Flexible printed circuit board and manufacturing method for the flexible printed circuit board

0001The present invention relates to a flexible printed circuit board and a method for manufacturing a flexible printed circuit board.

0002In recent years, the development of robots has been remarkable, such as the appearance of robots that move in various ways. In addition, wearable electronic devices that can be worn on the human body and clothing are being developed and put into practical use in various devices. Many electric wires for power supply and electric signal transmission are used in these robots and wearable electronic devices, but in general, the electric wires have a structure in which a copper wire is used as a core and the outer circumference thereof is covered with an insulator. Therefore, the electric wire itself has almost no elasticity. For this reason, for example, in a robot or the like, it is necessary to allow a margin in the wire length so as not to hinder the movement of the joints, which is a practical obstacle in terms of design and weight reduction. Become.

0003In particular, in applications such as state-of-the-art humanoid robots and power assist devices that are attached to the human body to assist muscle strength, electric wires for moving end motors via multi-degree-of-freedom joints and terminals are placed at the ends. Many electric wires for transmitting electrical signals from various sensors are wired. And, in order to increase the degree of freedom of these wirings in the multi-degree-of-freedom joint, there is an increasing demand for an electric wire configured to be expandable.

0004On the other hand, in recent years, arm robots are often used as industrial robots. In this type of arm robot, depending on the end effector (corresponding to the hand in the human body) attached to the tip side of the robot arm and the drive method of the joint part of the robot arm, from the root side to the tip side of the robot arm In addition to the electric cable, it may be necessary to wire an air hose or hydraulic hose for applying pneumatic pressure. If such cables and hoses are wired to the joints, the cables may be bent or broken. Therefore, once the cables and hoses are pulled out at a position closer to the base end than the joints of the robot arms, the cables are placed in the space outside the joints, and inside the arm again at a position closer to the tip than the joints. Wiring method such as introduction to is adopted. However, in the method of arranging the cable in the outer space of the robot arm, a space for loosening the cable is required around the joint portion of the robot arm.

0005Further, for example, in Patent Document 1, a support rod is provided at the joint rotation center position in the joint portion of the robot arm, a cable is wound around the support rod, and the support rod in which the cable is wound in advance is stored inside the robot arm. By doing so, a structure for preventing the cable from being bent or broken is disclosed. However, there is a possibility that functional deterioration (operating speed, accuracy, etc.) may occur due to an increase in weight due to the provision of a support rod separately. In some cases, a motor with high specifications or the like may be used to compensate for the functional deterioration, or the number of required members may increase, but in that case, the manufacturing cost increases. Further, since the structure of the cable storage portion becomes complicated, there is a problem that it becomes very complicated when the cable is disassembled for wiring, maintenance, etc. at the time of assembling the robot arm, and the cable is taken out and replaced. For this reason, there is an increasing demand for a telescopic electric transmission member that can avoid such a problem even in a robot arm.

0006As a method for responding to the demand for such an electric transmission member, for example, there is a technique disclosed in Patent Document 2. In Patent Document 2, a plurality of pins formed of a desired R are arranged in a jig at intervals through which a flexible printed circuit board can pass, and the flexible printed circuit board is passed through the jig while applying a constant tension to heat the jig. The method of molding is described.

0007Further, Patent Document 2 discloses, regarding the structure of a flexible printed circuit board, in addition to a single-sided flexible printed circuit board having a conductor layer on only one side, a three-layer flexible printed circuit board having three conductor layers is also disclosed. There is. Applications using a three-layer flexible printed circuit board generally include a so-called stripline transmission line in which a signal line whose characteristic impedance is matched is arranged in the inner layer and the outer layer is GND (ground). For example, an image sensor is attached to the tip side of the movable part described above, and it is required when transmitting a large amount of data such as high-definition moving image data via a stretchable flexible printed circuit board, and noise from the outside is generated. The aim is to cut off and achieve both high-quality signal transmission and elasticity.

0008Further, Patent Document 3 discloses a configuration in which the ground of the outer layer of the flexible printed circuit board is a mesh structure instead of a solid GND in a solid coated state to alleviate stress concentration in the bent portion. ..

<p num="0009"><patcit num="1"><text>Japanese Unexamined Patent Publication No. 8-57792</text></patcit><patcit num="2"><text>Japanese Unexamined Patent Publication No. 2011-233822</text></patcit><patcit num="3"><text>Japanese Unexamined Patent Publication No. 2009-176901</text></patcit></p>

<p num="0010"> By the way, in the stripline transmission line as disclosed in Patent Document 2, since the outer layer is a solid GND, a plating film is also present on the outer layer. Therefore, it is hard as a flexible printed circuit board. Therefore, the followability to the jig is also poor, and it is difficult to form a pleated shape having a plurality of bent portions. In particular, the outer layer side has a large bending stress during molding into a pleated shape, and there is a high possibility that the bent portion in the pleated shape will be broken by expansion and contraction within 1000 times. Therefore, it is necessary to frequently replace the broken flexible printed circuit board, which increases maintenance cost. Further, when the above-mentioned flexible printed circuit board is used in the production equipment, there is a problem that the production is interrupted due to the disconnection.</p><p num="0011"> Therefore, in a stripline transmission line as disclosed in Patent Document 2, it is conceivable that the outer layer of the flexible printed circuit board has a mesh structure as disclosed in Patent Document 3. However, when the configuration of Patent Document 3 is applied to the configuration of Patent Document 2, the signal lines are close to each other in the pleated portion. Then, electrical interference may occur due to the proximity thereof, and the characteristic impedance may fluctuate.</p><p num="0012"> The present invention has been made based on the above circumstances, and an object of the present invention is a flexible printed circuit board and a flexible printed circuit board that do not easily break even when repeatedly expanded and contracted while maintaining electrical characteristics. It is an object of the present invention to provide the manufacturing method of.</p>

