Patent ID: 12250773

DESCRIPTION OF EMBODIMENTS

Embodiments of a wiring board and a wiring board manufacturing method disclosed in the present application will be described in detail below with reference to the drawings. The present invention is not limited by the embodiments below.

First Embodiment

FIG.1is a partial cross-sectional view illustrating a configuration of a core substrate100that is included in a multi-layer wiring board according to a first embodiment. As illustrated inFIG.1, the core substrate100is a wiring board that includes a base material110, a through hole portion120, and an inductor portion130.

The base material110is a base material of the core substrate100and includes a plate member that has insulating property. As the base material110, for example, a glass epoxy substrate, in which insulating resin, such as epoxy resin or polyimide resin, is impregnated in a glass cloth, or the like may be used. Further, it may be possible to use, as the base material110, a substrate in which epoxy resin or the like is impregnated in a woven fabric or a non-woven fabric that is made of a glass fiber, a carbon fiber, or the like, for example. A thickness of the base material110may be set to, for example, about 700 to 2000 micrometers (nm).

The through hole portion120is arranged at a position of a through hole112that penetrates through the base material110, and ensures conduction between surfaces110aon both sides of the base material110. The through hole portion120includes conductor layers140athat are formed on the surfaces110aof the base material110, and insulating resin125that penetrates through the through hole112.

Each of the conductor layers140aincludes a metallic foil111, a first electroless plating film141a, a first electroplating film141b, a second electroless plating film142a, and a second electroplating film142b, and forms a pad of the through hole portion120. The pads formed of the conductor layers140aare included in wiring layers that are arranged on the surfaces of the base material110. The metallic foils111are metallic foils that are arranged on the surfaces110aof the base material110in advance and that are removable by etching. As the metallic foils111, for example, copper foils, copper alloy foils, or the like may be used, and a thickness of each of the metallic foils111is, for example, 4 to 12 μm.

The first electroless plating films141aand the second electroless plating films142aare electroless plating films that are formed by, for example, copper electroless plating. In contrast, the first electroplating films141band the second electroplating films142bare electroplating films that are formed by, for example, electro copper plating. The first electroless plating films141aare laminated on the metallic foils111, and cover an inner wall of the through hole112. The first electroplating films141bare laminated on the first electroless plating films141a. The second electroless plating films142aare laminated on the first electroplating films141b, and cover end faces of the insulating resin125. The second electroplating films142bare laminated on the second electroless plating films142a.

The insulating resin125is insulating resin that is filled in an inner through hole on inner sides of the first electroless plating films141aand the first electroplating films141bthat cover the inner wall of the through hole112. As the insulating resin125, for example, epoxy resin containing filler, such as silica, may be used. Both end faces of the insulating resin125are covered by the second electroless plating films142aand the second electroplating films142b.

The inductor portion130is arranged at a position of a through hole113that penetrates through the base material110, and functions as an inductor. The inductor portion130includes conductor layers140bthat are formed on the surfaces110aof the base material110, and a magnetic member135that penetrates through the through hole113.

Each of the conductor layers140bincludes, similarly to the conductor layers140a, the metallic foil111, the first electroless plating film141a, the first electroplating film141b, the second electroless plating film142a, and the second electroplating film142b, and forms a pad of the inductor portion130. The pads formed of the conductor layers140bare included in the wiring layers that are arranged on the surfaces of the base material110.

In the inductor portion130, the first electroless plating films141a, the first electroplating films141b, the second electroless plating films142a, and the second electroplating films142bare laminated on the metallic foils111, and cover end faces of the magnetic member135. In other words, the first electroless plating films141aare formed so as to cover the metallic foils111and the end faces of the magnetic member135, and the first electroplating films141b, the second electroless plating films142a, and the second electroplating films142bare laminated in this order on the first electroless plating films141a.

Meanwhile, the first electroless plating films141a, the first electroplating films141b, the second electroless plating films142a, and the second electroplating films142bof the conductor layers140aand140bare electroless plating films or electroplating films that are formed simultaneously.

The magnetic member135is a member that includes a magnetic body and a conductor, and is embedded in the through hole113that is formed in the base material110. Specifically, the magnetic member135is, for example, a member that is formed by covering a conductor wire132by a magnetic body131, and is formed so as to have a certain size that fits to the through hole113. The both end faces of the magnetic member135are covered by the first electroless plating films141a, the first electroplating films141b, the second electroless plating films142a, and the second electroplating films142b.

