JPH05287583A - Method for directly forming electroplating layer on non-electroconductive material surface - Google Patents

Abstract

PURPOSE:To make an insulating part electroconductive only by an electrolytic copper plating process without necessitating an electroless copper plating process. CONSTITUTION:Processes are as follows. The non-electroconductive material is treated by an alkaline permanganate solution to form a manganese oxide layer on the surface. Next, the non-electroconductive material is dipped into an aq. catalyst solution containing at least one kind of palladium, platinum, gold, silver and copper and at least one kind of nitrogen-containing sulfur compounds composed of thiourea and its derivative. The non-electroconductive material is reduction treated by an alkaline solution containing at least one kind of sodium borohydride, sodium hypophosphite, hydrazine and dimethyl amine borane. Next, the non-electroconductive material is activated and an electroplating layer is formed on the non-electroconductive material.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for directly forming an electroplating layer on the surface of a non-conductive material, and more particularly to a method for directly forming an electroplating layer on a through hole of a printed wiring board.

In this specification, "%" means
It shall mean "% by weight".

[0003]

2. Description of the Related Art A subtractive method is mainly used as a method for performing through-hole plating on a printed wiring board. In this method, a surface material made of an insulating base material and a substrate having copper foil adhered to the inner surface are punched, and a thin electroless copper plating is deposited on the insulating portion inside the hole to make the insulating portion conductive. After that, a thick copper film is formed by electrolytic copper plating to ensure continuity between the copper foils and to create an electric circuit.

This method is a highly reliable method that has already been technically established and has a track record of being used for about 20 years. However, this method requires an electroless plating step that requires a complicated pretreatment step in order to make the insulating portion conductive. Since the plating solution used in this electroless plating process has strong self-decomposition property, strict bath management is required, and it is necessary to use highly toxic formalin as a reducing agent for precipitating copper. It has various drawbacks such that it takes a long time to obtain a thin copper film.

[0005]

Therefore, the present invention does not require the electroless copper plating step, which has been a major technical limitation in the conventional method, but makes the insulating portion conductive only by the electrolytic copper plating step. The main purpose is to improve productivity by simplifying the processing steps, shortening the processing time, and improving the working environment.

[0006]

Means for Solving the Problems As a result of earnest studies in view of the current state of the art as described above, the present inventor has achieved the above-mentioned object when a specific process is used in combination. Found to get. It has also been found that this combination of specific steps is also useful when a general non-conductive material is directly formed with an electrolytic copper plating layer.

That is, the present invention provides the following methods: 1. A method for plating a non-conductive material characterized by treating a non-conductive material in the following steps: (1) Non-conductive Treating the material with an alkaline permanganate solution to form a manganese oxide layer on its surface, (2) adding the non-conductive material from step (1) above to palladium, platinum, gold, silver and copper. Immersing in an aqueous catalyst solution containing at least one salt and at least one nitrogen-containing sulfur compound consisting of thiourea and its derivatives;
(3) A step of reducing the non-conductive material from the step (2) with an alkaline solution containing at least one of sodium borohydride, sodium hypophosphite, hydrazine and dimethylamine borane, (4) the above ( 3) activating the non-conductive material from step, and (5)
A step of forming an electroplating layer on the non-conductive material from the step (4).

2. In the plating method according to the above item 1, the metal ion concentration in the catalyst aqueous solution in the step (2) is in the range of 0.1 to 10 g / l, and the nitrogen-containing sulfur compound concentration is the metal ion. A plating method in the range of 1 to 4 mol per mol.

3. In the plating method according to the above item 2, the nitrogen-containing sulfur compound is thiourea, thioacetamide,
A plating method that is either thiosemicarbazide or dimethylthiourea.

4 Through-hole plating method for a printed wiring board, characterized in that a double-sided printed wiring board or a multilayer printed wiring board is processed in the following steps: (1) A printed wiring board washed with holes is washed with alkaline permanganese. A step of treating with an acid salt solution to form a manganese oxide layer on the non-conductive portion of the inner wall of the through hole,
(2) A catalyst aqueous solution containing the printed wiring board from the above step (1) containing at least one salt of palladium, platinum, gold, silver and copper and at least one nitrogen-containing sulfur compound consisting of thiourea and its derivative. Step of immersing in (3)
Reducing the printed wiring board from step (2) with an alkaline solution containing at least one of sodium borohydride, sodium hypophosphite, hydrazine and dimethylamine borane; (4) from step (3) The step of etching and cleaning the copper foil portion of the printed wiring board of 1) with an oxidizing aqueous solution containing persulfated sulfate or sulfuric acid-hydrogen peroxide, and (5) the through hole portion of the printed wiring board from step (4) above is activated. And (6) a step of forming an electroplating layer in the through hole portion of the printed wiring board from the step (5).

5 In the plating method according to the above item 4, the metal ion concentration in the catalyst aqueous solution in the step (2) is in the range of 0.1 to 10 g / l, and the nitrogen-containing sulfur compound concentration is the metal ion. A plating method in the range of 1 to 4 mol per mol.

6. In the plating method according to the above item 5, the nitrogen-containing sulfur compound is thiourea, thioacetamide,
A plating method that is either thiosemicarbazide or dimethylthiourea.

The method of the present invention comprises the general non-conductive material surface,
The electrolytic copper plating layer can be directly formed on the insulating portion of the through hole of the double-sided printed wiring board and the multilayer printed wiring board. However, in the following, the formation of the direct electrolytic copper plating layer on the through-hole insulating portion of the double-sided printed wiring board or the multilayer printed wiring board will be described as an example, and the steps will be sequentially described.

Swelling In the method of the present invention, first, a printed wiring board (hereinafter referred to as a test material) that has been perforated and washed is subjected to a swelling treatment according to a conventional method. The swelling treatment condition is not particularly limited, but an example thereof is as follows.

Glycol ether solvent 50 to 900 ml / l, more preferably 100 to 300 ml / l sodium hydroxide 1 to 50 g / l, more preferably 5 to 30 g / l surfactant suitable amount treatment temperature 20 to 80 ° C. Treatment time is preferably 40 to 70 ° C., 1 to 10 minutes, more preferably 2 to 7 minutes Permanganate solution treatment Then, the test material is subjected to etching treatment with a permanganate solution according to a conventional method. The etching treatment conditions are not particularly limited, but one example thereof is as follows.

KMnO ₄ or NaMnO ₄ 20-100 g / l, more preferably 40-60 g / l KOH or NaOH 5-50 g / l, more preferably 30-40 g / l Surfactant Suitable amount Treatment temperature 50-95 ° C. More preferably 70 to 90 ° C Treatment time 1 to 15 minutes, more preferably 2 to 8 minutes In the conventional method, the swelling treatment and the test material subjected to the etching treatment with the permanganate solution are continuously neutralized. Then, the formed manganese oxide layer is removed, but in the present invention, it is left as it is in order to increase the adsorption amount of the catalytic metal ion in the subsequent catalytic treatment.

Next, the test material is treated with an aqueous catalyst solution containing at least one salt of palladium, platinum, gold, silver and copper and at least one nitrogen-containing sulfur compound consisting of thiourea and its derivatives. Soak. Examples of the salt of the catalytic metal include water-soluble salts such as chlorides, sulfates, nitrates, nitrites and cyanide salts. Examples of thiourea derivatives include thioacetamide, thiosemicarbazide, and dimethylthiourea. The specific liquid composition and conditions for treating the catalyst aqueous solution are as follows.

Catalyst metal ion 0.1 to 10 g / l, more preferably 0.2 to 5 g / l nitrogen-containing sulfur compound 1 mol to 1 mol of metal ion, 1 to 4 mol, more preferably 1.5 to 3 mol Treatment temperature 5 to 50 ° C., more preferably 10 to 30 ° C. Treatment time 0.1 to 10 minutes, more preferably 1 to 3 minutes In the present invention, at least one nitrogen-containing sulfur compound contained in the aqueous catalyst solution is the surface of the copper foil of the substrate. It is strongly adsorbed by and prevents the deposition of catalytic metal on the copper foil, and
It significantly promotes the adsorption of the catalytic metal ion to the manganese oxide layer.

The reduction treatment is then the test materials, reduction treatment of sodium borohydride, sodium hypophosphite, with an alkaline aqueous solution containing a reducing agent comprising at least one of hydrazine and dimethyl amine borane. Examples of the alkaline salt used include sodium hydroxide, potassium hydroxide, sodium carbonate, sodium phosphate, sodium acetate and the like. The specific liquid composition and conditions for the reduction treatment are
The outline is as follows.

Reducing agent 0.5 to 20 g / l, more preferably 1 to 10 g / l alkaline salt 0 to 10 g / l, more preferably 0.5 to 5 g / l treatment temperature 20 to 60 ° C., more preferably 30 to 50 ° C. treatment Time 0.5 to 10 minutes, more preferably 1 to 5 minutes Since the catalytic metal ions adsorbed in the above step are reduced to pure conductive metal in this step, direct electrolysis is performed without electroless plating. It becomes possible to perform plating.

Soft Etching Treatment Next, the test material is subjected to a soft etching treatment according to a conventional method. The soft etching treatment liquid and its condition are not particularly limited, but specific examples thereof are:
It is as follows.

Persulfate type sodium persulfate or ammonium persulfate 50 to 300 g / l, more preferably 100 to 200 g / l sulfuric acid (98%) 0 to 50 ml / l, more preferably 5 to 20 ml / l treatment temperature 10 to 40 ° C, more preferably 20 to 30 ° C Treatment time 0.5 to 3 minutes, more preferably 1 to 2 minutes Sulfuric acid-hydrogen peroxide type sulfuric acid (98%) 10 to 150 ml / l, more preferably 30 to 100 ml / l Hydrogen oxide (35%) 30 to 200 ml / l, more preferably 50 to 150 ml / l Stabilizer Suitable amount Treatment temperature 10 to 50 ° C, more preferably 20 to 40 ° C Treatment time 0.5 to 5 minutes, more preferably 1 to 3 min activation process is then subjected to the test material in the activation process according to a conventional method. The activation treatment liquid and its condition are not particularly limited, but specific examples thereof are as follows.

Sulfuric acid (98%) 10 to 150 ml / l, more preferably 50 to 100 ml / l Treatment temperature 10 to 30 ° C., more preferably 15 to 25 ° C. Treatment time 0.1 to 3 minutes, more preferably 0.5 to 1 minute Electroplating treatment Next, the test material is subjected to electroplating treatment according to a conventional method. The electroplating bath and treatment conditions are not particularly limited, but specific examples thereof are as follows.

Copper Sulfate Plating Bath Copper sulfate 40 to 100 g / l, more preferably 60 to 80 g / l sulfuric acid 100 to 300 g / l, more preferably 150 to 250 g / l chloride ion 30 to 100 mg / l, more preferably 40 〜80mg / l Brightener Appropriate amount Treatment temperature 10〜40 ℃, More preferably 15〜30 ℃ Cathode current density 0.5〜10A / dm ² , More preferably 1〜5A / dm ² Pyrophosphate plating bath Pyrophosphate 50〜 100 g / l, more preferably 60-80 g / l potassium pyrophosphate 200-500 g / l, more preferably 250-400 g / l ammonia water (28%) 1-7 ml / l, more preferably 2-4 ml / l gloss Agent Appropriate amount Treatment temperature 40 to 70 ° C, more preferably 50 to 60 ° C Cathode current density 0.5 to 8 A / dm ² , more preferably 1 to 5 A / dm ² The method of the present invention is a general non-copper foil layer. It can also be applied to the formation of a direct copper electroplating layer on a conductive material.

[0025]

According to the present invention, an electrolytic copper plating layer can be directly formed on the surface of a non-conductive material without going through an electroless copper plating process. Therefore, the time required until the formation of the electrolytic copper plating layer is shortened to about 1/3 as compared with the conventional method that requires the electroless copper plating step, and the industrial advantage is extremely large. ..

[0026]

EXAMPLES Examples will be shown below to further clarify the features of the present invention.

Example 1 A punched FR-4 substrate was treated in an alkaline solution (swelling solution) containing a water-soluble solvent and a surfactant at 60 ° C. for 5 minutes and then washed with water to give 50 g / l of potassium permanganate. It was treated at 80 ° C. for 8 minutes in an aqueous solution (permanganate etching solution) containing 20 g / l of sodium hydroxide.

After thoroughly washing the substrate treated as described above with water, a catalyst solution containing 1 g / l of palladium chloride, 1 ml / l of hydrochloric acid and 1 g / l of dimethylthiourea was added at 25 ° C. for 3 hours.
Soaked for a minute. Then, the substrate was washed with water and treated with a reducing solution containing 10 g / l of dimethylamine borane and 5 g / l of sodium hydroxide at 50 ° C. for 2 minutes. Then, the substrate was washed with water, and sodium persulfate 200 g / l and sulfuric acid 1
2 in an aqueous solution containing 0 ml / l (soft etching solution)
Etching and cleaning the copper foil part at 5 ° C for 1 minute
After activation for about 30 seconds with an active solution containing 0 ml / l, electroplating was performed for 5 minutes under the conditions of a temperature of 25 ° C. and a cathode current density of 2.5 A / dm ² using the following copper sulfate plating bath. It was

Copper sulfate 80 g / l Sulfuric acid 180 g / l Chloride ion 50 mg / l Copper sulfate copper brightener for printed wiring boards 2.5 ml / l (Trade mark “Top Lucina 81-HL”, Okuno Chemical Industries Co., Ltd.)
After the plating was completed, the inner wall of the through hole of the substrate was completely covered with the copper plating film.

