JPS6337187B2 - - Google Patents

Description

[Detailed description of the invention]

[Field of Application of the Invention] The present invention relates to a chemical copper plating solution capable of obtaining a high-strength copper coating. [Prior art] Chemical copper plating solutions usually contain copper as the main component.
ions, reducing agents for copper() ions, complexing agents for copper() ions, hydroxide ions, etc. Copper plating films obtained from such chemical copper plating solutions do not have sufficient mechanical properties such as strength and elongation. Therefore,
A problem arises in which conductors on printed circuit boards break due to thermal shock, repeated thermal stress, etc. In order to solve this problem, methods have been published to improve the mechanical properties of copper plating films obtained by chemical copper plating. Examples include the above principal components and 2,
A chemical copper plating solution containing 2'-dipyridyl, polyethylene glycol, and an alkali-soluble inorganic silicon compound. In this chemical copper plating solution, the alkali-soluble inorganic silicon compound is converted to silicon dioxide and is 5~
If 100mg/l (0.08~1.7mmol/ as Si) is included, the tensile strength of the chemical copper plating film will be 50~58Kgw/
mm ² and elongation of 4.4 to 6.7%. However, when using this chemical copper plating solution, it was impossible to use it due to the following drawbacks. To prepare a chemical copper plating solution, ion-exchanged water obtained by ion-exchanging tap water is used. Waterworks contain a large amount of silicon compounds, which exist as nonionic silicon compounds or polymerized anions that are difficult to ion exchange. Therefore, even with ion exchange treatment, silicon compounds cannot be completely removed and are contained in ion exchange water. According to measurements by the inventors, the silicon content in ion-exchanged water is 0.04 to 0.43 mmol/(Si) on average.
Contains 0.2mmol/). Silicon-free water can be obtained by distillation. However, since chemical copper plating solutions are used on a scale of several hundred to several thousand liters, expensive distilled water cannot be used. Since chemical copper plating is used repeatedly, it introduces silicon into the plating solution.
When plating is used repeatedly, in order to maintain a constant concentration of the main components of the plating solution (copper ions, hydroxide ions, formaldehyde, etc.), an aqueous solution containing sodium copper sulfate hydroxide and formalin is replenished. The replenishment amounts of these compounds are: copper sulfate: 0.05 mol/, sodium hydroxide: 0.2 mol/, formaldehyde: 0.1 mol/, when plating 35 μm of Cu on an area of 100 cm ³ in one plating.
, Total amount of aqueous solution: 0.1 per plating solution. For example, JIS standard for sodium hydroxide (grade 1)
According to, the SiO ₂ content in sodium hydroxide is
It is set at 0.04% or less, but it has not been standardized for other compounds, and SiO ₂ is regulated as a substance that does not precipitate as an ignition residue or sulfide. Copper sulfate: 0.3%, formalin: 0.01% . Then,
Approximately 0.3 mmol/Si may be introduced through replenishment. On the other hand, the main components of the plating solution are copper sulfate: 0.04mol/, sodium hydroxide: 0.4mol/
, formalin: 0.04 mol/copper ion complexing agent: 0.12 mol/dissolved in the ion-exchanged water. As a representative copper ion complexing agent, EDTA-2Na has a ignition content of 3.8% according to the JIS standard (special grade). Therefore, the maximum Si content in the plating solution is 5.1 mmol/by just preparing the bath. Therefore, when plating is repeated, the content of Si in the plating solution increases according to the following formula. Si (mmol/) in plating solution 1 = 5.1 + 0.3n-
(1) (where n is the number of times of plating) As is clear from the above, there are many factors in which Si is contained as an impurity in the plating solution. Tokukai Akira
54-19430, from the first plating (n=1), from the first plating (n=1), the optimum amount (Si: 0.08~
There is a possibility that the amount exceeds 1.7 mmol/), and the probability is extremely high. Using chemicals with high purity will significantly increase plating costs, so
Industrial chemicals below JIS standards are used. Then,
According to formula (1), the content of Si as an impurity increases significantly. Therefore, according to the prior art, the objective could not be achieved from the first time of plating unless very expensive water and chemicals were used and the concentrations of liquid components were strictly controlled. Furthermore, even if plating becomes possible by chance, the characteristics of the plating film are sensitively affected by the Si concentration, so it may not be possible to stabilize the properties, which are the most important industrially for quality control. Ta. Furthermore, even when plating is performed using the most expensive expensive water and chemicals, the following problem occurs. According to the prior art, the Si concentration in the plating solution has a sensitive effect on the properties of the plating film, so it is necessary to strictly control the Si concentration. Analysis of Si is extremely difficult, especially when Na coexists (in liquid), such as in chemical copper plating.
(Na is 235 times as much as Si), so analyzing Si is said to be difficult. Even with atomic absorption spectrometry, the detection sensitivity is said to be about 2 mmol/. Therefore, the Si content is
When the detection sensitivity was lower than the detection sensitivity, a concentration operation of the analytical sample with poor accuracy was also used, making a rigorous analysis impossible. From this point of view as well, a plating solution with a low Si content has not been commercially viable. [Object of the Invention] The object of the present invention is to significantly improve the strength and elongation of metallic copper deposited by chemical copper plating, even if industrial chemicals are used, so that the properties are always 50 Kg/mm ² or more and 3% or more. To provide a chemical copper plating solution that is stably obtained, easy to manage, and practical. [Summary of the Invention] To achieve the above object, the inventors focused on the effects of an amine-based ethoxy surfactant and a compound of group 4B elements, and obtained a high-strength matte film within an easily controllable concentration range. The liquid composition was extensively explored. As a result, among the elements that form oxygen acid ions in an alkaline plating solution, group 4B element compounds of silicon, germanium, tin, and lead, amine-based ethoxy surfactants, αα′-dipyridyl, and O-phenylene It has been found that the objects of the present invention can be achieved by using a chemical copper plating solution containing nanthroline or a derivative thereof. The chemical copper plating solution of the present invention is a known chemical copper plating solution containing an amine-based ethoxy surfactant and αα′-dipyridyl or O-phenanthroline or a derivative thereof, to which a group 4B element compound is added. The composition is as follows. Here, amine-based ethoxy surfactants are generally

[Embodiments of the invention]

In order to explain the present invention more specifically, Examples and Comparative Examples will be given below. The plating method of chemical copper plating used in Examples and Comparative Examples is as follows. A chemical copper plating solution was adjusted to a predetermined composition, and plating was performed at 70°C. The plating load is constant at 1 dm ² /. The stainless steel plate to which chemical copper plating was applied was instantaneously applied with pyrophosphate electrolytic copper plating to form plating nuclei, and then chemical copper plating was performed. During long plating, copper () ions and other components are consumed by the plating reaction, so the concentration of the components was automatically detected and the shortage was automatically replenished. Through this operation, plating is performed while keeping the component concentration constant, and the thickness of the deposited metallic copper is approximately 50 μm.
When this was reached, the plating film was peeled off from the stainless steel plate and subjected to a tensile test. Example 1 Using the chemical copper plating solutions shown in Nos. 1 to 10 in Table 1, the characteristics of the plating film were determined. This chemical copper plating solution contains 0.3 to 300 mmol of sodium metasilicate as a silicon compound related to the present invention. Nos. 1 to 9 had a plating speed of approximately 0.5 to 3.0 μm/h, and the liquid during plating was extremely stable. Furthermore, there was no tendency for the liquid to decompose, which is characteristic of chemical copper plating. The deposited copper film had an excellent metallic copper luster. In No. 10, the plating reaction stopped due to excessive silicate ions adsorbed on the reaction surface, making it impossible to obtain a plating film. The properties of the dusting film obtained in this example are as follows:
It was found that Nos. 3 to 8 had a strength of 50 Kg/mm ² or more and an elongation of 4% or more. This characteristic is due to electrolytic copper plating,
In particular, the film properties obtained from copper pyrophosphate baths (50~
65Kg/mm ² , 4-6%). It has been found that the amount of sodium metasilicate necessary to obtain such excellent properties is 3 to 30 mmol/(85 to 850 mg/as Si). The lower limit value is a concentration effective for improving film properties, and the upper limit value is determined because adding more than that concentration will stop the plating reaction or significantly reduce elongation. As described above, in the chemical copper plating of the present invention, the properties of the plating film can be improved at a practical concentration of the silicon compound added. Therefore, it was found to be an extremely practical plating solution. Furthermore, as shown in Table 1, it was found that the effects of the present invention did not change even when various amine-based ethoxy surfactants were used. Also, instead of αα′-dipyridyl, neocuproine (2,9-dimethyl-
It was also found that the effect was the same even when a phenanthroline derivative such as phenanthroline (1,10-phenanthroline) was used.

【table】

【table】 \
R ₃
Example 2 The properties of the plating film were determined using the chemical copper plating solutions shown in Nos. 11 to 20 of Table 2. This chemical copper plating solution contains 0.3 to 100 mmol of sodium orthosilicate as a silicon compound related to the present invention. All of the matted films obtained from this chemical copper plating solution had metallic luster, and in particular, Nos. 13 to 19 were comparable to electroplated films. The amount of sodium orthosilicate added at this time was 3 to 30 mmol/, which was the same as in Example 1. Furthermore, it has been found that combinations of αα'-dipyridyl, phenanthroline, and their derivatives with amine-based ethoxy surfactants are all effective in improving the elongation and strength of the plated film. Therefore, No.13
It has been found that chemical copper plating solutions such as ~19 are extremely excellent practical plating solutions.

【table】

【table】 \ /
EPE〓1… NCH ₂ CH ₂ NR〓−(C ₂ H ₄ O−) _1
20 −(C ₃ H ₆ O−) ₄ −(C ₂ H ₄ O−) ₁₂₀ H
／ ＼
RR
Example 3 Using a chemical copper plating solution to which 10 g/each of a Si source that does not dissolve rapidly was added,
The properties of the plating film were determined as shown in Table 3. In this study, the following method was used to dissolve Si in the plating solution. A predetermined amount of the listed silicon compound was placed in a polypropylene filter installed in a system in which the plating solution was circulated by a pump. Thereafter, the solution was circulated and dissolved at a temperature of 70° C. for 5 to 50 hours without plating. After consideration, Si in the plating solution was analyzed using an atomic absorption spectrophotometer, and the result was 4 to 15 mmol/
It was found that some Si was dissolved. That is,
The compounds shown in Table 3 are gradually dissolved in the plating solution,
It is clear that the effective concentration of Si has been reached.

[Table] Example 4 The properties of deposited metallic copper were determined using the chemical copper plating solutions shown in Nos. 25 to 29 of Table 4. This chemical copper plating solution contains 1 to 100 mmol/germanium oxide as the germanium compound related to the present invention. The film obtained from this chemical copper plating solution is
It had excellent metallic luster, and its strength and elongation were similar to Examples 1 to 3. Germanium oxide added to the plating solution easily dissolves in the alkaline plating solution, resulting in [GeO(OH) ₃ ] ^- , [GeO ₂ (OH) ₂ ] ^2- ,
It was estimated that it would become a germanate ion such as {[Ge(OH) ₄ ] ₈ (OH) ₃ } ^3- . It was also presumed that these ions were effective in improving the properties of the plating film due to the same effect as silicate ions. It has also been revealed that the effective concentration of addition is 3 to 30 mmol/m, which is the same as that of silicon compounds.

[Table] Example 5 Using the chemical copper plating solutions shown in Nos. 30 to 34 in Table 5, the characteristics of deposited metallic copper were determined. This chemical copper plating solution contains 1 to 100 mmol/potassium stannate as a tin compound related to the present invention. When the concentration of tin added was in the range of 3 to 30 mmol/m, the same remarkable property improvement effect as in Examples 1 to 4 was observed. From this, it was found that the present invention is an extremely practical and excellent tamping liquid.

[Table] Example 6 The properties of deposited metallic copper were determined using the plating solutions shown in Nos. 35 to 39 of Table 6. This plating solution contains 1 to 100 mmol of basic lead carbonate as a lead compound related to the present invention. When the concentration of lead added was in the range of 3 to 30 mmol/min, remarkable property improvement effects similar to those of Examples 1 to 5 were observed. From this, it was found that the present invention is an extremely practical and excellent tamping liquid.

[Table] Comparative Example In order to further clarify the effects of the present invention, the properties of the plating film were compared using the chemical copper plating solutions shown in Table 7. The plating solutions No. 40 to 44 contain 3 to 10 mmol of sodium metasilicate.
In addition, surfactants necessary for stabilizing the plating solution,
The complexing agent for copper() ions is different from the example. As shown in No. 40, when the surfactant is different from that of the present invention, the elongation of the plated film is insufficient within the practical silicon concentration range. As shown in No. 41, this tendency is common when using surfactants that do not contain amines in their molecules. Also, No.
When the complexing agent for copper () ions is 2-mercaptobenzothiazole as in No. 42, the present invention has no effect because the plating reaction stops. Furthermore, even when a phosphoric acid ester surfactant having a polyoxyethylene group shown in No. 43 is used, the plating reaction stops. It is thought that the plating reaction stops because the adsorption power of the added component is excessive. In the example shown in No. 44, SH-192 was used as the surfactant, and the effect of the present invention was not exhibited in this case as well. Furthermore, No.45 does not contain silicon compounds.
In this case, there was no strength improvement effect at all. As is clear from the above examples, only the combination of an amine-based ethoxy surfactant, αα′-dipyridyl or O-phenanthroline or their derivatives, and a Group 4B element compound can be used in electrolytic copper in an appropriate concentration range that is easy to manage. It has properties comparable to plating.

【table】

〔Effect of the invention〕

The present invention provides a practical plating solution that could not be achieved with conventional chemical copper plating solutions. In other words, it is possible to stably obtain film properties comparable to electrolytic copper plating within a concentration range that can be easily controlled.

Claims (1)

[Claims] 1 copper() ion, copper() ion complexing agent,
A chemical copper plating solution containing a reducing agent for copper () ions, an alkali metal hydroxide, an amine-based ethoxy surfactant, αα′-dipyridyl or O-phenanthroline, or a derivative thereof, A chemical copper plating solution characterized by containing any one of the following inorganic compounds: , Ge, Sn or Pb.