JPH0317239B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to a method for manufacturing a printed wiring board by an additive method. (Prior art) Conventionally, when manufacturing a printed wiring board by forming a circuit by electroless plating using an additive method such as the CC-4 method, an adhesive containing a plating catalyst is applied to the surface of an insulating substrate in advance. There are layers. In this case, if the insulating substrate has holes for through holes, after the holes are formed and before electroless plating, a plating catalyst is applied to the holes. ing. (Problems to be Solved by the Invention) By the way, in order to improve the adhesion between the adhesive layer and the plating circuit formed by electroless plating, after a plating catalyst is attached to the holes,
The adhesive layer is roughened. The adhesive layer is roughened by dipping the insulating substrate in a roughening solution such as a borofluoric acid solution or an anhydrous chromic acid/sulfuric acid solution. Most of the catalyst is washed away. Therefore, even if electroless plating is performed later, it takes time for the plating to precipitate at the hole locations, and the deposited plating film is thin and has low peel strength. Therefore, when applying solder to lands or connecting electronic components using the solder dip method, gas in the insulating substrate peels off the plating film on the hole wall and is released, filling the hole and causing solder to fill the hole. It is pushed out from inside and covers only the surface of the entrance (hereinafter referred to as a blowhole). In such a state, there are disadvantages in that connection failures of electronic components are likely to occur and adhesive strength is also likely to decrease. In order to improve such drawbacks, a step of applying a plating catalyst after roughening the adhesive layer and further forming a plating resist layer is sometimes performed.
There was a drawback that the insulation resistance decreased because the plating catalyst remained between the adhesive layer and the plating resist layer. Another method is to roughen the adhesive layer after forming the plating resist layer and then attach a plating catalyst. However, the plating catalyst also adheres to the surface of the plating resist layer, which causes electroless When the plating treatment is performed, plating precipitates on the surface of the plating resist layer, resulting in a drawback that short-circuiting defects are likely to occur. (Objective) The present invention improves the above-mentioned drawbacks, facilitates plating deposition in through-hole holes, shortens manufacturing time, prevents blowholes, and provides high reliability with good insulation properties. The object of the present invention is to provide a method for manufacturing a printed wiring board. (Means for Solving the Problems) In order to achieve the above object, the present invention applies a plating catalyst-containing adhesive to the surface of an insulating substrate, then forms holes for through holes, and electrolessly A method for manufacturing a printed wiring board on which a predetermined circuit can be formed by a plating method includes a step of applying a low-viscosity emulsion-type thermosetting resin to the wall surface of the hole to form a thermosetting resin layer; Provided is a method for manufacturing a printed wiring board, which comprises: applying a plating catalyst after the process; roughening the adhesive after the process; and providing a plating resist layer after the process. It is something. (Function) That is, in the present invention, a thermosetting resin layer is provided in advance on the wall surface of a through hole provided in an insulating substrate, and a plating catalyst is attached to this.
The adhesion of the plating catalyst is strong, and its effect is particularly remarkable when the plating catalyst is attached to the thermosetting resin layer in an uncured state. Therefore, even if the insulating substrate is subsequently immersed in a roughening liquid, the hardening catalyst attached to the thermosetting resin layer is hardly peeled off. Therefore, by performing the electroless plating process, a sufficient thickness of plating is deposited on the hole wall in a short time to form a plating layer. Moreover, since the thermosetting resin layer can prevent the gas in the insulating substrate from being released through the hole walls, the drawbacks of blow holes caused by solder plating or the like can be prevented. Further, since the plating catalyst adhering to the adhesive surface is removed by the roughening process, the insulation resistance is maintained at a sufficiently high value even if a plating resist layer is provided. (Example) First, as shown in FIG. 1, an insulating substrate 1 made of a paper-phenol resin base material or a paper-epoxy resin base material is prepared.
An adhesive containing a plating catalyst such as palladium is applied to the adhesive layer 2 to form an adhesive layer 2. Next, as shown in FIG. 2, holes 3 for predetermined through holes are formed by punching the insulating substrate 1 on which the adhesive layer 2 is formed. After forming the holes 3, the surface of the insulating substrate 1 is leveled and washed with high-pressure water to remove substrate debris caused by punching.
The insulating substrate 1 after washing with water is immersed in a thermosetting resin emulsion to form a thermosetting resin layer 4 with a thickness of about 2 to 10 μm on the inner peripheral surface of the hole 3, as shown in FIG. establish. As the thermosetting resin, epoxy resin, urethane resin, polyester resin, etc. are used, but when the insulating substrate 1 is made of phenol resin or epoxy resin, epoxy resin is preferred because of its good adhesion to the substrate. In addition, as the curing agent, an amine type curing agent is preferable because a stable emulsion can be obtained, and its concentration is 0.3
Particularly preferred is a range of ~5wt%. In other words, if the concentration is less than 0.3wt%, the curing effect as a curing agent will be low and the resin will be difficult to cure, and if the concentration is less than 5wt%
If the amount is larger than this, the resin may cover the hole 3 so as to block it, which requires removal work, which is not preferable in terms of work. After the insulating substrate 1 is immersed in the emulsion, the emulsion on the surface is removed by a squeezing roller, and then dried in a high-temperature atmosphere to semi-cure the thermosetting resin layer provided on the inner peripheral surface of the hole 3. do. After providing a thermosetting resin layer 4 on the wall of the hole 3, the insulating substrate 1 is immersed in a plating catalyst solution to adhere a plating catalyst 5 as shown in FIG. Layer 4 is heated and cured. After curing the thermosetting resin layer 4, the insulating substrate 1 is immersed in a roughening solution consisting of a borofluoric acid solution or an anhydrous chromic acid/sulfuric acid solution to roughen the adhesive layer 2, as shown in FIG. become After roughening the adhesive layer 2, a plating resist ink is applied to the surface of the adhesive layer 2 in a predetermined pattern and dried to form a plating resist layer 6 as shown in FIG. After forming the plating resist layer 6, the insulating substrate 1 is immersed in an electroless copper plating solution to deposit plating in a predetermined pattern to form a circuit 7 as shown in FIG. After forming the circuit 7, the insulating substrate 1 is processed in a conventional manner to produce a printed wiring board. Next, regarding the present invention and the conventional example, we measured the plating adhesion inside the through-hole, the blowhole occurrence rate, the moisture absorption insulation property, and the plating precipitation on the surface of the plating resist layer, and the results are shown in the table. was gotten.

