JPS5838956B2 - High quality pattern - Google Patents

Description

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

2. Description of the Related Art Conventionally, a screen method, a photoprinting method, etc. have been generally used as a pattern forming method for making electrical connections on printed wiring boards and the like.

Among these, the screen printing method uses an expensive stencil screen made of silk, Tetoron, stainless steel, etc. attached to a frame, so it is not suitable for high-mix, low-volume production, and there are limits to pattern accuracy.

Furthermore, since the printing process itself requires a high level of skill on the part of the operator, it is becoming less and less used.

On the other hand, in the photoprinting method, a photosensitive resin thin film is fixed to a printed wiring board having a conductive layer, and then exposed to light to form a portion that is not soluble in a developer (i.e., a desired pattern), and then developed with a predetermined developer. The process of forming a circuit by etching the undissolved portion as a mask or etching the necessary circuits and through-holes with gold,
Mask part after plating metal such as solder (unmelted part)
The gold plating or solder plating layer was removed with a stripping solution and used as an etching resist to form a circuit.

The above conventional methods have the following drawbacks.

That is, a developing solution and a large-scale developing device are required in the developing process for dissolving the photosensitive resin thin film.

This developing solution is expensive because it is used in large quantities, and it is generally necessary to install a regenerating device in order to minimize the amount of solution consumed.

Furthermore, since this developer usually uses a chlorine-based solvent, it has a very strong odor, and an exhaust system is required to maintain a good working environment.

Furthermore, even when exhausting the solvent outside the factory, a device for recovering the solvent was required to prevent air pollution.

Further, since the developer is mixed into the washing water in the step of washing with water to remove the developer immediately after development, it is necessary to treat the washing water as waste.

Furthermore, there is a drawback that the installation floor space of these devices requires a very large amount of floor space.

On the other hand, on the board itself, during the development process before plating metals such as gold and solder onto the circuits and through holes, the residue of the photosensitive resin thin film dissolved in the developer adheres to the inside of the through holes of the printed wiring board. As a result, metals such as gold and solder do not adhere well during the subsequent plating process.

Furthermore, in the development process, it was also observed that the developer corroded the insulating base material portion of the printed wiring board, resulting in partial discoloration.

It is an object of the present invention to provide a highly safe, highly reliable, and highly accurate method of forming electrical connections that eliminates these drawbacks.

That is, the method for forming a wiring pattern according to the present invention includes the steps of coating a conductive layer provided on a substrate with a photosensitive resin whose mechanical adhesion can be changed by exposure to light, and selectively applying the photosensitive resin. The method is characterized in that it includes a step of mechanically removing the conductive layer from above.

Alternatively, in the present invention, one side of a photosensitive resin film whose mechanical adhesion can be changed by exposure to light is adhered to the surface of a release material layer, and the other side of the photosensitive resin film layer is provided on a substrate. After fixing it on the conductive layer and selectively exposing the photosensitive resin film to light, the pattern of the resin layer is formed by mechanically peeling off the release material layer from the substrate, and then,
The conductive layer is etched using the photosensitive resin layer left on the conductive layer as a resist mask, or a plating layer is formed on the conductive layer using the photosensitive resin layer as a plating mask, and the conductive layer is removed using the plating layer or another resist mask as a mask. The electrical connection is formed on the insulating substrate by etching the insulating substrate.

"Exposure" in this application refers to infrared rays, visible light, ultraviolet rays,
The term "photosensitive resin" refers to a resin that is sensitive to infrared rays, visible light, ultraviolet rays, X-rays, or electron beam irradiation.

As the photosensitive resin whose physical properties, especially mechanical adhesion strength, can be changed by exposure to light, cinnamate, polymethacrylic acid amide, and diad compound-based resins can be used.

Next, a first embodiment of the present invention will be described with reference to FIG. 1 in the case of a printed wiring board.

Glass-epoxy double-sided copper-clad laminate 1 with plate thickness L6mrrt
Through-holes 3 are drilled at the required locations of 1 using a drilling machine (Fig. 1 a, b), and this laminate 11 is coated with palladium
．． The entire surface is immersed in a pH 1 solution containing 5% to perform surface activation treatment.