The configuration of the magnetic member135will be described below using a specific example.FIGS.2A to2Care diagrams illustrating a specific example of a method of forming the magnetic member135. The magnetic member135illustrated inFIGS.2A to2Cis formed by covering a conductor wire by a magnetic body.

Specifically, a conductor wire201illustrated inFIG.2Afor example is covered by a magnetic body202as illustrated inFIG.2B, so that a magnetic-body-covered conductor wire is formed. As the conductor wire201, for example, a metal wire, such as a copper wire, may be used.

As the magnetic body202, for example, insulating resin, such as epoxy resin, that contains magnetic particles may be used. Examples of the magnetic particles include filler, such as iron, iron oxide, cobalt iron oxide, silicon iron, nickel, nickel oxide, magnetic alloy, or ferrite. If resin containing magnetic filler as described above is used as the magnetic body202, for example, a periphery of the conductor wire201with a diameter of about 100 to 200 μm is covered by the magnetic body202with a thickness of about 75 to 175 μm. Consequently, it is possible to form the magnetic-body-covered conductor wire with a diameter of 250 to 550 μm, for example.

Furthermore, as the magnetic body202, for example, magnetic metal, such as iron, nickel, or chromium, may be used. If the magnetic metal as described above is used as the magnetic body202, for example, a plating film formed of the magnetic body202with the thickness of about 50 to 200 μm is formed around the conductor wire201with the diameter of 50 to 300 μm by electroplating. Consequently, it is possible to form the magnetic-body-covered conductor wire with the diameter of 150 to 700 μm, for example.

A diameter of each of the magnetic-body-covered conductor wires as described above is approximately the same as a diameter of the through hole113of the base material110in which the magnetic member135is embedded, but it is preferable that the diameter is slightly larger than the diameter of the through hole113.

After the magnetic-body-covered conductor wire is formed, the magnetic-body-covered conductor wire is cut to a predetermined length as illustrated inFIG.2Cfor example. Specifically, the magnetic-body-covered conductor wire is cut to approximately the same length, such as 700 to 2000 μm, as the thickness of the base material110, so that the magnetic member135is obtained. At this time, it is preferable that the length of the magnetic member135is slightly longer than the thickness of the base material110such that when the magnetic member135is embedded in the through hole113, both ends of the magnetic member135protrude from the surfaces of the base material110.

FIGS.3A to3Eare diagrams illustrating another specific example of the method of forming the magnetic member135. The magnetic member135illustrated inFIGS.3A to3Eis formed by forming a strand wire by twisting a plurality of magnetic-body-covered conductor wires together, and covering the strand wire by insulating resin.

Specifically, the conductor wire201as illustrated inFIG.3Afor example is covered by the magnetic body202as illustrated inFIG.3B, so that a magnetic-body-covered conductor wire is formed. As the conductor wire201, for example, a copper wire may be used. As the magnetic body202, similarly to the above, resin that contains magnetic filler or magnetic metal may be used, for example.

After the plurality of magnetic-body-covered conductor wires are formed as described above, the plurality of magnetic-body-covered conductor wires are twisted together as illustrated inFIG.3C, so that a strand wire is formed. Further, the strand wire is covered by insulating resin203as illustrated inFIG.3D. The strand wire covered by the insulating resin203is cut to a predetermined length as illustrated inFIG.3Efor example. Specifically, the strand wire covered by the insulating resin203is cut to approximately the same length, such as 700 to 2000 μm, as the thickness of the base material110, so that the magnetic member135is obtained. At this time, it is preferable that the length of the magnetic member135is slightly longer than the thickness of the base material110such that when the magnetic member135is embedded in the through hole113, the both ends of the magnetic member135protrude from the surfaces of the base material110.

When the magnetic member135is formed by using the strand wire, an arbitrary number of magnetic-body-covered conductor wires may be twisted together. Specifically, it may be possible to form the magnetic member135from a strand wire having a double helix structure in which two magnetic-body-covered conductor wires are twisted together as illustrated inFIG.4Afor example, or it may be possible to form the magnetic member135from a strand wire having a triple helix structure in which three magnetic-body-covered conductor wires are twisted together as illustrated inFIG.4Bfor example.

