Wiring board and electronic module

Abstract

This wiring board comprises: an insulating substrate having a first surface, a second surface, and a stepped portion; a first electrode positioned from the first surface through the stepped portion to the second surface; and at least one conductor extending along a second direction orthogonal to a first direction that is the thickness direction of the insulating substrate. The height of the stepped portion is smaller than the distance between the first surface and a first conductor closest to the first electrode among the at least one conductor.

Description

Wiring Board and Electronic Module

[0001] The present disclosure relates to a wiring board and an electronic module.

[0002] Conventionally, a ceramic package for accommodating elements has been known (see, for example, Patent Document 1).

[0003] Japanese Patent Application Laid-Open No. 2010-069620

[0004] The wiring board according to one aspect of the present disclosure includes an insulating substrate, a first electrode, and at least one conductor. The insulating substrate has a first surface, a second surface, and a stepped portion connecting the first surface and the second surface. The first electrode is located from the first surface through the stepped portion to the second surface. The at least one conductor extends along a second direction that is parallel to a first direction which is the thickness direction of the insulating substrate and intersects the first surface and the second surface and is orthogonal to the first direction in a cross section including the first electrode. In the cross section, the height of the stepped portion in the first direction is smaller than the distance in the first direction between the first conductor closest to the first electrode among the at least one conductor and the first surface.

[0005] It is a perspective view schematically showing the configuration of a wiring board in an embodiment of the present disclosure. It is a plan view schematically showing the configuration of a wiring board in an embodiment of the present disclosure. It is a cross-sectional view schematically showing the cross section taken along line III-III shown in FIG. 2. It is a perspective view schematically showing an enlarged view of region IV shown in FIG. 1. It is a plan view schematically showing the configuration of a wiring board in an embodiment of the present disclosure. It is a cross-sectional view schematically showing the configuration of a wiring board in an embodiment of the present disclosure. It is a cross-sectional view schematically showing the cross section taken along line VII-VII shown in FIG. 2. It is a cross-sectional view schematically showing the configuration of a wiring board in an embodiment of the present disclosure. It is a cross-sectional view schematically showing the configuration of a wiring board in an embodiment of the present disclosure. It is a cross-sectional view schematically showing the configuration of a wiring board in an embodiment of the present disclosure. It is a cross-sectional view schematically showing the configuration of a wiring board in an embodiment of the present disclosure. It is a perspective view schematically showing the configuration of a wiring board in an embodiment of the present disclosure.

[0006] Hereinafter, one embodiment of the present disclosure will be described in detail with reference to the drawings. However, the following description is intended to provide a better understanding of the spirit of the invention and does not limit the present disclosure unless otherwise specified. For the sake of clarity, the drawings referenced in the following description show only the main components necessary to explain the embodiment, and for the sake of brevity, explanations of known technical matters will be omitted as appropriate.

[0007] Generally, wiring boards on which components are mounted have terminals, and these terminals have an area (hereinafter also referred to as the effective area or connection area) that allows for stable electrical connection with the electrodes of the component. When mounting components on a wiring board, it is required that the electrodes of the component and the connection area be able to be stably connected.

[0008] According to one aspect of this disclosure, it is possible to provide a wiring board that facilitates stable connection between electrodes of an element and connection areas of electrodes on the wiring board.

[0009] Figure 1 is a schematic perspective view showing the configuration of a wiring board in one embodiment of the present disclosure. Figure 2 is a schematic plan view showing the configuration of a wiring board in one embodiment of the present disclosure. Figure 3 is a schematic cross-sectional view showing the cross-section of line III-III shown in Figure 2. Figure 1 also shows an example of how electronic elements are mounted on the wiring board.

[0010] As shown in Figures 1 to 3, a wiring board 1 in one embodiment of the present disclosure comprises an insulating substrate 10 having a first surface F1, a second surface F2, and a stepped portion 15 connected to the first surface F1 and the second surface F2; a first electrode 51 located from the first surface F1 through the stepped portion 15 to the second surface F2; and at least one conductor 60 (see Figure 3). The conductor 60 extends along a second direction parallel to the first direction, which is the thickness direction of the insulating substrate 10, intersects the first surface F1 and the second surface F2, and is perpendicular to the first direction in a cross-section including the first electrode 51 (a cross-section illustrated in Figure 3). Of the at least one conductor 60, the conductor 60 closest to the first electrode 51 in the above cross-section is referred to as the first conductor 61. In the wiring board 1, in the above cross-section, the height H1 of the stepped portion 15 in the first direction is smaller than the distance D1 between the first conductor 61 and the first surface F1 in the first direction.

[0011] As shown in Figure 1, the wiring board 1 may be used to mount electronic elements 2. As shown in Figures 2 and 3, the wiring board 1 has a connection area 51A that is suitable for electrical connection with the electronic elements 2. The connection area 51A may be a region set according to the specific design of the wiring board 1. Typically, the connection area 51A may be set in a portion of the uninsulated, electrically conductive portion of the first electrode 51 where an electrical junction can be formed relatively stably. The specific expression for the portion suitable for electrical connection with the electronic elements 2 is not particularly limited, and "connection area" can also be expressed as, for example, an effective area, a joining area, a joining target area, etc. Normally, when mounting or mounting electronic elements 2 on the wiring board 1, the portions of the electrodes formed on the wiring board 1 where an electrical junction can be formed relatively stably are a part of the region that can ideally be used for electrical connection with the electronic elements 2. This is because, in the electrodes formed on the wiring board 1, for example, at the longitudinal ends and near the second inner surface 21 described later, it is difficult to connect the bonding wire to the electrode or to apply solder to the electrode. Therefore, for example, the connection area 51A in this disclosure can be more specifically described as a location at a certain distance from the second inner surface 21 where it is relatively easy to form an electrical junction with the bonding wire or solder.

[0012] In the wiring board 1, the insulating substrate 10 has a stepped portion 15 with a small height difference located between the first surface F1 and the second surface F2. In the examples shown in Figures 1 and 2, the stepped portion 15 is schematically depicted as a vertical stepped surface connecting the first surface F1 and the second surface F2, but as will be described later, the stepped portion 15 does not necessarily have to be vertical. The first surface F1 and the second surface F2 are connected to each other by the step, and the second surface F2 is slightly higher than the first surface F1. The first surface F1, the stepped portion 15, and the second surface F2 are each included in the upper surface 10T of the insulating substrate 10.

[0013] As shown in Figure 3, the first electrode 51 has a first portion 511 located on the first surface F1, a second portion 512 located on the second surface F2, and a third portion 513 located along the stepped portion 15 and connecting the first portion 511 and the second portion 512.

