JP2008060119A - Printed wiring board - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a printed wiring board having improved rigidity by enabling connection between wiring layers via an insulating layer (or core material) containing a plurality of sheet-like reinforcing materials such as glass cloths. <P>SOLUTION: The insulating plate-like first core material 1 having a first wiring layer 29 on one surface, and a second wiring layer 18 on the other surface is stuck on the plate-like second core material 1, having insulating performance and a third wiring layer 8 on one surface and a fourth wiring layer 27 on the other surface via the insulating layer 23, so that the second and third wiring layers face with each other. The first and second wiring layers are electrically connected to each other via a first via 14 piercing through the first core material, the second and third wiring layers are electrically connected to each other via bumps 21 piercing through the insulating layer and having conductivity, and the third and fourth wiring layers are electrically connected to each other via a second via 4 piercing through the second core material. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a printed wiring board, and more particularly to a multilayer printed wiring board.

In order to meet the demands for higher performance and downsizing of electronic devices, printed wiring boards are required to have higher density and smaller size, and printed wiring corresponding to such higher density and smaller size is required. An example of the plate is described in Patent Document 1.
The printed wiring board described in Patent Document 1 has a laminated structure in which a plurality of wiring layers and insulating layers are alternately laminated in the thickness direction, and adjacent wiring layers are provided with an insulating layer (resin sheet). ) Are electrically connected by bumps penetrating each other.
JP-A-8-195561

By the way, when mounting electronic components on a printed wiring board using solder or the like, the difference in thermal expansion coefficient between the printed wiring board and the electronic component is accompanied by downsizing of the land portion connecting the printed wiring board and the electronic component. The possibility of poor connection between the printed wiring board and the electronic component is increasing due to (particularly, the difference in thermal expansion coefficient in the surface direction of the printed wiring board) and warpage of the printed wiring board.
Therefore, it is desired to further improve the rigidity of the printed wiring board.

For example, as one means for improving the rigidity of a printed wiring board, there is a method of increasing the number of sheet-like reinforcing materials such as glass cloth included in an insulating layer.
However, since it is difficult for the printed wiring board described in Patent Document 1 to penetrate through an insulating layer having a plurality of overlapping sheet-like reinforcing materials with bumps, there is a case in which conduction failure occurs between adjacent wiring layers. .
Therefore, normally, in the printed wiring board described in Patent Document 1, since the number of sheet-like reinforcing materials included in each insulating layer is one, further improvement in rigidity is desired.

  Accordingly, the problem to be solved by the present invention is a printed wiring board having improved rigidity by allowing wiring layers to be connected via an insulating layer (or a core material) including a sheet-like reinforcing material such as a plurality of glass cloths. Is to provide.

In order to solve the above problems, each invention of the present application has the following means.
1) a first core material (1) that is in the form of a plate having insulating properties and has a first wiring layer (29) on one side and a second wiring layer (18) on the other side; A second core material (1) that is insulative and has a third wiring layer (8) on one side and a fourth wiring layer (27) on the other side; The second wiring layer and the third wiring layer are bonded to each other through an insulating layer (23) so as to face each other, and the first wiring layer and the second wiring layer are bonded to each other. The second wiring layer and the third wiring layer are electrically connected by a conductive bump (21) penetrating the insulating layer, and are electrically connected by a first via (14) penetrating the core material. The third wiring layer and the fourth wiring layer are electrically connected by a second via (4) penetrating the second core material. It is a printed circuit board (40, 60, 80), characterized in comprising Te.
2) The second via includes a through hole (4) penetrating the second core material and a conductive filler (51) filled in the through hole, and the bump and the filling The printed wiring board according to 1), wherein the printed wiring board is in contact with a material.
3) The first core material includes a first resin (1b) having an insulating property, and a plurality of first core materials that are disposed inside the first resin so as to overlap along the surface of the first core material. The second core material is an insulating second resin (1b) and the surface of the second core material inside the second resin. A printed wiring board according to 1) or 2), characterized in that a plurality of second sheet-shaped reinforcing members (1a) are disposed so as to overlap with each other.
4) The printed wiring according to 3), wherein the first sheet-shaped reinforcing material and the second sheet-shaped reinforcing material are any of glass cloth, aramid cloth, glass nonwoven fabric, and aramid nonwoven fabric. It is a board.

  ADVANTAGE OF THE INVENTION According to this invention, there exists an effect that the rigidity of a printed wiring board improves by setting it as the structure which connects the wiring layers via the core material containing sheet-like reinforcement materials, such as a some glass cloth.

