Wiring board and semiconductor device

Abstract

This wiring board comprises an insulation board, a first electrode, a first conductor, a second conductor, and a second electrode. The insulation board has a first surface and a second surface which is located opposite to the first surface. The insulation board includes a first base material which contains ceramic, and a second base material which contains an organic resin and is joined to the first base material. The first electrode is located on the first base material and electrically connected to an electronic element. The first conductor extends from the first electrode to the inside of the first base material. The second conductor is located in the second base material and electrically connected to the first conductor. The second electrode is electrically connected to the first electrode via at least the first conductor, among the first conductor and the second conductor. The first conductor contains a first metal. The second conductor contains a second metal which is different from the first metal. The electric resistivity of the first metal is higher than that of the second metal.

Description

Wiring board and semiconductor device

[0001] The present disclosure relates to a wiring substrate and a semiconductor device.

[0002] 2. Description of the Related Art Conventionally, wiring boards having a base material made of ceramic have been known (see Patent Document 1).

[0003] Patent No. 5491628

[0004] The wiring board of the present disclosure includes an insulating substrate, a first electrode, a first conductor, a second conductor, and a second electrode. The insulating substrate has a first surface and a second surface opposite the first surface. The insulating substrate includes a first substrate containing a ceramic and a second substrate containing an organic resin and bonded to the first substrate. The first electrode is located on the first substrate and electrically connected to an electronic element. The first conductor extends from the first electrode into the first substrate. The second conductor is located in the second substrate and electrically connected to the first conductor. The second electrode is electrically connected to the first electrode via at least the first conductor of the first and second conductors. The first conductor includes a first metal. The second conductor includes a second metal different from the first metal. The electrical resistivity of the first metal is higher than the electrical resistivity of the second metal.

[0005] FIG. 1 is a perspective view showing an example of the configuration of a wiring board according to an embodiment. FIG. 2 is a plan view showing an example of the configuration of a wiring board according to an embodiment. FIG. 3 is a cross-sectional view taken along the arrows A-A shown in FIG. 1. FIG. 4 is a cross-sectional view showing an example of the configuration of a first conductor, a second conductor, and a third conductor. FIG. 5 is an explanatory diagram illustrating the transfer of heat between a first conductor and a first base material. FIG. 6 is a cross-sectional view showing an example of the configuration of a wiring board according to an embodiment. FIG. 7 is a cross-sectional view showing an example of the configuration of a wiring board according to an embodiment. FIG. 8 is a cross-sectional view showing an example of the configuration of a semiconductor device according to an embodiment.

[0006] Hereinafter, embodiments for carrying out a wiring board and a semiconductor device according to the present disclosure (hereinafter referred to as "embodiments") will be described in detail with reference to the drawings. Note that the present disclosure is not limited to these embodiments. Furthermore, the embodiments can be appropriately combined as long as the processing content is not contradictory. Furthermore, the same components in the following embodiments will be assigned the same reference numerals, and redundant explanations will be omitted.

[0007] In addition, in the drawings referred to below, to make the explanation easier to understand, an orthogonal coordinate system may be shown in which the X-axis direction, Y-axis direction, and Z-axis direction, which are perpendicular to each other, are defined, and the Z-axis direction is the thickness direction of the wiring board.

[0008] The above-mentioned conventional techniques have room for further improvement in terms of weight reduction.

[0009] The present disclosure provides a technique that can reduce the weight of a wiring board.

[0010] <Embodiments> Fig. 1 is a perspective view showing an example of the configuration of a wiring board according to an embodiment. Fig. 2 is a plan view showing an example of the configuration of a wiring board according to an embodiment. Fig. 3 is a cross-sectional view taken along line A-A shown in Fig. 1. Fig. 4 is a cross-sectional view showing an example of the configuration of a first conductor, a second conductor, and a third conductor.

[0011] As shown in FIGS. 1 to 4, the wiring board 100 according to the embodiment includes an insulating substrate 101, a first conductor 30, a second conductor 40, a first electrode 15, and a second electrode 65.

[0012] The insulating substrate 101 may be a laminate including a first substrate 10 and a second substrate 20. The insulating substrate 101 has a first surface 102 and a second surface 103 located on the opposite side of the first surface 102. The first substrate 10 contains ceramic. The second substrate 20 contains an organic resin. Detailed configurations of the first conductor 30, the second conductor 40, the first electrode 15, and the second electrode 65 will be described later with reference to FIGS. 3 and 4 .

[0013] In this embodiment, the plan view refers to a plan view seen from a direction perpendicular to the third surface 11 of the insulating substrate 101, and is a concept that includes a planar perspective view in which some components are seen through from the Z direction. In addition, the horizontal direction in this disclosure refers to the XY plane direction.

[0014] The wiring substrate 100 may be, for example, a polygonal shape such as a rectangle in plan view, or may be a shape including a curved surface such as a circle or an ellipse. The wiring substrate 100 may also have a through hole 110 in the center or a position offset from the center in plan view, or may have a recessed portion that does not penetrate through. The through hole 110 or the recessed portion may be a polygonal shape such as a rectangle in plan view, or may be a shape including a curved surface such as a circle or an ellipse. The through hole 110 or the recessed portion may be configured such that the second surface 103 side is larger in the horizontal direction than the first surface 102 side. Without being limited to the above, the wiring substrate 100 may be configured without the through hole 110 or the recessed portion.

