JPH05259611A - Production of printed wiring board - Google Patents

Abstract

PURPOSE:To provide a method of producing a printed wiring board which allows excellent efficient adhesion of a metal to a resin layer without using adhesive. CONSTITUTION:Copper foil 1 is oxidized so as to form finely shaped copper oxide 2 on the surface of the copper foil and the copper oxide on the surface of the copper foil is reduced to be metallic copper or low oxidized reduced copper 3. After overlaying the copper foil with a resin layer through the processed plane of the copper foil 1, at least the oxidized and reduced copper foil is removed from the resin board 4 in a position wherein wiring is to be formed by the method which includes etching, a wiring process including electroless plating is performed on the resin board 4 and a circuit is formed.

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 In recent years, electronic devices have become more and more demanded to be smaller, lighter and more multifunctional, and accordingly, printed wiring boards are required to have higher density and higher reliability. .. In response to such demands, the subtractive method is currently the mainstream of printed wiring boards, but it is difficult to make thin wires and small-diameter through holes with this manufacturing method, and it is sufficient for high density. There is a limit to the correspondence. On the other hand, an additive method has been proposed in which a conductive metal is plated on an insulating substrate to a desired thickness by electroless plating to form a wiring pattern. Since the additive method has good throwing power of the electroless plating on the through hole, uniform plating can be obtained even in the through hole having a high aspect ratio as compared with the subtractive method. The pattern formability is affected by the resist resolution and etching accuracy in the subtractive method, but is high in the additive method because it depends only on the resist resolution. Therefore, it is in principle suitable for manufacturing a high density wiring board having a fine pattern and a high aspect ratio.

In the production of a printed wiring board by such an additive method, the adhesion between the insulating substrate and the conductive metal formed by electroless plating is extremely important for the various characteristics of the printed wiring board. Typical methods for ensuring the adhesion between the insulating substrate and the plated metal are ABS,
By providing an adhesive layer of rubber or the like on the surface of the substrate and treating it with a chemical roughening liquid, fine irregularities are imparted to the surface of the adhesive, and the anchor effect of this roughened surface is utilized.

In addition to this, there is also a method of roughening without using an adhesive. In the method disclosed in Japanese Patent Laid-Open No. 63-168077, a fine uneven shape of copper oxide is provided on the surface of a copper foil by an oxidation treatment, and this is laminated with a prepreg to remove the copper foil and the copper oxide. This is a method of exposing the roughened surface transferred to the substrate surface.

[0005]

In the method of roughening the adhesive described above, a roughening liquid must be used. Most of the roughening liquids that can be used contain an oxidizing agent and are highly toxic. Therefore, the working environment is bad and special waste liquid treatment is required. In addition, such an adhesive that can be roughened generally has poor electrical insulation properties, and has poor moisture-resistant insulation properties and high-temperature insulation properties. In addition, because the heat resistance of the adhesive is insufficient,
In addition to a large decrease in adhesion at high temperatures, the dimensional change rate is high,
Its application was limited.

On the other hand, the method disclosed in Japanese Patent Laid-Open No. 63-168077 does not use an adhesive, but transfers the fine shape of copper oxide to roughen the surface. It is possible to eliminate the danger of handling and the deterioration of the environment due to the roughening of. However, the copper foil for transfer has a two-layer structure of metallic copper and copper oxide, and since copper oxide is insoluble or hardly soluble in an ammonium-based alkaline copper etching solution, this etching solution can remove metallic copper. Copper oxide could not be removed and remained on the surface of the substrate. In this case, copper oxide had to be removed separately. An etching system using an ammonia-based alkaline copper etching solution has high versatility in current printed wiring board manufacturing,
For these reasons, the transfer copper foil composed of two layers of metallic copper / copper oxide was not always suitable for the current system.

[0007]

The method for manufacturing a printed wiring board according to the present invention comprises the steps of oxidizing a copper foil to form copper oxide having a fine shape on the surface of the copper foil, and then subjecting it to a reduction treatment to form a copper foil surface. In the method, the copper oxide is used as metallic copper or reduced copper in a low oxidation state, and after laminating with the resin layer via the copper foil-treated surface, at least the copper foil subjected to the oxidation / reduction treatment is etched from the resin substrate at the wiring formation planned position. Then, the resin substrate is subjected to wiring processing including electroless plating to form a circuit.

There are various methods for forming copper oxide on the surface of the copper foil used in the present invention. For example, a method of treating a copper foil by immersing it in a treatment liquid containing an oxidizing agent such as sodium chlorite, sodium hypochlorite, potassium chlorate, potassium perchlorate, sodium persulfate, potassium persulfate, and ammonium persulfate. Is. As an example of the composition of the treatment liquid, NaClO ₂ : 5 to 150 g / l Na ₃ PO ₄ / 12H ₂ O: 10 to 60 g / l NaOH: 1 to 50 g / l is preferable. The treatment temperature of the treatment liquid is 50 to 95 ° C.,
The immersion time of the copper foil is 15 seconds to 5 minutes. The treatment liquid may be sprayed instead of dipping. Copper oxide can also be formed by anodic oxidation. Electrolysis with a copper foil as an anode in a basic solution containing NaOH or the like for 1 to 15 Adm ^-2 for 10 to 40 minutes is good.

The copper foil used may be another metal foil or a copper foil formed on a support of an organic film. When the support is not used, the thickness of the copper foil is not particularly limited, but it is 18 to 70 μm in terms of handling and price.
Things are good. Further, in order to enhance the adhesion between the printed wiring board produced by the method of the present invention and the plated metal,
It is preferable to roughen the surface of the copper foil in advance. The surface roughening method includes polishing, honing, etching, electroplating, electroless plating and the like. For example, a copper foil for a copper-clad laminate can be favorably used. Before the oxidation treatment, the copper foil is preferably degreased and washed or treated with an aqueous solution of hydrochloric acid or an aqueous solution of sulfuric acid so that the copper oxide is uniformly formed.

There are various methods for reducing the copper oxide formed on the surface of the copper foil to metallic copper or a low oxidation state. For example,
Treatment is performed by immersing a copper foil on which copper oxide is formed in at least one treatment liquid containing a reducing agent such as dimethylamine borane, diborane, sodium borohydride, potassium borohydride, hydrazine, formaldehyde, and active hydrogen. Is the way to do it. As an example of the composition of the treatment liquid, (CH ₃ ) ₂ NH.BH ₃ : _{2 to 20} g / l NaOH: 1 to 30 g / l is preferable. The processing conditions for the above processing liquid are temperature 10 to 80.
The immersion time of the copper foil on which copper oxide is formed at 15 ° C. is 15 seconds to 5 minutes. The treatment liquid may be sprayed instead of immersion. Further, the copper oxide can be reduced by electrolysis using a copper foil on which copper oxide is formed as a cathode or by contact with or in proximity to a metal having a lower redox potential than copper such as Al.

When a silane coupling agent is applied to a copper foil surface that has been subjected to oxidation / reduction treatment, NH ₂ C ₃ H ₆ Si (OC ₂ H ₅ ) ₃ , NH ₂ C _{2
H 4 NHC 3 H 6 Si (} OC 2 H 5) 3, HSC 3 H 6 Si (OC 2 H 5) 3, C 6 H 5 CH 2 NH 2 + C
₂ H ₄ NHC ₃ H ₆ Si (OCH ₃ ) ₃ · Cl ^{− and the} like can be used. These silane coupling agents are sold by Nippon Unicar Co., Ltd., Shin-Etsu Silicone Co., Ltd., Toshiba Silicone Co., Ltd., etc. These silane coupling agents are used by dissolving them in water, an organic solvent or a mixed solution thereof. The concentration of the silane coupling agent is usually 0.1 g / l or more, and the optimum concentration is 0.5-
A range of 50 g / l is good. The coating method includes dipping in a silane coupling agent solution or spraying the silane coupling agent solution. It is preferable to dry after applying the silane coupling agent. One example of drying conditions is a temperature of 110 ° C. and a time of 30 minutes.

The resin layer made of an insulating material to be laminated with an oxidized / reduced copper foil or, if necessary, a copper foil coated with a silane coupling agent is an ordinary copper such as epoxy, modified polyimide, polyimide or phenol. A thermosetting resin used for the stretched laminated board or a thermoplastic resin such as polyethylene, Teflon, polyether sulfone, or polyetherimide is used. These can be used as a prepreg or an adhesive film obtained by impregnating a base material such as paper or glass cloth with a resin. Alternatively, the liquid varnish may be applied to a copper foil obtained by oxidation / reduction, or a copper foil coated with a silane coupling agent if necessary, and may be dried under appropriate conditions before use.

An etching solution is used to remove the copper foil after the resin layer is laminated with the oxidized / reduced copper foil, or the copper foil coated with a silane coupling agent as required. This etching solution includes ammonium persulfate, which is generally used as an etching solution for printed wiring boards, an aqueous solution of copper chloride and hydrochloric acid, an aqueous solution of iron chloride and hydrochloric acid, and an alkaline aqueous solution mainly containing a copper ammonium complex. Can be used. It is desirable to mechanically polish the surface of the copper foil before etching.

When the silane coupling agent is applied to the resin substrate after removal of the copper foil, the same silane coupling agent as that applied to the above-mentioned oxidized / reduced copper foil can be used in the same manner. The catalyst treatment prior to electroless plating may use a palladium catalyst or the like. A catalyst-containing material may be used instead of the catalyst treatment. As the electroless plating, electroless copper plating, electroless nickel plating, or the like is used.
Electroless copper plating is generally used as a conductor of a printed wiring board. When the conductor is formed only by electroless copper plating, it is preferable to use an electroless copper plating solution for thickening, which has excellent mechanical properties of plated copper. When using electroplating together, after performing electroless plating after the above catalyst treatment,
Perform electroplating.

[0015]

The copper oxide formed on the copper foil is a fibrous to columnar or granular crystal having a size of submicron or less. When this is subjected to reduction treatment, the oxidation number of copper decreases and the physical properties change to metallic copper or a low oxidation state, but the shape of copper oxide remains almost the same, and the size on the copper foil is submicron. Copper (metal) having the following fine shape is formed. Therefore, after the copper foil subjected to the oxidation / reduction treatment and the resin layer are laminated, the unevenness of the above-described copper reduced copper oxide is transferred / formed on the surface of the resin substrate from which the copper foil has been removed. In order to secure / improve the adhesion between the electroless plating and the resin substrate, the submicron or smaller fine shape is important.

The surface of the copper foil used is preferably roughened. A suitable material is a rough surface of copper foil for copper clad laminates. The rough surface of the copper foil has a surface roughness (10-point average roughness) of about 1 to 12 μm. On this rough surface of 1-12 μm,
Further, by transferring the surface shape imparted with a fine shape of submicron or less by the above method to the organic insulating material, a resin substrate for a printed wiring board having a high adhesion with the electroless plated metal can be obtained. In this method, when the silane coupling agent is applied to the oxidized / reduced copper foil surface, or when the silane coupling agent is applied to the insulating organic material from which the oxidized / reduced copper foil after lamination is removed, The adhesion of electroless plating is significantly improved as compared with the case where no silane coupling agent is applied.

[0017]

