Wiring board, electronic module, and method for manufacturing a wiring board

Abstract

In the present invention, a first insulating film is provided with a through hole which penetrates the first insulating film in the thickness direction. A first conductor pattern is disposed on a first surface, which is one of the surfaces of the first insulating film. The first conductor pattern closes an opening on the first surface-side of the through hole. A first connection conductor is disposed in the through hole. The first connection conductor is connected to the first conductor pattern, and the thickness-direction dimension of the first connection conductor is smaller than the thickness direction dimension of the first insulating film. The metal element for which the content thereof in the first conductor pattern is greatest and the metal element for which the content thereof in the first connection conductor is the greatest are the same.

Description

Technical Field

[0001] The present invention relates to a wiring board, an electronic module, and a method for manufacturing a wiring board.

Background Art

[0002] Various wiring boards for mounting electronic components are known (Patent Documents 1, 2, and 3). The wiring boards disclosed in Patent Documents 1 and 2 include an inner layer conductor pattern on a substrate and a coating layer (insulator layer) covering the inner layer conductor pattern. An opening is provided in the coating layer, and a part of the surface of the inner layer conductor pattern is exposed on the bottom surface of the opening. The surface of the inner layer conductor pattern exposed within the opening is covered with a surface treatment portion (surface layer). The portion of the inner layer conductor pattern exposed within the opening is used as a terminal for mounting an electronic component. The surface treatment portion functions as a connection conductor for connecting a solder bump or the like of an electronic component to the inner layer conductor pattern.

[0003] A copper foil is used for the inner layer conductor pattern disclosed in Patent Document 1, and solder, an alloy, gold, silver, nickel, etc. are used for the surface treatment portion. A metal having copper as a main component is used for the inner layer conductor pattern disclosed in Patent Document 2, and Ni-Au plating and Sn (solder) plating are used for the surface layer. The surface layer protects the underlying inner layer conductor pattern.

[0004] In the wiring board disclosed in Patent Document 3, a connection conductor is filled in a through hole directed toward a first resin layer. The connection conductor is connected to an inner layer conductor pattern in the lower layer. A second resin layer is disposed on the first resin layer, and an opening for exposing the connection conductor is provided in the second resin layer. The connection conductor exposed within the opening is used as a terminal for mounting an electronic component. A melting point change type bonding material is used for the connection conductor.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

[0006] In the wiring boards disclosed in Patent Documents 1, 2, and 3, stress tends to concentrate at the interface between the conductor pattern of the inner layer and the connecting conductor due to shape discontinuities. Furthermore, the conductor pattern of the inner layer and the connecting conductor are formed from different materials. Therefore, cracks due to stress concentration are likely to occur at the interface between the conductor pattern of the inner layer and the connecting conductor. An object of the present invention is to provide a wiring board that is less prone to crack formation at the interface between the conductor pattern and the connecting conductor. Another object of the present invention is to provide an electronic module using this wiring board. Yet another object of the present invention is to provide a method for manufacturing this wiring board. [Means for solving the problem]

[0007] According to one aspect of the present invention, A first insulating film having through holes that penetrate in the thickness direction, A first conductor pattern is arranged on the first surface, which is one of the surfaces of the first insulating film, and closes the opening of the through hole on the first surface side, A first connecting conductor is disposed within the through-hole and connected to the first conductor pattern, and its dimension in the thickness direction is smaller than the dimension in the thickness direction of the first insulating film. Equipped with, A wiring board is provided in which the metal element with the highest content in the first conductor pattern and the metal element with the highest content in the first connecting conductor are the same.

[0008] According to another aspect of the present invention, The aforementioned wiring board, Electronic components mounted on the aforementioned wiring board via solder bumps and Equipped with, The solder bump provides an electronic module connected to the connecting conductor.

