Printed wiring board and manufacturing method of the same

Abstract

To provide a printed wiring board in which deterioration in quality is suppressed by a simple process.SOLUTION: The present invention provides a manufacturing method of a printed wiring board including: a base material 110; a printed circuit board 100 having a printed wiring including a land 124 provided on a surface of the base material 110; and a solder resist layer selectively covering the surface of the base material 110 and a part of the surface of the printed wiring. The manufacturing method includes a step of selectively forming a resist ink layer 131 on the surface of the base material 110 and the surface of the printed wiring. The screen printing is used to selectively perform the step of forming the resist ink layer such that the resist ink layer 131 is not provided in a region of the surface of the base material 110 not covered with the solder resist layer and a region of the surface of the printed wiring, and the resist ink layer 131 is provided in the region covered with the solder resist layer. The resist ink 310 is a photographic development type solder resist ink.SELECTED DRAWING: Figure 4B

Description

[Technical Field]

[0001] The present invention relates to a printed wiring board and a method for manufacturing the same. [Background technology]

[0002] A printed wiring board comprises a substrate and printed wiring provided on the substrate, which forms a predetermined circuit pattern and includes lands for mounting electronic components by soldering. In order to prevent short circuits and oxidation of the printed wiring, a solder resist layer made of insulating resin (solder resist) is further formed on the surface of the printed wiring board on which the printed wiring is formed, except for the areas corresponding to the lands. In other words, only the lands are exposed on the surface of the printed wiring board, and the other areas of the printed wiring and the surface of the printed board are covered with the solder resist layer.

[0003] A conventional method for manufacturing a printed wiring board will be described below with reference to Fig. 9. Here, Fig. 9 is a cross-sectional view for explaining a conventional method for manufacturing a printed wiring board.

[0004] First, a laminate is prepared in which a copper foil layer 12, which serves as the base of the printed wiring, is bonded to the surface of a substrate 2.

[0005] Next, a mask having a planar shape corresponding to the circuit pattern of the printed wiring is prepared.

[0006] Next, an etching resist layer having a circuit pattern is formed on the copper foil layer using a mask.

[0007] Next, the laminate with the etching resist layer formed thereon is etched to remove the copper foil layer except for the portion covered by the etching resist layer, so that the planar shape of the copper foil layer forms a wiring board pattern that reflects the planar shape of the etching resist layer.

[0008] Next, the etching resist layer is removed from the laminate by peeling it off with an ink remover, thereby obtaining a printed circuit board 1. Figure 9(A) shows the state in which the etching resist layer has been removed from the laminate, resulting in a printed circuit board 1 having a substrate 2 and a printed wiring 20 provided on the substrate 2.

[0009] Subsequently, on the printed circuit board 1, a solder resist layer 30 is formed.

[0010] First, as shown in Fig. 9(B), resist ink is applied to the entire surface of the printed wiring 20 by screen printing as a solid printing to form a resist ink layer 31. After screen printing, the printed circuit board 1 is left to stand for a predetermined time (10 minutes or more). Note that, during the time between the time of screen printing and the time of leaving the printed circuit board 1 to stand, the printed circuit board 1 is moved manually or automatically to a rack serving as a workbench.

[0011] Next, the resist ink layer 31 on the printed circuit board 1 is temporarily cured by heating. Here, the heating is performed by placing the printed circuit board 1 in a tunnel oven or a hot air oven maintained at a predetermined temperature (about 80°C) for a predetermined time.

[0012] 9(C), a film 50 that does not transmit ultraviolet light is placed on the temporarily cured resist ink layer 31 and directly above the lands 24. The film 50 is rectangular in plan view (hereinafter simply referred to as "plan view") of the printed circuit board 1, and is placed so that the lands 24 of the printed wiring 20 overlap inside the film 50. Specifically, a film aligner is used to place the film 50, and the printed circuit board 1 and the film 50 are sequentially set in the film aligner to align their positions, and then fixed with adhesive tape.

[0013] Next, the resist ink layer 31 after the film 50 is placed is baked using a UV exposure machine. Specifically, the printed circuit board 1 is placed in the UV exposure machine, the pressure is reduced to bring the film 50 into close contact with the resist ink layer 31, and the printed circuit board 1 is exposed to light. After the pressure is released, the printed circuit board 1 is removed from the UV exposure machine. As a result, the exposed portion of the resist ink layer 31 around the film 50 is UV-cured.

