Composite material of copper and lower thermal expansion metal than copper, printed wiring board, printed wiring board device, and manufacturing method of composite material of copper and lower thermal expansion metal than copper

Abstract

To provide a composite material of copper and lower thermal expansion metal than copper, a printed wiring board with the composite material of the copper and the lower thermal expansion metal than copper, and a printed wiring board device with the printed wiring board.SOLUTION: A composite material 100 of copper and lower thermal expansion metal than copper comprises: a plurality of copper layers 101a and 101b laminated and disposed in a first direction; a lower thermal expansion metal layer 102 which is disposed between the plurality of copper layers in the first direction and of which the thermal expansion coefficient is lower than copper; and a plurality of conductive adhesion layers 103a and 103b adhering each of the plurality of copper layers and the lower thermal expansion metal layer. The plurality of copper layers includes a plurality of outermost copper layers disposed at an outermost side in the first direction.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to a composite of copper and a metal having a lower thermal expansion than copper (referred to in this specification as a copper-metal composite having a lower thermal expansion than copper), a printed wiring board including a copper-metal composite having a lower thermal expansion than copper, a printed wiring board device including a printed wiring board including a copper-metal composite having a lower thermal expansion than copper, and methods for manufacturing these. [Background technology]

[0002] Generally, electronic components having a smaller thermal expansion coefficient than the printed wiring board are mounted on the printed wiring board. A printed wiring board having a core is known as a conventional technique for reducing the thermal expansion difference between the printed wiring board and the electronic components.

[0003] Also, composite materials containing copper and molybdenum are known (see, for example, JP 2017-160501 A (Patent Document 1), JP 2007-115731 A (Patent Document 2), or Japanese Patent No. 3862737 (Patent Document 3)). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2017-160501 A [Patent Document 2] JP 2007-115731 A [Patent Document 3] Patent No. 3862737 Summary of the Invention [Problem to be solved by the invention]

[0005] In a printed wiring board having such a core, a through hole having an inner diameter larger than that of the through hole of the printed wiring board must be formed in advance in the core, and therefore the manufacturing method of the printed wiring board as described above requires more steps and is more expensive than a manufacturing method of a printed wiring board not having a core.

[0006] In addition, the copper-molybdenum composite material is produced by pressing a laminate in which copper layers and molybdenum layers are alternately laminated while heating it at a high temperature, as described in Patent Documents 1 to 3. Therefore, the production cost of the conventional copper-molybdenum composite material is high.

[0007] A primary object of the present disclosure is to provide a copper-metal composite material with a lower thermal expansion than copper that can be manufactured at reduced costs, a printed wiring board including the copper-metal composite material with a lower thermal expansion than copper, and a printed wiring board device including the printed wiring board. [Means for solving the problem]

[0008] The copper-metal composite material having a thermal expansion coefficient lower than that of copper according to the present disclosure includes a plurality of copper layers arranged in a first direction, at least one low thermal expansion metal layer arranged between the plurality of copper layers in the first direction and made of a metal material having a thermal expansion coefficient lower than that of copper, and a plurality of conductive adhesive layers bonding each of the plurality of copper layers to the at least one low thermal expansion metal layer. The plurality of copper layers includes a plurality of outermost copper layers arranged on the outermost sides in the first direction. Effect of the Invention

[0009] According to the present disclosure, it is possible to provide a copper-metal composite material with a lower thermal expansion than copper that has a reduced manufacturing cost, a printed wiring board including the copper-metal composite material with a lower thermal expansion than copper, and a printed wiring board device including the printed wiring board. [Brief description of the drawings]

[0010] [Figure 1] 1 is a cross-sectional view of a copper-molybdenum composite material according to a first embodiment. [Diagram 2] FIG. 4 is a cross-sectional view illustrating a modified example of the copper-molybdenum composite material according to the first embodiment. [Diagram 3] 1 is a cross-sectional view of a printed wiring board and a printed wiring board device according to a first embodiment. [Figure 4] 2 is a cross-sectional view showing a step of a method for producing the copper-molybdenum composite material shown in FIG. 1. [Diagram 5] 2 is a cross-sectional view showing a modified example of the method for producing the copper-molybdenum composite material shown in FIG. 1. [Figure 6] 3 is a cross-sectional view showing a step of a method for producing the copper-molybdenum composite material shown in FIG. 2. [Figure 7] 4 is a cross-sectional view showing one step of a method for manufacturing the printed wiring board shown in FIG. [Figure 8] 8 is a cross-sectional view showing a step performed after the step shown in FIG. 7 in the method for manufacturing the printed wiring board shown in FIG. [Figure 9] 9 is a cross-sectional view showing a step performed after the step shown in FIG. 8 in the method for manufacturing the printed wiring board shown in FIG. [Figure 10] 10 is a cross-sectional view showing a step performed after the step shown in FIG. 9 in the method for manufacturing the printed wiring board shown in FIG. [Figure 11] 11 is a cross-sectional view showing a step performed after the step shown in FIG. 10 in the method for manufacturing the printed wiring board shown in FIG. [Figure 12] 12 is a cross-sectional view showing a step performed after the step shown in FIG. 11 in the method for manufacturing the printed wiring board shown in FIG. [Figure 13] 13 is a cross-sectional view showing a step performed after the step shown in FIG. 12 in the method for manufacturing the printed wiring board shown in FIG. [Figure 14] 14 is a cross-sectional view showing a step performed after the step shown in FIG. 13 in the method for manufacturing the printed wiring board shown in FIG. [Figure 15] 15 is a cross-sectional view showing a step performed after the step shown in FIG. 14 in the method for manufacturing the printed wiring board shown in FIG. [Figure 16]16 is a cross-sectional view showing a step performed after the step shown in FIG. 15 in the method for manufacturing the printed wiring board shown in FIG. [Figure 17] 17 is a cross-sectional view showing a step performed after the step shown in FIG. 16 in the method for manufacturing the printed wiring board shown in FIG. [Figure 18] FIG. 11 is a cross-sectional view of a copper-molybdenum composite material according to a second embodiment. [Figure 19] FIG. 11 is a cross-sectional view illustrating a modified example of the copper-molybdenum composite material according to the second embodiment. [Figure 20] 19 is a cross-sectional view showing a step of a method for producing the copper-molybdenum composite material shown in FIG. 18. [Figure 21] 20 is a cross-sectional view showing a modified example of the method for producing the copper-molybdenum composite material shown in FIG. 19. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. In the following drawings, the same or corresponding parts are designated by the same reference numerals, and description thereof will not be repeated. The copper-metal composite material having a thermal expansion coefficient lower than that of copper according to each embodiment of the present disclosure may contain any metal material having a thermal expansion coefficient lower than that of copper (Cu). The metal having a thermal expansion coefficient lower than that of copper may contain at least one selected from the group consisting of molybdenum (Mo), a molybdenum alloy having molybdenum as the first component, tungsten (W), a tungsten alloy having tungsten as the first component, invar (Fe-Ni), and kovar (Fe-Ni-Co). In each embodiment of the present disclosure below, a case where molybdenum is used as a metal having a thermal expansion lower than that of copper will be described.

[0012] Embodiment 1 <Composition of copper-molybdenum composite material> 1, a copper-molybdenum composite (hereinafter also referred to as a Cu-Mo composite) 100 according to the first embodiment includes multiple copper layers 101a, 101b, a molybdenum layer 102 as a low thermal expansion metal layer, and multiple conductive adhesive layers 103a, 103b. In this specification, the terms "layer," "foil," and "sheet" refer to a member whose thickness is sufficiently smaller (for example, 1 / 1000 or less) than its length and width.

[0013] The multiple copper layers 101a, 101b are stacked in a first direction DR1. The multiple copper layers 101a, 101b are outermost copper layers arranged on the outermost side in the first direction DR1. The copper layer 101a has a first surface SF1 forming one of the outermost surfaces of the Cu-Mo composite material 100, and a surface located on the opposite side of the first surface SF1 in the first direction DR1 and facing the molybdenum layer 102. The copper layer 101b has a second surface SF2 forming the other outermost surface of the Cu-Mo composite material 100, and a surface located on the opposite side of the second surface SF2 in the first direction DR1 and facing the molybdenum layer 102.

