Wiring board, package, and piezoelectric device

Abstract

The present invention improves bonding strength between a substrate and a conductive bonding material for bonding elements. This wiring board comprises: a base made of a ceramic material; a frame part; and a plurality of connection electrodes. The base has at least one recess that opens in a first surface on which an element is mounted. Each of the connection electrodes is positioned on the bottom surface of the recess, and the bottom surface of the recess is exposed around the connection electrode.

Description

Wiring board, package, and piezoelectric device

[0001] The present disclosure relates to a wiring substrate, a package, and a piezoelectric device.

[0002] Prior Art Document 1 discloses a fixing structure for a quartz crystal unit. In Prior Art Document 1, in order to increase the bonding strength between the substrate and the conductive bonding material, the conductive bonding material is filled into holes provided in the substrate and protrudes above the surface. The quartz crystal unit is then fixed onto the substrate by the protruding conductive bonding material.

[0003] Japanese Patent Application Publication No. 2005-223755

[0004] A wiring board according to one aspect of the present disclosure has a first surface including a mounting area for mounting an element, and comprises a base made of a ceramic material, a frame portion positioned on the first surface surrounding the mounting area, and a plurality of connection electrodes connected to separate terminals of the element, wherein the base has at least one recess opening into the first surface, the connection electrodes are each positioned on the bottom surface of the recess, and the bottom surface of the recess is exposed around the connection electrodes.

[0005] A package according to one aspect of the present disclosure includes the wiring substrate and a lid.

[0006] A piezoelectric device according to one aspect of the present disclosure includes the above package and a piezoelectric vibration element.

[0007] FIG. 1 is an exploded perspective view of a piezoelectric device according to embodiment 1 of the present disclosure; FIG. 2 is a top view of a wiring substrate according to embodiment 1 of the present disclosure; FIG. 3 is a cross-sectional view of the piezoelectric device according to embodiment 1 of the present disclosure; FIG. 4 is a bottom view of a wiring substrate according to embodiment 1 of the present disclosure; FIG. 5 is a partial cross-sectional view of another aspect of the piezoelectric device according to embodiment 1 of the present disclosure; FIG. 6 is a top view of another aspect of the wiring substrate according to embodiment 1 of the present disclosure; FIG. 7 is a partial cross-sectional view of another aspect of the piezoelectric device according to embodiment 1 of the present disclosure; FIG. 8 is a partial cross-sectional view of another aspect of the piezoelectric device according to embodiment 1 of the present disclosure; FIG. 9 is a perspective view of a piezoelectric device according to embodiment 2 of the present disclosure; FIG. 10 is a top view of a wiring substrate according to embodiment 2 of the present disclosure; FIG. 11 is a cross-sectional view of the piezoelectric device according to embodiment 2 of the present disclosure; FIG. 12 is a top view of a wiring substrate according to embodiment 3 of the present disclosure; FIG. 13 is a top view of a wiring substrate according to embodiment 4 of the present disclosure; FIG. 14 is a top view of another wiring substrate according to embodiment 4 of the present disclosure;

[0008] In the fixing structure of the crystal resonator as described in Prior Art Document 1, when the substrate is made thinner, there is a possibility that the bonding strength between the conductive bonding material and the substrate will be insufficient.

[0009] According to one aspect of the present disclosure, the bonding strength between the conductive bonding material for bonding an element and the substrate can be improved.

[0010] First Embodiment A wiring board, a package, and a piezoelectric device according to a first embodiment of the present disclosure will be described in detail with reference to the accompanying drawings.

[0011] The distinction between top and bottom in the following description is for convenience and does not limit the top and bottom when the wiring board, package, and piezoelectric device are actually used. In this specification, the surface of the wiring board on which the piezoelectric vibration element is mounted is defined as the top surface. In the drawings, the positive direction of the Z axis is the upward direction. The X axis is the longitudinal axis direction of the wiring board, and the Y axis is an axis that intersects perpendicularly with the X axis and the Z axis. The Z axis is also defined as the thickness direction of the wiring board.

[0012] Fig. 1 is an exploded perspective view of an exemplary piezoelectric device 500 according to the present disclosure. Fig. 2 is a top view of an exemplary wiring substrate 100 according to the present disclosure. Fig. 3 is a cross-sectional view of the piezoelectric device 500. Specifically, Fig. 3 is a cross-sectional view of the wiring substrate 100 shown in Fig. 2 taken along line III-III, with a piezoelectric vibrating element 400 and a lid 200 added. Fig. 4 is a bottom view of the wiring substrate 100.

[0013] 1, the piezoelectric device 500 includes a package 300 and a piezoelectric vibration element 400. The package 300 includes a wiring substrate 100 and a lid 200. In reality, the wiring substrate 100 and the piezoelectric vibration element 400 are bonded via a bonding material 410, but the bonding material is omitted from Fig. 1. The electrodes of the piezoelectric vibration element 400 are also omitted from illustration.

