Circuit board and method for producing circuit board

Abstract

This circuit board 1A comprises: an insulation layer 10 that has a first main surface 10a and a second main surface 10b facing each other in the thickness direction; a first conductor layer 21 that is provided to the first main surface 10a of the insulation layer 10; a second conductor layer 22 that is provided to the second main surface 10b of the insulation layer 10; an interlayer connection conductor 30 that is provided penetrating the insulation layer 10 in a thickness direction, the interlayer connection conductor 30 being connected to the first conductor layer 21 and the second conductor layer 22; and a rust prevention layer 40 that is provided to the surface of the first conductor layer 21 or the second conductor layer 22. The interlayer connection conductor 30 includes, in the thickness direction, a first portion 31 that is made of a single metal and a second portion 32 that contains at least a metal different from that of the first portion 31. The first portion 31 is joined to the second portion 32 with a first intermediate layer 51 interposed therebetween, the first intermediate layer 51 including the metal contained in the first portion 31 and the metal contained in the second portion 32, and the first portion 31 is joined to the first conductor layer 21 without a first intermediate layer 51 interposed therebetween. The second portion 32 is joined to the second conductor layer 22 with a second intermediate layer 52 interposed therebetween, the second intermediate layer 52 including the metal contained in the second portion 32 and the metal contained in the second conductor layer 22. The rust prevention layer 40 is disposed at least on an interface between the first conductor layer 21 and the insulation layer 10, and is not disposed between the second portion 32 and the second conductor layer 22.

Description

Circuit board and method for manufacturing the circuit board

[0001] The present invention relates to a circuit board and a method for manufacturing the circuit board.

[0002] Patent Document 1 discloses a wiring board including an insulating layer and a conductor layer formed on one main surface of the insulating layer, wherein the insulating layer has a hole with the conductor layer as a bottom and opening toward the other main surface of the insulating layer, and the hole is provided with a first via portion connected to the conductor layer and a second via portion connected to the first via portion, the first via portion includes a conductive member but does not include a resin member, the first via portion has a protrusion at the end face of the first via portion on the second via portion side that protrudes toward the second via portion, and a portion of the second via portion extends between the protrusion of the first via portion and the insulating layer and does not contact the conductor layer connected to the first via portion.

[0003] International Publication No. 2022 / 202322

[0004] Patent document 1 describes a method of forming an interlayer connecting conductor including a first via portion and a second via portion by plating a hole provided in an insulating layer with a conductor foil, and then forming a second via portion by filling the remaining part of the hole where the first via portion was formed with a conductive paste.

[0005] Furthermore, Patent Document 1 describes a method of producing a laminated substrate (hereinafter also referred to as a multilayer circuit board) by sequentially stacking insulating layers including an insulating layer with a conductor foil in which a first via portion and a second via portion are formed, and then hot pressing (collectively pressing) the obtained laminate in the stacking direction.

[0006] Generally, the surface of a conductor foil such as a Cu foil is subjected to an anti-rust treatment. The formation of an anti-rust layer on the surface of the conductor foil can prevent oxidation of the conductor foil and suppress the inhibition of adhesion with the insulating layer. On the other hand, the anti-rust layer can inhibit the reaction between the conductive paste and the conductor foil, which may reduce the reliability of connection between the interlayer connection conductor including the first and second via portions and the conductor layer.

[0007] The present invention has been made to solve the above problems, and an object of the present invention is to provide a circuit board having excellent connection reliability between an interlayer connection conductor and a conductor layer, and a method for manufacturing the circuit board.

[0008] The circuit board of the present invention comprises an insulating layer having a first main surface and a second main surface opposing each other in a thickness direction, a first conductor layer provided on the first main surface of the insulating layer, a second conductor layer provided on the second main surface of the insulating layer, an interlayer connection conductor penetrating the insulating layer in the thickness direction and connected to the first conductor layer and the second conductor layer, and an anticorrosion layer provided on the surface of the first conductor layer or the second conductor layer. The interlayer connection conductor includes, in the thickness direction, a first portion made of a single metal and a second portion containing at least a metal different from that of the first portion. The first portion is bonded to the second portion via a first intermediate layer containing a metal contained in the first portion and a metal contained in the second portion, and is bonded to the first conductor layer without the first intermediate layer. The second portion is bonded to the second conductor layer via a second intermediate layer containing a metal contained in the second portion and a metal contained in the second conductor layer. The anticorrosive layer is disposed at least at the interface between the first conductive layer and the insulating layer, and is not disposed between the second portion and the second conductive layer.

[0009] The method for manufacturing a circuit board of the present invention includes the steps of: preparing a substrate having a conductor layer formed on one surface of an insulating layer and an anticorrosion layer provided on at least the surface of the conductor layer facing the insulating layer; forming a via hole in the substrate, the via hole penetrating the insulating layer and exposing a portion of the upper surface of the conductor layer; removing the anticorrosion layer provided on the exposed portion of the conductor layer; filling the via hole after the anticorrosion layer has been removed with a first material consisting of a single metal, and then filling it with a second material containing at least a metal different from the first material; and stacking a plurality of substrates, including the substrates filled with the first material and the second material, and pressing them together by applying heat and pressure.

[0010] According to the present invention, it is possible to provide a circuit board having excellent connection reliability between the interlayer connection conductor and the conductor layer, and further, it is possible to provide a method for manufacturing the circuit board.

[0011] FIG. 1 is a perspective view schematically showing an example of a circuit board of the present invention. FIG. 2 is a cross-sectional view taken along line II-II of the circuit board shown in FIG. 1. FIG. 3 is a cross-sectional view schematically showing an example of a circuit board according to a first embodiment of the present invention. FIGS. 4A to 4G are cross-sectional views schematically showing an example of a manufacturing method for a circuit board 1A. FIG. 5 is a cross-sectional view schematically showing an example of a circuit board according to a second embodiment of the present invention. FIG. 6 is a cross-sectional view schematically showing an example of a circuit board according to a third embodiment of the present invention. FIG. 7 is a cross-sectional view schematically showing an example of a circuit board according to a fourth embodiment of the present invention. FIG. 8 is a cross-sectional view schematically showing an example of a circuit board according to a fifth embodiment of the present invention. FIG. 9 is a cross-sectional view schematically showing another example of a circuit board according to the fifth embodiment of the present invention. FIG. 10 is a cross-sectional view schematically showing an example of a circuit board according to a sixth embodiment of the present invention. FIG. 11 is a cross-sectional view schematically showing another example of a circuit board according to the sixth embodiment of the present invention. FIG. 12 is a cross-sectional view schematically showing an example of a circuit board according to a seventh embodiment of the present invention. FIG. 13 is a cross-sectional view schematically showing an example of a circuit board according to an eighth embodiment of the present invention. FIG. 14 is a cross-sectional view schematically showing another example of a circuit board according to the eighth embodiment of the present invention. FIG. 15 is a cross-sectional view schematically showing an example of a circuit board according to the ninth embodiment of the present invention. FIG. 16 is a cross-sectional view schematically showing an example of a circuit board according to the tenth embodiment of the present invention. FIG. 17 is a cross-sectional view schematically showing another example of a circuit board according to the tenth embodiment of the present invention. FIGS. 18A, 18B, and 18C are cross-sectional views schematically showing an example of a circuit board according to the eleventh embodiment of the present invention. FIG. 19 is a cross-sectional view schematically showing an example of a circuit board according to the eleventh embodiment of the present invention. FIG. 20 is a cross-sectional view schematically showing another example of a circuit board according to the eleventh embodiment of the present invention. FIG. 21 is a cross-sectional view schematically showing an example of a circuit board according to the twelfth embodiment of the present invention. FIG. 22 is a cross-sectional view schematically showing an example of a circuit board on which electronic components are mounted. FIG. 23 is a cross-sectional view schematically showing an example of a circuit board having a bent portion.

