Multilayer wiring board

Abstract

A flat plate-shaped multilayer wiring board 1 comprises: an inner layer 10 including, in the thickness direction, at least two insulating resin layers 11, each having provided on a surface thereof a wiring layer 12 comprising a conductor pattern; and a surface layer 20 including an insulating resin layer 21 bonded to at least one surface of the inner layer 10 in the thickness direction. In the multilayer wiring board 1, the bonding surfaces of an insulating resin layer 11 of the inner layer 10 and the insulating resin layer 21 of the surface layer 20 have protrusions and recesses. The at least one surface layer 20 also includes interlayer connection conductors 30 that are provided so as to be electrically connected to the wiring layer 12 of the inner layer 10 and that penetrate the insulating resin layer 21 of the surface layer 20 in the thickness direction. The interlayer connection conductors 30 of the surface layer 20 include first surface layer via conductors 31 and a second surface layer via conductor 32. The first surface layer via conductors 31 are, compared to the second surface layer via conductor 32, smaller in the thickness direction and smaller in the radial direction perpendicular to the thickness direction.

Description

multilayer wiring board

[0001] The present invention relates to a multilayer wiring board.

[0002] Patent Document 1 discloses a flat multilayer wiring board in which at least two resin layers each including an insulating substrate and a conductive pattern provided on the insulating substrate are laminated, and a surface layer having a higher elastic modulus than the insulating substrate is bonded thereon, the multilayer wiring board being characterized in that the bonding surface between the resin layer and the surface layer has irregularities.

[0003] According to Patent Document 1, since the surface of the resin layer has an uneven shape, the surface layer is less likely to peel off from the resin layer even due to differences in thermal expansion coefficients or impacts, making it possible to obtain a highly reliable multilayer wiring board with a flat surface.

[0004] International Publication No. 2018 / 100922

[0005] Patent Document 1 describes that interlayer connection conductors penetrating the surface layer may be provided. In such a multilayer wiring board, by reducing the diameter of the interlayer connection conductors in the surface layer, the interlayer connection conductors can be arranged at a narrow pitch, enabling high-density wiring and high-density mounting of electronic components thereon.

[0006] However, in the multilayer wiring board described in Patent Document 1, since the conductive pattern is provided on the uneven surface of the resin layer, there are differences in the distance from the substrate surface to the conductive pattern, and as a result, there are differences in the length of the interlayer connection conductor that penetrates the surface layer. Therefore, in areas where the distance from the substrate surface to the conductive pattern is long, that is, where the interlayer connection conductor that penetrates the surface layer is long, if the diameter of the interlayer connection conductor becomes small, it becomes difficult to ensure the connection reliability between the interlayer connection conductor and the conductive pattern.

[0007] The present invention has been made to solve the above problems, and aims to provide a multilayer wiring board that has high connection reliability between the inner wiring layer and the surface interlayer connecting conductor, even if the inner insulating resin layer has an uneven surface.

[0008] The multilayer wiring board of the present invention is a flat multilayer wiring board including an inner layer including at least two insulating resin layers in a thickness direction, each having a wiring layer formed on its surface, the insulating resin layer being formed of a conductor pattern, and a surface layer including an insulating resin layer bonded to at least one surface of the inner layer in the thickness direction. In the multilayer wiring board of the present invention, the bonding surface between the insulating resin layer of the inner layer and the insulating resin layer of the surface layer has an uneven surface. At least one of the surface layers further includes an interlayer connection conductor that penetrates the insulating resin layer of the surface layer in the thickness direction and is provided so as to be electrically connected to the wiring layer of the inner layer. The interlayer connection conductor of the surface layer includes a first surface via conductor and a second surface via conductor. The first surface via conductor has a smaller dimension in the thickness direction and a smaller dimension in a radial direction perpendicular to the thickness direction than the second surface via conductor.

[0009] According to the present invention, it is possible to provide a multilayer wiring board having high connection reliability between the inner wiring layer and the surface interlayer connection conductor, even if the inner insulating resin layer has an uneven surface.

[0010] FIG. 1 is a cross-sectional view schematically showing an example of a multilayer wiring board according to a first embodiment of the present invention. FIG. 2 is a cross-sectional view schematically showing a first modified example of the multilayer wiring board according to the first embodiment of the present invention. FIG. 3 is a cross-sectional view schematically showing a second modified example of the multilayer wiring board according to the first embodiment of the present invention. FIG. 4 is a cross-sectional view schematically showing an example of a step of preparing an insulating resin layer having a wiring layer formed on its surface. FIG. 5 is a cross-sectional view schematically showing an example of a step of stacking insulating resin layers having wiring layers formed on their surfaces. FIG. 6 is a cross-sectional view schematically showing an example of a step of forming a surface insulating resin layer. FIG. 7 is a cross-sectional view schematically showing an example of a step of forming a through hole in a surface insulating resin layer. FIG. 8 is a cross-sectional view schematically showing an example of a step of forming a surface interlayer connection conductor and a wiring layer. FIG. 9 is a cross-sectional view schematically showing an example of a step of forming a protective film. FIG. 10 is a cross-sectional view schematically showing another example of a step of preparing an insulating resin layer having a wiring layer formed on its surface. FIG. 11 is a cross-sectional view schematically showing another example of a step of stacking insulating resin layers having wiring layers formed on their surfaces. FIG. 12 is a cross-sectional view schematically showing another example of a step of forming a surface insulating resin layer. FIG. 13 is a cross-sectional view schematically showing another example of a step of forming a through hole in a surface insulating resin layer. FIG. 14 is a cross-sectional view schematically showing another example of a step of forming a surface interlayer connection conductor and a wiring layer. FIG. 15 is a cross-sectional view schematically showing another example of a step of forming a protective film. FIG. 16 is a cross-sectional view schematically showing a third modified example of the multilayer wiring board according to the first embodiment of the present invention. FIG. 17 is a cross-sectional view schematically showing an example of a multilayer wiring board according to the second embodiment of the present invention. FIG. 18 is a cross-sectional view schematically showing a first modified example of the multilayer wiring board according to the second embodiment of the present invention. FIG. 19 is a cross-sectional view schematically showing a second modified example of the multilayer wiring board according to the second embodiment of the present invention.

[0011] The multilayer wiring board of the present invention will be described below. Note that the present invention is not limited to the following embodiments and may be modified as appropriate within the scope of the present invention. Furthermore, a combination of multiple individual preferred configurations described in the following embodiments also constitutes the present invention.

[0012] 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, descriptions of matters common to the first embodiment will be omitted, and differences will be mainly described. In particular, similar effects resulting from similar configurations will not be mentioned one after the other for each embodiment.

[0013] In the following description, when no particular distinction is made between the embodiments, they will simply be referred to as "the multilayer wiring board of the present invention."

[0014] 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 a range of substantial equivalence, for example, a difference of about several percent, is also included. Furthermore, in this specification, "constant" is not an expression that means only when something is completely constant, but is an expression that means when something is substantially constant, for example, a difference of about several percent.

[0015] 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.

[0016] 1 is a cross-sectional view schematically illustrating an example of a multilayer wiring board according to a first embodiment of the present invention. In FIG. 1, the Z-axis direction is the thickness direction, and the positive side of the Z-axis is called the top and the negative side is called the bottom. This also applies to the other figures.