[0014] The material constituting the copper layers 101a and 101b contains copper (Cu), and is either pure copper or a copper alloy containing copper as a first component.

[0015] The molybdenum layer 102 is disposed between the copper layers 101a and 101b in the first direction DR1.

[0016] The material constituting the molybdenum layer 102 contains molybdenum (Mo). The material constituting the molybdenum layer 102 is pure molybdenum or a molybdenum alloy containing molybdenum as a first component.

[0017] The plurality of conductive adhesive layers 103a and 103b bond between each of the plurality of copper layers 101a and 101b and the molybdenum layer 102. The conductive adhesive layer 103a bonds between the copper layer 101a and the molybdenum layer 102. The conductive adhesive layer 103b bonds between the copper layer 101b and the molybdenum layer 102. The thickness of each of the plurality of conductive adhesive layers 103a and 103b is, for example, 10 μm or more and 20 μm or less.

[0018] The material constituting each of the plurality of conductive adhesive layers 103a and 103b is a hybrid material of a binder and a conductive filler. The binder includes at least any one selected from the group consisting of an epoxy resin, a polyester resin, an acrylic resin, and a urethane resin. The conductive filler includes copper powder whose surface is covered with silver. The shape of the copper powder may be any shape, but is preferably needle-like.

[0019] In the Cu-Mo composite material 100, the respective content ratios of Cu and Mo can be arbitrarily set according to the performance required for the printed wiring board 200 described later. The Cu-Mo composite material 100 has the characteristic that its physical properties are variable by changing the composition ratio of Cu and Mo. Thereby, a Cu-Mo composite material having an arbitrary coefficient of thermal expansion and thermal conductivity can be produced. For example, by increasing the composition ratio of Cu, a Cu-Mo composite material having high thermal conductivity, which is a characteristic of Cu, and by decreasing the composition ratio of Cu, a Cu-Mo composite material having low thermal expansion, which is a characteristic of Mo, can be realized, and it becomes possible to select appropriately according to the performance required for the printed wiring board 200. The thermal conductivity of the Cu-Mo composite material is higher than that of the above-described low thermal expansion metals such as Mo, W, Fe-Ni, and Fe-Ni-Co.

[0020] <Modification Example of Cu-Mo Composite Material> The Cu-Mo composite material 100 only needs to include two or more copper layers and at least one molybdenum layer. As shown in FIG. 2, the Cu-Mo composite material 100 may include a plurality of molybdenum layers 102a and 102b and a copper layer 101c (intermediate copper layer) sandwiched between the plurality of molybdenum layers 102a and 102b.

[0021] In the modification shown in FIG. 2, two molybdenum layers 102a and 102b and one copper layer 101c are stacked in a first direction DR1.

[0022] The copper layers 101 further include at least one intermediate copper layer 101c disposed between the molybdenum layers 102a and 102b in the first direction DR1. The variation shown in Fig. 2 includes a plurality of conductive adhesive layers 103a, 103b, 103c, and 103d. The conductive adhesive layers 103a, 103b, 103c, and 103d include a first conductive adhesive layer 103a bonding between the molybdenum layer 102a and the copper layer 101a, a first conductive adhesive layer 103b bonding between the molybdenum layer 102b and the copper layer 101b, and a plurality of second conductive adhesive layers 103c and 103d bonding between each of the molybdenum layers 102a and 102b and the at least one intermediate copper layer 101c.

[0023] The plurality of conductive adhesive layers 103a, 103b, 103c, and 103d may have the same configuration as each other, for example. Note that the plurality of conductive adhesive layers 103a, 103b, 103c, and 103d may have different configurations from each other.

[0024] The Cu-Mo composite 100 may include three or more molybdenum layers and two or more intermediate copper layers.

[0025] <Configuration of the printed wiring board and the printed wiring board device> As shown in FIG. 3, the printed wiring board device 300 according to the first embodiment includes a printed wiring board 200, an electronic component 220, and a joining member 230 that joins the printed wiring board 200 and the electronic component.

[0026] The printed wiring board 200 is a substrate having typical manufacturing dimensions (work size, for example, 610 mm×610 mm). The printed wiring board 200 has a first surface SF1 as the main surface of the substrate, and a second surface SF2 located on the opposite side to the first surface SF1. The first surface SF1 is provided with a surface wiring layer 5a and a circuit protection film 11a that protects the surface wiring layer 5a. The second surface SF2 is provided with a surface wiring layer 5b and a circuit protection film 11b that protects the surface wiring layer 5b.

[0027] A part of the surface wiring layer 5a is configured as a pad 23 on which an electronic component 220 is mounted. An opening is formed in the circuit protection film 11a to open an area of ​​the surface wiring layer 5a to be bonded to the bonding member 230. The first surface SF1 and the second surface SF2 are each, for example, substantially rectangular in shape. A direction parallel to one side of the rectangle is called an in-plane first direction, and a direction perpendicular to the in-plane first direction is called an in-plane second direction. The in-plane first direction and the in-plane second direction are directions that intersect with the stacking direction of the printed wiring board 200 described later. A plane including the in-plane first direction and the in-plane second direction is also called an in-plane direction.

[0028] The printed wiring board 200 includes a plurality of internal wiring layers 1a, 1b, an insulating section 2 including a plurality of insulating layers 2a-2b, and a plurality of Cu-Mo composite wiring layers 9a, 9b. The plurality of internal wiring layers 1a, 1b and the plurality of Cu-Mo composite wiring layers 9a, 9b are formed inside a substrate having a plurality of insulating layers 2a-2b.

[0029] Each of the plurality of internal wiring layers 1a, 1b is made of, for example, a material having a higher thermal conductivity than the Cu-Mo composite material 100. Each of the plurality of internal wiring layers 1a, 1b has, for example, the same configuration as each other.

[0030] Each of the multiple Cu-Mo composite wiring layers 9a, 9b is a composite wiring layer of a metal having a lower thermal expansion than copper, which is formed by processing (e.g., patterning) a Cu-Mo composite material 100 as a composite material of a metal having a lower thermal expansion than copper in a manufacturing method of a printed wiring board described later. Each of the multiple Cu-Mo composite wiring layers 9a, 9b has, for example, the same configuration as each other. For example, at least one through hole 9c is formed in each of the multiple Cu-Mo composite wiring layers 9a, 9b. A first conductive via 6 described later is passed through the inside of the through hole 9c, and an insulating part 2 is filled between the outer peripheral surface of the first conductive via 6 and the inner peripheral surface of the through hole 9c. The through hole 9c is formed in an area that does not overlap with the pad 23 when the printed wiring board 200 is viewed in a plane in the first direction DR1. Hereinafter, a plan view means a plan view in the first direction DR1. The through hole 9c is not formed in an area overlapping with the pad 23 when the printed wiring board 200 is viewed in a plan view. The through hole 9c is formed so as to overlap with a part of each of the internal wiring layers 1a, 1b when the printed wiring board 200 is viewed in a plan view. In other words, each of the internal wiring layers 1a, 1b has a pattern formed so as to overlap with the through hole 9c when the printed wiring board 200 is viewed in a plan view.

[0031] The multiple internal wiring layers 1a, 1b and the Cu-Mo composite wiring layers 9a, 9b are stacked in a stacking direction intersecting with the first surface SF1. The stacking direction in the printed wiring board 200 is aligned with the first direction DR1 in the Cu-Mo composite 100. The Cu-Mo composite wiring layers 9a, 9b are arranged to sandwich the internal wiring layers 1a, 1b in the first direction DR1, for example.