[0014] For example, when an electrode located on the upper surface 2A of an electronic element 2 is electrically connected to a first electrode 51 of a wiring board 1 using a conductive bonding material such as a bonding wire or solder, the following can be said.

[0015] The connection area 51A, which is a region suitable for wire joining or soldering, is set on the first portion 511 of the first electrode 51. The connection area 51A may be a part of the surface of the first portion 511, or a part of the surface of the plating layer covering the first portion 511. When mounting electronic elements 2 on the wiring board 1, for example, a wire joining device or soldering device identifies the spatial position of the connection area 51A and joins a bonding wire or applies solder to the identified connection area 51A. When using the wiring board 1 of this disclosure, the wire joining device or soldering device can detect the position of the third portion 513 relatively easily by optical processing. This is because, in a plan view, the appearance of the third portion 513 is different from that of the first portion 511 and the second portion 512. Alternatively, the wire joining device may detect the position of the stepped portion 15 near the first electrode 51 by optical processing and detect the position of the third portion 513 on the first electrode 51 based on the position of the stepped portion 15. The wire joining device or soldering device can then determine the position of the first portion 511 based on the detected position of the third portion 513. As described above, by using the wiring board 1, the position of the first portion 511 can be determined relatively easily. Therefore, the position of the connection area 51A can be easily determined. As a result, when mounting the electronic element 2 on the wiring board 1, it is easier to stably connect the electrodes and the connection area 51A.

[0016] Furthermore, the following also applies when, for example, the electrode located on the lower surface 2B of the electronic element 2 is electrically connected to the first electrode 51 via a conductive bonding material. That is, by using the wiring board 1, the position of the first portion 511 can be relatively easily determined based on the position of the third portion 513 or the stepped portion 15. Therefore, the position of the connection area 51A can be easily determined. As a result, the electrode of the electronic element 2 and the connection area 51A can be stably connected.

[0017] An electronic module 100 comprising a wiring board 1 and an electronic element 2 in one aspect of this disclosure is also included in the scope of this disclosure. The electronic element 2 may be a light-receiving element such as an image sensor, or a light-emitting element such as a laser diode. The electronic element 2 may be a semiconductor element, a piezoelectric element, a sensor element, a passive element, etc., for example, a CCD (Charge-Coupled Device) element, a CMOS (Complementary Metal-Oxide Semiconductor) element, etc. The electronic element 2 may be a display element such as a liquid crystal display. The electronic element 2 may be a piezoelectric element, a capacitive element, or a passive component such as a resistor. The electronic element 2 may be a semiconductor integrated circuit element, an optoelectronic semiconductor element, a sensor element, a MEMS (Micro electro mechanical system) element, etc. In the electronic module 100, multiple electronic elements 2 of multiple types may be mounted on the wiring board 1.

[0018] The following describes a wiring board 1 in one aspect of this disclosure. For convenience of explanation, the thickness direction (height direction) of the wiring board 1 is referred to as the X-axis direction or the first direction, and viewing an object with a line of sight parallel to the X-axis is referred to as "planar view," while viewing it through perspective is sometimes referred to as "planar perspective." The side on which the frame portion 20 is located relative to the insulating substrate 10 is defined as the upper side (positive X-axis direction side). A YZ plane perpendicular to the X-axis direction is defined, and the Cartesian coordinate system (in other words, the XYZ coordinate system) shown in Figure 1 is introduced. The second direction described above is referred to as the Y-axis direction, and the direction perpendicular to the Y-axis direction is referred to as the Z-axis direction or the third direction. The following description in this specification also defines and explains the XYZ axis directions in the same way, and the XYZ axes are shown in each figure for reference.

[0019] In the wiring board 1, the height H1 of the stepped portion 15 in the first direction (see Figure 3) is defined as follows. That is, in the cross-sectional view illustrated in Figure 3, P1 is the intersection point of the line corresponding to the first surface F1 extending along the second direction and the line corresponding to the stepped portion 15, and P2 is the intersection point of the line corresponding to the second surface F2 extending along the second direction and the line corresponding to the stepped portion 15. The distance between intersection point P1 and intersection point P2 in the first direction can be the height H1 of the stepped portion 15. The stepped portion 15 may be an inclined surface shown as a straight line in the cross-sectional view, or it may be a curved surface shown as a curved line in the cross-sectional view. The stepped portion 15 may be inclined with respect to the first direction and connected to the first surface F1 and the second surface F2, respectively. The specific shape of the stepped portion 15 is not particularly limited.

[0020] The height H1 of the stepped portion 15 may be, for example, 50 μm or less, 1.0 μm or more, or 1.0 μm or more and 50 μm or less. The height H1 may be measured, for example, on the upper surface 10T of the insulating substrate 10 in a portion where the first electrode 51 is not formed. The insulating substrate 10 has a back surface 10U located on the opposite side of the upper surface 10T in the first direction. The height H1 may be defined as the difference between the distance between the second surface F2 and the back surface 10U and the distance between the first surface F1 and the back surface 10U, in other words, the difference between the thickness of the insulating substrate 10 in the portion of the second surface F2 and the thickness of the insulating substrate 10 in the portion of the first surface F1. The thickness of the insulating substrate 10 can be appropriately measured using known measuring means.

[0021] The distance D1 between the first conductor 61 and the first surface F1 in the first direction may be, for example, 30 μm or more, 30 μm or more and 3000 μm or less, and more specifically, 30 μm or more and 500 μm or less. In the example shown in Figure 3, the first conductor 61 may be an inner layer conductor located inside the insulating substrate 10.

[0022] The first electrode 51 may be made of a conductive material, for example, a metallic material. The specific material of the first electrode 51 is not particularly limited. In the examples shown in Figures 1 to 3, the first electrode 51 has a longitudinal shape with the second direction as the longitudinal direction. The thickness of the first electrode 51 may be 5 μm or more and 30 μm or less. The thickness of the first electrode 51 may be less than the height H1 of the stepped portion 15.

[0023] In the wiring board 1, the height H1 of the stepped portion 15 may be greater than the thickness of the first electrode 51 and less than the distance D1. A relatively small height H1 of the stepped portion 15 makes it easier to continuously form the thin first electrode 51 from the first surface F1 through the stepped portion 15 to the second surface F2. However, the height H1 of the stepped portion 15 only needs to be less than the distance D1, and may also be less than the thickness of the first electrode 51.

[0024] The first surface F1 may have higher flatness than the second surface F2. Relatively high flatness may mean, for example, that both the surface roughness and the surface waviness height are relatively small. The surface properties of the first surface F1 are related to the surface properties of the first portion 511 of the first electrode 51. If the first surface F1 has relatively high flatness, it is easier to improve the surface flatness of the first portion 511 of the first electrode 51. It is also easier to improve the bonding strength between the first portion 511 and the first surface F1. Therefore, it is easier to connect the electrode of the electronic element 2 and the connection area 51A more stably.

