Wiring board

Abstract

To provide a wiring board with high connection reliability with an external element.SOLUTION: A wiring board 1 in an embodiment includes a first insulating layer 11, a first conductive layer 12 formed on the first insulating layer 11, a second insulating layer 13 formed on the first conductive layer 12 and the first insulating layer 11, and a first opening 131 and a second opening 132 penetrating the second insulating layer 13 in a thickness direction. At a bottom surface of the first opening 131, the first conductive layer 12 is exposed, and at a bottom surface of the second opening 132, the first conductive layer 12 is not exposed. A value of a first angle θ1 between a side wall surface and the bottom surface of the first opening 131 outside the first opening 131 is different from a value of a second angle θ2 between a side wall surface and the bottom surface of the second opening outside the second opening 132. The size of the top diameter of the second opening 132 on the side opposite to the bottom surface is larger than the size of the bottom diameter of the second opening 132 on the bottom surface side.SELECTED DRAWING: Figure 2

Description

[Technical field]

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

[0002] Patent Document 1 discloses a wiring board having an insulating layer, a connection pad formed on the insulating layer, and a solder resist formed on the insulating layer and the connection pad. The solder resist has an opening that exposes the connection pad. The wall surface of the opening formed in the solder resist has a convex portion that protrudes toward the inside of the opening in the middle part in the thickness direction of the solder resist, and has a concave portion that is recessed toward the outside of the opening in the part near the connection pad. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2005-217054 A Summary of the Invention [Problem to be solved by the invention]

[0004] In the wiring board of Patent Document 1, when an external element is inserted into an opening formed in the solder resist, it is thought that the external element may interfere with the wall surface of the opening, making the insertion difficult. [Means for solving the problem]

[0005] The wiring board of the present invention has a first insulating layer, a first conductor layer formed on the first insulating layer, a second insulating layer formed on the first conductor layer and the first insulating layer, and a first opening and a second opening penetrating the second insulating layer in a thickness direction, the first conductor layer is exposed at a bottom surface of the first opening, the first conductor layer is not exposed at a bottom surface of the second opening, a first angle formed between a sidewall surface and a bottom surface of the first opening on the outside of the first opening is different from a second angle formed between a sidewall surface and a bottom surface of the second opening on the outside of the second opening, and a top diameter dimension of the second opening opposite to the bottom surface is larger than a bottom diameter dimension of the second opening on the bottom surface side.

[0006] According to the embodiment of the present invention, a wiring board can be provided that includes a second opening whose top diameter is larger than its bottom diameter, and that allows external elements to be mounted relatively easily on the wiring board. [Brief description of the drawings]

[0007] [Figure 1] FIG. 1 is a cross-sectional view showing an example of a wiring board according to an embodiment of the present invention. [Diagram 2] FIG. 2 is a partially enlarged cross-sectional view of the wiring board of FIG. 1. [Diagram 3] 3 is a cross-sectional view showing another example of the wiring board shown in FIG. 2. [Figure 4A] 5A to 5C are cross-sectional views showing a method for manufacturing a wiring board according to an embodiment of the present invention. [Figure 4B] 5A to 5C are cross-sectional views showing a method for manufacturing a wiring board according to an embodiment of the present invention. [Figure 4C] 5A to 5C are cross-sectional views showing a method for manufacturing a wiring board according to an embodiment of the present invention. [Figure 4D] 5A to 5C are cross-sectional views showing a method for manufacturing a wiring board according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] A wiring board according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows a cross-sectional view of a wiring board 1, which is an example of a wiring board according to an embodiment, and FIG. 2 shows an enlarged view of a portion II of the wiring board 1 surrounded by a dashed line shown in FIG. 1. Note that the drawings referred to below are not intended to show the exact ratio of each component, but are drawn so that the features of the embodiment can be easily understood. The wiring board 1 shown in the drawings is merely an example of the wiring board according to the present embodiment. The laminated structure of the wiring board according to the embodiment, and the number of each of the conductor layers and the insulating layers are not limited to the laminated structure of the wiring board 1 shown in the drawings, and the number of each of the conductor layers and the insulating layers included in the wiring board 1.