[0032] The insulating portion 2 is disposed between adjacent wiring layers in the lamination direction, and electrically insulates the wiring layers. The insulating portion 2 includes, for example, a plurality of insulating layers 2a to 2e laminated in the lamination direction. The insulating layer 2a is disposed between the surface wiring layer 5a and the Cu-Mo composite wiring layer 9a. The insulating layer 2b is disposed between the Cu-Mo composite wiring layer 9b and the internal wiring layer 1a. The insulating layer 2c is disposed between the internal wiring layer 1a and the internal wiring layer 1b. The insulating layer 2d is disposed between the internal wiring layer 1b and the Cu-Mo composite wiring layer 9b. The insulating layer 2e is disposed between the Cu-Mo composite wiring layer 9b and the surface wiring layer 5b. As described in the manufacturing method of the printed wiring board device 300, each of the plurality of insulating layers 2a to 2e can be individually formed by sandwiching a prepreg between conductor layers that will become the internal wiring layers, and then thermally curing the prepreg after melting. Each of the insulating layers 2a to 2e includes a fiber reinforcement material 3a to 3e and a thermosetting resin portion 4a to 4e that is disposed around the fiber reinforcement material 3a to 3e and is thermally cured.

[0033] The material constituting the fiber reinforcement 3a-3e may be any fiber material having higher rigidity than the material constituting the thermosetting resin parts 4a-4e, for example, a fiber containing carbon (C) or glass (SiO2). The material constituting the thermosetting resin parts 4a-4e may be any resin material having thermosetting properties and electrical insulation properties, for example, epoxy resin, modified polyphenylene ether resin, bismaleimide triazine resin, etc. The material constituting each of the surface wiring layers 5a, 5b, the first conductive via 6, and the second conductive via 7 may be any material having electrical conductivity, for example, Cu.

[0034] Each of the internal wiring layers 1a, 1b and the Cu-Mo composite wiring layers 9a, 9b has an adjustment target portion formed in an area overlapping an area including the entire electronic component 220 when the printed wiring board device 300 is viewed in a plane, and an adjustment non-target portion formed in an area not overlapping the electronic component 220. The area including the entire electronic component 220 is a convex area including all the pads 23 connected to the connection terminals 221 of the electronic component 220. The adjustment target portion of each wiring layer is formed in an area overlapping an area including the entire pads 23 when the printed wiring board 200 is viewed in a plane. The adjustment non-target portion of each wiring layer is formed in an area located outside the overlapping area and not overlapping the pads 23 when the printed wiring board 200 is viewed in a plane.

[0035] The adjustment target portion of each wiring layer is a wiring portion provided to bring the thermal expansion coefficient of printed wiring board 200 closer to the thermal expansion coefficient of electronic component 220. The adjustment non-target portion is a wiring portion of each wiring layer that is not the adjustment target portion.

[0036] When the printed wiring board 200 is viewed in plan, each of the adjustment target portions of the Cu-Mo composite wiring layers 9a and 9b has a central region overlapping with each of the adjustment target portions of the internal wiring layers 1a and 1b, and an outer region extending outward from the central region. From a different perspective, the dimensions of each of the adjustment target portions of the Cu-Mo composite wiring layers 9a and 9b in the first in-plane direction and the second in-plane direction (hereinafter also referred to as planar dimensions) are larger than the planar dimensions of each of the adjustment target portions of the internal wiring layers 1a and 1b. The through holes 9c of each of the Cu-Mo composite wiring layers 9a and 9b are formed, for example, between each of the adjustment target portions of the Cu-Mo composite wiring layers 9a and 9b and each of the non-adjustment target portions of the Cu-Mo composite wiring layers 9a and 9b.

[0037] In the printed wiring board 200, the adjustment target portion and the non-adjustment target portion are configured to be equal in each wiring layer. That is, the thickness of each of the internal wiring layers 1a, 1b and the Cu-Mo composite wiring layers 9a, 9b is constant in the first in-plane direction and the second in-plane direction. The thickness of each of the adjustment target portions of the internal wiring layers 1a, 1b is equal to the thickness of each of the non-adjustment target portions of the internal wiring layers 1a, 1b. The thickness of each of the adjustment target portions of the Cu-Mo composite wiring layers 9a, 9b is equal to the thickness of each of the non-adjustment target portions of the Cu-Mo composite wiring layers 9a, 9b. The thicknesses of the adjustment target portions and the non-adjustment target portions of each wiring layer can be appropriately set according to the purpose and the use environment of the printed wiring board device 300.

[0038] Each of the insulating layers 2a-2e of the insulating section 2 includes a portion that is arranged between the adjustment portions of each wiring layer in the first direction DR1 and a portion that is arranged between the adjustment portions of each wiring layer in the first direction DR1. In the printed wiring board 200, the portions of each of the insulating layers 2a-2e that are arranged between the adjustment portions of each wiring layer in the first direction DR1 are configured equivalently to the portions that are arranged between the adjustment portions of each wiring layer in the first direction DR1.

[0039] The printed wiring board 200 has a first conductive via 6 and a second conductive via 7 formed therein, which penetrate in the stacking direction. The printed wiring board 200 has, for example, a plurality of first conductive vias 6 and second conductive vias 7 formed therein. The first conductive via 6 is formed in a region that does not overlap with a region including the entire pad 23 when the printed wiring board 200 is viewed in a plane. The second conductive via 7 is formed in a region that overlaps with a region including the entire pad 23 when the printed wiring board 200 is viewed in a plane.

[0040] The first conductive via 6 electrically connects the surface wiring layers 5a, 5b and the internal wiring layers 1a, 1b. The first conductive via 6 is not electrically connected to the Cu-Mo composite wiring layer 9. The first conductive via 6 penetrates the internal wiring layers 1a, 1b, the insulating layers 2a to 2e, and the surface wiring layers 5a, 5b. The first conductive via 6 does not penetrate each of the Cu-Mo composite wiring layers 9a, 9b. The first conductive via 6 does not penetrate each of the Cu-Mo composite wiring layers 9a, 9b. The first conductive via 6 is passed through the through holes 9c of each of the Cu-Mo composite wiring layers 9a, 9b. The first conductive via 6 is formed, for example, by plating copper on the inner wall surface of a through hole penetrating the printed wiring board 200 in the stacking direction. The first conductive via 6 is provided, for example, in a tubular shape. A cavity is formed inside the through hole and on the inner side of the first conductive via 6.

[0041] The second conductive via 7 electrically connects the surface wiring layers 5a, 5b, the internal wiring layers 1a, 1b, and the Cu-Mo composite wiring layers 9a, 9b. The second conductive via 7 penetrates the internal wiring layers 1a, 1b, the insulating layers 2a to 2e, the Cu-Mo composite wiring layers 9a, 9b, and the surface wiring layers 5a, 5b. The second conductive via 7 is formed, for example, by plating copper on the inner wall surface of a through hole penetrating the printed wiring board 200 in the stacking direction. The second conductive via 7 is provided, for example, in a tubular shape. A filling member 8 is formed inside the through hole of the second conductive via 7. The material constituting the filling member 8 is a composite material of a thermosetting resin and a functional material filler. The thermosetting resin is, for example, an epoxy resin. The functional material filler is, for example, at least one of an inorganic filler and a conductive filler. The inorganic filler is, for example, silica. The conductive filler is, for example, a silver-coated copper filler. Pads 23 are formed on one end and the other end of each of the second conductive vias 7 and the filling member in the stacking direction.

[0042] The electronic component 220 is mounted on the first surface SF1 of the printed wiring board 200. Specifically, the electronic component 220 has a plurality of connection terminals 221 on the back surface. The connection terminals 221 are connected to a part of the front wiring layer 5a configured as pads 23 via bonding members 230. The electronic component 220 is, for example, a BGA (Ball Grid Array). In the BGA, the connection terminals 221 are arranged vertically and horizontally on the back surface. On the first surface SF1 of the printed wiring board 200, pads 23 are arranged at positions corresponding to the connection terminals 221 of the electronic component 220. In the case where the electronic component 220 is a BGA, the pads 23 are also arranged vertically and horizontally. The bonding members 230 may be made of any material having electrical conductivity, and are, for example, solder. The connection terminals 221 may be arranged at a position other than the back surface of the electronic component 220. The back surface of the electronic component 220 is the surface on which the electronic component 220 is mounted on the printed wiring board 200.

[0043] The shape of outermost end 222 of electronic component 220 connected to printed wiring board 200 when printed wiring board device 300 is viewed in plan is not particularly limited, but may be, for example, an angular shape having multiple corners, such as a rectangular shape. Outermost end 222 is a portion having a determined width that surrounds all pads 23 to which connection terminals 221 are connected.