[0017] The multilayer wiring board 1 shown in FIG. 1 includes an inner layer 10 and a surface layer 20 .

[0018] The multilayer wiring board 1 has a flat plate shape as a whole. Note that the flat plate shape does not necessarily mean that the upper and lower surfaces are smooth, as long as they are approximately flat.

[0019] The inner layer 10 includes at least two insulating resin layers 11 arranged in the thickness direction (Z-axis direction in FIG. 1) on the surface of which a wiring layer 12 made of a conductor pattern is provided.

[0020] 1, the inner layer 10 includes, in the thickness direction, an insulating resin layer 11A having a wiring layer 12A formed thereon, an insulating resin layer 11B having a wiring layer 12B formed thereon, and an insulating resin layer 11C having a wiring layer 12C formed thereon. The number of insulating resin layers 11 in the inner layer 10 may be two, three, or four or more. The thicknesses of the wiring layers 12 in the inner layer 10 may be the same or different.

[0021] The surface layer 20 includes an insulating resin layer 21 bonded to at least one surface in the thickness direction of the inner layer 10. In the example shown in Fig. 1 , the surface layer 20 includes an insulating resin layer 21A bonded to one surface in the thickness direction of the inner layer 10 (the upper surface of the inner layer 10 in Fig. 1 ). The number of insulating resin layers 21 in the surface layer 20 may be one layer or two or more layers on one surface in the thickness direction of the inner layer 10.

[0022] It is preferable that the surface layer 20 further includes a wiring layer 22 provided on the surface of the insulating resin layer 21 opposite to the inner layer 10. In the example shown in Fig. 1, the surface layer 20 further includes a wiring layer 22A provided on the surface of the insulating resin layer 21A opposite to the inner layer 10.

[0023] The thickness of the wiring layer 22 of the surface layer 20 may be the same as the thickness of the wiring layer 12 of the inner layer 10, may be greater than the thickness of the wiring layer 12 of the inner layer 10, or may be smaller than the thickness of the wiring layer 12 of the inner layer 10.

[0024] The joint surface between the insulating resin layer 11 of the inner layer 10 and the insulating resin layer 21 of the surface layer 20 has irregularities due to the influence of the wiring layer 12 of the inner layer 10, etc. In the example shown in Fig. 1, the joint surface between the insulating resin layer 11C of the inner layer 10 and the insulating resin layer 21A of the surface layer 20 has irregularities. Of the insulating resin layers 11 of the inner layer 10, the top surfaces of the insulating resin layers 11B and 11C are irregular. On the other hand, the top surface of the surface layer 20 is flat.

[0025] The surface layer 20 further includes an interlayer connection conductor 30 that penetrates the insulating resin layer 21 of the surface layer 20 in the thickness direction. The interlayer connection conductor 30 of the surface layer 20 is provided so as to be electrically connected to the wiring layer 12 of the inner layer 10. When the surface layer 20 includes a wiring layer 22, the wiring layer 22 of the surface layer 20 is provided so as to be electrically connected to the interlayer connection conductor 30 of the surface layer 20. In the example shown in Fig. 1, the interlayer connection conductor 30 is provided so as to penetrate the insulating resin layer 21A in the thickness direction.

[0026] The interlayer connection conductors 30 on the surface layer 20 include first surface via conductors 31 and second surface via conductors 32 .

[0027] The first surface via conductor 31 has a smaller dimension in the thickness direction and a smaller dimension in the radial direction perpendicular to the thickness direction than the second surface via conductor 32 .

[0028] In the multilayer wiring board 1, first surface via conductors 31 having small radial dimensions can be formed in locations where the distance between the wiring layer 12 of the inner layer 10 and the wiring layer 22 of the surface layer 20 is short. Therefore, even if the insulating resin layer 11 of the inner layer 10 has an uneven surface, the connection reliability between the wiring layer 12 of the inner layer 10 and the interlayer connection conductor 30 of the surface layer 20 can be increased.

[0029] Furthermore, by forming first surface via conductors 31 with small radial dimensions on surface layer 20, it is possible to increase the density of wiring layer 22 on surface layer 20. Therefore, electronic components can be mounted on the surface of multilayer wiring board 1 with high density.

[0030] As the radial dimension of the interlayer connection conductor 30 becomes smaller, the resistance increases, but by reducing the thickness dimension of the first surface via conductor 31, the increase in resistance can be suppressed, thereby preventing deterioration of the electrical characteristics.

[0031] Furthermore, by including a second surface via conductor 32 with a large radial dimension in the interlayer connection conductor 30, the interlayer connection conductor 30 can be formed even in locations where the distance between the wiring layer 12 of the inner layer 10 and the wiring layer 22 of the surface layer 20 is long.

[0032] The second surface via conductor 32 has a larger radial dimension than the first surface via conductor 31, and therefore can have a lower resistance.

[0033] In the multilayer wiring board 1, the density of the wiring layer 12 of the inner layer 10 at a position overlapping the first surface via conductor 31 in the thickness direction is preferably higher than the density of the wiring layer 12 of the inner layer 10 at a position overlapping the second surface via conductor 32 in the thickness direction. At a location where the density of the wiring layer 12 of the inner layer 10 is high, the surface of the insulating resin layer 11C of the inner layer 10 is higher than at a location where the density of the wiring layer 12 of the inner layer 10 is low. Therefore, the dimension of the first surface via conductor 31 in the thickness direction can be smaller than that of the second surface via conductor 32.

[0034] In the example shown in Figure 1, the wiring layer 12 of the inner layer 10 located directly below the first surface via conductor 31 is three layers, while the wiring layer 12 of the inner layer 10 located directly below the second surface via conductor 32 is one layer, so the density of the wiring layer 12 of the inner layer 10 at the position overlapping the first surface via conductor 31 in the thickness direction is higher than the density of the wiring layer 12 of the inner layer 10 at the position overlapping the second surface via conductor 32 in the thickness direction.

[0035] For example, as shown in Figure 1, by extending wiring layer 12B of inner layer 10 to a position directly below first surface via conductor 31 to form wiring layer 12D, the density of wiring layer 12 of inner layer 10 at a position overlapping first surface via conductor 31 in the thickness direction can be made higher than the density of wiring layer 12 of inner layer 10 at a position overlapping second surface via conductor 32 in the thickness direction.

[0036] In particular, the total thickness of the insulating resin layer 21 of the surface layer 20 is T [μm], the thickness of one wiring layer 12 of the inner layer 10 is t [μm], and the number of wiring layers 12 of the inner layer 10 that are positioned to overlap the first surface via conductor 31 in the thickness direction is n １ , the number of wiring layers 12 in the inner layer 10 that overlap the second surface via conductors 32 in the thickness direction is n ２ Then, 60<T+t×(n １ -n ２ In this case, even if the radial dimension of first surface via conductor 31 is reduced, the connection reliability between wiring layer 12 of inner layer 10 and first surface via conductor 31 can be ensured.

