Base for piezoelectric devices and piezoelectric device

Abstract

To provide a base for piezoelectric devices having a novel structure.SOLUTION: A base for piezoelectric devices comprises: a substrate 11 consisting of glass or crystal; loading patterns 21a and 21b for piezoelectric elements which are provided on a first face of the substrate 11; a frame-shaped wall part 12 which is provided in a portion along an edge of the substrate 11 of the first face, consists of the same material as the substrate 11 and is bonded to the substrate 11 by a first metal film 13 for inter-metal bonding; external mounting terminals 22a-22d provided on a second face which is an opposite face of the first face of the substrate 11; contact parts 23a and 23b which are insulated from the first metal film 13 in a region just below the wall part 12, penetrate the substrate 11 and electrically connect the loading patterns 21a and 21b with the external mounting terminals 22a-22d; and second metal films 24a and 24b which are provided in portions opposed to the contact parts 23a and 23b on a face of the wall part 12 on the side of the substrate, form inter-metal bonding with the contact parts 23a and 23b and form air-tightness of the contact parts 23a and 23b.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a base for a piezoelectric device and a piezoelectric device using the same. [Background technology]

[0002] Piezoelectric devices require a container to house the piezoelectric element. For this reason, various containers are used or researched for quartz crystal devices, which are a type of piezoelectric device, such as metal containers, ceramic containers, and containers made of glass or quartz crystal. Surface-mount containers are particularly popular for mass-produced quartz crystal devices, as there is a high demand for surface-mounted containers.

[0003] A typical example of a surface-mountable container suitable for mass production is a ceramic container. Specifically, it is a container in which a ceramic base is joined to a metal or ceramic lid. For example, Patent Document 1 discloses a ceramic base in which a bottom plate made of a ceramic material and having a rectangular shape in plan view and a bank portion made of a ceramic material laminated on the bottom plate are integrally fired (paragraph 0026, Figure 1, etc.).

[0004] Furthermore, as an example of a container using quartz crystal and glass, Patent Document 2 discloses a container having a structure in which a quartz crystal structure in which a quartz crystal vibrating piece and an outer frame are integrally formed, an upper glass plate, and a lower glass plate are joined by anodic bonding (abstract, Figures 1 and 3, etc.).

[0005] As another example of a glass container, Patent Document 3 discloses a container having a structure in which a lid and a base made of borosilicate glass are directly bonded together (paragraphs 0018, 0032, and FIG. 1(b), etc.).

[0006] Furthermore, as an example of a quartz container, there is a container having a structure formed by bonding a lid wafer, a piezoelectric wafer, and a base wafer made of quartz wafers together using a bonding material or by direct bonding, and then dicing this into individual piezoelectric devices, as disclosed in Patent Document 4 (paragraphs 0072, 0075, 0076, Figures 8 and 9, etc.). [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Laid-Open No. 2007-274071 [Patent Document 2] Japanese Patent Application Laid-Open No. 2000-68780 [Patent Document 3] Japanese Patent Application Laid-Open No. 2014-192644 [Patent Document 4] Japanese Patent Application Laid-Open No. 2015-33035 Summary of the Invention [Problem to be solved by the invention]

[0008] Among the various containers mentioned above, the most excellent ones at present are those using ceramic bases. However, as piezoelectric devices become thinner and smaller, ceramic bases are facing limitations in terms of structure, precision, and cost. Therefore, a base with a novel structure that can replace ceramic bases and surpass the conventional containers using glass and / or quartz crystal is desired.

[0009] The present disclosure has been made in view of the above-mentioned problems, and an object of the present disclosure is to provide a base having a novel structure for a piezoelectric device, and a piezoelectric device using the base. [Means for solving the problem]

[0010] According to one aspect of the present disclosure, there is provided "a base for a piezoelectric device, comprising: a substrate made of glass or quartz; a mounting pattern for a piezoelectric element provided on a first surface of the substrate; a frame-shaped wall portion provided on the first surface along the edge of the substrate, made of the same material as the substrate, and joined to the substrate by a first metal film for metal-to-metal bonding; an external mounting terminal provided on a second surface of the substrate opposite the first surface; a contact portion insulated from the first metal film in a region directly below the wall portion, penetrating the substrate and electrically connecting the mounting pattern and the external mounting terminal; and a second metal film provided on the substrate-side surface of the wall portion in a portion facing the contact portion, forming a metal-to-metal bond with the contact portion to make the contact portion airtight."

[0011] According to one aspect of the present disclosure, there is provided a piezoelectric device having the above-mentioned base, a piezoelectric element connected and fixed to the mounting pattern by a conductive member, and a lid member joined to the base and sealing the piezoelectric element. [Effects of the Invention]

[0012] According to the present disclosure, it is possible to provide a base having a novel structure for a piezoelectric device, and a piezoelectric device using the base.

[0013] It should be noted that the above effects are merely examples for the sake of convenience of explanation, and the effects of the present disclosure are not limited to these. In addition to the above effects, the present disclosure can achieve any of the effects described herein. [Brief explanation of the drawings]

