KR101045101B1 - Method for fabricating super-hydrophilicity surface and metal substrate with the super-hydrophilicity surface by the same method - Google Patents

Abstract

The present invention provides a method for processing an surface of a metal substrate to produce an extremely hydrophilic surface and a metal substrate having an extremely hydrophilic surface produced by the method. In the method of processing a very hydrophilic surface according to the present invention, i) plasma-etch the surface of the metal substrate to form microscale fine irregularities on the surface of the metal substrate, and ii) the surface of the metal substrate by anodizing the surface of the metal substrate. Forming nanoscale micro holes on the surface.

Metal, Surface Finish, Extreme Hydrophilic, Hydrophilic, Plasma Etch, Micro-Scale, Anodized, Nano-Scale

Description

METHOD FOR FABRICATING SUPER-HYDROPHILICITY SURFACE AND METAL SUBSTRATE WITH THE SUPER-HYDROPHILICITY SURFACE BY THE SAME METHOD}

The present invention relates to a method for processing an extremely hydrophilic surface, and more particularly, to a method for manufacturing an extremely hydrophilic surface by processing the surface of the metal substrate, and a metal substrate having an extremely hydrophilic surface produced by the method.

Generally, the surface of a metal substrate has inherent surface energy. This surface energy appears as the contact angle of the liquid with respect to the metal substrate when any liquid contacts the metal substrate. If the contact angle is smaller than 90 °, the water droplets lose their shape and exhibit hydrophilicity, which wets the surface of the metal substrate. On the other hand, when the contact angle is greater than 90 °, the water droplets exhibit hydrophobicity that easily flows according to external forces without wetting the surface of the metal substrate while maintaining the shape of the sphere.

The inherent contact angle of the surface of the metal substrate can be changed through surface treatment. That is, a hydrophilic surface having a contact angle of less than 90 ° may exhibit extremely hydrophilicity due to a smaller contact angle through surface treatment. The extremely hydrophilic surface can for example be applied to the fin of the heat exchanger. In this case, it is possible to improve the efficiency of the heat exchanger by improving the flow of condensate generated on the surface of the fin.

Micro Electro Mechanical Systems (MEMS) processes are known as techniques for varying the contact angle of the surface of metal substrates for specific applications. MEMS process is an application of a semiconductor manufacturing technology, it is possible to form micro-scale or nano-scale fine irregularities on the surface of the metal substrate using the MEMS process. The MEMS process is a state-of-the-art technology in which the semiconductor technology is mechanically applied, but it is an expensive process, difficult to process a large area, and has a limitation in that the processing effect does not last long.

The present invention provides an extremely hydrophilic surface processing method capable of simplifying a manufacturing process, reducing manufacturing costs, and easily surface-treating a large and large area metal substrate, and a metal substrate having an extremely hydrophilic surface produced by the method. To provide.

According to an embodiment of the present invention, an extremely hydrophilic surface processing method includes: i) plasma etching a surface of a metal substrate to form microscale irregularities on the surface of the metal substrate, and ii) anodizing the surface of the metal substrate. To form nanoscale micro holes in the surface of the metal substrate.

Plasma etching may be performed in an inductively coupled plasma etching apparatus. Plasma etching may use a mixed gas of Ar, Cl ₂ and BCl ₃ as the source gas. Plasma etching may be performed for 3 to 10 minutes at a power in the range of 100W to 500W and a pressure of 30mTorr or less.

The fine holes may have a diameter in the range of 20 nm to 200 nm and an aspect ratio in the range of 5 or more and 50 or less. The metal substrate may include at least one of aluminum and titanium.

Metal substrates according to one embodiment of the present invention have an extremely hydrophilic surface processed by the method described above. The metal substrate may include at least one of aluminum and titanium.

According to the extremely hydrophilic surface processing method according to the present invention, plasma etching and anodizing process can be used to simplify the manufacturing process and reduce the manufacturing cost. In addition, large-scale and large-area metal substrates can be easily surface-treated, and the processing effect can be sustained for a long time.

In addition, the metal substrate according to the present invention increases the hydrophilicity by the dual-scale concavo-convex structure in which the micro-scale concavo-convex and nano-scale micro holes are formed together, and the contact angle is 10 ° or less. Extremely hydrophilic surfaces can be achieved.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art may easily implement the present invention. As those skilled in the art would realize, the described embodiments may be modified in various different ways, all without departing from the spirit or scope of the present invention.

1 is a process flow chart showing an extremely hydrophilic surface processing method according to an embodiment of the present invention.

Referring to FIG. 1, the method of processing an extremely hydrophilic surface according to the present embodiment may include a first step S1 of forming microscale irregularities on a surface of a metal substrate by plasma etching, and a surface of the metal substrate by anodizing. The second step (S2) to form a nano-scale micro holes in.

Here, the micro scale means a size in the range of 1 μm or more and less than 1000 μm, and the nano scale means a size in the range of 1 nm or more and less than 1000 nm. The metal substrate of the present embodiment implements an extremely hydrophilic surface having a contact angle of 10 ° or less by the aforementioned micro scale irregularities and nano scale fine holes.

2 is a schematic cross-sectional view of a plasma etching apparatus.

Referring to FIG. 2, an inductively coupled plasma etcher 100 may be used as the plasma etching device. The inductively coupled plasma etching apparatus 100 includes a process chamber 12, a substrate electrode 14 provided inside the process chamber 12, a discharge coil 16 provided on an outer circumferential surface of the process chamber 12, A first high frequency power source 18 connected to the discharge coil 16 and a second high frequency power source 20 connected to the substrate electrode 14 are included. The metal substrate 22 to be etched is mounted on the substrate electrode 14.

Injecting a source gas consisting of a mixture of Ar, Cl ₂ and BCl ₃ into the process chamber 12, and discharge coil from the first high frequency power source 18 while maintaining the interior of the process chamber 12 at a pressure of 30 mTorr or less Electric power in the range of 100W to 500W is applied to (16) for 3 to 10 minutes. Then, a plasma is generated in the process chamber 12 to etch the surface of the metal substrate 22. At this time, the ion energy reaching the metal substrate 22 may be adjusted by selectively applying power to the substrate electrode 14 from the second high frequency power source 20.

If the applied power of the discharge coil 16, the pressure in the process chamber 12, and the process time do not satisfy the above-described conditions, it is difficult to form microscale fine irregularities. Metal substrates 22 to which plasma etching may be applied include aluminum and titanium. Although the plasma etching process using the inductively coupled plasma etching apparatus has been described above, other types of plasma etching apparatuses may be applied.

3 is a cross-sectional view schematically illustrating a surface of the metal substrate that has passed through the first step of FIG. 1.

Referring to FIG. 3, micro-scale fine unevenness 24 is formed on the surface of the metal substrate 22 through plasma etching. The size of the fine concave-convex 24, that is, the height of the convex portion 241, the depth of the concave portion 241, the interval between the concave portions 241, and the like may be used to determine the type of source gas, the pressure in the process chamber 12, and the discharge coil 16. It may vary depending on the strength and etching time of the applied power, and by controlling these values appropriately, the shape of the fine unevenness 24 may be controlled.

Conventional metals are hydrophilic substances whose liquid contact angle is less than 90 degrees. When the surface of the metal substrate 22 is plasma-etched to form microscale fine concavo-convex 24, a phenomenon in which the contact angle becomes small and the hydrophilicity becomes strong appears.

4 is an electron micrograph showing the surface of the metal substrate before plasma etching, and FIG. 5 is a photograph showing the results of experiments on contact angles by dropping water droplets on the surface of the metal substrate shown in FIG. 4. The metal substrate shown in FIG. 4 is aluminum and exhibits a contact angle of approximately 82 °. In all the photographs described below, the metal substrate is aluminum.

6 is an electron micrograph showing the surface of the metal substrate subjected to the first step of FIG. 1, and FIG. 7 is a photograph showing the results of experiments of contact angles by dropping water droplets on the surface of the metal substrate shown in FIG.

Plasma etching conditions of the metal substrate shown in FIG. 6 are as follows.

① Etching Device: Inductively Coupled Plasma Etching Device

② discharge coil applied power: 300W

③ Pressure of process chamber: 15mTorr

④ source gas: a mixture of Ar (50sccm) and Cl ₂ (15sccm) and BCl ₃ (40sccm)

⑤ Etching time: 10 minutes

Referring to FIGS. 6 and 7, micro-scale irregularities are formed on the surface of the metal substrate by plasma etching, and the metal substrate on which plasma etching is completed has a contact angle of about 58 °. This contact angle is smaller than the contact angle observed before plasma etching, and it can be confirmed that the hydrophilicity of the metal substrate is increased by plasma etching.

As such, by forming the fine concavo-convex through plasma etching, compared to the conventional MEMS process, the manufacturing process can be simplified and the manufacturing cost can be lowered. In addition, large-scale and large-area metal substrates can be easily surface-treated, and the processing effect can be sustained for a long time.

8 is a schematic cross-sectional view of the anodic oxidation apparatus.

Referring to FIG. 8, the anodic oxidation device 200 includes a circulating water tank 26 through which cooling water is circulated, and a magnetic stirrer 28 for stirring the electrolyte solution inside the water tank 26 at a constant speed. The metal substrate 22 and the counter electrode 30 are immersed in the electrolyte in the water tank 26, and an anode power supply and a cathode power supply are applied to the metal base 22 and the counter electrode 30, respectively, to perform anodization. The electrolyte may include at least one of sulfuric acid, phosphoric acid, and oxalic acid, and the counter electrode 30 may be platinum (Pt).

FIG. 9 is a schematic cross-sectional view of the surface of the metal substrate that has passed through the second step of FIG. 1.

Referring to FIG. 9, as the anodic oxidation process is performed, an oxide film 21 is formed on the surface of the metal substrate 22, and nanoscale micro holes 32 are formed in the oxide film 21. The fine holes 32 are formed along the fine irregularities of the micro scale. The diameter and depth of the fine holes 32 can be easily controlled by adjusting the concentration of the electrolyte, the intensity of the applied voltage or the etching time.

The nano-scale fine hole 32 serves to maximize the hydrophilicity by making the contact angle smaller on the surface of the metal substrate 22 having the hydrophilicity enhanced by plasma etching. Therefore, the metal substrate 22 of the present embodiment can obtain a hydrophilic enhancement effect by the dual-scale uneven structure in which the micro scale and the nano scale are mixed, and have an extremely hydrophilic surface.

In the present embodiment, the fine holes 32 may have a diameter in a range of 20 nm to 200 nm, and may have an aspect ratio in a range of 5 or more and 50 or less. When the diameter of the fine holes 32 is large, hydrophilicity is exhibited even at a small aspect ratio. However, when the aspect ratio is less than 5, the hydrophilicity is weakened. Therefore, the aspect ratio 32 of the fine holes is preferably 5 or more. In the case where the diameter of the fine holes 32 is small, hydrophilicity is exhibited better as the aspect ratio is larger. However, even when the aspect ratio exceeds 50, the hydrophilicity is not significantly improved. Therefore, the aspect ratio of the fine holes 32 is 50 or less in consideration of the process time. Is preferred.

FIG. 10 is an electron micrograph showing a surface of the metal substrate subjected to the second step of FIG. 1, and FIG. 11 is a photograph showing a result of experiments on contact angles by dropping water droplets on the surface of the metal substrate shown in FIG. 10. For reference, the vertical bar floating on the metal substrate in FIG. 11 is an experimental tool used to drop water droplets.

The anodic oxidation conditions of the metal substrate shown in FIG. 10 are as follows.

① Electrolyte: Oxalic acid with 0.3 molarity

② Constant voltage applied to metal base and counter electrode: 40V

③ electrolyte temperature: 15 ℃

④ Process time: 10 hours

Referring to FIGS. 10 and 11, nano-scale micro holes are formed on the surface of the metal substrate by an anodizing process, and the metal substrate on which the anodic oxidation process is completed shows a contact angle close to zero.

As described above, the metal substrate 22 of the present embodiment has a micro-scale fine unevenness 24 by plasma etching and nano-scale fine holes 32 by anodization simultaneously, so that the contact angle is 10 ° or less. It has an extremely hydrophilic surface. The metal substrate 22 is used in various mechanical parts that need to improve the flow-through characteristics of the liquid, and may be applied to, for example, fins of a heat exchanger.

While the present invention has been described in connection with what is presently considered to be practical exemplary embodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, Of course.

1 is a process flow chart showing an extremely hydrophilic surface processing method according to an embodiment of the present invention.

2 is a schematic cross-sectional view of a plasma etching apparatus.

3 is a cross-sectional view schematically illustrating a surface of the metal substrate that has passed through the first step of FIG. 1.

4 is an electron micrograph showing the surface of the metal substrate before plasma etching.

5 is a photograph showing the results of experiments on contact angles by dropping water droplets on the surface of the metal substrate shown in FIG. 4.

6 is an electron micrograph showing the surface of the metal substrate subjected to the first step of FIG. 1.

7 is a photograph showing the results of experiments on contact angles by dropping water droplets on the surface of the metal substrate shown in FIG. 6.

8 is a schematic cross-sectional view of the anodic oxidation apparatus.

FIG. 9 is a schematic cross-sectional view of the surface of the metal substrate that has passed through the second step of FIG. 1.

FIG. 10 is an electron micrograph showing the surface of the metal substrate subjected to the second step of FIG. 1.

11 is a photograph showing the results of experiments on contact angles by dropping water droplets on the surface of the metal substrate shown in FIG. 10.

Claims (9)

Micro-scale fine unevenness is formed on the surface of the metal substrate by plasma etching the surface of the metal substrate directly by plasma exposure; Anodizing the surface of the metal substrate to form nanoscale micro holes on the surface of the metal substrate Ultra-hydrophilic surface processing method comprising a. The method of claim 1, The plasma etching method is an extremely hydrophilic surface processing method performed in an inductively coupled plasma etching apparatus. The method of claim 2, The plasma etching method is an extremely hydrophilic surface processing method using a mixed gas of Ar, Cl ₂ and BCl ₃ as a source gas. The method of claim 3, The plasma etching is performed for 3 to 10 minutes at a power in the range of 100W to 500W and a pressure of 30mTorr or less. The method of claim 1, The microholes are extremely hydrophilic surface processing method having a diameter in the range of 20nm to 200nm. The method of claim 5, The microhole has an extremely hydrophilic surface processing method having an aspect ratio in the range of 5 to 50. The method according to any one of claims 1 to 6, And the metal substrate comprises at least one of aluminum and titanium. A metal substrate having an extremely hydrophilic surface processed by the method of any one of claims 1 to 6. The method of claim 8, The metal substrate includes at least one of aluminum and titanium.

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