JPS5858833B2 - High quality pattern - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of forming a wiring pattern, and particularly to a method of manufacturing a printed wiring board.

Conventional methods for forming wiring patterns, such as manufacturing printed wiring boards, involve drilling desired holes in an insulating substrate, performing activation treatment for electroless plating, and then applying conductive metal to the entire surface of the insulating substrate by electroless plating. After forming a thin layer (often nickel, copper, etc.), it is coated with a photosensitive polymeric organic resin (liquid or film) that is developed by a solvent, and after exposure it is developed by an organic solvent such as chlorocene. Then, a plating resist pattern is formed, or an organic ink plating resist pattern is formed by a screen printing method.

Next, a thick metal layer was applied to the circuit portion by electroplating, the metal layer was removed, and then the thin metal layer other than the circuit was etched away using a chemical etching solution to produce printed wiring.

However, with these methods, when forming an electroplating resist, the solvent (developer of photosensitive polymeric organic resin or diluent in organic ink) may penetrate into the pinholes of the thin metal conductive layer formed by electroless plating. If the surface of the insulating substrate is damaged, there are drawbacks such as peeling of the thin metal layer around the pinholes.

In addition, during electroplating, the electroplating solution penetrated through the pinholes, causing flakes in the plated film after electroplating.

It is an object of the present invention to provide a method for forming a wiring pattern that eliminates these drawbacks, has high reliability, and has a high yield.

The present invention provides a method for forming a wiring pattern, which includes a step of forming a first conductive electroless plated metal layer on a substrate, a step of forming an electroless plated catalyst metal layer, and a second conductive plated metal layer. It is characterized by including the step of forming.

Alternatively, after forming a first conductive metal layer on the substrate by electroless plating, the substrate is immersed in an electroless plating metal catalyst solution, and then a second conductive metal layer is formed by electroless plating on the first conductive metal layer. The method is characterized in that it includes a step of selectively forming the conductive metal layer on the conductive metal layer.

Alternatively, in the present invention, after a first metal layer is formed on a substrate by electroless metal plating, it is immersed in an electroless metal plating catalyst solution to form an electroless plating catalyst metal thin film on the first metal layer.

Through this step, the electroless plating catalyst metal penetrates into the pinholes in the first metal layer and is adsorbed.

Next, a photosensitive resin layer which can be mechanically peeled and developed, that is, whose mechanical adhesion can be changed by exposure, is applied to the first layer.
The second conductive metal layer is formed on the thin film metal layer, exposed to light, mechanically peeled and developed, and formed into a metal resist, and then again formed by conductive metal plating to form a second conductive metal layer. It is.

The above-mentioned second conductive metal layer may be formed by either electroless plating or electroplating, but it is preferable to perform electroless plating and then thicken it by electroplating.

Here, as the electroless plating catalyst metal mentioned above, palladium chloride, tin chloride, or a mixture thereof can be used in the form of an aqueous solution, and these electroless plating catalyst metals can be used to form palladium in the pinholes of the first electroless metal layer. , has the effect of blocking pinholes by depositing and adsorbing tin, and furthermore, a second metal layer is formed by plating, preferably electroless plating, on the first metal layer in which the pinholes are significantly reduced. By performing electrolytic plating thereon, the contact between the first metal layer and the substrate is mechanically and chemically stabilized.

In addition, as photosensitive resins whose mechanical adhesion changes with exposure to light, polycinnamate esters, diad compounds, and polymethacrylic acid amine resins can be used. Since the exposed pattern is mechanically developed by selectively changing the exposure pattern (by changing the exposure pattern), it is possible to eliminate the influence of the developing solution on the substrate and metal layer.

That is, in the present invention, there is no opportunity for the metal layer to come into contact with the organic solvent during the formation of the mesh resist, and the corrosion of the insulating substrate caused by the organic solvent through the pinholes is completely removed.

Furthermore, since the pinholes in the first metal layer of the circuit portion are covered with the electroless plating catalyst metal and the second metal layer, blisters in the plating film of the circuit portion after electroplating are removed.

Furthermore, since the second metal layer forms only the circuit part,
Even in etching with a chemical etching solution after removal of the metal resist, the amount of etched metal is small and economical.

Next, one embodiment of the present invention will be described in detail in the case of a printed wiring board with reference to FIG.