[0014] [Figure 1] FIG. 1(a) is a perspective view of the piezoelectric device according to the first embodiment, FIG. 1(b) is an end view taken along dashed line AA in FIG. 1(a), and FIG. 1(c) is an end view taken along dashed line BB in FIG. 1(a). [Figure 2]2(a) is a plan view of a base substrate for a piezoelectric device according to the first embodiment, FIG. 2(b) is a bottom view of the base substrate for a piezoelectric device according to the first embodiment, FIG. 2(c) is a cross-sectional view taken along dashed line CC in FIG. 2(a), and FIG. 2(d) is a cross-sectional view taken along dashed line DD in FIG. 2(a). [Figure 3] FIG. 3(a) is a plan view of the wall portion of the base for the piezoelectric device according to the first embodiment, and FIG. 3(b) is a bottom view of the wall portion of the base for the piezoelectric device according to the first embodiment. [Figure 4] FIG. 4 is an enlarged plan view showing the positional relationship of the contact portion, metal film, etc. of the base for the piezoelectric device according to the first embodiment. [Figure 5] 5(a) to 5(d) are plan views of the base of the piezoelectric device according to the first embodiment in the manufacturing process. [Figure 6] Figure 6(a) is an enlarged plan view showing the positional relationship between the contact portion and metal film of a base for a piezoelectric device according to a modified example of the first embodiment, and Figure 6(b) is an enlarged plan view showing the positional relationship between the contact portion and metal film of a base for a piezoelectric device according to another modified example of the first embodiment. [Figure 7] Figure 7(a) is a plan view of the substrate of the base for the piezoelectric device according to the second embodiment, Figure 7(b) is a bottom view of the wall portion of the base for the piezoelectric device according to the second embodiment, and Figure 7(c) is an enlarged plan view showing the positional relationship of the contact portion and metal film, etc. of the base for the piezoelectric device according to the second embodiment. [Figure 8] Figure 8(a) is a plan view of the substrate of the base for the piezoelectric device according to the third embodiment, Figure 8(b) is a bottom view of the wall portion of the base for the piezoelectric device according to the third embodiment, and Figure 8(c) is an enlarged plan view showing the positional relationship of the contact portion and metal film, etc. of the base for the piezoelectric device according to the third embodiment. [Figure 9] 9(a) to 9(c) are enlarged plan views showing the positional relationship of the contact portion, metal film, etc. of the base for the piezoelectric device according to a modified example of the third embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0015] The piezoelectric device and the base for the piezoelectric device used therein according to the present disclosure will be described in detail below with reference to the drawings. The present disclosure is not limited to the content described below and can be modified as desired without departing from the spirit and scope of the present disclosure. The drawings used in each embodiment are schematic illustrations of the piezoelectric device and the base for the piezoelectric device according to the present disclosure. To facilitate understanding, some parts may be emphasized, enlarged, reduced, or omitted, and the scale and shape of each component may not be accurately represented. Furthermore, some numerical values ​​used in each embodiment and its modified examples are merely examples and can be modified as necessary. The same reference symbols are used to designate common components in the drawings.

[0016] (First embodiment) <Structure of piezoelectric device> First, the basic structure of a piezoelectric device and a base for the piezoelectric device according to the present disclosure will be described with reference to Figures 1(a) and 1(b). Figure 1(a) is a perspective view of the piezoelectric device according to the first embodiment, Figure 1(b) is an end view taken along dashed line AA in Figure 1, and Figure 1(c) is an end view taken along dashed line BB in Figure 1.

[0017] 1(a) to 1(c), the piezoelectric device 1 includes a base 2 for the piezoelectric device (hereinafter simply referred to as the base 2), a piezoelectric element 3 mounted in a mounting space 2a of the base 2, and a lid member 4 bonded to the base 2 to seal the piezoelectric element 3. In this embodiment, the piezoelectric device 1 is a quartz crystal resonator in which a quartz crystal vibrating piece is mounted as the piezoelectric element 3, and is a type of electronic device used to generate oscillations with high frequency accuracy by utilizing the piezoelectric effect.

[0018] The base 2 has a flat substrate 11 made of glass or quartz, a rectangular frame-shaped wall 12 connected to the substrate 11 by intermetallic bonding, and a bonding metal film (first metal film) 13 that forms the intermetallic bond between the substrate 11 and the wall 12. A sealing metal film 14 that bonds the lid member 4 to the wall 12 by intermetallic bonding is provided above the wall 12 of the base 2 (above in the thickness direction of the piezoelectric device 1). The wall 12 is made of the same material as the substrate 11, that is, glass or quartz. The wall 12 is provided on a first surface (element mounting surface) 11a of the substrate 11, along the edge of the substrate 11. The bonding between the wall 12 and the lid member 4 is not limited to intermetallic bonding, and may be bonding using, for example, brazing material.

[0019] When the material of the substrate 11 and the wall portion 12 is quartz, the quartz is preferably a Z-cut plate or an AT-cut plate. Z-cut and AT-cut quartz plates are mass-produced substrates for quartz crystal oscillators, and are therefore advantageous in terms of cost. On the other hand, when the material of the substrate 11 and the wall portion 12 is glass, any suitable glass, such as soda glass, may be used.

[0020] Furthermore, the base 2 has mounting patterns 21a and 21b for piezoelectric elements provided in an area on the first surface 11a of the substrate 11 inside the area where the bonding metal film 13 is formed, and spaced apart from the bonding metal film 13. In particular, a conductive adhesive 5 is provided in a mounting portion of each mounting pattern that is rectangular in plan view, and the piezoelectric element 3 is fixed and mounted on each mounting pattern by the conductive adhesive 5. Details of the mounting patterns 21a and 21b will be described later with reference to FIG. 2(a).

[0021] Furthermore, the base 2 has four external mounting terminals 22a, 22b, 22c, and 22d provided on a second surface (bottom surface) 11b, which is the surface opposite to the first surface 11a of the substrate 11. Each external mounting terminal is fixed to a pad of the circuit board on which the piezoelectric device 1 is mounted via a bonding member such as solder.

[0022] Furthermore, the base 2 has contact portions 23a and 23b provided in a region directly below the wall portion 12 (below in the thickness direction of the piezoelectric device 1). Each contact portion penetrates the substrate 11 and electrically connects one of the mounting patterns 21a and 21b to one of the four external mounting terminals 22a, 22b, 22c, and 22d. A specific connection configuration will be described later with reference to Figures 2(a) and 2(b).

[0023] The base 2 has airtightness-forming films (second metal films) 24a, 24b provided on the substrate-side surface of the wall 12 in portions facing the contact portions 23a, 23b. In particular, each airtightness-forming film forms an intermetallic bond with each contact portion, thereby ensuring airtightness of each contact portion. The positional relationship between each airtightness-forming film and each contact portion in contact therewith will be described later with reference to Figures 2(a), 3(b), and 4.

[0024] <Base structure> Next, the structure of the substrate 11 side constituting the base 2 will be described with reference to Figures 2(a) to 2(d). Here, Figure 2(a) is a plan view of the substrate of the base for the piezoelectric device according to the first embodiment, Figure 2(b) is a bottom view of the substrate of the base for the piezoelectric device according to the first embodiment, Figure 2(c) is a cross-sectional view taken along dashed line CC in Figure 2(a), and Figure 2(d) is a cross-sectional view taken along dashed line DD in Figure 2(a). In particular, Figures 2(a) to 2(d) show the configuration of the substrate 11 in a state before the substrate 11 and the wall portion 12 are integrated by metal-to-metal bonding.

[0025] 2(a), a substrate-side metal film 31 having a substantially rectangular frame shape is provided on the first surface 11a of the substrate 11 in a portion along the edge of the substrate 11. That is, the substrate-side metal film 31 is formed so as to surround the outer periphery of the first surface 11a of the substrate 11. Here, the substrate-side metal film 31 is intermetallic-bonded to a wall-side metal film, which will be described later, to form the above-mentioned bonding metal film 13.

[0026] 2(a), mounting patterns 21a and 21b are provided on the first surface 11a of the substrate 11 in an area inside the area where the substrate-side metal film 31 is formed. The mounting pattern 21a is composed of a pad portion 32a to which a conductive adhesive 5 is applied for fixing and holding the piezoelectric element 3, a substantially rectangular substrate-side lid portion 32b formed on the contact portion 23a at the corner of the substrate 11, and a wiring portion 32c connecting the pad portion 32a and the substrate-side lid portion 32b. Similarly, the mounting pattern 21b is composed of a pad portion 33a to which a conductive adhesive 5 is applied for fixing and holding the piezoelectric element 3, a substantially rectangular substrate-side lid portion 33b formed on the contact portion 23b at the corner of the substrate 11, and a wiring portion 33c connecting the pad portion 33a and the substrate-side lid portion 33b. Here, the substrate-side lid portions 32b and 33b are provided at two diagonal areas of the four corners of the substrate-side metal film 31, spaced apart from the substrate-side metal film 31.

[0027] 2(b), four external mounting terminals 22a, 22b, 22c, and 22d are provided on the second surface 11b of the substrate 11. Each external mounting terminal is formed at one of the four corners of the substrate and has a rectangular planar shape. In addition, in the external mounting terminals 22b and 22d, contact holes 35a and 35b constituting the contact portions 23a and 23b are formed so as to be visible from the bottom.

[0028] 2(c), a contact portion 23a is formed between the substrate-side lid portion 32b and the external mounting terminal 22d that constitute the mounting pattern 21a. The contact portion 23a is composed of a cylindrical contact hole 34a that penetrates the substrate 11 and a contact hole wiring 34b formed in the contact hole 34a. In this embodiment, the contact hole wiring 34b is composed of a metal film (film-like conductor) formed along the inner surface (inner wall) of the contact hole 34a, but the contact hole 34a may also be filled with a conductor, for example.

[0029] 2(d), a contact portion 23b is formed between the substrate-side lid portion 33b and the external mounting terminal 22b that constitute the mounting pattern 21b. The contact portion 23b is composed of a cylindrical contact hole 35a that penetrates the substrate 11 and a contact hole wiring 35b formed in the contact hole 35a. In this embodiment, the contact hole wiring 35b is composed of a metal film (film-like conductor) formed along the inner surface (inner wall) of the contact hole 35a, but the contact hole 35a may also be filled with a conductor, for example.

[0030] The substrate-side metal film 31, the mounting patterns 21a and 21b, the external mounting terminals 22a, 22b, 22c, and 22d, and the contact portions 23a and 23b may be formed, for example, as a three-layer laminate film with a chromium (Cr) film as a base film, a nickel (Ni) film or a nickel-tungsten (NiW) alloy film as an intermediate film, and a gold (Au) film as an upper film. The nickel or nickel-tungsten alloy film as an intermediate film prevents the chromium in the base film from diffusing into the gold film as an upper film, thereby achieving better intermetallic bonding. Furthermore, this three-layer laminate film is believed to prevent the chromium from diffusing into the gold film over time.

[0031] The substrate-side metal film 31, mounting patterns 21a and 21b, external mounting terminals 22a, 22b, 22c, and 22d, and contact portions 23a and 23b may further include a titanium (Ti) film laminated on the gold film, with an additional gold film laminated on the titanium film. Even with nickel or a nickel-tungsten alloy, chromium may diffuse into the gold film. The titanium film prevents chromium from diffusing into the top gold film, further improving intermetallic bonding. This five-layer laminated film is also believed to further prevent chromium from diffusing into the gold film over time.

[0032] Next, the structure of the wall 12 side constituting the base 2 will be described with reference to Figures 3(a) and 3(b). Here, Figure 3(a) is a plan view of the wall of the base for the piezoelectric device according to the first embodiment, and Figure 3(b) is a bottom view of the wall of the base for the piezoelectric device according to the first embodiment. In particular, Figures 3(a) and 3(b) show the configuration of the wall 12 in a state before the substrate 11 and the wall 12 are integrated by metal-to-metal bonding.

[0033] 3(a), a sealing metal film 41 is provided on the first surface 12a of the wall portion 12 so as to follow the wall portion 12. That is, the metal film 41 is formed so as to entirely cover the first surface 12a of the wall portion 12, and forms the above-mentioned sealing metal film 14 by metal-to-metal bonding with the metal film included in the lid member 4.

[0034] As shown in FIG. 3(b), a wall-side metal film 42 having a substantially rectangular frame shape is provided on the second surface 12b of the wall portion 12 so as to follow the wall portion 12. That is, the wall-side metal film 42 is formed so as to cover most of the second surface 12b of the wall portion 12. Wall-side lid portions 43a and 43b are provided in two diagonally opposite corners of the second surface 12b of the wall portion 12. The wall-side lid portions 43a and 43b are formed so as to be spaced apart from the wall-side metal film 42 by gaps 44a and 44b. The wall-side lid portion 43a faces parts of the substrate-side lid portion 32b and the wiring portion 32c provided on the substrate 11 and forms metal-to-metal bonding with the substrate-side lid portion 32b and the wiring portion 32c to form the airtight seal film 24a. Similarly, the wall-side lid portion 43b faces the substrate-side lid portion 33b and part of the wiring portion 33c provided on the substrate 11, and forms a metal-to-metal bond with the substrate-side lid portion 33b and the wiring portion 33c to form the above-mentioned airtight forming film 24b.

[0035] The wall-side metal film 42 and the wall-side lid portions 43a, 43b may be configured, similarly to the metal film on the substrate 11, as a three-layer laminate film, for example, with a chromium (Cr) film as a base film, a nickel (Ni) film or a nickel-tungsten (NiW) alloy film as an intermediate film, and a gold (Au) film as an upper film. A configuration with a nickel film or a nickel-tungsten alloy film as an intermediate film can prevent the chromium in the base film from diffusing into the gold film as an upper film, thereby achieving better intermetallic bonding. Furthermore, this three-layer laminate film is believed to prevent the chromium from diffusing into the gold film over time.

