JPH05145221A - Manufacture of printed circuit board - Google Patents

Abstract

PURPOSE:To eliminate pits of a printed circuit board by applying silane-coupling agent to a plating resist layer to be copper-plated so that the resist surface may become hydrophilic to prevent bubbles from attaching. CONSTITUTION:Through holes 3 are opened in a glass-epoxy board 1 having copper foil on each side. After the whole surface is activated, electroless plating 4 is formed. Plating resist is applied in a circuit pattern on the board surface. After degreased and soft-etched, the board is immersed in an aqueous solution of a silane-coupling agent expressed by NH2C2H4NHC3H6Si(OCH3)3 to form a silane-coupling layer on the surface of the board. Copper plating 7 is applied to the board where the resist does not exist. After solder plating 8 is applied to the copper plating, the plating resist is removed, and then excess copper plating is removed using aqueous ammonium chloride.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a printed wiring board.

[0002]

2. Description of the Related Art As a method of manufacturing a printed wiring board, there is a pattern plating method. The method for producing a printed wiring board by the pattern plating method will be described below. First, through holes are formed in a glass epoxy substrate having copper foil adhered to both front and back surfaces. Next, after activating the entire surface of the substrate, electroless copper plating is performed to form an electroless copper plated film. Next, attach a dry film on the entire surface of the substrate and expose it in a circuit diagram.
Development is performed to form a plating resist, and an electrolytic copper plating film is formed by the electrolytic copper plating method. Next, after forming an electric solder plating film on the electric copper plating film by an electric solder plating method, the dry film is peeled and removed, and then unnecessary copper foil is etched and removed to manufacture a printed wiring board.

In this method, the electrolytic copper plating film forming step is a degreasing step, a soft etching step of the electroless copper plating film,
An electrolytic copper plating is performed after a surface treatment of an electroless copper plating film which is a base material to be plated of the electrolytic copper plating film, which is composed of an acid washing step and electrolytic copper plating.

[0004]

When the printed wiring board is manufactured by the pattern plating method as described above, the purpose is to stir the electroplating solution and prevent the decomposition of additives such as a brightener during electroplating. Bubbles generated by aeration and foaming of the surfactant contained as an additive adhere to the plating resist (dry film), hinder the growth of the electroplated film, and cause pit defects that reduce the electroplated film thickness. There is.

The mechanism of pit generation will be described below with reference to FIGS. 8 to 11. 8 to 11 are sectional views showing generation of pits in stages.

As shown in FIG. 8, a plating resist 12 is formed in a circuit diagram shape on a printed wiring board in which an electroless copper plating film 11 is formed on the surface of a glass epoxy material 9 on which a copper foil 10 is spread, and an electrolytic copper plating solution is formed. When the plating resist 12 is dipped in
Due to its low wettability, bubbles 13 adhere to the surface of the plating resist 12 and the cross section of the plating resist 12 as shown in FIG. When the electroplating is performed in the state where the bubbles 13 are adhered in this way, the deposition of the electrolytic copper plating 14 is inhibited at the portion where the bubbles 13 are adhered as shown in FIG. You can This is a defect in the pit 15 and is a cause of poor performance in the printed wiring board such as disconnection due to reduction in film thickness.

[0007]

In order to solve this problem, a method for manufacturing a printed wiring board of the present invention is a pattern plating method, in which at least the plating resist is formed after the step of forming the plating resist layer and before the electrolytic copper plating step. It is characterized in that the surface of the layer is treated with a silane coupling agent having a hydrophilicity with a functional group bonded to the functional group present on the surface of the plating resist.

[0008]

According to the present invention, the surface of the plating resist is hydrophilized by the treatment with the silane coupling agent before the electrolytic copper plating to eliminate the adherence of bubbles, and the growth inhibition of the electroplated film is eliminated to eliminate the pit defect. be able to.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A method of manufacturing a printed wiring board according to an embodiment of the present invention will be described below with reference to the drawings of FIGS.

(Embodiment 1) FIGS. 1 to 7 are sectional views showing a method of manufacturing a printed wiring board in an embodiment of the present invention.