<p num="0013"> In order to solve the above problems, according to the first aspect of the present invention, a signal line, an insulating layer that covers the signal line from both sides and is made of a thermoplastic resin, and a signal line that sandwiches each insulating layer. A flexible printed substrate having at least one set of stripline transmission lines by providing a pair of ground layers facing each other, and curved portions curved at a plurality of locations are formed, and the curved portions are opened. Alternatively, the ground layer is provided with a pleated portion that is curved so as to close, and the ground layer has a mesh ground layer in which the conductive portion is provided in a mesh shape by having a conductive portion so as to surround the opening, and the conductive portion is planarized. It is characterized in that the provided Betagland layer is provided, the mesh ground layer is arranged on the outer peripheral side of the curved portion, and the Betagland layer is arranged on the inner peripheral side of the curved portion. Flexible printed substrates are provided.</p><p num="0014"> Further, another aspect of the present invention is that, in the above-described invention, the pleated portion is provided in a bellows shape by alternately switching the direction of the curve of the curved portion, and the mesh ground layer is provided on the surface side of the signal line. It is preferable that they are arranged on the outer peripheral side of the curved portion so as to be alternately present on the back surface side.</p><p num="0015"> Further, another aspect of the present invention is that, in the above invention, the pleated portion is provided in a bellows shape by alternately switching the direction of the curve of the curved portion, and the mesh ground layer is on the surface side of the signal line. It is preferable that it is arranged on the outer peripheral side of the curved portion so as to be present on either one of the back surface sides.</p><p num="0016"> Further, as for another aspect of the present invention, in the above-mentioned invention, it is preferable that the insulating layer is formed of LCP (Liquid Crystal Polymer) which is a thermoplastic resin as a material.</p><p num="0017"> Further, as for another aspect of the present invention, in the above-mentioned invention, it is preferable that the ground layer located at the curved portion is not formed with a plating film for interlayer connection.</p><p num="0018"> Further, according to the second aspect of the present invention, a signal line, an insulating layer that covers the signal line from both sides and is made of a thermoplastic resin, and a pair of grounds that face the signal line with the respective insulating layers interposed therebetween. A method for manufacturing a flexible printed substrate having at least one set of strip line transmission lines by providing layers, and at least one of double-sided copper-clad laminates having base copper foil layers on both sides of the insulating layer. The first step of forming a signal line on the base copper foil layer on one side, and the second step of laminating a single-sided copper-clad laminate having a base copper-clad laminate on one side of the insulating layer via a laminated adhesive. In the third step of forming a through hole with respect to a predetermined portion of the intermediate product formed in the second step, and a conductive film is formed around the through hole and its opening to form a conductive through hole. Of the intermediate products formed in the 4th step and the 4th step, the conductive portion is formed so as to surround the opening on one of the surfaces by patterning the base copper foil layer facing the signal line. The fifth step of forming a mesh gland layer in which copper is present and forming a betagland layer in which a conductive portion is provided in a planar shape on the opposite surface side, and at least heat molding of the mesh gland layer and the betagland layer. A plurality of parts were curved with respect to the sixth step of coating the curved portion to be curved later with an insulating resin layer via an adhesive layer and the flexible printed substrate before heat molding formed in the sixth step. A flexible printed substrate comprising: performing heat molding in a state, and after the heat molding, a seventh step of forming a pleated portion having a plurality of curved portions located on the outer peripheral side of the mesh ground layer. A manufacturing method is provided.</p>

<p num="0019"> According to the present invention, the flexible printed circuit board is in a state where it does not easily break even when it is repeatedly expanded and contracted while maintaining its electrical characteristics.</p>

0020<figref num="1">It is a top view which shows the structure of the flexible printed circuit board of the 1st structure example before molding according to one Embodiment of this invention.</figref><figref num="2">It is sectional drawing of the flexible printed circuit board before and after molding, and is the figure which shows the state which cut along the AA line of FIG.</figref><figref num="3">It is sectional drawing of the flexible printed circuit board before and after molding, and is the figure which shows the state which cut along the BB line of FIG.</figref><figref num="4">It is sectional drawing of the flexible printed circuit board before and after molding, and is the figure which shows the state which cut along the CC line of FIG.</figref><figref num="5">It is sectional drawing of the flexible printed circuit board before and after molding, and is the figure which shows the state which cut along the DD line of FIG.</figref><figref num="6">It is a side view which shows the shape of the flexible printed circuit board after molding.</figref><figref num="7">It is a top view which shows the image of the change of the width of a signal line.</figref><figref num="8">It is a top view which shows the 2nd structural example of the flexible printed circuit board before molding corresponding to the modification of FIG.</figref><figref num="9">It is a side view which shows the shape of the flexible printed circuit board after molding in 2nd configuration example.</figref><figref num="10">It is a figure which shows the image which applied the flexible printed circuit board which concerns on 2nd configuration example to the rotating part of an external device such as the joint of the arm of a robot, and shows the state which keeps a horizontal state of two arms. It is a figure.</figref><figref num="11">It is a figure which shows the state which two arms in FIG. 10 are rotated.</figref><figref num="12">It is a figure which shows the state which the signal line and the receiving land were formed in the AA cross section of FIG. 1 and FIG. 8 related to the 1st process.</figref><figref num="13">It is a figure which shows the state which the signal line was formed in the BB cross section, CC cross section, and DD cross section of FIGS. 1 and 8 in relation to the 1st process.</figref><figref num="14">It is a figure which shows the state in which the single-sided copper-clad laminate is laminated on the double-sided copper-clad laminate in the AA cross section of FIGS. 1 and 8 in relation to the second step.</figref><figref num="15">It is a figure which shows the mode that the single-sided copper-clad laminate is laminated on the double-sided copper-clad laminate in the BB cross section, CC cross section, and DD cross section of FIGS. 1 and 8 in relation to the second step .</figref><figref num="16">It is a figure which shows the state which formed the conductive through hole in the AA cross section of FIG. 1 and FIG. 8 which concerns on 3rd process.</figref><figref num="17">It is a side cross-sectional view which shows the structure in the BB cross section, CC cross section, and DD cross section of FIGS.</figref><figref num="18">FIG. 5 is a diagram showing a state in which a conductive coating layer for forming a conductive coating is formed in the through holes in the AA cross section of FIGS. 1 and 8 according to the fourth step.</figref><figref num="19">It is a figure which shows the state which the patterning was made in the AA cross section of FIG. 1 and FIG. 8 which concerns on 5th process.</figref><figref num="20">It is a figure which shows the state which the patterning was made in the BB cross section of FIG. 1 and FIG. 8 related to the 5th step.</figref><figref num="21">It is a figure which shows the state which the patterning was made in the CC cross section of FIG. 1 and FIG.</figref><figref num="22">It is a figure which shows the state which the patterning was made in the DD cross section of FIG. 1 and FIG.</figref><figref num="23">It is a figure which shows the structure in the AA cross section of FIG. 1 and FIG. 8 when the cover layer was formed in relation to the 6th step.</figref><figref num="24">It is a figure which shows the state which the cover layer was formed in the BB cross section of FIG. 1 and FIG. 8 related to the 6th step.</figref><figref num="25">It is a figure which shows the state which the cover layer was formed in the CC cross section of FIG. 1 and FIG.</figref><figref num="26">It is a figure which shows the state which the cover layer was formed in the DD cross section of FIG. 1 and FIG.</figref><figref num="27">It is a figure which shows the state in which the flexible printed circuit board before molding is set in the jig which concerns on 7th process.</figref><figref num="28">It is a top view which shows the structure of the flexible printed circuit board of the conventional structure.</figref><figref num="29">It is sectional drawing of the flexible printed circuit board of a conventional structure, and is the figure which shows the state which cut along the AA line of FIG.</figref><figref num="30">It is sectional drawing of the flexible printed circuit board of a conventional structure, and is the figure which shows the state which cut along the BB line of FIG.</figref>