[0009] According to yet another aspect of the present invention, A first insulating film is prepared, on which a first conductive pattern is formed on one of its surfaces, the first surface. A through-hole is formed in the first insulating film, extending from the surface opposite to the first surface to the first conductor pattern. A method for manufacturing a wiring board in which a first connecting conductor is formed in the through-hole by a plating method, using the first conductor pattern as a seed, The metal element with the highest content in the first conductor pattern and the metal element with the highest content in the first connecting conductor are the same. A method for manufacturing a wiring board is provided in which the thickness dimension of the first connecting conductor is smaller than the thickness dimension of the first insulating film on the first conductor pattern. [Effects of the Invention]

[0010] Since the metal element with the highest content in the conductor pattern and the metal element with the highest content in the connecting conductor are the same, the discontinuity of the materials at the interface between them is mitigated. This suppresses the occurrence of cracks and delamination caused by stress concentration at the interface between the conductor pattern and the connecting conductor. [Brief explanation of the drawing]

[0011] [Figure 1] Figure 1 is a cross-sectional view of a wiring board according to the first embodiment. [Figure 2] Figures 2A and 2B are cross-sectional views of the wiring board during the manufacturing process according to the first embodiment. [Figure 3] Figure 3 is a cross-sectional view of the wiring board according to the second embodiment. [Figure 4] Figure 4 is a cross-sectional view of a wiring board illustrating the superior effects of the second embodiment. [Figure 5] Figure 5 is a cross-sectional view of an electronic module according to the third embodiment. [Figure 6]FIG. 6 is a cross-sectional view of a wiring board according to the fourth embodiment. [Figure 7] FIG. 7 is a cross-sectional view of a wiring board according to a modified example of the fourth embodiment. [Figure 8] FIG. 8 is a cross-sectional view of a wiring board according to another modified example of the fourth embodiment. [Figure 9] FIG. 9 is a cross-sectional view of a wiring board according to still another modified example of the fourth embodiment. [Figure 10] FIG. 10 is a cross-sectional view of a wiring board according to the fifth embodiment. [Figure 11] FIG. 11 is a cross-sectional view of a wiring board according to a modified example of the fifth embodiment.

BEST MODE FOR CARRYING OUT THE INVENTION

[0012] [First Embodiment] The wiring board according to the first embodiment will be described with reference to the drawings from FIG. 1 to FIG. 2B. FIG. 1 is a cross-sectional view of a wiring board 50 according to the first embodiment. The wiring board 50 according to the first embodiment includes a first insulating film 21 in which through holes 21A are formed, a first conductor pattern 20, a first connection conductor 22 disposed in the through holes 21A, and a surface treatment layer 23 disposed on the surface of the first connection conductor 22. Although a plurality of through holes 21A are provided, for example, FIG. 1 shows one through hole 21A.

[0013] The first conductor pattern 20 is disposed on the first surface 21B which is one surface of the first insulating film 21. The first conductor pattern 20 closes the opening on the first surface 21B side of the through hole 21A. Hereinafter, the surface facing the opposite direction to the first surface 21B of various components is referred to as the upper surface. Also, the direction perpendicular to the first surface 21B may be referred to as the thickness direction.

[0014] The side surface of the through-hole 21A is inclined such that the area of ​​the planar cross-section (cross-section parallel to the first surface 21B) of the through-hole 21A increases as it moves away from the first conductor pattern 20 upwards. In other words, the through-hole 21A has an inverse tapered shape that narrows downwards. When the first insulating film 21 is viewed from above (hereinafter sometimes simply referred to as "in a planar view"), the through-hole 21A is contained within the first conductor pattern 20.

[0015] The first connecting conductor 22, positioned within the through-hole 21A, is in contact with the first conductor pattern 20. The first connecting conductor 22 and the first conductor pattern 20 are made of the same metal, for example, copper.

[0016] The surface treatment layer 23 formed on the upper surface of the first connecting conductor 22 contains at least one material selected from the group consisting of Ni, Au, solder, and flux. When the first surface 21B is used as the height reference, the height h2 to the upper surface of the first connecting conductor 22 and the height h3 to the upper surface of the surface treatment layer 23 are lower than the height h1 to the upper surface of the first insulating film 21. As a result, a depression 51 appears on the upper surface of the wiring board 50. The bottom surface of this depression 51 is exposed, with the surface treatment layer 23 visible.

[0017] Next, the manufacturing method of the wiring board 50 according to the first embodiment will be described with reference to Figures 2A and 2B. Figures 2A and 2B are cross-sectional views of the wiring board 50 during the manufacturing process according to the second embodiment.

[0018] As shown in Figure 2A, a laminated structure having a first insulating film 21 and a first conductive pattern 20 is formed by patterning the conductive foil of a resin sheet with conductive foil. For example, copper foil is used as the conductive foil, and a sheet mainly made of thermoplastic polyimide (PI) is used as the resin sheet. Polyether ether ketone (PEEK), polyetherimide (PEI), polyphenylene sulfide (PPS), liquid crystal polymer (LCP), etc. may be used as the material for the resin sheet.