[0012] The circuit board and the method for manufacturing the circuit board of the present invention will be described below. However, the present invention is not limited to the following configurations, and can be appropriately modified and applied within the scope of the present invention. A combination of two or more of the individual preferred configurations of the present invention described below also constitutes the present invention.

[0013] In this specification, terms indicating the relationship between elements (e.g., "perpendicular," "parallel," "orthogonal," etc.) and terms indicating the shapes of elements are not expressions that only express a strict meaning, but are expressions that mean that they are substantially equivalent, for example, including a difference of about a few percent. Furthermore, in this specification, "equivalent" is not an expression that means only complete equivalent, but is an expression that means that they are substantially equivalent, for example, including a difference of about a few percent.

[0014] The drawings shown below are schematic diagrams, and the dimensions, aspect ratio, and other scales may differ from those of the actual product. In the drawings, the same or equivalent parts will be designated by the same reference numerals. In addition, the same elements will be designated by the same reference numerals in each drawing, and duplicate explanations will be omitted.

[0015] Fig. 1 is a perspective view schematically showing an example of a circuit board of the present invention, and Fig. 2 is a cross-sectional view taken along line II-II of the circuit board shown in Fig. 1.

[0016] The circuit board 1 shown in FIG. 1 includes an insulating base material 100 formed by laminating insulating layers (first insulating layer 110, second insulating layer 120, third insulating layer 130, fourth insulating layer 140), conductor layers (mounting electrode 150, ground wiring 160, signal line 170, wiring 180, wiring 185) provided on the surface of or inside the insulating base material 100, interlayer connection conductors 190, 195, 200, and a protective layer 210.

[0017] In the example shown in FIG. 1, the circuit board 1 is a multilayer circuit board having a plurality of insulating layers.

[0018] The circuit board 1 may be a rigid board or a flexible board, and may have a bent portion.

[0019] Mounting electrodes 150, wiring 180, and a protective layer 210 are provided on one main surface (the bottom surface in FIG. 2 ) of the insulating substrate 100. Ground wiring 160 is provided on the other main surface (the top surface in FIG. 2 ) of the insulating substrate 100. Signal lines 170 and wiring 185 are provided between the first insulating layer 110 and the second insulating layer 120, and between the second insulating layer 120 and the third insulating layer 130.

[0020] Interlayer connection conductors 190 and 200 are provided inside the first insulating layer 110 and the second insulating layer 120. Of these, the interlayer connection conductors 190 connected to the signal lines 170 overlap in the stacking direction (Z direction in FIG. 2 ). Therefore, the signal lines 170 are connected to each other by the interlayer connection conductors 190 provided inside the first insulating layer 110 and the interlayer connection conductors 190 provided inside the second insulating layer 120, thereby forming a transmission line. Furthermore, the signal line 170 is connected to the mounting electrode 150 by the interlayer connection conductors 190 provided inside the first insulating layer 110.

[0021] An interlayer connection conductor 195 is provided inside the third insulating layer 130 and the fourth insulating layer 140 .

[0022] The ground wiring 160 is connected to the wiring 180 by an interlayer connection conductor 200 provided inside the first insulating layer 110, an interlayer connection conductor 200 provided inside the second insulating layer 120, an interlayer connection conductor 195 provided inside the third insulating layer 130, and an interlayer connection conductor 195 provided inside the fourth insulating layer 140.

[0023] Wiring 185 is provided between the interlayer connection conductor 200 provided inside the first insulating layer 110 and the interlayer connection conductor 200 provided inside the second insulating layer 120, and between the interlayer connection conductor 200 provided inside the second insulating layer 120 and the interlayer connection conductor 195 provided inside the third insulating layer 130.

[0024] Although no wiring is provided between the interlayer connection conductor 195 provided inside the third insulating layer 130 and the interlayer connection conductor 195 provided inside the fourth insulating layer 140, wiring may be provided. In addition, wiring may or may not be provided between the interlayer connection conductors 200 and between the interlayer connection conductors 195 and 200.

[0025] The protective layer 210 is, for example, a coverlay, a resist layer, etc. The protective layer 210 may be provided on both main surfaces of the insulating substrate 100, or on one of the main surfaces.

[0026] The circuit board 1 includes at least one interlayer connection conductor, which will be described in each of the following embodiments. For example, it is preferable that the circuit board 1 includes an interlayer connection conductor, which will be described in each of the following embodiments, as the interlayer connection conductor 190 connected to the signal line 170.

[0027] The following embodiments are merely examples, and it goes without saying that partial substitution or combination of the configurations shown in different embodiments is possible. From the second embodiment onwards, a description of the matters common to the first embodiment will be omitted, and only the differences will be described. In particular, similar effects due to similar configurations will not be mentioned in each embodiment.

[0028] FIG. 3 is a cross-sectional view schematically showing an example of the circuit board according to the first embodiment of the present invention.

[0029] Although the overall configuration is not shown in Figure 3, the circuit board 1A includes an insulating layer 10 having a first main surface 10a and a second main surface 10b that face each other in the thickness direction (the up-down direction in Figure 3), a first conductor layer 21 provided on the first main surface 10a of the insulating layer 10, a second conductor layer 22 provided on the second main surface 10b of the insulating layer 10, an interlayer connection conductor 30 that penetrates the insulating layer 10 in the thickness direction and is connected to the first conductor layer 21 and the second conductor layer 22, and an anti-corrosion layer 40 provided on the surface of the first conductor layer 21 or the second conductor layer 22.

[0030] The insulating layer 10 is, for example, a resin insulating layer containing a resin as a main component. When the first conductor layer 21 or the second conductor layer 22 is a signal line, loss during signal transmission can be reduced by forming the insulating layer 10 from a resin having a low dielectric constant.

[0031] Alternatively, the insulating layer 10 may be a ceramic insulating layer containing ceramic as a main component. When the first conductor layer 21 or the second conductor layer 22 is an antenna electrode, the insulating layer 10 can be made of ceramic having a high dielectric constant, thereby enabling radiation or reception over a wide band.

[0032] The resin constituting the resin insulation layer may be a thermosetting resin or a thermoplastic resin, but is preferably a thermoplastic resin. When the resin insulation layer is made of a thermoplastic resin, multiple resin sheets on which conductor layers are formed can be stacked and collectively pressure-bonded (collectively pressed) by heat treatment.

[0033] Examples of the thermosetting resin include epoxy resin, phenol resin, polyimide resin or modified resin thereof, and acrylic resin.

[0034] Examples of thermoplastic resins include liquid crystal polymers (LCP), fluororesins, thermoplastic polyimide resins, polyether ether ketone resins (PEEK), and polyphenylene sulfide resins (PPS).

[0035] The resin insulation layer is preferably made of a liquid crystal polymer (LCP), which has a lower water absorption rate than other thermoplastic resins. Therefore, when the resin insulation layer is made of a liquid crystal polymer, the amount of moisture remaining in the resin insulation layer can be reduced.

[0036] The resin insulating layer may contain an inorganic material such as a ceramic filler.

[0037] Examples of ceramic fillers include boron nitride, talc, and fused silica.

[0038] Examples of ceramics that form the ceramic insulating layer include low temperature co-fired ceramics (LTCC) and high temperature co-fired ceramics (HTCC).

