JP7368693B2 - Inductor built-in board - Google Patents

Description

The present invention relates to an inductor-embedded substrate containing an inductor.

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

JP2016-197624

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, making it difficult to increase the inductance. On the other hand, when a through-hole conductor and a magnetic material are brought into contact, it is thought that the reliability of the through-hole conductor decreases.

An object of the present invention is to provide an inductor-embedded substrate with highly reliable through-hole conductors.

The inductor-embedded substrate according to the present invention includes a core substrate in which an opening is formed, a magnetic resin filled in the opening and having a first through hole, and a first through hole made of a metal film formed in the first through hole. 1 through-hole conductor. The magnetic resin contains 60% by weight or more of iron oxide filler, and a resin residue layer having an average thickness of 0.01 μm or more and 1 μm or less is formed on the surface of the first through hole , and is further formed on the core substrate. a second through-hole conductor made of a metal film formed in the second through-hole, a resin residue layer is formed on the surface of the second through-hole, and a resin residue layer is formed on the surface of the second through-hole; The thickness of the resin residue layer is thicker than the thickness of the resin residue layer of the second through hole.

In the inductor-embedded substrate of the present invention, since the first through-hole conductor made of a metal film is directly formed in the first through-hole of the magnetic resin, it is possible to increase the volume of the magnetic resin of the inductor component and increase the inductance. can. Since the magnetic resin contains 60% by weight or more of iron oxide filler, it has high heat conductivity and improves the heat dissipation of the inductor-embedded substrate. Since the resin residue layer on the surface of the first through hole has an average thickness of 0.01 μm or more and 1 μm or less, the iron oxide filler exposed from the surface of the first through hole is connected to the metal film forming the first through hole conductor. This increases the reliability of the first through-hole conductor.

FIG. 1(A) is a cross-sectional view of the inductor built-in board of the embodiment, FIG. 1(B) is a plan view of a through-hole land, and FIG. 1(C) is an enlarged view of the core board of the inductor built-in board. . FIG. 3 is a process diagram showing a method for manufacturing an inductor-embedded substrate according to an embodiment. FIG. 3 is a process diagram showing a method for manufacturing an inductor-embedded substrate according to an embodiment. FIG. 3 is a process diagram showing a method for manufacturing an inductor-embedded substrate according to an embodiment. 1 is a cross-sectional micrograph of a first through-hole conductor of an inductor-embedded board according to an embodiment. FIG. 3 is a cross-sectional micrograph of the center portion of the first through-hole conductor of the inductor-embedded board according to the embodiment. A cross-sectional micrograph of a first through-hole conductor of an inductor-embedded board according to a reference example. FIG. 3 is a cross-sectional micrograph of the center portion of the first through-hole conductor of the inductor-embedded board according to the reference example.

FIG. 1A shows a cross-sectional view of an inductor-embedded substrate 10 that incorporates an inductor according to an embodiment. 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 layer) 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 reinforcing core material 14 such as glass cloth. The insulating base material 20 may further include inorganic particles such as silica.

The inductor-embedded substrate 10 further includes an upper buildup layer 450F on the first surface F of the core substrate 30. The upper buildup 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 connects the first conductor layer 58F and the conductor layer 458A. It has a connected via conductor 460A. The upper buildup 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 to connect the conductor layer 458A, the via conductor 460A, and the conductor layer 458C. It has a via conductor 460C.

The inductor-embedded substrate 10 further includes a lower buildup layer 450S on the second surface S of the core substrate 30. The lower buildup 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 passes through the second conductor layer 58S and the conductor layer 458B. and a via conductor 460B that connects the via conductor 460B. The lower buildup layer 450S 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, the via conductor 460B, and the conductor layer 458D. It has a via conductor 460D for connection.

The inductor built-in substrate of the embodiment further includes a solder resist layer 470F having an opening 471F on the upper buildup layer 450F, and a solder resist layer 470S having an opening 471S on the lower buildup layer 450S.