Next, after washing with water and drying, electroless steel plating is applied under the following conditions.

The pH of the electroless plating bath is adjusted to 12.5 to 12.8, the bath temperature is maintained at 20 to 25° C., and plating is performed for about 15 minutes.

Through this electroless plating work, the inner wall of the through hole 3 is coated with 0.5
After depositing a copper layer of 1 to 1 μm in thickness, in order to thicken the copper layer, the copper layer is transferred to the electrolytic copper plating bath described below and plated on the electroless copper plating layer so that the plating film thickness is 20 to 35 μm. form 5.

(FIG. 1C) A pyrophosphate copper plating bath is used as the electrolytic copper plating bath, and the plating is carried out for about 1 hour at a current density of about 3 A/dd.

After forming through holes by electrolytic copper plating, one side of the photosensitive resin thin film layer 7 is attached to the surface of the Mylar film 6 as a release material layer on both sides of the laminated substrate 11 using a laminator. , temperature 40 to 50℃,
It is fixed onto the laminate 11 at a speed of about 250 cvt/min (FIG. 1g).

A silver emulsion film 8 with a polyester film support of about 175 μm having a desired pattern and a desired pattern was pasted onto the plate at predetermined positions on the front and back pots, and an exposure device (Scanix ■, Connetex)
(Fig. 1e).

The laminate plate 11 on which the pattern has been baked is heated to a temperature of 40~
The laminate 11 was passed through a peeling device at a speed of about 150 CIIL/min at 50° C., and the Mylar film 6 as a release material layer was peeled off from one end surface of the laminate 11 together with the uncured photosensitive resin thin film layer 7. The photosensitive resin thin film layer 7 cured by exposure remains as a desired pattern on the copper layer 2 (first
Figure f).

Next, using the remaining photosensitive resin thin film layer 7 as a mask, the unnecessary copper layer 2 is etched away by spraying a ferric chloride etching solution maintained at a temperature of about 35°C (Fig. 1g), and finally The photosensitive resin thin film layer 7 used as a mask is removed with methylene chloride to produce a printed wiring board (Fig. 1h)
.

Further, the case where it is necessary to gold plate the circuit and through-hole portions will be explained using FIGS. 1g''-e and FIGS. 2a to 2d.

The photosensitive resin 7 on the laminate 11 that has gone through the steps of FIG. After that, the unnecessary photosensitive resin thin film layer I is removed using a peeling device (Fig. 2g), and gold plating is applied under the following conditions using the photosensitive resin thin film layer 7 remaining on the copper layer 5 as a mask (Fig. 2g). Figure 2 b).

As this gold plating bath, a cyan bath was used, and the liquid temperature was 40
Plating is carried out for about 15 minutes at a current density of 0.3 A/di.

By this plating, a gold plating layer 9 of about 3 μm is deposited on desired circuits and through holes, and the photosensitive resin film layer used as a mask is removed with methylene chloride.

Finally, using this gold plating pattern 9 as a mask, unnecessary copper layer 5 is removed by etching to produce a printed wiring board.

As described above, by using the manufacturing method of the present invention, there is no need for a developing solution and a large-scale developing device, which were conventionally required in the developing process for dissolving the photosensitive resin thin film.
This eliminates the need for developer regeneration equipment, exhaust equipment to prevent developer odor, and waste water treatment for developer rinse water.
Therefore, the installation floor area can be reduced.

On the other hand, as for the substrate itself, since there is no development process to dissolve the photosensitive resin thin film layer, residues of the photosensitive resin thin film adhere to the through holes, and as a result, gold, solder, etc. are removed during the subsequent plating process. There will be no adhesion defects, no discoloration of the base material portion of the printed wiring board, and high precision printed wiring boards can be provided at low cost.

Next, a second embodiment of the present invention will be explained in detail using FIG. 3.

A hole is made in the insulating substrate 21 (FIG. 3g) using a drill or a punch (FIG. 3b).

Next, after activating the substrate 21 for electroless copper plating, a copper thin film 23 of 1 to 5 microns is formed on the surface of the insulating substrate 21 and the hole wall by electroless copper plating (FIG. 3C).
.

Next, a mechanically peelable and developable photosensitive film 24 is thermocompression bonded to both sides of the insulating substrate 21 (FIG. 3d).

Here, the photosensitive film 24 is a Mylar film 24a,
It has a double structure of photosensitive resin 4b, and photosensitive resin 2
Only the exposed portion of the photosensitive resin 24b increases in adhesion due to exposure and remains on the thin film layer 23, while the non-exposed portion of the photosensitive resin 24b is peeled off by mechanical peeling while remaining in close contact with the Mylar film 24a, and remains on the thin film layer 23. can be developed.

Next, an exposure film 25 having a predetermined pattern is brought into close contact with both sides of the photosensitive film 24 and exposed to ultraviolet light.

Next, when the Mylar film 24a of the photosensitive film 24 and the non-exposed portion of the photosensitive resin 24b are mechanically peeled off, the exposed portion of the photosensitive resin 24b remains on the thin film layer 23.
An electrometal resist pattern is formed (FIG. 3f)
.

Next, a copper layer 26 is formed by electroplating on the thin copper layer 23 by electroplating (FIG. 3g).

As the electrolytic copper plating solution, a copper sulfate plating solution, a copper pyrophosphate plating solution, etc. can be used.

Next, when the photosensitive resin 24b (electromechanical resin) is immersed in the triwarene solution at room temperature for about 3 minutes, it swells and peels off.

Next, it was immersed in a chemical etching solution (ferric chloride aqueous solution or cupric chloride aqueous solution) to etch away the thin film layer 23a of the copper-uncoated portion by electroplating, thereby producing a printed wiring board (FIG. 3h). .

In the present invention as described above, the thin film layer 23 of the printed wiring circuit portion has no chance of coming into contact with the organic solvent used in conventional photosensitive resin development, and there is no infiltration of the organic solvent through the vinyl holes of the thin film layer 23. Since the vinyl holes in the thin film layer are covered and repaired with electrolytic copper 26, a high precision printed wiring board can be manufactured.

Furthermore, the present invention is not limited to manufacturing double-sided printed wiring boards.
It can be applied to the production of single-sided printed wiring boards and multilayer printed wiring boards, and its practical value is extremely large.

Although each of the above-mentioned embodiments describes the case where the present invention is applied to a printed wiring board, the present invention is not limited to such embodiments, and the present invention is not limited to such embodiments. For example, in addition to printed wiring boards, it can be applied to forming wiring patterns of hybrid integrated circuits on glass substrates,
The present invention can also be applied to the case where a wiring pattern is formed on a semiconductor substrate (including one whose surface is mostly covered with an insulating film) without impairing the above-mentioned effects.

In each case, the mechanical adhesion of the resin was changed by ultraviolet rays, but in addition to such light, electron beams, X-rays, etc. can be irradiated to the resin to change the mechanical adhesion as described above. It is also possible to cause a change such as that shown in FIG.
It goes without saying that the coating may be carried out by other methods, such as by applying a liquid form of the resin.

[Brief explanation of drawings]

1 and 2 are partial sectional views showing the manufacturing process of a printed wiring board according to the first embodiment of the present invention, and FIG. 3 is a partial sectional view showing the manufacturing process of the printed wiring board according to the second embodiment of the present invention. FIG. Codes in the figure, 1, 21...Insulating substrate, 2...
...Copper foil, 3,22...Through hole, 5,23.
...Copper layer, 6゜24a...Mylar film, 7,24b...Photosensitive resin layer, 8,25
. . . Pattern mask for exposure, 9 . . . Plated metal layer, 26 . . . Copper layer by electroplating.

Claims (1)

[Claims] 1. A step of coating a conductive layer provided on a substrate with a photosensitive resin whose mechanical adhesion can be changed by exposure to light, a step of selectively exposing the photosensitive resin, and a step of selecting the photosensitive resin. A method for forming a wiring pattern, comprising the step of mechanically removing the conductive layer from above.