[0039] The thickness of one insulating layer 10 is preferably 10 μm or more and 100 μm or less.

[0040] The first conductor layer 21 and the second conductor layer 22 may each have a patterned shape such as a wiring, or may have a planar shape that extends over a surface. The shapes of the first conductor layer 21 and the second conductor layer 22 may be the same as or different from each other.

[0041] The first conductor layer 21 and the second conductor layer 22 are each a metal layer containing, for example, copper, silver, aluminum, stainless steel, nickel, gold, or at least one of these metals. The materials of the first conductor layer 21 and the second conductor layer 22 may be the same or different. The first conductor layer 21 and the second conductor layer 22 are both preferably made of metal foil, more preferably copper (Cu) foil.

[0042] The first conductor layer 21 and the second conductor layer 22 may each have a matte surface on one main surface and a shiny surface on the other main surface.

[0043] The thickness (length in the stacking direction) of each of the first conductor layer 21 and the second conductor layer 22 is preferably 1 μm or more and 35 μm or less, and more preferably 6 μm or more and 18 μm or less. The thicknesses of the first conductor layer 21 and the second conductor layer 22 may be the same as or different from each other.

[0044] The first conductor layer 21 and the second conductor layer 22 may or may not be parallel to each other.

[0045] One insulating layer 10 may be provided between the first conductor layer 21 and the second conductor layer 22, or two or more insulating layers 10 may be provided. When two or more insulating layers 10 are provided between the first conductor layer 21 and the second conductor layer 22, the configurations of the insulating layers 10 may be the same as or different from each other. Furthermore, when two or more insulating layers 10 are provided between the first conductor layer 21 and the second conductor layer 22, the thicknesses of the insulating layers 10 may be the same as or different from each other.

[0046] The interlayer connection conductor 30 is provided so as to penetrate the insulating layer 10 in the thickness direction but not through the first conductor layer 21 and the second conductor layer 22, and to be connected to the first conductor layer 21 and the second conductor layer 22. Therefore, the interlayer connection conductor 30 penetrates the insulating layer 10 in the thickness direction by the number of layers provided between the first conductor layer 21 and the second conductor layer 22.

[0047] In a cross section perpendicular to the thickness direction, the shape of the interlayer connection conductor 30 is preferably circular. In this case, not only a perfect circle but also an ellipse, an oval, etc. are included in the circle.

[0048] The interlayer connection conductor 30 includes a first portion 31 and a second portion 32 in the thickness direction.

[0049] The first portion 31 is made of a single metal.

[0050] The first portion 31 is, for example, a plated via. Here, the plated via means a film grown by a liquid phase method or a vapor phase method.

[0051] When the first portion 31 is a plated via, the metal contained in the first portion 31 is preferably the same as the metal constituting the first conductor layer 21, for example, Cu.

[0052] The second portion 32 contains at least a metal different from that of the first portion 31 .

[0053] The second portion 32 is, for example, a paste via. Here, the paste via refers to a solidified paste. When the circuit board 1A is fabricated by batch pressing, which will be described later, the second portion 32 functions as a bonding material, thereby electrically connecting the first portion 31 and the second conductor layer 22.

[0054] When the second portion 32 is a paste via, examples of the metal contained in the second portion 32 include Cu, Sn, Ag, Ni, Cr, Pt, Mo, Ga, Ge, Sb, In, Pb, and alloys containing at least one of these metals. The metal contained in the second portion 32 may be the same as or different from the metal contained in the first portion 31. The metal contained in the second portion 32 is, for example, an alloy containing Cu and Sn.

[0055] Alternatively, the second portion 32 may be a plated via.

[0056] When the second portion 32 is a plated via, for example, Sn can be used as the metal contained in the second portion 32. By using Sn, which has a low melting point, the second portion 32 can easily function as a bonding material.

[0057] The first portion 31 is joined to the second portion 32 via a first intermediate layer 51 containing the metal contained in the first portion 31 and the metal contained in the second portion 32, and is joined to the first conductor layer 21 without the first intermediate layer 51.

[0058] As an example, a first intermediate layer 51 containing Cu and Sn is formed on the end of the second portion 32 on the side of the first portion 31. In this case, for example, the first intermediate layer 51 contains Cu. ３ Sn, Cu ５ The first intermediate layer 51 is made of a Cu—Sn alloy such as Sn, but the composition of the first intermediate layer 51 is different from the composition of the second portion 32 .

[0059] The first portion 31 and the first conductor layer 21 are directly bonded without a dissimilar material therebetween, so that the interface between the first portion 31 and the first conductor layer 21 includes a portion where no dissimilar material exists, i.e., a portion where the first portion 31 and the first conductor layer 21 are in direct contact with each other.

[0060] The second portion 32 is joined to the second conductor layer 22 via a second intermediate layer 52 containing the metal contained in the second portion 32 and the metal contained in the second conductor layer 22 .

[0061] As an example, a second intermediate layer 52 containing Cu and Sn is formed on the end of the second portion 32 on the second conductor layer 22 side. In this case, for example, the second intermediate layer 52 contains Cu. ３ Sn, Cu ５ The second intermediate layer 52 is made of a Cu—Sn alloy such as Sn, but the composition of the second intermediate layer 52 is different from the composition of the second portion 32 .

[0062] In the example shown in Figure 3, the second intermediate layer 52 extends to the interface between the second conductor layer 22 and the insulating layer 10, but as will be described later, the second intermediate layer 52 does not have to extend to the interface between the second conductor layer 22 and the insulating layer 10.

[0063] The first intermediate layer 51 may be one layer or two or more layers, and similarly, the second intermediate layer 52 may be one layer or two or more layers.

[0064] The first intermediate layer 51 and the second intermediate layer 52 can be confirmed, for example, by using a scanning electron microscope (SEM) to observe a cross section of the insulating layer 10 cut in a direction parallel to the thickness direction. The first intermediate layer 51 and the second intermediate layer 52 have compositions different from those of both the first portion 31 and the second portion 32, and therefore appear in a different color tone from those of the first portion 31 and the second portion 32 in the SEM photograph.

[0065] Even if the types of metal elements contained are the same, the case where the content ratios of the respective metal elements are different is also considered to be "different in composition." For example, Cu ５ Sn, Cu ３ Sn, Cu ６ Sn ５ The compositions all contain Cu and Sn as metal species, but since the content ratios of the metal species are different, they can be said to be different compositions.

[0066] The anticorrosive layer 40 is formed by applying an anticorrosive treatment to the surface of the metal foil using a metal such as Zn, Ni, Cr, Mo, or Pt.

[0067] The anticorrosive layer 40 is disposed at least at the interface between the first conductor layer 21 and the insulating layer 10 , and is not disposed between the second portion 32 and the second conductor layer 22 .

[0068] When the circuit board 1A is manufactured by the batch pressing described below, by placing an anti-rust layer 40 at the interface between the first conductor layer 21 and the insulating layer 10, oxidation of the metal foil such as Cu foil that constitutes the first conductor layer 21 is prevented, thereby suppressing a decrease in adhesion between the first conductor layer 21 and the insulating layer 10.

[0069] When the circuit board 1A is fabricated by batch pressing, the thermal load on the interface between the first conductor layer 21 and the insulating layer 10 is greater than that on the interface between the second conductor layer 22 and the insulating layer 10. Therefore, it is preferable that the anticorrosive layer 40 be disposed at least on the interface between the first conductor layer 21 and the insulating layer 10.

