JPH0118594B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application The present invention relates to improvements in multilayer wiring boards, and particularly to a method for manufacturing multilayer wiring boards suitable for miniaturization.

(b) Prior Art In the conventional manufacturing method of a multilayer wiring board, in order to realize the multilayer wiring shown in FIG. 1, as shown in FIG. is formed, and an insulating material layer 3 made sufficiently thick by screen-printing an insulating material twice is provided thereon,
Further, a second conductive pattern 4 was formed thereon.

In the above structure, a window 5 is selectively formed at the connection portion between the first conductive pattern 2 and the second conductive pattern 4 during screen printing of the insulating material so that the two can come into contact with each other. However, since the insulating material is screen printed as a paste using an organic solvent,
The edges of the window 5 could not be printed clearly, and as shown in Figure 2, there was a risk that the window 5 would be crushed due to bleeding inside. For this reason, the window 5 is formed to be sufficiently large, for example, 300 μm in diameter, in consideration of bleeding. As a result, the first conductive pattern 2 and the second conductive pattern 4 must be spaced apart from each other sufficiently to form a window 5 of this size, which has been an obstacle to fine pattern processing.

(c) Object of the Invention The present invention has been made in view of the above, and provides a method for manufacturing a multilayer wiring board that completely eliminates the conventional drawbacks and is suitable for extremely fine processing.

(d) Structure of the invention The present invention is comprised of the following steps.

(1) A step of forming a first conductive pattern on an insulating substrate.

(2) selectively depositing a dry film layer on the first conductive pattern;

(3) A step of forming an insulating layer covering the first conductive pattern on the substrate.

(4) Step of removing the dry film layer and forming through holes.

(5) A step of forming a second conductive pattern on the insulating layer and connecting it to the first conductive pattern through a through hole.

(E) Embodiment The first step of the present invention is to form a first conductive pattern 12 on an insulating substrate 11, as shown in FIG. 3A. The insulating substrate 11 is made of ceramics or aluminum whose surface is coated with an oxide film, and the first conductive pattern 12 is formed by attaching copper foil to the entire surface of the substrate 11 and then etching it into a desired pattern.

In the second step of the present invention, as shown in FIG. 3B, a dry film layer 13 is formed on the first conductive pattern 12.
The purpose is to selectively attach. As the dry film layer 13, a photoresist processed into a film shape is used, and after thermocompression bonding on the substrate 11 at about 80 to 100°C, through holes are formed on the first conductive pattern 12 by a well-known photolithography method. will be left on the intended part. Since this process uses photolithography, the diameter of the through hole can be finely processed to about 80μ.

The third step of the present invention is to form an insulating layer 14 on the substrate 11, covering the first conductive pattern 12, as shown in FIG. 3C. Insulator layer 14
Polyimide is used as the substrate, and polyimide is printed twice over the entire surface of the substrate 11, leaving an area slightly larger than the dry film layer 13 where through holes are formed, to prevent pinholes and ensure a sufficient film thickness. Specifically, the insulator layer 14 can be formed up to the ends of the dry film layer 13 by screen printing so as to have a thickness of about 30 to 40 μm after drying, and by bleeding.

The fourth step of the present invention is to remove the dry film layer 13 and form through holes 15, as shown in FIG. 3D. In this step, only the dry film layer 13 is selectively removed using an organic solvent. Note that since polyimide is insoluble in organic solvents, fine through holes 15 having the same structure as the dry film layer 13 can be formed.

The final step of the present invention is to form a second conductive pattern 16 on the insulating layer 14 and connect it to the first conductive pattern 12 through a through hole 15, as shown in FIG. In this process, the through hole 15
A copper or nickel plating layer is formed on the entire surface of the insulating layer 14 by electroless plating of copper or nickel, and then etched into a desired shape to form the second conductive pattern 16. Therefore, the second
The conductive pattern 16 is connected to the first conductive pattern by a plating layer which is also formed at the same time in the through hole 15.

(F) Effects of the Invention According to the present invention, by using the dry film layer 13, the through-holes 15 can be formed with fine processing precision by photolithography, so that the width of the first conductive pattern 12 can be reduced to 300 μm compared to the conventional width. The width can be narrowed from 100μ to about 100μ. As a result, the mounting density of the multilayer wiring board can be greatly improved, and the density of electronic components can be increased.

[Brief explanation of drawings]

Fig. 1 is a top view illustrating a general multilayer wiring board, Fig. 2 is a sectional view taken along line A-A in Fig. 1 illustrating a multilayer wiring board with a conventional structure, and Figs. 3A to 3E are main views. FIG. 2 is a cross-sectional view illustrating a method for manufacturing a multilayer wiring board according to the invention. 11 is an insulating substrate, 12 is a first conductive pattern,
13 is a dry film layer, 14 is an insulating layer, 15
16 is a through hole, and 16 is a second conductive pattern.

Claims (1)

[Claims] 1 forming a first conductive pattern on an insulating substrate, selectively attaching a dry film layer on the first conductive pattern, and forming an insulating layer covering the first conductive pattern by screen printing. a step of forming a second conductive pattern on the substrate, a step of completely removing the dry film layer to form a through hole, and forming a second conductive pattern on the insulating layer and connecting the first conductive pattern with the through hole. 1. A method for manufacturing a multilayer wiring board, comprising the step of connecting.