JP2009010266A - Printed circuit board and method of manufacturing same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a printed circuit board in particular having through holes or IVHs (Interstitial Via Holes) and a method of manufacturing the printed circuit board, which can form a fine wiring pattern. <P>SOLUTION: A through hole 10 passing through a substrate 1 is formed in the substrate 1 having first and second conductive layers 7 and 8 formed on its both surfaces, an electrolessly-plated film 11 for electrically connecting the first and second conductive layers is formed so as to cover the inner surface of the through hole and the surfaces of the first and second conductive layers, the through hole having the electrolessly-plated film covered on its inner surface is buried with a conductive member 13, the conductive member projected from the surfaces of the substrate are removed together with the electrolessly-plated film formed on the respective surfaces. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a printed wiring board manufacturing method and a printed wiring board, and more particularly to a printed wiring board manufacturing method and printed wiring board having through holes and IVH (Interstitial Via Hole).

In a printed wiring board in which a plurality of wiring layers are laminated via insulating layers, there are through holes and IVH (Interstitial Via Hole) as means for electrically connecting the wiring layers.
Further, the through hole or IVH may be covered with a lid plating layer.
By covering the through hole with the lid plating layer, it is possible to mount an electronic component or the like on the through hole, and the electronic component mounting density of the printed wiring board can be improved.
Further, by covering IVH with a lid plating layer, a via (referred to as a stacked via) can be formed immediately above IVH, and the wiring density of the printed wiring board can be improved.
Patent Document 1 discloses an example of a printed wiring board having a through hole.
Japanese Patent Laid-Open No. 10-135629

Incidentally, the wiring layer is generally formed by partially etching the conductive layer by photolithography.
However, in a printed wiring board as disclosed in Patent Document 1, this conductive layer has a laminated structure of a copper foil and a copper plating film, and the copper plating film is generally made of electroless copper plating. After forming a thin electroless copper plating film, electrolytic copper plating is performed using the electroless copper plating film as a plating conductive film to further form a thick electrolytic copper plating film on the electroless copper plating film Therefore, it is difficult to form a fine wiring pattern and the improvement is desired.

  Moreover, when the lid plating layer is formed, since it has a further laminated structure of the conductive layer and the lid plating layer, it is more difficult to form a fine wiring pattern, and an improvement thereof is desired.

  In addition, there is a method of directly filling the through hole or IVH with the conductive paste without covering the inner surface of the through hole or IVH with the copper plating film, but the conductive particles dispersed in the conductive paste and the above Due to variations in the contact area between the inner wiring layer exposed on the inner surface and the contact area is small, the contact resistance may increase or the wire may be disconnected.

  Therefore, the problems to be solved by the present invention are, in particular, a printed wiring board manufacturing method and printed wiring board capable of forming a fine wiring pattern in a printed wiring board manufacturing method and printed wiring board having through holes and IVH. To provide a board.

In order to solve the above problems, each invention of the present application has the following means.
1) Drilling a through hole for drilling a through hole (10) penetrating the substrate (1) having the first conductive layer (7) and the second conductive layer (8) on both sides. After the step and the through hole drilling step, the first conductive layer and the second conductive layer cover the inner surface of the through hole and the surfaces of the first conductive layer and the second conductive layer. An electroless plating step for forming an electroless plating film (11) for electrically connecting the layers; and after the electroless plating step, the through hole whose inner surface is covered with the electroless plating film is connected to a conductive member ( The conductive member filling step 13) and the conductive member protruding from each surface of the substrate are removed together with the electroless plating film formed on each surface after the conductive member filling step. A printed wiring board (20, 50, 60, 70) having a removal step A.
2) Production of a printed wiring board according to 1), comprising a conductive layer forming step of forming a third conductive layer (61, 62, 71, 72) covering the conductive member and the respective surfaces after the removing step. Is the method.
3) In a printed wiring board having a laminated structure in which a plurality of wiring layers (3, 4, 15, 16) and insulating layers (2, 5, 6) are alternately stacked, the plurality of wiring layers are exposed. A hole (10) having an inner surface, an electroless plating film (11) covering the inner surface and electrically connecting the plurality of wiring layers to each other, and the hole whose inner surface is covered with the electroless plating film A printed wiring board (20, 50, 60, 70) having a conductive member (13) filling the portion.
4) The printed wiring board according to item 3), wherein the conductive member is covered with a conductive layer (61, 62).

