JPH11284343A - Multi-layer printed wiring board and manufacture thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a multi-layer printed circuit board with high-density mounting at an uppermost surface. SOLUTION: A multi-layer printed wiring boards includes an upper core board 11 and a lower core board 12 with each conductor pattern 5, and an adhesive layer 2 for bonding the upper and lower boards 11 and 12. The upper core board 11 and/or the lower core board 12 has an outer blind viahole 3 with an closed outer edge with a covering pad 51 and an inner opened edge. In this case, a part of adhesive 2 flows from the inner edge into the inside of the outer blind via hole 3.

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 for manufacturing the same, and more particularly to a structure for high-density mounting of an outer surface.

[0002]

2. Description of the Related Art A large number of conductor patterns are stacked on a multilayer printed wiring board. Therefore, on the outermost surface of the multilayer printed wiring board, all the electrical information of the board is concentrated for connection of external terminals, and very high density is required.

[0003]

However, in the prior art, few have sufficiently considered high-density wiring on the outermost surface of a multilayer printed wiring board. The cause is that the multilayer printed wiring board requires via holes to electrically connect between the layers, and these via holes are opened in the outermost surface of the multilayer printed wiring board, which hinders the increase in the density of the outermost surface. Because it is.

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 capable of realizing high-density mounting on the outermost surface and a method of manufacturing the same.

[0005]

The present invention relates to a multilayer printed wiring board comprising an upper core substrate and a lower core substrate having a conductor pattern, and an adhesive layer for adhering the upper core substrate and the lower core substrate. The core substrate and / or the lower core substrate has an outer blind via hole whose outer end is closed by a covering pad and whose inner end is open. A multilayer printed wiring board characterized in that a part of the multilayer printed wiring board is penetrated.

The most remarkable point in the present invention is that an outer blind via hole is provided in the upper core substrate and / or the lower core substrate, and the bottom is covered with a covering pad to cover the upper and lower surfaces of the multilayer printed wiring board. It is arranged to face. Thus, the covering pads of the outer blind via holes are arranged on the upper surface and / or the lower surface of the multilayer printed wiring board, while the openings of the outer blind via holes are arranged inside the multilayer printed wiring board. For this reason, a conductor pattern using a covering pad can be formed on the upper surface and / or the lower surface where high-density mounting is required. For example, the covering pad can be used as a number of conductive patterns, such as pads for connecting external terminals, pads for mounting electronic components, and wiring patterns.

Further, since a part of the adhesive layer has penetrated into the outer blind via hole, the penetrated portion increases the adhesive strength between the upper core substrate and the lower core substrate.
Therefore, the multilayer printed wiring board has excellent adhesive strength between the layers.

[0008] The covering pad located at the bottom of the outer blind via hole is preferably rough.
As a result, the adhesive layer bites into the rough surface, and the adhesive strength of the adhesive layer at the bottom of the outer blind via hole is increased by the so-called anchor effect.

In the present invention, the upper core substrate refers to the core substrate disposed on the uppermost side of the multilayer printed wiring board. Further, the lower core substrate refers to a core substrate arranged at the lowermost side of the multilayer printed wiring board. The outer blind via hole refers to a blind via hole provided in at least one of the upper core substrate and the lower core substrate. In the outer blind via hole, the outer end of the multilayer printed wiring board is covered with a covering pad, and the inner end is open.

As the upper core substrate and the lower core substrate, for example, an insulating substrate such as a glass epoxy substrate, a polyimide substrate, and a bismaleimide triazine substrate can be used. As the adhesive layer, for example, a prepreg in which a glass cloth is impregnated with a resin can be used. The conductive pattern and the covering pad are formed using a conductive material formed by etching a metal foil and a metal plating film.

The outer blind via hole preferably has a diameter of, for example, 0.03 to 0.3 mm.
Thus, the required area of the outer blind via hole can be increased, and the conduction reliability can be improved. On the other hand, if it is less than 0.03 mm, the metal plating may not be sufficiently thick in the via hole. If it exceeds 0.3 mm, the wiring density may decrease.

