JPH048512B2 - - Google Patents

Description

[Detailed description of the invention]

[Field of Application of the Invention] The present invention relates to a chemical copper plating solution. In particular, it relates to a chemical copper plating solution that can obtain high plating efficiency even when prepared with inexpensive chemicals. [Prior Art] It is best to prepare chemical copper plating solutions using chemicals of high purity. This is because the plating efficiency is better, the liquid stability is better, and the life is longer. However, for economical reasons, it has traditionally been the practice to obtain copper plating solutions using inexpensive industrial chemicals with low purity. In this case, it is necessary to prevent a decrease in the life of the solution, the stability of the solution, and the plating efficiency as much as possible. That is, in general, chemical copper plating solutions contain divalent copper ions,
Complexing agent for divalent copper ions, reducing agent for divalent copper ions,
Contains a PH adjuster as the main ingredient to stabilize the liquid.
A small amount of a monovalent copper ion complexing agent or a nonionic surfactant having a polyoxyethylene chain is used. Although the reaction mechanism of such chemical copper plating is not strictly clear, it is known that the use of the above additives actually stabilizes the liquid. Therefore, if the concentration of the main component is constantly controlled so as not to cause a decrease in the concentration of the main component due to the plating reaction, continuous plating becomes possible and is put to practical use. However, in the conventional chemical copper plating solution,
The use of inexpensive chemicals as described above has the following drawbacks. In other words, the chemical copper plating solution removes divalent copper ions, hydroxide ions, and
Reducing agent is consumed. Therefore, it is necessary to constantly replenish divalent copper ions, hydroxide ions, and reducing agents in the amount necessary to maintain the concentration of the liquid components at a constant optimum value. For economic reasons, aqueous solutions of inexpensive chemicals such as copper sulfate and sodium hydroxide are generally used as supply sources for these, and among these, some industrial chemicals may be used. And when the reducing agent is formaldehyde, formalin is used. On the other hand, in chemical copper plating, the stability of the solution is ensured with a small amount of additives as described above, so if components other than essential components are introduced into the solution, the plating reaction is acutely affected. Typical phenomena include decomposition of the liquid and plating on the tank wall or filter surface. As a result, unnecessary copper adhering to the plating equipment can be removed by etching,
Furthermore, it is necessary to process the etching solution, which shortens the life of the solution, and due to plating on objects other than those to be plated, the copper plating efficiency does not reach 100% of the theoretical value, and the It drops to 90%.
If a chemical with low purity, such as an industrial chemical, is used, the impurities contained therein will inevitably cause the above-mentioned adverse effects. However, conventionally, although it is desirable to use the purest chemicals for the above-mentioned supplies, low-purity but inexpensive industrial chemicals are used at the expense of the lifespan and stability of the solution. It was hot. [Object of the invention] The object of the present invention is that even if a chemical with low purity is used,
It is an object of the present invention to provide an advantageous chemical copper plating solution that is free from the adverse effects of impurities, has a long life, is highly stable, and has high plating efficiency. [Summary of the Invention] A chemical copper plating solution comprising divalent copper ions, a complexing agent for divalent copper ions, a reducing agent for divalent copper ions, a PH adjuster, and a solution stabilizer, which includes at least the aforementioned solution. A complexing agent for divalent copper ions consisting of an aminocarboxylic acid in an amount equal to or greater than the ion concentration in the composition, and a trace amount of triethanolamine capable of complexing the iron ions contained in the composition. It includes. The present inventors have investigated the cause of the decrease in the lifespan and stability of the chemical copper plating solution due to the replenishment chemicals mentioned above, and have found that colloid formation due to iron ions contained as impurities in the replenishment chemicals. I discovered that there is a reason. Based on this knowledge, the present inventors further investigated various compounds that prevent the formation of the colloid, and found that the addition of triethanolamine was extremely effective, and thereby arrived at the present invention. . In other words, if the aminocarboxylic acid and triethanolamine, which is a trace amount compared to the amount of the aminocarboxylic acid added, coexists in the chemical copper plating solution, the stability constant of triethanolamine with respect to divalent copper ions is extremely small. , divalent copper ion forms a complex with aminocarboxylic acid, which has an extremely large stability constant for the divalent copper ion, and does not form a complex with triethanolamine;
The stability constant of triethanolamine for valent iron ions is larger than that of aminocarboxylic acids, so it forms extremely stable complexes with trivalent iron ions, so trivalent iron ions do not form complexes with aminocarboxylic acids. . Therefore, trivalent iron ions brought in as impurities in low-purity supplementary chemicals do not destroy the complex formed between divalent copper ions and aminocarboxylic acids, and without forming colloids. By selectively complexing with triethanolamine, it has become possible to prevent the deterioration of the plating solution and improve the solution life, solution stability, and plating efficiency. [Embodiment of the Invention] An embodiment of the present invention will be specifically described below. The equipment used for chemical copper plating in this example is a plating tank with a capacity of 5000, and the plating solution is pumped every minute.
It was circulated at a flow rate of 5000 μm through a polypropylene filter with a porosity of 5 μm, a Teflon heat exchanger, and maintained at a given temperature. This circulation system is equipped with an injection system for supplying copper sulfate, an aqueous solution of sodium hydroxide, formalin, etc.
A device that automatically analyzes and replenishes the concentration of the main components in the liquid ensures a constant concentration at all times. The stability of the solution was determined by determining the copper plating efficiency. The plating conditions were such that the plating speed was constant at approximately 2 μm/h, and the plating area of the plated object was 1 dm ² /h. The compositions of the chemical copper plating solution and replenishment solution in this example are as shown below. Also write down the plating conditions. [] Chemical copper plating solution composition, conditions CuSO ₄・5H ₂ O (industrial chemical)...10g EDTA-2Na (industrial chemical)...30g NaOH (first grade chemical)...Amount to give PH: 12.05 Formalin (special grade chemical)... 3ml α,α′-dipyridyl (special grade chemical)…40mg Polyethylene glycol stearylamine (special grade chemical)…50mg Triethanolamine (special grade chemical)…as shown in the table below Ion exchange water…amount equal to 1 Plating temperature: 75 °C [] Replenishment liquid composition ○Copper sulfate CuSO ₄・5H ₂ O (industrial chemical)
…200g Ion-exchanged water…amount considering the whole as 1 ○B Caustic soda NaOH (first class chemical)…40
0g Ion-exchanged water...amount that makes the whole 1 ○ Ha Formalin Formalin (special grade chemical)...500ml Ion-exchanged water...amount that makes the whole 1 Continuously under the above plating composition and conditions using the above-mentioned plating chemicals After plating for 50 hours, triethanolamine was added as shown in the table below to determine the copper plating efficiency. As a reference example, No. 1 in Table 1 shows a case where special grade chemicals with good purity were used as all chemicals. When using this special grade chemical with good purity,
Plating was performed without adding triethanolamine, and the copper plating efficiency after 50 hours of plating was approximately 100%. On the other hand, as a comparative example, when plating was performed using the above-mentioned industrial chemicals without adding triethanolamine, the copper plating efficiency was about 87%. As shown in No. 2 of the table.
At this time, after plating was completed, precipitation of plating was observed on the bottom of the plating tank and inside the polypropylene filter. This is a manifestation of the adverse effects caused by components other than the essential components mentioned above. Therefore, as an example of the present invention, when 0.001 g/g of triethanolamine was added, the copper plating efficiency could be improved to 90% (No. 3). As the amount of triethanolamine added increases, the copper plating efficiency increases, ranging from 0.01 to
A copper plating efficiency close to the theoretical value was obtained in the range of 0.5 g/(No. 4 to No. 6). The plating film obtained at this time had the same level of gloss as the plating film of all special grade chemicals, and was smooth. Furthermore, when the amount of triethanolamine added was further increased, decomposition of the plating solution was observed, and the copper plating efficiency decreased (No.
7).

〔Effect of the invention〕

As described above, the effect of increasing copper plating efficiency by adding triethanolamine according to the present invention is obvious. Therefore, according to the present invention, the practicality of chemical copper plating in cases where there is a possibility of containing impurities, such as when industrial chemicals are used, can be dramatically improved, and low-cost chemical copper plating can be achieved. There is an effect that it can be done. This effect is extremely significant, and is not limited to economic effects such as the use of inexpensive industrial chemicals and improved efficiency in the use of copper, but also prevents negative effects such as adhesion of plating on plating equipment. To eliminate the need to remove copper adhering to a chemical copper plating device by etching, and also to eliminate the need for waste liquid treatment of the etching solution. Therefore, it even has an economical effect on chemical copper plating as a whole. It goes without saying that the effect of adding triethanolamine is due to the above effect and is not related to the composition of chemical copper plating.

Claims (1)

[Scope of Claims] 1. A chemical copper plating solution comprising divalent copper ions, a complexing agent for divalent copper ions, a reducing agent for divalent copper ions, a PH adjuster, and a liquid stabilizer, at least A complexing agent for divalent copper ions made of aminocarboxylic acid in an amount equal to or greater than the ion concentration in the solution, and a trace amount of triethanol capable of complexing the iron ions contained in the composition. A chemical copper plating solution characterized by containing an amine. 2. Claim 1, wherein the weight ratio of the divalent copper ion complexing agent made of aminocarboxylic acid and triethanolamine contained in the chemical copper plating solution is 60 to 3000:1. chemical copper plating solution.