[0019] As shown in Figure 2B, a through-hole 21A is formed in the first insulating film 21 from the side opposite to the side on which the first conductor pattern 20 is located, reaching the first conductor pattern 20. For example, a laser processing method using a carbon dioxide laser can be applied to form the through-hole 21A. This laser processing is performed under conditions that cause almost no damage to the first conductor pattern 20.

[0020] After forming the through-hole 21A, as shown in Figure 1, the first connecting conductor 22 is formed by using the first conductor pattern 20 as a seed and applying copper plating to the first conductor pattern 20 exposed in the through-hole 21A. Electroless plating or electrolytic plating is used for this plating. Subsequently, the resin sheet constituting the first insulating film 21 is hardened by applying pressure and heating.

[0021] The wiring board 50 according to the first embodiment is used, for example, as the top layer of a mounting board for mounting electronic components equipped with solder bumps. The electronic components are mounted on the wiring board 50 by connecting the solder bumps of the electronic components to the first connecting conductor 22 via the surface treatment layer 23. The surface treatment layer 23 has the function of protecting the surface of the first connecting conductor 22 and improving the mountability when mounting electronic components.

[0022] Next, we will describe the excellent effects of the first embodiment. Because the interface between the first connecting conductor 22 and the first conductor pattern 20 is geometrically discontinuous, stress tends to concentrate at the interface between the first connecting conductor 22 and the first conductor pattern 20 due to the difference in thermal expansion coefficients between the wiring board 50 and the electronic components. For example, if copper is used for the first conductor pattern 20 and solder is used for the first connecting conductor 22, a material discontinuity will also occur at the interface between the two. When stress concentrates at an interface where a material discontinuity occurs, cracks and delamination are more likely to occur.

[0023] In the first embodiment, since both the first conductor pattern 20 and the first connecting conductor 22 are made of copper, no material discontinuity occurs at their interface. As a result, the mechanical strength of the interface between the first conductor pattern 20 and the first connecting conductor 22 is increased. Consequently, cracks, delamination, and other defects are less likely to occur at their interface.

[0024] If solder paste is used on the first connecting conductor 22, a phenomenon occurs in which the metal constituting the first conductor pattern 20 melts into the solder (sometimes called "solder erosion"). In the first embodiment, since the first connecting conductor 22 and the first conductor pattern 20 are formed from the same metal, solder erosion does not occur.

[0025] Furthermore, in the first embodiment, a depression 51 is generated in the area where the first connecting conductor 22 is placed. After forming the through hole 21A, the first connecting conductor 22 is filled into a portion of the lower side of the through hole 21A, so that the center positions of the through hole 21A and the first connecting conductor 22 in a plan view are almost coincident. When mounting electronic components on the wiring board 50, the solder bumps of the electronic components are positioned in the depression 51 that has been generated at the location of the through hole 21A. As a result, the first connecting conductor 22 and the solder bumps of the electronic components can be positioned with high precision.

[0026] To suppress the occurrence of cracks and delamination at the interface between the first conductor pattern 20 and the first connecting conductor 22, it is preferable that the height h2 of the first connecting conductor 22 be greater than or equal to the thickness of the first conductor pattern 20. Furthermore, to facilitate positioning during electronic component mounting, it is preferable that the height h2 of the first connecting conductor 22 be 90% or less of the height h1 of the first insulating film 21. It is preferable that the combined height h2 of the first connecting conductor 22 and the surface treatment layer 23 be less than the height h1 of the first insulating film 21.

[0027] Next, a wiring board according to a modified example of the first embodiment will be described. In the first embodiment, copper is used for the first conductor pattern 20 and the first connecting conductor 22, but other identical metals may be used for the first conductor pattern 20 and the first connecting conductor 22. For example, silver, gold, etc. may be used.

[0028] In addition, alloys mainly composed of copper, silver, or gold may be used for the first conductor pattern 20 and the first connecting conductor 22. When alloys are used for the first conductor pattern 20 and the first connecting conductor 22, it is preferable that the constituent elements of the alloy are the same, and it is even more preferable that the ratio of the content of the constituent elements is the same.

[0029] Furthermore, even if not all of the constituent elements of the alloy are identical, if the main constituent elements are the same, the discontinuity of the material can be mitigated and sufficient mechanical strength can be ensured. To ensure sufficient mechanical strength, it is preferable that the metal element with the highest content in the first conductor pattern 20 and the metal element with the highest content in the first connecting conductor 22 are the same.

