JP6600503B2 - Flexible printed circuit board and method for manufacturing flexible printed circuit board - Google Patents

Description

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

  In recent years, there has been an increasing demand for miniaturization and higher density of mounting boards mounted on small electronic devices such as smartphones and digital cameras. As part of this, double-sided flexible printed wiring boards and single-sided flexible printed wiring boards that have a flexible cable unit integrated with a flexible flat cable have become widespread mainly in small electronic devices such as smartphones and watch-type wearable devices. Yes. The double-sided flexible printed wiring board is disclosed in Patent Document 1, for example.

  In addition, printed wiring boards used in recent small electronic devices are required to have a current capacity of several A for high-speed power supply that was not required before, such as wireless charging and USB 3.1. It is coming. For this reason, in order to secure a current capacity in a limited area, there are cases in which the copper wiring is made thick to meet the required current capacity (for example, a 35 μm thick copper foil).

  On the other hand, when the copper foil is thickened, it becomes difficult to form fine wiring by an etching method (so-called subtracting method) by photofabrication. Thus, when the copper foil is thick, a relatively thick wiring (100 μm width or more) for feeding can be formed, but there is a problem that it is difficult to form a wiring for a fine terminal or a lead-out portion. In this way, even when the conductor thickness is increased, as a method capable of forming fine wiring, there is a semi-additive method, but the process is complicated. Specifically, as shown in Patent Document 2, a thin film metal layer is formed on the base resin, and steps such as plating resist formation, electroplating, and seed layer removal are necessary.

  Patent Document 3 discloses a technique in which a rough conductive pattern is formed by screen printing and a fine conductive pattern is formed by etching. Further, Patent Document 4 discloses that a silver paste is screen-printed and then a terminal portion or the like is formed by laser cutting.

Japanese Patent Laid-Open No. 2003-229552 JP 2012-59923 A JP-A 61-187294 JP2015-26618A

  As described above, when the copper foil is made thick in order to secure the current capacity, it is difficult to form fine wiring when the subtracting method is employed. Therefore, it is conceivable to form fine wiring using the methods disclosed in Patent Document 2, Patent Document 3 and Patent Document 4.

  However, the method disclosed in Patent Document 2 has a problem that the process becomes complicated because the semi-additive construction method is used. Further, in the method disclosed in Patent Document 3, since rough wiring is formed by screen printing, it is difficult to make further finer than the subtracting method, and the copper foil thickness is increased and the current capacity is increased. It is also difficult to secure.

  In the method disclosed in Patent Document 4, although silver paste is screen-printed, the volume resistivity of the silver paste alone is generally higher by one digit or more than that of the copper foil. Therefore, it is difficult to secure a current capacity for a long current path with a single silver paste wiring. It is also conceivable to combine the silver paste with a thick copper foil. However, although a copper foil with a large thickness also has a corresponding level difference, it is difficult to screen-print on such a copper foil with a large level difference.

  The present invention has been made on the basis of the above circumstances, and the object thereof is to have a portion for securing a sufficient current capacity and a portion to be a fine wiring while being formed using a simple process. An object of the present invention is to provide a flexible printed circuit board and a method for manufacturing the flexible printed circuit board.

In order to solve the above problems, according to a first aspect of the present invention, a base material made of a sheet-like member having electrical insulation and a plurality of copper wirings are provided, and the side walls of the respective copper wirings are provided. A copper pattern portion laminated on the base material and a plurality of conductive paste wirings obtained by curing the conductive paste, and at least a part of the copper wiring is provided with an inclined surface that is inclined with respect to the base material; A paste pattern portion provided so as to overlap, provided with a thickness thinner than the copper wiring, and provided with a minimum width between the conductive paste wirings narrower than a minimum width between the copper wirings , Copper pattern portions are provided on both sides of the base material, and the base material has through holes penetrating in the thickness direction. The through holes are made of conductive paste and the surface side of the base material And back side In order to ensure conductivity, an interlayer connection portion is provided, and on the surface side of the base material, an opening portion of the through hole is located in a space existing between adjacent copper wirings and exposed to the outside. At the same time, a flexible printed board is provided in which the opening of the through hole is closed with copper wiring on the back surface side of the base material .

