KR101612500B1 - A Method to Fabricate Ultra Low Density Three-Dimensional Thin-Film Structures Using Beads - Google Patents

Abstract

(B) connecting the beads to each other; (c) forming a thin film on the surface of the beads; (d) (E) removing the internal material of the thin film, thereby manufacturing an ultra-low density three-dimensional thin film structure using beads capable of large-scale and mass production of an extremely low-density three-dimensional thin film structure at low cost .

Description

Technical Field [0001] The present invention relates to a method of fabricating ultra-low density three-dimensional thin film structures using beads,

The present invention relates to a method of manufacturing an extremely low-density three-dimensional thin film structure, and more particularly, to a method of manufacturing an extremely low-density three-dimensional thin film structure using a bead capable of miniaturizing and mass- .

Conventionally, low-density materials such as styrofoam, sponge, aerogels, and foamed metal have been disadvantageous in terms of mechanical strength and stiffness because defects are present in irregular cells existing therein.

Recently, TA Schaedler, et al., Science, Vol.334 pp.962-965 November 18, 2011.) has a three-dimensional lattice truss structure and has a density of 1 / 1000 levels of ultra-low-density metal micro-lattice has been introduced.

Hereinafter, a method for manufacturing a metal micro-grid will be described with reference to FIG.

First, a mask having a pattern in which fine holes are regularly punctured is disposed on a specific surface of a liquid photo-polymer bulk solidified when exposed to ultraviolet rays. Thereafter, when ultraviolet rays are irradiated onto the mask, the liquid photosensitive resin is exposed to a plurality of beams passing through the mask and solidified. In this case, since the solid resin has a density higher than that of the liquid photosensitive resin, so-called " self propagating " phenomenon occurs in which ultraviolet light is totally guided into the solid resin and dispersed without being dispersed. When this process is repeated with different ultraviolet irradiation directions, a lattice made of a solid resin is formed inside the bulk of the liquid photosensitive resin. Finally, the liquid photosensitive resin is removed from the solid-phase resin lattice, the nickel-based alloy NiP is subjected to autocatalytic electroless plating on the surface of the solid-state resin lattice, and the solid phase resin is removed by chemical etching, The micro-grid is completed.

These micro-gratings are based on a lithography technique well-established in semiconductor manufacturing processes, and have advantages of relatively low density and relatively high strength and rigidity. However, according to the manufacturing method described above, since the truss elements are formed by the ultraviolet rays irradiated only in the out-of-plane direction, there is a disadvantage in that the truss elements are lacking in the in-plane direction, . In other words, as shown in FIG. 3, since the in-plane directional truss element at the red dotted line is absent in the unit cell indicated by yellow, when the compression load is applied at the upper portion, the outward direction truss element tends to collapse prematurely as shown in the right figure.

On the other hand, Japanese Patent No. 10-1341216 (hereinafter referred to as "Prior Art 1") discloses an extremely low-density three-dimensional thin film structure capable of overcoming the structural instability of a conventional microgrid and a method of manufacturing the same. As shown in FIG. 4, in the case of Prior Art 1, a three-dimensional resin structure is formed by first irradiating parallel ultraviolet rays through a hole of a mask disposed on the surface of a liquid photosensitive resin in a plurality of directions and curing. Thereafter, the liquid resin is removed, and the surface of the three-dimensional resin structure is entirely plated with metal. Finally, the outermost surface of the three-dimensional resin structure is polished to selectively remove the metal plating layer, and then the solid resin in the metal plating layer is removed by etching or the like to complete a very low-density three-dimensional thin film structure. For reference, FIG. 5 exemplifies the mask and the ultraviolet ray irradiation direction used in the conventional art 1 as described above, the solid resin structure obtained by irradiating the mask and ultraviolet rays in FIG. 5 at the upper part of FIG. 6, The extremely low density three-dimensional thin film structure finally produced by plating and etching the resin structure is shown.