[0014] As shown in FIG. 3 , the wiring substrate 100 has a base 110, a frame 140, and wiring conductors located on the surface and inside of the wiring substrate 100. The planar size of the package 300 according to the present disclosure may be, for example, a long side of 1.2 mm or less and a short side of 1.0 mm or less, a long side of 1.0 mm or less and a short side of 0.8 mm or less, or a long side of 0.8 mm or less and a short side of 0.6 mm or less. The thickness of the package 300 according to the present disclosure may be, for example, 0.2 mm or less, 0.15 mm or less, or 0.1 mm or less. The height of the base 110 according to the present disclosure may be, for example, 0.1 mm or less, 0.075 mm or less, or 0.05 mm or less. The height of the frame 140 according to the present disclosure may be, for example, 0.1 mm or less, 0.75 mm or less, or 0.05 mm or less.

[0015] When the thickness of the package 300 is 0.2 mm, the heights of the base 110, frame 140, and lid 200 may be, for example, approximately 0.08 mm, 0.07 mm, and 0.05 mm, respectively. When the thickness of the package 300 is 0.15 mm, the heights of the base 110, frame 140, and lid 200 may be, for example, approximately 0.05 mm, 0.06 mm, and 0.04 mm, respectively. When the thickness of the package 300 is 0.1 mm, the heights of the base 110, frame 140, and lid 200 may be, for example, approximately 0.03 mm, 0.04 mm, and 0.03 mm, respectively. In either case, the thickness of the frame-shaped metallized layer 173 (described later) may be, for example, approximately 0.015 mm.

[0016] The two-dot chain line in FIG. 2 represents the outer edge of the piezoelectric vibration element 400 when the piezoelectric vibration element 400 is disposed on the wiring substrate 100 as a virtual line. The mounting area 180 of the wiring substrate 100 may be a region of the wiring substrate 100 that overlaps with the piezoelectric vibration element 400 when viewed from above. That is, it may be the region indicated by the two-dot chain line in FIG. 2. Alternatively, the mounting area 180 may be a region surrounded by virtual lines connecting alignment marks (not shown) used when disposing the piezoelectric vibration element 400. The mounting area 180 may be determined based on the size of the piezoelectric vibration element 400 to be mounted. For ease of explanation, FIG. 2 shows the first through conductor 171A, the second through conductor 171B, and the inner-frame wiring 174 as viewed from above with dashed lines. The outer edge of the portion of the wiring substrate 100 that corresponds to the coating layer 110C during manufacturing is also shown with a dashed line. The first through conductor 171A, the second through conductor 171B, the in-frame wiring 174, and the coating layer 110C will be described later.

[0017] The base 110 may be a flat insulator having a first surface 111 including a mounting region 180 on which an element is mounted, and a second surface 112 located opposite the first surface 111. The base 110 may have, for example, a rectangular shape in a plan view. The base 110 has a recess 120 that opens to the first surface 111.

[0018] The frame 140 is positioned on the first surface 111, surrounding the mounting region 180 and the recess 120. By providing the frame 140 on the wiring substrate 100, the piezoelectric vibration element 400 and the like can be protected when the lid 200 is not present. The frame 140 may be integral with the base 110. In a plan view, the outer edge of the frame 140 may overlap the outer edge of the base 110.

[0019] The base 110 and the frame 140 may be made of an insulating inorganic material. Examples of the insulating inorganic material include ceramic materials such as aluminum oxide sintered body (alumina ceramics), aluminum nitride sintered body, mullite sintered body, and glass ceramic sintered body. The base 110 and the frame 140 may be integrally formed, or may be made of a single insulating layer or multiple laminated insulating layers.

[0020] The wiring conductors provided on the wiring substrate 100 include a connection electrode 150 , a through conductor 171 , an external electrode 172 , and a frame-shaped metallized layer 173 .

[0021] The connection electrodes 150 are electrodes that are electrically connected to the terminals of the piezoelectric vibration element 400. In the attached drawings, the connection electrodes 150 are indicated by dot hatching in the top views and perspective views.

[0022] The connection electrode 150 is located on the bottom surface of the recess 120, and the bottom surface of the recess 120 is exposed around the connection electrode 150. In other words, the size of the connection electrode 150 in a plan view is smaller than the size of the bottom surface of the recess 120. In a thinned wiring substrate 100, it is difficult to increase the depth of the recess 120 in order to ensure the substrate strength. Because the bottom surface of the recess 120 is exposed around the connection electrode 150, the bonding material 410 may come into contact with the bottom surface of the recess 120, as shown in FIG. 3 . The bonding material 410 is an example of a conductive bonding material according to the present disclosure and may be, for example, a conductive resin. The bottom surface of the recess 120 is a ceramic surface and has a rougher surface than the surface of the connection electrode 150. Therefore, due to the anchor effect between the bonding material 410 and the bottom surface of the recess 120, the bonding strength between the bonding material 410 and the wiring substrate 100 can be improved even in a wiring substrate 100 with a shallow recess 120.

