Method for manufacturing flexible wiring circuit board

Abstract

To provide a method for manufacturing a flexible wiring circuit board which can manufacture the flexible wiring circuit board having miniaturized wiring at low cost.SOLUTION: In a step of manufacturing a flexible wiring circuit board, a solution (varnish) of a positive type photosensitive resin is applied onto a circuit formation surface 3 including a first region surface 3a and a second region surface 3b at different positions in a thickness direction. A photosensitive film 5 is formed by curing the applied solution. A first part positioned on the first region surface 3a in the photosensitive film 5 is irradiated in a first pattern with exposure light, and simultaneously a second part positioned on the second region surface 3b in the photosensitive film 5 is irradiated in a second pattern with the exposure light, so that the photosensitive film 5 is developed. A first opening of the first pattern and a second opening of the second pattern are simultaneously formed in the photosensitive film 5. A plurality of conductor layers are formed in the first opening and the second opening, respectively.SELECTED DRAWING: Figure 6

Description

[Technical field]

[0001] The present invention relates to a method for producing a flexible printed circuit board. [Background technology]

[0002] Conventionally, various wirings provided on a wiring circuit board are formed using, for example, photolithography technology. In a manufacturing method for a wiring circuit board using photolithography technology, a photosensitive film is formed on a circuit formation surface, and then the photosensitive film is exposed to light in a predetermined pattern. Thereafter, the exposed photosensitive film is developed to form openings in the photosensitive film in the predetermined pattern or its inverse pattern. A conductor layer is formed in the openings, and the conductor layer formed in the openings is used as wiring.

[0003] In the case of a wiring circuit board, in order to form wiring at a high density on a board of a limited size, it is desirable to make the wiring finer. In the above-mentioned method for manufacturing a wiring circuit board, in order to make the wiring finer, it is necessary to form openings in the photosensitive film with higher accuracy. That is, the photosensitive film needs to be exposed and developed with high resolution.

[0004] It is known that a positive photosensitive film can be exposed and developed with higher resolution than a negative photosensitive film. Patent Document 1 describes an example of a method for manufacturing a printed circuit board using a positive photosensitive film. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2014-33174 A Summary of the Invention [Problem to be solved by the invention]

[0006] Among wired circuit boards, there are multilayer wired circuit boards that have a multilayer structure in which multiple wirings are formed on multiple insulating layers. In multilayer wired circuit boards, vias are formed that penetrate one or more insulating layers to ensure electrical continuity between the multiple insulating layers.

[0007] In the method for manufacturing a printed circuit board using a positive photosensitive film described in Patent Document 1, a first exposure and a first development are performed on one photosensitive insulating layer. As a result, an upper part of a via hole (upper half of a via hole) and a circuit pattern (opening for forming wiring) are formed on the upper part of the one photosensitive insulating layer. Thereafter, a second exposure and a second development are performed on a lower part of the upper part of the via hole in the one photosensitive insulating layer. As a result, a lower part of the via hole (lower half of the via hole) is formed. That is, the entire via hole is formed.

[0008] As described above, when multiple exposures and multiple developments are performed to form one via hole, if the position of the processing object (particularly the exposure position) shifts each time exposure and development are performed, distortion occurs in the one via hole. In addition, the positional relationship between the one via hole and the circuit pattern also shifts. Therefore, in the above manufacturing method, the photosensitive insulating layer needs to be positioned with high accuracy each time exposure and development are performed. The required positioning accuracy becomes higher as the wiring becomes finer. Repeated exposure and development together with high-precision positioning complicates the manufacturing process of the wiring circuit board and increases the manufacturing cost.

[0009] An object of the present invention is to provide a method for producing a flexible wired circuit board, which enables a flexible wired circuit board having fine wiring to be produced at low cost. [Means for solving the problem]

[0010] A method for manufacturing a flexible wired circuit board according to one aspect of the present invention is a method for manufacturing a flexible wired circuit board having a plurality of conductor layers on a circuit formation surface, the circuit formation surface including a first area surface and a second area surface located at different positions from each other in a thickness direction, the method for manufacturing the flexible wired circuit board includes the steps of: applying a solution (varnish) of a positive photosensitive resin onto the circuit formation surface and curing the applied solution to form a photosensitive film; irradiating a first portion of the photosensitive film located on the first area surface with exposure light in a predetermined first pattern, and simultaneously irradiating a second portion of the photosensitive film located on the second area surface with the exposure light in a predetermined second pattern; developing the photosensitive film after exposure to simultaneously form a first opening of the first pattern and a second opening of the second pattern in the photosensitive film; and forming the plurality of conductor layers in the first opening and the second opening formed in the photosensitive film, respectively. Effect of the Invention

[0011] According to the present invention, it is possible to manufacture a flexible wired circuit board having fine wiring at low cost. [Brief description of the drawings]

[0012] [Figure 1] 1A to 1C are manufacturing process diagrams illustrating a method for manufacturing a flexible wired circuit board according to an embodiment of the present invention. [Diagram 2] 1A to 1C are manufacturing process diagrams illustrating a method for manufacturing a flexible wired circuit board according to an embodiment of the present invention. [Diagram 3] 1A to 1C are manufacturing process diagrams illustrating a method for manufacturing a flexible wired circuit board according to an embodiment of the present invention. [Figure 4] 1A to 1C are manufacturing process diagrams illustrating a method for manufacturing a flexible wired circuit board according to an embodiment of the present invention. [Diagram 5] 1A to 1C are manufacturing process diagrams illustrating a method for manufacturing a flexible wired circuit board according to an embodiment of the present invention. [Figure 6] 1A to 1C are manufacturing process diagrams illustrating a method for manufacturing a flexible wired circuit board according to an embodiment of the present invention. [Figure 7] 1A to 1C are manufacturing process diagrams illustrating a method for manufacturing a flexible wired circuit board according to an embodiment of the present invention. [Figure 8] 1A to 1C are manufacturing process diagrams illustrating a method for manufacturing a flexible wired circuit board according to an embodiment of the present invention. [Figure 9] 1A to 1C are manufacturing process diagrams illustrating a method for manufacturing a flexible wired circuit board according to an embodiment of the present invention. [Figure 10] 1A to 1C are manufacturing process diagrams illustrating a method for manufacturing a flexible wired circuit board according to an embodiment of the present invention. [Figure 11] 1A to 1C are manufacturing process diagrams illustrating a method for manufacturing a flexible wired circuit board according to an embodiment of the present invention. [Figure 12] 1A to 1C are manufacturing process diagrams illustrating a method for manufacturing a flexible wired circuit board according to an embodiment of the present invention. [Figure 13] FIG. 1 is a schematic diagram showing an example of the configuration of a roll-to-roll apparatus used in a method for producing a flexible wired circuit board. [Figure 14] 1 is a diagram showing an example of a travel path of light when exposure light is irradiated onto an exposure target portion of a photosensitive film by projection exposure; [Figure 15] 1 is a reference diagram showing an example of a travel path of light when exposure light is irradiated onto an exposure target portion of a photosensitive film by proximity exposure. [Figure 16] 1 is a table showing the differences in the production methods and the various evaluation results of Examples 1 to 3 and Comparative Examples 1 to 3. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Hereinafter, a method for producing a flexible wired circuit board according to an embodiment of the present invention will be described with reference to the drawings.

