JPS6356719B2 - - Google Patents

Description

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

(b) Conventional technology In the conventional manufacturing method of a multilayer wiring board, in order to realize the multilayer wiring shown in FIG. 2, as shown in FIG. 2 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.

For example, this type of technology is disclosed in Japanese Patent Application No. 118697/1983.

However, in the manufacturing method described above, the insulating material is screen printed in the form of a paste using an organic solvent, so the edges of the window 5 cannot be clearly printed, and as shown in Figure 2, there is a risk that bleeding may occur on the inside and the window 5 may be crushed. It was hot. 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. Furthermore, due to the thickness of the first conductive pattern 2, a step is created on the surface of the insulating layer 3,
There was also a problem in which it was difficult to process the second conductive pattern 4 into a finer pattern.

The present invention aims to improve the drawbacks shown in FIG.
We proposed a method for manufacturing a multilayer wiring board shown in E. That is, as shown in FIG. 4A, a first conductive pattern 12 is formed on an insulating substrate 11. Next, as shown in FIG. 4B, a liquid resist layer 13 is applied between the first conductive patterns 12 by spin-on, and the wiring layer 12
Flattening the depression between the two. Subsequently, as shown in FIG. 4C, a film resist layer 14 is roll coated on the liquid resist layer 13. The film-like resist layer 14 is made by coating and drying a photosensitive resist on a polyester film, and has a constant thickness and a flat surface, so that a substantially flat surface can be formed on the film-like resist layer 14. Further, as shown in FIG. 1D, a liquid resist layer 13 and a film resist layer 14 are formed on the first conductive pattern 12.
A through hole 15 is formed in the photoetching technique. Then, as shown in FIG.

(c) Problems to be Solved by the Invention In the above manufacturing method, an extremely flat top surface can be achieved by forming the interlayer insulating film with two layers, the liquid resist layer 13 and the film resist layer 14. This has the advantage that miniaturization of the conductive pattern 16 of No. 2 can be realized.

However, on the other hand, the adhesion strength between the second conductive pattern 16 and the film-like resist layer 14 could not be maintained high, so there was a risk that the second conductive pattern 16 would peel off.

(d) Means for Solving the Problems The present invention has been made in view of the above points, and uses a liquid resist layer and a film-like resist layer as an interlayer insulating film, and appropriately roughens the surface of the film-like resist layer. The present invention provides a method for manufacturing a multilayer wiring board that is optimal for miniaturization.

(e) Effect Since the present invention uses a liquid resist layer and a film resist layer as the interlayer insulating film, through holes can be formed by photoetching technology suitable for miniaturization. Furthermore, in the present invention, since a liquid resist layer is used as a part of the interlayer insulating film, it is possible to eliminate the step difference in the first conductive pattern, form an interlayer insulating film with a flat top surface, and perform fine processing of the second conductive pattern. . Furthermore, in the present invention, since the surface of the film-like resist layer is roughened, the adhesive force of the second conductive pattern can be strengthened, making it suitable for microfabrication processing.

(F) Example The first step of the present invention is to form a first conductive pattern 22 on an insulating substrate 21, as shown in FIG. 1A. The insulating substrate 21 is made of ceramics or aluminum whose surface is coated with an oxide film, and the first conductive pattern 22 is formed by attaching copper foil to the entire surface of the substrate 21 and then etching it into a desired pattern. Note that when microfabrication of the first conductive pattern 22 is performed in this step, photoetching technology may be used, and a line width of approximately 50 μm can be sufficiently achieved even if copper foil is used.

The second step of the present invention consists in depositing a liquid resist layer 23 between the first conductive patterns 22, as shown in FIG. 1B. The liquid resist layer 23 is dropped onto the surface of the substrate 21 and then applied to the entire surface by spin-on. As a result, since the liquid resist layer 23 is a liquid, it fills the recessed portions between the wiring layers 22, hardly adheres to the wiring layers 22, and can adhere so as to flatten the space between the wiring layers 22. This allows the wiring layer 22 and the liquid resist layer 23 to form a substantially flat surface. Liquid resist layer 23 is baked and hardened.

