Wiring board and method for manufacturing the same

Abstract

To provide a wiring board and a method for manufacturing a wiring board capable of suppressing bonding defects.SOLUTION: A wiring board has an insulating resin layer having a first surface and a second surface opposite the first surface, a rewiring layer provided on the first surface of the insulating resin layer, a first connection terminal exposed from the second surface of the insulating resin layer, and a conductive via provided in the insulating resin layer and electrically connecting the rewiring layer and the first connection terminal, the insulating resin layer has a first resin layer comprising the second surface and containing a first filler, a second resin layer provided on the first side of the first resin layer, and a third resin layer provided on the first side of the second resin layer, containing a second filler and comprising the first surface, and an average particle diameter of the first filler is larger than an average particle diameter of the second filler.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present disclosure relates to a wiring board and a method for manufacturing a wiring board. [Background technology]

[0002] A wiring board in which an interposer is mounted on a build-up board has been disclosed (Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2020-205331 A Summary of the Invention [Problem to be solved by the invention]

[0004] Although the wiring board described in Patent Document 1 achieves the intended purpose, there is a risk of poor bonding between the interposer and the build-up board.

[0005] An object of the present disclosure is to provide a wiring board capable of suppressing bonding defects and a method for manufacturing the wiring board. [Means for solving the problem]

[0006] According to one embodiment of the present disclosure, there is provided an insulating resin layer having a first surface and a second surface opposite to the first surface, a rewiring layer provided on the first surface of the insulating resin layer, a first connection terminal exposed from the second surface of the insulating resin layer, and a conductive via provided in the insulating resin layer and electrically connecting the rewiring layer and the first connection terminal, wherein the insulating resin layer includes a first resin layer constituting the second surface and containing a first filler, a second resin layer provided on the first surface side of the first resin layer, and a third resin layer provided on the first surface side of the second resin layer, containing a second filler, and constituting the first surface, and an average particle size of the first filler is larger than an average particle size of the second filler.In a cross section perpendicular to the first surface of the insulating resin layer, the ratio of the first filler in the first resin layer is 40% to 70%, and the ratio of the second filler in the third resin layer is 50% to 80%. A wiring substrate is provided. Effect of the Invention

[0007] According to the disclosed technique, poor bonding can be suppressed. [Brief description of the drawings]

[0008] [Figure 1] 1 is a cross-sectional view showing a wiring board according to a first embodiment. [Diagram 2] FIG. 4 is a cross-sectional view showing an insulating resin layer. [Diagram 3] 1A to 1C are cross-sectional views (part 1) illustrating the method for manufacturing a wiring board according to a first embodiment. [Figure 4] 5A to 5C are cross-sectional views (part 2) illustrating the method for manufacturing the wiring board according to the first embodiment. [Diagram 5] 5A to 5C are cross-sectional views (part 3) illustrating the method for manufacturing the wiring board according to the first embodiment. [Figure 6] 4 is a cross-sectional view (part 4) illustrating the method for manufacturing the wiring board according to the first embodiment. [Figure 7] 5 is a cross-sectional view (part 5) illustrating the method for manufacturing the wiring board according to the first embodiment. FIG. [Figure 8] FIG. 13 is a diagram showing the results of a simulation. [Figure 9] FIG. 11 is a cross-sectional view showing a semiconductor device according to a second embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, the embodiments will be described in detail with reference to the accompanying drawings. In this specification and the drawings, components having substantially the same functional configurations are denoted by the same reference numerals, and redundant description may be omitted.

[0010] (First embodiment) The first embodiment relates to a wiring board and a manufacturing method thereof.

[0011] [Wiring board structure] First, a description will be given of the structure of the wiring board according to the first embodiment. Fig. 1 is a cross-sectional view showing the wiring board according to the first embodiment.

[0012] The wiring board 1 according to the first embodiment includes a buildup board 100, an interposer 200, a bonding material 300, and an adhesive layer 400. In this disclosure, for convenience, the direction in which the interposer 200 is located as viewed from the buildup board 100 is defined as the upper side, and the opposite direction is defined as the lower side. In addition, a plan view refers to viewing an object from a direction perpendicular to the upper surface of the buildup board 100. However, the wiring board can be used upside down and in any position.

[0013] The build-up board 100 has, for example, a core layer 110 , a build-up layer 120 provided on the upper surface of the core layer 110 , and a build-up layer 130 provided on the lower surface of the core layer 110 .