[0044] In the printed wiring board device 300, the composition ratio of Cu and Mo in the Cu-Mo composite wiring layers 9a and 9b is appropriately adjusted, so that the thermal expansion coefficient of the printed wiring board 200 is equivalent to that of the electronic component 220. In other words, the thermal expansion coefficient of the printed wiring board 200 is 90% or more and 110% or less of the thermal expansion coefficient of the electronic component 220. Preferably, the thermal expansion coefficient of the printed wiring board 200 is 95% or more and 105% or less of the thermal expansion coefficient of the electronic component 220. However, in order to reduce manufacturing costs, the thermal expansion coefficient of the printed wiring board 200 can be designed to be less than the difference in thermal expansion coefficient between the electronic component 220 and the printed wiring board device 300 by specifying the amount of shear strain applied to the solder joint 230 based on the temperature cycle conditions applied to the printed wiring board device 300 and the number of cycles required for the solder joint 230.

[0045] <Modifications of the printed wiring board and the printed wiring board device> 3 includes two Cu-Mo composite wiring layers 9a, 9b, but is not limited to this. The number of Cu-Mo composite wiring layers 9a, 9b included in the printed wiring board 200 and the printed wiring board device 300 can be set to any number equal to or greater than 1, taking into account the thermal expansion coefficient and thermal conductivity required for the printed wiring board 200. The thermal expansion coefficient required for the printed wiring board 200 can be estimated, as described above, taking into account the residual conductivity.

[0046] <Method of manufacturing copper-molybdenum composite material> With reference to FIG. 4, an example of a manufacturing method of the Cu-Mo composite material 100 shown in FIG. 1 will be described. First, a plurality of copper foils 51a, 51b, a molybdenum foil 52, and a plurality of conductive adhesive sheets 53a, 53b are prepared. The conductive adhesive sheets 53a, 53b may have a thickness of 40 μm or 60 μm, which is generally available. The conductive adhesive sheets 53a, 53b are cut out from a roll material, which is generally available, according to the respective lengths of the copper foils 51a, 51b and the molybdenum foil 52. The copper foils 51a, 51b are prepared as, for example, electrolytic copper foils or rolled copper foils, and the molybdenum foil 52 is prepared as, for example, a rolled material. The thicknesses of the copper foils 51a, 51b and the molybdenum foil 52 are set based on the thermal expansion coefficient and thermal conductivity required for the printed wiring board 200. The surfaces of the copper foils 51a, 51b and the molybdenum foil 52 are each subjected to a treatment for enhancing adhesive strength with the thermosetting resin that is the binder of the conductive adhesive sheet. Examples of treatment for enhancing adhesive strength include roughening the surfaces of the copper foil and the molybdenum foil by microetching, or forming an organic coating on the surface of at least one of the copper and molybdenum foils.

[0047] The thermal expansion coefficient α of the printed wiring board 200 is estimated taking into consideration the respective residual conductivity of the internal wiring layers 1a, 1b and the Cu-Mo composite wiring layers 9a, 9b. It is assumed that the printed wiring board 200 is composed of, for example, N types of materials (Cu-Mo composite, Cu, resin, etc.). The thermal expansion coefficient of type i of material is αi, the Young's modulus Ei, and the volume Vi. The volume Vi changes depending on the residual conductivity. The thermal expansion coefficient α of the printed wiring board 200 is estimated by the following formula.

[0048] α=Σ(αi·Ei·Vi) / Σ(Ei·Vi) (1)

[0049] In formula (1), Σ means to take the sum over i=1, . . . , N. The residual conductivity of the internal wiring layers 1a, 1b is the area ratio of the surface facing the lamination direction of the conductor foil (e.g., copper foil) to be processed into the internal wiring layers 1a, 1b before and after processing. For example, the residual conductivity of the internal wiring layers 1a, 1b is the ratio of the area of ​​the surface facing the lamination direction of the internal wiring layers 1a, 1b to the area of ​​the surface facing the lamination direction of the copper foils 51a, 51b before being processed into the internal wiring layers 1a, 1b. The residual conductivity of the Cu-Mo composite wiring layers 9a, 9b is the ratio of the area of ​​the surface facing the first direction DR1 of the copper layer 101a of the outermost layer of the Cu-Mo composite 100 before being processed into the Cu-Mo composite wiring layers 9a, 9b.

[0050] As shown in FIG. 4, a laminate is formed by stacking a plurality of copper foils 51a, 51b and molybdenum foils 52 sandwiched between conductive adhesive sheets 53a, 53b. The outermost layers of the laminate are the copper foils 51a, 51b. The laminate is set in a vacuum press device and heated and pressed in a vacuum environment according to the temperature-melting and hardening characteristics of the binder resin. For example, the heating temperature is 200° C. or less, and the pressure is 1 MPa or more and 3 MPa or less. In this manner, the Cu-Mo composite material 100 shown in FIG. 1 can be manufactured from the laminate shown in FIG. 4. Copper layers 101a, 101b are formed from the copper foils 51a, 51b, a molybdenum layer 102 is formed from the molybdenum foil 52, and conductive adhesive layers 103a, 103b are formed from the conductive adhesive sheets 53a, 53b, respectively. The thickness of the conductive adhesive layers 103a, 103b can be reduced by heating and pressing to 10 μm or more and 20 μm or less than the thickness of the conductive adhesive sheets 53a, 53b. The copper layers 101a, 101b and the molybdenum layer 102 can be electrically connected by silver-coated needle-like copper powder in the conductive adhesive layers 103a, 103b. The thermal expansion coefficient of the thermosetting resin, which is the binder, is relatively high, but its Young's modulus is low. For example, the linear expansion coefficient of the epoxy resin is about 150 ppm / °C in the α2 region (50°C or more). On the other hand, the Young's modulus of the epoxy resin is 0.8 Gpa. Therefore, the thermal expansion coefficient of the Cu-Mo composite material 100 having the conductive adhesive layers 103a, 103b is higher than that of a conventional Cu-Mo composite material not having a conductive adhesive layer, but this has little effect on the thermal expansion coefficient of the printed wiring board 200.

[0051] The Cu-Mo composite material 100 shown in Fig. 2 can be manufactured in the same manner as the Cu-Mo composite material 100 shown in Fig. 1. An example of a method for manufacturing the Cu-Mo composite material 100 shown in Fig. 2 will be described with reference to Fig. 5. First, a plurality of copper foils 51a, 51b, and 51c, a plurality of molybdenum foils 52a and 52b, and a plurality of conductive adhesive sheets 53a, 53b, 53c, and 53d are prepared.

[0052] As shown in FIG. 5, a laminate is formed by sandwiching a plurality of copper foils 51a, 51b, 51c and a plurality of molybdenum foils 52a, 52b between conductive adhesive sheets 53a, 53b, 53c, 53d and stacking them. The outermost layers of the laminate are the copper foils 51a, 51b. The laminate is set in a vacuum press device and heated and pressed in a vacuum environment according to the temperature-melting and hardening characteristics of the binder resin. In this way, the Cu-Mo composite material 100 shown in FIG. 2 can be manufactured from the laminate shown in FIG. 5. Copper layers 101a, 101b, 101c are formed from the copper foils 51a, 51b, 51c, molybdenum layers 102a, 102b are formed from the molybdenum foils 52a, 52b, and conductive adhesive layers 103a, 103b, 103c, 103d are formed from the conductive adhesive sheets 53a, 53b, 53c, 53d, respectively.

[0053] In addition, when the width of the conductive adhesive sheets 53a, 53b is smaller than the width of the copper foils 51a, 51b and the molybdenum foil 52, the conductive adhesive sheets 53a1, 53a2 and the conductive adhesive sheets 53b1, 53b2b may be arranged in a second direction DR2 perpendicular to the first direction DR1 as shown in Fig. 6. The second direction DR2 is, for example, along the above-mentioned in-plane first direction or in-plane second direction. In this way, one conductive adhesive layer 103a can be formed from the conductive adhesive sheets 53a1, 53a2, and one conductive adhesive layer 103b can be formed from the conductive adhesive sheets 53b1, 53b2.

