JPH0634443B2 - Method for manufacturing printed wiring board - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a printed wiring board, and more particularly to a method for manufacturing a printed wiring board suitable for forming a through hole by chemical plating.

[Background of the Invention]

Conventionally, in the production of a printed wiring board having a through hole, there is a problem that the plating resist is peeled off from the circuit pattern when the through hole is plated by a chemical plating method. -52196 has been proposed. It forms a chemical copper plating layer on the copper foil surface of a copper clad laminate, and then forms a circuit pattern having a double structure of the copper foil and the chemical copper plating layer by etching. After that, an oxide film layer is provided on the surface of the circuit pattern-like chemical copper plating layer, and a necessary portion of the oxide film layer is masked with a plating resist also serving as a solder mask. Next, a method of forming a circuit by applying a chemical copper plating to a desired portion including the inner surface of the hole to achieve a close contact between the circuit pattern and the plating resist through the oxide film. By doing so, problems such as reduction in insulation resistance between circuits, poor appearance, and solder bridging due to the peeling were solved.

However, in the above-mentioned conventional method, the chemical copper plating layer must be previously formed on the surface of the copper foil, which is complicated. This is because if the oxide film layer is formed directly on the copper foil without forming this chemical copper plating layer, sufficient adhesion cannot be obtained, and the nature of the oxide film is that of the copper film on which the film is formed. It is believed to be due to the nature.

Further, in the above method, there is a problem that the plating resist must be formed thick so that defects such as pinholes reaching the circuit pattern can be reduced from the resist surface as much as possible. Otherwise, in the subsequent step of the chemical copper plating solution, a part of the plating solution permeates through a pinhole or the like to reduce the oxide film and cause peeling of the resist.

[Object of the Invention]

An object of the present invention is to eliminate the above-mentioned drawbacks of the prior art, and to provide a method for manufacturing a printed wiring board having a through hole in which the circuit pattern and the plating resist are well adhered and are not separated.

[Outline of Invention]

It has been known in the past that when a metal and an organic substance are adhered, if an oxide film is formed between them to adhere them, the adhesive force between them is improved. As a result of various investigations on this point, it was found that the oxide film does not improve the adhesion growth, but that the adhesion becomes mechanically increased because the surface becomes rough and the surface area increases when the oxide film is formed. I reached the idea. Therefore, by forming an oxide film and reducing the oxide film to a metal while keeping the surface shape as it is, even if it comes into contact with an acid, an alkali, or a reducing agent, they are not easily affected by them and have good adhesion. I thought that I could get a sex. The validity of this idea was discovered as a result of actual species studies.

The present invention is based on the above-mentioned idea, and its feature is that a desired conductor circuit pattern is formed on the surface of an insulating plate, and after forming holes at necessary positions, necessary parts are masked with a plating resist. In the method for manufacturing a printed wiring board in which a circuit is formed by chemically plating the conductor circuit pattern portion not masked with the holes and the resist, in the step before the step of masking with the plating resist,
This is to provide a circuit pattern having a surface formed by forming an oxide film on the surface of the conductor and then reducing the film.

Next, the outline of the present invention will be specifically described.

As the metal for forming a conductor circuit pattern, copper is most preferable from the viewpoint of conductivity and the like. The circuit pattern may be formed by an additive method or the like, but generally a copper clad laminate is used as a starting material, and a conductor circuit pattern is formed by etching or the like. Alternatively, the conductor pattern may be formed by printing a conductive paste containing a conductive metal. Make holes where necessary. Subsequently, an oxide film is formed on the surface of the conductor circuit pattern portion, and the oxide film is further reduced. Finally, a printed wiring board having through holes is finished by a chemical plating method. These are a) the step of forming a conductor circuit pattern, b) the step of forming a through hole, c) the step of forming an oxide film on the conductor surface, d) the step of reducing the oxide film, and g) the through hole plating. The steps do not have to be performed in the order of a), b), c), d), and g), and for example, c), a), b), d),
g), or b), a), c), d), g), etc., the order may be appropriately changed without any problem.

First, the formation of an oxide film on the metal surface and the reduction formation from the film, which are the features of the present invention, will be described. Prior to forming the oxide film, it is appropriate to roughen the metal surface. For example, in the case of copper, an acidic aqueous solution of cupric chloride can be used as the roughening liquid. Upon oxidation, a copper oxide layer can be formed on the surface of copper by immersing in an aqueous solution of sodium chlorite and sodium phosphate sodium hydroxide, for example. After forming an oxide film, it is desirable to subsequently reduce the film.