[0009] As shown in FIG. 1, the wiring board 1 has a first main surface 1F and a second main surface 1S opposite to the first main surface 1F. The wiring board 1 has an insulating layer 11, a conductor layer 12 formed on the insulating layer 11 and including a conductor pad P1, and an insulating layer 13 formed on the conductor layer 12 and having openings 131 and 132 on at least one side (the first main surface 1F side in the example of FIG. 1) of the first main surface 1F and the second main surface 1S. The insulating layer 13 may be a solder resist layer. As will be described in detail later, in the wiring board of the embodiment, the openings 131 and 132 provided in the insulating layer 13, which may be a solder resist layer, have a predetermined shape. The conductor pad P1 is exposed on the bottom surface of the opening 131, and the insulating layer 11 is exposed on the bottom surface of the opening 132. In the example of FIG. 1, the wiring board 1 is a so-called multilayer wiring board. However, the wiring board of the embodiment may be a so-called double-sided wiring board.

[0010] In the example of Figure 1, the wiring board 1 includes a core substrate 100, a first wiring structure 10 formed on one main surface (first surface 100F) of the core substrate 100, and a second wiring structure 20 formed on the other main surface (second surface 100S) of the core substrate 100.

[0011] In the description of the wiring board of this embodiment, the side farther from core substrate 100 is referred to as "top", "upper side", "outer side", or "outside", and the side closer to core substrate 100 is referred to as "bottom", "lower side", "inner side", or "inside". In addition, in each component, the surface facing the side opposite core substrate 100 is also referred to as the "top surface", and the surface facing core substrate 100 is also referred to as the "bottom surface".

[0012] In the example of Fig. 1, the core substrate 100 includes an insulating layer (core insulating layer) 101 and a conductor layer (core conductor layer) 102 formed on both sides of the core insulating layer 101. The core conductor layer 102 is patterned to have a predetermined conductor pattern. The core insulating layer 101 of the core substrate 100 is formed with a through-hole conductor 103 that connects the conductor pattern of the conductor layer 102 constituting the first surface 100F of the core substrate 100 with the conductor pattern of the conductor layer 102 constituting the second surface 100S. The inside of the cylindrical through-hole conductor 103 is filled with a resin body 104 containing any resin such as an epoxy resin.

[0013] In the example of FIG. 1, the first wiring structure 10 includes insulating layers and conductor layers alternately stacked on the first surface 100F of the core substrate 100. Specifically, the first wiring structure 10 has a multilayer wiring structure in which a plurality of insulating layers 11 and conductor layers 12, as well as an insulating layer 13, are stacked on the first surface 100F of the core substrate 100. Each insulating layer 11 includes a via conductor 14. Each conductor layer 12 of the first wiring structure 10 is connected to the via conductor 14. The first main surface 1F of the wiring substrate 1 is configured by the upper surface of the insulating layer 13 in the first wiring structure 10, the sidewall surfaces of the openings 131 and 132, the exposed surface of the outermost conductor layer 12 (the bottom surface of the opening 131), and the exposed surface of the outermost insulating layer 11 (the bottom surface of the opening 132).

[0014] The outermost insulating layer 11 constituting the first main surface 1F is also referred to as the first insulating layer 11. The outermost conductor layer 12 formed on the first insulating layer 11 is also referred to as the first conductor layer 12. The insulating layer 13 formed on the first conductor layer 12 is also referred to as the second insulating layer 13. In addition, the opening 131 formed in the second insulating layer 13 is also referred to as the first opening 131, and the opening 132 is also referred to as the second opening 132.

[0015] In the example of FIG. 1, the second wiring structure 20 includes insulating layers and conductor layers alternately stacked on the second surface 100S of the core substrate 100. Specifically, the second wiring structure 20 has a multilayer wiring structure in which a plurality of insulating layers 21, conductor layers 22, and an insulating layer 23 are stacked on the second surface 100S side of the core substrate 100. Each insulating layer 21 includes a via conductor 24. Each conductor layer 22 of the second wiring structure 20 is connected to the via conductor 24. In the illustrated example, an opening 231 is formed in the insulating layer 23, and the outermost conductor layer 22 is exposed at the bottom surface of the opening 231. The upper surface of the outermost insulating layer 23 of the second wiring structure 20, the sidewall surface of the opening 231, and the exposed surface of the conductor layer 22 constitute the second main surface 1S of the wiring substrate 1.