[0054] In the manufacturing method of the Cu-Mo composite material 100, a conductive adhesive sheet may be further used that is spaced apart from at least one of the plurality of conductive adhesive sheets 53b1, 53b2b in a third direction (direction perpendicular to the paper surface of FIG. 6) that is perpendicular to each of the first direction DR1 and the second direction DR2. In other words, the plurality of conductive adhesive sheets may be spaced apart from each other in each of the above-mentioned in-plane first direction and in-plane second direction.

[0055] <Manufacturing method for printed wiring boards> 3 will be described with reference to Figures 7 to 16. The method for manufacturing printed wiring board 200 includes a step of preparing a plurality of members constituting printed wiring board 200, a step of forming laminate 80 using the prepared plurality of members, and a step of processing laminate 80.

[0056] In the process of preparing the multiple components that make up the printed wiring board 200, Cu-Mo composite wiring layers 9a, 9b (see FIG. 7), an inner layer core 75 including internal wiring layers 1a, 1b (see FIG. 9), multiple conductor foils 76a, 76b (see FIG. 10), and multiple prepregs 77a, 77b, 77c, 77d (see FIG. 10) are prepared.

[0057] As shown in FIG. 7, the Cu-Mo composite wiring layers 9a, 9b are formed from a Cu-Mo composite material 100 manufactured by the above-mentioned manufacturing method for a Cu-Mo composite material.

[0058] Specifically, the through hole 9c is formed in the Cu-Mo composite material 100. The method for forming the through hole 9c may be selected from the group consisting of drilling, laser processing, and electric discharge processing, but it is preferable to select drilling from the viewpoint of reducing manufacturing costs. The diameter of the through hole 9c may be set in consideration of the machining tolerance of the pilot hole of the first conductive via 6 in the manufacturing method of the printed wiring board 200 described later, and the positional deviation tolerance when the Cu-Mo composite material 100 is laminated with other components of the printed wiring board 200. For example, the diameter of the through hole 9c is set to a diameter that can provide a clearance of 0.15 mm or more on one side with respect to the pilot hole diameter of the first conductive via 6. In order not to deteriorate the characteristics of the Cu-Mo composite wiring layers 9a and 9b, i.e., high heat dissipation and low cure shrinkage, it is preferable to make the diameter of the through hole 9c as small as possible. Furthermore, a treatment is performed on the surface of the Cu-Mo composite material 100 in which the through hole 9c is formed to increase the adhesive strength with the resin constituting the insulating part 2. As the treatment for enhancing the adhesive strength, a standard treatment used for copper layers in the manufacturing method of printed wiring boards can be selected since the outermost layer of the Cu-Mo composite material 100 is a copper layer. For example, the treatment for enhancing the adhesive strength may be a treatment for roughening the surface of the Cu-Mo composite material 100 by microetching, a treatment for forming an organic coating on the surface of the Cu-Mo composite material 100, or a combination of both. In this manner, the Cu-Mo composite wiring layers 9a and 9b are formed from the Cu-Mo composite material 100.

[0059] As shown in FIGS. 8 and 9, the inner layer core 75 is formed from a laminate 70 of a first conductor foil 71a, a second conductor foil 71b, and an insulating layer 2c.

[0060] Specifically, the first conductor foil 71a and the second conductor foil 71b are prepared as conductor sheets having planar dimensions of the printed wiring board 200. Furthermore, a prepreg to become the insulating layer 2c is prepared. The first conductor foil 71a, the second conductor foil 71b, and the prepreg are laminated such that the first conductor foil 71a and the second conductor foil 71b sandwich the prepreg.

[0061] Next, the laminate is heated while being pressurized. Pressurization is performed so as to apply a force along the lamination direction of the laminate to the first conductor foil 71a, the second conductor foil 71b, and the prepreg. The thermosetting resin of the prepreg melts due to the pressurization and heating, and the molten thermosetting resin is thermally cured. As a result, a laminate 70 including an insulating layer 2c formed from the prepreg is formed, as shown in FIG. 8.

[0062] Next, the first conductor foil 71a and the second conductor foil 71b of the laminate 70 shown in FIG. 8 are patterned. The patterning is to form a circuit pattern on the conductor layer. The patterning is performed by, for example, photolithography and dry etching processes. As a result, the internal wiring layer 1a is formed from the first conductor foil 71a, and the internal wiring layer 1b is formed from the second conductor foil 71b. As a result, the inner layer core 75 shown in FIG. 9 is formed. The surface of the inner layer core 75 is subjected to a treatment to enhance the adhesive strength with the resin constituting the insulating part 2. For example, the treatment to enhance the adhesive strength may be a treatment to roughen the surface of the Cu-Mo composite material 100 by microetching, or a treatment to form an organic coating on the surface of the Cu-Mo composite material 100.

[0063] In the above patterning, the portions of the first conductor foil 71a and the second conductor foil 71b that are arranged in a region that overlaps with the outermost end 222 of the electronic component 220 when the printed wiring board device 300 is viewed in a plan view are not removed and are left in the internal wiring layers 1a, 1b. Similarly, the portions of the first conductor foil 71a and the second conductor foil 71b that are connected to the second conductive via 7 in the printed wiring board 200 are not removed and are left in the internal wiring layers 1a, 1b.

[0064] The conductor foils 76a and 76b are made of, for example, pure copper or a copper alloy containing copper as the first component. The prepregs 77a, 77b, 77c, and 77d include a fiber reinforcement material and a thermosetting resin.

[0065] In the process of forming the laminate 80 using the prepared components, the Cu-Mo composite wiring layers 9a, 9b, the inner layer core 75, the multiple conductor foils 76a, 76b, and the multiple prepregs 77a, 77b, 77c, 77d are stacked in the first direction DR1 of the Cu-Mo composite wiring layers 9a, 9b, and then the entire assembly is heated while being pressurized to form the laminate 80.

[0066] Specifically, as shown in FIG. 10, the Cu-Mo composite wiring layers 9a, 9b, the inner core 75, the conductive foils 76a, 76b, and the prepregs 77a, 77b, 77c, 77d are aligned in a direction perpendicular to the first direction DR1 and stacked in the first direction DR1. Next, the entire laminate shown in FIG. 10 is heated while being pressurized. Pressurization is performed so as to apply a force along the first direction DR1 to the laminate. As a result, the insulating layers 2a, 2b, 2d, 2e are formed from the prepregs 77a, 77b, 77c, 77d, respectively. The thermosetting resin of the molten prepregs 77a, 77b, 77c, 77d enters the through holes 9c of the Cu-Mo composite wiring layers 9a, 9b and the inner core 75 in the areas where the internal wiring layers 1a, 1b are not formed, and the insulating part 2 is formed by thermally curing the thermosetting resin. In this way, the laminate 80 shown in Fig. 11 is formed. Note that the pressure and heating conditions in this step are set according to the thermosetting resin contained in the prepregs 77a, 77b, 77c, and 77d.

[0067] The laminate 80 shown in Fig. 11 can also be formed by heating the entire laminate shown in Fig. 12 while applying pressure. The laminate shown in Fig. 12 differs from the laminate shown in Fig. 11 in that the conductor foils 76a and 76b are not prepared individually, but are prepared as a laminate of the conductor foil 76a and the insulating layer 78a, and a laminate of the conductor foil 76b and the insulating layer 78b.

[0068] In the process of processing the laminate 80, the steps shown in Figs. 13 to 17 are carried out in order.

[0069] First, as shown in Fig. 13, a plurality of through holes 81, 82 are formed penetrating the laminate 80 shown in Fig. 11 in the lamination direction. Each of the plurality of through holes 81, 82 penetrates from the conductor foil 76a to the conductor foil 76b of the laminate 80. Each of the plurality of through holes 81, 82 is formed in a position necessary or appropriate for the printed wiring board device 300. The plurality of through holes 81 are formed in a position where the first conductive vias 6 should be formed. The plurality of through holes 82 are formed in a position where the second conductive vias 7 should be formed.

