JPS647517B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a printed wiring board similar to a full additive method, in which an electroless metal is formed on an insulating substrate 1 in a portion that will become a circuit portion 2 and a circuit connection portion 3 that connects the circuit portions 2. a step of printing an adhesive 4 containing catalyst nuclei for plating, a step of semi-curing the adhesive 4, and a step of electroless metal plating a thin metal layer 5 on the semi-cured adhesive 4; A process of printing a plating resist 6 on the thin metal layer 5 on the electric circuit connecting part 3, and a process of electrolytically plating the electric circuit layer 7 on the thin metal layer 5 on the electric circuit part 2 by applying electricity to the thin metal layer 5. , the step of removing the plating resist 6 on the electric circuit connecting part 3 and etching the thin metal layer 5 on the electric circuit connecting part 3, and the step of removing a thin electroless metal plating on the semi-cured adhesive 4 as described above. The present invention relates to a method for manufacturing a printed wiring board characterized by including a step of completely curing the adhesive 4 after forming the metal layer 5.

In manufacturing printed wiring boards, various methods such as additive methods have been studied in order to reduce the amount of metal to be removed by etching. An example of this is to pre-treat the entire surface of an additive insulating substrate with a catalyst for electroless metal plating, then coat the surface of the insulating substrate with an adhesive in areas other than the electrical circuits. Form the electrical circuit pattern and then use electroless metal plating to 35μ
There is a method of forming an electrical circuit layer on a portion other than the adhesive to a thickness of approximately the same thickness. However, with this method, it is necessary to plate a thickness of 35μ using only electroless copper plating, so the electroless copper plating process takes a long time, and the cost of electroless metal plating is high. In order to ensure adhesion with the metal layer, it is necessary to use an additive-use insulating substrate with a roughened surface, and it is also necessary to perform catalyst treatment on the entire surface of the substrate, which increases the substrate cost. It was hot. Further, as another example of these, as shown in FIG.
After performing a pretreatment to deposit a catalyst for electroless metal plating on the entire surface of the circuit section 18,
A curable resin film 12 is applied to the surface of the insulating substrate 11, leaving the portion that will become the electric circuit connecting portion 19 (FIG. 1a), and then electroless metal plating is applied to the electric circuit portion 18 and the electric circuit connecting portion 19. After forming a very thin metal layer 13 (FIG. 1b), and then coating the surface of the metal layer 13 of the electric circuit connection part 19 with a peelable resin layer 14 (FIG. 1c), the metal layer 13 is energized. Then, a circuit layer 15 is formed by electroplating on the metal layer 13 of the circuit section 18 (FIG. 1d), and then the resin layer 14 on the very thin metal layer 13 of the circuit connection section 19 is removed (FIG. 1d). 1e) There is a method of etching away the extremely thin metal layer 13 of the electrical circuit connecting portion 19 (FIG. 1f) to form a thick electrical circuit layer (35 μm) by electroplating. However, in this method, as with the above method, it is necessary to perform catalyst treatment on the entire surface of the substrate, and it is necessary to use an insulating substrate for additive use, which increases the substrate cost.Furthermore, according to this method, Thin metal layer 1 of electric circuit connection part 19
When coating the removable resin layer 14 on the surface of the resin film 12 (FIG. 1c), it is necessary to coat the resin layer 14 on a portion recessed from the surrounding hardening resin film 12, and this recessed portion It is extremely difficult to completely cover the resin layer 14 by screen printing or the like, and there is a fear that this portion may be electroplated.

The present invention has been made in view of the above points, and there is no need to use a substrate for additive use with a roughened surface as an insulating substrate, and there is no need to apply catalyst treatment to the entire surface of the insulating substrate, thereby reducing the substrate cost. A printed wiring board that can be made at low cost, eliminates the risk of electroplating in unnecessary areas, does not require a long time for electroless metal plating, and has high adhesion strength to the insulating substrate in the electrical circuit section. The purpose of this invention is to provide a method for manufacturing.

The present invention will be explained in detail below. As the insulating substrate 1, any commonly used material can be used, such as a rigid type in which a paper base material or a glass fiber base material is impregnated with a phenol resin or epoxy resin, and polyimide-based, polysulfin-based, and polyester-based materials. Any material can be used, such as a flexible type obtained from a film or a prepreg type obtained from an epoxy or phenol prepreg. An adhesive 4 containing catalyst nuclei for electroless metal plating is printed on this insulating substrate 1 as shown in FIG. 2a. This adhesive 4 is printed in a pattern by, for example, screen printing, only on the electric circuit portions 2 and the portions that will become the electric circuit connection portions 3 that connect the electric circuit portions 2. As the catalyst core, colloidal silver or the like can be used by kneading it into the adhesive 4.
Further, as the adhesive 4, epoxy resin or the like can be used. After printing the adhesive 4 in a pattern shape in this manner, the adhesive 4 is semi-cured by heating for a short time or by leaving it at room temperature.