[0016] The insulating layers 101, 11, and 21 constituting the wiring board 1 may each be formed using an insulating resin such as an epoxy resin, a bismaleimide triazine resin (BT resin), or a phenol resin. Each of the insulating layers 101, 11, and 21 may contain a reinforcing material (core material) such as glass fiber and / or an inorganic filler such as silica or alumina. The insulating layers 13 and 23, which may be solder resist layers, may each be formed using a photosensitive epoxy resin or polyimide resin.

[0017] The conductor layers 102, 12, 22, the via conductors 14, 24, and the through-hole conductor 103 are formed using any metal such as copper or nickel, and may be composed of, for example, a metal foil such as copper foil, and / or a metal film formed by plating or sputtering. The conductor layers 102, 12, 22, the via conductors 14, 24, and the through-hole conductor 103 are shown as single-layer structures in FIG. 1, but may have a multi-layer structure having two or more metal layers. For example, the conductor layer 102 formed on the surface of the insulating layer 101 may have a five-layer structure including a metal foil (preferably copper foil), an electroless plating film (preferably electroless copper plating film), and an electrolytic plating film (preferably electrolytic copper plating film). The conductor layers 12, 22, the via conductors 14, 24, and the through-hole conductor 103 may have, for example, a two-layer structure including an electroless plating film and an electrolytic plating film.

[0018] The conductor layer 12 of the first wiring structure 10 and the conductor layer 22 of the second wiring structure 20 are patterned to have a predetermined conductor pattern. The outermost first conductor layer 12 of the multiple conductor layers 12 constituting the first wiring structure 10 includes a conductor pad P1. In the example of FIG. 1, the outermost conductor layer 22 of the multiple conductor layers 22 constituting the second wiring structure 20 has a conductor pad P2. The conductor pad P1 can be electrically connected to a connection pad E1p of an external element E1 that can be an electronic component connected to the wiring board 1 when the wiring board 1 is used. That is, the first main surface 1F of the wiring board 1 is configured as a component mounting surface on which an external electronic component can be mounted. The first main surface 1F configured as the component mounting surface includes a component mounting area EA as an area on which the external element E1 is mounted. The conductor pad P2 exposed on the second main surface 1S can be used to connect the wiring board 1 to, for example, a motherboard of an electronic device or a package substrate of a semiconductor device having a laminated structure.

[0019] Although not shown in FIG. 1, the conductor pads P1 and P2 may include a surface treatment layer on their surfaces. The surface treatment layer that may be formed on the surfaces of the conductor pads P1 and P2 is, for example, a coating formed by anticorrosion treatment and / or antirust treatment of the exposed parts of the conductor pads P1 and P2. The surface treatment layer can prevent corrosion, oxidation, and the like of the conductor pads P1 and P2. The surface treatment layer that may be formed on the surfaces of the conductor pads P1 and P2 is, for example, a metal coating containing a metal different from that of the core parts of the conductor pads P1 and P2, or an organic coating containing an organic substance such as an imidazole compound. When the core parts of the conductor pads P1 and P2 are made of copper, the surface treatment layer may be made of nickel, palladium, silver, gold, or an alloy thereof, or solder, or the like.

[0020] The first opening 131, which exposes the upper surface of the first conductor layer 12 (specifically, the conductor pad P1) at the bottom surface, and the second opening 132, which exposes the upper surface of the insulating layer 11 at the bottom surface but does not expose the first conductor layer 12, are formed to be located within the component mounting area EA. When the external element E1 is connected to the wiring board 1, the conductor pad P1 constituting the bottom surface of the first opening 131 can be connected to the connection pad E1p of the external element E1 via a connection element such as a solder ball. On the other hand, when the external element E1 is connected to the wiring board 1, the inside of the second opening 132 can accommodate a protruding portion EP constituting the external element E1. The protruding portion EP is, for example, a portion located on the side where the connection pad E1p of the external element E1 is formed, as shown in the figure, and is a portion protruding toward the wiring board 1 side beyond the connection pad E1p. The protruding portion EP can be, for example, a passive component electrically connected to a main part of the external element E1. When an external element having such a protrusion EP is connected to the wiring board, the surface of the wiring board and the protrusion may interfere (contact), making it impossible to connect the external element to the wiring board. In the wiring board of the embodiment, the second opening 132 is formed, so that interference between the protrusion EP and the wiring board 1 is avoided, and the external element E1 can be satisfactorily mounted on the wiring board 1.