[0036] The wall-side metal film 42 and the wall-side lids 43a, 43b may have a titanium (Ti) film laminated on a gold film, and an additional gold film laminated on the titanium film, similar to the metal film on the substrate 11 side. Even when nickel or a nickel-tungsten alloy is provided, chromium may diffuse into the gold film. Therefore, the titanium film can prevent chromium from diffusing into the top gold film, resulting in better intermetallic bonding. It is believed that this five-layer laminated film can also further prevent chromium from diffusing into the gold film over time.

[0037] Next, the positional relationship between the bonding metal film 13, the airtight forming film 24b, and the contact portion 23b in the base 2 will be described with reference to Fig. 4. Fig. 4 is an enlarged plan view showing the positional relationship between the contact portion, the metal film, etc. of the base for the piezoelectric device according to the first embodiment. Note that Fig. 4 does not show the positional relationship between the bonding metal film 13, the airtight forming film 24a, and the contact portion 23a in the base 2, but since it is the same as the positional relationship between the bonding metal film 13, the airtight forming film 24b, and the contact portion 23b in the base 2, a description thereof will be omitted.

[0038] As can be seen from Fig. 4, an airtight film 24b formed by intermetallic bonding between the substrate-side lid 33b, a portion of the wiring portion 33c, and the wall-side lid 43b is located on the contact portion 23b formed to penetrate the substrate 11. In particular, because the contact portion 23b is located inside the formation area of ​​the airtight film 24b, the contact portion 23b is not exposed between the substrate 11 and the wall 12, and airtightness for the contact portion 23b is ensured with high precision. The remaining portion of the wiring portion 33c (shown by a solid line in Fig. 4) that does not form an intermetallic bond with the wall-side lid 43b is exposed on the first surface 11a of the substrate 11.

[0039] 4, the bonding metal film 13, which is formed by intermetallic bonding between the substrate-side metal film 31 and the wall-side metal film 42, is separated from the airtight-forming film 24b by a gap 44b. That is, the bonding metal film 13 is insulated from the airtight-forming film 24b and the contact portion 23b. Therefore, the mounting pattern 21b for mounting the piezoelectric element 3 does not short-circuit with the bonding metal film 13, and the reliability of the input or output related to the piezoelectric element 3 can be ensured.

[0040] <Base manufacturing method> Next, a method for manufacturing the base 2 will be described with reference to Figures 5(a) to 5(d), where Figures 5(a) to 5(d) are plan views showing manufacturing steps for the base 2 of the piezoelectric device according to the first embodiment.

[0041] 5(a), a quartz crystal wafer W1 is prepared for forming the wall portion 12, and a quartz crystal wafer W2 is prepared for forming the substrate 11. Next, rectangular openings 51 penetrating the wafer W1 are formed in a matrix pattern in the wafer W1 using known photolithography and etching techniques. Also, contact holes 34a and 35a penetrating the wafer W2 are formed using known photolithography and etching techniques.

[0042] Next, as shown in FIG. 5(b), wafers W1 and W2 are patterned using known photolithography, film formation, and etching techniques. Specifically, a sealing metal film 41 is formed on the front surface of wafer W1 so as to surround the periphery of opening 51. Although not shown in FIG. 5(b), a wall-side metal film 42 and wall-side lid portions 43a and 43b are formed on the rear surface of wafer W1 so as to surround opening 51 and face metal film 41. Meanwhile, mounting patterns 21a and 21b and a rectangular frame-shaped substrate-side metal film 31 are formed on the front surface of wafer W2. Although not shown in FIG. 5(b), external mounting terminals 22a, 22b, 22c, and 22d are formed on the rear surface of wafer W2 so as to face mounting patterns 21a and 21b and substrate-side metal film 31. Then, metal films (contact hole wirings 34b, 35b) are formed on the inner surfaces of the contact holes 34a, 35a, thereby forming the contact portions 23a, 23b. The external mounting terminals 22a, 22b, 22c, 22d and the contact hole wirings 34b, 35b can be formed by sputtering or photolithography, but the external mounting terminals 22a, 22b, 22c, 22d and the contact hole wirings 34b, 35b may also be thickened by electrolytic plating or electroless plating.

[0043] 5(c), wafers W1 and W2 are stacked in a predetermined positional relationship, and then heated and pressed with a predetermined force in a low-pressure atmosphere in a vacuum chamber to bond wafers W1 and W2. Here, the predetermined positional relationship refers to a state in which the metal film 41, wall-side metal film 42, and substrate-side metal film 31 of wafer W1 overlap, and the mounting patterns 21a and 21b are exposed in the opening 51. In this case, one ends of the contact portions 23a and 23b are covered by the substrate-side lid portions 32b and 33b and the wall-side lid portions 43a and 43b, and the other ends of the contact portions 23a and 23b are covered by the external mounting terminals 22b and 22d.

[0044] The heating and pressurizing process forms a metal-to-metal bond between the wall-side metal film 42 and the substrate-side metal film 31, and forms a metal-to-metal bond between portions of the mounting patterns 21a and 21b (substrate-side lid 32b, portions of the wiring portion 32c, substrate-side lid 33b, and portions of the wiring portion 33c) and the wall-side lids 43a and 43b. This forms the bonding metal film 13 and the airtight forming films 24a and 24b, which integrates the wafers W1 and W2 and ensures the airtightness of the contact portions 23a and 23b.

[0045] Next, as shown in FIG. 5(d), the bonded wafer is diced along predetermined lines, for example, using a dicing saw, to obtain a plurality of individual bases 2. This completes the manufacturing process for the base 2 according to this embodiment. In this manufacturing process, the metal-to-metal bonding process is performed only once, which reduces the number of processes and reduces manufacturing costs. Furthermore, since the substrate 11 and the wall portion 12 are made of the same material, quartz crystal or glass, there is no deformation due to heating or the like, and the accuracy of bonding positioning during the manufacturing process can be improved, which reduces the number of processes and manufacturing costs.

[0046] As described above, the contact portions 23a, 23b arranged directly below the wall portion 12 are covered by the airtight forming films 24a, 24b in a state where airtightness is ensured, thereby realizing a base structure with excellent reliability in terms of airtightness, etc.