[0014] The core layer 110 has an insulating base material 111 in which a through hole 111x is formed, a conductive through via 112 formed on the inner wall surface of the through hole 111x, and a filler 113 filled inside the conductive through via 112.

[0015] The build-up layer 120 has an insulating layer 121, a wiring layer 122, and a solder resist layer 123. The wiring layer 122 includes an electrode pad 124 on the uppermost surface of the insulating layer 121. The material of the wiring layer 122 is a conductor such as copper. The electrode pad 124 is used as a connection terminal when the build-up substrate 100 is joined to the interposer 200. The electrode pad 124 is an example of a second connection terminal.

[0016] The build-up layer 130 has an insulating layer 131, a wiring layer 132, and a solder resist layer 133. The wiring layer 132 includes an electrode pad 134 on the bottom surface of the insulating layer 131. The material of the wiring layer 132 is a conductor such as copper. The electrode pad 134 is used as a connection terminal when the build-up board 100 is joined to an external component such as a motherboard.

[0017] The electrode pads 124 and 134 are electrically connected to each other via the wiring layer 122, the through conductive vias 112, and the wiring layer 132. The number of insulating layers 121 and wiring layers 122 included in the build-up layer 120, and the number of insulating layers 131 and wiring layers 132 included in the build-up layer 130 are not particularly limited.

[0018] Interposer 200 has, for example, a first wiring structure 210 and a second wiring structure 220 provided on an upper surface of first wiring structure 210.

[0019] The first wiring structure 210 includes an electrode pad 211 , an insulating resin layer 212 , and a conductive via 213 .

[0020] Here, a description will be given of the insulating resin layer 212. FIG.

[0021] The insulating resin layer 212 includes a first resin layer 10, a second resin layer 20 on the first resin layer 10, and a third resin layer 30 on the second resin layer 20. The third resin layer 30 may be thinner than the first resin layer 10 and the second resin layer 20. For example, the thickness of the first resin layer 10 and the thickness of the second resin layer 20 are each about 20 μm, and the thickness of the third resin layer 30 is about 18 μm. The insulating resin layer 212 includes an upper surface 212A and a lower surface 212B opposite to the upper surface 212A. The third resin layer 30 constitutes the upper surface 212A, and the first resin layer 10 constitutes the lower surface 212B. The upper surface 212A is an example of a first surface, and the lower surface 212B is an example of a second surface.

[0022] The second resin layer 20 is formed by impregnating glass fibers 21 with an insulating resin. The insulating resin impregnated into the reinforcing member of the second resin layer 20 is cured, for example, by thermosetting. The first resin layer 10 and the third resin layer 30 contain a thermosetting resin but do not contain glass fibers. The first resin layer 10 contains a first filler 11, and the third resin layer 30 contains a second filler 31. The first filler 11 and the second filler 31 are, for example, silica filler or alumina filler. The average particle size of the first filler 11 is larger than the average particle size of the second filler 31.

[0023] The electrode pad 211 is embedded in the first resin layer 10. The lower surface of the first resin layer 10 and the lower surface of the electrode pad 211 are flush with each other, and the electrode pad 211 is exposed from the lower surface 212B of the insulating resin layer 212. The side surfaces of the electrode pad 211 are covered with the first resin layer 10.

[0024] A via hole 212x is formed in the insulating resin layer 212, extending from the upper surface 212A to the upper surface of the electrode pad 211. The conductive via 213 is provided in the via hole 212x. The conductive via 213 contacts the electrode pad 211. The upper surface of the third resin layer 30 and the upper surface of the conductive via 213 are flush with each other. The material of the electrode pad 211 and the conductive via 213 is a conductor such as copper. The electrode pad 211 is used as a connection terminal when the interposer 200 is joined to the build-up substrate 100. The electrode pad 211 is an example of a first connection terminal.

[0025] The second wiring structure 220 has an insulating layer 221 and a wiring layer 222. A part of the wiring layer 222 is in contact with the conductive via 213. The wiring layer 222 includes an electrode pad 224 on the uppermost surface of the insulating layer 221. The material of the insulating layer 221 is, for example, an organic resin. The material of the wiring layer 222 is, for example, a conductor such as copper. The electrode pad 224 is used as a connection terminal when a semiconductor chip is mounted. For example, the thickness of the second wiring structure 220 is about 20 μm. The number of the insulating layer 221 and the wiring layer 222 included in the second wiring structure 220 is not particularly limited. The second wiring structure 220 is an example of a rewiring layer.