[0025] The first surface F1 and the second surface F2 may each be planar, or they may be substantially planar with some undulation. The first surface F1 and the second surface F2 may have a slightly curved shape. When the first direction is the vertical direction, the first surface F1 and the second surface F2 may be aligned with the horizontal direction. The first surface F1 and the second surface F2 may be inclined with respect to the horizontal direction. In the first direction, the entirety of the first surface F1 may be lower than the second surface F2. In the first direction, a part of the first surface F1 may be higher than the second surface F2, and even in this case, the wiring board 1 has the effect of making it easier to stably connect the electrodes of the electronic element 2 and the connection area 51A by having the stepped portion 15.

[0026] In the examples shown in Figures 1 to 3, the insulating substrate 10 may have an opening 35 on the first surface F1 that is located on the side opposite to the side connected to the stepped portion 15 on the first surface F1. The insulating substrate 10 may have a bottomed first recess 30. The opening 35 may be an opening in the first recess 30. Having an opening 35 on the first surface F1 provides, for example, the following effects: By having the first recess 30 in the insulating substrate 10, the volume of the insulating substrate 10 is reduced compared to when the first recess 30 is not present, because the spatial volume of the first recess 30 is removed. Therefore, the wiring board 1 can be made lighter. In addition, the electronic module 100 can be made lower in height by housing electronic elements 2 or various components in the opening 35. Note that the first recess 30 does not necessarily have to be bottomed and may penetrate the insulating substrate 10.

[0027] In the examples shown in Figures 1 to 3, the opening 35 has a rectangular shape with rounded corners in plan view, but is not limited to this. The opening 35 may, for example, have a square shape or a polygonal shape in plan view. In that case, the opening 35 may have rounded corners.

[0028] In the examples shown in Figures 1 to 3, the wiring board 1 may have a gap D2 between the first portion 511, which is the part located on the first surface F1 of the first electrode 51, and the opening 35 in a plan view. When mounting the electronic element 2 on the wiring board 1, for example, solder or conductive adhesive is used. By having the above gap D2 in the wiring board 1, the possibility of solder or conductive adhesive dripping into the opening 35 can be reduced. Furthermore, if the above configuration is not provided, that is, if the first electrode 51 extends to the opening 35, the following possibility exists. That is, other components or debris may be positioned to come into contact with the opening 35 and come into contact with the first electrode 51. As a result, the first electrode 51 may be damaged or a short circuit may occur between the other components and the first electrode 51. Furthermore, as in the examples shown in Figures 1 to 3, if the wiring board 1 has multiple other electrodes arranged adjacent to the first electrode 51, the following can be said. In other words, if multiple adjacent electrodes each extend to the opening 35, a short circuit may occur between the electrodes if other components or debris are positioned to come into contact with the opening 35. By using the wiring board 1, the possibility of such a short circuit occurring can be effectively reduced by having a gap D2.

[0029] The spacing D2 may be, for example, 1 μm or more, 1 μm to 2000 μm, 10 μm to 2000 μm, or 50 μm to 1000 μm. The spacing D2 may be measured in a plan view of the wiring board 1, or it may be measured in the cross-section shown in Figure 3. Note that the wiring board 1 does not have to have spacing D2; that is, the first portion 511 of the first electrode 51 and the opening 35 may be in contact.

[0030] In the examples shown in Figures 1 to 3, the insulating substrate 10 may include a first substrate portion 11 and a second substrate portion 12 located on the first substrate portion 11. The upper surface 10T of the insulating substrate 10 may be the upper surface of the second substrate portion 12, and the back surface 10U of the insulating substrate 10 may be the lower surface of the first substrate portion 11. The second substrate portion 12 is provided with a through hole, and the inner wall of the through hole in the second substrate portion 12 is referred to as the first inner surface 32. In the first recess 30, one side of the through hole surrounded by the first inner surface 32 is closed by the first bottom surface 31 of the first substrate portion 11, and the other side of the through hole is an opening 35. The first bottom surface 31 may be included in the upper surface of the first substrate portion 11.

[0031] In the examples shown in Figures 1 to 3, the wiring board 1 may further include a frame portion 20 and an internal conductor 515 on the insulating substrate 10. The frame portion 20 may be located along the outer edge of the insulating substrate 10 in a plan view on the side opposite to the side connected to the stepped portion 15 on the second surface F2. The internal conductor 515 may be located between the insulating substrate 10 and the frame portion 20. The first electrode 51 may pass over the second surface F2 and be connected to the internal conductor 515.

[0032] The internal conductor 515 is positioned overlapping with the frame portion 20 in a planar perspective view. The internal conductor 515 can be connected to various other conductors. Examples of other conductors include branch wiring and other conductors in the same plane, via conductors extending in the first direction, flat plate-shaped conductors with grounding functions, castellations, and side electrodes.

[0033] The wiring board 1 includes a wiring conductor 510. The wiring conductor 510 includes a first electrode 51 and an internal conductor 515 connected to the first electrode 51. The connection of the first electrode 51 to the internal conductor 515 has the following effects. Specifically, by having the internal conductor 515 connect to other conductors in the relatively thicker portion of the wiring board 1, it is easier to improve the strength of the wiring board 1 compared to when the first electrode 51 connects to other conductors in the relatively thinner portion. Furthermore, for example, the first electrode 51 does not have to be connected to a via conductor, which makes it easier to improve the flatness of the first portion 511 located on the first surface F1. As a result, it is easier to improve the flatness of the connection area 51A.

[0034] In the examples shown in Figures 1 to 3, the upper surface 10T of the insulating substrate 10 may be located between the frame portion 20 and the opening 35. The first surface F1 may be located on the upper surface 10T, extending from the stepped portion 15 to the opening 35; in other words, the entire portion of the upper surface 10T between the stepped portion 15 and the opening 35 may be the first surface F1. The side of the frame portion 20 closest to the opening 35 is referred to as the second inner surface 21. The second surface F2 may be located on the upper surface 10T, extending from the stepped portion 15 to the second inner surface 21; in other words, the entire portion of the upper surface 10T between the stepped portion 15 and the second inner surface 21 may be the second surface F2.

[0035] In the examples shown in Figures 1 to 3, the wiring board 1 may have a second recess 40. The second recess 40 is a space enclosed by the frame portion 20, and the bottom of the second recess 40 is formed by the upper surface 10T of the insulating substrate 10 and the opening 35. The second recess 40 is open upward and communicates with the first recess 30 below.