The manufacturing method according to the above-described prior art 1 is expected to solve the problem of low strength and rigidity due to the structural instability of the conventional micro-grating, and it is expected that the miniaturization of the micro-grating, the mass productivity and the manufacturing cost can be reduced . In this regard, an apparatus for practically implementing a very low density three-dimensional thin film structure of the prior art 1 is specifically disclosed in Patent Application No. 10-2014-0032162 (hereinafter referred to as "Prior Art 2"), Shows such a device.

However, all of the fabrication methods of the ultra-low density three-dimensional thin film structure described above are based on the technology of the photolithography technology, and thus expensive expensive optical materials can not be used as materials, resulting in a high manufacturing cost. In addition, due to the nature of the optical resin, there is a limit in the depth of penetration due to the attenuation of the ultraviolet energy passing through the photoresist, so that it is difficult to manufacture the total thickness of the product to a maximum of 10 mm or more.

Separately, Patent Application No. 10-2012-0070122 (hereinafter referred to as "Prior Art 3") has been proposed as a technique for manufacturing a very low-density three-dimensional thin film structure irrespective of a photolithography technique. In the prior art 3, a resin wire is woven to form a three-dimensional lattice truss structure; a metal tube is formed by coating or plating a metal on the surface of the three-dimensional lattice truss structure; And all the truss elements constituting the three-dimensional lattice truss structure are embodied as thin metal tubes to have a stable rigidity structure. FIG. 8 shows a very low density metal structure manufactured according to the prior art 3. As shown in FIG. 8, the extremely low density metal structure 10 according to the prior art 3 has an empty hollow tube shape, so that the density can be minimized. Specifically, thin-walled tube-shaped wires are crossed to form truss elements, and these truss elements are gathered to form a three-dimensional lattice truss structure, thereby providing a multi-scale hierarchical structure, Is expected to be achieved.

However, in order to put the conventional technology 3 into practical use, a three-dimensional loom that forms a three-dimensional lattice truss with a resin wire is required. However, a three-dimensional loom that can be practically used has not been developed yet. It is expected that the cost will rise because it has to have a complex and elaborate structure.

Disclosure of the Invention The present invention has been made in order to solve the problems of the prior art described above, and it is an object of the present invention to provide a method of manufacturing an ultra-low density three-dimensional thin film structure by using beads capable of large- And to provide a method for manufacturing an extremely low density three-dimensional thin film structure.

As means for solving the above-mentioned technical problem,

(A) placing a plurality of beads in contact with each other; (b) connecting the beads together; (c) forming a thin film on the surface of the beads; (d) removing a portion of the thin film; And (e) removing the internal material of the thin film. The present invention also provides a method for manufacturing a very low-density three-dimensional thin film structure using beads.

In this case, the step (a) may be performed by arranging the beads in a two-dimensional or three-dimensional pattern.

In this case, the beads may have the same or different sizes.

In this case, the step (b) may be carried out by any one of the following methods: thermal bonding by heating, solvent bonding by chemical dissolution, and bonding by curing of a liquid material.

In this case, the connection portion of the beads may have a fillet shape.

In this case, the step (c) may be performed by any one of CVD, PVD, ALD, electroplating, electroless plating, coating and powder metallurgy, liquid immersion and spraying.

In this case, the step (d) may be performed by any one of sandpaper, electric discharge machining, laser, focused ion beam, and electrolytic polishing.

According to the present invention, since the extremely low density three-dimensional thin film structure is manufactured without using the photolithography technique, it is possible to reduce the cost due to the use of the expensive optical resin and to solve the problem of the thickness limitation of the product.

In addition, since it is not based on a three-dimensional weaving technique using a resin wire, an expensive weaving device is unnecessary, and thus a very low-density three-dimensional thin film structure can be manufactured at a lower cost.

In addition, since the manufactured three-dimensional thin film structure has a spherical shell shape, high strength and rigidity can be obtained.

In addition, by adjusting the number of beads and the number of arrays in preparation for photolithography, it is possible to mass-produce a three-dimensional thin film structure without any size limitation from small size to large size.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic view showing a process for producing a metal micro-
FIG. 2 is a schematic view of a metal micro-grid fabricated according to the manufacturing method of FIG.
FIG. 3 is a schematic view showing a collapse state of the metal micro-grid shown in FIG.
FIG. 4 is a schematic view showing a process for producing a very low density three-dimensional thin film structure according to Prior Art 1,
5 is a view showing a mask and an ultraviolet ray irradiation used in the fabrication of the ultra-low density three-dimensional thin film structure of FIG. 4,
6 shows a solid-state resin structure obtained by irradiating the mask and ultraviolet rays shown in Fig. 5, and Fig. 6 shows a very low-density three-dimensional thin film structure finally manufactured by plating and etching a resin structure,
FIG. 7 shows a manufacturing apparatus capable of implementing the manufacturing method of FIG. 4,
8 shows a very low density metal structure fabricated according to the prior art 3,
FIG. 9 is a process flow diagram illustrating a method of manufacturing a very low-density three-dimensional thin film structure using beads according to a preferred embodiment of the present invention,
FIGS. 10 to 13 are views illustrating a bead arrangement type applicable to a method of manufacturing a very low-density three-dimensional thin film structure using beads according to a preferred embodiment of the present invention,
14 is a diagram illustrating a method of connecting beads arranged in the pattern of FIG. 10 to each other,
15 to 21 are diagrams of a very low density three-dimensional thin film structure manufactured according to a preferred embodiment of the present invention,
22 is a structural analysis model for evaluating the strength and rigidity of the ultra-low density three-dimensional thin film structure manufactured according to the preferred embodiment of the present invention,
23 is a diagram showing a boundary condition of the model shown in Fig. 22,
Figs. 24 to 26 are diagrams showing the results of structural analysis of the model shown in Fig. 22; Fig.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art can easily carry out the present invention. The present invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. In order to clearly explain the present invention, parts not related to the description are omitted, and similar parts are denoted by similar reference numerals throughout the specification.

FIG. 9 is a flowchart illustrating a method of manufacturing a very low-density three-dimensional thin film structure using beads according to a preferred embodiment of the present invention.

As shown in FIG. 9, a method of fabricating a very low-density three-dimensional thin film structure using beads according to a preferred embodiment of the present invention includes steps of arranging beads, connecting beads, A step of removing a portion of the thin film, and a step of removing an inner material of the thin film. The respective steps will be sequentially described below.

Arrangement of beads

The step of arranging the beads is a process for determining the shape of the very low density three-dimensional thin film structure to be manufactured, and a plurality of beads are prepared and placed in contact with a desired pattern. The arrangement of the beads may be a two-dimensional pattern or a three-dimensional pattern in which two or more layers are superimposed on each other. In consideration of the physical, mechanical, thermal, chemical, electrical, and electromagnetic characteristics required for the final product, . In this case, the beads may all be composed of the same size, or be composed of two or more different sizes, and are not particularly limited. Also, the material of the beads and whether the beads are filled inside are not particularly limited. However, when the beads are manufactured in an empty form using the resin, the beads can be easily removed later. On the other hand, the method of laminating beads is also not particularly limited. For example, it is also possible to sequentially laminate beads inside a frame having a certain shape, or to arrange the beads in a single layer structure and then stack them in a plurality of layers.

Hereinafter, the arrangement of beads will be described as an example.

FIGS. 10 to 13 are views illustrating a bead arrangement type applicable to a method of manufacturing a very low-density three-dimensional thin film structure using beads according to a preferred embodiment of the present invention.

First, as shown in FIG. 10, beads 110 of one size may be arranged to have a rectangular grid pattern in the xy plane and the xz plane, respectively. It is also possible to use a bead arrangement pattern from the crystal structure of various solids present in the natural world. For example, as shown in FIG. 11, a bead 110 of one size may be divided into a face centered cubic (FCC), a body centered cubic (BCC), a hexagonal close packed (HCP) 12), or the best of FCC, BCC, and HCP, as shown in FIG. 12, as shown in FIG. 12, The beads 110 may be disposed such that the close packed plane is parallel to the bottom surface. As shown in FIG. 13, the beads 110, 120, and 130 having different sizes may be arranged in a pattern similar to the atoms of NaCl and CsCl. In addition, beads may be irregularly arranged without a certain pattern It is possible.

Connection of beads

Once the placement of the beads is complete, connect the beads that are in contact with each other. The connection of the beads can be achieved by any of the following methods: thermal bonding by local heating by contact heating using external heating or electric conduction, solvent bonding by chemical dissolution of beads, and bonding by applying a separate liquid resin between the beads and curing Can be selected and applied. In this case, for the sake of convenience of explanation, only a liquid phase is used as a substance used in curing, but it is not limited thereto, and it should be understood that other liquid substances are applicable if the beads can be connected to each other through a curing process.

Hereinafter, the connection structure of the beads will be described in more detail with reference to a curing method using a liquid resin as an example.

FIG. 14 is a view illustrating a method of connecting beads arranged in the pattern of FIG. 10 to each other.

As shown in FIG. 14, a connection portion between the beads 110 and the beads 110 'is formed into a fillet shape through solidification from a liquid phase to a solid phase. In this case, the size of the connecting part depends on the capillary phenomenon of the liquid resin and the degree of shrinkage upon curing. The enlarged view of FIG. 14 shows a fillet-shaped connection portion, which shows that the liquid resin is filled in the connection portion and thinly coated on the surfaces of the beads 110 and 110 '. Therefore, the inside of the liquid resin has an open cell structure that is connected to each other through the connection portion, and thus, the internal space can be utilized. That is, when the open cell structure is opened as in the present invention, it can be used as a heat exchange medium such as a radiator through a coolant such as air or water through an internal space, or as a fluid storage, passage, or wiring. On the other hand, unlike the present invention, a closed cell structure, for example, a foamed resin or a foamed metal composed of a foam such as styrofoam or a foamed metal in which a plurality of spheres are simply bonded to each other can not be utilized.

Thin film formation

After the beads are connected to each other, a solid film is formed on the surface of the beads. Thin film formation can be performed by physical, chemical, electrical, and thermal methods, and is not particularly limited. For example, various vacuum deposition methods (see: http://en.wikipedia.org/wiki/Vacuum_deposition), electroplating, electroless plating, coating and powder metallurgy, liquid immersion Spraying or the like can be applied.

Some thin film removal

Some thin film removal is a process of forming a passage for removing the inner material of the thin film, and a part of the thin film formed on the surface of the beads is removed to expose the inner material, that is, the beads, the connecting portion and the surface coating material. The removal of the thin film can be carried out by physical, chemical, electrical and thermal methods, and is not particularly limited. For example, sanding of the outer surface, electric discharge machining (EDM), local cutting of the thin film by laser, focused ion beam (FIB), electropolishing and the like can be applied.

Removal of thin film materials

When a part of the thin film is removed to expose the internal material of the thin film, internal materials are removed by physical, chemical, electrical and thermal methods through the part. For example, if the temperature at which the internal material is melted, the boiling temperature or the burning temperature is lower than that of the surface film, heat can be applied to each of them to make them liquid, gaseous or burnable. It is also possible to dissolve only the internal material. In this case, since the inner material of the thin film is connected to the open cell structure through the fillet-shaped connecting portion as described above, the entire inner material can be removed even if only a part of the thin film is removed. Therefore, according to the present invention, the thin film surface remains without damage, so that a very low-density three-dimensional thin film structure composed of a spherical shell, which is the final product desired, can be obtained.

15 to 21 show the extremely low density three-dimensional thin film structure fabricated as described above.

15 and 16 are cross-sectional diagrams illustrating a method of connecting beads by the method shown in FIG. 14, wherein the diameter d of the connecting portion and the diameter D / D of the bead are 0.3 and 0.6, Dimensional spherical shell composed of spherical shells. 15 and 16 show the unit cell observed in three directions, and the lower part shows the shape observed in three directions of the 3 * 3 * 3 cell cluster and the shape of the connection part of one cell.

17 to 19 show a very low density three-dimensional thin film structure manufactured from a shape in which the beads of FIG. 12 are arranged in a pattern similar to FCC, BCC, and HCP in a perspective view and a projection view.

20 and 21 show a very low density three-dimensional thin film structure fabricated from a pattern in which a plurality of beads of two sizes in FIG. 13 are arranged in a pattern similar to the atoms of NaCl and CsCl, in a perspective view and a projection view.

On the other hand, the present inventor has conducted a structural analysis to evaluate the strength and rigidity that can be obtained when the three-dimensional thin film structure is manufactured according to the present invention.

First, as shown in FIG. 22, hollow spheres having a diameter of 10 mm were simply joined to each other, and a shape manufactured according to the present invention with the same size was selected as a model. The boundary between the spheres and the spheres The conditions were set as shown in Fig.

Thereafter, structural analysis was carried out under the above-mentioned conditions, and the results are shown in Figs. 24 to 26. Specifically, Fig. 24 shows the load-displacement curve when two models are subjected to a compressive load, and Fig. 25 and Fig. 26 show the stress distributions according to the deformation of the two models, respectively.

24 and 25, in the case of the hollow spheres, the contact area between the ball and the ball is narrow and the ball is pushed horizontally, so that the ball is broken at the contact portion at a very low load and the stiffness is also very low.

On the other hand, as shown in FIGS. 24 and 26, in the case of the embodiment according to the present invention, the contact portion of the ball and the ball is relatively large, and the ball has a shape erected up and down, so that the yield is delayed and the stiffness is also high.

That is, in the present invention, since the connecting portion is implemented in a soft fillet shape, high strength and rigidity can be obtained compared to hollow spheres.

The preferred embodiments of the present invention have been described in detail with reference to the drawings. It will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present invention as defined by the appended claims.

Therefore, the scope of the present invention is defined by the appended claims rather than the foregoing detailed description, and all changes or modifications derived from the meaning, range, and equivalence of the claims are included in the scope of the present invention. .

110, 110 ', 120, 130: beads

Claims (7)

A method for manufacturing a three-dimensional thin film structure in which both inside and outside are empty based on a thin film,
(a) placing a plurality of beads in contact with each other;
(b) connecting the beads together;
(c) forming a thin film on the surface of the beads;
(d) removing a portion of the thin film; And
(e) removing the internal material of the thin film;
Lt; / RTI >
(B) is performed in such a manner that a liquid resin is applied to the entire surface of the beads and is then cured to form a fillet-shaped connection portion with respect to the beads, so that the inner region of the liquid resin is opened Wherein the beads are formed in a cell structure and communicate with each other through the connection portion. The method according to claim 1,
Wherein the beads are arranged in a two-dimensional or three-dimensional pattern in the step (a). The method according to claim 1,
Wherein the beads have the same or different sizes. ≪ RTI ID = 0.0 > 11. < / RTI > delete delete The method according to claim 1,
Wherein the step (c) is performed by any one of CVD, PVD, ALD, electroplating, electroless plating, coating and powder metallurgy, liquid immersion and spraying. ≪ / RTI > The method according to claim 1,
Wherein the step (d) is performed by any one method selected from the group consisting of sandblasting, electric discharge machining, laser, focused ion beam, and electrolytic polishing.

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