JPH10224041A - Multilayer wiring board and its manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate the need for separately forming a via hole on an inner- layer circuit board and to reduce the number of manufacturing processes and cost by electrically connecting an inner-layer conductor layer and an outer-layer conductor layer and then breaking the electrical connection with the outer-layer conductor layer, and forming 11 via hole for electrically connecting the inner- layer conductor layers. SOLUTION: For manufacturing a multilayer wiring board, a plurality of inner-layer conductor layers and outer-layer conductor layers are electrically connected via a hole, then the electrical connection with the outer-layer conductor layers is broken, and a via hole 10 for electrically connecting the inner-layer conductor layers is formed. More specifically, the conductor layer 1 and the insulator layer 2 are laminated, laser beams are applied to a desired position of a hole, and a hole is formed on the insulation layer 2. Then, a hole is electrically connected to the formed hole by a connection treatment and the electrical connection of a desired position with the outer-layer conductor layer being electrically connected via the hole is eliminated, thus forming the via hole 10 between the inner-layer conductor layers and hence reducing the number of manufacturing processes and hence cost.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multilayer wiring board and a method for manufacturing the same.

[0002]

2. Description of the Related Art In recent years, with the miniaturization of electronic devices, the conductor width, conductor spacing, through holes, via holes, etc. of a multilayer wiring board have been developed in order to reduce the size, density, and weight of a copper-clad multilayer wiring board. Miniaturization and small diameter are required. In order to reduce the diameters of through holes and via holes, a method of drilling by laser has been proposed as compared with the conventional drilling. For example, JP-A-58-
64097.

This publication discloses that a hole is previously formed in a conductive layer above a lowermost layer among conductive layers to be electrically connected on a multilayer printed circuit board, and a laser is used as a mask for forming the hole from above. Irradiation is performed to remove holes in the resin layer between the conductor layers from the uppermost layer to the lowermost layer, and then a manufacturing method is proposed by a general technique of a multilayer printed circuit board, such as smearing, copper plating, and etching. Have been.

[0004]

The conventional multilayer wiring board as described above (sometimes called a multilayer printed circuit board, a multilayer printed board, a multilayer printed wiring board, PWB, PCB, etc.).
The method of drilling requires a manufacturing step of drilling holes in the conductor layer in advance. The hole making process of this conductor layer
Depending on a method such as drilling and etching, a method using a drill requires a hole to be formed in a desired conductor layer. In the method by etching, application, exposure, removal of a photoresist, removal of a conductor layer, and the like are required for each of the desired conductor layers to be perforated. It is necessary to perform such a process of making a hole in the conductor layer for each layer of the multilayer wiring board. Alternatively, even if the desired inner conductor layer is formed by the etching method simultaneously with the wiring pattern, the outer conductor layer needs to be separately formed. Further, in order to make an electrical connection (blind via hole) between the inner conductor layers, a circuit board manufactured by a step of making a hole in the inner layer circuit board, a step of making an electrical connection through the hole, a circuit pattern forming step, and the like. It is necessary to form a via hole by stacking. These have problems such as an increase in manufacturing steps and an increase in manufacturing cost.

[0005]

SUMMARY OF THE INVENTION According to the present invention, a plurality of inner conductor layers and an outer conductor layer are electrically connected to each other through a hole, and thereafter, the electric connection with the outer conductor layer is cut off. It is an object of the present invention to provide a multilayer wiring board which forms a via hole for electrical connection, does not separately form a via hole in an inner circuit board, reduces the number of manufacturing steps, and reduces the cost, and a method for manufacturing the same.

Hereinafter, a method for manufacturing a multilayer wiring board according to the present invention will be described in detail. 1 and 2 (a), (b),
1C and 1D are schematic cross-sectional views of one embodiment showing a multilayer wiring board according to the present invention and a method for manufacturing the multilayer wiring board.

A multilayer wiring board and a method of manufacturing the same according to the present invention generally provide a method for electrically connecting a plurality of inner conductor layers and outer conductor layers through holes as shown in FIG. And via holes are formed to electrically connect the inner conductor layers. A step of laminating the conductor layer 1 and the insulator layer 2 as shown in FIGS.
A step of irradiating a desired position of a hole (a through hole, a via hole, etc.) with a laser 3 to form a hole 4 in the conductor layer and the insulating layer, and connecting the formed hole 4 to the conductor layer through the hole by a connection process. A manufacturing method including a step of electrically connecting and a step of forming a via hole 10 between the inner conductor layers by removing an electric connection at a desired position with the outer conductor layer electrically connected through the hole.

