Wiring board and method of manufacturing the same

Abstract

To improve a quality of a wiring board.SOLUTION: A wiring board of an embodiment contains: a glass board 1 provided with a penetration hole 11; and a conductor 4 in the penetration hole 11 for connecting both of two conductive layers 31 and 32 nipping the glass board 1. The penetration hole 11 contains: a first part 11a which becomes thin toward a second surface 1b side from a first surface 1a of the glass board 1; and a second part 11b which becomes thin toward the first surface 1a side from a second surface 1b. One and the other one of two inner wall nipping the first part 11a in a longitudinal section along a Z direction as a thickness direction of the glass board 1 include a first angle θ1 and a second angle θ2 in a space between each inner wall and the Z direction, respectively. One and the other one of the two inner walls nipping the second part 11b in the longitudinal section include a third angle θ3 and a fourth angle θ4 in the space between each inner wall and the Z direction, respectively. The first to fourth angles θ1 to θ4 are different from each other.SELECTED DRAWING: Figure 2

Description

[Technical Field]

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

[0002] Patent Document 1 discloses an interposer including a glass substrate having through-holes formed by laser processing. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-198093 Summary of the Invention [Problem to be solved by the invention]

[0004] In the interposer disclosed in Patent Document 1, it is believed that the glass substrate may crack or chip due to mechanical and / or thermal stress applied to the glass substrate by the laser light when the through holes are formed. Furthermore, even if such defects do not occur in the through hole formation process or subsequent processes, it is conceivable that latent defects such as microcracks may be present in the glass substrate and become apparent in the market. [Means for solving the problem]

[0005] The wiring board of the present invention includes a glass plate having a first surface and a second surface opposite to the first surface and a through hole penetrating between the first surface and the second surface, two conductor layers sandwiching the glass plate in the thickness direction of the glass plate, and a conductor passing through the inside of the through hole and connecting the two conductor layers to each other. The through hole includes a first portion tapering from the first surface toward the second surface, and a second portion tapering from the second surface toward the first surface and communicating with the first portion, wherein in a cross section passing through the through hole along the thickness direction, one of two inner walls of the glass plate facing each other across the first portion has a first angle with the thickness direction and the other of the two inner walls has a second angle with the thickness direction, one of two inner walls of the glass plate facing each other across the second portion in the cross section has a third angle with the thickness direction, and the other of the two inner walls facing each other across the second portion has a fourth angle with the thickness direction, and the first angle, the second angle, the third angle, and the fourth angle are different from one another.

[0006] A method for manufacturing a wiring board of the present invention includes forming a through hole in a glass plate having a first surface and a second surface opposite to the first surface, the through hole including a first portion tapering from the first surface toward the second surface and a second portion tapering from the second surface toward the first surface and communicating with the first portion, penetrating the glass plate in the thickness direction of the glass plate; forming two conductor layers sandwiching the glass plate in the thickness direction; and forming a conductor that passes through the inside of the through hole and connects the two conductor layers together. Forming the through hole includes forming a plurality of openings in each of the first surface and the second surface, each having a diameter smaller than the diameter of the through hole, while shifting their positions so that they partially overlap each other along the outline of the through hole to be formed, and the through hole is formed so that one and the other of two inner walls of the glass plate that face each other across the first portion in a cross section passing through the through hole along the thickness direction, and one and the other of two inner walls of the glass plate that face each other across the second portion in the cross section, have different angles from each other with respect to the thickness direction in the cross section.

[0007] According to the embodiment of the present invention, it may be possible to suppress the occurrence of defects such as cracks in the glass plate, and the quality of the wiring board may be improved. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a cross-sectional view showing an example of a wiring substrate according to an embodiment of the present invention. [Figure 2] Enlarged view of part II in Figure 1. [Figure 3] FIG. 3 is a perspective view schematically showing a through hole in an insulating layer according to an embodiment. [Figure 4] FIG. 4 is a plan view showing an example of an inner wall around a through hole in an insulating layer according to an embodiment. [Figure 5] 10A and 10B are cross-sectional views showing other examples of the shape of the through-hole in the embodiment. [Figure 6] 10 is an SEM image of a cross section of a through hole in an example of a wiring board according to an embodiment. [Figure 7A]5A to 5C are cross-sectional views showing an example of a method for manufacturing a wiring board according to an embodiment of the present invention. [Figure 7B] 5A to 5C are cross-sectional views showing an example of a method for manufacturing a wiring board according to an embodiment of the present invention. [Figure 7C] 5A to 5C are cross-sectional views showing an example of a method for manufacturing a wiring board according to an embodiment of the present invention. [Figure 7D] An enlarged view of the VIID portion of Figure 7C. [Figure 7E] 5A and 5B are perspective views showing an example of a method for forming a through hole in the method for manufacturing a wiring board according to an embodiment of the present invention. [Figure 7F] 10A and 10B are plan views showing another example of a method for forming a through hole in the method for manufacturing a wiring board according to an embodiment of the present invention. [Figure 7G] 10A and 10B are plan views showing another example of a method for forming a through hole in the method for manufacturing a wiring board according to an embodiment of the present invention. [Figure 7H] 5A to 5C are cross-sectional views showing an example of a method for manufacturing a wiring board according to an embodiment of the present invention. [Figure 7I] 5A to 5C are cross-sectional views showing an example of a method for manufacturing a wiring board according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0009] A wiring board according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a cross-sectional view showing a wiring board 100, which is an example of a wiring board according to an embodiment, and FIG. 2 is an enlarged view of part II in FIG. 1. Note that the wiring board 100 is merely an example of a wiring board according to this embodiment. The layered structure of the wiring board according to this embodiment and the number of conductor layers and insulating layers included in the wiring board 100 are not limited to the layered structure of the wiring board 100 shown in FIG. 1 and the number of conductor layers and insulating layers included in the wiring board 100. In addition, in the drawings referred to in the following description, certain portions may be enlarged to facilitate understanding of the disclosed embodiments, and the components may not be drawn to exact proportions with respect to size or length.

[0010] As shown in FIG. 1, the wiring board 100 includes an insulating layer (core layer) 1 having a through hole 11 (first through hole), two conductor layers (conductor layer 31 and conductor layer 32) sandwiching the insulating layer 1, and a through-hole conductor 4 connecting the two conductor layers. The insulating layer 1 has two main surfaces, a first surface 1a and a second surface 1b opposite the first surface 1a, which are substantially perpendicular to the thickness direction of the insulating layer 1. The conductor layers 31 and 32 sandwich the insulating layer 1 in the thickness direction of the insulating layer 1. The through-hole 11 penetrates the insulating layer 1 between the first surface 1a and the second surface 1b in the thickness direction. The through-hole conductor 4 passes through the insulating layer 1 through the inside of the through-hole 11 and connects the conductor layer 31 and the conductor layer 32. The through-hole conductor 4 is made of any conductor having suitable conductivity, such as a metal such as copper, nickel, or silver, and electrically connects the conductor layer 31 and the conductor layer 32. In Figure 1, only conductor pads (through-hole pads) connected to through-hole conductors 4 are shown as conductor patterns included in conductor layer 31 and conductor layer 32, but conductor layer 31 and conductor layer 32 may each include any conductor pattern.