  Embodiments of the present invention will be described with reference to FIGS. 1 to 9 according to first to third embodiments which are preferable examples.

<First embodiment>
First, the 1st Example of the printed wiring board of this invention is described using FIGS. 1-5 as A1 process-A5 process.
FIGS. 1-5 is typical sectional drawing for demonstrating the A1 process-A5 process in 1st Example of the printed wiring board of this invention, respectively.

(Step A1) [See FIG. 1]
Two so-called double-sided copper-clad plates are prepared in which copper foils 2a and 2b are bonded to both sides of a plate-like core material 1 having insulating properties.
The core material 1 includes an insulating resin 1b such as an epoxy resin, and two sheet-like reinforcements disposed in the resin 1b in a direction perpendicular to the surface of the core material 1, that is, in the thickness direction of the core material 1. And a material 1a.
As the sheet-like reinforcing material 1a, glass cloth, aramid cloth, glass nonwoven fabric, aramid nonwoven fabric or the like can be used.
In the first example, the thickness of the core material 1 was 0.2 mm, and the thicknesses of the copper foils 2a and 2b were each 12 μm.

Here, for convenience, of the two double-sided copper-clad plates, one double-sided copper-clad plate {FIG. 1 (a)} is referred to as a first double-sided copper-clad plate 3 and the other double-sided copper-clad plate {FIG. b)} is referred to as a second double-sided copper-clad plate 13.
In the first double-sided copper-clad plate 3 and the second double-sided copper-clad plate 13, the thickness of the core material 1 and the thickness of the copper foils 2a, 2b are not limited to this, and the first double-sided copper-clad plate 13 and the second double-sided copper-clad plate 13 The thickness of the core material 1 and the thickness of the copper foils 2a and 2b may be different between the copper-clad plate 3 and the second double-sided copper-clad plate 13, respectively.

Next, the through hole 4 is formed at a predetermined position of the first double-sided copper-clad plate 3, and the through-hole 14 is formed at a predetermined position of the second double-sided copper-clad plate 13.
The through holes 4 and 14 can be formed by drilling or laser processing.
In the first embodiment, the diameters of the through holes 4 and 14 are each 0.1 mm.
Therefore, the aspect ratio of the through hole 4 (ratio of the thickness of the core material 1 to the hole diameter of the through hole 4) and the aspect ratio of the through hole 14 (ratio of the thickness of the core material 1 to the hole diameter of the through hole 14) are as follows. , 2 respectively.

(Process A2) [Refer to FIG. 2]
In the first double-sided copper-clad plate 3, for example, a first plating layer 5 made of copper is formed on each surface of the copper foils 2 a and 2 b so as to cover the inner wall of the through hole 4.
Further, in the second double-sided copper-clad plate 13, for example, a second plating layer 15 made of copper is formed on each surface of the copper foils 2 a and 2 b so as to cover the inner wall of the through hole 14.
The first plating layer 5 and the second plating layer 15 can be formed, for example, by performing electroless copper plating and then performing electrolytic copper plating.
In the first example, the plating conditions were set so that the thicknesses of the first plating layer 5 and the second plating layer 15 were each about 15 μm.

Next, the filler 6 is filled into each of the through hole 4 whose inner wall is covered with the first plating layer 5 and the through hole 14 whose inner wall is covered with the second plating layer 15.
Specifically, the insulating resin ink for hole filling, which is the filler 6, is filled into each of the through holes 4 and 14 by, for example, screen printing, and then cured, and the first plating layer 5 and the second plating layer are then cured. Excess ink that protrudes and hardens from the surface 15 is removed by, for example, buffing to form a flat surface. As the hole filling ink, a commercially available hole filling ink can be used. In addition, a roll coating method can be used as another filling method.

(Step A3) [Refer to FIG. 3]
In the 1st double-sided copper-clad board 3, the 3rd plating layer 7 which consists of copper, for example is formed in the surface of the 1st plating layer 5 so that the exposed part of the filler 6 may be covered.
In the second double-sided copper-clad plate 13, for example, a fourth plating layer 17 made of copper is formed on the surface of the second plating layer 15 so as to cover the exposed portion of the filler 6.
The third plating layer 7 and the fourth plating layer 17 can be formed by the same method as the first plating layer 5 and the second plating layer 15 described above.
In the first example, the plating conditions were set so that the thicknesses of the third plating layer 7 and the fourth plating layer 17 were about 10 μm, respectively.

Next, the third plating layer 7, the first plating layer 5, and the copper foil 2a on the one surface A3 side of the first double-sided copper-clad plate 3 are partially etched by photolithography, so that the first wiring layer 8 is formed. Form.
Further, the second wiring layer 18 is formed by partially etching the fourth plating layer 17, the second plating layer 15, and the copper foil 2a on the one surface A13 side of the second double-sided copper-clad plate 13 by photolithography. To do.

Thereafter, a substantially conical bump 21 having conductivity is formed at a predetermined position of the second wiring layer 18 of the second double-sided copper-clad plate 13.
The bump 21 can be formed by a known method.
In the first example, an Ag (silver) paste was printed by screen printing to form a bump 21 having a height H21 of 80 μm and a bottom diameter R21 in contact with the second wiring layer 18 of 80 μm.

(Step A4) [Refer to FIG. 4]
As shown in FIG. 4 (a), one surface A3 of the first double-sided copper-clad plate 3 and one surface A13 of the second double-sided copper-clad plate 13 face each other, and the first double-sided copper-clad plate 3 and the second The two double-sided copper-clad plates 13 are pressed and heated through an uncured prepreg 23, whereby the prepreg 23 is cured, and the first double-sided copper-clad plate 3 shown in FIG. A four-layer shield plate 25 bonded to the second double-sided copper-clad plate 13 is obtained.
The prepreg 23 includes an insulating resin 23b such as an uncured epoxy resin, and a sheet-like reinforcing material 23a disposed inside the resin 23b.
As the sheet-like reinforcing material 23a, glass cloth, aramid cloth, glass nonwoven fabric, aramid nonwoven fabric, or the like can be used.
In the first example, the thickness of the uncured prepreg 23 was 60 μm.
Moreover, the bump 21 penetrates the prepreg 23 and is electrically connected to the first wiring layer 8 by the above-described bonding.

(Step A5) [Refer to FIG. 5]
The third wiring layer 27 is formed by partially etching the third plating layer 7, the first plating layer 5, and the copper foil 2b on the one surface B3 side of the four-layer shield plate 25 by the photolithography method, and the four-layer shield plate 25, the fourth plating layer 17, the second plating layer 15, and the copper foil 2b on the other surface B13 side are partially etched to form a fourth wiring layer 29.

  The four-layer printed wiring board 40 having four wiring layers of the first wiring layer 8, the second wiring layer 18, the third wiring layer 27, and the fourth wiring layer 29 is obtained by the above-described steps A1 to A5.

The four-layer printed wiring board 40 is electrically connected to the first wiring layer 8 and the third wiring layer 27 through a through-hole (sometimes referred to as a conduction hole or via) 4 whose inner wall is covered with the first plating layer 5. Since the wiring layers can be connected to each other through a core material including a sheet-like reinforcing material such as a glass cloth arranged in a plurality of layers along the surface. The rigidity of can be improved.
The four-layer printed wiring board 40 has a through-hole (sometimes referred to as a conduction hole or a via) in which the second wiring layer 18 and the fourth wiring layer 29 are covered with the second plating layer 15 on the inner wall. Since it is electrically connected, it is possible to connect the wiring layers through a core material that includes a sheet-like reinforcing material such as a glass cloth that is arranged in multiple layers along the surface. The rigidity of the wiring board can be improved.

<Second embodiment>
Next, a second embodiment of the printed wiring board according to the present invention will be described as a B1 process to a B3 process with reference to FIGS.
FIGS. 6-8 is typical sectional drawing for demonstrating the B1 process-B3 process in 2nd Example of the printed wiring board of this invention, respectively.
In the first embodiment, the first plating layer 5 and the second plating layer 15 are formed. However, in the second embodiment, the conductive filler 51 is used without forming these plating layers 5 and 15. One of the features is that the wiring layers are electrically connected to each other.
In addition, the same code | symbol as 1st Example shall be attached | subjected to the same component as 1st Example.

(Step B1) [Refer to FIG. 6]
First, the same process as the A1 process of the first embodiment described above is performed.
Next, a conductive filler 51 is filled in each of the through holes 4 and 14.
Specifically, the Cu (copper) paste as the filler 51 is cured after being filled into each of the through holes 4 and 14 by, for example, screen printing, and is projected and cured from the surfaces of the copper foils 2a and 2b. Excess Cu paste is removed by, for example, buffing to form a flat surface.