[0070] Secondly, as shown in Fig. 14, a first conductive via 6 is formed inside each of the plurality of through holes 81, and a second conductive via 7 is formed inside each of the plurality of through holes 82. The first conductive via 6 and the second conductive via 7 are formed on the inner wall surface of each of the through holes 81, 82 by, for example, a known plating method (Cu plating as one example). In this process, surface conductor layers 83a, 83b are formed on the conductor foils 76a, 76b. Inside the through holes 81, 82, for example, a cavity penetrating the laminate 80 is formed on the inner side of the first conductive via 6 and the second conductive via 7.

[0071] Thirdly, as shown in FIG. 15, a filling member 8 is formed to fill the inner cavity of the second conductive via 7 located under the pad 23. As described above, the material constituting the filling member 8 is a composite material of a thermosetting resin and a functional material filler. An example of the thermosetting resin is an epoxy resin. An example of the functional material filler is an inorganic filler such as silica, and a conductive filler such as a silver-coated copper filler. The filling member 8 is formed by filling the inner cavity of the second conductive via 7 with the composite material and then heating and curing it. After the filling member 8 is formed, surface conductor layers 84a and 84b are formed on the surface conductor layers 83a and 83b. The surface conductor layers 84a and 84b are formed, for example, by a known plating method.

[0072] Fourthly, the conductor foil 76a and the surface conductor layer 84a are patterned. As a result, the surface wiring layer 5a including the pads 23 is formed from the conductor foil 76a and the surface conductor layer 84a. Furthermore, the conductor foil 76b and the surface conductor layer 84b are patterned. As a result, the surface wiring layer 5b is formed from the conductor foil 76b and the surface conductor layer 84b. The patterning is performed by, for example, photolithography and dry etching processes. In this manner, the laminate 85 shown in FIG. 16 is formed.

[0073] Fifthly, a circuit protection film 11a (see FIG. 3) is formed on the surface of the insulating layer 2a on which the surface wiring layer 5a is provided, to protect the surface wiring layer 5a. A circuit protection film 11b (see FIG. 3) is formed on the surface of the insulating layer 2e on which the surface wiring layer 5b is provided, to protect the surface wiring layer 5b. The circuit protection film 11a has an opening for exposing the pad 23 of the surface wiring layer 5a. The opening is formed by, for example, photolithography and dry etching processes. In this manner, the printed wiring board 200 shown in FIG. 17 is formed. In order to prevent oxidation of the surface wiring layer 5a exposed in the printed wiring board 200, the surface wiring layer 5a of the printed wiring board 200 may be subjected to a surface treatment. Examples of such surface treatment include water-soluble preflux treatment, lead-containing solder coating treatment, lead-free solder coating treatment, electroless nickel gold plating treatment, electroless nickel palladium gold plating, electroless gold palladium gold plating, and the like.

[0074] <Manufacturing Method of Printed Wiring Board Device> 3 and 17, an example of a manufacturing method for a printed wiring board device 300 will be described. The manufacturing method for a printed wiring board device 300 includes a step of preparing a printed wiring board 200 shown in FIG. 17, and a step of mounting an electronic component 220 on a pad 23 of the printed wiring board 200.

[0075] In the process of mounting electronic component 220, a plurality of connection terminals 221 of electronic component 220 are connected to a plurality of pads 23, respectively. By bonding connection terminals 221 of electronic component 220 to pads 23 via bonding members 230, printed wiring board device 300 shown in FIG. 3 is formed.

[0076] <Action and effect> The function and effect of the Cu-Mo composite material 100 will be described based on a comparison with a conventional Cu-Mo composite material that does not have a conductive adhesive layer.

[0077] Known methods for manufacturing conventional Cu-Mo composite materials without a conductive adhesive layer include a method of diffusion bonding a Cu layer and a Mo layer, a method of rolling a laminate of a copper plate and a molybdenum plate prepared as a coil material, and a method of copper plating on Mo foil.

[0078] In the method of diffusion bonding the Cu layer and the Mo layer, it is necessary to press the laminate of the Cu layer and the Mo layer under a high temperature of 850° C. or more. The cost of the manufacturing equipment for simultaneously performing such high-temperature heating and pressurization is higher than that of the manufacturing equipment for performing heating and pressurization in the manufacturing method of the Cu-Mo composite material 100. In addition, since a long time is required for cooling after the heating and pressurization treatment, the manufacturing cost of the Cu-Mo composite material is high.

[0079] In the method of rolling a laminate of copper and molybdenum sheets prepared as coil material, it is difficult to suppress the occurrence of processing distortion during rolling, and waste parts are generated, which reduces the yield and results in high manufacturing costs for the Cu-Mo composite material. In addition, in this method, the width and thickness of the Cu-Mo composite material are restricted by the dimensions of the rolling equipment, making it difficult to manufacture a Cu-Mo composite material with an arbitrary thermal expansion coefficient and thermal conductivity.

[0080] In the method of copper plating on Mo foil, in order to secure the adhesion between the Mo foil and the copper plating film, the following pretreatments are required before the copper plating process: a process to remove the oxide film formed on the surface of the Mo foil, a Ni plating process to form a nickel (Ni) film on the surface of the Mo foil after the oxide film removal process, a high-temperature heat treatment to diffusion bond the Mo foil and the Ni film, and a strike copper plating process. Therefore, the manufacturing cost of the Cu-Mo composite material produced by the above plating processes is high.

[0081] In contrast, the Cu-Mo composite material 100 according to the present embodiment includes a plurality of conductive adhesive layers 103a, 103b, and 103c that bond between each of the plurality of copper layers 101a and 101b and the molybdenum layer 102. Such a Cu-Mo composite material 100 can be manufactured by applying heat and pressure to a laminate formed by sandwiching and stacking a plurality of copper foils 51a and 51b and a molybdenum foil 52 between conductive adhesive sheets 53a and 53b in a vacuum environment according to the temperature-melting and hardening properties of the binder resin. For example, the Cu-Mo composite material 100 can be manufactured by heating a laminate of a plurality of copper foils, a molybdenum foil, and a plurality of conductive adhesive sheets in a vacuum environment at a temperature of 200° C. or less and applying pressure at a pressure of 1 MPa or more and 3 MPa or less. Therefore, the Cu-Mo composite material 100 can be manufactured more cheaply and easily than a conventional Cu-Mo composite material that does not include a conductive adhesive layer.

[0082] 2, the Cu-Mo composite material 100 according to this embodiment may include a plurality of copper layers 101a, 101b (outermost copper layers), a plurality of molybdenum layers 102a, 102b, at least one copper layer 101c (middle copper layer), a plurality of first conductive adhesive layers 103a, 103b, and a plurality of second conductive adhesive layers 103c, 103d. According to the Cu-Mo composite material 100 according to this embodiment, the number of copper layers and molybdenum layers stacked can be increased relatively easily.

[0083] In the Cu-Mo composite 100, the material constituting the multiple conductive adhesive layers 103a, 103b is a composite material of a binder and a conductive filler. The binder includes at least one selected from the group consisting of epoxy resin, polyester resin, acrylic resin, and urethane resin. The conductive filler includes acicular copper powder whose surface is covered with silver. Since such conductive adhesive layers 103a, 103b can be easily formed from a relatively inexpensive conductive adhesive sheet, the Cu-Mo composite 100 can be manufactured more inexpensively and easily than a conventional Cu-Mo composite that does not include a conductive adhesive layer.

[0084] The printed wiring board 200 according to the present embodiment includes Cu-Mo composite wiring layers 9a and 9b formed inside the substrate. Therefore, the manufacturing cost of the printed wiring board 200 is lower than that of a printed wiring board including a conventional Cu-Mo composite that does not include a conductive adhesive layer.