[0014] 1. Manufacturing method for flexible printed circuit board 1 to 12 are manufacturing process diagrams for explaining a manufacturing method of a flexible wired circuit board according to an embodiment of the present invention. First, a roll (hereinafter referred to as a pay-out roll) on which a strip-shaped metal supporting board 1 is wound is prepared, and the metal supporting board 1 is paid out from the prepared pay-out roll. The metal supporting board 1 paid out from the pay-out roll is taken up on another roll (hereinafter referred to as a take-up roll). FIG. 1 shows a part of the metal supporting board 1 paid out from the pay-out roll. The metal supporting board 1 according to this embodiment is a supporting board made of stainless steel. The metal supporting board 1 may be formed of a metal material other than stainless steel (gold, silver, copper, iron, aluminum, or an alloy thereof, etc.).

[0015] The thickness of the metal supporting board 1 is preferably 10 μm or more and 100 μm or less, and is 20 μm in this embodiment. When the thickness of the metal supporting board 1 is 10 μm or more, the rigidity required for fabricating a flexible wired circuit board by roll-to-roll is ensured in the metal supporting board 1. When the thickness of the metal supporting board 1 is 100 μm or less, the flexibility required for fabricating a flexible wired circuit board by roll-to-roll is ensured.

[0016] 2, a first insulating layer 21 made of photosensitive polyimide is formed on part of the upper surface of the unrolled metal supporting board 1. The thickness of the first insulating layer 21 is 1 μm or more and 30 μm or less.

[0017] Next, as shown in FIG. 3, a seed layer 3 is formed so as to cover the upper surface of the first insulating layer 21, the side surface of the first insulating layer 21, and the upper surface of the metal supporting board 1 where the first insulating layer 21 is not formed. The seed layer 3 has a configuration in which a copper thin film is further laminated on an underlayer in which two or more thin films selected from a chromium thin film, a nickel thin film, a titanium thin film, and an alloy thin film of chromium and nickel are laminated. The seed layer 3 may have a configuration in which one thin film selected from a chromium thin film, a nickel thin film, a titanium thin film, and an alloy thin film of chromium and nickel is used as an underlayer, and a copper thin film is laminated on the underlayer. Each thin film constituting the seed layer 3 is formed by, for example, sputtering or electroless plating. The thickness of the seed layer 3 is 0.01 μm or more and 1 μm or less.

[0018] In the present embodiment, a first insulating layer 21 is formed on a part of the upper surface of the metal supporting board 1. Therefore, the upper surface of the seed layer 3 includes a first regional surface 3a and a second regional surface 3b located at different positions in the thickness direction of the metal supporting board 1. The first regional surface 3a is located on the first insulating layer 21 and is higher than the second regional surface 3b.

[0019] Next, as shown in FIG. 4, a positive photosensitive resin solution (varnish) 4 is applied onto the seed layer 3. Specifically, the photosensitive resin solution 4 is supplied from a photosensitive resin nozzle provided above the unwinding roll and the winding roll toward the metal supporting substrate 1 transported between the unwinding roll and the winding roll. The supplied solution 4 flows on the seed layer 3 and spreads over the entire upper surface of the seed layer 3. At this time, the upper surface of the liquid film of the solution 4 is formed flat over the entire surface. Therefore, the thickness of the liquid film of the solution 4 formed on the first region surface 3a is different from the thickness of the liquid film of the solution 4 formed on the second region surface 3b. Specifically, the thickness of the liquid film of the solution 4 formed on the second region surface 3b is greater than the thickness of the liquid film of the solution 4 formed on the first region surface 3a.

[0020] The positive photosensitive resin may be a positive photosensitive phenol resin, etc. The amount of the solution 4 supplied onto the metal supporting board 1 is adjusted so that the thickness of the liquid film is 1 μm or more and 100 μm or less.

[0021] Next, the liquid film of the photosensitive resin solution 4 is subjected to a heat treatment. The solution 4 contains a solvent component. The heat treatment removes the solvent component contained in the solution 4. That is, the solution 4 is dried and hardened. As a result, as shown in FIG. 5, a photosensitive film 5 in an unexposed state is formed. The photosensitive film 5 has a plurality of portions with different thicknesses. The thickness of the photosensitive film 5 is 1 μm or more and 100 μm or less.

[0022] Here, during the heat treatment for drying the solution 4, the amount of heat energy given to each of the multiple parts of the solution 4 varies. Specifically, the metal supporting board 1 has high thermal conductivity with respect to the first insulating layer 21 made of resin. Therefore, during the heat treatment, higher heat energy is transferred to the part of the solution 4 formed on the metal supporting board 1 without going through the first insulating layer 21 than the heat energy transferred to the part of the solution 4 formed on the metal supporting board 1 via the first insulating layer 21.

[0023] Furthermore, the degree of progress of drying of the solution 4 differs depending on the amount of thermal energy given to the solution 4. Therefore, the solution 4 has different degrees of drying in multiple parts, resulting in variation in the cured state of the photosensitive film 5. In FIG. 5, among the multiple parts of the photosensitive film 5, the parts located on the second region surface 3b of the seed layer 3 are framed with a thick dotted line. The degree of curing of the part of the photosensitive film 5 located within this dotted line frame is more advanced (greater) than the degree of curing of the other parts of the photosensitive film 5.

[0024] Next, the photosensitive film 5 is exposed to light in a predetermined pattern. The photosensitive film 5 is exposed to light by a first exposure device 50 shown in Fig. 6. The first exposure device 50 includes a light source 51, a mask 52, and a projection lens 53, and is disposed at a position above the metal supporting board 1 being transported.

[0025] The light source 51 mainly comprises a lamp 51a and a mirror 51b. The lamp 51a generates exposure light corresponding to the photosensitive film 5. The mirror 51b reflects the exposure light generated by the lamp 51a toward the metal supporting board 1 being transported.

[0026] The mask 52 has light-transmitting portions 52a and light-shielding portions 52b, and is disposed at a position between the light source 51 and the metal supporting board 1 to be transported. The light-transmitting portions 52a are formed in a predetermined pattern in the mask 52. The projection lens 53 is disposed at a position between the mask 52 and the metal supporting board 1 to be transported, and at a predetermined distance from the photosensitive film 5.

[0027] Moreover, the projection lens 53 shapes the exposure light emitted from the light source 51 and passing through the multiple light-transmitting portions 52a of the mask 52 and passes it toward the metal supporting board 1. This method of irradiating the exposure light passing through the mask onto the exposure target via a predetermined optical system (projection lens 53 in this example) is called projection exposure. In this embodiment, the projection exposure irradiates multiple portions of the photosensitive film 5 having different thicknesses with the exposure light simultaneously in a predetermined pattern.

[0028] Next, the exposed photosensitive film 5 is developed. Specifically, a developer is supplied from a developer nozzle provided above the unwinding roll and the winding roll toward the metal supporting substrate 1 transported between the unwinding roll and the winding roll. When the photosensitive film 5 is made of a positive photosensitive resin, the exposed portion is dissolved in the developer and removed. As a result, a plurality of openings 55 in a predetermined pattern are formed in the photosensitive film 5. In each opening 55, the seed layer 3 is exposed upward. In this embodiment, an organic alkaline developer is used as the developer for the photosensitive film 5. An example of an organic alkaline developer is a developer containing tetraalkylammonium (TAA) ions.

[0029] In the following description, among the multiple openings 55, the openings 55 located on the first region surface 3a of the seed layer 3 (openings 55 formed in a portion of the photosensitive film 5 where the thickness is small) will be referred to as a first opening 55a as appropriate. Also, among the multiple openings 55, the openings 55 located on the second region surface 3b of the seed layer 3 (openings 55 formed in a portion of the photosensitive film 5 where the thickness is large) will be referred to as a second opening 55b as appropriate. In FIG. 7, two first openings 55a and one second opening 55b are shown.

[0030] Each of the first openings 55a is an opening for forming a wiring in a flexible wired circuit board, and is formed so as to extend in a direction perpendicular to the thickness direction of the metal supporting board 1 on the first region surface 3a of the seed layer 3. The pattern width of the first openings 55a is 1 μm or more and 10 μm or less.

[0031] The second opening 55b is an opening for forming a via in the flexible wiring circuit board, and has a circular, elliptical or polygonal shape when viewed in the thickness direction of the metal supporting board 1. The maximum dimension of the second opening 55b perpendicular to the thickness direction of the metal supporting board 1 is 10 μm or more and 250 μm or less. The maximum dimension of the second opening 55b represents the maximum dimension of the second opening 55b when viewed in the thickness direction of the metal supporting board 1. For example, the maximum dimension of the second opening 55b is the diameter of the second opening 55b when the second opening 55b has a circular shape when viewed in the thickness direction of the metal supporting board 1. Moreover, the maximum dimension of the second opening 55b is the maximum value of the diagonal of the second opening 55b when the second opening 55b has a rectangular shape when viewed in the thickness direction of the metal supporting board 1.

[0032] Next, as shown in FIG. 8, a conductor layer 6 having a predetermined pattern is formed by electrolytic plating on the portion of the seed layer 3 exposed in each of the multiple openings 55 (in this example, the two first openings 55a and the second opening 55b) of the photosensitive film 5. The conductor layer 6 is made of, for example, copper. Here, the thickness of the conductor layer 6 formed in each of the two first openings 55a is 1 μm or more and 20 μm or less. The pattern width of the conductor layer 6 formed in each of the first openings 55a is 1 μm or more and 20 μm or less. The thickness of the conductor layer 6 formed in the second openings 55b is 4 μm or more and 25 μm or less.

[0033] 9, the entire photosensitive film 5 formed on the seed layer 3 is exposed so that the exposure light is incident on the entire photosensitive film 5 (hereinafter referred to as full-surface exposure). The exposure of the photosensitive film 5 is performed by a second exposure device 80. The second exposure device 80 includes a light source 81, but does not have a mask or a projection lens. The light source 81, like the light source 51, is mainly composed of a lamp 81a and a mirror 81b.

[0034] The energy of the exposure light irradiated per unit area of ​​the object when it is exposed is called the exposure dose. The unit of exposure dose is, for example, "mJ / cm 2 ". The exposure amount of the photosensitive film 5 is the integrated amount of exposure light irradiated from the first exposure device 50 and the second exposure device 80 toward the photosensitive film 5, and is determined by the illuminance of the exposure light irradiated toward the photosensitive film 5 and the irradiation time of the exposure light on the photosensitive film 5. Therefore, when each of the first exposure device 50 and the second exposure device 80 irradiates the photosensitive film 5 with exposure light at a constant illuminance, the exposure amount of the photosensitive film 5 can be easily adjusted by adjusting the irradiation time.

[0035] Next, the exposed photosensitive film 5 is developed. Specifically, similar to the formation of the first opening 55a and the second opening 55b in FIG. 7, a developer is supplied toward the metal supporting substrate 1 from a developer nozzle provided above the unwinding roll and the winding roll. As a result, the remaining photosensitive film 5 is entirely dissolved in the developer and removed. FIG. 10 shows a state in which only a plurality of conductor layers 6 remain on the seed layer 3 and the entire photosensitive film 5 has been removed. In this case, the portion of the seed layer 3 on which the conductor layer 6 is not formed is exposed.

[0036] 11, the exposed unnecessary portion of the seed layer 3 is removed by, for example, wet etching. As a result, two wirings 7 in a predetermined pattern, each made of the seed layer 3 and the conductor layer 6, are formed on the first insulating layer 21. Also, a via 8 made of the seed layer 3 and the conductor layer 6 is formed on the upper surface of the metal supporting board 1 on which the first insulating layer 21 is not formed.

[0037] Finally, as shown in Fig. 12, a second insulating layer 22 made of photosensitive polyimide is formed in an area of ​​the upper surfaces of the metal supporting board 1 and the first insulating layer 21 where the two wirings 7 and the vias 8 are not formed. Furthermore, terminal parts T are formed on parts of the two wirings 7 and parts of the vias 8 as necessary. In this manner, a laminate including the metal supporting board 1, the first insulating layer 21, the second insulating layer 22, the two wirings 7, and the vias 8 is completed as a flexible wired circuit board 9. The completed flexible wired circuit board 9 is wound up on a winding roll.

[0038] 2. Example of a roll-to-roll device configuration The above series of processes are continuously performed, for example, in one roll-to-roll apparatus. Fig. 13 is a schematic diagram showing one configuration example of a roll-to-roll apparatus used in the manufacturing method of the flexible wired circuit board 9.

[0039] 13 includes a payout roll 110, a first insulating layer forming apparatus 10, a seed layer forming apparatus 20, a resist coating apparatus 30, a heat treatment apparatus 40, and a first exposure apparatus 50. The roll-to-roll apparatus 100 also includes a first developing apparatus 60, a plating apparatus 70, a second exposure apparatus 80, a second developing apparatus 90, an etching apparatus 91, a second insulating layer forming apparatus 92, a terminal forming apparatus 93, and a take-up roll 120.

[0040] In the pay-out roll 110, a long metal supporting board 1 (FIG. 1) is wound around a bobbin (not shown). The metal supporting board 1 is paid out from the pay-out roll 110 as the pay-out roll 110 rotates. The paid-out metal supporting board 1 is sent to the first insulating layer forming apparatus 10. In FIG. 13, the transport direction of the metal supporting board 1 paid out from the pay-out roll 110 is indicated by a dotted arrow.