[0070] On the other hand, if the anticorrosive layer 40 is disposed between the second portion 32 and the second conductor layer 22, the reaction between the material (e.g., conductive paste) constituting the second portion 32 and the material (e.g., metal foil) constituting the second conductor layer 22 is inhibited by the anticorrosive layer 40, making it difficult to form the second intermediate layer 52. Therefore, by not disposing the anticorrosive layer 40 between the second portion 32 and the second conductor layer 22, the second intermediate layer 52 is more easily formed, thereby improving the connection reliability between the interlayer connection conductor 30 and the second conductor layer 22.

[0071] 3, the anticorrosive layer 40 is not disposed at the interface between the second conductor layer 22 and the insulating layer 10. This prevents the reaction between the material (e.g., conductive paste) constituting the second portion 32 and the material (e.g., metal foil) constituting the second conductor layer 22 from being inhibited.

[0072] The anticorrosive layer 40 disposed at the interface between the first conductor layer 21 and the insulating layer 10 may or may not be in contact with the first portion 31 .

[0073] 3 , it is preferable that the anticorrosive layer 40 is not disposed between the first portion 31 and the first conductor layer 21. As described above, the first portion 31 is joined to the first conductor layer 21 without the first intermediate layer 51. This makes it possible to increase the connection strength between the interlayer connection conductor 30 and the first conductor layer 21.

[0074] The shape of the interlayer connection conductor 30 is not limited to that shown in FIG.

[0075] The second portion 32 may have a tapered shape in which the area of ​​the end face on the first conductor layer 21 side is smaller than the area of ​​the end face on the second conductor layer 22 side. Although a weak second intermediate layer 52 may be formed at the end of the second portion 32 on the second conductor layer 22 side, by increasing the area of ​​the second portion 32 at the portion connected to the second conductor layer 22, the connection strength between the second portion 32 and the second conductor layer 22 can be increased.

[0076] Furthermore, the first portion 31 may have a tapered shape in which the area of ​​the end face on the first conductor layer 21 side is smaller than the area of ​​the end face on the second conductor layer 22 side.

[0077] Therefore, as shown in FIG. 3, the interlayer connection conductor 30 may have a tapered shape in which the area of ​​the end face on the first conductor layer 21 side is smaller than the area of ​​the end face on the second conductor layer 22 side.

[0078] When the interlayer connection conductor 30 has a tapered shape, the height t １ is the height t of the second portion 32 ２ and the height t of the second portion 32 may be equal to ２ Lower than (t １ <t ２ ) may be used, but the height t ２ higher than (t １ >t ２ When the interlayer connection conductor 30 has a tapered shape, the height t １ The height t of the second portion 32 ２ By making the height higher than 100° C., the connection area between the first portion 31 and the second portion 32 becomes larger, and therefore the connection reliability of the interlayer connection conductor 30 can be improved.

[0079] In the example shown in Figure 3, the end face of the first portion 31 on the second conductor layer 22 side is flat, but as described below, it may protrude toward the second conductor layer 22 or may be recessed toward the first conductor layer 21.

[0080] The circuit board 1A is manufactured, for example, by the following method.

[0081] 4A to 4G are cross-sectional views schematically illustrating an example of a method for manufacturing the circuit board 1A. The circuit board 1A may be manufactured in the form of a single chip (individual piece), or may be manufactured by producing an aggregate substrate and then separating the individual pieces. The aggregate substrate here refers to a substrate that includes multiple circuit boards 1A.

[0082] First, as shown in FIG. 4A, a substrate 60 is prepared in which a conductor layer 20 is formed on one surface of an insulating layer 10 and an anticorrosive layer 40 is provided on at least the surface of the conductor layer 20 on the insulating layer 10 side.

[0083] For example, a metal foil such as a Cu foil is laminated on one main surface of the insulating layer 10, and the metal foil is patterned by photolithography to form the conductor layer 20. The insulating layer 10 is, for example, a resin sheet whose main component is a thermoplastic resin such as a liquid crystal polymer.

[0084] 4B, a via hole 70 is formed in the substrate 60 so as to penetrate the insulating layer 10 and expose a portion of the upper surface of the conductor layer 20. The via hole 70 preferably has a tapered shape.

[0085] For example, a via hole 70 is formed in the insulating layer 10 using a laser or the like so that the upper surface of the conductor layer 20 is exposed.

[0086] Subsequently, as shown in FIG. 4C, the anticorrosive layer 40 provided on the exposed portion of the conductor layer 20 is removed.

[0087] For example, after the upper surface of the conductor layer 20 exposed from the via hole 70 is washed with acid, the anticorrosive layer 40 is removed by soft etching or the like.

[0088] 4A to 4C, it is preferable to remove an anticorrosion layer (not shown) provided on the surface of the conductor layer 20 opposite to the insulating layer 10. For example, the anticorrosion layers provided on the top and bottom surfaces of the conductor layer 20 may be removed simultaneously at the stage shown in FIG. 4C, or the anticorrosion layer provided on the bottom surface of the conductor layer 20 may be removed at an earlier stage than that shown in FIG. 4A.

[0089] 4D , after the anticorrosive layer 40 has been removed, the via hole 70 is filled with a first material 71 made of a single metal. The first material 71 is filled partway into the via hole 70. There are no particular restrictions on the height of the first material 71, as long as it does not exceed the thickness of the insulating layer 10.

[0090] For example, after the anticorrosive layer 40 is removed by plating such as electrolytic plating, the via hole 70 is filled with a plating metal such as Cu as a first material 71. The first material 71 forms the first portion 31 (see FIG. 4G ).

[0091] 4E , the via hole 70 filled with the first material 71 is then filled with a second material 72 containing at least a metal different from the first material 71. The space in the via hole 70 is filled with the first material 71 and the second material 72.

[0092] For example, after the via hole 70 is filled with the first material 71, a conductive paste containing a metal material such as Cu or Sn and a resin material is filled as the second material 72. The second material 72 is solidified by a heating press described later, thereby forming the second portion 32 (see FIG. 4G ).

[0093] It is also possible to fill a plated metal such as Sn as the second material 72, but there is a risk that the underlying metal of the first material 71 may re-melt depending on the metal selected as the second material 72. Therefore, from the viewpoint of increasing the degree of freedom in selecting the first material 71 and the second material 72, it is preferable to fill the via hole 70 after the anticorrosive layer 40 has been removed with a plated metal as the first material 71, and then fill it with a conductive paste as the second material 72.

[0094] As shown in Fig. 4F , a plurality of substrates are stacked, including substrates 60 filled with a first material 71 and a second material 72. Fig. 4F shows an example in which substrates 60 filled with a first material 71 and a second material 72 are stacked continuously, but is not particularly limited as long as the substrates include substrates 60 filled with a first material 71 and a second material 72.

[0095] 4G, heat and pressure are applied to press the components together, thereby completing the circuit board 1A.

[0096] According to this manufacturing method, the circuit board 1A can be easily manufactured by batch pressing the insulating layer 10. Therefore, the number of manufacturing steps for the circuit board 1A can be reduced, and manufacturing costs can be kept low.

[0097] FIG. 5 is a cross-sectional view schematically showing an example of a circuit board according to a second embodiment of the present invention.

[0098] 5, the anticorrosive layer 40 is disposed at the interface between the second conductor layer 22 and the insulating layer 10, without contacting the second intermediate layer 52. This prevents the reaction between the material constituting the second portion 32 (e.g., conductive paste) and the material constituting the second conductor layer 22 (e.g., metal foil) from being inhibited.

[0099] FIG. 6 is a cross-sectional view schematically showing an example of a circuit board according to a third embodiment of the present invention.