[0030] In the first embodiment, a plating method is used to form the first connecting conductor 22, but the first connecting conductor 22 may be formed by other methods. For example, a conductive paste may be placed in the through hole 21A, and then the conductive paste may be cured to form the first connecting conductor 22. When this method is used, binder resin remains on the first connecting conductor 22. In this case, it is preferable to use the same metal for the conductive particles contained in the first connecting conductor 22 and the first conductor pattern 20.

[0031] Furthermore, by employing the plating method, the first connecting conductor 22 can be filled into the lower part of the through-hole 21A with good reproducibility, even if the size of the through-hole 21A in plan view is reduced, compared to the case where conductive paste is used. Whether to employ the plating method or the conductive paste method should be decided based on the size of the through-hole 21A, etc. Also, by employing the plating method, a metallic first connecting conductor 22 can be formed without binder resin, etc. When the wiring board 50 is used as the uppermost layer of the mounting board, the thickness of the first insulating film 21 is at most about 40 μm, so even if the plating method is adopted, it will not be a major cost increase compared to the method using conductive paste. [Second Example] Next, the wiring board according to the second embodiment will be described with reference to Figures 3 and 4. Hereinafter, the configuration common to the wiring board 50 according to the first embodiment, as described with reference to Figures 1, 2A, and 2B, will be omitted from the explanation.

[0032] Figure 3 is a cross-sectional view of a wiring board 50 according to the second embodiment. The wiring board 50 according to the second embodiment includes a base substrate 10, a first conductor pattern 20, a first insulating film 21, a first connecting conductor 22, and a surface treatment layer 23. The configuration of the first conductor pattern 20, the first insulating film 21, the first connecting conductor 22, and the surface treatment layer 23 is the same as that of the wiring board 50 according to the first embodiment (Figure 1). The first insulating film 21 is positioned on the upper surface of the base substrate 10 with its first surface 21B facing the base substrate 10. The first conductor pattern 20 is positioned between the base substrate 10 and the first insulating film 21. The wiring board 50 according to the second embodiment can be used, for example, as a mounting substrate for mounting electronic components equipped with solder bumps, etc.

[0033] Next, a method for manufacturing the wiring board 50 according to the second embodiment will be described. The first insulating film 21, before heat treatment, has its first surface 21B, on which the first conductor pattern 20 and the first connecting conductor 22 are provided, facing the upper surface of the base substrate 10, such as a resin sheet, and the first insulating film 21 is bonded to the base substrate 10. With the first insulating film 21 bonded to the base substrate 10, the laminate including the base substrate 10, the first conductor pattern 20, and the first insulating film 21 is heated and pressurized to form an integral laminate. The surface treatment layer 23 may be formed after this heat treatment.

[0034] Next, we will describe the excellent effects of the second embodiment. In the second embodiment, as in the first embodiment, the mechanical strength of the interface between the first conductor pattern 20 and the first connecting conductor 22 is increased, making it less likely for cracks or delamination to occur at the interface between the two. When mounting electronic components on the wiring board 50, the solder bumps of the electronic components are positioned in the recesses 51 that occur at the location of the through holes 21A. As a result, the first connecting conductor 22 and the solder bumps of the electronic components can be positioned with high precision.

[0035] Next, with reference to Figure 4, other excellent effects of the second embodiment will be described. Figure 4 is a cross-sectional view of the wiring board 50 to illustrate another excellent effect of the second embodiment. When mounting electronic components on the wiring board 50, solder paste 30 may be filled into recesses 51 formed on the surface of the wiring board 50. In the second embodiment, the sides of the through holes 21A are inclined such that the area of ​​the flat cross-section of the through holes 21A increases as you move away from the first conductor pattern 20 upwards. As a result, an excellent effect is obtained in that air voids are less likely to occur when filling the recesses 51 with solder paste 30.

[0036] [Third Embodiment] Next, an electronic module according to the third embodiment will be described with reference to Figure 5. The electronic module according to the third embodiment includes a wiring board 50 (Figure 3) according to the second embodiment, and electronic components mounted on this wiring board 50.