[0041] The first insulating layer forming apparatus 10 forms a first insulating layer 21 on the metal supporting board 1, as shown in the example of FIG. 2. The metal supporting board 1 on which the first insulating layer 21 has been formed is sent to the seed layer forming apparatus 20. The seed layer forming apparatus 20 forms a seed layer 3 on the metal supporting board 1 so as to cover the first insulating layer 21, as shown in the example of FIG. 3. The laminate consisting of the metal supporting board 1, the first insulating layer 21, and the seed layer 3 is sent to the resist coating apparatus 30.

[0042] The resist coating apparatus 30 forms a liquid film of a photosensitive resin solution 4 on the seed layer 3, as shown in the example of FIG. 4. The laminate on which the liquid film has been formed is sent to a heat treatment apparatus 40. The heat treatment apparatus 40 includes, for example, a heater, and performs heat treatment on the liquid film of the solution 4. Thereby, as shown in the example of FIG. 5, a photosensitive film 5 is formed on the metal supporting board 1 and the first insulating layer 21. The laminate on which the photosensitive film 5 has been formed is sent to a first exposure apparatus 50.

[0043] 6, the first exposure device 50 includes a light source 51, a mask 52, and a projection lens 53. The first exposure device 50 projects and exposes the photosensitive film 5 in a predetermined pattern. The laminate in which the photosensitive film 5 has been exposed in the predetermined pattern is sent to the first developing device 60.

[0044] The first developing device 60 supplies a developer onto the photosensitive film 5, thereby removing the exposed portions of the photosensitive film 5, as shown in the example of FIG. 7. This forms a plurality of openings 55 in a predetermined pattern in the photosensitive film 5. The laminate including the developed photosensitive film 5 is sent to a plating device 70.

[0045] As shown in the example of FIG. 8, the plating device 70 forms a conductor layer 6 in the multiple openings 55 of the photosensitive film 5 by electrolytic plating. The laminate on which the conductor layer 6 of a predetermined pattern has been formed is sent to a second exposure device 80. As shown in the example of FIG. 9, the second exposure device 80 includes a light source 81. The second exposure device 80 exposes the entire surface of the photosensitive film 5. The laminate on which the entire photosensitive film 5 has been exposed is sent to a second development device 90.

[0046] The second developing device 90 supplies a developer onto the photosensitive film 5, thereby removing the entire exposed photosensitive film 5, as shown in the example of FIG. 10. In this state, a plurality of conductor layers 6 remain on the seed layer 3. The laminate from which the photosensitive film 5 has been removed is sent to an etching device 91.

[0047] 11, the etching apparatus 91 removes the exposed portion of the seed layer 3 by, for example, wet etching. As a result, the seed layer 3 and the conductor layer 6 present on the first insulating layer 21 are formed as two wirings 7. In addition, the seed layer 3 and the conductor layer 6 having a large thickness present on the metal supporting board 1 are formed as a via 8. The laminate including the two wirings 7 and the via 8 is sent to a second insulating layer forming apparatus 92.

[0048] As shown in the example of FIG. 12, the second insulating layer forming apparatus 92 forms a second insulating layer 22 on the exposed upper surface of the metal supporting board 1 and the exposed upper surface of the first insulating layer 21. The laminate including the second insulating layer 22 is sent to a terminal forming apparatus 93. The terminal forming apparatus 93 forms terminal portions T on parts of the wiring 7 and vias 8 as necessary. This completes the flexible wired circuit board 9. The completed flexible wired circuit board 9 is taken up by a take-up roll 120.

[0049] 3.Effects (a) In the manufacturing method of the flexible wired circuit board 9 according to the present embodiment, a solution 4 of a positive photosensitive resin is applied onto the seed layer 3 to form a photosensitive film 5. The applied solution 4 flows onto the seed layer 3. The upper surface of the liquid film of the solution 4 is formed flat over the entire surface. Therefore, the thickness of the liquid film of the solution 4 formed on the first region surface 3a of the seed layer 3 is different from the thickness of the liquid film of the solution 4 formed on the second region surface 3b of the seed layer 3. In this state, the solution 4 is cured by heat treatment. As a result, a photosensitive film 5 having a plurality of portions with different thicknesses is formed.

[0050] The thinner portion of the photosensitive film 5 (the portion located on the first area surface 3a of the seed layer 3) is exposed to light in a predetermined pattern. Simultaneously with this exposure, the thicker portion of the photosensitive film 5 (the portion located on the second area surface 3b of the seed layer 3) is exposed to light in a predetermined pattern.

[0051] Thereafter, the entire photosensitive film 5 is simultaneously developed, and first openings 55a and second openings 55b are formed in the portions of the photosensitive film 5 that have different thicknesses. In this manner, the portions of the photosensitive film 5 formed on the seed layer 3 that have different thicknesses are simultaneously exposed and developed. This allows the number of manufacturing steps for the flexible wired circuit board 9 to be reduced compared to the case where the portions of the photosensitive film 5 are exposed and developed multiple times according to their thicknesses.

[0052] Furthermore, according to the manufacturing method of the flexible wired circuit board 9 according to the present embodiment, multiple exposures and multiple developments are not performed in a common pattern even when an opening is formed in a thicker portion of the photosensitive film 5. As a result, it is not necessary to position the photosensitive film 5 to be processed with high precision every time exposure and development are performed.

[0053] In the present embodiment, a positive photosensitive resin is used as the material constituting the photosensitive film 5. This allows the photosensitive film 5 to be exposed and developed with higher resolution than when a negative photosensitive resin is used. This allows the conductor layer 6 to be formed with high accuracy in the first opening 55a and the second opening 55b.

[0054] As a result, it becomes possible to manufacture the flexible wired circuit board 9 having the fine wiring 7 at low cost.

[0055] (b) Fig. 14 is a diagram showing an example of a travel path of light when exposure light is irradiated onto an exposure target portion of photosensitive film 5 by projection exposure. When exposure light passes through light-transmitting portion 52a of mask 52, diffuse light is generated in the vicinity of light-transmitting portion 52a, as shown by the dotted arrow in Fig. 14. The incidence of diffuse light on photosensitive film 5 reduces the resolution of the exposed region on photosensitive film 5. Therefore, in this embodiment, projection exposure is performed to form a predetermined pattern of openings 55 (Fig. 7) in photosensitive film 5.

[0056] According to the projection exposure of this example, even if the exposure light is diffused near the light-transmitting portion 52a when it passes through the mask 52, the diffused light is blocked from traveling to the photosensitive film 5 by the exposure light control function of the projection lens 53. As a result, the exposure light can be irradiated onto the photosensitive film 5 to be exposed as parallel light with reduced spread.

[0057] In this case, as shown by the thick dashed line in FIG. 14, the area where the exposure light is incident on the photosensitive film 5 does not expand in a direction perpendicular to the traveling direction of the exposure light. Therefore, a high contrast of the exposure state can be obtained at the boundary between the part to be exposed and the part not to be exposed, regardless of the thickness of the photosensitive film 5. Therefore, even if the exposure time is long to expose a part of the photosensitive film 5 with a large thickness, the state of the boundary between the part to be exposed and the part not to be exposed is not easily affected by the exposure time. As a result, it is possible to form the openings 55 with high accuracy in a plurality of parts of the photosensitive film 5 having different thicknesses.