[0026] The bonding material 300 bonds the electrode pads 124 of the build-up substrate 100 and the electrode pads 211 of the interposer 200. The material of the bonding material 300 is, for example, a tin (Sn) layer or a solder layer. The material of the solder layer may be, for example, a Sn-silver (Ag)-based, Sn-Cu-based, or Sn-Ag-Cu-based lead (Pb)-free solder.

[0027] The adhesive layer 400 is provided between the build-up substrate 100 and the interposer 200, and bonds the build-up substrate 100 and the interposer 200 to each other. The adhesive layer 400 is mainly made of epoxy, for example. The adhesive layer 400 may cover a part of the side surface of the interposer 200.

[0028] [Method of manufacturing wiring board] Next, a method for manufacturing wiring board 1 according to the first embodiment will be described. Figures 3 to 7 are cross-sectional views showing the method for manufacturing wiring board 1 according to the first embodiment.

[0029] First, as shown in FIG. 3(a), a support substrate 50 is prepared. The support substrate 50 has a support 51, a release layer 52, and a copper foil 53. The release layer 52 and the copper foil 53 are formed on the upper and lower surfaces of the support 51. The release layer 52 is between the support 51 and the copper foil 53. For example, the support 51 contains a resin, and the release layer 52 is an inorganic layer. A large-sized substrate from which multiple interposers 200 can be obtained is used as the support substrate 50. In other words, the support substrate 50 has multiple regions in which structures corresponding to the interposers 200 are formed.

[0030] 3(b), electrode pads 211 are formed on the copper foil 53 on the upper and lower sides of the support substrate 50. The electrode pads 211 can be formed by, for example, a semi-additive method. That is, a plating resist layer (not shown) having openings in the areas where the electrode pads 211 are to be formed is formed on the copper foil 53, and the electrode pads 211 made of copper or the like are formed in the openings by an electrolytic plating method that uses the copper foil 53 as a plating power supply path. Thereafter, the plating resist layer is removed.

[0031] 4(a), an insulating resin layer 212 is formed on the upper and lower sides of the support substrate 50 so as to cover the electrode pads 211, the copper foil 53, and the support 51. In forming the insulating resin layer 212, first, a first resin layer 10 is formed, then a second resin layer 20 is formed on the first resin layer 10, and a third resin layer 30 is formed on the second resin layer 20. The first resin layer 10 contains a first filler 11, the second resin layer 20 contains a glass fiber 21, and the third resin layer 30 contains a second filler 31. For example, the thickness of the first resin layer 10, the thickness of the second resin layer 20, and the thickness of the third resin layer 30 are each about 20 μm.

[0032] 4(b), via holes 212x reaching the electrode pads 211 are formed in the insulating resin layer 212 on the upper and lower sides of the support substrate 50. The via holes 212x can be formed by, for example, laser processing. After the via holes 212x are formed, it is preferable to perform a desmear process to remove resin residues adhering to the surfaces of the electrode pads 211 exposed at the bottoms of the via holes 212x.

[0033] Next, on the upper and lower sides of the support substrate 50, a conductive layer 213A is formed on the insulating resin layer 212, which is connected to the electrode pad 211 through the via hole 212x. The conductive layer 213A can be formed by, for example, a semi-additive method. Here, a method for forming the conductive layer 213A will be described in detail. First, a seed layer (not shown) made of copper or the like is formed on the insulating resin layer 212 and the inner surface of the via hole 212x by electroless plating or sputtering. Next, a plating resist layer (not shown) having an opening in a portion where the conductive layer 213A is to be formed is formed on the seed layer. Next, a metal plating layer made of copper or the like is formed in the opening of the plating resist layer by electrolytic plating using the seed layer as a plating power supply path. Then, the plating resist layer is removed. Next, the seed layer is removed by wet etching using the metal plating layer as a mask. In this manner, the conductive layer 213A including the seed layer and the metal plating layer can be formed.

[0034] 5(a), on the upper side of the support substrate 50, the conductive layer 213A and the surface portion of the insulating resin layer 212 are polished by a chemical mechanical polishing (CMP) method to make the upper surface of the conductive layer 213A and the upper surface 212A of the insulating resin layer 212 flush with each other. As a result of this polishing, the conductive vias 213 are formed in the via holes 212x. As a result, the thickness of the third resin layer 30 becomes about 18 μm, which is thinner than the first resin layer 10 and the second resin layer 20.

