Printed wiring board and build-up printed wiring board

Abstract

This printed wiring board comprises an insulating plate, a first metal layer, a resin, a second metal layer, and a third metal layer. The insulating plate has a first surface, a second surface, and a through hole. The first metal layer includes a through-hole conductor, a first wiring conductor, and a second wiring conductor. The resin is positioned inside the through-hole conductor of the through-hole, and has a first end positioned on the first surface side and a second end positioned on the second surface side. The second metal layer covers the first wiring conductor and the first end of the resin. The third metal layer covers the second wiring conductor and the second end of the resin. At least one of the second metal layer and the third metal layer has a first portion located in the through-hole and between the through-hole conductor and the resin.

Description

Printed wiring boards and build-up printed wiring boards

[0001] The present disclosure relates to printed wiring boards and build-up printed wiring boards.

[0002] In a printed wiring board, a technique is known in which the inside of a through-hole conductor is filled with resin and then a cap plating is formed on the through-hole conductor and the filled resin (see, for example, Patent Document 1).

[0003] Japanese Patent Application Publication No. 9-8424

[0004] In the printed wiring boards described above, peeling easily occurs between the metal layer and the cover plating, and the connection reliability is insufficient.

[0005] An object of the present disclosure is to provide a printed wiring board and a build-up printed wiring board with higher connection reliability.

[0006] One aspect of the printed wiring board according to the present disclosure is: (1) an insulating plate having a first surface, a second surface located opposite the first surface, and a through hole having a first opening in the first surface and a second opening in the second surface; a first metal layer located as a single unit across the first surface, an inner wall surface of the through hole, and the second surface, and including a through hole conductor located on the inner wall surface of the through hole, a first wiring conductor located on the first surface, and a second wiring conductor located on the second surface; a resin located in the through hole more inward than the through hole conductor, and having a first end located on the first surface side in a thickness direction of the insulating plate and a second end located on the second surface side; a second metal layer covering the first wiring conductor and the first end of the resin; and a third metal layer covering the second ends of the second wiring conductor and the resin, wherein at least one of the second metal layer and the third metal layer has a first portion located within the through hole between the through hole conductor and the resin.

[0007] (2) In the printed wiring board of (1) above, in a cross-sectional view in the thickness direction of the insulating plate, the dimension of the first portion in the direction along the first surface decreases from the first surface or the second surface toward the center position of the insulating plate in the thickness direction of the insulating plate.

[0008] (3) The printed wiring board of (1) or (2) above further has at least one of a first metal foil positioned between the first surface and the first wiring conductor and a second metal foil positioned between the second surface and the second wiring conductor.

[0009] (4) In any of the printed wiring boards (1) to (3) above, the second metal layer and the third metal layer each have the first portion, the resin has a first diameter at a center position of the insulating plate in the thickness direction of the insulating plate, the first diameter being equal to the inner diameter of the through-hole conductor at the center position, the resin has a second diameter on the first opening side of the center position that is the smallest diameter of the resin on the first opening side of the center position and smaller than the first diameter, and the resin has a third diameter on the second opening side of the center position that is the smallest diameter of the resin on the second opening side of the center position and smaller than the first diameter.

[0010] (5) In the printed wiring board of (4) above, the diameter of the resin has a portion where it gradually decreases from the first diameter to the second diameter in the thickness direction of the insulating plate, and has a portion where it gradually decreases from the first diameter to the third diameter in the thickness direction of the insulating plate.

[0011] (6) In the printed wiring board of (4) or (5) above, the resin has a curved shape between the position having the first diameter and the position having the second diameter in a cross-sectional view in the thickness direction of the insulating plate, and also has a curved shape between the position having the first diameter and the position having the third diameter.

[0012] (7) In any of the printed wiring boards (4) to (6) above, the distance from the first surface to the first end of the resin in the thickness direction of the insulating plate is greater than the distance from the first surface to the surface of the first wiring conductor, and the distance from the second surface to the second end of the resin in the thickness direction of the insulating plate is greater than the distance from the second surface to the surface of the second wiring conductor.

[0013] (8) In any of the printed wiring boards (4) to (7) above, a fourth diameter of the resin at the first end is larger than the second diameter, the diameter of the resin gradually decreases from the fourth diameter to the second diameter in the thickness direction of the insulating plate, a fifth diameter of the resin at the second end is larger than the third diameter, and the diameter of the resin gradually decreases from the fifth diameter to the third diameter in the thickness direction of the insulating plate.

[0014] (9) A build-up printed wiring board has: a printed wiring board according to any one of (1) to (8); and a build-up structure in which insulating resin layers and conductor layers are alternately positioned on at least one of the first surface and the second surface of the printed wiring board.

[0015] According to the present disclosure, the connection reliability of printed wiring boards and build-up printed wiring boards can be further improved.