The magnetic member135as described above is formed by using the magnetic-body-covered conductor wire in which the conductor wire201is arranged in the center of the magnetic body202, and the conductor wire201and the magnetic body202are uniformly arranged. As a result, in the core substrate100in which the magnetic member135is embedded in the base material110, it is possible to reduce variation of inductance of the inductor portion130. Further, the conductor wire201is included in the center of the magnetic member135, so that a volume of the conductor in the magnetic member135increases and it is possible to reduce electrical resistance. In this manner, with use of the magnetic member135, it is possible to improve electrical characteristics of the built-in inductor that is included in the core substrate100.

Furthermore, the conductor wire201is included in the magnetic member135in advance, so that after the magnetic member135is embedded in the base material110, a plating process of establishing electrical connection of the both ends of the magnetic member135is not needed. Therefore, it is possible to simplify the process of manufacturing the core substrate100, and reduce the number of plating processes, so that it is possible to make a plating thickness uniform.

Each of the electroless plating films and the electroplating films will be described below.

The first electroless plating films141aare formed on the surfaces of the metallic foils111, an inner wall surface of the through hole112, and the end faces of the magnetic member135. Specifically, in the through hole portion120, the first electroless plating films141aare formed on the surfaces of the metallic foils111and the inner wall surface of the through hole112in a continuous manner. In contrast, in the inductor portion130, the first electroless plating films141aare laminated on the surfaces of the metallic foils111and the end faces of the magnetic member135. A thickness of each of the first electroless plating films141ais, for example, about 0.1 to 2.0 μm.

The first electroplating films141bare laminated on the first electroless plating films141a. Specifically, in the through hole portion120, the first electroplating films141bare laminated on the first electroless plating films141aon an upper side and a lower side of the metallic foils111and the inner side of the through hole112in a continuous manner. In contrast, in the inductor portion130, the first electroplating films141bare laminated on the first electroless plating films141ain a planar manner. A thickness of each of the first electroplating films141bis, for example, about 2 to 18 μm.

The second electroless plating films142aare formed on the surfaces of the first electroplating films141band the end faces of the insulating resin125. Specifically, in the through hole portion120, the second electroless plating films142aare laminated on the first electroplating films141band the end faces of the insulating resin125. In contrast, in the inductor portion130, the second electroless plating films142aare laminated on the first electroplating films141bin a planar manner. A thickness of each of the second electroless plating films142ais, for example, about 0.1 to 2.0 μm, similarly to the first electroless plating films141a.

The second electroplating films142bare laminated on the second electroless plating films142a. Specifically, in the through hole portion120and the inductor portion130, the second electroplating films142bare laminated on the second electroless plating films142ain a planar manner. A thickness of each of the second electroplating films142bis, for example, about 2 to 18 μm, similarly to the first electroplating films141b.

A method of manufacturing a multi-layer wiring board including the core substrate100that is configured as described above will be described below with reference to a flowchart illustrated inFIG.5by using a specific example.

First, the through holes112and113for forming the through hole portion120and the inductor portion130are formed in the base material110that includes an insulating plate member (Step S101). The base material110is obtained by forming the metallic foils111on the surfaces110aof the insulating plate member as illustrated inFIG.6, for example. A thickness of the base material110is, for example, about 700 to 2000 μm. The through hole112having a cylindrical shape in which a diameter of an opening portion is about 100 to 200 μm and the through hole113having a cylindrical shape in which a diameter of an opening portion is about 250 to 550 μm are formed in the base material110as illustrated inFIG.7, for example. The through holes112and113are formed by, for example, laser processing or drilling, and after the through holes112and113are formed, desmear processing for removing resinous residue on inner wall surfaces is performed. In the desmear processing, for example, a potassium permanganate solution may be used.

Further, the magnetic member135is embedded in the through hole113(Step S102). Specifically, as illustrated inFIG.8for example, the magnetic member135including the magnetic body131and the conductor wire132is inserted in the through hole113that is formed in the base material110, for example. At this time, the magnetic member135is embedded in the through hole113such that the conductor wire132that is arranged in the center of the magnetic member135is located at a central axis of the through hole113. A diameter of the magnetic member135is approximately the same or slightly larger than the diameter of the through hole113, so that it is possible to insert the magnetic member135in the through hole113without a gap due to elasticity of the magnetic body131. Meanwhile, even if the magnetic member135has the configuration as illustrated inFIG.3, it is possible to insert the magnetic member135in the through hole113without a gap due to elasticity of the insulating resin203that covers the strand wire.