[0035] In this manner, a first wiring structure 210 is formed, which includes the insulating resin layer 212, the conductive vias 213 in the insulating resin layer 212, and the electrode pads 211 connected to the conductive vias 213.

[0036] 5(b), a second wiring structure 220 having an insulating layer 221 and a wiring layer 222 is formed on the insulating resin layer 212 and the conductive via 213. The second wiring structure 220 can be formed by, for example, a semi-additive method. A part of the wiring layer 222 is in contact with the conductive via 213, and the wiring layer 222 includes an electrode pad 224 on the uppermost surface of the insulating layer 221.

[0037] Next, as shown in FIG. 6(a), first wiring structure 210 and second wiring structure 220 are peeled off from release layer 52 together with copper foil 53.

[0038] 6(b), the copper foil 53 is removed. Thereafter, a bonding material 300 is provided on the lower surface of the electrode pad 211, and an adhesive layer 400 that covers the bonding material 300 is formed on the lower surface 212B of the insulating resin layer 212. As the adhesive layer 400, for example, an NCF (non-conductive film) mainly composed of epoxy can be used.

[0039] 6(c), the structure that has been subjected to the processes up to the formation of the adhesive layer 400 is cut along a predetermined cutting line by a slicer or the like. As a result, the structures corresponding to the interposers 200 are separated into individual pieces, and a plurality of interposers 200 are obtained from the large-sized support substrate 50.

[0040] 7, a build-up substrate 100 is prepared separately. Then, the interposer 200 on which the adhesive layer 400 is formed is flip-chip mounted on the build-up substrate 100 while the electrode pad 211 faces the electrode pad 124. At this time, the electrode pad 211 and the electrode pad 124 are bonded to each other by the bonding material 300.

[0041] In this manner, the wiring board 1 according to the first embodiment can be manufactured.

[0042] In the first embodiment, the interposer 200 including the first wiring structure 210 and the second wiring structure 220 is restrained by the support substrate 50 before being peeled off from the peeling layer 52. Therefore, even if there is a stress inside the interposer 200 that causes the interposer 200 to warp, the interposer 200 does not deform before being peeled off from the peeling layer 52. However, if there is a stress inside the interposer 200 that causes the interposer 200 to warp, when the interposer 200 is peeled off from the peeling layer 52, the interposer 200 is released from the restraint by the support substrate 50, and thus the interposer 200 warps. For example, when the average particle size of the first filler 11 contained in the first resin layer 10 and the average particle size of the second filler 31 contained in the third resin layer 30 are approximately the same, the interposer 200 is likely to deform so as to be convex downward (toward the first wiring structure 210). If such warping occurs, the removal of the copper foil 53 may become uneven, or the distance between the electrode pads 211 of the interposer 200 and the electrode pads 124 of the build-up substrate 100 may become uneven, which may result in poor bonding.

[0043] In contrast, in the first embodiment, the average particle size of the first filler 11 is larger than the average particle size of the second filler 31. This can reduce the stress inside the interposer 200. Therefore, even after the interposer 200 is peeled off from the peeling layer 52, the interposer 200 is less likely to warp, and poor bonding between the interposer 200 and the build-up substrate 100 can be suppressed.

[0044] The average particle size of the first filler 11 is preferably 0.05 μm to 1.00 μm, and more preferably 0.10 μm to 0.80 μm. The average particle size of the second filler 31 is preferably 0.01 μm to 0.50 μm, and more preferably 0.05 μm to 0.30 μm.

[0045] The average particle size of the first filler 11 is preferably 3 to 100 times, and more preferably 3 to 40 times, the average particle size of the second filler 31.

[0046] The maximum particle size of the first filler 11 is preferably 0.05 μm to 5.00 μm, and more preferably 0.50 μm to 5.00 μm. The maximum particle size of the second filler 31 is preferably 0.10 μm to 1.00 μm, and more preferably 0.30 μm to 1.00 μm.

[0047] The particle diameters of the first filler 11 and the second filler 31 can be measured by observing a cross section perpendicular to the upper surface 212A of the insulating resin layer 212 using a scanning electron microscope (SEM). For example, the cross section is observed at a magnification of 30,000 times.

[0048] Furthermore, in a cross section perpendicular to the upper surface 212A of the insulating resin layer 212, the proportion of the first filler 11 in the first resin layer 10 may be lower than the proportion of the second filler 31 in the third resin layer 30. In the above cross section, the proportion of the first filler in the first resin layer 10 is preferably 40% to 70%, and more preferably 50% to 60%. In the above cross section, the proportion of the second filler 31 in the third resin layer 30 is preferably 50% to 80%, and more preferably 60% to 70%.