[0016] 1 is a cross-sectional view of a printed wiring board; 2 is an enlarged cross-sectional view of a resin; 3 is a cross-sectional view of a printed wiring board; 4 is a cross-sectional view illustrating a method for manufacturing a printed wiring board; 5 is a cross-sectional view illustrating a method for manufacturing a printed wiring board; 6 is a cross-sectional view illustrating a method for manufacturing a printed wiring board; 7 is a cross-sectional view illustrating a method for manufacturing a printed wiring board; 8 is a cross-sectional view illustrating a method for manufacturing a printed wiring board; 9 is a cross-sectional view illustrating a method for manufacturing a printed wiring board; 10 is an enlarged cross-sectional view illustrating a method for manufacturing a printed wiring board; 11 is a cross-sectional view of a build-up printed wiring board;

[0017] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. However, for the sake of convenience, the drawings referred to below show only the main components necessary for explaining the embodiments in a simplified form. Therefore, the printed wiring board and build-up printed wiring board of the present disclosure may include any components not shown in the drawings. Furthermore, the dimensions of the components in the drawings do not faithfully represent the dimensions, dimensional ratios, etc. of the actual components.

[0018] 1 is a cross-sectional view of an embodiment of a printed wiring board 1 according to the present disclosure, taken along a line passing through the central axis of a through hole 2c in the thickness direction of an insulating board 2. The printed wiring board 1 of this embodiment includes an insulating board 2, a first metal layer 5, a resin 6, a second metal layer 7, and a third metal layer 8.

[0019] The insulating plate 2 has a first surface 2a, a second surface 2b, and a through hole 2c. The second surface 2b is located on the opposite side to the first surface 2a of the insulating plate 2. The through hole 2c penetrates the insulating plate 2 in the thickness direction, and has a first opening 2d in the first surface 2a and a second opening 2e in the second surface 2b.

[0020] The material of the insulating plate 2 is, for example, an organic resin, but is not particularly limited thereto. Examples of organic resins include epoxy resin, bismaleimide-triazine resin, polyimide resin, polyphenylene ether (PPE) resin, polyphenylene oxide (PPO) resin, phenolic resin, polytetrafluoroethylene (PTFE) resin, silicon resin, polybutadiene resin, polyester resin, melamine resin, urea resin, polyphenylene sulfide (PPS) resin, and cyanate ester resin. Two or more of these organic resins may be mixed and used. The material of the insulating plate 2 is not limited to these, and may be other insulating materials. The insulating plate 2 may include a reinforcing material such as glass cloth. The insulating plate 2 may be blended with inorganic fillers (inorganic particles) such as aluminum hydroxide, silica, or barium sulfate, or organic fillers such as phenolic resin or methacrylic resin.

[0021] The shape of the through-hole 2c is, for example, a circular cylindrical shape in a plan view seen from above the first surface 2a, but is not particularly limited thereto. Furthermore, the shape of the through-hole 2c may or may not be uniform in the thickness direction of the insulating plate 2. Therefore, the diameter of the first opening 2d and the diameter of the second opening 2e may be the same or different. The diameters of the first opening 2d and the second opening 2e are, for example, 0.25 to 0.40 mm when converted into the diameter of a circle with the same area, but are not particularly limited thereto.

[0022] The first metal layer 5 is located as a single piece across the first surface 2a, the inner wall surface of the through hole 2c, and the second surface 2b. The first metal layer 5 includes a through hole conductor 5a, a first wiring conductor 5b, and a second wiring conductor 5c. The through hole conductor 5a is located on the inner wall surface of the through hole 2c. The first wiring conductor 5b is located on the first surface 2a. The second wiring conductor 5c is located on the second surface 2b. The material of the first metal layer 5 is, for example, copper, but is not particularly limited. The thickness of the first metal layer 5 is, for example, 10 to 30 μm, but is not particularly limited.

[0023] The resin 6 is located inside the through-hole 2c (closer to the central axis of the through-hole 2c) than the through-hole conductor 5a. The resin 6 has a first end 6a located on the first surface 2a side and a second end 6b located on the second surface 2b side in the thickness direction of the insulating plate 2. The resin 6 functions as a filler for the through-hole 2c. The type of resin 6 is, for example, an organic resin such as an epoxy resin, but is not particularly limited.

[0024] The second metal layer 7 covers the first wiring conductor 5b and the first end 6a of the resin 6. The third metal layer 8 covers the second wiring conductor 5c and the second end 6b of the resin 6. In this case, the second metal layer 7 and the third metal layer 8 may cover a portion of the through-hole conductor 5a. The second metal layer 7 and the third metal layer 8 function as cap plating for the through-hole 2c. The material of the second metal layer 7 and the third metal layer 8 is, for example, copper, but is not particularly limited. The thickness of the second metal layer 7 and the third metal layer 8 in the region excluding the through-hole 2c is, for example, several μm to 10 μm, but is not particularly limited.

[0025] At least one of the second metal layer 7 and the third metal layer 8 has a first portion 9 located in the through-hole 2c between the through-hole conductor 5a and the resin 6.

[0026] Generally, the coefficient of thermal expansion of the filling resin is higher than the coefficient of thermal expansion of the metal conductors corresponding to the first metal layer 5, the second metal layer 7, and the third metal layer 8. Therefore, generally, when a printed wiring board having a metal conductor, a filling resin, and a cap plating is heated, the cap plating is pushed up by the filling resin and is subjected to stress in a direction that causes it to peel off from the metal conductor corresponding to the first metal layer 5. Furthermore, the filling resin near the opening of the through hole may expand outward of the through hole (away from the central axis of the through hole) due to an increase in temperature, and may try to enter between the wiring conductors corresponding to the first wiring conductor 5b and the second wiring conductor 5c and the cap plating. Due to these effects, conventional printed wiring boards are prone to peeling between the wiring conductors and the cap plating, resulting in insufficient connection reliability.

