JPH10313177A - Manufacture of multilayered printed wiring board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a multilayered printed wiring board, possessed of a part mounting pad which is located on a blind through-hole and high in electric connection reliability after a part is mounted on it. SOLUTION: Outer boards 8 each provided with through-holes (via holes), metal foils 11 each with a roughened surface, release films 12, and plates 13 as outermost layers are provided to each surface of an inner circuit board through the intermediary of a prepreg for the formation of a press target body, and the metal foil 11 and the release film 12 are made to encroach into the through-holes (via holes) provided to the outer boards 8 in an initial laminating press stage. By this setup, in this press laminating process, prepreg molten resin injected into the through-holes (via holes) is set back from the outer surface, and the roughened surface of the metal foil 11 is transferred onto the surface of the prepreg molten resin.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for manufacturing a multilayer printed wiring board, and more particularly to a method for manufacturing a multilayer printed wiring board having a component mounting pad on a via hole (hereinafter, referred to as BVH).

[0002]

2. Description of the Related Art The use of multilayer printed wiring boards having pads for component mounting on a BVH is increasing because chip electronic components can be mounted at a high density.

Conventionally, a method of manufacturing a multilayer printed wiring board having a pad for component mounting on a BVH is to first form a through hole at a predetermined position of a copper-clad laminate by a drill, and then to use a known chemical copper plating and electric After copper plating is applied to the entire surface of the copper-clad laminate by copper plating, etching is performed to form a predetermined pattern on one side of the substrate, and a printed wiring board (substrate for an outer layer) having through holes is obtained. Next, the outer layer substrate is arranged via prepregs on both sides of the inner layer substrate on which a desired pattern has been formed in advance, and a release film and a laminated plate are sequentially arranged outside the outer layer substrate to form a pressure-receiving body. Is configured. The pressure-receiving body is heated and pressurized and laminated and integrated to obtain a multilayer printed wiring board. When the pressure-receiving body is heated and pressed, the inside of the through hole of the outer layer substrate is completely filled with the molten prepreg resin, and the through hole of the outer layer substrate becomes BVH.

[0004] Next, excess resin blown out of the BVH of the outer layer substrate by melting of the prepreg is planar-polished by belt sander polishing or the like and removed. Thereafter, a through-hole is formed by a drill in the multilayer laminate obtained in a resin (hereinafter referred to as BVH resin) filled in the through-hole (BVH) of the outer layer substrate, and then the multilayer laminate including the through-hole is formed. Copper plating is performed on the entire surface. Then, a multilayer printed wiring board having component mounting pads on the BVH was obtained by etching.

[0005]

However, in this prior art, the pad formed on the BVH has poor adhesion, and the pad expands due to the thermal stress of soldering when mounting an electronic component on the multilayer printed wiring board. Had occurred frequently. This swelling is more likely to occur as the diameter of the BVH increases.

As a method of roughening the surface of the BVH resin and improving the adhesion between the resin and the copper plating, a method of liquid honing or permanganate treatment (Japanese Patent Laid-Open No. 5-829)
No. 77 gazette) and the roughened surface of a metal foil having one roughened surface
A technique of transferring a roughened surface to a resin surface by pressing the resin surface (Japanese Patent Laid-Open No. Hei 7-226575) is disclosed. However, the former method is difficult to obtain a good roughened surface, and the latter method is difficult. Thus, it was difficult to prevent pad swelling on the BVH during resin soldering because the roughened surface was erased by mechanical polishing in the plating pretreatment.

As a method for preventing swelling of the pad on the BVH during soldering, Japanese Patent Application Laid-Open No. 5-327216 discloses a method.
Using the technique disclosed in Japanese Patent Application Laid-Open Publication No. H10-260, the surface of the BVH resin is made concave and the roughened surface of the metal foil is made concave B
Transfer to VH resin surface, B by mechanical polishing before plating
At the same time as preventing the erasure of the roughened surface of the VH resin surface,
Diffusion of heat stress at H corner, B
Methods have been considered to prevent solder bulging of pads on the VH. However, in this method, the concave B
It is difficult to effectively transfer the roughened surface of the copper foil to the surface of the VH resin, and the swelling of pads on the BVH during soldering has not been completely prevented.