0021Hereinafter, the flexible printed circuit board 10 according to the embodiment of the present invention will be described below. In the following description, the XYZ Cartesian coordinate system may be used. Of these, the X direction is the longitudinal direction of the flexible printed circuit board 10, the X1 side is the right side of FIG. 1, and the X2 side is the left side. The Y direction is the width direction of the flexible printed circuit board 10, the Y1 side is the front side of the paper surface in FIG. 1, and the Y2 side is the back side of the paper surface. The Z direction is the thickness direction of the flexible printed circuit board 10, Z1 is the back side of the paper surface in FIG. 2, and Z2 is the front side of the paper surface.

0022&lt;About flexible printed circuit boards&gt; FIG. 1 is a plan view showing the configuration of the flexible printed circuit board 10 before molding. FIG. 2 is a cross-sectional view of the flexible printed circuit board 10 before and after molding, and is a diagram showing a state of being cut along the AA line of FIG. FIG. 3 is a cross-sectional view of the flexible printed circuit board 10 before and after molding, and is a diagram showing a state of being cut along the BB line of FIG. FIG. 4 is a cross-sectional view of the flexible printed circuit board 10 before and after molding, and is a diagram showing a state of being cut along the CC line of FIG. FIG. 5 is a cross-sectional view of the flexible printed circuit board 10 before and after molding, and is a diagram showing a state of being cut along the DD line of FIG.

0023As shown in FIGS. 1 to 5, the flexible printed circuit board 10 in the present embodiment is a three-layer flexible printed circuit board which is a kind of multilayer flexible printed circuit board, and has a configuration in which three conductor portions are present. Specifically, the flexible printed circuit board 10 has a signal line 20 on the inner layer side. The signal line 20 is a portion formed by removing a copper foil portion that transmits a signal by etching or the like so that the characteristic impedance is matched for high-speed transmission by a manufacturing method as described later.

0024As shown in FIG. 1, the flexible printed circuit board 10 is provided in an elongated shape. In the present embodiment, the flexible printed circuit board 10 has, for example, a width (dimension in the Y direction) of 5 mm and a length before molding (dimension in the X direction) of 400 mm. However, as shown in FIG. 6 described later, when the curved portion PL2 is formed into a pleated shape (bellows shape) so that the radius is 1 mm, the length is, for example, about 150 mm. However, the dimensional example is not limited to this, and can be set to various dimensions (the same applies to the dimensional example described later).

0025Further, as shown in FIG. 1, the flexible printed circuit board 10 is provided with signal pads 11 exposed on the front and back surfaces thereof. That is, the signal pad 11 is not covered with the cover layers 80 and 90 described later, but is exposed to the outside on the front surface side and the back surface side, respectively. The signal pad 11 is a portion that is electrically interconnected with respect to the signal line 20 to input or output a signal to the signal line 20. Therefore, the conductive through hole 12 is electrically connected to the signal pad 11. The conductive through hole 12 has a through hole 12a penetrating the flexible printed circuit board 10 and a conductive film 12b such as plating formed on the inner wall side of the through hole 12a, and the conductive through hole 12 is formed through the conductive film 12b. The signal pad 11 is electrically connected to the signal line 20.

0026Further, similarly to the signal pad 11 described above, the flexible printed circuit board 10 is also provided with a GND pad 13 that is exposed on the front and back of the flexible printed circuit board 10 without being covered by the cover layers 80 and 90 described later. .. The GND pad 13 is also electrically interconnected with the two ground layers 60 and 70 on the front and back sides via conductive through holes 14. Similar to the above-mentioned conductive through hole 12, the conductive through hole 14 also has a through hole 14a penetrating the flexible printed circuit board 10 and a conductive coating 14b such as plating formed on the inner wall side of the through hole 14a. The GND pad 13 and the ground layers 60 and 70 are electrically connected to each other via the conductive coating 14b.

0027The diameters of the conductive through holes 12 and 14 may be, for example, 25 μm.

0028As shown in FIG. 3, the signal line 20 is laminated on the insulating layer 30. Further, the insulating layer 40 is laminated on the upper surface side of the signal line 20 and the insulating layer 30 via the adhesive layer 50. In the present embodiment, the insulating layers 30 and 40 are made of a thermoplastic resin such as LCP (Liquid Crystal Polymer: LCP). Further, the adhesive layer 50 is a portion having adhesiveness and electrical insulation. The thickness of the insulating layers 30 and 40 may be, for example, 25 μm. Further, the thickness of the adhesive layer 50 may be, for example, 15 μm.

0029Further, as shown in FIG. 3, a ground layer 60 is provided on the upper surface side of the insulating layer 30. Further, a ground layer 70 is also provided on the lower surface side of the insulating layer 40. The ground layers 60 and 70 are conductive portions made of, for example, copper foil. The ground layers 60 and 70 are present on both the upper and lower sides of the signal line 20, and the signal lines 20 are covered with an insulator such as the insulating layers 30 and 40 to form a strip transmission line for propagating electromagnetic waves.

0030The thickness of the signal line 20 and the ground layers 60 and 70 may be, for example, 12 μm.

0031The ground layer 60,70 has a beta land layer 61,71 and a mesh ground layer 62,72. As shown in FIG. 3, the bettaland layers 61 and 71 are portions of the ground layers 60 and 70 having a uniform thickness in the width direction (Y direction). On the other hand, the mesh ground layers 62 and 72 are different from the beta land layers 61 and 71 in that the conductive portions 62a and 72a such as copper foil are formed in a mesh shape (mesh shape). That is, as shown in FIGS. 1, 4 and 5, the mesh ground layers 62,72 surround the openings 62b, 72b in which the conductive portions 62a, 72a are absent (the conductive portions 62a, 72a are removed). , The conductive portions 62a and 72a are provided so as to surround them. As a result, the mesh ground layers 62 and 72 are provided in a mesh shape (mesh shape).

