JP2003273488A - Wiring board and manufacturing method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a wiring board where reduction in reliability is prevented in interlayer connection in a through hole having a high aspect ratio and a fine pattern is formed, and to provide a method for manufacturing the wiring board. <P>SOLUTION: A plating film having a thickness of 30 μm or more is formed on the wall surface of the through hole by a plating process. Then, the inside of the through hole is filled with a protection agent by a paste fill process. As a result, the plating film of the through hole is not affected by etching in a succeeding process or the like. Conductor layers on the front and rear are thinned until a fine pattern can be formed by etching and polishing processes. Then, the fine pattern is formed by a pattern formation process. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laminated wiring board formed by laminating a conductor layer and an interlayer insulating layer, and a method for manufacturing the same. More specifically, the present invention relates to a wiring board having a through hole for establishing conduction between the front and back and a method for manufacturing the wiring board.

[0002]

2. Description of the Related Art In recent years, a laminated wiring board in which 20 or more conductor layers and insulating layers are laminated has been manufactured. As such a laminated wiring board, for example, there is a so-called infrastructure board used for industrial applications such as a base station of a telephone. Since this infrastructure board has a longer service life than ordinary wiring boards, durability and long-term reliability are required. Because of this, the board thickness is larger than that of ordinary wiring boards. Furthermore, the through hole formed in this laminated wiring board has a large aspect ratio as compared with a normal wiring board. The aspect ratio here means a value obtained by dividing the thickness of the wiring board by the hole diameter of the through hole. When the laminated wiring board is subjected to through-hole plating, it is necessary to form a plating film having a large film thickness in order to secure reliability of interlayer connection.

Further, in the wiring board, the wiring board and the electronic parts may be connected by inserting pins into the through holes provided in the wiring board. However, when the pin is frequently inserted and removed, the plating film on the wall surface of the through hole is worn. Therefore, it is necessary to make the plated film of the through hole thicker. Specifically, it is necessary to form a plating film having a thickness of 30 μm or more by electrolytic plating or the like. By forming such a plating film, contact failure will not occur even if the plating film is worn to some extent.

[0004]

However, the above-mentioned conventional technique has the following problems. That is, when electrolytic plating is performed at a normal current density (1 to 10 A / dm ² ), more metal is deposited on the conductor layer on the surface than on the wall surface of the through hole. In particular, when electrolytic plating is performed on a through hole having an aspect ratio of 10 or more, a plated layer having a thickness twice or more is formed on the conductor layer as compared with the thickness of the plated film of the through hole. Will be done. That is, when a plating film having a film thickness of 30 μm or more is formed in the through hole, the thickness of the conductor layer on the surface becomes 60 μm or more. Therefore, it is difficult to form a fine pattern.

As a concrete example of this, the wiring board 10 of FIG.
It will be described using 0. In this wiring board 100, a through hole 5 having a hole diameter of 0.3 mm is formed in a substrate 1 having a board thickness of 3.0 mm. That is, the aspect ratio of the through hole 5 is 1
It is 0. Therefore, when the plating film 3 having a thickness of 30 μm is formed on the wall surface of the through hole 5, the plating layer 2 having a thickness of about 60 μm is formed on the surface. That is, if the copper foil 6 having a thickness of 12 μm is included, the conductor layer 8 having a thickness of 72 μm is formed. Therefore, it is difficult to form a fine pattern on the conductor layer 8.

Also, low current density (0.1 to 1.0 A / d)
By performing the electroplating with m ² ), it is possible to reduce the nonuniformity between the thickness of the plating layer formed on the surface and the thickness of the plating film formed on the wall surface of the through hole. However, the thickness of the plating layer on the surface never becomes thinner than that on the wall surface of the through hole. Therefore, when a plating film having a thickness of 30 μm or more is formed on the wall surface of the through hole, a plating layer having a thickness of 30 μm or more is formed on the conductor layer. Therefore, it is difficult to form a fine pattern.

Further, the conductor layer on the surface can be thinned by soft etching. However, as the conductor layer on the surface becomes thinner, the plating film on the wall surface of the through hole also becomes thinner.

The present invention has been made to solve the above-mentioned problems of the conventional technique. That is, it is an object of the invention to provide a wiring board on which a fine pattern is formed and a method for manufacturing the wiring board, which prevents deterioration of reliability of interlayer connection in a through hole having a high aspect ratio.

[0009]

A wiring board made for the purpose of solving this problem is a wiring board in which conductor layers and insulating layers are alternately laminated, and the wiring board is provided with through holes and front and back surfaces. A surface conductor layer and a wall conductor layer provided on the wall surface of the through hole for establishing conduction between the front and back surfaces, and the thickness of the wall conductor layer is larger than that of the surface conductor layer. is there. This wiring board has thin front and back surface conductor layers.
Therefore, a fine pattern can be formed.
In addition, the film thickness of the wall surface conductor layer on the wall surface of the through hole is large. Therefore, it is possible to prevent the reliability of the interlayer connection from decreasing.
Therefore, with this wiring board, it is possible to form a fine pattern while preventing a decrease in reliability of interlayer connection. In addition, the through hole referred to here may be penetrated at the time of being formed, and may be thereafter filled with a protective agent or the like.

The wiring board of the present invention is particularly significant in the case of a wiring board having a large thickness. Specifically, it is meaningful for a wiring board having a through hole having an aspect ratio of 5 or more (particularly 7 or more, and further 10 or more). As a result, fine patterns can be formed on the surface conductor layers on the front and back surfaces even with a wiring board having a large thickness such as an infrastructure board.

The through hole of the wiring board of the present invention is particularly significant when it is used for inserting a terminal pin of a component. This is because the wall surface conductor layer having a sufficient thickness is formed on the wall surface of the through hole, so that even if the thickness of the wall surface conductor layer is reduced to some extent due to abrasion, contact failure does not occur.

Further, in the wiring board of the present invention, a wall surface conductor layer is formed on the wall surface of the through hole, the through hole is filled with a protective agent, and the through hole is filled with the protective agent. The thickness of the conductor layer is reduced. That is, in the wiring board of the present invention, the thickness of the surface conductor layer is reduced until a fine pattern can be formed. Therefore, a fine pattern can be formed on the wiring board of the present invention. Further, at the time of performing the process of reducing the thickness of the surface conductor layer, since the through hole is protected by the protective agent, the thickness of the wall surface conductor layer on the wall surface of the through hole does not decrease. Therefore, the reliability of the interlayer connection is prevented from decreasing.

The method of manufacturing a wiring board according to the present invention is a method of manufacturing a wiring board in which conductor layers and insulating layers are alternately laminated, wherein a wall surface conductor layer is formed on the wall surface of the through hole. A layer forming step, a step of filling a through hole in which the wall surface conductor layer is formed with a protective agent, and a thin layer for thinning the surface conductive layer on the front and back surfaces in a state where the through hole is filled with the protective agent by the hole filling step And a chemical conversion step.

In the manufacturing method of the present invention, first, in the wall surface conductor layer forming step, a wall surface conductor layer having a required thickness is formed on the wall surface of the through hole. Next, a through hole is filled with a protective agent in a hole filling process. As a result, the wall surface conductor layer is not affected by etching or the like in a later process. Therefore, the wall surface conductor layer can maintain the required thickness. Next, the surface conductor layers on the front and back surfaces are thinned by a thinning step. That is, the surface conductor layer is thinned to the extent that it does not hinder the formation of the fine pattern. As a result, fine patterns can be formed on the surface conductor layers on the front and back surfaces.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments embodying the present invention will be described in detail below with reference to the accompanying drawings.

The laminated wiring board 10 according to the present embodiment has a sectional structure shown in FIG. The laminated wiring board 10 is a laminated wiring board including the substrate 1 and the conductor layers 8 on the front and back surfaces of the substrate 1. This substrate 1 is one in which conductor layers and insulating layers are alternately laminated, but is omitted in the drawing. The plate thickness of the substrate 1 is about 3.0 mm. Each conductor layer 8 is composed of a copper foil 6 and a copper plating layer 2. Of course, each conductor layer is appropriately patterned. The thickness of each conductor layer 8 is about 28 μm, of which the copper foil 6 is about 12 μm.

Further, a through hole 5 is formed in the laminated wiring board 10. In addition, a copper plating film 3 is formed on the wall surface of the through hole 5 in order to establish conduction between the conductor layers 8 on the front and back surfaces. The diameter of the through hole 5 is about 0.3 mm. That is, the aspect ratio of the through hole 5 is about 1
It is 0. The thickness of the copper plating film 3 on the wall surface of the through hole 5 is about 30 μm. That is, the conductive portion (thickness: 30 μm) on the wall surface of the through hole 5 is thicker than the conductor portion (thickness: 28 μm) on the surface.

Next, the manufacturing process of the laminated wiring board 10 will be described with reference to the flowchart of FIG. First, electrolytic copper plating is performed to establish conduction between the conductor layers 8 on the front and back surfaces (S1: plating step). As a result, the copper plating film 3 having a thickness of about 30 μm is formed on the wall surface of the through hole 5. Further, copper plating layers 2 and 2 having a thickness of about 60 μm are formed on each copper foil 6. That is, the conductor layers 8 having a thickness of about 72 μm are formed together with the copper foil 6 having a thickness of 12 μm. The electrolytic copper plating may be performed at a normal current density or a low current density.

Next, the through hole 5 is filled with a soluble paste-like protective agent (S2: paste filling step, FIG. 3).
Since the copper plating film 3 is shielded from the outside by the protective agent, the copper plating film 3 is protected. As a protective agent,
For example, San Nopco's "Nopco Cure F701"
(Product name) can be used.

Next, half etching is performed to thin the conductor layers 8 (S3: etching step). As a result, the thickness of each conductor layer 8 is reduced to about 36 μm. The protective agent is not dissolved in this etching.

Next, buffing is performed to make the conductor layers 8 and 8 thinner (S4: polishing step). As a result, each conductor layer 8 is further thinned to have a thickness of about 28 μm. Further, in this buffing step, fine irregularities on the surface are also removed.