[0036] The second recess 40 and the first recess 30 may constitute a housing space for housing at least a portion of the electronic element 2. The wiring board 1 may have an element mounting area within the housing space. The element mounting area may be an area on which at least one or more electronic elements 2 are mounted, and can be set in various ways depending on the specific manner in which the electronic elements 2 are mounted on the wiring board 1. The electronic element 2 may be joined to the element mounting area via a bonding material such as brazing material, glass, or adhesive, or it may be indirectly mounted to the element mounting area via a member such as a base or a submount substrate. The element mounting area may be a combination of the electronic element 2 and an inorganic substrate, in which case, for example, the electronic element 2 may be mounted on an inorganic substrate, and a submount substrate on which the electronic element 2 is mounted may be joined to the element mounting area. As the submount substrate, an insulating substrate such as an inorganic substrate can be used. The submount substrate may also be referred to as a carrier.

[0037] Furthermore, as shown in the example in Figure 3, the wiring board 1 does not need to have a conductor 60 (inner layer conductor) exposed on the first inner surface 32. Also, the wiring board 1 may have an inner layer conductor within the frame portion 20, in which case the inner layer conductor of the frame portion does not need to be exposed on the second inner surface 21. With this configuration, when electrically connecting the electronic element 2 to the first electrode 51, the possibility of the electronic element 2 coming into contact with a conductor exposed on the second inner surface 21 and causing a short circuit can be reduced.

[0038] Figure 4 is a schematic perspective view showing an enlarged view of region IV shown in Figure 1. As shown in Figure 4, in the wiring board 1, the frame portion 20 is positioned surrounding the opening 35, sandwiching the first surface F1, the stepped portion 15, and the second surface F2, and has a second inner surface 21 that extends along the outer edge of the opening 35. The opening 35 has a shape with a corner portion C1, and the second inner surface 21 includes a curved corner surface 21C that faces the corner portion C1 of the opening 35. The wiring board 1 may have a surface conductor 55 positioned between the corner portion C1 and the curved corner surface 21C that faces the corner portion C1, extending from the first surface F1 through the stepped portion 15 to the second surface F2.

[0039] The surface conductor 55 may be used, for example, as an alignment mark, or for checking electrical connections. The surface conductor 55 may also be a ground conductor. The surface conductor 55 may be electrically connected to the electrodes of the electronic element 2. The applications of the surface conductor 55 are not particularly limited.

[0040] A connection area is also defined for the surface conductor 55, which is a region suitable for electrical connection with other components. The portion of the surface conductor 55 that overlaps with the stepped portion 15 can be detected relatively easily, for example, optically. Therefore, the location of the connection area of ​​the surface conductor 55 can be easily identified. The surface conductor 55 only needs to contain a conductive material. The specific shape of the surface conductor 55 is not particularly limited.

[0041] Figure 5 is a schematic plan view showing the configuration of a wiring board in one embodiment of the present disclosure. As shown in Figure 5, the stepped portion 15 may be positioned at a distance from the opening 35 and surrounding the periphery of the opening 35.

[0042] In the example shown in FIG. 5, the frame portion 20 has an upper surface 20T, and the upper surface 20T has an opening 25. The opening 25 has a shape with a corner portion C2. In the example shown in FIG. 5, the opening 25 has a rectangular shape with rounded corners in plan view, but is not limited thereto. The opening 25 may have, for example, a square shape or a polygonal shape in plan view. The opening 25 may have a shape with rounded corners. In plan view, the corner portion C2 may be positioned opposite to the corner portion C1 across the upper surface 10T. In plan view, a surface conductor 55 may be positioned between the corner portion C1 and the corner portion C2.

[0043] In the example shown in FIG. 5, the opening 35 includes a first base side S11 extending in the second direction and a second base side S12 extending in the third direction, and the first base side S11 and the second base side S12 are connected by a corner portion C1. The opening 35 may be constituted by two first base sides S11 parallel to each other, two second base sides S12 parallel to each other, and four corner portions C1. The first base side S11 and the second base side S12 may be linear or substantially linear.

[0044] Also, in the example shown in FIG. 5, the opening 25 includes a first frame side S21 extending in the second direction and a second frame side S22 extending in the third direction, and the first frame side S21 and the second frame side S22 are connected by a corner portion C2. The opening 也可以由彼此平行的两个第一框架边S21、彼此平行的两个第二框架边S22和四个角部C2构成。第一框架边S21和第二框架边S22可以是直线状的,或者是大致直线状的。开口25可以与开口35具有相似形状,或者具有类似形状。

[0045] The second inner surface 21 of the frame portion 20 includes a first frame surface 211, which is connected to the first frame edge S21 and extends downward from the first frame edge S21 until it contacts the upper surface 10T of the insulating substrate 10, and a second frame surface 212, which is connected to the second frame edge S22 and extends downward from the second frame edge S22 until it contacts the upper surface 10T of the insulating substrate 10. The angular curved surface 21C is located between the first frame surface 211 and the second frame surface 212 and connects the first frame surface 211 and the second frame surface 212. The angular curved surface 21C may, for example, have a curved shape that is recessed in the direction away from the opening 35 in a plan view. The second inner surface 21 may be composed of a set of two first frame surfaces 211 extending in the second direction, a set of two second frame surfaces 212 extending in the third direction, and four angular curved surfaces 21C.

[0046] The stepped portion 15 may include a first linear portion 151 extending linearly along a second direction, a second linear portion 152 extending linearly along a third direction, and a curved portion 15C connecting the first linear portion 151 and the second linear portion 152. The stepped portion 15 may be composed of two first linear portions 151, two second linear portions 152, and four curved portions 15C. The first linear portions 151 and the second linear portions 152 may each be straight in plan view. The curved portions 15C may be curved in plan view.

[0047] In a plan view, the distance between the second linear portion 152 and the second base edge S12 in the second direction is denoted as D3. The distance D3 may be, for example, 50 μm or more, 100 μm or more and 5000 μm or less, or 500 μm or more and 3000 μm or less. The distance D3 may be 70% or more and 95% or less of the distance between the second base edge S12 and the second frame edge S22 in a plan view. The distance between the first linear portion 151 and the first base edge S11 may be the same as the above distance D3.

[0048] As shown in FIG. 5, the wiring board 1 may include a first electrode group 51G composed of a plurality of first electrodes 51 arranged in the third direction. Further, the wiring board 1 may include a longitudinal second electrode 52 having the third direction as its longitudinal direction. The second electrode 52 may have the same configuration as the first electrode 51 except that the extending direction is different, and repeated description thereof will be omitted. The wiring board 1 may include a second electrode group 52G composed of a plurality of second electrodes 52 arranged in the second direction.