[0027] Furthermore, the stress applied to the lid plating when the printed wiring board is heated may exceed the yield stress of the lid plating. If the stress applied to the lid plating exceeds the yield stress of the lid plating, the lid plating will no longer follow the contraction of the filled resin even when the printed wiring board is cooled, and peeling may occur between the metal conductor corresponding to the first metal layer 5 and the lid plating. Furthermore, even if the stress applied to the lid plating does not exceed the yield stress of the lid plating, repeated application of stress to the lid plating may cause metal fatigue and cracks in the lid plating. For these reasons, conventional printed wiring boards have not had sufficient connection reliability.

[0028] As described above, in printed wiring board 1 of the present disclosure, at least one of second metal layer 7 and third metal layer 8 has first portion 9 located within through hole 2c between through-hole conductor 5a and resin 6. First portion 9 acts to suppress expansion of resin 6 near first opening 2d and / or near second opening 2e toward the outside of through hole 2c (direction away from the central axis of through hole 2c). Due to this action of first portion 9, printed wiring board 1 of the present disclosure reduces peeling between through-hole conductor 5a and cover plating (second metal layer 7 and / or third metal layer 8), resulting in high connection reliability.

[0029] 1 , both the second metal layer 7 and the third metal layer 8 may have the first portion 9. This reduces peeling between the through-hole conductor 5 a and the second metal layer 7 and peeling between the through-hole conductor 5 a and the third metal layer 8, further improving connection reliability.

[0030] In the cross-sectional view, the dimension of the first portion 9 in the direction along the first surface 2a may decrease from the first surface 2a or the second surface 2b toward a center position O of the insulating plate 2 in the thickness direction of the insulating plate 2. This allows the stress applied to the second metal layer 7 and / or the third metal layer 8, when the resin 6 expands, to be dispersed from the direction from the center position O toward the first surface 2a and / or the second surface 2b to a direction pressing against the through-hole conductor 5a (a direction inclined toward the central axis of the through-hole 2c). This further reduces peeling of the cover plating (the second metal layer 7 and / or the third metal layer 8).

[0031] 1 , in a cross-sectional view in the thickness direction of the insulating plate 2, the dimension of the first portion 9 of the second metal layer 7 in the direction along the first surface 2a may decrease from the first surface 2a toward the center position O of the insulating plate 2 in the thickness direction of the insulating plate 2, and the dimension of the first portion 9 of the third metal layer 8 in the direction along the first surface 2a may decrease from the second surface 2b toward the center position O of the insulating plate 2 in the thickness direction of the insulating plate 2. This reduces both peeling between the through-hole conductor 5a and the second metal layer 7 and peeling between the through-hole conductor 5a and the third metal layer 8, further improving connection reliability.

[0032] The printed wiring board 1 may have a seed layer between the first surface 2a and the first wiring conductor 5b and / or between the second surface 2b and the second wiring conductor 5c. The seed layer may be, for example, a metal foil, electroless plating, or the like. The seed layer can form the first wiring conductor 5b on the first surface 2a of the insulating board 2 and / or the second wiring conductor 5c on the second surface 2b of the insulating board 2. In particular, when the seed layer is a metal foil, adhesion between the insulating board 2 and the first wiring conductor 5b and / or the second wiring conductor 5c is further improved. Therefore, the printed wiring board 1 may have at least one of a first metal foil 3 located between the first surface 2a and the first wiring conductor 5b and a second metal foil 4 located between the second surface 2b and the second wiring conductor 5c.

[0033] 1, the printed wiring board 1 may have both the first metal foil 3 and the second metal foil 4. This further improves the adhesion between the insulating plate 2 and the first wiring conductor 5b and the second wiring conductor 5c, thereby further improving the connection reliability.

[0034] The first metal foil 3 and the second metal foil 4 are, for example, copper foil, but are not particularly limited thereto. The thickness of each of the first metal foil 3 and the second metal foil 4 is, for example, 2 to 18 μm, but are not particularly limited thereto. The thickness of the first metal foil 3 and the second metal foil 4 does not have to be the same.

[0035] As described above, the resin 6 is located inside the through-hole 2c relative to the through-hole conductor 5a, and has a first end 6a located on the first surface 2a side and a second end 6b located on the second surface 2b side in the thickness direction of the insulating plate 2. The resin 6 may have any of the shapes exemplified below, but is not particularly limited thereto.

[0036] FIG. 2 is an enlarged cross-sectional view of the resin 6 included in the printed wiring board 1 shown in FIG.

