Flexible printed circuit boards and electrical wiring

Abstract

To provide a flexible printed wiring board and electrical wiring that can suppress quality deterioration due to soldering.SOLUTION: A flexible printed wiring board includes a base film 110, a first conductor layer 111 provided on one surface of the base film 110 and used as wiring, a through hole 113 provided to be electrically connected to the first conductor layer 111 and penetrating from one surface of the base film 110 to the other surface, and a second conductor layer 112 that is provided only near the area where soldering can be performed on the other surface of the base film 110, and is provided to be electrically connected to the through hole 113 and used as an electrical connection by soldering.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a flexible printed wiring board and an electrical wiring.

Background Art

[0002] In various devices, wirings are provided to electrically connect electrical components. For example, a flexible printed wiring board (hereinafter referred to as FPC) that integrally includes a large number of wirings is preferably used. The wiring (conductor layer) provided in the FPC is electrically connected to the wiring of a rigid substrate or a terminal attached to the tip of an electric wire, and the wirings of the FPC may also be electrically connected to each other. For example, in an automotive steering column, when arranging a wiring made of an FPC between a stator and a rotor, a long wiring is required, and thus, the electrical wiring may be configured by connecting a plurality of FPCs. In order to electrically connect the wiring provided in the FPC and the wiring of a rigid substrate or the like, connection by soldering is widely used.

[0003] Referring to FIGS. 7 and 8, an FPC according to the prior art will be described. FIG. 7 is a schematic diagram of an FPC according to the prior art, (a) of which is a partial plan view of the FPC, and (b) of which is a cross-sectional view taken along line EE in (a). FIG. 8 is a schematic cross-sectional view showing a state where the wirings of the FPC are electrically connected to each other.

[0004] The FPC 500 includes a base film 510 that is an insulating layer, a conductor layer 520 provided on the surface of the base film 510, and a cover film 530 that is an insulating layer provided on the opposite side of the base film 510 via the conductor layer 520. The cover film 530 is adhered to the conductor layer 520 and the base film 510 by an adhesive layer 540. Note that a metal foil such as a copper foil provided on the base film 510 is etched to form a desired wiring (circuit). This wiring corresponds to the conductor layer 520. Then, as shown in FIG. 7, a part of the conductor layer 520 is exposed, and the wiring or terminal in another member is electrically connected to this exposed part by soldering.

[0005] Figure 8 shows how the wiring of two FPCs (Flexible Printed Circuits) are electrically connected. In the figure, the basic configuration of the FPC500 on the right and the FPC500A on the left are identical. For example, paste-like solder is applied to the exposed portion of the conductor layer 520 of the FPC500 on the right, and the exposed portions of the conductor layer 520 of the FPC500A on the left are joined together. In this state, the joined portions are heated from both sides by the first heating tool 610 and the second heating tool 620. For example, the first heating tool 610 is heated to 315°C and the second heating tool 620 is heated to 400°C. As a result, the paste-like solder S melts, and then the first heating tool 610 and the second heating tool 620 separate, electrically connecting the conductor layer 520 of the FPC500 and the conductor layer 520 of the FPC500A with the solder S.

[0006] During the soldering process described above, the soldered area becomes hot, and the heat is transferred away from the soldered area, particularly through the highly thermally conductive conductor layer 520. This can lead to a decrease in quality, such as the formation of air bubbles inside the adhesive layer 540 or the peeling of part of the cover film 530. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Patent No. 6975053 [Patent Document 2] Patent No. 6636628 [Overview of the project] [Problems that the invention aims to solve]

[0008] The object of the present invention is to provide a flexible printed circuit board and electrical wiring that can suppress quality degradation caused by soldering. [Means for solving the problem]

[0009] To solve the above problems, the present invention employs the following means.

[0010] In other words, flexible printed circuit boards are Insulating layer and, A first conductor layer is provided on one side of the insulating layer and used as wiring, A through-hole is provided to be electrically connected to the first conductor layer and penetrates from one surface of the insulating layer to the other surface, A second conductor layer is provided only in the vicinity of the area where soldering can be performed on the other surface of the insulating layer, and is provided so as to be electrically connected to the through-hole, and is used as an electrical connection part by soldering, It is characterized by having the following features.

[0011] According to the present invention, when soldering is performed, the heat from the heated second conductor layer is transferred to the first conductor layer through the through-holes, thereby suppressing the heat transferred to the first conductor layer.

[0012] The distance between the area where soldering can be performed and the through-hole should preferably be 20 mm or less.

[0013] It is preferable that the width of the first conductor layer near the point of connection to the through-hole be partially narrowed.

[0014] This allows for reduced heat conduction in narrower sections.

[0015] Furthermore, the electrical wiring of the present invention is characterized by comprising a plurality of the above-mentioned flexible printed circuit boards, wherein the second conductor layers of each board are electrically connected to each other by soldering.

[0016] Furthermore, the above configurations can be combined and adopted as much as possible. [Effects of the Invention]

[0017] As described above, according to the present invention, deterioration in quality due to soldering can be suppressed.

Brief Description of the Drawings

[0018] [Figure 1] FIG. 1 is a schematic view of a flexible printed wiring board according to an embodiment of the present invention. [Figure 2] FIG. 2 is a schematic view of an electrical wiring according to an embodiment of the present invention. [Figure 3] FIG. 3 is a schematic view showing an example of use of a flexible printed wiring board according to an embodiment of the present invention. [Figure 4] FIG. 4 is a schematic view showing an example of use of a flexible printed wiring board according to an embodiment of the present invention. [Figure 5] FIG. 5 is a schematic view showing an example of use of a flexible printed wiring board according to an embodiment of the present invention. [Figure 6] FIG. 6 is a schematic view showing a modified example of a flexible printed wiring board according to an embodiment of the present invention. [Figure 7] FIG. 7 is a schematic view of a flexible printed wiring board according to the prior art. [Figure 8] FIG. 8 is a schematic cross-sectional view showing a state in which flexible printed wiring boards according to the prior art are electrically connected to each other.

Modes for Carrying Out the Invention

[0019] Hereinafter, with reference to the drawings, modes for carrying out this invention will be exemplarily and specifically described based on examples. However, the dimensions, materials, shapes, relative arrangements, etc. of the components described in this example are not intended to limit the scope of this invention only to those, unless there are specific descriptions.

[0020] (Example) Referring to FIGS. 1 to 6, a flexible printed wiring board (hereinafter referred to as "FPC") according to an embodiment of the present invention will be described. In the plan views shown below, a part of the internal main configuration is shown in perspective and indicated by dotted lines.

[0021] <Configuration of FPC> Referring to FIG. 1, the configuration of the FPC 100 according to this embodiment will be described. FIG. 1 is a schematic diagram of the FPC 100 according to an embodiment of the present invention. FIG. 1(a) is a partial plan view of the FPC 100, and FIG. 1(b) is a cross-sectional view taken along line AA in FIG. 1(a).

[0022] The FPC 100 includes a base film 110 which is an insulating layer, a first conductor layer 111 provided on one surface of the base film 110, and a first cover film 121 which is an insulating layer provided on the side opposite to the base film 110 via the first conductor layer 111. The first cover film 121 is adhered to the first conductor layer 111 and the base film 110 by an adhesive layer 131. Note that a metal foil such as a copper foil provided on the base film 110 is etched to form a desired wiring (circuit). This wiring corresponds to the first conductor layer 111. Thus, the first conductor layer 111 is used as wiring.

[0023] In the FPC 100 according to this embodiment, there is a through hole (via) 113 provided so as to be electrically connected to the first conductor layer 111 and penetrating from one surface of the base film 110 to the other surface. Further, in the FPC 100 according to this embodiment, there is a second conductor layer 112 provided only in the vicinity of an area where soldering can be performed on the other surface of the base film 110 and provided so as to be electrically connected to the through hole 113, which is used as an electrical connection portion by soldering. Note that by applying copper plating 113a to the inner peripheral surface of the through hole 113, the surface of the first conductor layer 111, and the surface of the second conductor layer 112, they are electrically connected.

[0024] Furthermore, in the FPC 100 according to this embodiment, there is a second cover film 122 which is an insulating layer provided on the side opposite to the first cover film 121 via the base film 110. This second cover film 122 is adhered to the base film 110 and the second conductor layer 112 by an adhesive layer 132.

[0025] And only a part of the second conductor layer 112 is covered by the second cover film 122, and most of it is exposed. The entire exposed portion corresponds to an area where soldering can be performed. The distance H between this soldering possible area and the through hole 113 is configured to be 20 mm or less. As materials for the base film 110, the first cover film 121, and the second cover film 122, polyimide, polyethylene naphthalate, polyethylene terephthalate, etc. can be applied.

[0026] <Advantages of the FPC according to this embodiment> According to the FPC 100 according to this embodiment, when soldering is performed, the heat of the second conductor layer 112 that is heated is transmitted to the first conductor layer 111 through the through hole 113. The thermal resistance between the second conductor layer 112 and the first conductor layer 111 is the thermal resistance of the through hole 113 and the thermal resistance of the portion of the base film 110 sandwiched between the first conductor layer 111 and the second conductor layer 112. Since the thermal resistance of the through hole 113 and the base film 110 is large compared to the conductor layer, it is possible to suppress the transmission of heat compared to the case where heat is transmitted only through the conductor layer as in the conventional case. Therefore, the heat transmitted to the first conductor layer 111 can be suppressed. Also, in this embodiment, the distance H between the area where soldering can be performed and the through hole 113 is configured to be 20 mm or less. Therefore, the heat of the second conductor layer 112 is transmitted to the first conductor layer 111 through the through hole 113 without reaching deep inside the FPC 100, so that the way heat is transmitted can be suppressed. From the above, it is possible to suppress the generation of bubbles inside the adhesive layers 131 and 132 and the peeling of the first cover film 121 and the second cover film 122. Therefore, it is possible to suppress the deterioration of quality due to soldering. Also, when performing soldering, there is no need to lower the temperature, so soldering can be performed stably. Furthermore, soldering is possible with the conventional manufacturing processes and equipment, and no special processes or equipment are required, so the cost does not increase.

[0027] <Application example of FPC100> <<Application Example 1>> Referring to Figures 2 and 3, an application example 1 of the FPC100 according to this embodiment will be described. Here, a case in which electrical wiring is configured using multiple FPC100s will be described. Figure 2 is a schematic diagram of electrical wiring according to an embodiment of the present invention.

[0028] When long electrical wiring is required, it is generally possible to obtain long electrical wiring by connecting multiple FPC100s, which have a length limit due to their manufacturing process. In other words, the electrical wiring according to this embodiment is constructed by connecting multiple FPCs to each other. Figure 2 shows the state near where two FPC100,100A are connected. Figure 2(a) is a plan view showing the state near where the two FPC100,100A are connected, and Figure 2(b) is a cross-sectional view of BB in Figure 2(a). The configuration of FPC100,100A is as described in the above embodiment, and the basic configuration of both is the same.

[0029] For example, a paste-like solder is applied to the exposed portion of the second conductor layer 112 in FPC100, and the exposed portion of the second conductor layer 112 in FPC100A is then bonded together. In this state, as explained in the background art, the bonded portion is heated from both sides by two heating tools. This melts the paste-like solder, and then the two heating tools separate, electrically connecting the second conductor layer 112 of FPC100 and the conductor layer 112 of FPC100A with solder S. In this way, the second conductor layers 112 are electrically connected to each other by soldering. As described above, in this embodiment, heat is not easily transferred to the respective first conductor layers 111 in FPC100 and FPC100A during soldering, thus suppressing quality degradation.

[0030] In Figure 2, an example is shown where two FPCs 100 and 100A are connected orthogonally to each other, but it is also possible to extend the length by connecting multiple FPCs in a straight line.