0032A large number of the above-mentioned openings 62b and 72b are provided, and openings 62b and 72b having the same shape are arranged in a predetermined direction and in a direction orthogonal to the predetermined direction. Therefore, the conductive portions 62a and 72b provided so as to surround the openings 62b and 72b also form a regular pattern.

0033In this embodiment, the openings 62b, 72b are provided in a square or rhombus. Therefore, one unit (one element) of the mesh ground layers 62 and 72 is also square or rhombic. However, the openings 62b, 72b may have a shape other than a square or a rhombus. For example, it may be rectangular, circular, triangular or other polygonal, oval, elliptical, or any other regular or irregular shape. ..

0034The arrangement of the mesh ground layers 62 and 72 on the flexible printed circuit board 10 will be described later. Further, in the mesh ground layers 62 and 72, the openings 62b and 72b have an opening size smaller than the wavelength of the electromagnetic wave assumed to be transmitted by the signal line 20.

0035The cover layers 80 and 90 are arranged so as to cover the ground layers 60 and 70 having the betaland layers 61 and 71 and the mesh ground layers 62 and 72 as described above (FIGS. 3 to 5). See). That is, a cover layer 80 is provided on the upper surface side of the ground layer 60, and the cover layer 80 covers the ground layer 60. A cover layer 90 is provided on the lower surface side of the ground layer 70, and the cover layer 90 covers the ground layer 70.

0036The cover layers 80 and 90 have an insulating resin layer 81 and 91 made of a thermoplastic resin such as LCP (Liquid Crystal Polymer: LCP), and also have an adhesive layer 82 and an electrically insulating property. Has 92. The thickness of the insulating resin layer 81,91 is, for example, 25 μm with respect to the ground layer 60,70 having a thickness of 12 μm, and the thickness of the adhesive layer 82,92 is, for example, 15 μm. There is something. In this case, there is no problem such as delamination and the bonding can be performed.

0037&lt;Arrangement of mesh ground layers 62,72 (first configuration example)&gt; Next, a first configuration example in the arrangement of the mesh ground layers 62 and 72 on the flexible printed circuit board 10 will be described. As shown in FIG. 1, the mesh ground layers 62 and 72 are provided so as to alternately exist on the front surface side and the back surface side of the flexible printed circuit board 10. That is, in the vicinity of the CC line in FIG. 1, as shown in FIG. 4, the mesh ground layers 62 and 72 are arranged on the surface side of the flexible printed circuit board 10. On the other hand, in the vicinity of the DD line in FIG. 1, as shown in FIG. 5, the mesh ground layers 62 and 72 are arranged on the back surface side of the flexible printed circuit board 10.

0038The above arrangement will be described with reference to FIG. FIG. 6 is a side view showing the shape of the flexible printed circuit board 10 after molding. As shown in FIG. 6, the molded flexible printed circuit board 10 has a pleated portion PL formed in a pleated shape (bellows shape). The pleated portion PL is provided with a straight portion PL1 and a curved portion PL2. By deforming the curved portion PL2, the flexible printed circuit board 10 after molding can be folded short or expanded long at the pleated portion PL. That is, in the molded flexible printed circuit board 10, the entire length of the flexible printed circuit board 10 is stretchable due to the presence of the pleated portion PL. Further, the flexible printed circuit board 10 after molding can be easily deformed so as to bend in each direction due to the presence of the pleated portion PL.

0039Here, the mesh ground layers 62 and 72 are located on the outer peripheral side of the curve drawn by the curved portion PL2 in the curved portion PL2 of the pleated portion PL. Moreover, as the process proceeds along the side surface of the molded flexible printed circuit board 10 shown in FIG. 6, the directions of the curves drawn by the curved portion PL2 are provided so as to be alternately switched. In FIG. 6, when traveling along the flexible printed circuit board 10, the directions of the curves drawn by the curved portion PL2 are provided so as to be alternately switched. Therefore, as shown in FIG. 1, the mesh ground layers 62 and 72 are provided so as to alternately exist on the front surface side and the back surface side of the flexible printed circuit board 10.

0040The BB line part in FIG. 6 corresponds to FIG. 3, the CC line part corresponds to FIG. 4, and the DD line part corresponds to FIG.

0041Here, when the mesh ground layers 62 and 72 are present on the inner peripheral side of the curve drawn by the curved portion PL2, there may be some electrical interference at the portion where the signal lines 20 face each other in the pleated portion PL. May occur. This is because there is a portion where the openings 62b and 72b of the mesh ground layers 62 and 72 are in a positional relationship facing each other.

0042However, as in the present embodiment, when the mesh ground layers 62 and 72 are present on the outer peripheral side of the curved portion PL2 and the bettaland layers 61 and 71 are present on the inner peripheral side of the curved portion PL2. There is no portion where the openings 62b and 72b of the mesh ground layers 62 and 72 are in a positional relationship facing each other. Therefore, it is possible to prevent electrical interference between the signal lines 20 and prevent fluctuations in the characteristic impedance of the flexible printed circuit board 10.

0043In addition, when the mesh ground layers 62 and 72 are present on the outer peripheral side of the curve drawn by the curved portion PL2 as in the present embodiment, when the flexible printed circuit board 10 is formed into a pleated shape (bellows shape). Bending stress can be reduced. Moreover, since the bending stress is reduced, the structure is such that the durability when the flexible printed circuit board 10 is repeatedly expanded and contracted is ensured. Further, since the flexible printed circuit board 10 is configured with a strip transmission line for propagating electromagnetic waves, the function of blocking noise from the outside is not impaired.

0044In the flexible printed circuit board 10 having the above configuration, the line width of the signal line 20 having the characteristic impedance of 50Ω (dimension A in FIG. 7) is shown in the cross section along the AA line shown in FIG. 2 and in FIG. The cross section along the BB line is 35 μm. Further, in the cross section along the CC line shown in FIG. 4 and the cross section along the DD line shown in FIG. 5, the line width of the signal line 20 (dimension B in FIG. 7) is the aperture ratio of the mesh ground layers 62 and 72 (dimension B in FIG. 7). Although it depends on the ratio of removing the copper foil), when the aperture ratio is 75%, the line width at which the characteristic impedance is 50Ω is 50μm.

0045Further, as a dimensional example of the mesh ground layer 62,72 having an aperture ratio of 75% as described above, there is one in which the line width of the conductive portion 62a is 120 μm and the vertical and horizontal dimensions of the opening are 800 μm.