Moreover, it may be possible to inject insulating resin, such as epoxy resin, along the inner wall surface of the through hole113such that the diameter of the through hole113conforms to the diameter of the magnetic member135. With this operation, the filled insulating resin is located between the inner wall surface of the through hole113and the magnetic member135, so that even if the magnetic body131that forms the magnetic member135does not have elasticity, it is possible to prevent a gap from being generated between the inner wall surface of the through hole113and the magnetic member135.

When the magnetic member135is inserted in the through hole113, both end portions of the magnetic member135protrude upward and downward from the metallic foils111on the base material110because the length of the magnetic member135is slightly larger than the thickness of the base material110.

Therefore, the protruding portions are subjected to surface polishing such that the both end portions of the magnetic member135flush with the surfaces of the metallic foils111(Step S103). Specifically, as illustrated inFIG.9for example, the both ends of the magnetic member135are polished such that the surfaces of the metallic foils111flush with the both end faces of the magnetic member135.

After the surfaces of the metallic foils111flush with the both end faces of the magnetic member135, the first electroless plating films141afor covering portions that are exposed to the surfaces are formed (Step S104). Specifically, as illustrated inFIG.10for example, the surfaces of the metallic foils111, the end faces of the magnetic member135, and the inner wall surface of the through hole112are subjected to, for example, electroless copper plating, so that the first electroless plating films141aare formed. A thickness of each of the first electroless plating films141ais, for example, about 0.1 to 2.0 μm.

Furthermore, the first electroplating films141bare laminated on the first electroless plating films141a(Step S105). Specifically, as illustrated inFIG.11for example, the surfaces on which the first electroless plating films141aare formed are subjected to, for example, electro copper plating, so that the first electroplating films141bare formed. A thickness of each of the first electroplating films141bis, for example, about 2 to 18 μm.

By forming the first electroless plating films141aand the first electroplating films141b, the through hole is formed on inner sides of the first electroplating films141bin the through hole112. The through hole is filled with the insulating resin125(Step S106). Specifically, as illustrated inFIG.12for example, the insulating resin125is filled on the inner sides of the first electroplating films141bin the through hole112. As the insulating resin125, for example, epoxy resin containing filler, such as silica, may be used. The insulating resin125is filled on the inner sides of the first electroplating films141bwithout a gap, and both end portions of the insulating resin125protrude upward and downward from the first electroless plating films141aand the first electroplating films141blaminated on the metallic foils111.

Therefore, the protruding portions are subjected to surface polishing such that the both end portions of the insulating resin125flush with the surfaces of the first electroplating films141b(Step S107). Specifically, as illustrated inFIG.13for example, the both ends of the insulating resin125are polished such that an upper surface and a lower surface of the first electroplating films141bflush with the both end faces of the insulating resin125. Further, resinous residue that remains on the surfaces of the first electroplating films141bdue to polishing of the insulating resin125are removed by desmear processing. At this time, the both end faces of the magnetic member135are covered by the first electroless plating films141aand the first electroplating film141b, and therefore the magnetic body131is protected from a solution that is used in the desmear processing.

After the upper surface and the lower surface of the first electroplating films141bflush with the both end faces of the insulating resin125, the second electroless plating films142afor covering portions that are exposed to the surfaces are formed (Step S108). Specifically, as illustrated inFIG.14for example, the surfaces of the first electroplating films141band the end faces of the insulating resin125are subjected to, for example, electroless copper plating, so that the second electroless plating films142aare formed. A thickness of each of the second electroless plating films142ais, for example, about 0.1 to 2.0 μm, similarly to the first electroless plating films141a.

Furthermore, the second electroplating films142bare laminated on the second electroless plating films142a(Step S109). Specifically, as illustrated inFIG.15for example, the surfaces on which the second electroless plating films142aare formed are subjected to, for example, electro copper plating, so that the second electroplating films142bare laminated in a planar manner. A thickness of each of the second electroplating films142bis, for example, 2 to 18 μm, similarly to the first electroplating films141b.

Through the electroless plating and the electroplating as described above, all of the electroless plating films and the electroplating films are formed, and therefore, etching for forming the conductor layers140aand the conductor layers140bof the through hole portion120and the inductor portion130is performed (Step S110). Specifically, as illustrated inFIG.16for example, etching resists210are formed in portions in which the plating films are maintained as the conductor layers140aand140b. InFIG.16, the etching resists210for forming the conductor layers140aand140bas pads at the positions of the insulating resin125and the magnetic member135are illustrated. The etching resists210are formed so as to cover wider areas than the through holes112and113on the surfaces of the second electroplating films142b. The etching resists210are formed of a material that has desired resolution and etching resistance.

Then, the metallic foils111, the first electroless plating films141a, the first electroplating films141b, the second electroless plating films142a, and the second electroplating films142bare removed by wet etching by using the etching resists210as masks. Consequently, as illustrated inFIG.17for example, the through hole portion120that includes the conductor layers140aas the pads and the inductor portion130that includes the conductor layers140bas the pads are formed. By removing the etching resists210from the conductor layers140aand140b, the core substrate100is completed.

Insulating layers and wiring layers are built up in this order on an upper surface and a lower surface of the core substrate100, so that a multi-layer wiring board is formed (Step S111). Specifically, as illustrated inFIG.18for example, insulating layers230and wiring layers220are laminated on the upper surface and the lower surface of the core substrate100, and the wiring layers220that are laminated in a vertical direction are electrically connected to each other by via wires225that are arranged in the insulating layers230. Furthermore, the wiring layers220that are located closest to the core substrate100are electrically connected to the conductor layers140aand140bof the core substrate100by the via wires225that are arranged in the insulating layers230.

Moreover, the topmost wiring layer220is covered by a solder resist layer240. Through holes are formed in the solder resist layer240, and connection terminals250that are formed of solder or the like for electrically connecting an electronic component, such as a semiconductor chip, and the wiring layer220are formed in the through holes, for example. In contrast, the lowermost wiring layer220is covered by a solder resist layer260. Furthermore, opening portions are formed in the solder resist layer260, and an external connection pad270that is formed on the lowermost wiring layer220is exposed from the opening portions. The external connection pad270is electrically connectable to an external component or device.

In this manner, it is possible to form the multi-layer wiring board including the plurality of wiring layers220from the core substrate100in which the inductor portion130using the magnetic member135is built. The multi-layer wiring board may be used for, for example, a semiconductor device on which a component, such as a semiconductor chip, is mounted. Specifically, as illustrated inFIG.19, a semiconductor chip310is mounted on an upper surface of the multi-layer wiring board. For example, the connection terminals250of the multi-layer wiring board and electrodes315that are formed of solder or the like in the semiconductor chip310are bonded together. Then, bonding portions between the connection terminals250and the electrodes315are sealed with underfill resin320, so that a semiconductor device on which the semiconductor chip310is mounted is obtained.

As described above, according to the present embodiment, the magnetic member that is formed using the magnetic-body-covered conductor wire is embedded in the through hole of the base material, and the end faces of the magnetic member exposed from the opening portions of the through hole form an inductor that is covered by the electroless plating films and the electroplating films. Therefore, the conductor wire and the magnetic body are uniformly arranged in the inductor, so that it is possible to reduce variation of the inductance. Furthermore, it is possible to increase a volume of the conductor in the inductor, so that it is possible to reduce electrical resistance. In other words, it is possible to improve the electrical characteristics of the built-in inductor that is included in the core substrate.

Second Embodiment

In the first embodiment as described above, the magnetic member135is embedded in the through hole113of the base material110, and thereafter the through hole112is filled with the insulating resin125; however, it may be possible to fill the through hole112with the insulating resin125in advance, and thereafter embed the magnetic member135in the through hole113. Therefore, in a second embodiment, a method of manufacturing a multi-layer wiring board in a case where the magnetic member135is embedded at a later time will be described.

FIG.20is a flowchart illustrating a multi-layer wiring board manufacturing method according to the second embodiment. InFIG.20, the same processes as those illustrated inFIG.5are denoted by the same reference symbols. In the multi-layer wiring board manufacturing method illustrated inFIG.20, after the insulating resin125is filled at Step S106, the magnetic member135is embedded at Step S102.

First, the through hole112for forming the through hole portion120is formed in the base material110that includes an insulating plate member (Step S201). Specifically, the through hole112having the cylindrical shape in which the diameter of the opening portion is about 100 to 200 μm is formed in the base material110as illustrated inFIG.21for example. The through hole112is formed by, for example, laser processing or drilling, and after the through hole112is formed, desmear processing for removing resinous residue on the inner wall surface is performed. In the desmear processing, for example, a potassium permanganate solution may be used.