[0058] In contrast to projection exposure, the method of irradiating the photosensitive film with exposure light through a mask while the mask is in contact with the photosensitive film is called contact exposure. In addition, the method of irradiating the photosensitive film with exposure light through a mask while the mask is placed in close proximity to the photosensitive film (a position about a few μm away from the photosensitive film) is called proximity exposure. In contact exposure and proximity exposure, the distance between the mask and the photosensitive film is zero or very small compared to projection exposure, and the projection lens used in projection exposure is not used.

[0059] A specific example of proximity exposure will be described as a reference example. FIG. 15 is a reference diagram showing an example of the travel path of light when the exposure light is irradiated to the exposure target portion of the photosensitive film 5 by the proximity exposure. As shown in FIG. 15, in the proximity exposure, the diffused light generated near the light-transmitting portion 52a of the mask 52 is directly incident on the boundary portion between the portion to be exposed and the portion not to be exposed in the photosensitive film 5. In this case, as shown by the thick dashed line in FIG. 15, the area where the exposure light is incident on the photosensitive film 5 spreads in a direction perpendicular to the travel direction of the exposure light. As a result, the contrast of the exposure state is lowered at the boundary portion between the portion to be exposed and the portion not to be exposed. In the contact exposure, a phenomenon similar to that of the example of the proximity exposure in FIG. 15 occurs.

[0060] (c) During development of the photosensitive film 5, the smaller the size of ions contained in the developer, the more likely it is that the developer will penetrate into the photosensitive film 5, causing swelling. If the degree of swelling is large, the pattern of the openings 55 cannot be maintained at high resolution after development, even if the photosensitive film 5 is exposed with high resolution.

[0061] Therefore, in the manufacturing method of the flexible wired circuit board 9 according to the present embodiment, an organic alkaline developer is used. The size of the organic ions (such as tetraalkylammonium ions) contained in the organic alkaline developer is larger than the size of the inorganic ions contained in the inorganic alkaline developer. Therefore, when an organic alkaline developer is used, swelling of the photosensitive film 5 is less likely to occur during development than when an inorganic alkaline developer is used.

[0062] (d) The above-mentioned effect that swelling of the photosensitive film 5 is less likely to occur by using an organic alkaline developer is particularly effective in producing the flexible wired circuit board 9 including the metal supporting board 1. The reason for this will be explained.

[0063] The time required for developing the photosensitive film 5 formed by heat-treating the photosensitive resin solution 4 is longer as the degree of hardening of the photosensitive film 5 is greater, and shorter as the degree of hardening of the photosensitive film 5 is less. On the other hand, as described with reference to FIG. 5, the hardening state varies among the multiple portions of the photosensitive film 5. When multiple portions of the photosensitive film 5 having such varying hardening states are simultaneously developed, the development time is determined by the portion of the photosensitive film 5 having a greater degree of hardening. Therefore, in the above-mentioned method for manufacturing the flexible wired circuit board 9, the time during which the developer is in contact with the photosensitive film 5 tends to be relatively long.

[0064] Even in such a case, when the developer used for developing the photosensitive film 5 is an organic alkaline developer, the photosensitive film 5 is less likely to swell. Therefore, a decrease in the resolution of the plurality of openings 55 caused by the swelling of the photosensitive film is suppressed.

[0065] (e) In the manufacturing method of the flexible wired circuit board 9 according to the present embodiment, the surface on which the photosensitive film 5 is formed, i.e., the upper surface of the seed layer 3, is insoluble in a developer. This makes it possible to simultaneously expose and develop the portion of the photosensitive film 5 formed on the first region surface 3a of the seed layer 3 and the portion of the photosensitive film 5 formed on the second region surface 3b of the seed layer 3.

[0066] (f) In the method for manufacturing the flexible wired circuit board 9 according to the present embodiment, after the formation of the plurality of conductor layers 6, the entire surface of the photosensitive film 5 is exposed to light, and the exposed photosensitive film 5 is developed. In this case, residues generated during the formation of the plurality of openings 55 in the previous step are removed in the steps of the entire surface exposure and the corresponding development.

[0067] (g) As described above, the multiple wirings 7 and the vias 8 in the flexible wired circuit board 9 are formed simultaneously. This allows the number of manufacturing steps for the flexible wired circuit board 9 to be reduced compared to the case where the multiple wirings 7 and the vias 8 are formed separately.

[0068] 4. Other embodiments (a) In the manufacturing method of the flexible wired circuit board 9 according to the above embodiment, projection exposure is performed to form the multiple openings 55 in the multiple parts of the photosensitive film 5, but the present invention is not limited to this. As an exposure method for forming the multiple openings 55 in the multiple parts of the photosensitive film 5, contact exposure or proximity exposure may be adopted instead of projection exposure.

[0069] Even in this case, by using a positive-type photosensitive resin as the material for at least the photosensitive film 5, the multiple conductor layers 6 can be formed with greater precision than when the photosensitive film 5 is formed from a negative-type photosensitive resin.

[0070] (b) In the manufacturing method of the flexible wired circuit board 9 according to the above embodiment, the photosensitive film 5 is formed by applying the photosensitive resin solution 4 onto the seed layer 3 and performing a heat treatment, but the present invention is not limited to this. The photosensitive film 5 may be formed of a dry film resist containing a positive photosensitive resin. In this case, the number of manufacturing steps of the flexible wired circuit board 9 is further reduced.

[0071] (c) In the manufacturing method of the flexible wired circuit board 9 according to the above embodiment, an organic alkaline developer is used as the developer used for developing the photosensitive film 5, but the present invention is not limited thereto. Instead of the organic alkaline developer, an inorganic alkaline developer may be used.

[0072] Even in this case, by using a positive-type photosensitive resin as the material for at least the photosensitive film 5, the multiple conductor layers 6 can be formed with greater precision than when the photosensitive film 5 is formed from a negative-type photosensitive resin.

[0073] (d) In the manufacturing method of the flexible wired circuit board 9 according to the above embodiment, the first exposure tool 50 used for projection exposure has a projection lens 53 as an optical system arranged between the mask 52 and the object to be exposed, but the present invention is not limited to this. The first exposure tool 50 may have other optical members such as a mirror in addition to or instead of the projection lens 53 as an optical system arranged between the mask 52 and the object to be exposed.

[0074] (e) In one roll-to-roll apparatus 100 used in the above embodiment, all steps for manufacturing the flexible wired circuit board 9 are performed. That is, one roll-to-roll apparatus 100 includes a plurality of apparatuses (10, 20, 30, 40, 50, 60, 70, 80, 90, 91, 92, 93) respectively corresponding to all steps for manufacturing the flexible wired circuit board 9. However, the present invention is not limited to this.