[0023] The bottom surface of the recess 120 may be exposed at least partially around the connection electrode 150, or may be exposed around the entire circumference of the connection electrode 150. By exposing the entire circumference of the connection electrode 150, the anchor effect is enhanced around the entire circumference of the connection electrode 150, and the bonding strength between the bonding material 410 and the wiring substrate 100 can be further improved.

[0024] 3 has a bonding material 410 that bonds the piezoelectric vibration element 400 and the connection electrode 150. The bonding material 410 is bonded to the bottom surface of the recess 120, which is exposed around the connection electrode 150. The bonding material 410 may be bonded to the bottom surface of the recess 120 around the entire periphery of the connection electrode 150. This provides an anchor effect between the bonding material 410 and the bottom surface of the recess 120, which has a rougher surface than the connection electrode 150, making it possible to provide a piezoelectric device 500 with improved bonding strength to the wiring substrate 100.

[0025] The connection electrode 150 may be located at the center of the recess 120. Alternatively, as shown in FIG. 2 , the connection electrode 150 may be located closer to the center of the wiring substrate 100 than the center of the recess 120. This widens the gap between the connection electrode 150 and the frame 140, reducing the possibility that the bonding material 410 will creep up along the frame 140. This reduces the possibility of a short circuit occurring between the connection electrode 150 and the frame-shaped metallization layer 173 on the frame 140. Furthermore, the bonding material 410 creeping up onto the frame-shaped metallization layer 173 reduces the possibility that the bonding strength between the frame-shaped metallization layer 173 and the lid 200 will be reduced, reducing the possibility that the airtight sealing will be reduced.

[0026] The connection electrode 150 includes a metallized layer 151 as a wiring conductor and a plating layer 152 deposited on the metallized layer 151. The plating layer 152 may be a layer containing nickel and / or gold. For example, nickel plating may be applied to the exposed surface of the metallized layer 151, and gold plating may be applied to the nickel plating layer. This reduces the possibility of oxidation corrosion of the wiring conductor surface.

[0027] At least a portion of the metallization layer 151 may be embedded in the base 110. In a thinned piezoelectric device 500, improved height accuracy is required for the height of the piezoelectric vibration element 400 (distance from the first surface 111). The metallization layer 151 has lower thickness accuracy than the plating layer 152, and therefore, if the portion of the metallization layer 151 that is convex from the base 110 (the protruding portion) is higher, the height accuracy will be low. By embedding a portion of the metallization layer 151 in the base 110, the portion that is convex from the base 110 (the bottom surface of the recess 120) is reduced, thereby improving the height accuracy of the piezoelectric vibration element 400.

[0028] Furthermore, because at least a portion of the metallization layer 151 is buried in the base 110, the bonding strength with the base 110 is improved even if the size of the metallization layer 151 is small. Furthermore, because the portion protruding from the bottom surface of the recess 120 is reduced, a larger amount of bonding material 410 can be injected into the recess 120, improving the bonding strength of the piezoelectric vibration element 400. Furthermore, because the portion protruding from the bottom surface of the recess 120 is reduced, the depth of the recess 120 can be designed to be thinner, making it easier to ensure the strength of the wiring substrate 100.

[0029] The upper surface of the metallized layer 151 may be flush with the bottom surface of the recess 120. The plating layer 152 is easy to form with a thin thickness and high precision. By making the upper surface of the metallized layer 151 flush with the bottom surface of the recess 120, the protruding height of the connection electrode 150 from the bottom surface of the recess 120 is determined only by the thickness of the plating layer 152. Therefore, by appropriately controlling the plating thickness, the height precision can be further improved.

[0030] In the first embodiment, the wiring substrate 100 has two recesses 120 and two connection electrodes 150, and each connection electrode 150 is located in a different recess 120. Since each connection electrode 150 is located in a different recess 120, when the piezoelectric vibration element 400 is bonded with the bonding material 410, the base 110 between the two recesses 120 acts as a bank, thereby reducing the possibility of a short circuit occurring due to the bonding material 410.

[0031] Furthermore, in the wiring substrate 100, the inner surface of the recess 120 is flush with the inner surface of the frame portion 140. With this configuration, the recess 120 and the connection electrode 150 are disposed at the outermost parts within the frame portion 140, thereby enabling the wiring substrate 100 to be made more compact. Alternatively, the recess 120 is extended to the frame portion 140, increasing the bonding area between the bonding material 410 and the bottom surface of the recess 120, thereby enabling the bonding strength to be further increased.

[0032] The external electrodes 172 include a first external electrode 172A and a second external electrode 172B. As shown in FIGS. 1 and 4 , the first external electrode 172A and the second external electrode 172B are each located on the second surface 112 of the base 110. The first external electrode 172A is an electrode electrically connected to the connection electrode 150. The number of connection electrodes 150 and the number of first external electrodes 172A may be the same, and each connection electrode 150 may be connected to a different first external electrode 172A. The second external electrode 172B is an electrode electrically connected to the lid 200.

