Substrate with built-in heating element

Abstract

A substrate 1 with a built-in heating element comprises: a substrate 10 having a first main surface 11 and a second main surface 12 facing each other in a thickness direction; a cavity 20 opened on the first main surface 11 of the substrate 10 and having a bottom surface 21; a heating element 60 mounted on the cavity 20; and a sealing material 70 that seals the inside of the cavity 20. A land portion 31 for mounting the heating element 60 is provided on the bottom surface 21 of the cavity 20, and the land portion 31 forms a planar conductor 30 that is continuous and flush with a portion of a wiring 13 in the substrate 10.

Description

Heating element built-in board

[0001] The present invention relates to a substrate with a built-in heating element.

[0002] Patent Document 1 describes a high-frequency module comprising a dielectric substrate on one of its main surfaces, on which a power amplifier element and a filter element are mounted, a conductor formed below the power amplifier element that passes through the dielectric substrate from one main surface to the other, and holes with a maximum diameter of 0.2 mm or less scattered inside the dielectric substrate below the filter element mounting surface.

[0003] Patent Document 2 describes a multilayer wiring board with built-in electronic components, in which electronic components connected to an inner conductor layer formed on the surface of an insulating substrate are mounted, characterized in that the electronic components are mounted on the surface of the inner conductor layer, the area in which the electronic components are mounted is completely sealed from the outside, and an airtight space is formed inside this sealed area.

[0004] JP 2005-101366 A JP 2002-84070 A

[0005] In the technology described in Patent Document 1, a power amplifier element is mounted in a power amplifier element mounting section, which is a cavity provided in a dielectric substrate. The power amplifier element is a heat-generating element, and a through conductor is provided directly below the power amplifier element in the thickness direction, so that heat generated by the power amplifier element can be dissipated in the thickness direction through the through conductor. However, there is no heat dissipation path in the planar directions (X and Y directions) perpendicular to the thickness direction, which poses a problem of insufficient heat dissipation in the X and Y directions.

[0006] In the technology described in Patent Document 2, an electronic component, which is a heat-generating element, is mounted in an airtight cavity of a substrate. The electronic component is connected to connection lands only by bumps, and there is space around the electronic component, which causes a problem of poor heat dissipation from the electronic component.

[0007] The present invention has been made to solve the above problems, and has an object to provide a substrate with a built-in heater element that is excellent in heat dissipation from a heater element mounted in a cavity of the substrate.

[0008] The substrate with a built-in heater element of the present invention comprises a substrate having a first main surface and a second main surface that are opposite to each other in the thickness direction, a cavity that opens to the first main surface of the substrate and has a bottom surface, a heater element mounted in the cavity, and a sealing material that seals the inside of the cavity, wherein a land portion on which the heater element is mounted is provided on the bottom surface of the cavity, and the land portion forms a continuous planar conductor on the same plane as a portion of the wiring in the substrate.

[0009] According to the present invention, it is possible to provide a substrate with a built-in heater element that is excellent in heat dissipation from a heater element mounted in a cavity of the substrate.

[0010] FIG. 1 is a cross-sectional view schematically showing an example of the configuration of a heater-embedded element substrate of the present invention. FIG. 2 is a top view schematically showing the bottom of a cavity. FIG. 3A is a top view schematically showing a planar conductor and a second conductor. FIG. 3B is a top view schematically showing a first ceramic layer and a second ceramic layer. FIG. 4 is a process diagram schematically showing an example of the configuration of a green sheet laminate. FIG. 5 is a process diagram schematically showing a masking process. FIG. 6 is a process diagram schematically showing a cavity forming process. FIG. 7 is a process diagram schematically showing a cavity forming process. FIG. 8 is a process diagram schematically showing a metal layer forming process. FIG. 9 is a process diagram schematically showing a cavity bottom cleaning process. FIG. 10 is a process diagram schematically showing a masking removal process. FIG. 11 is a cross-sectional view schematically showing another example of the configuration of a heater-embedded element substrate of the present invention. FIG. 12 is a cross-sectional view schematically showing another example of the configuration of a heater-embedded element substrate of the present invention. 13 is a top view of the cavity of the heater element built-in substrate shown in FIG.