[0011] In the description of the embodiments, the side of the wiring board 100 farther from the insulating layer 1 in the thickness direction is also referred to as the "outside," "upper side," or "upper," or simply "upper," and the side closer to the insulating layer 1 is also referred to as the "inside," "lower side," or "lower," or simply "lower." Furthermore, the surface of each component of the wiring board 100, such as the conductor layer 31, the conductor layer 32, and their conductor patterns, facing away from the insulating layer 1 is also referred to as the "upper surface," and the surface facing the insulating layer 1 is also referred to as the "lower surface." The thickness direction of the wiring board 100 is the same as the thickness direction of the insulating layer 1, and both are also referred to as the "Z direction." The thickness direction of the insulating layer 1 is parallel to the normal to the plane of symmetry that positions the first surface 1a and the second surface 1b in plane symmetry.

[0012] In the wiring board of this embodiment, the insulating layer 1 is made of a glass plate that is mainly made of glass. Examples of glass that can form the insulating layer 1 include soda-lime glass, alkali-free glass, quartz glass, and borosilicate glass. Since the insulating layer 1 is generally made of glass that has high rigidity, it is believed that the wiring board 100 is less likely to warp.

[0013] The wiring board 100 of the example in FIG. 1 further includes a resin layer 21 formed between the first surface 1a of the insulating layer 1 and the conductor layer 31, and a resin layer 22 formed between the second surface 1b of the insulating layer 1 and the conductor layer 32. That is, the conductor layer 31 is formed on the resin layer 21 laminated on the first surface 1a of the insulating layer 1, and the conductor layer 32 is formed on the resin layer 22 laminated on the second surface 1b of the insulating layer 1. The resin layers 21 and 22 can function as insulating layers that further enhance the insulation between the conductor layers 31 and 32 provided by the insulating layer 1. Furthermore, the resin layers 21 and 22 may improve the adhesion between the insulating layer 1 made of a glass plate and the conductor layers 31 and 32.

[0014] Through-hole conductor 4 penetrates resin layer 21 and resin layer 22 in addition to insulating layer 1. Through hole 11 is filled with a conductor that forms through-hole conductor 4.

[0015] 1 further includes buildup sections 10 laminated on the conductor layer 31 and the resin layer 21, and on the conductor layer 32 and the resin layer 22. The buildup sections 10 are composed of insulating layers 23 and conductor layers 33 laminated alternately. The buildup sections 10 further include a plurality of via conductors 41 that penetrate each insulating layer 23 and connect two conductor layers sandwiching each insulating layer 23. Each via conductor 41 connects the conductor layer 31 to the conductor layer 33, connects the conductor layer 32 to the conductor layer 33, or connects the conductor layers 33 to each other.

[0016] The wiring board 100 in the example of FIG. 1 further includes a solder resist 5 on each buildup portion 10. The solder resist 5 can cover and protect the outermost insulating layer 23 and conductor layer 33 in each buildup portion 10. The solder resist 5 has openings 5a that expose conductor pads included in the conductor layer 33. The solder resist 5 is formed of any insulating resin, such as a photosensitive epoxy resin or polyimide resin.

[0017] The resin layer 21, the resin layer 22, and the insulating layer 23 are mainly formed of a thermosetting resin such as an epoxy resin, a bismaleimide triazine resin (BT resin), or a phenolic resin. The resin layer 21, the resin layer 22, and the insulating layer 23 may also be mainly formed of a thermoplastic resin such as a fluororesin or a liquid crystal polymer (LCP).

[0018] In the example of FIG. 1, resin layer 21 and resin layer 22 each contain a reinforcing material (core material) 2a made of, for example, glass fiber or aramid fiber. Reinforcing material 2a may increase the rigidity of each of resin layers 21 and 22. Furthermore, resin layers 21 and 22 may have a thermal expansion coefficient close to that of insulating layer 1 made of a glass plate. Although not shown in FIG. 1, insulating layer 23 may also contain a reinforcing material such as reinforcing material 2a. Resin layers 21 and 22 and insulating layer 23 may further contain an inorganic filler (not shown) made of, for example, particles of silicon dioxide or alumina.

[0019] The conductor layers 31 to 33 and the via conductor 41 are formed of any metal having suitable conductivity, such as copper or nickel. Although the conductor layers 31 and 32 and the through-hole conductor 4 are shown in Fig. 1 as being composed of a single layer for simplicity, they may each have a multilayer structure including two or more layers, as shown in Fig. 2. The conductor layer 33 and the via conductor 41 may also have a multilayer structure.

[0020] In the example of FIG. 2, the conductor layer 31 and the conductor layer 32 are each composed of a metal foil 3a, a first metal film 3b, and a second metal film 3c. The metal foil 3a is disposed on the surface of the resin layer 21 or the surface of the resin layer 22. The first metal film 3b is formed on the metal foil 3a, and the second metal film 3c is formed on the first metal film 3b. The first metal film 3b and the second metal film 3c form a through-hole conductor 4. The first metal film 3b may be, for example, an electroless plated film or a sputtered film, and the second metal film 3c may be, for example, an electrolytic plated film. The conductor layer 33 and the via conductor 41 (see FIG. 1) may also be composed of two stacked metal films, such as the first metal film 3b and the second metal film 3c.

[0021] In this embodiment, the width of the through hole 11 decreases from each of the openings on the first surface 1a side and the second surface 1b side of the insulating layer 1 toward the center of the insulating layer 1 in the Z direction. Therefore, both the through hole 11 and the through-hole conductor 4 have the smallest width near the approximate center in the Z direction, and have a constriction near this center. For example, when the through hole 11 is formed by drilling from both the first surface 1a side and the second surface 1b side of the insulating layer 1, it may have a constriction as shown in the example of Figure 2. Note that the "width" of the through hole 11 or the like is the distance between the two furthest points on the periphery of the cross section or end face of the through hole 11 or the like perpendicular to the Z direction.

[0022] Fig. 3 shows a perspective view of the insulating layer 1, schematically illustrating the through hole 11. The shape of the through hole 11 in this embodiment will be further described with reference to Fig. 3 as appropriate and continuing to Fig. 2. Note that, unless otherwise specified, the "tilt angle" mentioned in the following description means the angle of inclination of each target element in the description with respect to the Z direction (the thickness direction of the insulating layer 1 and the wiring substrate 100) (the angle between the target element and an axis along the Z direction).

[0023] As shown in Figures 2 and 3, the through hole 11 includes a first portion 11a tapering from the first surface 1a of the insulating layer 1 toward the second surface 1b, and a second portion 11b tapering from the second surface 1b toward the first surface 1a. The first portion 11a and the second portion 11b are connected to each other. This "connection" includes not only a configuration in which the tapered cavities of the first portion 11a and the second portion 11b are directly connected to each other, as in the example of Figures 2 and 3, but also a configuration such as the example of Figure 5, which will be referred to later. In other words, the "connection" also includes a configuration in which the tapered cavities of the first portion 11a and the second portion 11b are connected to each other via a cavity having a substantially constant width over an arbitrary length in the Z direction.

