JPH11261230A - Multi-layer printed wiring board and manufacture thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a multi-layer printed wiring board, together with its manufacturing method, which is, of high surface mounting efficiency, excellent in electrical connection reliability between a core hole and a surface hole. SOLUTION: A core hole 3 is formed on a core substrate 5, and the opening part of the core hole is coated with a conductive coat 21. A coat through hole for surface-hole intrusion is formed at the conductive coat 21, and a surface layer 6 is laminated on the surface of the core substrate 5. A surface-hole formation part of the surface layer 6 is irradiated with laser to form a surface hole 1 comprising a surface through part 1a and a coat through part 1b penetrating the surface layer 6 and the conductive coat 21, as well as an intrusion recessed part 1c intruding from the coat through part 1b into the core hole, thus a metal plating film 4 is formed inside the surface hole 1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multilayer printed wiring board and a method of manufacturing the same, and more particularly, to a structure of a conductive hole for electrically connecting layers.

[0002]

2. Description of the Related Art Conventionally, as a multilayer printed wiring board, FIG.
As shown in FIG. 3, there is a type having a via-on-via structure in which two conductive holes are stacked. That is, in the multilayer printed wiring board 9, a surface layer 96 is laminated on the surface of a core substrate 95, a core hole 93 is formed in the core substrate 95, and a surface hole electrically connected to the core hole 93 is formed in the surface layer 96. 91 are provided. The inside of the core hole 93 is filled with a resin material 930, and the opening is covered with a conductive film 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 has a core hole 93 and a surface hole 9
Through 1, electrical conduction between the conductor patterns 97 provided on different layers is performed.

In manufacturing the multilayer printed wiring board 9, first, a core hole 95 is formed in a core substrate 95 by using a drill.
Is formed, the inside is filled with a resin material 930, the opening is covered with a conductive film 92, and then a surface layer 96 made of prepreg is laminated on the surface thereof, and a surface hole 91 is formed by laser irradiation. According to this laser irradiation, a surface hole having a small 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]

However, in the conventional multilayer printed wiring board 9 described above, the laser irradiation causes the conductive coating 92 located at the bottom of the surface hole 91 to be damaged or broken by the laser irradiation, as shown in FIG. Sometimes.
When such damage occurs, the broken piece 929 becomes the surface hole 91.
And the deposition of the metal plating film on the inner wall of the surface hole 91 may be insufficient. For this reason, the reliability of electrical conduction between the surface hole and the core hole may be reduced.

The present invention has been made in view of the above-mentioned conventional problems, and has as its object to provide a multilayer printed wiring board having excellent electrical connection reliability between a core hole and a surface hole and having high surface mounting efficiency and a method of manufacturing the same. .

[0006]

The present invention comprises a step of forming a core hole in a core substrate, a step of covering the opening of the core hole with a conductive film, and a step of penetrating the conductive film with a film for entering surface holes. Forming a hole, laminating a surface layer on the surface of the core substrate, and irradiating a laser to a surface hole forming portion of the surface layer to penetrate the surface layer and the conductive coating. Forming a surface hole consisting of a portion, a coating penetrating portion, and an indentation penetrating into the core hole with respect to the coating penetrating portion; and forming a metal plating film inside the surface hole. This is a method for manufacturing a multilayer printed wiring board, which is a feature.

The most remarkable point in the present invention is that when forming a surface hole, a film through hole is previously formed in a conductive film covering the core hole opening, and after forming the surface layer,
By laser irradiation, a surface hole penetrating the surface layer and the conductive coating and further entering the inside of the core hole is formed.

[0008] Since the conductive coating has a coating through-hole formed in advance, irradiating the coating through-hole with a laser may cause damage to the conductive coating disposed in the middle of the surface hole. There is no. Therefore, after forming the surface holes,
No broken pieces remain inside, and the metal plating film is sufficiently deposited. Further, the deposited metal plating film has a high bonding property with the conductive film. Therefore, the surface hole is reliably electrically connected to the core hole through the conductive coating. Therefore,
ADVANTAGE OF THE INVENTION According to this invention, the multilayer printed wiring board excellent in the electrical connection of a surface hole and a core hole can be manufactured.

Further, since the surface holes are formed by a laser, they can be formed to a small diameter. Therefore, the area occupied by the surface holes occupying the surface layer can be reduced, and another conductive member can be provided in the surplus space, so that high-density mounting can be realized.

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 becomes difficult to form a metal plating film in the surface layer, and if the thickness exceeds 0.3 mm, surface high-density mounting may be hindered. The irradiation conditions of the laser for irradiating to form the surface hole are appropriately adjusted so that the drilling stops inside the core hole.

[0011] It is preferable that the coating through hole for entering the surface hole is formed to have 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 through-hole in the surface hole. This is because surface hole formation by laser irradiation depends on the shape of the coating through-hole.
That is, the laser burns off the surface layer exposed inside the through-hole of the coating and forms a hole, but the hole is not formed by reflection from the conductive coating outside the through-hole of the coating.