[0037] The insulating resin layer 11 of the inner layer 10 is made of a thermoplastic resin such as liquid crystal polymer (LCP), polyetheretherketone (PEEK), polyetheretherketone / polyetherimide (PEEK / PEI), perfluoroalkoxy resin (PFA), polyphenylene sulfide (PPS), thermoplastic polyimide (TPI), or polyphenylene ether (PPE). The insulating resin layers 11 of the inner layers 10 located in different layers may be made of the same type of thermoplastic resin or different types of thermoplastic resin. Furthermore, even if the insulating resin layers 11 of the inner layers 10 located in different layers are made of the same type of thermoplastic resin, the thermoplastic resin compositions may be different.

[0038] For example, the insulating resin layers 11A, 11B, and 11C of the inner layer 10 are made of the same or different thermoplastic resins and are directly bonded by thermocompression bonding without sandwiching an adhesive made of a different material between them, which improves the connection strength between the insulating resin layers 11 compared to when an adhesive is sandwiched between them.

[0039] The wiring layer 12 of the inner layer 10 is made of a conductive metal such as copper (Cu), and may have a base layer made of a metal such as nickel (Ni), nickel chromium (NiCr), titanium (Ti), or chromium (Cr).

[0040] Preferably, the inner layer 10 further includes an interlayer connection conductor 40 that penetrates the insulating resin layer 11 of the inner layer 10 in the thickness direction. The interlayer connection conductor 40 of the inner layer 10 is provided so as to electrically connect the wiring layers 12 of the inner layer 10 to each other. The inner layer 10 may include an interlayer connection conductor 40 that penetrates one insulating resin layer 11 in the thickness direction, or may include an interlayer connection conductor 40 that penetrates two or more insulating resin layers 11 in the thickness direction.

[0041] There are no particular limitations on the number, size, shape, arrangement, etc. of the interlayer connection conductors 40 in the inner layer 10. In the example shown in Fig. 1, the interlayer connection conductors 40 are provided penetrating the insulating resin layer 11B so as to electrically connect the wiring layer 12A and the wiring layer 12B.

[0042] The interlayer connection conductor 40 of the inner layer 10 is made of a conductive metal such as copper (Cu). The type of conductive metal making up the interlayer connection conductor 40 of the inner layer 10 may be the same as or different from the type of conductive metal making up the wiring layer 12 of the inner layer 10. The interlayer connection conductor 40 of the inner layer 10 may have a base layer made of a metal such as nickel (Ni), nickel chromium (NiCr), titanium (Ti), or chromium (Cr).

[0043] The interlayer connection conductor 40 of the inner layer 10 preferably has a portion containing a resin component. The portion containing a resin component is formed, for example, by solidifying a conductive paste such as a copper paste.

[0044] In the example shown in FIG. 1, the interlayer connection conductor 40 of the inner layer 10 includes a first inner layer via conductor 41 having only a portion containing a resin component.

[0045] The radial dimension of the interlayer connection conductor 40 of the inner layer 10 may or may not be constant along the thickness direction. For example, the interlayer connection conductor 40 of the inner layer 10 may have a tapered shape in which the radial dimension decreases along the thickness direction. In this case, the radial dimension of the interlayer connection conductor 40 of the inner layer 10 may decrease from the lower surface to the upper surface of the insulating resin layer 11, or may decrease from the upper surface to the lower surface of the insulating resin layer 11.

[0046] The radial dimension of the interlayer connection conductor 40 on the inner layer 10 may be the same as the radial dimension of the interlayer connection conductor 30 on the surface layer 20, or may be larger than or smaller than the radial dimension of the interlayer connection conductor 30 on the surface layer 20. Specifically, the radial dimension of the interlayer connection conductor 40 on the inner layer 10 may be the same as the radial dimension of the first surface via conductor 31, or may be larger than or smaller than the radial dimension of the first surface via conductor 31. Furthermore, the radial dimension of the interlayer connection conductor 40 on the inner layer 10 may be the same as the radial dimension of the second surface via conductor 32, or may be larger than or smaller than the radial dimension of the second surface via conductor 32. When the radial dimension of the interlayer connection conductor 40 of the inner layer 10 varies along the thickness direction, the dimension of the smallest part is defined as the radial dimension of the interlayer connection conductor 40 of the inner layer 10. The same applies to the radial dimension of the interlayer connection conductor 30, first surface via conductor 31, or second surface via conductor 32 of the surface layer 20.

[0047] The insulating resin layer 21 of the surface layer 20 is made of, for example, a thermosetting resin such as an epoxy resin. In this case, the insulating resin layer 21 of the surface layer 20 preferably contains a filler such as an inorganic filler. The inorganic filler may be a glass filler such as glass fiber or spherical glass, or a ceramic filler.

[0048] When the insulating resin layer 21 of the surface layer 20 is made of a thermosetting resin, it is preferable that the insulating resin layer 21 of the surface layer 20 has a higher modulus of elasticity than the insulating resin layer 11 of the inner layer 10 .

[0049] When the insulating resin layer 21 of the surface layer 20 contains a glass filler, the particle size of the glass filler may be smaller than the unevenness of the joining surface. By having the particle size of the glass filler smaller than the unevenness of the joining surface, the glass filler can be filled uniformly even in a narrow area.

[0050] When the particle size of the glass filler is smaller than the step difference between the concave and convex portions of the joining surface, a part of the glass filler may be disposed in the concave portion of the joining surface, or the entire glass filler may be disposed in the concave portion of the joining surface, which makes it possible to make the physical properties of the surface layer 20 uniform.

[0051] When insulating resin layer 21 of surface layer 20 contains a glass filler, the particle size of the glass filler may be smaller than the thickness of one wiring layer 12 of inner layer 10. When the particle size of the glass filler is smaller than the thickness of one wiring layer 12, the glass filler can be filled uniformly even in a narrow region.

[0052] When the insulating resin layer 21 of the surface layer 20 contains a glass filler, the particle size of the glass filler may be one-third or less of the smaller of the unevenness of the bonding surface and the thickness of one wiring layer 12 of the inner layer 10. This allows the glass filler to be filled uniformly even in a narrow region.

[0053] When the insulating resin layer 21 of the surface layer 20 contains a glass filler, the glass filler may be present in the thinnest part of the insulating resin layer 21 of the surface layer 20. By uniformly filling the glass filler, the characteristics of the surface layer 20 can be made uniform.

[0054] When the insulating resin layer 21 of the surface layer 20 contains a glass filler, the particle size distribution of the glass filler may be a unimodal distribution or a bimodal distribution. In particular, when the particle size distribution of the glass filler is a bimodal distribution, the glass filler can be closest packed, and the rigidity of the surface layer 20 can be improved while the properties can be made uniform.

[0055] The particle size of the glass filler is measured by cutting a cross section of an arbitrary location of the glass filler, projecting the exposed cross section using a scanning electron microscope (SEM), and measuring the size of the glass filler within the field of view. In this measurement method, the average of the maximum and minimum lengths of the cross section of the glass filler is defined as the particle size of the glass filler. The magnification of the SEM observation is, for example, 5000 times.

[0056] Alternatively, the insulating resin layer 21 of the surface layer 20 may be made of a thermoplastic resin such as liquid crystal polymer (LCP), polyetheretherketone (PEEK), polyetheretherketone / polyetherimide (PEEK / PEI), perfluoroalkoxy resin (PFA), polyphenylene sulfide (PPS), thermoplastic polyimide (TPI), or polyphenylene ether (PPE). In this case, the insulating resin layer 21 of the surface layer 20 may be made of the same type of thermoplastic resin as the insulating resin layer 11 of the inner layer 10, or may be made of a different type of thermoplastic resin. Even if the insulating resin layer 21 of the surface layer 20 is made of the same type of thermoplastic resin as the insulating resin layer 11 of the inner layer 10, the composition of the thermoplastic resin may be different.