  According to the present invention, there is an effect that a fine wiring pattern can be formed particularly in a printed wiring board manufacturing method and a printed wiring board having through holes and IVH.

  DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described with reference to FIGS. 1 to 8 according to a first embodiment and a second embodiment which are preferred embodiments.

<First embodiment>
1st Example is the Example of the manufacturing method of a printed wiring board which has a through-hole especially based on this invention, and a printed wiring board, The manufacturing process is made into A1 process-A4 process using FIGS. 1-4. explain.
1 to 4 are schematic cross-sectional views for explaining each of A1 process to A4 process in the first embodiment of the printed wiring board manufacturing method and the printed wiring board according to the present invention, in particular, according to the present invention. .

[Step A1] (see FIG. 1)
The shield plate 1 is produced by a known method.
The shield plate 1 includes a core material 2, a first wiring layer 3 and a second wiring layer 4 formed on both surfaces of the core material 2, and the first wiring layer 3 and the second wiring layer 4. A first insulating layer 5 and a second insulating layer 6 formed so as to cover; a copper foil 7 and a copper foil 8 which are formed so as to cover the first insulating layer 5 and the second insulating layer 6; , Is configured.
The core material 2, the first insulating layer 5, and the second insulating layer 6 are obtained by impregnating an insulating resin such as an epoxy resin into a sheet-like reinforcing material such as a glass cloth.

In the first embodiment, the thickness of the core material 2 is 100 μm, the thickness of the first wiring layer 3 and the second wiring layer 4 is 18 μm, respectively, and the thickness of the first insulating layer 5 and the second insulating layer 6 The thicknesses (thickness on the first wiring layer 3 and the second wiring layer 4) were 60 μm, and the thicknesses of the copper foil 7 and the copper foil 8 were 18 μm, respectively.
Therefore, the thickness of the shield plate 1 is 292 μm.

[Step A2] (see FIG. 2)
First, a through hole 10 penetrating the shield plate 1 is drilled at a predetermined position of the shield plate 1 by, for example, drilling.
Next, the electroless plating film 11 is formed so as to cover the surface of the shield plate 1 and the inner surface of the through hole 10.
By this electroless plating film 11, the second wiring layer 4, which is the inner wiring layer, and the copper foil 7 and the copper foil 8 are reliably electrically connected to each other.

  In the first example, the hole diameter (diameter) of the through hole 10 was 250 μm, the material of the electroless plating film 11 was copper, and the thickness was 0.2 to 0.5 μm.

[Step A3] (See FIG. 3)
First, as shown in FIG. 3A, the through-hole 10 whose inner surface is covered with the electroless plating film 11 is filled with a conductive paste 13 using, for example, a screen printing method, and this filling is further performed. The conductive paste 13 is cured.
Next, as shown in FIG. 3B, the excess conductive paste 13 that protrudes and hardens from each surface of the shield plate 1 is removed together with the electroless plating film 11 on each surface by, for example, buffing. To do.
By this removal step, each surface of the shield plate 1 (copper foils 6 and 7) after the electroless plating film 11 is removed and the exposed surface of the conductive paste 13 are substantially flat surfaces that are continuous with each other. .

As the conductive paste 13, a commercially available copper paste, silver paste, or the like can be used. In the example, a thermosetting copper paste was used as the conductive paste 13 and cured by performing a heat treatment at an environmental temperature of 120 ° C. to 150 ° C. for 1 hour.
In addition, a roll coating method or the like can be used as another filling method for filling the conductive paste 13.