The third step of the present invention is to form a film resist layer 24 on a liquid resist layer 23, as shown in FIG.
It consists in attaching. Film resist layer 2
4 is a polyester film 25 coated with a photosensitive resist and dried to have a certain thickness. Another feature of the present invention is that the surface of the polyester film 25 is roughened in advance by mechanical brushing, chemical etching with an acid or alkaline solvent, or reverse sputtering. Initially, the polyester film 25 has an unevenness of 0.5 μm or less, but by the above-described roughening treatment, an unevenness of 3 to 5 μm can be formed. A photosensitive resist is applied and dried on the polyester film 25 whose surface has been roughened to form a film-like resist layer 25.
form. This film-like resist layer 24 is adhered onto the liquid resist layer 23 using a roll coater, and the two form an interlayer insulating film. Note that the polyester film 25 is peeled off and removed after attachment.
Irregularities of 3 to 5 μm are formed on the upper surface of the film-like resist layer 24 . The film-like resist layer 24 deposited in this step is characterized by having a substantially flat surface and appropriate surface roughness.

In the fourth step of the present invention, as shown in FIG.
6. In this step, using a well-known photoetching technique, both resist layers 23 and 24 on the first conductive path 22 where the through hole 26 is to be formed are exposed and developed, and then dissolved with an organic solvent to form the through hole 26. . As a result, the through-holes 26 can be formed by photo-etching technology, which has the advantage of being able to be formed with extremely high precision.

In the fifth step of the present invention, as shown in FIG.
The purpose is to form a conductive pattern 27. The liquid resist layer 23 and the film resist layer 24 described above are used as a permanent resist layer and an interlayer insulating film. The second conductive pattern 27 is formed by forming a copper or nickel plating layer on the entire surface of the film-like resist layer 24 including the through holes 26, and then etching it into a desired pattern. At this time, since the second conductive pattern 27 is formed on a substantially flat surface, it is possible to completely prevent exposure blur caused by the step caused by the first conductive pattern even if photoetching technology is used, and furthermore, the film-like resist layer Since the adhesive strength of the second conductive pattern 27 can be greatly improved by roughening the surface of the pattern 24, miniaturization can be easily realized. Furthermore, the second conductive pattern 27 can be reliably connected to the first conductive pattern 22 by a plating layer that is simultaneously formed on the through holes 26 as well.

(G) Effects of the Invention The first effect of the present invention is that by forming the interlayer insulating film into two layers, the liquid resist layer 23 and the film resist layer 24, an interlayer insulating film having an extremely flat upper surface can be realized. Second conductive pattern 27
It has the advantage of realizing finer processing.

The second effect of the present invention is that by forming the interlayer insulating film with a permanent resist layer, the through-holes 26 can be formed using photoetching technology, which has the advantage that the through-holes 26 can be formed with extremely high precision and are suitable for miniaturization processing. .

The third effect of the present invention is that the surface of the film-like resist layer 24 of the interlayer insulating film can be appropriately roughened.
This has the advantage that the adhesive strength of the conductive pattern 27 can be improved and peeling can be prevented even with a fine pattern.

The fourth advantage of the present invention is that since the interlayer insulating film can be formed using both resist layers 23 and 24, high-temperature heat treatment is not required and the present invention can be applied to any type of insulating substrate 21.

[Brief explanation of the drawing]

Figure 1 A, B, C, D, and Ho are cross-sectional views explaining the method for manufacturing a multilayer wiring board of the present invention, Figure 2 is a top view explaining a conventional multilayer wiring board, and Figure 3 is a cross-sectional view explaining the method for manufacturing a multilayer wiring board of the present invention.
A cross-sectional view taken along the line A--A in FIG. 4, and FIGS. Explanation of the main drawing numbers, 21 is the insulating substrate, 22 is the first
conductive pattern, 23 is a liquid resist layer, 24 is a film resist layer, 26 is a through hole, 2
7 is a second conductive pattern.

Claims (1)

[Claims] 1. A step of forming a first conductive pattern on an insulating substrate, a step of attaching a liquid resist layer between the first conductive patterns, and a step of attaching a film-like resist layer with a roughened surface on the liquid resist layer. forming a through hole in the liquid resist layer and the film resist layer on the first conductive pattern, which is connected to the first conductive pattern through the through hole and is roughened in the film resist layer; A method for manufacturing a multilayer wiring board, comprising the step of forming a second conductive pattern extending on the surface.