Method of manufacturing rigid-flexible printed circuit board

Abstract

A method of manufacturing a rigid-flexible printed circuit board, which including: providing a first flexible film having a first metal layer on one or both surfaces; forming a circuit pattern by patterning the first metal layer; forming a second flexible film, which has a second metal layer on one surface, on one or both surfaces of the first flexible film; forming a circuit pattern by patterning the second metal layer in a rigid domain R; providing an anti-oxidation protective layer on the second metal layer in a flexible domain F; laminating at least one circuit layer on the second flexible film; and removing the circuit layer in the flexible domain F.

Claims

1. A multilayer rigid flexible printed circuit board having a rigid portion and a flexible portion, the multilayer rigid flexible printed circuit board comprising: a first flexible film including a first circuit pattern on one or both surfaces; a second flexible film disposed on the first flexible film and including a second circuit pattern on a portion of the second flexible film, positioned in the rigid portion; a bonding sheet between the first flexible film and the second flexible film; a pattern stack disposed on a part of the portion of the second flexible film to be adjacent to the flexible portion, and having a metal pattern and a protective pattern on the metal pattern; a first insulating layer disposed on the portion of the second flexible film and covering the pattern stack and including a third circuit pattern on the first insulating layer.

2. The multilayer rigid flexible printed circuit board according to claim 1, wherein the metal pattern includes substantially the same material as that of the second circuit pattern.

3. The multilayer rigid flexible printed circuit board according to claim 1, wherein the metal pattern and the second circuit pattern include a metal-plating layer.

4. The multilayer rigid flexible printed circuit board according to claim 1, wherein the metal pattern is exposed on a side surface of the rigid portion facing the flexible portion.

5. The multilayer rigid flexible printed circuit board according to claim 1, wherein the multilayer rigid flexible printed circuit board has a thickness of the rigid portion being greater than that of the flexible portion thereof.

6. The multilayer rigid flexible printed circuit board according to claim 1, wherein the bonding sheet includes at least one of an epoxy thermosetting resin and a prepreg material.

7. The multilayer rigid flexible printed circuit board according to claim 1, further comprising a bonding material layer between the second flexible film and the protective pattern.

8. The multilayer rigid flexible printed circuit board according to claim 1, wherein the protective pattern comprises a polymer material.

9. The multilayer rigid flexible printed circuit board according to claim 8, wherein the protective pattern comprises an adhesive material including polyimide.

10. The multilayer rigid flexible printed circuit board according to claim 1, wherein the second flexible film is disposed on an entire area of the first flexible film.

11. The multilayer rigid flexible printed circuit board according to claim 1, wherein the first insulating layer is disposed in contact with the protective pattern of the pattern stack.

12. The multilayer rigid flexible printed circuit board according to claim 1, wherein the second flexible film is disposed in contact with the metal pattern of the pattern stack.

13. The multilayer rigid flexible printed circuit board according to claim 1, wherein the metal pattern is physically isolated from the second circuit pattern.

14. The multilayer rigid flexible printed circuit board according to claim 1, further comprising a through hole penetrating the first flexible film and the second flexible film and a plating layer disposed on an inner wall of the through hole.

15. A multilayer rigid flexible printed circuit board having a rigid portion and a flexible portion, the multilayer rigid flexible printed circuit board comprising: a first flexible film having upper and lower surfaces and including a first circuit pattern on at least one of the upper and lower surfaces; second upper and lower flexible films disposed on the upper and lower surfaces of the first flexible film, respectively, each of the second upper and lower flexible films including a second circuit pattern on portions of the second upper and lower flexible films, positioned in the rigid portion; first and second bonding sheets disposed between the first flexible film and the second upper flexible film, and between the first flexible film and the second lower flexible film, respectively; first and second pattern stacks disposed on parts of the portions of the second upper and lower flexible films to be adjacent to the flexible portion, respectively, each of the first and second pattern stacks having a metal pattern and a protective pattern on the metal pattern; first and second insulating layers disposed on the portions of the second upper and lower flexible film to cover the first and second pattern stacks, respectively; and a third circuit pattern disposed on each of the first and second insulating layers.

16. The multilayer rigid flexible printed circuit board according to claim 15, wherein the metal pattern includes substantially the same material as that of the second circuit pattern.

17. The multilayer rigid flexible printed circuit board according to claim 16, wherein the metal pattern and the second circuit pattern include a metal-plating layer.

18. The multilayer rigid flexible printed circuit board according to claim 15, wherein the metal pattern is exposed on a side surface of the rigid portion facing the flexible portion.

19. The multilayer rigid flexible printed circuit board according to claim 15, wherein the protective pattern comprises an adhesive material including polyimide.

20. The multilayer rigid flexible printed circuit board according to claim 15, further comprising a third insulating layer disposed on at least one of the first and second insulating layers and including a fourth circuit pattern on the third insulating layer.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) These and/or other aspects and advantages of the present general inventive concept will become apparent and more readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings of which:

(2) FIGS. 1 through 15 are process diagrams showing a method of manufacturing a rigid-flexible printed circuit board in accordance with the present invention; and

(3) FIGS. 16 through 24 are process diagrams showing a method of manufacturing a rigid-flexible printed circuit board in accordance with another embodiment of the present invention.

DESCRIPTION OF EMBODIMENTS

(4) Advantages and features of the present invention and methods of accomplishing the same will be apparent by referring to embodiments described below in detail in connection with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below and may be implemented in various different forms. The exemplary embodiments are provided only for completing the disclosure of the present invention and for fully representing the scope of the present invention to those skilled in the art. Like reference numerals refer to like elements throughout the specification.

(5) Terms used herein are provided to explain embodiments, not limiting the present invention. Throughout this specification, the singular form includes the plural form unless the context clearly indicates otherwise. When terms comprises and/or comprising used herein do not preclude existence and addition of another component, step, operation and/or device, in addition to the above-mentioned component, step, operation and/or device.

(6) Hereinafter, configuration and operational effect of the present invention will be described in detail with reference to the accompanying drawings.

(7) FIGS. 1 through 15 are process diagrams showing a method of manufacturing a rigid-flexible printed circuit board in accordance with the present invention.

(8) First, as shown in FIG. 1, a method of manufacturing a rigid-flexible printed circuit board in accordance with the present invention performs the step of providing a first flexible film 10 having a first metal layer 11 on one or both surfaces.

(9) Here, the first flexible film 10 is a film made of a soft and flexible material and mainly made of a polyimide material.

(10) The first metal layer 11 is formed by one or a combination of electroless plating, electroplating, screen printing, sputtering, evaporation, ink-jetting, and dispensing using one of Cu, Ag, Sn, Au, Ni, and Pd.

(11) Next, as shown in FIG. 2, the step of forming a circuit pattern by patterning the first metal layer 11 is performed.

(12) The circuit pattern may be formed by one of photolithography, E-beam lithography, focused ion beam lithography, dry etching, wet etching, and nano-imprinting through processes such as exposure, developing, and etching after attaching a photosensitive film with a predetermined pattern on the metal layer.

(13) Next, the step of forming a second flexible film 20, which has a second metal layer 21 on one surface, on one or both surfaces of the first flexible film 10 is performed. Since a method of forming the second metal layer 21 is the same as a method of forming the first metal layer 11, detailed description will be omitted.

(14) When forming the second flexible film 20 on the first flexible film 10, as shown in FIG. 3, one surface of the second flexible film 20, where the second metal layer 21 is not formed, is bonded to the first flexible film 10.

(15) At this time, as shown in FIG. 4, the step of providing a bonding sheet 22 between the first flexible film 10 and the second flexible film 20 may be additionally performed. The bonding sheet 22 may be made of an epoxy thermosetting resin or a prepreg material.

(16) Accordingly, the second flexible film 20 can be formed on the first flexible film 10 by temporarily attaching the bonding sheet 22 to one surface of the second flexible film 20, where the second metal layer 21 is not formed, and being pressed with a press in a state of being laminated on the first flexible film 10.

(17) Next, the step of forming a circuit pattern by patterning the second metal layer 21 except a flexible domain F is performed.

(18) Meanwhile, as shown in FIG. 5, a through-hole 23, which penetrates the first flexible film 10 and the second flexible film 20, is processed in a rigid domain R. For example, the through-hole 23 may be processed by a computer numerical control (CNC) drill and so on.

(19) And, as shown in FIG. 6, a plating layer 24 is formed on the second metal layer 21 including an inner wall of the through-hole 23. The plating layer 24 may be formed by one or a combination of electroless plating, electroplating, screen printing, sputtering, evaporation, ink-jetting, and dispensing using one of Cu, Ag, Sn, Au, Ni, and Pd.

(20) Like this, when the plating layer 24 is formed on the second metal layer 21 including the inner wall of the through-hole 23, as shown in FIG. 7, the step of forming a circuit pattern by patterning the plating layer 24 in the rigid domain R except the flexible domain F is performed.

(21) The circuit pattern may be implemented by one of photolithography, E-beam lithography, focused ion beam lithography, dry etching, wet etching, and nano-imprinting.

(22) Here, a point that specially needs attention is that the plating layer 24 in the flexible domain F is not patterned. This is to irradiate laser light only to a circuit layer 30 of FIG. 9 positioned directly on the second flexible film 20 in the flexible domain F in the subsequent step of removing the circuit layer 30 in the flexible domain F. That is, the second metal layer 21 in the flexible domain F, which is not patterned, functions as a laser stopper.

(23) Next, as shown in FIG. 8, the step of providing an anti-oxidation protective layer 25 on the second metal layer 21 in the flexible domain F is performed.

(24) In general, when laminating a plurality of circuit layers, oxidation (for example, brown or black oxidation) is performed on a surface of the circuit layer, that is, a surface of a metal layer on which a circuit pattern is formed, for improvement of interlayer adhesion. However, according to the method of manufacturing a rigid-flexible printed circuit board in accordance with the present invention, the anti-oxidation protective layer 25 is provided so that a surface of the second metal layer 21 in the flexible domain F is not oxidized. Accordingly, the second metal layer 21 in the flexible domain F is not discolored by an oxidation solution. The second metal layer 21 in the flexible domain F, which is not discolored, prevents laser light from being irradiated to the second flexible film 20 in the flexible domain F by reflecting the laser light in the subsequent step of removing the circuit layer 30 in the flexible domain F (that is, functioning as a laser stopper).

(25) This anti-oxidation protective layer 25 may be made of an adhesive material including polyimide.

(26) More specifically, the anti-oxidation protective layer 25 may be formed through the steps of applying slurry, which is made of an adhesive material including polyimide, on the second metal layer 21 corresponding to the flexible domain F and curing the slurry.

(27) Meanwhile, in order to fix the second metal layer 21 and the anti-oxidation protective layer 25, the step of attaching a bonding sheet (not shown) between the second metal layer 21 and the anti-oxidation protective layer 25 may be additionally performed. The bonding sheet may be made of an epoxy thermosetting resin or a prepreg material.

(28) Next, as shown in FIG. 9, the step of laminating at least one circuit layer 30 on the second flexible film is performed. At this time, the surface of the second metal layer (specifically, the plating layer 24 plated on the second metal layer) is oxidized to increase interlayer adhesion. At this time, the surface of the second metal layer in the flexible domain F is not oxidized by the anti-oxidization protective layer 25.

(29) The circuit layer 30 is a layer including a circuit pattern and may be formed through the steps of forming an insulating layer 31 which covers the circuit pattern under the circuit layer 30 (that is, the circuit pattern formed on the second metal layer 21), forming a metal layer 32 on the insulating layer 31, and forming a circuit pattern by patterning the metal layer 32.

(30) A process of forming the circuit pattern in the circuit layer 30 is similar to the step of forming the circuit pattern by patterning the second metal layer 21. That is, as shown in FIG. 10, the circuit pattern is formed by processing a via-hole 34 in the rigid domain R, forming a plating layer 33 on the metal layer 32 including an inner wall of the via-hole 34, and patterning the plating layer 33.

(31) At this time, the metal layer in the flexible domain F is removed as well. This is to irradiate laser light to the circuit layer 30 positioned directly on the second flexible film 20 in the subsequent step of removing the circuit layer 30 in the flexible domain F.

(32) For this, a window 35, which exposes the insulating layer 31 in the flexible domain F, is formed by applying resist on a surface of the plating layer 33 in the flexible domain F and sequentially performing exposure, developing, etching, and resist stripping processes.

(33) This circuit layer 30, as shown in FIG. 11, may be formed in a plurality of layers 30 and 40. At this time, in order to improve interlayer adhesion, it is preferred to laminate the circuit layer after oxidizing the circuit pattern under the upper circuit layer.

(34) As shown in FIG. 12, the circuit pattern is formed by patterning the plating layer included in each circuit layer even when forming a plurality of circuit layers 30. That is, the circuit pattern is formed by processing a via-hole 44 in the rigid domain R, forming a plating layer 43 on the metal layer 42 including the via-hole 44, and patterning the plating layer 43.

(35) Like this, in a state in which the at least one circuit layer is formed, as shown in FIG. 13, a rigid-flexible printed circuit board manufactured by the method of manufacturing a rigid-flexible printed circuit board of the present invention is completed by performing the step of removing a portion of the circuit layer 30, 40, and 50, which corresponds to the flexible domain F.

(36) When specifically looking into the step of removing the portion of the circuit layer 30, 40, and 50, which corresponds to the flexible domain F, first, as shown in FIG. 13, a cavity 54 is processed in the flexible domain F at the same time when forming a via-hole in the uppermost circuit layer 50.

(37) The cavity 54 may be processed by a CO2 laser drilling process or a YAG laser drilling process, and it is preferred to remove a metal layer 52 of the uppermost circuit layer 50 before the laser drilling process. That is, a window, which exposes an insulating layer in the flexible domain F, is formed by applying resist on a surface of the metal layer 52 and sequentially performing exposure, developing, etching, and resist stripping processes.

(38) When processing the cavity 54, the anti-oxidation protective layer 25 is removed as well. As described above, since the anti-oxidation protective layer 25 is made of an adhesive material including polyimide, it can be removed by being irradiated together with the circuit layer in the flexible domain F by the CO2 laser drilling process or the YAG laser drilling process.

(39) When the cavity 54 is processed, as shown in FIG. 14, a plating layer 53 is formed on the metal layer 52 including the via-hole formed in the uppermost circuit layer 50 and an inner wall of the cavity 54.

(40) And, as shown in FIG. 15, a finished rigid-flexible printed circuit board is manufactured by removing the second metal layer 21 and the plating layer 24 in the flexible domain F at the same time when forming a circuit pattern on the plating layer 53 of the uppermost circuit layer 50.

(41) Like this, according to the method of manufacturing a rigid-flexible printed circuit board, it is possible to prevent discoloration of the metal layer due to the oxidation process by including the step of providing the anti-oxidation protective layer 25. Accordingly, it is possible to improve reliability of products by preventing damage to the flexible film when removing the circuit layer in the flexible domain F.

(42) Now, a method of manufacturing a rigid-flexible printed circuit board in accordance with another embodiment of the present invention will be described. Hereinafter, description of processes similar to those of the above-described method of manufacturing a rigid-flexible printed circuit board will be omitted to avoid repeated description.

(43) FIGS. 16 through 24 are process diagrams showing a method of manufacturing a rigid-flexible printed circuit board in accordance with another embodiment of the present invention.

(44) First, a method of manufacturing a rigid-flexible printed circuit board in accordance with another embodiment of the present invention, as shown in FIG. 16, performs the step of providing a flexible film 100 having a metal layer 110 on one or both surfaces.

(45) Next, as shown in FIG. 17, the step of forming a circuit pattern by patterning the metal layer 110 is performed.

(46) Next, as shown in FIG. 18, the step of forming a stopper metal layer 120 on the metal layer 110 in a flexible domain F.

(47) The stopper metal layer 120 allows laser light to be irradiated only to a circuit layer positioned directly on the metal layer 110 in the subsequent step of removing the circuit layer in the flexible domain F. That is, the stopper metal layer 120 functions as a stopper during a laser process.

(48) At this time, the step of providing a release film (not shown) between the metal layer 110 and the stopper metal layer 120 may be additionally performed. The release film, which is made of a resin and so on, is a film which is easily peeled off when some shear is applied after inserting, for example, a sharp blade, between materials in contact with the release film and commonly used in the art to which the present invention belongs.

(49) Next, as shown in FIG. 19, the step of providing an anti-oxidation protective layer 130 on the stopper metal layer 120 is performed.

(50) In general, when laminating a plurality of circuit layers, oxidation (for example, brown or black oxidation) is performed on a surface of the circuit layer, that is, a surface of a metal layer on which a circuit pattern is formed, for improvement of interlayer adhesion. However, according to the method of manufacturing a rigid-flexible printed circuit board in accordance with another embodiment of the present invention, the anti-oxidation protective layer 130 is provided so that the metal layer 110 in the flexible domain F is not oxidized. Accordingly, a surface of the metal layer 110 in the flexible domain F is not discolored by an oxidation solution and protects the flexible film 100 by reflecting laser light in the subsequent step of removing the circuit layer in the flexible domain F (that is, functioning as a laser stopper) to prevent the laser light from being irradiated to the metal layer 110 in the flexible domain F.

(51) At this time, in order to fix the stopper metal layer 120 and the anti-oxidation protective layer 130, the step of attaching a bonding sheet (not shown) between the stopper metal layer 120 and the anti-oxidation protective layer 130 may be additionally performed.

(52) Next, as shown in FIG. 20, the step of laminating at least one circuit layer 200 on the flexible film is performed.

(53) The circuit layer 200 is a layer including a circuit pattern and, as shown in FIG. 21, may be formed through the steps of forming an insulating layer 210 which covers a circuit pattern under the circuit layer 200, forming a metal layer 220 on the insulating layer 210, and forming a circuit pattern by patterning the metal layer 220.

(54) At this time, a through-hole 230 or a via-hole may be formed simultaneously with the circuit pattern, and in the subsequent step of removing the circuit layer in the flexible domain F, in order to irradiate laser light to the circuit layer positioned directly on the flexible film 100, a window 240 is formed to expose the insulating layer 210 in the flexible domain F.

(55) When this circuit layer 200 is formed in a plurality of layers 200, 300, and 400 as shown in FIG. 22, it is possible to manufacture a finished rigid-flexible printed circuit board by performing the step of removing the circuit layer in the flexible domain F.

(56) The step of removing the circuit layer in the flexible domain F may be performed by a CO2 laser drilling process or a YAG laser drilling process, and at this time, the anti-oxidation protective film 130 is also irradiated and removed by laser light.

(57) When specifically looking into the step of removing the circuit layer in the flexible domain F, first, as shown in FIG. 22, a cavity 440 is processed in the flexible domain F by a CO2 laser drilling process or a YAG laser drilling process. Next, as shown in FIG. 23, a plating layer 450 is plated on the uppermost circuit layer 400, and as shown in FIG. 24, the stopper metal layer 120 is also removed when forming a circuit pattern on the uppermost circuit layer 400. This stopper metal layer 120 can be removed by separating the release film provided between the stopper metal layer 120 and the metal layer 110.

(58) According to the method of manufacturing a rigid-flexible printed circuit board, it is possible to prevent discoloration of the metal layer due to the oxidation process by including the step of providing the anti-oxidation protective layer. Accordingly, it is possible to improve reliability of products by preventing damage to the flexible film in the step of removing the circuit layer in the flexible domain F.

(59) The foregoing description illustrates the present invention. Additionally, the foregoing description shows and explains only the preferred embodiments of the present invention, but it is to be understood that the present invention is capable of use in various other combinations, modifications, and environments and is capable of changes and modifications within the scope of the inventive concept as expressed herein, commensurate with the above teachings and/or the skill or knowledge of the related art. The embodiments described hereinabove are further intended to explain best modes known of practicing the invention and to enable others skilled in the art to utilize the invention in such, or other, embodiments and with the various modifications required by the particular applications or uses of the invention. Accordingly, the description is not intended to limit the invention to the form disclosed herein. Also, it is intended that the appended claims be construed to include alternative embodiments.