[0049] In addition, in a cross section perpendicular to the upper surface 212A of the insulating resin layer 212, the number density of the first filler 11 in the first resin layer 10 may be lower than the number density of the second filler 31 in the third resin layer 30. In the above cross section, the number density of the first filler 11 in the first resin layer 10 is preferably 2 particles / μm 2 ~10 pieces / μm 2 More preferably, 5 particles / μm 2 ~6 pieces / μm 2 In addition, in the above cross section, the number density of the second filler 31 in the third resin layer 30 is preferably 20 particles / μm 2 ~40 pieces / μm 2 and more preferably 26 particles / μm 2 ~29 pieces / μm 2 It is.

[0050] Here, a simulation performed by the inventor of the present application will be described. In this simulation, the amount of warping of the interposer after the support substrate was peeled off was calculated for four types of conditions (Condition No. 1, Condition No. 2, Condition No. 3, Condition No. 4) in which the sizes of the fillers contained in the first resin layer and the second resin layer were different. Table 1 shows the relationship between each condition and the filler. In Table 1, Filler A is a filler with a maximum particle size of 1 μm and an average particle size of 0.1 μm, and Filler B is a filler with a maximum particle size of 5 μm and an average particle size of 0.5 μm. The amount of warping is the amount of displacement of the corners of the planar shape of the interposer with the center as the reference when the length of one side is 300 mm. The results of the simulation are shown in FIG. 8.

[0051] [Table 1]

[0052] As shown in FIG. 8, under condition No. 2, in which the average particle size of the filler contained in the first resin layer is larger than the average particle size of the filler contained in the third resin layer, the amount of warping was significantly lower than under conditions No. 1, No. 3, and No. 4.

[0053] Second embodiment Next, a second embodiment will be described. The second embodiment relates to a semiconductor device. Fig. 9 is a cross-sectional view showing the semiconductor device according to the second embodiment.

[0054] In the semiconductor device 2 according to the second embodiment, a semiconductor chip 60 is mounted on the interposer 200 of the wiring board 1 according to the first embodiment. That is, a connection terminal (not shown) provided on the semiconductor chip 60 is connected to an electrode pad 224 via a bonding material (not shown) such as solder.

[0055] Although the preferred embodiments have been described in detail above, the present invention is not limited to the above-described embodiments, and various modifications and substitutions can be made to the above-described embodiments without departing from the scope of the claims. [Explanation of symbols]

[0056] 1. Wiring board 2. Semiconductor Devices 10 1st resin layer 11 First Filler 20 Second resin layer 21 Glass fiber 30 Third resin layer 31 Second Filler 60 Semiconductor Chips 100 Build-up board 200 Interposer 210 1st wiring structure 211 Electrode Pads 212 Insulating resin layer 213 Conductive Via 220 2nd wiring structure

Claims

1. an insulating resin layer having a first surface and a second surface opposite to the first surface; a rewiring layer provided on the first surface of the insulating resin layer; a first connection terminal exposed from the second surface of the insulating resin layer; a conductive via provided in the insulating resin layer and electrically connecting the redistribution layer and the first connection terminal; having The insulating resin layer is a first resin layer that constitutes the second surface and contains a first filler; A second resin layer provided on the first surface side of the first resin layer; a third resin layer provided on the first surface side of the second resin layer, containing a second filler, and constituting the first surface; having The average particle size of the first filler is larger than the average particle size of the second filler, In a cross section perpendicular to the first surface of the insulating resin layer, The ratio of the first filler in the first resin layer is 40% to 70%; A wiring board, characterized in that the proportion of the second filler in the third resin layer is 50% to 80%.

2. In a cross section perpendicular to the first surface of the insulating resin layer, The number density of the first filler in the first resin layer is 2 particles / μm ２ ~10 pieces / μm ２ and The density of the second filler in the third resin layer is 20 particles / μm ２ ~40 pieces / μm ２ 2. The wiring board according to claim 1,

3. An insulating resin layer having a first surface and a second surface opposite the first surface; a rewiring layer provided on the first surface of the insulating resin layer; a first connection terminal exposed from the second surface of the insulating resin layer; a conductive via provided in the insulating resin layer and electrically connecting the redistribution layer and the first connection terminal; having The insulating resin layer is a first resin layer that constitutes the second surface and contains a first filler; A second resin layer provided on the first surface side of the first resin layer; a third resin layer provided on the first surface side of the second resin layer, containing a second filler, and constituting the first surface; having The average particle size of the first filler is larger than the average particle size of the second filler, In a cross section perpendicular to the first surface of the insulating resin layer, the number density of the first filler in the first resin layer is 2 particles / μm 2 to 10 particles / μm 2 ; A wiring board, characterized in that the density of the second filler particles in the third resin layer is 20 particles / μm 2 to 40 particles / μm 2 .