As a method of reducing the oxide film, there are an electric method and a chemical method. The reduction by an electric method is performed, for example, by applying electricity in an aqueous solution with the oxide film as a cathode. Specifically, when the oxide film is copper oxide,
In an aqueous solution containing 20 g / sodium chloride as a supporting salt, a copper electrode formed on the surface of the copper oxide was used as a cathode, a stainless steel plate was used as an anode, and a current density of 100 was obtained at room temperature.
It is carried out by energizing at about mA / dm ² . Depending on the thickness of the oxide film, the energization time may be several minutes or less. Further, as the method of chemically reducing, there are a method of contacting with a reducing gas and a method of contacting with a solution containing a reducing agent. As the reducing gas, there are hydrogen, carbon monoxide, diborane, formaldehyde, etc., and upon contact with these, heating or the like is necessary in order to proceed the reaction sufficiently. Further, in the reduction by contact with a solution containing a reducing agent, formaldehyde, sodium hypophosphite, hydrazine, sodium borohydride, borazines such as dimethylamine borane and diethylamine borane, borazenes, borazines, etc. It is useful. Particularly, strong reducing agents such as borazanes, borazenes and borazines are preferable. When formaldehyde or hypophosphite is used, a reduced metal surface can be formed by previously applying a noble metal such as palladium colloid to the oxide film surface or by contacting with metal powder in a solution. .

The various methods described above can be applied to the reduction of the oxide film, which is the key to the present invention. Among them, the chemical reduction method using a reducing agent is the simplest. That is, an electrode is required for electrically reducing the oxide film, and it is difficult to reduce the oxide film after the conductor circuit pattern is formed. Therefore, the order of steps for forming the oxide film is limited. . Further, when the conductor circuit pattern is formed after reducing the oxide film, the reduction surface may be contaminated by the handling during the process. On the other hand, the chemical reduction method has an advantage that the position of the reduction step can be freely selected in the printed circuit board manufacturing process.

In the present invention, by reducing the oxide film to a metal, fine irregularities are formed on the surface of the conductor circuit pattern to enhance the adhesion between the circuit pattern and the plating resist. Conventional mechanical and chemical roughening methods, for example secondary chloride
The adhesion effect as in the present invention cannot be obtained by a method such as roughening using a hydrochloric acid acidic aqueous solution of copper.

Next, the through hole forming step will be described.

The catalyst for chemical plating is first applied in the pores. As a catalyst, an acidic aqueous hydrochloric acid solution containing palladium and tin is generally used. By immersing the substrate, which has been subjected to the above-mentioned treatment, in this catalyst solution, the catalyst can be provided in the holes.

However, this catalyst application is not limited to being performed after the reduction surface is formed, and can be appropriately performed as long as the through holes are formed. For example, after the above-mentioned b) hole forming step, catalyst is applied, a) conductive circuit pattern formation, c) oxide film formation, and d) reduction film formation, and then the required portions are masked with a plating resist. There is a method of forming through holes by chemical plating. In this case, chemical plating can be performed only on the holes and the metal surface not masked by the plating resist. Alternatively, the catalyst application operation
After masking the necessary parts with a resist,
The present invention can also be achieved by selectively leaving the catalyst in the pores and on an unmasked metal surface. As described above, in the present invention, a) formation of a conductor circuit pattern, b) formation of holes, c) formation of an oxide film, d) reduction treatment of the film, e) application of a catalyst, and f) plating resist formation as required. It is possible to change the order in which the various steps are performed.

Prior to the chemical plating, the holes and the periphery of the conductor circuit pattern connecting the LSI flat package are masked with the plating resist. As the plating resist, generally used inks such as epoxy type, melamine type and polyamide type can be applied. Also, the plating resist must be substantially resistant to chemical plating. The masking of the plating resist can be formed by exposure and development using a photoreaction, but it is advantageous to form it by a printing method in view of mass productivity.

Furthermore, through-hole plating is performed by chemical plating.
Here, copper having a large electric conductivity is suitable, and a copper coating is formed by chemical copper plating. Besides, chemical nickel plating etc. can be applied. Further, the through-hole plating film is preferably a plating film of good quality from the viewpoint of reliability. In chemical copper plating, 2,2'-bipyridyl, sodium cyanide, etc. are added to the plating solution for the purpose of improving the mechanical properties of the plating film.

By the method described above, it is possible to manufacture a printed wiring board having through holes with excellent adhesion between the plating resist and the conductor circuit in contact therewith.

Example of Invention

Next, the present invention will be described more specifically with reference to examples.

Example 1 Step A: The copper foil surface of the double-sided copper-clad laminate was cleaned by brushing, and then etching resist ink was screen-printed on the copper foil surfaces of the conductor circuit and through-hole forming portions on both surfaces and dried. . Then, the exposed copper was removed by etching with a hydrochloric acid-acidic cupric chloride aqueous solution, and the etching resist was further removed to form a conductor circuit pattern.

Step B: A hole for forming a through hole was opened at a required place.

Step C: Next, the copper foil surface was treated at 45 ° C. for 1 minute using an aqueous solution of the following composition CuCl ₂ .2H ₂ O 40 g / 35% HCl 400 ml /.
Then, it was washed with water and immersed in an aqueous solution of the following composition: NaOH 5 g / NaClO ₂ 30 g / Na ₃ PO ₄ 10 g / for 1 minute at 70 ° C. to form an oxide film layer on the copper surface in the conductor circuit pattern. Then washed again with water.

Step D: The oxide film was reduced by immersing it in a treatment liquid having the following composition: NaOH 5 g / (CH ₃ ) ₂ NH.BH ₃ 6 g / for 2 minutes at room temperature.
Then, I washed with water.

Step E: After immersed in 18% hydrochloric acid for 1 minute, it was immersed in a catalyst solution (sensitizer HS101B, manufactured by Hitachi Chemical Co., Ltd.) at room temperature for 5 minutes. Next, it was washed with water, immersed in 3.5% hydrochloric acid for 5 minutes, washed with water again, and dried.

Step F: The following composition (unit: parts by weight) on one surface of the substrate that has undergone the above steps: Epoxy resin Epicoat 1007 (manufactured by Ciel Chemical Co., Ltd.) 65 Epicoat 828 (manufactured by Ciel Chemical Co., Ltd.) 35 Polyvinyl butyral Esretsk BL-2 (Sekisui Chemical Co., Ltd.) 2.5 Silicone oxide Aerosil # 300 (manufactured by Nippon Aerosil Co., Ltd.) 4 Zirconium silicate 4 Phthalocyanine green 2 Acrylate ester type copolymer Modaflo (manufactured by Monsanto) 3 Dicyandiamide 5 N, N, N, N- Tetramethylbutanediamine 1.1 Butyrocellosolve Total viscosity of 300 poise (20
The amount of the plating resist ink that becomes the liquid (at ℃) was screen-printed, and the holes, lands, and parts other than the portions that needed soldering later were masked. Then, it was dried by heating at 130 ° C. for 20 minutes.

Further, the other surface was screen-printed in the same manner to mask a necessary portion, and then heated at 150 ° C. for 40 minutes to cure the plating resist ink.

Step G: a substrate subjected to plated resist, the following composition CuSO ₄ · _5H 2 O 10g / disodium ethylenediaminetetraacetate 30g / HCHO (37%) 2ml / 2,2'- bipyridyl 30 mg / polyethylene glycol (average molecular weight 600 ) It was immersed in a chemical copper plating solution of 10 g / NaOH 10 g / at 70 ° C. and plated to a thickness of about 35 μm. After plating, wash with water and dry,
A double-sided through-hole printed wiring board was created.

The printed wiring board thus obtained did not have any peeling between the plating resist and the conductor circuit and showed good adhesion.

Example 2 The copper foil surface of the double-sided copper-clad laminate was cleaned by brushing, and holes for forming through-holes were formed in necessary places. Then, after treating the copper foil surface in the same manner as described in Steps C and D of Example 1, a catalyst was applied to the holes and the substrate surface in the same manner as in Step E of Example 1. A photosensitive dry film was laminated on both surfaces of this substrate, and exposed and developed to remove the dry film other than the conductor circuit forming portion to form an etching resist. Next, the exposed copper is treated with an ammonium persulfate aqueous solution (concentration: 200 g /
) And removed by etching. Further, the dry film was removed by peeling. Next, steps F and G of Example 1 were sequentially performed to prepare a double-sided through hole printed wiring board.

The obtained printed wiring board showed good adhesion without peeling between the plating resist and the conductor circuit.

Example 3 The copper foil surface of the double-sided copper-clad laminate was cleaned by brushing, and holes for forming through-holes were formed at necessary places. Next, the copper foil surface was treated with an aqueous solution of the following composition CuCl ₂ .2H ₂ O 40 g / 35% HCl 500 ml / at 45 ° C. for 1 minute.

After washing with water, a solution of the following composition CuSO ₄ .5H ₂ O 3 g / (CH ₃ COO) ₂ Cu 20 g / (CH ₃ COO) NH ₄ 60 g / NH ₄ Cl 5 g / NH ₄ OH 10 g / at 75 ° C., 15 It was immersed for a minute to form an oxide film layer on the surface of the copper foil. After washing with water here, electrolytic reduction was performed in a NaOH aqueous solution (concentration 4 g /). At this time, the counter electrode was a stainless plate. The current density was set to 50 mA / dm ^2, and current was supplied for 10 minutes at room temperature to reduce the oxide film. After washing with water, a catalyst was applied to the holes and the substrate surface in the same manner as in Step E of Example 1. Next, a photosensitive dry film is laminated on both surfaces of the substrate, and after exposure and development, the exposed copper is treated with an ammonium persulfate aqueous solution (concentration: 200 g /).
Etching was carried out by immersing in. Further, the dry film was removed to form a conductor circuit pattern. Thereafter, the same processes as those in Steps F and G of Example 1 were sequentially performed to complete a double-sided through-hole printed wiring board.

The resulting printed wiring board showed good adhesion without any peeling between the plating resist and the conductor circuit.

Example 4 Steps A, B, C and D of Example 1 were sequentially performed. After washing with water and drying, the step F of Example 1 was performed to form a plating resist. Then, the surface of the substrate other than the holes on one surface was masked by screen-printing an alkali-soluble ink. After drying
The other surface was also screen-printed with an alkali-soluble ink in the same manner and masked. After drying, the step E of Example 1 was performed to apply the catalyst into the pores. After removing the alkali-soluble ink, step G of Example 1 was performed to prepare a double-sided through-hole printed wiring board.

The resulting printed wiring board showed good adhesion without any peeling between the plating resist and the conductor circuit.

Comparative Example A double-sided through-hole printed wiring board was prepared in the same manner as in Example 1 except that steps C and D were not performed in Example 1.

The obtained printed wiring board was partially peeled off between the plating resist and the conductor circuit, and the adhesion was insufficient.

〔The invention's effect〕

As described in detail in the examples, by applying the method of the present invention, good adhesion can be obtained between the plating resist and the conductor circuit pattern.

Further, the method of the present invention can be widely applied not only to double-sided through-hole printed wiring boards, but also to multilayer printed wiring boards, single-sided through-hole printed wiring boards and the like.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Motoyo Wajima 4026 Kuji Town, Hitachi City, Ibaraki Prefecture, Hitachi Research Institute Ltd. (72) Inventor Akio Tazo 4026 Kuji Town, Hitachi City, Ibaraki Prefecture Hitachi, Ltd. Inside Hitachi Research Laboratory (72) Inventor Kaneharu Kawabo 1410 Inada, Katsuta City, Ibaraki Prefecture Inada Hitachi Ltd. Tokai Plant (72) Inventor Ritsuji Toba 1 Horiyamashita, Hadano City, Kanagawa Prefecture Within

Claims (4)

[Claims] 1. A desired conductor circuit pattern is formed on a surface of an insulating plate, holes are formed at necessary positions, and then necessary parts are masked with a resist, and the holes and the resist are masked. In a method for manufacturing a printed wiring board in which a circuit is formed by chemically plating an unexposed conductor circuit pattern portion, an oxide film is formed on the conductor surface and then the film is reduced in a step before the step of masking with a plating resist. A method of manufacturing a printed wiring board, comprising providing a circuit pattern having a surface formed by 2. A method for manufacturing a printed wiring board according to claim 1, wherein the conductor circuit is made of copper. 3. A method for manufacturing a printed wiring board according to claim 2, wherein the chemical plating is chemical copper plating. 4. A method of manufacturing a printed wiring board according to claim 1, wherein the oxide film is reduced by a chemical reaction with a compound having a reducing power.