  Further, according to another aspect of the present invention, in the above-described invention, it is preferable that the copper wiring side is provided at 45 degrees in the inclination angle formed by the inclined surface with respect to the base material.

  Furthermore, in another aspect of the present invention, in the above-described invention, it is preferable that the conductive paste wiring has a portion reaching the upper surface continuous to the inclined surface in the copper wiring.

According to the third aspect of the present invention, on both sides of a double-sided copper clad laminate in which a base copper foil layer is laminated on both sides of a base material made of a sheet-like member having electrical insulation. On the other hand, a fourth step of forming a copper pattern portion that includes a plurality of copper wirings and includes an inclined surface in which the side walls of the respective copper wirings are inclined with respect to the base material; a fifth step of forming a through hole penetrating through the base member, for securing the conductivity between the front surface and the rear surface of the base material in the through-hole also covering Ukoto covers a portion of at least one copper wire The conductive paste is printed, and the printed portion is dried to form a paste print portion having a thickness smaller than that of the copper pattern portion, and the paste print portion is scanned while irradiating a laser beam. Remove unnecessary parts from the paste printing section Forming a paste pattern portion including a plurality of conductive paste wirings, and forming a paste pattern portion in which the minimum width between the conductive paste wirings is smaller than the minimum width between the copper wirings; The opening portion of the through-hole formed in the fifth step is located on the surface side of the base material and is exposed to the outside in a space existing between adjacent copper wirings, and the back side of the base material Then, the manufacturing method of the flexible printed circuit board characterized by the opening part of a through-hole being plugged up with copper wiring is provided.

  Further, another aspect of the present invention relates to the above-described invention, in the first step or the fourth step, the copper wiring side is formed to be 45 degrees in the inclination angle formed by the inclined surface with respect to the base material. It is preferable.

  According to the present invention, there is provided a flexible printed circuit board and a method for manufacturing a flexible printed circuit board that can be formed using a simple process and have a portion that ensures a sufficient current capacity and a portion that becomes a fine wiring. Can be provided.

It is a top view which shows the structure of the flexible printed circuit board concerning the 1st Embodiment of this invention. It is sectional drawing of the flexible printed circuit board concerning the 1st Embodiment of this invention, and is a figure which shows the state cut | disconnected along the AA line of FIG. It is sectional drawing of the flexible printed circuit board concerning the 1st Embodiment of this invention, and is a figure which shows the state cut | disconnected along the BB line of FIG. It is a top view which shows the state in which the copper pattern part was formed in the base material. It is sectional drawing which shows the state which cut | disconnected the intermediate product shown in FIG. 4 along CC line. It is a top view which shows the state by which the silver paste was screen-printed with respect to the intermediate product shown in FIG. It is sectional drawing which shows the state which cut | disconnected the intermediate product shown in FIG. 6 along the DD line. It is a top view which shows the structure of the flexible printed circuit board concerning the 2nd Embodiment of this invention. It is a fragmentary sectional view of the flexible printed circuit board concerning a 2nd embodiment of the present invention, and is a figure showing the state where it cut along the EE line of Drawing 8. It is a top view which shows the intermediate product in the state in which the copper pattern part was formed in both surfaces of the base material. It is a fragmentary sectional view showing the state where the intermediate product shown in FIG. 10 was cut along the line FF. FIG. 12 is a partial cross-sectional view illustrating a state in which a through hole is formed in the intermediate product illustrated in FIGS. 10 and 11. It is a top view which shows the state by which the silver paste was screen-printed with respect to the intermediate product shown in FIG.

(First embodiment)
Hereinafter, a flexible printed circuit board 10A according to a first embodiment of the present invention will be described with reference to the drawings. In the following description, an XYZ orthogonal coordinate system may be used for explanation. Of these, the X direction is the longitudinal direction of the flexible printed circuit board 10A, the X1 side is the front side of the paper in FIG. 1, and the X2 side is the back side of the paper. The Y direction is the width direction of the flexible printed circuit board 10A, the Y1 side is the right side in FIG. 1, and the Y2 side is the left side. The Z direction is the thickness direction of the flexible printed circuit board 10A, Z1 is the back side of the paper surface in FIG. 2, and Z2 is the front side of the paper surface.

<Configuration of Flexible Printed Circuit Board 10A>
FIG. 1 is a plan view showing a configuration of a flexible printed circuit board 10A according to the first embodiment. FIG. 2 is a cross-sectional view of the flexible printed circuit board 10A according to the first embodiment, and shows a state cut along the line AA in FIG. FIG. 3 is a cross-sectional view of the flexible printed board 10A according to the first embodiment, and shows a state cut along the line BB in FIG.

  As shown in FIGS. 1 to 3, the flexible printed circuit board 10 </ b> A according to the present embodiment includes a base material 20, a copper pattern portion 30, and a paste pattern portion 40. The base material 20 is formed of a material having insulation and flexibility, such as a polyimide film corresponding to a sheet-like member. The material of the base material 20 may be other as long as it has flexibility and insulation. The base material 20 has a thickness of 12.5 μm (1/2 mil), for example, but may have any thickness including 25 μm (1 mil).

  The copper pattern portion 30 includes a plurality of copper wirings 31. Each copper wiring 31 is a thick copper foil portion made of copper. For example, the copper wiring 31 has a thickness of 35 μm. Here, in the case of a general copper foil that does not require much current capacity and therefore does not require much thickness, the copper foil is 12 μm (1/3 oz) or 17.5 μm (1/2 oz). In many cases. However, the copper wiring 31 is thicker than a general copper foil in order to ensure current capacity. Thereby, for example, several A of current can be conducted to the copper wiring 31. The thickness of the copper wiring 31 is not limited to 35 μm, and any thickness can be used as long as the required current capacity can be secured.

  Further, the copper pattern portion 30 forms the respective copper wirings 31 by a photofabrication technique such as an etching process using a chemical solution or the like as will be described later. An inclined surface 32 is provided on the side surface of the copper wiring 31. In general, when the copper foil is thin, the copper foil after the etching process has a cross-sectional shape close to a rectangle, but when the copper foil is thick, the copper foil after the etching process has a cross-sectional shape close to a trapezoid. At this time, the lower bottom width L1 (width on the base material 20 side; width on the Z2 side) of the copper wiring 31 and the upper bottom width L2 (width on the Z1 side) of the copper wiring 31 are measured in a sampled manner. The inclination angle of the inclined surface 32 can be controlled by managing the time for performing the etching process based on the above.

  In the present embodiment, the inclination angle of the inclined surface 32 (inner inclination angle θ where the copper wiring 31 is located) is about 45 degrees. However, the inclination angle θ may be an angle other than 45 degrees. For example, in order to perform screen printing appropriately, the inclination angle θ is preferably set to 45 degrees or less. When the thickness of the copper wiring 31 is 35 μm, if the dimension M1 in the Y direction of the inclined surface 32 is 35 μm, the inclination angle θ is 45 degrees. However, the dimension M1 may be an inclination angle θ that is within a range of ± 10 μm with respect to 35 μm.

  The inclined surface 32 is preferably configured to be provided not only on the side surface of the copper wiring 31 but also on the end surface in the X direction of the copper wiring 31 (for example, the end surface on the X1 side).

  The copper wiring 31 has a width corresponding to the current capacity. As shown in FIG. 3, a space 50 is provided between adjacent copper wirings 31. The line width / space width, which is the ratio of the width between the copper wiring 31 and the space 50, is limited to about 100 μm / 100 μm in view of the difficulty in forming fine wiring by etching. The line width referred to here may be the lower bottom width of the copper wiring 31, the upper bottom width of the copper wiring 31, or between the lower and upper bottom widths of the copper wiring 31. It may be an intermediate position width.

  The paste pattern portion 40 is a portion formed by curing a silver paste. In the formation of the paste pattern portion 40, a plurality of silver paste wirings 41 are formed by laser beam irradiation as will be described later. A configured wiring pattern is formed. That is, as shown in FIG. 3, a space 51 is provided between adjacent silver paste wirings 41, and this space 51 is formed by irradiation with a laser beam. The silver paste wiring 41 corresponds to a conductive paste wiring. The silver paste corresponds to the conductive paste.

  As shown in FIG. 1, each silver paste wiring 41 is provided with a connecting portion 42. The connecting portion 42 is provided at the end portion on the X2 side of the silver paste wiring 41 and is provided so as to have a larger area than other portions. As shown in FIG. 2, the connecting portion 42 is provided with an overlapping portion 43 that overlaps the end portion of the copper wiring 31. The overlapping portion 43 is in a state of being electrically connected to the copper wiring 31. Here, in the configuration shown in FIG. 2, the overlapping portion 43 reaches the upper surface 31 a of the copper wiring 31 beyond the inclined surface 32. However, the overlapping portion 43 may be configured to exist only on the inclined surface 32 without reaching the upper surface 31a. That is, the overlapping portion 43 may be configured to cover at least a part of the inclined surface 32.

  Here, when the inclined surface 32 does not exist on the side surface of the copper wiring 31 and the side surface of the copper wiring 31 has a stepped shape, for example, when the overlapping portion 43 is formed by screen printing, an extremely thin portion May be formed, or the overlapping portion 43 may not be continuous but may be interrupted. However, since the copper wiring 31 is provided with the inclined surface 32, even if the overlap portion 43 is formed by screen printing, for example, an extremely thin portion is formed in the overlap portion 43, or the overlap portion 43 is continuous. It is possible to prevent the formation of a portion that is interrupted without being broken.

  The silver paste wiring 41 is a portion where a fine wiring such as a terminal portion and a routing portion can be formed on the flexible printed circuit board 10A. Therefore, in the silver paste wiring 41, the line width / space width can be 20 μm / 20 μm or less. That is, the minimum width between adjacent silver paste wirings 41 is narrower than the minimum width between adjacent copper wirings 31.

<About manufacturing method of flexible printed circuit board 10A>
Then, the manufacturing method of 10 A of flexible printed circuit boards is demonstrated below. In the following description, the first step to the third step will be sequentially described, but it is needless to say that various other steps may exist in the manufacturing method of the flexible printed circuit board 10A.

(1) 1st process: Formation of the copper pattern part 30 FIG. 4: is a top view which shows the intermediate product C1 in the state by which the copper pattern part 30 was formed in the base material 20. FIG. FIG. 5 is a cross-sectional view showing a state where the intermediate product C1 shown in FIG. 4 is cut along the line CC. As shown in FIGS. 4 and 5, a single-sided copper-clad laminate having a base copper foil layer having a thickness of 35 μm, for example, is prepared on one side of a base material 20 made of a polyimide film having a thickness of 12.5 μm, for example. To do. And the copper pattern part 30 which has the copper wiring 31 is formed with respect to this base copper foil layer using normal photofabrication methods, such as an etching process.

  Here, prior to the treatment with the etching solution (chemical solution), conditions are measured such that the lower base width L1 and the upper base width L2 of the copper wiring 31 described above are within a specified range. Such conditions include, for example, spraying pressure when spraying an etching solution using a spray, processing time during wet etching, and the like, but other conditions may be taken into consideration. Then, by forming the copper pattern portion 30 under conditions that fall within the specified range, the above-described inclination angle θ becomes a desired angle such as 45 degrees, for example.

