JP2001024324A - Manufacture of build-up printed wiring board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress the dent quantity of resin which is brought into contact with a copper foil surface and copper foil by stacking copper foil with resin by vacuum pressing for forming the build-up layer of a build-up printed wiring board, and using thick copper foil for copper foil with resin. SOLUTION: A stack object is vacuum-extracted at the time of starting stacking by vacuum pressing and inner air is made to be a thin state. The object is heated in such a state and semi-cured resin is softened. Softened resin is pulled into the through hole of a core layer which is decompressed and the hole is filled with resin. For compensating resin which is made to flow into the hole, resin at the periphery of the through hole in the core layer is drawn, and copper foil on the surface of resin is also drawn to a core layer side so as to form copper foil with resin. Thick copper foil is used for copper foil with resin. Thus, the finishing precision of the characteristic impedance of a pattern can be improved.

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 build-up printed wiring board.

[0002]

2. Description of the Related Art There are various methods for forming a build-up layer (hereinafter referred to as a build layer) on a build-up printed wiring board. A method of forming a build layer by laminating copper foil with resin is also available. One of them. Since the present technology relates to a method of laminating a copper foil with a resin, the following description is limited to this method. There are also various pattern forming methods. Hereinafter, the semi-additive method will be described as an example, but the present invention is not limited to the semi-additive method. FIG. 2 and FIG. 3 are schematic diagrams showing an example from the build layer lamination to the build layer conductor pattern formation in the order of steps. In order to form a pattern by a semi-additive method which is advantageous for forming a fine pattern, the copper foil 2 of the resin-coated copper foil 1 is laminated with a build layer (FIG. 2B).
All are removed by post-etching (FIG. 2C). After drilling the via hole 3 for the build layer via laser (FIG. 2D), electroless copper plating and thin electrolytic copper plating 4 of several μm (primary copper plating, FIG. 2E) are applied. Through a series of resist processing steps of attaching a dry film 5 (FIG. 2F), pattern exposure (FIG. 3G) with a pattern positive film 6 in close contact, and development (FIG. 3H), secondary copper plating 7 called pattern plating
(FIG. 3I). After removing the resist 5 (FIG. 3J), the pattern formation is completed by removing a few μm of copper by soft etching (FIG. 3K).

A method of laminating a resin-coated copper foil on a core layer is superior to a method of applying a liquid resin on a core layer because the build layer resin thickness is uniform and the build layer resin surface is smooth. In addition, the finished dimensional accuracy of the build layer conductive pattern and the finished accuracy of the characteristic impedance of the conductive pattern are good. Further, as shown in FIG. 2, the core layer 8 generally has a through hole 9 (hereinafter, referred to as IVH) for connecting the conductor pattern of each layer between the layers.
It is also advantageous that the resin 10 of the copper foil with resin 1 fills the IVH 9 during lamination by vacuum pressing.

[0004]

However, FIG. 2B
As shown in the figure, the resin adjacent to the IVH9 flows into the IVH9, and accordingly, the depression 1
1 results. Due to the depression 11, when the resist dry film 5 of FIG. 2F is attached, the air bubbles 12 are trapped between the copper plating 4 and the dry film 5 in the portion of the depression 11. The pattern exposure (FIG. 3)
In the case of G), exposure blur occurs, resulting in thinning and disconnection of the conductor pattern, and in the development (FIG. 3H), the resist floats, and the plating solution of the secondary copper plating shown in FIG. Or short circuit between wires.
The present invention has been made to solve the above problems,
It is an object of the present invention to provide a method for manufacturing a build-up printed wiring board that suppresses the surface of a copper foil and the amount of dent of a resin in contact with the copper foil.

[0005]

According to a first aspect of the present invention, there is provided a method of manufacturing a build-up printed wiring board, comprising: forming a build-up layer of the build-up printed wiring board; It is characterized in that a thick copper foil is used as the attached copper foil.

According to the method of manufacturing a build-up printed wiring board of the first aspect, the core layer IV is formed when the build-up layers are laminated.
Since the occurrence of copper foil dents near H is suppressed, bubbles are not trapped when a dry film is attached in the resist process.