[0015] Ceramics have higher rigidity than organic materials. Therefore, a wiring substrate 100 composed of a first substrate 10 containing ceramic and a second substrate 20 containing an organic material can improve rigidity and suppress warping compared to a wiring substrate composed only of organic materials. This makes it easy to ensure the rigidity of the wiring substrate 100, even if the wiring substrate 100 is made thin, without adding reinforcing members or the like. Furthermore, the through-hole 110 is surrounded by the highly rigid first substrate 10. This makes it possible to make the wiring substrate 100 less susceptible to distortion even when the wiring substrate 100 has a through-hole 110.

[0016] Furthermore, the wiring substrate 100 can be made lighter because the volumes of the first substrate 10 and the second substrate 20 can be reduced by the amount of the through holes 110. Furthermore, when the electronic element 310 (see FIG. 8 ) mounted on the wiring substrate 100 is a light-receiving element such as an image sensor, light can be irradiated onto the light-receiving element through the through holes 110. Alternatively, when the electronic element 310 (see FIG. 8 ) mounted on the wiring substrate 100 is a light-emitting element such as a semiconductor laser, light can be irradiated from the light-emitting element through the through holes 110. This configuration improves design flexibility. For example, even if a light-receiving element or a light-emitting element is disposed on the opposite side of the insulating substrate 101 from the source or destination of light irradiation, light can be irradiated onto the light-receiving element or light can be irradiated from the light-emitting element.

[0017] <First Substrate> The first substrate 10 may contain ceramic or may be primarily composed of ceramic. Examples of ceramic include ceramics primarily composed of at least one selected from the group consisting of aluminum oxide, silicon oxide, zirconium oxide, silicon carbide, silicon nitride, and aluminum nitride, or ceramics primarily composed of a composite oxide such as mullite, zircon, steatite, enstatite, glass ceramics, and glass. The first substrate 10 may also contain a silica component such as glass in addition to ceramic. In this disclosure, a "major component" refers to a material that accounts for 50% or more by mass of the material. The first substrate 10 may be high-temperature co-fired ceramic (HTCC) or low-temperature co-fired ceramic (LTCC).

[0018] 1 , the first substrate 10 may have a third surface 11 and a fourth surface 12 located on the opposite side to the third surface 11. The first substrate 10 may be a plate-like body having the third surface 11 and the fourth surface 12 as main surfaces. The first substrate 10 may also have a first side surface 13 connecting the third surface 11 and the fourth surface 12. The first side surface 13 is the outer surface of the first substrate 10.

[0019] The first substrate 10 may also have a plurality of ceramic layers 14. The plurality of ceramic layers 14 may be stacked along the thickness direction of the first substrate 10. By configuring the first substrate 10 using a plurality of ceramic layers 14 in this way, it is possible to obtain a first substrate 10 that has therein first interlayer conductors 32 (described below) and conductors with wiring shapes suitable for various purposes. Furthermore, by making the plurality of ceramic layers 14 each have a different shape, it is possible to improve the degree of freedom in designing the shape of the wiring board 100.

[0020] The wiring board 100 having such a first substrate 10 has a high degree of freedom in design. Furthermore, by forming the first substrate 10 using a plurality of ceramic layers 14, it is possible to fabricate the first substrate 10 while checking, layer by layer, whether the first interlayer conductors 32 (described below) and internal conductors having wiring shapes according to various purposes are properly formed, and whether each layer is processed into the desired shape. This allows for an improved yield of the first substrate 10.

[0021] In this embodiment, the first substrate 10 has two ceramic layers 14, but the number of ceramic layers 14 is not limited to two. The number of ceramic layers 14 may be three or more. Furthermore, the first substrate 10 does not necessarily have to have a multi-layer structure. In other words, the first substrate 10 may be a single layer.

[0022] <Second Base Material> As described above, the second base material 20 may contain an organic material. The organic material may be an organic resin. The organic resin may be, for example, an epoxy resin, an acrylic resin, a polycarbonate resin, a polyimide resin, an olefin resin, or a polyphenylene resin. Furthermore, the second base material 20 may contain multiple types of organic resins.

[0023] The organic resin may be, for example, polytetrafluoroethylene (PTFE) or other fluororesins or polyphenylene ether resins. The second substrate 20 may contain components other than the organic resin. Examples of components other than the organic resin contained in the second substrate 20 include inorganic materials such as silica and rubber materials. The content of the inorganic material such as silica in the second substrate 20, in terms of mass %, may be greater than the content of the organic resin in the second substrate 20. More specifically, the content of the inorganic material such as silica in the second substrate 20 may be 50 mass % or more of the second substrate 20, and the content of the organic resin in the second substrate 20 may be 50 mass % or less of the second substrate 20.

[0024] As shown in FIG. 1 , the second substrate 20 may have a second substrate 20A on the first surface 102 side and a second substrate 20B on the second surface 103 side, with the first substrate 10 interposed therebetween. The second substrate 20A may have the first surface 102 and a fifth surface 21 located opposite the first surface 102. The second substrate 20A may be a plate-like body having the first surface 102 and the fifth surface 21 as its main surfaces. The second substrate 20A may also have a second side surface 23 connecting the first surface 102 and the fifth surface 21. The second side surface 23 is the outer surface of the second substrate 20A. Note that, hereinafter, when there is no need to distinguish between the second substrate 20A and the second substrate 20B, they may be referred to as the second substrate 20.

[0025] The second substrate 20A may have multiple organic resin layers 24. The multiple organic resin layers 24 may be stacked along the thickness direction of the second substrate 20A. By configuring the second substrate 20 using multiple organic resin layers 24, it is possible to obtain a second substrate 20 that internally contains second interlayer conductors 42 (described below) and conductors with wiring shapes suitable for various purposes. Furthermore, by making the multiple organic resin layers 24 different shapes, it is possible to improve the degree of freedom in designing the shape of the wiring board 100. A wiring board 100 having such a second substrate 20 has a high degree of design freedom.