After the through hole112is formed, the first electroless plating films141afor covering portions that are exposed to the surfaces are formed (Step S104), and subsequently, the first electroplating films141bare laminated on the first electroless plating films141a(Step S105). Specifically, as illustrated inFIG.22for example, the surfaces of the metallic foils111and the inner wall surface of the through hole112are subjected to, for example, electroless copper plating, so that the first electroless plating films141aare formed. Further, the surfaces on which the first electroless plating films141aare formed are subjected to, for example, electro copper plating, so that the first electroplating films141bare formed. A thickness of each of the first electroless plating films141ais, for example, about 0.1 to 2.0 μm. Furthermore, a thickness of each of the first electroplating films141bis, for example, about 2 to 18 μm.

By forming the first electroless plating films141aand the first electroplating films141b, the through hole is formed on the inner sides of the first electroplating films141bin the through hole112. The through hole is filled with the insulating resin125(Step S106). Specifically, as illustrated inFIG.23for example, the insulating resin125is filled on the inner sides of the first electroplating films141bin the through hole112. As the insulating resin125, for example, epoxy resin containing filler, such as silica, may be used. The insulating resin125is filled on the inner sides of the first electroplating films141bwithout a gap, and the both end portions of the insulating resin125protrude upward and downward from the first electroless plating films141aand the first electroplating films141blaminated on the metallic foils111.

The protruding both end portions of the insulating resin125are subjected to surface polishing (Step S107), and if the upper surface and the lower surface of the first electroplating films141bflush with the both end faces of the insulating resin125, the through hole113for forming the inductor portion130is formed (Step S202). Specifically, the through hole113having the cylindrical shape in which the diameter of the opening portion is about 250 to 550 μm is formed in the base material110on which the first electroless plating films141aand the first electroplating films141bare formed as illustrated inFIG.24, for example. The through hole113is formed by, for example, laser processing or drilling, and after the through hole113is formed, desmear processing for removing resinous residue on the inner wall surface is performed.

Further, the magnetic member135is embedded in the through hole113(Step S102). Specifically, as illustrated inFIG.25for example, the magnetic member135including the magnetic body131and the conductor wire132is inserted in the through hole113, for example. The diameter of the magnetic member135is approximately the same or slightly larger than the diameter of the through hole113, so that it is possible to insert the magnetic member135in the through hole113without a gap due to the elasticity of the magnetic body131. Furthermore, the length of the magnetic member135is slightly larger than the thickness of the base material110, so that the both end portions of the magnetic member135protrude upward and downward from the first electroless plating films141aand the first electroplating films141blaminated on the metallic foils111.

The protruding both end portions of the magnetic member135are subjected to surface polishing (Step S103), and if the upper surface and the lower surface of the first electroplating films141bflush with the both end faces of the magnetic member135, the second electroless plating films142aand the second electroplating films142bare formed on portions that are exposed to the surfaces (Steps S108and S109). Specifically, as illustrated inFIG.26for example, the surfaces of the first electroplating films141b, the end faces of the insulating resin125, and the end faces of the magnetic member135are subjected to, for example, electroless copper plating, so that the second electroless plating films142aare formed. Further, the surfaces on which the second electroless plating films142aare formed are subjected to, for example, electro copper plating, so that the second electroplating films142bare laminated in a planar manner. A thickness of each of the second electroless plating films142ais, for example, about 0.1 to 2.0 μm. Furthermore, a thickness of each of the second electroplating films142bis, for example, about 2 to 18 μm.

Through the electroless plating and the electroplating as described above, all of the electroless plating films and the electroplating films are formed, and therefore, etching for forming the conductor layers140aand the conductor layers140bof the through hole portion120and the inductor portion130is performed (Step S110). Specifically, etching resists are formed in portions in which the plating films are maintained as the conductor layers140aand140b, and the metallic foils111, the first electroless plating films141a, the first electroplating films141b, the second electroless plating films142a, and the second electroplating films142bare removed by wet etching. Consequently, as illustrated inFIG.27for example, the through hole portion120that includes the conductor layers140aas the pads and the inductor portion130that includes the conductor layers140bas the pads are formed.

Insulating layers and wiring layers are built up in this order on the upper surface and the lower surface of the core substrate100, so that a multi-layer wiring board is formed (Step S111). Further, it may be possible to mount a semiconductor chip on the multi-layer wiring board to form a semiconductor device. The core substrate100according to the present embodiment is different from the core substrate100according to the first embodiment in that the both end faces of the magnetic member135are covered by the second electroless plating films142a. Specifically, in the core substrate100according to the first embodiment, the magnetic member135is embedded and formed in advance of filling of the insulating resin125, so that the both end faces of the magnetic member135are covered by the first electroless plating films141a. In contrast, in the core substrate100according to the present embodiment, the magnetic member135is embedded and formed after filling of the insulating resin125, so that the both end faces of the magnetic member135are covered by the second electroless plating films142a. Other configurations of the core substrate100are the same between the first embodiment and the second embodiment, and the configuration of the multi-layer wiring board and the semiconductor device that are formed using the core substrate100are the same between the first embodiment and the second embodiment.

