JPH0474870A - Electroless copper plating solution - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to an electroless copper plating solution.

[Conventional technology]

Demand for electroless steel plating solutions has increased in recent years for the production of electronic circuit boards and other electronic components.

Conventional electroless steel plating solutions usually contain cupric ions, a chelating agent to keep the copper ions in a stable solution state, a reducing agent to reduce the copper ions forming the chelate compound to metallic copper, and an alkali necessary to keep the plating solution alkaline and form a stable copper chelate compound. In many cases, sulfuric acid steel, cupric chloride, oxidized steel, etc. are used as copper ion sources, and ED is used as a chelating agent.
TA sodium salt, Rochelle salt, quatrol, etc. are used, and formalin, paraformaldehyde, hypophosphorous acid, dimethylamineporan, etc. are used as reducing agents. As the alkali, sodium hydroxide, potassium hydroxide, etc. are usually used. However, pH
It has been pointed out that in conventional electroless copper plating solutions that use alkali metal compounds as modifiers and chelating agents, alkali metals are mixed into the resulting copper plating film, impairing its electrical properties. In addition, those that use formalin or paraformaldehyde as reducing agents are difficult to handle because they self-decompose due to the allo-reaction, and those that use hypophosphorous acid or dimethylamine borane are difficult to handle due to their toxicity. There is a drawback that boron gets mixed into the plating film and deteriorates the electrical properties.

Japanese Unexamined Patent Publication No. 51-47535 and Japanese Patent Publication No. 56-4311
Publication No. 0 describes hydrazine as an example of a reducing agent for the electroless steel plating solution disclosed therein, but since hydrazine has strong reducing properties and is an extremely unstable substance, it cannot be used in the plating solution. It has never been used in practice because it is difficult to ensure stability and control the plating reaction. Further, since the use of alkali is required for pi-1 adjustment, there are the above-mentioned problems associated with this.

[Problem to be solved by the invention]

In view of the fact that conventional electroless steel plating solutions had the problems described above, the present invention provides an electroless steel plating solution that is easy to handle and free from the risk of alkali metals being mixed into the plating film. This is what I am trying to do.

[Means to solve the problem]

The electroless steel plating solution provided by the present invention contains a chelate compound formed from an aminocarboxylic acid and cupric ions as a copper source, and contains hydrazine or a reducing hydrazine compound as a reducing agent, and has a pH of 7.5 or higher. The aqueous solution is characterized in that it does not substantially contain alkali metal ions because the alkali metal compound is not used as a pH adjuster or a chelating agent.

The pH of 75 or more required for the electroless steel plating solution of the present invention is
All are achieved by selective combinations of aminocarboxylic acids, copper compounds and hydrazine compounds. pH is 7.
When lower than 5, the pH is suitable for depositing a copper film.
It is necessary to heat to a significantly higher temperature (80 to 90°C) than in the case of plating, and even if high temperature is used, the deposition rate is slow and it takes about 4 to 5 times as long to obtain a sufficient plating thickness. come to need it.

The aminocarboxylic acids used as chelating agents include aliphatic monoamino monocarboxylic acids (e.g., gurin, alanine, loin), aliphatic oxyamino M (e.g., serine), aliphatic monoaminodicarboxylic acids (e.g., aspartic acid, glutamic acid), Suitable examples include diaminomonocarbon # (eg, lysine, arginine), amino acids with an aromatic nucleus (eg, phenylalanine), and amino acids with a heterocycle (eg, histidine). However, alkali metal salts of these aminocarboxylic acids cannot be used.

Suitable copper compounds include cupric hydroxide, basic steel carbonate, copper amine complex salts, and the like. Salts of strong acids such as copper sulfate are not suitable as it is difficult to achieve the required pH without adding alkali.

The hydrazine compound used as a reducing agent is hydrated hydrazine NH! NH,・Hlo, neutral fE acid hydrazine (NzH*) g・H! So, etc. are appropriate.

To prepare the electroless copper plating solution of the present invention from the raw material compounds as described above, each raw material compound is added to water at about 40° C. or lower and stirred until a uniform solution is formed.

Cupric hydroxide does not dissolve in water by itself, but by adding an aminocarboxylic acid and continuing stirring, it forms a chelate compound and dissolves.

The appropriate concentration of each component is 0.2 to 0 for aminocarboxylic acid.
．． 7 mol/1 (preferably 0.3-0.4 m
ol/n), the cupric compound is about 0.0 as a copper ion
2 to 0, 1 mol/ff1 (preferably 0.03 to
0.05 mol, l ), hydrazine compound is approximately 0.0
5 to 0.3 mol/l (preferably 0.07 to 0,
15 mat/1).

The prepared plating solution is stable at room temperature and can be stored for 2 to 3 weeks to 2 to 3 months, depending on the composition.

If stored in a cool, dark place, it can be stored for up to six months.

The electroless copper plating solution of the present invention can be applied to plastics, glass,
It can be used on all materials that can be plated with conventional electroless copper plating solutions, such as ceramics. In that case, the object to be plated should be plated according to the conventional method of electroless copper plating.
Desirably, degreasing by alkaline cleaning or alkaline electrolytic cleaning, active acid treatment, etc. are performed. In the case of printed wiring boards, pre-treatments such as soft etching, activation, pre-dipping, catalyzing, and accelerating are further applied as necessary.

Thereafter, when it is immersed in the electroless steel plating solution of the present invention heated to about 60 to 80° C. for about 5 to 60 minutes, a reduction reaction by the hydrazine compound starts, metal copper is precipitated, and plating is performed.

〔Example〕

The present invention will be described below with reference to Examples and Comparative Examples.

Using cupric hydroxide as a copper source, using hydrazine hydrate as a reducing agent, and using the compounds shown in Table 1 as a chelating agent, the copper ion concentration was 0.04 mol/L.
Electroless copper plating solutions with hydrazine concentrations of 0 and 1 + mol/Q were prepared (chelating agent concentrations are listed in the table).

Table 1 It was on the street.

Chelating agent concentration (i+ol/Q) Example I
Glycine 0.4tt 2 Roynone 0.4tt 3 Serine 0.4// 4 Aspartic acid 0.4// 5 Arginine 0.3// 6 Phenylalanine 0.3tt 7 Histidine
0.3 Comparative Example I DL-Sodium Malate 0,2712 Trisodium Citrate 0.2tt 3 Sodium Gluconate
0.1//4 Rosocel salt
Q, 14//5 EDTA-disodium
0.1 Electroless copper plating was performed using each of the above plating solutions.

The object to be plated was vacuum-deposited with palladium, followed by alkali immersion cleaning and pretreatment with a sulfuric acid-based active acid. Plating is carried out in a plating solution at a temperature of 70°C for 20 minutes.
This was done by soaking for a minute.

The stability of the plating solution and the precipitation status of the copper film are shown in Table 2. Plating solution stability Copper film deposition Example 1 Good Good tt 2
Good Good // 3
Good Good // 4 Good
Good〃 5 Good Good // 6 Good Good〃 7
Good Good Comparative Example 1 Good No copper precipitation/
/ 2 Good No copper precipitation
3 Self-decomposition before temperature rise // 4 Self-decomposition before temperature rise // 5 Good No copper precipitation In addition, regarding the plating film according to Example 1, sodium and potassium were quantified and the electrical resistance was measured.

For comparison, similar analyzes and tests were conducted on a plated film made of an electroless copper plating solution (Comparative Example 6) having the following composition using formalin as a reducing agent.

Second oxide $0.04 mol#IEDT
A-2 Sodium 0.057 + iol/It Formalin 0, 1 mol # Sodium hydroxide 0.11 mol/1 The results are as shown in Table 3.

Table 3 Plating solution Sodium Potassium Electrical resistance Example 1 Not detected Not detected 1,91Ω・CI Comparative Example 6 700-800ppm 20G-HOppm
2,8*Ω"cm [Effects of the Invention] As described above, according to the present invention, it is possible to obtain an electroless steel plating film with excellent electrical properties without alkali metal contamination, and bath management is also easy.

Claims (1)

[Claims] An electroless solution containing a chelate compound formed from an aminocarboxylic acid and a cupric ion and a hydrazine or a reducing hydrazine compound and having a pH of 7.5 or higher, and which is characterized in that it does not substantially contain alkali metal ions. Copper plating solution.