Flexible printed circuit board, and method for manufacturing a flexible printed circuit board

Abstract

To provide a flexible printed circuit board that can achieve a longer lifespan. [Solution] The flexible printed circuit board 1 comprises a substrate 10 having a base film 11 and a wiring pattern 12, and a coverlay 20 laminated on the substrate 10 so as to cover the wiring pattern 12. The coverlay 20 comprises a protective layer 21 and an adhesive layer 22 that adheres the protective layer 21 to the substrate 10. A portion of the wiring pattern 12 is exposed from the coverlay 20, and the protective layer 21 has an inclined portion 24 that slopes away from the substrate 10 as it approaches the edge of the coverlay 20, with the space between the inclined portion 24 and the substrate 10 being filled with the adhesive layer 22.

Description

Technical Field

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

Background Art

[0002] A flexible printed wiring board (FPC) is known in which an opening formed in a coverlay film is positioned with respect to a terminal portion of a conductor pattern by inserting a positioning pin into a positioning hole provided in the coverlay film having a thermosetting adhesive layer (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the above-described FPC, when the FPC is bent with the surface on which the coverlay film is formed facing inward, the edge of the coverlay film contacts the conductor pattern exposed from the opening, causing stress to concentrate on the conductor pattern and possibly resulting in disconnection of the conductor pattern.

[0005] The problem to be solved by the present invention is to provide a flexible printed wiring board capable of achieving a long service life and a method for manufacturing the flexible printed wiring board.

Means for Solving the Problems

[0006] [1] The flexible printed circuit board according to the present invention comprises a substrate having a base material and wiring arranged on the base material, and a coverlay laminated on the substrate so as to cover the wiring, wherein the coverlay comprises a protective layer and an adhesive layer for bonding the protective layer to the substrate, a portion of the wiring is exposed from the coverlay, the protective layer has an inclined portion that slopes away from the substrate toward the edge of the coverlay, and the space between the inclined portion and the substrate is filled with the adhesive layer.

[0007] [2] In the above invention, the inclination angle of the inclined portion with respect to the substrate may be 0° to 30°.

[0008] [3] In the above invention, the distance in the extending direction of the substrate between the end of the inclined portion and the end of the adhesive layer may be 1 μm to 30 μm.

[0009] [4] In the above invention, the longitudinal length of the wiring board is 600 mm or more, and the protective layer of the coverlay may be made of a single resin film.

[0010] [5] The present invention relates to a method for manufacturing a flexible printed circuit board, comprising a base material, wiring arranged on the base material, and a coverlay laminated on the base material so as to cover the wiring, comprising: a first step of preparing the base material on which the wiring is arranged; a second step of placing a release layer on the base material so as to cover a part of the wiring; a third step of placing a coverlay on the base material so as to cover the wiring and the release layer and partially curing the coverlay; a fourth step of peeling the release layer from the base material to remove the portion of the coverlay laminated on the release layer, thereby exposing a part of the wiring from the coverlay; and a fifth step of fully curing the coverlay.

[0011] [6] In the above invention, the third step may include heating the coverlay while it is pressed against the substrate to partially cure the adhesive layer of the coverlay, and the fifth step may include heating the coverlay while it is pressed against the substrate to fully cure the adhesive layer of the coverlay.

[0012] [7] In the above invention, the fourth step may include peeling off the release layer to form an inclined portion on the coverlay that slopes away from the substrate made of the substrate and the wiring as it approaches the edge of the coverlay, and the fifth step may include pressing the coverlay toward the substrate to fill the space between the inclined portion and the substrate with the adhesive layer.

[0013] [8] In the above invention, the release layer is a slightly tacky film in which the release strength of the release layer to the substrate is less than the release strength of the coverlay to the substrate, and the second step may include attaching the slightly tacky film to the substrate so as to cover a portion of the wiring.

[0014] [9] In the above invention, the fourth step may include peeling the release layer from the substrate while holding down the portion of the coverlay other than the removal portion with a holding means.

[0015]

[10] In the above invention, the method for manufacturing the wiring board may further include a sixth step before the fourth step, in which the coverlay, the release layer, and the substrate are cut to expose the release layer from the edge of the wiring board. [Effects of the Invention]

[0016] In the present invention, an inclined portion that inclines away from the substrate is formed in the protective layer of the coverlay as it approaches the edge of the coverlay. Thereby, when the flexible printed wiring board is bent, it is possible to suppress the wiring exposed from the coverlay from contacting the coverlay, and even when the wiring contacts the coverlay by bending the flexible printed wiring board, the stress applied to the wiring due to the contact can be relaxed. Therefore, disconnection of the wiring can be suppressed, and the long life of the flexible printed wiring board can be achieved.

[0017] Further, in the present invention, after the coverlay is semi-cured, the release layer is peeled off, and then the coverlay is fully cured, so that the flexible printed wiring board having the above inclined portion can be easily manufactured.

Brief Description of the Drawings

[0018] [Figure 1] FIG. 1 is a plan view showing a flexible printed wiring board according to an embodiment of the present invention. [Figure 2] FIG. 2 is a cross-sectional view showing a flexible printed wiring board according to an embodiment of the present invention, and is a view taken along line II-II of FIG. 1. [Figure 3] [[ID=...]] (注:原文中从ID=18到ID=24的内容,在提供的翻译内容中以省略号表示,因为没有完整翻译这部分内容的需求。如果有完整翻译需求,请补充完整翻译要求后继续提问。) FIGS. 3(a) to 3(d) are cross-sectional views showing a method of manufacturing a flexible printed wiring board according to an embodiment of the present invention. [Figure 4] FIGS. 4(a) to 4(f) are cross-sectional views showing a method of manufacturing a flexible printed wiring board according to an embodiment of the present invention. [Figure 5] FIG. 5(a) is a plan view corresponding to FIG. 3(b), and FIG. 5(b) is a view showing a modification of the method of manufacturing a flexible printed wiring board according to an embodiment of the present invention and is also a plan view corresponding to FIG. 3(b).

Embodiments for Carrying Out the Invention

[0019] Hereinafter, embodiments of the present invention will be described based on the drawings.

[0020] FIG. 1 is a plan view showing a flexible printed wiring board according to an embodiment of the present invention.

[0021] The flexible printed wiring board 1 in the present embodiment is a flexible printed circuit board (FPC) having an overall long rectangular shape. Although not particularly limited, the length L1 along the longitudinal direction (X direction in the figure) of the flexible printed wiring board 1 is 600 mm to 5000 mm (600 mm ≦ L1 ≦ 5000 mm), and the width W along the short side direction (Y direction in the figure) of the flexible printed wiring board 1 is 1 mm to 250 mm (1 mm ≦ W ≦ 250 mm).

[0022] The planar shape of the flexible printed wiring board 1 is not limited to only a rectangular shape, and any shape can be selected. For example, it may partially have a branched shape that extends in multiple branches. Also, the width of the flexible printed wiring board 1 does not have to be constant throughout the longitudinal direction, and the width of the flexible printed wiring board 1 may be wider or narrower in a part of the longitudinal direction.

[0023] Alternatively, the flexible printed wiring board 1 may have a large rectangular planar shape by having a width W greater than 250 mm (250 mm < W ≦ 1000 mm). The planar shape of the large flexible printed wiring board is not particularly limited to the above and can be any shape. At this time, it is only necessary that the virtual rectangle circumscribing the planar shape of the large flexible printed wiring board has the above length L1 and width W.

[0024] The flexible printed wiring board 1 having such a long or large planar shape is used, for example, in applications such as automobiles, industrial machines, and medical devices. The usage of the flexible printed wiring board 1 in the present embodiment is not particularly limited.

[0025] As shown in Figure 2, the flexible printed circuit board 1 comprises a substrate 10 and a coverlay 20. The substrate 10 has a base film 11 and a plurality of wiring patterns 12 arranged on the base film 11. In this embodiment, the substrate 10 corresponds to an example of a "substrate" in the present invention, the base film 11 corresponds to an example of a "base material" in the present invention, the wiring patterns 12 correspond to an example of a "wiring" in the present invention, and the coverlay 20 corresponds to an example of a "coverlay" in the present invention.

[0026] The base film 11 is a flexible film with a long, strip-like shape. This base film 11 is made of an electrically insulating material such as a resin material. While not particularly limited, examples of materials that make up this base film 11 include polyimide (PI), liquid crystal polymer (LCP), polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polyetherimide (PEI), polyetheretherketone (PEEK), and aramid.

[0027] The wiring pattern 12 is made of a conductive material such as metal or carbon. Examples of metals that make up the wiring pattern 12 include copper, silver, and gold. In this embodiment, copper is used as the material that makes up the wiring pattern 12. Note that the number of wiring patterns 12 is not limited to multiple, and there may be just one.

[0028] In this embodiment, as shown in Figure 1, multiple wiring patterns 12 of the same length extend linearly along the X direction on the base film 11. The multiple wiring patterns 12 are arranged parallel to each other at equal intervals. The multiple wiring patterns 12 are arranged so that their positions in the X-axis direction are equal to each other. The number, shape, and arrangement of the wiring patterns 12 are not particularly limited and can be set arbitrarily. In addition, wiring patterns may be formed on both sides of the base film 11, and via holes may be included in the wiring patterns.

[0029] Furthermore, as shown in Figure 1, terminal portions 13 are formed at both ends of each wiring pattern 12. These terminal portions 13 are connected to, for example, connectors provided on other printed circuit boards or cables, thereby electrically connecting the flexible printed circuit board 1 to external electronic circuits. Note that the position of the terminal portions 13 is not limited to the ends of the wiring pattern 12, but can be selected at any position on the wiring pattern 12. Also, there is no particular limit to the number of terminal portions 13 on the wiring pattern 12.

[0030] As shown in Figure 2, the coverlay 20 has a two-layer structure consisting of a protective layer 21 and an adhesive layer 22. The coverlay 20 has an open portion 23 formed by removing the edge of the coverlay 20, and the terminal portion 13 of the wiring pattern 12 is exposed through this open portion 23.

[0031] The protective layer 21 is a layer for protecting the wiring pattern 12. The protective layer 21 is made of a flexible film that has a long, strip-like shape. This protective layer 21 is made of an electrically insulating material such as a resin material. Although not particularly limited, examples of materials that make up this protective layer 21 include polyimide (PI), liquid crystal polymer (LCP), polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polyetherimide (PEI), polyetheretherketone (PEEK), and aramid.

[0032] While not particularly limited, the protective layer 21 has a length equal to the length of the flexible printed circuit board 1 minus the length of the open portion 23, and the protective layer 21 is made of a single long film. Here, one possible method for forming a long coverlay used in the manufacture of a long flexible printed circuit board is to arrange multiple resin films, each having openings or open portions corresponding to terminals, in a straight line and overlap the edges of the resin films. Coverlays manufactured by this method have overlapping portions formed by the overlapping of resin films. In contrast, since the protective layer 21 in this embodiment is made of a single long resin film, the coverlay 20 in this embodiment does not have overlapping portions.

[0033] The protective layer 21 has an inclined portion 24 formed on its edge along the open portion 23. This inclined portion 24 is inclined to move away from the substrate 10 as it approaches the edge of the coverlay 20. The inclined portion 24 is formed when the coverlay 20 is cut by the manufacturing method of the flexible printed circuit board 1 described later. The inclined portion 34 in this embodiment corresponds to an example of the "inclined portion" in the present invention.

[0034] The inclination angle θ' of the inclined portion 24 with respect to the substrate 10 is between 0° and 30° (0° < θ' < 30°), preferably between 1° and 10° (1° < θ' < 10°). If the inclination angle θ' of the inclined portion 24 is too large, the workability when mounting the flexible printed circuit board 1 onto a product may decrease.

[0035] In this embodiment of the flexible printed circuit board 1, as described above, the inclined portion 24 of the protective layer 21 is inclined upward so as to be away from the substrate 10. This prevents the edge of the protective layer 21 from contacting the wiring pattern 12 when the flexible printed circuit board 1 is bent so that the coverlay 20 is on the inside. Furthermore, even if the edge of the protective layer 21 does come into contact with the wiring pattern 12 when the flexible printed circuit board 1 is bent, the inclined portion 24 is inclined away from the substrate 10, which reduces the stress on the wiring pattern 12. This prevents the wiring pattern 12 from breaking and extends the lifespan of the flexible printed circuit board 1.

[0036] Furthermore, in the flexible printed circuit board 1 of this embodiment, the presence of inclined portions 24 in the protective layer 21 prevents solder from riding up onto the coverlay 20 when soldering to the terminal portions 13.

[0037] The adhesive layer 22 is a layer for bonding the protective layer 21 to the upper surface of the substrate 10. The adhesive layer 22 is composed of, for example, a thermosetting epoxy adhesive or a thermosetting acrylic adhesive. The adhesive layer 22 extends beyond the outer edge of the protective layer 21 in the X direction in the figure. The adhesive layer 22 also fills the space 25 between the inclined portion 24 and the substrate 10 (see Figure 4(e)), and the inclined portion 24 is bonded to the substrate 10 by the adhesive layer 22.

[0038] In the flexible printed circuit board 1 of this embodiment, the space 25 between the inclined portion 24 and the substrate 10 is filled with an adhesive layer 22. This prevents the plating solution from entering the space 25 between the inclined portion 24 and the substrate 10 and causing staining when plating the terminal portion 13, thereby suppressing the occurrence of defects in the appearance of the flexible printed circuit board 1.

[0039] The distance L2 in the X direction (the extending direction of the substrate 10) in the drawing between the end of the adhesive layer 22 and the end of the inclined portion 24 is 1 μm to 30 μm (1 μm < L2 < 30 μm). That is, in the flexible printed wiring board 1 of the present embodiment, the amount (flow amount) of the adhesive layer 22 existing outside the outer edge of the protective layer 21 in the X direction in the drawing is suppressed to a small amount, and the open portion 23 and the terminal portion 13 are formed with high positional accuracy. Thereby, the connection reliability of the terminal portion 13 can be improved, and the workability when performing soldering, plating, etc. on the terminal portion 13 can be improved.

[0040] Hereinafter, a method for manufacturing the flexible printed wiring board 1 in the present embodiment will be described with reference to FIGS. 3(a) to 3(d), FIGS. 4(a) to 4(f), FIG. 5(a), and FIG. 5(b). FIGS. 3(a) to 3(d) and FIGS. 4(a) to 4(f) are cross-sectional views showing the method for manufacturing the flexible printed wiring board in the present embodiment. FIG. 5(a) is a plan view corresponding to FIG. 3(b). FIG. 5(b) is a view showing a modified example of the method for manufacturing the flexible printed wiring board in the present embodiment and is also a plan view corresponding to FIG. 3(b).

[0041] First, as shown in FIG. 3(a), a base film 11 on which one or more wiring patterns 12 are formed is prepared on a jig 100 (preparation step). The method for forming the wiring pattern 12 on the base film 11 is not particularly limited, and examples thereof include methods such as a subtractive method and a semi-additive method. The preparation step in the present embodiment corresponds to an example of the "first step" in the present invention.

[0042] Next, as shown in Figure 3(b), a rectangular, slightly adhesive film 30 is placed on the base film 11 so as to cover a portion of the wiring pattern 12 (release layer placement step). Specifically, as shown in Figure 5(a), the slightly adhesive film 30 is placed across multiple wiring patterns 12 so as to cover a portion of each wiring pattern 12. In this case, the slightly adhesive film 30 is placed so that its long side is perpendicular to each wiring pattern 12. The release layer placement step in this embodiment corresponds to an example of the "second step" in the present invention. Note that, as shown in Figure 5(b), multiple slightly adhesive films 30 may be individually placed for multiple wiring patterns 12 such that one slightly adhesive film 30 covers only one wiring pattern 12.

[0043] Although not specifically shown in the diagram, the adhesive film 30 can be positioned on the base film 11 by inserting positioning pins provided on the base film 11 into through holes formed in the adhesive film 30. Alternatively, the positioning of the adhesive film 30 may be performed by image recognition.

[0044] As shown in Figure 3(b), the slightly adhesive film 30 has a structure in which a base material 41 and an adhesive layer 42 are laminated. In the release layer placement step, the slightly adhesive film 30 is placed on the base film 11 so that the adhesive layer 42 is in contact with the base film 11. The material constituting the base material 41 of the slightly adhesive film 30 is not particularly limited, but polyester can be exemplified. The adhesive layer 42 of the slightly adhesive film 30 is not particularly limited, but an acrylic adhesive can be exemplified.

[0045] The peel strength of such a slightly tacky film 30 to the base film 11 is weaker than the peel strength of the adhesive layer 22 to the base film 11 when measured under the same conditions. Test methods for peel strength include the 90-degree peel test specified in JIS K 6854-1 and JIS Z 0237.

[0046] The material constituting the slightly adhesive film 30 is not particularly limited as long as the above-mentioned peel strength relationship is satisfied. Alternatively, instead of the slightly adhesive film 30, a resin material may be applied to the base film 11 so as to cover a part of the wiring pattern 12, and the release layer may be formed by curing the resin material.

[0047] Next, as shown in Figure 3(c), the coverlay 20 is placed on the base film 11 so as to cover the wiring pattern 12 and the low-tack film 30, and the adhesive layer 22 is brought into contact with the base film 11 (coverlay application step). At this time, the adhesive layer 22 does not come into contact with the portion of the wiring pattern 12 where the low-tack film 30 is placed. The size and shape of the coverlay 20 are not limited as long as the coverlay 20 is large enough to cover the wiring pattern 12 and the low-tack film 30.

[0048] Furthermore, as shown in Figure 3(d), the adhesive layer 22 is partially cured by pressing the coverlay 20 onto the base film 11 with a predetermined pressure using a heating plate 50 and heating the entire structure at a predetermined temperature for a predetermined time. The curing of the adhesive layer 22 is performed to the extent that, in the peeling process described later, the coverlay 20 does not peel off from the base film 11 when the slightly tacky film 30 is peeled off, and that the adhesive layer 22 can be filled into the space 25 (see Figure 4(e)) in the adhesive layer filling process described later. Specifically, the adhesive layer 22 is cured so that the degree of curing of the adhesive layer 22 after partial curing is 30-60%. Known measurement methods such as gel fraction testing, thermal analysis, and Fourier transform infrared spectroscopy can be used to measure the degree of curing of the adhesive layer 22. The degree of curing of the adhesive layer 22 can be controlled by the conditions in the pressing process. The conditions in the pressing process can be appropriately set according to the materials that make up the adhesive layer 22 used. The coverlay application step in this embodiment corresponds to an example of the "third step" in the present invention.

[0049] Although not specifically shown in the diagram, a release film may be placed between the heating plate 50 and the coverlay 20 when pressing the coverlay 20. The release film is made of, for example, polyethylene. By placing this release film before pressing, pressure can be applied more uniformly to the entire coverlay 20.

[0050] Next, as shown in Figure 4(a), the coverlay 20 and base film 11 are cut using a mold 70 for external shaping to match the external shape of the flexible printed circuit board 1 to be manufactured (external shape formation step). At this time, as shown in Figures 4(a) and 4(b), in areas where the low-tack film 30 is laminated, the coverlay 20 and base film 11 are cut, including the low-tack film 30, to expose the end face of the low-tack film 30 from the coverlay 20 in the X-axis direction. The external shape formation step in this embodiment corresponds to an example of the "sixth step" in the present invention. The method for forming the external shape of the flexible printed circuit board 1 is not limited to the above, and for example, the external shape of the flexible printed circuit board 1 may be formed using a laser.

[0051] In addition, if the adhesive film 30 is placed on the base film 11 in the above-described release layer placement step such that the end face of the adhesive film 30 or a part of the adhesive film 30 is exposed from the flexible printed circuit board 1, this outline forming step may be omitted.

[0052] Next, as shown in Figure 4(c), the slightly adhesive film 30 and the portion of the coverlay 20 laminated on the slightly adhesive film 30 are peeled from the base film 11. At this time, since the peel strength of the slightly adhesive film 30 from the base film 11 is weaker than the peel strength of the adhesive layer 22 from the base film 11, only the slightly adhesive film 30 is peeled from the base film 11, and the adhesive layer 22 is not peeled from the base film 11.

[0053] Next, as shown in Figures 4(d) and 4(e), a plate-shaped pressing jig 40 is placed on the main body portion 202 of the coverlay 20, excluding the removal portion 201 which is laminated on the low-tack film 30, and the main body portion 202 is pressed down onto the base film 11. With the main body portion 202 held down by the pressing jig 40, the removal portion 201 and the low-tack film 30 are pressed against the pressing jig 40 to separate them from the main body portion 202 (peeling step). Note that the pressing jig 40 is not limited to this and may be a cutting tool such as a cutter knife blade.

[0054] As a result, an open portion 23 is formed in the coverlay 20 where the removed portion 201 was located. In addition, a part of the wiring pattern 12 is exposed through this open portion 23, and a terminal portion 13 is formed. Furthermore, in the coverlay 20, the portion that was peeled off together with the slightly adhesive film 30 but was not cut from the main body portion 202 is formed as an inclined portion 24 of the protective layer 21. A space 25 exists between the inclined portion 24 and the base film 11, and the inclined portion 24 is not adhered to the base film 11. In this embodiment, the removed portion 201 corresponds to an example of the "removed portion" in the present invention, the peeling process in this embodiment corresponds to an example of the "fourth process" in the present invention, and the cutting tool 40 in this embodiment corresponds to an example of the "holding means" in the present invention.

[0055] The inclination angle θ of the inclined portion 24 with respect to the base film 11 can be controlled by adjusting the degree of curing of the adhesive layer 22 during the coverlay application process. Specifically, by lowering the temperature and shortening the pressing time with the hot plate 50 during the coverlay application process, the curing of the adhesive layer 22 is slower, and the inclination angle θ of the inclined portion 24 with respect to the base film 11 becomes smaller. Conversely, by raising the temperature and lengthening the pressing time, the adhesive layer 22 hardens more easily, and the inclination angle θ of the inclined portion 24 becomes larger.

[0056] In this peeling process, the timing of peeling the slightly adhesive film 30 from the base film 11 and the timing of separating the removal portion 201 of the coverlay 20 while it is held down by the pressing jig 40 may be substantially simultaneous. Specifically, the pressing jig 40 may be placed on the main body portion 202 of the coverlay 20, and while the main body portion 202 is held down by the pressing jig 40, the slightly adhesive film 30 may be peeled from the base film 11 at the same time as the removal portion 201 of the coverlay 20 and the slightly adhesive film 30 are separated from the main body portion 202.

[0057] Furthermore, if the removal portion 201 of the coverlay 20 can be separated without using the pressing jig 40, the pressing jig 40 may not be used in this peeling process.

[0058] Next, the pressing jig 40 is removed from the coverlay 20, and as shown in Figure 4(f), the coverlay 20 is pressed onto the base film 11 while the entire coverlay 20 is heated again using the heating plate 50. At this time, the heating plate 50 presses the inclined portion 24 of the protective layer 21 toward the base film 11, causing the adhesive layer 22 to fill the space 25 between the inclined portion 24 and the base film 11, thereby bonding the inclined portion 24 to the base film 11 (adhesive layer filling step). Here, due to the effect of surface tension, the adhesive layer 22 preferentially fills the space 25 rather than flowing toward the terminal portion 13 in the lateral direction in the figure. Therefore, the outflow of the adhesive layer 22 toward the terminal portion 13 is suppressed.

[0059] In this embodiment, the inclined portion 24 is pressed toward the base film 11, so that the final inclination angle θ' of the inclined portion 24 becomes smaller than the inclination angle θ in the peeling process (θ' < θ). However, it is not limited to this, and the inclination angle θ' may be equal to the inclination angle θ (θ' = θ).

[0060] Finally, the entire laminate consisting of the substrate 10 and the coverlay 20 is heated in an oven (baking) to fully cure the adhesive layer 22 (adhesive layer curing step). Specifically, the adhesive layer 22 is cured so that the degree of curing of the adhesive layer 22 after curing is 80-100%. The degree of curing of the adhesive layer 22 can be measured in the same way as the degree of curing of the adhesive layer 22 after partial curing in the coverlay application step. The adhesive layer filling step and adhesive layer curing step in this embodiment correspond to an example of the "fifth step" in the present invention. The flexible printed circuit board 1 in this embodiment is manufactured as described above.

[0061] The pressing conditions in the coverlay application process and the pressing conditions in the adhesive layer filling process may be the same or different. The pressing conditions in the adhesive layer filling process can be set appropriately, for example, according to the degree to which the adhesive layer 22 fills the space 25.

[0062] Furthermore, in this embodiment, the adhesive layer curing step is performed after the adhesive layer filling step, but this is not limited to this. For example, depending on the type of adhesive used, if the adhesive layer is fully cured by pressing in the adhesive layer filling step, the adhesive layer curing step may be omitted.

[0063] As described above, in the manufacturing method of the flexible printed circuit board 1 in this embodiment, the coverlay 20 is partially cured, the slightly adhesive film 30 is peeled off, and then the coverlay 20 is fully cured, so that the flexible printed circuit board 1 having the inclined portion 24 can be easily manufactured.

[0064] Furthermore, in the manufacturing method of the flexible printed circuit board 1 in this embodiment, the inclined portion 24 is formed on the protective layer 21 of the coverlay 20 by peeling off the slightly tacky film 30 when the adhesive layer 22 is semi-cured. As a result, when the adhesive layer 22 is fully cured, the adhesive layer 22 can fill the space 25 between the inclined portion 24 and the base film 11, thereby suppressing the adhesive layer 22 from flowing out into the open portion 23 and the terminal portion 13. Therefore, the terminal portion 13 can be formed with high precision.

[0065] In this case, if the adhesive layer 22 is completely cured during the coverlay application process, it becomes impossible to fill the space 25 between the inclined portion 24 and the substrate 10 with the adhesive layer 22 after the inclined portion 24 has been formed. Therefore, it is necessary to seal the space 25 with a separate resin material or the like to prevent plating solution or the like from flowing into the space 25. In contrast, in this embodiment, the adhesive layer 22 is not completely cured during the coverlay application process, and after the inclined portion 24 has been formed, the adhesive layer 22 is fully cured in the adhesive layer curing process. As a result, the space 25 between the inclined portion 24 and the base film 11 can be filled with the adhesive layer 22, eliminating the need for sealing with a resin material and improving productivity.

[0066] Furthermore, in the manufacturing method of the flexible printed circuit board 1 in this embodiment, as described above, the outflow of the adhesive layer 22 to the terminal portion 13 can be suppressed by filling the space 25 with the adhesive layer 22. As a result, an adhesive with high fluidity can be selected as the adhesive constituting the adhesive layer 22, thereby obtaining good surface smoothness of the flexible printed circuit board 1 and suppressing the formation of voids between the adhesive layer 22 and the wiring pattern 12.

[0067] Furthermore, in the manufacturing method of the flexible printed circuit board 1 in this embodiment, a coverlay 20 is laminated on top of a slightly adhesive film 30 that is placed to cover the wiring pattern 12 on the base film 11, and the wiring pattern 12 is exposed by peeling off the slightly adhesive film 30, thereby forming the terminal portion 13. Since the slightly adhesive film 30 only needs to be placed on the portion of the wiring pattern 12 corresponding to the terminal portion 13, it can be positioned with high positional accuracy relative to the base film 11 regardless of the size of the coverlay 20. Therefore, the terminal portion 13 can be formed with high accuracy.

[0068] The embodiments described above are provided to facilitate understanding of the present invention and are not intended to limit it. Therefore, each element disclosed in the above embodiments is intended to include all design modifications and equivalents that fall within the technical scope of the present invention. [Explanation of symbols]

[0069] 1… Flexible printed circuit board 10... Circuit board 11…Base film 12…Wiring Pattern 13...Terminal section 20…Coverlay 21…Protective layer 22...adhesive layer 23...Open part 24…Slope part 201...Removed part 202…Body part 30...Slightly adhesive film 40…Pressing jig 50…heat plate 100... Jig

Claims

1. A method for manufacturing a flexible printed circuit board comprising a base material, wiring arranged on the base material, and a coverlay laminated on the base material so as to cover the wiring, A first step of preparing the substrate on which the wiring is arranged, A second step involves placing a release layer on the substrate so as to cover a portion of the wiring, A third step involves placing a coverlay on the substrate so as to cover the wiring and the release layer, and partially curing the coverlay. A fourth step involves peeling the release layer from the substrate, thereby removing the portion of the coverlay laminated on the release layer, and exposing a portion of the wiring from the coverlay. A method for manufacturing a flexible printed circuit board, comprising a fifth step of fully curing the coverlay.

2. A method for manufacturing a flexible printed circuit board according to claim 1, A method for manufacturing a flexible printed circuit board, comprising the fourth step of peeling off the release layer to form an inclined portion on the coverlay that slopes away from the substrate consisting of the substrate and the wiring as it approaches the edge of the coverlay.

3. A method for manufacturing a flexible printed circuit board according to claim 1 or 2, The fifth step is a method for manufacturing a flexible printed circuit board, comprising filling the space between the inclined portion and the substrate with the adhesive layer of the coverlay.

4. A method for manufacturing a flexible printed circuit board according to any one of claims 1 to 3, The third step includes heating the coverlay while it is placed on the substrate to partially cure the adhesive layer of the coverlay, A method for manufacturing a flexible printed circuit board, comprising the fifth step of heating the coverlay while it is placed on the substrate to fully cure the adhesive layer of the coverlay.

5. A method for manufacturing a flexible printed circuit board according to any one of claims 1 to 4, The release layer is a slightly tacky film in which the release strength of the release layer to the substrate is less than the release strength of the coverlay to the substrate. The second step is a method for manufacturing a flexible printed circuit board, comprising attaching the slightly adhesive film to the substrate so as to cover a portion of the wiring.

6. A method for manufacturing a flexible printed circuit board according to any one of claims 1 to 5, The fourth step is a method for manufacturing a flexible printed circuit board, comprising peeling the release layer from the substrate while holding down the portion of the coverlay other than the removal portion with a holding means.

7. A method for manufacturing a flexible printed circuit board according to any one of claims 1 to 6, The method for manufacturing a flexible printed circuit board further comprises a sixth step, before the fourth step, of cutting the coverlay, the release layer, and the substrate to expose the release layer from the edge of the flexible printed circuit board.

Images