[0026] The second substrate 20A is overlaid on the third surface 11 of the first substrate 10. The fifth surface 21 of the second substrate 20A is bonded to the third surface 11 of the first substrate 10. That is, the second substrate 20A is directly bonded to the first substrate 10 without an adhesive layer. Specifically, the organic resin layer 24 of the second substrate 20A may contain an epoxy-based resin. The ceramic layer 14 of the first substrate 10 may contain a ceramic containing hydroxyl groups. In this case, the second substrate 20A may be chemically bonded to the first substrate 10 via the hydroxyl groups. This allows the first substrate 10 and the second substrate 20A to be hydrogen bonded via the hydroxyl groups.

[0027] On the other hand, the second substrate 20B may have a sixth surface 61 and a seventh surface 62 located opposite the sixth surface 61. The second substrate 20B may be a plate-like body having the sixth surface 61 and the seventh surface 62 as its main surfaces. The second substrate 20B may also have a third side surface 63 connecting the sixth surface 61 and the seventh surface 62. The third side surface 63 is the outer surface of the second substrate 20B. The second surface 103 of the insulating substrate 101 configured in this manner may have the seventh surface 62 and a fourth surface 12 facing the through hole 110. In other words, in this specification, the second surface 103 of the insulating substrate 101 includes the seventh surface 62 and the fourth surface 12 located at a different level from the seventh surface 62.

[0028] The second base material 20B may have a plurality of organic resin layers (not shown). The plurality of organic resin layers may be stacked along the thickness direction of the second base material 20B.

[0029] The second substrate 20B has the first substrate 10 superimposed on the sixth surface 61. The second substrate 20B has the sixth surface 61 bonded to the fourth surface 12 of the first substrate 10. That is, the second substrate 20B is directly bonded to the first substrate 10 without an adhesive layer. Specifically, the organic resin layer of the second substrate 20B may contain an epoxy-based resin. The ceramic layer 14 of the first substrate 10 may contain a ceramic containing hydroxyl groups. In this case, the second substrate 20B may be chemically bonded to the first substrate 10 via the hydroxyl groups. This allows the first substrate 10 and the second substrate 20B to be hydrogen bonded via the hydroxyl groups.

[0030] In this way, since there is no adhesive layer for joining the first base material 10 and the second base material 20, the thickness of the wiring board 100 is reduced, and miniaturization is possible.

[0031] In this embodiment, the second substrate 20A has two organic resin layers 24, but the number of organic resin layers 24 is not limited to two. The number of organic resin layers 24 of the second substrate 20A may be three or more. Furthermore, the second substrate 20A does not necessarily have to have a multilayer structure. That is, the second substrate 20A may be a single layer. Note that the second substrate 20B may also have multiple organic resin layers like the second substrate 20A, or may be a single layer.

[0032] The second substrate 20 containing an organic material allows the internal conductors to be formed using a chemical solution, photolithography, or the like using a mask corresponding to the shape of the internal conductor, making it easier to form a fine wiring pattern or a narrow-pitch wiring pattern than a substrate containing an inorganic material. On the other hand, the first substrate 10 containing a ceramic has higher rigidity than the second substrate 20. The first substrate 10 containing a ceramic may also have a higher density than the second substrate 20.

[0033] By combining the first substrate 10 and the second substrate 20, the wiring substrate 100 can achieve finer wiring, narrower pitch, and improved freedom in electrode arrangement while also increasing rigidity. Since warping of the substrate becomes more pronounced as the substrate becomes larger, the configuration of the wiring substrate 100 in which the first substrate 10 compensates for the low rigidity of the second substrate 20 is particularly useful for increasing the size of the substrate.

[0034] The substrate containing an organic material may be lighter than a substrate containing a ceramic, and in this case, the wiring board 100 according to the present disclosure, which has the first substrate 10 containing a ceramic and the second substrate 20 containing an organic material, can be lighter than a wiring board composed only of substrates containing a ceramic.

[0035] Furthermore, since ceramic-containing substrates have higher thermal conductivity than organic-containing substrates, wiring board 100 having first substrate 10 containing ceramic and second substrate 20 containing organic material can have improved heat dissipation compared to a wiring board made only of organic-containing substrates.

[0036] The insulating substrate 101 including the first substrate 10 and the second substrate 20 has been described above, but the arrangement of the first substrate 10 and the second substrate 20 is not particularly limited. For example, the insulating substrate 101 may be configured such that the second substrate 20 is located only on the first surface 102 side. That is, the insulating substrate 101 may be configured such that the second substrate 20 is located on the first surface 102 side, and the first substrate 10 is located on the second surface 103 side. For example, the insulating substrate 101 may be configured such that the second substrate 20 is located only on the second surface 103 side. That is, the insulating substrate 101 may be configured such that the second substrate 20 is located on the second surface 103 side, and the first substrate 10 is located on the first surface 102 side.

[0037] <Physical Properties of First Substrate and Second Substrate> The thermal expansion coefficient of the second substrate 20 may be different from that of the first substrate 10. Specifically, the thermal expansion coefficient of the first substrate 10 in the direction along the third surface 11 may be different from that of the second substrate 20 in the direction along the third surface 11. For example, the thermal expansion coefficient of the first substrate 10 may be smaller than that of the second substrate 20. Because the second substrate 20 is bonded to the first substrate 10, the above configuration allows the first substrate 10 to restrain the second substrate 20 when the second substrate 20 attempts to thermally deform due to a temperature change, thereby reducing thermal deformation of the second substrate 20 or the resulting warpage. Therefore, the mounting surface on which the first electrode 15 is located, the external connection surface on which the second electrode 65 is located, and the first surface 102 on which the third electrode 75 is located are all stable.

[0038] <First Conductor and Second Conductor> Fig. 5 is an explanatory diagram illustrating the transfer of heat between the first conductor 30 and the first substrate 10. Note that the white arrows in Fig. 5 indicate the path of heat transfer.

[0039] As shown in Fig. 4, the first conductor 30 is located inside the first substrate 10. The first conductor 30 may extend in a direction perpendicular to the third surface 11. Note that "extending" here does not necessarily mean extending the shortest distance. Furthermore, a portion of the first conductor 30 may be exposed to the fourth surface 12 or a side surface such as the first side surface 13.

[0040] The first conductor 30 may include a first via conductor 31 penetrating at least a portion of the first substrate 10 and a first interlayer conductor 32 electrically connected to the first via conductor 31. The first interlayer conductor 32 may extend in one or more directions from the periphery of the first via conductor 31. In other words, the first interlayer conductor 32 may have a structure including only a first portion located around the periphery of the first via conductor 31, or may have a configuration including the first portion and a second portion extending from the first portion in one direction, multiple directions, or in all 360° directions, i.e., a so-called solid pattern. The first interlayer conductor 32 may be in contact with other conductors on the same horizontal plane. In other words, the conductor region of the first interlayer conductor 32 may extend in a partial direction or in all 360° directions. The first via conductor 31 penetrates at least one ceramic layer 14. 4 illustrates one first via conductor 31 penetrating one ceramic layer 14, but multiple first via conductors 31 may penetrating one ceramic layer 14, or multiple first via conductors 31 may penetrating each of multiple ceramic layers 14. In this case, the multiple first via conductors 31 may be located at different positions in the horizontal direction. The first interlayer conductor 32 may be located between two adjacent ceramic layers 14. In this case, the first interlayer conductor 32 may be electrically connected to two first via conductors 31 penetrating each of two adjacent ceramic layers 14.

[0041] In this way, since the wiring board 100 has the first conductor 30 on the first base material 10, the degree of freedom in wiring design is higher compared to conventional wiring boards that have wiring only on a substrate containing an organic resin. On the other hand, when a configuration is adopted in which wiring is provided on both the first base material 10 and the second base material 20, specifically when a configuration is adopted in which the first conductor 30 and the second conductor 40 are provided, it is desirable to increase the bonding strength between the first base material 10 and the second base material 20 so that misalignment between the first conductor 30 and the second conductor 40 does not occur.

[0042] The second conductor 40 is located inside the second substrate 20 and extends in a direction perpendicular to the third surface 11. Note that "extending" here does not necessarily mean extending the shortest distance. Furthermore, a portion of the second conductor 40 may be exposed on a side surface, such as the first surface 102, the second surface 103, the second side surface 23, or the third side surface 63.

[0043] The second conductor 40 may include a second via conductor 41 penetrating at least a portion of the second base material 20 and a second interlayer conductor 42 electrically connected to the second via conductor 41. The second interlayer conductor 42 may extend in one or more directions from the periphery of the second via conductor 41. In other words, the second interlayer conductor 42 may have a structure including only a first portion located around the periphery of the second via conductor 41, or may have a configuration including the first portion and a second portion extending from the first portion in one direction, multiple directions, or in all 360° directions, i.e., a so-called solid pattern. The second interlayer conductor 42 may be in contact with other conductors on the same horizontal plane. In other words, the conductor region of the second interlayer conductor 42 may extend in a partial direction or in all 360° directions. The second via conductor 41 penetrates at least one organic resin layer 24. 4 illustrates one second via conductor 41 penetrating one organic resin layer 24, but multiple second via conductors 41 may penetrate one organic resin layer 24, or multiple second via conductors 41 may penetrate multiple organic resin layers 24, respectively. In this case, the multiple second via conductors 41 may be located at different positions in the horizontal direction. The second interlayer conductor 42 may be located between two adjacent organic resin layers 24. In this case, the second interlayer conductor 42 may be electrically connected to two second via conductors 41 penetrating two adjacent organic resin layers 24, respectively.

[0044] The first conductor 30 includes a first metal. The second conductor 40 includes a second metal different from the first metal. The electrical resistivity of the first metal is higher than the electrical resistivity of the second metal. The first metal may be, for example, tungsten or molybdenum. The second metal may be, for example, copper.

[0045] This makes it possible to select a second metal having a lower electrical resistivity than the first metal in the second substrate 20 containing an organic resin, thereby reducing the electrical resistance of the conductor as a whole compared to when the conductor is composed only of the first conductor 30 containing the first metal.

[0046] Furthermore, a metal having a higher electrical resistivity than the second metal can be selected as the first metal, and since the amount of heat generated increases with an increase in power consumption when a current flows due to the high electrical resistivity, it is possible to prevent a decrease in the operating temperature of the electronic element 310 (see FIG. 8 ) even in a low-temperature environment.

[0047] The melting point of the first metal may be higher than that of the second metal. By selecting a metal with a higher melting point than the second metal as the first metal, the firing temperature of the first substrate 10 can be increased. This allows for a higher thermal history in the manufacturing process, thereby increasing the flexibility of process design. For example, this allows for the combustion of the binder, which is an organic material, and the melting of the silica component that provides the anchoring effect.