[0033] The first external electrode 172A and the second external electrode 172B may each be disposed at a corner of the second surface 112. For example, the first external electrode 172A and the second external electrode 172B may each be located at a corner along a diagonal of the second surface 112. Alternatively, the first external electrode 172A and the second external electrode 172B may each be located at a corner along the short side direction (Y direction) of the wiring substrate 100. The first external electrode 172A and the second external electrode 172B may extend from the second surface 112 of the base 110 to the side surfaces (including the corners between the side surfaces).

[0034] Since the first external electrode 172A and the second external electrode 172B are both located on the second surface 112 of the base 110, the package 300 and the piezoelectric device 500 can be surface-mounted on a mounting substrate.

[0035] The first through conductor 171A is a wiring that penetrates the base 110 and connects the connection electrode 150 and the first external electrode 172A. The second through conductor 171B and the intra-frame wiring 174 are wiring that connect the frame-shaped metallization layer 173 and the second external electrode 172B. In other words, the frame-shaped metallization layer 173 is connected to the second external electrode 172B via the intra-frame wiring 174 and the second through conductor 171B. The second through conductor 171B extends in the Z-axis direction in the base 110 and connects the second external electrode 172B and the intra-frame wiring 174. The intra-frame wiring 174 is located inside the base 110 and inside the frame 140 and connects the second through conductor 171B and the frame-shaped metallization layer 173.

[0036] The frame-shaped metallized layer 173 is a conductive layer located on the upper surface of the frame portion 140. The frame-shaped metallized layer 173 is joined to the lid body 200 using a sealing material (not shown) such as a gold-tin alloy (AuSn) or silver solder.

[0037] The exposed surfaces of the frame-shaped metallization layer 173 and the external electrode 172 may be covered with a plating layer of nickel and / or gold, similar to the connection electrode 150. Covering the frame-shaped metallization layer 173 with a plating layer can facilitate and strengthen the connection between the frame-shaped metallization layer 173 and the lid 200, which is a metal conductor. Covering the external electrode 172 with a plating layer can facilitate and strengthen the connection with an electrode of a mounting substrate on which the piezoelectric device 500 is mounted.

[0038] The piezoelectric vibrating element 400 may be a quartz crystal vibrating element such as an AT-cut quartz crystal vibrating element, an SC-cut quartz crystal vibrating element, or a BT-cut quartz crystal vibrating element. The piezoelectric vibrating element 400 may also be a step type or an inverted mesa type in which the region where the vibrating portion is located on the underside thereof is located above the bonding region with the bonding material 410. When the piezoelectric vibrating element 400 is a step type or an inverted mesa type, the possibility of the vibrating portion coming into contact with the wiring substrate 100 can be reduced even if the wiring substrate 100 is warped.

[0039] The lid 200 is made of, for example, a conductive metal and is bonded to the frame-shaped metallization layer 173 to hermetically seal the package 300. The lid 200 may be made of, for example, an iron-nickel alloy or an iron-nickel-cobalt alloy. The lid 200 can be formed into a predetermined shape by employing a conventional metal processing method such as a rolling method or a punching method. The lid 200 may be grounded. More specifically, by grounding the second external electrode 172B, the lid 200 can obtain a ground potential. By grounding the lid 200, it is possible to reduce the propagation of external noise into the package 300.

[0040] (Method for Manufacturing Wiring Board) Next, an example of a method for manufacturing the wiring board 100 will be described.

[0041] First, through holes are formed in the ceramic green sheets that will become the base 110 and the frame 140, and a conductor is injected into the through holes to form the first through conductors 171A and the second through conductors 171B.

[0042] Then, a metallization paste is applied using a mask to the upper surface of the ceramic green sheet at the positions of the connection electrodes 150, the in-frame wiring 174, and the frame-shaped metallization layer 173. The frame-shaped metallization layer 173 may be formed by forming the frame 140 with a pressing jig, as described below, and then applying the metallization paste to the upper surface of the frame 140. Next, a ceramic paste (coating layer 110C) made of the same material as the ceramic green sheet is applied using a mask to an appropriate internal position range that covers the portion of the metallization paste corresponding to the in-frame wiring 174.

[0043] A mask is used to apply metallization paste to the lower surface of the ceramic green sheet at each position of the external electrodes 172. Metallization paste is also applied to the lower surface of the ceramic green sheet at the positions of internal wiring (not shown), including wiring connecting the external electrodes 172 together. Furthermore, ceramic paste is applied to the lower surface of the ceramic green sheet to cover the internal wiring connecting the external electrodes 172 together. The application of the metallization paste and the ceramic paste is carried out by, for example, screen printing.