Example 1 A copper foil NDGA-35 for copper clad laminate (Nippon Electrolytic Co., Ltd., trade name) was prepared, and the degreasing liquid neutral clean (Shipley Co., trade name) was used as a pretreatment for this copper foil. To 5
After dipping for 1 minute, washing with running water, dipping in 10 vol.% Sulfuric acid for 2 minutes, washing with running water, and then oxidation treatment under the following conditions. NaClO ₂ : 90 g / l Na ₃ PO ₄ / 12H ₂ O: 10 g / l NaOH: 15 g / l Pure water: 1 l Amount Temperature: 85 ° C Treatment time: 2 minutes After oxidation treatment, rinse with running water Then, reduction treatment was performed under the following conditions. (CH ₃ ) 2NH ・ BH ₃ : 5 g / l NaOH: 5 g / l Pure water: 1 l Amount Temperature: 50 ℃ Treatment time: 2 minutes After reduction treatment, wash with running water and then at 80 ℃ for 30 minutes Dried. Then oxidation-reduction treatment surface of the copper foil, glass cloth-based epoxy prepreg GE-67WG ₂ L (manufactured by Hitachi Chemical Co., Ltd., trade name) so as to be in contact with, glass cloth-based epoxy substrate E-67 (Hitachi The product was manufactured by Kasei Kogyo Co., Ltd. and was laminated and pressed. Laminating condition is molding pressure 30kg / c
m ² , temperature 170 ° C., time 60 minutes. Next, after making a hole with an NC drill, the copper foil was completely removed using an ammonium-based alkaline copper etching solution Alfain 9106 (manufactured by Uemura Kogyo Co., Ltd.), washed with water, and then containing palladium chloride. A palladium catalyst for initiating the electroless copper plating reaction was applied by dipping in the treatment liquid. Then, using a dry film photoresist, Fotec SR-3000-35 (manufactured by Hitachi Chemical Co., Ltd., trade name), lamination, exposure, and development are sequentially performed,
A plating resist was formed. Next, electroless copper plating was performed under the following conditions. CuSO ₄・ 5H ₂ O: 1 g / l EDTA ・ 4Na: 40 g / l 37% CH ₂ O: 3 ml / l Plating solution additive: Little pH: 12.4 Plating solution temperature: 70 ℃ Plating film thickness: 35 μm

Example 2 The copper foil used in Example 1 was pretreated in the same manner as in Example 1,
The oxidation treatment and the reduction treatment were sequentially performed. Then, this copper foil
Immerse in a 10 g / l aqueous solution of NH ₂ C ₃ H ₆ Si (OC ₂ H ₅ ) ₃ for 3 minutes,
It was dried at 110 ° C. for 30 minutes. Then, lamination, drilling, copper foil etching, palladium catalyst application, plating resist formation, and electroless copper plating were sequentially performed in the same manner as in Example 1.

Example 3 The copper foil used in Example 1 was pretreated in the same manner as in Example 1,
The oxidation treatment and the reduction treatment were sequentially performed. Then, the copper foil laminated, punched, and oxidized / reduced in the same manner as in Example 1 was dissolved and removed, and then ₃ g was added to a 5 g / l aqueous solution of NH ₂ C ₃ H ₆ Si (OC ₂ H ₅ ) 3.
It was soaked for 1 minute and dried at 110 ° C. for 30 minutes. Then, in the same manner as in Example 1, a palladium catalyst was applied, a plating resist was formed, and electroless copper plating was performed.

Comparative Example 1 Using the copper foil used in Example 1, lamination, drilling, etching of the copper foil, application of a palladium catalyst, formation of a plating resist, and electroless copper plating were carried out in the same manner as in Example 1. went.

Comparative Example 2 Acrylonitrile butadiene rubber, alkylphenol resin, epoxy resin, silica and zirconium silicate were dissolved in a mixed solvent of cellosolve acetate and methyl ethyl ketone using a kneader and a stirrer to prepare an adhesive solution having a solid content of 25%. , Glass cloth base epoxy board E-67
(Manufactured by Hitachi Chemical Co., Ltd .; trade name) The surface is dip-coated so that the thickness after drying is about 25 μm, and the temperature is 6 ° C at 170 ° C.
A substrate with an adhesive was prepared by heating and curing for 0 minutes. Example 1
After drilling by the same method as above, in order to chemically roughen this adhesive layer, chromic acid mixed acid (chromic acid: 55 g / l, sulfuric acid 300
(ml / l) at 40 ° C for 15 minutes and washed with water to neutralize.
After that, applying a palladium catalyst in the same manner as in Example 1,
Formation of a plating resist and electroless copper plating were sequentially performed.