[0049] The wiring board 1 may include a third electrode group 53G composed of a plurality of electrodes. The third electrode group 53G may be located on the upper surface 10T on the opposite side of the second direction across the opening 25 from the first electrode group 51G. The third electrode group 53G may have the same configuration as the first electrode group 51G. Further, the wiring board 1 may include a fourth electrode group 54G composed of a plurality of electrodes. The fourth electrode group 54G may be located on the upper surface 10T on the opposite side of the third direction across the opening 25 from the second electrode group 52G. The fourth electrode group 54G may have the same configuration as the second electrode group 52G.

[0050] In the example shown in FIG. 5, the wiring board 1 has a shape in which the opening 35 has straight portions (first base side S11, second base side S12) that extend linearly in a plan view, and the stepped portion 15 has linear portions (first linear portion 151, second linear portion 152) that extend linearly at positions facing the straight portions in a plan view. The distance between the straight portion and the linear portion of the wiring board 1 may be constant. Specifically, for example, the wiring board 1 may have a constant distance from the first linear portion 151 at any position on the first base side S11. Further, for example, the wiring board 1 may have a constant distance from the second linear portion 152 at any position on the second base side S12. According to the above configuration, for example, when the first electrode group 51G is provided, it is easy to balance the connection areas 51A of the respective first electrodes 51 in the first electrode group 51G. Therefore, it is easy to reduce the possibility that the electronic element 2 is mounted unevenly in a plan view.

[0051] Figure 5 shows an example in which the stepped portion 15 is continuously positioned around the periphery of the opening 35 between the opening 35 and the frame portion 20, but is not limited to this. In the wiring board 1, the stepped portion 15 may be located in a part of the periphery of the opening 35.

[0052] Figure 6 is a schematic cross-sectional view showing the configuration of a wiring board in one embodiment of the present disclosure. In the cross-section illustrated in Figure 6, the width L1 of the first portion 511 located on the first surface F1 of the first electrode 51 may be larger than the width L2 of the second portion 512 located on the second surface F2. Widths L1 and L2 are lengths in the second direction, respectively. With the above configuration, it is relatively easy to secure a large connection area 51A set in the first portion 511.

[0053] As shown in Figure 6, in a planar view, the wiring board 1 does not need to have at least one conductor 60 positioned between the first electrode 51 and the opening 35. With this configuration, when the electrode or bonding wire of the electronic element 2 is connected to the first portion 511 of the first electrode 51, the amount of capacitance component generated can be easily reduced.

[0054] In the wiring board 1, at least one conductor 60 may include an inner layer conductor 65 located inside the insulating substrate 10. In the example shown in Figure 6, the conductor closest to the first electrode 51 in the first direction among the inner layer conductors 65 is the first conductor 61. In the cross-section illustrated in Figure 6, the distance L4 between the inner layer conductor 65 and the opening 35 in the second direction is greater than the distance L3 between the first electrode 51 and the opening 35 in the second direction. With the above configuration, it is possible to bring the first electrode 51 as close as possible to the electronic element 2 mounted on the wiring board 1. Also, the portion between the end of the inner layer conductor 65 and the opening 35 on the first surface F1 is defined as the empty space F12. The portion of the insulating substrate 10 that overlaps with the empty space F12 in a planar perspective view is defined as region A1. In region A1 of the insulating substrate 10, the insulating layer is continuous in the first direction without any conductors between the layers; in other words, the materials constituting each layer are continuous in the first direction, which makes it easier to improve the strength of region A1.

[0055] In Figure 6, the first direction is the vertical direction, and a horizontal virtual line HL passing through the lower end of the stepped portion 15 is shown. The first surface F1 may be inclined such that the portion away from the stepped portion 15 in the second direction is located below the virtual line HL. The inclination angle of the first surface F1 with respect to the virtual line HL may be 4° or less. The inclination angle of the first surface F1 with respect to the virtual line HL may be greater than 0° and 4° or less. The first surface F1 may have an inclined shape due to the effects of, for example, thermal shrinkage during manufacturing or stress when laminating and pressing each layer.

[0056] In the cross-section illustrated in Figure 6, the distance T2 in the first direction from the lower end of the stepped portion 15 to the back surface 10U of the insulating substrate 10 may be greater than the distance T1 in the first direction from the opening 35 of the first surface F1 to the back surface 10U. The lower end of the stepped portion 15 may be the aforementioned intersection P1 (see Figure 3). A relatively large distance T2, in other words, a relatively large thickness of the insulating substrate 10 below the stepped portion 15, makes it easier to increase the strength of the wiring board 1. Also, a relatively small distance T1 reduces the volume of the portion of the insulating substrate 10 located below the first surface F1, and also reduces the surface area of ​​the first inner surface 32. Here, the rate of reduction in the volume of the portion of the insulating substrate 10 located below the first surface F1 is greater than the rate of reduction in the surface area of ​​the first inner surface 32. Therefore, the ratio of surface area to volume (mass) can be made relatively large. As a result, it is easier to improve the heat dissipation of the wiring board 1. Therefore, in an electronic module 100 in which electronic elements 2 are mounted on a wiring board 1, the heat generated when the electronic elements 2 are driven can be easily dissipated.

[0057] The insulating substrate 10 has a first inner surface 32 that connects to the first surface F1 at the periphery of the opening 35, and the first inner surface 32 may be curved in a cross-section (a cross-section illustrated in Figure 6) when the insulating substrate 10 is cut in a plane parallel to the first direction. The first inner surface 32 being curved means that the position of the first inner surface 32 in the second direction changes depending on its position in the first direction. The curved shape of the first inner surface 32 is the shape observed in a cross-sectional view. The first inner surface 32 may have a gently uneven shape. The first inner surface 32 may include a portion that is convex toward the inside of the opening 35, and may include a portion that is convex toward the direction in which the stepped portion 15 is located (a recessed portion), and may include both of the above two portions. For example, the upper portion of the first inner surface 32 may be convex toward the direction in which the stepped portion 15 is located, while the lower portion of the first inner surface 32 may be convex toward the inside of the opening 35.

[0058] The curvature of the first inner surface 32 makes it easier to recognize the first inner surface 32 when it is imaged from above with a camera or the like, compared to when the first inner surface 32 is vertical. Therefore, it is easier to stably mount the electronic elements 2 onto the wiring board 1. In addition, the increased surface area of ​​the first inner surface 32 makes it easier to improve heat dissipation. When a photodetector or light-emitting element is mounted on the wiring board 1 as the electronic element 2, light is scattered by the first inner surface 32. Therefore, it is easier to reduce the possibility of stray light entering the electronic element 2 at a specific reflection angle. The first inner surface 32 may have a curved shape due to, for example, thermal shrinkage during manufacturing or stress when laminating and pressing each layer.