[0044] A ceramic green sheet coated with metallization paste on both sides is placed on a flat plate and pressed from above by a pressing jig having concaves and convexes corresponding to frame 140, recess 120, and connection electrode 150. This forms frame 140, recess 120, and connection electrode 150 located on the bottom surface of recess 120. In this pressing step, by burying connection electrode 150 so that it is flush with the bottom surface of recess 120, wiring substrate 100 can be produced with high precision, in which metallization layer 151 of connection electrode 150 is flush with the bottom surface of recess 120.

[0045] The inner-frame wiring 174 of the metallization paste is sandwiched and embedded between the coating layer 110C and the ceramic green sheet. The upper end of the second through conductor 171B is pressed downward by the metallization paste that becomes the inner-frame wiring 174 and the coating layer 110C.

[0046] The metallization paste and ceramic paste are formed into a planar shape on the underside of the ceramic green sheet, forming external electrodes 172 connected via internal wiring. A firing process is then performed at a temperature of 1300 to 1600°C, thereby obtaining the wiring substrate 100. Thereafter, plating processes, attachment of the piezoelectric vibration element 400, and bonding of the lid 200 are performed as necessary, thereby obtaining the piezoelectric device 500.

[0047] Alternatively, the wiring substrate 100 may be fabricated as follows. That is, a plurality of ceramic green sheets are fabricated, each having a frame 140, a recess 120, and through holes for a through conductor at appropriate positions. Then, a conductor is injected, a metallization paste is applied, and the sheets are laminated, followed by firing at a temperature of 1300 to 1600°C. Alternatively, the base 110 and the frame 140 may be fabricated by laminating a plurality of ceramic green sheets each having a through hole, and the recess 120 may be formed using a pressure jig. The recess 120 may be formed using a mold on the ceramic green sheets before lamination, or may be formed using a lamination mold during lamination, or may be formed by pressure molding using a mold after lamination.

[0048] (Other Aspects of Wiring Substrate 100 and Piezoelectric Device 500) Fig. 5 is a partial cross-sectional view showing another aspect of the piezoelectric device 500, illustrating an example in which the bonding material 410 is also bonded to the inner wall of the recess 120. As shown in Fig. 5, in the piezoelectric device 500, the bonding material 410 may be bonded to the inner side surface as well as the bottom surface of the recess 120. This can further improve the bonding strength between the bonding material 410 and the wiring substrate 100.

[0049] 6 is a partial cross-sectional view showing another embodiment of the piezoelectric device 500, illustrating an example in which the connection electrode 150 is located adjacent to the inner wall of the recess 120. As shown in FIG. 6, in the wiring substrate 100, the bottom surface of the recess 120 does not need to be exposed around the entire periphery of the connection electrode 150; only a portion of it may be exposed. Furthermore, if the distance between the connection electrode 150 and the inner wall of the recess 120 is very small or they are in contact, a portion of the bonding material 410 may be bonded to the first surface 111 of the base 110 adjacent to the inner wall. This allows the bonding material 410 and the base 110 to be bonded around the entire periphery of the connection electrode 150, further improving the bonding strength.

[0050] 7 is a top view of the wiring substrate 100A. The wiring substrate 100A differs from the recess 120 of the wiring substrate 100 in the position and planar shape of the recess 120A. In other respects, the wiring substrate 100A may have the same configuration as the wiring substrate 100 of the first embodiment.

[0051] Specifically, in a plan view, the recess 120A of the wiring substrate 100A is located away from the frame portion 140. By locating the recess 120A away from the frame portion 140, the possibility that the bonding material 410 will creep up along the frame portion 140 can be reduced.

[0052] Furthermore, the recess 120A is polygonal in plan view, and at least one of the corners between adjacent inner surfaces has a curved shape. In other words, the recess 120A has at least one curved corner in plan view. The recess 120A may be rectangular, triangular, pentagonal, hexagonal, parallelogram, rhombus, etc. in plan view. The curved corners between adjacent inner surfaces reduce the likelihood of cracks originating from the corners compared to cases where the corners at the boundaries between the inner surfaces are right angles. Furthermore, thermal stresses applied when the lid 200 is bonded to the wiring substrate 100A or when the piezoelectric device 500 is mounted on a mounting substrate tend to be large at the corners of the wiring substrate 100A. Therefore, the corners of the recess 120A near the corners of the wiring substrate 100A may be curved.

[0053] Among the corners of the recess 120A, the curved corners may be corners located inside the base 110 in a plan view. In other words, among the inner surfaces of the recess 120, the corner between two inner surfaces located inside the base 110 may have a curved shape. When the recesses 120A are adjacent along one side of the base 110, as in the wiring substrate 100A, the distance between the recesses 120A is short in the miniaturized wiring substrate 100A. By having the corners located inside the base 110 have a curved shape, the possibility of cracks originating from the corners between the recesses 120A can be reduced. Rounding the corners between the inner surfaces can be easily achieved by changing the shape of the pressing jig in the manufacturing method using the pressing jig described above.

