Description

FILM SUBSTRATE FORMED WITH FINE CIRCUIT THEREON AND MANUFACTURING METHOD THEREOF

Technical Field

[1] The present invention relates to a film substrate including a fine circuit formed thereon and a method of manufacturing the film substrate, and, more particularly, to a film substrate and a method of manufacturing the film substrate, which enables a fine circuit to be easily and reliably formed on a thin film, which is not a rigid film but a flexible film. Background Art

[2] Among typical processes of forming a circuit on a substrate, two processes are extensively used, namely, a photo-etching process, in which a photosensitive material is applied to the surface of a copper plate which is layered on an insulating substrate, a positive circuit is printed thereon, and the material is then developed and immersed in a chemical etching solution to remove portions of the copper plate other than the circuit region, and a screen printing process, in which incised and raised portions, which are to constitute a circuit, are formed on the surface of a print master, conductive ink is applied to the incised and raised portions, and the conductive ink, applied to the incised and raised portions, is transferred to a screen, thus forming a circuit substrate.

[3] However, the photo-etching process is problematic in that the amount of expensive metal material that is lost and the amount of etching solution that is required are somewhat high, the etching process inevitably involves chemical pollutants, and all of the instruments used in the manufacture of circuit substrates are expensive, which increases the cost of manufacturing circuit substrates and complicates the manufacturing operation, thus hindering mass production, while the screen printing process does not involve an etching procedure, so that it entails little or no loss of metal material and almost no problem of pollution attributable to the chemicals. However, in the screen printing process, the electrical resistance value of the circuit is not consistent depending on the screen printing conditions applied to the print master, and thus the reliability of the circuit is deteriorated, thus restricting application to a limited range. Further, it is impossible in practice to realize a circuit having a line width within a highly-restricted range of several nanometers to tens of nanometers through the process.

[4] To overcome the above problems, a process has been proposed, in which a fine circuit is formed on a substrate through an imprinting technique, and which may be

classified into a thermal transfer process and an ultraviolet process.

[5] As shown in FIG. 7, the thermal transfer process is conducted in such a way that a substrate, which is coated with a resist made of polymethylmethacrylate (PMMA), is pressed with a stamp, on which a nano-sized pattern is formed in a relief fashion, under conditions of high temperature, the substrate is removed after a cooling procedure, and the resist remaining on the substrate is thoroughly removed through anisotropic etching. However, this process has a problem in that it is difficult to achieve the alignment of multiple layers because of thermal deformation.

[6] Further, as shown in FIG. 8, the ultraviolet process is conducted in such a way that a transfer layer is applied on a silicon substrate, an ultraviolet transmitting stamp is held at a position that is spaced apart from the transfer layer, a low- viscosity UV- curable resin is charged between the transfer layer and the stamp using surface tension, the stamp is brought into contact with the transfer layer, ultraviolet light is radiated on the UV-curable resin to cure the resin, the stamp is removed therefrom, and the UV- curable resin is subjected to an etching process and a lift-off process, thus forming a nano-structure in relief on the substrate. However, this process has a problem in that it is highly complex.

[7] Furthermore, the above processes are hard to apply to substrates that are made of tin flexible material. Disclosure of Invention

Technical Problem

[8] Accordingly, the present invention has been made keeping in mind the above problems occurring in the prior art, and an object of the present invention is to provide a film substrate including a fine circuit formed thereon and a method of manufacturing the film substrate, the manufacturing process of which is simplified without causing thermal deformation of the substrate. Technical Solution

[9] In order to accomplish the above object, the present invention provides a method of manufacturing a film substrate including a fine circuit formed thereon, including: preparing a master which includes a raised fine circuit pattern formed on one or both surfaces thereof; stamping the master on a film substrate so as to form an incised fine circuit corresponding to the raised fine circuit on the film substrate; removing the master from the film substrate; sputtering metal on the film substrate so as to fill the incised fine circuit pattern with the metal; and removing the metal sputtered on the surface of the film substrate such that the metal charged in the incised fine circuit pattern remains therein.

[10] The method may further include forming a protective layer covering the remaining

metal constituting a circuit.

[11] In the method according to the present invention, the stamping the master may be conducted under conditions in which the film substrate is not completely cured but is soft, under conditions in which the film substrate is softened by heating, or under conditions in which the film substrate is cured at an ambient temperature.

[12] In the method according to the present invention, the film substrate may be made of polyimide or polyester, or may be made by applying liquid epoxy, thermoplastic resin or UV-curable resin on a polyimide or polyester sheet.

[13] In the method according to the present invention, the removing the metal may be conducted by removing the metal using a grinding tool.