[0011] The following describes the heater element-embedded substrate of the present invention. However, the present invention is not limited to the following configuration, and can be appropriately modified and applied within the scope of the present invention. Note that a combination of two or more of the individual preferred configurations described below also constitutes the present invention.

[0012] Fig. 1 is a cross-sectional view showing a schematic example of the configuration of a heater-embedded substrate of the present invention. The heater-embedded substrate 1 shown in Fig. 1 includes a substrate 10 having a first main surface 11 and a second main surface 12 that face each other in the thickness direction (Z direction in Fig. 1), a cavity 20 that opens to the first main surface 11 of the substrate 10 and has a bottom surface 21, a heater element 60 mounted in the cavity 20, and a sealant 70 that seals the inside of the cavity 20.

[0013] The substrate 10 is formed by laminating insulating layers 17 made of a ceramic material, and is provided with wiring 13 (internal wiring) and via conductors 14 inside. Furthermore, electrodes 15 and 16 are provided on the first and second main surfaces 11 and 12 of the substrate 10, respectively. The wiring, via conductors, and electrodes are preferably made of a material that can be co-fired with the low-temperature co-fired ceramic material, such as Cu, Ag, Au, and alloys thereof. Cu, Ag, and Au have low resistance, making them particularly suitable for use in high-frequency applications of the heating element-embedded substrate. The wiring pattern and via conductor pattern are not particularly limited.

[0014] An example of the ceramic material is low-temperature co-fired ceramic (LTCC). A substrate using LTCC as the ceramic material is also called an LTCC substrate.

[0015] Low-temperature co-fired ceramic materials are ceramic materials that can be fired at temperatures of 1000°C or less and can be co-fired with Au, Ag, Cu, etc., which have low resistivity. Specific examples of low-temperature co-fired ceramic materials include glass composite low-temperature co-fired ceramic materials obtained by mixing ceramic powders such as alumina, zirconia, magnesia, and forsterite with borosilicate glass; ZnO-MgO-Al ２ O ３ -SiO ２ Glass-ceramic low-temperature fired ceramic material using BaO-Al ２ O ３ -SiO ２ ceramic powder and Al ２ O ３ -CaO-SiO ２ -MgO-B ２ O ３Examples of suitable ceramic materials include non-glass-based low-temperature fired ceramic materials using ceramic powders.

[0016] The cavity 20 is a bottomed cavity having a bottom surface 21 and a side surface 22. A heating element 60 is mounted in the cavity 20. The heating element 60 may be entirely housed within the cavity 20, or the heating element 60 may protrude beyond the opening of the cavity 20.

[0017] Examples of the heat generating element 60 include semiconductor chips (dies), passive components such as capacitors and coils, filters, light emitting elements, etc. In particular, power semiconductors (GaAs semiconductor elements) generate a large amount of heat, so the effects of using the configuration of the present invention are effectively exhibited.

[0018] The sealing material 70 is made of a sealing resin, and either a thermosetting resin or a thermoplastic resin may be used as the sealing resin. Examples of thermosetting resins include phenolic resin, epoxy resin, polyester resin, silicone resin, and polyimide resin. Examples of thermoplastic resins include thermoplastic liquid crystal polymer (LCP), thermoplastic polyimide resin, polyether ether ketone resin (PEEK), and polyphenylene sulfide resin (PPS).

[0019] The sealing resin may contain additives such as fillers, for example, glass, silica, aluminum oxide, aluminum nitride, boron nitride, and the like.

[0020] In the heater-embedded substrate 1 shown in Figure 1, electronic components 61 and 62 are mounted on electrodes 15 provided on a first main surface 11 of a substrate 10. Electronic component 61 is a semiconductor chip, and electronic component 62 is a passive component. Electrodes 16 provided on a second main surface 12 of the substrate 10 are used as electrodes for mounting the heater-embedded substrate 1 on another substrate, etc. An external shielding film 90 is provided around the heater-embedded substrate 1. Note that in the heater-embedded substrate of the present invention, electronic components do not have to be mounted on the first main surface of the substrate, and an external shielding film does not have to be provided around the heater-embedded substrate.