[0024] In this embodiment, in a cross section passing through the through hole 11 in the thickness direction (Z direction) of the wiring substrate 100 as shown in FIG. 2, the first angle θ1, the second angle θ2, the third angle θ3, and the fourth angle θ4 are different from one another. Such a magnitude relationship among the first angle θ1 to the fourth angle θ4 is hereinafter simply referred to as the "first magnitude relationship of the embodiment." Furthermore, the first angle θ1 and the fourth angle θ4 are preferably larger than both the second angle θ2 and the third angle θ3, respectively. Such a magnitude relationship among the first angle θ1 to the fourth angle θ4 is hereinafter simply referred to as the "second magnitude relationship of the embodiment." Furthermore, in the first angle θ1 to the fourth angle θ4 that satisfy the second magnitude relationship of the embodiment, the second angle θ2 may be larger than the third angle θ3 when the first angle θ1 is larger than the fourth angle θ4, and the second angle θ2 may be smaller than the third angle θ3 when the first angle θ1 is smaller than the fourth angle θ4. Such magnitude relationships among the first angle θ1 to the fourth angle θ4 will hereinafter be simply referred to as the “third magnitude relationships of the embodiment.” Note that a cross section passing through through hole 11 in the thickness direction of wiring substrate 100 will also be simply referred to as the “longitudinal cross section.”

[0025] Here, the first angle θ1 is the angle that the first inner wall 111 has with the Z direction. The second angle θ2 is the angle that the second inner wall 112 has with the Z direction. The first inner wall 111 is one of two inner walls of the insulating layer 1 made of a glass plate that face each other across the first portion 11a in the vertical cross section of the through hole 11, and the second inner wall 112 is the other of the two inner walls.

[0026] On the other hand, the third angle θ3 is the angle that the third inner wall 113 has with the Z direction. The fourth angle θ4 is the angle that the fourth inner wall 114 has with the Z direction. The third inner wall 113 is one of two inner walls of the insulating layer 1 made of a glass plate that face each other across the second portion 11b in the vertical cross section of the through hole 11, and the fourth inner wall 114 is the other of the two inner walls.

[0027] That is, in wiring board 100 having the second magnitude relationship of the embodiment, the larger of the inclination angles of two inner walls of insulating layer 1 that face each other on one side of two main surfaces of insulating layer 1, sandwiching through hole 11 therebetween (e.g., first angle θ1), is larger than the smaller of the inclination angles of two inner walls of insulating layer 1 that face each other on the other main surface, sandwiching through hole 11 therebetween (e.g., third angle θ3). In addition, the larger of the inclination angles of two inner walls of insulating layer 1 that face each other on the other main surface, sandwiching through hole 11 therebetween (e.g., fourth angle θ4), is larger than the smaller of the inclination angles of two inner walls of insulating layer 1 that face each other on one main surface, sandwiching through hole 11 therebetween (e.g., second angle θ2).

[0028] In other words, in wiring board 100 having the second magnitude relationship, the smaller of the inclination angles of two inner walls of insulating layer 1 that face each other on one side of two main surfaces of insulating layer 1, sandwiching through hole 11 therebetween (e.g., second angle θ2) is smaller than the larger of the inclination angles of two inner walls of insulating layer 1 that face each other on the other main surface, sandwiching through hole 11 (e.g., fourth angle θ4). In addition, the smaller of the inclination angles of two inner walls of insulating layer 1 that face each other on the other main surface, sandwiching through hole 11 therebetween (e.g., third angle θ3) is smaller than the larger of the inclination angles of two inner walls of insulating layer 1 that face each other on one main surface, sandwiching through hole 11 therebetween (e.g., first angle θ4).

[0029] Since the first angle θ1 to the fourth angle θ4 have the first magnitude relationship, the first and second magnitude relationship, or the first to third magnitude relationships of the above embodiment, the stress applied to the insulating layer 1 surrounding the through hole 11 may be reduced in the wiring board 100 of the embodiment. The reason for this will be explained in detail below.

[0030] When the hard insulating layer 1 made of a glass plate is relatively thick, the through holes 11 may be drilled from both sides of the insulating layer 1, as described above. For example, the insulating layer 1 in the embodiment may have a thickness of 0.5 mm or more and 2.5 mm or less to obtain appropriate rigidity in the wiring substrate 100. When the through holes 11 are drilled from both sides of the insulating layer 1 by laser processing, the through holes 11 tend to have a shape including portions (first portion 11a and second portion 11b) that taper from the first surface 1a side and the second surface 1b side of the insulating layer 1 toward the center of the insulating layer 1, as shown in the examples of FIGS. 2 and 3 . Furthermore, the inner wall of the insulating layer 1 surrounding the through holes 11 may have a vertex P that protrudes toward the central axis of the through holes 11, as shown in FIG. 2 . It is believed that stress generated inside the insulating layer 1 due to the difference in thermal expansion coefficient between the insulating layer 1 and the filler (e.g., the through-hole conductor 4) in the through holes 11 tends to concentrate at the top portion such as the vertex P.

[0031] Furthermore, if the inner wall surrounding through hole 11 has the same inclination angle over the entire circumference of each of first portion 11a and second portion 11b, vertices such as vertex P are likely to occur at approximately the same position in the Z direction around the entire circumference of through hole 11 at the boundary between first portion 11a and second portion 11b. Because the distance between opposing vertices across through hole 11 is short, it is believed that stress due to thermal expansion of the filler in through hole 11 is more severely applied to the vertices of the inner wall surrounding through hole 11 at approximately the same position in the Z direction than between vertices occurring at different positions in the Z direction. Therefore, if the inner wall surrounding through hole 11 has the same inclination angle over the entire circumference of each of first portion 11a and second portion 11b, fractures or cracks may easily occur at the vertices of the inner wall in insulating layer 1 made of a glass plate. Furthermore, potential defects occurring near the top of the inner wall, such as microcracks, may spread during use of the wiring board and become apparent as breaks or cracks in the insulating layer 1 .

[0032] In contrast, in this embodiment, the first angle θ1 to the fourth angle θ4 have at least the first magnitude relationship of the above embodiment, so that the apexes of the inner walls of the insulating layer 1 surrounding the through hole 11 are unlikely to be located at approximately the same position in the Z direction around the entire periphery of the through hole 11. For example, in the example of FIG. 2 , one and the other of two inner walls facing each other across the first portion 11a in the longitudinal cross section are in contact with one or the other of two inner walls facing each other across the second portion 11b at different positions in the Z direction. Specifically, the first inner wall 111 of the first inner wall 111 and the second inner wall 112 facing each other across the first portion 11a is in contact with the fourth inner wall 114 of the third inner wall 113 and the fourth inner wall 114 facing each other across the second portion 11b. Meanwhile, the second inner wall 112 is in contact with the third inner wall 113.

[0033] The vertex P where the first inner wall 111 and the fourth inner wall 114 meet, and the vertex P where the second inner wall 112 and the third inner wall 113 meet, are both apexes of the inner walls of the insulating layer 1 surrounding the through hole 11, but are located at different positions in the Z direction. The vertex P between the first inner wall 111 and the fourth inner wall 114 is located closer to the second surface 1b than the center line C in the thickness direction of the insulating layer 1, and the vertex P between the second inner wall 112 and the third inner wall 113 is located closer to the first surface 1a than the center line C. Therefore, in this embodiment, it is believed that excessive local stress is unlikely to be applied to the inner walls of the insulating layer 1 surrounding the through hole 11. This reduces the occurrence of breakages and cracks in the insulating layer 1, which may improve the quality of the wiring substrate 100.