0046FIG. 7 is a plan view showing an image of a change in the width of the signal line 20. As shown in FIG. 7 and the above-mentioned dimensional example, the line width of the signal line 20 is different between the portion where the mesh ground layers 62 and 72 are present and the portion where it is not present. Therefore, bridging portions 63 and 73 are provided so that the line widths of the signal lines 20 change continuously so that the parts having different line widths do not become discontinuous. The length of the bridging portions 63,73 (dimension C in FIG. 7) is, for example, about 0.5 mm, and the line width changes continuously from the portion where the mesh ground layer 62,72 exists to the portion where it does not exist. It is provided to do so. In the configuration shown in FIG. 7, the line width changes proportionally toward the X direction, but the change may be other than proportional.

0047However, the line width of the signal line 20 may be unified with an intermediate line width between the portion where the mesh ground layers 62 and 72 are present and the portion where the mesh ground layers 62 and 72 are not present. An example of such a dimension is, for example, 40 μm. It has been confirmed that even in the intermediate line width of such a dimensional example, the transmission characteristics are equivalent to those in which the above-mentioned bridging portions 63 and 73 exist up to the frequency band up to about 5 GHz.

0048In the flexible printed circuit board 10 of the first configuration example, since the mesh ground layers 62 and 72 are arranged on the outer peripheral side of the curved portion PL2, the outer peripheral side of the curved portion PL2 is easily deformed. On the other hand, the Betagland layers 61 and 71 are arranged on the inner peripheral side of the curved portion PL2. Therefore, the mesh ground layers 62,72 are easily deformed to be compressed, which makes it possible to generate compressive stress in the signal line 20.

0049&lt;Arrangement of mesh ground layers 62,72 (second configuration example)&gt; Next, a second configuration example in the arrangement of the mesh ground layer 62 (mesh ground layer 72) on the flexible printed circuit board 10 will be described. FIG. 8 is a plan view showing a second configuration example of the flexible printed circuit board 10 before molding, which corresponds to the modification of FIG. 1. In the following description of the flexible printed circuit board 10 in the second configuration example, the description of the parts common to the flexible printed circuit board 10 in the first configuration example will be omitted.

0050As shown in FIG. 8, the flexible printed circuit board 10 in the second configuration example has almost the same configuration as the flexible printed circuit board 10 in the first configuration example as shown in FIG. However, in the flexible printed circuit board 10 of the second configuration example, the arrangement of the mesh ground layer 62 (mesh ground layer 72) is different from that of the flexible printed circuit board 10 of the first configuration example.

0051FIG. 9 is a side view showing the shape of the flexible printed circuit board 10 after molding in the second configuration example. As shown in FIGS. 8 and 9, in the second configuration example, of the pleated portion PL of the flexible printed circuit board 10 after molding, the outer peripheral side of the right-bending curved portion PL2 or the left-curved curved portion PL2. The mesh ground layers 62 and 72 are arranged on the outer peripheral side. Therefore, the mesh ground layer 62 (mesh ground layer 72) is provided in a certain curved portion PL2, but is not provided in the curved portion PL2 next to the mesh ground layer 62 (one jump). In this state, it is provided on the outer peripheral side of the curved portion PL2.

0052Note that FIGS. 9 to 11 show a configuration in which only the mesh ground layer 72 exists and the mesh ground layer 62 does not exist, but only the mesh ground layer 62 exists and the mesh ground layer 72 does not exist. Of course, may be adopted.

0053Therefore, the flexible printed circuit board 10 of the second configuration example is significantly different from the configuration in which the mesh ground layers 62 and 72 are alternately present on the front surface side and the back surface side of the flexible printed circuit board 10 as in the first configuration example. It's different. That is, in the flexible printed circuit board 10 of the second configuration example, the mesh ground layer 62 exists only on the front surface side (upper surface side) of the flexible printed circuit board 10, or the mesh is present only on the back surface side (lower surface side) of the flexible printed circuit board 10. Either there is a ground layer 72.

0054In the flexible printed circuit board 10 of the second configuration example, as is clear from FIG. 9, the mesh ground layer 72 (or the mesh ground layer 62 in configurations other than those shown in FIG. 9; the same applies hereinafter) is a curve drawn by the curved portion PL2. It exists on the outer peripheral side of. Therefore, there is no portion where the openings 72b (openings 72b) of the mesh ground layer 72 (mesh ground layer 62) are in a positional relationship facing each other. As a result, electrical interference between the signal lines 20 can be prevented, and fluctuations in the characteristic impedance of the flexible printed circuit board 10 can also be prevented.

0055FIG. 10 is a diagram showing an image in which the flexible printed circuit board 10 according to the second configuration example is applied to a rotating portion of an external device such as an arm joint of a robot or the like, and the two arms are maintained in a horizontal state. It is a figure which shows the state which is. Further, FIG. 11 is a diagram showing a state in which the two arms in FIG. 10 are rotated. In the application examples shown in FIGS. 10 and 11, the mesh ground layer 72 is located at the curved portion PL2 on the inner diameter side of the rotating portion. That is, the mesh ground layer 62 located at the curved portion PL2 on the outer diameter side of the rotating portion does not exist.

0056As shown in FIG. 10, when the flexible printed circuit board 10 of the second configuration example is placed along the rotating portion, the curved portion PL2 located on the inner diameter side (inside) is deformed so as to be wide open. Therefore, by arranging the mesh ground layer 72 on the outer peripheral side (that is, the side located at the innermost inner diameter) of the curved portion PL2 on the inner diameter side (inner side), the curved portion PL2 located on the inner diameter side (inner side) can be changed. Deforms to easily open wide.

0057At this time, in the curved portion PL2 on the inner diameter side, the mesh ground layer 72 on the outer peripheral side is greatly deformed by the action of compressive stress, but the betaland layer 61 on the inner peripheral side is subjected to tensile stress, but inside. The betta land layer 61 on the peripheral side is less likely to be deformed than the mesh ground layer 72 on the outer peripheral side. Therefore, the neutral axis of stress moves to the outer peripheral side and separates from the inner peripheral side. As a result, compressive stress acts on the signal line 20 instead of tensile stress.

0058As shown in FIG. 11, the curved portion PL2 located on the outer diameter side (outside) is deformed so as to close. However, in the curved portion PL2 located on the outer diameter side (outer side), the betta land layer 61 is provided on both the inner peripheral side and the outer peripheral side thereof. Therefore, in the curved portion PL2 located on the outer diameter side (outside), the deformation in the closing direction is smaller than the deformation in the mesh ground layer 72 so as to open. That is, as shown in FIG. 11, the curved portion PL2 located on the inner diameter side (inside) is deformed so as to selectively open wide due to the difference in the presence or absence of the mesh ground layer 72, but the outer diameter side (outside). The curved part PL2 located at) is deformed only small.