First, as shown in FIG. 1, through holes 3 are formed in a glass epoxy substrate 1 in which copper foils 2 are attached to both front and back surfaces, and then an activation treatment is applied to the entire surface of the substrate as shown in FIG. An activation layer made of palladium is formed, and then electroless copper plating is performed under the conditions shown in (Table 1) below to form an electroless copper plating film 4 having a thickness of 1 μm. Next, as shown in FIG. 3, a dry film is attached to the entire surface of the substrate and exposed and developed in a circuit diagram shape to form a plating resist layer 5 having a circuit diagram shape.

After degreasing and soft etching,
A silane coupling agent represented by NH ₂ C ₂ H ₄ NHC ₃ H ₆ Si (OCH ₃ ) ₃ (KBM-603 manufactured by Shin-Etsu Chemical) was immersed in an aqueous solution in which water was dissolved at a ratio of 1:99 for 1 minute. A silane coupling agent layer 6 is formed on the surface of the substrate as shown in FIG. Then, as shown in FIG. 5, electrolytic copper plating is performed under the conditions shown in (Table 2) to form an electrolytic copper plating film 7 of 30 μm in a portion where the plating resist is not formed. Next, as shown in FIG. 6, after forming a solder plating film 8 on the electrolytic copper plating film 7, the plating resist 5 is removed, and unnecessary copper is removed by using an ammonium chloride aqueous solution.
A printed wiring board as shown in was obtained.

As a result of inspecting the pit generation rate of the printed wiring board thus produced, no pit was generated. Also, in this experiment, the same experiment was conducted by the process except the treatment with the silane coupling agent.
% Pit has occurred. In addition, the electro-copper plated film obtained from the process treated with the silane coupling agent was superior in ductility to the electro-copper plated film obtained from the process excluding the treatment with the silane coupling agent.

The electrolytic copper plating film obtained from the process in which the treatment with the silane coupling agent was carried out, was subjected to a plasma emission spectroscopic analysis for composition analysis and found to be 1 to 5 pp.
m of silicon was detected, and no silicon was detected in the electrolytic copper-plated film obtained from the process except the treatment with the silane coupling agent.

[0015]

[Table 1]

[0016]

[Table 2]

Example 2 Next, a silane coupling agent was added to NH ₂ C ₂ H _{4 in the same} manner as in the process shown in Example 1.
NHC ₃ H ₆ Si (OC ₂ H ₅ ) ₃ , NH ₂ C ₂ H ₄ NHC ₃ H ₆
SiCH ₃ (OCH ₃ ) ₂ , NH ₂ C ₃ H ₆ Si (OC ₂ H ₅ )
₃ , NH ₂ C ₃ H ₆ Si (OCH ₃ ) ₃ , NH ₂ CONHC ₃ H
_A printed wiring board was manufactured using ₆ Si (OC ₂ H ₅ ) ₃ . In any case, no pit was generated.

(Example 3) Next, the pH of the silane coupling agent aqueous solution was adjusted to a value between 1 and 13, and an experiment was conducted by the process shown in Example 1. As a result, no pits were generated at pH 3 or above. 20% pits were observed at pH 2 and 35% at pH 1.

Example 4 Next, when performing electrolytic copper plating under the conditions shown in (Table 2), NH ₂ C ₂ H ₄ NHC ₃ H ₆ Si (O
CH ₃ ) ₃ (KBM-603 manufactured by Shin-Etsu Chemical Co., Ltd.) was used as a silane coupling agent at 1 ppm, 10 ppm, 100 p.
pm, add 1000ppm, 10000ppm, 30
As a result of forming a plated film having a thickness of μm and measuring ductility, the ductility of the added film was improved as compared with the non-added film. When the composition was examined by plasma emission spectroscopic analysis, the composition containing the silane coupling agent was 1 to 10 p depending on the addition amount.
Silicon of pm was detected, and no silicon was detected from the undoped film.

(Example 5) Next, when the printed wiring board prepared by the process shown in Example 1 was heat-treated at 100 ° C for 5 minutes in the atmosphere, the adhesion strength between the electroless plating film and the electrolytic copper plating film was It was improved by 20% as compared with the printed wiring board prepared by the process without adding the silane coupling agent. Also, when a silane coupling agent was added to the electroplating solution, the adhesion strength was similarly improved. Regarding the heat treatment temperature, as a result of experiments, the upper limit is 80 ° C. or higher, and the upper limit is determined by the heat resistant temperature of the substrate material.