[0047] (Modification of the first embodiment) The planar shapes of the contact portions 23a, 23b and the airtight film 24a, 24b in the above embodiment are merely examples, and other shapes may be used as long as electrical connection and airtightness are ensured. For example, shapes such as those shown in FIGS. 6(a) and 6(b) may be used. Here, FIG. 6(a) is an enlarged plan view showing the arrangement of the contact portions and metal film of a base for a piezoelectric device according to a modification of the first embodiment, and FIG. 6(b) is an enlarged plan view showing the arrangement of the contact portions and metal film of a base for a piezoelectric device according to another modification of the first embodiment. Note that the same components as those in the above embodiment are designated by the same reference numerals, and their description will be omitted.

[0048] In the modification shown in FIG. 6(a), the planar shape of the contact portion 23b' is elliptical. That is, the contact portion 23b' has an elliptical cylindrical shape. By adopting such a shape, it is possible to increase the volume of the contact portion 23b' without exposing the contact portion 23b' from the airtight forming film 24b. Therefore, it is possible to reduce the resistance of the contact portion 23b' while maintaining airtightness.

[0049] In the modified example shown in FIG. 6(b), the airtightness forming film 24b' covering the circular contact portion 23b has a substantially circular planar shape similar to that of the contact portion 23b. In this case, the pad portion and wall-side cover portion of the mounting pattern constituting the airtightness forming film 24b' are formed in a substantially circular shape. A substantially annular gap 44b' surrounds the airtightness forming film 24b', ensuring insulation between the airtightness forming film 24b' and the contact portion 23b and the bonding metal film 13. In this structure, the distance from the contact portion 23b to the end of the airtightness forming film 24b' can be made substantially constant, thereby ensuring stable airtightness at the contact portion 23b.

[0050] 6(b) has a rectangular frame shape, but the four inner corners are rounded in plan view. This allows the area of ​​the four corners to be increased, allowing the area for forming the airtight film 24b' to be increased, further improving airtightness. Although not shown, the four corners may be chamfered, and in this case, the area for forming the airtight film 24b' can also be increased, further improving airtightness.

[0051] (Second embodiment) In the first embodiment, the contact portion has a cylindrical or elliptical cylindrical shape, but it may also have a square prism shape. As an example of such a case, a second embodiment will be described in which the contact portion has a square prism shape, with reference to Figures 7(a) to 7(c).

[0052] 7(a) is a plan view of the substrate of the base for the piezoelectric device according to the second embodiment, Fig. 7(b) is a bottom view of the wall portion of the base for the piezoelectric device according to the second embodiment, and Fig. 7(c) is an enlarged plan view showing the arrangement of the contact portion, metal film, etc. of the base for the piezoelectric device according to the second embodiment. Note that only the parts that differ from the first embodiment and its modifications will be described, and the same parts will not be described again, and the same reference numerals will be used in the drawings.

[0053] As shown in FIG. 7(a), a substrate-side metal film 131 having a substantially rectangular frame shape is provided on a first surface 111a of a base substrate 111 according to the second embodiment along the edge of the substrate 111. Furthermore, mounting patterns 21a and 21b are provided on the first surface 111a of the substrate 111 in an area inside the area where the substrate-side metal film 131 is formed. The mounting pattern 21a is composed of a pad portion 32a, a substrate-side lid portion 32b, and a wiring portion 32c, and the mounting pattern 21b is composed of a pad portion 33a, a substrate-side lid portion 33b, and a wiring portion 33c. Furthermore, the substrate 111 is provided with rectangular pillar-shaped contact portions 123a and 123b, one end of which is covered by the substrate-side lid portions 32b and 33b.

[0054] Although not shown, as in the first embodiment, four rectangular external mounting terminals are provided at the four corners of the second surface opposite to the first surface 111a of the substrate 111. As in the first embodiment, contact portions 123a and 123b are connected to two of the external mounting terminals.

[0055] 7(b), a substantially rectangular frame-shaped wall-side metal film 142 is provided on the second surface 112b of the rectangular frame-shaped wall portion 112 of the base according to the second embodiment so as to follow the wall portion 112. That is, the wall-side metal film 142 is formed so as to cover most of the second surface 112b of the wall portion 112. Furthermore, wall-side lid portions 143a and 143b are provided in two diagonally opposite corners of the second surface 112b of the wall portion 112. Here, the wall-side lid portions 143a and 143b are formed to be spaced apart from the wall-side metal film 142 by gaps 144a and 144b.

[0056] In this embodiment, the planar shapes of the wall-side lid portions 143a, 143b and the gaps 144a, 144b are different from those of the wall-side lid portions 43a, 43b and the gaps 44a, 44b in the first embodiment. Specifically, the wall-side lid portions 143a, 143b do not have narrow portions corresponding to portions of the wiring portions 32c, 33c, and have an overall substantially rectangular planar shape with one of the four corners missing. Furthermore, the planar shape of the gaps 144a, 144b also follows the outer shape of the wall-side lid portions 143a, 143b, and is an overall substantially rectangular ring-shaped planar shape with one of the four corners missing.

[0057] Next, the positional relationship between the bonding metal film 113, the airtightness forming film 124b, and the contact portion 123b in the base 102 according to the second embodiment will be described with reference to Fig. 7(c). Although Fig. 7(c) does not show the positional relationship between the bonding metal film 113, the airtightness forming film 124a, and the contact portion 123a in the base 102, the positional relationship is the same as the positional relationship between the bonding metal film 113, the airtightness forming film 124b, and the contact portion 123b in the base 102, and therefore the description thereof will be omitted.

[0058] 7(c), an airtight film 124b formed by intermetallic bonding between the substrate-side lid portion 133b and the wall-side lid portion 143b is located on the contact portion 123b formed to penetrate the substrate 111. In particular, since the contact portion 123b is located inside the formation area of ​​the airtight film 124b, the contact portion 123b is not exposed between the substrate 111 and the wall portion 112, and airtightness for the contact portion 123b is ensured with high precision. Furthermore, the wiring portion 33c that does not form an intermetallic bond with the wall-side lid portion 143b is exposed on the first surface 111a of the substrate 111.

[0059] 7(c), the bonding metal film 113 formed by intermetallic bonding between the substrate-side metal film 131 and the wall-side metal film 142 is separated from the airtightness-forming film 124b by a gap 144b. That is, the bonding metal film 113 is insulated from the airtightness-forming film 124b and the contact portion 123b. Therefore, the mounting pattern 21b for mounting the piezoelectric element does not short-circuit with the bonding metal film 113, and the reliability of the input or output related to the piezoelectric element can be ensured.

