JP2021097130A - Inductor built-in substrate and manufacturing method thereof - Google Patents

Abstract

To provide an inductor built-in board that has large inductance and is highly reliable.SOLUTION: In an inductor built-in substrate 10, a second through hole conductor 36B connecting a first conductor layer 58F and a second conductor layer 58S is directly formed in a second through hole 18b formed in a magnetic resin 18. The position where a protrusion 18d is formed in the second through hole 18b is a position closer to a second surface S of an insulating base material 20.SELECTED DRAWING: Figure 1

Description

The present invention relates to a board with a built-in inductor and a method for manufacturing a board with a built-in inductor.

Patent Document 1 discloses a method for manufacturing an inductor component incorporated in a wiring board. In Patent Document 1, a magnetic material is housed in the resin layer, and a through-hole conductor is provided in the resin layer to prevent the through-hole conductor and the magnetic material from coming into contact with each other.

JP 2016-197624

In Patent Document 1, since the through-hole conductor is arranged in the resin layer, the ratio of the magnetic material to the size of the inductor component is low, and it is considered difficult to increase the inductance.

An object of the present invention is to provide a substrate having a built-in inductor and a method for manufacturing a substrate having a built-in inductor, which are small in size, have a large inductance, and are highly reliable.

The inductor-embedded substrate according to the present invention has a plurality of openings and first through holes formed therein, and is filled in the core substrate having the first surface and the second surface on the opposite side of the first surface, and the plurality of openings. A substrate with a built-in inductor having a magnetic resin having a plurality of second through holes, a first through-hole conductor made of a metal film formed in the first through holes, and the plurality of second through holes. It has a plurality of second through-hole conductors made of a metal film formed on the surface of the conductor. A protrusion formed by adhering a residue of the magnetic resin is formed on the inner wall of the plurality of second through holes, and the position of the protrusion in the plurality of second through holes is the core. It is a position closer to either the first surface or the second surface of the substrate.

The method for manufacturing an inductor-embedded substrate according to the present invention is to form a plurality of openings in an insulating base material having a first surface and a second surface opposite to the first surface, and magnetism in the plurality of openings. Filling with a magnetic resin containing body particles, forming a first through hole in the insulating base material, forming a plurality of second through holes in the magnetic resin, and forming the first through hole. It includes forming a through-hole conductor made of a metal film in the holes and in the plurality of second through holes. Then, after the formation of the first through hole, a desmear treatment is performed, and when the plurality of second through holes are formed, the position where the protrusion is formed in the plurality of second through holes is the first of the insulating base material. Protrusions formed by adhering magnetic resin residues to the inner walls of the plurality of second through holes are formed so as to be closer to either the surface or the second surface.

In the method for manufacturing an inductor-embedded substrate and an inductor-embedded substrate of the present invention, a second through-hole conductor (through-hole conductor) made of a metal film is formed directly in the second through hole of the magnetic resin, so that the magnetic resin of the inductor component. The volume of the can be increased and the inductance can be increased. The protrusion made of the residue of the magnetic resin formed on the inner wall of the second through hole is located near either the first surface or the second surface of the core substrate. Since the protrusions are formed on one side, the stress balance of the core substrate is balanced and the reliability of the inductor-embedded substrate is improved as compared with the case where the protrusions are formed randomly.

FIG. 1A is a cross-sectional view of the inductor built-in substrate of the embodiment, and FIG. 1B is an enlarged view of a core substrate of the inductor built-in substrate. The process chart which shows the manufacturing method of the inductor built-in substrate which concerns on embodiment. The process chart which shows the manufacturing method of the inductor built-in substrate which concerns on embodiment. The process chart which shows the manufacturing method of the inductor built-in substrate which concerns on embodiment.

FIG. 1A shows a cross-sectional view of an inductor built-in substrate 10 having an inductor of the embodiment built-in. The inductor-embedded substrate 10 includes an insulating base material 20 having a first surface F and a second surface S opposite to the first surface F, and a first conductor layer (conductor) on the first surface F of the insulating base material 20. Circuit) 58F, a second conductor layer 58S on the second surface S of the insulating base material 20, and a through-hole conductor 36 connecting the first conductor layer 58F and the second conductor layer 58S. It has a core substrate 30. The core substrate 30 has a first surface F and a second surface S opposite to the first surface F. The first surface F of the core substrate 30 and the first surface F of the insulating base material 20 are the same surface, and the second surface S of the core substrate 30 and the second surface S of the insulating base material 20 are the same surface. The insulating base material 20 is formed of a resin such as epoxy and a core material 14 such as glass cloth for reinforcement. The insulating base material 20 may further have inorganic particles such as silica.