[0048] The first via conductor 31 may be a metal conductor containing tungsten, and the first interlayer conductor 32 may be a metal conductor containing molybdenum. Alternatively, the first via conductor 31 may be a metal conductor containing molybdenum, and the first interlayer conductor 32 may be a metal conductor containing tungsten. Alternatively, both the first via conductor 31 and the first interlayer conductor 32 may be metal conductors containing tungsten, or both the first via conductor 31 and the first interlayer conductor 32 may be metal conductors containing molybdenum. The first conductor 30 may be, for example, a metal conductor containing tungsten or molybdenum with copper or silver as the main component.

[0049] The second conductor 40 may be, for example, a metal conductor containing copper. Alternatively, the second conductor 40 may be a metal conductor containing copper, tin, and bismuth. The second via conductor 41 and the second interlayer conductor 42 may be made of different materials. For example, when the second via conductor 41 and the second interlayer conductor 42 both contain copper, the copper contents in weight percent in the second via conductor 41 and the second interlayer conductor 42 may be different.

[0050] More specifically, the weight percentage of copper contained in second via conductor 41 may be 15% or more and 45% or less. In this case, second interlayer conductor 42 may be made of copper foil. That is, second interlayer conductor 42 may have 70% or more copper by weight of the entire second interlayer conductor 42. Note that when the weight percentage of copper contained in second via conductor 41 is within the above numerical range, the weight percentage of tin contained in second via conductor 41 may be 35% or more and 55% or less.

[0051] Furthermore, the second via conductors 41 may contain 1% to 10% by weight of resin. This configuration can impart fluidity to the second via conductors 41. Furthermore, the bonding strength between the second via conductors 41 and the second substrate 20, which contains a resin as an organic material, can be improved. The resin contained in the second via conductors 41 and the resin contained in the second substrate 20 may be the same. This configuration can improve the bonding strength between the second via conductors 41 and the second substrate 20. The weight percentage of the resin contained in the second substrate 20 may be greater than the weight percentage of the resin contained in the second via conductors 41. The resin contained in the second via conductors 41 may be an epoxy resin.

[0052] Furthermore, the second via conductor 41 may contain at least one of bismuth and indium. In this case, when the second via conductor 41 contains tin and bismuth, the tin contained in the second via conductor 41 may exist as a eutectic with the bismuth.

[0053] When the metal contained in the second via conductor 41 is copper, the surface of the copper may be coated. This configuration can reduce oxidation and deterioration of the copper. Examples of coating materials include silver.

[0054] The first conductor 30 may contain a silica component such as glass. In this case, the first conductor 30 is bonded to the first substrate 10, which also contains a silica component, via the silica component. Specifically, the silica component contained in the first conductor 30 is integrated with the silica component contained in the first substrate 10 by firing. As a result, as shown in FIG. 5 , heat transfer between the first conductor 30 and the first substrate 10 is facilitated via the integrated silica component. Furthermore, heat from the first substrate 10 can be efficiently transferred to the second conductor 40, which serves as a heat dissipation path for the second substrate 20. Furthermore, the anchoring effect of the silica component strengthens the bond between the first substrate 10 and the first conductor 30, thereby increasing the rigidity of the first substrate 10. Furthermore, the risk of peeling of the first conductor 30 can be reduced.

[0055] Furthermore, when the first conductor 30 contains a silica component, the firing temperatures of the first substrate 10 and the first conductor 30 can be made closer to each other in the firing process during the manufacturing of the wiring substrate 100. Furthermore, the shrinkage rates of the first substrate 10 and the first conductor 30 can be adjusted.

[0056] <First Electrode> As shown in Fig. 4 , the first electrode 15 is located on the first substrate 10. For example, the first electrode 15 may be located on the fourth surface 12. The first electrode 15 is electrically connected to the first conductor 30. For example, the first electrode 15 may be electrically connected to the first via conductor 31. The first electrode 15 is also electrically connected to the electronic element 310 (see Fig. 8 ). In this way, the first electrode 15 electrically connects the electronic element 310 and the first conductor 30.

[0057] 3 , some of the multiple first electrodes 15 and other first electrodes 15 may be located on either side of the through hole 110 in a cross-sectional view of the wiring substrate 100 along the thickness direction of the base material, or may be located outside two intersecting sides or all sides of the through hole 110 in a plan view. Furthermore, the multiple first electrodes 15 may be located outside one side of the through hole 110 in a direction parallel to one side of the through hole 110. When the through hole 110 includes an arc-shaped curved surface such as a circle or an ellipse, some of the first electrodes 15 may be located outside a part of the arc forming the through hole 110, or the multiple first electrodes 15 may be located so as to surround the circle or ellipse forming the through hole 110.

[0058] <Second Electrode> As shown in FIG. 3 , the second electrode 65 may be located on the second substrate 20B. For example, the second electrode 65 may be located on the seventh surface 62. The second electrode 65 may be electrically connected to a second conductor 40 located inside the second substrate 20B. The second electrode 65 may be electrically connected to a second via conductor 41 located inside the second substrate 20B. Alternatively, the second electrode 65 may be electrically connected to the first conductor 30 without the second conductor 40 when, for example, the second surface 103 described below is planar. That is, the second electrode 65 may be electrically connected to the first electrode 15 through at least the first conductor 30 of the first conductor 30 and the second conductor 40. The second electrode 65 may be electrically connected to, for example, a lower wiring member 64 (see FIG. 8 ) that is an anisotropic conductive film. The anisotropic conductive film may be, for example, an ACF.