[0057] The wiring layer 22 of the surface layer 20 is made of a conductive metal such as copper (Cu). The type of conductive metal making up the wiring layer 22 of the surface layer 20 may be the same as or different from the type of conductive metal making up the wiring layer 12 of the inner layer 10. The wiring layer 22 of the surface layer 20 may have a base layer made of a metal such as nickel (Ni), nickel chromium (NiCr), titanium (Ti), or chromium (Cr).

[0058] The interlayer connection conductor 30 of the surface layer 20 is made of a conductive metal such as copper (Cu). The type of conductive metal making up the interlayer connection conductor 30 of the surface layer 20 may be the same as or different from the type of conductive metal making up the wiring layer 22 of the surface layer 20. The type of conductive metal making up the interlayer connection conductor 30 of the surface layer 20 may be the same as or different from the type of conductive metal making up the wiring layer 12 of the inner layer 10. The type of conductive metal making up the interlayer connection conductor 30 of the surface layer 20 may be the same as or different from the type of conductive metal making up the interlayer connection conductor 40 of the inner layer 10. The interlayer connection conductor 30 of the surface layer 20 may have an underlayer made of a metal such as nickel (Ni), nickel chromium (NiCr), titanium (Ti), or chromium (Cr).

[0059] The interlayer connection conductor 30 of the surface layer 20 preferably does not contain a resin component. That is, the first surface via conductor 31 and the second surface via conductor 32 preferably do not contain a resin component. In this case, the content of the conductive component in the interlayer connection conductor 30 of the surface layer 20 is preferably 90.0% by volume or more and 100% by volume or less.

[0060] In this specification, "resin component-free" means that the resin component content is 0.1% by volume or less. The resin component-free portion is formed by growing a film using, for example, a liquid phase method or a vapor phase method. As an example, it is formed from a plating material such as copper (Cu) plating.

[0061] The interlayer connection conductor 30 of the surface layer 20 may be provided at least on the inner wall surface of the through hole that penetrates the insulating resin layer 21 of the surface layer 20 in the thickness direction. Therefore, the interlayer connection conductor 30 of the surface layer 20 may be provided only on the inner wall surface of the through hole, or may be provided throughout the entire interior of the through hole.

[0062] The radial dimension of the interlayer connection conductor 30 of the surface layer 20 may or may not be constant along the thickness direction. For example, the interlayer connection conductor 30 of the surface layer 20 may have a tapered shape in which the radial dimension decreases along the thickness direction. In this case, the radial dimension of the interlayer connection conductor 30 of the surface layer 20 may decrease from the lower surface to the upper surface of the insulating resin layer 21, or may decrease from the upper surface to the lower surface of the insulating resin layer 21.

[0063] As long as the interlayer connection conductor 30 on the surface layer 20 includes the first surface via conductor 31 and the second surface via conductor 32, it may also include other surface via conductors.

[0064] FIG. 2 is a cross-sectional view schematically showing a first modified example of the multilayer wiring board according to the first embodiment of the present invention.

[0065] 2 further includes a protective film 50 provided to cover the interlayer connection conductors 30 of the surface layer 20 and the wiring layer 22 of the surface layer 20. The protective film 50 is, for example, a solder resist layer.

[0066] Protective film 50 has openings 55 through which wiring layer 22 (wiring layer 22A in FIG. 2) of surface layer 20 electrically connected to first surface via conductor 31 is exposed.

[0067] An electrode 60 is preferably provided inside opening 55, and is electrically connected to first surface via conductor 31. Electrode 60 is formed from a plating material such as gold (Au) plating, for example.

[0068] The opening 55 may be located in a position where it overlaps with at least a portion of the first surface via conductor 31 in the thickness direction, as shown on the right side of Figure 2, or it may be located in a position where it does not overlap with the first surface via conductor 31 in the thickness direction, as shown on the left side of Figure 2.

[0069] As described above, the radial dimension of the first surface via conductor 31 can be reduced, which makes it possible to form the electrodes 60 at a narrow pitch on the wiring layer 22 of the surface layer 20. Furthermore, the area of ​​the wiring layer 22 (wiring layer 22A in FIG. 2 ) of the surface layer 20 electrically connected to the first surface via conductor 31 can be reduced, which makes it possible to form the electrodes 60 at a narrow pitch.

[0070] Except for the above-mentioned configuration, the multilayer wiring board 1A shown in FIG. 2 has the same configuration as the multilayer wiring board 1 shown in FIG.

[0071] FIG. 3 is a cross-sectional view schematically showing a second modified example of the multilayer wiring board according to the first embodiment of the present invention.

[0072] 3 further includes an electronic component 70 disposed on the surface of protective film 50 and electrically connected to first surface via conductor 31. Electronic component 70 is electrically connected to electrode 60 via, for example, solder bump 75. As a result, electronic component 70 is electrically connected to wiring layer 22 of surface layer 20.

[0073] In the multilayer wiring board 1B, the upper surface of the insulating resin layer 21 (insulating resin layer 21A in FIG. 3) of the surface layer 20 is flat. Therefore, the surfaces of the wiring layer 22 and the protective film 50 of the surface layer 20 are also flat. This can improve the connection reliability of the electronic component 70.

[0074] Furthermore, as with the multilayer wiring board 1A, the electrodes 60 can be formed at a narrow pitch, so that electronic components 70 with narrow electrode spacing can be mounted, or the electronic components 70 can be mounted at a high density.

[0075] Except for the above-mentioned configuration, the multilayer wiring board 1B shown in FIG. 3 has a common configuration with the multilayer wiring board 1 shown in FIG. 1 or the multilayer wiring board 1A shown in FIG.

[0076] The multilayer wiring board according to the first embodiment of the present invention is manufactured, for example, by the following method.

[0077] [First Manufacturing Method] FIG. 4 is a cross-sectional view schematically showing an example of a step of preparing an insulating resin layer having a wiring layer provided on the surface thereof.

[0078] 4, an insulating resin layer 11 is prepared, on the surface of which a wiring layer 12 made of a conductor pattern is provided. The wiring layer 12 is formed, for example, by attaching a conductive material layer such as copper foil to the surface of the insulating resin layer 11 and patterning it using photolithography and etching.

[0079] 4, insulating resin layer 11A having wiring layer 12A formed on its surface, insulating resin layer 11B having wiring layer 12B formed on its surface, and insulating resin layer 11C having wiring layer 12C formed on its surface are prepared. On the surface of insulating resin layer 11B, wiring layer 12B is extended to a position directly below first surface via conductor 31 (described later), and wiring layer 12D is formed.

[0080] Furthermore, openings 45 are provided in the insulating resin layer 11B, and the interior of the openings 45 is filled with a conductive paste 46 such as copper paste. If necessary, openings may be provided in the insulating resin layers 11A and 11C, and the interior of the openings may be filled with a conductive paste.

[0081] FIG. 5 is a cross-sectional view schematically showing an example of a process for stacking insulating resin layers on the surfaces of which wiring layers are provided.