As described above, according to the present embodiment, after the through hole is filled with the insulating resin, the magnetic member that is formed by using the magnetic-body-covered conductor wire is embedded in the through hole of the base material, so that the inductor is formed. Therefore, even when the core substrate is formed by forming the through hole that is filled with the insulating resin and thereafter forming the inductor using the magnetic member, it is possible to improve the electrical characteristics of the built-in inductor that is included in the core substrate.

Third Embodiment

In the first and the second embodiments as described above, the through hole112is already formed when the magnetic member135is embedded in the through hole113of the base material110; however, it may be possible to form the through hole112after embedding the magnetic member135in the through hole113. Therefore, in a third embodiment, a multi-layer wiring board manufacturing method in a case where the through hole112is formed at a later time will be described.

FIG.28is a flowchart illustrating a multi-layer wiring board manufacturing method according to the third embodiment. InFIG.28, the same processes as those illustrated inFIG.5are denoted by the same reference symbols. In the multi-layer wiring board manufacturing method illustrated inFIG.28, after surface polishing is performed on the magnetic member135at Step S103, the through hole112to be filled with the insulating resin125is formed.

First, the through hole113for forming the inductor portion130is formed in the base material110that includes an insulating plate member (Step S301). Specifically, the through hole113having the cylindrical shape in which the diameter of the opening portion is about 250 to 550 μm is formed in the base material110as illustrated inFIG.29for example. The through hole113is formed by, for example, laser processing or drilling, and after the through hole113is formed, desmear processing for removing resinous residue on the inner wall surface is performed. In the desmear processing, for example, a potassium permanganate solution may be used.

Then, the magnetic member135is embedded in the through hole113(Step S102). Specifically, as illustrated inFIG.30for example, the magnetic member135including the magnetic body131and the conductor wire132is inserted in the through hole113, for example. The diameter of the magnetic member135is approximately the same or slightly larger than the diameter of the through hole113, so that it is possible to insert the magnetic member135in the through hole113without a gap due to the elasticity of the magnetic body131. Furthermore, the length of the magnetic member135is slightly larger than the thickness of the base material110, so that the both end portions of the magnetic member135protrude upward and downward from the metallic foils111of the base material110.

Therefore, the protruding portions are subjected to surface polishing such that the both end portions of the magnetic member135flush with the surfaces of the metallic foils111(Step S103). Specifically, as illustrated inFIG.31for example, the both ends of the magnetic member135are polished such that the surfaces of the metallic foils111flush with the both end faces of the magnetic member135. In the present embodiment, when the both ends of the magnetic member135are polished, the through hole112for forming the through hole portion120is not yet formed. Therefore, residue or the like that is generated due to polishing of the magnetic member135does not enter and remain in the through hole112.

After the surfaces of the metallic foils111flush with the both end faces of the magnetic member135, the through hole112for forming the through hole portion120is formed (Step S302). Specifically, the through hole112having the cylindrical shape in which the diameter of the opening portion is about 100 to 200 μm is formed in the base material110as illustrated inFIG.32, for example. The through hole112is formed by, for example, laser processing or drilling, and after the through hole112is formed, desmear processing for removing resinous residue on the inner wall surface is performed. At this time, the magnetic body131included in the magnetic member135may be made of magnetic metal in order to reduce an influence of a solution that it used to desmear on the both end faces of the magnetic member135that are exposed to the surface.

After the through hole112is formed, the first electroless plating films141afor covering portions that are exposed to the surfaces (Step S104), and thereafter the first electroplating films141bare laminated on the first electroless plating films141a(Step S105). In other words, similarly to the first embodiment, the surfaces of the metallic foils111, the end faces of the magnetic member135, and the inner wall surface of the through hole112are subjected to, for example, electroless copper plating and electro copper plating, so that the first electroless plating films141aand the first electroplating films141bare formed.