The inductor-embedded substrate 10 further has an upper build-up layer 450F on the first surface F of the core substrate 30. The upper build-up layer 450F penetrates the insulating layer 450A formed on the first surface F of the core substrate 30, the conductor layer 458A on the insulating layer 450A, and the insulating layer 450A, and passes through the first conductor layer 58F and the conductor layer 458A. It has a via conductor 460A connected to it. The upper build-up layer 450F further penetrates the insulating layer 450A, the insulating layer 450C on the conductor layer 458A, the conductor layer 458C on the insulating layer 450C, and the insulating layer 450C, and connects the conductor layer 458A and the conductor layer 458C to the via conductor 460C. Has.

The inductor-embedded substrate 10 further has a lower build-up layer 450S on the second surface S of the core substrate 30. The lower build-up layer 450S penetrates the insulating layer 450B formed on the second surface S of the core substrate 30, the conductor layer 458B on the insulating layer 450B, and the insulating layer 450B, and the second conductor layer 58S and the conductor layer 458B. Has a via conductor 460B connecting the above. The lower build-up layer 450S is a via conductor that further penetrates the insulating layer 450B, the insulating layer 450D on the conductor layer 458B, the conductor layer 458D on the insulating layer 450D, and the insulating layer 450D, and connects the conductor layer 458B and the conductor layer 458D. It has 460D.

The inductor-embedded substrate of the embodiment further has a solder resist layer 470F having an opening 471F on the upper build-up layer 450F and a solder resist layer 470S having an opening 471S on the lower build-up layer 450S.

The upper surfaces of the conductor layers 458C and 458D and the via conductors 460C and 460D exposed by the openings 471F and 471S of the solder resist layers 470F and 470S function as pads. A protective film 472 made of Ni / Au, Ni / Pd / Au, Pd / Au, OSP, or the like is formed on the pad. Solder bumps 476F and 476S are formed on the protective film. An IC chip (not shown) is mounted on the inductor built-in substrate 10 via a solder bump 476F formed on the upper build-up layer 450F. The inductor built-in substrate 10 is mounted on a motherboard (not shown) via a solder bump 476S formed on the lower build-up layer 450S.

FIG. 1 (B) shows an enlarged part of the core substrate 30 in FIG. 1 (A). In the core substrate 30, the through-hole conductor 36 connecting the first conductor layer 58F and the second conductor layer 58S includes the first through-hole conductor 36A formed in the first through hole 20a penetrating the core substrate 30 and the core. It is composed of a second through-hole conductor 36B formed in the second through hole 18b of the magnetic resin 18 filled in the opening 20b of the substrate 30. The diameter da of the first through hole 20a and the diameter db of the second through hole 18b are substantially equal to each other. The first through-hole conductor 36A and the second through-hole conductor 36B are filled with the resin filler 16, and the through-hole land 58SR is made of lid plating. The through-hole land 58SR includes a first through-hole land 58SRA formed on the first through-hole conductor 36A and a second through-hole land 58SRB formed on the second through-hole conductor 36B.

The magnetic resin 18 contains an iron oxide filler (magnetic particles) and a resin such as epoxy. As magnetic particles, _FeO, include iron oxide filler such as _{Fe 2 O 3, Fe 3 O} 4. The content of the iron oxide filler in the magnetic resin is preferably 60% by weight or more. It is desirable that the particle size of the iron oxide filler is not uniform because the weight% can be increased and the magnetic permeability and heat transfer property can be increased.

As shown in FIG. 1B, the first through-hole conductor 36A formed in the first through-hole 20a penetrating the core substrate 30 comes into contact with the first through-hole 20a. The first through-hole conductor 36A includes a second electrolytic plating film 32 on the first through hole 20a and a second electrolytic plating film 34 on the second electrolytic plating film 32. The second through-hole conductor 36B formed in the second through-hole 18b penetrating the magnetic resin 18 comes into contact with the second through-hole 18b. The second through-hole conductor 36B includes a second electrolytic plating film 32 on the second through hole 18b and a second electrolytic plating film 34 on the second electrolytic plating film 32.