[Step A4] (see FIG. 4)
The copper foil 7 and the copper foil 8 are partially removed by using a photolithography method to form a third wiring layer 15 and a fourth wiring layer 16 each having a plurality of wiring patterns.
The through hole 10 whose inner surface is covered with the electroless plating film 11 and filled with the conductive paste 13 electrically connects the second wiring layer 4, the third wiring layer 15, and the fourth wiring layer 16 to each other. It becomes the through hole 18 to be connected.

  The printed wiring board 20 having the through hole 18 is obtained by the above-described steps A1 to A4.

  According to the printed wiring board manufacturing method and the printed wiring board described above, the wiring layer that is electrically connected by the through hole can have a single-layer structure made of copper foil. Since the thickness of the conductive layer can be reduced, a fine wiring pattern can be formed.

  Also, according to the above-described printed wiring board manufacturing method and printed wiring board, by covering the inner surface of the through hole with the electroless plating film, the through hole is directly filled with the conductive paste without being covered with the electroless plating film. Compared with the case, each wiring layer can be reliably electrically connected with low contact resistance.

<Second embodiment>
The second embodiment is an embodiment of a method of manufacturing a printed wiring board and particularly a printed wiring board having IVH (Interstitial Via Hole) according to the present invention. The manufacturing process is shown as B1 to B4 in FIGS. 8 will be used for explanation.
FIGS. 5-8 is typical sectional drawing for demonstrating each B1 process-B4 process in the manufacturing method of the printed wiring board which has IVH especially based on this invention, and 2nd Example of a printed wiring board.

[Step B1] (see FIG. 5)
First, the above-described printed wiring board 20 is manufactured by performing the same steps as the steps A1 to A4 of the first embodiment described above.
The same components as those of the first embodiment are denoted by the same reference numerals as those of the first embodiment.

Next, the third insulating layer 30 and the fourth insulating layer 31 are formed on both surfaces of the printed wiring board 20 so as to cover the third wiring layer 15 and the fourth wiring layer 16, respectively.
The third insulating layer 30 and the fourth insulating layer 31 are formed by applying and curing an ink-like insulating resin using a coating method such as a roll coating method, a screen printing method, and a curtain coating method, Moreover, it can form by carrying out the thermocompression bonding of the prepreg by which insulating resin was impregnated in sheet-like reinforcement materials, such as a glass cloth, using the lamination method or the lamination press method.

In the second embodiment, an epoxy resin, which is an ink-like insulating resin, is applied using a roll coating method, and the applied epoxy resin is cured, whereby the above-described third insulating layer 30 and the fourth insulating resin are cured. An insulating layer 31 was formed.
In the second embodiment, the thicknesses of the third insulating layer 30 and the fourth insulating layer 31 (the thicknesses on the third wiring layer 15 and the fourth wiring layer 16) are 50 μm, respectively. .

[Step B2] (see FIG. 6)
A first bottomed hole 33 that exposes the third wiring layer 15 and a second hole that exposes the fourth wiring layer 16 at predetermined locations of the third insulating layer 30 and the fourth insulating layer 31. The bottomed holes 34 are respectively formed by, for example, laser processing.

[Step B3] (see FIG. 7)
After the residue due to laser processing generated in the first bottomed hole 33 and the second bottomed hole 34 is removed by a known desmear process, each of the first bottomed hole 33 and the second bottomed hole 34 is A first conductive layer 36 and a second conductive layer 37 are formed so as to cover the inner surface and the surfaces of the third insulating layer 30 and the fourth insulating layer 31.
The first conductive layer 36 and the second conductive layer 37 are formed by electroless plating to form a thin electroless plating film, and then electroplating using the electroless plating film as a plating conductive film. It is obtained by forming a thick electroplated film on the film.
In the second embodiment, the material of the first conductive layer 36 and the second conductive layer 37 is copper, and the thickness thereof is 30 μm.

[Step B4] (see FIG. 8)
The first conductive layer 36 and the second conductive layer 37 are partially etched using a photolithography method, so that a fifth wiring layer 39 and a sixth wiring layer 40 each having a plurality of wiring patterns are obtained. Form.
The first bottomed hole 33 whose inner surface is covered with the first conductive layer 36 becomes the first via 42 that electrically connects the third wiring layer 15 and the fifth wiring layer 39, and the inner surface is The second bottomed hole 34 covered with the second conductive layer 37 serves as a second via 43 that electrically connects the fourth wiring layer 16 and the sixth wiring layer 40.
Further, the through hole 10 whose inner surface is covered with the electroless plating film 11 and filled with the conductive paste 13 electrically connects the second wiring layer 4, the third wiring layer 15, and the fourth wiring layer 16 to each other. It becomes IVH (Interstitial Via Hole) 45 to be connected.

  The printed wiring board 50 having IVH45 is obtained by the above-described B1 to B4 processes.

  According to the printed wiring board manufacturing method and the printed wiring board described above, the wiring layer electrically connected by IVH can have a single-layer structure made of copper foil. Since the thickness of the layer can be reduced, a fine wiring pattern can be formed.

  Further, according to the above-described printed wiring board manufacturing method and printed wiring board, when the inner surface of IVH is covered with an electroless plating film, IVH is directly filled with a conductive paste without being covered with the electroless plating film. In comparison, each wiring layer can be reliably electrically connected with a low contact resistance.

  The embodiment of the present invention is not limited to the configuration and procedure described above, and it goes without saying that modifications may be made without departing from the scope of the present invention.

Here, a modification of the first embodiment will be described with reference to FIG. 9 and a modification of the second embodiment will be described with reference to FIG.
9 and 10 are schematic cross-sectional views for explaining modifications of the first embodiment and the second embodiment, respectively.

  First, a modification of the first embodiment described above will be described with reference to FIG.

First, the same steps as the steps A1 to A3 of the first embodiment described above are performed.
Next, lid plating layers 61 and 62 are formed so as to cover the conductive paste 13, the copper foil 7, and the copper foil 8.
The lid plating layers 61 and 62 are electrolessly plated to form a thin electroless plating film, and then electroplating is performed using the electroless plating film as a plating conductive film, and a thick film is further formed on the electroless plating film. It is obtained by forming an electroplated film.
In the modification, the material of the lid plating layers 61 and 62 is copper, and the thickness thereof is 10 μm.

  Thereafter, the lid plating layers 61 and 62 and the copper foils 7 and 8 are partially removed by using a photolithography method, whereby a third wiring layer 63 and a fourth wiring layer each formed of a plurality of wiring patterns. 64 is formed.

  The printed wiring board 60 which is a modification of the first embodiment is obtained by the procedure described above.

  According to the printed wiring board 60, since the copper foils 7 and 8 and the conductive paste 13 are further connected by the lid plating layers 61 and 62, the connection resistance can be reduced and the connection strength can be improved.

  Moreover, according to this printed wiring board 60, since electronic components can be mounted on the lid plating layers 61 and 62 via a conductive member such as solder, the electronic component mounting density of the printed wiring board can be improved. .

  Next, a modification of the above-described second embodiment will be described with reference to FIG.

First, on both surfaces of the printed wiring board 60 described above, the third insulating layer 30 and the fourth wiring layer 64 are respectively covered so as to cover the third wiring layer 63 and the fourth wiring layer 64 in the same manner as in the B1 step of the second embodiment. A fourth insulating layer 31 is formed.
Next, a printed wiring board 70 which is a modification of the second embodiment is obtained by performing the same processes as the B2 process to the B4 process of the second embodiment.

  According to this printed wiring board 70, since the copper foils 7 and 8 and the conductive paste 13 are further connected by the lid plating layers 61 and 62 as in the above-described printed wiring board 60, the connection resistance can be reduced. Connection strength can be improved.

