JP3988664B2 - Multilayer printed wiring board and manufacturing method thereof - Google Patents

Description

[0001]
【Technical field】
The present invention relates to a multilayer printed wiring board and a method for manufacturing the same, and more particularly to a structure of a conductive hole for electrically conducting each layer.
[0002]
[Prior art]
Conventionally, some multilayer printed wiring boards have a via-on-via structure in which two conductive holes are laminated as shown in FIG. That is, in the multilayer printed wiring board 9, the surface layer 96 is laminated on the surface of the core substrate 95, the core hole 93 is formed in the core substrate 95, and the surface hole electrically connected to the core hole 93 is formed in the surface layer 96. 91 is provided. The core hole 93 is filled with a resin material 930, and the opening is covered with a conductive coating 92. The core hole 93 and the surface hole 91 are provided with conductivity by covering the inner wall with a metal plating film 94.
The multilayer printed wiring board conducts electrical continuity between conductor patterns 97 provided in different layers through the core hole 93 and the surface hole 91.
[0003]
In manufacturing the multilayer printed wiring board 9, first, a core hole 93 is formed in the core substrate 95 using a drill, the inside is filled with a resin material 930, and the opening is covered with a conductive coating 92. The surface layer 96 made of prepreg is laminated on the surface, and the surface hole 91 is formed by laser irradiation.
By this laser irradiation, a surface hole having a minute diameter can be formed, and the area occupied by the surface hole 91 in the surface layer 96 can be reduced. For this reason, the surface mounting efficiency of the multilayer printed wiring board 9 can be improved.
[0004]
[Problems to be solved]
However, in the conventional multilayer printed wiring board 9, damage such as tearing may occur in the conductive coating 92 located at the bottom of the surface hole 91 as shown in FIG. 14 due to laser irradiation. When such damage occurs, the broken piece 929 remains in the surface hole 91, and deposition of the metal plating film on the inner wall of the surface hole 91 may be insufficient. For this reason, there exists a possibility that the electrical conduction | electrical_connection reliability of a surface hole and a core hole may fall.
[0005]
In view of the conventional problems, the present invention is intended to provide a multilayer printed wiring board excellent in electrical connection reliability between a core hole and a surface hole and having high surface mounting efficiency, and a method for manufacturing the same.
[0006]
[Means for solving problems]
The present invention includes a step of forming a core hole in a core substrate,
Coating the opening of the core hole with a conductive coating;
Forming a coating through-hole for entering a surface hole in the conductive coating;
Laminating a surface layer on the surface of the core substrate;
By irradiating the surface hole forming portion of the surface layer with a laser, a surface penetrating portion and a coating penetrating portion penetrating the surface layer and the conductive coating, and an entrance recess entering the core hole from the coating penetrating portion, Forming a surface hole comprising:
A method of manufacturing a multilayer printed wiring board, comprising: forming a metal plating film inside the surface hole.
[0007]
The most notable point in the present invention is that, in forming the surface hole, a coating through-hole is previously formed in the conductive film covering the core hole opening, and after the surface layer is formed, the surface layer and A surface hole that penetrates the conductive coating and enters the core hole is formed.
[0008]
Since a coating through-hole is formed in advance in the conductive coating, the conductive coating disposed in the middle part of the surface hole is not damaged by irradiating the coating through-hole with laser. Therefore, after the surface hole is formed, no broken pieces remain inside, and the metal plating film is sufficiently deposited. In addition, the deposited metal plating film has high bondability with the conductive film. For this reason, the surface hole is reliably electrically connected to the core hole through the conductive coating.
Therefore, according to the present invention, a multilayer printed wiring board excellent in electrical connectivity between the surface hole and the core hole can be manufactured.
[0009]
Further, since the surface hole is formed by a laser, it can be formed in a minute diameter. For this reason, the area occupied by the surface holes in the surface layer can be reduced, and another conductive member can be provided in the surplus space, thereby realizing high-density mounting.