[0021] A land portion 31 is provided on the bottom surface 21 of the cavity 20, and a heating element 60 is mounted on the land portion 31. More specifically, an electrode 63 of the heating element 60 is connected to the land portion 31 by solder 64. The electrode 63 of the heating element 60 is a ground electrode of the heating element 60.

[0022] The land portion 31 is continuous on the same plane with a wiring 32 that is part of the wiring 13 in the substrate 10, and forms a planar conductor 30. The planar conductor 30 is a so-called solid conductor provided in the substrate 10.

[0023] Furthermore, a signal conductor portion 41 is provided on the bottom surface 21 of the cavity 20. The signal conductor portion 41 is connected to an electrode 65 of the heating element 60 via solder 64. The electrode 65 of the heating element 60 is a signal electrode of the heating element 60. The signal conductor portion 41 does not form a continuous conductor on the same plane as the land portion 31.

[0024] A first ceramic layer is provided on a portion of the surface of the planar conductor on the bottom surface of the cavity, and the portion of the planar conductor surrounded by the first ceramic layer and exposed from the first ceramic layer constitutes a land portion. A second conductor, which is flush with the planar conductor but not continuous with it, is disposed on the bottom surface of the cavity, and the second ceramic layer is provided at a position overlapping a portion of the surface of the planar conductor and a portion of the surface of the second conductor, and the portion of the second conductor surrounded by the second ceramic layer and exposed from the second ceramic layer constitutes a signal conductor. In other words, the positions of the land portion and the signal conductor portion are determined by the provision of the ceramic layer. The ceramic layer preferably contains the same ceramic material as the substrate 10, and is preferably a layer containing the low-temperature co-fired ceramic material described above.

[0025] The positional relationship between the ceramic layer, the land portion, the signal conductor portion, the planar conductor, and the second conductor will be described below with reference to the drawings.

[0026] Fig. 2 is a top view schematically showing the bottom surface of the cavity. Fig. 3A is a top view schematically showing the planar conductor and the second conductor. Fig. 3B is a top view schematically showing the first ceramic layer and the second ceramic layer. The shape of the top view of Fig. 2 is obtained by superimposing the top view of Fig. 3B on the top view of Fig. 3A.

[0027] 3A shows a second conductor 42 including a portion that will become the signal conductor portion 41, and a planar conductor 30 including a portion that will become the land portion 31. At the stage of FIG. 3A, the positions of the signal conductor portion 41 and the land portion 31 have not been determined. The second conductor 42 and the planar conductor 30 are located on the same plane (same layer), and are not continuous with each other. A space 43, which is a portion where no conductor exists, exists between the second conductor 42 and the planar conductor 30.

[0028] 3B shows an example of the shape of the first ceramic layer 51. Three holes 51a, 51b, and 51c are provided in the first ceramic layer 51. When the first ceramic layer 51 is placed on the surface of the planar conductor 30, the portions of the planar conductor 30 exposed through the holes 51a, 51b, and 51c of the first ceramic layer 51 become the land portions 31. The land portions 31 are surrounded by the first ceramic layer 51.

[0029] The left side of FIG. 3B shows an example of the shape of the second ceramic layer 52. Two donut-shaped ceramic layers are shown as the second ceramic layer 52. Two holes 52a and 52b are provided in the second ceramic layer 52. When the second ceramic layer 52 is placed on the surface of the planar conductor 30 and the surface of the second conductor 42, the portion of the second conductor 42 exposed through the holes 52a and 52b in the second ceramic layer 52 becomes the signal conductor portion 41. The signal conductor portion 41 is surrounded by the second ceramic layer 52. When the second ceramic layer 52 is placed on the surface of the planar conductor 30 and the surface of the second conductor 42, the second ceramic layer 52 is also placed on the space 43 between the second conductor 42 and the planar conductor 30. The space 43 is filled with the second ceramic layer 52.