[0054] FIG. 8 is a partial cross-sectional view of a piezoelectric device 500B. The wiring substrate 100B of the piezoelectric device 500B has a recess 120B. As shown in FIG. 8, the corners between the inner surface and the bottom surface of the recess 120B may be curved. This wiring substrate 100B can reduce the possibility of cracks originating from the corners compared to a case in which the corners between the inner surface and the bottom surface are right angles. Rounding the corners between the inner surface and the bottom surface can be easily achieved by changing the shape of the pressure jig in the manufacturing method using the pressure jig described above. The planar shape of the recess 120B is not particularly limited and may be, for example, circular or polygonal.

[0055] In addition, the corners between the inner surface of the frame 140 and the first surface 111 of the base 110 may also be curved. This reduces the possibility of cracks originating from the corners. The shape of the frame 140 as well as the shape of the recess 120B can be easily formed by changing the shape of the pressing jig in the manufacturing method using the pressing jig described above.

[0056] FIG. 9 is a partial cross-sectional view of a piezoelectric device 500C. The wiring substrate 100C of the piezoelectric device 500C has a recess 120C. As shown in FIG. 9 , the angle between the inner surface and the bottom surface of the recess 120C may be an obtuse angle. This wiring substrate 100C can reduce the likelihood of cracks originating from the corners, compared to a wiring substrate 100C in which the corner between the inner surface and the bottom surface is a right angle. Furthermore, the angle between the inner surface and the bottom surface of the recess 120C may be an obtuse angle, and the corner between the inner surface and the bottom surface may have a curved shape. This further reduces the likelihood of cracks. Forming a recess 120C with an obtuse angle between the inner surface and the bottom surface can be easily achieved by modifying the shape of the pressure jig in the manufacturing method using the pressure jig described above.

[0057] FIG. 9 illustrates an example in which the inner surface of the recess 120C and the inner surface of the frame 140 are flush with each other, and the angle between the inner surface of the frame 140 and the first surface 111 of the base 110 is also an obtuse angle. The recess 120C may be inclined from the first surface 111, and the angle between the frame 140 and the first surface 111 may be a right angle. Furthermore, the angle between the inner surface of the recess 120C and the bottom surface and the angle between the frame 140 and the first surface 111 may be different obtuse angles. This type of shape can also be easily formed by modifying the shape of the pressure jig in the manufacturing method using the pressure jig described above. Even with this configuration, the possibility of cracks originating from the corner between the inner surface and the bottom surface can be reduced.

[0058] [Embodiment 2] A second embodiment of the present disclosure will be described below. For convenience of explanation, the same reference numerals will be used to designate components having the same functions as those described in the above embodiment, and the description thereof will not be repeated.

[0059] Fig. 10 is a perspective view of a piezoelectric device 500D according to the second embodiment. Fig. 11 is a top view of a wiring substrate 100D according to the second embodiment. Fig. 12 is a cross-sectional view of the piezoelectric device 500D. Specifically, this is a cross-sectional view taken along the XII-XII arrows of the wiring substrate 100D shown in Fig. 11, with a piezoelectric vibrating element 400 and a lid 200 added.

[0060] The piezoelectric device 500D includes a wiring substrate 100D. The wiring substrate 100D differs from the wiring substrate 100 of the first embodiment in the positions of two recesses 120D of the wiring substrate 100D. In other respects, the wiring substrate 100D may have the same configuration as the wiring substrate 100 of the first embodiment.

[0061] As shown in the examples of FIGS. 10 and 11 , two recesses 120D in the wiring substrate 100D may be located at opposite corners along a diagonal line of the wiring substrate 100D (or the base 110). In other words, the two recesses 120D may be located at diagonal corners on the first surface 111 of the rectangular base 110 in a top view. This configuration increases the distance between the recesses 120D, thereby reducing the possibility of cracks occurring between the recesses 120D. Furthermore, in the wiring substrate 100D, the positions of the recesses 120D where the substrate thickness becomes thinner are not biased within the substrate, thereby increasing the substrate strength and reducing substrate warpage. Furthermore, by making the corners between the inner surfaces of the recesses 120D curved in a plan view, the possibility of cracks occurring in the wiring substrate 100D can be further reduced (see FIG. 15 ).

[0062] 13 is a top view of a wiring substrate 100E according to a third embodiment. The wiring substrate 100E differs from the wiring substrate 100 of the first embodiment in that two connection electrodes 150 are located on the bottom surface of one recess 120E. The length of the recess 120E in the Y-axis direction of the wiring substrate 100E is longer than the length of the piezoelectric vibration element 400 in the Y-axis direction, and the two connection electrodes 150 are located adjacent to each other. Therefore, the wiring substrate 100E can be used, for example, as a substrate on which a step-type piezoelectric vibration element 400 is mounted. Furthermore, because the wiring substrate 100E has only one recess 120E, cracks do not occur between the corners of the recesses, which would occur if the recesses were adjacent to each other.