The first through hole land 58SRA and the second conductor layer 58S on the insulating base material 20 are the lowest layer copper foil 22, the first electroplating film 24m on the copper foil 22, and the first electroplating film. The first electroplating film 24d on 24 m, the second electroplating film 32 on the first electroplating film 24d, the second electroplating film 34 on the second electroplating film 32, and the second electroplating. It is composed of a third electroplating film 35 on the film 34 and a third electroplating film 37 on the third electroplating film 35. The second through hole land 58SRB and the second conductor layer 58S on the magnetic resin 18 are the first electroplating film 24m on the lowermost layer, the first electroplating film 24d on the first electroplating film 24m, and the first. 1 The second electroplating film 32 on the electroplating film 24d, the second electroplating film 34 on the second electroplating film 32, and the third electroplating film 35 on the second electroplating film 34. It is composed of a third electroplating film 37 on the third electroplating film 35. The first electrolytic plating film 24m and the first electrolytic plating film 24d form a shield layer 24.

The core substrate 30 of the embodiment has a first conductor layer 58F (connection pattern 58FL) and a second through hole conductor 36B formed in the magnetic resin 18 shown in FIG. 1A. The conductor layer 58S (connection pattern 58SL) is arranged in a helical shape (spiral along the axis in the direction parallel to the front and back surfaces of the core substrate), and forms an inductor 59 together with the second through-hole conductor 36B.

In the inductor-embedded substrate 10 of the embodiment, the first conductor layer 58F and the second conductor layer 58S are formed on the surface of the core substrate 30, and the second through hole connecting the first conductor layer 58F and the second conductor layer 58S. The conductor 36B is directly formed in the second through hole 18b that penetrates the magnetic resin 18. Therefore, the proportion of the magnetic material in the inductor built-in substrate 10 becomes large, and the inductance can be increased.

As shown in FIG. 1 (B), in the inductor-embedded substrate 10 of the embodiment, a protrusion 18d formed by adhering a residue of the magnetic resin is formed on the inner wall of the second through hole 18b. The height of the protrusion 18d is 10 microns or more and 50 microns or less. The position of the protrusion 18d in the second through hole 18b is a position closer to the second surface S of the insulating base material 20 forming the core substrate. In the embodiment, the formation positions of almost all the protrusions 18d are close to the second surface S, but it is also possible that the formation positions of almost all the protrusions 18d are close to the first surface F. is there. That is, the protrusion 18d is formed at a position closer to either the first surface F or the second surface S of the core substrate. Since the protrusion is formed on one of the second through holes, the stress balance of the core substrate is balanced and the reliability of the inductor built-in substrate 10 is improved as compared with the case where the protrusion is randomly formed in the second through hole. ..

As shown in FIG. 1A, in the inductor built-in substrate 10, the forming position of the protrusion 18d in the plurality of second through holes 18b is located on the second surface S rather than the central position CC in the thickness direction of the core substrate 30. It is a close position. That is, the distance d2 from the central position CC to the protrusion 18d is larger than the distance d1 from the protrusion 18d to the opening 18os on the second surface S side of the second through hole 18. In the embodiment, the protrusion 18d is formed at a position closer to the opening 18os on the second surface S side of the second through hole 18, but almost all the protrusions 18d are formed at a position closer to the first surface F. In some cases, it is formed at a position closer to the opening 18of on the first surface F side of the second through hole 18 from the protrusion 18d. In the manufacturing process, when the protrusion 18d is formed at a position closer to the opening 18os on the second surface S side or the opening 18of on the first surface F side of the second through hole 18b, it is formed on the second through hole 18b. When the resin filler is filled in the second through-hole conductor, it is difficult to generate air bubbles in the resin filler that cause disconnection of the second through-hole conductor.