[14] In the method according to the present invention, the forming the protective layer may be conducted by attaching a solid sheet-shaped resin to the film substrate over the entire surface thereof to cover the metal constituting the circuit, by applying liquid resin over the entire surface of the film substrate, by plating only an area on the metal constituting the circuit and a peripheral area thereof with gold or silver, one or more times so as to improve conductivity, or by plating only an area on the metal constituting the circuit and a peripheral area thereof with gold or silver one or more times so as to improve conductivity, and then attaching a solid sheet-shaped resin to the film substrate over the entire surface thereof or applying liquid resin over the entire surface of the film substrate.

[15] In the method according to the present invention, the preparing the master may include: forming an insulating area and a receptive groove on the surface of a metal plate, thus providing a base electrodeposited plate; subjecting the base electrodeposited plate to an electrocasting process, thus forming an electrodeposited metal layer in the receptive groove in the surface of the metal plate; and growing the electrodeposited metal layer in the receptive groove, from a peripheral region toward the center of the insulating area, by continuously performing electrocasting. In this case, the method may further include preparing a master electrodeposited plate by continuously performing electrocasting, in which a gap between the electrodeposited metal layers has a predetermined size, and applying a release agent to the master electrodeposited plate and subjecting the master electrodeposited plate to an electrocasting process, thus providing a master that includes a raised circuit pattern corresponding to the gap.

[16] Alternatively, the method may include forming an insulating area and a receptive groove on the surface of a metal plate, thus providing a base electrodeposited plate; subjecting the base electrodeposited plate to an electrocasting process, thus forming an electrodeposited metal layer in the receptive groove in the surface of the metal plate; and growing the electrodeposited metal layer in the receptive groove, from a peripheral region toward the center of the insulating area, by continuously performing elec-

trocasting. In this case, the method may further include preparing a master elec- trodeposited plate by continuously performing electrocasting, in which the gap between the electrodeposited metal layers has a predetermined size, and applying a release agent to the master electrodeposited plate and subjecting the master electrodeposited plate to an electrocasting process, thus providing a master which includes a raised circuit pattern corresponding to the gap.

[17] Further, the present invention provides a film substrate including a fine circuit formed thereon, which is manufactured using the method.

[18] The features and advantages of the present invention will be more clearly understood from the following detailed description, taken in conjunction with the accompanying drawings.

[19] The terms and words used in the specification and the claims must not be construed to have exclusive and literal meanings but must be understood to include a broad range of meanings within which the inventors can most suitably explain the present invention.

Advantageous Effects

[20] According to the method of the present invention, which is intended to manufacture a film substrate including a fine circuit, the method of the present invention can be applied to a film substrate made of thin flexible material in a simple and stable manner.

[21] Further, the present invention is capable of protecting the fine circuit formed on the film substrate from the external environment, and is capable of increasing the conductivity of the circuit. Brief Description of the Drawings

[22] FIG. 1 is a flow chart showing a method of manufacturing a film substrate including a fine circuit formed thereon, according to a preferred embodiment of the present invention;

[23] FIG. 2 is a schematic process view illustrating the flow chart of FIG. 1;

[24] FIGS. 3 to 5 are schematic views showing different examples of the formation of the protective layer of FIG. 2;

[25] FIG. 6 is a schematic process view illustrating the method of manufacturing the master of FIG. 2;

[26] FIG. 7 is a view illustrating a method of manufacturing a master using a thermal transfer process; and

[27] FIG. 8 is a view illustrating a conventional method of manufacturing a master using an ultraviolet process. Best Mode for Carrying Out the Invention

[28] The above objects, features and advantages of the present invention will be more

clearly understood from the following detailed description.

[29] Hereinafter, a film substrate which includes a fine circuit according to a preferred embodiment of the present invention is explained with reference to the accompanying drawings.

[30] Prior to describing the present invention, it should be noted that the same reference numerals are used throughout the different drawings to designate the same or similar components. In the description of the present invention, the concrete descriptions of functions and structures relating to the associated prior art are omitted so as not to obscure the description of the present invention.

[31] As shown in FIG. 1, the method of manufacturing a film substrate including a fine circuit formed thereon, according to the present invention, comprises a master- preparing step (SI lO), a master-stamping step (S 120), a master-removing step (S 130), a metal sputtering step (S 140), a sputtered metal-removing step (S 150) and a protective layer- forming step (S 160). The method is more specifically described with reference to FIG. 2.

[32] As shown in FIG. 2, in the master-preparing step (Sl 10), a master 20, which includes a circuit pattern 21 formed on one or both surfaces thereof in a raised fashion, is prepared. The process of preparing the master 20 will be described in greater detail later.

[33] In the master-stamping step (S 120), an external force is constantly applied to the upper surface of the master 20, and thus a film substrate 11 is stamped with the master 20. This stamping operation may be conducted under conditions in which the film substrate 11 is not completely cured but is in a softened state, in which the film substrate 11 is softened due to the application of heat thereto, or in which the film substrate 11 is completely cured at ambient temperature.

[34] In this regard, the film substrate 11 may be prepared simply by providing a substrate made of polyimide or polyester, or by providing a substrate which is produced by applying liquid epoxy, thermoplastic resin or UV-curable resin on a polyimide or polyester sheet. In the latter case, it is preferable that the stamping operation be conducted prior to the complete curing of the liquid epoxy, thermoplastic resin or UV-curable resin, followed by allowing the complete curing.

[35] In the master-removing step (S130), the film substrate 11 is provided with an incised circuit pattern having a desired pattern shape.

[36] In the metal sputtering step (S 140), the film substrate 11 is evenly subjected at the upper surface thereof to a sputtering process such that the incised circuit pattern 12 formed on the film substrate 11 is filled with metal 13. This sputtering process may selectively include any appropriate one of the known processes according to the operation conditions, and is not limited to any specific process.

[37] In the sputtered metal-removing step (S 150), the metal sputtered on the surface of the film substrate 11 is entirely removed using a known grinding tool 41. At this point, the metal charged in the incised circuit pattern 12 is not removed, but remains therein, thus forming a fine circuit.

[38] In the protective layer-forming step (S 160), a solid sheet-shaped resin 14 is attached to the entire surface of the film substrate 11, or liquid resin 14 is evenly applied to the film substrate 11, thus forming a protective layer covering the metal 13 constituting the circuit.

[39] Alternatively, the protective layer may be prepared by subjecting only an area on the metal 13 constituting the circuit and a peripheral area thereof, to a single plating process using gold or silver, as shown in FIG. 3, or may be prepared by subjecting the plated area of the metal 13 to a further plating process using gold or silver, as shown in FIG. 4. Depending on the process conditions, the plating process may be conducted three times or more. In the case where the protective layer is formed through the plating, as described above, the protective layer has conductivity, thus increasing the conductivity of the metal 13.

[40] Furthermore, as shown in FIG. 5, the protective layer may be formed in such a manner that only the area on the metal 13 constituting the circuit and a peripheral area thereof are subjected to first plating and/or second plating, and then a solid sheet- shaped resin 14 is attached to the entire surface of the film substrate 11, or a liquid resin 14 is evenly applied to the entire surface of the film substrate 11.

[41] Referring now to FIG. 6, the process of preparing the master 20 is described below.

[42] In FIG. 6(a), a photosensitive material is first applied to the upper surface of a metal plate 31, a pattern film having various desired pattern lines is placed on the photosensitive material, and the photosensitive material is subjected to an exposure process through the pattern film, thus providing a base electrodeposited plate 30a including an insulating area 32 and a receptive groove 33.

[43] In FIG. 6(b), the base electrodeposited plate 30a is subjected to an electrocasting process, so that an electrodeposited metal layer 34 is formed in the receptive groove in the surface of the metal plate 31.

[44] In FIG. 6(c), as the electrocasting process continues, the electrodeposited metal layer 34 grows upwards and then laterally, so that the electrodeposited metal layer 34 grows from the peripheral region toward the center of the insulating area 32.

[45] In FIG. 6(d), with the continuing electrocasting process, the electrodeposited metal layer 34 continually grows, and thus the gap 35 between the electrodeposited metal layers 34 become narrow. When the gap 35 grows to the desired size, the electrocasting operation is stopped. The resulting product may be referred to as a master electrodeposited plate 30. The master electrodeposited plate 30 may be directly

employed as a master without requiring a separate process for manufacturing the master 20.

[46] Next, in FIG. 6(e), a release agent is applied to the master electrodeposited plate 30 for later release of the plate. Subsequently, additional electrodeposition is conducted on the master electrodeposited plate 30 to thus provide a master 20 including a raised circuit pattern 21 formed thereon. Alternatively, through a liquid resin process, liquid resin is applied at a predetermined thickness to the master electrodeposited plate 30 so as to fill all of the gaps 35 with the liquid resin, and then the applied resin is allowed to cure, resulting in the master 20 including a raised circuit pattern 21. In this case, a releasing agent may be applied to assure easy release of the master 20.

[47] As such, the master 20 may be made of rigid material through the electrodeposition process, or may be made of soft material though the liquid resin process.

[48] The present invention should not be construed as being limited to the above- described embodiments, and those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention. Such modifications, additions and substitutions fall within the scope defined by the accompanying claims.

[49]