With formation of the first electroless plating films141aand the first electroplating films141b, the through hole is formed on the inner sides of the first electroplating films141bin the through hole112. The through hole is filled with the insulating resin125(Step S106). As the insulating resin125, for example, epoxy resin containing filler, such as silica, may be used. The insulating resin125is filled on the inner sides of the first electroplating films141bwithout a gap, and the both end portions of the insulating resin125protrude upward and downward from the first electroless plating films141aand the first electroplating films141blaminated on the metallic foils111.

The both end portions of the insulating resin125are subjected to surface polishing (Step S107), and if the upper surface and the lower surface of the first electroplating films141bflush with the both end faces of the insulating resin125, the second electroless plating films142aand the second electroplating films142bare formed in portions that are exposed to the surfaces (Steps S108and S109). Specifically, similarly to the first embodiment, the surfaces of the first electroplating films141band the end faces of the insulating resin125are subjected to, for example, electroless copper plating and electro copper plating, so that the second electroless plating films142aand the second electroplating films142bare formed.

Through the electroless plating and the electroplating as described above, all of the electroless plating films and the electroplating films are formed, and etching for forming the conductor layers140aand the conductor layers140bof the through hole portion120and the inductor portion130is performed (Step S110). Specifically, etching resists are formed in portions in which the plating films are maintained as the conductor layers140aand140b, and the metallic foils111, the first electroless plating films141a, the first electroplating films141b, the second electroless plating films142a, and the second electroplating films142bare removed by wet etching. With this configuration, similarly to the first embodiment (FIG.17), the through hole portion120including the conductor layers140aas the pads and the inductor portion130including the conductor layers140bas the pad are formed.

Insulating layers and wiring layers are built up in this order on the upper surface and the lower surface of the core substrate100that is formed as described above, the, so that a multi-layer wiring board is formed (Step S111). Furthermore, it may be possible to mount a semiconductor chip on the multi-layer wiring board to form a semiconductor device.

As described above, according to the present embodiment, the magnetic member that is formed by using the magnetic-body-covered conductor wire is embedded in the through hole of the base material, and thereafter the through hole is formed by forming the through hole in the base material. Therefore, it is possible to prevent residue that is generated when the magnetic member is polished from entering and remaining in the through hole, and it is possible to improve the electrical characteristics of the built-in inductor that is included in the core substrate.

Meanwhile, in each of the embodiments as described above, the conductor layers140bcover the entire end faces of the magnetic member135, but the conductor layers140bneed not always cover the entire end faces of the magnetic member135. Specifically, as illustrated inFIG.33for example, a part of the end faces of the magnetic member135of the core substrate100according to the first and the third embodiments need not be covered by the conductor layers140b. Specifically, inFIG.33, the conductor wire132of the magnetic member135is covered by the conductor layers140b, but a part of the magnetic body131is exposed without being covered by the conductor layers140b. In this case, the conductor layers140binclude the first electroless plating films141a, the first electroplating films141b, the second electroless plating films142a, and the second electroplating films142b.

Similarly, as illustrated inFIG.34for example, a part of the end faces of the magnetic member135of the core substrate100according to the second embodiment need not be covered by the conductor layers140b. Specifically, inFIG.34, the conductor wire132of the magnetic member135is covered by the conductor layers140b, but a part of the magnetic body131is exposed without being covered by the conductor layers140b. In this case, the conductor layers140binclude the second electroless plating films142aand the second electroplating films142b.

The core substrate100in which a part of the magnetic member135is not covered by the conductor layers140bmay be formed by adjusting sizes of the etching resists210. Specifically, after all of the electroless plating films and the electroplating films are formed, the etching resists210are formed in only portions corresponding to central portions of the end faces of the magnetic member135, and etching is performed by using the etching resists210as masks. With this configuration, the electroless plating films and the electroplating films around the etching resists210and the metallic foils111are removed, so that peripheries of the end faces of the magnetic member135are exposed.

As described above, the conductor layers140bthat cover the end faces of the magnetic member135may be formed with various configurations.

According to one embodiment of the wiring board and the wiring board manufacturing method disclosed in the present application, it is possible to improve electrical characteristics of a built-in inductor.

All examples and conditional language recited herein are intended for pedagogical purposes of aiding the reader in understanding the invention and the concepts contributed by the inventor to further the art, and are not to be construed as limitations to such specifically recited examples and conditions, nor does the organization of such examples in the specification relate to a showing of the superiority and inferiority of the invention. Although the embodiments of the present invention have been described in detail, it should be understood that the various changes, substitutions, and alterations could be made hereto without departing from the spirit and scope of the invention.