[0100] 6 , the second intermediate layer 52 does not extend to the interface between the second conductor layer 22 and the insulating layer 10. In FIG. 6 , the anticorrosive layer 40 is not disposed at the interface between the second conductor layer 22 and the insulating layer 10, but it may be disposed at the interface between the second conductor layer 22 and the insulating layer 10 as long as it does not come into contact with the second intermediate layer 52.

[0101] FIG. 7 is a cross-sectional view schematically showing an example of a circuit board according to a fourth embodiment of the present invention.

[0102] In the circuit board 1D shown in Figure 7, the second portion 32 has a tapered shape in which the area of ​​the end face on the first conductor layer 21 side is smaller than the area of ​​the end face on the second conductor layer 22 side, and the tapered shape has a gradually changing inclination angle.

[0103] 7, the area of ​​the second portion 32 connected to the second conductor layer 22 can be made larger than that of the circuit board 1A shown in Fig. 3. Therefore, the connection strength between the second portion 32 and the second conductor layer 22 can be further increased.

[0104] In the example shown in FIG. 7, the inclination angle of the tapered shape changes in two steps, but it may also change in three steps, or in four or more steps.

[0105] Furthermore, the first portion 31 may have a tapered shape in which the area of ​​the end face on the first conductor layer 21 side is smaller than the area of ​​the end face on the second conductor layer 22 side. In this case, the tapered shape may have a slope angle that varies stepwise.

[0106] FIG. 8 is a cross-sectional view schematically showing an example of a circuit board according to a fifth embodiment of the present invention.

[0107] In the circuit board 1E shown in Fig. 8, the end face of the first portion 31 on the second conductor layer 22 side protrudes toward the second conductor layer 22. In the example shown in Fig. 8, the end faces of the first portion 31 on the second conductor layer 22 side protrude symmetrically.

[0108] FIG. 9 is a cross-sectional view schematically showing another example of a circuit board according to the fifth embodiment of the present invention.

[0109] 9, similarly to Fig. 8, the end face of the first portion 31 on the second conductor layer 22 side protrudes toward the second conductor layer 22. On the other hand, in the example shown in Fig. 9, the end face of the first portion 31 on the second conductor layer 22 side protrudes asymmetrically.

[0110] As shown in Figure 8 or Figure 9, if the end face of the first part 31 on the second conductor layer 22 side protrudes toward the second conductor layer 22, the connection area between the first part 31 and the second part 32 becomes larger, and the connection strength between the first part 31 and the second part 32 can be increased.

[0111] Height t of the first portion 31 １ is the height t of the second portion 32 ２ and the height t of the second portion 32 may be equal to ２ Lower than (t １ <t ２ ) may be used, but the height t ２ higher than (t １ >t ２ ) is preferable. １ is the height of the highest part, and the height t of the second part 32 ２ is defined as the height of the lowest part.

[0112] 8 and 9, there is one peak, but there may be two or more peaks. When there are two or more peaks, the peaks may be the same or different in size, height, shape, etc.

[0113] FIG. 10 is a cross-sectional view schematically showing an example of a circuit board according to a sixth embodiment of the present invention.

[0114] 10, the end face of the first portion 31 on the second conductor layer 22 side is recessed toward the first conductor layer 21. In the example shown in Fig. 10, the end face of the first portion 31 on the second conductor layer 22 side is recessed symmetrically.

[0115] FIG. 11 is a cross-sectional view schematically showing another example of a circuit board according to the sixth embodiment of the present invention.

[0116] 11, similarly to Fig. 10, the end face of the first portion 31 on the second conductor layer 22 side is recessed toward the first conductor layer 21. On the other hand, in the example shown in Fig. 11, the end face of the first portion 31 on the second conductor layer 22 side is recessed asymmetrically.

[0117] As shown in Figure 10 or 11, if the end face of the first part 31 on the second conductor layer 22 side is recessed toward the first conductor layer 21, the connection area between the first part 31 and the second part 32 becomes larger, and the connection strength between the first part 31 and the second part 32 can be increased.

[0118] Height t of the first portion 31 １ is the height t of the second portion 32 ２ and the height t of the second portion 32 may be equal to ２ Lower than (t １ <t ２ ) may be used, but the height t ２ higher than (t １ >t ２ ) is preferable. １ is the height of the lowest part, and the height t of the second part 32 ２ is defined as the height of the highest part.

[0119] 10 and 11, the valley has one apex, but two or more apexes may exist. When two or more apexes exist, the size, depth, shape, etc. of the valleys may be the same or different.

[0120] The end face of the first portion 31 on the second conductor layer 22 side may include a portion that protrudes toward the second conductor layer 22 and a portion that is recessed toward the first conductor layer 21 .

[0121] FIG. 12 is a cross-sectional view schematically showing an example of a circuit board according to a seventh embodiment of the present invention.

[0122] In the circuit board 1I shown in FIG. 12, the end face of the first portion 31 on the first conductor layer 21 side protrudes toward the first conductor layer 21 side beyond the interface between the first conductor layer 21 and the insulating layer 10 .

[0123] As shown in Figure 12, if the end face of the first portion 31 on the first conductor layer 21 side protrudes toward the first conductor layer 21 further than the interface between the first conductor layer 21 and the insulating layer 10, the connection area between the first portion 31 and the first conductor layer 21 becomes larger, and the connection strength between the first portion 31 and the first conductor layer 21 can be increased.

[0124] In the example shown in FIG. 12, the end face of the first portion 31 on the first conductor layer 21 side protrudes symmetrically, but it may also protrude asymmetrically.

[0125] 12, there is one peak, but there may be two or more peaks. When there are two or more peaks, the peaks may have the same size, height, shape, etc.

[0126] FIG. 13 is a cross-sectional view schematically showing an example of a circuit board according to an eighth embodiment of the present invention.

[0127] As in the circuit board 1J shown in FIG. 13, the first intermediate layer 51 may extend to the interface between the first portion 31 and the insulating layer 10.

[0128] FIG. 14 is a cross-sectional view schematically showing another example of the circuit board according to the eighth embodiment of the present invention.

[0129] 14 , the first intermediate layer 51 extends to the interface between the first portion 31 and the insulating layer 10, and also reaches the interface between the first conductor layer 21 and the insulating layer 10. This further increases the connection strength between the first portion 31 and the first conductor layer 21.

[0130] FIG. 15 is a cross-sectional view schematically showing an example of a circuit board according to a ninth embodiment of the present invention.

[0131] In the circuit board 1L shown in FIG. 15, the end face of the first portion 31 on the second conductor layer 22 side has a portion that protrudes toward the second conductor layer 22.

[0132] As shown in Figure 15, if there is a protruding portion (hereinafter also referred to as a protruding portion) on a part of the end face of the first part 31 on the second conductor layer 22 side, the connection area between the first part 31 and the second part 32 becomes larger, as in Figure 8 or Figure 9, and therefore the connection strength between the first part 31 and the second part 32 can be increased.

[0133] One protrusion or two or more protrusions may be present on a part of the end surface of the first portion 31 on the side of the second conductor layer 22. When two or more protrusions are present, the size, height, shape, etc. of the protrusions may be the same or different.

[0134] The height of the protrusion is, for example, 1 μm or more and 20 μm or less. Note that the shape of the protrusion is not limited to the shape shown in FIG.

[0135] The maximum diameter of the protrusion is, for example, 1 μm or more and 10 μm or less. Here, the maximum diameter of the protrusion refers to the diameter when the cross-sectional shape is circular, or the maximum length passing through the center of the cross-section when the cross-section shape is other than circular.