[0021] Specifically, in order to realize a good connection between the external element E1 and the wiring board 1, the second opening 132 has a tapered shape that reduces in diameter from the outside to the inside. That is, the dimension of the diameter (top diameter) at the outermost part (on the upper surface of the second insulating layer 13) of the second opening 132 is larger than the dimension of the diameter (bottom diameter) at the bottom surface of the second opening 132. By having the second opening 132 have such a shape, interference between the protrusion EP and the side wall surface of the second opening 132 can be effectively suppressed in connecting the external element E1 to the wiring board 1. A wiring board on which the external element E1 having the protrusion EP can be mounted relatively easily can be realized.

[0022] For convenience, the term "reduced diameter" is used, but the opening shape of the second opening 132 in plan view is not necessarily limited to a circle. For example, the opening shape may be any shape, such as a circle, an ellipse, or a rectangle, in plan view. "Diameter" means the distance between the longest two points on the circumference of the opening in a horizontal cross section, and "reduced diameter" simply means that the distance between the longest two points on the circumference of the opening in a horizontal cross section becomes smaller. Note that "plan view" means viewing the wiring board 1 along a line of sight along its thickness direction.

[0023] Furthermore, the conductor layer 12 is not exposed in the second opening 132 in which the protrusion EP can be accommodated, and the bottom surface of the second opening 132 is formed of the first insulating layer 11. This allows the second opening 132 to be configured as an opening having a relatively large dimension (relatively deep) in the thickness direction of the wiring board 1. Therefore, even if there is an external element E1 having a protrusion EP with a relatively large dimension in the thickness direction of the wiring board 1, there are cases in which the protrusion EP can be relatively easily accommodated in the second opening 132 when mounted on the wiring board 1. There are cases in which a good connection can be achieved between the external element E1 having a relatively large protrusion EP and the wiring board 1.

[0024] The shapes of the first opening 131 and the second opening 132 formed on the first main surface 1F side of the wiring board 1 will be described in more detail below with reference to FIG. 2. The cross-sectional view shown in FIG. 2 is an enlarged view of the area in the vicinity of the first main surface 1F surrounded by the dashed line indicated by the symbol II in FIG. 1. As shown in the figure, the sidewall surface and the bottom surface of the first opening 131 form an angle θ1 outside the first opening 131, and the sidewall surface and the bottom surface of the second opening 132 form an angle θ2 outside the second opening 132. The angle θ1 is also referred to as the first angle θ1, and the angle θ2 is also referred to as the second angle θ2.

[0025] The first opening 131 exposing the conductor pad P1 on the bottom surface can be formed to have a first angle θ1 within a predetermined range, for example, to accommodate a connection element used for connecting the external element E1 to the connection pad E1p therein and suppress wet spreading on the upper surface of the second insulating layer 13. In contrast, the second opening 132 is formed to have a second angle θ2 within a predetermined range, taking into consideration the ease of accommodating the protruding portion EP in the second opening 132 when the external element E1 is mounted on the wiring board 1. In the wiring board of the embodiment, the value of the second angle θ2 is different from the value of the first angle θ1. As described above, the second opening 132 is tapered from the outside to the inside, and the second angle θ2 is smaller than 90 degrees.

[0026] When the second angle θ2 of the second opening 132 is relatively small, when the external element E1 is mounted on the wiring board 1 (specifically, when the protrusion EP is accommodated in the second opening 132), the risk of interference between the protrusion EP and the side wall surface of the second opening 132 can be reduced. Therefore, the arrangement of the protrusion EP at the position to be accommodated in the second opening 132 can be realized relatively easily. The mounting of the external element E1 on the wiring board 1 can be realized relatively easily. Also, when the second angle θ2 is relatively large, the range occupied by the opening 132 in the planar direction (extension direction of the first main surface 1F) can be limited to a relatively small range. Therefore, even if the connection pad E1p and the protrusion EP are arranged relatively close to each other, the mounting of the external element E1 on the wiring board 1 may be realized relatively well. From these viewpoints, the second angle θ2 may have a value within a range of 45 degrees or more and 74 degrees or less.