[0037] The resin 6 may have a first diameter r1 at a center position O of the insulating plate 2 in the thickness direction of the insulating plate 2. The first diameter r1 is equal to the inner diameter of the through-hole conductor 5a at the center position O of the insulating plate 2. The resin 6 may have a second diameter r2 on a side S1 of the insulating plate 2 closer to the first opening 2d than the center position O. The second diameter r2 is the minimum diameter of the resin 6 on the side S1 of the insulating plate 2 closer to the first opening 2d than the center position O, and is smaller than the first diameter r1. The resin 6 may have a third diameter r3 on a side S2 of the insulating plate 2 closer to the second opening 2e than the center position O. The third diameter r3 is the minimum diameter of the resin 6 on the side S2 of the insulating plate 2 closer to the second opening 2e than the center position O, and is smaller than the first diameter r1. By having the first diameter r1, the second diameter r2, and the third diameter r3 in the resin 6 at the above-mentioned positions, the second metal layer 7 or the third metal layer 8 including the first portion 9 penetrates into the resin 6 (the side of the central axis of the through-hole 2c), reducing expansion of the resin 6 in the thickness direction of the insulating plate 2. The second diameter r2 and the third diameter r3 may be the same or different. The centers of the second diameter r2 and the third diameter r3 may be offset from the central axis including the center point of the first diameter r1.

[0038] 2, the diameter of the resin 6 may have a portion where it gradually decreases from the first diameter r1 to the second diameter r2, or may have a portion where it gradually decreases from the first diameter r1 to the third diameter r3 in the thickness direction of the insulating plate 2. This allows the printed wiring board 1 to distribute the direction of the stress that the first portion 9 receives from the resin 6.

[0039] 2, the resin 6 may have a curved shape between the position having the first radius r1 and the position having the second radius r2, or may have a curved shape between the position having the first radius r1 and the position having the third radius r3, in a cross-sectional view in the thickness direction of the insulating plate 2. This allows the direction of the stress that the first portion 9 receives from the resin 6 to be dispersed in more directions than when the radius gradually decreases linearly from the first radius r1 to the second radius r2 or from the first radius r1 to the third radius r3.

[0040] 2 , the fourth diameter r4 at the first end 6a of the resin 6 may be larger than the second diameter r2, and the fifth diameter r5 at the second end 6b of the resin 6 may be larger than the third diameter r3. In this case, the diameter of the resin 6 may gradually decrease from the fourth diameter r4 to the second diameter r2 or from the fifth diameter r5 to the third diameter r3 in the thickness direction of the insulating plate 2. This causes stresses near the first end 6a and the second end 6b of the resin 6 to press the first portion 9 inward in the thickness direction of the insulating plate 2 (toward the center position O) during heating, further reducing peeling between the through-hole conductor 5a and the cover plating (the second metal layer 7 and the third metal layer 8). The fourth diameter r4 and the fifth diameter r5 may be the same or different.

[0041] As shown in FIG. 1 , in the thickness direction of the insulating plate 2, the distance from the first surface 2a to the first end 6a of the resin 6 may be greater than the distance from the first surface 2a to the surface of the first wiring conductor 5b. That is, the first end 6a of the resin 6 may protrude from the surface of the first wiring conductor 5b. Furthermore, in the thickness direction of the insulating plate 2, the distance from the second surface 2b to the second end 6b of the resin 6 may be greater than the distance from the second surface 2b to the surface of the second wiring conductor 5c. That is, the second end 6b of the resin 6 may protrude from the surface of the second wiring conductor 5c. This makes it possible to distance corners of the resin 6, where stress is likely to concentrate, from the starting point of peeling of the second metal layer 7 (the boundary between the resin 6, the through-hole conductor 5a, and the second metal layer 7) and / or the starting point of peeling of the third metal layer 8 (the boundary between the resin 6, the through-hole conductor 5a, and the third metal layer 8). Therefore, peeling between the first metal layer 5 and the cover plating (the second metal layer 7 and / or the third metal layer 8) is further reduced. At this time, the distance from the surface of the first wiring conductor 5b to the first end 6a of the resin 6 and the distance from the surface of the second wiring conductor 5c to the second end 6b of the resin 6 are, for example, 2 to 5 μm, but are not particularly limited thereto.

[0042] The printed wiring board 1 according to the present disclosure is not limited to the embodiment shown in FIG.

[0043] 3 is a cross-sectional view of another embodiment of the printed wiring board 1 according to the present disclosure. In the embodiment shown in FIG. 3 , the fourth diameter r4 at the first end 6a of the resin 6 is the smallest diameter (second diameter r2) of the resin 6 on the side S1 of the first opening 2d relative to the center position O of the insulating plate 2, and the fifth diameter r5 at the second end 6b of the resin 6 is the smallest diameter (third diameter r3) of the resin 6 on the side S2 of the second opening 2e relative to the center position O of the insulating plate 2. When the resin 6 has such a shape, the second metal layer 7 and the third metal layer 8 can more easily enter between the through-hole conductor 5a and the resin 6 in the through-hole, which is advantageous in reducing peeling between the through-hole conductor 5a and the second metal layer 7 and / or the third metal layer 8.

[0044] 4A to 4G, an example of a method for manufacturing printed wiring board 1 according to the embodiment shown in Fig. 1 will be described. Note that the following description does not limit the method for manufacturing printed wiring board 1 according to the present disclosure.

[0045] 4A, a through-hole 2c is formed in a laminate having an insulating plate 2, a first metal foil 3, and a second metal foil 4. The laminate may be a copper-clad laminate in which the first metal foil 3 and the second metal foil 4 are copper foils. The through-hole 2c is formed by, for example, drilling.

