JPH11330702A - Manufacturing method of multilayer printed wiring board - Google Patents

Abstract

(57) [Problem] To provide a method of manufacturing a multilayer printed wiring board capable of efficiently forming a blind via hole having high connection reliability without leaving a residue of an insulating layer. SOLUTION: A step of forming a photosensitive insulating resin film on both circuit surfaces by using a substrate having a circuit formed on both surfaces as a core material, and forming a through hole for a blind via hole on both photosensitive insulating resin films. Laminating the applied single-sided copper-clad laminate, exposing and developing the photosensitive insulating resin film in the blind via-hole through-hole and removing the same, and using the blind via-hole through-hole after the removal. Forming a blind via hole connecting the inner layer circuit and the outer layer circuit.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention 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 small-diameter, non-through conductive hole for connecting an inner layer circuit and an outer layer circuit, that is, a blind via hole (BVH). About the method.

[0002]

2. Description of the Related Art Conventionally, as a method of forming a blind via hole in a multilayer printed wiring board, a method of manufacturing a multilayer printed wiring board comprising a plurality of conductor layers and a resin layer provided between each of the conductor layers has been known. In the outermost conductor layer, a hole having a diameter smaller than the laser beam diameter is previously formed in the outermost conductor layer, and a laser is irradiated through the hole while using the outermost conductor layer as a mask, and a resin from the outermost layer to the lowermost layer is formed. The method of removing is already known.

However, when the resin layer between layers is removed by irradiating, for example, a carbon dioxide gas laser using the outermost conductor layer as a mask by such a drilling method, a residual film of the resin layer is formed on the bottom copper foil. However, two steps of excimer laser treatment and desmear treatment are required in order to remove the residual film of the resin, and even if these treatments are performed, the residual film of the resin layer cannot be completely removed. there were.

Further, the cost of the carbon dioxide laser and the excimer laser is high, and the cost of the excimer laser is high even from the viewpoint of productivity.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned conventional problems, and does not involve a laser drilling process. It is an object of the present invention to provide a method for manufacturing a multilayer printed wiring board in which via holes can be efficiently formed.

[0006]

According to the present invention, there is provided a process of forming a photosensitive insulating resin film on both circuit surfaces by using a substrate having a circuit formed on both surfaces as a core material, A step of laminating a single-sided copper-clad laminate provided with through holes for blind via holes, a step of exposing and developing the photosensitive insulating resin film in the through holes for blind via holes, and a step of removing the same. The above object has been achieved by a method for manufacturing a multilayer printed wiring board, comprising: a step of forming a blind via hole for connecting an inner layer circuit and an outer layer circuit using a blind via hole through hole.

In the present invention, the photosensitive insulating resin film may be formed by any method, but it is preferable to apply a photosensitive insulating ink or to bond a photosensitive insulating sheet. The film is preferably of a positive type.

In the present invention, a preferred specific method for forming a blind via hole is, for example, the following method. First, for the outer layer circuit, φ80 μm was formed on a single-sided copper-clad laminate of FR-4 material (plate thickness 0.8 mm, insulating layer 72 μm, copper foil 8 μm) by using an NC drill machine to form a blind via hole. Drilling is performed to make through holes. On the other hand, for an inner layer circuit, a circuit is formed on a double-sided copper-clad laminate of FR-4 material (thickness: 0.1 mm, insulating layer: 64 μm, copper foil: 18 μm) by a photographic method or the like. Then, an insulating resin film is formed by a screen printing method or the like, and thereafter, it is bonded to the single-sided copper-clad laminate having the through-hole and laminated. As the insulating resin used at this time, for example, a positive photosensitive insulating resin (main material: LMB7082 / curing agent: LMB7092) manufactured by Ciba Special Chemicals Co., Ltd. can be mentioned. Because the insulating resin is exposed at the UV-irradiated portion, the exposed portion of the through-hole for the blind via hole is removed by exposure and development when the outer layer and the inner layer are laminated. Therefore, the blind via hole forming hole can be easily formed without any resin residue. Next, copper plating is performed for electrical connection between the inner layer circuit and the outer layer circuit. From the viewpoint of plating adhesion, desmearing is performed before copper plating regardless of whether through-hole processing is performed. The outer layer circuit after the copper plating is formed by a photographic method or the like.

[0009]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a sectional explanatory view of each step showing an embodiment of the method of the present invention. First, a through hole 2 is previously formed in a portion of a single-sided copper-clad laminate 1 in which a blind via hole is to be formed (see FIG. 1). A). Next, on the double-sided copper-clad laminate 3, a laminate 3 in which an inner layer circuit 4 is formed in advance is used as a core material, and a photosensitive insulating resin film 5 is formed on the surfaces of both circuits 4 (B). Next, on both photosensitive insulating resin films 5, the through holes 2 were formed.
After laminating the single-sided copper-clad laminates 1 in a sandwich shape, the unnecessary photosensitive insulating resin film 5a in the through hole 2
Exposure is performed by irradiating V light P (C). Next, the exposed portion is developed with a liquid mixture of an organic solvent such as alcohol and water to remove the unnecessary photosensitive insulating resin film 5a (D). next,
The through hole 6 is formed, and after desmearing, the entire surface including the through hole 2 and the inner wall surface of the through hole 6 is subjected to copper plating to form a copper plating layer 7 (E). Next, when an outer layer circuit 8 is formed on the copper plating layer 7 by a photo method or the like, a multilayer printed wiring board having a blind via hole 2a connecting the inner layer circuit 4 and the outer layer circuit 8 and a plated through hole 6a is obtained ( F).

Although this embodiment relates to a four-layer substrate, the blind via holes are filled with an insulating resin, the surface is smoothed, and then a photosensitive resin film is laminated.
A through-hole is formed in the area where the blind via hole is to be formed in advance, and the laminated photosensitive insulating resin film is exposed to UV irradiation, developed with an organic solvent, and finally a through-hole is formed. The processing and circuit formation are performed by etching to complete a six-layer substrate. Further, an eight-layer substrate can be obtained by repeating the same steps.

[0012]

According to the present invention, when forming a hole for a blind via hole having a small diameter, it is possible to form the hole reliably and efficiently without leaving a residue of the insulating layer. A multilayer printed wiring board having a blind via hole having a high density can be efficiently manufactured.

In particular, since a hole for a blind via hole can be formed by UV exposure and development processing, there is no need to worry about a residual film of an insulating layer on an inner circuit, which is inevitably generated by laser drilling. In this case, continuous processing is possible and mass productivity is high. Further, since the production equipment can be realized by the conventional equipment, it is not necessary to use an expensive apparatus such as a laser apparatus, and the production efficiency is excellent in terms of cost.

[Brief description of the drawings]

FIG. 1 is a sectional explanatory view of each step showing an embodiment of a method of the present invention.

[Explanation of symbols]

 1: Single-sided copper-clad laminate 2: Through hole for blind via hole 2a: Blind via-hole 3: Double-sided copper-clad laminate 4: Inner layer circuit 5: Photosensitive insulating resin film 5a: Unnecessary photosensitive insulating resin film 6: Through hole 6a: Plating through hole 7: Copper plating layer 8: Outer layer circuit P: UV light

Claims (3)

[Claims] 1. A step of forming a photosensitive insulating resin film on both circuit surfaces by using a substrate having a circuit formed on both sides as a core material, and forming a through hole for a blind via hole on both photosensitive insulating resin films. Laminating the single-sided copper-clad laminate subjected to the above, the step of exposing and developing the photosensitive insulating resin film in the blind via-hole through hole, and removing the blind via-hole through hole using the removed via hole Forming a blind via hole connecting the inner layer circuit and the outer layer circuit. 2. The method for manufacturing a multilayer printed wiring board according to claim 1, wherein the photosensitive insulating resin film is formed of a photosensitive insulating ink or a photosensitive insulating sheet. 3. The method for manufacturing a multilayer printed wiring board according to claim 1, wherein the photosensitive insulating resin film is of a positive type.