[0027] As shown in the figure, the top surface of the first conductor layer 12 is exposed at the bottom surface of the first opening 131, and the top surface of the first insulating layer 11 is exposed at the bottom surface of the second opening 132. That is, regarding the depths of the first opening 131 and the second opening 132 (dimension in the thickness direction of the wiring board 1), the depth of the second opening 132 is greater than the depth of the first opening 131. The depth of the second opening 132 is substantially equal to the thickness of the second insulating layer 13. The second insulating layer 13 has a thickness of, for example, 15 μm or more and 40 μm or less, and therefore the second opening 132 may have a depth substantially equal to the thickness of the second insulating layer 13, 15 μm or more and 40 μm or less. Note that the depth t of the second opening 132 may have a value greater than the thickness of the second insulating layer 13. The bottom surface of the second opening 132 may be formed inside the first insulating layer 11, which is further inward from the top surface of the first insulating layer 11. In this case, the sidewall surface near the bottom surface of second opening 132 is also formed by first insulating layer 11. A deeper second opening 132 can be formed. With this configuration, second opening 132 with a greater depth t can be realized that can accommodate protrusion EP with a larger dimension in the thickness direction of the wiring board.

[0028] In addition, with respect to the dimensions of the first opening 131 and the second opening 132 in the planar direction (i.e., in the extending direction of the first main surface 1F), the diameter of the second opening 132 is larger than the diameter of the first opening 131. Specifically, the dimension of the top diameter of the second opening 132 may be 5 times or more the dimension of the top diameter of the first opening 131. More specifically, the top diameter of the first opening 131 may have a value of 30 μm or more and 50 μm or less, whereas the top diameter of the second opening 132 may have a value of 220 μm or more and 450 μm or less. In this way, since the dimension of the second opening 132 in the planar direction is formed relatively large compared to the dimension of the first opening 131 in the planar direction, it may be possible to relatively easily realize the connection of the external element E1 having the protrusion EP with a relatively large dimension in the planar direction to the wiring board 1.

[0029] FIG. 2 shows an example in which the first opening 131 and the second opening 132 have a shape that tapers from the outside to the inside of the wiring board 1 (i.e., an example in which the first angle θ1 and the second angle θ2 are 90 degrees or less), but the first angle θ1 of the first opening 131 is not limited to the example shown in FIG. 2. The first angle θ1 may have a value of 90 degrees or more. For example, the first angle θ1 may have a value in the range of 75 degrees or more and 105 degrees or less. FIG. 3 shows an example in which the first angle θ1 is greater than 90 degrees. That is, as shown in the figure, the first opening 131 tapers from the inside (from the first insulating layer 11 side) to the outside (to the upper surface side of the second insulating layer 13).

[0030] When the first opening 131 has such a tapered shape that the diameter decreases from the inside to the outside, the spreading of the connection element that is interposed between the connection pad E1p of the external element E1 and the conductor pad P1 and that can be accommodated in the opening 131 on the upper surface of the insulating layer 13 may be more effectively suppressed. Therefore, when the external element E1 is connected to the wiring board 1, a short circuit between adjacent conductor pads P1 may be more effectively suppressed. The connection reliability between the external element E1 and the wiring board 1 may be improved.

[0031] 1, 2, and 3, the shapes of the first opening 131 and the second opening 132 can be adjusted when forming the second insulating layer 13, which may be a solder resist layer, as described in detail later in the description of the manufacturing method of the wiring board. Specifically, for example, the shapes can be adjusted by the exposure and development conditions in the photolithography process for forming the openings 131 and 132 in the second insulating layer 13.

[0032] The wiring board of the embodiment can be manufactured by any general method for manufacturing a wiring board. With reference to Figs. 4A to 4D, a method for manufacturing a wiring board will be described by taking the case where the wiring board 1 shown in Fig. 1 is manufactured as an example. First, as shown in Fig. 4A, a core board 100 is prepared. In preparing the core board 100, for example, a double-sided copper-clad laminate having a metal foil provided on the surface of a core insulating layer 101 is prepared. A through hole 103o is formed in the double-sided copper-clad laminate by, for example, drilling, and an electroless plating film is formed on the inner wall of the through hole 103o and the upper surface of the metal foil, and an electrolytic plating film is formed on the electroless plating film using the electroless plating film as a power supply layer.

[0033] The inside of the through-hole conductor 103 formed on the inner wall of the through-hole 103o is filled with a resin body 104 by, for example, injecting an epoxy resin. After the filled resin body 104 is solidified, an electroless plating film and an electrolytic plating film are further formed on the upper surface of the resin body 104 and the electrolytic plating film. As a result, although shown as a single layer in the figure, a conductor layer 102 having a five-layer structure of a metal foil, an electroless plating film, an electrolytic plating film, an electroless plating film, and an electrolytic plating film is formed on both sides of the insulating layer 101. Then, the conductor layer 102 is patterned by a subtractive method to obtain a core substrate 100 having a predetermined conductor pattern.