[0136] FIG. 16 is a cross-sectional view schematically showing an example of a circuit board according to a tenth embodiment of the present invention.

[0137] In the circuit board 1M shown in FIG. 16, a portion of the end face of the first portion 31 on the second conductor layer 22 side is recessed toward the first conductor layer 21 .

[0138] As shown in Figure 16, if there is a recessed portion (hereinafter also referred to as a recessed portion) on part of the end face of the first part 31 on the second conductor layer 22 side, the connection area between the first part 31 and the second part 32 becomes larger, as in Figure 10 or Figure 11, and the connection strength between the first part 31 and the second part 32 can be increased.

[0139] There may be one recessed portion or two or more recessed portions in a part of the end face of the first portion 31 on the side of the second conductor layer 22. When there are two or more recessed portions, the size, depth, shape, etc. of the recessed portions may be the same or different.

[0140] The depth of the recess is, for example, 1 μm or more and 20 μm or less. Note that the shape of the recess is not limited to the shape shown in FIG.

[0141] The maximum diameter of the recessed portion is, for example, 1 μm or more and 10 μm or less. Here, the maximum diameter of the recessed portion refers to the diameter when the cross-sectional shape is circular, and refers to the maximum length passing through the center of the cross-section when the cross-section shape is other than circular.

[0142] A part of the end face of the first portion 31 on the second conductor layer 22 side may have a mixture of a protruding portion and a recessed portion.

[0143] FIG. 17 is a cross-sectional view schematically showing another example of a circuit board according to the tenth embodiment of the present invention.

[0144] 17 , a part of the second portion 32 may be joined to the first conductor layer 21. In this case, the first conductor layer 21 is joined to the second portion 32 via the first intermediate layer 51.

[0145] 18A, 18B, and 18C are cross-sectional views schematically showing examples of a circuit board according to an eleventh embodiment of the present invention.

[0146] As in the circuit board 1O shown in FIG. 18A , the circuit board 1P shown in FIG. 18B , or the circuit board 1Q shown in FIG. 18C , voids may be present inside the first portion 31. The number, size, location, etc. of the voids are not particularly limited. For example, the voids may be present near the interface between the first portion 31 and the first conductor layer 21 as shown in FIG. 18A , near the interface between the insulating layer 10 and the first conductor layer 21 as shown in FIG. 18B , or near the first intermediate layer 51 as shown in FIG. 18C . In addition to or instead of the voids, resin residues (carbides), copper foil oxides (copper oxide), etc. may be present.

[0147] FIG. 19 is a cross-sectional view schematically showing an example of a circuit board according to an eleventh embodiment of the present invention.

[0148] In the circuit board 1R shown in FIG. 19, the surface roughness of the first conductor layer 21 in contact with the insulating layer 10 is greater than the surface roughness of the second conductor layer 22 in contact with the insulating layer 10.

[0149] 19, by increasing the surface roughness of the first conductor layer 21 in contact with the insulating layer 10, the adhesive area between the insulating layer 10 and the first conductor layer 21 increases, thereby increasing the adhesive strength between them. Therefore, when electronic components or the like are mounted on the first conductor layer 21, they are less likely to be peeled off.

[0150] FIG. 20 is a cross-sectional view schematically showing another example of the circuit board according to the eleventh embodiment of the present invention.

[0151] In the circuit board 1S shown in FIG. 20, the surface roughness of the first conductor layer 21 in contact with the insulating layer 10 is also greater than the surface roughness of the second conductor layer 22 in contact with the insulating layer 10.

[0152] As in the circuit board 1S shown in FIG. 20, the anticorrosive layer 40 does not have to be disposed at the interface between the first conductor layer 21 and the insulating layer 10.

[0153] In the circuit board 1S shown in Figure 20, the surface roughness of the first conductor layer 21 in contact with the insulating layer 10 is greater than the surface roughness of the second conductor layer 22 in contact with the insulating layer 10, so that the adhesion strength between the first conductor layer 21 and the insulating layer 10 can be increased even if an anti-corrosion layer 40 is not placed at the interface between the two.

[0154] FIG. 21 is a cross-sectional view schematically showing an example of a circuit board according to a twelfth embodiment of the present invention.

[0155] 21 , the interlayer connection conductor 30 has a shape in which the area of ​​the end face on the first conductor layer 21 side is equal to the area of ​​the end face on the second conductor layer 22 side. In other words, the interlayer connection conductor 30 does not have a tapered shape.

[0156] Specifically, the first portion 31 has a shape in which the area of ​​the end face on the first conductor layer 21 side is equal to the area of ​​the end face on the second conductor layer 22 side, and the second portion 32 has a shape in which the area of ​​the end face on the first conductor layer 21 side is equal to the area of ​​the end face on the second conductor layer 22 side.

[0157] If the interlayer connection conductor 30 has a tapered shape as in the circuit board 1A shown in Fig. 3, strain stress tends to concentrate at the necking portion of the interlayer connection conductor 30 (particularly the necking portion between the interlayer connection conductor 30 and the first conductor layer 21). In contrast, if the interlayer connection conductor 30 does not have a tapered shape as in the circuit board 1T shown in Fig. 21, strain stress does not concentrate at the necking portion of the interlayer connection conductor 30. Therefore, the stress acting on the interlayer connection conductor 30 is dispersed, improving connection reliability.

[0158] The circuit board of the present invention is not limited to the above-described embodiment, and various applications and modifications can be made within the scope of the present invention with respect to the configuration of the circuit board, manufacturing conditions, and the like.

[0159] The circuit board of the present invention is used, for example, as follows.

[0160] FIG. 22 is a cross-sectional view schematically showing an example of a circuit board on which electronic components are mounted.

[0161] 22, a mounting electrode 150 of a circuit board 2 is connected to an external electrode 240 of an electronic component 230 via a conductive bonding material 220 such as solder. Examples of the electronic component 230 include an integrated circuit (IC) and a connector.

[0162] FIG. 23 is a cross-sectional view schematically showing an example of a circuit board having a bent portion.

[0163] 23, the circuit board 3 has bent portions 3P1 and 3P2. The number and shape of the bent portions are not particularly limited.

[0164] The insulating layer constituting the circuit board 3 is preferably a resin insulating layer containing a thermoplastic resin such as a liquid crystal polymer as a main component. In this case, the circuit board 3 can be produced by the above-mentioned batch pressing.

[0165] Since the circuit board of the present invention has the configuration described in the above embodiment, even if it has a bent portion, it can be expected to be prevented from breaking due to bending stress.

[0166] The present specification discloses the following:

[0167] <1> An insulating layer having a first main surface and a second main surface opposing each other in a thickness direction, a first conductor layer provided on the first main surface of the insulating layer, a second conductor layer provided on the second main surface of the insulating layer, an interlayer connection conductor provided to penetrate the insulating layer in the thickness direction and connected to the first conductor layer and the second conductor layer, and an anticorrosion layer provided on a surface of the first conductor layer or the second conductor layer, wherein the interlayer connection conductor includes, in the thickness direction, a first portion made of a single metal and a second portion containing at least a metal different from that of the first portion, the first portion is bonded to the second portion via a first intermediate layer containing a metal contained in the first portion and a metal contained in the second portion, and is bonded to the first conductor layer without the first intermediate layer, and the second portion is bonded to the second conductor layer via a second intermediate layer containing a metal contained in the second portion and a metal contained in the second conductor layer, A circuit board, wherein the anticorrosive layer is disposed at least at the interface between the first conductor layer and the insulating layer, and is not disposed between the second portion and the second conductor layer.

[0168] <2> The circuit board according to <1>, wherein the anticorrosive layer is not disposed at an interface between the second conductor layer and the insulating layer.

[0169] <3> The circuit board according to <1>, wherein the anticorrosive layer is disposed at the interface between the second conductor layer and the insulating layer in a range not in contact with the second intermediate layer.

[0170] <4> The circuit board according to any one of <1> to <3>, wherein the second portion has a tapered shape in which an area of ​​an end face on the first conductor layer side is smaller than an area of ​​an end face on the second conductor layer side.

[0171] <5> The circuit board according to <4>, wherein the tapered shape has an inclination angle that varies stepwise.

[0172] <6> The circuit board according to any one of <1> to <3>, wherein the interlayer connection conductor has a shape in which an area of ​​an end face on the first conductor layer side is equal to an area of ​​an end face on the second conductor layer side, the first portion has a shape in which an area of ​​an end face on the first conductor layer side is equal to an area of ​​an end face on the second conductor layer side, and the second portion has a shape in which an area of ​​an end face on the first conductor layer side is equal to an area of ​​an end face on the second conductor layer side.

[0173] <7> The circuit board according to any one of <1> to <6>, wherein an end face of the first portion on the second conductor layer side protrudes toward the second conductor layer or is recessed toward the first conductor layer.

[0174] <8> The circuit board according to any one of <1> to <7>, wherein an end face of the first portion on the first conductor layer side protrudes toward the first conductor layer beyond an interface between the first conductor layer and the insulating layer.

[0175] <9> The circuit board according to any one of <1> to <8>, wherein the first intermediate layer extends to an interface between the first portion and the insulating layer.

[0176] <10> The circuit board according to <9>, wherein the first intermediate layer reaches an interface between the first conductor layer and the insulating layer.

[0177] <11> The circuit board according to any one of <1> to <10>, wherein a part of an end face of the first portion on the second conductor layer side has a part that protrudes toward the second conductor layer or a part that is recessed toward the first conductor layer.

[0178] <12> The circuit board according to any one of <1> to <11>, wherein the surface roughness of the first conductor layer in contact with the insulating layer is greater than the surface roughness of the second conductor layer in contact with the insulating layer.

[0179] <13> The circuit board according to any one of <1> to <12>, wherein the second intermediate layer extends to an interface between the second conductor layer and the insulating layer.

[0180] <14> The circuit board according to any one of <1> to <13>, wherein the anticorrosive layer is not disposed between the first portion and the first conductor layer.

[0181] <15> The circuit board according to any one of <1> to <14>, wherein the insulating layer contains a resin as a main component.

[0182] <16> The circuit board according to any one of <1> to <14>, wherein the insulating layer is mainly composed of ceramic.

[0183] <17> The circuit board according to any one of <1> to <16>, wherein the first conductor layer and the second conductor layer are both made of metal foil.

[0184] <18> A method for manufacturing a circuit board, comprising: a step of preparing a substrate having a conductor layer formed on one surface of an insulating layer and an anticorrosive layer provided on at least a surface of the conductor layer facing the insulating layer; a step of forming a via hole in the substrate, the via hole penetrating the insulating layer and exposing a part of an upper surface of the conductor layer; a step of removing the anticorrosive layer provided on the exposed part of the conductor layer; a step of filling the via hole after the anticorrosive layer has been removed with a first material made of a single metal, and then filling with a second material containing at least a metal different from the first material; and a step of stacking a plurality of substrates including the substrates filled with the first material and the second material, and pressing them together by applying heat and pressure.

[0185] <19> The method for manufacturing a circuit board according to <18>, wherein after the anticorrosive layer is removed, a plating metal is filled as the first material into the via hole, and then a conductive paste is filled as the second material.

[0186] <20> The method for manufacturing a circuit board according to <18> or <19>, wherein the insulating layer contains a thermoplastic resin as a main component.

[0187] Furthermore, the present specification discloses the following:

[0188] <31> An insulating layer having a first main surface and a second main surface opposing each other in a thickness direction; a first conductor layer provided on the first main surface of the insulating layer; a second conductor layer provided on the second main surface of the insulating layer; and an interlayer connection conductor provided to penetrate the insulating layer in the thickness direction and connected to the first conductor layer and the second conductor layer, wherein the interlayer connection conductor includes, in the thickness direction, a first portion made of a single metal and a second portion containing at least a metal different from that of the first portion, the first portion is bonded to the second portion via a first intermediate layer containing a metal contained in the first portion and a metal contained in the second portion, and is bonded to the first conductor layer without the first intermediate layer, and the second portion is bonded to the second conductor layer via a second intermediate layer containing a metal contained in the second portion and a metal contained in the second conductor layer, A circuit board, wherein the surface roughness of the first conductor layer in contact with the insulating layer is greater than the surface roughness of the second conductor layer in contact with the insulating layer.

[0189] <32> The circuit board according to <31>, wherein the second portion has a tapered shape in which an area of ​​an end face on the first conductor layer side is smaller than an area of ​​an end face on the second conductor layer side.

[0190] <33> The circuit board according to <32>, wherein the tapered shape has an inclination angle that varies stepwise.

[0191] <34> The circuit board according to <31>, wherein the interlayer connection conductor has a shape in which an area of ​​an end face on the first conductor layer side is equal to an area of ​​an end face on the second conductor layer side, the first portion has a shape in which an area of ​​an end face on the first conductor layer side is equal to an area of ​​an end face on the second conductor layer side, and the second portion has a shape in which an area of ​​an end face on the first conductor layer side is equal to an area of ​​an end face on the second conductor layer side.

[0192] <35> The circuit board according to any one of <31> to <34>, wherein an end face of the first portion on the second conductor layer side protrudes toward the second conductor layer or is recessed toward the first conductor layer.

[0193] <36> The circuit board according to any one of <31> to <35>, wherein an end face of the first portion on the first conductor layer side protrudes toward the first conductor layer beyond an interface between the first conductor layer and the insulating layer.

[0194] <37> The circuit board according to any one of <31> to <36>, wherein the first intermediate layer extends to an interface between the first portion and the insulating layer.

[0195] <38> The circuit board according to <37>, wherein the first intermediate layer reaches an interface between the first conductor layer and the insulating layer.

[0196] <39> The circuit board according to any one of <31> to <38>, wherein a part of an end face of the first portion on the second conductor layer side has a part that protrudes toward the second conductor layer or a part that is recessed toward the first conductor layer.

[0197] <40> The circuit board according to any one of <31> to <39>, wherein the second intermediate layer extends to an interface between the second conductor layer and the insulating layer.

[0198] <41> The circuit board according to any one of <31> to <40>, wherein the insulating layer contains a resin as a main component.

[0199] <42> The circuit board according to any one of <31> to <40>, wherein the insulating layer is mainly composed of ceramic.

[0200] <43> The circuit board according to any one of <31> to <42>, wherein the first conductor layer and the second conductor layer are both made of metal foil.

[0201] <44> The circuit board according to any one of <31> to <43>, further comprising an anticorrosive layer provided on a surface of the first conductor layer or the second conductor layer, wherein the anticorrosive layer is disposed at least at an interface between the first conductor layer and the insulating layer, and is not disposed between the second portion and the second conductor layer.

[0202] <45> The circuit board according to <44>, wherein the anticorrosive layer is not disposed at the interface between the second conductor layer and the insulating layer.

[0203] <46> The circuit board according to <44>, wherein the anticorrosive layer is disposed at the interface between the second conductor layer and the insulating layer in a range not in contact with the second intermediate layer.

[0204] <47> The circuit board according to any one of <44> to <46>, wherein the anticorrosive layer is not disposed between the first portion and the first conductor layer.

[0205] <48> A method for manufacturing a circuit board, comprising: a step of preparing a substrate having an insulating layer on one surface thereof, the insulating layer having a conductor layer formed thereon, the conductor layer having a surface roughness on the insulating layer side greater than the surface roughness on the side opposite to the insulating layer; a step of forming a via hole in the substrate, the via hole penetrating the insulating layer and exposing a portion of an upper surface of the conductor layer; a step of filling the via hole with a first material made of a single metal, and then filling the via hole with a second material containing at least a metal different from the first material; and a step of stacking a plurality of substrates, including the substrates filled with the first material and the second material, and pressing them together by applying heat and pressure.

[0206] <49> The method for manufacturing a circuit board according to <48>, wherein the via holes are filled with a plating metal as the first material, and then filled with a conductive paste as the second material.

[0207] <50> The method for manufacturing a circuit board according to <48> or <49>, wherein the insulating layer contains a thermoplastic resin as a main component.

[0208] 1, 1A, 1B, 1C, 1D, 1E, 1F, 1G, 1H, 1I, 1J, 1K, 1L, 1M, 1N, 1O, 1P, 1Q, 1R, 1S, 1T, 2, 3 Circuit board 3P1, 3P2 Bent portion 10 Insulating layer 10a First main surface 10b Second main surface 20 Conductor layer 21 First conductor layer 22 Second conductor layer 30 Interlayer connection conductor 31 First portion 32 Second portion 40 Anti-corrosion layer 51 First intermediate layer 52 Second intermediate layer 60 Base material 70 Via hole 71 First material 72 Second material 100 Insulating base material 110 First insulating layer 120 Second insulating layer 130 Third insulating layer 140 Fourth insulating layer 150 Mounting electrode 160 Ground wiring 170 Signal line 180, 185 Wiring 190, 195, 200 Interlayer connection conductor 210 Protective layer 220 Conductive bonding material 230 Electronic component 240 External electrode t １ Height of the first part t ２ Second part height

Claims

1. an insulating layer having a first main surface and a second main surface opposed to each other in a thickness direction; a first conductor layer provided on the first main surface of the insulating layer; a second conductor layer provided on the second main surface of the insulating layer; an interlayer connection conductor provided to penetrate the insulating layer in the thickness direction and connected to the first conductor layer and the second conductor layer; an anticorrosion layer provided on a surface of the first conductor layer or the second conductor layer; the interlayer connection conductor includes a first portion made of a single metal and a second portion containing at least a metal different from that of the first portion in the thickness direction; the first portion is bonded to the second portion via a first intermediate layer including a metal contained in the first portion and a metal contained in the second portion, and is bonded to the first conductor layer without the first intermediate layer; the second portion is bonded to the second conductor layer via a second intermediate layer containing a metal contained in the second portion and a metal contained in the second conductor layer; A circuit board, wherein the anticorrosive layer is disposed at least at the interface between the first conductor layer and the insulating layer, but is not disposed at the interface between the second conductor layer and the insulating layer, and is not disposed between the second portion and the second conductor layer.

2. The circuit board according to claim 1 , wherein the second portion has a tapered shape in which an area of ​​an end face on the first conductor layer side is smaller than an area of ​​an end face on the second conductor layer side.

3. The circuit board according to claim 2 , wherein the tapered shape has an inclination angle that varies stepwise.

4. the interlayer connection conductor has a shape in which the area of ​​an end face on the side of the first conductor layer is equal to the area of ​​an end face on the side of the second conductor layer, the first portion has a shape in which an area of ​​an end face on the first conductor layer side is equal to an area of ​​an end face on the second conductor layer side, The circuit board according to claim 1 , wherein the second portion has a shape in which an area of ​​an end face on the side of the first conductor layer is equal to an area of ​​an end face on the side of the second conductor layer.

5. The circuit board according to any one of claims 1 to 4, wherein an end face of the first portion on the second conductor layer side protrudes toward the second conductor layer or is recessed toward the first conductor layer.

6. The circuit board according to any one of claims 1 to 4, wherein the end face of the first portion on the first conductor layer side protrudes toward the first conductor layer side beyond the interface between the first conductor layer and the insulating layer.

7. 5. The circuit board according to claim 1, wherein the first intermediate layer extends to an interface between the first portion and the insulating layer.

8. The circuit board according to claim 7 , wherein the first intermediate layer extends to an interface between the first conductor layer and the insulating layer.

9. The circuit board according to any one of claims 1 to 4, wherein a part of the end face of the first portion on the side of the second conductor layer has a part that protrudes toward the second conductor layer or a part that is recessed toward the first conductor layer.

10. The circuit board according to any one of claims 1 to 4, wherein the surface roughness of the first conductor layer in contact with the insulating layer is greater than the surface roughness of the second conductor layer in contact with the insulating layer.

11. 5. The circuit board according to claim 1, wherein the second intermediate layer extends to an interface between the second conductor layer and the insulating layer.

12. 5. The circuit board according to claim 1, wherein the anticorrosive layer is not disposed between the first portion and the first conductor layer.

13. 5. The circuit board according to claim 1, wherein the insulating layer is mainly composed of a resin.

14. 5. The circuit board according to claim 1, wherein the insulating layer is mainly made of ceramic.

15. 5. The circuit board according to claim 1, wherein the first conductor layer and the second conductor layer are both made of metal foil.

16. An insulating layer having a first main surface and a second main surface opposed to each other in a thickness direction; a first conductor layer provided on the first main surface of the insulating layer; a second conductor layer provided on the second main surface of the insulating layer; an interlayer connection conductor provided to penetrate the insulating layer in the thickness direction and connected to the first conductor layer and the second conductor layer; an anticorrosion layer provided on a surface of the first conductor layer or the second conductor layer; the interlayer connection conductor includes a first portion made of a single metal and a second portion containing at least a metal different from that of the first portion in the thickness direction; the first portion is bonded to the second portion via a first intermediate layer including a metal contained in the first portion and a metal contained in the second portion, and is bonded to the first conductor layer without the first intermediate layer; the second portion is bonded to the second conductor layer via a second intermediate layer containing a metal contained in the second portion and a metal contained in the second conductor layer; the anticorrosion layer is disposed at least at an interface between the first conductor layer and the insulating layer, and is not disposed between the second portion and the second conductor layer; The first intermediate layer extends to the interface between the first portion and the insulating layer, and further reaches the interface between the first conductor layer and the insulating layer.

17. preparing a substrate having an insulating layer on one surface thereof and an anticorrosive layer on at least the insulating layer side of the conductive layer; forming a via hole in the base material that penetrates the insulating layer and exposes a portion of an upper surface of the conductor layer; removing the anticorrosive layer provided on the exposed portion of the conductor layer; filling the via hole after the anticorrosive layer has been removed with a first material made of a single metal, and then filling the via hole with a second material containing at least a metal different from the first material; a step of stacking a plurality of base materials including the base material filled with the first material and the second material, and pressing them together by applying heat and pressure, a first conductive layer formed on one of the main surfaces of the insulating layer and the insulating layer, and a second conductive layer formed on the other main surface of the insulating layer, and the insulating layer;

18. 18. The method for manufacturing a circuit board according to claim 17, wherein the via holes after the anticorrosive layer has been removed are filled with a plating metal as the first material, and then filled with a conductive paste as the second material.

19. The method for manufacturing a circuit board according to claim 17 or 18, wherein the insulating layer is mainly composed of a thermoplastic resin.