[0046] 4B , a first metal layer 5 including a through-hole conductor 5a, a first wiring conductor 5b, and a second wiring conductor 5c is formed. At this time, the first metal layer 5 is formed so that the corners near the first opening 2d and the second opening 2e protrude toward the central axis of the through-hole 2c. The corners near the first opening 2d and the second opening 2e may also protrude toward the surface of the insulating plate 2, as long as they protrude toward the central axis of the through-hole 2c.

[0047] The first metal layer 5 is formed, for example, by electrolytic plating. In electrolytic plating, current density tends to concentrate at corners, which makes it easier to concentrate metal deposition at the corners. This concentrated metal deposition at corners can be reduced by adjusting the components of the plating solution. In conventional printed wiring board manufacturing, a plating solution that can reduce concentrated metal deposition at corners is generally used, for example, to make it easier to uniform the thickness of the through-hole conductor. In contrast, by deliberately using a plating solution that concentrates metal deposition at the corners, it is possible to form the first metal layer 5 whose corners protrude toward the central axis of the through-hole 2c.

[0048] 5 is an enlarged view of the area surrounded by the dashed line in FIG. 4B. The arrow in FIG. 5 indicates that the corner of the first metal layer 5 near the first opening 2d protrudes toward the central axis A of the through hole 2c.

[0049] The hole formed in first metal layer 5, whose corners protrude toward central axis A of through hole 2c, may be annular or non-annular in plan view. If the hole is annular in plan view, first portion 9 can be easily formed large, which makes it easier to manufacture printed wiring board 1 in which the effects of expansion of resin 6 are further reduced.

[0050] 4C , the inside of the through-hole conductor 5a is filled with resin 6, which is then cured. The resin 6 is filled by, for example, screen printing. After filling and curing, the resin 6 has a constriction at a position corresponding to the protrusion toward the central axis of the through-hole 2c at the corner of the first metal layer 5 formed by electrolytic plating.

[0051] Next, as shown in Fig. 4D, the resin 6 and the first metal layer 5 are polished to adjust the size and shape of the resin 6. At this time, to obtain the shape of the resin 6 in the embodiment shown in Fig. 1, polishing should be stopped just before the constrictions formed by filling and hardening the resin 6. To obtain the shape of the resin 6 in the embodiment shown in Fig. 3, polishing should be stopped at the positions of the constrictions near the first opening 2d and the second opening 2e.

[0052] Next, as shown in FIG. 4E, a portion of the first metal layer 5 is removed by etching to adjust the thickness of the first wiring conductor 5b and the thickness of the second wiring conductor 5c, and to adjust the shape of the gap between the through-hole conductor 5a and the resin 6, which affects the shape of the first portion 9.

[0053] At this time, the protruding corners can be preferentially removed by using an etching solution that easily penetrates into the interface between the through-hole conductor 5a and the resin 6. An example of such an etching solution is a dichloromethane solution.

[0054] The etching of the first metal layer 5 may be performed so that no protrusions remain at the corners of the first metal layer 5, or so that the protrusions remain to an extent that they do not affect the formation of the first portion 9. If no protrusions remain after etching, the plating can easily penetrate into the gap between the through-hole conductor 5 a and the resin 6 when forming the cover plating (the second metal layer 7 and the third metal layer 8), making it easier to form the first portion 9.

[0055] 4F , cap plating (second metal layer 7 and third metal layer 8) is formed by, for example, electrolytic plating. The cap plating (second metal layer 7 and third metal layer 8) fills the gap between the through-hole conductor 5a and the resin 6 to form the first portion 9. After the electrolytic plating, the cap plating (second metal layer 7 and third metal layer 8) may be subjected to thickness adjustment and flattening by polishing, soft etching, or the like.

[0056] Next, the first metal foil 3, the first wiring conductor 5b, and the second metal layer 7 are patterned to form a wiring pattern. The wiring pattern is formed by, for example, a subtractive process in which the steps of etching resist formation, exposure, development, etching, and etching resist removal are performed in order. Simultaneously with the patterning of the first metal foil 3, the first wiring conductor 5b, and the second metal layer 7, or before or after the patterning, the second metal foil 4, the second wiring conductor 5c, and the third metal layer 8 are similarly patterned.

[0057] Note that, instead of the subtractive process, a semi-additive process (SAP), a modified semi-additive process (MSAP), etc. may be used to form the wiring pattern. In this case, in the step shown in FIG. 4F , pattern plating may be performed instead of the method of plating the entire surface of the laminate.

[0058] 4G, prior to the wiring pattern formation step, plating (fourth metal layer 10 and fifth metal layer 11) may be formed on the cover plating (second metal layer 7 and third metal layer 8). In this case, the wiring pattern is formed including the fourth metal layer 10 and fifth metal layer 11. The material of the fourth metal layer 10 and fifth metal layer 11 is, for example, copper, but is not particularly limited.

[0059] The printed wiring board 1 can be manufactured by the above steps.

[0060] 6 is a cross-sectional view of an embodiment of a buildup printed wiring board 12 according to the present disclosure, taken in the thickness direction of the insulating board 2. The buildup printed wiring board 12 of this embodiment has a buildup structure 15 in which insulating resin layers 14 and conductor layers 13 are alternately positioned on both the surface on the first surface 2a side and the surface on the second surface 2b side of the printed wiring board 1 of the present disclosure. In other words, the printed wiring board 1 of the present disclosure may be used as a core layer of the buildup printed wiring board 12.