[0085] Furthermore, the thermal expansion coefficient of the printed wiring board 200 can be set to be equal to the thermal expansion coefficient of the electronic component 220 mounted on the printed wiring board 200 in the printed wiring board device 300 by appropriately adjusting the composition ratio of Cu and Mo in the Cu-Mo composite wiring layers 9a, 9b. In the printed wiring board device 300 including such a printed wiring board 200 and electronic component 220, the stress acting on the connection between the pad 23 and the connection terminal 221 due to the difference in the thermal expansion coefficient between the printed wiring board 200 and the electronic component 220 is reduced. As a result, in the printed wiring board device 300, the risk of the electrical connection between the pad 23 and the connection terminal 221 via the bonding member 230 becoming defective due to the repeated application of the stress is reduced.

[0086] Embodiment 2 Referring to FIGS. 18 to 21, the Cu-Mo composite material 120 according to Embodiment 2, its modified examples, and their manufacturing methods will be described. The Cu-Mo composite material 120 according to Embodiment 2 has the same configuration and effects as the Cu-Mo composite material 100 according to Embodiment 1 above, unless otherwise specified. Therefore, the same components as those of the above Cu-Mo composite material 100 are denoted by the same reference numerals, and the description will not be repeated. As described above, in Embodiment 2 as well, the low thermal expansion metal having a lower coefficient of thermal expansion than copper is not limited to Mo, and may be, for example, an Mo alloy, W, a W alloy, Fe-Ni, or Fe-Ni-Co.

[0087] The Cu-Mo composite material 120 includes a plurality of molybdenum layers 102c, 102d arranged side by side with a space therebetween in a second direction DR2 orthogonal to a first direction DR1.

[0088] The plurality of conductive adhesive layers 103a, 103b bond between each of the plurality of molybdenum layers 102c, 102d and each of the plurality of copper layers 101a, 101b, and are filled between the plurality of adjacent molybdenum layers 102c, 102d in the second direction DR2. From a different perspective, the plurality of conductive adhesive layers 103a, 103b have a filling portion 103ab filled between the plurality of adjacent molybdenum layers 102c, 102d in the second direction DR2.

[0089] Each of the plurality of copper layers 101a, 101b is arranged to sandwich the plurality of molybdenum layers 102c, 102d and the filling portion 103ab in the first direction DR1. The width of each of the plurality of copper layers 101a, 101b in the second direction DR2 is equal to the sum of the widths in the second direction of each of the plurality of molybdenum layers 102c, 102d and the filling portion 103ab.

[0090] <Modified Example of Cu-Mo Composite Material> The Cu-Mo composite 120 may further include a molybdenum layer that is spaced apart from at least one of the multiple molybdenum layers 102c, 102d in a third direction (a direction perpendicular to the paper surface of FIG. 19) that is perpendicular to each of the first direction DR1 and the second direction DR2. In other words, the multiple molybdenum layers may be spaced apart from each other in each of the second direction DR2 and the third direction.

[0091] The Cu-Mo composite material 120 may be modified in the same manner as the Cu-Mo composite material 100. As shown in Fig. 19, the number of stacked molybdenum layers in the Cu-Mo composite material 120 may be two or more. The Cu-Mo composite material 120 may include a pair of molybdenum layers 102ac, bc stacked in a first direction DR1, and another pair of molybdenum layers 102ad, bd arranged in a second direction DR2 with a gap therebetween from the pair of molybdenum layers 102ac, bc.

[0092] Such a Cu-Mo composite material 120 further includes a plurality of copper layers 101a, 101b, and 101c, and a plurality of conductive adhesive layers 103a, 103b, 103c, and 103d. The plurality of conductive adhesive layers 103a and 103c have a filling portion 103ac that is filled between the plurality of molybdenum layers 102ac and 102ad that are adjacent to each other in the second direction DR2. The plurality of conductive adhesive layers 103b and 103d have a filling portion 103bd that is filled between the plurality of molybdenum layers 102bc and 102bd that are adjacent to each other in the second direction DR2. The filling portion 103bd is arranged so as to overlap with the filling portion 103ac in the first direction DR1. The plurality of copper layers 101a and 101c are arranged so as to sandwich the plurality of molybdenum layers 102ac and 102ad and the filling portion 103ac in the first direction DR1. The multiple copper layers 101b and 101c are arranged to sandwich the multiple molybdenum layers 102bc and 102bd and the filling portion 103bd in the first direction DR1.

[0093] Unless otherwise specified, the method for producing the Cu-Mo composite material 120 has the same configuration and effects as the method for producing the Cu-Mo composite material 100. Below, differences between the method for producing the Cu-Mo composite material 120 and the method for producing the Cu-Mo composite material 100 will be mainly described with reference to Fig. 20.

[0094] A plurality of copper foils 51a, 51b, a plurality of molybdenum foils 52c, 52d, and a plurality of conductive adhesive sheets 53a, 53b are prepared and arranged as shown in Fig. 20. At this time, the width in the second direction DR2 of each of the plurality of copper foils 51a, 51b, the plurality of molybdenum foils 52c, 52d, and the plurality of conductive adhesive sheets 53a, 53b is set so that the sum of the width in the second direction DR2 of each of the plurality of molybdenum foils 52c, 52d and the intervals in the second direction DR2 of the plurality of molybdenum foils 52c, 52d is equal to the width in the second direction DR2 of each of the plurality of copper foils 51a, 51b and the plurality of conductive adhesive sheets 53a, 53b.

[0095] The laminate is then set in a vacuum press and heated and pressurized in a vacuum environment according to the temperature-melting-curing characteristics of the binder resin. For example, the heating temperature is 200° C. or less, and the pressure is 1 MPa or more and 3 MPa or less. In this manner, the Cu-Mo composite material 120 shown in FIG. 18 can be manufactured from the laminate shown in FIG. 20. The conductive adhesive layers 103a, 103b including the filling portion 103ab are formed from the conductive adhesive sheets 53a, 53b.

[0096] The interval between the multiple molybdenum foils 52c, 52d in the second direction DR2 may be equal to, for example, the diameter of the through holes 9c in the Cu-Mo composite wiring layers 9a, 9b in the printed wiring board 200. In other words, the first conductive vias 6 may be formed to penetrate a part of the filling portion 103ab.

[0097] Unless otherwise specified, the printed wiring board and printed wiring board device according to embodiment 2 have the same configuration and effect as printed wiring board 200 and printed wiring board device 300 according to embodiment 1. Therefore, the same configuration as printed wiring board 200 and printed wiring board device 300 described above is given the same reference numerals and description will not be repeated.

[0098] In the printed wiring board and printed wiring board device according to the second embodiment, the filled portion 103ab of the conductive adhesive layers 103a, 103b formed in the Cu-Mo composite material 120 may or may not remain. In the former printed wiring board and printed wiring board device, the first conductive via 6 is formed to penetrate a part of the filled portion 103ab as described above, so that another part of the filled portion 103ab may remain. In the latter printed wiring board and printed wiring board device, the second conductive via 7 may be formed in the Cu-Mo composite material 120 at the place where the filled portion 103ab was formed.