  Moreover, according to this printed wiring board 70, since the vias 42 and 43 can be formed on the lid plating layers 61 and 62, the wiring density of the printed wiring board can be improved.

  By the way, in the first embodiment, the second embodiment, and the modified example, the four-layer shield plate 1 is used. However, the present invention is not limited to this, and the shield plate 1 is replaced with five or more layers of shields. The plate 1 may be used, or a so-called double-sided copper-clad plate in which copper foils are bonded to both sides of the core material may be used.

In the A3 process of the first embodiment, the B1 process of the second embodiment, and the modification, the electroless plating film 11 on each surface of the shield plate 1 (copper foils 7 and 8) is removed. However, the present invention is not limited to this.
For example, in the above removal step, the electroless plating film 11 on each surface of the copper foils 7 and 8 may be removed, and the copper foils 7 and 8 may be removed to a predetermined thickness. A method for adjusting the thickness of the conductive layer to a predetermined thickness is referred to as copper thickness adjustment.

It is typical sectional drawing for demonstrating the A1 process in the manufacturing method of the printed wiring board of this invention, and 1st Example of a printed wiring board. It is typical sectional drawing for demonstrating the A2 process in the manufacturing method of the printed wiring board of this invention, and 1st Example of a printed wiring board. It is typical sectional drawing for demonstrating the A3 process in the manufacturing method of the printed wiring board of this invention, and 1st Example of a printed wiring board. It is typical sectional drawing for demonstrating the A4 process in the manufacturing method of the printed wiring board of this invention, and 1st Example of a printed wiring board. It is typical sectional drawing for demonstrating the B1 process in the manufacturing method of the printed wiring board of this invention, and 2nd Example of a printed wiring board. It is typical sectional drawing for demonstrating the B2 process in the manufacturing method of the printed wiring board of this invention, and 2nd Example of a printed wiring board. It is typical sectional drawing for demonstrating the B3 process in the manufacturing method of the printed wiring board of this invention, and 2nd Example of a printed wiring board. It is typical sectional drawing for demonstrating the B4 process in the manufacturing method of the printed wiring board of this invention, and 2nd Example of a printed wiring board. It is typical sectional drawing for demonstrating the modification of 1st Example. It is typical sectional drawing for demonstrating the modification of 2nd Example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Shield plate, 2 Core materials, 3, 4, 15, 16, 39, 40 Wiring layer, 5, 6, 30, 31 Insulating layer, 7, 8 Copper foil, 10 Through hole, 11 Electroless plating film, 13 Conductivity Paste, 18 through hole, 20, 50 printed wiring board, 33, 34 bottomed hole, 36, 37 conductive layer, 42, 43 via, 45 IVH

Claims (4)

A through-hole drilling step of drilling a through-hole penetrating the substrate on the substrate provided with the first conductive layer and the second conductive layer on both sides;
After the through-hole drilling step, covering the inner surface of the through-hole and the surfaces of the first conductive layer and the second conductive layer, the first conductive layer and the second conductive layer An electroless plating process for forming an electroless plating film to be electrically connected;
After the electroless plating step, a conductive member filling step of filling the through hole whose inner surface is covered with the electroless plating film with a conductive member;
After the conductive member filling step, the removal step of removing the conductive member protruding from each surface of the substrate together with the electroless plating film formed on each surface;
The manufacturing method of the printed wiring board which has this.   The method for manufacturing a printed wiring board according to claim 1, further comprising a conductive layer forming step of forming a third conductive layer covering the conductive member and the surfaces after the removing step. In a printed wiring board having a laminated structure in which a plurality of wiring layers and insulating layers are alternately laminated,
A hole having an inner surface from which the plurality of wiring layers are exposed;
An electroless plating film covering the inner surface and electrically connecting the plurality of wiring layers to each other;
A conductive member filling the hole whose inner surface is covered with the electroless plating film;
A printed wiring board having:   The printed wiring board according to claim 3, wherein the conductive member is covered with a conductive layer.

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