[0014] Next, the UV-cured printed circuit board 1 is developed. Here, the development is performed by alkaline development. As a result, the film 50 and the part of the resist ink layer 31 directly below the film 50 that has not been UV-cured are dissolved and removed, and only the remaining UV-cured part of the resist ink layer 31 remains on the printed circuit board 1.

[0015] Next, the developed printed circuit board 1 is heated to fully harden it. Here, the heating is performed by placing the printed circuit board 1 in a hot air oven maintained at a predetermined temperature (approximately 100°C to 150°C). As a result, a solder resist layer 30 is formed, as shown in FIG. 9(D). In addition, in the solder resist layer 30, openings 30x that are rectangular in plan view, which are the inverted shape of the film 50, are formed to expose the lands 24.

[0016] Finally, the printed circuit board 1 on which the solder resist layer 30 has been formed is subjected to outline and hole processing and surface finishing, thereby manufacturing the printed wiring board 5.

[0017] In the printed wiring board 5 described above, the solder resist layer 30 is formed by a photographic method (see, for example, Patent Document 1), and a photoimageable solder resist ink is used as the resist ink. The photoimageable solder resist ink is, for example, a two-component mixed ink containing an acrylic ultraviolet curable resin as a base material, an epoxy thermosetting resin as a curing agent, an organic solvent, an inorganic pigment, etc. [Prior art documents] [Patent documents]

[0018] [Patent Document 1] Patent No. 6359605 Summary of the Invention [Problem to be solved by the invention]

[0019] In the above-described conventional method for manufacturing a printed wiring board, the formation of the solder resist layer 30 by the photographic method involves many complicated steps, including film placement, development, and the like.

[0020] Furthermore, performing UV exposure and development to form the solder resist layer 30 tends to dissolve the hardened portion of the resist ink layer 31 at the boundary between the unexposed and exposed portions, near the copper foil of the printed wiring 20, creating a gap, known as an undercut. The undercut can cause moisture, chemicals, and other foreign matter to enter the printed wiring board in subsequent processes and can cause rust, discoloration, and even cracks, thereby reducing the quality of the printed wiring board.

[0021] SUMMARY OF THE INVENTION Therefore, a primary object of the present invention is to provide a method for manufacturing a printed wiring board that can obtain a printed wiring board with reduced deterioration in quality through simple steps. [Means for solving the problem]

[0022] The method for manufacturing a printed wiring board according to the present invention is a method for manufacturing a printed wiring board comprising a base material, a printed substrate having printed wiring provided on the surface of the base material, and a solder resist layer selectively covering the surface of the base material and part of the surface of the printed wiring, the method for manufacturing a printed wiring board comprising a step of forming a solder resist layer including a step of selectively applying a coating of resist ink on the surface of the base material and the surface of the printed wiring, the step of applying the coating of resist ink is selectively carried out using screen printing so that no coating of resist ink is applied to regions of the surface of the base material and the surface of the printed wiring that are not covered by the solder resist layer, and a coating of resist ink is applied to regions that are covered by the solder resist layer, and the resist ink is a photoimageable solder resist ink. [Effects of the Invention]

[0023] According to the present invention, it is possible to obtain a printed wiring board with reduced deterioration in quality through a simple process.

[0024] The above and other objects, features, and advantages of the present invention will become more apparent from the following detailed description of the preferred embodiments of the present invention, which proceeds with reference to the accompanying drawings. [Brief explanation of the drawings]