[0034] Next, as shown in FIG. 4B, a plurality of insulating layers 11 and conductor layers 12 are alternately laminated on the first surface 100F of the core substrate 100, and a plurality of insulating layers 21 and conductor layers 22 are alternately laminated on the second surface 100S. For example, each insulating layer 11, 21 in contact with the core substrate 100 may be formed by thermocompression bonding a film-like insulating resin onto the core substrate 100. The conductor layers 12, 22 are formed by using any conductor pattern forming method such as a semi-additive method at the same time as via conductors 14, 24 that fill openings that may be formed in the insulating layers 11, 21 by, for example, laser light. The formation of the insulating layers 11, 21 and the conductor layers 12, 22 is repeated, and as shown in the figure, the outermost conductor layer (first conductor layer) 12 on the first surface 100F side and the outermost conductor layer 22 on the second surface 100S side are laminated. The outermost first conductor layer 12 is formed into a pattern including a first conductor pad P1. The outermost conductor layer 21 is formed into a pattern including a conductor pad P2.

[0035] 4C, a second insulating layer 13 is formed of a photosensitive film on the surfaces of the first insulating layer 11 and the first conductor layer 12. An insulating layer 23 is formed of a photosensitive film on the surfaces of the insulating layer 21 and the conductor layer 22. The insulating layers 13 and 23 are made of, for example, a photosensitive resin (e.g., an epoxy resin), and can be formed by spray coating, curtain coating, lamination, or the like.

[0036] Next, as shown in FIG. 4D, the openings 131 and 132 are formed in the second insulating layer 13, and the opening 231 is formed in the insulating layer 23. In forming the openings 131 and 132, the openings 131 and 132 are formed by exposing the second insulating layer 13 to light using a photomask and developing using a chemical solution. For the exposure, a photomask having a light-transmitting portion corresponding to the pattern of the openings 131 and 132 to be formed may be used. Light irradiated from a light source positioned outside the photomask passes through the light-transmitting portion of the photomask and is irradiated onto the insulating layer 13. Depending on the attribute (positive / negative) of the photosensitive resin constituting the insulating layer 13, the exposed portion of the insulating layer 13 is altered. Thereafter, the exposed portion (in the case of positive) or the unexposed portion (in the case of negative) of the resist film is removed by development, thereby forming the first opening 131 and the second opening 132.

[0037] Specifically, for example, when a negative photosensitive resin is used for the second insulating layer 13, a photomask having a pattern that shields the areas where the openings 131 and 132 are to be formed in the second insulating layer 13 may be used in forming the first opening 131 and the second opening 132 in the second insulating layer 13. The irradiated light that has passed through the light-transmitting portion of the photomask may expand in a planar direction due to diffraction as it moves away from the photomask (as it approaches the first insulating layer 11). That is, the portion of the insulating layer 13 that is altered by the effect of exposure expands in the planar direction as it approaches the insulating layer 11. Therefore, the portion that is not exposed and is not altered is removed in the subsequent development process, and the openings 131 and 132 that decrease in diameter from the outside to the inside may be formed.

[0038] The first angle θ1 of the first opening 131 and the second angle θ2 of the second opening 132 (see FIG. 2) can be adjusted by the exposure conditions, the development conditions, and the like. For example, when a negative photosensitive resin is used for the second insulating layer 13 as described above, the light transmittance of the light-transmitting portion located on the periphery of the shielding portion (the position where the openings 131 and 132 are to be formed) of the photomask used for exposure can be adjusted. By making the light transmittance of the light-transmitting portion located on the periphery of the shielding portion different, the first opening 131 and the second opening 132 having different taper angles can be formed. Also, for example, in order to form the first angle θ1 of the first opening 131 and the second angle θ2 of the second opening 132 (see FIG. 2) to angles of preferred magnitudes, different photomasks may be used for forming the first opening 131 and the second opening 132. In this case, the exposure using the mask for forming the first opening 131 and the exposure using the mask for forming the second opening 132 may be performed under different conditions.