[0034] Furthermore, in this embodiment, when the second magnitude relationship of the above embodiment exists, a situation does not occur in which the inclination angles of both of the two inner walls sandwiching one of the first portion 11a and the second portion 11b in the longitudinal cross section are greater than or smaller than the inclination angles of both of the two inner walls sandwiching the other of the first portion 11a and the second portion 11b. In other words, in the longitudinal cross section, at least one of the two inner walls sandwiching one of the first portion 11a and the second portion 11b is greater than one of the two inner walls sandwiching the other of the first portion 11a and the second portion 11b and smaller than the other. For example, a situation does not occur in which both the first angle θ1 and the second angle θ2 are greater than or smaller than both the third angle θ3 and the fourth angle θ4. Either at least one of the first angle θ1 and the second angle θ2 is greater than the third angle θ3 and smaller than the fourth angle θ4, or at least one of the third angle θ3 and the fourth angle θ4 is greater than the second angle θ2 and smaller than the first angle θ1. Therefore, there is unlikely to be a significant difference between the opening area of ​​the through hole 11 on the first surface 1a of the insulating layer 1 and the opening area of ​​the through hole 11 on the second surface 1b. Therefore, it may be possible to arrange conductor patterns at approximately the same density on the conductor layer 31 and the conductor layer 32. Therefore, the size relationship of each embodiment may contribute to facilitating the pattern design of the wiring board 100 and reducing the size of the wiring board 100.

[0035] The first to fourth angles θ1 to θ4 are, for example, angles equal to or greater than 5° and equal to or less than 25°. The first to fourth inner walls 111 to 114 each having an inclination angle of this order are likely to have the first to third magnitude relationships of the embodiment, are easily formed, and are unlikely to increase the planar size of the wiring board 100.

[0036] The first portion 11a and the second portion 11b of the through hole 11, which have at least the first magnitude relationship in the above-described embodiment with respect to the surrounding inner wall, may have an interface (virtual interface) 11c that is inclined with respect to a virtual plane perpendicular to the axial direction of the through hole 11 (the Z direction, which is the thickness direction of the insulating layer 1), as shown in FIG. 3 . The outer periphery of the interface 11c is defined by the vertices Pa of the inner wall of the insulating layer 11 that surrounds the through hole 11. Unlike the present embodiment, if the inner wall of the insulating layer 1 that surrounds the through hole 11 has a constant inclination angle over its entire periphery on both the first surface 1a side and the second surface 1b side, the virtual interface Sa of the first portion 11a and the second portion 11b that is defined by the vertices of the inner wall is considered to be perpendicular to the Z direction. In this embodiment, the perimeter of the vertices Pa that define the interface 11c (the length of the outer periphery of the interface 11c) is considered to be longer than the perimeter of the vertices that define the interface Sa. That is, it is considered that the high concentration of internal stress of the insulating layer 1 on the top portion Pa is suppressed. From this point of view, it is presumed that the magnitude relationships of the embodiments contribute to the reduction of stress on the insulating layer 1.

[0037] The through hole 11 can be formed, for example, by a processing method (trepanning) described below, in which a plurality of recesses or holes having a width smaller than the width of the hole to be formed are sequentially formed on both surfaces of an object to be processed, such as the insulating layer 1, while sequentially shifting their positions along the contour of the hole to be formed. By using such a method, the through hole 11 surrounded by inner walls having the respective size relationships of the embodiment can be easily formed. In the following description, the recesses or holes having a width smaller than the width of the through hole 11 formed for the purpose of forming the through hole 11 will be collectively referred to simply as "openings."

[0038] In particular, laser trepanning using carbon dioxide laser light or YAG laser light may be preferable for forming the through holes 11 in this embodiment. In laser processing, the power of the laser light transmitted to the insulating layer 1 is easily weakened as it progresses from the processed surface (first surface 1a or second surface 1b) of the insulating layer 1 to the opposite surface in the Z direction, making it easy to form tapered openings. Furthermore, gradually changing the movement distance of the laser light irradiation position as the formation of multiple openings progresses changes the overlap between the irradiation positions before and after the movement, thereby changing the processability. This may also enable gradually changing the inclination angle of the inner walls that appear as the openings are formed. Furthermore, gradually changing the power and spot diameter of the laser light as the formation of multiple openings progresses may facilitate the formation of through holes 11 surrounded by inner walls with different inclination angles.

[0039] 4 shows an example of a plan view, seen from the first surface side, of through hole 11 formed by trepanning from each of both surfaces (first surface 1a and second surface 1b in FIG. 1) of insulating layer 1. In the example of FIG. 4, through hole 11 is formed by sequentially forming a plurality of openings 110a in a clockwise direction toward the first surface, and sequentially forming a plurality of openings 110b in a clockwise direction toward the second surface. That is, the plurality of openings 110a formed from the first surface are sequentially formed in the direction of arrow AR1, and the plurality of openings 110b formed from the second surface are sequentially formed in the direction of arrow AR2.

[0040] Of the two inner peripheral edges 11α and 11β in Fig. 4, the inner peripheral edge 11α indicated by a solid line shows an example of the outer edge of the through hole 11 on the second surface after a plurality of openings 110a are formed from the first surface side prior to the second surface side, penetrating the insulating layer 1 along the contour of the through hole 11 to be formed. On the other hand, the inner peripheral edge 11β indicated by a two-dot chain line shows an example of the outer edge of the through hole 11 on the first surface 1a after a plurality of openings 110b are formed from the second surface side prior to the first surface side, penetrating the insulating layer 1 along the contour of the through hole 11 to be formed. The contour obtained by connecting either the inner peripheral edge 11α or the inner peripheral edge 11β, whichever is located on the outer side, all around the circumference may show the vertex Pa shown in Fig. 3 and the locus of the vertex P shown in Fig. 2 around the through hole 11.

[0041] Furthermore, the width 11aw between the inner peripheral edge 11α and the outer peripheral edge of the through hole 11 alternatively indicates the inclination angle of the inner wall of the insulating layer 1 surrounding the first portion 11a of the through hole 11 (see FIG. 2). Similarly, the width 11bw between the inner peripheral edge 11β and the outer peripheral edge of the through hole 11 alternatively indicates the inclination angle of the inner wall of the insulating layer 1 surrounding the second portion 11b of the through hole 11 (see FIG. 2). The larger the width 11aw, the larger the inclination angle of the inner wall of the insulating layer 1 surrounding the first portion 11a of the through hole 11 (i.e., the inner wall is more inclined from the Z direction). The larger the width 11bw, the larger the inclination angle of the inner wall of the insulating layer 1 surrounding the second portion 11b of the through hole 11 (i.e., the inner wall is more inclined from the Z direction). In the example of FIG. 4, the width 11aw gradually increases in the direction of the arrow AR1, and the width 11bw gradually increases in the direction of the arrow AR2. That is, the inclination angle of the inner wall of the insulating layer 1 surrounding the first portion 11a of the through hole 11 gradually increases (decreases) in the direction of arrow AR1 (arrow AR2), and the inclination angle of the inner wall of the insulating layer 1 surrounding the second portion 11b gradually increases (decreases) in the direction of arrow AR2 (arrow AR1).

[0042] As shown in FIG. 4, in this embodiment, the inclination angle of the inner wall of the insulating layer 1 made of a glass plate exposed in the through hole 11 may gradually change in a direction (circumferential direction) along the outline of the through hole 11 on both the first surface 1a side and the second surface 1b side of the apex of the inner wall. Furthermore, the inclination angle of the inner wall of the insulating layer 1 surrounding the first portion 11a and the inclination angle of the inner wall of the insulating layer 1 surrounding the second portion 11b may gradually increase or decrease in opposite directions along the circumferential direction along the outline of the through hole 11. The inner wall of the insulating layer 1 surrounding the through hole 11 and having a changing inclination angle as shown in FIG. 4 is likely to have the first to third magnitude relationships of the embodiment. It is considered that the third magnitude relationship of the embodiment is particularly likely to be provided.

[0043] FIG. 5 shows another example of the shape of the through hole 11 in this embodiment. Similar to FIG. 2, FIG. 5 shows a longitudinal cross section of the through hole 11 together with its surrounding area. Similar to the through hole 11 in the example of FIG. 2, the through hole 11 shown in FIG. 5 includes a first portion 11a tapering from the first surface 1a of the insulating layer 1 toward the second surface 1b, and a second portion 11b tapering from the second surface 1b toward the first surface 1a. In the example of FIG. 5, the hollow portion of the first portion 11a and the hollow portion of the second portion 11b are not directly connected to each other, but are connected to each other via a cylindrical intermediate portion 11d having a substantially constant width over an arbitrary length in the Z direction.

[0044] In this manner, the first portion 11a and the second portion 11b of the through hole 11 according to this embodiment may be connected via a portion that extends along the Z direction with a substantially constant width. As shown in Fig. 5, two peaks are formed on the inner wall of the insulating layer 1 in the Z direction, which is thought to further disperse stress applied to the insulating layer 1 and further suppress the occurrence of breakage or cracks in the insulating layer 1 made of a glass plate. Note that the through hole 11 having the shape shown in Fig. 5 can be formed, for example, by irradiating a sufficiently powerful laser beam onto the constricted portion of the through hole 11 shown in Fig. 2.

[0045] In the example of FIG. 5, the through-hole conductor 4 does not fill the entire interior of the through hole 11, but has a hollow portion, which is filled with a filler 4a. The filler 4a is made of, for example, epoxy resin, acrylic resin, or epoxy resin containing conductive particles such as silver. A third metal film 3d and a fourth metal film 3e, which may be an electroless-plated film or an electrolytic-plated film of copper, nickel, or the like, are formed on the end face of the filler 4a facing the conductor layer 31 and the end face facing the conductor layer 32, as well as on the second metal film 3c constituting each of these conductor layers. The metal foil 3a and the first to fourth metal films 3b, 3c, 3d, and 3e form the conductor layers 31 and 32, respectively. In the wiring board 100 of the embodiment, the interior of the through hole 11 and the two conductor layers 31 and 32 sandwiching the through hole 11 may have a configuration as shown in the example of FIG. 5.

[0046] FIG. 6 shows an image of a cross section of a through hole 11 in an example of a wiring board according to an embodiment, observed with a scanning electron microscope (SEM). As shown in FIG. 6, the through hole 11 includes a first portion 11a tapering from the first surface 1a of the insulating layer 1 toward the second surface 1b, and a second portion 11b tapering from the second surface 1b toward the first surface 1a. A first inner wall 111 and a second inner wall 112, which face each other across the first portion 11a, have a first angle θ1 and a second angle θ2, respectively, as angles with the Z direction. A third inner wall 113 and a fourth inner wall 114, which face each other across the second portion 11b, have a third angle θ3 and a fourth angle θ4, respectively, as angles with the Z direction. The first angle θ1 to the fourth angle θ4 are different from each other, and the first angle θ1 and the fourth angle θ4 are each greater than both the second angle θ2 and the third angle θ3. The first to fourth angles of the example shown in FIG. 6 have at least the magnitude relationship between the first and second angles of the embodiment.

[0047] Next, a method for manufacturing a wiring board according to one embodiment will be described with reference to Figures 7A to 7I, taking as an example the case where wiring board 100 illustrated in Figures 1 and 2 is manufactured. Hereinafter, the method for manufacturing a wiring board according to this embodiment will also be simply referred to as the "method of this embodiment."

[0048] As shown in FIG. 7A, a glass plate is prepared having a first surface 1a and a second surface 1b opposite to the first surface 1a. The glass plate prepared in the example of FIG. 7A constitutes the insulating layer 1 of the wiring substrate 100 of FIG. 1. Therefore, in FIG. 7A and the subsequent drawings, the glass plate is given the reference number "1" for the insulating layer 1, and in the following description of the method of the embodiment, the glass plate is also referred to as "glass plate 1." The thickness direction of the glass plate 1 is synonymous with the thickness direction of the insulating layer 1 in the example of FIG. 1, and is therefore also referred to as the "Z direction" in the same way as the thickness direction of the insulating layer 1.

[0049] The glass plate 1 may be, for example, a sheet of glass made of soda-lime glass, alkali-free glass, quartz glass, borosilicate glass, or the like. The glass plate 1 may be prepared by a common sheet glass manufacturing method, such as the float glass method. The thickness of the glass plate 1 may be, for example, 0.5 mm or more and 2.5 mm or less to ensure appropriate rigidity in the wiring substrate 100. Warping of the wiring substrate 100 may be suppressed.

[0050] When manufacturing the wiring board 100 of FIG. 1, as shown in FIGS. 7A and 7B, resin 24 is laminated on both sides of a glass plate 1 to form a resin layer 21 covering the first surface 1a of the glass plate 1 and a resin layer 22 covering the second surface 1b of the glass plate 1. In the example of FIG. 7A, the resin 24 is impregnated into a reinforcing material 2a, formed into a sheet in a B-stage state, and laminated on both sides of the glass plate 1. The reinforcing material 2a is, for example, glass fiber or aramid fiber. In other words, the resin 24 and the reinforcing material 2a may be so-called prepregs formed by impregnating a reinforcing material such as glass fiber or aramid fiber with an epoxy resin or the like.

[0051] 7A, a metal foil 3a is further laminated on the sheet-like resin 24. Therefore, as shown in FIG. 7B, a metal foil 3a is laminated on each of the resin layer 21 and the resin layer 22. The metal foil 3a may be made of any metal having suitable conductivity, such as copper foil or nickel foil. The metal foil 3a on the resin layer 21 constitutes part of the conductor layer 31 (see FIG. 7H) to be formed in a later process, and the metal foil 3a on the resin layer 22 constitutes part of the conductor layer 32 (see FIG. 7H) to be formed in a later process.

[0052] The resin 24 and the metal foil 3a laminated on both sides of the glass plate 1 are pressurized and heated at an appropriate pressure and temperature. The resin 24 is softened by the pressure and heat, and the resin 24 is bonded to the glass plate 1 and the metal foil 3a.

[0053] As shown in Fig. 7C, the method for manufacturing a wiring board according to this embodiment includes forming a through hole 11 that penetrates the glass plate 1 in the thickness direction. In the example of Fig. 7C, the through hole 11 is formed so as to penetrate the resin layer 21, the resin layer 22, and the metal foil 3a. The through hole 11 is formed at a location where a through-hole conductor 4 (see Fig. 7H), which will be described later, will be formed.

[0054] Fig. 7D shows an enlarged view of portion VIID of Fig. 7C. As shown in Fig. 7D, in the method of the embodiment, through hole 11 is formed to include a first portion 11a tapering from first surface 1a toward second surface 1b of glass plate 1, and a second portion 11b tapering from second surface 1b toward first surface 1a and communicating with first portion 11a. Furthermore, through hole 11 is formed such that first inner wall 111, second inner wall 112, third inner wall 113, and fourth inner wall 114 have different angles with respect to the Z direction in a cross section passing through through hole 11 along the thickness direction (Z direction) of glass plate 1.

[0055] Here, the first inner wall 111 and the second inner wall 112 are, respectively, one and the other of two inner walls of the glass plate 1 that face each other across the first portion 11a in a cross section passing through the through hole 11 along the Z direction. The third inner wall 113 and the fourth inner wall 114 are, respectively, one and the other of two inner walls of the glass plate 1 that face each other across the second portion 11b in a cross section passing through the through hole 11 along the Z direction. When the through hole 11 is formed in this manner, as described above in the description of the wiring board of the embodiment, it is considered that excessive local stress is unlikely to be applied to the inner wall of the insulating layer made of the glass plate 1 that surrounds the through hole 11 in the manufactured wiring board. Therefore, it is considered that a wiring board with less occurrence of breakage or cracks can be manufactured. The cross section passing through the through hole 11 along the thickness direction (Z direction) of the glass plate 1 is also simply referred to as a "longitudinal cross section," as in the description of the wiring board of the embodiment.

[0056] Furthermore, in the method of the embodiment, the through hole 11 may be formed so that the first angle θ1 is greater than the second angle θ2 and the third angle θ3, and the fourth angle θ4 is greater than the second angle θ2 and the third angle θ3. Here, the first angle θ1 is the angle between the first inner wall 111 of two inner walls (the first inner wall 111 and the second inner wall 112) of the glass plate 1 that face each other across the first portion 11a in the vertical cross section, and the Z direction, and the second angle θ2 is the angle between the second inner wall 112 and the Z direction. The third angle θ3 is the angle between the third inner wall 113 of two inner walls (the third inner wall 113 and the fourth inner wall 114) that face each other across the second portion 11b in the vertical cross section, and the Z direction, and the fourth angle θ4 is the angle between the fourth inner wall 114 and the Z direction. When through holes 11 are formed in this manner, as described above in the description of the wiring board of the embodiment, there is unlikely to be a significant difference between the opening area of ​​through holes 11 on first surface 1a of glass plate 1 and the opening area of ​​through holes 11 on second surface 1b in the manufactured wiring board, which may facilitate easier pattern design of the wiring board and facilitate miniaturization of the wiring board.

[0057] 7D is formed by so-called trepanning using a laser beam. Trepanning can form a small-diameter hole that does not receive a large mechanical or thermal shock during drilling, while also forming a large-diameter through hole 11. That is, it may be possible to form a large-diameter through hole 11 while suppressing cracking or chipping in the glass plate 1.

[0058] Furthermore, when drilling holes with a laser beam, the amount of energy transmitted from the laser beam to the glass plate 1 tends to decrease as the laser beam travels from each surface of the glass plate 1 toward the center of the glass plate 1, making it easy to form a tapered hole with a small diameter. Therefore, it may be easy to form a through hole 11 with a shape such as that shown in Fig. 7D. Examples of lasers that can be used to form the through hole 11 include a carbon dioxide laser and a UV-YAG laser, but the laser that can be used to form the through hole 11 is not limited to these.

[0059] FIG. 7E schematically shows an example of forming a through hole 11 by trepanning, in which a laser beam is irradiated in this manner. Laser beam L, for example, a carbon dioxide laser beam, is irradiated toward each of the first surface 1a and the second surface 1b of the glass plate 1 along the outline of the through hole 11 to be formed. Preferably, pulsed laser beam L is irradiated. By irradiating the laser beam L, an opening 110 having a diameter smaller than the diameter of the through hole 11 to be formed is formed in each of the first surface 1a and the second surface 1b. The opening 110 may be a hole that penetrates the glass plate 1, or may be a recess with a bottom.

[0060] The irradiation position of the laser light L irradiated onto the first surface 1a is successively moved a predetermined distance in the direction of arrow AR1 in accordance with the irradiation of the laser light L. The irradiation position of the laser light L irradiated onto the second surface 1b is successively moved a predetermined distance in the direction of arrow AR2 in accordance with the irradiation of the laser light L. The predetermined distance by which the irradiation position of the laser light L is moved can be set arbitrarily, but the irradiation position is preferably moved a distance in each movement such that the openings 110 formed before and after the movement partially overlap.

[0061] The irradiation position of the laser light L may be moved each time pulsed laser light L is irradiated, or may be moved after a predetermined number of irradiations of laser light L. That is, each irradiation position may be irradiated with laser light L only once, or each irradiation position may be irradiated with laser light L multiple times in succession. However, if the irradiation position is moved after each laser light irradiation, heat from the laser light is less likely to accumulate, which may reduce the thermal shock to the glass plate 1 and thereby prevent cracks or chips from occurring in the glass plate.

[0062] By repeatedly irradiating the glass plate 1 with the laser beam L while changing the irradiation position along the contour of the through hole 11 to be formed, a plurality of openings 110 are formed on each of the first surface 1a and the second surface 1b, with adjacent openings 110 partially overlapping each other. As a result, a through hole 11 consisting of a plurality of openings 110 is formed on the first surface 1a and the second surface 1b. As described above in the description of the wiring board of one embodiment, the processability by the laser beam L can be changed by changing the distance by which the irradiation position is moved to change the degree of overlap with the already formed openings 110. By doing so, the inclination angle of the inner wall of the glass plate 1, which appears as the openings 110 are formed, can be changed as the formation of the openings 110 progresses. Furthermore, by gradually changing the power and spot diameter of the laser beam L as the formation of the openings 110 progresses, the inclination angle of the inner wall of the glass plate 1 can be gradually changed as the formation of the openings 110 progresses.

[0063] The irradiation position of the laser light L is moved, for example, one full circle, along the contour of the through hole 11 to be formed as the laser light L is irradiated. Alternatively, the irradiation position of the laser light L may be moved sequentially along the contour of the through hole 11 and made to circle multiple times until the opening 110 on the first surface 1a side and the opening 110 on the second surface 1b side communicate with each other, or until a through hole 11 having a desired shape is obtained. During this time, the irradiation of the laser light may be continued in accordance with the movement of the irradiation position.

[0064] 7E, forming through hole 11 in the method of the embodiment includes forming a plurality of openings 110, each having a diameter smaller than that of through hole 11, on each of first surface 1a and second surface 1b of glass plate 1, while shifting positions of the openings 110 so as to partially overlap one another along the outline of through hole 11 to be formed. The plurality of openings 110 may be formed in sequence on first surface 1a in a first direction (e.g., the direction of arrow AR1) along the outline of through hole 11, and may be formed in sequence on second surface 1b in a second direction (e.g., the direction of arrow AR2) opposite to the first direction and along the outline of through hole 11.

[0065] Furthermore, forming the plurality of openings 110 in the method of the embodiment may include irradiating each of the first surface 1a and the second surface 1b of the glass plate 1 with carbon dioxide laser beam L while moving the irradiation position along the outline of the through hole 11 to be formed. Then, irradiating the carbon dioxide laser beam L may include moving the irradiation position of the carbon dioxide laser beam on the first surface 1a of the glass plate 1 in a first direction (for example, the direction of arrow AR1) along the outline of the through hole 11 to be formed, and moving the irradiation position of the carbon dioxide laser beam L on the second surface 1b of the glass plate 1 in a second direction (for example, the direction of arrow AR2) that is opposite to the first direction and along the outline of the through hole 11 to be formed.

[0066] Furthermore, the irradiation of the carbon dioxide laser beam L may include moving the irradiation position of the carbon dioxide laser beam L so that the beam makes a plurality of revolutions along the contour of the through-hole 11 to be formed. The irradiation position of the carbon dioxide laser beam L may be moved for each irradiation of the carbon dioxide laser beam L.

[0067] The irradiation of the first surface 1a with the laser beam L and the irradiation of the second surface 1b with the laser beam L may be performed simultaneously or sequentially. When the irradiation of the first surface 1a with the laser beam L and the irradiation of the second surface 1b with the laser beam L are performed sequentially, the glass plate 1 may be inverted after the irradiation of one surface with the laser beam L and before the irradiation of the other surface with the laser beam L.

[0068] The diameter of the opening 110 formed by irradiation with each laser beam L can have any length. For example, as in the example of Fig. 7E, when the diameter of the opening 110 is approximately half or more the diameter of the through hole 11 to be formed, by sequentially forming a plurality of openings 110 in the area where the through hole 11 is to be formed so that the outer edge of each opening 110 follows the outline of the through hole 11, a plurality of openings 110 occupying the entire area can be formed.

[0069] 7F and 7G show examples of the movement path of the laser beam irradiation position for forming multiple openings 110 when the diameter of each opening 110 is less than half the diameter of the through hole 11 to be formed. As shown in FIG. 7F , even when the diameter of each opening 110 is less than half the diameter of the through hole 11, the laser beam irradiation position only needs to circle the area where the through hole 11 is to be formed, as indicated by arrow AR3. Even in this case, multiple openings 110 are formed along the outer edge of the area where the through hole 11 is to be formed. When holes penetrating the glass plate 1 are formed as the individual openings 110, as in the example of FIG. 7F , the central portion of the through hole 11 formation area where no openings 110 are formed is separated from its surroundings and can be removed. When bottomed recesses are formed as the individual openings 110, the central portion of the through hole 11 formation area is separated from its surroundings by the openings 110 formed on both sides of the glass plate 1 communicating with each other, and can be removed.

[0070] 7G, the irradiation position of the laser light may be moved in a spiral path as indicated by arrow AR4 so that the laser light is irradiated onto the entire region where through hole 11 is to be formed. Even if the irradiation position of the laser light is shifted from the intended position, it is thought that unintended, unremoved portions are unlikely to remain on glass plate 1. In this case, the irradiation position of the laser light may be moved from the outside to the inside of the region where through hole 11 is to be formed, or from the inside to the outside.

[0071] When forming the plurality of openings 110 while moving the irradiation position along the contour of the through hole 11 to be formed, the number of irradiations of the carbon dioxide laser light L (see FIG. 7E) required for one revolution (one circuit) can be appropriately determined depending on the diameter of the through hole 11 and the diameters of the plurality of openings 110. FIG. 7E shows the number of irradiations required for one revolution as 8, FIG. 7F as 12, and FIG. 7G as 15, but these examples are not limiting as long as the final shape of the through hole 11 in plan view is substantially circular. If the number of irradiations is too small, it is difficult to obtain a shape of the through hole 11 that conforms to the first to third size relationships of the above-described embodiment. If the number of irradiations is large, the through hole 11 approaches a circular shape, which is preferable. However, from the viewpoints of quality and productivity, 3 to 24 irradiations are desirable.

[0072] As shown in Fig. 7H, the method of this embodiment further includes forming two conductor layers (conductor layer 31 and conductor layer 32) that sandwich the glass plate 1 in the thickness direction of the glass plate 1, and forming a conductor that connects the two conductor layers together. In the example of Fig. 7H, the two conductor layers that sandwich the glass plate 1 are conductor layer 31 formed on resin layer 21 on the first surface 1a, and conductor layer 32 formed on resin layer 22 on the second surface 1b. Then, a through-hole conductor 4 is formed as a conductor that connects conductor layer 31 and conductor layer 32. The through-hole conductor 4 passes through the inside of through hole 11 and electrically and mechanically connects conductor layer 31 and conductor layer 32.

[0073] Although the conductor layer 31 and the conductor layer 32 are shown in FIG. 7H as including only one layer, they may be formed to have a laminated structure consisting of two or more layers including the metal foil 3a shown in FIG. 7C. The conductor layer 31 and the conductor layer 32 may be formed by any method, such as a subtractive method or a semi-additive method. For example, when the conductor layer 31 and the conductor layer 32 are formed by a semi-additive method, a metal film such as the first metal film 3b illustrated in FIG. 2 is formed on the entire surface of the metal foil 3a (see FIG. 7C) and on the entire inner wall surface of the glass plate 1 exposed in the through hole 11. This metal film is formed by, for example, electroless plating or sputtering using any metal having suitable conductivity, such as copper or nickel.

[0074] Furthermore, a resist such as a dry film is laminated on this metal film, and openings are formed in the desired pattern, including through-holes, by exposure and development. Then, by pattern plating, including electrolytic plating, using this metal film as a power supply layer, an electrolytic plated film made of a metal such as copper or nickel is formed, like the second metal film 3c illustrated in FIG. 2 . As a result, a through-hole conductor 4 made of a conductor such as a metal film is formed inside the through-hole 11. The resist is then peeled off, and the portions of the metal film formed on the entire surface of the metal foil 3a (see FIG. 7C ) that are not covered by the electrolytic plated film are removed by quick etching or the like, and the exposed portions of the metal foil 3a are then removed. As a result, conductor layers 31 and 32, each of which has a three-layer structure and includes a predetermined conductor pattern, are formed.

[0075] 1, when the wiring board 100 of FIG. 1 is manufactured, a buildup portion 10 is formed on the conductor layer 31 and the resin layer 21. A buildup portion 10 is also formed on the conductor layer 32 and the resin layer 22. Each buildup portion 10 is formed by repeatedly forming an insulating layer 23 and a conductor layer 33 on the conductor layer 31 and the conductor layer 32, respectively.

[0076] The insulating layer 23 is formed, for example, by laminating insulating resin formed into a film shape on each of the conductor layers 31 and 32, and then applying heat and pressure. Through holes 41a for forming via conductors 41 are formed in each insulating layer 23 by, for example, irradiation with carbon dioxide laser light. Examples of the insulating resin constituting the insulating layer 23 include thermosetting resins such as epoxy resin, BT resin, and phenolic resin, and thermoplastic resins such as fluororesin, LCP, PTFE, PE, and MPI. The insulating layer 23 may be a resin layer containing a reinforcing material (not shown) made of glass fiber, aramid fiber, or the like, and / or a filler (not shown) made of particles of silicon dioxide, alumina, or the like.

[0077] The conductor layer 33 and the via conductor 41 may be formed using any metal such as copper or nickel, similar to the conductor layer 31 and the through-hole conductor 4. The conductor layer 33 and the via conductor 41 may have a multilayer structure including, for example, an electroless plated film and an electrolytic plated film, similar to the conductor layer 31 and the through-hole conductor 4. The conductor layer 33 and the via conductor 41 may be formed by any method, such as a semi-additive method, a full-additive method, or a subtractive method.

[0078] Furthermore, a solder resist 5 is formed on each build-up portion 10. The solder resist 5 can be formed, for example, by supplying a photosensitive epoxy resin or polyimide resin by spraying, laminating, printing, or the like. An opening 5a that exposes a portion of the outermost conductor layer 33 is formed in the solder resist 5, for example, by exposure using an exposure mask (not shown) with appropriate openings, and development. Through the above steps, the wiring board 100 illustrated in FIG. 1 is obtained.

[0079] In the case of forming the through-hole conductor 4 shown in FIG. 5, after the first metal film 3b is formed, a second metal film 3c is formed by panel plating to a thickness that does not fill the entire through hole 11. A suitable resin, such as epoxy resin, is injected into the unfilled portion of the through hole 11 inside the second metal film 3c and hardened to form a filler 4a. The inside of the through hole 11 is then filled with the filler 4a. Furthermore, a third metal film 3d is formed on the second metal film 3c and the filler 4a by, for example, electroless panel plating or sputtering, and a fourth metal film 3e is formed by electrolytic plating using the third metal film 3d as a power supply layer. Subsequently, conductor layers 31 and 32 having a predetermined conductor pattern are obtained by etching using an etching resist (not shown) with appropriate openings.

[0080] The wiring board of the embodiment is not limited to those having the structure illustrated in each drawing and the structure, shape, and material illustrated in this specification. For example, the wiring board of the embodiment may have a resin body embedded in the inner wall surface of the insulating layer 1 (glass plate 1) surrounding the through hole 11, in addition to the resin layers 21 and 22, and the through-hole conductor 4 formed to penetrate the resin body. Such a resin body may be formed by a portion of the resin forming the resin layer 21 or the resin layer 22 flowing into the through hole 11. Such a resin body may improve adhesion between the through-hole conductor 4 and the insulating layer 1 made of a glass plate. Furthermore, for example, the wiring board of the embodiment does not need to include the resin layers 21 and 22. That is, the conductor layers 31 and 32 and the through-hole conductor 4 may be formed directly on each surface of the glass plate 1 or on the inner wall surface surrounding the through hole 11. Furthermore, the through-hole conductor 4 does not necessarily have to fill the through hole 11, but may be formed at least on the side wall of the through hole 11, as in the example of FIG. 5. Furthermore, each of the conductor layers 31 and 32 does not necessarily have to include the metal foil 3a. Furthermore, the wiring board of the embodiment does not necessarily have to include the build-up portion 10 of the example of FIG.

[0081] The method for manufacturing a wiring board according to the embodiment is not limited to the method described with reference to the drawings. For example, the irradiation position of the laser light L on the first surface 1a and the irradiation position of the laser light L on the second surface 1b shown in FIG. 7E may be moved in the same direction in a plan view of the glass plate 1 observed from either the first surface 1a or the second surface 1b. The method for manufacturing a wiring board according to the embodiment may include any additional process in addition to the above-described processes, or some of the above-described processes may be omitted. [Explanation of symbols]

[0082] 100 wiring board 1. Insulating layer (glass plate) 1a 1st page 1b 2nd side 10 Build-up section 11 Through hole 11a Part 1 11aw, 11bw Width of the inner wall of the glass plate (slope of the inner wall) 11b Part 2 110, 110a, 110b aperture 111~114 1st~4th inner walls 21, 22 Resin layer 31~33 Conductor layers 4 Through-hole conductors (conductors) θ1~θ4 1st to 4th angles Z: Thickness direction of wiring board and insulating layer

Claims

1. a glass plate having a first surface and a second surface opposite to the first surface, and having a through hole penetrating between the first surface and the second surface; two conductor layers sandwiching the glass plate in a thickness direction of the glass plate; a conductor that passes through the through hole and connects the two conductor layers to each other; A wiring board comprising: the through hole includes a first portion tapering from the first surface toward the second surface, and a second portion tapering from the second surface toward the first surface and communicating with the first portion, one of two inner walls of the glass plate that face each other across the first portion in a cross section passing through the through hole along the thickness direction has a first angle with respect to the thickness direction, the other of the two inner walls has a second angle with the thickness direction; one of two inner walls of the glass plate facing each other across the second portion in the cross section has a third angle with respect to the thickness direction, the other of the two inner walls facing each other across the second portion has a fourth angle with respect to the thickness direction, The first angle, the second angle, the third angle, and the fourth angle are different from each other.

2. 2. The wiring board according to claim 1, wherein the first angle and the fourth angle are each greater than both the second angle and the third angle.

3. 3. The wiring board according to claim 2, wherein the first angle is larger than the fourth angle, and the second angle is larger than the third angle.

4. 2. A wiring board according to claim 1, wherein the inclination angle of the inner wall of the glass plate exposed in the through hole relative to the thickness direction gradually changes in the circumferential direction along the contour of the through hole on the first surface and the second surface.

5. 5. The wiring board according to claim 4, wherein the inclination angle of the first portion and the inclination angle of the second portion change so as to gradually increase in opposite directions along the circumferential direction.

6. 2. A wiring board according to claim 1, wherein one or the other of the two inner walls that face each other across the first portion in the cross section contacts one or the other of the two inner walls that face each other across the second portion at different positions in the thickness direction.

7. 2. The wiring board according to claim 1, further comprising a resin layer formed between one of the first surface and the second surface and one of the two conductor layers.

8. 8. The wiring board according to claim 7, wherein the resin layer includes a reinforcing material that increases the rigidity of the resin layer.

9. 2. The wiring board according to claim 1, further comprising build-up portions each formed on one of said two conductor layers and each made up of an insulating layer and a conductor layer.

10. forming a through hole in a glass plate having a first surface and a second surface opposite to the first surface, the through hole including a first portion tapering from the first surface toward the second surface and a second portion tapering from the second surface toward the first surface and communicating with the first portion, the through hole penetrating the glass plate in a thickness direction of the glass plate; forming two conductor layers sandwiching the glass plate in the thickness direction; forming a conductor that passes through the through hole and connects the two conductor layers; A method for manufacturing a wiring substrate, comprising: forming the through hole includes forming a plurality of openings, each having a diameter smaller than a diameter of the through hole, in the first surface and the second surface while shifting the positions of the openings so as to partially overlap each other along a contour of the through hole to be formed; The through hole is formed so that one and the other of two inner walls of the glass plate that face each other across the first portion in a cross section passing through the through hole along the thickness direction, and one and the other of two inner walls of the glass plate that face each other across the second portion in the cross section, have different angles from each other with respect to the thickness direction in the cross section.

11. 11. The method for manufacturing a wiring board according to claim 10, wherein the through hole is a first angle that is an angle between one of the two inner walls that face each other across the first portion in the cross section and the thickness direction is larger than a second angle that is an angle between the other of the two inner walls that face each other across the first portion in the cross section and the thickness direction, and a third angle that is an angle between one of the two inner walls that face each other across the second portion in the cross section and the thickness direction; and a fourth angle between the other of the two inner walls facing each other across the second portion and the thickness direction is larger than the second angle and the third angle, is formed.

12. 11. A method for manufacturing a wiring board according to claim 10, wherein the plurality of openings are formed in sequence on the first surface in a first direction along the contour, and are formed in sequence on the second surface in a second direction along the contour that is opposite to the first direction.

13. A method for manufacturing a wiring board according to claim 10, wherein forming the plurality of openings includes irradiating each of the first surface and the second surface with carbon dioxide laser light while moving the irradiation position along the contour.

14. 14. The method for manufacturing a wiring board according to claim 13, wherein the carbon dioxide laser light irradiation comprises: moving an irradiation position of the carbon dioxide laser light on the first surface in a first direction along the contour; moving the irradiation position of the carbon dioxide laser light on the second surface in a second direction along the contour and opposite to the first direction; Contains:

15. 14. The method for manufacturing a wiring board according to claim 13, wherein the step of irradiating the carbon dioxide laser light includes moving the irradiation position of the carbon dioxide laser light so as to make a plurality of revolutions along the contour.

16. 14. A method for manufacturing a wiring board according to claim 13, wherein the position to be irradiated with the carbon dioxide laser light is moved for each irradiation of the carbon dioxide laser light.

Images