Thereafter, in the first double-sided copper-clad plate 3, a third plating layer 7 made of, for example, copper is formed on the surfaces of the copper foils 2a and 2b so as to cover the exposed portion of the filler 51.
In the second double-sided copper-clad plate 13, for example, a fourth plating layer 17 made of copper is formed on the surface of the second plating layer 15 so as to cover the exposed portion of the filler 51.
The formation method and thickness of the third plating layer 7 and the fourth plating layer 17 in the second embodiment are the same as those in the first embodiment.

(Step B2) [Refer to FIG. 7]
Next, the first wiring layer 8a is formed by partially etching the third plating layer 7 and the copper foil 2a on the one surface A3 side of the first double-sided copper-clad plate 3 by photolithography.
In addition, the second wiring layer 18a is formed by partially etching the fourth plating layer 17 and the copper foil 2a on the one surface A13 side of the second double-sided copper-clad plate 13 by photolithography.

(Step B3) [Refer to FIG. 8]
Thereafter, the same process as in the first embodiment is performed to form the four-layer shield plate 25a.
Next, the third plating layer 7 and the copper foil 2b on the one surface B3a side of the four-layer shield plate 25a are partially etched by photolithography to form a third wiring layer 27a, and the other surface of the four-layer shield plate 25a The fourth plating layer 17 and the copper foil 2b on the B13a side are partially etched to form a fourth wiring layer 29a.

  The four-layer printed wiring board 60 having four wiring layers including the first wiring layer 8a, the second wiring layer 18a, the third wiring layer 27a, and the fourth wiring layer 29a is obtained by the above-described B1 to B3 processes. .

This four-layer printed wiring board 60 is formed by through holes (sometimes referred to as conduction holes or vias) 4 in which the first wiring layer 8a and the third wiring layer 27a are filled with a conductive filler 51. Since it is electrically connected, it is possible to connect the wiring layers through a core material that includes a sheet-like reinforcing material such as a glass cloth that is arranged in multiple layers along the surface. The rigidity of the wiring board can be improved.
Further, in the four-layer printed wiring board 60, the second wiring layer 18a and the fourth wiring layer 29a have through holes filled with a conductive filler 51 inside (sometimes referred to as conduction holes or vias). Since the wiring layers 14 are electrically connected to each other, the wiring layers can be connected to each other via a core material including a sheet-like reinforcing material such as a glass cloth arranged in a plurality of layers along the surface. The rigidity of the printed wiring board can be improved.

  Further, according to the four-layer printed wiring board 60, since the first plating layer 5 and the second plating layer 15 in the first embodiment are not formed, the four-layer printed wiring board 60 is more than the four-layer printed wiring board 40 in the first embodiment. The manufacturing process can be simplified.

<Third embodiment>
Next, a third embodiment of the printed wiring board of the present invention will be described with reference to FIG.
FIG. 9 is a schematic cross-sectional view for explaining a third embodiment of the printed wiring board of the present invention.
The same components as those in the first and second embodiments are denoted by the same reference numerals as those in the first and second embodiments.

  In the second embodiment, the third plating layer 7 and the fourth plating layer 17 are formed. However, in the third embodiment, as shown in FIG. 9, the third plating layer 7 and the fourth plating layer 17 are not formed. When the first double-sided copper-clad plate 3 and the second double-sided copper-clad plate 13 are bonded together via an uncured prepreg 23, at least a part of the bump 21 is embedded in the filler 51. One of the features is that the wiring layers are electrically connected by electrically connecting the bump 21 and the filler 51.

The four-layer printed wiring board 80 of the third embodiment shown in FIG. 9 has through holes (conduction holes or vias) in which the first wiring layer 8b and the third wiring layer 27b are filled with a conductive filler 51 inside. The wiring layers can be connected to each other via a core material including a sheet-like reinforcing material such as a glass cloth arranged in a plurality of layers along the surface. Therefore, the rigidity of the produced printed wiring board can be improved.
Further, in the four-layer printed wiring board 80, the second wiring layer 18b and the fourth wiring layer 29b have through-holes filled with a conductive filler 51 inside (sometimes referred to as conduction holes or vias). Since the wiring layers 14 are electrically connected to each other, the wiring layers can be connected to each other via a core material including a sheet-like reinforcing material such as a glass cloth arranged in a plurality of layers along the surface. The rigidity of the printed wiring board can be improved.

  Moreover, according to this four-layer printed wiring board 80, since it is the structure which does not form the 3rd plating layer 7 and the 4th plating layer 17 in 2nd Example, rather than the 4 layer printed wiring board 60 of 2nd Example. The manufacturing process can be further simplified.

  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.