[Table] The adhesion of plating inside the hole for through-holes is determined by the time it takes for plating to deposit on the entire surface of the inner wall of the hole, the blowhole occurrence rate is determined by the soldering conditions at 240℃ for 5 seconds, and the moisture absorption insulation at 40℃. The insulation resistance was measured after being left in an atmosphere of 90% RH for 7 days, and the plating precipitation on the surface of the plating resist layer was visually observed. The manufacturing conditions are as follows. Examples of the present invention are as follows: (a) Insulating substrate: An epoxy resin laminate plate coated with a plating catalyst-containing adhesive (HA-04 manufactured by Hitachi Chemical Co., Ltd.) and cured. (b) Thermosetting resin layer forming process: Epoxy resin emulsion (Epolsion EA manufactured by Kanebo NSC)
Add hardening agent EB-1 to 100 parts by weight of solid content of -1.
The adhesive layer was diluted to a concentration of 1% by adding 80 parts by weight), the emulsion on the surface of the adhesive layer was removed with a buff, and the adhesive layer was heated for 10 seconds at a temperature of 100°C. (c) Plating catalyst deposition step: A plating catalyst (HS-101B manufactured by Hitachi Chemical Co., Ltd.) is applied and heated at a temperature of 150°C for 30 minutes. (d) Roughening step: The surface of the adhesive layer is roughened using a borofluoric acid-based roughening solution, washed, and dried. (e) Plating resist step: Plating resist ink (HGM-02BK-1 manufactured by Hitachi Chemical Co., Ltd.) is screen printed and cured by heating at a temperature of 160° C. for 30 minutes. (f) Electroless plating process: A 30μ thick copper layer is formed by normal electroless plating process (CC-4 plating process). In the conventional example (1), the thermosetting resin forming step (b) is omitted in the embodiment of the present invention, and in the conventional example (2), the degree of roughening in (b) is reduced in the conventional example (1). (c) Prior to the plating catalyst adhesion process, the conventional example
In (3), in conventional example (1), the roughening step (b) was performed after the plating resist step (e). In other words, according to the present invention, the plating adhesion is less than half that of the conventional example, and the plating deposition rate is 2 times lower.
The blowhole generation rate was more than double that, the blowhole occurrence rate was less than 40%, and the moisture absorption and insulation properties were sufficiently high for practical use, and almost no plating was deposited on the surface of the plating resist layer, preventing short circuit failures. Ru. (Effects) As described above, according to the manufacturing method of the present invention, plating can be quickly deposited on the wall surface of a through-hole, reducing manufacturing time, reducing the incidence of blowholes, providing high insulation resistance, and providing reliability. A printed wiring board with high properties can be obtained. Furthermore, according to the manufacturing method of the present invention, since the step of attaching the plating catalyst is performed before the step of providing the plating resist layer, the surface of the plating resist layer is coated during the electroless plating process. Plating only occurs when conductive dust adheres to the plating resist layer and becomes a nucleus. Therefore, plating does not precipitate on the plating resist layer and short circuit failures occur. A printed wiring board that can prevent this can be obtained. Furthermore, according to the manufacturing method of the present invention, a low viscosity emulsion type thermosetting resin is applied to the wall surface of the hole to form a thermosetting resin, so compared to ordinary adhesives, the Never get bored,
A printed wiring board that can form a thermosetting resin layer of a predetermined thickness, easily prevents blowholes, and is easy to manufacture can be obtained.

[Brief explanation of the drawing]

1 to 7 show the manufacturing process of the present invention, and FIG. 1 is a cross-sectional view of an insulating substrate provided with an adhesive layer, and FIG.
Figure 3 is a sectional view of an insulating substrate with holes formed therein, Figure 3 is a sectional view of an insulating substrate provided with a thermosetting resin layer, Figure 4 is a sectional view of an insulating substrate with a plating catalyst attached, and Figure 5 is a sectional view of an insulating substrate with a plating catalyst attached.
The figure is a cross-sectional view of an insulating substrate with a roughened adhesive layer.
The figure shows a sectional view of an insulating substrate provided with a plating resist layer, and FIG. 7 shows a sectional view of an insulating substrate on which a circuit is formed. 1... Insulating substrate, 2... Adhesive layer, 3... Hole,
4...Thermosetting resin layer, 5...Plating catalyst, 6...
...Plated resist layer, 7...Circuit.

Claims (1)

[Claims] 1. Manufacture of a printed wiring board in which a plating catalyst-containing adhesive is applied to the surface of an insulating substrate, holes for through holes are then formed, and a predetermined circuit can be formed by electroless plating. The method includes a step of applying a low-viscosity emulsion-type thermosetting resin to the wall surface of the hole to form a thermosetting resin layer, a step of attaching a plating catalyst after this step, and a step of applying an adhesive after this step. 1. A method for manufacturing a printed wiring board, comprising: a step of roughening the substrate; and a step of providing a plating resist layer after the step. 2. Claim 1, characterized in that the plating catalyst is attached to the thermosetting resin layer in an uncured state.
A method for manufacturing a printed wiring board as described in Section 1.