JPH01248597A - Multilayer interconnection board - Google Patents

Abstract

PURPOSE:To avoid crackings developed from the edge of a film thickness measuring window composed of a laminated multilayer structure by a stress or the like by a method wherein a lower insulating layer is always covered with an upper insulating layer. CONSTITUTION:An insulating film thickness measuring window 2 of a multilayer interconnection board 1 is composed of a laminated multilayer structure of insulating layers 4-6. In other words, a first layer filler polyimide film 4 is covered with a second layer filler polyimide film 5 and, further, the second layer filler polyimide film 5 is covered with a third filler polyimide film 6 to form the film thickness measuring window 2. Since the insulating film thickness measuring window 2 of the multilayer interconnection board 1 is composed of the multilayer structure and the lower insulating layer is always covered with the upper insulating layer, crackings from the edge developed by a stress caused by curing or the like can be avoided.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a multilayer wiring board, and particularly to a high-density multilayer wiring board for LSI mounting used in electronic devices such as computers.

[Conventional technology]

Conventionally, this type of high-density multilayer wiring board usually has a film thickness measurement window 2' on the end surface of the board 1 on which the wiring pattern 3 is provided, as shown in FIG. 2 due to the need for a film thickness control method. Multiple layers were provided to overlap each other, and the end faces of each film layer (first, second, and third filler polyimide films 4, 5, and 6) were provided in the same position.

[Problem to be solved by the invention]

However, in the case of the method of forming film thickness measurement windows in which the end faces of each insulating layer are overlapped so that the positions of the end surfaces coincide with each other as shown in FIG. 2, the film thickness measurement windows 2'' shown in FIG. If the lower layer is constantly exposed to the outside due to misalignment during exposure, cracks are likely to occur during the curing process due to thermal stress, etc., and the cracks can progress to the wiring pattern, resulting in pattern shorts and opens. The disadvantage is that it can sometimes happen.

[Means to solve the problem]

The multilayer wiring board of the present invention is characterized in that the upper insulating layer always covers the lower insulating layer in the film thickness measurement windows stacked for multiple layers.

〔Example〕

Next, one embodiment of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a cross-sectional view of an embodiment of the present invention, in which a substrate 1 includes
A film thickness 7 measurement window 2 is provided in a structure in which a first layer of filler polyimide film 4 is covered with a second layer of filler polyimide film 5, and further covered with a third layer of filler polyimide film 6, Figures 4(a) to (j) show the film thickness measurement window 2 of the insulating layer shown in Figure 1, which makes it possible to prevent cracks from occurring from the end face.
One manufacturing method is shown. First, a lower wiring pattern 3 is formed on a substrate 1 (FIG. 4(a)). A filler polyimide film 4 is spin coated over the entire surface of this substrate 1 and dried at low temperature (FIG. 4(b)). Therefore, in this state, the filler polyimide film is not imidized. Next, it is exposed to ultraviolet light through a glass mask 7 and dried at a low temperature (FIG. 4(C)). Next, when development is performed, the portions not irradiated with ultraviolet rays are removed, and finally, the dry unimidized filler polyimide film 4 is cured and imidized to form the first layer of insulating film ( Fourth
Figure (d)).

Next, a second layer of filler polyimide M5 is spin coated on the substrate surface and dried at low temperature (Fig. 4(e)).
Next, the film is exposed to ultraviolet light through a glass mask 8 whose area corresponding to the film thickness measurement window 2 of the glass mask 7 has a reduced ultraviolet transmission area, and dried at a low temperature (FIG. 4(f)). Next, when developed, the second layer of filler polyimide film 5 covers the first layer of filler polyimide film 4 in the film thickness measurement window 2, and when cured, the second layer of insulating film is formed (Fig. 4). (g)).

Next, a third layer of filler polyimide film 6 is spin-coated on the substrate surface and dried at low temperature (Fig. 4 (h)).
. Next, the glass mask 9 is passed through a glass mask 9 which has a small ultraviolet transmission area in the portion corresponding to the film thickness measurement window 2 of the glass mask 8.
It is exposed to ultraviolet light and dried at low temperature (Fig. 4(i)). Next, when development is performed, the third filler polyimide film 6 covers the second filler polyimide film 5 in the film thickness measurement window 2, and when cured, a third insulating layer is formed (the fourth
Figure (j)).

〔Effect of the invention〕

As explained above, the present invention has a structure in which the upper insulating layer always covers the lower insulating layer when the windows for measuring the insulating film thickness of a multilayer wiring board are stacked in multiple layers, thereby reducing stress caused by curing, etc. This has the effect of preventing cracks from occurring from the end face.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view showing an embodiment of the present invention, FIG. 2 is a cross-sectional view showing a film thickness measurement window of a conventional multilayer wiring board, and FIG. 3 is a conventional manufacturing process of a multilayer wiring board. A cross-sectional view showing the film thickness measurement window when there is a positional shift during exposure.
FIGS. 4(a) to 4(j) are cross-sectional views showing the manufacturing method of the embodiment shown in FIG. 1 in the order of steps. DESCRIPTION OF SYMBOLS 1... Substrate, 2... Window for film thickness measurement, 3... Wiring pattern, 4... First layer filler polyimide film, 5
...Second layer filler polyimide film, 6...Third layer
Layer filler polyimide film, 7... glass mask,
8...Glass mask, 9...Glass mask.

Claims (1)

[Claims] A multilayer wiring board characterized in that an upper insulating layer always covers a lower insulating layer in film thickness measurement windows stacked on multiple layers.