[0061] The build-up printed wiring board 12 may have the printed wiring board 1 (core layer) of the present disclosure and a build-up structure 15 in which insulating resin layers 14 and conductor layers 13 are alternately positioned on at least one of the surfaces on the first surface 2a side and the second surface 2b side.

[0062] The buildup structure 15 has one or more buildup layers, each of which is a set of one insulating resin layer 14 and one conductor layer 13. The number of buildup layers is not particularly limited and may be determined according to the application. In the embodiment shown in Fig. 6, the number of buildup layers is two in both the buildup structure 15 located on the surface on the first surface 2a side of the printed wiring board 1 (core layer) and the buildup structure 15 located on the surface on the second surface 2b side.

[0063] Examples of materials for the insulating resin layer 14 include epoxy resin, bismaleimide-triazine resin, polyimide resin, polyphenylene ether (PPE) resin, phenolic resin, polytetrafluoroethylene (PTFE) resin, silicon resin, polybutadiene resin, polyester resin, melamine resin, urea resin, polyphenylene sulfide (PPS) resin, polyphenylene oxide (PPO) resin, and cyanate ester resin. Two or more of these resins may be mixed. Furthermore, the insulating resin layer 14 may contain inorganic fillers such as aluminum hydroxide, silica, and barium sulfate, or organic fillers such as phenolic resin and methacrylic resin.

[0064] The material of the conductor layer 13 is, for example, copper, but is not particularly limited. The thickness of the conductor layer 13 is, for example, 10 to 30 μm, but is not particularly limited.

[0065] 6, the insulating resin layer 14 may have via conductors 16 for electrically connecting the wiring pattern of the core layer and each conductor layer 13 of the build-up layer. The positions and number of the via conductors 16 may be determined appropriately depending on the wiring pattern of each layer.

[0066] [Method for Manufacturing Buildup Printed Wiring Board] The buildup printed wiring board 12 can be manufactured, for example, by the following procedure. Note that the following description does not limit the method for manufacturing the buildup printed wiring board 12 according to the present disclosure.

[0067] First, a prepreg or resin film that will become the insulating resin layer 14 and copper foil that will become the conductor layer 13 are laminated on the upper surface of the printed wiring board 1 (core layer), followed by heating and pressure. Alternatively, a resin-coated copper foil containing a prepreg or resin film that will become the insulating resin layer 14 and copper foil that will become the conductor layer 13 is laminated on the first surface 2a of the printed wiring board 1 (core layer), followed by heating and pressure. As a result, the prepreg or resin film melts and then hardens, becoming the insulating resin layer 14 and adhering to the upper surface of the printed wiring board 1 (core layer). At this time, the resin contained in the prepreg or resin film also fills the gaps in the wiring pattern formed on the printed wiring board 1 (core layer). The insulating resin layer 14 and conductor layer 13 on the second surface 2b of the printed wiring board 1 (core layer) can also be formed using a similar method.

[0068] On the formed conductor layer 13, a wiring pattern and via conductors 16 are formed as required by a conventionally known method.

[0069] The above steps are repeated according to the number of buildup layers required to be laminated, thereby manufacturing the buildup printed wiring board 12 .

[0070] As described above, the printed wiring board 1 of this embodiment includes an insulating board 2, a first metal layer 5, a resin 6, a second metal layer 7, and a third metal layer 8. The insulating board 2 includes a first surface 2a, a second surface 2b, and a through-hole 2c. The second surface 2b is located on the side opposite the first surface 2a of the insulating board 2. The through-hole 2c has a first opening 2d on the first surface 2a and a second opening 2e on the second surface 2b. The first metal layer 5 is located as a continuous layer across the first surface 2a, the inner wall surface of the through-hole 2c, and the second surface 2b. The first metal layer 5 includes a through-hole conductor 5a, a first wiring conductor 5b, and a second wiring conductor 5c. The through-hole conductor 5a is located on the inner wall surface of the through-hole 2c. The first wiring conductor 5b is located on the first surface 2a. The second wiring conductor 5c is located on the second surface 2b. The resin 6 is located inside the through-hole conductor 5a of the through-hole 2c. The resin 6 has a first end 6a located on the first surface 2a side and a second end 6b located on the second surface 2b side in the thickness direction of the insulating plate 2. The second metal layer 7 covers the first wiring conductor 5b and the first end 6a of the resin 6. The third metal layer 8 covers the second wiring conductor 5c and the second end 6b of the resin 6. In this case, the second metal layer 7 and the third metal layer 8 may cover a portion of the through-hole conductor 5a. At least one of the second metal layer 7 and the third metal layer 8 has a first portion 9 located within the through-hole 2c between the through-hole conductor 5a and the resin 6. The first portion 9 acts to suppress expansion of the resin 6 toward the outside of the through-hole 2c (away from the central axis of the through-hole 2c) near the first opening 2d and / or the second opening 2e. Due to this action of the first portion 9, the printed wiring board 1 of the present disclosure reduces peeling between the through-hole conductor 5a and the cap plating (second metal layer 7 and / or third metal layer 8), resulting in high connection reliability.