[0031] Figure 3 shows a schematic configuration of a rotary connector 10 to be installed on the steering column of an automobile. The rotary connector 10 comprises a first case 11 and a second case 12 that is rotatably mounted relative to the first case 11. The first case 11 integrally comprises a case body 11a and a connector 11b. The second case 12 integrally comprises a case body 12a and a connector 12b. An FPC 100 is installed inside the first case 11 and the second case 12. The FPC 100 is shown as a dotted line in transparency. One end of the FPC 100 is connected to the connector part 11b, and the other end is connected to the connector part 12b. Furthermore, the FPC 100 is wound, for example, in a spiral shape with sufficient space inside the first case 11 and the second case 12 so as not to hinder the rotation of the second case 12 relative to the first case 11. In the case of an FPC used in a rotary connector 10 configured as described above, there are cases where a longer length is required. Therefore, as described above, the length can be increased by connecting multiple FPCs.

[0032] <<Application Example 2>> Referring to Figure 4, an application example 2 of the FPC100 according to this embodiment will be described. Here, the case of connecting the FPC100 to a rigid substrate will be described. Figure 4 is a schematic diagram showing an example of the use of the FPC according to an embodiment of the present invention.

[0033] The FPC100 may be connected to the rigid substrate 200. Figure 4 shows the area around where the FPC100 and the rigid substrate 200 are connected. Figure (a) is a plan view showing the area around the connection, and Figure (b) is a cross-sectional view of CC in Figure (a). The configuration of the FPC100 is as described in the above embodiment.

[0034] The rigid substrate 200 comprises a substrate body 210 and wiring 220 provided on the surface of the substrate body 210. For example, with paste-like solder applied to the exposed portion of the second conductor layer 112 of the FPC 100, a portion of the wiring 220 of the rigid substrate 200 is bonded to it. In this state, as explained in the background art, the bonded portion is heated by two heating tools, sandwiching it from both sides. This melts the paste-like solder, and then the two heating tools separate, electrically connecting the second conductor layer 112 of the FPC 100 and the wiring 220 of the rigid substrate 200 with solder S. As described above, in this embodiment, heat is not easily transferred to the first conductor layer 111 of the FPC 100 during soldering, thus suppressing quality degradation.

[0035] <<Application Example 3>> Referring to Figure 5, Application Example 3 of the FPC100 according to this embodiment will be described. Here, the case of connecting the FPC100 to a wire with terminals will be described. Figure 5 is a schematic diagram showing an example of using the FPC according to an embodiment of the present invention.

[0036] In the FPC100, a wire with a terminal may be connected. Figure 5 shows the area around where the FPC100 and the wire with a terminal 300 are connected. Figure (a) is a plan view showing the area around the connection, and Figure (b) is a cross-sectional view of DD in Figure (a). The configuration of the FPC100 is as described in the above embodiment.

[0037] The wire 300 with a terminal includes a wire 310 and a terminal 320 attached to the tip of the wire 310. For example, a part of the terminal 320 is bonded to a part where the second conductor layer 112 in the FPC 100 is exposed, with a paste-like solder applied. In this state, as described in the background art, the bonded part is heated with two heating tools sandwiching it from both sides. As a result, the paste-like solder melts, and then the two heating tools separate, and the second conductor layer 112 of the FPC 100 and the terminal 320 are electrically connected by the solder S. As described above, in this embodiment, during soldering, heat is less likely to be transmitted to the first conductor layer 111 in the FPC 100, so deterioration in quality is suppressed.

[0038] <Modified Example of FPC> Referring to FIG. 6, a modified example of the FPC will be described. FIG. 6 is a schematic diagram showing a modified example of the FPC according to an embodiment of the present invention. In FIG. 6, a part of the plan view of the FPC is shown.