Next, electroless metal plating is applied to the surface of the insulating substrate 1. The thin metal layer 5 by electroless metal plating is formed only on the adhesive 4 provided with catalyst nuclei, that is, only on the electric circuit section 2 and the electric circuit connection section 3, as shown in FIG. 2b. This thin metal layer 5 only needs to be able to conduct electricity, and a thickness of approximately 0.1 to 2.0 μm is sufficient. Here, since the thin metal layer 5 is formed by electroless metal plating on the adhesive 4 at the stage where the adhesive 4 is semi-cured in this way, the adhesive 4 is The metal particles adhering to the surface dig deeply into the surface of the semi-cured adhesive 4,
This increases the adhesion strength of the thin metal layer 5 formed on the adhesive 4. On the other hand, when forming a thin metal layer 5 of electroless metal plating on the completely cured adhesive 4, metal particles only adhere to the surface of the cured adhesive 4, so the thin metal layer 5 cannot be obtained sufficiently.

Next, a plating resist 6 is attached to the upper surface of the thin metal layer 5 on the electric circuit connection part 3 by screen printing or the like, and the thin metal layer 5 of the electric circuit connection part 3 is covered with the plating resist 6 as shown in FIG. 2c. This plating resist 6 is one that can be dissolved and removed with an alkali or the like.

After applying the plating resist 6 in this manner, electricity is applied to the thin metal layer 5 to perform electroplating. The thin metal layer 5 of each electric circuit section 2 is the thin metal layer 5 of the electric circuit connection section.
Since they are connected as shown in Fig. 3, current flows across the thin metal layer 5 when current is applied from one place, and the electrical circuit layer 7 is formed on the thin metal layer 5 in the electrical circuit section 2 as shown in Fig. 2 (d). It is formed. Since the thin metal layer 5 in the electric circuit connection part 3 is covered with a plating resist 6, no electric circuit layer 7 is formed there, and the electric circuit layer 7 has a thickness sufficient to be used as an electric circuit, for example.
Form to about 35μ thickness.

Next, the plating resist 6 on the thin metal layer 5 in the electric circuit connection part 3 is removed and peeled off using an alkali treatment or the like as shown in FIG. The thin metal layer 5 in the electrical circuit connection part 3
is removed by etching as shown in Figure 2f. At this time, since only the thin metal layer 5 is etched, a light etching process is sufficient, and the surface of the electric circuit layer 7 is also corroded by this etching process.
The thickness is comparable to that of the thin metal layer 5 and is only slightly corroded. Thereafter, the adhesive 4 is completely cured to completely integrate the insulating substrate 1 and the circuit layer 7.
The adhesive 4 only needs to be completely cured after the thin metal layer 5 of electroless metal plating is formed thereon, and as described above, the thin metal layer 5 of the electrical circuit connection part 3
The adhesive 4 may be completely cured not only after the etching process but also immediately after forming the thin metal layer 5 of electroless metal plating.

As described above, a printed wiring board is obtained in which the electrical circuit layer 5 is formed in the shape of a circuit pattern on the insulating substrate 1 in separate areas.

As mentioned above, in the present invention, since the adhesive containing catalyst nuclei for electroless metal plating is printed on the parts that will become the electric circuit parts and the electric circuit connection parts,
There is no need to treat the entire surface of the insulating substrate with catalyst nuclei, and since the electrical circuit layer is formed on this adhesive, the surface can be roughened, unlike when plating metal directly on the insulating substrate. There is no need to use an additive-use insulating substrate, and a general inexpensive insulating substrate can be used, and the substrate cost can be reduced. Furthermore, since a thin metal layer of electroless metal plating is formed on top of the adhesive while it is in a semi-cured state, the metal particles of the electroless metal plating dig deep into the semi-cured adhesive, creating a large adhesion between the thin metal layer. It provides strength. In addition, since a thin metal layer is formed by electroless metal plating on the electric circuit connection part that connects the electric circuit parts, electricity can be applied to the entire electric circuit part at once through the electric circuit connection part.
Electrolytic plating can be easily performed on the electrical circuit section. Moreover, since the thickness of the electrical circuit layer can be achieved by electroplating, the production can be carried out in a short time without requiring a long time as required when the thickness is achieved by electroless metal plating. Since the thin metal layer of the electrical circuit connection part is provided on the adhesive layer printed on the insulating substrate, the plating resist formed on this thin metal layer does not need to be applied to the recessed parts, and is applied to the adhesive layer. It is possible to apply a plating resist in an accurate pattern, and there is no fear that the plating resist will be electroplated in areas other than the required areas due to inaccurate printing. In addition, since the plating resist only needs to be provided on the thin metal layer of the electrical circuit connection, the amount of plating resist that needs to be removed after electroplating can be reduced, reducing material costs and removing the plating resist. This can reduce the problem of pollution when discharging resist.