An object of the present invention is to provide a method of manufacturing a multilayer printed wiring board which solves the problems of the conventional method.

[0009]

The method for manufacturing a multilayer printed wiring board according to the present invention is characterized by comprising the following steps (A) to (D). (A) A step of forming a through-hole in a double-sided copper-clad laminate, plating the through-hole, and forming a through-hole. (B) forming a conductive circuit on one side of the plated double-sided copper-clad laminate; (C) The copper-clad multilayer substrate is disposed on both sides of an inner layer substrate having conductive circuits on both sides, with the conductive circuit surfaces of the copper-clad multilayer substrate facing each other via prepregs to form a pressure-receiving body. A metal foil having a roughened surface on both sides and a release film are sequentially disposed on both sides of the pressure body, and heated and pressed to a through hole of the copper-clad laminated substrate from outside the copper-clad laminated substrate of the pressure-receiving body. A step of forming the multi-layer laminate by making the metal foil and the release film penetrate, and laminating and integrating the pressure-receiving bodies. (D) removing the metal foil and the release film from the multilayer laminate, forming a through hole in the multilayer laminate, plating the entire surface of the multilayer laminate including the through hole, and etching. Step of forming a desired outer layer circuit.

According to the present invention, in the production of a multilayer printed wiring board, a metal foil having a roughened surface on both sides and a release film are arranged on the outer side of a pressure-receiving body, and then heated and pressed, so that the pressure at the time of pressing is reduced. The slip between the release film and the metal foil is reduced, the surface of the BVH resin can be formed in a concave shape, and the roughened surface shape of the metal foil can be effectively transferred to the concave surface, thereby improving the adhesion of the plating pad on the BVH. It has been found that it can be improved.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to FIGS. 1 (a) to 1 (e) are diagrams illustrating a process of forming an inner layer surface circuit of an outer layer substrate of a multilayer printed wiring board.
First, a copper-clad laminated substrate 1 is prepared by using an epoxy insulating resin material or the like as a base and bonding a copper foil 3 having a thickness of 12 to 70 μm as a conductor layer to both surfaces of the insulating resin material. A through hole 2 is provided at a predetermined position of the substrate 1 by a drill (FIG. 1).
(A)). The thickness of the copper-clad laminated substrate 1 is 0.1.
A drill having a diameter of 0.15 to 0.8 mm was used, and a drill having a diameter of 0.15 to 0.8 mm was used.

Next, as shown in FIG. 1B, a copper plating film 4 is formed on the entire surface of the copper-clad laminate 1 in which the through holes 2 have been formed by known chemical copper plating and electrolytic copper plating. 5 is formed.

Next, a photosensitive resin sheet of a negative curing type is laminated on both sides of the copper clad laminate 1 as an etching resist, and an etching resist layer 6 is formed on the copper clad laminate 1 by a known exposure and development technique. (FIG. 1 (c)). Next, the copper-clad laminate 1 is etched using an etching solution such as an aqueous solution of cupric chloride or an aqueous solution of ferric chloride to remove the exposed conductor layer (copper). An inner layer circuit 7 is formed on one side (FIG. 1D). After this, FIG.
As shown in (e), a stripping solution such as an aqueous solution of sodium hydroxide is sprayed on the copper-clad laminate 1 to form an etching resist layer 6.
Is peeled off to obtain an outer layer substrate 8 having a through hole 5 (which becomes BVH after lamination) in which an inner layer circuit 7 is formed on one side.

Next, using a copper-clad laminated board having a copper foil thickness of 35 μm and a plate thickness of 0.8 mm by a normal printing etching technique,
An inner circuit board having an inner power / ground layer is formed.