[0025] [Figure 1] 1 is a plan view showing an example of a partial region of a printed wiring board according to an embodiment of the present invention; [Figure 2] FIG. 2 is a cross-sectional view taken along line II-II in FIG. [Figure 3] FIG. 1 is a flowchart illustrating a method for manufacturing a printed wiring board according to an embodiment of the present invention. [Figure 4A] 1A to 1C are cross-sectional views illustrating a method for manufacturing a printed wiring board according to an embodiment of the present invention. [Figure 4B]5(D) to 5(F) are cross-sectional views illustrating a method for manufacturing a printed wiring board according to an embodiment of the present invention. [Figure 5] 1A and 1B are plan views illustrating a method for manufacturing a printed wiring board according to an embodiment of the present invention. [Figure 6] 1A to 1F are cross-sectional views showing examples of the structure of a laminate according to an embodiment of the present invention. [Figure 7] 1 is a cross-sectional photograph of a printed wiring board according to an embodiment of the present invention; [Figure 8] FIG. 1 is a cross-sectional photograph of a printed wiring board according to a conventional technique. [Figure 9] 1(A) to 1(D) are cross-sectional views illustrating a method for manufacturing a printed wiring board according to a conventional technique. DETAILED DESCRIPTION OF THE INVENTION

[0026] Hereinafter, a method for manufacturing a printed wiring board will be described as an example of the present invention.

[0027] 1. Printed wiring board A printed wiring board 10, which is an example of a printed wiring board according to an embodiment of the present invention, will be described. Fig. 1 is a plan view showing an example of a partial region of a printed wiring board according to an embodiment of the present invention. Fig. 2 is a schematic cross-sectional view taken along line II-II in Fig. 1.

[0028] The printed wiring board 10 includes a printed circuit board 100 and a solder resist layer 130 provided on the printed circuit board 100.

[0029] (printed circuit board) The printed circuit board 100 includes a base material 110 and printed wiring 120 provided on a surface 110a of the base material 110. The base material 110 can have various configurations, as will be described later, but for example, a glass epoxy board can be used.

[0030] The printed wiring 120 is a thin film layer of a conductive material that is processed to form a predetermined circuit pattern by etching or other means after being bonded to the surface 110a of the base material 110. The conductive material for the printed wiring 120 may be, for example, copper foil.

[0031] The printed wiring 120 is composed of a plurality of wirings, and a predetermined number of lands are provided at arbitrary locations on each of the plurality of wirings for soldering to electronic components. In this embodiment, as an example in which the configuration is simplified for the purpose of explanation, a land 124 is provided at an end of the second printed wiring 122 in the first printed wiring 121, the second printed wiring 122, and the third printed wiring 123 that constitute the printed wiring 120. Although the land 124 is shown as having a rectangular shape that is wider than the second printed wiring 122 in a plan view, it may have a circular or any other shape.

[0032] (solder resist layer) The solder resist layer 130 is an insulating layer provided in the printed wiring board 10 so as to cover all surfaces to be insulated except for a portion of the printed circuit board 100 including the lands 124 and their surroundings.

[0033] The solder resist layer 130 is disposed around the lands 124 in a plan view of the printed circuit board 100 (hereinafter simply referred to as "plan view"). Details will be described below.

[0034] The solder resist layer 130 is an insulating layer having openings 130x that are rectangular in plan view and are arranged to seamlessly surround the lands 124, including part of the second printed wiring 122. Specifically, the solder resist layer 130 has openings 130x that are rectangular in plan view so as to expose the lands 124, and the lands 124 are thereby positioned within the openings 130x. An edge 130a of the openings 130x in the solder resist layer 130 adjacent to the periphery of the lands 124 is spaced apart from an edge 124a of the lands 124 by a predetermined distance G. In other words, the solder resist layer 130 is arranged so as not to overlap or contact the lands 124. The dimension of the distance G can be any value depending on the shape and dimensions of the lands 124, but is preferably, for example, in the range of 50 μm or greater.

[0035] The shape of the openings 130x preferably corresponds to the shape of the lands 124. That is, if the lands 124 are circular or have any other shape, the openings 130x preferably have a similar shape to the lands 124.

[0036] The solder resist layer 130 is disposed so as to cover the first printed wiring 121, the second printed wiring 122, and the third printed wiring 123 that constitute the printed wiring 120.

[0037] The thickness of the solder resist layer 130 can be any value depending on the design conditions of the printed wiring board 10. Specifically, it is preferable that the thickness T1 of the solder resist layer 130 in a portion where the first printed wiring 121 and the third printed wiring 123 are not present and the thickness T2 of the portion where the first printed wiring 121 and the third printed wiring 123 are present are both 10 μm or more. Therefore, the distance from the surface 110a of the substrate 110 to the surface of the solder resist layer 130 in the portion where the first printed wiring 121 and the third printed wiring 123 are present is the sum of the thicknesses of the first printed wiring 121 and the third printed wiring 123 and the thickness T2 of the solder resist layer 130.

[0038] The printed wiring board 10 according to the present invention includes a solder resist layer 130 that is arranged to selectively cover an area of ​​the surface 110a of the base material 110 and a portion of the surface of the printed wiring 120. At an edge 130a of an opening 130x in the solder resist layer 130, the entire surface is in close contact with the surface of the copper foil layer 112, and the edge 130a is arranged to have a shape that is continuously and gently inclined toward the edge 130a, as shown in FIG.

[0039] The solder resist layer 130 is formed on the printed wiring board 10 having one land 124 as a land, and has an opening 131x in the resist ink layer 131 that exposes the land 124. However, the solder resist layer 130 may be selectively coated so that all or part of the surface of the land included in the printed wiring is exposed, depending on the various circuit patterns of the printed wiring 120 on the printed wiring board 10.

[0040] 2. Manufacturing method of printed wiring board A method for manufacturing a printed wiring board 10, which is an example of a printed wiring board according to an embodiment of the present invention, will be described. Fig. 3 is a flowchart showing the method for manufacturing a printed wiring board 10 according to an embodiment of the present invention. Fig. 4 is a schematic cross-sectional view showing the state of the printed wiring board 10 in the process shown in the flowchart of Fig. 3, and is a cross-sectional view corresponding to the II-II cross-sectional view of Fig. 2. Fig. 5 is a plan view showing the state of the printed wiring board 10 in the process shown in the flowchart of Fig. 3.

[0041] (Printed circuit board manufacturing) First, a copper-clad laminate 200 is prepared (step S001), in which a copper foil layer 112, which serves as the base of a printed wiring 120, is bonded to the surface of a substrate 110. FIG. 6(A) shows a cross section of the laminate 200 prepared in step S001. In the laminate 200, the substrate 110 is made of paper impregnated with phenolic resin. This results in a printed circuit board 100 as a paper-phenolic board in which paper is impregnated with phenolic resin. In this case, the thickness of the substrate 110 is preferably 0.8 mm or more and 2.0 mm or less, and the thickness of the copper foil layer 112 is preferably 35 μm or more and 70 μm or less.

[0042] The laminate 200 can be configured as follows. Specifically, as shown in FIG. 6B, the substrate 110 may be configured by bonding a glass cloth laminate 111b to both sides of a paper core 111a, and impregnating both materials with epoxy resin. This results in a composite substrate-epoxy substrate 100. In this case, the thickness of the substrate 110 is preferably 0.8 mm or more and 1.6 mm or less, and the thickness of the copper foil layer 112 is preferably 35 μm.

[0043] Similarly, as shown in Fig. 6(C), the substrate 110 may be configured by bonding a laminated material 111b made of glass cloth to both sides of a core material 111a made of glass nonwoven fabric, and impregnating both materials with epoxy resin. This results in a printed circuit board 100 as a glass composite substrate. In this case, the thickness of the substrate 110 is preferably 0.8 mm to 1.6 mm, and the thickness of the copper foil layer 112 is preferably 18 μm to 70 μm.

[0044] 6(D), the substrate 110 may be formed by impregnating the surface of the glass cloth core 111a with epoxy resin on the side where the copper foil layer 112 is bonded. This results in the printed circuit board 100 being a glass epoxy board. In this case, the thickness of the substrate 110 is preferably 0.1 mm or more and 2.0 mm or less, and the thickness of the copper foil layer 112 is preferably 18 μm or more and 70 μm or less.

[0045] Similarly, as shown in FIG. 6(E), the substrate 110 may be configured by bonding a laminate material 111b, an insulating layer with excellent thermal conductivity, which is a mixture of epoxy resin and filler, to the surface of a core material 111a, an aluminum plate, on which the copper foil layer 112 is bonded. The filler may be any of metal oxide, metal hydroxide, and glass cloth. This results in an aluminum-based printed circuit board 100. In this case, it is preferable that the thickness of the core material 111a is 1.0 mm to 3.0 mm, the thickness of the laminate material 111b is 80 μm to 120 μm, and the thickness of the copper foil layer 112 is 35 μm to 105 μm.