[0071] Furthermore, in a cross-sectional view in the thickness direction of the insulating plate 2, the dimension of the first portion 9 in the direction along the first surface 2a may decrease from the first surface 2a or the second surface 2b toward the center position of the insulating plate 2 in the thickness direction of the insulating plate 2. This allows stress to be distributed in the direction pressing the first portion 9 of the cover plating (the second metal layer 7 and / or the third metal layer 8) against the through-hole conductor 5a (a direction inclined toward the central axis of the through-hole 2c) even if the resin 6 expands. This further reduces peeling of the cover plating (the second metal layer 7 and / or the third metal layer 8).

[0072] The printed wiring board 1 may further include at least one of a first metal foil 3 located between the first surface 2a and the first wiring conductor 5b and a second metal foil 4 located between the second surface 2b and the second wiring conductor 5c, thereby further improving the adhesion between the insulating plate 2 and the first wiring conductor 5b and the second wiring conductor 5c, and further improving the connection reliability.

[0073] At least one of the second metal layer 7 and the third metal layer 8 may have a first portion 9, and the resin 6 may have a first diameter equal to the inner diameter of the through-hole conductor 5a at the center of the insulating plate 2 in the thickness direction of the insulating plate 2, a second diameter that is the smallest diameter on the side of the first opening 2d from the center of the insulating plate 2, and a third diameter that is the smallest diameter on the side of the second opening 2e from the center of the insulating plate 2. This allows the first portion 9 to penetrate into the resin 6 (the side of the central axis of the through-hole 2c), reducing expansion of the resin 6 in the thickness direction of the insulating plate 2.

[0074] Furthermore, resin 6 may have a portion where the diameter gradually decreases from a first diameter to a second diameter in the thickness direction of insulating plate 2, and may have a portion where the diameter gradually decreases from the first diameter to a third diameter in the thickness direction of insulating plate 2. This allows printed wiring board 1 to distribute the direction of the stress that first portion 9 receives from resin 6.

[0075] Furthermore, the resin 6 may have a curved shape between the position having the first radius and the position having the second radius, and may have a curved shape between the position having the first radius and the position having the third radius, in a cross section seen in the thickness direction of the insulating plate 2. This allows the direction of the stress that the first portion 9 receives from the resin 6 to be dispersed in more directions than when the radius gradually decreases linearly from the first radius r1 to the second radius r2 or from the first radius r1 to the third radius r3.

[0076] Furthermore, in the thickness direction of the insulating plate 2, the distance from the first surface 2a to the first end 6a of the resin 6 may be greater than the distance from the first surface 2a to the surface of the first wiring conductor 5b, and the distance from the second surface 2b to the second end 6b of the resin 6 may be greater than the distance from the second surface 2b to the surface of the second wiring conductor 5c. This allows the corners of the resin 6, where stress is likely to concentrate, to be located away from the starting point of peeling of the second metal layer 7 (the boundary between the resin 6, the through-hole conductor 5a, and the second metal layer 7) and the starting point of peeling of the third metal layer 8 (the boundary between the resin 6, the through-hole conductor 5a, and the third metal layer 8). This further reduces peeling between the first metal layer 5 and the cover plating (the second metal layer 7 and the third metal layer 8).

[0077] Alternatively, a fourth diameter at the first end 6 a of the resin 6 may be larger than the second diameter, and the diameter of the resin 6 may gradually decrease from the fourth diameter to the second diameter in the thickness direction of the insulating plate 2, and a fifth diameter at the second end 6 b of the resin 6 may be larger than the third diameter, and the diameter of the resin 6 may gradually decrease from the fifth diameter to the third diameter in the thickness direction of the insulating plate 2. This causes stress to act near the first end 6 a and the second end 6 b of the resin 6 during heating, pushing the first portion 9 inward in the thickness direction of the insulating plate 2, thereby further reducing peeling between the through-hole conductor 5 a and the cover plating (the second metal layer 7 and the third metal layer 8).

[0078] Moreover, buildup printed wiring board 12 of the present embodiment has printed wiring board 1 described above and buildup structure 15 in which insulating resin layers 14 and conductor layers 13 are alternately positioned on at least one of the surface on first surface 2a side and the surface on second surface 2b side of printed wiring board 1. By having printed wiring board 1 in which peeling between through-hole conductors 5a and cover plating (second metal layer 7 and / or third metal layer 8) is reduced, buildup printed wiring board 12 of the present embodiment has high connection reliability.

[0079] Although the embodiments of the present disclosure have been described above, the printed wiring board and build-up printed wiring board of the present disclosure are not limited to the above-described embodiments.

[0080] For example, in the above embodiment, the through hole 2c, the resin 6, the first portion 9, etc. are described as being symmetrical with respect to the central axis of the through hole 2c, but this is not limiting. That is, the through hole 2c, the resin 6, the first portion 9, etc. may be asymmetrical with respect to the central axis of the through hole 2c.

[0081] The dimension of the first portion 9 in the direction along the first surface 2a does not have to simply decrease from the first surface 2a or the second surface 2b toward the center position of the insulating plate 2 in the thickness direction of the insulating plate 2. The surface of the first portion 9 (the surface in contact with the resin 6) may have an uneven shape.

[0082] The diameter of the resin 6 does not have to gradually decrease between the first diameter position and the second diameter position and between the first diameter position and the third diameter position, and may change discontinuously, for example.