[0082] As shown in FIG. 5 , an insulating resin layer 11A having a wiring layer 12A formed on its surface is placed on a flat, hard base (not shown). An insulating resin layer 11B having a wiring layer 12B formed on its surface and an insulating resin layer 11C having a wiring layer 12C formed on its surface are then sequentially stacked on top of the insulating resin layer 11A. In this state, the base is heated to, for example, 250°C or higher and 300°C or lower, and isostatic pressing or pseudo-isostatic pressing is performed using hydrostatic pressure or the like. For example, a cushion layer such as a silicone resin may be placed on the insulating resin layer 11C having the wiring layer 12C formed on its surface and pressed. When the insulating resin layers 11A, 11B, and 11C are made of thermoplastic resin, they are bonded to each other by applying pressure in a softened state. In the process shown in FIG. 5 , the conductive paste 46 filled inside the opening 45 is also heated and hardened to form the interlayer connection conductor 40 (first inner-layer via conductor 41). The first inner-layer via conductor 41 contains a resin component.

[0083] 5, the insulating resin layer 11 made of a thermoplastic resin softens, but the wiring layer 12 and the interlayer connection conductors 40 made of a metal such as copper do not soften. Therefore, as shown in Fig. 5, the lower surface of the insulating resin layer 11 that comes into contact with the smooth base made of a hard material is flat, while the upper surface that is pressed is deformed, resulting in an uneven upper surface of the insulating resin layer 11.

[0084] As a result of the above, an inner layer 10 is formed which includes at least two insulating resin layers 11 in the thickness direction, each having a wiring layer 12 made of a conductor pattern provided on its surface.

[0085] FIG. 6 is a cross-sectional view schematically showing an example of a process for forming a surface insulating resin layer.

[0086] As shown in Fig. 6, the inner layer 10 is placed on a flat and smooth base (not shown) made of a hard material, and then an insulating resin layer 21 is formed on the surface of the insulating resin layer 11C. In the example shown in Fig. 6, an insulating resin layer 21A is formed on one surface of the inner layer 10 in the thickness direction (the upper surface of the inner layer 10 in Fig. 6). The insulating resin layer 21 is made of a thermosetting resin, such as an epoxy resin or an epoxy resin containing a glass filler (glass epoxy resin).

[0087] In this state, the insulating resin layer 21 is heated to soften it and deform it into a shape that conforms to the irregularities on the surface of the insulating resin layer 21. Thereafter, pressure is applied to the upper surface of the insulating resin layer 21. For example, a vacuum pressure press performed in a vacuum state is used for the pressure application. At this time, it is preferable to apply the vacuum pressure while placing a flat plate on the upper surface of the insulating resin layer 21.

[0088] As a result, as shown in Fig. 6, the insulating resin layer 21 of the surface layer 20 is bonded onto the insulating resin layer 11 of the inner layer 10. The upper surface of the insulating resin layer 21 of the surface layer 20 becomes flat. In this process, since the upper surface of the insulating resin layer 11 has an uneven shape, the bonding strength with the insulating resin layer 21 is improved compared to when the upper surface of the insulating resin layer 11 is flat. Note that if there are two or more insulating resin layers 21, the process shown in Fig. 6 can be repeated.

[0089] FIG. 7 is a cross-sectional view schematically showing an example of a process for forming a through hole in the surface insulating resin layer.

[0090] 7, a through-hole 80 is formed by, for example, laser irradiation, penetrating the insulating resin layer 21 of the surface layer 20 in the thickness direction. In the through-hole 80, the wiring layer 12C of the inner layer 10 is exposed.

[0091] The through-holes 80 include a first through-hole 81 and a second through-hole 82 .

[0092] The first through-hole 81 has a smaller dimension in the thickness direction and a smaller dimension in the radial direction perpendicular to the thickness direction than the second through-hole 82 .

[0093] FIG. 8 is a cross-sectional view schematically showing an example of a process for forming surface interlayer connection conductors and wiring layers.

[0094] 8 , an interlayer connection conductor 30 is formed inside a through hole 80. Specifically, a first surface via conductor 31 is formed inside a first through hole 81, and a second surface via conductor 32 is formed inside a second through hole 82.

[0095] Furthermore, it is preferable to form a wiring layer 22 on the surface of the insulating resin layer 21 opposite to the inner layer 10. In the example shown in Figure 8, a wiring layer 22A is formed on the surface of the insulating resin layer 21A opposite to the inner layer 10.

[0096] In the process shown in FIG. 8, the interlayer connection conductors 30 and the wiring layer 22 of the surface layer 20 can be simultaneously formed by plating, such as copper (Cu) plating.

[0097] In this way, the multilayer wiring board 1 is manufactured.

[0098] FIG. 9 is a cross-sectional view schematically showing an example of a step of forming a protective film.

[0099] 9 , a protective film 50 such as a solder resist layer is formed to cover the interlayer connection conductors 30 on the surface layer 20 and the wiring layer 22 on the surface layer 20. The protective film 50 is patterned to form openings 55. The wiring layer 22 (wiring layer 22A in FIG. 9 ) on the surface layer 20, which is electrically connected to the first surface via conductor 31, is exposed in the openings 55.

[0100] Inside opening 55, electrode 60 electrically connected to first surface via conductor 31 is formed by plating such as gold (Au) plating.

[0101] In this way, the multilayer wiring board 1A is manufactured.

[0102] Although not shown, electronic components 70 (see FIG. 3) may be disposed on the surface of protective film 50 so as to be electrically connected to first surface via conductors 31. In this manner, multilayer wiring board 1B is manufactured.

[0103] [Second Manufacturing Method] In the first manufacturing method, the wiring layer 12D is formed by extending the wiring layer 12B, whereas in the second manufacturing method, the wiring layer 12D is formed in a layer different from the wiring layer 12B.

[0104] FIG. 10 is a cross-sectional view schematically showing another example of the step of preparing an insulating resin layer having a wiring layer provided on the surface thereof.

[0105] 10, an insulating resin layer 11 is prepared, on the surface of which a wiring layer 12 made of a conductor pattern is provided. The wiring layer 12 is formed, for example, by attaching a conductive material layer such as copper foil to the surface of the insulating resin layer 11 and patterning it using photolithography and etching.

[0106] 10, insulating resin layer 11A having wiring layer 12A provided on its surface, insulating resin layer 11B having wiring layer 12B provided on its surface, insulating resin layer 11C having wiring layer 12D provided on its surface, and insulating resin layer 11C having wiring layer 12C provided on its surface are prepared. Unlike the example shown in Fig. 4, insulating resin layer 11C is divided into two layers, and wiring layer 12D is formed on the surface of lower insulating resin layer 11C at a position directly below first surface via conductors 31 described later.

[0107] Furthermore, openings 45 are provided in the insulating resin layer 11B, and the interior of the openings 45 is filled with a conductive paste 46 such as copper paste. If necessary, openings may be provided in the insulating resin layers 11A and 11C, and the interior of the openings may be filled with a conductive paste.

[0108] FIG. 11 is a cross-sectional view schematically showing another example of the step of stacking insulating resin layers on the surfaces of which wiring layers are provided.