The core substrate is, for example, a resin substrate obtained by impregnating a glass cloth or a glass fiber with a resin. Examples of the resin include an epoxy resin, a bismaleimide triazine resin, and a polyimide resin. Also,
The same material as that of the core substrate can be used for the surface layer.

The conductive film is made of a metal foil such as a copper foil,
It is made of a metal plating film of copper, nickel, gold or the like. A conductive pattern can be formed between the core substrate and the surface layer together with the formation of the conductive film. After the surface holes are formed, a conductive pattern can be formed on the surface of the surface layer by etching the conductive layer or the like.

The multilayer printed wiring board that can be manufactured by the above-described manufacturing method includes, for example, a core substrate and a surface layer laminated on the surface of the core substrate. In a multilayer printed wiring board comprising a conductive film covering an opening of a core hole and a conductive surface hole provided in a surface layer above the opening of the core hole, the surface hole is formed by the surface layer and the conductive layer. There is a multilayer printed wiring board comprising a surface penetrating portion penetrating a conductive film, a film penetrating portion, and a concave portion penetrating into the core hole from the film penetrating portion.

In this multilayer printed wiring board, the surface hole penetrates through the surface layer and the conductive film and enters the inside of the core hole. Therefore, the connectivity between the metal plating film on the inner wall of the surface hole and the conductive film is improved. Therefore, the reliability of the electrical connection between the surface hole and the core hole is high. Further, since the surface holes have a small diameter, high-density mounting on the surface can be realized. It is preferable that a filling material is filled in the core hole. This increases the mechanical strength of the core hole.
Examples of the filling material include a resin and a resin containing a filler. It is preferable that a step is provided between the surface penetrating part and the coating penetrating part. In this step, 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 improved.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS First Embodiment 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 embodiment is a four-layer printed wiring board, and includes a core substrate 5 and a surface layer 6 laminated on the surface thereof.
Consists of The core substrate 5 is provided with a conductive core hole 3. The opening of the core hole 3 is covered with a conductive film 21. The surface layer 6 has conductive surface holes 1,
10 are provided. 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 inside of the core hole 3 is filled with a filling material 30 for reinforcing the strength.
The multilayer printed wiring board 8 has conductor patterns 20 and 22 on the surfaces of the core substrate 5 and the surface layer 6.

Next, a method of manufacturing the multilayer printed wiring board 8 will be described. First, as shown in FIG.
A copper-clad glass epoxy substrate having a thickness of 2 mm is prepared, and is used as a core substrate 5 having a copper layer 29 provided on the surface. Next, as shown in FIG. 3, a core hole 3 having a diameter of 0.3 mm was formed using a drill.
Drilling. 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.

Next, as shown in FIG. 5, a resin material 30 made of epoxy resin is formed inside the core hole 3 by a printing method.
Fill. 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.
As shown in FIG. 3, the copper plating film 2 is etched to form a conductive film 21 covering the opening of the core hole 3 and a conductive pattern 20, and the conductive film 21 has substantially the same shape as the surface hole forming portion. Sectional shape, ie 0.15mm diameter
A coating through hole 210 having a circular shape is formed.

Next, as shown in FIG. 8, a surface layer 6 of prepreg having a thickness of 0.08 mm is laminated on the surface of the core substrate 5, and the surface is further covered with a copper foil 28. The prepreg is obtained by impregnating a glass cloth with an epoxy resin to make the resin in a semi-cured state. Next, copper foil 2
8 is etched to form a circular coating through hole 280 having substantially the same cross section as the surface hole, that is, a circular shape having a diameter of 0.15 mm, in the surface hole forming portion of the copper foil 28.

Next, as shown in FIG. 9, the laser beam 7 is applied to the surface hole forming portion 19 of the surface layer 6. Thereby, as shown in FIG. 10, the surface layer 6 and the conductive film 21 are formed.
, And further penetrates into the core hole 3 to form a cylindrical surface hole 1. That is, the formed surface hole 1
Consists of a surface penetrating portion 1a penetrating the surface layer 6, a coating penetrating portion 1b penetrating the conductive coating 21, and an indentation recess 1c penetrating into the core hole 3. The diameter of the surface hole 1 is 0.1
5 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, a multilayer printed wiring board 8 is obtained.

Next, the operation and effect of this embodiment will be described. In this example, when forming the surface hole 1, FIG.
As shown in FIG. 9, a coating through hole 210 is formed in advance in the conductive coating 21 covering the core hole opening, and as shown in FIG. In addition, a surface hole 1 penetrating the conductive film 21 and further entering the inside of the core hole 5 is formed.

The conductive coating 21 has a through-hole 21 in advance.
Since 0 is formed, the conductive coating 21 disposed on the middle part of the surface hole 1 is not damaged by irradiating the laser 7 to the coating through hole 210. Therefore, as shown in FIG. 1, after the surface holes are formed, no broken pieces remain inside, and the metal plating film 4 is sufficiently deposited. Further, the deposited metal plating film 4 has a high bonding property with the conductive film 21. Therefore, the surface hole 1 is reliably electrically connected to the core hole 3 through the conductive coating 21.
Therefore, according to this example, it is possible to manufacture the multilayer printed wiring board 8 having excellent electrical connection between the surface hole 1 and the core hole 3.