[0063] 14 to 16, an example will be described in which a wiring substrate includes a pillow portion that supports a piezoelectric vibration element 400. Fig. 14 is a top view of a wiring substrate 100F. Fig. 15 is a top view of a wiring substrate 100G. Fig. 16 is a top view of a wiring substrate 100H.

[0064] 14 includes a pillow portion 130. The wiring board 100F has two recesses 120 along one side of the first surface 111. The pillow portion 130 is an insulating body that has a U-shape in top view and is convex with respect to the first surface 111. The outer edge of the pillow portion 130 may be adjacent to or joined to the frame portion 140.

[0065] The height of the pillow portion 130 may be approximately the same as the height of the upper surface of the connection electrode 150. Alternatively, the height of the pillow portion 130 may be approximately the same as the height of the connection electrode 150 plus the thickness of the bonding material 410.

[0066] The pillow portion 130 may be made of an insulating inorganic material. Examples of insulating inorganic materials include ceramics such as aluminum oxide sintered body (alumina ceramics), aluminum nitride sintered body, mullite sintered body, or glass ceramic sintered body. The base portion 110, pillow portion 130, and frame portion 140 may be integrally formed, or may be made of a single insulating layer or multiple laminated insulating layers.

[0067] Since the pillow portion 130 is joined to the first surface 111 and the frame portion 140, the strength of the wiring board 100F can be improved.

[0068] 15 has pillow portions 130A, 130B, and 130C. Pillow portion 130A is inscribed in a corner of frame portion 140 and has a rectangular shape. Pillow portion 130B is inscribed in any side of frame portion 140 and has a rectangular shape. Pillow portion 130C is inscribed in a corner of frame portion 140 and has an L-shape that follows the corner.

[0069] The wiring board 100G does not need to include all of the pillow portion 130A, the pillow portion 130B, and the pillow portion 130C, and may include a plurality of any of them. Alternatively, the wiring board 100G may include any combination of the pillow portion 130A, the pillow portion 130B, and the pillow portion 130C. In the wiring board 100G, the pillow portion 130 is joined to the first surface 111 and the frame portion 140, which improves the strength of the wiring board 100F.

[0070] The wiring board 100H shown in FIG. 16 has a pillow portion 130D and a pillow portion 130E. The pillow portion 130D is provided at a corner of the wiring board 100, away from the frame portion 140, and has a convex shape relative to the first surface 111. The pillow portion 130D may be made of an insulating material or a metallized layer. The pillow portion 130E is obtained by forming the coating layer 110C described in the first embodiment so as to be convex relative to the first surface 111. Alternatively, the inner-frame wiring 174 may not be covered with the coating layer 110C, and a portion of the inner-frame wiring 174 formed so as to be convex relative to the first surface 111 may be used as the pillow portion. By using a portion of the inner-frame wiring 174 connected to the ground electrode as the pillow portion, charging of the element can be reduced.

[0071] [Summary] The wiring board according to aspect 1 of the present disclosure has a first surface including a mounting area for mounting an element, and comprises a base made of a ceramic material, a frame portion located on the first surface surrounding the mounting area, and a plurality of connection electrodes connected to separate terminals of the element, wherein the base has at least one recess that opens onto the first surface, and the connection electrodes are each located on the bottom surface of the recess, and the bottom surface of the recess is exposed around the connection electrodes.

[0072] A wiring board according to aspect 2 of the present disclosure is the same as that according to aspect 1 above, wherein the connection electrode includes a metallized layer as a wiring conductor and a plating layer deposited on the metallized layer, and at least a portion of the metallized layer is embedded in the base.

[0073] A wiring board according to a third aspect of the present disclosure is the wiring board of the second aspect, wherein the upper surface of the metallization layer is flush with the bottom surface of the recess.

[0074] A wiring board according to aspect 4 of the present disclosure is a wiring board according to any one of aspects 1 to 3 above, in which the number of connection electrodes is two, the base portion has two recesses, and the two connection electrodes are each located in a different recess.

[0075] The wiring board according to aspect 5 of the present disclosure is the same as aspect 4 above, except that the base has a rectangular shape when viewed from above, and the two recesses are located at opposite corners along a diagonal line of the base.

[0076] A wiring board according to a sixth aspect of the present disclosure is the wiring board of any one of the first to fifth aspects, wherein a corner between at least one inner side surface and the bottom surface of the recess is curved.

[0077] A wiring board according to a seventh aspect of the present disclosure is the wiring board of any one of the first to fifth aspects, wherein an angle formed between at least one inner side surface of the recess and the bottom surface is an obtuse angle.

[0078] In the wiring board according to Aspect 8 of the present disclosure, in addition to Aspect 6, an angle formed between at least one inner side surface of the recess and the bottom surface is an obtuse angle.

[0079] A wiring board according to aspect 9 of the present disclosure is any one of aspects 1 to 8 above, wherein the recess is polygonal in top view, and corners between adjacent inner surfaces of the recess are curved.