[0039] 3, the shape of the first opening 131 can be formed by adjusting the conditions of the exposure process and the development process. For example, by adjusting the light transmittance of the light-transmitting portion located on the periphery of the shielding portion corresponding to the position where the first opening 131 of the photomask is to be formed to be relatively low, the portion of the insulating layer 13 that is not altered by exposure can be expanded toward the inside of the insulating layer 13 (as it approaches the conductor pad P1). Therefore, the first opening 131 that decreases in diameter from the inside to the outside can be formed by development. Note that an opening is also formed in the insulating layer 23 on the second main surface 1S side by the process of exposing and developing the insulating layer 23. On the first main surface 1F side, the first opening 131 that exposes the conductor pad P1 on the bottom surface and the second opening 132 that exposes the upper surface of the first insulating layer 11 on the bottom surface are formed, and on the second main surface 1S side, the opening 231 that exposes the conductor pad P2 on the bottom surface is formed. The formation of the wiring board 1 is completed.

[0040] Although the method of forming the openings by photolithography has been described, the method of forming the openings 131, 132, 231 is not limited to this. The openings 131, 132, 231 may be formed, for example, by irradiating the hardened insulating layers 13, 23 with laser light. In this case, in particular, the shape of the openings 131, 132 to be formed can be adjusted by the irradiation conditions of the laser light (for example, laser diameter, laser intensity, etc.) and the conditions of the smear removal process (desmear process) that may be subsequently performed using a chemical solution (for example, chemical solution concentration, process temperature, process time, etc.).

[0041] A surface treatment layer may be formed on the surfaces of the conductor pads P1, P2 exposed by the formation of the openings 131, 132, 231. For example, an organic coating containing an organic substance such as an imidazole compound may be formed by applying a heat-resistant organic substance by spraying. Alternatively, a metal coating may be formed by depositing a metal such as nickel, palladium, or gold by electroless plating or the like. A surface protection film (not shown) made of Au, Ni / Au, Ni / Pd / Au, solder, heat-resistant preflux, or the like may be formed on the conductor pads P1, P2 exposed from the openings 131, 132, 231 by electroless plating, solder leveler, spray coating, or the like.

[0042] The wiring board of the embodiment is not limited to those having the structures illustrated in the drawings and the structures, shapes, and materials illustrated in this specification. For example, the first buildup section 10 and the second buildup section 20 in the wiring board of the embodiment may include any number of conductor layers and insulating layers. The wiring board is not limited to an embodiment having a core substrate, and may be a coreless substrate. [Explanation of symbols]

[0043] 1. Wiring board 100 core board 101 Core insulation layer 102 Core conductor layer 103 Through-hole conductor 11 Insulating layer (first insulating layer) 12 Conductive layer (first conductive layer) 13 Insulating layer (second insulating layer) 131 Aperture (1st Aperture) 132 Aperture (2nd Aperture) 231 Aperture P1, P2 contact pads E1 External elements EP protrusion E1p connection pad θ1 1st angle θ2 2nd angle

Claims

1. A first insulating layer; a first conductor layer formed on the first insulating layer; a second insulating layer formed on the first conductor layer and the first insulating layer; a first opening and a second opening penetrating the second insulating layer in a thickness direction; A wiring board having the first conductor layer is exposed at a bottom surface of the first opening, the first conductor layer is not exposed at a bottom surface of the second opening, a value of a first angle formed between a side wall surface and a bottom surface of the first opening at an outside of the first opening is different from a value of a second angle formed between a side wall surface and a bottom surface of the second opening at an outside of the second opening, A top diameter of the second opening on the side opposite to the bottom surface is larger than a bottom diameter of the second opening on the bottom surface side.

2. 2. A wiring board as described in claim 1, wherein an upper surface of the second insulating layer, an inner surface of the first opening, and an inner surface of the second opening constitute a component mounting surface having a component mounting area where an external component is to be mounted, and the first opening and the second opening are formed within the component mounting area.

3. 2. The wiring board according to claim 1, wherein the value of the second angle is not less than 45 degrees and not more than 74 degrees, and the value of the first angle is not less than 75 degrees and not more than 105 degrees.

4. 2. The wiring board according to claim 1, wherein a bottom diameter dimension on the bottom surface side of the first opening is larger than a top diameter dimension on the opposite side to the bottom surface of the first opening.

5. 2. The wiring board according to claim 1, wherein a top diameter of the second opening is at least five times a top diameter of the first opening.

6. 2. The wiring board according to claim 1, wherein the second opening has a depth of 15 [mu]m or more and 40 [mu]m or less.

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