[Manufacturing Method of Inductor Built-in Substrate of the Embodiment]
2 to 4 show a method of manufacturing the inductor-embedded substrate of the embodiment.
A substrate 20z made of a copper-clad laminate in which copper foil 22 is laminated on both sides of the insulating base material 20 is prepared (FIG. 2 (A)). An opening 20b for filling the magnetic resin is formed in the insulating base material 20 (FIG. 2B). A resin paste composed of 90% by weight of iron oxide filler (magnetic particles) and epoxy resin is vacuum-printed in the opening 20b. The resin paste is temporarily cured (semi-cured) at a temperature at which the viscosity of the resin paste is twice or less the room temperature to form the temporarily cured magnetic resin 18β (FIG. 2 (C)).

A first electroless plating film 24m is formed by electroless plating treatment and a first electrolytic plating film 24d is formed by electroplating treatment on the surface of the insulating base material 20 and the surface of the temporarily cured magnetic resin 18β exposed from the opening 20b. (Fig. 2 (D)). The first electrolytic plating film 24m and the first electrolytic plating film 24d form a shield layer 24.

The first through hole 20a is formed in the insulating base material 20 by mechanical drilling, laser machining, or the like (FIG. 2 (E)). At this time, protrusions 20d made of the residue of the insulating base material are formed at random positions of the first through holes 20a. After that, the first through hole 20a is desmeared with the chemical solution, and the protrusion 20d is deleted (FIG. 3 (A)). During the desmear treatment, the temporarily cured magnetic resin 18β covered with the shield layer 24 composed of the first electrolytic plating film 24m and the first electrolytic plating film 24d is not affected by the chemical solution. The iron oxide filler on the surface of the temporarily cured magnetic resin 18β is not affected by the desmear treatment.

The second through hole 18b is formed in the temporarily cured magnetic resin 18β by mechanical drilling, laser machining, or the like (FIG. 3 (B)). By adjusting the machining conditions of the mechanical drill or the irradiation conditions of laser machining, the formation position of the protrusion 18d in the second through hole 18b is a position closer to the second surface S of the insulating base material 20. In the embodiment, the formation positions of almost all the protrusions 18d are close to the second surface S, but it is also possible that the formation positions of almost all the protrusions 18d are close to the first surface F. is there. That is, the protrusion 18d is formed at a position closer to either the first surface F or the second surface S of the core substrate.

Further, the forming position of the protrusion 18d in the plurality of second through holes 18b is a position closer to the second surface S than the central position CC in the thickness direction of the insulating base material 20. That is, the distance d2 from the central position CC to the protrusion 18d is larger than the distance d1 from the protrusion 18d to the opening 18os on the second surface S side of the second through hole 18. In the embodiment, the protrusion 18d is formed at a position closer to the opening 18os on the second surface S side of the second through hole 18, but almost all the protrusions 18d are formed at a position closer to the first surface F. In some cases, it is formed at a position closer to the opening 18of on the first surface F side of the second through hole 18 from the protrusion 18d.

In this embodiment, since 90% by weight of the iron oxide filler is contained, it is not easy to make holes after the main curing, but since it is formed before the main curing, through holes can be easily formed. The magnetic material layer in the temporarily cured state is heated to crosslink the contained resin, and the magnetic material resin 18 is formed in the main cured state. Here, it is heated at 150 ° C. to 190 ° C. for 1 hour. By high-pressure washing, the processed smear at the time of drilling is removed to the extent that it can be removed. Normally, desmear is performed with an alkaline chemical, but since the alkaline chemical may cause the iron oxide filler contained in the magnetic resin 18 to fall off in the process of swelling and peeling the resin, high-pressure water washing is performed here. On the surface of the insulating base material 20 and the magnetic resin 18 on the first electrolytic plating film 24d, on the surfaces of the first through hole 20a and the second through hole 18b, the second electroless plating film 32 was formed by electroless plating. The second electroplating film 34 is formed by the electroplating treatment. The second electrolytic plating film 32 and the second electrolytic plating film 34 form a first through-hole conductor 36A in the first through hole 20a and a second through-hole conductor 36B in the second through hole 18b (FIG. 3). (C)). The second through-hole conductor 36B is formed with a through-hole protrusion 36Bd caused by the protrusion 18d.