A hole is made in the insulating substrate 1 (FIG. 1g) by a drill or punch (FIG. 1b), and then chromic acid is added at a temperature of 40°C.
The surface of the insulating substrate 1 is made hydrophilic by immersing it in a mixed aqueous solution of sulfuric acid for about 10 minutes.

Next, after washing with water, it is immersed in an aqueous palladium chloride solution as an electroless plating catalyst solution at room temperature for about 5 minutes, and after washing with water, it is immersed in an electroless copper plating solution to form the first thin copper film 3 with a thickness of 1 to 5 microns on an insulating substrate. 10 surface and the pore wall 2 (FIG. 1C).

Next, after washing with water, it is immersed in an aqueous palladium chloride solution as an electroless plating catalyst solution for about 5 minutes to form a coating 4 of electroless plating catalyst metal, that is, palladium, on the first thin copper film 3, and after washing with water, it is dried (Fig. 1d). ).

Next, after exposure to light, a photosensitive film 5 that can be mechanically peeled off and developed is bonded to both sides of the insulating substrate 10 by thermocompression.

The photosensitive film 5 has a double structure of a Mylar film 5a and a photosensitive resin 5b, and only the exposed portion of the photosensitive resin 5b increases in adhesion upon exposure to the electroless plated catalyst metal (palladium) coating 4. Remaining photosensitive resin 5b
The non-exposed areas of
It can be peeled off and developed while remaining in close contact with a (Fig. 1e).

Next, the mask film 6 for pattern exposure is brought into close contact with both sides of the photosensitive film 5, and exposed to ultraviolet rays (the first
Figure f).

Next, by peeling off the Mylar film 5a of the photosensitive film 5 from one end, the unexposed portion of the photosensitive resin 5b is mechanically peeled off, and the photosensitive resin 5b is removed as shown in FIG. 1g.
The exposed portion remains on the electroless plating catalyst metal film 4, forming a plating resist pattern.

A second thin copper film 7 of 1 to 5 microns is then formed by electroless steel plating on the electroless plating catalyst metal coating 4 in the areas not covered with the metal resist.

Next, electrolytic copper 8 is formed on the second thin film copper 7 by electrolytic copper plating (FIG. 1h).

As the electrolytic copper plating solution, a sulfuric acid steel plating solution, a copper pyrophosphate plating solution, etc. can be used.

Next, the photosensitive resin 5b (Metsuki Resyst) is immersed in a trichloride solution for about 3 minutes, causing swelling and peeling.

Next, it was immersed in a chemical etching solution (ferric chloride aqueous solution or cupric chloride aqueous solution) to etch away the first thin copper film and the electroless plating catalyst metal coating on the areas not coated with electrolytic copper, thereby producing a printed wiring board.

As described above, in the present invention, the thin film copper in the printed wiring circuit part has no chance of coming into contact with organic solvents, and the number of pinholes in the thin film copper in the circuit part is significantly reduced compared to the conventional method, so that the plated film does not blister after electrolytic copper plating. We were able to manufacture a high-precision printed wiring board with no problems.

The present invention uses less organic solvent than conventional manufacturing methods, has advantages in terms of pollution control, and is economical.

In addition, it can be applied not only to the production of double-sided printed wiring boards, but also to single-sided printed wiring boards and multilayer printed wiring boards, and other conductive metals such as nickel and aluminum other than copper plates can be used as the metal layer. Its value is extremely high.

Furthermore, the present invention is not limited to the above-mentioned embodiments, and can be applied to a wide variety of cases where wiring layers are formed on a substrate, and can also be applied to wiring of hybrid integrated circuits and integrated circuits without impairing its effects. It is something that can be mourned appropriately.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of the main parts of a printed wiring board in the method of manufacturing a printed wiring board of the present invention. Codes in the figure 1... Insulating substrate, 2: Perforated part, 3: First thin film copper, 4: Electroless plating catalyst metal, 5: Photosensitive film, 5a: Mylar film, 5b 22 Photosensitive resin,
6: pattern film for exposure, 7: second thin film copper, 8: electrolytic copper.

Claims (1)

[Claims] 1. A step of forming a first conductive electroless plating metal layer on a substrate, a step of forming an electroless plating catalyst metal layer,
A method for forming a wiring pattern, the method comprising: forming a second conductive plated metal layer.