[0083] The resin 6 does not have to have a curved shape when viewed in cross section in the thickness direction of the insulating plate 2, and may have, for example, a linear or broken line shape. The cross-sectional shape of the resin 6 may be a combination of a curved shape, a linear shape, and a broken line shape.

[0084] In the thickness direction of the insulating plate 2, the distance from the first surface 2a to the first end 6a of the resin 6 does not have to be greater than the distance from the first surface 2a to the surface of the first wiring conductor 5b. That is, the first end 6a of the resin 6 does not have to protrude from the surface of the first wiring conductor 5b. Similarly, in the thickness direction of the insulating plate 2, the distance from the second surface 2b to the second end 6b of the resin 6 does not have to be greater than the distance from the second surface 2b to the surface of the second wiring conductor 5c. That is, the second end 6b of the resin 6 does not have to protrude from the surface of the second wiring conductor 5c.

[0085] The first end 6a and the second end 6b of the resin 6 do not have to be flat, and may have, for example, irregularities.

[0086] In addition, the details shown in the above embodiment can be appropriately modified without departing from the spirit of the present disclosure. The scope of the present invention includes the scope of the invention described in the claims and its equivalents.

[0087] The present disclosure can be used for printed wiring boards and build-up printed wiring boards.

[0088] REFERENCE SIGNS LIST 1 Printed wiring board 2 Insulating board 2a First surface 2b Second surface 2c Through hole 2d First opening 2e Second opening 3 First metal foil 4 Second metal foil 5 First metal layer 5a Through hole conductor 5b First wiring conductor 5c Second wiring conductor 6 Resin 6a First end 6b Second end 7 Second metal layer 8 Third metal layer 9 First portion 10 Fourth metal layer 11 Fifth metal layer 12 Build-up printed wiring board 13 Conductor layer 14 Insulating resin layer 15 Build-up structure 16 Via conductor A Central axis of through hole O Central position of the insulating board in the thickness direction of the insulating board S1 Side of first opening S2 Side of second opening r1 First diameter r2 Second diameter r3 Third diameter r4 Fourth diameter r5 Fifth diameter

Claims

1. An insulating plate having a first surface, a second surface located opposite to the first surface, and a through-hole having a first opening on the first surface and a second opening on the second surface, A first metal layer comprising: a through-hole conductor located on the inner wall surface of the through-hole, a first wiring conductor located on the first surface, and a second wiring conductor located on the second surface, which are positioned in a continuous manner across the first surface, the inner wall surface of the through-hole, and the second surface; A resin having a first end located on the first surface side and a second end located on the second surface side in the thickness direction of the insulating plate, located inside the through-hole conductor of the through-hole, A second metal layer covering the first end of the first wiring conductor and the resin, A third metal layer covering the second end of the second wiring conductor and the resin, It has, At least one of the second metal layer and the third metal layer has a first portion located within the through-hole and between the through-hole conductor and the resin. Printed wiring board.

2. In a cross-sectional view of the insulating plate in the thickness direction, the dimensions of the first portion in the direction along the first surface decrease as you move from the first or second surface toward the center of the insulating plate in the thickness direction. The printed circuit board according to claim 1.

3. The present invention further comprises at least one of a first metal foil located between the first surface and the first wiring conductor, and a second metal foil located between the second surface and the second wiring conductor. The printed circuit board according to claim 1.

4. Both the second metal layer and the third metal layer have the first portion, The resin has a first diameter equal to the inner diameter of the through-hole conductor at the center of the insulating plate in the thickness direction of the insulating plate. The resin has a second diameter smaller than the first diameter, which is the minimum diameter of the resin on the first opening side of the center position. The resin has a third diameter that is smaller than the first diameter and is the minimum diameter of the resin on the second opening side of the center position. The printed circuit board according to claim 1.

5. The diameter of the resin has a portion that gradually decreases from the first diameter to the second diameter in the thickness direction of the insulating plate, and a portion that gradually decreases from the first diameter to the third diameter in the thickness direction of the insulating plate. The printed circuit board according to claim 4.

6. The resin has a curved shape in a cross-sectional view in the thickness direction of the insulating plate between the position having the first diameter and the position having the second diameter, and between the position having the first diameter and the position having the third diameter. The printed circuit board according to claim 4.

7. In the thickness direction of the insulating plate, the distance from the first surface to the first end of the resin is greater than the distance from the first surface to the surface of the first wiring conductor. In the thickness direction of the insulating plate, the distance from the second surface to the second end of the resin is greater than the distance from the second surface to the surface of the second wiring conductor. The printed circuit board according to claim 5.

8. The fourth diameter at the first end of the resin is larger than the second diameter. The diameter of the resin gradually decreases from the fourth diameter to the second diameter in the thickness direction of the insulating plate. The fifth diameter at the second end of the resin is larger than the third diameter. The diameter of the resin gradually decreases from the fifth diameter to the third diameter in the thickness direction of the insulating plate. The printed circuit board according to claim 7.

9. A printed circuit board according to any one of claims 1 to 8, A build-up structure in which an insulating resin layer and a conductor layer are alternately positioned on at least one of the first surface and the second surface of the printed circuit board, It has Build-up printed circuit board.