[0037] Figure 5 is a cross-sectional view of an electronic module according to a third embodiment. A plurality of first connecting conductors 22 and a surface treatment layer 23 are provided on the wiring board 50. Each of the plurality of terminals 41 of the electronic component 40 is connected to the first conductor pattern 20 via solder bumps 45, the surface treatment layer 23, and the first connecting conductor 22. A portion of each of the plurality of solder bumps 45 on the wiring board 50 side is embedded in a recess 51 formed on the surface of the wiring board 50.

[0038] Next, the excellent effects of the third embodiment will be described. In the third embodiment, as in the second embodiment, the excellent effect of making it difficult for cracks and delamination to occur at the interface between the first conductor pattern 20 and the first connecting conductor 22 is obtained. Furthermore, since multiple solder bumps 45 each fit into the recesses 51, the excellent effect of increased shear strength is obtained.

[0039] [Fourth embodiment] Next, the wiring board according to the fourth embodiment will be described with reference to Figure 6. The following description will omit details of components common to the wiring board 50 according to the second embodiment, which was described with reference to Figure 3.

[0040] Figure 6 is a cross-sectional view of a wiring board 50 according to the fourth embodiment. In the second embodiment (Figure 3), the detailed configuration of the base substrate 10 is not particularly limited. In the fourth embodiment, the base substrate 10 includes a second insulating film 11, a second conductor pattern 12, and a second connecting conductor 13. The second conductor pattern 12 is located on the lower surface of the second insulating film 11. Via holes penetrating in the thickness direction are provided in the second insulating film 11. The second connecting conductor 13 is filled into these via holes. The second connecting conductor 13 connects the first conductor pattern 20 and the second conductor pattern 12. The second connecting conductor 13 is made of the same conductive material as the second conductor pattern 12, for example, copper. The second insulating film 11 and the first insulating film 21 may be made of the same insulating material or of different insulating materials.

[0041] Next, a method for manufacturing the wiring board 50 according to the fourth embodiment will be described. First, the base substrate 10 is manufactured in the same manner as the manufacturing method for the wiring board 50 according to the first embodiment, as described with reference to Figures 2A and 2B. In the step of filling the second connecting conductor 13, plating is performed until its surface is almost flush with the surface of the second insulating film 11. At this stage, no heat treatment has been performed yet.

[0042] The first insulating film 21, on which the first conductor pattern 20 and the first connecting conductor 22 are provided, is bonded to the base substrate 10 before heat treatment, and then heated and pressed to form an integral laminate. The surface treatment layer 23 may be formed after the heat treatment.

[0043] Next, we will describe the excellent effects of the fourth embodiment. In the fourth embodiment, as in the second embodiment, the occurrence of cracks and delamination at the interface between the first conductor pattern 20 and the first connecting conductor 22 can be suppressed. Furthermore, the occurrence of cracks and delamination at the interface between the second conductor pattern 12 and the second connecting conductor 13 can also be suppressed.

[0044] Next, a modified version of the fourth embodiment will be described. In the fourth embodiment, copper is used for the second conductor pattern 12 and the second connecting conductor 13, but other identical metals may be used for the second conductor pattern 12 and the second connecting conductor 13. For example, silver, gold, etc. may be used.

[0045] In addition, alloys mainly composed of copper, silver, or gold may be used for the second conductor pattern 12 and the second connecting conductor 13. When alloys are used for the second conductor pattern 12 and the second connecting conductor 13, it is preferable that the constituent elements of the alloy are the same, and it is even more preferable that the ratio of the content of the constituent elements is the same.

[0046] Furthermore, even if not all of the constituent elements of the alloy are identical, if the main constituent elements are the same, the discontinuity of the material can be mitigated and sufficient mechanical strength can be ensured. To ensure sufficient mechanical strength, it is preferable that the metal element with the highest content in the second conductor pattern 12 and the metal element with the highest content in the second connecting conductor 13 are the same.

[0047] Next, a wiring board according to a modified example of the fourth embodiment will be described with reference to Figure 7. Figure 7 is a cross-sectional view of a wiring board 50 according to a modified example of the fourth embodiment. In the fourth embodiment (Figure 6), the base substrate 10 has a single-layer wiring structure, but in the modified example shown in Figure 7, the base substrate 10 has a multilayer wiring structure. Each layer of the multilayer wiring structure includes a second insulating film 11, a second conductor pattern 12, and a second connecting conductor 13. As in this modified example, the base substrate 10 may have a multilayer wiring structure.