[0059] <Third Conductor> As shown in FIG. 4 , the first substrate 10 may have an interface with the second substrate 20. The interface may be, for example, the third surface 11 on which the second substrate 20A is located. A third conductor 50 for joining the first conductor 30 and the second conductor 40 may be located at the interface. The third conductor 50 may be wider than the first conductor 30 and the second conductor 40 in a planar direction parallel to the interface. Specifically, the third conductor 50 may be electrically connected to the first via conductor 31 and the second via conductor 41. The wiring board 100 having such a third conductor 50 has a high degree of design freedom because the third conductor 50 allows the first via conductor 31 and the second via conductor 41 to be electrically connected to each other even if their positions are misaligned in the horizontal direction.

[0060] Furthermore, even if the positions of the first conductor 30 and the second conductor 40 are misaligned due to differences in positional tolerance between the second substrate 20 and the first substrate 10 during manufacturing or due to misalignment of the entire substrates during bonding, the electrical connection between the first conductor 30 and the third conductor 50 is likely to be maintained, and the electrical connection between the second conductor 40 and the third conductor 50 is also likely to be maintained. Therefore, the possibility of the electrical connection between the first conductor 30 and the second conductor 40 being interrupted can be reduced. In other words, the connection stability between the first conductor 30 and the second conductor 40 can be improved. The third conductor 50 may be a metal conductor containing tungsten or molybdenum. The third conductor 50 may also contain a silica component.

[0061] The third conductor 50 may be located at a position overlapping at least the first via conductor 31 and the second via conductor 41 in a plan view. The third conductor 50 may extend in one or more directions from the periphery of the first via conductor 31 and the second via conductor 41. In other words, the third conductor 50 may have a structure having only a first portion located around the first via conductor 31 and the second via conductor 41, or may have a configuration having the first portion and a second portion extending from the first portion in one direction, multiple directions, or in all directions 360°, i.e., a so-called solid pattern. From another perspective, the third conductor 50 may be in contact with another conductor on the same plane in the horizontal direction.

[0062] <Third Electrode> As shown in FIG. 3 , the third electrode 75 may be located on the second substrate 20A. For example, the third electrode 75 may be located on the first surface 102. The third electrode 75 may be electrically connected to the second conductor 40 located inside the second substrate 20A. The third electrode 75 may be electrically connected to the second via conductor 41 located inside the second substrate 20A. Alternatively, the third electrode 75 may be electrically connected to the first conductor 30 without the second conductor 40 in a configuration in which the second substrate 20 is located only on the second surface 103 side and the third electrode 75 is located on the first substrate 10. In this way, the third electrode 75 may be electrically connected to the first electrode 15 via at least the first conductor 30 of the first conductor 30 and the second conductor 40.

[0063] <Arrangement of First Electrode and Second Electrode> As described above, in the embodiment, the first electrode 15 and the second electrode 65 are located on the second surface 103 of the insulating substrate 101, and the third electrode 75 is located on the first surface 102. The third electrode 75 is electrically connected to at least one of the first electrode 15 and the second electrode 65 via at least the first conductor 30 of the first conductor 30 and the second conductor 40. Furthermore, by having electrodes on both the first surface 102 and the second surface 103, the wiring substrate 100 can be connected to more components and electronic elements. Furthermore, compared to when the first electrode 15, the second electrode 65, and the third electrode 75 are all located on the same surface, wasted space can be eliminated.

[0064] As shown in FIG. 3 , the second surface 103 may include a mounting surface on which the first electrode 15 is located and an external connection surface located outward from the mounting surface in a direction parallel to the mounting surface and on which the second electrode 65 is located. The mounting surface may be, for example, the fourth surface 12 facing the through hole 110. The external connection surface may be, for example, the seventh surface 62. The mounting surface may be located between the first surface 102 and the external connection surface in a direction perpendicular to the mounting surface. This results in a difference in height between the first electrode 15 and the second electrode 65, making it difficult for heat to be transferred between the first electrode 15 and the second electrode 65. Furthermore, the step space between the mounting surface and the external connection surface allows the thickness of the entire module including the electronic element 310 (see FIG. 8 ) to be reduced while protecting the electronic element 310.

[0065] 6 is a cross-sectional view showing an example of the configuration of a wiring board according to an embodiment. As shown in FIG. 6, insulating substrate 101 may be configured such that second base material 20 is located only on first surface 102. That is, insulating substrate 101 may be configured such that second base material 20 is located on first surface 102 and first base material 10 is located on second surface 103. In this case, the mounting surface on which first electrode 15 is located and the external connection surface on which second electrode 65 is located may be located on planar second surface 103.

[0066] As a result, the first electrode 15 and the second electrode 65 have the same height, allowing for a thinner wiring substrate 100. Furthermore, the wiring length between the first electrode 15 and the second electrode 65 can be shortened, thereby reducing electrical resistance and improving the flexibility of wiring length setting to achieve desired high-frequency characteristics. Furthermore, the lack of a step on the second surface 103 reduces the risk of other components getting caught on the step during mounting, causing misalignment or orientation, or damaging other components. Furthermore, the lack of a step on the second surface 103 reduces the risk of liquid or debris adhering to or remaining on the step. In particular, if the liquid or debris is conductive, the risk of short circuits due to the liquid or debris can be reduced. Furthermore, during manufacturing, the first electrode 15 and the second electrode 65 can be simultaneously formed by a single screen printing process.