For example, in the first to third embodiments, the core material 1 has a configuration in which two sheet-shaped reinforcing materials 1a are arranged in the thickness direction, but the present invention is not limited to this, and is described above. As described above, according to the present invention, the thickness of the core material 1 can be set to an arbitrary thickness. Therefore, by increasing the thickness of the core material 1, the sheet-like reinforcing material 1 a included in the core material 1 is obtained. It is also possible to set the number of sheets to 3 or more.
By increasing the number of sheet-like reinforcing materials 1a included in the core material 1, the rigidity of the printed wiring board can be further improved.

In the first to third embodiments, the four-layer printed wiring boards 40, 60, and 80 have been described as examples. However, the present invention is not limited to this, and is further limited to multiple layers (for example, six layers and eight layers). Layer) printed wiring board.
Even in the case of manufacturing a multilayer printed wiring board more than the first to third embodiments, a plurality of substrates are bonded at a time by forming a bump on one of the substrates to be bonded. Can do.

  In the first to third embodiments, the aspect ratio of the through hole 4 (ratio of the thickness of the core material 1 to the hole diameter of the through hole 4) and the aspect ratio of the through hole 14 (hole diameter of the through hole 14). The ratio of the thickness of the core material 1 to 2) is set to 2, but the present invention is not limited to this. By setting the thickness of the core material 1 and the diameters of the through holes 4 and 14 to arbitrary values, The aspect ratios of the through holes 4 and 14 can be set to arbitrary values, respectively.

In the first to third embodiments, the double-sided copper-clad plate in which the copper foils 2a and 2b are bonded to both sides of the core material 1 is used. However, the present invention is not limited to this. Instead of the plate, a multilayer shield plate having an inner wiring layer may be used.
By using a multilayer shield board instead of the double-sided copper-clad board, a multilayer printed wiring board can be manufactured.

It is typical sectional drawing for demonstrating A1 process in 1st Example of the printed wiring board of this invention. It is typical sectional drawing for demonstrating A2 process in 1st Example of the printed wiring board of this invention. It is typical sectional drawing for demonstrating A3 process in 1st Example of the printed wiring board of this invention. It is typical sectional drawing for demonstrating A4 process in 1st Example of the printed wiring board of this invention. It is typical sectional drawing for demonstrating A5 process in 1st Example of the printed wiring board of this invention. It is typical sectional drawing for demonstrating B1 process in 2nd Example of the printed wiring board of this invention. It is typical sectional drawing for demonstrating the B2 process in 2nd Example of the printed wiring board of this invention. It is typical sectional drawing for demonstrating B3 process in 2nd Example of the printed wiring board of this invention. It is typical sectional drawing for demonstrating the 3rd Example of the printed wiring board of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Core material, 1a, 23a Sheet-like reinforcement material, 1b, 23b Resin, 2a, 2b Core material, 3,13 Double-sided copper-clad board, 4,14 Through-hole, 5, 7, 15, 17 Plating layer, 6,51 Filler, 8, 8a, 18, 18a, 27, 27a, 29, 29a Wiring layer, 21 bump, 23 prepreg, 25, 25a Shield plate, 40, 60, 80 Printed wiring board, A3, A13, B3, B13 , H21 height, R21 diameter

Claims (4)

A first core material that is insulative and has a first wiring layer on one side and a second wiring layer on the other side;
A second core material that is insulative and has a third wiring layer on one side and a fourth wiring layer on the other side;
The second wiring layer and the third wiring layer are bonded together via an insulating layer so as to face each other,
The first wiring layer and the second wiring layer are electrically connected by a first via penetrating the first core material,
The second wiring layer and the third wiring layer are electrically connected by a conductive bump penetrating the insulating layer,
The printed wiring board, wherein the third wiring layer and the fourth wiring layer are electrically connected by a second via penetrating the second core material. The second via includes a through-hole penetrating the second core material, and a conductive filler filled in the through-hole,
The printed wiring board according to claim 1, wherein the bump and the filler are in contact with each other. The first core material includes a first resin having insulating properties, and a plurality of first sheet-like reinforcing members arranged inside the first resin so as to overlap along the surface of the first core material. And
The second core material includes a second resin having insulation properties, and a second sheet-shaped reinforcing material that is disposed inside the second resin so as to overlap along the surface of the second core material. The printed wiring board according to claim 1, further comprising:   The printed wiring board according to claim 3, wherein the first sheet-shaped reinforcing material and the second sheet-shaped reinforcing material are any one of glass cloth, aramid cloth, glass nonwoven fabric, and aramid nonwoven fabric.

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