[0109] As shown in FIG. 11 , an insulating resin layer 11A having a wiring layer 12A formed on its surface is placed on a smooth base (not shown) made of a hard material. An insulating resin layer 11B having a wiring layer 12B formed on its surface, an insulating resin layer 11C having a wiring layer 12D formed on its surface, and an insulating resin layer 11C having a wiring layer 12C formed on its surface are sequentially stacked on top of the insulating resin layer 11A. In this state, the insulating resin layer 11A is heated to, for example, 250°C or higher and 300°C or lower, and is subjected to isostatic pressing or pseudo-isostatic pressing using hydrostatic pressure or the like. For example, a cushion layer such as a silicone resin may be placed on the insulating resin layer 11C having the wiring layer 12C formed on its surface and pressed. When the insulating resin layers 11A, 11B, and 11C are made of thermoplastic resin, they are bonded to each other by applying pressure in a softened state. In the process shown in FIG. 11 , the conductive paste 46 filled inside the opening 45 is also heated and hardened to form the interlayer connection conductor 40 (first inner-layer via conductor 41). The first inner-layer via conductor 41 contains a resin component.

[0110] 11, the insulating resin layer 11 made of a thermoplastic resin softens, but the wiring layer 12 and the interlayer connection conductors 40 made of a metal such as copper do not soften. Therefore, as shown in Fig. 11, the lower surface of the insulating resin layer 11 that comes into contact with the smooth base made of a hard material is flat, while the upper surface that is pressed is deformed, resulting in an uneven upper surface of the insulating resin layer 11.

[0111] As a result of the above, an inner layer 10 is formed which includes at least two insulating resin layers 11 in the thickness direction, each having a wiring layer 12 made of a conductor pattern provided on its surface.

[0112] FIG. 12 is a cross-sectional view schematically showing another example of the step of forming a surface insulating resin layer.

[0113] As shown in Fig. 12, the inner layer 10 is placed on a smooth base (not shown) made of a hard material, and an insulating resin layer 21 is formed on the surface of the insulating resin layer 11C. In the example shown in Fig. 12, an insulating resin layer 21A is formed on one surface of the inner layer 10 in the thickness direction (the upper surface of the inner layer 10 in Fig. 12). The insulating resin layer 21 is made of a thermosetting resin, such as an epoxy resin or an epoxy resin containing a glass filler (glass epoxy resin).

[0114] In this state, the insulating resin layer 21 is heated to soften it and deform it into a shape that conforms to the irregularities on the surface of the insulating resin layer 21. Thereafter, pressure is applied to the upper surface of the insulating resin layer 21. For example, a vacuum pressure press performed in a vacuum state is used for the pressure application. At this time, it is preferable to apply the vacuum pressure while placing a flat plate on the upper surface of the insulating resin layer 21.

[0115] As a result, as shown in Fig. 12, the insulating resin layer 21 of the surface layer 20 is bonded onto the insulating resin layer 11 of the inner layer 10. The upper surface of the insulating resin layer 21 of the surface layer 20 becomes flat. In this process, since the upper surface of the insulating resin layer 11 has an uneven shape, the bonding strength with the insulating resin layer 21 is improved compared to when the upper surface of the insulating resin layer 11 is flat. Note that if there are two or more insulating resin layers 21, the process shown in Fig. 12 can be repeated.

[0116] FIG. 13 is a cross-sectional view schematically showing another example of the step of forming a through hole in the surface insulating resin layer.

[0117] 13, a through-hole 80 is formed by, for example, laser irradiation, penetrating the insulating resin layer 21 of the surface layer 20 in the thickness direction. In the through-hole 80, the wiring layer 12C of the inner layer 10 is exposed.

[0118] The through-holes 80 include a first through-hole 81 and a second through-hole 82 .

[0119] The first through-hole 81 has a smaller dimension in the thickness direction and a smaller dimension in the radial direction perpendicular to the thickness direction than the second through-hole 82 .

[0120] FIG. 14 is a cross-sectional view schematically showing another example of the process of forming the surface interlayer connection conductors and the wiring layer.

[0121] 14 , an interlayer connection conductor 30 is formed inside a through hole 80. Specifically, a first surface via conductor 31 is formed inside a first through hole 81, and a second surface via conductor 32 is formed inside a second through hole 82.

[0122] Furthermore, it is preferable to form a wiring layer 22 on the surface of the insulating resin layer 21 opposite to the inner layer 10. In the example shown in Figure 14, a wiring layer 22A is formed on the surface of the insulating resin layer 21A opposite to the inner layer 10.

[0123] In the step shown in FIG. 14, the interlayer connection conductors 30 and the wiring layer 22 of the surface layer 20 can be simultaneously formed by plating, such as copper (Cu) plating.

[0124] In this way, the multilayer wiring board 1C is manufactured.

[0125] FIG. 15 is a cross-sectional view schematically showing another example of the step of forming a protective film.

[0126] 15 , a protective film 50 such as a solder resist layer is formed to cover the interlayer connection conductors 30 on the surface layer 20 and the wiring layer 22 on the surface layer 20. The protective film 50 is patterned to form openings 55. The wiring layer 22 (wiring layer 22A in FIG. 15 ) on the surface layer 20, which is electrically connected to the first surface via conductor 31, is exposed in the openings 55.

[0127] Inside opening 55, electrode 60 electrically connected to first surface via conductor 31 is formed by plating such as gold (Au) plating.

[0128] In this way, the multilayer wiring board 1D is manufactured.

[0129] Although not shown, electronic components 70 (see FIG. 3) may be disposed on the surface of protective film 50 so as to be electrically connected to first surface via conductors 31 .

[0130] [Third Manufacturing Method] In the first and second manufacturing methods, the insulating resin layer 21 of the surface layer 20 is formed using a thermosetting resin, whereas in the third manufacturing method, the insulating resin layer 21 of the surface layer 20 is formed using a thermoplastic resin.

[0131] For example, an insulating resin layer 11A having a wiring layer 12A formed on its surface, an insulating resin layer 11B having a wiring layer 12B (and wiring layer 12D) formed on its surface, an insulating resin layer 11C having a wiring layer 12C formed on its surface, and an insulating resin layer 21A are stacked in this order and bonded to each other by applying pressure in a softened state.

[0132] In the above method, not only the upper surface of the insulating resin layer 11 of the inner layer 10 but also the upper surface of the insulating resin layer 21 of the surface layer 20 has irregularities. Therefore, the irregularities on the upper surface of the insulating resin layer 21 of the surface layer 20 are flattened by processing such as polishing or grinding.

[0133] Thereafter, a multilayer wiring board is manufactured by the same steps as in the first manufacturing method, or alternatively, a multilayer wiring board is manufactured by the same steps as in the second manufacturing method.

[0134] FIG. 16 is a cross-sectional view schematically showing a third modified example of the multilayer wiring board according to the first embodiment of the present invention.

[0135] In the multilayer wiring board 1E shown in Figure 16, the surface layer 20 includes an insulating resin layer 21A bonded to one surface of the inner layer 10 in the thickness direction (the upper surface of the inner layer 10 in Figure 16), and further includes an insulating resin layer 21B bonded to the other surface of the inner layer 10 in the thickness direction (the lower surface of the inner layer 10 in Figure 16).

[0136] In the example shown in FIG. 16, a wiring layer 22A is provided on the surface of an insulating resin layer 21A opposite to the inner layer 10.

[0137] 16, a wiring layer may be provided on the surface of the insulating resin layer 21B opposite to the inner layer 10. Also, an interlayer connection conductor may be provided that penetrates the insulating resin layer 21B in the thickness direction.

[0138] [Second embodiment] In a second embodiment of the present invention, the inner layer includes two or more interlayer connection conductor layers in the thickness direction. In the second embodiment of the present invention, the inner layer may include two, three, or four or more interlayer connection conductor layers in the thickness direction.

[0139] FIG. 17 is a cross-sectional view schematically showing an example of a multilayer wiring board according to the second embodiment of the present invention.

[0140] 17, the inner layer 10 includes, in the thickness direction, an insulating resin layer 11A having a wiring layer 12A provided on its surface, an insulating resin layer 11B having a wiring layer 12B provided on its surface, and an insulating resin layer 11C having a wiring layer 12C provided on its surface. A wiring layer 12E is provided on the surface of the insulating resin layer 11A opposite to the wiring layer 12A.

[0141] Furthermore, the insulating resin layer 11A and the insulating resin layer 11B are each provided with an interlayer connection conductor 40. The interlayer connection conductor 40 penetrating the insulating resin layer 11A is provided so as to electrically connect the wiring layer 12A and the wiring layer 12E, and the interlayer connection conductor 40 penetrating the insulating resin layer 11B is provided so as to electrically connect the wiring layer 12A and the wiring layer 12B.

[0142] As described in the first embodiment, the interlayer connection conductor 40 of the inner layer 10 preferably has a portion containing a resin component.

[0143] In the multilayer wiring board 2 shown in FIG. 17, the interlayer connection conductor 40 of the inner layer 10 includes a first inner layer via conductor 41 having only a portion containing a resin component.

[0144] FIG. 18 is a cross-sectional view schematically showing a first modified example of the multilayer wiring board according to the second embodiment of the present invention.

[0145] In the multilayer wiring board 2A shown in Figure 18, the interlayer connection conductor 40 of the inner layer 10 includes a first inner layer via conductor 41 having only a portion containing a resin component, as well as a second inner layer via conductor 42 having a portion containing a resin component and a portion not containing a resin component.

[0146] 18, the portion of the second inner layer via conductor 42 that contains a resin component is located on the lower surface side, and the portion that does not contain a resin component is located on the upper surface side, but their arrangement, ratio, etc. are not particularly limited. Also, the first inner layer via conductor 41 is located on the lower layer, and the second inner layer via conductor 42 is located on the upper layer, but their arrangement, number, etc. are not particularly limited.

[0147] FIG. 19 is a cross-sectional view schematically showing a second modified example of the multilayer wiring board according to the second embodiment of the present invention.

[0148] In the multilayer wiring board 2B shown in Figure 19, the interlayer connection conductor 40 of the inner layer 10 includes a first inner layer via conductor 41 having only a portion containing a resin component, as well as a third inner layer via conductor 43 that does not contain a resin component.

[0149] In the example shown in FIG. 19, the first inner layer via conductor 41 is located in the lower layer and the third inner layer via conductor 43 is located in the upper layer, but there are no particular limitations on their arrangement, number, etc.

[0150] When the inner layer 10 includes two or more layers of interlayer connection conductors 40 in the thickness direction, it is preferable that the interlayer connection conductors 40 overlap each other in the thickness direction. This enables high-density wiring. Note that, in at least one pair of interlayer connection conductors 40 adjacent in the thickness direction, it is sufficient that at least a portion of the interlayer connection conductor 40 in the upper layer and at least a portion of the interlayer connection conductor 40 in the lower layer overlap in the thickness direction. However, it is preferable that, in all pairs of interlayer connection conductors 40 adjacent in the thickness direction, at least a portion of the interlayer connection conductor 40 in the upper layer and at least a portion of the interlayer connection conductor 40 in the lower layer overlap in the thickness direction.

[0151] When the inner layer 10 includes two or more layers of interlayer connection conductors 40 in the thickness direction, the interlayer connection conductors 40 of the inner layer 10 may include only one of the first inner layer via conductor 41, the second inner layer via conductor 42, and the third inner layer via conductor 43, or may include two or more of them.

[0152] For example, when the interlayer connection conductor 40 includes the second inner-layer via conductor 42, the diameter and pitch of the interlayer connection conductor 40 can be made smaller than those of the first inner-layer via conductor 41. Therefore, by arranging the interlayer connection conductors 40 so as to overlap each other in the thickness direction, high-density wiring can be formed.

[0153] Furthermore, when the interlayer connection conductor 40 includes the third inner-layer via conductor 43, the diameter and pitch of the interlayer connection conductor 40 can be further reduced, thereby enabling even higher density wiring to be formed.

[0154] In the first and second embodiments of the present invention, the number of interlayer connection conductors 40 in the inner layer 10 is not particularly limited. For example, the inner layer 10 may include multiple interlayer connection conductors 40 in the same insulating resin layer 11. Furthermore, the size, shape, arrangement, etc. of the interlayer connection conductors 40 in the inner layer 10 are not particularly limited. When the inner layer 10 includes multiple interlayer connection conductors 40, the sizes, shapes, etc. of the interlayer connection conductors 40 may be the same or different.

[0155] The present specification discloses the following:

[0156] <1> A flat multilayer wiring board comprising: an inner layer including at least two insulating resin layers in a thickness direction, each having a wiring layer made of a conductor pattern provided on its surface; and a surface layer including an insulating resin layer bonded to at least one surface of the inner layer in the thickness direction, wherein a bonding surface between the insulating resin layer of the inner layer and the insulating resin layer of the surface layer has unevenness; at least one of the surface layers further includes an interlayer connection conductor that penetrates the insulating resin layer of the surface layer in the thickness direction and is arranged so as to be electrically connected to the wiring layer of the inner layer; the interlayer connection conductor of the surface layer includes a first surface via conductor and a second surface via conductor; and the first surface via conductor has a smaller dimension in the thickness direction and a smaller dimension in a radial direction perpendicular to the thickness direction than the second surface via conductor.

[0157] <2> A multilayer wiring board as described in <1>, wherein the density of the inner wiring layer at a position overlapping the first surface via conductor in the thickness direction is higher than the density of the inner wiring layer at a position overlapping the second surface via conductor in the thickness direction.

[0158] <3> The total thickness of the surface insulating resin layers is T [μm], the thickness of one of the inner wiring layers is t [μm], and the number of the inner wiring layers that overlap the first surface via conductor in the thickness direction is n １ The number of the inner wiring layers that overlap the second surface via conductor in the thickness direction is n ２ Then, 60<T+t×(n １ -n ２ The multilayer wiring board according to <2>, wherein

[0159] <4> The multilayer wiring board according to any one of <1> to <3>, wherein the first surface via conductor and the second surface via conductor do not contain a resin component.

[0160] <5> The multilayer wiring board according to any one of <1> to <4>, wherein the inner layer further includes an interlayer connection conductor that penetrates the insulating resin layer of the inner layer in the thickness direction and is provided so as to electrically connect the wiring layers of the inner layer to each other.

[0161] <6> The multilayer wiring board according to <5>, wherein the interlayer connection conductor of the inner layer has a portion containing a resin component.