4. 4. The wiring board according to claim 1, wherein the second resin layer contains glass fiber.

5. An insulating resin layer having a first surface and a second surface opposite the first surface; a rewiring layer provided on the first surface of the insulating resin layer; a first connection terminal exposed from the second surface of the insulating resin layer; a conductive via provided in the insulating resin layer and electrically connecting the redistribution layer and the first connection terminal; having The insulating resin layer is a first resin layer that constitutes the second surface and contains a first filler; A second resin layer provided on the first surface side of the first resin layer; a third resin layer provided on the first surface side of the second resin layer, containing a second filler, and constituting the first surface; having The average particle size of the first filler is larger than the average particle size of the second filler, The wiring board according to claim 1, wherein the second resin layer contains glass fiber.

6. The first filler has an average particle size of 0.05 μm to 1.00 μm; 6. The wiring board according to claim 1, wherein the second filler has an average particle size of 0.01 μm to 0.50 μm.

7. 7. The wiring board according to claim 1, wherein the average particle size of the first filler is 3 to 100 times the average particle size of the second filler.

8. 8. The wiring board according to claim 1, wherein the third resin layer is thinner than the first resin layer and the second resin layer.

9. 9. The wiring board according to claim 1, further comprising a build-up substrate having a second connection terminal to which the first connection terminal is joined.

10. forming a connection terminal on a support substrate; forming an insulating resin layer on the support substrate to cover the connection terminals and to have a second surface facing the support substrate and a first surface opposite to the second surface; forming a conductive via connected to the connection terminal in the insulating resin layer; forming a rewiring layer on the first surface of the insulating resin layer; having The step of forming the insulating resin layer includes: forming a first resin layer that constitutes the second surface and contains a first filler; forming a second resin layer on the first surface side of the first resin layer; forming a third resin layer on the first surface side of the second resin layer, the third resin layer containing a second filler and constituting the first surface; having The average particle size of the first filler is larger than the average particle size of the second filler, In a cross section perpendicular to the first surface of the insulating resin layer, The ratio of the first filler in the first resin layer is 40% to 70%; A method for manufacturing a wiring board, wherein the proportion of the second filler in the third resin layer is 50% to 80%.

11. A step of forming a connection terminal on a support substrate; forming an insulating resin layer on the support substrate to cover the connection terminals and to have a second surface facing the support substrate and a first surface opposite to the second surface; forming a conductive via connected to the connection terminal in the insulating resin layer; forming a rewiring layer on the first surface of the insulating resin layer; having The step of forming the insulating resin layer includes: forming a first resin layer that constitutes the second surface and contains a first filler; forming a second resin layer on the first surface side of the first resin layer; forming a third resin layer on the first surface side of the second resin layer, the third resin layer containing a second filler and constituting the first surface; having The average particle size of the first filler is larger than the average particle size of the second filler, In a cross section perpendicular to the first surface of the insulating resin layer, the number density of the first filler in the first resin layer is 2 particles / μm 2 to 10 particles / μm 2 ; A method for manufacturing a wiring board, wherein the density of the second filler particles in the third resin layer is 20 particles / μm 2 to 40 particles / μm 2 .

12. A step of forming a connection terminal on a support substrate; forming an insulating resin layer on the support substrate to cover the connection terminals and to have a second surface facing the support substrate and a first surface opposite to the second surface; forming a conductive via connected to the connection terminal in the insulating resin layer; forming a rewiring layer on the first surface of the insulating resin layer; having The step of forming the insulating resin layer includes: forming a first resin layer that constitutes the second surface and contains a first filler; forming a second resin layer on the first surface side of the first resin layer; forming a third resin layer on the first surface side of the second resin layer, the third resin layer containing a second filler and constituting the first surface; having The average particle size of the first filler is larger than the average particle size of the second filler, The method for manufacturing a wiring board, wherein the second resin layer contains glass fiber.

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