According to a second aspect of the present invention, there is provided a method of manufacturing a build-up printed wiring board, wherein a copper foil having a thickness of 18 μm or more is used as the resin-coated copper foil.

According to the method of manufacturing a build-up printed wiring board of the second aspect, the core layer IV is formed when the build-up layers are laminated.
Since the copper foil dent near H is suppressed to 2 μm or less, bubbles are not trapped when a dry film is attached in the resist process.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows an IVH in the middle of build layer lamination.
The vicinity is shown in a schematic sectional view. The course of the depression of the copper foil is considered as follows. At the start of lamination by vacuum press, the lamination target is evacuated and the air inside is in a dilute state. In this state, the semi-cured resin is heated and softened, and the softened resin is drawn into the reduced-pressure IVH hole by external pressure, and the hole is filled with the resin. The resin around the IVH is about to be drawn to make up for the resin that has flowed into the holes. At the same time, the copper foil on the surface of the resin is also drawn toward the core layer. Here, since the softened resin has a low flow and a high viscosity, the amount of resin movement in a portion away from the IVH is not large. Therefore, resin migration and dents in the copper foil occur near the IVH,
The amount of resin is balanced, and then the resin cures.

[0010] In order to grasp the depression of the copper foil numerically, lamination is performed using four variables of the resin thickness of the resin-coated copper foil, the thickness of the copper foil, the thickness of the core layer and the IVH diameter, which are considered to be related to the depression of the copper foil. An experiment was performed. In the experiment, the resin thickness was 60 and 80 μm, and the copper foil thickness was 12, 18 and 35 μm.
m, the core layer thickness was 0.5 and 1.3 mm, and the core layer IVH diameter was 0.25 and 0.3 mm.
As a result of measuring the dent amount of the copper foil in the above experiment, it was found that mainly the copper foil thickness and the IVH diameter contributed to the dent amount of the copper foil, and the resin thickness and the core layer plate thickness were negligible in the above-mentioned fluctuation range. .
"Table 1" shows the results of the experiment, in which the amount of dent at 100 measurement points was actually measured and the range of the numerical values was shown.

[Table 1]

As a conclusion drawn from the above experimental results and the conformability of the dry film for resist which was separately confirmed, when the IVH diameter is 0.25 mm, the copper foil thickness is 18 μm.
By doing so, it was found that the dent could be reduced to 2 μm or less, and the dry film could follow without bubbles. Further, in the case of an IVH diameter of 0.3 mm, if a copper foil thickness of 35 μm is used, the dent amount does not adversely affect the attachment of the dry film.

[0012]

According to the present invention, if the copper foil thickness is selected according to the present invention, the copper foil of the resin-coated copper foil can be laminated on the core layer with almost no depression. The surface of copper plating to be applied also has a flat finish. Accordingly, the finished line width accuracy of the conductor pattern formed thereafter and the finished thickness accuracy of the resin under the pattern are high, and as a result, the finishing accuracy of the characteristic impedance of the pattern is increased.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view showing the vicinity of an IVH in the middle of build-up layer lamination.

FIG. 2 shows the first half of the manufacturing process of the build-up printed wiring board semi-additive method.

FIG. 3 shows the latter half of the manufacturing process of the build-up printed wiring board semi-additive method.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Copper foil with resin 2 Copper foil of copper foil with resin 3 Hole for build layer via hole 4 Electroless copper plating and thin electrolytic copper plating of several μm (primary copper plating) 5 Dry film for resist 6 Positive film of pattern 7 Pattern plating (Secondary copper plating) 8 Core layer 9 Through hole (IVH) in core layer 10 Resin of copper foil with resin 11 Depression of copper foil 12 Bubbles when attaching dry film

Claims (2)

[Claims] 1. A method for producing a build-up layer of a wiring board, in which a copper foil with a resin is laminated by a vacuum press, wherein a thick copper foil is used as the copper foil with a resin. Manufacturing method of wiring board. 2. The method according to claim 1, wherein a copper foil having a thickness of 18 μm or more is used as the copper foil with resin.