The upper surfaces of conductor layers 458C and 458D and via conductors 460C and 460D exposed through openings 471F and 471S of solder resist layers 470F and 470S function as pads. A protective film 472 made of Ni/Au, Ni/Pd/Au, Pd/Au, or OSP 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-embedded substrate 10 via solder bumps 476F formed on the upper buildup layer 450F. The inductor built-in board 10 is mounted on the motherboard via solder bumps 476S formed on the lower buildup layer 450S.

FIG. 1(C) shows an enlarged portion of the core substrate 30 in FIG. 1(A). In the core board 30, the through-hole conductor 36 connecting the first conductor layer 58F and the second conductor layer 58S is connected to the second through-hole conductor 36A formed in the second through-hole 20a penetrating the core board 30, and the core The first through-hole conductor 36B is formed in the first through-hole 18b of the magnetic resin 18 filled in the opening 20b of the substrate 30. The diameter da of the second through hole 20a and the diameter db of the first through hole 18b are approximately equal. The second through-hole conductor 36A and the first through-hole conductor 36B are filled with a resin filler 16, and the through-hole land 58FR is made of lid plating. The through-hole land 58FR includes a second through-hole land 58FRA formed on the second through-hole conductor 36A and a first through-hole land 58FRB formed on the first through-hole conductor 36B.

FIG. 1(B) is a plan view of a second through-hole land 58FRA formed on the second through-hole conductor 36A and a first through-hole land 58FRB formed on the first through-hole conductor 36B. The second through-hole land 58FRA is formed concentrically with the second through-hole conductor 36A, and the first through-hole land 58FRB is formed concentrically with the first through-hole conductor 36B. The diameter Da of the second through-hole land 58FRA and the diameter Db of the first through-hole land 58FRB are approximately equal. The second through-hole land 58FRA and the first through-hole land 58FRB are connected by a first conductor layer (circuit pattern) 58F. The diameter Db of the first through-hole land 58FRB is smaller than the diameter DB of the opening 20b filled with the magnetic resin 18. That is, the first through-hole land 58FRB does not extend from above the magnetic resin 18 to the insulating base material 20.

The magnetic resin 18 includes an iron oxide filler (magnetic particles) and a resin such as epoxy. Examples of magnetic particles include iron oxide fillers such as iron (III) oxide. The content of iron oxide filler in the magnetic resin is preferably 60% to 90% by weight. It is preferable that the particle size of the iron oxide filler is not uniform because the weight percentage can be increased and the magnetic permeability and heat conductivity can be increased.

As shown in FIG. 1C, the second through-hole conductor 36A formed in the second through-hole 20a that penetrates the core substrate 30 contacts the second through-hole 20a. The second through-hole conductor 36A includes a second electroless plated film 32 on the second through hole 20a, and a second electrolytic plated film 34 on the second electroless plated film 32. The first through-hole conductor 36B formed in the first through-hole 18b that penetrates the magnetic resin 18 contacts the first through-hole 18b. The first through-hole conductor 36B includes a second electroless plated film 32 on the first through hole 18b and a second electrolytic plated film 34 on the second electroless plated film 32. The thickness ta of the second electroless plated film 32 and the second electrolytic plated film 34 forming the second through-hole conductor 36A is the same as the thickness ta of the second electroless plated film 32 and the second electrolytic plated film 34 forming the first through-hole conductor 36B. It is thicker than the thickness tb with the film 34. The thickness ta of the second through-hole conductor 36A formed in the second through-hole 20a of the insulating base material 20 with low thermal conductivity is the same as that of the second through-hole conductor 36A formed in the first through-hole 18b of the magnetic resin 18 with high thermal conductivity. By making the thickness thicker than the thickness tb of the first through-hole conductor 36B, the heat radiation balance between the second through-hole conductor 36A and the first through-hole conductor 36B is adjusted.

FIG. 5 is a cross-sectional micrograph of the first through-hole conductor 36B of the embodiment.
The central I-shaped portion is the first through-hole conductor 36B (second electroless plated film 32, second electrolytic plated film 34). The left side of the I-shaped first through-hole conductor 36B is the magnetic resin 18. A first through-hole conductor 36B is formed above the first through-hole 18b provided in the magnetic resin 18. The resin filler 16 is on the right side of the I-shaped first through-hole conductor 36B. The round particles in the magnetic resin 18 are iron oxide filler 17. The round particles in the resin filler 16 are inorganic fillers 21. The left side of the magnetic resin 18 is an insulating base material 20, and the boundary between the magnetic resin 18 and the insulating base material 20 is an opening 20b.

FIG. 6 is a cross-sectional micrograph with increased magnification of the central portion of the first through-hole conductor 36B indicated by arrow A in FIG. The black portion existing at the interface between the first through-hole conductor 36B and the magnetic resin 18 is the resin residue layer 19. The resin residue layer 19 is a resin residue in which a resin component separated from the magnetic resin when forming the first through hole 18b in the magnetic resin 18 with a drill is reattached to the magnetic resin side. Since it is once separated and reattached, it is easy to peel off from the magnetic resin. In the first through-hole conductor 36B of the embodiment, the resin residue layer 19 on the surface of the first through-hole 18b has an average thickness of 0.01 μm or more and 1 μm or less. Since the resin residue layer 19 has an average thickness of 1 μm or less, breaks in the resin residue layer 19 exist. The iron oxide filler 17 exposed from the surface of the first through-hole 18b at the break in the resin residue layer 19 comes into contact with the metal film forming the first through-hole conductor 36B, increasing the reliability of the first through-hole conductor. Note that when the average thickness of the resin-rich layer exceeds 1 μm, the resin-rich layer covers the entire surface of the first through hole almost seamlessly. The reliability of the first through-hole conductor becomes low.

FIG. 7 is a cross-sectional micrograph of the first through-hole conductor 36B of the reference example.
The central I-shaped portion is the first through-hole conductor 36B. The right side of the I-shaped first through-hole conductor 36B is the magnetic resin 18. A first through-hole conductor 36B is formed above the first through-hole 18b provided in the magnetic resin 18. The left side of the I-shaped first through-hole conductor 36B is the resin filler 16. The round particles in the magnetic resin 18 are iron oxide filler 17. The round particles in the resin filler 16 are inorganic fillers 21. The right side of the magnetic resin 18 is an insulating base material 20, and the boundary between the magnetic resin 18 and the insulating base material 20 is an opening 20b.

FIG. 8 is a cross-sectional micrograph with increased magnification of the central portion of the first through-hole conductor 36B indicated by arrow B in FIG. The black portion existing at the interface between the first through-hole conductor 36B and the magnetic resin 18 is the resin residue layer 19. In the first through-hole conductor 36B of the reference example, the resin residue layer 19 on the surface of the first through-hole 18b has an average thickness of 1 μm or more. Since the resin residue layer 19 has an average thickness of 1 μm or more, the resin residue layer is formed seamlessly between the iron oxide filler 17 exposed from the surface of the first through hole 18b and the metal film forming the first through hole conductor 36B. 19 intervenes. In the reference example, the metal film forming the first through-hole conductor 36B together with the resin residue layer 19 is likely to peel off from the iron oxide filler 17 exposed from the first through-hole 18b, and the reliability of the first through-hole conductor is low.

As shown in FIG. 1(C), the second through-hole land 58FRA and the first conductor layer 58F on the insulating base material 20 are connected to the bottom copper foil 22 and the first electroless layer on the copper foil 22. The plating film 24m, the first electrolytic plating film 24d on the first electroless plating film 24m, the second electroless plating film 32 on the first electrolytic plating film 24d, and the second electroless plating film 32 on the second electroless plating film 32. It consists of an electrolytic plated film 34, a third electroless plated film 35 on the second electrolytic plated film 34, and a third electrolytic plated film 37 on the third electroless plated film 35. The first conductor layer 58F on the first through-hole land 58FRB and the magnetic resin 18 includes the first electroless plated film 24m at the bottom layer, the first electrolytic plated film 24d on the first electroless plated film 24m, and the first electroless plated film 24d on the first electroless plated film 24m. A second electroless plating film 32 on the first electrolytic plating film 24d, a second electrolytic plating film 34 on the second electroless plating film 32, and a third electroless plating film 35 on the second electrolytic plating film 34. , and a third electrolytic plated film 37 on the third electroless plated film 35. The first electroless plated film 24m and the first electrolytic plated film 24d constitute the shield layer 24. The thickness tA of the first conductor layer 58F on the second through-hole land 58FRA and the insulating base material 20 is thicker than the thickness tB of the first conductor layer 58F on the first through-hole land 58FRB and the magnetic resin 18. 22 thick. The thickness tA of the second through-hole land 58FRA formed on the insulating base material 20 with low thermal conductivity is greater than the thickness tB of the first through-hole land 58FRB formed on the magnetic resin 18 with high thermal conductivity. By making the copper foil 22 with high thermal conductivity thick, the heat radiation balance between the second through-hole conductor 36A and the first through-hole conductor 36B is adjusted.

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

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

[Method for manufacturing the inductor built-in board of the embodiment]
2 to 4 show a method of manufacturing an inductor-embedded substrate according to an embodiment.
A substrate 20z made of a copper-clad laminate in which copper foil 22 is laminated on both sides of an insulating base material 20 is prepared (FIG. 2(A)). An opening 20b for filling with magnetic resin is formed in the insulating base material 20 (FIG. 2(B)). A resin paste consisting of 60% to 90% by weight iron oxide filler (magnetic particles) and epoxy resin is vacuum printed in the opening 20b. The resin paste is temporarily hardened (semi-hardened) at a temperature at which the viscosity of the resin paste is less than twice that of room temperature to form a temporarily hardened magnetic resin 18β (FIG. 2(C)).

A first electroless plated film 24m is formed by electroless plating on the surface of the insulating base material 20 and the surface of the temporarily hardened magnetic resin 18β exposed from the opening 20b, and a first electrolytic plated film 24d is formed by electrolytic plating. (Figure 2(D)). The first electroless plated film 24m and the first electrolytic plated film 24d constitute the shield layer 24.

A second through hole 20a is formed in the insulating base material 20 by drilling (FIG. 2(E)). Thereafter, the second through hole 20a is desmeared using a chemical solution, and the resin rich layer made of resin residue adhering to the side wall of the second through hole 20a is removed. The average thickness of the resin-rich layer is set to 0.5 μm or less. During the desmear process, the temporarily hardened magnetic resin 18β covered with the shield layer 24 made up of the first electroless plated film 24m and the first electrolytic plated film 24d is not affected by the chemical solution. The iron oxide filler on the surface of the temporarily hardened magnetic resin 18β is not affected by the desmear treatment.

A first through hole 18b is formed in the temporarily hardened magnetic resin 18β by drilling. For drilling, the same drill that formed the second through hole 20a in the insulating base material 20 is used. By lowering the drill rotation speed, the average thickness of the resin-rich layer (resin residue) adhering to the surface of the first through hole 18b is reduced. In this embodiment, since the iron oxide filler is contained in an amount of 60% to 90% by weight, it is not easy to make holes after the main curing, but since the holes are formed before the main curing, the through holes can be easily formed. . The magnetic material layer of the temporarily hardened magnetic base material in a temporarily hardened state is heated to crosslink the resin contained therein, and brought into a fully hardened state to form the magnetic resin 18 (FIG. 3(A)). Here, it is heated at 150°C to 190°C for 1 hour. Processing smear from drilling is removed by high-pressure water washing (Figure 3(B)). Desmearing is usually performed using an alkaline chemical, but since the alkaline chemical may cause the iron oxide filler contained in the magnetic resin 18 to fall off during the process of swelling and peeling off the resin, high-pressure water washing is performed here. Further, by dry desmearing using O2 plasma, the resin residue layer 19 on the surface of the first through hole 18b is reduced to an average thickness of 1 μm or less, as shown in FIG. Here, even if dry desmear is used, the average thickness of the resin residue layer 19 cannot be made less than 0.01 μm. The average thickness of the resin residue layer 19 on the surface of the first through hole 18b is thicker than the average thickness of the resin rich layer on the surface of the second through hole 20a from which the resin rich layer is removed by chemical treatment. On the first electrolytic plated film 24d on the surface of the insulating base material 20 and the magnetic resin 18, and on the surfaces of the second through hole 20a and the first through hole 18b, a second electroless plated film 32 is formed by electroless plating treatment, A second electrolytic plated film 34 is formed by electrolytic plating. A second through-hole conductor 36A is formed in the second through-hole 20a and a first through-hole conductor 36B is formed in the first through-hole 18b by the second electroless plating film 32 and the second electrolytic plating film 34 (FIG. 3). (C)).