[0075] The multiple steps for producing the flexible wired circuit board 9 may be performed by multiple roll-to-roll devices. For example, the first half of the series of steps for producing the flexible wired circuit board 9 may be performed by one roll-to-roll device, and the second half of the steps may be performed by another roll-to-roll device. Furthermore, the multiple steps for producing the flexible wired circuit board 9 may be performed using three or more roll-to-roll devices. Furthermore, only some of the multiple steps for producing the flexible wired circuit board 9 may be performed by a roll-to-roll device.

[0076] (f) In the manufacturing method of the flexible wired circuit board 9 according to the above embodiment, the photosensitive film 5 may be formed on the upper surface of the metal supporting board 1 so as to cover the first insulating layer 21 before the formation of the seed layer 3. In this case, after a plurality of openings 55 are formed in the photosensitive film 5, the seed layer 3 for electrolytic plating may be formed in the plurality of openings 55.

[0077] (g) The flexible wired circuit board 9 produced by the manufacturing method for a flexible wired circuit board 9 according to the above embodiment includes a metal supporting board 1, but the present invention is not limited thereto. The flexible wired circuit board 9 to be produced does not need to have a metal supporting board 1. In this case, instead of the metal supporting board 1, the above-mentioned first insulating layer 21, wiring 7, vias 8, etc. are formed in sequence on a predetermined sheet-like member.

[0078] (h) The manufacturing method of the flexible wired circuit board 9 according to the above embodiment may be applied to the manufacture of a rewiring board having a plurality of wires and a plurality of vias. The rewiring board is, for example, a board that plays a role in converting the pitch between a fine pattern of a semiconductor chip and a coarse pattern of a package board, and is also called an interposer board.

[0079] 5. Correspondence between each component of the claims and each part of the embodiment Below, examples of the correspondence between each component of the claims and each element of the embodiment will be described, but the present invention is not limited to the following examples. Various other elements having the configuration or function described in the claims can also be used as each component of the claims.

[0080] In the above embodiment, the flexible wired circuit board 9 is an example of a flexible wired circuit board, the upper surface of the seed layer 3 is an example of a circuit forming surface, the multiple conductor layers 6 are an example of multiple conductor layers, the first area surface 3a of the seed layer 3 is an example of a first area surface, and the second area surface 3b of the seed layer 3 is an example of a second area surface.

[0081] In addition, the photosensitive resin solution 4 is an example of a solution, the photosensitive film 5 is an example of a photosensitive film, a portion of the photosensitive film 5 located on the first region surface 3a of the seed layer 3 is an example of a first portion, a portion of the photosensitive film 5 located on the second region surface 3b of the seed layer 3 is an example of a second portion, the first opening 55a is an example of a first opening, and the second opening 55b is an example of a second opening.

[0082] In addition, the projection lens 53 is an example of an optical system, the metal supporting board 1 is an example of a metal support and a base member, the upper surface of the metal supporting board 1 is an example of one surface of a metal support, the first insulating layer 21 is an example of an insulating layer, the wiring 7 is an example of a wiring, the via 8 is an example of a via, the pay-out roll 110 is an example of a first roll, and the take-up roll 120 is an example of a second roll.

[0083] 6. Examples and Comparative Examples <1> Preparation of Examples 1 to 3 and Comparative Examples 1 to 3 In order to confirm the effects of the manufacturing method for the flexible wired circuit board according to the above embodiment, the present inventors manufactured flexible wired circuit boards of Examples 1 to 3 and Comparative Examples 1 to 3. The flexible wired circuit boards of Examples 1 to 3 and Comparative Examples 1 to 3 were manufactured under different conditions. Specific manufacturing methods for the flexible wired circuit boards of Examples 1 to 3 and Comparative Examples 1 to 3 will be described.

[0084] The flexible wired circuit board of Example 1 was produced according to the manufacturing method of the flexible wired circuit board according to the above embodiment (see Figs. 1 to 12). Specifically, when producing the flexible wired circuit board of Example 1, a first insulating layer 21 made of photosensitive polyimide was formed on a metal supporting board 1, and a seed layer 3 was further formed on the first insulating layer 21. In addition, a solution 4 made of a positive novolac resin was applied onto the seed layer 3 as a photosensitive resin. Furthermore, a photosensitive film 5 was formed on the seed layer 3 by heat-treating the solution 4.

[0085] Next, the formed photosensitive film 5 was subjected to contact exposure in a plurality of patterns corresponding to the two wirings 7 and the vias 8, and was developed using tetramethylammonium hydroxide (TMAH). Tetramethylammonium hydroxide contains tetraalkylammonium ions as organic ions, and its molecular radius was 2.8 Å. Thereafter, a plurality of conductor layers 6 were formed, the entire surface of the remaining photosensitive film 5 was exposed to light, developed, a second insulating layer 22 was formed, and a terminal portion T was formed, thereby completing the flexible wired circuit board of Example 1.

[0086] During the contact exposure, a test mask 52 was used in which a plurality of light transmitting portions 52a were formed in a pattern corresponding to the two types of lines and spaces. Here, the lines and spaces refer to the width of each wiring 7 in the flexible wired circuit board and the distance between two adjacent wirings 7, and are expressed as L / S. The two types of L / S are 5 μm / 5 μm and 10 μm / 10 μm. In the following description, the mask 52 in which a plurality of light transmitting portions 52a corresponding to the above two types of lines and spaces are formed is called the test mask.

[0087] The flexible wired circuit board of Example 2 was produced in the same manner as the flexible wired circuit board of Example 1, except that the photosensitive film 5 was exposed by projection in a plurality of patterns corresponding to the two wires 7 and the vias 8, and that development was carried out using sodium hydroxide (NaOH). The sodium hydroxide used for development contained metal ions (sodium ions) as inorganic ions, and had a molecular radius of 0.9 Å.

[0088] The flexible wired circuit board of Example 3 was produced in the same manner as the flexible wired circuit board of Example 1, except that the photosensitive film 5 was exposed by projection exposure in a plurality of patterns corresponding to the two wires 7 and the vias 8, respectively.

[0089] The flexible wired circuit board of Comparative Example 1 was produced in the same manner as the flexible wired circuit board of Example 3, except that instead of forming the second opening 55b for the via 8 by photolithography technology, the second opening 55b for the via 8 was formed by laser processing.

[0090] The flexible wired circuit board of Comparative Example 2 was produced in the same manner as the flexible wired circuit board of Example 3, except that instead of forming the second opening 55b for the via 8 by photolithography, the second opening 55b for the via 8 was formed by drilling.

[0091] The flexible wired circuit board of Comparative Example 3 is characterized in that the photosensitive film 5 is formed using a dry film resist containing a negative acrylic resin as the photosensitive resin, and that sodium carbonate (Na 2 CO 3 The flexible wired circuit board was produced in the same manner as in Example 1, except that development was carried out using a fluorine-based compound.

[0092] <2> Evaluation of Examples 1 to 3 and Comparative Examples 1 to 3 (a) For each of the manufactured flexible wired circuit boards, the two wires 7 formed with the target of L / S=10μm / 10μm were observed using a laser microscope and a scanning electron microscope (SEM) to confirm whether they were actually formed with an L / S of 10μm / 10μm. In addition, a continuity test was performed on each of the two wires 7 and vias 8 formed with the target of L / S=10μm / 10μm to confirm whether or not there was a continuity defect (unintended short circuit or open circuit).

[0093] Furthermore, for each of the manufactured flexible wired circuit boards, the two wirings 7 formed with the target L / S=5 μm / 5 μm were observed using a laser microscope and a scanning electron microscope (SEM) to confirm whether they were actually formed with an L / S of 5 μm / 5 μm.

[0094] (b) Fig. 16 is a table showing the differences in the manufacturing methods and the various evaluation results of Examples 1 to 3 and Comparative Examples 1 to 3. As shown in the table of Fig. 16, it was confirmed that the two wirings 7 were precisely formed with an L / S of 10 µm / 10 µm in each of the flexible wired circuit boards of Examples 1 to 3 and Comparative Examples 1 and 2. Furthermore, as a result of the continuity test, no continuity defects were confirmed in the flexible wired circuit boards of Examples 1 to 3 and Comparative Examples 1 and 2. On the other hand, it was confirmed that the two wirings 7 were not precisely formed with an L / S of 10 µm / 10 µm in the flexible wired circuit board of Comparative Example 3. Furthermore, as a result of the continuity test, it was confirmed that continuity defects were confirmed in the flexible wired circuit board of Comparative Example 3.

[0095] As a result of these, it was found that when a positive-type photosensitive resin is used, it is possible to form multiple wirings 7 with an L / S of about 10 μm / 10 μm. On the other hand, it was found that when a negative-type photosensitive resin is used, it is not possible to form multiple wirings 7 with an L / S of about 10 μm / 10 μm.

[0096] Also, as shown in the table of FIG. 16, it was confirmed that in each of the flexible wired circuit boards of Example 3 and Comparative Examples 1 and 2, the two wires 7 were formed with high precision with an L / S of 5 μm / 5 μm. On the other hand, it was confirmed that in the flexible wired circuit boards of Examples 1 and 2, the two wires 7 were not formed with high precision with an L / S of 5 μm / 5 μm. The difference in these observation results is considered to be due to the exposure method of the photosensitive film 5 and the type of developer. Therefore, it was found that in order to form the two wires 7 with high precision with an L / S of 5 μm / 5 μm, it is necessary to expose the photosensitive film 5 by projection exposure and develop it with an organic alkaline developer.

[0097] (c) In the flexible wired circuit boards of Comparative Examples 1 and 2, the second opening 55b for the via 8 is formed by a method other than photolithography (laser processing and drilling). Therefore, the number of manufacturing steps was greater than in the case of manufacturing the flexible wired circuit boards of Comparative Examples 1 and 2, and it took a long time to manufacture them. In addition, it was necessary to prepare separate equipment for machining such as laser processing and drilling.

[0098] 7. Summary of the embodiment (Item 1) A method for producing a flexible printed circuit board according to item 1 includes the steps of: A method for manufacturing a flexible wired circuit board having a plurality of conductor layers on a circuit formation surface, comprising the steps of: the circuit formation surface includes a first area surface and a second area surface that are located at different positions in a thickness direction; The method for producing the flexible printed circuit board includes the steps of: A step of applying a solution (varnish) of a positive photosensitive resin onto the circuit formation surface and curing the applied solution to form a photosensitive film; irradiating a first portion of the photosensitive film located on the first area surface with exposure light in a predetermined first pattern and simultaneously irradiating a second portion of the photosensitive film located on the second area surface with the exposure light in a predetermined second pattern; developing the exposed photosensitive film to simultaneously form a first opening of the first pattern and a second opening of the second pattern in the photosensitive film; forming the plurality of conductor layers in the first opening and the second opening formed in the photosensitive film, respectively.

[0099] In the manufacturing method for the flexible wired circuit board, a photosensitive resin solution (varnish) is applied onto the circuit formation surface when the photosensitive film is formed. The applied solution flows on the circuit formation surface. As a result, the thickness of the liquid film of the solution formed on the first area surface differs from the thickness of the liquid film of the solution formed on the second area surface. The solution is cured in this state to form a photosensitive film having a first portion and a second portion that are different in thickness from each other.

[0100] A first portion of the photosensitive film is exposed to a first pattern, and at the same time, a second portion of the photosensitive film is exposed to a second pattern. The exposed portions of the first and second portions are developed simultaneously, and a first opening and a second opening are formed in the first and second portions, respectively. In this manner, a plurality of portions of the photosensitive film formed on the circuit formation surface, each having a different thickness, are exposed and developed simultaneously. This allows the number of manufacturing steps for the flexible wiring circuit board to be reduced, compared to the case where multiple exposures and multiple developments are performed on multiple portions of the photosensitive film according to the thickness.

[0101] Furthermore, since multiple exposures and multiple developments are not performed to form one opening, there is no need to position the photosensitive film to be processed with high precision each time exposure and development are performed.

[0102] In addition, in the manufacturing method of the flexible wired circuit board, a positive photosensitive resin is used as a material for forming the photosensitive film. This allows the photosensitive film to be exposed and developed with higher resolution than when a negative photosensitive resin is used. Therefore, the conductor layer can be formed in the first opening and the second opening with high accuracy.

[0103] As a result, it becomes possible to manufacture flexible wired circuit boards having fine wiring at low cost.

[0104] (2) In the method for producing a flexible printed circuit board according to the first aspect, The step of irradiating the exposure light with the first pattern and the second pattern may include performing projection exposure in which the exposure light that has passed through a mask corresponding to the first pattern and the second pattern is irradiated onto the circuit forming surface through an optical system arranged at a distance from the circuit forming surface.

[0105] In this case, the diffused light generated by the exposure light passing through the mask is prevented from being directly incident on the photosensitive film. The exposure light passing through the mask is shaped by the optical system and incident on the photosensitive film. Therefore, by irradiating the first and second portions of the photosensitive film with the exposure light as parallel light, a high contrast of the exposure state can be obtained at the boundary between the exposed and unexposed portions regardless of the thickness of the photosensitive film.

[0106] (Item 3) In the method for producing a flexible wired circuit board according to item 1 or 2, The developer used for developing the photosensitive film may be an organic alkaline developer.

[0107] When a developer comes into contact with a photosensitive film, the smaller the size of the ions contained in the developer, the more likely it is that the developer will penetrate into the photosensitive film and cause swelling. The size of organic ions contained in an organic alkaline developer is larger than the size of inorganic ions contained in an inorganic alkaline developer. Therefore, when an organic alkaline developer is used, swelling of the photosensitive film is less likely to occur than when an inorganic alkaline developer is used. Therefore, even if the time required for development is long, the reduction in resolution of the first opening and the second opening caused by swelling of the photosensitive film is suppressed.

[0108] (4) In the method for producing a flexible printed circuit board according to the third aspect, The developer may include tetraalkylammonium ions.

[0109] In this case, the degradation of the resolution of the first opening and the second opening caused by the swelling of the photosensitive film is reduced.