[0162] <7> The multilayer wiring board according to <5> or <6>, wherein the interlayer connection conductor of the inner layer includes a first inner layer via conductor having only a portion containing a resin component.

[0163] <8> The multilayer wiring board according to any one of <5> to <7>, wherein the interlayer connection conductor of the inner layer includes a second inner layer via conductor having a portion containing a resin component and a portion not containing a resin component.

[0164] <9> The multilayer wiring board according to any one of <5> to <8>, wherein the interlayer connection conductors of the inner layers include third inner layer via conductors that do not contain a resin component.

[0165] <10> The multilayer wiring board according to any one of <1> to <9>, wherein at least one of the surface layers further includes a wiring layer provided on a surface of the insulating resin layer opposite the inner layer so as to be electrically connected to the interlayer connection conductor of the surface layer.

[0166] <11> The multilayer wiring board according to <10>, further comprising a protective film provided to cover the surface interlayer connection conductor and the surface wiring layer, wherein the protective film has an opening through which the surface wiring layer electrically connected to the first surface via conductor is exposed.

[0167] <12> The multilayer wiring board according to <11>, wherein at least one of the openings is positioned so as to overlap at least a portion of the first surface via conductor in the thickness direction.

[0168] <13> The multilayer wiring board according to <11> or <12>, wherein at least one of the openings is located so as not to overlap the first surface via conductor in the thickness direction.

[0169] <14> The multilayer wiring board according to any one of <11> to <13>, further comprising an electronic component disposed on the surface of the protective film and electrically connected to the first surface via conductor.

[0170] <15> The multilayer wiring board according to any one of <1> to <14>, wherein the surface insulating resin layer is made of a thermosetting resin.

[0171] <16> The multilayer wiring board according to <15>, wherein the surface insulating resin layer contains a glass filler.

[0172] <17> The multilayer wiring board according to <15> or <16>, wherein the outer insulating resin layer has a higher elastic modulus than the inner insulating resin layer.

[0173] <18> The multilayer wiring board according to any one of <1> to <14>, wherein the surface insulating resin layer is made of a thermoplastic resin.

[0174] <19> The multilayer wiring board according to any one of <1> to <18>, wherein the inner insulating resin layer is made of a thermoplastic resin.

[0175] DESCRIPTION OF SYMBOLS 1, 1A, 1B, 1C, 1D, 1E, 2, 2A, 2B Multilayer wiring board 10 Inner layer 11, 11A, 11B, 11C Insulating resin layer (inner layer insulating resin layer) 12, 12A, 12B, 12C, 12D, 12E Wiring layer (inner layer wiring layer) 20 Surface layer 21, 21A, 21B Insulating resin layer (surface layer insulating resin layer) 22, 22A Wiring layer (surface layer wiring layer) 30 Interlayer connection conductor (surface layer interlayer connection conductor) 31 First surface layer via conductor 32 Second surface layer via conductor 40 Interlayer connection conductor (inner layer interlayer connection conductor) 41 First inner layer via conductor 42 Second inner layer via conductor 43 Third inner layer via conductor 45 Opening 46 Conductive paste 50 Protective film 55 Opening 60 Electrode 70 Electronic component 75 Solder bump 80 Through hole 81 First through hole 82 Second through hole

Claims

1. A flat multilayer wiring board comprising an inner layer including at least two insulating resin layers in the thickness direction with a wiring layer consisting of a conductor pattern provided on the surface, and a surface layer including an insulating resin layer bonded to at least one surface of the inner layer in the thickness direction, wherein a bonding surface between the insulating resin layer of the inner layer and the insulating resin layer of the surface layer has unevenness, and at least one of the surface layers further includes an interlayer connection conductor that penetrates the insulating resin layer of the surface layer in the thickness direction and is provided so as to be electrically connected to the wiring layer of the inner layer, the interlayer connection conductor of the surface layer includes a first surface layer via conductor and a second surface layer via conductor, and the first surface layer via conductor has a smaller dimension in the thickness direction and a smaller radial dimension perpendicular to the thickness direction than the second surface layer via conductor.

2. The multilayer wiring board as described in claim 1, wherein the density of the inner wiring layer at a position overlapping the first surface via conductor in the thickness direction is higher than the density of the inner wiring layer at a position overlapping the second surface via conductor in the thickness direction.

3. The total thickness of the surface insulating resin layer is T [μm], the thickness of one of the inner wiring layers is t [μm], and the number of the inner wiring layers that overlap the first surface via conductor in the thickness direction is n １ The number of the inner wiring layers that overlap the second surface via conductor in the thickness direction is n ２ Then, 60<T+t×(n １ -n ２ The multilayer wiring board according to claim 2 , wherein 4. The multilayer wiring board according to any one of claims 1 to 3, wherein the first surface via conductor and the second surface via conductor each do not contain a resin component.

5. A multilayer wiring board according to any one of claims 1 to 4, wherein the inner layer further includes an interlayer connection conductor penetrating the insulating resin layer of the inner layer in the thickness direction, the interlayer connection conductor being arranged so as to electrically connect the wiring layers of the inner layer to each other.

6. The multilayer wiring board according to claim 5, wherein the interlayer connection conductor of the inner layer has a portion containing a resin component.

7. The multilayer wiring board according to claim 5 or 6, wherein the interlayer connection conductor of the inner layer includes a first inner layer via conductor having only a portion containing a resin component.

8. A multilayer wiring board according to any one of claims 5 to 7, wherein the interlayer connection conductor of the inner layer includes a second inner layer via conductor having a portion containing a resin component and a portion not containing a resin component.

9. The multilayer wiring board according to any one of claims 5 to 8, wherein the interlayer connection conductor of the inner layer includes a third inner layer via conductor that does not contain a resin component.

10. A multilayer wiring board according to any one of claims 1 to 9, wherein at least one of the surface layers further includes a wiring layer provided on the surface of the insulating resin layer opposite the inner layer so as to be electrically connected to the interlayer connection conductor of the surface layer.

11. The multilayer wiring board described in claim 10, further comprising a protective film provided to cover the surface interlayer connection conductor and the surface wiring layer, the protective film having an opening through which the surface wiring layer electrically connected to the first surface via conductor is exposed.

12. The multilayer wiring board according to claim 11, wherein at least one of the openings is positioned so as to overlap at least a portion of the first surface via conductor in the thickness direction.

13. The multilayer wiring board according to claim 11 or 12, wherein at least one of the openings is located so as not to overlap with the first surface via conductor in the thickness direction.

14. The multilayer wiring board according to any one of claims 11 to 13, further comprising an electronic component disposed on the surface of the protective film and electrically connected to the first surface via conductor.

15. The multilayer wiring board according to any one of claims 1 to 14, wherein the surface insulating resin layer is made of a thermosetting resin.

16. The multilayer wiring board according to claim 15, wherein the surface insulating resin layer contains a glass filler.

17. The multilayer wiring board according to claim 15 or 16, wherein the outer insulating resin layer has a higher elastic modulus than the inner insulating resin layer.

18. The multilayer wiring board according to any one of claims 1 to 14, wherein the surface insulating resin layer is made of a thermoplastic resin.

19. The multilayer wiring board according to any one of claims 1 to 18, wherein the inner insulating resin layer is made of a thermoplastic resin.

Images