Next, in manufacturing the multilayer printed wiring board, for example, a conductor pattern is formed on an insulating substrate to form an upper core substrate and a lower core substrate, and the upper core substrate and / or the lower core substrate are formed. A coating pad is formed on at least one of the side core substrates at a portion located at the bottom of the outer blind via hole, and a metal plating film is formed on the outer blind via hole forming portion by laser irradiation to form an outer blind via hole. And a step of laminating and pressing the upper core substrate and the lower core substrate via an adhesive layer such that the opening of the outer blind via hole faces the inside. There is a method of manufacturing a wiring board.

In this manufacturing method, the upper core substrate and the lower core substrate are laminated and pressure-bonded via an adhesive layer such that the opening of the outer blind via hole faces the inside. Therefore, at the time of press bonding, a part of the adhesive layer enters the outer blind via holes provided in the upper core substrate and the lower core substrate, respectively, and the inside of the holes is filled with the adhesive layer. Therefore, the adhesive strength of the upper core substrate and the lower core substrate to the adhesive layer increases.

Further, since the covering pad arranged at the bottom of the outer blind via hole is arranged toward the outside of the multilayer printed wiring board, it can be used as a part of a conductor pattern provided on the outermost layer.

Further, in the above-mentioned manufacturing method, it is preferable that the covering pad located at the bottom of the outer blind via hole is subjected to a surface roughening treatment. As a result, the adhesive layer bites into the rough surface, and the adhesive strength of the adhesive layer at the bottom of the outer blind via hole is increased by the so-called anchor effect.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 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 the present embodiment includes an upper core substrate 11 and a lower core substrate 12 each having a conductor pattern 5, and
It comprises an adhesive layer 2 for adhering the upper core substrate 11 and the lower core substrate 12.

Upper core substrate 11 and lower core substrate 12
Has an outer blind via hole 3 whose outer end is closed by a covering pad 51 and whose inner end is open. A part of the adhesive layer 2 enters the inside of the outer blind via hole 3 from the inner end.

The covering pad 51 located at the bottom of the outer blind via hole 3 has a rough surface 511 (FIG. 7). The outer blind via hole 3 has a diameter of 0.1
mm. Also, the upper surface of the multilayer printed wiring board 8,
An inner blind via hole 35 is opened on the lower surface. The bottom of the inner blind via hole 35 is covered with a covering pad 51 similarly to the outer blind via hole 3.

The upper surface and the lower surface of the multilayer printed wiring board 8 are covered with a solder resist 19. Part of the solder resist 19 has penetrated into the inner blind via hole 35. An external connection pad 54 is provided on the upper side surface of the multilayer printed wiring board 8, and an external connection pad 54 is provided here via an external terminal such as a solder ball.
The multilayer printed wiring board 8 and the motherboard are electrically connected.

Next, in manufacturing the above-mentioned multilayer printed wiring board, the steps shown in FIG. 2 are performed. That is, in the S0 to S6 steps shown in FIG. 2, the lower core substrate 12 is manufactured as shown in FIG.

That is, first, in the S0 step, one surface of a copper foil is subjected to a surface roughening treatment to obtain a rough surface. Next, in step S1, copper foils 50 are adhered to both surfaces of the insulating substrate 1 made of a glass epoxy substrate (FIG. 3A). Then, S
In two steps, an opening 501 is formed in the outer blind via hole forming portion 30 of the copper foil 50 by etching the copper foil 50 (FIG. 3A). Opening 50
1 is a round hole having a diameter of 0.2 mm.

Next, in the step S3, the outer blind via hole forming portion 30 is irradiated with a laser. Then, the laser burns off the portion of the insulating substrate where the outer blind via hole 50 is formed, and when the laser reaches the bottom copper foil 50, the drilling stops there. Thereby, the outer blind via hole 3 having the same cross-sectional shape as the opening 501 is formed in the insulating substrate 1 (FIG. 3B).