The resin filler 16 is filled in the first through-hole conductor 36A formed in the first through-hole 20a and the second through-hole conductor 36B formed in the second through-hole 18b, and the surface of the core substrate 30 is polished. (Fig. 3 (D)). The resin filler in the second through-hole conductor 36B is filled with the resin filler from the opening 36Bf side on the first surface side in a state where the opening 36Bs side on the second surface S side of the second through hole 36B is depressurized. It is done by. Since the protrusion 18d is formed at a position closer to the opening 18os on the second surface S side of the second through hole 18b, the resin filler is formed in the second through hole conductor 36B formed on the second through hole 18b. Is not interfered with by the through-hole protrusion 36Bd, and bubbles that cause disconnection of the second through-hole conductor are unlikely to be generated in the resin filler 16.

A third electroless plating film 35 is formed on the second electrolytic plating film 34 and on the exposed surface of the resin filler 16 by electroless plating, and a third electrolytic plating film 37 is formed on the third electroless plating film 35. (Fig. 4 (A)). An etching resist 54 having a predetermined pattern is formed on the third electrolytic plating film 37 (FIG. 4 (B)).

The third electrolytic plating film 37, the third electrolytic plating film 35, the second electrolytic plating film 34, the second electrolytic plating film 32, the first electrolytic plating film 24d, and the first electrolytic plating film 24m exposed from the etching resist 54. After the copper foil 22 is removed, the etching resist is removed, the first conductor layer 58F and the second conductor layer 58S are formed, and the core substrate 30 is completed (FIG. 4 (C)).

An upper build-up layer 450F, a lower build-up layer 450S, a solder resist layer 470F, 470S, and solder bumps 476F and 476S are formed on the core substrate 30 by a known manufacturing method (FIG. 1 (A)).

In the method for manufacturing an inductor-embedded substrate of the embodiment, an inductor is formed in order to form a second through-hole conductor 36B composed of a second electroless plating film 32 and a second electrolytic plating film 34 in the second through hole 18b of the magnetic resin 18. The volume of the magnetic resin 18 of the built-in substrate 10 can be increased to increase the inductance.

10 Inductor built-in substrate 16 Resin filler 18 Magnetic resin 18b Second through hole 18d Protrusion 20 Insulating base material 20a First through hole 20b Opening 30 Core substrate 36A First through hole conductor 36B Second through hole conductor

Claims (8)

A core substrate in which a plurality of openings and a first through hole are formed and has a first surface and a second surface opposite to the first surface.
A magnetic resin filled in the plurality of openings and having a plurality of second through holes,
It is a board with a built-in inductor that has
A first through-hole conductor made of a metal film formed in the first through hole,
An inductor-embedded substrate having a plurality of second through-hole conductors made of a metal film formed in the plurality of second through holes.
On the inner walls of the plurality of second through holes, protrusions formed by adhering the residue of the magnetic resin are formed.
The position of forming the protrusion in the plurality of second through holes is a position closer to either the first surface or the second surface of the core substrate. The substrate with a built-in inductor according to claim 1.
The forming position of the protrusion in the plurality of second through holes is a position closer to either the first surface or the second surface than the central position in the thickness direction of the core substrate. The substrate with a built-in inductor according to claim 1 or 2.
The core substrate contains a core material, inorganic particles, and a resin.
The magnetic resin does not contain a core material. A substrate with a built-in inductor according to any one of claims 1 to 3.
No metal film is formed on the inner walls of the plurality of openings of the core substrate. A substrate with a built-in inductor according to any one of claims 1 to 4.
A resin filler is filled inside the plurality of second through-hole conductors. Forming a plurality of openings in an insulating base material having a first surface and a second surface opposite to the first surface, and
Filling the plurality of openings with a magnetic resin containing magnetic particles,
Forming the first through hole in the insulating base material and
Forming a plurality of second through holes in the magnetic resin and
A method for manufacturing an inductor-embedded substrate, which comprises forming a through-hole conductor made of a metal film in the first through hole and in the plurality of second through holes.
After the formation of the first through hole, a desmear treatment is performed.
When the plurality of second through holes are formed, the positions of the protrusions in the plurality of second through holes are set to be closer to either the first surface or the second surface of the insulating base material. In addition, a protrusion formed by the residue of the magnetic resin adhering to the inner walls of the plurality of second through holes is formed. The method for manufacturing a substrate with a built-in inductor according to claim 6.
After forming the plurality of second through holes, a washing treatment is performed. The method for manufacturing a substrate with a built-in inductor according to claim 7.
After forming through-hole conductors made of a metal film in the first through hole and the plurality of second through holes,
The through-hole conductor is filled with a resin filler.

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