[0030] After the first ceramic layer 51 is provided on the surface of the planar conductor 30, the holes 51a, 51b, and 51c of the first ceramic layer 51 become spaces above the land portion 31, and this space becomes a space into which the solder 64 fills when the heating element 60 is mounted. Similarly, after the second ceramic layer 52 is provided on the surface of the second conductor 42, the holes 52a and 52b of the second ceramic layer 52 become spaces above the signal conductor portion 41, and this space becomes a space into which the solder 64 fills when the heating element 60 is mounted. The surfaces of the land portion 31 and the signal conductor portion 41 may be subjected to a surface treatment such as Ni-Au plating or Ni-Pd-Au plating.

[0031] In each drawing, the first ceramic layer and the second ceramic layer are depicted as separate, discontinuous ceramic layers, but the first ceramic layer and the second ceramic layer may be integrated. In this case, the portion surrounding the land portion is the first ceramic layer, and the portion surrounding the signal conductor portion is the second ceramic layer. The boundary between the first ceramic layer and the second ceramic layer does not need to be strictly considered.

[0032] With the above structure, the heat generated by the heating element 60 can be transferred from the electrode 63, which is the ground electrode of the heating element, to the land portion 31, and the heat can be dissipated in the direction in which the planar conductor 30 extends (XY direction) by utilizing the planar conductor 30, which is continuous on the same plane as the land portion 31.

[0033] As mentioned above, the cavity is sealed with a sealant, leaving no space around the heat-generating element. Since the sealant has a higher thermal conductivity than air, heat dissipation from the heat-generating element to the surroundings can be improved.

[0034] These effects enable the substrate to have an internal heating element that is excellent in heat dissipation from the heating element mounted in the cavity of the substrate.

[0035] The heater-embedded substrate of the present invention further includes a metal layer that forms part of the side surface of the cavity or is arranged along the side surface of the cavity, and the metal layer is preferably electrically connected to the planar conductor. The metal layer is preferably a metal film that covers the side surface of the cavity. Figure 1 shows an embodiment in which a metal film 81 is provided as the metal layer 80 on the side surface 22 of the cavity 20.

[0036] The provision of the metal film 81 improves the shielding effect against noise radiated from the heating element 60 toward the side surface 22 of the cavity 20, and suppresses interference with the wiring 13 located near the cavity 20 of the substrate 10.

[0037] Examples of the metal film include films formed by plating, sputtering, spraying, inkjet, etc. Materials for the metal film include copper, Ag, SUS, etc. The thickness of the metal film is not particularly limited, but is preferably 0.1 μm or more and 10 μm or less.

[0038] It is preferable that the metal layer be connected to a ground electrode. For example, in FIG. 1 , electrode 16 a provided on second main surface 12 can be the ground electrode. For example, the metal layer may be connected to an electrode exposed on a side surface of the substrate, and the electrode exposed on the side surface may be connected to ground electrode 16 a via wiring inside the substrate. Alternatively, the metal layer may be connected to a planar conductor, which may be connected to ground electrode 16 a. This improves shielding. Furthermore, from the perspective of heat dissipation, when the metal layer is connected to the planar conductor, heat transferred from the sealing material to the metal layer is diffused in the thickness direction by the metal layer and further transferred to the planar conductor, dissipating heat in the direction in which the planar conductor extends (X and Y directions). This widens the heat dissipation path, further improving heat dissipation.

[0039] From the viewpoint of shielding, the planar conductor provided on the bottom surface of the cavity can function as a shielding film against noise radiated from the heating element toward the bottom surface of the cavity.

[0040] An example of a manufacturing method for a heater element-embedded substrate of the present invention will be described. <LTCC green sheet preparation step> A slurry is prepared by mixing ceramic powder, binder, and plasticizer in desired amounts. The slurry is applied to a carrier film and formed into a sheet to obtain a green sheet. A lip coater or doctor blade can be used to apply the slurry. The thickness of the green sheet is preferably 5 μm or more and 100 μm or less.

[0041] <Step of opening via holes in LTCC green sheets> Via holes are formed in the green sheets. ２ They can be formed using a laser, a UV laser, etc. The opening diameter of the via hole is preferably 20 μm or more and 200 μm or less.

[0042] <Step of filling via holes in LTCC green sheet> The via holes are filled with a via conductor paste, which is a conductive paste containing conductive powder, a plasticizer, and a binder. The via conductor paste may contain ceramic powder that constitutes the green sheet.