Next, in step S4, the inner wall of the outer blind via hole 3 is subjected to chemical copper plating and electrolytic copper plating to cover the metal plating film 59 (FIG. 3).
(C)). Next, in step S5, the conductor pattern 5 and the covering pad 51 are formed by etching the copper foil 50 on the surface of the insulating substrate 1 that becomes the inside during lamination (see FIGS. 3D and 5B). ).

Next, in step S6, a blackening process is performed on the surface of the insulating substrate 1 on which the conductor pattern 5 and the like are formed. This is a process for increasing the adhesiveness with the adhesive layer at the time of lamination. Thus, the lower core substrate 12 is obtained.

Next, the same steps (S0 to S6) as those for manufacturing the lower core substrate 12 are performed, and as shown in FIG.
The upper core substrate 11 is manufactured.

Next, in step S7, as shown in FIG. 5, the upper core substrate 11 is laminated on the lower core substrate 12 with the adhesive layer 2 made of a prepreg interposed therebetween, and is heat-pressed to form a multilayer. A substrate 10 is obtained (FIG. 5A). At this time, a part of the adhesive layer 2 enters the inside of the outer blind via hole 3 from the opening side, and is filled in the entire inside. On both surfaces of the multilayer substrate 10, copper foils 50 on which no pattern is formed are arranged.

Next, in step S8, an opening 501 is formed in the copper foil 50 on the surface of the multilayer substrate 10 on the opening side of the inner blind via hole forming portion 350 (FIG. 5B). The opening 502 has a diameter of 0.2 mm.
It is a round hole. Next, in step S9, as shown in FIG. 6, the inner blind via hole forming portion 350 of the multilayer substrate 10 is irradiated with a laser, and, like the outer blind via hole 3, the inner blind via hole 35 having the cover pad 51 as the bottom is provided. Is drilled (FIG. 6A).

Next, in step S10, the inner wall of the inner blind via hole 35 is subjected to chemical copper plating and electrolytic copper plating to cover the metal plating film 59 (FIG. 6).
(B)). Next, in the step S11, the conductive pattern 5 and the external connection pads 54 are etched by etching the copper foil 50.
Is formed (FIG. 6C).

Next, in step S12, as shown in FIG. 1, the multilayer substrate 10 is covered with a solder resist 19. At this time, a part of the solder resist 19 enters the inside of the inner blind via hole 34 and the inside is filled with the solder resist 19. Next, S1
In three steps, a nickel / gold plating film 55 is formed on the surface of the external connection pad 54. Next, in step S14, the multilayer substrate is cut into individual multilayer printed wiring boards. Thus, the multilayer printed wiring board 8 shown in FIG. 1 is obtained.

The operation and effect of this embodiment will be described. In this example, the upper core substrate 11 and the lower core substrate 12
An outer blind via hole 3 is provided at the bottom of the multilayer printed wiring board 8 and the bottom thereof is covered with a covering pad 51 so as to face the upper side and the lower side.

As a result, the covering pads 51 of the outer blind via hole 3 are arranged on the upper side and the lower side of the multilayer printed wiring board 8, while the opening of the outer blind via hole 3 is arranged inside the multilayer printed wiring board 8. Is done. For this reason, the conductor patterns 5 using the covering pads 51 are provided on the upper and lower surfaces where high-density mounting is required.
Can be formed.

As shown in FIG. 1 and FIG. 7, since a part of the adhesive layer 2 has penetrated into the outer blind via hole 3,
And the lower core substrate 12 in bonding strength. for that reason,
The multilayer printed wiring board 8 has excellent adhesive strength between the layers.

As shown in FIG. 7, the covering pad 51 located at the bottom of the outer blind via hole 3 is
It is a rough surface 511. As a result, the adhesive layer 2
Of the adhesive layer 2 at the bottom of the outer blind via hole 3 is enhanced by the so-called anchor effect.