Example 2 A perforated FR-4 substrate was subjected to a swelling treatment in the same manner as in Example 1, followed by permanganic acid etching and sufficient washing with water.
It was immersed for 3 minutes at 25 ° C. in a catalyst solution containing 1 g / l of palladium chloride, 1 ml / l of hydrochloric acid and 1 g / l of thiourea. Then, the substrate is washed with water and sodium hypophosphite 10 g / l
And 5 with a reducing solution containing 2 g / l of sodium hydroxide
It was treated at 0 ° C. for 3 minutes. Next, the substrate is washed with water, and the copper foil portion is etched and washed in an aqueous solution (soft etching solution) containing 50 ml / l of hydrogen peroxide, 100 ml / l of sulfuric acid and a small amount of a stabilizer at 30 ° C. for 30 seconds to obtain 50 m of sulfuric acid.
After activation with an active solution containing 1 / l for about 30 seconds, the same copper sulfate plating bath as in Example 1 was used and the temperature was 25
Electroplating was carried out for 1 minute under conditions of the temperature of the cathode current density of 2.5 A / dm ² .

After the completion of plating, the inner wall of the through hole of the substrate was completely covered with the copper plating film.

Example 3 A perforated FR-4 substrate was subjected to a swelling treatment in the same manner as in Example 1, followed by permanganic acid etching and sufficient washing with water.
It was immersed in a catalyst solution containing 1 g / l of palladium sulfate, 1 ml / l of sulfuric acid and 2 g / l of thioacetamide at 35 ° C. for 1 minute. Then, the substrate was washed with water and treated with a reducing solution containing 5 g / l of sodium borohydride and 10 g / l of sodium hydroxide at 50 ° C. for 2 minutes. Next, the substrate is washed with water and an aqueous solution containing 50 ml / l of hydrogen peroxide, 100 ml / l of sulfuric acid and a small amount of a stabilizer (soft etching solution).
Etching and cleaning the copper foil part at 30 ° C for 30 seconds,
After activating for about 30 seconds with an active solution containing 50 ml / l of sulfuric acid, the same copper sulfate plating bath as in Example 1 was used,
Electroplating was performed for 1 minute under conditions of a temperature of 25 ° C. and a cathode current density of 2.5 A / dm ² .

After the completion of plating, the inner wall of the through hole of the substrate was completely covered with the copper plating film.

Example 4 Using a 10-layer multilayer substrate having a thickness of 3.2 mm, Example 2 was used.
The same process was carried out.

After the plating treatment for 1 minute, the inner wall of the through hole of the substrate was completely covered with the copper plating film.

Claims (6)

[Claims] 1. A method for plating a non-conductive material, which comprises treating the non-conductive material in the following steps: (1) The non-conductive material is treated with an alkaline permanganate solution and the surface thereof is treated. A step of forming a manganese oxide layer on (2) a nitrogen-containing material containing at least one salt of palladium, platinum, gold, silver and copper, and thiourea and a derivative thereof as the non-conductive material from the step (1). Immersing in an aqueous catalyst solution containing at least one sulfur compound,
(3) A step of reducing the non-conductive material from the step (2) with an alkaline solution containing at least one of sodium borohydride, sodium hypophosphite, hydrazine and dimethylamine borane, (4) the above ( 3) activating the non-conductive material from step, and (5)
A step of forming an electroplating layer on the non-conductive material from the step (4). 2. The plating method according to claim 1,
The metal ion concentration in the catalyst aqueous solution in the step (2) is
The plating method is in the range of 0.1 to 10 g / l, and the concentration of the nitrogen-containing sulfur compound is in the range of 1 to 4 mol with respect to 1 mol of the metal ion. 3. The plating method according to claim 2, wherein the nitrogen-containing sulfur compound is any one of thiourea, thioacetamide, thiosemicarbazide and dimethylthiourea. 4. A through-hole plating method for a printed wiring board, which comprises treating a double-sided printed wiring board or a multilayer printed wiring board in the following steps: A step of treating with a manganate solution to form a manganese oxide layer on the non-conductive portion of the inner wall of the through hole,
(2) A catalyst aqueous solution containing the printed wiring board from the above step (1) containing at least one salt of palladium, platinum, gold, silver and copper and at least one nitrogen-containing sulfur compound consisting of thiourea and its derivative. Step of immersing in (3)
Reducing the printed wiring board from step (2) with an alkaline solution containing at least one of sodium borohydride, sodium hypophosphite, hydrazine and dimethylamine borane; (4) from step (3) The step of etching and cleaning the copper foil portion of the printed wiring board of 1) with an oxidizing aqueous solution containing persulfated sulfate or sulfuric acid-hydrogen peroxide, and (5) the through hole portion of the printed wiring board from step (4) above is activated. And (6) a step of forming an electroplating layer in the through hole portion of the printed wiring board from the step (5). 5. The plating method according to claim 4,
The metal ion concentration in the catalyst aqueous solution in the step (2) is
The plating method is in the range of 0.1 to 10 g / l, and the concentration of the nitrogen-containing sulfur compound is in the range of 1 to 4 mol with respect to 1 mol of the metal ion. 6. The plating method according to claim 5, wherein the nitrogen-containing sulfur compound is any one of thiourea, thioacetamide, thiosemicarbazide and dimethylthiourea.