Next, as a laminating step, first, a pressure-receiving body shown in FIG. 2 is formed. That is, prepregs 10 serving as an insulating adhesive layer are arranged on both surfaces of the inner circuit board 9 obtained in the above step, and the through holes 5 are provided outside through the prepregs 10.
The outer layer substrate 8 having the inner layer circuit 7 on the inner layer circuit board 9 side, the metal foil 11 having a roughened surface on both sides, and the release film 12 on the outer surface are further arranged in this order. The plate 13 is arranged to form a pressure-receiving body.

In the initial stage of heating and pressing, the metal foil 11 having the roughened surfaces on both sides and the release film 12 are heated and pressed to form a multilayer laminate. The through-hole 5 of the substrate 8 is cut into the through-hole 5 so that the through-hole 5 is closed.

Using a metal foil having a roughened surface on both sides, the slip between the release film and the metal foil is suppressed in the initial stage of heating and pressing, and the metal foil 11 and the release film 12 are effectively passed through. You can cut into hole 5.

Here, as shown in FIG. 3, since the through-hole 3 is closed at the initial stage of heating and pressurizing in the laminating press, the following items are required as characteristics required for the release film 12. That is, the film itself tends to elongate even at a lamination temperature of 150 to 200 ° C., and must have heat resistance and releasability to the lamination temperature described above. The release film 12 may be composed of a single layer or multiple layers, but needs to have a thickness of 50 to 150 μm in order to increase the pressing force into the through hole 5.

The type of the metal foil 11 used in the present invention is not particularly limited, and may be a foil formed of a single metal or a composite foil composed of two or more metal layers. For example, the metal foil includes a single metal of Cu or Al or Cu
A composite metal foil obtained by laminating a composite metal foil obtained by laminating Al and Al with a chemical treatment or an electrolytic treatment, or a composite metal foil in which Cu or Al is plated with a convex surface of Ni can be used. The thickness of the metal foil 11 is preferably 12 to 35 μm in consideration of the embedding property in the BVH at the time of laminating press. The roughened surface of the metal foil 11 has a ten-point average roughness (Rz) of 5 to 15
μm, and the center line average roughness (Ra) is desirably in the range of 0.8 to 2.0 μm (Rz and Ra are surface roughness in Japanese Industrial Standard JlSB0601 “Definition and Display of Surface Roughness”). This is a parameter in the notation method.) In this example, a copper foil having a roughened surface on both sides, which is usually used for a copper-clad laminate, was used.

In the above-described laminating step, the inside of the through hole 5 of the outer layer substrate 8 is filled with the BVH resin 14 that has melted and blown out into the BVH, and the through hole 5 of the outer layer substrate 8 becomes the BVH 15. Next, after press molding,
The multilayer foil 17 is obtained by removing the metal foil 11. still,
As the resin of the outer layer substrate 8, the inner layer circuit board 9, and the prepreg 10, an epoxy resin was used in the present embodiment, but other resins such as a polyimide resin, a fluororesin, a phenolic resin, an unsaturated polyester resin, or the like may be used. A modified resin as a base resin, a resin obtained by mixing these resins, and the like can also be used. Here, the most remarkable point in the present invention is that the depth of the dent on the surface of the BVH resin is 10 to 30 from the outer layer body.
The purpose is to adjust the combination of the thickness of the copper foil and the thickness of the release film so as to be in the range of μm. When the dent is less than 10 μm, there is a high possibility that the roughened surface will be removed by the planar polishing operation after the lamination press molding. In addition, dent depth is 30μm
In the case of exceeding, the corner portion of the outer layer corner portion of the BVH may be disconnected.

Taking these factors into consideration, in the present embodiment, a cellulose film having a thickness of 70 μm is used as the release film 12, a copper foil having a thickness of 18 μm is used as the metal foil 11, and the laminate is pressed at 170 ° C. for 2 hours. The laminate-body treatment was performed by applying pressure.