[0067] FIG. 7 is a cross-sectional view showing an example of the configuration of a wiring board according to an embodiment. As shown in FIG. 7 , the wiring board 100 may be configured such that a first substrate 10A, which is another first substrate 10, is located on the fourth surface 12 of the first substrate 10. The first substrate 10A may be located on the central side of the insulating substrate 101 in a planar view. The through-hole 110 may have a rectangular shape of a constant size along the thickness direction of the insulating substrate 101. The through-hole 110 may be larger or smaller on the second surface 103 side than on the first surface 102 side. In this case, the external connection surface may be located between the first surface 102 and the mounting surface in a direction perpendicular to the mounting surface. The mounting surface may be, for example, the seventh surface 62 of the first substrate 10A. The external connection surface may be, for example, a portion that does not overlap with the sixth surface 61 in a planar view, and may be on the outer edge side of the fourth surface 12 of the first substrate 10A in a planar view. As a result, the first electrode 15 and the second electrode 65 are at different heights, which makes it difficult for heat to be transferred between the first electrode 15 and the second electrode 65. Furthermore, because the thickness between the external connection surface and the first surface 102 can be reduced, the weight can be reduced compared to a configuration in which the second substrate 20 is located on the fourth surface 12 of the first substrate 10. In particular, when the wiring substrate 100 is moved mechanically, the operating power can be reduced due to the reduced weight.

[0068] 8 is a cross-sectional view showing an example of the configuration of a semiconductor device according to the embodiment. As shown in Fig. 8, the semiconductor device 300 may include a wiring substrate 100, an electronic element 310, a cover 320 such as an optical filter, and an electronic component 77.

[0069] The electronic element 310 is mounted on the wiring substrate 100. In the example shown in FIG. 8 , the electronic element 310 is mounted on the fourth surface 12 of the first base material 10 of the wiring substrate 100. The electrodes 311 of the electronic element 310 may be joined to the wiring substrate 100 via, for example, a conductive joining member 16. The joining member 16 may be, for example, a solder bump, a gold bump, or a conductive resin (such as an anisotropic conductive resin). The electronic element 310 may be, for example, flip-chip mounted, wire-bond mounted, die-attach mounted, or BGA (ball grid array) mounted to the wiring substrate 100. The electronic element 310 may be located inside the through-hole 110.

[0070] Furthermore, the lid 320 is mounted on the first surface 102 of the wiring substrate 100 via an adhesive 322. The lid 320 is positioned to face the open end of the through hole 110 on the first surface 102. The third electrode 75 may be positioned to surround the attachment portion of the lid 320 on the first surface 102.

[0071] The electronic component 77 is mounted on the first surface 102 of the wiring substrate 100 via a bonding member 76 such as solder. The electronic component 77 is located on the third electrode 75.

[0072] The electronic element 310 is, for example, a light-receiving element such as an image sensor or a light-emitting element such as a semiconductor laser, and generates heat when the electronic element 310 operates. The wiring board 100 can provide high thermal conductivity to the second conductor 40, which serves as a heat dissipation path for the second base material 20. Furthermore, when a thin layer containing the same material as that contained in the first base material 10, such as an alumina coating, is integrally formed with the first base material 10 on the fourth surface 12 of the first base material 10, which is the element mounting surface, the resistance to peeling and deterioration of the conductor formed on the fourth surface 12 and covered by the thin layer can be improved at the location where the thin layer is formed.

[0073] Because the first substrate 10 containing ceramic has higher rigidity than the second substrate 20, the flatness of the first surface 102, the second surface 103, and the fourth surface 12 is reduced compared to when the insulating substrate 101 is formed entirely of the second substrate 20 containing an organic material. This prevents the electronic element 310 from protruding toward the lower wiring member 64 or toward the lid 320. Furthermore, the height of the first electrode 15 relative to the first surface 102 becomes more constant, thereby preventing the electronic element 310 from tilting relative to the horizontal direction. Furthermore, the tilt of the first electrode 15 relative to the electrode surface of the electronic element 310 is reduced, bringing the electrodes closer to parallel, allowing the distance between the electrodes to be maintained at a distance that optimizes the amount of bonding material 16. This configuration ensures a sufficient contact area between the bonding material 16 and the first electrode 15, preventing a decrease in the adhesive strength of the electronic element 310 and reducing the amount of adhesive used. Furthermore, since the inclination of the tip of the first electrode 15 on the through-hole 110 side is small, electrical connection is possible up to the tip. Furthermore, by including the highly rigid first substrate 10, warping of the mounting surface of the housing, such as a lens holder (not shown), can be suppressed, thereby suppressing tilting of the electronic element 310, the housing, and the lid 320. The mounting surface of the housing is, for example, the outer edge of the first surface 102 in a plan view.

[0074] Furthermore, by configuring the wiring board 100 from the first substrate 10 and the first conductor 30 containing a high-melting-point metal, the wiring board 100 can be sufficiently resistant to high temperatures during mounting. Furthermore, the second substrate 20 is more easily deformed than the first substrate 10, and therefore can absorb impacts on the wiring board 100. Furthermore, by configuring the surface other than the element mounting surface with the second substrate 20, which has a small relative permittivity and dielectric loss tangent, high-frequency transmission loss can be reduced.

[0075] The present disclosure has been described in detail above, but the present disclosure is not limited to the above-described embodiments, and various modifications, improvements, etc. are possible within the scope that does not deviate from the gist of the present disclosure.

[0076] The disclosed embodiments should be considered in all respects as illustrative and not restrictive. Indeed, the above-described embodiments may be embodied in various forms. Furthermore, the above-described embodiments may be omitted, substituted, or modified in various ways without departing from the scope and spirit of the appended claims.