[0043] <Process for forming wiring patterns on LTCC green sheets> A wiring pattern is printed on the surface of a green sheet using a conductive paste containing conductive powder, a plasticizer, and a binder. Printing methods that can be used include screen printing, inkjet printing, and gravure printing. In a later process, a wiring pattern that will become a planar conductor is formed on the green sheet, the upper surface of which will become the bottom of the cavity. A wiring pattern that will become a second conductor that is not continuous with the planar conductor is also formed. A ceramic coating paste that contains ceramic powder, a binder, and a plasticizer is printed on the wiring pattern in the area that will become the bottom of the cavity. The positions of the land portion and signal conductor portion are determined by printing the ceramic coating paste.

[0044] A ceramic paste consisting of ceramic powder, binder, and plasticizer is then printed on top of the green sheet. The ceramic powder contained in the ceramic paste is a material that does not sinter at the firing temperature of the LTCC green sheet, such as alumina or zirconia. Alternatively, a sheet-like material (ceramic sheet) may be laminated instead of the ceramic paste.

[0045] <LTCC Green Sheet Lamination Process> A plurality of green sheets are laminated to form a green sheet laminate. The number of layers is preferably determined appropriately according to the design. The green sheet laminate is then placed in a mold and pressure-bonded. The pressure and temperature are preferably set as desired according to the design.

[0046] 4 is a process diagram schematically illustrating an example of the configuration of a green sheet laminate. This diagram shows a green sheet 110a provided with via conductor paste 114 and a wiring pattern 113, and a green sheet 110b further provided with ceramic coating paste 150 and ceramic paste 160. The green sheet 110b is the green sheet that will become the bottom surface of the cavity. The green sheets 110a and 110b are laminated and pressed together to form a green sheet laminate.

[0047] <LTCC Green Sheet Laminate Firing Process> The green sheet laminate is heated and fired to form a multilayer ceramic substrate. By performing this process, the ceramic paste becomes an unsintered ceramic layer (unsintered ceramic layer 160a, see FIG. 5). Firing can be performed using a firing furnace such as a batch furnace or a belt furnace. Firing conditions are preferably 800°C or higher and 1000°C or lower. Note that if the conductive paste contains copper, firing is preferably performed in a reducing atmosphere.

[0048] <Masking Step> Figure 5 is a process diagram that schematically illustrates the masking step. Masking tape 170 is applied to the first main surface 11 of the multilayer ceramic substrate (substrate 10). The masking tape is applied to prevent a metal film from adhering to unnecessary portions of the substrate surface in a subsequent step of forming a metal layer on the side surface of the cavity. As the masking tape, a weak adhesive tape that can be peeled off in a subsequent step, a heat-foaming tape, a UV tape, or the like can be used. Alternatively, the masking step may be performed by forming a masking layer using a washable printing paste instead of masking tape.

[0049] 6 and 7 are process diagrams that schematically show the cavity formation process. The masking tape 170 of the substrate 10 is cut down to the inner green ceramic layer 160a, and the material inside the cut area is separated to form the cavity 20. The insulating layer that contacts the green ceramic layer 160a is not bonded to the green ceramic layer 160a, so it can be easily separated from the green ceramic layer 160a. The cutting when forming the cavity is performed using a CO ２ This can be done using a laser, a UV laser, a YAG laser, or the like.

[0050] 8 is a process diagram schematically illustrating the metal layer forming process. A metal layer 80 (metal film 81) is formed on the side surface 22 of the cavity 20. The metal film can be formed by plating, sputtering, spraying, inkjet printing, or the like.

[0051] <Cavity Bottom Cleaning Process> Figure 9 is a process diagram that schematically illustrates the cavity bottom cleaning process. The unnecessary metal film 81 and unsintered ceramic layer 160a adhering to the bottom surface 21 of the cavity 20 are removed. This process makes it possible to expose the land portion 31 and the signal conductor portion 41. The cavity bottom cleaning process can be performed by wet blasting, ultrasonic cleaning, or the like.