[0010]
The core hole can be formed by, for example, a drill or a laser. The surface hole is preferably 0.03 to 0.3 mm. If the thickness is less than 0.03 mm, it is difficult to form a metal plating film in the surface layer, and if it exceeds 0.3 mm, high-density surface mounting may be hindered.
The irradiation conditions of the laser used to form the surface hole are adjusted as appropriate so that the drilling stops inside the core hole.
[0011]
The coating through-hole for entering the surface hole is preferably opened in substantially the same cross-sectional shape as the surface hole to be formed. That is, it is preferable that the coating through-hole is substantially the same as the coating penetration in the surface hole. This is because the formation of surface holes by laser irradiation depends on the shape of the coating through-holes. That is, the laser burns away the surface layer exposed to the inside of the coating through-hole, but forms a hole by reflecting off the conductive coating outside the coating through-hole.
[0012]
The core substrate is made of, for example, a resin substrate in which a glass cloth or glass fiber is impregnated with a resin. Examples of the resin include an epoxy resin, a bismaleimide triazine resin, and a polyimide resin. The surface layer can be made of the same material as the core substrate.
[0013]
The conductive film is made of a metal foil such as a copper foil, a metal plating film such as copper, nickel, or gold.
Between the core substrate and the surface layer, a conductive pattern can be formed along with the formation of the conductive film. Also, a conductor pattern can be formed on the surface of the surface layer by etching the conductive layer after forming the surface holes.
[0014]
The multilayer printed wiring board that can be manufactured by the above manufacturing method includes, for example, a core substrate and a surface layer laminated on the surface of the core substrate. The conductive core hole provided in the core substrate, In a multilayer printed wiring board comprising a conductive coating covering the opening, and a conductive surface hole provided in a surface layer above the opening of the core hole,
The surface pores, Ri Do from the surface through portion and coatings through portion that penetrates the surface layer and the conductive film, the approach recess enters the inner core hole from the coating through portion,
There is a multilayer printed wiring board in which a step portion is provided between the surface penetration portion and the coating penetration portion .
[0015]
In this multilayer printed wiring board, the surface hole penetrates the surface layer and the conductive film and enters the core hole. Therefore, the connectivity between the metal plating film on the inner wall of the surface hole and the conductive coating is enhanced. Therefore, the electrical connection reliability between the surface hole and the core hole is high. In addition, since the surface hole has a small diameter, it is possible to realize high-density mounting on the surface.
The core hole is preferably filled with a filling material. This increases the mechanical strength of the core hole. Examples of the filling material include resin and filler-filled resin.
Further, between the surface through portion and the coating penetrations, that have stepped portion is provided. In this step portion, the metal plating film on the inner wall of the surface hole is firmly bonded to the conductive film, so that the electrical connection reliability between the surface hole and the core hole is further increased.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
Embodiment 1
A multilayer printed wiring board according to an embodiment of the present invention will be described with reference to FIGS.
As shown in FIG. 1, the multilayer printed wiring board 8 of this example is a four-layer printed wiring board, and includes a core substrate 5 and a surface layer 6 laminated on the surface thereof. A conductive core hole 3 is provided in the core substrate 5. The opening of the core hole 3 is covered with a conductive film 21. The surface layer 6 is provided with conductive surface holes 1 and 10. One surface hole 1 is provided above and below the opening of the core hole 3, and the other surface hole 10 is electrically connected to the conductor pattern 20 provided between the surface hole 6 and the core substrate 5. Connected.
The core hole 3 is filled with a filling material 30 for reinforcing the strength.
The multilayer printed wiring board 8 is provided with conductor patterns 20 and 22 on the surfaces of the core substrate 5 and the surface layer 6.
[0017]
Next, a method for manufacturing the multilayer printed wiring board 8 will be described.
First, as shown in FIG. 2, a copper-clad glass epoxy substrate having a thickness of 0.3 mm is prepared, and this is used as a core substrate 5 provided with a copper layer 29 on the surface. Next, as shown in FIG. 3, a core hole 3 having a diameter of 0.3 mm is drilled using a drill. Next, as shown in FIG. 4, the entire surface of the core substrate 5 including the inner wall of the core hole 3 is coated with the metal plating film 4 by chemical copper plating and electrolytic copper plating.