Next, the present invention will be specifically explained using examples.

<Example> Using a paper epoxy general-purpose board as an insulating board,
Adhesive was printed by screen printing on the surface of this insulating substrate, on the parts that would become the electric circuit parts and the electric circuit connection parts. This adhesive consists of 25 c.c. of ethylene glycol and 1 part of silver nitrate.
0.02 to 0.1 cc of glyoxal was added dropwise to a solution consisting of glyoxal, and then irradiated with ultraviolet rays to generate silver colloid, which becomes the catalyst nucleus. It was obtained by adding 1 c.c. and thoroughly kneading it.

Next, the adhesive was semi-cured. This semi-curing can be carried out either by heat treatment at 70°C for 1 to 5 minutes (preferably 1 to 3 minutes) or by leaving it at 25°C to 30°C for 1 hour. Ta.

Next, the insulating substrate was immersed in an electroless copper plating bath for 30 to 60 minutes to form a thin metal layer of copper on the electrical circuit portions and electrical circuit connection portions of the insulating substrate. The composition of the electroless copper plating bath is as follows.

CuSO ₄・5H ₂ O 10g / Nicl ₂・6H ₂ O 2 〃 NaOH 10g / 37% formalin K・Na (C ₄ H ₄ O ₆ )・H ₂ O 30 〃 Na ₂ CO ₃ 20 〃 Water 1 Electroless copper After plating, apply etch resist UR-450B (Tamura Kaken
Co., Ltd.) and cured by UV irradiation to form a plating resist.

Next, this is immersed in a plating bath and electrolytic copper plating is performed. Electrolytic copper plating can be applied to both insulating substrates and copper plates.
By passing a direct current of 5 V from 1 to 3 A/dm ² onto the thin metal layer of the insulating substrate, an electrical circuit layer is formed by copper plating on the thin metal layer of the electrical circuit section. The composition of the copper plating bath is as follows.

CuSO ₄ .5H ₂ O 250g/H ₂ SO ₄ 60 After electrolytic copper plating is completed, the plating resist on the electrical circuit connection part is dissolved and removed with a 5% NaOH solution.

Next, the thin metal layer on the electrical circuit connection part is removed by soft etching by treatment with a 5-20% sulfuric acid solution (10% sulfuric acid solution is particularly good) for 3 minutes, and then heated to 130°C using a flat plate press or heating roll. By performing the treatment for 15 minutes, the adhesive is completely cured, and a printed wiring board on which a circuit layer is formed is obtained.

[Brief explanation of drawings]

Figures 1a to 1f are cross-sectional views showing the conventional manufacturing method;
FIGS. 2a to 2f are cross-sectional views showing one embodiment of the manufacturing method of the present invention, and FIG. 3 is a front view showing a pattern of the electric circuit portion and the electric circuit connection portion same as above. 1 is an insulating substrate, 2 is an electric circuit section, 3 is an electric circuit connection section,
4 is an adhesive, 5 is a thin metal layer, 6 is a plating resist, and 7 is an electric circuit layer.

Claims (1)

[Claims] 1. A step of printing an adhesive containing catalyst nuclei for electroless metal plating on an insulating substrate on a portion that will become an electric circuit section and an electric circuit connecting section that connects the electric circuit sections, and a step of semi-curing the adhesive, A process of electroless metal plating a thin metal layer on this semi-cured adhesive,
a step of printing a plating resist on the thin metal layer on the electric circuit connection section; a step of electroplating the electric circuit layer on the thin metal layer on the electric circuit section by applying electricity to the thin metal layer; and a step of electroplating the electric circuit layer on the thin metal layer on the electric circuit connection section. The process of removing the plating resist and etching away the thin metal layer on the electrical circuit connection part, and forming a thin metal layer of electroless metal plating on the semi-cured adhesive as described above, and then completely curing the adhesive. A method for manufacturing a printed wiring board, comprising the steps of: