JPS6138637B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for manufacturing a printed circuit board in which metal is deposited by electroless plating only on the portions of an insulating substrate that will become conductor circuits, and particularly relates to a method for manufacturing a printed circuit board in which blistering does not occur in the metal deposited on the conductor circuits. . In recent years, full additive methods have been gaining popularity, in which conductor circuits are formed by depositing metal on necessary parts of an insulating substrate using only electroless plating. Full additive methods are gaining popularity.
The feature of the fully additive method is that it has excellent workability and can be mass-produced. Examples of methods for manufacturing printed circuit boards using the full additive method are shown in (1) to (7). (1) Form a phenolic resin-rubber adhesive layer on the surface on which the conductor circuit will be formed on the insulating substrate (after drilling holes as necessary) (2) Titanium, It is masked with a thermosetting resin containing an oxide solid solution of three metals, nickel and antimony, to form a plating resist for electroless plating, and then (3) a roughening liquid containing chromium (hexavalent) and the above substrate is applied. (4) A catalyst for starting electroless plating, such as palladium, gold, platinum, etc. activating the substrate by contacting the substrate with a catalyst solution containing a salt of
After that, (5) the substrate is brought into contact with an alkaline solution or an acidic solution, and (6) the catalyst on the plating resist is selectively removed by bringing the substrate into contact with a treatment solution containing a combination of hydrochloric acid and ammonium monopersulfate. Finally, (7) immerse it in an electroless plating solution to deposit metal only on the parts that will become conductive circuits. A printed circuit board can be manufactured by the methods (1) to (7) above. However, minute bulges may occur in some parts of the metal deposited on the conductor circuit portion. If such blisters occur, the yield will decrease, which is not preferable. SUMMARY OF THE INVENTION An object of the present invention is to eliminate the above-mentioned drawbacks of the prior art and to provide an improved method of manufacturing a printed circuit board in which micro-bulges do not occur in a portion of the conductive circuit. The feature of the present invention is that in the printed circuit board manufacturing method according to the conventional methods (1) to (7) described above,
After step (3), it is treated with an alkaline solution. This alkali treatment eliminates minute blisters because the roughened residue of the adhesive is removed, and if plating is deposited thereon, the adhesion to the plating is improved. Next, the present invention will be specifically explained. Insulating substrates that can be used in the present invention include, for example, paper phenol laminates,
There are various known substrates such as paper epoxy laminates, glass epoxy laminates, and ceramic boards. Further, the adhesive used to strongly adhere the electroless plated film to the base layer usually contains rubber or phenol resin. Here, suitable rubbers are selected from nitrile rubber, butadiene rubber, nitrile-butadiene copolymer rubber, isoprene rubber, chloroprene rubber, and the like. Next, as a resist ink for electroless plating that masks areas other than those that will become conductor circuits, a solid solution of oxides of three metals, titanium, nickel, and antimony, can be used to sufficiently prevent plating on the ink during electroless plating. and epoxy resin are preferred. Details on this point are given in Tokusho No. 52-65797. In addition, methods for selectively roughening the exposed adhesive surface include chromic acid-sulfuric acid mixture, dichromic acid-sulfuric acid mixture, chromic acid-fluoric acid mixture, dichromic acid-fluoric acid mixture, chromic acid-sulfuric acid mixture, -Chemical roughening methods such as boric acid mixture and dichromic acid-boric acid mixture are suitable. Next, regarding the alkaline aqueous solution used for the alkali treatment, which is a feature of the present invention, alkalis applicable for this purpose include sodium hydroxide, potassium hydroxide, lithium hydroxide, ammonium hydroxide, sodium carbonate, triethylamine, There are various amines such as diethyl monoethanolamine, monoethyl diethanolamine, and triethanolamine. However, from the viewpoint of handling and economy, sodium hydroxide and potassium hydroxide are preferred. In addition, the alkaline solution must have a pH of 12 or higher,
If it is less than that, the object of the present invention cannot be fully achieved. Furthermore, the treatment time with the alkaline solution is required to be at least 2 minutes, and if it is shorter than that, minute blisters may still occur. Room temperature is usually sufficient for the alkali treatment, and no particular temperature control is required. As the activation liquid containing a catalyst for starting electroless plating, a commonly used solution containing a noble metal salt can be used. For example, there is an activation liquid whose main components are palladium chloride, stannous chloride, and hydrochloric acid. Next, alkali or acid treatment is performed after activation treatment, and acid treatment is more effective in the present invention. In other words, in the case of alkaline treatment,
It is easy to create areas where important metals are difficult to deposit in the conductor circuit forming area. Oxidation after activation treatment includes hydrochloric acid, sulfuric acid, oxalic acid, tartaric acid, citric acid,
Those containing malic acid are preferred. In addition, it is also possible to apply a combination of the various acids mentioned above, and in particular, a combination of hydrochloric acid and an organic acid,
Effective for uniform metal deposition on conductor circuit formation areas during electroless plating. Furthermore, ammonium persulfate is a treatment liquid that selectively removes only the catalyst on the plating resist and leaves the catalyst only on the exposed adhesive surface and inside the holes, and is described in Japanese Patent Application No. 52-25975. It has been done. Ammonium persulfate can be used in the present invention, but from the viewpoint of workability, ferric chloride or cupric chloride, as well as their ferric chloride
It has been found that a solution containing iron, cupric chloride and hydrochloric acid is effective. Next, regarding electroless plating for forming a conductor circuit, electroless copper plating and electroless nickel plating can be applied. Electroless copper plating is preferred due to the electrical conductivity and mechanical properties of the deposited metal. An ordinary electroless copper plating solution containing copper salt, complexing agent, reducing agent, and PH adjuster as main components can be used. Next, the present invention will be described in more detail with reference to Examples. Example 1 Paper phenol laminate (LP made by Hitachi Chemical Co., Ltd.)
43N) was coated with a phenolic resin-modified nitrile rubber adhesive (NB manufactured by Cel Chirny Japan Co., Ltd.).
3033) An adhesive containing 2 parts of calcium carbonate as a filler per 100 parts was applied by curtain coating and cured by heating at 160°C for 80 minutes. next,
An electroless plating resist ink having the following composition (A) was applied to the entire surface of the other surface of the laminate to which no adhesive was applied. Composition (A) Epoxy resin: Epicoat 1007 (manufactured by Ciel Chemical Co., Ltd.) 65 parts 〃: Epicoat 828 (manufactured by Ciel Chemical Co., Ltd.) 35 parts Polyvinyl butyral resin Eslec BL-
2 (manufactured by Sekisui Chemical Co., Ltd.): 2.5 parts Filler: Silicon oxide 2 parts 〃 : Zirconium silicate 4 parts Oxide solid solution: TiO ₂ - NiO - Sb ₂ O ₅ (manufactured by Ishihara Sangyo Co., Ltd.) 20 parts Pigment: Phthalocyanine green 2 parts Curing agent: dicyandiamide 5 parts 〃 : N ₁ N,N' ₁ N'-Tetramethylbutanediamine 1.1 parts Solvent: Butyl carbitol 40 parts 〃 : Methyl cellosolve Amount to achieve a viscosity of 200 poise at 20°C Next, The ink of composition (A) was cured by heating at 130°C for 60 minutes. Next, holes were made in the necessary locations, and the area on the surface on which the adhesive layer was provided, other than the part that would become the circuit, was masked with ink of composition A above. The mask was made by silkscreen printing, and the ink was cured by heating at 160°C for 60 minutes. Next, anhydrous chromium-sulfuric acid mixture (CrO ₃ 60
g, 220 ml of concentrated sulfuric acid diluted with water to a total volume of 1) at 45°C for 5 minutes to selectively roughen the exposed adhesive surface. Next, it was washed with water at room temperature for 5 minutes and immersed in an aqueous hydrochloric acid solution (3.6% HC) for 5 minutes to remove residual chromium. After washing with water for 2 minutes, it was immersed in an aqueous sodium hydroxide solution (PH 13.0) for 10 minutes at room temperature to perform alkali treatment. Continuing, 2
After washing with water for 1 minute and immersing in 18% hydrochloric acid aqueous solution for 1 minute, activating solution containing palladium chloride, stannous chloride and hydrochloric acid (sensitizer manufactured by Hitachi Chemical Co., Ltd.)
HS101B) for 10 minutes at room temperature.
After washing with water for 2 minutes at room temperature, it was immersed in a solution containing hydrochloric acid and oxalic acid (100 ml of 36% HC, 10 g of oxalic acid diluted with water to make a total of 1) for 5 minutes at room temperature, and then washed with water for 2 minutes at room temperature. . Continuing,
Liquid containing ferric chloride and hydrochloric acid (FeC _{3.6H 2} O0.1
The catalyst on the ink was selectively removed by immersing the ink in a solution (100 ml of 36% HC diluted with water to give a total composition of 1) at room temperature for 20 minutes. Next, after washing with water for 2 minutes at room temperature, the following composition (B)
Electroless copper plating solution was immersed at 72°C for 8 hours, and electroless copper was applied only to the exposed adhesive surface and holes.
We grew it to a thickness of 28 μm and completed 25 single-sided through-hole printed circuit boards with a 10 cm square piece size. The results are shown in Table 1. Composition (B) Copper sulfate: 10g Ethylenediaminetetraacetic acid: 30g 37% formalin: 4m Polyethylene glycol (average molecular weight 600)
20g 2,2' dipyridyl: 30mmg Sodium hydroxide: Amount to make PH12.8 (at 20℃) Water: Amount to make the whole 1

[Table] Examples 2 to 19 Twenty-five 10 cm square piece-sized printed circuit boards were completed in the same manner as in Example 1, except that the alkali treatment conditions were changed as shown in Table 1. The results are shown in Table 1. Examples 20 to 29 Twenty-five 10 cm square piece-sized printed circuit boards were completed in the same manner as in Example 1, except that a liquid with the composition shown in Table 2 was used instead of the liquid containing hydrochloric acid and oxalic acid. Ta. The results are shown in Table 2.

[Table] Examples 30 to 32 25 10 cm square pieces were prepared in the same manner as in Example 1, except that a liquid with the composition shown in Table 3 was used instead of the liquid containing ferric chloride and hydrochloric acid. Finished the printed circuit board. The results are shown in Table 3.

[Table] Comparative example Example 1 except that no alkali treatment was performed
Using exactly the same method as above, we completed 25 10cm square piece-sized printed circuit boards. The results are shown in Table 3.

Claims (1)

[Claims] 1. A method for manufacturing a printed circuit board in which a circuit is formed on an insulating substrate by electroless plating, including: (a) at least rubber or phenolic resin is applied to the surface of the insulating substrate on which the conductive circuit is to be formed; The process of providing an adhesive layer that serves as the base for the electroless plating film. (b) Next, a step of applying a matte resist ink containing an oxide solid solution of three metals, titanium, nickel, and antimony, on the surface of the insulating substrate excluding the portion where the conductor circuit is to be formed. (c) A step of selectively roughening the conductive circuit forming portion where the adhesive of the insulating substrate is exposed. (d) A process of treatment with an alkaline aqueous solution with a pH of 12 or higher. (e) Further, a step of treating with an activation liquid containing an electroless plating catalyst. (f) Hydrochloric acid, sulfuric acid, oxalic acid, tartaric acid, citric acid,
A process of treating with an aqueous solution containing at least one type of malic acid. (g) The catalyst on the plating resist ink is treated with an aqueous solution containing at least one of ferric chloride and cupric chloride, or at least one of ferric chloride and cupric chloride, and hydrochloric acid. The process of removing. (h) A process of selectively forming a plating film only on the circuit forming area by electroless plating. A method for manufacturing a printed circuit board, comprising: