Method for manufacturing circuit pattern assembly with release film, method for manufacturing circuit board, and circuit pattern assembly with release film

Abstract

Provided is a method for manufacturing a circuit pattern assembly with a release film, said method being capable of preventing problems due to front-surface etching.　In the method for manufacturing a circuit pattern assembly with a release film, a circuit pattern assembly (2) is configured to include: a dummy pattern (4) disposed in a gap (G) positioned between a plurality of circuit patterns (3); and first gaps (G1) positioned between the dummy pattern (4) and the circuit patterns (3). The method comprises a step for providing a rear surface of a metal plate (9) with first rear surface recesses (G1R) corresponding to the first gaps (G1), and second rear surface recesses (G2R) corresponding to second gaps (G2) positioned between conductive patterns (3a); a step for adhering a release film (5) to the rear surface of the metal plate (9) provided with the first rear surface recesses (G1R) and the second rear surface recesses (G2R); and a step for removing, by etching, first portions corresponding to the first rear surface recesses (G1R) and second portions corresponding to the second rear surface recesses (G2R) in the surface of the metal plate (9).

Description

Method for manufacturing a circuit pattern assembly with a release film, method for manufacturing a circuit board, and circuit pattern assembly with a release film

[0001] The present invention relates to a method for manufacturing a circuit pattern assembly with a release film, a method for manufacturing a circuit board, and a circuit pattern assembly with a release film.

[0002] Various types of circuit boards have been used for some time. For example, Patent Document 1 discloses a method for manufacturing a circuit board used to mount electronic components used in a power module or the like.

[0003] In the manufacturing method described in Patent Document 1, a metal plate is bonded to a ceramic substrate, a circuit pattern resist is printed on the metal plate, and then unnecessary portions are removed by etching to form the circuit pattern.Then, the surface of the circuit pattern is plated to form a circuit board.

[0004] On the other hand, since the electronic components in power modules generate a large amount of heat, circuit boards in which a circuit pattern is laminated via an insulating layer on a metal base substrate such as a heat sink are being considered in order to improve heat dissipation. Furthermore, the need for larger currents in power modules has been increasing in recent years, and there is also a growing demand for the development of circuit patterns with a thickness of more than 0.5 mm.

[0005] Here, Patent Document 2 discloses a technique in which an electrolytic metal foil is removably provided on a transfer sheet (release film), the electrolytic metal foil is etched to form a circuit pattern, the formed circuit pattern is adhered to an object, and the transfer sheet is peeled off, thereby transferring the circuit pattern to the object. Patent Document 3 also discloses a technique in which a thick circuit pattern can be formed by etching from both the front and back surfaces of a metal plate. Therefore, by utilizing these techniques, it is possible to obtain the above-mentioned circuit board.

[0006] Patent No. 3795354 Patent No. 2572071 Japanese Patent Application Laid-Open No. 10-178256

[0007] Some circuit boards have multiple circuit patterns arranged on a single base substrate, each circuit pattern being configured to perform a specific function when electronic components or the like are mounted thereon. In such cases, a relatively large gap (e.g., approximately 10 mm) is typically provided between adjacent circuit patterns. However, when a circuit pattern assembly consisting of multiple circuit patterns is transferred to a base substrate using techniques such as those disclosed in Patent Documents 2 and 3, problems have been observed during etching. This issue will be explained with reference to FIG. 6A and other figures.

[0008] The metal plate 101 shown in FIG. 6A is ultimately formed into a circuit pattern assembly 102 (comprised of three circuit patterns 106 in this embodiment) shown in FIGS. 6B and 6C . Here, FIG. 6A is a side view of the metal plate 101. FIG. 6B is a side view of the circuit pattern assembly 102 formed from the metal plate 101, and FIG. 6C is a bottom view of the circuit pattern assembly 102 of FIG. 6B from below. As shown in FIG. 6D , the circuit pattern assembly 102 is laminated on a base substrate 104, such as a heat sink, via an insulating layer 103 to form a circuit board 105. The illustrated circuit pattern assembly 102 includes a plurality of circuit patterns 106 (three in this embodiment), with a gap 107 between adjacent circuit patterns 106. Furthermore, the circuit pattern 106 is composed of a plurality of conductive patterns 108, with a second gap 109 between the conductive patterns 108.

[0009] 6A has recesses formed on its front surface (lower surface in FIG. 6A ) and back surface (upper surface in FIG. 6A ) by, for example, etching, etc. Among the recesses shown here, the wider recesses (the recess on the back surface is referred to as back surface recess 107R, and the recess on the front surface is referred to as front surface recess 107F) will eventually become gap 107, and the narrower recesses (the recess on the back surface is referred to as second back surface recess 109R, and the recess on the front surface is referred to as second front surface recess 109F) will eventually become second gap 109.

[0010] Then, as shown in the figure, with the release film 110 attached to the rear surface of the metal plate 101, etching is performed on the front surface of the metal plate 101. To attach the release film 110 to the rear surface of the metal plate 101, a laminating device is typically used, taking into consideration mass production and the like. The laminating device is equipped with a circular roller that presses the long release film 110 against the rear surface of the metal plate 101, and is configured to feed out the release film 110 and the metal plate 101 while rotating this roller to attach the release film 110 to the metal plate 101. Although not shown in the figure, the surface of the metal plate 101, except for the surface recess 107F and the second surface recess 109F, is covered with a hardened dry film obtained by performing an exposure process before etching. Then, when etching is performed using, for example, an apparatus that sprays an etching solution onto the surface of metal plate 101, the portions excluding the portion covered with the hardened dry film (surface recess 107F and second surface recess 109F) dissolve in the thickness direction, so that surface recess 107F and back surface recess 107R are connected, and second surface recess 109F and second back surface recess 109R are connected, thereby forming circuit pattern assembly 102 shown in Figure 6B.

[0011] The circuit pattern assembly 102 shown in Figures 6B and 6C has a release film 110 attached to its back surface, and a transfer body (not shown) is pressed against the surface of the circuit pattern assembly 102 to transfer it to the transfer body.The release film 110 is then peeled off from the circuit pattern assembly 102 that has been transferred to the transfer body, and the circuit pattern assembly 102 is then transferred from the transfer body to an insulating layer 103 laminated on a base substrate 104, thereby forming the circuit board 105 shown in Figure 6D.

[0012] However, when etching was performed with release film 110 attached to the back surface of metal plate 101, a portion of the back surface of circuit pattern 106 adjacent to gap 107 was dissolved in some cases. If such dissolution occurs, there is a risk that circuit pattern 106 will not be bonded well to insulating layer 103.

[0013] In view of these problems, the present invention relates to a circuit pattern assembly with a release film attached to the back surface, and aims to provide a method for manufacturing such a circuit pattern assembly with a release film, which can prevent defects caused by etching from the front surface. In addition, the present invention also provides a circuit board manufacturing method using technology related to this method for manufacturing a circuit pattern assembly with a release film, and a circuit pattern assembly with a release film.

[0014] The present invention is a method for manufacturing a circuit pattern, including the steps of plating predetermined portions on the surface of a metal plate, adhering a release film to the back surface of the plated metal plate, providing a resist pattern on the surface of the metal plate to cover the plating, and etching the metal plate with the resist pattern to form a circuit pattern adhered to the release film.

[0015] The present invention also provides a method for manufacturing a circuit board, in which the circuit pattern obtained by the above-mentioned method for manufacturing a circuit pattern is laminated onto an insulating layer laminated on a base substrate, the method including the steps of transferring the circuit pattern to a transfer body, peeling the release film from the circuit pattern, and transferring the circuit pattern from the transfer body to the insulating layer.

[0016] The present invention also provides a circuit pattern assembly with a release film formed from a metal plate and having a release film attached to the back surface, the circuit pattern assembly comprising a plurality of circuit patterns formed from conductive patterns, dummy patterns arranged in gaps located between the plurality of circuit patterns, and a first gap located between the dummy pattern and the circuit pattern adjacent to the dummy pattern.

[0017] The dummy pattern preferably includes a portion extending outside the circuit pattern assembly.

[0018] It is preferable that the gaps between the plurality of circuit patterns are greater than 2 mm, and the first gaps are 0.8 mm or more and 3 mm or less.

[0019]

[0003] After extensive research, the inventors of the present application found that, because the gaps between adjacent circuit patterns are generally relatively large, when a release film is attached to the back surface of a metal plate having a back surface recess, the release film is attached so that it sinks into the back surface recess, and as a result, the release film does not adhere sufficiently near the edge of the metal plate adjacent to the back surface recess. When etching is performed from the front surface in this state, the etching solution penetrates into the gap between the laminated metal plate and the release film from near the edge of the metal plate adjacent to the back surface recess, resulting in the dissolution of the back surface of the metal plate.

[0020] On the other hand, in the method for manufacturing a circuit pattern assembly with a release film, the method for manufacturing a circuit board, and the circuit pattern assembly with a release film according to the present invention, dummy patterns are arranged in the gaps between adjacent circuit patterns, so that the release film is not attached so as to sink into the recesses on the back surface as in the conventional method, and the release film is attached well over the entire back surface of the metal plate. Therefore, when etching is performed from the front surface on a circuit pattern assembly with a release film attached to the back surface, it is possible to prevent the problem of part of the back surface of the circuit pattern being dissolved.

[0021] 1B is a side view showing one embodiment of a circuit pattern assembly with a release film according to the present invention; FIG. 1C is a bottom view of the circuit pattern assembly with a release film shown in FIG. 1A; FIG. 1D is a side view of a circuit board using the circuit pattern assembly with a release film of FIG. 1A; FIG. 1E is a diagram (related to step S1) showing a method for manufacturing a circuit pattern assembly with a release film according to the present invention; FIG. 1F is a diagram (related to step S2) showing a method for manufacturing a circuit pattern assembly with a release film according to the present invention; FIG. 1G is a diagram (related to step S3) showing a method for manufacturing a circuit pattern assembly with a release film according to the present invention; FIG. 1H is a diagram (related to step S4) showing a method for manufacturing a circuit pattern assembly with a release film according to the present invention; FIG. 1I is a diagram (related to step S5) showing a method for manufacturing a circuit pattern assembly with a release film according to the present invention; FIG. 1J is a diagram (related to step S6) showing a method for manufacturing a circuit pattern assembly with a release film according to the present invention; FIG. 1J is a diagram (related to step S9) showing a method for manufacturing a circuit board according to the present invention; FIG. 1K is a diagram (related to step S11) showing a method for manufacturing a circuit board according to the present invention; FIG. 1K is a diagram (related to step S12) showing a method for manufacturing a circuit board according to the present invention; FIG. 1K is a diagram (related to step S13) showing a method for manufacturing a circuit board according to the present invention. 6A is a diagram relating to a method for manufacturing a circuit board according to the present invention (a diagram relating to step S14); FIG. 6B is a diagram showing steps relating to a method for manufacturing a circuit pattern and a method for manufacturing a circuit board according to the present invention; FIG. 6C is a side view of a metal plate based on Patent Documents 2 and 3; FIG. 6D is a side view of a circuit pattern aggregate formed from the metal plate of FIG. 6A; FIG. 6E is a bottom view of the circuit pattern aggregate shown in FIG. 6B; and FIG. 6F is a side view of a circuit board using the circuit pattern aggregate of FIG. 6B.

[0022] Hereinafter, an embodiment of a method for manufacturing a circuit pattern assembly with a release film, a method for manufacturing a circuit board, and a circuit pattern assembly with a release film according to the present invention will be described with reference to the accompanying drawings. Note that the drawings are schematic, and the thickness and width of each part, the ratio between each part, etc. may differ from those actually implemented.

[0023] First, a circuit pattern assembly with a release film, which is an example of a product produced by the method for producing a circuit pattern assembly with a release film according to this embodiment, and a circuit board, which is an example of a product produced by the method for producing a circuit board according to this embodiment, will be described. Circuit pattern assembly 1 with a release film shown in Figures 1A and 1B has a release film 5 attached to the back surface of circuit pattern assembly 2. In the description of this embodiment, the upper surface of circuit pattern assembly 2 shown in Figure 1A will be referred to as the back surface of circuit pattern assembly 2, and the lower surface of circuit pattern assembly 2 shown in Figure 1A will be referred to as the front surface of circuit pattern assembly 2.

[0024] As will be described later, the circuit pattern assembly 2 is formed by etching a metal plate into a predetermined pattern. The circuit pattern assembly 2 is formed by etching a relatively thick copper plate (rolled copper). The thickness of the circuit pattern assembly 2 (thick copper thickness) can be selected appropriately depending on the application, but in this embodiment it is selected in the range of 0.3 to 2.5 mm.

[0025] As shown in the figure, the circuit pattern assembly 2 of this embodiment includes a total of three circuit patterns 3. Note that the number of circuit patterns 3 in this embodiment is merely an example, and the circuit pattern assembly 2 may include multiple circuit patterns 3. Each circuit pattern 3 is configured to perform a predetermined function when electronic components or the like are mounted thereon. In the circuit pattern assembly 2 of this embodiment, three circuit patterns 3 are arranged horizontally in a row, and a dummy pattern 4 (more specifically, a partition portion 4a extending to separate the adjacent circuit patterns 3) is provided in the gap G between adjacent circuit patterns 3. The dummy pattern 4 of this embodiment includes an outer portion 4b that is connected to the partition portion 4a and extends outside the circuit pattern assembly 2. The outer portion 4b of this embodiment is shaped like a rectangular frame, as shown in FIG. 1B . The dummy pattern 4 is separate from the circuit pattern 3 and electrically independent of the circuit pattern 3. The circuit pattern 3 is composed of a plurality of electrically independent conductive patterns 3a.

[0026] Here, the gap between the dummy pattern 4 and the circuit pattern 3 adjacent to the dummy pattern 4 is referred to as the first gap G1. The gap between the conductive patterns 3a is referred to as the second gap G2. As shown in the figure, the dummy pattern 4 is located between adjacent first gaps G1 (between two first gaps G1 where the second gap G2 is not included). The gap G is wider than the second gap G2. For example, the width of the gap G is 10 mm, the width of the first gap G1 is 1 mm, and the width of the second gap G2 is 1 mm. The width of the first gap G1 is preferably 0.8 mm to 3 mm, more preferably 0.8 mm to 2 mm, and even more preferably 0.8 mm to 1 mm, as described below. The second gap G2 is preferably set to 1 mm or more and 3 mm or less, more preferably 1 mm or more and 2.5 mm or less, and even more preferably 1 mm or more and 2 mm or less. If the second gap G2 exceeds 3 mm, it is preferable to arrange another dummy pattern electrically independent of the circuit pattern 3, such as the dummy pattern 4, in the second gap G2 so that the second gap G2 is 1 mm or more and 3 mm or less. There are no particular restrictions on the gap G as long as the first gap G1 can be set within the above range, but if the gap G is too small, the width of the dummy pattern 4 will also be small, making it difficult to manufacture the circuit pattern assembly 2. Therefore, the gap G is greater than 2 mm, and generally 3 mm or more.

[0027] The release film 5 is a film whose initial adhesive strength can be reduced by, for example, applying heat or irradiating it with ultraviolet light. The release film 5 of this embodiment is a UV film whose initial adhesive strength is reduced by irradiating it with ultraviolet light.

[0028] By carrying out the circuit board manufacturing method described later using the above-described circuit pattern assembly 1 with a release film, it is possible to manufacture the circuit board 6 shown in Fig. 1C. The circuit board 6 of this embodiment is formed by laminating the above-described circuit pattern assembly 2, an insulating layer 7, and a base substrate 8 in this order. By carrying out the circuit board manufacturing method described later, the circuit board 6 is provided with a circuit pattern assembly 2 from which the dummy patterns 4 have been removed.

[0029] The insulating layer 7 is formed from an insulating material and serves to electrically insulate the circuit pattern assembly 2 from the base substrate 8 and also to attach them to each other. Furthermore, when electronic components used in a power module or the like are mounted on the circuit pattern assembly 2, the insulating layer 7 preferably has high heat resistance against heat generated from the electronic components and high thermal conductivity for transferring this heat to the base substrate 8. The insulating layer 7 may cover the entire surface of the base substrate 8 or may cover only a portion of the surface.

[0030] An example of a material for the insulating layer 7 is a resin composition containing a thermosetting resin. Examples of thermosetting resins include epoxy resin, phenolic resin, melamine resin, urea resin, unsaturated polyester resin, alkyd resin, and cyanate resin. One type of thermosetting resin may be used alone, or two or more types may be used in combination. In addition to the thermosetting resin, the resin composition may also contain a curing agent. The curing agent is selected depending on the type of thermosetting resin, and is not particularly limited as long as it reacts with the thermosetting resin. For example, when an epoxy resin is used, examples of the curing agent include amine-based curing agents, imidazole-based curing agents, and phenol-based curing agents. The resin composition may also contain a filler (inorganic filler). Fillers with excellent insulating properties and high thermal conductivity are preferred, such as aluminum oxide, silica, aluminum nitride, boron nitride, silicon nitride, and magnesium oxide. The resin composition may also contain a curing accelerator, stabilizer, ion scavenger, solvent, and the like. The resin composition may also contain a flexibility-imparting agent.

[0031] The base substrate 8 can be formed from various materials, but is preferably formed from a material with particularly high thermal conductivity, such as a metal (which may be a simple metal or an alloy) such as copper, aluminum, or iron. The base substrate 8 of this embodiment is formed from copper. The illustrated base substrate 8 is provided with fins to enhance the effect of dissipating heat to the outside, but a plate-like substrate without fins may also be used. The base substrate 8 is not limited to being formed from a single member, but may be formed by combining multiple members. The base substrate 8 may also include a structure that further enhances the effect of dissipating heat to the outside, such as a metal plate with a vapor chamber or heat pipe embedded in it.

[0032] Next, a method for producing a circuit pattern assembly with a release film and a method for producing a circuit board according to this embodiment will be described with reference to FIGS. 2A to 5. FIG.

[0033] First, dry films 10 are attached to both the front and back surfaces of the metal plate 9 shown in FIG. 2A (step S1 in FIG. 5). The metal plate 9 is a metal plate made of aluminum, copper, or the like. In this embodiment, a copper plate having a thickness of 0.5 to 2.0 mm is used as described above. As an example, a dry film 10 having a thickness of approximately 25 to 150 μm is used. The dry film 10 is preferably attached to the metal plate 9 using a laminating device equipped with rollers R on both the front and back surfaces of the metal plate 9, as shown in FIG. 2A. In the laminating device, the dry films 10 are disposed on both the front and back surfaces of the metal plate 9. Then, the front-side roller R presses the front-side dry film 10 against the front surface of the metal plate 9, and the back-side roller R presses the back-side dry film 10 against the back surface of the metal plate 9, while rotating the rollers R. This allows the dry film 10 to be attached to both the front and back surfaces of the metal plate 9.

[0034] Next, as shown in FIG. 2B , an exposed film 11 is placed on the front-side dry film 10 and the back-side dry film 10. The exposed film 11 has openings at least in the portions corresponding to the conductive patterns 3 a and the dummy patterns 4 in the circuit pattern 3 shown in FIG. 1A (in other words, the portions excluding the portions corresponding to the first gap G1 and the second gap G2). The exposed film 11 is then exposed to light from an exposure device (step S2 in FIG. 5 ). Upon exposure, the light passing through the openings in the exposed film 11 hardens the portions of the dry film 10 directly below the openings.

[0035] Thereafter, development is performed using, for example, a developing device to remove the portions of the dry film 10 that have not been hardened by exposure, as shown in FIG. 2C (step S3 in FIG. 5). As a result, portions of the dry film 10 that have been hardened by exposure remain on the front and back surfaces of the metal plate 9 in the portions corresponding to the conductive patterns 3a and the dummy patterns 4 in the circuit pattern 3 shown in FIG. 1A (see FIG. 2C). Hereinafter, the dry film 10 remaining on the surface of the metal plate 9 after development will be referred to as a resist pattern 12. Openings in the resist pattern 12 are provided in the portions corresponding to the first gap G1 and the second gap G2 shown in FIG. 1A.

[0036] Thereafter, etching is performed on the metal plate 9 having the resist pattern 12 (step S4 in FIG. 5). In this embodiment, double-sided etching is performed, in which etching is performed from both the front and back sides of the metal plate 9 (see FIG. 2D). When performing such double-sided etching, for example, an etching apparatus that sprays an etching solution from both the front and back sides of the metal plate 9 (see, for example, International Publication No. WO 2022 / 102357) can be used. As a result, the front and back sides of the metal plate 9 are dissolved in the thickness direction at the portions where the openings of the resist pattern 12 are provided. In this double-sided etching, etching is performed to the extent that the middle portion of the metal plate 9 in the thickness direction is left. As a result, recesses are formed on the front and back sides of the metal plate 9 at positions corresponding to the first gap G1 and the second gap G2. Here, of the recesses provided at positions corresponding to the first gap G1, the recess on the front side is referred to as the first front recess G1F, and the recess on the back side is referred to as the first back recess G1R. Of the recesses provided at positions corresponding to the second gaps G2, the recesses on the front surface are referred to as second front surface recesses G2F, and the recesses on the rear surface are referred to as second rear surface recesses G2R. Note that the partition portions 4a of the dummy patterns 4 shown in FIG. 1A are located between adjacent first front surface recesses G1F (between adjacent first rear surface recesses G1R).

[0037] Thereafter, the resist pattern 12 covering the front and back surfaces of the metal plate 9 is removed with an alkaline solution using an alkaline stripping device (step S5 in FIG. 5 ), thereby forming the metal plate 9 having the first front surface recess G1F and the second front surface recess G2F on the front surface and the first back surface recess G1R and the second back surface recess G2R on the back surface, as shown in FIG. 3A .

[0038] Next, as shown in FIG. 3B , the dry film 10 is attached to the front surface of the metal plate 9, and the release film 5 described with reference to FIG. 1A is attached to the back surface of the metal plate 9 (step S6 in FIG. 5 ). The dry film 10 and the release film 5 are preferably attached to the metal plate 9 using a laminating device equipped with rollers R on both the front and back surfaces of the metal plate 9, as shown in FIG. 2A . The front-side roller R presses the dry film 10 against the front surface of the metal plate 9, and the back-side roller R presses the release film 5 against the back surface of the metal plate 9, while rotating the rollers R, thereby adhering the dry film 10 to the front surface of the metal plate 9 and the release film 5 to the back surface of the metal plate 9. Here, when a dummy pattern is not provided, as in the circuit pattern assembly 102 shown in FIGS. 6B and 6C , when the release film 110 is attached to the back surface of the metal plate 101, the release film 5 is often attached so as to sink into the back surface recess 107R, which can result in insufficient adhesion of the release film 5 to the back surface of the metal plate 9. On the other hand, when a first rear surface recess G1R is provided to form a dummy pattern 4, the problem of the release film 5 being adhered in a sagging manner is prevented, and the release film 5 can be sufficiently adhered to the rear surface of the metal plate 9.

[0039] Thereafter, similar to the exposure step on the front side of the metal plate 9 shown in FIG. 2B , an exposed film 11 is placed on the dry film 10 on the front side shown in FIG. 3B , and light is irradiated from an exposure device onto the exposed film 11 to perform exposure (step S7 in FIG. 5 ). Illustration of step S7 is omitted. The same exposed film 11 as in step S2 is used in the exposure step in step S7. Therefore, when exposure is performed in step S7, at least the portions of the dry film 10 attached to the surface of the metal plate 9 corresponding to the conductive patterns 3 a in the circuit pattern 3 and the portions corresponding to the dummy patterns 4 (in other words, the portions excluding the portions corresponding to the first gap G1 and the second gap G2) are hardened, similar to FIG. 2B .

[0040] Thereafter, similar to the developing step on the front side of the metal plate 9 shown in Fig. 2C , development is performed to remove the portions of the dry film 10 attached to the surface of the metal plate 9 that have not been hardened by exposure (step S8 in Fig. 5 ). As a result, similar to Fig. 2B , portions of the dry film 10 that have been hardened by exposure remain on the surface of the metal plate 9 in the portions corresponding to the conductive patterns 3a in the circuit pattern 3 and the portions corresponding to the dummy patterns 4. Note that although step S8 is not shown, a resist pattern 12 such as that shown in Fig. 2B is also provided on the surface of the metal plate 9 after development in the developing step of step S8.

[0041] Next, as shown in FIG. 3C , the metal plate 9 having the resist pattern 12 is etched from the front side (step S9 in FIG. 5 ). In this embodiment, an etching apparatus such as that shown in FIG. 2B is used, and an etching solution is sprayed only from the front side as shown in FIG. 3C . This causes the surface of the metal plate 9 to dissolve in the thickness direction at the portions where the openings of the resist pattern 12 are provided (the portions where the first front-side recess G1F and the second front-side recess G2F are located). Therefore, the first front-side recess G1F and the first back-side recess G1R are connected, and the second front-side recess G2F and the second back-side recess G2R are connected, forming a first gap G1 and a second gap G2 in the metal plate 9. As described above, by providing the first back-side recess G1R to form the dummy pattern 4, the release film 5 is sufficiently adhered to the back side of the metal plate 9, preventing the etching solution sprayed from the etching apparatus from penetrating between the release film 5 and the metal plate 9.

[0042] Here, the width of the first gap G1 (i.e., the width of the first front-surface recess G1F and the first back-surface recess G1R) will be described in detail. After extensive studies, the inventors of the present application found that if the first gap G1 is too small, there are problems with mass productivity during etching and with workability when removing the dummy pattern 4 (described later), while if the first gap G1 is too large, there is a risk that the release film 5 will not adhere sufficiently around the first back-surface recess G1R. On the other hand, when the width of the first gap G1 is 0.8 mm or more and 3 mm or less, the adhesion of the release film 5 is also good in addition to the above-mentioned mass productivity and workability. Further studies have revealed that a width of 0.8 mm or more and 2 mm or less is more preferable, and a width of 0.8 mm or more and 1 mm or less is even more preferable.

[0043] Thereafter, similar to the alkaline stripping step on the front side of the metal plate 9 shown in Fig. 2B, the resist pattern 12 covering the front surface of the metal plate 9 shown in Fig. 3C is removed with an alkaline solution (step S10 in Fig. 5), thereby forming a circuit pattern assembly 1 with a release film, in which the release film 5 is attached to the back surface of the circuit pattern assembly 2 shown in Fig. 1A.

[0044] After forming the circuit pattern assembly 1 with a release film in this manner, the dummy patterns 4 are removed from the circuit pattern assembly 2 as shown in Fig. 4A (step S11 in Fig. 5). To remove the dummy patterns 4, for example, a robot chuck may be used to grasp and lift a portion of the dummy patterns 4, and the dummy patterns 4 are then peeled off from the release film 5, or a worker may perform this task instead of a robot. The dummy patterns 4 of this embodiment have outer portions 4b extending outside the circuit pattern assembly 2, and because the outer portions 4b can be grasped, it is possible to prevent the arrangement of the conductive patterns 3a constituting the circuit pattern 3 from being disturbed when the dummy patterns 4 are removed. In particular, the outer portion 4b in this embodiment is shaped like a rectangular frame, and the outer portion 4b can be grasped by pinching the outer surfaces of opposing sides of the four sides that make up the frame (for example, in Figure 4A, the outer portion 4b can be grasped by pinching the right side surface of the outer portion 4b located on the right and the left side surface of the outer portion 4b located on the left), making it easy to remove the dummy pattern 4.

[0045] 4B, a step of pressing the transfer body 13 against the surface of the circuit pattern assembly 2 is carried out (step S12 in FIG. 5). The transfer body 13 is composed of, for example, a urethane cushion material with an adhesive layer on its surface, and a backing plate laminated on the back surface of the cushion material. By pressing the surface of the transfer body 13 with the adhesive layer against the surface of the circuit pattern assembly 2, the circuit pattern assembly 2 is adhered and held to the transfer body 13.

[0046] Next, the release film 5 attached to the back surface of the circuit pattern assembly 2 is irradiated with ultraviolet light to reduce the adhesive strength of the release film 5, and the release film 5 is peeled off from the circuit pattern assembly 2 (step S13 in FIG. 5). That is, by carrying out steps S12 and S13, the circuit pattern assembly 2 held by the release film 5 is transferred to the transfer body 13.

[0047] Thereafter, as shown in Fig. 4C, the circuit pattern assembly 2 held by the transfer body 13 is pressed against the insulating layer 7 laminated on the base substrate 8 and heated. In this embodiment, a vacuum press is used to press the transfer body 13 in a vacuum atmosphere at a predetermined temperature. Then, as shown in Fig. 4C, after the insulating layer 7 has hardened, the transfer body 13 is peeled off, and the circuit pattern assembly 2 is transferred to the insulating layer 7 (step S14 in Fig. 5). Through these steps, the circuit board 6 is completed.

[0048] Although one embodiment of the present invention has been described above, the present invention is not limited to this specific embodiment, and unless otherwise specifically limited in the above description, various modifications and variations are possible within the spirit and scope of the present invention as defined in the claims. For example, the configurations of the above-described embodiment can be added or deleted as appropriate, and the configurations of one embodiment can be incorporated into other embodiments. Furthermore, the effects of the above-described embodiment are merely examples of the effects resulting from the present invention, and do not mean that the effects of the present invention are limited to the above-described effects.

[0049] For example, the dummy pattern 4 preferably includes a portion extending outside the circuit pattern assembly 2, such as the outer portion 4b described above, but may also include only the partition portion 4a. Furthermore, the outer portion 4b is not limited to being shaped like the rectangular frame described above. For example, of the two long sides and two short sides of the outer portion 4b shown in FIG. 1B, only one long side connected to the partition portion 4a may constitute the outer portion 4b. Furthermore, the removal of the dummy pattern 4 shown in FIG. 4A may be performed after transferring the circuit pattern assembly 2 to the transfer body 13 and peeling off the release film 5, as shown in FIG. 4C. In the above-described embodiment, when etching is performed from the front side of the metal plate 9 having the release film 5 attached to its back surface as shown in FIG. 3C, the first surface recess G1F and the second surface recess G2F are provided on the surface of the metal plate 9. However, the present invention also includes a case where a metal plate 9 without recesses such as the first surface recess G1F or the second surface recess G2F is used.

[0050] 1: Circuit pattern assembly with release film 2: Circuit pattern assembly 3: Circuit pattern 3a: Conductive pattern 4: Dummy pattern 5: Release film 6: Circuit board 7: Insulating layer 8: Base board 9: Metal plate G: Gap G1: First gap G1R: First rear recess G2: Second gap G2R: Second rear recess

Claims

1. A method for manufacturing a circuit pattern assembly with a release film formed from a metal plate and having a release film attached to its back surface, the circuit pattern assembly being configured to include a plurality of circuit patterns formed from conductive patterns, a dummy pattern disposed in a gap located between the plurality of circuit patterns, and a first gap located between the dummy pattern and the circuit pattern adjacent to the dummy pattern, the method comprising the steps of: providing, on the back surface of the metal plate, a first back surface recess corresponding to the first gap and a second back surface recess corresponding to a second gap located between the conductive patterns; adhering the release film to the back surface of the metal plate provided with the first back surface recess and the second back surface recess; and removing by etching a first portion corresponding to the first back surface recess and a second portion corresponding to the second back surface recess on the front surface of the metal plate.

2. A method for manufacturing a circuit board, in which the circuit pattern assembly obtained by the method for manufacturing a circuit pattern assembly with a release film described in claim 1 is laminated onto an insulating layer laminated on a base substrate, the method comprising the steps of: transferring the circuit pattern assembly to a transfer body; peeling the release film from the transferred circuit pattern assembly; removing the dummy pattern from the circuit pattern assembly before transferring the circuit pattern assembly to the transfer body or after peeling the release film from the circuit pattern assembly; and transferring the circuit pattern assembly from which the dummy pattern has been removed, from the transfer body to the insulating layer.

3. A circuit pattern assembly with a release film formed from a metal plate and having a release film attached to the back surface, the circuit pattern assembly including a plurality of circuit patterns formed from conductive patterns, a dummy pattern disposed in a gap located between the plurality of circuit patterns, and a first gap located between the dummy pattern and the circuit pattern adjacent to the dummy pattern.

4. A circuit pattern assembly with a release film according to claim 3, wherein the dummy pattern includes a portion extending outside the circuit pattern assembly.

5. A circuit pattern assembly with a release film as described in claim 3, wherein the gaps located between the multiple circuit patterns are greater than 2 mm, and the first gap is 0.8 mm or more and 3 mm or less.

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