0059With the above configuration, the stress acting on the signal line 20 during operation is reduced by using the flexible printed circuit board 10 of the second configuration example for the rotating portion of the external device such as the joint of the arm of the robot or the like. It has a structure that can withstand repeated operations.

0060&lt;Manufacturing method of flexible printed circuit board 10&gt; Subsequently, the manufacturing method of the flexible printed circuit board 10 in the first configuration example and the second configuration example will be described below. In the following description, the first step to the seventh step will be described in order, but in the method of manufacturing the flexible printed circuit board 10 in each embodiment, various steps other than this may exist. Of course.

0061(1) First step: Formation of signal line 20 FIG. 12 is a diagram showing a state in which a signal line 20 and a receiving land 21 are formed in the AA cross section of FIGS. 1 and 8 in relation to the first step. FIG. 13 is a diagram showing a state in which the signal line 20 is formed in the BB cross section, CC cross section, and DD cross section of FIGS. 1 and 8 in relation to the first step. As shown in FIGS. 12 and 13, a double-sided copper-clad laminate 100 having base copper foil layers 101 and 102 on both sides of the insulating layer 30 is prepared. Then, the signal line 20 which will be located on the inner layer side later and the receiving land 21 of the conductive through holes 12 and 14 are formed by using a normal photofabrication technique such as etching. As a result, the intermediate product C1 as shown in FIGS. 12 and 13 is formed.

0062(2) Second step: Lamination of single-sided copper-clad laminate 200 FIG. 14 is a diagram showing a state in which the single-sided copper-clad laminate 200 is laminated on the double-sided copper-clad laminate 100 in the AA cross section of FIGS. 1 and 8 according to the second step. FIG. 15 is a diagram showing how the single-sided copper-clad laminate 200 is laminated on the double-sided copper-clad laminate 100 in the BB cross section, CC cross section, and DD cross section of FIGS. 1 and 8 in relation to the second step.

0063As shown in FIGS. 14 and 15, a single-sided copper-clad laminate 200 and a laminated adhesive 300 are prepared. Then, the laminated adhesive 300 is attached so as to cover the upper surface side of the insulating layer 30, and then the single-sided copper-clad laminate 200 is attached to the upper surface side of the laminated adhesive 300. The single-sided copper-clad laminate 200 is provided with an insulating layer 40, and a base copper foil layer 201 is provided on one side surface (upper surface) thereof. The product after pasting is referred to as an intermediate product C2.

0064The laminated adhesive 300 is a portion that becomes the adhesive layer 50 after being attached. The laminated adhesive 300 preferably has low elasticity so as not to interfere with later molding. Specifically, since the elastic modulus of the LCP film is about 3 to 4 GPa, it is possible to bond the LCP film without affecting the moldability by using a laminated adhesive 300 having an elastic modulus of 2 GPa or less, which is less than half of this. It is possible. At the time of molding, it is heated at about 200 ° C for about 30 minutes. Therefore, the laminated adhesive material 300 is preferably one in which the adhesiveness and electrical insulation characteristics do not significantly deteriorate due to such thermal history.

0065(3) Third step: Formation of through holes 12a and 14a FIG. 16 is a diagram showing a state in which through holes 12a and 14a are formed in the AA cross section of FIGS. 1 and 8 in relation to the third step. FIG. 17 is a side sectional view showing the configurations of the BB cross section, CC cross section, and DD cross section of FIGS. 1 and 8 according to the third step. As shown in FIG. 16, through holes 12a and 14a are formed in the intermediate product C2 for later making an interlayer connection with the signal pad 11 and the GND pad 13. Such drilling may be performed by an NC drill, or may be an interlayer connection at a non-penetrating bottomed via hole by a laser or the like. The product after such drilling is referred to as an intermediate product C3.

0066(4) Fourth step: Formation of conductive coatings 12b and 14b FIG. 18 is a diagram showing a state in which the conductive coating layer 15 for forming the conductive coatings 12b and 14b is formed in the through holes 12a and 14a in the AA cross section of FIGS. 1 and 8 according to the fourth step. As shown in FIG. 18, in the intermediate product C3 after the drilling process, the portion corresponding to the AA cross section is partially plated to form the conductive coating layer 15 which is the source of the conductive coatings 12b and 14b. As a result, interlayer conduction in which the three layers are electrically connected can be obtained. The product obtained by partial plating is referred to as intermediate product C4.

0067(5) Fifth step: Patterning of base copper foil layers 101 and 102 FIG. 19 is a diagram showing a state in which patterning is performed in the AA cross section of FIGS. 1 and 8 according to the fifth step. FIG. 20 is a diagram showing a state in which patterning is performed in the BB cross sections of FIGS. 1 and 8 according to the fifth step. In addition, FIG. 21 is a diagram showing a state in which patterning is performed in the CC cross sections of FIGS. 1 and 8. FIG. 22 is a diagram showing a state in which patterning is performed in the DD cross sections of FIGS. 1 and 8.

0068As shown in FIGS. 19 to 22, the conductive coating layer 15 and the base copper foil layers 101 and 102 are patterned by using a normal photofabrication method such as etching to form a necessary pattern. As shown in FIGS. 19 to 22, what is formed by such patterning is in a flexible printed circuit board 10 such as a signal pad 11, a GND pad 13, a beta land layer 61, 71, a mesh ground layer 62, 72, and the like. It is a necessary pattern. The product obtained by patterning is designated as an intermediate product C5.

0069(6) 6th step: Formation of cover layers 80 and 90 FIG. 23 is a diagram showing the configuration in the AA cross section of FIGS. 1 and 8 when the cover layers 80 and 90 are formed in the sixth step. FIG. 24 is a diagram showing a state in which cover layers 80 and 90 are formed in the BB cross sections of FIGS. 1 and 8 in relation to the sixth step. Further, FIG. 25 is a diagram showing a state in which the cover layers 80 and 90 are formed in the CC cross sections of FIGS. 1 and 8. FIG. 26 is a diagram showing a state in which cover layers 80 and 90 are formed in the DD cross sections of FIGS. 1 and 8.

0070As shown in FIGS. 23 to 26, the cover layers 80 and 90 including the insulating resin layers 81 and 91 and the adhesive layers 82 and 92 are formed on the intermediate product C5. The cover layers 80 and 90 are formed by attaching the adhesive layers 82 and 92 to the intermediate product C5. It is necessary to prevent the signal pad 11 and the GND pad 13 from being covered with the cover layers 80 and 90. Therefore, of the cover layers 80 and 90, the portion corresponding to the signal pad 11 and the GND pad 13 can be provided with a fine opening by a method such as a photo solder resist. However, the other Betagland layers 61,71 and mesh ground layers 62,72 are covered with the cover layers 80,90.

0071If necessary, it is also possible to perform surface treatment such as electroless gold plating on the parts not covered with the cover layers 80 and 90. Through the above steps, the flexible printed circuit board 10 before molding is obtained.

0072(7) 7th step: Heat molding of flexible printed circuit board 10 FIG. 27 is a diagram showing a state in which the flexible printed circuit board 10 before molding is set on the jig 400 in connection with the seventh step. As shown in FIG. 27, the flexible printed circuit board 10 before molding is set in the jig 400 in a aligned state. Here, the jig 400 is provided with a tip fixing member 410. The tip fixing member 410 is provided with a tip receiving portion 411 on which the tip side of the flexible printed circuit board 10 is placed, and a hook pin 412 inserted into a hole on the tip side of the flexible printed circuit board 10 (not shown). Is provided.

0073A hole on the tip side of the flexible printed circuit board 10 is inserted into the hook pin 412, and in that state, the flexible printed circuit board 10 is meandered along the jig pin 420 arranged at a predetermined position of the jig 400. , Complete the setting of the flexible printed circuit board 10 on the jig 400. After the set, a constant tension is applied to the rear end side of the flexible printed circuit board 10. In this state, by heating in an oven or the like, the flexible printed circuit board 10 having a three-layer structure containing the thermoplastic LCP material is formed in a pleated shape (bellows shape), and the flexible printed circuit board 10 is shown in FIGS. It is in a state of having a pleated portion PL as shown in.

0074Here, heat molding in an oven or the like is performed by heating at 200 ° C. for 30 minutes, for example. In the case of heat molding in this way, the flexible printed circuit board 10 is heat-molded in a state where the setting position and the tension at the time of setting on the jig 400 are stable. Therefore, in the flexible printed circuit board 10 after molding, the product shape is stable, and the mesh ground layers 62 and 72 are arranged on the outer peripheral side of the desired portion of the curved portion PL2 as intended. ..

0075As described above, when the total length of the flexible printed circuit board 10 before molding is, for example, 400 mm, the total length of the flexible printed circuit board 10 after molding having the pleated portion PL may be about 150 mm.

0076Further, after this molding, if necessary, an unnecessary portion of the flexible printed circuit board 10 such as the tip side positioned by the tip fixing member 410 or the like is cut to complete the final product. As a method of cutting such an unnecessary portion, the hole portion into which the hook pin 412 is inserted is diverted from the flexible printed circuit board 10, the starting point side is positioned, and the opposite side is positioned by abutting or the like. Then, it is possible to cut using a cutting jig such as a pinnacle or a mold. However, a method other than the above-mentioned method may be used for cutting the unnecessary portion. Examples of such a method include laser cutting using a laser, router cutting using a router bit, and the like.

0077&lt;About test results&gt; Table 1 shows the results of expansion and contraction tests on the flexible printed circuit board 10 having the pleated portion PL formed as described above. In this expansion / contraction test, the flexible printed circuit board 10 is repeatedly expanded / contracted, and the presence or absence of disconnection of the signal line 20 during the test, the amount of elongation of the flexible printed circuit board 10 before and after the test, and the flexible printed circuit board 10 before and after the test. Fluctuations in DC resistance and characteristic impedance before and after the test were evaluated.

0078In addition, the same test was conducted for the conventional configuration and comparative examples for evaluation. The flexible printed circuit board 10F as shown in FIGS. 28 to 30 corresponds to the conventional configuration. This flexible printed circuit board 10F has a configuration in which mesh ground layers 62 and 72 do not exist. Note that FIG. 28 is a plan view showing the configuration of the flexible printed circuit board 10F having the conventional configuration. FIG. 29 is a cross-sectional view of the flexible printed circuit board 10F having the conventional configuration, and is a diagram showing a state of being cut along the AA line of FIG. 28. FIG. 30 is a cross-sectional view of the flexible printed circuit board 10F having the conventional configuration, and is a diagram showing a state of being cut along the BB line of FIG. 28. Further, the comparative example corresponds to a configuration in which mesh ground layers 62 and 72 are formed on both the inner peripheral side and the outer peripheral side of the curved portion PL2 (not shown).

0079In this expansion / contraction test, the total length of the flexible printed circuit boards 10 and 10F was extended by 50%, and the expansion was performed up to 5 million times. In addition, after this test, if the amount of elongation is within 10%, the test for elongation was passed. In addition, 10 pieces were used for each structure in the test.

0080<tables num="1"><img id="000003" he="95" wi="167" file="JP2016004875A_D0001.tif" img-format="tif" img-content="drawing" /></tables>

0081As can be seen from the results in Table 1, the flexible printed circuit board 10 of the first configuration example and the flexible printed circuit board 10 of the second configuration example have high resistance to expansion and contraction tests, and the electrical characteristics change even after the test. It was confirmed that it could not be seen. It was also confirmed that the characteristic impedance did not change before and after molding, and that the influence of electrical interference between the signal lines 20 was not observed.

0082On the other hand, in the conventional configuration, the signal line 20 was disconnected in all of the 10 tested within 1000 times. In the evaluation of the conventional configuration, although the wire is broken, the elongation rate is 5% or less, the resistance value is OPEN because the wire is broken, and the characteristic impedance is also broken, so that the measurement is impossible. In the configuration of the comparative example, the signal line 20 is not broken, and the rate of change of the DC resistance is 3% or less. However, it was confirmed that the characteristic impedance changed during the expansion and contraction operation, and that the characteristic impedance changed by 10% or more between when it expanded and when it contracted. From the above results, it was confirmed that the conventional configuration cannot be used due to disconnection, and that the performance of the comparative example is inferior due to the fluctuation of the characteristic impedance.

0083From the above results, it was found that the flexible printed circuit board 10 of the first configuration example and the flexible printed circuit board 10 of the second configuration example of the present embodiment can achieve both high-quality signal transmission and elasticity. did.

0084&lt;About the effect&gt; According to the flexible printed circuit board 10 and the method for manufacturing the flexible printed circuit board 10 having the above configuration, the following effects are obtained.

0085That is, a plurality of curved portions PL2 in the pleated portion PL of the flexible printed circuit board 10 provided with the stripline transmission line are deformed to open or close. On the other hand, the ground layers 60 and 70 have the conductive portions 62a and 72a so as to surround the openings 62b and 72b, so that the conductive portions 62a and 72a have a mesh shape. Betagland layers 61 and 71, in which the conductive portion is provided in a planar shape, are provided. The mesh ground layers 62 and 72 are arranged on the outer peripheral side of the curved portion PL2, and the betta land layers 61 and 71 are arranged on the inner peripheral side of the curved portion PL2.

0086Therefore, in the curved portion PL2, the mesh ground layers 62 and 72 are present on the outer peripheral side of the curved portion PL2, so that the bending stress when the flexible printed circuit board 10 is formed into a pleated shape (bellows shape) is reduced. be able to. Moreover, since the bending stress is reduced, the structure is such that the durability when the flexible printed circuit board 10 is repeatedly expanded and contracted is ensured. In particular, the mesh ground layer 62,72 is arranged on the outer peripheral side of the curved portion PL2, and the bettaland layer 61,71 is arranged on the inner peripheral side of the curved portion PL2. Is easily deformed to be compressed. As a result, compressive stress can be generated in the signal line 20, and the signal line 20 is less likely to be disconnected.

0087Further, in the present embodiment, since the flexible printed circuit board 10 is configured with a strip transmission line that propagates electromagnetic waves, the function of blocking noise from the outside is not impaired. In particular, in the curved portion PL2, when the betta land layers 61 and 71 are present on the inner peripheral side of the curved portion PL2, the openings 62b and 72b of the mesh ground layers 62 and 72 are in a positional relationship facing each other. Does not exist. Therefore, even if the linear portions PL1 of the pleated portion PL are close to each other, it is possible to prevent electrical interference between the signal lines 20 and to prevent fluctuations in the characteristic impedance of the flexible printed circuit board 10.

0088Further, in the present embodiment, as described in the first configuration example, the mesh ground layers 62 and 72 of the pleated portion PL of the curved portion PL2 are present alternately on the front surface side and the back surface side of the signal line 20. It is arranged on the outer peripheral side. Therefore, the flexible printed circuit board 10 can be easily expanded and contracted. That is, in the flexible printed circuit board 10 of the first configuration example, it is possible to improve the elasticity.

0089Further, in the present embodiment, as described in the second configuration example, in the pleated portion PL, the mesh ground layers 62 and 72 are curved portions in a state of being present on either the front surface side or the back surface side of the signal line 20. It is located on the outer peripheral side of PL2. Therefore, by using the flexible printed circuit board 10 of the second configuration example for the rotating portion of the external device such as the joint of the arm of the robot or the like, the stress acting on the signal line 20 during operation can be reduced, and the stress acting on the signal line 20 can be reduced. It has a structure that can withstand repeated operations.

0090Further, in the present embodiment, the insulating layers 30, 40 and the insulating resin layers 81, 91 are formed of LCP (Liquid Crystal Polymer), which is a thermoplastic resin, as a material. Therefore, when the flexible printed circuit board 10 before heat molding is heat-molded, it becomes possible to easily form a pleated portion PL having a plurality of curved portions PL2.

0091Further, in the present embodiment, the ground layers 60 and 70 located at the curved portion PL2 are not formed with a plating film for interlayer connection. Therefore, the curved portion PL2 is in a state of being easily bent.

0092Further, in the present embodiment, the flexible printed circuit board 10 before heat molding is heat-molded using the jig 400. Therefore, by positioning the tip side of the flexible printed circuit board 10 with the tip fixing member 410 and heat-molding the flexible printed circuit board 10 with tension applied, the flexible printed circuit board has a good pleated portion PL with no misalignment. The substrate 10 can be molded.

0093&lt;Modification example&gt; Although one embodiment of the present invention has been described above, the present invention can be modified in various ways. It will be described below.

0094In the above embodiment, only one signal line 20 is shown. However, the number of signal lines 20 is not limited to one, and two or more signal lines 20 may exist as long as they constitute a stripline transmission line.

0095Further, in the second configuration example in the above-described embodiment, the mesh ground layer 72 is formed on the curved portion PL2 on the inner diameter side of the rotating portion of the external device such as the joint of the arm of the robot or the like. Is located. That is, the mesh ground layer 62 located at the curved portion PL2 on the outer diameter side of the rotating portion does not exist. However, a configuration may be adopted in which the mesh ground layer 62 is arranged on the curved portion PL2 on the outer diameter side of the rotating portion. In this configuration, the curved portion PL2 on the outer diameter side is deformed so as to be largely closed, but even in that case, the configuration is easier to bend than the conventional configuration and the signal line 20 is less likely to be broken. ..

0096In the first configuration example and the second configuration example, the mesh ground layers 62 and 72 are arranged on the inner peripheral side of the curved portion PL2, and the betta land layers 61 and 71 are arranged on the outer peripheral side of the curved portion PL2. You may. Also in this case, the signal line 20 can be configured to be more easily bent than the conventional configuration and less likely to be broken.

0097Further, in the above-described embodiment, the flexible printed circuit board 10 has a pleated portion PL in which curved portions PL2 having the same pitch and the same size are arranged. However, the pitches at which the curved portions PL2 are arranged do not have to be the same, and the curved portions PL2 may be arranged so that the pitches are different from each other or partly different pitches. Further, the size (radius, etc.) of a certain curved portion PL2 may be different from the size (radius, etc.) of another curved portion PL2. Further, a combination in which a plurality of curved portions PL2 are arranged at a certain pitch and size may be combined with a combination in which a plurality of curved portions PL2 are arranged at different pitches and sizes.

009810,10F ... Flexible printed circuit board, 11 ... Signal pad, 12 ... Conductive through hole, 12a ... Through hole, 12b ... Conductive coating, 13 ... GND pad, 14 ... Conductive through holes, 14a ... through holes, 14b ... conductive coatings, 15 ... conductive coating layers, 20 ... signal lines, 21 ... receiving lands, 30, 40 ... insulating layers, 50 ... Adhesive layer, 60,70 ... Ground layer, 61,71 ... Betagland layer, 62,72 ... Mesh ground layer, 62a, 72a ... Conductive part, 62b, 72b .. .Opening, 63 ... bridging, 80,90 ... cover layer, 81,91 ... insulating resin layer, 82,92 ... adhesive layer, 100 ... double-sided copper-clad laminate, 101 ... base copper foil layer, 200 ... single-sided copper-clad laminate, 201 ... base copper foil layer, 300 ... laminated adhesive, 400 ... jig, 410 ... tip fixing member , 411 ... Tip receiving part, 412 ... Hook pin, 420 ... Jig pin, C1 ~ C5 ... Intermediate product, PL ... Pleated part, PL1 ... Straight part, PL2 ... curved part