[0052] 10 is a process diagram schematically illustrating the masking removal step. The masking tape 170 is removed. The masking tape can be removed by a method suited to the tape, such as heating or UV irradiation. This exposes the electrodes 15 on the first main surface 11 of the substrate 10.

[0053] <Processes after Mounting Heating Element> The heating element 60 is mounted in the cavity 20, electronic components 61, 62 are mounted on the first main surface 11 of the substrate 10, and the cavity 20 and the periphery of the electronic components 61, 62 on the first main surface 11 are sealed with a sealant 70. Finally, an external shielding film 90 is formed on the surfaces of the substrate 10 other than the second main surface 12, thereby completing the manufacturing process for the heater-embedded substrate 1 shown in Figure 1. Note that, before mounting the heating element 60, the surfaces of the land portion 31 and the signal conductor portion 41 may be subjected to surface treatment such as Ni-Au plating or Ni-Pd-Au plating.

[0054] Another embodiment will be described below, in which the metal layer that forms part of the side surface of the cavity or that is arranged along the side surface of the cavity has a different shape. Other than the shape of the metal layer, the shape of each component of the heater-embedded substrate described above can be the same as that of the heater-embedded substrate.

[0055] Fig. 11 is a cross-sectional view schematically showing another example of the configuration of the heater element built-in substrate of the present invention. In the heater element built-in substrate 2 shown in Fig. 11, the metal layer 80 is provided in the substrate 10 so as to be exposed on the side surface 22 of the cavity 20, and includes side surface exposed wiring 82 extending along the side surface 22. The metal layer 80 also includes a plurality of side surface exposed wirings 82 arranged at intervals in the thickness direction (Z direction) of the substrate 10. The number of side surface exposed wirings is not particularly limited, and may be a plurality or a single wiring.

[0056] In Figure 11, in order to clearly show the presence of multiple side-exposed wirings 82, the number of insulating layers 17 that make up the side surface 22 of the cavity 20 is shown increased by one compared to the substrate 1 with built-in heating elements shown in Figure 1.

[0057] The side surface exposed wiring 82 is provided in the substrate 10 so as to be exposed on the side surface 22 of the cavity 20, and is composed of side surface exposed wirings 82a and 82b that extend along the side surface 22 of the cavity 20 (in the direction of arrow Y in Figure 11).

[0058] The side surface exposed wirings 82a and 82b are wirings formed in the substrate 10 that are exposed on the side surface 22 of the cavity 20 as a result of the formation of the cavity 20. Therefore, the side surface exposed wirings 82a and 82b are also wirings 13 in the substrate 10.

[0059] When multiple layers of the substrate are exposed on the side surface of the cavity, the side surface exposed wiring may be exposed in all of those layers, or may be exposed in some of the layers. For example, among the multiple layers exposed on the side surface of the cavity, the side surface exposed wiring may be present only in the layer facing the side surface of the heating element, and the side surface exposed wiring may not be present in the layer not facing the side surface of the heating element.

[0060] When the side exposed wiring 82 is provided as the metal layer 80, the shielding against noise radiated from the heating element 60 toward the side 22 of the cavity 20 is improved, and interference with the wiring 13 located near the cavity 20 of the substrate 10 can be suppressed.

[0061] The side surface exposed wiring 82 is electrically connected to the planar conductor 30 through the via conductor 14. When the side surface exposed wiring is electrically connected to the planar conductor, heat transferred from the sealing material to the side surface exposed wiring is transferred to the planar conductor through the via conductor, and heat dissipation proceeds in the direction in which the planar conductor expands (X and Y directions), thereby expanding the heat dissipation path and further improving heat dissipation.

[0062] Fig. 12 is a cross-sectional view schematically showing another example of the configuration of the heater element built-in substrate of the present invention. Fig. 13 is a top view of a cavity in the heater element built-in substrate shown in Fig. 12. Fig. 13 is also a partial cross-sectional view taken along line A-A in Fig. 12.

[0063] In the substrate 3 with built-in heating elements shown in Figure 12, the metal layer 80 is provided within the substrate 10 so as to be exposed on the side surface 22 of the cavity 20, and includes a cut via conductor 83 that extends along the thickness direction (Z direction) of the substrate 10.