[0046] Similarly, as shown in Fig. 6(F), the substrate 110 may have a configuration in which a laminate material 111b, which is an insulating layer having a configuration similar to that of the insulating layer in Fig. 6(E), is bonded to the surface of a core material 111a, which is a copper plate, on the side where the copper foil layer 112 is bonded. This results in a printed circuit board 100 as a copper-based substrate. In this case, it is preferable that the thickness of the core material 111a is 1.0 mm or more and 1.5 mm or less, the thickness of the laminate material 111b is 120 µm, and the thickness of the copper foil layer 112 is 35 µm or more and 105 µm or less.

[0047] Next, a mask having a planar shape corresponding to the circuit pattern of the printed wiring 120 is prepared (step S002). When the printed wiring 120 is formed by a photography method, the mask is prepared as a metal mask having the circuit pattern as an opening. When the printed wiring 120 is formed by a printing method, the mask is prepared as, for example, CAD data of the printing pattern so that it can be used by software.

[0048] Next, an etching resist layer having a circuit pattern is formed on the copper foil layer 112 using a mask (step S003). When the printed wiring 120 is formed by a photography method, an etching resist ink is uniformly applied to the copper foil layer 112, and a mask is laminated thereon. Unnecessary portions of the applied etching resist ink are removed through exposure and development processes. When the printed wiring 120 is formed by a printing method, the shape of the mask is input into a printer as CAD data on the copper foil layer 112, and the printer prints the etching resist ink directly onto the copper foil layer 112. Figure 4A (A) shows the state in which the etching resist layer 140 has been formed on the surface of the laminate 200 in step S003.

[0049] Next, the laminate 200 on which the etching resist layer 140 has been formed is etched to remove the copper foil layer 112 except for the portion of the copper foil layer 112 covered by the etching resist layer 140 (step S004). As a result, the planar shape of the copper foil layer 112 forms a circuit pattern that reflects the planar shape of the etching resist layer 140. Fig. 4A(B) shows a state in which the planar shape of the copper foil layer 112 forms a circuit pattern on the surface of the laminate 200 by the etching resist layer 140 in step S004.

[0050] Next, the etching resist layer 140 is removed from the laminate 200 by peeling it off with an ink remover (step S005). This results in the printed circuit board 100. Figures 4A(C) and 5(A) show the state in which the printed circuit board 100 is obtained by removing the etching resist layer 140 from the laminate 200 in step S005.

[0051] (Process for forming a solder resist layer) Next, the solder resist layer 130 is formed on the printed circuit board 100 .

[0052] First, a resist ink layer 131 is formed by a coating of resist ink 310 by screen printing as direct printing (step S006). The resist ink layer 131 is formed so as to surround the periphery of the exposed portion of the printed circuit board 100 from the outside and to cover all parts of the printed circuit board 100 except for the lands 124 and their surroundings. This resist ink layer 131 becomes the solder resist layer 130 by a main curing step described later.

[0053] Here, direct printing refers to screen printing using a screen plate 300 that has a print pattern in advance that represents the shape in plan view in which the resist ink layer 131 will be formed. The screen plate 300 has a masking portion 300a in the area where the resist ink 310 is not printed, and has screen openings 300x as the print pattern. A mesh portion 300b with a predetermined mesh is then arranged on the surface of the screen plate 300.

[0054] As a result, during the formation of the resist ink layer 131 by direct printing, the masking portions 300a of the screen plate 300 prevent the formation of a coating of resist ink 310 on the lands 124 and their surrounding areas that are not covered by the solder resist layer 130 on the surface 110a of the base material 110 of the printed circuit board 100 and on the surface of the printed wiring 120. On the other hand, the areas covered by the solder resist layer 130, i.e., the areas other than the lands 124 and their surrounding areas, have the coating of resist ink 310 applied through the mesh portions 300b of the screen openings 300x of the screen plate 300. In this way, the resist ink layer 131 selectively forms a coating of resist ink 310 on the surface 110a of the base material 110 and the surface of the printed wiring 120.