[0099] Various aspects of the present disclosure are summarized below as appendices. [Appendix 1] A plurality of copper layers arranged in a first direction; At least one low thermal expansion metal layer is disposed between the plurality of copper layers in the first direction and is made of a metal material having a thermal expansion coefficient lower than that of copper; a plurality of conductive adhesive layers bonded between each of the plurality of copper layers and the at least one low thermal expansion metal layer; The copper layers include a plurality of outermost copper layers disposed outermost in the first direction, the copper-metal composite having a thermal expansion lower than that of copper. [Appendix 2] the at least one low thermal expansion metal layer includes a plurality of first low thermal expansion metal layers stacked in the first direction; the plurality of copper layers further includes at least one intermediate copper layer disposed between the plurality of first low thermal expansion metal layers in the first direction; The copper-metal composite having a thermal expansion lower than copper described in Appendix 1, wherein the plurality of conductive adhesive layers include a plurality of first conductive adhesive layers bonding between each of the plurality of first low thermal expansion metal layers and each of the plurality of outermost copper layers, and a plurality of second conductive adhesive layers bonding between each of the plurality of first low thermal expansion metal layers and the at least one intermediate copper layer. [Appendix 3] the material constituting the plurality of conductive adhesive layers is a composite material of a binder and a conductive filler, the binder includes at least one selected from the group consisting of an epoxy resin, a polyester resin, an acrylic resin, and a urethane resin; 3. The copper-metal composite having a thermal expansion lower than that of copper described in Appendix 1 or 2, wherein the conductive filler contains acicular copper powder having a surface covered with silver. [Appendix 4] the at least one low thermal expansion metal layer includes a plurality of second low thermal expansion metal layers arranged side by side at intervals in an in-plane direction perpendicular to the first direction, A copper-metal composite material having a thermal expansion lower than that of copper according to any one of Appendices 1 to 3, wherein the plurality of conductive adhesive layers bond each of the plurality of second low thermal expansion metal layers to each of the plurality of outermost copper layers, and are filled between the plurality of second low thermal expansion metal layers adjacent to each other in the second direction. [Appendix 5] The at least one low thermal expansion metal layer comprises at least one selected from the group consisting of molybdenum (Mo), a molybdenum alloy, tungsten (W), a tungsten alloy, invar (Fe-Ni), and kovar (Fe-Ni-Co), etc. The copper-metal composite material according to any one of appendices 1 to 4, [Appendix 6] a surface wiring layer formed on a main surface of the substrate; A copper-low thermal expansion metal composite wiring layer formed inside the substrate and made of a composite material of copper and a metal having a thermal expansion lower than that of copper according to any one of appendices 1 to 5; a printed wiring board comprising an insulating layer that insulates the surface wiring layer from the copper-low thermal expansion metal composite wiring layer. [Appendix 7] 7. The printed wiring board according to claim 6, further comprising a through-hole conductor electrically connecting the surface wiring layer and the copper-low thermal expansion metal composite wiring layer. [Appendix 8] A printed wiring board according to appendix 6 or 7; a printed wiring board device comprising: an electronic component electrically connected to the surface wiring layer of the printed wiring board via a bonding member; [Appendix 9] A step of preparing a laminate including a plurality of copper foils stacked in a first direction, at least one low thermal expansion metal foil arranged between the plurality of copper foils in the first direction and made of a metal material having a thermal expansion coefficient lower than that of copper, and a plurality of conductive adhesive sheets arranged between each of the plurality of copper foils and the at least one low thermal expansion metal foil in the first direction; A method for producing a copper-metal composite material having a thermal expansion lower than that of copper, comprising the steps of heating the laminate at a temperature of 200° C. or less in a vacuum environment and pressurizing the laminate at a pressure of 1 MPa or more and 3 MPa or less. [Appendix 10] The at least one low thermal expansion metal foil comprises at least one selected from the group consisting of molybdenum (Mo), a molybdenum alloy, tungsten (W), a tungsten alloy, invar (Fe-Ni), and kovar (Fe-Ni-Co), etc.

[0100] Although the embodiment of the present disclosure has been described above, the above-mentioned embodiment can be modified in various ways. The scope of the present disclosure is not limited to the above-mentioned embodiment. The scope of the present disclosure is defined by the claims, and is intended to include all modifications within the meaning and scope of the claims. [Explanation of symbols]

[0101] 1a,1b Internal wiring layer, 2 Insulating part, 2a,2b,2c,2d,2e,78a,78b Insulating layer, 3a,3e Fiber reinforcement material, 4a,4e Thermosetting resin part, 5a,5b,b Surface wiring layer, 6 First conductive via, 7 Second conductive via, 8 Filling member, 9,9a,9b Cu-Mo composite wiring layer, 9c,81,82 Through hole, 11a,11b Circuit protection film, 23 pad, 51a,51b,51c Copper foil, 52,52a,52b,52c,52d Molybdenum foil, 53a1,53a2,53a,53b1,53b2b,53b2,53b,53c,53d Conductive adhesive sheet, 70,80,85 laminate, 71a First conductor foil, 71b Second conductor foil, 75 Inner layer core, 76a, 76b Conductor foil, 77a, 77b, 77c, 77d Prepreg, 83a, 83b, 84a, 84b Surface conductor layer, 100, 120 Cu-Mo composite, 101, 101a, 101b, 101c Copper layer, 101c Intermediate copper layer, 102, 102a, 102ac, 102ad, 102b, 102bc, 102bd, 102c, 102d Molybdenum layer, 103a, 103b, 103c, 103d Conductive adhesive layer, 103ab, 103bd Filling portion, 103c, 103d Second conductive adhesive layer, 200 Printed wiring board, 220 Electronic component, 221 Connection terminal, 222 Outermost end, 230 joining member, 300 printed wiring board device.

Claims

1. A plurality of copper layers arranged in a stack in a first direction; At least one low thermal expansion metal layer is disposed between the plurality of copper layers in the first direction and is made of a metal material having a thermal expansion coefficient lower than that of copper; a plurality of conductive adhesive layers bonded between each of the plurality of copper layers and the at least one low thermal expansion metal layer; The copper layers include a plurality of outermost copper layers disposed outermost in the first direction, the copper-metal composite having a thermal expansion lower than that of copper.

2. The at least one low thermal expansion metal layer includes a plurality of first low thermal expansion metal layers stacked in the first direction, the plurality of copper layers further includes at least one intermediate copper layer disposed between the plurality of first low thermal expansion metal layers in the first direction; 2. The copper-metal having a thermal expansion lower than copper composite material according to claim 1, wherein the plurality of conductive adhesive layers include a plurality of first conductive adhesive layers bonding between each of the plurality of first low thermal expansion metal layers and each of the plurality of outermost copper layers, and a plurality of second conductive adhesive layers bonding between each of the plurality of first low thermal expansion metal layers and the at least one intermediate copper layer.

3. the material constituting the plurality of conductive adhesive layers is a composite material of a binder and a conductive filler, the binder includes at least one selected from the group consisting of an epoxy resin, a polyester resin, an acrylic resin, and a urethane resin; 3. The copper-metal composite material having a thermal expansion lower than that of copper according to claim 1, wherein the conductive filler comprises acicular copper powder having a surface covered with silver.

4. the at least one low thermal expansion metal layer includes a plurality of second low thermal expansion metal layers arranged side by side at intervals in an in-plane direction perpendicular to the first direction, The copper-metal composite material having a thermal expansion lower than that of copper according to claim 1 or 2, wherein the plurality of conductive adhesive layers bond each of the plurality of second low thermal expansion metal layers to each of the plurality of outermost copper layers, and are filled between the plurality of second low thermal expansion metal layers adjacent to each other in the second direction.

5. The at least one low thermal expansion metal layer comprises at least one selected from the group consisting of molybdenum, molybdenum alloy, tungsten, tungsten alloy, invar (Fe-Ni), and kovar (Fe-Ni-Co). The copper-metal composite material having a thermal expansion lower than that of copper according to claim 1 or 2.

6. a surface wiring layer formed on a main surface of the substrate; a copper-low thermal expansion metal composite wiring layer formed inside the substrate and made of the copper-metal composite having a thermal expansion lower than that of copper according to claim 1 or 2; a printed wiring board comprising an insulating layer that insulates the surface wiring layer from the copper-low thermal expansion metal composite wiring layer.

7. 7. The printed wiring board according to claim 6, further comprising a through-hole conductor electrically connecting said surface wiring layer and said copper-low thermal expansion metal composite wiring layer.

8. The printed wiring board according to claim 6 ; a printed wiring board device comprising: an electronic component electrically connected to the surface wiring layer of the printed wiring board via a bonding member;

9. A step of preparing a laminate including a plurality of copper foils stacked in a first direction, at least one low thermal expansion metal foil arranged between the plurality of copper foils in the first direction and made of a metal material having a thermal expansion coefficient lower than that of copper, and a plurality of conductive adhesive sheets arranged between each of the plurality of copper foils and the at least one low thermal expansion metal foil in the first direction; and heating the laminate at a temperature of 200° C. or less in a vacuum environment and applying a pressure of 1 MPa or more and 3 MPa or less to the laminate.

10. The at least one low thermal expansion metal foil comprises at least one selected from the group consisting of molybdenum, molybdenum alloy, tungsten, tungsten alloy, invar (Fe-Ni), and kovar (Fe-Ni-Co). The method for producing a copper-metal composite having a thermal expansion lower than that of copper according to claim 9.

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