[0048] Next, a wiring board according to another modification of the fourth embodiment will be described with reference to Figure 8. Figure 8 is a cross-sectional view of the wiring board 50 according to this modified example. In the modified example shown in Figure 7, the second connecting conductor 13 is formed by plating using the same conductive material as the second conductor pattern 12. In contrast, in the modified example shown in Figure 8, the second connecting conductor 13 is formed by hardening a conductive paste. Copper paste, silver paste, gold paste, solder paste, etc., can be used as the conductive paste.

[0049] As shown in this modified example, using a conductive paste for the second connecting conductor 13 improves the electrical connectivity at the interface between the second connecting conductor 13 and the second conductor pattern 12, which is bonded thereon by pressure and heat, compared to the case where it is formed by a plating method as in the fourth embodiment.

[0050] Next, with reference to Figure 9, a wiring board according to yet another modification of the fourth embodiment will be described. Figure 9 is a cross-sectional view of the wiring board 50 according to this modified example. In this modified example, the second connecting conductor 13 is composed of a first portion 13A on the side farther from the first insulating film 21 (lower side) and a second portion 13B on the side closer to the first insulating film 21 (upper side). The first portion 13A is formed of the same conductive material as the second conductor pattern 12, similar to the modified example of the fourth embodiment shown in Figure 7, and the second portion 13B is formed of a conductive material obtained by curing a conductive paste, similar to the modified example shown in Figure 8.

[0051] In this modified example, the electrical connectivity between the lower first portion 13A of the second connecting conductor 13 and the second conductor pattern 12, and the electrical connectivity between the upper second portion 13B of the second connecting conductor 13 and the second conductor pattern 12 can be improved. Compared to the modified example shown in Figure 8, less conductive paste is used, thus reducing the amount of gas generated during the curing of the conductive paste. Furthermore, compared to the modified example shown in Figure 8, the depth of the depressions to be filled with conductive paste is shallower, making it possible to reduce the diameter and pitch of the second connecting conductor 13.

[0052] [Fifth Example] Next, the wiring board according to the fifth embodiment will be described with reference to Figure 10. The following description will omit details of components common to the wiring board 50 according to the second embodiment, which was described with reference to Figure 3.

[0053] Figure 10 is a cross-sectional view of the wiring board 50 according to the fifth embodiment. In the second embodiment (Figure 3), the upper surface of the first connecting conductor 22 is substantially flat. In contrast, in the fifth embodiment, the upper surface of the first connecting conductor 22 has a concave shape that curves downward. That is, the center of the upper surface is lower than the outer periphery. When the upper surface of the first conductor pattern 20 is used as the height reference, the height h2 to the highest point on the upper surface of the first connecting conductor 22 is lower than the height h1 to the upper surface of the first insulating film 21. This shape of the upper surface of the first connecting conductor 22 can be obtained by adjusting the plating conditions. The surface treatment layer 23 covers the curved upper surface of the first connecting conductor 22 with a substantially uniform thickness.

[0054] Next, we will describe the excellent effects of the fifth embodiment. In the fifth embodiment, as in the second embodiment (Figure 1), the excellent effect of making it difficult for cracks and delamination to occur at the interface between the first conductor pattern 20 and the first connecting conductor 22 is obtained. Furthermore, in the fifth embodiment, when mounting electronic components with solder balls onto the wiring board 50, the solder balls provided on the electronic components are positioned at the lowest position on the upper surface of the first connecting conductor 22, resulting in a stable position of the electronic components and an excellent effect of improving positional accuracy during mounting.

[0055] Next, a wiring board according to a modified example of the fifth embodiment will be described with reference to Figure 11. Figure 11 is a cross-sectional view of a wiring board 50 according to a modified example of the fifth embodiment. In the fifth embodiment (Figure 10), the upper surface of the first connecting conductor 22 is curved downwards, but in the modified example shown in Figure 11, the upper surface of the first connecting conductor 22 has a convex shape that is curved upwards. That is, when the upper surface of the first conductor pattern 20 is used as the height reference, the height of the central part of the first connecting conductor 22 is higher than the height of the outer periphery. When the upper surface of the first conductor pattern 20 is used as the height reference, the height h2 to the highest point on the upper surface of the first connecting conductor 22 is lower than the height h1 to the upper surface of the first insulating film 21. Such a shape can be achieved by adjusting the plating conditions or surface treatment.

[0056] In this modified configuration, when mounting an electronic component with solder balls onto the wiring board 50, the solder balls on the electronic component make point contact with the highest point of the first connecting conductor 22 or the surface treatment layer 23. This results in the excellent effect of improved connectivity between the solder balls and the first connecting conductor 22.