Next, the conductor layers 8 and 8 are patterned (S5: pattern forming step). Here, each conductor layer 8
Since it has been thinned to a thickness of about 28 μm, it is possible to form a fine pattern. In this pattern forming process, as a resist, "H-9 manufactured by Hitachi Chemical Co., Ltd."
040 "or the like can be used, and a sodium carbonate-based developer or the like is used to develop the resist. Note that the protective agent is not hardened by exposure during patterning of the resist. Moreover, the protective agent is not dissolved even when the resist is developed. Further, a copper chloride-based etching solution or the like is used for pattern etching. The protective agent is not dissolved even by this etching. That is, the copper plating film 3 is not affected by the pattern formation.

Next, the protective agent is removed if necessary.
As a result, the wiring board 10 shown in FIG. 1 is manufactured. A pin such as an electronic component can be connected to the through hole 5 from which the protective agent has been removed. And the copper plating film 3 of the through hole 5
Has a sufficient film thickness of 30 μm or more, the reliability of the interlayer connection is not deteriorated even if the pin is removed and attached to cause some abrasion. In addition, to dissolve this protective agent, "SN Solver 861" manufactured by San Nopco
Developer solutions such as the above can be used. Note that the protective agent may be left if the pin is not inserted and removed.

As described above in detail, in the manufacturing method of this embodiment, first, the copper plating film 3 having a thickness of 30 μm or more is formed on the wall surface of the through hole 5 by the plating process. Next, in the paste filling step, the inside of the through hole 5 is filled with a protective agent. As a result, the copper plating film 3 on the wall surface of the through hole 5 is not affected by etching or the like in a subsequent process, and a film thickness of 30 μm or more can be secured. Therefore, the reliability of interlayer connection is high. Next, the conductor layers 8 are thinned by an etching process and a polishing process. Thereby, the thickness of each conductor layer 8 can be made thinner than the thickness of the copper plating film 3 of the through hole 5. That is, each conductor layer 8 can have a thickness of 30 μm or less. Therefore, a fine pattern can be formed in the pattern forming step. Therefore, even in the case of a through hole with a large aspect ratio, it is possible to prevent deterioration of reliability of interlayer connection,
A wiring board having a fine pattern and a manufacturing method thereof have been realized.

Further, the protective agent filling the through holes 5 may be dissolved after the pattern forming step. Pins can be inserted into and removed from the through holes 5 in the wiring board 10 after the melting. Also in this case, since the plating film 3 on the wall surface of the through hole 5 has a thickness of 30 μm or more, reliability of interlayer connection is high.

The present embodiment is merely an example and does not limit the present invention. Therefore, naturally, the present invention can be variously improved and modified without departing from the gist thereof. For example, the substrate 1 in FIG. 1 may be an insulating layer only.

[0027]

As is apparent from the above description, according to the present invention, there is provided a wiring board having a fine pattern formed, which prevents deterioration of reliability of interlayer connection in a through hole having a high aspect ratio, and a manufacturing method thereof. It is provided.

[Brief description of drawings]

FIG. 1 is a diagram showing a cross section of a wiring board formed by a manufacturing method according to an embodiment.

FIG. 2 is a flowchart showing a manufacturing method according to an embodiment.

FIG. 3 is a view showing a cross section of the wiring board after the paste filling step.

FIG. 4 is a view showing a cross section of a wiring board formed by a conventional manufacturing method.

[Explanation of symbols]

1 substrate 2 conductor layers 3 plating film 5 through holes 6 copper foil 8 conductor layers

   ─────────────────────────────────────────────────── ─── Continued front page    F term (reference) 5E317 AA24 BB01 BB12 CC33 CD17                       CD25 CD27 CD40 GG14 GG20                 5E319 AA02 AA08 AA09 AB01 AC01                       GG01 GG20                 5E339 AC01 AD03 AE01 BC02 BD02                       BD08 BE13 CE06 CE11 CE14                       CF16 CF17 CG04 DD04 GG10

Claims (5)

[Claims] 1. A wiring board having conductor layers and insulating layers alternately laminated, wherein a through hole, a surface conductor layer provided on the front and back surfaces, and conduction between the front and back surfaces provided on the wall surface of the through hole. A wiring board having a wall conductor layer having a thickness greater than that of the surface conductor layer. 2. The wiring board according to claim 1, wherein the through hole has an aspect ratio of 10 or more. 3. The wiring board according to claim 1, wherein the through hole is for inserting a terminal pin of a component. 4. The wiring board according to claim 1, wherein a wall surface conductor layer is formed on a wall surface of the through hole, and the through hole is filled with a protective agent. The wiring board is characterized in that the thickness of the surface conductor layers on the front and back surfaces is reduced in a state in which the through holes are filled. 5. A method of manufacturing a wiring board, which comprises alternately stacking conductor layers and insulating layers, wherein a wall conductor layer forming step of forming a wall conductor layer on a wall surface of a through hole and the wall conductor layer are formed. And a hole filling step of filling the through hole with a protective agent,
A thinning step of thinning the surface conductor layer on the front and back surfaces in a state where the through hole is filled with a protective agent by the hole filling step;
A method for manufacturing a wiring board, comprising: