JPH0682898B2 - Multilayer printed circuit board and manufacturing method thereof - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention relates to an organic polymer insulating film used for a multilayer wiring circuit board, particularly for a thermal printer head, an optical printer head, a circuit board for mounting a highly integrated high frequency IC, and the like. And a multi-layer printed circuit board.

(Prior Art) With the remarkable development of electronic technology in recent years, demands for miniaturization, weight reduction, and high performance of electronic devices are increasing more and more, and accordingly, high integration of device parts is actively pursued. Is being measured by.

As a method of high integration, there is adopted a method of using a multilayer wiring board for integration into a film circuit component such as a thermal printer head, an optical printer head and a circuit board for mounting a highly integrated high frequency IC.

At present, there is a strong demand for miniaturization, high density, and high-speed signal transmission for such multilayer wiring board parts. In response to the demand for miniaturization and high density, the multi-layer wiring structure has been changed to high-speed signal transmission. In order to meet the requirement, various methods and materials such as using an insulating material having a low relative dielectric constant are adopted.

For example, in a multilayer wiring structure having a wiring layer formed on the surface of a resin substrate, in order to improve the adhesiveness between the resin substrate and the wiring layer, a metal oxide such as aluminum oxide is formed at the interface between the wiring layer and the resin substrate material. A multilayer wiring structure has been proposed in which a resin layer such as a polyimide resin mixed with fine particles or glass powder is interposed.

(Problems to be Solved by the Invention) However, in a miniaturized and highly densified membrane circuit component, generally, it has a multilayer wiring structure in which two or more wiring conductors are stacked with an insulating layer interposed therebetween. The adhesive strength between the respective layers needs to be sufficiently higher than that of the single-layer product, otherwise the phenomenon of peeling from the interface frequently occurs during wiring processing and heat treatment.

If the adhesive strength is not sufficient, in the step of applying a photoresist on the formed wiring conductor and film-forming,
The photoresist sometimes floats or peels off from the wiring conductor, which causes a problem that the portion which should be originally left as wiring is corroded when the wiring conductor is etched.

All of these occur because the chemical bond at the interface is weak and the effective area of the adhesive interface is not sufficient because the underlying surface is sufficiently flat.

When the surface of the insulating layer is sufficiently flat, peeling of the film occurs because internal stress between the insulating layer and the wiring conductor is hardly absorbed and relaxed by the insulating layer during wiring processing or heat treatment. There is a problem of causing cracks and cracks.

In the proposed known invention, the coefficient of thermal expansion of glass or metal oxide is 4 to 8 × 10 ⁻⁶ / ° C., whereas the coefficient of thermal expansion of polyimide resin is 20 to 50 × 10 ^{−. 6} / ° C
However, the coefficient of thermal expansion between the two is very different, so that when heat is applied to the polyimide resin in which glass or metal oxide is mixed (filled), the polyimide resin and the glass or metal oxide are At the same time, thermal stress is generated due to the difference in thermal expansion coefficient between the two, which causes a problem that the wiring layer is separated by the thermal stress.

Further, since the dielectric constant of glass or metal oxide is as high as 4.5 to 10, the dielectric constant of the polyimide resin mixed with the glass or metal oxide is also high, and as a result, the signal transmission speed of the wiring layer is slow. As a result, the mounting of semiconductor elements and the like, in which electric signals are taken in and out at high speed, is restricted.

(Means for Solving Problems) The present invention is to solve the above-mentioned problems of the prior art. That is, the present invention provides (1) a wiring conductor and an organic polymer insulating film on an electrically insulating substrate. In the multilayer printed circuit board formed in multiple layers, the surface roughness of the organic polymer insulating film is 1.5 at the center line average roughness Ra.
To 0.5 μm, the solid fine particles are filled, and the organic polymer insulating film and the solid fine particles are both made of a polyimide resin, and a multilayer wiring circuit board, (2) A multilayer wiring circuit board characterized in that an organic polymer insulating film made of a polyimide resin filled with solid particles of a polyimide resin and wiring conductors are formed in multiple layers on an electrically insulating substrate. Manufacturing method.

Next, in a combination in which an electric wiring conductor and a polyimide resin insulating film layer are formed on an electrically insulating substrate such as ceramic or glass, the polyimide resin solid material particles of the same quality having a strong affinity with the polyimide resin insulating material. The multilayer printed circuit board of the present invention having a surface-roughened insulating film obtained by filling and mixing the body will be described.

First, as the wiring conductor, a conductive material such as aluminum (Al), copper (Cu), gold (Au), and silver-palladium (Ag-Pd) is used. The film is formed by a thin film method such as CVD, and the wiring pattern is processed by printing technology or photolithography technology.

Here, as the organic polymer insulating material, an electric insulating material having excellent heat resistance and chemical resistance of a polyimide resin is used, and as the solid fine particles to be filled in the electric insulating material, the polyimide resin insulating material is used. It is preferable to use polyimide-based cured resin solid fine particles of the same type as the polymer insulating material, which is a material having a strong affinity with the material.

Regarding the size of the polyimide resin solid fine particles to be filled in the polyimide resin insulating material, when the electric wiring conductor is formed on the insulating film formed of the polyimide resin insulating material, the diameter is 1 to 15 μm. Volume average diameter is 7μ
It is preferable that the thickness is about m or less, and by doing so, the step coverage of the electric wiring conductor with respect to the insulating film, the step coverage of the photoresist film used when patterning the electric wiring conductor, and the insulation film It is possible to suppress variations in film thickness. The filling amount of the solid fine particles is 10
The content is ˜35% by weight, and the shape may be spherical or amorphous.

And the polyimide resin insulating material filled with the polyimide resin solid fine particles is a spinner, a roll coater,
A film is formed on the electric wiring conductor formed on the electric insulating substrate by a technique such as printing, and through the use of well-known photolithography technology and printing technology, the through holes for connecting the upper and lower electric wiring conductors or the lower layer electric wiring conductor protection The working pattern is formed.

Here, an insulating layer forming method in which the film formation of the polyimide-based resin insulating material containing solid fine particles and the through hole processing for connecting the upper and lower electric wiring conductors are simultaneously performed will be described. That is, after forming an electric wiring conductor on an electrically insulating substrate, a metal mask or PVA (polyvinyl alcohol)
The forming method is carried out by screen printing using a solvent-resistant stainless screen plate-making plate such as a mask. At this time, it is important to perform printing so that the surface roughness of the dry-heat treated insulating film has a center line average roughness (JIS-B0601-1976) Ra of about 1.5 μm or less. The reason is to suppress the unevenness of the step coverage and the insulating layer thickness of each film when forming the electric wiring conductor on the insulating film and when processing the photoresist film on the wiring conductor. When the roughness Ra exceeds 1.5 μm, as shown in FIG. 2, a part of the polyimide resin solid particles 2 is projected and exposed from the surfaces of the polyimide resin insulating film 1 and the electric wiring conductor layer 3, and as a result, There is a problem that the electrical wiring conductor layer 3 is broken.

If the surface roughness is less than 0.5 μm, the adhesive strength between the film layers becomes small, and the multilayer wiring circuit board having a film having a strong adhesive strength, which is the object of the present invention, cannot be obtained.

Therefore, the surface roughness is preferably in the range of Ra 0.5 to 1.5 μm, and in this case, the cross sectional state is as shown in FIG.

In order to confirm the adhesive strength of the insulating film according to the present invention, a photolithography technique in which a conductor material of aluminum (Al) is formed by a vacuum deposition method on a polyimide resin insulating film having a center line average roughness Ra of 0.2 μm or less. To form a pad by
A tensile test with an adhesive tape showed that 20% of the pads showed peeling. On the other hand, the centerline average roughness Ra is
Aluminum deposited on the polyimide resin insulating film of 0.5 to 1.5 μm did not show peeling of the pad (note that the polyimide drying heat treatment condition at this time was 200 ° C. × 30 minutes).

(Effects of the Invention) Since the present invention is configured as described above, it has the following operational effects.

(A) The polyimide resin solid film has excellent affinity with the polyimide resin solid fine particles of the same quality as the polyimide resin insulating film, and both adhere firmly to each other, so that the solid fine particles are polyimide-based even when an external force is applied. It does not come off from the resin insulating film, which allows the wiring conductor to be firmly adhered to the polyimide resin insulating film.

(B) Even if heat is applied to both the polyimide resin insulating film and the solid fine particles of the same quality, the thermal expansion coefficients of both are substantially the same, so that thermal stress is generated in the resin insulating film. In addition, the thermal stress hardly causes peeling between the polyimide resin insulating film and the wiring conductor.

(C) Since the insulating film and the solid fine particles are made of the same polyimide resin, and the dielectric constant thereof is as small as 2.8 to 3.5, a wiring conductor is formed on the polyimide resin insulating film filled with the polyimide resin solid fine particles. When formed, the transmission speed of the signal transmitted through the wiring conductor becomes high, and as a result, it is advantageous for mounting a semiconductor element or the like in which electric signals are taken in and out at high speed.

(D) Adhesion at the interface between the polyimide-based resin insulating film and the upper wiring conductor because the effective surface area of the adhesive interface increases when the polyimide-based resin insulating material is filled with the polyimide-based resin solid fine particles to roughen the surface of the insulating film. Is improved.

(E) Further, the adhesiveness of the photoresist used for processing the wiring conductor on the surface-roughened polyimide resin insulating film is also improved.

(F) Since the surface of the polyimide-based resin insulation film is roughened, the insulation film absorbs and relaxes the internal stress between the insulation film and the wiring conductor above it even if the insulation film is processed or heat-treated. The occurrence of peeling and cracks can be suppressed.

[Brief description of drawings]

FIG. 1 shows a partially enlarged sectional view of an embodiment of the present invention, and FIG. 2 shows the same sectional view deviated from the embodiment. 1: Polyimide resin insulation film 2: Polyimide resin solid fine particles 3: Electrical wiring conductor layer

Claims (2)

[Claims] 1. A multilayer printed circuit board in which a wiring conductor and an organic polymer insulating film are formed in multiple layers on an electrically insulating substrate, wherein the organic polymer insulating film has a surface roughness of center line average roughness Ra.
Is filled with solid fine particles so as to have a thickness of 1.5 to 0.5 μm, and both the organic polymer insulating film and the solid fine particles are made of a polyimide resin. . 2. A multi-layer wiring circuit characterized in that an organic polymer insulating film made of a polyimide resin filled with solid particles of a polyimide resin and a wiring conductor are formed in multiple layers on an electrically insulating substrate. Substrate manufacturing method.