[0008] The method of laminating the multilayer wiring board may be performed by a generally performed method of laminating the multilayer wiring board. For example, the circuit board 9 on which the desired circuit pattern is formed by the subtractive method, the additive method, and the like, and the resin-attached metal foil 7 are positioned and stacked (FIG. 2A), and closely adhered and laminated by heating and pressing in a vacuum (FIG. b)).

The metal foil 1 as the conductor layer is not particularly limited, but copper, stainless steel, nichrome, tungsten, aluminum and the like are preferable. More preferred are copper and stainless steel. Particularly preferred is copper, which is produced by a method of a rolled copper foil or an electrolytic copper foil, and the electrolytic copper foil is particularly excellent in adhesion and adhesion to an insulating layer resin.
Such a metal has good electric conductivity, is easy to form a foil, and is easily available. The thickness of the metal foil is not particularly limited, but is preferably 0.5 to 50 μm.
More preferably, it is 1 to 40 μm. Particularly preferably, it is 3 to 20 μm. A metal having such a thickness is flexible, and laser processing and etching are easy.

The insulating layer 2 is not particularly limited but is preferably epoxy, polyimide, polyester, phenol, polyphenylene ether, polyphenylene oxide, bismaleimide / triazine, cyanate, fluorine, silicon, polybutadiene, polysulfone, polyetherimide. , Polyethersulfone, urea, polycarbonate, polyarylate and / or polyethylene. More preferably, a resin containing epoxy, polyimide, polyester, phenol, polyphenylene ether, polyphenylene oxide and / or bismaleimide-triazine as a main component is used.

The insulating layer 2 may be made of glass, aramid, paper, porous polytetrafluoroethylene and / or quartz woven and / or non-woven fabric impregnated with the resin group. Preferably, a glass and / or aramid woven and / or nonwoven fabric impregnated with the resin group may be used.

The insulator layer 2 may be filled with an organic or inorganic filler. For example, resin beads, alumina powder, titanium oxide powder, calcium carbonate powder, and the like.

It is preferable to perform a process 6 for increasing the laser absorptivity at least at the laser irradiation point on the laser irradiation side of the conductor layer desired for laser processing. More preferably, the six sizes of the process for increasing the laser absorptance are not more than the desired size for drilling. This is because by performing such a treatment, the conductor layer can be melted and drilled with lower energy (FIG. 2C). Examples of the treatment having a high laser absorptivity include formation of a material layer having a high laser sensitivity and coloring to a color that absorbs the laser wavelength range well. NiO _X is as sensitive materials, CuO _X or copper oxide, iron oxide, cobalt oxide, molybdenum oxide, iridium oxide,
Metal oxides containing tin oxide, lead oxide, antimony oxide and the like as main components are preferable, and NiO _x ,
CuO _x , and particularly preferably, an oxide film of CuO _x is formed. The coloring is Congo Red,
Coating with a dye such as methyl violet or a pigment such as carbon. Preferably, it is coated with a material colored brown to black with a pigment such as carbon.

In forming the hole 4, a desired position of a hole (a through hole, a via hole, etc.) is irradiated with a laser 3 to melt and sublimate the metal foil as the conductor layer and the insulator as the insulator layer to form the hole. I do. Laser types include carbon dioxide laser, Xe laser, excimer laser,
YAG laser, Ar laser and the like are preferable. More preferred are a carbon dioxide gas laser and a YAG laser. It is particularly preferable to process the conductor layer and the insulating layer with a high energy carbon dioxide gas laser which can change the processing conditions (pulse width, pulse number, peak output, etc.) during the processing and has high energy.

The electrical connection between the conductors in the hole 4 by the connection process may be made by a general method. For example, an etching back process is performed to remove smearing in the holes, and the conductive layers are electrically connected by electroless plating, electrolytic plating, conductive paste, or the like (FIG. 2D).

Thereafter, the conductor layer is omitted so that the outer conductor layer 1 has a desired circuit and electrical connection with a hole at a desired position is removed (formation of a via hole 10) to form a multilayer wiring board. (FIG. 1).

Such a multilayer wiring board and a multilayer wiring board manufactured by the method for manufacturing the same can reduce the number of manufacturing steps and reduce the cost, and can form a small-diameter hole and can be downsized.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of a multilayer wiring board and a method of manufacturing the same according to the present invention will be described below. The multilayer wiring board and the method of manufacturing the same according to the present invention are not limited to the following embodiments.