[0059] In the example shown in Figure 6, the frame portion 20 has a second inner surface 21 located on the side closer to the second surface F2, and in the cross-section (the cross-section illustrated in Figure 6) obtained by cutting the wiring board 1 with a plane parallel to the first direction, the second inner surface 21 may be curved. The curvature of the second inner surface 21 means that the position of the second inner surface 21 in the second direction changes depending on its position in the first direction. The curved shape of the second inner surface 21 is the shape observed in cross-sectional view. The second inner surface 21 may have a gently uneven shape. The second inner surface 21 may include a convex portion toward the direction in which the stepped portion 15 is located, and may include a convex portion (recessed portion) toward the direction away from the stepped portion 15, and may include both of the above two portions. The curvature of the second inner surface 21 has the same effect as the curvature of the first inner surface 32. The second inner surface 21 may have a curved shape due to, for example, thermal shrinkage during manufacturing or stress when laminating and pressing each layer together.

[0060] The thickness of the frame portion 20 is greater than the height H1 of the stepped portion 15. The thickness of the frame portion 20 may also be greater than the thickness of the insulating substrate 10 (distance T1, distance T2).

[0061] Figure 7 is a schematic cross-sectional view showing the cross-section of line VII-VII shown in Figure 2. As shown in Figure 7, in one embodiment of the present disclosure, the wiring board 1 includes, for example, a plurality of stacked insulating layers, and may have inner layer conductors 65 between the plurality of insulating layers. The insulating layers may include, for example, electrically insulating ceramics or resin. The specific material of the inner layer conductors 65 is not particularly limited. In the wiring board 1, the distance D5 from the second surface F2 to the first conductor 61 may be greater than the distance D1 from the first surface F1 to the first conductor 61. In the insulating substrate 10, the upper surface 10T may be part of the surface of one insulating layer, that is, the first surface F1, the stepped portion 15, and the second surface F2 may be surfaces of a common insulating layer.

[0062] Distance D1 may be defined in a cross-section exemplified in Figure 7 that does not include the first electrode 51. Distance D5 may be defined in a cross-section that includes the first electrode 51 (see Figure 3), or in a cross-section that does not include the first electrode 51 (see Figure 7). The first electrode 51 and the first conductor 61 may or may not overlap each other in a planar perspective view. The first conductor 61 may overlap the entire surface of the first electrode 51 in a planar perspective view, or it may overlap a part of the first electrode 51.

[0063] The frame portion 20 may be an insulator, and may, for example, include a plurality of laminated insulating layers. The frame portion 20 may be a single insulating layer. The frame portion 20 may be made of the same material as the insulating substrate 10, may contain the same material as the insulating substrate 10, or may contain a different material from the insulating substrate 10.

[0064] The insulating substrate 10 does not necessarily have an inner layer conductor 65 in the second substrate portion 12. The insulating substrate 10 may have at least one conductor 60 (inner layer conductor 65) in the first substrate portion 11, and even in this case, the conductor 60 closest to the first electrode 51 can be designated as the first conductor 61.

[0065] The method for manufacturing the wiring board 1 in one embodiment of this disclosure is not particularly limited, as long as it can form an insulating substrate 10 having stepped portions 15. The wiring board 1 may be formed, for example, by sintering. The wiring board 1 does not need to have a clear boundary between the first substrate portion 11 and the second substrate portion 12. Also, there does not need to be a clear boundary between the insulating substrate 10 and the frame portion 20.

[0066] If the wiring board 1 is a ceramic substrate, for example, a ceramic substrate can be manufactured by laminating and firing green sheets that have been processed by punching or cutting. For example, an insulating base 10 may be formed by processing a green sheet to have a shape corresponding to the upper surface 10T and firing the green sheet. Alternatively, for example, a stepped portion 15 may be formed on the insulating base 10 after firing by processing such as polishing, or a stepped portion 15 may be formed by partially pressing the portion that will become the first surface F1 after laminating the green sheets but before firing. The first base portion 11 and the second base portion 12 may be integral with each other. In this disclosure, integral with each other means that there is no boundary, and includes, for example, a case where each insulating layer is sintered so that the boundary between each insulating layer is not discernible.

[0067] Figure 8 is a schematic cross-sectional view showing the configuration of a wiring board in one embodiment of the present disclosure. In the example shown in Figure 8, the wiring board 1 does not necessarily have a conductor 60 (inner layer conductor 65) within the insulating substrate 10. The wiring board 1 may have an external electrode 58 located on the back surface 10U, in which case the external electrode 58 may be the first conductor 61. Even in this case, the presence of the stepped portion 15 makes it easier to stably connect the electrode of the electronic element 2 (see Figure 1) to the connection area 51A. The external electrode 58 and the first electrode 51 may be connected by vias extending in a first direction within the insulating substrate 10.

[0068] Figure 9 is a schematic cross-sectional view showing the configuration of a wiring board in one embodiment of the present disclosure. In the example shown in Figure 9, the insulating substrate 10 may be, for example, an integrally formed member (a single unit). A frame portion 20 may be joined to the insulating substrate 10. An external electrode 58 located on the back surface 10U may be the first conductor 61. The insulating substrate 10 may have a first recess 30, or it may have a through hole penetrating from the upper surface 10T to the back surface 10U.

[0069] Figure 10 is a schematic cross-sectional view showing the configuration of a wiring board in one embodiment of the present disclosure. As shown in Figure 10, the wiring board 1 may further include a first coating layer 70 that covers at least a portion of the first electrode 511 located on the first surface F1. The first coating layer 70 may contain a different metallic material than the first electrode 51. The first coating layer 70 may be, for example, a plating layer. The plating layer may be, for example, a layer containing gold (Au) or platinum (Pt), and the specific material is not particularly limited.

[0070] The connection area 51A may be set on the surface of the first coating layer 70 located on the first portion 511. For example, if the first coating layer 70 has a glossy metal (such as Au or Pt) on its surface, the visibility of the connection area 51A can be further improved. This makes it easier to connect the electrode of the electronic element 2 (see Figure 1) to the connection area 51A more stably. In addition, the possibility of oxidation or corrosion occurring on the first electrode 51 can be effectively reduced.

[0071] The first coating layer 70 may have, for example, a two-layer structure, in which case a total of three layers consisting of the first portion 511 and the first coating layer 70 may be laminated on the first surface F1.