[0077] The present technology can also be configured as follows: (1) A wiring board comprising: an insulating substrate having a first surface and a second surface located opposite the first surface, the insulating substrate including a first base material containing ceramic and a second base material containing an organic resin and bonded to the first base material; a first electrode located on the first base material and electrically connected to an electronic element; a first conductor extending from the first electrode into the first base material; a second conductor located in the second base material and electrically connected to the first conductor; and a second electrode electrically connected to the first electrode via at least the first conductor of the first conductor and the second conductor, wherein the first conductor includes a first metal, and the second conductor includes a second metal different from the first metal, and the electrical resistivity of the first metal is higher than the electrical resistivity of the second metal. (2) The wiring board according to (1), wherein the melting point of the first metal is higher than the melting point of the second metal. (3) The wiring board according to (1) or (2), comprising a plurality of the first electrodes, wherein the insulating substrate has through holes penetrating the first base material and the second base material, and in a cross-sectional view of the wiring board along the thickness direction of the insulating substrate, some of the plurality of first electrodes and other parts are positioned on either side of the through holes. (4) The wiring board according to any one of (1) to (3), wherein the first base material and the first conductor contain a silica component. (5) The wiring board according to any one of (1) to (4), comprising a third conductor located at the interface between the first base material and the second base material and joining the first conductor and the second conductor, wherein the third conductor is wider than the first conductor and the second conductor in a planar direction parallel to the interface. (6) The wiring board according to any one of (1) to (5), wherein the first electrode and the second electrode are both located on the second surface of the insulating substrate, the insulating substrate has a third electrode on the first surface, and the third electrode is electrically connected to at least one of the first electrode and the second electrode via at least the first conductor of the first conductor and the second conductor.(7) The wiring board according to (6), wherein the second surface comprises: a mounting surface on which the first electrode is located; and an external connection surface located outward from the mounting surface in a direction parallel to the mounting surface and on which the second electrode is located, and in a direction perpendicular to the mounting surface, the mounting surface is located between the first surface and the external connection surface. (8) The wiring board according to (6), wherein the second surface is planar. (9) The wiring board according to (6), wherein the second surface comprises: a mounting surface on which the first electrode is located; and an external connection surface located outward from the mounting surface in a direction parallel to the mounting surface and on which the second electrode is located, and in a direction perpendicular to the mounting surface, the external connection surface is located between the first surface and the mounting surface. (10) A semiconductor device comprising: the wiring board according to (1) or (2), and the electronic element electrically connected to the first electrode of the wiring board. (11) The semiconductor device according to (10), wherein the insulating substrate has a through hole penetrating the first base material and the second base material. (12) The semiconductor device according to (10) or (11), further comprising a lid located on the first surface, the insulating substrate having a third electrode on the first surface, the third electrode being located so as to surround an attachment portion of the lid on the first surface.

[0078] REFERENCE SIGNS LIST 10 First substrate 10A First substrate 11 Third surface (interface) 20 Second substrate 20A Second substrate 20B Second substrate 30 First conductor 40 Second conductor 50 Third conductor 100 Wiring substrate 101 Insulating substrate 102 First surface 103 Second surface 110 Through hole 300 Semiconductor device 310 Electronic element 320 Lid

Claims

1. An insulating substrate having a first surface and a second surface located opposite to the first surface, the insulating substrate including a first base material containing ceramic and a second base material containing an organic resin and bonded to the first base material, a first electrode located on the first base material and electrically connected to an electronic element, a first conductor extending from the first electrode into the first base material, a second conductor located in the second base material and electrically connected to the first conductor, and a second electrode electrically connected to the first electrode through at least the first conductor of the first conductor and the second conductor, the first conductor including a first metal, the second conductor including a second metal different from the first metal, and the electrical resistivity of the first metal being higher than the electrical resistivity of the second metal. Wiring substrate.

2. The melting point of the first metal is higher than the melting point of the second metal. The wiring substrate according to claim 1.

3. Comprising a plurality of the first electrodes, the insulating substrate comprising a through hole penetrating the first base material and the second base material, and in a cross-sectional view of the wiring substrate along the thickness direction of the insulating substrate, a part of the plurality of the first electrodes and another part are located with the through hole therebetween. The wiring substrate according to claim 1 or 2.

4. The first base material and the first conductor contain a silica component. The wiring substrate according to any one of claims 1 to 3.

5. A third conductor located at the interface between the first base material and the second base material and joining the first conductor and the second conductor, the third conductor being wider than the first conductor and the second conductor in a plane direction parallel to the interface. The wiring substrate according to any one of claims 1 to 4.

6. Both the first electrode and the second electrode are located on the second surface of the insulating substrate, the insulating substrate includes a third electrode on the first surface, and the third electrode is electrically connected to at least one of the first electrode and the second electrode through at least the first conductor of the first conductor and the second conductor. The wiring substrate according to any one of claims 1 to 5.

7. The second surface includes a mounting surface on which the first electrode is located, and an external connection surface that is located outward of the mounting surface in a direction parallel to the mounting surface and on which the second electrode is located. In a direction orthogonal to the mounting surface, the mounting surface is located between the first surface and the external connection surface. The wiring board according to claim 6.

8. The second surface is planar. The wiring board according to claim 6.

9. The second surface includes a mounting surface on which the first electrode is located, and an external connection surface that is located outward of the mounting surface in a direction parallel to the mounting surface and on which the second electrode is located. In a direction orthogonal to the mounting surface, the external connection surface is located between the first surface and the mounting surface. The wiring board according to claim 6.

10. A semiconductor device comprising the wiring board according to claim 1 or 2, and an electronic element electrically connected to the first electrode included in the wiring board.

11. The insulating substrate includes a through hole that penetrates the first base material and the second base material. The semiconductor device according to claim 10.

12. The semiconductor device according to claim 10 or 11, comprising a lid located on the first surface, the insulating substrate including a third electrode on the first surface, and the third electrode being located so as to surround a mounting portion of the lid on the first surface.

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