[0080] A wiring board according to a tenth aspect of the present disclosure is the wiring board according to the ninth aspect, wherein the adjacent inner surfaces are two inner surfaces located inside the base portion.

[0081] The wiring board according to an eleventh aspect of the present disclosure is the wiring board of any one of the first to tenth aspects, wherein at least one inner side surface of the recess is flush with the inner surface of the frame portion.

[0082] A wiring board according to a twelfth aspect of the present disclosure is the wiring board of any one of the first to tenth aspects, wherein the recess is located away from the frame portion.

[0083] A wiring board according to a thirteenth aspect of the present disclosure is any one of the first to twelfth aspects, wherein the bottom surface of the recess is exposed around the entire periphery of the connection electrode.

[0084] A package according to a fourteenth aspect of the present disclosure includes the wiring substrate according to any one of the first to thirteenth aspects and a lid.

[0085] A piezoelectric device according to aspect 15 of the present disclosure includes the package of aspect 14 and a piezoelectric vibration element.

[0086] The piezoelectric device of aspect 16 of the present disclosure is, in the above-mentioned aspect 15, a conductive bonding material that bonds the piezoelectric vibration element and the connecting electrode, and the conductive bonding material is bonded to at least a portion of the bottom surface that is exposed around the connecting electrode.

[0087] The invention according to the present disclosure has been described above based on the drawings and examples. However, the invention according to the present disclosure is not limited to the above-described embodiments. In other words, the invention according to the present disclosure can be modified in various ways within the scope of the present disclosure, and embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included in the technical scope of the invention according to the present disclosure. In other words, it should be noted that a person skilled in the art can easily make various modifications or corrections based on the present disclosure. It should also be noted that these modifications or corrections are included in the scope of the present disclosure.

[0088] DESCRIPTION OF SYMBOLS 100, 100A, 100B, 100C, 100D, 100E, 100F, 100G, 100H... Wiring substrate 110... Base 120, 120A, 120B, 120C, 120D, 120E... Recess 130, 130A, 130B, 130C, 130D, 130E... Pillow portion 140... Frame portion 150... Connection electrode 151... Metallization layer 171... Through conductor 171A... First through conductor 171B... Second through conductor 172... External electrode 172A... First external electrode 172B... Second external electrode 173... Frame-shaped metallization layer 174... Wiring within frame 180... Mounting area 200... Lid 300... Package 400... Piezoelectric vibration element 410... Bonding material 500, 500B, 500C, 500D... Piezoelectric devices

Claims

1. A wiring board comprising: a base made of a ceramic material and having a first surface including a mounting area for mounting an element; a frame portion located on said first surface surrounding said mounting area; and a plurality of connection electrodes connected to separate terminals of said element, said base having at least one recess opening into said first surface, said connection electrodes being located on the bottom surface of said recess, and the bottom surface of said recess being exposed around said connection electrodes.

2. The wiring board according to claim 1, wherein the connection electrode includes a metallization layer as a wiring conductor and a plating layer deposited on the metallization layer, and at least a portion of the metallization layer is embedded in the base.

3. The wiring board according to claim 2, wherein an upper surface of said metallization layer is flush with a bottom surface of said recess.

4. A wiring board according to any one of claims 1 to 3, wherein the number of said connection electrodes is two, said base portion has two of said recesses, and said two connection electrodes are each located in a different of said recesses.

5. The wiring board according to claim 4, wherein said base has a rectangular shape when viewed from above, and said two recesses are located at diagonally opposite corners of said base.

6. The wiring board according to any one of claims 1 to 5, wherein a corner between at least one inner side surface and a bottom surface of the recess is curved.

7. The wiring board according to any one of claims 1 to 5, wherein an angle formed between at least one inner side surface of the recess and a bottom surface is an obtuse angle.

8. The wiring board according to claim 6, wherein an angle formed between at least one inner side surface of the recess and a bottom surface is an obtuse angle.

9. The wiring board according to any one of claims 1 to 8, wherein the recess is polygonal in top view, and corners between adjacent inner sides of the recess are curved.

10. The wiring board according to claim 9, wherein the adjacent inner surfaces are two inner surfaces located inside the base.

11. The wiring board according to any one of claims 1 to 10, wherein at least one inner side surface of the recess and an inner surface of the frame are flush with each other.

12. The wiring board according to any one of claims 1 to 10, wherein the recess is located away from the frame.

13. The wiring board according to claim 1, wherein the bottom surface of the recess is exposed around the entire periphery of the connection electrode.

14. A package comprising the wiring board according to any one of claims 1 to 13 and a lid.

15. A piezoelectric device comprising the package according to claim 14 and a piezoelectric vibration element.

16. The piezoelectric device according to claim 15, further comprising a conductive bonding material that bonds the piezoelectric vibration element and the connection electrode, the conductive bonding material being bonded to at least a portion of the bottom surface that is exposed around the connection electrode.

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