[0018]
Next, as shown in FIG. 5, a resin material 30 made of an epoxy resin is filled into the core hole 3 by a printing method. Next, as shown in FIG. 6, the surface of the core substrate 5 is covered with the copper plating film 2, and then, as shown in FIGS. 7 and 1, the copper plating film 2 is etched to cover the opening of the core hole 3. The conductive film 21 and the conductor pattern 20 are formed, and the conductive film 21 is formed with a film through-hole 210 having substantially the same cross-sectional shape as the surface hole forming portion, that is, a circular shape having a diameter of 0.15 mm.
[0019]
Next, as shown in FIG. 8, a surface layer 6 made of prepreg and having a thickness of 0.08 mm is laminated on the surface of the core substrate 5, and a copper foil 28 is further coated on the surface. A prepreg is made by impregnating a glass cloth with an epoxy resin to make the resin semi-cured. Next, the copper foil 28 is etched to form a circular film through-hole 280 having substantially the same cross-sectional shape as the surface hole, that is, a diameter of 0.15 mm, in the surface hole forming portion of the copper foil 28.
[0020]
Next, as shown in FIG. 9, the surface hole forming portion 19 of the surface layer 6 is irradiated with the laser 7. As a result, as shown in FIG. 10, a cylindrical surface hole 1 that penetrates through the surface layer 6 and the conductive coating 21 and enters the core hole 3 is formed. That is, the formed surface hole 1 includes a surface penetration portion 1 a that penetrates the surface layer 6, a coating penetration portion 1 b that penetrates the conductive coating 21, and an entry recess 1 c that enters the core hole 3. The diameter of the surface hole 1 is 0.15 mm.
Next, as shown in FIG. 1, a metal plating film 4 is formed inside the surface hole 1 by chemical copper plating and electrolytic copper plating. Further, the conductor pattern 22 is formed by etching the copper foil 28. Thus, the multilayer printed wiring board 8 is obtained.
[0021]
Next, the operation and effect of this example will be described.
In this example, in forming the surface hole 1, as shown in FIG. 7, the coating through-hole 210 is formed in the conductive coating 21 covering the core hole opening in advance, and as shown in FIG. After forming the surface hole 1, the surface hole 1 penetrating the surface layer 6 and the conductive coating 21 and entering the core hole 5 is formed by irradiation of the laser 7.
[0022]
Since the coating through-hole 210 is formed in the conductive coating 21 in advance, damage to the conductive coating 21 disposed in the middle portion of the surface hole 1 occurs when the coating through-hole 210 is irradiated with the laser 7. Never do. Therefore, as shown in FIG. 1, after the surface hole is formed, no damaged piece remains inside, and the metal plating film 4 is sufficiently deposited. Further, the deposited metal plating film 4 has a high bondability with the conductive coating 21. For this reason, the surface hole 1 is reliably electrically connected to the core hole 3 through the conductive coating 21.
Therefore, according to this example, the multilayer printed wiring board 8 excellent in electrical connectivity between the surface hole 1 and the core hole 3 can be manufactured.
[0023]
Further, since the surface hole 1 is formed by a laser, it can be formed in a minute diameter. For this reason, the occupied area of the surface hole 1 occupying the surface layer 6 can be reduced, and another conductive member such as the conductor pattern 22 can be further provided in the excess space, thereby realizing high-density mounting.
[0024]
Embodiment 2
The multilayer printed wiring board of this example is provided with a surface hole 1 having a step portion 1d as shown in FIG. The step portion 1 d is provided between the coating penetration portion 1 b that penetrates the conductive coating 21 and the entry recess 1 c that enters the core hole 3. The entry recess 1c has a diameter of 0.05 mm and is smaller than the surface penetration portion 1a and the coating penetration portion 1b having a diameter of 0.1 mm.
Others are the same as in the first embodiment.