[0055] Specifically, as shown in Fig. 4B(D), a screen plate 300 having a printing pattern corresponding to the planar shape in which the resist ink layer 131 is to be formed is placed on the printed circuit board 100. Then, while a squeegee 320 is pressed against the screen plate 300 parallel to the printed circuit board 100, resist ink 310, which is an ink for photoimageable solder resist, is printed through the mesh portion 300b of the screen plate 300 and filled into the screen openings 300x of the screen plate 300, as shown in Fig. 4B(E). Thereafter, as shown in Fig. 4B(F), the screen plate 300 is removed from the printed circuit board 100, and only the resist ink layer 131 remains on the printed circuit board 100.

[0056] When printing using the screen plate 300, a gap is provided between the screen plate 300 and the printed circuit board 100, and printing is performed on the printed circuit board 100 while the screen plate 300 is being pulled.

[0057] The resist ink 310 used in the resist ink layer 131 is a two-component mixed ink containing an acrylic ultraviolet curable resin as a base, an epoxy thermosetting resin as a curing agent, an organic solvent, an inorganic pigment, etc. The epoxy thermosetting resin may be, for example, a visphenol A type epoxy resin or a novolac type epoxy resin.

[0058] The viscosity of the photoimageable solder resist ink used as the resist ink 310 is preferably in the range of 15 Pa·s to 190 Pa·s.

[0059] When printing the resist ink layer 131 by screen printing, the screen plate 300 can be aligned as follows: A work guide (not shown) is installed on the printing machine to which the screen plate 300 is attached, and the printed circuit board 100 is brought into contact with the work guide during printing, thereby achieving alignment based on the assembly accuracy of the screen plate 300 and the work guide.

[0060] The alignment may be performed by providing alignment through-holes in the printed circuit board 100 and inserting pins, the positions of which are predetermined for combination with the screen plate 300, into the through-holes. Furthermore, the alignment may be performed by visually comparing the pattern of the screen plate 300 with the printed wiring 120 of the printed circuit board 100.

[0061] The screen plate 300 is made of, for example, stainless steel, polyester, polyarylate, or other gauze, and has screen openings 300x in areas other than the masking areas 300a where the resist ink layer 131 is not formed. In addition, it is preferable that the mesh portions 300b of the screen plate 300 have obliquely intersecting meshes. This allows the resist ink layer 131 to be formed with high precision.

[0062] The printing conditions for the screen printing are an environment with a temperature of 18° C. to 28° C. and a humidity of 40% to 70%. The mesh portion 300b of the screen plate 300 is preferably made of a mesh with a mesh size of 200 to 300.

[0063] The thickness of the resist ink layer 131 formed by screen printing, that is, the coating thickness of the resist ink, is preferably in the range of 5 μm to 55 μm.

[0064] As shown in FIG. 5(B), the resist ink layer 131 is formed so that an opening 131x having a rectangular shape in plan view is formed in the center thereof, and the land 124 of the printed wiring 120 is disposed within the opening 131x.

[0065] In this way, by performing screen printing using a photoimageable solder resist ink to form the resist ink layer 131 and obtaining the planar shape of the solder resist layer 130 in advance, it is possible to omit the conventional photographic steps such as film placement and exposure, and form the resist ink layer 131 in a simpler process.

[0066] Next, the printed circuit board 100 on which the resist ink layer 131 has been formed is heated to be fully cured (fully cured (1)) (step S007). Here, the heating is performed by placing the printed circuit board 100 in a far-infrared heating furnace (far-infrared furnace) or a hot air furnace maintained at a predetermined temperature.

[0067] In particular, in the present invention, it is preferable to use a conveyor-type far-infrared oven for the main curing (1).

[0068] By using a conveyor-type far-infrared furnace, the main curing (1) step can be carried out continuously from the previous steps on the same production line, simplifying the heating work and completing the heating in a shorter time, thereby improving production efficiency. When a conveyor-type far-infrared furnace is used, the heating conditions are preferably a conveyor speed of 2 m / min to 3 m / min, a heating temperature of the surface temperature of the heating element of the far-infrared furnace in the range of 400°C to 500°C, and a heating time of 3 minutes to 10 minutes.

[0069] When a hot air oven is used, the main curing step (1) is performed by batch processing in which a predetermined number of printed circuit boards 100 are heated at once. When a hot air oven is used, the heating temperature is preferably in the range of 160°C or higher and 160°C or lower, and the heating time is preferably in the range of 20 minutes or higher and 70 minutes or lower.