[0039] As shown in FIG. 6(a), a configuration can also be adopted in which a narrow wire part 111a with a partially narrow width near the connection with the through hole 113 in the first conductor layer 111 is provided. As a result, since the thermal resistance becomes high in the narrow wire part 111a, heat of the second conductor layer 112 can be made difficult to be transmitted at the part of the narrow wire part 111a. Thereby, deterioration in quality can be further suppressed.

[0040] Furthermore, as shown in Figure 6(b), the first conductor layer 111 and the second conductor layer 112 can be electrically connected by multiple through-holes 113 to improve the reliability of the electrical connection. When adopting such a configuration, it is sufficient to ensure that the distance between the through-hole 113 closest to the area where soldering may be performed is 20 mm or less. Of course, it goes without saying that it is desirable to ensure that the distance to the area where soldering may be performed is 20 mm or less for all through-holes 113. Also, even when adopting a configuration with multiple through-holes 113, the configuration of the thin wire section 111a shown in Figure 6(a) can be adopted. [Explanation of Symbols]

[0041] 10 Rotating Connectors 11. Case 1 11a Case body 11b Connector section 12. Case 2 12a Case body 12b Connector section 100, 100A FPC (Flexible Printed Circuit Board) 110 base film 111 First Conductor Layer 111a Fine line part 112 Second Conductor Layer 113 Through-hole 121 First cover film 122 Second cover film 131,132 Adhesive layer 200 Rigid Circuit Boards 210 Main board 220 Wiring 300 wire with terminals 310 Electric wire 320 terminals S Handa

Claims

1. Insulating layer and, A first conductor layer is provided on one side of the insulating layer and used as wiring, A through-hole is provided to be electrically connected to the first conductor layer and penetrates from one surface to the other surface of the insulating layer, A second conductor layer is provided only in the vicinity of the area where soldering can be performed on the other surface of the insulating layer, and is provided so as to be electrically connected to the through-hole, and is used as an electrical connection part by soldering, Equipped with, A flexible printed circuit board characterized in that, when soldering is performed, the heat of the second conductor layer, which is heated, is transferred to the first conductor layer through the through-holes.

2. The flexible printed circuit board according to claim 1, characterized in that the distance between the area where soldering can be performed and the through-hole is 20 mm or less.

3. The flexible printed circuit board according to claim 1 or 2, characterized in that the width of the first conductor layer near the connection to the through-hole is partially narrowed.

4. Electrical wiring comprising a plurality of flexible printed circuit boards as described in claim 1 or 2, wherein the second conductor layers of each board are electrically connected to each other by soldering.

5. Electrical wiring comprising a plurality of flexible printed circuit boards as described in claim 3, wherein the second conductor layers of each board are electrically connected to each other by soldering.

6. Insulating layer and, A first conductor layer is provided on one side of the insulating layer and used as wiring, A through-hole is provided to be electrically connected to the first conductor layer and penetrates from one surface to the other surface of the insulating layer, The other surface of the insulating layer is provided only near the area where soldering can be performed, and the A second conductor layer is provided to be electrically connected to the hole and used as an electrical connection point by soldering, Equipped with, A flexible printed circuit board characterized in that the width of the first conductor layer is partially narrower in the area where it is connected to the through-hole.

7. The flexible printed circuit board according to claim 6, characterized in that the distance between the area where soldering can be performed and the through-hole is 20 mm or less.

8. Electrical wiring comprising a plurality of flexible printed circuit boards as described in claim 6 or 7, wherein the second conductor layers of each board are electrically connected to each other by soldering.

9. The flexible printed circuit board comprises multiple flexible printed circuit boards, each having an insulating layer, a first conductor layer provided on one side of the insulating layer and used as wiring, a through-hole provided to be electrically connected to the first conductor layer and penetrating from one side of the insulating layer to the other side, and a second conductor layer provided only near the area on the other side of the insulating layer where soldering is possible, and provided to be electrically connected to the through-hole, and used as an electrical connection part by soldering. Electrical wiring characterized in that each second conductor layer is electrically connected to the others by soldering.

10. The electrical wiring according to claim 9, characterized in that the distance between the area where soldering can be performed and the through-hole is 20 mm or less.

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