JP2003324258A - Copper-clad board for printed wiring board - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a copper-clad board for a printed wiring board in which a wiring pattern of a fine pitch is suitably formed, and the printed wiring board using it. <P>SOLUTION: The copper-clad board for the printed wiring board has a structure wherein the grain diameter of a crystal grain 2 of copper foil sequentially gets smaller as it approaches an insulating base material 1 side from the surface of the copper-clad board in a thickness direction. By applying a subtractive construction method for the copper-clad board for the printed wiring board having such a structure as above, a wiring pattern 3 of a large etching factor is formed. Thereby a desired upper part dimension and an inter-wiring gap are easily acquired even in the wiring pattern of the fine pitch. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a copper clad board for a printed wiring board, which can form a wiring pattern with a fine pitch.

[0002]

2. Description of the Related Art In recent years, circuit pitches have become finer in printed wiring boards due to higher density packaging. When a fine pitch circuit is formed by the conventional subtractive method, since the etching factor of the wiring pattern 11 formed on the insulating base material 10 is small as shown in FIG. In that case, the inter-wiring gap dimension 13 becomes small and insulation failure is likely to occur.

On the contrary, if the etching time is lengthened in order to secure a desired inter-wiring gap dimension, the upper dimension of the wiring pattern 14 becomes smaller as shown in FIG.
The mounting part with the chip may have a poor connection.

[0004]

Therefore, the present invention is a subtractive copper-clad board for a printed wiring board having a structure in which the crystal grain size of the copper foil gradually decreases in the thickness direction from the surface of the copper-clad board toward the insulating base material side. By applying the construction method, a wiring pattern having a large etching factor is formed.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be further described below with reference to the illustrated embodiments. In the copper clad board for printed wiring board according to the present invention, the grain size of the crystal grains 2 of the copper foil formed on the insulating base material 1 is directed from the surface of the copper clad board to the insulating base material 1 side as shown in FIG. It is structured so that it becomes smaller in the thickness direction.

Using such a copper clad board for a printed wiring board, a wiring pattern 3 is formed by a subtractive method using a resist 4 as shown in FIG. In the etching by the subtractive method, once the etching has proceeded to the lower bottom, if the etching is continued, the etching proceeds in the lateral direction.

In this case, generally, the smaller the grain size of the copper foil is, the faster the etching rate is. Therefore, when the copper clad plate of the present invention is used, the upper part of the wiring pattern is the slowest and the insulating base material 1
The etching rate increases in the thickness direction toward the side. As a result, the shape of the wiring pattern 3 having a large etching factor as shown in FIG. 2 can be suitably formed by etching in a short time.

[0008]

According to the present invention, since a large etching factor is obtained as described above, desired upper dimensions and inter-wiring gap dimensions can be easily secured even with a fine pitch wiring pattern.

[Brief description of drawings]

FIG. 1 is a conceptual diagram of a copper foil cross section according to the present invention.

FIG. 2 is an explanatory view of a cross-sectional shape of a wiring pattern at the end of etching when the copper clad plate of the present invention is used.

FIG. 3 is a cross-sectional view of a wiring pattern formed by a conventional subtractive method.

FIG. 4 is a diagram for explaining a problem when a large inter-wiring gap dimension is formed by a conventional subtractive method.

[Explanation of symbols]

1 Insulating base material 2 Copper foil crystal grains 3 wiring patterns 4 resist

Continued front page    F-term (reference) 4E351 AA01 BB01 BB24 BB30 BB35                       DD04 DD52 DD54 GG01 GG11                 4F100 AB17A AB33A AT00B BA02                       GB43 JG04B JL01                 5E339 AB01 AD01 AD03 BC02 BD03                       BD05 BE11 FF02 GG10

Claims (2)

[Claims] 1. A copper clad board for a printed wiring board having a structure in which the crystal grain size of the copper foil is gradually reduced in the thickness direction from the surface of the copper clad board toward the insulating base material side. 2. An etching factor is obtained by applying a subtractive method to a copper clad board for printed wiring board having a structure in which the crystal grain size of the copper foil is gradually reduced from the surface of the copper clad board toward the insulating base material side. A printed wiring board characterized by forming a large wiring pattern.