by increasing the size of the joining electrodes 11 and 12 while maintaining the length of the base portion 30, the impact resistance is improved, making it suitable for use as a timing device in the automobile, aircraft, and space industries. [Explanation of symbols]

[0045] 1 Tuning fork type piezoelectric element 2 ceramic bases 4. Conductive adhesive 5,6 Main surface excitation electrode 7,8 Back surface excitation electrode 9,10 Side excitation electrode 11,12 Junction electrode 13, 14, 15, 18 Wiring pattern 16,17 Separation part 30 base 31,32 Vibrating arms 141,142 Through holes 100 Tuning fork type piezoelectric vibrator 101 Tuning fork type piezoelectric element 102 Ceramic Base 103 Metal Lid 104 Conductive adhesive 130 base 131,132 Vibrating arms 111,112 Junction electrode 107,108 Back principal surface excitation electrode 105,106 Main surface excitation electrode 109, 110 Side excitation electrode L1, L2 Total length of tuning fork piezoelectric element M1, M2 Adhesion length G1, G2 Minimum length considering the wet spread of conductive adhesive

Claims

1. A base and A pair of vibrating arms extending from the base; First excitation electrodes formed on the front and back surfaces of the vibrating arms; a second excitation electrode formed on a side surface of the vibrating arm; a pair of bonding electrodes formed on the rear surface of the base; a first wiring pattern electrically connected to the first excitation electrode of one of the vibrating arms, the second excitation electrode of the other of the vibrating arms, and one of the bonding electrodes; a second wiring pattern electrically connected to the first excitation electrode of the other vibrating arm, the second excitation electrode of one of the vibrating arms, and the other bonding electrode; In a tuning fork type piezoelectric element comprising: The vibrating arm has a through hole penetrating between the front surface and the back surface of the vibrating arm, the first excitation electrode formed on the front surface of the vibrating arm and the first excitation electrode formed on the back surface are electrically connected via a conductive layer formed in the through hole, the first wiring pattern and the second wiring pattern are formed only on the front surface of the base, out of the front surface or the back surface; A tuning fork type piezoelectric element characterized by:

2. 2. The tuning-fork type piezoelectric element according to claim 1, wherein the bonding electrode formed on the rear surface of the base is a mounting portion for mounting the tuning-fork type piezoelectric vibrator on a support member that supports the tuning-fork type piezoelectric vibrator.

3. 2. The tuning-fork type piezoelectric element according to claim 1, wherein a groove is formed on at least one of the front and back surfaces of the vibrating arm, and at least one of the openings of the through-hole opens into the groove.

4. 2. The tuning fork type piezoelectric element according to claim 1, wherein the through holes are formed by laser processing.

5. A base and A pair of vibrating arms extending from the base; First excitation electrodes formed on the front and back surfaces of the vibrating arms; a second excitation electrode formed on a side surface of the vibrating arm; a pair of bonding electrodes formed on the rear surface of the base; a first wiring pattern electrically connected to the first excitation electrode of one of the vibrating arms, the second excitation electrode of the other of the vibrating arms, and one of the bonding electrodes; a second wiring pattern electrically connected to the first excitation electrode of the other vibrating arm, the second excitation electrode of one of the vibrating arms, and the other bonding electrode, In a method for manufacturing a tuning-fork type piezoelectric element, the first wiring pattern and the second wiring pattern are formed only on the front surface of the base, out of the front surface or the back surface of the base, a tuning fork shape forming step of forming a piezoelectric substrate into the outer shape of the base and the vibrating arms; a through-hole forming step of forming a through-hole that penetrates between the front surface and the rear surface of the tuning-fork-shaped vibrating arm; an electrode forming step of forming the first excitation electrode, the second excitation electrode, the bonding electrode, a first wiring pattern, and a second wiring pattern; Equipped with The electrode forming step includes a step of forming a conductive layer in the through hole, and electrically connecting the first excitation electrode formed on the front surface of the vibrating arm and the first excitation electrode formed on the back surface via the conductive layer formed in the through hole.

10. A method for manufacturing a tuning fork type piezoelectric element, comprising:

6. 6. The method for manufacturing a tuning-fork type piezoelectric element according to claim 5, wherein the through-hole forming step is performed by either wet etching or laser processing.

7. 6. The method for manufacturing a tuning-fork type piezoelectric element according to claim 5, wherein the tuning-fork shape forming step is performed by wet etching, and the through-hole forming step is performed by laser processing.

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