[0064] When a cut via conductor 83 is provided as the metal layer 80, the shielding properties against noise radiated from the heating element 60 toward the side surface 22 of the cavity 20 are improved, and interference with the wiring 13 near the cavity 20 of the substrate 10 can be suppressed.

[0065] 13 , a plurality of cut via conductors 83 are provided around the cavity 20 when viewed from above the cavity 20. Fig. 13 shows a configuration in which a large number of via conductors 83 surround the entire periphery of the cavity 20. By surrounding the entire periphery of the cavity 20 with a large number of via conductors 83, a shielding effect can be achieved against noise radiated in any direction from the side surface 22 of the cavity 20.

[0066] The cut via conductors 83 are electrically connected to the planar conductor 30. When the cut via conductors are electrically connected to the planar conductor, heat transferred from the sealing material to the cut via conductors is transferred to the planar conductor, and heat dissipation proceeds in the direction in which the planar conductor expands (X and Y directions), thereby expanding the heat dissipation path and further improving heat dissipation.

[0067] 12, side surface exposed wiring 82 is also provided on the side surface 22 of the cavity 20, and functions as the metal layer 80. When cut via conductors 83 are provided as the metal layer 80, the side surface exposed wiring 82 may or may not be provided.

[0068] In the embodiment shown in Figure 12, a side-exposed wiring 82 is sandwiched between two via conductors 83 that exist along the thickness direction, but the two via conductors may also be in direct contact with each other without the side-exposed wiring 82 being sandwiched between them.

[0069] In the manufacturing process of a heater element-embedded substrate using side-exposed wiring or cut via conductors as the metal layer, as described with reference to Figures 11, 12, and 13, the metal layer can be provided by cutting at a position where the side-exposed wiring is exposed or the via conductor is cut during the cutting in the cavity formation process. In this case, since the step of forming a metal film is not performed, there is an advantage that the masking step and the mask removal step are not necessary, and the process is simplified.

[0070] The present specification discloses the following:

[0071] The present disclosure (1) is a substrate with a built-in heater element, comprising: a substrate having a first main surface and a second main surface that are opposed in the thickness direction; a cavity that opens to the first main surface of the substrate and has a bottom surface; a heater element mounted in the cavity; and a sealing material that seals the inside of the cavity, wherein a land portion for mounting the heater element is provided on the bottom surface of the cavity, and the land portion forms a continuous planar conductor on the same plane as a portion of the wiring in the substrate.

[0072] The present disclosure (2) is a substrate with an embedded heating element as described in the present disclosure (1), in which a first ceramic layer is provided on a portion of the surface of the planar conductor at the bottom surface of the cavity, and the portion of the planar conductor that is surrounded by the first ceramic layer and exposed from the first ceramic layer becomes the land portion.

[0073] The present disclosure (3) is a substrate with an embedded heating element as described in the present disclosure (1) or (2), in which a signal conductor portion is provided on the bottom surface of the cavity, and the signal conductor portion does not form a continuous conductor on the same plane as the land portion.

[0074] The present disclosure (4) is a substrate with an embedded heating element as described in the present disclosure (3), in which a second conductor that is not continuous with the planar conductor and is arranged on the bottom surface of the cavity in the same plane as the planar conductor, a second ceramic layer is provided in a position overlapping a part of the surface of the planar conductor and a part of the surface of the second conductor, and the part of the second conductor that is surrounded by the second ceramic layer and exposed from the second ceramic layer becomes the signal conductor part.

[0075] The present disclosure (5) is a substrate with a built-in heating element according to any one of the present disclosures (1) to (4), further comprising a metal layer that forms part of the side surface of the cavity or is arranged along the side surface of the cavity, and the metal layer is electrically connected to the planar conductor.

[0076] The present disclosure (6) is the heater-embedded substrate according to the present disclosure (5), wherein the metal layer includes a metal film covering the side surface of the cavity.

[0077] The present disclosure (7) is a substrate with a built-in heating element according to the present disclosure (5) or (6), in which the metal layer is provided within the substrate so as to be exposed on the side surface of the cavity, and includes side-exposed wiring extending along the side surface.

