JPS59141293A - Multilayer circuit board - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

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

(B) Prior Art In a conventional multilayer wiring board, in order to realize the multilayer wiring shown in FIG. 2), an insulating material layer (3) made sufficiently thick by screen printing an insulating material twice is provided thereon, and a second conductive pattern (4) is further formed thereon. Ta.

In the top structure, the connection between the first conductive pattern (2) and the second conductive pattern (4) is selectively formed with a window (5) during screen printing of the insulating material to allow contact between the two. . However, since the insulating material is screen printed in the form of 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 bleeding would occur on the inside and the window (5) would be crushed. . 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) had to be spaced apart from each other sufficiently to form a window (5) of this size, which was an obstacle to fine pattern processing.

(c) Purpose The present invention has been made in view of the top, and provides a multilayer wiring board suitable for extremely fine processing, completely eliminating the drawbacks of the conventional method.

B) Structure According to the present invention, an insulating substrate and a first
a conductive pattern, an insulating layer covering the first conductive pattern with an insulating material, and a second conductive pattern formed thereon, the first conductive pattern at the connection portion being selectively thickened. formed and composed.

(e) Embodiment As shown in FIG. 3, in the present invention, a first conductive pattern (2) is formed on an insulating substrate (1) made of ceramic or aluminum whose surface is coated with an oxide film. The first conductive pattern (2) is formed by pasting copper foil over the entire surface of the insulating substrate (1) and then etching it into a desired pattern. The most distinctive feature of the present invention is that there is a protrusion (6) of approximately 2 to 50 μm on the first conductive pattern (2) that serves as the connection point.
form. The protrusion (6) is formed by selectively depositing a plating layer by electroless copper plating or electric field nickel plating, or by half-etching the other first conductive pattern (2).

Next, an insulating layer (
3) Print the screen immediately. Polyimide is used as the insulating material, and it is printed twice over the entire surface of the substrate (1), leaving windows (5) formed corresponding to the connection points, to prevent peen holes and ensure a sufficient film thickness. . Specifically, after drying 30
Screen print to a thickness of ~40μ. The size of this transparent window (5) is determined by the size of the first conductive pattern (2) of the connection part.
) may be slightly larger than the protrusion (6), and specifically, a diameter of 200μ can be achieved. This means that even if bleeding occurs inside the window (5) during screen printing, the bleeding will not occur on the protrusion (
6), the insulating layer (3) is not printed at least on the protrusion (6).

Thereafter, a second conductive pattern (4) is formed on the insulating layer (3) by screen printing a conductive paste such as silver paste or by electroless nickel plating.

As a result, the second conductive pattern (4) is reliably connected to the protrusion (6) of the first conductive pattern (2) at the connection point.

(f) Effect According to the present invention, the protrusion (6) of the first conductive pattern (2)
Since the window (5) of the insulator layer (3) can be formed with extremely high precision, the first and second conductive patterns (2) (4
) can be made smaller. As a result, a multilayer wiring board suitable for microfabrication can be realized, and electronic components can be mounted at high density.

[Brief explanation of drawings]

FIG. 1 is a sectional view taken along the line A--A in FIG. 1 illustrating a top plate of a general multilayer wiring board. (1) is an insulating substrate, (2) is a first conductive pattern, (3
) is an insulating layer, (5) is a window, (6) is a protrusion, and (4) is a second conductive pattern. Figure 1

Claims (1)

[Claims] 1- A first conductive pattern provided on an insulating substrate, an insulating layer covering the first conductive pattern, and a second conductive pattern provided on the insulating layer, A multilayer wiring board, characterized in that the first conductive pattern at the connection portion between the first conductive pattern and the second conductive pattern is formed thick. 2. In claim 1, the first connecting portion
A multilayer wiring board characterized in that a plating layer is selectively provided on a conductive pattern.