Embodiment 2 In the multilayer printed wiring board of this embodiment, an intermediate core substrate 13 is provided between an upper core substrate 11 and a lower core substrate 12, as shown in FIG. The intermediate core substrate 13 is provided with a conductor pattern 5 and blind via holes 34 at both ends.

In manufacturing the multilayer printed wiring board 8 of this embodiment, the same steps as the steps S0 to S6 in the first embodiment are performed, and the upper core board 11 and the lower core board 12 are manufactured.
And an intermediate core substrate 13. Next, the lower core substrate 1
2, the adhesive layer 2, the intermediate core substrate 13, the adhesive layer 2, and the upper core substrate 11 are laminated in this order from below, and these are heat-pressed (see step S7). Then, S8 to S1 of the first embodiment
The same steps as the four steps are performed to obtain the multilayer printed wiring board 8 of this example.

In this embodiment, as in the first embodiment,
Since the outer blind via hole 3 is provided in the multilayer blind via hole 8, high-density mounting on the surface can be realized. In addition, in this embodiment, the same effects as those of the first embodiment can be obtained.

[0037]

According to the present invention, it is possible to provide a multilayer printed wiring board capable of realizing high-density mounting on the outermost surface and a method of manufacturing the same.

[Brief description of the drawings]

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

FIG. 2 is a manufacturing process diagram of the multilayer printed wiring board according to the first embodiment.

FIG. 3 is an explanatory view illustrating a method of manufacturing the lower core substrate according to the first embodiment.

FIG. 4 is a cross-sectional view of the upper core substrate according to the first embodiment.

FIG. 5 is an explanatory view showing a method for forming a conductor pattern on the surface of the multilayer substrate according to the first embodiment.

FIG. 6 is an explanatory view showing a method of forming an outer blind via hole and a conductor pattern in the first embodiment.

FIG. 7 is an enlarged sectional view of a part of the multilayer printed wiring board according to the first embodiment.

FIG. 8 is a sectional view of a multilayer printed wiring board according to a second embodiment.

[Explanation of Codes] . . 9. insulating substrate; . . 10. multilayer substrate; . . 11. upper core substrate; . . 12. lower core substrate; . . Intermediate core substrate, 19. . . 1. Solder resist, . . 2. adhesive layer; . . Outer blind via hole, 30. . . Outer blind via hole forming portion, 350. . . 34. Inner blind via hole forming portion, . . Both ends blind via hole, 35. . . 4. Inner blind via hole, . . Conductor pattern, 50. . . Copper foil, 51. . . Coated pad, 54. . . External connection pad, 55. . . Nickel / gold plating film, 59. . . Metal plating film, 501, 502. . . Opening, 511. . . 7. rough surface; . . Multilayer printed wiring board,

Claims (4)

[Claims] 1. A multilayer printed wiring board comprising an upper core substrate and a lower core substrate having a conductor pattern and an adhesive layer for adhering the upper core substrate and the lower core substrate, wherein the upper core substrate and / or The lower core substrate has an outer blind via hole whose outer end is closed by a covering pad and whose inner end is open, and a part of the adhesive layer penetrates into the outer blind via hole from the inner end. A multilayer printed wiring board characterized by the following. 2. The method according to claim 1, wherein the covering pad comprises:
A multilayer printed wiring board having a rough surface. 3. A conductive pattern is formed on an insulating substrate to form an upper core substrate and a lower core substrate, and at least one of the upper core substrate and / or the lower core substrate is located at the bottom of an outer blind via hole. Forming an outer blind via hole by forming a coating pad on a portion to be formed, and piercing the outer blind via hole forming portion by laser irradiation and applying a metal plating film; and forming the outer core via hole and the lower core substrate. A step of laminating and press-bonding via an adhesive layer such that the opening of the outer blind via hole faces inward. 4. The method for manufacturing a multilayer printed wiring board according to claim 3, wherein a surface of the covering pad located at the bottom of the outer blind via hole is subjected to a surface roughening treatment.