[0060] In this embodiment, the planar shape of the contact portions 123a and 123b is formed to have a side parallel to one side of the substrate 111, which is rectangular in plan view. Specifically, this embodiment is an example in which the shape of the contact portions 123a and 123b is a quadrangular prism, which is rectangular in plan view. In this case, compared to the cylindrical shape of the first embodiment, it has the following advantages.

[0061] First, compared to the contact portions 23, 23b that are circular in plan view, the contact portions 123a, 123b that are rectangular in plan view can have a side length that is smaller than the diameter of the contact portions 23, 23b. For example, for ease of calculation, assuming that the diameter of the contact portions 23, 23b is 1 mm, the circumference of the contact portions 23, 23b is 3.14 mm, and the area in plan view is 0.785 mm. 2A rectangle with the same circumference has a side length of 0.785 mm, and a rectangle with the same area has a side length of 0.886 mm. That is, to ensure the same perimeter or area, a rectangle can be made smaller than a circle. In other words, the contact portions 123a and 123b, which are rectangular in plan view, can have a larger perimeter and area than the contact portions 23a and 23b, which are circular in plan view. This allows the contact holes forming the contact portions 123a and 123b to be larger, making it easier to deposit films in the contact holes. Furthermore, since the inner surface area (inner wall surface area) of the contact holes is larger, it becomes easier to increase the wiring width of the contact hole wiring. In other words, it becomes easier to ensure the wiring width required to reduce the wiring resistance of the contact hole wiring. Furthermore, the above configuration allows for a larger area of ​​the metal-to-metal bond to ensure the airtightness of the contact portions 123a and 123b, thereby achieving higher airtightness of the base 102.

[0062] Next, as can be seen from FIG. 7(c), the sides of the contact portions 123a and 123b, which are rectangular in plan view, can be parallel to the sides of the rectangular base 102 in plan view. Furthermore, when comparing a contact hole that is circular in plan view with a contact hole that is rectangular in plan view, conversely considering the comparison in the above numerical example, if the perimeter and area of ​​both contact holes are the same, one side of the rectangular contact hole in plan view can be smaller than the diameter of the circular contact hole. This makes it easier to increase the width W1 of the bonding metal film 113 that forms the intermetallic bond between the substrate 111 and the wall portion 112 by the amount that the contact hole dimensions can be reduced. Furthermore, it also makes it easier to increase the insulation width W2, which is the distance between the bonding metal film 113 and the airtight film forming films 124a and 124b. This improves the airtightness and insulation of the wall portions near the contact portions 124a and 124b.

[0063] The planar shape of the contact portions 124a, 124b is not limited to a quadrangle, and may be other polygonal shapes. For example, it may be a triangle or a polygon with five or more sides. However, a pentagonal shape, which will be described later with reference to FIG. 8, in which the center side of the substrate is C-processed, is as preferable as a quadrangle.

[0064] (Third embodiment) In the first embodiment, the shape of the contact portion is a circular cylinder or an elliptical cylinder, and in the second embodiment, the shape of the contact portion is a square pillar, but the contact portion may also be formed in the shape of a polygonal pillar. As an example of such a case, a case in which the shape of the contact portion is a polygonal pillar will be described as a third embodiment with reference to Figures 8(a) to 8(c).

[0065] 8(a) is a plan view of the substrate of the base for the piezoelectric device according to the third embodiment, Fig. 8(b) is a bottom view of the wall portion of the base for the piezoelectric device according to the third embodiment, and Fig. 8(c) is an enlarged plan view showing the arrangement of the contact portion, metal film, etc. of the base for the piezoelectric device according to the third embodiment. Note that the first embodiment, its modified examples, and parts that differ from the second embodiment will basically be described, and explanations of the same contents will be omitted, and the same reference numerals will be used in the drawings.

[0066] As shown in FIG. 8(a), a substrate-side metal film 231 having a substantially rectangular frame shape is provided on a first surface 211a of a base substrate 211 according to the third embodiment along the edge of the substrate 211. Unlike the substrate-side metal film 131 according to the second embodiment, the substrate-side metal film 231 has C-chamfered edges at two of its four inner corners, located diagonally. This is to accommodate a wall portion 212 and a wall-side metal film 242, which will be described later. Furthermore, mounting patterns 21a and 21b are provided on the first surface 211a of the substrate 211 in an area inside the area where the substrate-side metal film 231 is formed. The mounting pattern 21a is composed of a pad portion 32a, a substrate-side lid portion 32b, and a wiring portion 32c, and the mounting pattern 21b is composed of a pad portion 33a, a substrate-side lid portion 33b, and a wiring portion 33c. Furthermore, pentagonal prism-shaped contact portions 223a and 223b, one end of which is covered by substrate-side lid portions 32b and 33b, are provided on substrate 211. In other words, contact portions 223a and 223b have a square shape with one of the four corners chamfered.

[0067] Although not shown, as in the first embodiment, four rectangular external mounting terminals are provided at the four corners of the substrate on a second surface opposite to the first surface 211a of the substrate 211. As in the first embodiment, contact portions 223a and 223b are connected to two of the external mounting terminals.

[0068] As shown in FIG. 8(b), the wall 212 of the base according to the third embodiment has a substantially rectangular frame-like outer shape, unlike the wall 112 of the second embodiment. However, the four inner corners are chamfered. That is, the wall 212 has a shape in which the four corners widen inward. Furthermore, a substantially rectangular frame-like wall-side metal film 242 is provided on the second surface 212b of the wall 212 so as to follow the wall 212. That is, the wall-side metal film 242 is formed so as to cover most of the second surface 212b of the wall 212. Furthermore, wall-side lids 243a and 243b are provided in two diagonally opposite corners of the second surface 212b of the wall 212. Here, the wall-side lids 243a and 243b are formed to be spaced apart from the wall-side metal film 242 by gaps 244a and 244b.