After performing the electroless plating as described above, in order to evaluate the adhesion between the substrate and the plated film, 25 ° C.
The peel strength of the plated film was measured at 150 ° C. and 150 ° C.
Stripping width of plating film is 10mm, stripping angle is 90
The peeling speed was 50 mm / min. The results are shown in Table 1. In the case of Comparative Example 1, since the adhesion between the substrate and the plating film was insufficient, the plating metal was peeled off in the electroless copper plating solution, and the peeling strength of the plating film could not be measured. It was

From these results, the method for manufacturing a printed wiring board according to the present invention has a sufficient adhesion between the plating film and the substrate, and is different from the conventional method of providing an adhesive layer and roughening it. In comparison, it can be seen that there is little decrease in adhesion at high temperatures.

[0024]

[Table 1]

[0025]

As described above, according to the present invention, since the surface is roughened without using the adhesive, the deterioration of the characteristics caused by the adhesive and the danger of handling due to the roughening of the adhesive and the environment. It is possible to manufacture a printed wiring board which eliminates the above-mentioned deterioration, has excellent heat resistance and electric insulation properties, and has sufficient adhesion between the plating film and the insulating substrate. Further, the removal of the copper foil for roughening can be performed with an ammonia-based alkaline copper etching solution, and its compatibility is wide.

[Brief description of drawings]

FIG. 1 is a sectional view for explaining a manufacturing method according to an embodiment of the present invention.

FIG. 2 is a sectional view for explaining a manufacturing method of another embodiment of the present invention.

FIG. 3 is a cross-sectional view for explaining the manufacturing method of still another embodiment of the present invention.

FIG. 4 is a cross-sectional view for explaining a manufacturing method of a conventional example.

FIG. 5 is a cross-sectional view for explaining the manufacturing method of another example.

[Explanation of symbols]

1. Copper foil 2. Copper oxide 3. Oxidized / reduced copper 4. Resin substrate 5. Through hole 6. Palladium catalyst 7. Plating resist 8. Electroless plating 9. Silane coupling agent 10. Adhesive (before roughening) 11. Adhesive (after roughening) 12. Oxidized copper foil 13. Oxidation / reduction treatment copper foil

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Juno Iwasaki 1500 Ogawa, Shimodate City, Ibaraki Prefecture Hitachi Chemical Co., Ltd. Shimodate Research Center

Claims (5)

[Claims] 1. A copper foil is subjected to an oxidation treatment to form copper oxide having a fine shape on the surface of the copper foil, and then subjected to a reduction treatment to convert the copper oxide on the surface of the copper foil to metallic copper or reduced copper in a low oxidation state. After laminating with the resin layer through the copper foil treated surface, at least the reduction-treated copper foil is removed from the resin substrate at the wiring formation planned position, and wiring processing including electroless plating is performed on the resin substrate to form a circuit. And a method for manufacturing a printed wiring board. 2. The method for producing a printed wiring board according to claim 1, wherein after the copper foil having been subjected to the reduction treatment is laminated, the resin substrate from which the copper foil has been removed is coated with a silane coupling agent. .. 3. The method of manufacturing a printed wiring board according to claim 2, wherein the resin layer laminated on the copper foil coated with the silane coupling agent is any of the following insulating materials. (A) prepreg (b) adhesive film (c) varnish 4. The method for manufacturing a printed wiring board according to claim 1, wherein the method for oxidizing the copper foil is any one of the following or a combination thereof. (A) Method of contacting copper foil with a treatment liquid containing an oxidant (b) Anodization of copper foil by electrolysis 5. The method for reducing copper oxide according to any one of the following or a combination thereof.
A method for manufacturing a printed wiring board according to any one of 1. (A) Method of contacting a copper foil on which copper oxide is formed with a treatment liquid containing a reducing agent (b) Cathodic reduction by electrolysis of copper foil on which copper oxide is formed (c) Copper foil on which copper oxide is formed rather than copper Method of contacting or approaching a metal with low redox potential