JPH04103196A - Coating method of high density multilayer wiring board - Google Patents

Abstract

PURPOSE:To protect an insulating layer against bulging caused by coating failure so as to form a thick insulating layer excellent in coating properties by a method wherein photosensitive polyimide of low viscosity and photosensitive polyimide of high viscosity are applied in succession lapping over. CONSTITUTION:A photosensitive polyimide 4 of low viscosity is applied onto the surface of a board 1 through a spin coating method, immediately a photosensitive polyimide 5 of high viscosity is applied thereon through a spin coating method, and the laminate concerned is dried up at a low temperature. Through this lap coating, a fine wiring pattern 2 is improved in coating properties by the photosensitive polyimide 4 of low viscosity, an insulating film can be formed thick by the photosensitive polyimide 5, and the surface of the insulating film can be made flat. Then, the surface of the photosensitive polyimide film is irradiated with ultraviolet rays S through a glass mask 6 provided with a shielded part 6a so as to enable the required part of the surface of the photosensitive polyimide film to be irradiated with light energy, and the substrate 1 is dried up at a low temperature. The dried substrate is developed to remove the non-irradiated part of the polyimide film 5 for the formation of viaholes 7.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for coating high-density multilayer wiring boards, particularly for high-density large-scale integrated circuit (LSI) devices for use in electronic equipment such as computers. The present invention relates to a method of coating an insulating layer of a multilayer wiring board.

[Conventional technology]

Conventionally, the coating method for this kind of high-density multilayer wiring board usually uses high-viscosity photosensitive polyimide, preheats the board on a hot plate as a pre-coating treatment, and then coats the photosensitive polyimide with a spin cord method. Coating is in progress. However, as shown in FIG. 2(a), the highly viscous photosensitive polyimide 5 does not fully wrap around between the fine metal wiring patterns 2, which tends to cause coating defects 8.

[Problem to be solved by the invention]

In the above-described conventional coating method for a high-density multilayer wiring board, the highly viscous photosensitive polyimide does not wrap around between the fine metal wiring patterns, causing poor coating. If the curing process is continued with poor adhesion due to poor coating, the insulation will swell, resulting in insulation bulges 9, or the insulation will crack, resulting in insulation cracks 10, as shown in Figure 2(b). or If the insulation bulges, the upper conductor layer will become convex in the next process of forming a conductor layer, and if the insulation cracks, a short circuit will occur between the upper and lower conductor layers in the next process of forming a conductor layer. There is a drawback.

[Means to solve the problem]

The coating method for a high-density multilayer wiring board of the present invention is a method of coating a photosensitive polyimide on a substrate having a fine metal wiring pattern, in which a low-viscosity photosensitive polyimide is applied so as to cover the entire surface of the metal wiring pattern on the substrate. In this method, a photosensitive polyimide with a high viscosity is coated on top of the photosensitive polyimide.

〔Example〕

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

FIGS. 1(a) to 1(f) are cross-sectional views showing an example of a high-density multilayer wiring board manufactured according to an embodiment of the present invention in the order of steps.

In this embodiment, as shown in FIG. 1(a), first, a wiring pattern 2 is formed on a substrate 1. This wiring pattern 2 is minute and has a thickness of about 10 μm. Then the first
As shown in Figure (b), the entire surface of the substrate 1 is preheated at 30° C. to 40° C. using a hot plate 3. Next, Figure 1 (
As shown in c), low viscosity (
A photosensitive polyimide 4 with a high viscosity (30 to 40 PS/25°C) is coated by a spin cord method, and immediately after that, a photosensitive polyimide 4 with a high viscosity (30 to 40 PS/25°C) 5 was applied by a spin code method and dried at a low temperature. By overcoating the low-viscosity photosensitive polyimide 4 and the high-viscosity photosensitive polyimide 5, the low-viscosity photosensitive polyimide 4 improves the coating properties on the fine wiring pattern 2, and the high-viscosity photosensitive polyimide 4 improves the coating properties of the fine wiring pattern 2. By using polyimide 5, the thickness of the insulating layer can be increased and the surface can be made flat. The film thickness in this state is 20 to 30 μm and has not yet been imidized.

Next, as shown in FIG. 1(e), ultraviolet light S is exposed through a glass mask 6 having a partially shielded shielding part 6a so that the light energy irradiates only a desired part of the surface of the photosensitive polyimide film. and dry at low temperature. When this is developed, the parts not irradiated with ultraviolet rays are removed and the first
As shown in Figure (f), a via hole 7 is formed.

In this state, due to the effect of overcoating, the photosensitive polyimide film is brought into close contact along the lines between the wiring patterns 2, and a photosensitive polyimide film with good paintability is observed. Finally, the photosensitive polyimide film patterned in this way was
It is cured and imidized at 0°C to 400°C.

〔Effect of the invention〕

As explained above, the method of coating a high-density multilayer wiring board of the present invention prevents blistering of insulation due to poor coating by overcoating low-viscosity photosensitive polyimide and high-viscosity photosensitive polyimide. This has the effect of forming a thick insulating layer with good paintability.

FIG. 2 is a cross-sectional view showing an example of a high-density multilayer wiring board in the order of steps. FIG. 2 is a cross-sectional view of an example of a high-density multilayer wiring board manufactured by a conventional technique.

DESCRIPTION OF SYMBOLS 1... Board, 2... Wiring pattern, 3... Hot plate, 4... Low viscosity photosensitive polyimide, 5...
・High viscosity photosensitive polyimide, 6...Glass mask,
7. Via hole, 8. Poor coating, 9. Insulation blistering, 10. Insulation crack.

Claims (1)

[Claims] In a method of coating photosensitive polyimide on a substrate having a fine metal wiring pattern, a low viscosity photosensitive polyimide is applied so as to cover the entire surface of the metal wiring pattern on the substrate, and a high viscosity photosensitive polyimide is coated on top of the metal wiring pattern. A method for coating a high-density multilayer wiring board, which is characterized by applying polyimide in layers.