The resin filler 16 is filled in the second through-hole conductor 36A formed in the second through-hole 20a and the first through-hole conductor 36B formed in the first through-hole 18b, so that the surface of the insulating base material 20 is Polished (FIG. 3(D)). A third electroless plating film 35 is formed on the second electrolytic plating film 34 and 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 plated film 37 (FIG. 4(B)).

The third electrolytic plated film 37, the third electroless plated film 35, the second electrolytic plated film 34, the second electroless plated film 32, the first electrolytic plated film 24d, and the first electroless plated film 24m exposed from the etching resist 54 After the copper foil 22 is removed, the etching resist is removed, and a first conductor layer 58F and a second conductor layer 58S are formed, completing the core substrate 30 (FIG. 4(C)). The first conductor layer 58F, the second conductor layer 58S, and the second through-hole land 58FRA on the first surface F side and the second through-hole land on the second surface S side of the second through-hole conductor 36A on the insulating base material 20 58SRA includes the lowest layer copper foil 22, the first electroless plating film 24m on the copper foil 22, the first electrolytic plating film 24d on the first electroless plating film 24m, and the first electrolytic plating film 24d on the first electroless plating film 24m. a second electroless plated film 32, a second electrolytic plated film 34 on the second electroless plated film 32, a third electroless plated film 35 on the second electrolytic plated film 34, and a second electroless plated film 34 on the second electroless plated film 32; It consists of a third electrolytic plated film 37 on a plated film 35. The first conductor layer 58F, the second conductor layer 58S, and the first through-hole land 58FRB on the first surface F side and the first through-hole land 58SRB on the second surface S side of the first through-hole conductor 36B on the magnetic resin 18. are the first electroless plating film 24m, the first electrolytic plating film 24d on the first electroless plating film 24m, the second electroless plating film 32 on the first electrolytic plating film 24d, and the second electroless plating film 24m. It consists of a second electrolytic plated film 34 on the membrane 32, a third electroless plated film 35 on the second electrolytic plated film 34, and a third electrolytic plated film 37 on the third electroless plated film 35.

An upper buildup layer 450F, a lower buildup layer 450S, solder resist layers 470F, 470S, and solder bumps 476F, 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 according to the embodiment, in order to form the first through-hole conductor 36B made of the second electroless plating film 32 and the second electrolytic plating film 34 in the first through hole 18b of the magnetic resin 18, the inductor The volume of the magnetic resin 18 of the built-in board 10 can be increased, and the inductance can be increased. Although the first through-hole conductor 36B is provided directly on the magnetic resin 18, since the average thickness of the resin-rich layer is 1 μm or less, the reliability of the first through-hole conductor does not decrease.

10 Inductor built-in board 18 Magnetic resin 18b First through hole 19 Resin residue layer 20 Core board 20a First through hole 20a Opening 22 Copper foil 30 Core board 36A Second through hole conductor 36B First through hole conductor

Claims (2)

a core substrate with an opening formed therein;
a magnetic resin filled in the opening and having a first through hole;
An inductor-embedded substrate having a first through-hole conductor made of a metal film formed in the first through-hole,
The magnetic resin contains 60% by weight or more of iron oxide filler,
A resin residue layer having an average thickness of 0.01 μm or more and 1 μm or less is formed on the surface of the first through hole,
further comprising a second through hole formed in the core substrate and a second through hole conductor made of a metal film formed in the second through hole;
A resin residue layer is formed on the surface of the second through hole,
The thickness of the resin residue layer in the first through hole is thicker than the thickness of the resin residue layer in the second through hole. The inductor built-in substrate according to claim 1 ,
The iron oxide filler exposed through the cut in the resin residue layer on the surface of the first through hole is in contact with the metal film formed in the first through hole.

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