JP2005015860A - Mirror finish etching liquid for copper and copper alloy - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an etching solution with which the surface of copper or a copper alloy can be subjected to mirror finish treatment by chemical treatment. <P>SOLUTION: The mirror finish etching liquid for copper or a copper alloy is obtained by blending the etching main agent of hydrogen peroxide and sulfuric acid with a mirror finish agent by the combination of aliphatic amines, azoles and a compound dissolved in water and dissociating chlorine ions. The etching liquid may further comprise a nonionic surfactant. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a mirror finish etching solution for copper and copper alloys.
[0002]
[Prior art]
Various etching processes are performed in the manufacturing process of the printed circuit board. Among these, in the pre-treatment process when nickel / gold plating is applied to the copper and copper alloy surface of the terminal portion of the printed circuit board and the printed circuit board manufacturing process by the transfer method, the surface of the copper and copper alloy There is a demand for the development of an etching method capable of mirror finishing.
[0003]
In response to this requirement, for example, an etching solution in which piperidine, which is an aliphatic amine, and phosphoric acid are blended with an etching main component of sulfuric acid and hydrogen peroxide has been proposed as a gloss treatment agent for copper and copper alloy surfaces. (Patent Document 1). However, with this composition, the surface of copper and copper alloy can be finished to a certain degree of brightness, but the surface cannot be completely smoothed to give a mirror surface. Therefore, at present, there is no practically usable etching solution that can mirror-treat the surfaces of copper and copper alloys, and the mirror-finishing of copper and copper alloys is performed exclusively by mechanical polishing. . However, in recent years, the printed circuit board has been thinned, and its thickness has become 30 μm or less, which is extremely difficult or impossible to cope with by mechanical polishing.
[0004]
[Patent Document 1] JP-A-2-236289
[Problems to be solved by the invention]
Under the present situation as described above, it is not difficult to expect that the demand for a mirror surface treatment method for copper and copper alloys by chemicals will increase more and more. In view of this situation, an object of the present invention is to provide an etching solution that can mirror-finish the surfaces of copper and copper alloys.
[0006]
[Means for Solving the Problems]
As a result of intensive studies to solve the above-mentioned problems, the inventors have dissolved in aliphatic amines, azoles, and water as an etching main component of hydrogen peroxide and sulfuric acid and as a mirror finish component. Thus, by adding a compound capable of dissociating chlorine ions, it has been found that an etching solution capable of mirror finishing the surfaces of copper and copper alloys is provided, and the present invention has been completed. That is, the present invention relates to a mirror-finishing etching solution for copper and copper alloy, which contains hydrogen peroxide, sulfuric acid, aliphatic amines, azoles, and a compound that dissolves in water to dissociate chloride ions.
[0007]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in more detail, but the present invention is not limited to the following description.
[0008]
As described above, the copper and copper alloy mirror finish etching solution according to the present invention includes hydrogen peroxide, sulfuric acid, aliphatic amines, azoles, and a compound that dissolves in water and dissociates chloride ions. Features.
[0009]
In the etching solution according to the present invention, hydrogen peroxide and sulfuric acid are used as etching main component. The amount of hydrogen peroxide used in the etching solution according to the present invention is preferably 0.1 g / L to 100 g / L, more preferably 1 g / L to 50 g / L, and 10 g / L to 20 g. More preferably, it is / L. The amount of sulfuric acid used is preferably 0.1 g / L to 500 g / L, more preferably 1 g / L to 200 g / L, and still more preferably 5 g / L to 100 g / L. .
[0010]
In the etching solution according to the present invention, aliphatic amines, azoles, and a compound that dissolves in water and dissociates chloride ions function as a mirror finish by a combination thereof. For example, aliphatic amines have been proposed in the art to be used as a gloss imparting agent for the surfaces of copper and copper alloys, as proposed in US Pat. However, when used alone, it was far from achieving a mirror finish. In the present invention, it has been found that a mirror finish can be applied to the surfaces of copper and copper alloy by combining and blending the above three components. According to the experiments by the present inventors, for an etching solution containing only two compounds of hydrogen peroxide and sulfuric acid, for example, an azole and a compound that dissolves in water and dissociates chloride ions, the surfaces of copper and copper alloy In the etching solution that contains only two compounds that dissolve aliphatic amines and water and dissociate chlorine ions in hydrogen peroxide and sulfuric acid, the surface of copper and copper alloy Was pear-shaped, and it was confirmed that both were far from the mirror finish of copper and copper alloy.
[0011]
Examples of aliphatic amines that can be used in the etching solution according to the present invention include piperidine, N-aminopiperidine, tri-n-butylamine, cyclohexylamine, dicyclohexylamine, pyrrolidine, diethylamine, and diisobutylamine. it can. The amount of aliphatic amines used in the etching solution according to the present invention is preferably 0.01 g / L to 50 g / L, more preferably 0.1 g / L to 20 g / L, and more preferably 1 g / L. More preferably, it is L-10g / L.
[0012]
Examples of azoles that can be used in the etching solution according to the present invention include 1H-5-amino-1,2,3,4-tetrazole and 1H-5-methyl-1,2,3,4-. Tetrazole, 1H-1,2,3,4-tetrazole, pyrazole, imidazole, 1H-1,2,3-benzotriazole, 1H-1,2,3-methylbenzotriazole, 1H-1,2,3-triazole And so on. The amount of azoles used in the etching solution according to the present invention is preferably 0.0001 g / L to 20 g / L, more preferably 0.001 g / L to 10 g / L, and 0.01 g / L. More preferably, it is L-5g / L.
[0013]
In the present invention, examples of the compound that dissolves in water and dissociates chloride ions include sodium chloride, potassium chloride, hydrochloric acid, magnesium chloride, calcium chloride, and cupric chloride. The amount of the compound used in the etching solution is preferably 0.00001 g / L to 0.02 g / L, more preferably 0.0001 g / L to 0.01 g / L as the amount of chlorine ions. Preferably, it is 0.0005 g / L-0.005 g / L.
[0014]
Although not bound by the following theory, in the present invention, a combination of aliphatic amines, azoles, and a compound that dissolves in water and dissociates chloride ions is added to the etching agent of hydrogen peroxide and sulfuric acid. By doing so, it is considered that the mechanism capable of performing mirror finishing of copper and the copper surface is as follows. As shown in FIG. 1, copper and a copper alloy are not mere single crystals, and a large number of crystal defects 11 exist on the surface of the copper (and copper alloy) foil 10. It tends to be more easily etched. When such a copper and copper alloy are treated with a normal etching agent, the crystal defect portion 11 is etched more, resulting in many fine irregularities 12 on the surface as shown in FIG. As a result, the surface has a lot of irregular reflection and a low glossiness. On the other hand, when the etching solution according to the present invention containing aliphatic amines, azoles, and a compound that dissolves in water and dissociates chloride ions is used, as shown in FIG. Amines 22 and chloride ions 23 are more adsorbed in the crystal defect portion 11, while azoles 21 are more adsorbed than in the defect portion. In addition, aliphatic amines are involved in film formation due to the ability to form complex ions with respect to copper ions, and chloride ions form a film of sparingly soluble cuprous chloride. Form. On the other hand, azoles form a film having an effect of increasing the etching of copper by performing the function of transferring the electrons of copper to hydrogen peroxide by involving π electrons. As a result, it is considered that the crystal defect portion 11 is protected from etching and the degree of etching other than the defect portion is increased, and these effects are combined to produce an extremely smooth mirror surface from which the crystal defect 11 has been removed.
[0015]
In addition, in the etching liquid concerning this invention, it is more preferable to mix | blend a nonionic surfactant further. The nonionic surfactant acts as a release accelerator (defoamer) for oxygen gas generated from the surface of copper and copper alloy by reaction with the etching agent, and oxygen gas bubbles adhere to the surface of copper and copper alloy. Thus, the subsequent etching is hindered, and the so-called etching spots are prevented from forming. As the nonionic surfactant used for this purpose, polyethylene glycol phenyl ether, polyethylene glycol styrenated phenyl ether, polyethylene glycol benzyl ether and the like can be used. The degree of polymerization of ethylene glycol in the above compound is desirably 4 or more, and a compound having a degree of polymerization of less than 4 produces an insoluble black-brown by-product over time, and adheres to the tank wall or the surface of the treated substrate and becomes fouled. This is not preferable. When a nonionic surfactant is blended in the etching solution according to the present invention, the amount used is preferably 0.01 g / L to 20 g / L, preferably 0.1 g / L to 10 g / L. More preferably, it is more preferably 0.5 g / L to 5 g / L.
[0016]
【Example】
The following examples further illustrate the present invention, but the present invention is not limited by the following description.
[0017]
Example 1
The etching liquid concerning this invention was formed by mix | blending the following components.
Hydrogen peroxide: 16g / L
Sulfuric acid: 9g / L
Piperidine: 1g / L
Tri-n-butylamine: 1 g / L
Cyclohexylamine: 1g / L
1H-5-amino-1,2,3,4-tetrazole: 0.05 g / L
Polyethylene glycol phenyl ether: 1g / L
Sodium chloride: 0.5 ppm as chlorine content
Copper sulfate pentahydrate: 40 g / L
Pure water: remaining amount Copper sulfate was added to reproduce the actual process conditions. That is, in the actual etching process, since the etching solution is repeatedly used, copper is dissolved by the etching to produce copper sulfate, which is accumulated in the etching solution. It has been pointed out that this copper sulfate may adversely affect the etching reaction, especially the gloss treatment by etching, and in fact, the case where the surface gloss of copper and copper alloys has decreased due to the accumulation of copper sulfate. Has also been reported. Therefore, in this example, an experiment was conducted by adding copper sulfate to the test etching solution in advance in order to bring it closer to the actual process conditions.
[0018]
The above etching solution was kept at 35 ° C., and an inner substrate MCL-E67 (copper foil: GTS-MP) manufactured by Hitachi Chemical Co., Ltd. was immersed as a test piece, and etching was performed for 2 minutes. At this time, assuming that the processing was performed in an actual etching apparatus, the test piece was swung vertically and horizontally so that the etching solution was parallel to the surface of the test piece without any stagnation. After the etching treatment, the test piece was washed with pure water and dried. It was also confirmed by visual inspection that the treated surface was finished in a mirror state. Moreover, the surface of the test piece was observed with a scanning electron microscope (SEM). An SEM photograph is shown as FIG. FIG. 4 shows that an extremely smooth surface with few defects was obtained.
[0019]
Comparative Example 1
As Comparative Example 1, an etching solution was formed by blending the following components (substantially the same composition as the etching solution used in the example of Patent Document 1).
[0020]
The etching liquid concerning this invention was formed by mix | blending the following components.
Hydrogen peroxide: 16g / L
Sulfuric acid: 9g / L
Phosphoric acid: 2 g / L
Piperidine: 1g / L
Pure water: remaining amount Etching test was conducted in the same manner as in Example 1 using the above etching solution. When the test piece subjected to the etching treatment was visually confirmed, the treated surface was uniformly cloudy and did not become a mirror surface state. Moreover, the SEM photograph of the surface of a test piece is shown as FIG. From FIG. 5, it is recognized that the surface of the treated piece has a larger number of defects and is in a rough surface state as compared with the surface treated in Example 1.
[0021]
Moreover, the brightness | luminance of the surface of the test piece processed in Example 1 and Comparative Example 1 was measured using the brightness | luminance measuring apparatus shown in FIG. KEYENCE MS-H50 was used as the power supply unit, KEYENCE LX2-10V was used as the amplifier, KEYENCE LX2-100T was used as the laser transmitter, and KEYENCE LX2-100R was used as the laser receiver. As shown in FIG. 9, the laser beam output from the laser transmitter strikes the luminance measurement sample and is reflected. At this time, if there is unevenness on the surface of the sample, the laser beam is scattered, and as a result, the amount of laser reflected light to the laser receiver decreases, whereas if the surface of the sample is smooth, the laser beam is transferred to the laser receiver. The amount of reflected light from the laser increases. In the measurement of the amount of reflected light, the laser reflected light amount value of a standard sample (the sample processed in Example 1 in the following experiment) is preset to 100%, and the laser reflected light amount of the comparative sample is relative to the standard sample. Measured by value.
[0022]
The surface brightness (reflected light amount) of the test piece treated in Comparative Example 1 was 4.6% compared to Example 1, which was significantly lower than that of the treated piece of Example 1.
Comparative Example 2
As Comparative Example 2, an etching solution was formed by blending the following components.
[0023]
The etching liquid concerning this invention was formed by mix | blending the following components.
Hydrogen peroxide: 16g / L
Sulfuric acid: 9g / L
1H-5-amino-1,2,3,4-tetrazole: 0.05 g / L
Polyethylene glycol phenyl ether: 1g / L
Sodium chloride: 0.5 ppm as chlorine content
Copper sulfate pentahydrate: 40 g / L
Pure water: remaining amount Etching test was conducted in the same manner as in Example 1 using the above etching solution. As a result of visually recognizing the test piece subjected to the etching treatment, the surface was partially roughened, lacking in uniformity, and a finish in which a glossy portion and a rough surface were mixed. Moreover, the SEM photograph of the surface of a test piece rough surface part is shown as FIG. From FIG. 6, it is recognized that the surface of the treated piece has a larger number of defects and is in a rough surface state as compared with the surface treated in Example 1. Moreover, when the brightness | luminance (reflected light quantity) of the surface of the rough surface part of a test piece was measured, it was 1.2% compared with Example 1, and was remarkably low compared with the process piece of Example 1. FIG.
[0024]
From the above results, it was found that the addition of azoles and a compound that dissolves in water and dissociates chlorine ions to the etching solution does not provide a mirror finish etching solution.
[0025]
Comparative Example 3
As Comparative Example 3, the following components were blended to form an etching solution.
The etching liquid concerning this invention was formed by mix | blending the following components.
Hydrogen peroxide: 16g / L
Sulfuric acid: 9g / L
Piperidine: 1g / L
Tri-n-butylamine: 1 g / L
Cyclohexylamine: 1g / L
Polyethylene glycol phenyl ether: 1g / L
Sodium chloride: 0.5 ppm as chlorine content
Copper sulfate pentahydrate: 40 g / L
Pure water: remaining amount Etching test was conducted in the same manner as in Example 1 using the above etching solution. When the test piece subjected to the etching treatment was visually confirmed, the surface exhibited a pear shape and was not glossy at all. Moreover, the SEM photograph of the surface of a test piece is shown as FIG. From FIG. 7, it can be seen that the surface of the treated piece has a larger number of defects and is in a rough state as compared with the surface treated in Example 1. Moreover, the luminance of the surface of the test piece was 1.4% compared with Example 1, which was significantly lower than that of the treated piece of Example 1.
[0026]
From the above results, it was found that the addition of an aliphatic amine and a compound that dissolves in water and dissociates chlorine ions to the etching solution does not provide a mirror finish etching solution.
[0027]
For reference, an SEM photograph of the surface of an untreated specimen is shown in FIG. From FIG. 8, it is recognized that the surface of the treated piece has a larger number of defects and is in a rough surface state as compared with the surface treated in Example 1. Moreover, when the brightness | luminance of the surface of the untreated test piece was measured, it was 2.4% compared with Example 1, and was remarkably low compared with the processed piece of Example 1. FIG.
[0028]
【The invention's effect】
ADVANTAGE OF THE INVENTION According to this invention, the etching liquid which can perform a mirror surface finish with respect to copper and copper alloy by a chemical | medical solution process is provided. The present invention provides a very useful means as a mirror finishing process for copper and copper alloys in the manufacturing process of printed circuit boards, which are undergoing remarkable thinning, and has a great industrial value.
[Brief description of the drawings]
FIG. 1 is a conceptual diagram showing the state of the surface of copper and a copper alloy.
FIG. 2 is a conceptual diagram showing the state of the surfaces of copper and copper alloy etched with a conventional etching solution.
FIG. 3 is a conceptual diagram showing a state when etching is performed with an etching solution according to the present invention.
4 is a SEM photograph of the surface of a copper test piece etched according to Example 1. FIG.
5 is an SEM photograph of the surface of a copper test piece etched according to Comparative Example 1. FIG.
6 is an SEM photograph of the surface of a copper test piece etched according to Comparative Example 2. FIG.
FIG. 4 is an SEM photograph of the surface of a copper test piece etched according to Comparative Example 3;
FIG. 8 is an SEM photograph of the surface of an untreated copper test piece.
FIG. 9 is a sample surface brightness (reflected light amount) measuring apparatus used in Examples / Comparative Examples of the present invention.

Claims (4)

A copper and copper alloy mirror finish etching solution comprising hydrogen peroxide, sulfuric acid, aliphatic amines, azoles, and a compound that dissolves in water to dissociate chloride ions. The mirror finish etching solution according to claim 1, further comprising a nonionic surfactant. 0.1 g / L to 100 g / L hydrogen peroxide, 0.1 g / L to 500 g / L sulfuric acid, 0.01 g / L to 50 g / L aliphatic amines, 0.0001 g / L to 20 g / L The mirror surface finish etching liquid of Claim 1 or 2 containing the compound which melt | dissolves in 0.00001 g / L-0.02 g / L of water as a chlorine amount, and dissociates a chlorine ion. The mirror surface finishing etching liquid in any one of Claims 1-3 containing 0.01 g / L-20 g / L nonionic surfactant.

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