[0072] As shown in the example in Figure 10, the wiring board 1 may further include an insulating coating layer 80 that covers at least the second portion 512. The insulating coating layer 80 may extend between the frame portion 20 and the insulating substrate 10 and may be in contact with at least a portion of the internal conductor 515. The insulating coating layer 80 may be in contact with the lower end of the second inner surface 21. The insulating coating layer 80 may cover the second portion 512 and the third portion 513, in which case the first coating layer 70 does not have to cover the third portion 513. In other words, the first coating layer 70 covers the first electrode 51 in the portion closer to the opening 35 than the stepped portion 15. By providing the insulating coating layer 80, the exposed area of ​​the first electrode 51 can be reduced. Therefore, the possibility of oxidation or corrosion occurring on the first electrode 51 can be reduced more effectively. The first coating layer 70 may be connected to the insulating coating layer 80. The insulating coating layer 80 may be made of an insulating material. The insulating coating layer 80 may contain electrically insulating ceramics or resin. The insulating coating layer 80 may be made of the same material as the wiring board 1.

[0073] Furthermore, by providing the insulating coating layer 80, even if a conductive substance adheres to the second inner surface 21, the insulating coating layer 80 in contact with the second inner surface 21 covers a portion of the first electrode 51, thereby reducing the possibility of a short circuit occurring between the first electrode 51 and another electrode or wiring conductor. Also, if plating is applied to various conductors provided on the wiring board 1, even if the plating material extends along the second inner surface 21, the possibility of a short circuit occurring between the first electrode 51 and another electrode or wiring conductor can be reduced. Moreover, because a portion of the first electrode 51 is covered by a portion of the insulating coating layer 80, the first electrode 51 is less likely to peel off from the upper surface 10T.

[0074] Figure 11 is a schematic cross-sectional view showing the configuration of a wiring board in one embodiment of the present disclosure. As shown in Figure 11, in the wiring board 1, the first coating layer 70 continuously covers the first portion 511 located on the first surface F1 and the third portion 513 located on the stepped portion 15 of the first electrode 51, and may also continuously cover a part of the second portion 512 located on the second surface F2 from the third portion 513 located on the stepped portion 15. With the above configuration, it is easy to enlarge the range of the connection area 51A on the first surface F1.

[0075] In the example shown in Figure 11, the insulating coating layer 80 covers a portion of the second portion 512 from the boundary between the frame portion 20 and the second portion 512. The insulating coating layer 80 does not need to cover the third portion 513. This makes it possible to secure a large area of ​​the connection area 51A on the first surface F1 while reducing the possibility of oxidation or corrosion occurring on the first electrode 51.

[0076] (Other configuration examples) (a) The wiring board 1 does not have to have a frame portion 20. Even in this case, having a stepped portion 15 makes it easier to stably connect the electrodes of the electronic element 2 (see Figure 1) to the connection area 51A.

[0077] (b) In a planar perspective view, the entirety of the second base portion 12 of the wiring board 1 may overlap with the first base portion 11. The outer edge of the second base portion 12 may be aligned with the outer edge of the first base portion 11. The portion of the upper surface of the first base portion 11 that is not in contact with the second base portion 12 may form the first bottom surface 31 of the first recess 30. For example, in a planar perspective view, the area of ​​the second base portion 12 of the wiring board 1 may be 10% or more and 90% or less of the area of ​​the first base portion 11 in a planar perspective view.

[0078] (c) Figure 12 is a schematic perspective view showing the configuration of a wiring board in one embodiment of the present disclosure. As shown in Figure 12, the wiring board 1 may further include an upper conductor 90 located on the upper surface 20T of the frame portion 20. The upper conductor 90 may be positioned to surround the opening 25 of the frame portion 20. The use of the upper conductor 90 is not particularly limited. For example, if the upper conductor 90 surrounds the opening 25, it may be used as a sealing ring, or as an electrode for connecting to a capacitor or control circuit element, etc.

[0079] (d) In one embodiment of the present disclosure, the wiring board 1 may have an opening instead of the first recess 30. In this case, the wiring board 1 may have a through hole in the insulating substrate 10 that penetrates the first substrate portion 11 and the second substrate portion 12 as an opening.

[0080] [Additional Notes] The inventions described herein have been explained above based on the drawings and embodiments (example configurations). However, the inventions described herein are not limited to the embodiments described above. That is, the inventions described herein can be modified in various ways within the scope shown in this disclosure, and embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included in the technical scope of the inventions described herein. In other words, it should be noted that it is easy for those skilled in the art to make various modifications or alterations based on this disclosure. Furthermore, it should be noted that these modifications or alterations are included in the scope of this disclosure.

[0081] [Summary] The wiring board in embodiment 1 of the present disclosure comprises an insulating substrate having a first surface, a second surface, and a stepped portion connected to the first surface and the second surface; a first electrode located from the first surface through the stepped portion and extending to the second surface; and at least one conductor extending along a second direction parallel to a first direction which is the thickness direction of the insulating substrate, intersecting the first surface and the second surface, and perpendicular to the first direction in a cross-section including the first electrode, wherein in the cross-section, the height of the stepped portion in the first direction is smaller than the distance in the first direction between the first conductor, which is the first conductor closest to the first electrode, and the first surface.

[0082] In embodiment 2 of the present disclosure, the wiring board, in embodiment 1, has an opening on the first surface that is located on the side opposite to the side connected to the stepped portion on the first surface.

[0083] In embodiment 3 of the present disclosure, the wiring board, in embodiment 2, has a gap between the portion of the first electrode located on the first surface and the opening in a plan view.

[0084] The wiring board in embodiment 4 of the present disclosure further comprises, in any one embodiment of embodiments 1 to 3, a frame portion located on the insulating substrate on the side opposite to the side connected to the stepped portion on the second surface, along the outer edge of the insulating substrate in a plan view, and an internal conductor located between the insulating substrate and the frame portion, wherein the first electrode passes over the second surface and is connected to the internal conductor.

[0085] In embodiment 5 of the present disclosure, the wiring board, in any one embodiment of embodiments 2 to 4, has a first inner surface that connects to the first surface at the periphery of the opening, and in the cross-section obtained by cutting the wiring board with a plane parallel to the first direction, the first inner surface is curved.

[0086] In embodiment 6 of the present disclosure, the wiring board is such that, in any one embodiment of embodiments 1 to 5, the width of the portion of the first electrode located on the first surface is greater than the width of the portion located on the second surface in the cross-section.

[0087] In the wiring board of embodiment 7 of the present disclosure, in any one of embodiments 3 to 6 (referencing embodiment 3), the at least one conductor is not located between the first electrode and the opening in a planar perspective view.

[0088] The wiring board in embodiment 8 of the present disclosure, in any one embodiment of embodiments 3 to 7 (referencing embodiment 3), wherein the at least one conductor includes an inner layer conductor located inside the insulating substrate, and in the cross-section, the distance in the second direction between the inner layer conductor and the opening is greater than the distance in the second direction between the first electrode and the opening.

[0089] In embodiment 9 of the present disclosure, in any one of embodiments 2 to 8 (referencing embodiment 2), the wiring board is such that, in the cross-section, the distance in the first direction from the lower end of the stepped portion to the back surface of the insulating substrate is greater than the distance in the first direction from the opening on the first surface to the back surface.

[0090] In any one embodiment of embodiments 1 to 9, the wiring board further comprises a first coating layer that covers at least a portion of the portion of the first electrode located on the first surface, wherein the first coating layer contains a metallic material different from that of the first electrode.

[0091] The wiring board in embodiment 11 of the present disclosure, in any one embodiment of embodiments 4 to 10 (referencing embodiment 4), wherein the frame portion, in a plan view, is positioned to surround the opening, sandwiching the first surface, the stepped portion, and the second surface, and has a second inner surface extending along the outer edge of the opening, the opening having a corner, the second inner surface including a curved corner surface facing the corner of the opening, and between the corner and the curved corner surface facing the corner, there is a surface conductor positioned from the first surface through the stepped portion and onto the second surface.

[0092] In embodiment 12 of the present disclosure, the wiring board, in any one of embodiments 4 to 11 (referencing embodiment 4), has a frame portion having a second inner surface located on the side closer to the second surface, and in the cross-section obtained by cutting the wiring board with a plane parallel to the first direction, the second inner surface is curved.

[0093] In embodiment 13 of the present disclosure, the wiring board, in any one of embodiments 2 to 12 (referencing embodiment 2), has an opening that, in plan view, has a linear portion extending in a straight line, and the stepped portion has a linear portion extending in a straight line at a position opposite the linear portion in plan view, and the distance between the linear portion and the linear portion is constant.

[0094] In embodiment 14 of the present disclosure, the wiring board, in any one of embodiments 10 to 13 (referencing embodiment 10), has a first coating layer that continuously covers the portion of the first electrode located on the first surface and the portion located on the stepped portion, and also continuously covers a portion of the portion located on the second surface from the portion located on the stepped portion.

[0095] The electronic module in embodiment 15 of the present disclosure comprises a wiring board in any one of embodiments 1 to 14 and an electronic element.

[0096] 1 Wiring board 2 Electronic element 2A Top surface 2B Bottom surface 10 Insulating substrate 10T Top surface 10U Back surface 11 First base portion 12 Second base portion 15 Step portion 15C Curved portion 151 First linear portion 152 Second linear portion 20 Frame portion 20T Top surface 21 Second inner surface 21C Corner curved surface 211 First frame surface 212 Second frame surface 25 Opening 30 First recess 31 First bottom surface 32 First inner surface 35 Opening 40 Second recess 51 First electrode 51A Connection area 51G First electrode group 510 Wiring conductor 511 First portion 512 Second portion 513 Third portion 515 Internal conductor 52 Second electrode 52G Second electrode group 53G Third electrode group 54G Fourth electrode group 55 Surface conductor 58 External electrode 60 Conductor 61 First conductor 65 Inner layer conductor 70 First coating layer 80 Insulating coating layer 90 Upper conductor 100 Electronic module A1 Region C1, C2 Corner F1 First surface F2 Second surface F12 Spare area HL Virtual lines P1, P2 Intersection S11 First base S12 Second base S21 First frame edge S22 Second frame edge

Claims

1. A wiring board comprising: an insulating substrate having a first surface, a second surface, and stepped portions connected to the first surface and the second surface; a first electrode located from the first surface through the stepped portion and extending to the second surface; and at least one conductor extending along a second direction parallel to a first direction which is the thickness direction of the insulating substrate, intersecting the first surface and the second surface, and perpendicular to the first direction in a cross-section including the first electrode, wherein in the cross-section, the height of the stepped portion in the first direction is less than the distance in the first direction between the first conductor, which is the first conductor closest to the first electrode, and the first surface.

2. The wiring board according to claim 1, wherein the insulating substrate has an opening on the first surface that is located on the side opposite to the side connected to the stepped portion on the first surface.

3. The wiring board according to claim 2, wherein, in a plan view, there is a gap between the portion of the first electrode located on the first surface and the opening.

4. The wiring board according to claim 2 or 3, further comprising: a frame portion located on the insulating substrate on the side opposite to the side connected to the stepped portion on the second surface, along the outer edge of the insulating substrate in a plan view; and an internal conductor located between the insulating substrate and the frame portion, wherein the first electrode passes over the second surface and is connected to the internal conductor.

5. The wiring board according to any one of claims 2 to 4, wherein the insulating substrate has a first inner surface that connects to the first surface at the periphery of the opening, and in a cross-section obtained by cutting the wiring board in a plane parallel to the first direction, the first inner surface is curved.

6. The wiring board according to any one of claims 1 to 5, wherein, in the cross-section, the width of the portion located on the first surface of the first electrode is greater than the width of the portion located on the second surface.

7. The wiring board according to claim 3, wherein, in a planar perspective view, the at least one conductor is not located between the first electrode and the opening.

8. The wiring board according to claim 3, wherein the at least one conductor includes an inner layer conductor located inside the insulating substrate, and in the cross-section, the distance between the inner layer conductor and the opening in the second direction is greater than the distance between the first electrode and the opening in the second direction.

9. The wiring board according to any one of claims 2 to 5, 7, or 8, wherein, in the cross-section, the distance in the first direction from the lower end of the stepped portion to the back surface of the insulating substrate is greater than the distance in the first direction from the opening on the first surface to the back surface.

10. The wiring board according to any one of claims 1 to 9, further comprising a first coating layer that covers at least a portion of the portion of the first electrode located on the first surface, wherein the first coating layer contains a metal material different from that of the first electrode.

11. The wiring board according to claim 4, wherein the frame portion, in a plan view, is positioned to surround the opening, sandwiching the first surface, the stepped portion, and the second surface, and has a second inner surface extending along the outer edge of the opening, the opening has a shape with corners, the second inner surface includes a curved corner surface facing the corner of the opening, and a surface conductor is provided between the corner and the curved corner surface facing the corner, extending from the first surface through the stepped portion to the second surface.

12. The wiring board according to claim 4, wherein the frame portion has a second inner surface located on the side closer to the second surface, and in the cross-section obtained when the wiring board is cut in a plane parallel to the first direction, the second inner surface is curved.

13. The wiring board according to any one of claims 2 to 5, 7 to 9, 11, or 12, wherein the opening has a shape having a linear portion extending in a straight line in a plan view, the stepped portion has a linear portion extending in a straight line at a position opposite the linear portion in a plan view, and the distance between the linear portion and the linear portion is constant.

14. The wiring board according to claim 10, wherein the first coating layer continuously covers the portion of the first electrode located on the first surface and the portion located on the stepped portion, and continuously covers a portion of the portion located on the second surface from the portion located on the stepped portion.

15. An electronic module comprising a wiring board according to any one of claims 1 to 14 and an electronic element.

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