Here, as a result of observing the cross section of the multilayer substrate after the above-mentioned press molding, the depth of the recess of the BVH resin portion was 15 μm from the outer layer surface, and the matte surface of the copper foil was one level above the DVH resin surface. It was confirmed that transcription was performed in the same manner.

Next, as shown in FIG. 4A, a through hole 16 is drilled at a desired position of the multilayer laminate 17 with a drill. Next, as shown in FIG. 4 (b), the multilayer laminate 17 is subjected to chemical copper plating and electrolytic copper plating to form through-holes 18, and then, as shown in FIG. By performing the etching process, the predetermined outer layer circuit 19 and the BV
By forming the component mounting pads 20 on H, a multilayer printed wiring board 21 according to the present invention is obtained.

In the multilayer printed wiring board formed as described above, no swelling was observed between the BVH resin and the component mounting pads in the evaluation of moisture absorption and heat resistance, and high connection reliability was obtained.

[0025]

As described above, according to the present invention,
In the formation of a multilayer laminate having BVH, transfer of the roughened surface of the metal foil to the surface of the BVH resin is effective and uniform.
Multi-layer printing with excellent adhesion between the BVH surface resin and copper plating because the roughened surface is not affected by polishing work in the subsequent process by providing a rough surface and denting the surface of the BVH resin. Production of wiring boards becomes possible. In particular, it is possible to cope with a BVH with a large diameter and a BVH designed product having a large number of holes.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a process of forming an inner layer surface circuit of an outer layer substrate of a multilayer printed wiring board according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view illustrating a configuration of a pressed body of the multilayer laminate according to the embodiment of the present invention.

FIG. 3 is a cross-sectional view showing a through hole portion of an outer layer substrate in an initial stage of a lamination press according to an embodiment of the present invention.

FIG. 4 is a cross-sectional view of a main part of the substrate, illustrating a manufacturing process sequence after the laminating process according to the embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Copper-clad laminated board 2, 16 Through hole 3 Copper foil 4 Copper plating film 5, 18 Through hole 6 Etching resist layer 7 Inner layer circuit 8 Outer layer substrate 9 Inner layer circuit board 10 Prepreg 11 Metal foil 12 Release film 13 Plate 14 BVH Resin 15 BVH 17 Multilayer laminate 19 Outer circuit 20 Pad for mounting components on BVH 21 Multilayer printed wiring board

Claims (3)

[Claims] 1. A method for producing a multilayer printed wiring board having blind via holes, comprising the following steps (A) to (D). (A) A step of forming a through-hole in a double-sided copper-clad laminate, plating the through-hole, and forming a through-hole. (B) forming a conductive circuit on one side of the plated double-sided copper-clad laminate; (C) The copper-clad multilayer substrate is disposed on both sides of an inner layer substrate having conductive circuits on both sides, with the conductive circuit surfaces of the copper-clad multilayer substrate facing each other via prepregs to form a pressure-receiving body. A metal foil having a roughened surface on both sides and a release film are sequentially arranged on both sides of the pressing body, and the metal is pressed into the through-hole of the copper-clad laminated substrate from the outside of the copper-clad laminated substrate of the pressed body by heating and pressing. A step of forming a multi-layer laminate by making the foil and the release film penetrate and laminating and integrating the pressure-receiving bodies. (D) peeling off the metal foil and the release film from the multilayer laminate, forming a through hole in the multilayer laminate, and plating the entire surface of the multilayer laminate including the through hole of the multilayer laminate. And then etching to form a desired outer layer circuit. 2. The metal foil having a roughened surface on both surfaces is C
2. The method for manufacturing a multilayer printed wiring board according to claim 1, wherein the method is u, Al, or a composite foil thereof. 3. The method for manufacturing a multilayer printed wiring board according to claim 1, wherein said metal foil having roughened surfaces on both sides is obtained by subjecting smooth Cu or Al to a convex plating of Ni.