[0069] In this embodiment, the wall-side lid portions 243a, 243b and the gaps 244a, 244b have different planar shapes from the wall-side lid portions 143a, 143b and the gaps 144a, 144b of the second embodiment. Specifically, the wall-side lid portions 243a, 243b have a pentagonal planar shape with one of the four corners of the quadrangle chamfered. That is, the C-chamfered portions of the wall-side lid portions 243a, 243b correspond to and are parallel to the C-chamfered shapes of the four inner corners of the wall 212. The planar shapes of the gaps 244a, 244b are also pentagonal rings that conform to the outer shapes of the wall-side lid portions 243a, 243b. Therefore, the wall-side lid portions 243a, 243b are separated from the wall-side metal film 242 by the gaps 244a, 244b and are formed like islands.

[0070] Next, the positional relationship between the bonding metal film 213, the airtightness forming film 224b, and the contact portion 223b in the base 202 according to the third embodiment will be described with reference to Fig. 8(c). Although Fig. 8(c) does not show the positional relationship between the bonding metal film 213, the airtightness forming film 224a, and the contact portion 223a in the base 202, the positional relationship between the bonding metal film 213, the airtightness forming film 224b, and the contact portion 223b in the base 202 is the same as the positional relationship between the bonding metal film 213, the airtightness forming film 224b, and the contact portion 223b in the base 202, so the description thereof will be omitted.

[0071] 8(c), an airtight film 224b formed by intermetallic bonding between the substrate-side lid portion 233b and the wall-side lid portion 243b is located on the contact portion 223b formed to penetrate the substrate 211. In particular, since the contact portion 223b is located inside the formation area of ​​the airtight film 224b, the contact portion 223b is not exposed between the substrate 211 and the wall portion 212, and airtightness for the contact portion 223b is ensured with high precision. Furthermore, the wiring portion 33c that does not form an intermetallic bond with the wall-side lid portion 243b is exposed on the first surface 211a of the substrate 211.

[0072] 8(c), the bonding metal film 213 formed by intermetallic bonding between the substrate-side metal film 231 and the wall-side metal film 242 is separated from the airtightness-forming film 224b by a gap 244b. That is, the bonding metal film 213 is insulated from the airtightness-forming film 224b and the contact portion 223b. Therefore, the mounting pattern 21b for mounting the piezoelectric element does not short-circuit with the bonding metal film 213, and the reliability of the input or output related to the piezoelectric element can be ensured.

[0073] 8(c), the C-chamfered portion (side 271) of the contact portion 223b, the C-chamfered portion (side 272) of the airtightness forming film 224b, and the C-chamfered portion (side 273) on the inside of the wall portion 212 are arranged parallel to each other. Furthermore, other portions of the contact portion 223b (sides other than side 271) are formed parallel to the outer periphery of the wall portion 212. In this way, the presence of the C-chamfered portion increases the bonding area surrounding one end of the contact portion 223b (the formation area of ​​the airtightness forming film 224b) compared to when there is no R-surface processing or processing, thereby enabling improvement in airtightness.

[0074] In this embodiment, the contact portions 223a and 223b have a pentagonal prism shape, which can improve airtightness compared to a cylindrical shape like the first embodiment. This is because the planar shape of the contact portion 223b is pentagonal, which can ensure a longer distance to the gaps 244a and 244b and a longer distance to the side surfaces of the substrate 211 and the wall portion 212 compared to a circular shape having the same area. That is, when the contact portions 223a and 223b have a pentagonal prism shape, the formation area of ​​the airtight forming films 224a and 224b around the contact portions 223a and 223b can be made larger compared to a cylindrical shape, and it is also possible to ensure a longer distance to the end of the bonding metal film 213 where no intermetallic bond is formed, thereby achieving higher airtightness of the base 202.

[0075] (Modification of the third embodiment) The shape of the contact portion is not limited to the above, and may be a planar shape such as those shown in Figures 9(a) to 9(c), which are enlarged plan views showing the positional relationship between the contact portion and the metal film of the base for the piezoelectric device according to a modified example of the third embodiment.

[0076] 9(a), the contact portion 291b may be a pentagon with one corner of a rectangle chamfered. Even in this case, the C-chamfered portion (side 271) of the contact portion 291b, the C-chamfered portion (side 272) of the airtightness forming film 224b, and the C-chamfered portion (side 273) on the inner side of the wall portion 212 are arranged parallel to each other. With this structure, as in the third embodiment, the bonding area surrounding one end of the contact portion 291b can be increased, thereby improving airtightness.

[0077] 9(b), the contact portion 292b may have a regular pentagonal planar shape. Even in this case, one side (side 271) of the contact portion 292b, the C-chamfered portion (side 272) of the airtightness forming film 224b, and the C-chamfered portion (side 273) on the inner side of the wall portion 212 are arranged parallel to one another. With this structure, as in the third embodiment, the bonding area surrounding one end of the contact portion 292b can be increased, thereby improving airtightness.

[0078] 9(c), the contact portion 293b may have an elliptical planar shape. Even in this case, the longitudinal diameter (side 271) of the contact portion 293b, the C-chamfered portion (side 272) of the airtightness forming film 224b, and the C-chamfered portion (side 273) on the inner side of the wall portion 212 are arranged parallel to each other. With this structure, as in the third embodiment, the bonding area surrounding one end of the contact portion 293b can be increased, thereby improving airtightness.

[0079] (Embodiments of the present disclosure) A first embodiment of the present disclosure is a base for a piezoelectric device, the base including: a substrate made of glass or quartz; a mounting pattern for a piezoelectric element provided on a first surface of the substrate; a frame-shaped wall portion provided on the first surface along an edge of the substrate, made of the same material as the substrate and joined to the substrate by a first metal film for metal-to-metal bonding; an external mounting terminal provided on a second surface of the substrate opposite the first surface; a contact portion directly below the wall portion, insulated from the first metal film, penetrating the substrate and electrically connecting the mounting pattern to the external mounting terminal; and a second metal film provided on the substrate-side surface of the wall portion facing the contact portion, forming a metal-to-metal bond with the contact portion to ensure airtightness of the contact portion. With this configuration, the contact portion located directly below the wall portion is covered by the second metal film in an airtight manner, thereby achieving a base structure with excellent reliability, such as airtightness.

[0080] A second embodiment of the present disclosure is the first embodiment, wherein the second metal film is provided in a region inside the region where the first metal film is formed and spaced apart from the first metal film. This configuration insulates the mounting pattern and contact portion from the first metal film, which is used to bond the substrate to the wall portion, and prevents short circuits within the base.

[0081] A third embodiment of the present disclosure is the first or second embodiment, in which the contact portion comprises a cylindrical contact hole and a contact hole wiring formed in the contact hole. This configuration simplifies the manufacturing process while ensuring airtightness of the contact portion.