[0070] Next, the resist ink layer 131 after the main curing (1) is further cured with UV (main curing (2)) (step S008). The main curing (2) is preferably performed using a conveyor-type UV exposure machine. In the main curing (2) step, the exposure conditions are a conveyor speed of 3 m / min or more and 5 m / min or less, and an integrated light dose of 1000 mJ / cm. 2 More than 1500mJ / cm 2 It is preferable that the range is:

[0071] As a result, the solder resist layer 130 is formed.

[0072] Finally, the outer shape and hole processing and surface finishing are performed to manufacture the printed wiring board 10 (step S009). At this time, the lands 124 and the surrounding surfaces on which the solder resist layer 130 is not formed are also cleaned, for example, by degreasing and removing rust with acid.

[0073] In the process of forming the solder resist layer of the present invention, performing the main curing by heating (1) before the main curing by UV curing (2) has the following advantage: When both the far-infrared furnace and the UV exposure machine are conveyor-type, the conveyor speed of the far-infrared furnace is slower than the conveyor speed of the UV exposure machine, which prevents the printed circuit boards 100 from overlapping on the production line.

[0074] In the method for manufacturing printed wiring board 10 according to the embodiment of the present invention, solder resist layer 130 is formed by applying resist ink, which is a photoimageable solder resist ink, by screen printing. Screen printing is performed using a screen plate 300 having a print pattern that corresponds to the planar shape of resist ink layer 131. This prevents the resist ink coating that forms resist ink layer 131 from being applied to the lands 124 and their surroundings, i.e., the areas of the surface of substrate 110 and the surface of printed wiring 120 that are not covered by solder resist layer 130. Meanwhile, the resist ink coating is applied to the areas covered by solder resist layer 130, i.e., the areas other than lands 124 and their surroundings. As a result, the following effects are achieved.

[0075] That is, the conventional photographic processes such as film placement, exposure, and development are omitted, and the solder resist layer 130 can be formed through a simpler process.

[0076] Furthermore, according to the method for manufacturing printed wiring board 10 according to the embodiment of the present invention, no light-shielding film is used in resist ink layer 131 during UV exposure, and therefore no undercut occurs in cured solder resist layer 130. That is, as shown in Fig. 7, in printed wiring board 10, solder resist layer 130 on printed board 100 is formed in such a manner that the entire surface thereof is in close contact with the surface of copper foil layer 112 and has a shape that continuously and gently slopes toward edge portion 130a. In contrast, as shown in Fig. 8, in printed wiring board 10 formed by the conventional photography method, gaps are formed between the edge of solder resist layer 130 on printed board 100 and the surface of copper foil layer 112, and the edge protrudes along the surface direction of printed board 100, resulting in undercut UC.

[0077] As described above, according to the method for manufacturing printed wiring board 10 according to the embodiment of the present invention, it is possible to obtain a printed wiring board with reduced deterioration in quality through simple steps.

[0078] The method for manufacturing a printed wiring board 10 according to an embodiment of the present invention is particularly suitable for manufacturing a printed wiring board as a substrate for mounting light-emitting diodes. Specifically, among printed wiring boards for consumer devices, those mounting light-emitting diodes require a solder resist layer color scheme of white with high reflectivity or black with high light absorption. However, photoimageable solder resist inks for such solder resist layers tend to reflect or absorb ultraviolet light due to the characteristics of the pigments used, resulting in poor transmittance. When a solder resist layer is formed using such photoimageable solder resist inks by a photographic method, a large amount of light is required for UV curing. Furthermore, deep portions are insufficiently cured, making them prone to dissolution during development, increasing the risk of undercutting.

[0079] According to the method for manufacturing the printed wiring board 10 of the embodiment of the present invention, even when using a photoimageable solder resist ink with poor UV transmittance, it is possible to obtain a solder resist layer with reduced quality degradation without increasing the amount of light required for UV curing and eliminating the risk of undercut.

[0080] Furthermore, using photoimageable solder resist ink as the resist ink has the following advantages. Photoimageable solder resist ink is more durable than UV-curable ink, and is therefore used for substrates that require plating or a solder leveler, or for substrates that require durability. Therefore, the method for manufacturing printed wiring board 10 according to the embodiment of the present invention is suitable for application to such substrates.