[0078] The present disclosure (8) is the substrate with built-in heater element according to the present disclosure (7), wherein the metal layer includes a plurality of the side exposed wirings arranged at intervals in the thickness direction of the substrate.

[0079] The present disclosure (9) is a substrate with an embedded heating element according to any one of the present disclosures (5) to (8), in which the metal layer is provided within the substrate so as to be exposed on the side surface of the cavity and includes a cut via conductor extending along the thickness direction of the substrate.

[0080] The present disclosure (10) is the heater element built-in substrate according to the present disclosure (9), wherein a plurality of the via conductors are provided around the cavity when viewed from above.

[0081] REFERENCE SIGNS LIST 1, 2, 3 Heating element built-in substrate 10 Substrate 11 First main surface 12 Second main surface 13 Wiring in substrate 14 Via conductor in substrate 15 Electrode on first main surface 16 Electrode on second main surface 16a Ground electrode 17 Insulating layer 20 Cavity 21 Bottom surface of cavity 22 Side surface of cavity 30 Planar conductor 31 Land portion 32 Wiring that is part of wiring in substrate 41 Signal conductor portion 42 Second conductor 43 Space 51 First ceramic layer 51a, 51b, 51c Hole in first ceramic layer 52 Second ceramic layer 52a, 52b Hole in second ceramic layer 60 Heating element 61, 62 Electronic component 63, 65 Electrode of heating element 64 Solder 70 Sealant 80 Metal layer 81 Metal film 82, 82a, 82b: side exposed wiring 83: cut via conductor 90: external shielding film 110a, 110b: green sheet 113: wiring pattern 114: via conductor paste 150: ceramic coating paste 160: ceramic paste 160a: unsintered ceramic layer 170: masking tape

Claims

1. A substrate with a built-in heater element comprising: a substrate having a first main surface and a second main surface that are opposed in the thickness direction; a cavity that opens to the first main surface of the substrate and has a bottom surface; a heater element mounted in the cavity; and a sealing material that seals the inside of the cavity, wherein a land portion for mounting the heater element is provided on the bottom surface of the cavity, and the land portion forms a continuous planar conductor on the same plane as a portion of the wiring within the substrate.

2. A substrate with an embedded heater element as described in claim 1, wherein a first ceramic layer is provided on a portion of the surface of the planar conductor at the bottom surface of the cavity, and the portion of the planar conductor that is surrounded by the first ceramic layer and exposed from the first ceramic layer becomes the land portion.

3. A substrate with a built-in heater element as described in claim 1 or 2, wherein a signal conductor portion is provided on the bottom surface of the cavity, and the signal conductor portion does not form a continuous conductor on the same plane as the land portion.

4. A substrate with built-in heater element as described in claim 3, wherein a second conductor is arranged on the bottom surface of the cavity, the second conductor being flush with the planar conductor and not continuous with the planar conductor, and a second ceramic layer is provided in a position overlapping part of the surface of the planar conductor and part of the surface of the second conductor, and the part of the second conductor surrounded by the second ceramic layer and exposed from the second ceramic layer forms the signal conductor section.

5. A substrate with a built-in heater element according to any one of claims 1 to 4, further comprising a metal layer that forms part of a side surface of the cavity or that is arranged along the side surface of the cavity, the metal layer being electrically connected to the planar conductor.

6. The heater element built-in substrate according to claim 5, wherein the metal layer includes a metal film covering the side surface of the cavity.

7. The heater-embedded substrate according to claim 5 or 6, wherein the metal layer is provided within the substrate so as to be exposed on a side surface of the cavity, and includes side-exposed wiring extending along the side surface.

8. The heater-embedded substrate according to claim 7, wherein the metal layer includes a plurality of the side-exposed wirings spaced apart in the thickness direction of the substrate.

9. A substrate with a built-in heater element as described in any one of claims 5 to 8, wherein the metal layer is provided within the substrate so as to be exposed on the side surface of the cavity and includes a cut via conductor extending along the thickness direction of the substrate.

10. The heater-embedded substrate according to claim 9, wherein a plurality of the via conductors are provided around the periphery of the cavity when viewed from above.

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