[0057] The embodiments described above are illustrative, and it goes without saying that partial substitution or combination of the configurations shown in different embodiments is possible. Similar effects and benefits from similar configurations in multiple embodiments will not be mentioned sequentially for each embodiment. Furthermore, the present invention is not limited to the embodiments described above. For example, it will be obvious to those skilled in the art that various modifications, improvements, and combinations are possible. [Explanation of symbols]

[0058] 10 Substrate 11. Second insulating film 12. Second conductor pattern 13. Second connecting conductor 13A First part of the second connecting conductor 13B Second part of the second connecting conductor 20 First Conductor Pattern 21 First insulating film 21A through hole 21B 1st page 22 First connecting conductor 23 Surface treatment layer 30 Solder paste 40 Electronic Components 41 terminals 45 Solder Bump 50 Wiring boards 51 Indentation

Claims

1. A first insulating film having through holes that penetrate in the thickness direction, A first conductor pattern is arranged on the first surface, which is one of the surfaces of the first insulating film, and closes the opening of the through hole on the first surface side, A first connecting conductor is disposed within the through hole and connected to the first conductor pattern, and its dimension in the thickness direction is smaller than the dimension in the thickness direction of the first insulating film. Equipped with, A wiring board in which the metal element with the highest content in the first conductor pattern and the metal element with the highest content in the first connecting conductor are the same.

2. Furthermore, it is equipped with a base substrate, The wiring board according to claim 1, wherein the first insulating film is disposed on the base substrate with its first surface facing the base substrate, and the first conductor pattern is disposed between the first insulating film and the base substrate.

3. The base substrate includes a plurality of second conductor patterns, a plurality of second insulating films, and a plurality of second connecting conductors. The wiring substrate according to claim 2, wherein the first insulating film is disposed on the surface of the uppermost of the plurality of second insulating films.

4. The wiring board according to claim 3, wherein the metal element with the highest content in each of the plurality of second conductor patterns and the metal element with the highest content in each of the plurality of second connecting conductors are the same.

5. The wiring board according to claim 3, wherein each of the plurality of second connecting conductors is formed of a conductive material formed from a hardened conductive paste, and each of the plurality of second conductor patterns is formed of a conductive material different from the plurality of second connecting conductors.

6. Each of the plurality of second connecting conductors includes a first portion that contacts the plurality of second conductor patterns and a second portion that contacts the second conductor pattern closer to the first insulating film, wherein the metal element with the highest content in the first portion is the same as the metal element with the highest content in the second conductor pattern that the first portion contacts, and the second portion is formed of a conductive material formed from a hardened conductive paste, as described in claim 3.

7. The wiring board according to any one of claims 1 to 6, wherein the upper surface of the first connecting conductor has a concave shape, with the center being lower than the outer periphery.

8. The wiring board according to any one of claims 1 to 6, wherein the upper surface of the first connecting conductor has a convex shape, with the center being higher than the outer periphery.

9. The wiring board according to any one of claims 1 to 6, wherein the through-hole has a shape that widens in a direction away from the first conductor pattern.

10. The wiring board according to any one of claims 1 to 6, wherein the first connecting conductor and the first conductor pattern are formed of copper, silver, gold, an alloy mainly composed of copper, an alloy mainly composed of silver, or an alloy mainly composed of gold.

11. The wiring board according to any one of claims 1 to 6, further comprising a surface treatment layer on the surface of the first connecting conductor, comprising at least one material selected from the group consisting of Ni, Au, solder, and flux.

12. A wiring board according to any one of claims 1 to 6, Electronic components mounted on the aforementioned wiring board via solder bumps and Equipped with, The solder bump is connected to the electronic module on the first connecting conductor.

13. A first insulating film is prepared, on which a first conductive pattern is formed on one of its surfaces, the first surface. A through hole is formed in the first insulating film, extending from the surface opposite to the first surface to the first conductor pattern. A method for manufacturing a wiring board in which a first connecting conductor is formed in the through-hole by a plating method, using the first conductor pattern as a seed, The metal element with the highest content in the first conductor pattern and the metal element with the highest content in the first connecting conductor are the same. A method for manufacturing a wiring board in which the thickness dimension of the first connecting conductor is smaller than the thickness dimension of the first insulating film on the first conductor pattern.

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