(Example 1) First, an insulating layer obtained by impregnating a nonwoven fabric of glass fiber with an epoxy resin has a thickness of 18 μm on both surfaces.
An inner layer board (circuit board 9) having a circuit pattern formed by a photo-etching method on a copper-clad double-sided board laminated with a copper foil is blackened to form copper oxide, and the copper oxide is chemically reduced to metallic copper. Was performed on one side.

Next, using a resin-coated copper foil 7 (approximately 12 μm of copper foil adhered to a glass nonwoven fabric impregnated with a semi-cured epoxy resin of approximately 50 μm), the resin-coated copper foil, the inner layer plate, and the resin-coated copper foil Are aligned and superimposed (FIG. 2A),
Lamination (pressure 25 kg, temperature 180 degrees, 120 minutes) was performed in a vacuum chamber to produce a laminated plate (FIG. 2).
(B)).

Next, as a process 6 for increasing the laser absorptivity, a circular blackening process smaller than the desired hole diameter by about 20 μm was performed on the surface of the laminate. (FIG. 2 (b)).

Next, the laminated plate subjected to the process of increasing the laser absorptivity is positioned and set on a processing table of a carbon dioxide gas laser apparatus, and a desired position of a hole is irradiated with a programmed laser beam to irradiate the copper foil 1 on the surface. The resin and the glass fiber of the insulating layer 2 which were subjected to the hole processing and subsequently cured were melted and sublimated to form holes reaching the copper foil of the inner layer plate 9. In another desired hole, holes were made in the copper foil, the insulator layer, the copper foil of the inner layer plate, and the inner layer insulator on the surface. FIG.
(C)).

Next, the inside of the hole is smeared by a potassium permanganate method, and copper is deposited on the inner wall of the hole, the copper foil of the inner layer plate and the copper foil by an electroless plating method. Copper was deposited by the method to form a plating layer 5 for electrically connecting the inner layer copper foil to the surface copper foil and between the inner layer copper foil and the surface copper foil (FIG. 2 (d)).

Next, the hole is filled with resin to fill the hole, a photoresist dry film is adhered to the surface in close contact, the copper foil on the surface is etched into a desired circuit pattern by a photo-etching method, and a desired position is etched. In order to eliminate the electrical connection between the hole and the copper foil on the surface, the copper is removed by etching to form a via hole 10, and then the dry film and the filling resin are removed, solder resist is applied, soldering, etc., and the multilayer wiring board is formed. (FIG. 1).

The multilayer wiring board thus produced not only ensures the electrical connection of the holes and the via holes but also has a sufficient quality in an environmental test such as a temperature cycle.

[0026]

According to the multilayer wiring board and the method of manufacturing the same according to the present invention, a via hole is formed by removing electrical connection with an outer conductor layer, and the conductor layer and the insulating layer can be formed without making a hole in the conductor layer before laser irradiation. Manufacturing steps such as the ability to make holes in the layer (even in the case of resin-impregnated fibrous insulating material) are omitted, resulting in simplification and cost reduction.

[0027]

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing one embodiment of a multilayer wiring board and a method of manufacturing the same according to the present invention.

FIGS. 2 (a), (b), (c) and (d) are cross-sectional views showing one embodiment of a multilayer wiring board and a method of manufacturing the same according to the present invention.

[0028]

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 conductor layer 2 insulator layer 3 laser 4 hole 5 plating layer 6 treatment to increase laser absorption 7 copper foil with resin 8 hole 9 circuit board 10 via hole

Claims (2)

[Claims] After a plurality of inner conductor layers and an outer conductor layer are electrically connected via holes, electrical connection with the outer conductor layers is cut off, and a via hole for electrically connecting the inner conductor layers is formed. A multilayer wiring board and a method of manufacturing the same. 2. A multilayer wiring board in which holes are formed in an insulator layer and a conductor layer and a method for manufacturing the same, wherein a step of laminating a plurality of insulator layers and the conductor layer is performed, and the conductor layer and the insulator layer are irradiated by laser irradiation. Forming a hole in the conductor layer, electrically connecting the conductor layer through the hole, and removing the electric connection with the outer conductor layer electrically connected through the hole at a desired position to remove the inner layer conductor. A method for manufacturing a multilayer wiring board, comprising a step of forming a via hole between layers.