The improvement of the wettability of the surface of the plating resist in this example due to the hydrophilicity was examined by the contact angle of the plating resist surface to the electroplating solution. As a result, the average value of the untreated silane coupling agent was 47 degrees. The contact angle which was the value of was reduced to a value of 24 degrees by the treatment with the silane coupling agent, and it was confirmed that the wettability was improved. In addition, as a result of observing the surface of the printed wiring board before electrolytic copper plating in a 10 × 20 × 20 cm plating tank made of a transparent acrylic resin, it was found that the treatment with the silane coupling agent showed no air bubble adhesion. On the other hand, in the untreated one, bubbles were observed to be attached to the entire area of the plating resist and the cross section of the plating resist. As a result of electroplating after observation, pits were formed on those with air bubbles, and no pits were observed on those without air bubbles.Thus, the wettability of the plating resist by the treatment with a silane coupling agent was confirmed. The prevention of air bubbles accompanying the improvement suppresses the generation of pits.

[0022]

As described above, according to the present invention, in the pattern plating method, after the step of forming the plating resist layer and before the electrolytic copper plating step, at least the plating resist layer surface is treated with a functional group existing on the plating resist surface. By treating with a silane coupling agent having a functional group to be bonded and a hydrophilic functional group, the surface of the plating resist can be made hydrophilic and the wettability can be improved, which prevents the adhesion of bubbles and suppresses the formation of pits. is there.

[Brief description of drawings]

FIG. 1 is a sectional view for explaining a process of a method for manufacturing a printed wiring board according to a first embodiment of the present invention.

FIG. 2 is a cross-sectional view for explaining the steps of the method for manufacturing a printed wiring board according to the first embodiment of the present invention.

FIG. 3 is a cross-sectional view for explaining the steps of the method for manufacturing a printed wiring board according to the first embodiment of the present invention.

FIG. 4 is a cross-sectional view for explaining the steps of the method for manufacturing a printed wiring board according to the first embodiment of the present invention.

FIG. 5 is a cross-sectional view for explaining the steps of the method for manufacturing a printed wiring board according to the first embodiment of the present invention.

FIG. 6 is a cross-sectional view for explaining the steps of the method for manufacturing a printed wiring board according to the first embodiment of the present invention.

FIG. 7 is a cross-sectional view for explaining the steps of the method for manufacturing a printed wiring board according to the first embodiment of the present invention.

FIG. 8 is a sectional view of a conventional printed wiring board.

FIG. 9 is a sectional view of a conventional printed wiring board.

FIG. 10 is a sectional view of a conventional printed wiring board.

FIG. 11 is a sectional view of a conventional printed wiring board.

[Explanation of symbols]

 1 Glass Epoxy Substrate 2 Copper Foil 3 Through Hole 4 Electroless Copper Plating Film 5 Plating Resist Layer 6 Silane Coupling Agent Layer 7 Copper Electroplating Film 8 Solder Plating Film

 ─────────────────────────────────────────────────── ─── Continued front page (72) Inventor Junji Mizukoshi 1006, Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd.

Claims (5)

[Claims] 1. In pattern plating, after the step of forming a plating resist layer and before the electrolytic copper plating step, at least the surface of the plating resist layer has a hydrophilicity with a functional group that bonds with a functional group present on the surface of the plating resist. A method for producing a printed wiring board, which comprises treating with a silane coupling agent having a functional group. 2. A silane coupling agent is NH₂C₂H_FourNH
C₃H₆Si (OCH₃) ₃, NH₂C₂H_FourNHC₃H₆Si
(OC₂H_Five)₃, NH₂C₂H_FourNHC₃H₆SiCH ₃(O
CH₃)₂, NH₂C₃H₆Si (OC₂H_Five)₃, NH₂C₃H
₆Si (OCH₃)₃, NH₂CONHC₃H₆Si (OC₂
H_Five)₃The printing according to claim 1, which is represented by at least one of
Wiring board manufacturing method. 3. The method for producing a printed wiring board according to claim 1, wherein the silane coupling agent is used at a pH of 3 or higher. 4. A method for producing a printed wiring board, which comprises plating with an electrolytic copper plating solution containing a silane coupling agent. 5. A method for producing a printed wiring board, which comprises heat-treating in air or in a reducing atmosphere after forming an electroless or electrolytic copper-plated film containing silicon in the film.