[0025]
In this example, a step 1d is provided between the coating surface portion 1a and the coating penetration 1b. The metal plating film 4 coated on the stepped portion 1d has a high bonding area with the conductive coating 21. Therefore, according to this example, the reliability of electrical conduction between the surface hole 1 and the core hole 3 is further improved.
In addition, in this example, the same effects as those of the first embodiment can be exhibited.
[0026]
Embodiment 3
The multilayer printed wiring board 8 of this example is a six-layer printed wiring board as shown in FIG. The printed wiring board 8 of this example is formed by forming a four-layer multilayer printed wiring board as in the first embodiment, and further forming a surface layer 61, a surface hole 100, and a conductor pattern 23 on the surface thereof. Therefore, in this example, the conductive member can be mounted at a higher density.
[0027]
【The invention's effect】
According to the present invention, it is possible to provide a multilayer printed wiring board excellent in electrical connection reliability between a core hole and a surface hole and having high surface mounting efficiency, and a method for manufacturing the same.
[Brief description of the drawings]
1 is a cross-sectional view of a multilayer printed wiring board according to Embodiment 1;
FIG. 2 is a cross-sectional view of a core substrate for illustrating a method for manufacturing a multilayer printed wiring board according to Embodiment 1;
FIG. 3 is a cross-sectional view of a core substrate in which a core hole is formed, following FIG. 2;
4 is a cross-sectional view of the core substrate in which a metal plating film is formed in the core hole, following FIG. 3;
FIG. 5 is a cross-sectional view of a core substrate in which a resin material is filled in a core hole, following FIG.
6 is a cross-sectional view of a core substrate coated with a copper foil, following FIG. 5;
7 is a cross-sectional view of a core substrate on which a conductor pattern is formed, following FIG. 6;
FIG. 8 is a cross-sectional view of the laminated board following FIG.
FIG. 9 is a cross-sectional view of a laminated board for illustrating a method for forming a surface hole, following FIG. 8;
FIG. 10 is a cross-sectional view of a laminated board in which surface holes are formed, following FIG. 9;
11 is a cross-sectional view of a multilayer printed wiring board according to Embodiment 2. FIG.
12 is a cross-sectional view of a multilayer printed wiring board according to Embodiment 3. FIG.
FIG. 13 is a cross-sectional view of a multilayer printed wiring board in a conventional example.
FIG. 14 is an explanatory diagram for illustrating problems in a conventional example.
[Explanation of symbols]
1, 10, 100. . . Surface holes,
1a. . . Surface penetration,
1b. . . Coating penetration,
1c. . . Entry recess,
1d. . . Step,
2. . . Copper plating film,
20, 22, 23. . . Conductor pattern,
21. . . Conductive coating,
28. . . Copper foil,
29. . . Copper layer,
210. . . Coating through-hole,
3. . . Core hole,
30. . . Resin material,
4). . . Metal plating film,
5). . . Core substrate,
6,61. . . Surface layer,
7). . . laser,
8). . . Multilayer printed wiring board,

Claims (3)

Forming a core hole in the core substrate;
Coating the opening of the core hole with a conductive coating;
Forming a coating through-hole for entering a surface hole in the conductive coating;
Laminating a surface layer on the surface of the core substrate;
By irradiating the surface hole forming portion of the surface layer with a laser, a surface penetrating portion and a coating penetrating portion penetrating the surface layer and the conductive coating, and an entrance recess entering the core hole from the coating penetrating portion, Forming a surface hole comprising:
A method for producing a multilayer printed wiring board, comprising: forming a metal plating film inside the surface hole. A core substrate and a surface layer laminated on the surface of the core substrate, the conductive core hole provided in the core substrate, a conductive coating covering the opening of the core hole, and the opening of the core hole In a multilayer printed wiring board composed of conductive surface holes provided in the upper surface layer,
The surface pores, Ri Do from the surface through portion and coatings through portion that penetrates the surface layer and the conductive film, the approach recess enters the inner core hole from the coating through portion,
A multilayer printed wiring board , wherein a step portion is provided between the surface penetration portion and the coating penetration portion .   The multilayer printed wiring board according to claim 2, wherein the core hole is filled with a filling material.

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