JP3227504B2 - Electroless copper plating solution - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an electroless copper plating solution.

[0002]

2. Description of the Related Art Electroless copper plating solutions are widely used in industry for the purpose of imparting conductivity to non-metallic materials such as plastics and resins, improving the surface strength, and modifying the surface of metallic materials. In particular, it is widely used for manufacturing printed circuit boards and electronic components.

[0003] Electroless copper plating solutions that have been put to practical use in the past generally include, in addition to cupric ions, complexing agents, reducing agents, pH adjusters, etc., various trace additives for maintaining the stability of the solution,
Formalin is the one containing a surfactant or the like and being industrially practically used as a reducing agent. However, formalin has the problem of deteriorating the working environment due to its volatilization and odor, and it is a fact that measures such as duct facilities are not sufficiently effective.

In recent years, an electroless copper plating solution using glyoxylic acid as a formalin substitute has been proposed, but this is liable to cause the decomposition of a reducing agent by the Cannizzaro reaction, and has a problem of accumulation of the formed hardly soluble oxalate. .

[0005] An electroless copper plating solution using hydrazines, which are odorless and have no accumulation of decomposition products, as reducing agents has also been reported (JP-A-51-47535, JP-B-56-56).
No. 31353), hydrazine has a strong reducing power and is liable to generate monovalent copper ions, and bath decomposition accompanied by copper powder precipitation in a liquid due to disproportionation reaction is apt to occur rapidly. There is a special usage and therefore,
There are problems such as being limited, and none of them are practically satisfactory.

JP-A-4-74870 describes an electroless copper plating solution containing a hydrazine compound as a reducing agent in a solution containing an aminocarboxylic acid and cupric ions and containing no alkali metal ions. However, in a bath in which a copper complex is formed with such an aminocarboxylic acid, sufficient bath stability cannot be obtained, and the bath is used at a high temperature (60 to 80).
° C), which is not suitable for an actual production line, and is not practical.

[0007] Galvano Technique Vol. 81 (199
0) No. 4, pp. 1235 to 1239, also show that HE is used as an electroless copper plating solution using hydrazine as a reducing agent.
A plating solution containing a DTA-Cu complex and a cyan stabilizer and using low-concentration hydrazine sulfate as a reducing agent is described, but this also has insufficient bath stability and is liable to be turbid, and is coated with an ABS resin. In the case of a plated material, even when activated with palladium, the plating does not precipitate and its use is limited.

Other reducing agents used in the electroless copper plating solution include, for example, hypophosphite and dimethylamine borane, which are reducing agents used in the electroless nickel plating solution. The one used has the disadvantage that phosphorus and boron are mixed in the deposited film and lowers the electrical characteristics of the film.In addition, hypophosphite has poor autocatalytic growth of copper plating, and dimethylamine borane has a unique Harmful with foul odor.

[0009]

The present inventors have conducted intensive studies in view of the state of the prior art as described above, and as a result, have used diethylenetriaminepentaacetic acid or a salt thereof as a complexing agent, and further stabilized the plating bath. In an electroless copper plating solution using at least one of monoethanolamine and N, N, N ', N'-tetrakis (2-hydroxypropyl) ethylenediamine as an agent, even when a hydrazine compound is used as a reducing agent, High plating bath stability,
In addition, they have found that plating can be stably performed, and have completed the present invention.

That is, the present invention relates to (i) a cupric compound, (ii)
An electroless solution comprising an aqueous solution containing diethylenetriaminepentaacetic acid or a salt thereof, (iii) monoethanolamine and at least one of N, N, N ', N'-tetrakis (2-hydroxypropyl) ethylenediamine, and (iv) a hydrazine compound. This is to provide a copper plating solution.

In the electroless copper plating solution of the present invention, as the copper compound, generally used cupric compounds, for example, copper sulfate, copper chloride, copper hydroxide, basic copper carbonate and the like can be used. The amount of the copper compound is about 0.005 to 0.2 mol / l, preferably 0.1 mol / l, as a cupric ion concentration.
It is about 01 to 0.1 mol / l.

In the electroless copper plating solution of the present invention, it is necessary to use diethylenetriaminepentaacetic acid (DTPA) or a salt thereof as a complexing agent. By using DTPA or a salt thereof as a complexing agent, the plating bath can be kept stable even when a hydrazine compound is used as a reducing agent,
Also, plating deposition becomes good. As a salt of DTPA,
For example, sodium salt, potassium salt, ammonium salt,
A lithium salt or the like can be used. It is necessary that the amount of DTPA or a salt thereof is equal to or higher than the molar concentration with respect to the copper ion concentration. When the amount of DTPA or a salt thereof is lower than the equimolar concentration with respect to the concentration of copper ions, sufficient bath stability cannot be obtained even when other complexing agents are used in combination. DT
The upper limit of the amount of PA or a salt thereof is about 0.4 mol / l.
It is .

The electroless copper plating solution of the present invention contains at least one of monoethanolamine and N, N, N ', N'-tetrakis (2-hydroxypropyl) ethylenediamine in order to improve the stability of the plating bath. Is necessary. By blending these compounds, the stability of the plating bath is remarkably improved, and the plating deposition property is also improved. The compounding amount of these compounds is
It is suitably about 0.0001 to 1 mol / l, and preferably about 0.0002 to 0.6 mol / l.

In the electroless copper plating solution of the present invention, a hydrazine compound is used as a reducing agent. The hydrazine compound is odorless and has no accumulation of decomposition products,
By using in combination with the above-mentioned complexing agent and bath stabilizing agent, an electroless copper plating solution having good bath stability and good precipitation properties can be obtained. As the hydrazine compound, any compound having a reducing property can be used.For example, hydrazine hydrate, hydrazinium chloride, hydrazinium sulfate, dimethylhydrazine, acetohydrazide, carbohydrazide, or the like may be used alone or in a suitable mixture. it can. The compounding amount of the hydrazine compound is 0.01 to 0.5 mol /% as the total hydrazine part concentration.
It is about l, preferably, 0.04 to 0.2 mol / l
It is about. Note that the total hydrazine moiety concentration is a concentration focusing on the amount of the hydrazine moiety. For example, for a compound having two hydrazine moieties in one molecule, the total concentration of the compound is 1 mol / l. The hydrazine part concentration becomes 2 mol / l.

Furthermore, in the electroless plating solution of the present invention, plating deposition properties can be improved by adding a water-soluble alkaline salt such as sodium acetate and sodium carbonate as necessary. The compounding amount of the water-soluble alkaline salt is preferably about 0.5 to 200 g / l, more preferably about 1 to 50 g / l.

Further, the electroless copper plating solution of the present invention is used for improving the stability of the plating solution, improving the plating deposition property, adjusting the color tone of the deposited film, and improving the wettability for preventing plating defects. For example, various additives blended in electroless copper plating such as formalin type can be used. Such additives include cyanide, cyano complex salt and the like;
Organic nitrogen compounds such as α, α′-dipyridyl and neocuproin; alkyleneamines such as ethylenediamine, diethylenetriamine and triethylenetetramine; masking agents for monovalent copper ions such as amino acid thiols; diethyldithiocarbamate, mercaptobenzothiazole and the like Jichiokaru market sentiment phosphate derivative; thiocyanates, thiourea, thiourea derivatives, rhodanine, sulfur compounds such as thiosulfates, polyethylene glycols and various surfactants; arsenic, antimony, bismuth, tellurium, catalyst poisons heavy metal ions such as thallium Additives for the purpose of releasing gas from the agent, improving the wettability of the surface, and stabilizing the plating reaction. The compounding amounts of these additives may be the same as the compounding amounts in the conventional electroless copper plating solution.

The electroless copper plating solution of the present invention can be used in the range of 5 to 85 ° C. at a pH of 9 or more. Is preferred. As the pH adjuster, common compounds such as sodium hydroxide, potassium hydroxide and aqueous ammonia can be used as the alkali compound, and sulfuric acid, hydrochloric acid, acetic acid and the like are preferable as the acid.

As a method for performing plating using the electroless copper plating solution of the present invention, a general pretreatment step for electroless copper plating can be applied as it is. In other words, if the plating target portion of the plating object is a non-conductive substance or a substance that does not easily undergo an electroless copper plating reaction, a metal catalyst is applied by palladium, platinum, copper, nickel, cobalt, or the like according to a conventional method, When the object to be plated has a catalytic property such as a metal, by performing a so-called activation treatment with an acid or an alkali, the object to be plated is brought into contact with an electroless plating solution by a method such as immersion. An electroless copper plating film can be deposited.

[0019] In an electroless copper plating solution of the present invention, the object to be plated is not particularly limited, typical object to be processed, for example, plastic molding, printed circuit board, a non-conductive material such as ceramic, copper wire A conductor such as a portion can be used.

[0020]

The electroless copper plating solution of the present invention uses a hydrazine compound, which is odorless and does not accumulate decomposition products, as a reducing agent, and has good bath stability and excellent plating depositability. It is possible to stably form a good copper plating film without deteriorating the working environment.

[0021]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to examples.

[0022] Example 1 AB S resin sulphate - used after etching with chromic acid as a test piece, palladium as a catalyst by commercial catalyst imparting solution (manufactured by Okuno Chemical Industries Co., Ltd. OPC-80 calibration data list) , An activation treatment was performed using 50 g / l diluted sulfuric acid, and then immersed in each of the electroless copper plating solutions shown in Tables 1 and 2 below to form a copper plating film. In the table, quad rolls are N,
Trade name of N, N ', N'-tetrakis (2-hydroxypropyl) ethylenediamine (manufactured by Asahi Denka Kogyo Co., Ltd.)
It is. EDTA · 2Na is ethylenediaminetetraacetic acid disodium salt. The abbreviations in Tables 1 and 2 represent the following compounds.

Copper salts OH: cupric hydroxide, CL: cupric chloride, SO: cupric sulfate reducing agent HH: hydrazine hydrate, HC: hydrazinium chloride (N ₂ H ₄ 2HCl), HS: hydrazinium sulfate (N ₂ H ₄ H ₂ SO ₄ ), CH: carbohydrazide,
AH: acetohydrazide The color tone and film thickness of the formed plating film are shown in Table 3 below.
In addition, when plating does not precipitate, it is represented by a mark x. Table 3 also shows the results of evaluating the stability of the plating solution based on the following criteria.

X: Decomposed during bathing or heating △: Gradual increase in turbidity during heating ○: No turbidity on bathing / use day ◎: No turbidity for one day or more

[0025]

[Table 1]

[0026]

[Table 2]

[0027]

[Table 3]

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Hiromi Hasegawa 2-155-1207, Tsukuda, Nishiyodogawa-ku, Osaka-shi, Osaka (72) Inventor Kaoru Naito 10-1-204, Ikaminami-cho, Hirakata-shi, Osaka (56) Reference Reference JP-A-3-287779 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C23C 18/00-18/54

Claims (1)

(57) [Claims] (1) at least one of (i) a cupric compound, (ii) diethylenetriaminepentaacetic acid or a salt thereof, (iii) monoethanolamine and N, N, N ', N'-tetrakis (2-hydroxypropyl) ethylenediamine. An electroless copper plating solution comprising one kind and (iv) an aqueous solution containing a hydrazine compound.