[0110] (Item 5) In the method for producing a flexible wired circuit board according to item 3 or 4, The method for producing the flexible printed circuit board includes the steps of: providing a metal support having one surface; forming an insulating layer on a predetermined portion of the surface of the metal support; the first area surface of the circuit formation surface is a surface formed on the one surface of the metal support via at least the insulating layer, The second area surface of the circuit formation surface may be a surface that is formed on the one surface of the metal support without at least the insulating layer being interposed therebetween.

[0111] When forming a photosensitive film, the temperature environment around the solution and the circuit formation surface rises in order to dry and harden the photosensitive resin solution (varnish). In this case, since the metal support has high thermal conductivity, a larger amount of thermal energy is transferred to the part of the solution formed on the metal support without an insulating layer than to the part of the solution formed on the metal support through an insulating layer. This causes differences in the degree of drying in multiple parts of the photosensitive film, resulting in variations in the hardening state.

[0112] The time required to develop a photosensitive film is longer the more cured the photosensitive film is, and shorter the more cured the photosensitive film is. Therefore, when multiple parts of a photosensitive film with varying curing states are developed simultaneously, the development time is determined by the part of the photosensitive film that is more cured.

[0113] Even in such a case, if the developer used to develop the photosensitive film is an organic alkaline developer, the photosensitive film is less likely to swell, and therefore the deterioration of the resolution of the first opening and the second opening caused by the swelling of the photosensitive film is suppressed.

[0114] (Item 6) In the method for producing a flexible wired circuit board according to any one of items 1 to 5, The method for producing the flexible printed circuit board includes the steps of: The method may further include, after the step of forming the conductor layer, irradiating the entire photosensitive film remaining on the circuit formation surface with exposure light, and developing the exposed photosensitive film.

[0115] In this case, residues generated during the formation of the first opening and the second opening are removed by exposing and developing the photosensitive film after the formation of the conductor layer.

[0116] (Item 7) In the method for producing a flexible wired circuit board according to any one of items 1 to 6, a thickness of the first portion of the photosensitive film is smaller than a thickness of the second portion; the conductor layer formed in the first opening constitutes wiring, The conductive layer formed in the second opening may form a via.

[0117] In this case, since the wiring and vias of the flexible wired circuit board can be formed simultaneously, the number of manufacturing steps for the flexible wired circuit board can be reduced compared to the case where the wiring and vias are formed separately.

[0118] (Item 8) In the method for producing a flexible wired circuit board according to any one of items 1 to 7, The method for producing the flexible printed circuit board includes the steps of: The method further includes a step of unwinding a strip-shaped base member from a first roll around which the base member is wound, and winding the base member unwound from the first roll onto a second roll, the circuit-forming surface is formed in advance on one surface of the base member, or is formed on a portion of the base member during transfer from the first roll to the second roll; At least one of the steps of forming the photosensitive film, irradiating the photosensitive film with the exposure light in the first pattern and the second pattern, forming the first opening and the second opening in the photosensitive film, and forming the conductor layer may be performed between the first roll and the second roll.

[0119] In this case, at least one of forming the photosensitive film, irradiating the photosensitive film with exposure light, forming the first opening and the second opening in the photosensitive film, and forming the conductor layer is performed by roll-to-roll, thereby making it possible to manufacture the flexible wired circuit board with high efficiency. [Explanation of symbols]

[0120] 1...metal support substrate, 3...seed layer, 3a...first area surface, 3b...second area surface, 4...solution, 5...photosensitive film, 6...conductor layer, 7...wiring, 8...via, 9...flexible wiring circuit board, 10...first insulating layer forming device, 20...seed layer forming device, 21...first insulating layer, 22...second insulating layer, 30...resist coating device, 40...heat treatment device, 50...first exposure device, 51, 81...light source, 51a, 81a...lamp, 51b, 8 1b...mirror, 52...mask, 52a...light-transmitting portion, 52b...light-shielding portion, 53...projection lens, 55...opening, 55a...first opening, 55b...second opening, 60...first developing device, 70...plating device, 80...second exposure device, 90...second developing device, 91...etching device, 92...second insulating layer forming device, 93...terminal forming device, 100...roll device, 110...feeding roll, 120...winding roll, T...terminal portion

Claims

1. A method for manufacturing a flexible wired circuit board having a plurality of conductor layers on a circuit formation surface, comprising the steps of: the circuit formation surface includes a first area surface and a second area surface that are located at different positions in a thickness direction; The method for producing the flexible printed circuit board includes the steps of: applying a solution of a positive photosensitive resin onto the circuit formation surface and curing the applied solution to form a photosensitive film; irradiating a first portion of the photosensitive film located on the first region surface with exposure light in a predetermined first pattern and simultaneously irradiating a second portion of the photosensitive film located on the second region surface with the exposure light in a predetermined second pattern; developing the exposed photosensitive film to simultaneously form a first opening of the first pattern and a second opening of the second pattern in the photosensitive film; forming the plurality of conductor layers in the first opening and the second opening formed in the photosensitive film, respectively.

2. 2. The method for manufacturing a flexible wired circuit board according to claim 1, wherein the step of irradiating the exposure light with the first pattern and the second pattern includes performing projection exposure in which the exposure light that has passed through a mask corresponding to the first pattern and the second pattern is irradiated onto the circuit formation surface through an optical system arranged at a distance from the circuit formation surface.

3. 3. The method for producing a flexible wired circuit board according to claim 1, wherein the developer used for developing the photosensitive film is an organic alkaline developer.

4. The method for producing a flexible printed circuit board according to claim 3 , wherein the developer contains tetraalkylammonium ions.

5. providing a metal support having one surface; forming an insulating layer on a predetermined portion of the surface of the metal support; the first area surface of the circuit formation surface is a surface formed on the one surface of the metal support via at least the insulating layer, 4. The method for producing a flexible wired circuit board according to claim 3, wherein the second region surface of the circuit formation surface is a surface formed on the one surface of the metal support without at least the insulating layer being interposed therebetween.

6. 3. The method for manufacturing a flexible wired circuit board according to claim 1, further comprising the steps of: irradiating the entire photosensitive film remaining on the circuit formation surface with exposure light after the step of forming the conductor layer; and developing the photosensitive film after exposure.

7. a thickness of the first portion of the photosensitive film is smaller than a thickness of the second portion; the conductor layer formed in the first opening constitutes wiring, 3. The method for producing a flexible wired circuit board according to claim 1, wherein the conductor layer formed in the second opening constitutes a via.

8. The method further includes a step of unwinding a strip-shaped base member from a first roll around which the base member is wound, and winding the base member unwound from the first roll onto a second roll, the circuit-forming surface is formed in advance on one surface of the base member, or is formed on a portion of the base member during transfer from the first roll to the second roll; 3. The method for manufacturing a flexible wired circuit board according to claim 1, wherein at least one of the steps of forming the photosensitive film, irradiating the photosensitive film with the exposure light in the first pattern and the second pattern, forming the first opening and the second opening in the photosensitive film, and forming the conductor layer is performed between the first roll and the second roll.

Images