Further, since the surface hole 1 is formed by a laser, it can be formed to a small diameter. Therefore, the area occupied by the surface holes 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 surplus space, so that high-density mounting can be realized.

Embodiment 2 As shown in FIG. 11, the multilayer printed wiring board of this embodiment is provided with a surface hole 1 having a step 1d. The step portion 1 d is provided between the coating penetrating portion 1 b penetrating the conductive coating 21 and the entry concave portion 1 c entering the inside of the core hole 3. The entry recess 1c has a diameter of 0.05 mm and a diameter of 0.1 mm.
Are smaller than the surface penetration portion 1a and the coating penetration portion 1b. Other configurations are the same as those of the first embodiment.

In this embodiment, a step 1d is provided between the coating surface 1a and the coating penetrating portion 1b. The metal plating film 4 that covers the step 1d has a large bonding area with the conductive film 21. Therefore, according to this example, the reliability of the electrical conduction between the surface hole 1 and the core hole 3 is further improved. In addition,
In this example, the same effects as in the first embodiment can be exhibited.

Embodiment 3 As shown in FIG. 12, a multilayer printed wiring board 8 of this embodiment
This is a six-layer printed wiring board. Printed wiring board 8 of this example
In this example, a multilayer printed wiring board having four layers is formed in the same manner as in the first embodiment, and a surface layer 61, a surface hole 100 and a conductor pattern 23 are further formed on the surface of the multilayer printed wiring board. Therefore, in this example, the conductive members can be mounted at a higher density.

[0027]

According to the present invention, it is possible to provide a multilayer printed wiring board having excellent 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]

FIG. 1 is a sectional view of a multilayer printed wiring board according to a first embodiment.

FIG. 2 is a cross-sectional view of a core substrate for illustrating a method for manufacturing a multilayer printed wiring board according to the first embodiment.

FIG. 3 is a cross-sectional view of the core substrate in which a core hole has been formed, following FIG. 2;

FIG. 4 is a cross-sectional view of the core substrate having a metal plating film formed in the core hole, following FIG. 3;

FIG. 5 is a cross-sectional view of the core substrate, in which the core hole is filled with a resin material, following FIG. 4;

FIG. 6 is a sectional view of the core substrate covered with the copper foil, following FIG. 5;

FIG. 7 is a sectional view of the core substrate on which a conductor pattern is formed, following FIG. 6;

FIG. 8 is a sectional view of the laminated plate, following FIG. 7;

FIG. 9 is a cross-sectional view of the laminate, illustrating a method of forming surface holes, following FIG. 8;

FIG. 10 is a cross-sectional view of the laminate having surface holes formed following FIG. 9;

FIG. 11 is a sectional view of a multilayer printed wiring board according to a second embodiment.

FIG. 12 is a sectional view of a multilayer printed wiring board according to a third embodiment.

FIG. 13 is a cross-sectional view of a conventional multilayer printed wiring board.

FIG. 14 is an explanatory diagram showing a problem in a conventional example.

[Explanation of symbols]

 1,10,100. . . Surface pores, 1a. . . Surface penetration, 1b. . . Coating penetration, 1c. . . Entry recess, 1d. . . Step, 2. . . Copper plating film, 20, 22, 23. . . Conductor pattern, 21. . . 28. conductive coating, . . Copper foil, 29. . . Copper layer, 210. . . 2. coating through-hole; . . Core hole, 30. . . 3. resin material, . . Metal plating film, 5. . . Core substrate, 6,61. . . 6. surface layer; . . Laser, 8. . . Multilayer printed wiring board,

Claims (4)

[Claims] A step of forming a core hole in a core substrate; a step of covering an opening of the core hole with a conductive film;
A step of forming a through-hole for entering a surface hole in the conductive film, a step of laminating a surface layer on the surface of the core substrate, and irradiating a laser to a surface-hole-forming portion of the surface layer. Forming a surface hole composed of a surface penetrating portion penetrating the surface layer and the conductive film, a film penetrating portion, and an indentation recess penetrating into the core hole beyond the film penetrating portion; Forming a metal plating film on the multilayer printed wiring board. 2. A core substrate comprising: a core substrate; a surface layer laminated on a surface of the core substrate; a conductive core hole provided in the core substrate; a conductive film covering an opening of the core hole; In a multilayer printed wiring board comprising a conductive surface hole provided in a surface layer above an opening of a core hole, the surface hole includes a surface penetrating portion penetrating the surface layer and the conductive film, and a film penetrating portion. A multi-layer printed wiring board, comprising: a recessed portion penetrating into the core hole from the film penetrating portion. 3. The multilayer printed wiring board according to claim 2, wherein a filling material is filled in the core hole. 4. The multilayer printed wiring board according to claim 2, wherein a step is provided between the surface penetrating part and the coating penetrating part.