[0082] A fourth embodiment of the present disclosure is the first or second embodiment, in which the contact portion comprises a prismatic contact hole and a contact hole wiring formed in the contact hole. This configuration makes it possible to enlarge the area in which the second metal film forming the intermetallic bond is formed around the contact portion, thereby further improving the airtightness of the contact portion.

[0083] A fifth embodiment of the present disclosure is any of the first to fourth embodiments, in which the wall portion has a rectangular frame shape, the first metal film is provided in a frame shape corresponding to the wall portion, and the second metal film is provided at any two of the four corners of the first metal film. This configuration simplifies the manufacturing process while improving the positioning accuracy during metal-to-metal bonding.

[0084] A sixth embodiment of the present disclosure is any of the first to fifth embodiments, wherein the wall portion has four inner corners that are rounded in plan view. This configuration makes it possible to increase the area where the second metal film that forms the metal-to-metal bond is formed around the contact portion, thereby further improving the airtightness of the contact portion.

[0085] A seventh embodiment of the present disclosure is any of the first to fifth embodiments, wherein the wall portion has four inner corners that are C-chamfered in plan view, which makes it possible to increase the area where the second metal film that forms the intermetallic bond is formed around the contact portion, thereby further improving the airtightness of the contact portion.

[0086] An eighth embodiment of the present disclosure is any of the first to fourth embodiments, in which the wall portion has a rectangular frame shape with four inner corners that are C-chamfered in plan view, the first metal film is provided in a frame shape corresponding to the wall portion, the second metal film is provided at any two of the four corners of the first metal film, and the contact portion has one of the four corners of the rectangle that is C-chamfered in plan view, and the corner of the C-chamfered shape is parallel to the C-chamfered part of the wall portion. This makes it possible to increase the formation area of ​​the second metal film that forms intermetallic bonds around the contact portion, thereby further improving the airtightness of the contact portion.

[0087] A ninth embodiment of the present disclosure is the first or second embodiment, in which the contact hole wiring is made of a conductor that fills the inside of the contact hole or is formed on the inner surface of the contact hole, thereby enabling a more reliable electrical connection between the mounting pattern and the external mounting terminal.

[0088] A tenth embodiment of the present disclosure is any of the first to ninth embodiments, in which the substrate has a rectangular shape in a plan view, and the planar shape of the contact portion is a polygon having a side parallel to one side of the rectangular substrate. This configuration allows for larger planar dimensions of the contact hole constituting the contact portion, facilitating film formation within the contact hole. Furthermore, larger planar dimensions of the contact hole also increase the area of ​​the inner surface (inner wall area) of the contact hole, making it easier to ensure a wiring width for reducing the wiring resistance of the contact hole wiring constituting the contact portion. This configuration also allows for a wider width of the first metal film bonding the wall portion to the substrate, and a wider insulation width from the first metal film to the second metal film airtightly sealing the contact portion.

[0089] An eleventh embodiment of the present disclosure is a piezoelectric device including the base of any one of the first to tenth embodiments, a piezoelectric element connected and fixed to the mounting pattern by a conductive member, and a lid member bonded to the base and sealing the piezoelectric element. This configuration makes it possible to provide a piezoelectric device with excellent reliability, such as airtightness. [Explanation of symbols]

[0090] 1. Piezoelectric devices 2 Base for piezoelectric device (base) 3 Piezoelectric element 4 Cover member 5. Conductive adhesive 11 Circuit Board 12 Wall 13 Bonding metal film (first metal film) 14 Sealing metal film 21a, 21b Mounting pattern 22a, 22b, 22c, 22d External mounting terminals 23a, 23b Contact part 24a, 24b Airtight forming film (second metal film) 31 Metal film on substrate side 41 Metal Film 42 Wall side metal film

Claims

1. 1. A base for a piezoelectric device, comprising: a substrate made of glass or quartz; a mounting pattern for a piezoelectric element provided on a first surface of the substrate; a frame-shaped wall portion provided on the first surface along an edge of the substrate, made of the same material as the substrate, and joined to the substrate by a first metal film for intermetallic bonding; an external mounting terminal provided on a second surface of the substrate opposite to the first surface; a contact portion insulated from the first metal film in a region directly below the wall portion, the contact portion penetrating the substrate and electrically connecting the mounting pattern and the external mounting terminal; a second metal film provided on a surface of the wall portion facing the substrate, the second metal film facing the contact portion, the second metal film forming an intermetallic bond with the contact portion to make the contact portion airtight; A base comprising:

2. The base according to claim 1 , wherein the second metal film is provided in a region inside a region where the first metal film is formed, and spaced apart from the first metal film.

3. 2. The base according to claim 1, wherein the contact portion comprises a cylindrical contact hole and a contact hole wiring formed in the contact hole.

4. 2. The base according to claim 1, wherein the contact portion comprises a prismatic contact hole and a contact hole wiring formed in the contact hole.

5. the substrate has a rectangular shape in a plan view, the first metal film is provided in a frame shape corresponding to the wall portion, The base according to claim 1 , wherein the second metal film is provided at any two of the four corners of the first metal film.

6. The base according to claim 5 , wherein the wall portion has four inner corners that are rounded in plan view.

7. The base according to claim 5 , wherein the wall portion has four inner corners that are chamfered in a plan view.

8. The wall portion has a rectangular frame shape and has four inner corners that are C-chamfered in a plan view, the first metal film is provided in a frame shape corresponding to the wall portion, the second metal film is provided at any two of the four corners of the first metal film, The base according to claim 4, characterized in that the contact portion has a rectangular shape in which one of the four corners is C-chamfered when viewed in a plane, and the corner of the C-chamfered shape is parallel to the C-chamfered portion of the wall portion.

9. 5. The base according to claim 3, wherein the contact hole wiring is made of a conductor that fills the inside of the contact hole or is formed on the inner surface of the contact hole.

10. 2. The base according to claim 1, wherein the substrate has a rectangular shape in a plan view, and the planar shape of the contact portion is a polygon having a side parallel to one side of the rectangular substrate.

11. 3. A piezoelectric device comprising: the base according to claim 1; a piezoelectric element connected and fixed to the mounting pattern by a conductive member; and a lid member bonded to the base and sealing the piezoelectric element.

Images