JPS633951B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an electroless copper plating solution, that is, a chemical copper plating solution, used in the manufacture of printed circuit boards, etc., which eliminates self-decomposition of the solution, enables high-speed deposition, and improves the mechanical properties of the film. This relates to a chemical copper plating solution. A chemical copper plating solution having an autocatalytic action that can continuously deposit copper electrolessly without using electricity is already known. Such chemical copper plating solutions typically include a water-soluble copper salt, a complexing agent for copper ions, a reducing agent for copper ions, and a pH adjusting agent. Known chemical copper plating solutions use ethylenediaminetetraacetate as a complexing agent.
There are EDTA baths and Rothsiel salt baths that use Rothsiel salt as a complexing agent. Furthermore, it is known that various additives are added to these baths in order to improve the mechanical properties of the plating film, such as elongation and tensile strength, and to stabilize the plating solution. Typical additives include cyanides, nitriles, nitrogen-containing heterocyclic compounds, sulfur-containing inorganic compounds, polyethylene oxide, phenanthroline and its derivatives, dipyridyl and its derivatives, polyethers, polyesters, etc. There are activators and the like, and these are used singly or in combination. However, when these conventional additives are used with emphasis on improving the mechanical properties of the plating film, the plating speed slows down, and when they are used with emphasis on the plating speed, the mechanical properties of the plating film decrease. This has caused a problem in that the stability of the eyelid solution deteriorates. It is an object of the present invention to solve the above-mentioned drawbacks of conventional chemical copper plating solutions and to improve chemical copper plating without adversely affecting the plating rate and the physical and mechanical properties of the deposited metallic copper produced. Provided is a chemical copper plating solution that enables the production of metallic copper with improved bath stability and improved physical and mechanical properties such as elongation and tensile strength of the plating film and appearance such as gloss. It is in. The features of the present invention include water-soluble copper salts, 2
In a chemical copper plating solution containing a copper ion complexing agent, a PH adjusting agent, and a copper ion reducing agent,
The cyclic polyether is added alone or in combination with a nonionic surfactant. According to the chemical copper plating solution of the present invention, it is possible to improve the heating plating speed and the physical and mechanical properties of the plating film, which were previously impossible to achieve at the same time. It is also possible to ensure the stability of The agents of the present invention can be applied to metal plating solutions in general, but are particularly effective in chemical copper plating solutions. The functions of the components of the chemical copper plating solution in the present invention include water-soluble copper salt serving as a source of copper ions,
A copper ion reducing agent provides electrons that reduce the copper ion to its metallic state. Complexing agents for divalent copper ions form stable complexes with divalent copper ions and prevent the formation of cupric hydroxide in alkaline solutions. PH regulators adjust the optimal deposition potential of the bath. Here, the additive prevents the self-decomposition of the plating solution, that is, the autodeposition due to the formation of cuprous oxide, thereby extending the life of the plating solution and improving the mechanical properties of the plating film. be. All of these components are indispensable and important, but additives are particularly important in solving conventional problems. The present invention is based on the discovery of a drug having extremely excellent properties in this additive. In other words, numerous experiments have shown that adding cyclic polyether to a chemical copper plating solution can stabilize the plating bath and improve the mechanical properties of the film without slowing down the deposition rate. I came to this conclusion from the results. The invention will be described in further detail below. The water-soluble copper salt used in the chemical copper plating solution of the present invention is
Commonly it is copper sulfate. The choice is primarily for economic reasons; other copper chlorides, copper nitrates, copper acetates and organic and inorganic copper salts can also be used.
However, since these copper salts dissolve in water to form acoions, hydroxides precipitate in alkaline regions. Therefore, a complexing agent (chelating agent) that strongly binds copper divalent ions and hydroxyl groups is required. Examples of complexing agents for divalent copper ions include Rothsiel's salt, sodium salt of ethylenediaminetetraacetic acid, nitrilotriacetic acid and its alkali salts, gluconic acid, triethanolamine, diethylenetriaminepentaacetic acid, etc.; From this point of view, ethylenediaminetetraacetic acid salts can be effectively used in large quantities. As reducing agents for copper ions used in alkaline chemical copper plating solutions, formaldehyde and its condensates and derivatives such as paraformaldehyde,
Includes glyoxal, trioxan and their analogs. In addition, as other reducing agents, alkali metal borohydrides such as sodium,
There are borohydrides of potassium, and also substituted borohydrides, such as trimethoxyborohydride of sodium. Additionally, amine borane, sodium and potassium hypophosphites and the like can be used. The pH adjuster consists of acids or bases, and the selection is based on cost considerations. The agent used to raise the pH is usually sodium hydroxide, and the agent used to lower it is sulfuric acid. The additive is cyclic polyether alone or mixed with a polymeric surfactant. These are considered to be effective from the following reactions. That is, the chemical copper plating reaction when formaldehyde is used as a reducing agent is CU ²⁺ (L) + 2HCHO + 4OH ^- → Cu + H ₂ + 2H ₂ O + L ... (1) 2HCHO + OH ^- → CH ₃ OH + HCOO ^- ... (2) 2Cu ²⁺ (L) + HCHO + 5OH ^- → Cu ₂ O + HCOO ^- + 3H ₂ O ...... (3) Cu ₂ O + H ₂ O → Cu + Cu ²⁺ + 2OH ^- ... (4) It is expressed as follows. Among these, formula (1) is the main reaction in chemical plating, in which formaldehyde reduces and precipitates copper ions on a copper catalyst. Equation (2) is
Cannizars reaction occurs slightly. Formulas (3) and (4) are natural decomposition reactions and side reactions. The Cu ₂ O produced in equation (3) promotes the reaction in equation (1) using metallic copper (Cu) in the liquid produced in equation (4) as a catalytic nucleus, increasing the decomposition of the liquid. Further, Cu ₂ O is mixed into the plating film and forms a film with poor mechanical properties, that is, a brittle film with low tensile strength and no elongation. Therefore, it is an important issue to suppress the reactions of formulas (3) and (4). Therefore, in chemical copper plating solutions, cyclic polyether acts as a complexing agent for monovalent copper ions to form a stable complex with Cu ⁺ and dissolves Cu ₂ O, and also serves as a polymeric surfactant. has the effect of adsorbing Cu ₂ O, fending off the attack reaction by reducing agents, and preventing self-decomposition. The former alone is effective, but combining the two further stabilizes the plating solution and improves the tensile strength, which is the mechanical property of the film.
Significantly improves elongation. The present invention mainly relates to a cyclic polyether belonging to the former category, which acts as a complexing agent for monovalent copper ions. The cyclic polyether in the present invention forms a ring as shown below, and is expected to selectively incorporate Cu ⁺ . n is an integer of 4 or more. Since the Cu ⁺ ion has a d ² sp or dsp ² orbital, it is thought to form a tetrahedral or planar structure. Therefore, it forms a very stable complex. Such a cyclic polyether is sold by Nippon Soda KK under the name Crown Ether. The cyclic polyether of the present invention is the first synthesized and most widely known crown compound, and is called a crown ether in a narrow sense. This cyclic polyether is described in detail in the literature entitled "Synthesis of Crown Compounds" in Kagaku Special Edition 74 [published February 15, 1978 by Kagaku Dojin Co., Ltd.] Chemistry of Crown Ethers, pp. 15-25. As usual, cyclic polyethers have a basic skeleton of a cyclic oligomer of alkylene oxide (mainly ethylene oxide), with one or more aromatic rings (benzene, binaphthyl, etc.), saturated alicyclic rings such as cyclohexane rings, etc. It is produced by constructing a polyether ring using O of a heterocyclic ring such as a furan ring or a tetrahydrofuran ring as a donor atom. Among these cyclic polyethers, aliphatic crown ethers having a crown-like structure based on (C ₂ H ₄ O) _o [where n is an integer of 4 or more], such as alkylene oxide cyclic oligomers, are chemical copper It has high solubility in the plating solution and can be suitably used in the chemical copper plating solution of the present invention. Specific examples of cyclic polyether compounds that can be used in the chemical copper plating solution of the present invention include 12-crown-4, 15-crown-5, and 18-crown-6 produced by the reactions shown below. can be mentioned. The cyclic polyether added to the chemical copper plating solution is effective in small amounts;
A range of from 200 mg/l to 200 mg/l is suitable. Although this cyclic polyether is sufficiently effective when added alone, the effect is significantly increased when mixed with a polymeric surfactant, that is, a known nonionic surfactant. That is, the stability of the plating solution is significantly increased, and the physical and mechanical properties of the plating film, such as tensile strength and elongation, are improved. Moreover, the plating speed is also faster by adding this cyclic polyether than when it is not used, which is a surprising fact that could not be considered based on conventional phenomena. As the nonionic surfactant, general polyethylene oxide, polyether other than cyclic polyether, polyester, etc., and alcohols added thereto are used. The appropriate amount of this nonionic surfactant to be added is approximately the same range as in the case of cyclic polyether. EXAMPLES The present invention will be specifically explained below with reference to Examples, and its usage and effects will also be described. In addition, comparative examples are also described so that the effects of the present invention can be better understood. Example 1 In this example, after pre-treating a substrate, chemical copper plating was performed using a chemical copper plating solution that is an example of the present invention, and the stability of the plating solution, plating speed, and yield were evaluated. The condition of the plating film and the mechanical properties of the plating film were observed and measured. A sample piece of phenolic resin was used as the substrate. First, the sample piece was pretreated by performing the following steps (1) to (8) in sequence. (1) Surface roughening; (2) Degreasing with water; (3) Surface cleaning (immersion in 50 g of chromic anhydride, 500 ml of water, and 200 ml of concentrated sulfuric acid (specific gravity 1.84) for 5 minutes); (4) Washing with water; (5) Increase (50 g of tin chloride, 100 ml of hydrochloric acid, immersed in 1 part of water for 3 minutes); (6) Washing with water; (7) Activation (0.1 g of palladium chloride, 1 part of water)
(8) Rinse with water. Next, the substrate subjected to the above pretreatment was subjected to chemical copper plating. The plating solution used for chemical copper plating has the following composition (). Chemical copper plating solution composition () CuSO ₄・5H ₂ O 12g EDTA-2Na 35g 37% formalin 10ml NaOH 12g Crown ether (15-Crown-5) 10mg Polyethylene glycol 50ml Water 1 volume Use the above plating solution Then, the pH was adjusted to 12.5, the liquid temperature was maintained at 70°C, and the sample was immersed for 1 hour to perform chemical copper plating. The copper plating film obtained by the above procedure was glossy and dense. The stability and plating speed of the plating solution having the above composition were as shown in Table 1. In addition, using this plating solution, a 2 mm thick stainless steel plate (100 mm x 10 mm) was plated for 10 hours to a thickness of approximately 30 μ.
The plating film was peeled off, and the mechanical properties of the thin film were measured using an Instron tensile tester. The results are shown in Table 1. From the results in Table 1, it can be clearly seen that the chemical copper plating solution of the present invention is superior in comparison with that in the comparative example described below. Example 2 The operation was exactly the same as in Example 1, except that a chemical copper plating solution having the following composition () was used.
I conducted a test. Chemical copper plating solution composition () CuSO ₄・5H ₂ O 12g EDTA-2Na 35g 37% formalin 10ml NaOH 12g Crown ether (12-Crown-4) 30mg Water 1 amount Copper plating film on the obtained substrate It was shiny and detailed. Further, as shown in Table 1, the results of various tests were extremely superior to those in the comparative examples described below.

[Table] Examples 3, 4, 5, 6, 7 For Examples 3, 4, 5, 6, and 7, chemical copper plating solutions with the following compositions (), (), (), (), and (), respectively. The operations and tests were carried out in exactly the same manner as in Example 1, except that . Chemical copper plating solution composition () CuSC ₄・5H ₂ O 12g EDTA-2Na 35g 37% formalin 6ml NaOH 13g Crown ether (18-crown-6) 15mg Alkylaryl ether 50mg Water 1 amount Chemical copper plating solution composition () CuSO ₄・5H ₂ O 12g EDTA-2Na 35g 37% formalin 20ml NaOH 15g Crown ether (18-crown-6) 18mg Polyoxyethylene oxide 20mg Water 1 amount Chemical copper plating solution composition () CuSO ₄・5H ₂ O 12g Rothsiel salt 40g 37% formalin 10ml NaOH 15g Crown ether (12-crown-4) 15mg Polyoxyethylene polyoxy propylene block polymer 50mg Water 1 amount Chemical copper plating solution composition () CuSO ₄・5H ₂ O 12g Rothsiel's salt 40g 37% Formalin 10ml NaOH 15g Crown ether (15-crown-5) 20mg Sulfuric acid ester 15mg Water 1 amount Chemical copper plating solution composition () CuSO ₄・5H ₂ O 12g Rothsiel's salt 40g 37% Formalin 10ml NaOH 15g Crown ether (15-Crown-5) 50mg Phosphate ester 50mg Water 1 volume The resulting copper plating film on each substrate was glossy and dense. In addition, the results of various tests in each example are shown in Table 1.
As shown in , all of the samples were extremely superior to those in the comparative examples described below. Comparative Example 1 Using the following chemical copper plating solution composition (ratio), the same pretreatment as in Example 1 was performed on the same substrate as in Example 1, and the same operation as in Example 1 was carried out. Chemical copper plating treatment was applied. Chemical copper plating solution composition (ratio) CuSO ₄・5H ₂ O 15g EDTA-2Na 35g 37% formalin 10ml NaOH 12g α,α′-dipyridyl 10mg Polyethylene glycol lauryl ether
80 mg water Amount equal to 1 As can be seen from the above, this chemical copper plating solution composition (ratio) is a conventional chemical copper plating solution to which no cyclic polyether is added. The copper plating film thus obtained on the substrate was inferior to that of the above-mentioned examples in terms of gloss and density. In addition, the results of the same observations and measurements as in Example 1 are listed in Table 1, and as can be seen from Table 1, the plating speed and coating mechanical Its physical properties, etc., were significantly superior. Comparative Example 2 Using the following chemical copper plating solution composition (ratio), the same substrate as in Example 1 was subjected to the same pretreatment as in Example 1, and the same operation as in Example 1 was carried out. Chemical copper plating treatment was applied. Chemical copper plating solution composition (ratio) CuSO ₄・5H ₂ O 12g EDTA-2Na 35g 37% formalin 10ml NaOH 12g NaCN 0.1mg Polyvinyl alcohol 50mg Water 1 amount This composition solution (ratio) is also the same as in Comparative Example 1. Similarly,
This is a conventional chemical copper plating solution without added cyclic polyether. The copper plating film thus obtained on the substrate was inferior to that of the above example in terms of gloss and density. In addition, the results of the same observations and measurements as in Example 1 are listed in Table 1, and as can be seen from Table 1, the stability of the plating solution in Example 2 was higher than that in Comparative Example 2. The adhesion speed and mechanical properties of the film were significantly superior. From the above explanation and the results of Examples and Comparative Examples, it can be seen that the chemical copper plating solution of the present invention has a remarkable effect compared to the conventional chemical copper plating solution.

Claims (1)

[Claims] 1. A product containing a water-soluble copper salt, a complexing agent for divalent copper ions, a PH adjuster, and a reducing agent for copper ions,
A chemical copper plating solution characterized by the addition of cyclic polyether. 2. The chemical copper plating solution according to claim 1, wherein the cyclic polyether is added in a mixture with a nonionic surfactant. 3 Cyclic polyether has a crown-shaped structural formula based on the chemical formula (C ₂ H ₄ O) _o ; Here, n is an integer of 4 or more, and 1 selected from the group consisting of compounds represented by
The chemical copper plating solution according to claim 1 or 2, which contains at least one species. 4 Reducing agents include formaldehyde, paraformaldehyde, glyoxal, trioxane and its formaldehyde condensate, sodium, potassium,
Alkali metal borohydride of lithium and its substituted derivatives, amine borane and its substituted derivatives,
Chemical copper plating according to claim 1 or 2, which is made of one or more selected from the group consisting of hypophosphites of alkali metals such as sodium, potassium, and lithium, and substituted derivatives thereof. liquid.