JPH0361756B2 - - Google Patents

Description

[Detailed description of the invention]

[Field of Application of the Invention] The present invention relates to a chemical copper plating solution, and more particularly, to a chemical copper plating solution that has a long life and is highly stable. [Background of the Invention] A chemical copper plating solution contains divalent copper ions, a complexing agent for divalent copper ions, a reducing agent for divalent copper ions, and a PH adjuster as main components. It is used by adding a complexing agent for monovalent copper ions, a nonionic surfactant having a polyoxyethylene chain, and the like. Although the reaction mechanism of chemical copper plating is not clear, the use of the above additives effectively
If the concentration of the main component is constantly controlled so that the liquid is stabilized and the concentration of the main component does not decrease due to the plating reaction, continuous plating becomes possible.
Can be put to practical use. The chemical copper plating solution mentioned above had the following drawbacks. In a chemical copper plating solution, divalent copper ions, hydroxide ions, and a reducing agent in the solution are consumed by the plating reaction. For this reason, divalent copper ions, hydroxide ions, and reducing agents are constantly replenished in amounts corresponding to the shortages so that the concentration of the liquid components remains constant at the optimum value. These sources are
Generally, for economic reasons, an aqueous solution of copper sulfate, sodium hydroxide, etc., or formalin when the reducing agent is formaldehyde, is used. As plating continues, the amount of these supplies increases, and sulfate ions, sodium ions, and formate ions, which are reaction products of formaldehyde, which are unrelated to the plating reaction, accumulate in the plating solution. That is,
With chemical copper plating solutions, when plating is repeated, sodium salts of sulfuric acid and formic acid accumulate in the solution, causing the solution to deteriorate. As liquid deterioration progresses, the liquid becomes unstable, causing precipitation in the plating tank and on parts of the object to be plated that should not be plated (for example, plating on the plating resist). precipitation) occurs,
It became unusable as a plating solution and was discarded. This pot life was generally within 150 μm based on the total plating thickness. [Object of the Invention] The object of the invention is to provide a long-life, highly stable chemical copper plating solution. [Summary of the Invention] The present invention has discovered that the liquid deterioration of the chemical copper plating solution described above is caused by the aggregation of the polyoxyethylene nonionic surfactant based on the accumulation of the alkali metal salt, and As a result of various studies on compounds that inhibit this, it has been found that the addition or combined use of an ionic surfactant exhibiting cationic properties to the plating solution is extremely effective. [Examples of the Invention] The present invention will be specifically described using examples. Focusing on the fact that the deterioration of the chemical copper plating solution becomes more severe as the accumulation of the alkali metal salts described above progresses, we investigated the accumulated concentration of these salts and the physical properties of the essential components (including additives) of the chemical copper plating solution described above. As a result of investigating the degree of change from various viewpoints, it was found that there is a correlation between the temperature at which aggregation of polyoxyethylene nonionic surfactants starts. In other words, the chemical copper plating solution shown below: CuSO ₄・5H ₂ O ...10g EDTA-2Na ...30g NaOH ...Amount to make PH 12.2 α,α'-dipyridyl ...50mg Polyoxyethylene nonionic surfactant
……100mg water ……When sodium sulfate and sodium formate were added at various concentrations as accumulated components in the liquid to an amount of 1, the aggregation temperature of polyethylene glycol stearylamine as a polyoxyethylene nonionic surfactant was determined. ,
It was measured as the cloud point at which the plating solution becomes cloudy. The measurement results are shown in Table 1, and the cloud point decreased linearly with the amount of sodium sulfate and sodium formate added. Therefore, as shown in the figure, the plating solution 1
When the ionic surfactant of the present invention is added to a plating solution containing 28.0 g of sodium sulfate and 20.4 g of sodium formate, as the amount added increases,
Cloud point increased. Among various ionic surfactants, cationic surfactants (cetyltrimethylammonium chloride, dodecylpyridinium chloride) have the greatest effect on increasing the cloud point, followed by zwitterionic surfactants (stearyl betaine). ). Anionic surfactants (dodecylbenzenesulfonic acid, sulfosuccinate, sodium polyoxyethylene lauryl sulfate) were effective in raising the cloud point, but the effect was smaller than the above two types. Next, in the figure, cetyltrimethylammonium chloride, which has the greatest addition effect, is added at 50 mg per plating solution, sodium sulfate: 28.0 g,
Sodium formate: 20.4 g was added to the above chemical copper plating solution, and the cloud point raising effect of various polyoxyethylene nonionic surfactants was measured. the result,
As shown in Table 2, the cloud point of all polyoxyethylene nonionic surfactants increased with the addition of cetyltrimethylammonium chloride. The above results clearly demonstrate that the addition of ionic surfactants is extremely effective in preventing the agglomeration of polyoxyethylene nonionic surfactants in chemical copper plating solutions due to deterioration of the plating solution. Ta. EXAMPLES Below, using Examples, it will be specifically explained that the present invention has a remarkable effect on improving the life and stability of chemical copper plating solutions. The device used for chemical copper plating was a plating tank with a capacity of 20, and was immersed in a water bath to reach a predetermined plating temperature. The plating solution was constantly circulated using a small pump through a filter having a pore size of 5 μm. The concentration of the main components of the plating solution was kept constant at all times using automatic management and a replenishment device. The lifespan and stability of the plating solution are determined when plating occurs on the wall of the plating tank, or when an epoxy resin plating resist is printed and applied at 5 mm intervals on a 10 cm square copper plate (thickness 0.3 mm). Then, plating was performed, and judgment was made based on the degree to which plating was deposited on the plating resist. The plating area is 1dm ² /
was kept constant. Comparative example Chemical copper plating liquid composition CuSO ₄・5H ₂ O ……10g EDTA−2Na ……30g NaOH ……Amount to make PH: 12.2 α, α′-Dipyridyl ……40mg Polyethylene glycol stearylamine
...100mg water ...amount equal to 1 Plating temperature 70°C Plating was carried out continuously using the above plating solution. As a result, plating precipitation was observed on the plating resist when 37.5 g of sodium sulfate and 30.2 g of sodium formate were accumulated per plating solution. The total plating time during this period, that is, the life of the plating solution was 50 hours. At this point, the plating solution is
Due to the addition of surfactant, foaming properties were no longer observed. Example 1 50 mg of cetyltrimethylammonium chloride was added to plating solution 1 of Comparative Example. Complete time
Even after 50 hours, foaming properties of the liquid were observed, and no plating precipitation was observed on the plating resist. Plating was continued for a total plating time of 100 hours, but no abnormalities in plating precipitation were observed. There is no difference in the plating film compared to the one without additives,
A good plating film was obtained. Example 2 Chemical copper plating solution composition CuSO ₄・5H ₂ O ...10g Hydroxyethylethylenediaminetriacetic acid trisodium (HEDTA) ...30g NaOH ...Amount to make PH: 12.2 α,α'-dipyridyl ...50mg Poly Oxyethylene/polyoxypropylene block polymer (Pluronic manufactured by Asahi Denka Kogyo)
F68)...100mg Water...Amount to be 1 Plating temperature 70°C When the above plating solution accumulated 28.0g of sodium sulfate and 24.5g of sodium formate, plating precipitated on the plating resist. The total plating time in this case was 35 hours. Plating was carried out by adding 100 mg of stearyl betaine per 1 portion of the main plating solution. As a result, no plating precipitation occurred on the plating resist during a plating time of 80 hours. Example 3 CuSO ₄・5H ₂ O ...10g EDTA-2Na ...30g NaOH ...Amount to make PH: 12.1 O-phenanthroline ...1mg Polyoxyethylene laurylamine ...200mg Water ...Amount to make 1 The above plating solution caused plating on the plating resist when the plating time was 70 hours, that is, 42 g of sodium sulfate and 46.9 g of sodium formate were accumulated.
When 50 mg of laurylbenzylmethylammonium chloride was added to this solution, no abnormal plating precipitation was observed even after 120 hours of plating. As mentioned above, it goes without saying that the present invention is not limited to the examples. In other words, the effect of adding an ionic surfactant is to prevent polyoxyethylene-based nonionic surfactants from agglomerating as the plating solution deteriorates. It has nothing to do with the type of just,
Needless to say, it is sufficient to select the concentration of the ionic surfactant that is compatible with the type and concentration of the polyoxyethylene nonionic surfactant used in the plating solution.

【table】

[Table] Tetronic, Pluronic: Polyoxyethylene/polyoxypropylene block polymer (manufactured by Asahi Denka Kogyo)
[Effects of the Invention] According to the present invention, divalent copper ions, complexing agents for divalent copper ions, reducing agents for divalent copper ions, PH regulators, 1
By adding an ionic surfactant to a chemical copper plating solution that contains a complexing agent for valence copper ions and a polyoxyethylene nonionic surfactant as an essential component, it is possible to reduce the accumulation of anions associated with the plating reaction. Since the agglomeration of the polyoxyethylene nonionic surfactant caused by this process is suppressed, the life of the plating solution is extended and the stability is significantly improved. Therefore, plating defects are reduced, plating costs are reduced, and this has significant industrial effects.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the state of the compounding elements.

Claims (1)

[Claims] 1 Contains divalent copper ions, complexing agents for divalent copper ions, reducing agents for divalent copper ions, PH regulators, complexing agents for monovalent copper ions, and polyoxyethylene nonionic surfactants as essential ingredients. A chemical copper plating solution comprising an ionic surfactant.