[0081] Furthermore, according to the method for manufacturing printed wiring board 10 according to the embodiment of the present invention, the process of forming solder resist layer 130 includes a main curing (1) process of thermally curing resist ink layer 131, which is a coating of resist ink, and a main curing (2) process of further UV-curing resist ink layer 131 that has been thermally cured in main curing (1). This makes it possible to prevent printed circuit boards 100 from overlapping on the production line when both the main curing (1) and main curing (2) equipment are conveyor-type.

[0082] Furthermore, in the method for manufacturing printed wiring board 10 according to the embodiment of the present invention, the step of thermally curing the coating of resist ink uses a far-infrared heating furnace.

[0083] This allows the main curing (1) step to be carried out on the same line, consecutively from the previous steps, particularly when a conveyor-type furnace is used, simplifying the heating work and completing the heating in a shorter time, thereby improving production efficiency.

[0084] Furthermore, according to the method for manufacturing printed wiring board 10 according to the embodiment of the present invention, solder resist layer 130 has an ultraviolet reflectance of 60% or more or an optical absorptance of 60% or more.

[0085] This brings about the following effect: As described above, the photoimageable solder resist ink for use in a solder resist layer on a printed wiring board suitable for mounting light-emitting diodes has a lower ultraviolet transmittance than green or blue resist inks, but the ultraviolet transmittance is specifically set within the above range.

[0086] According to the method for manufacturing printed wiring board 10 of the embodiment of the present invention, even when using a photoimageable solder resist ink with a low UV transmittance, such as an UV reflectance of 60% or more or a light absorptance of 60% or more, a high-quality solder resist layer can be obtained without increasing the amount of light required for UV curing and eliminating the risk of undercut.

[0087] As described above, the embodiment of the present invention has been disclosed in the above description, but the present invention is not limited to this.

[0088] In other words, various modifications can be made to the above-described embodiments and variants in terms of mechanism, shape, material, quantity, position, arrangement, etc., without departing from the scope of the technical idea and purpose of this invention, and such modifications are included in this invention. [Explanation of symbols]

[0089] 10 Printed wiring board 100 Printed Circuit Boards 110 Base material 110a surface 111a core material 111b Laminated wood 112 Copper foil layer 120 Printed Wiring 121 First printed wiring 122 Second Printed Wiring 123 Third Printed Wiring 124 rand 124a, 130a edge 130 Solder resist layer 130x, 131x aperture 131 Resist ink layer 140 Etching resist layer 150 films 200 Laminate 300 screen version 300a masking part 300b mesh part 300x screen opening

Claims

1. a printed circuit board having a base material and a printed wiring provided on a surface of the base material; a solder resist layer that selectively covers the surface of the base material and a portion of a surface of the printed wiring, the method for manufacturing a printed wiring board comprising: a step of forming the solder resist layer, the step including a step of selectively providing a coating film of resist ink on the surface of the base material and the surface of the printed wiring, The step of providing a coating film of the resist ink includes: screen printing is used to selectively provide a coating of the resist ink on the surface area of ​​the substrate that is not covered with the solder resist layer and on the surface area of ​​the printed wiring, while providing a coating of the resist ink on the surface area that is covered with the solder resist layer; The method for producing a printed wiring board, wherein the resist ink is an ink for a photoimageable solder resist.

2. The step of forming the solder resist layer includes: a step of thermally curing the coating film of the resist ink; a step of further UV-curing the thermally cured coating film of the resist ink; The method for manufacturing a printed wiring board according to claim 1 , further comprising:

3. 3. The method for manufacturing a printed wiring board according to claim 2, wherein the step of thermally curing the coating of the resist ink uses a far-infrared heating furnace.

4. 4. The method for manufacturing a printed wiring board according to claim 1, wherein the solder resist layer has an ultraviolet reflectance of 60% or more or an optical absorptance of 60% or more.

5. A substrate; a printed circuit board having a printed wiring provided on the surface of the base material; a solder resist layer disposed so as to selectively cover a surface of the base material and a portion of a surface of the printed wiring; Equipped with A printed wiring board, characterized in that the edge of the solder resist layer has a shape that is continuously and gently inclined toward the edge.

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