  When the inclined surface 32 is formed by the etching process, the inclined surface 32 can be formed approximately isotropic with respect to the copper wiring 31. Therefore, it is possible to execute a directional post process such as screen printing in which the squeegee advances in a predetermined direction without managing the direction. The product formed by the first step is referred to as an intermediate product C1.

(2) Second Step: Screen Printing of Silver Past FIG. 6 is a plan view showing a state where the silver paste is screen-printed on the intermediate product C1 shown in FIG. FIG. 7 is a cross-sectional view showing a state where the intermediate product C2 shown in FIG. 6 is cut along the line DD. As shown in FIGS. 6 and 7, a silver paste capable of laser processing is printed on the intermediate product C1 described above in a state where a portion overlapping the copper wiring 31 is formed using a technique such as screen printing. Then, the printed part is dried. In FIG. 6 and FIG. 7, this print portion is referred to as a paste print unit 44. Note that the paste printing unit 44 may be interpreted not only as the one immediately after printing but before drying, as well as the one dried after printing. At this time, since the copper wiring 31 is formed with the inclined surface 32 having an inclination angle θ of 45 degrees, for example, in the paste printing unit 44, the printed portion is not interrupted and the continuity is good. State is maintained.

  As an example of screen printing of silver paste, for example, using LS-470L-2F, a silver paste manufactured by Asahi Chemical Research Co., Ltd., screen printing so that the film thickness is about 10 μm after drying. And drying is performed at 130 ° C. for 30 minutes using an atmospheric oven.

  When this screen printing is performed, the screen plate and the intermediate product C1 are aligned with positioning accuracy in consideration of removing unnecessary portions in a subsequent process, and the printing range for the intermediate product C1 is determined to perform printing. Execute. Here, in order to make the followability of the silver paste more suitable at the time of screen printing, it is preferable to improve the discharge property of the silver paste by making the mesh opening of the screen plate used in the screen printing relatively large.

  Moreover, in order to further improve the discharge property of the silver paste, screen printing may be performed using a metal plate (metal mask). At this time, if a thick metal plate such as a metal plate having a thickness of 100 μm or more is used, the printing thickness of the silver paste in the screen printing becomes too thick, and the removal efficiency of unnecessary parts using a laser in a subsequent process is increased. Will fall. In addition, it becomes difficult to form a fine wiring such as the silver paste wiring 41 in a later process. Therefore, it is preferable to print using a thin metal plate such as a metal plate (metal mask) having a thickness of 50 μm or less.

  As described above, by using a screen plate with a large mesh opening or screen printing using a metal plate with a thickness of 50 μm or less, the silver paste discharge can be improved, and there is no need to use a laser. It becomes easy to perform a post-process such as removal of a portion. In addition, let the intermediate product formed by this 2nd process be the intermediate product C2.

(3) Third Step: Formation of Silver Paste Wiring 41 Next, with respect to the intermediate product C2, unnecessary portions are removed from the printed silver paste (paste printing unit 44) to form the silver paste wiring 41. . Then, a flexible printed circuit board 10A as shown in FIGS. 1 to 3 is formed.

  Here, when removing an unnecessary part from a silver paste, there exists removal which irradiated the infrared laser whose wavelength is 1064 nm, for example. In this case, for example, a Q-switched solid laser, a fiber laser, or the like can be used, but other laser types may be used. The spot diameter at the laser irradiation site is, for example, 10 μm, but it is preferable that the spot diameter is smaller, for example, 5 μm.

  A silver paste wiring 41 as shown in FIG. 1 is formed by performing scanning while irradiating unnecessary portions of the silver paste application site with such laser light. Note that a space 51 for electrically insulating adjacent silver paste wirings 41 is formed in a portion removed between the silver paste wirings 41 in the silver paste application portion. In scanning with laser light, the same part may be scanned a plurality of times.

  Here, in the present embodiment, a silver paste is applied to the inclined surface 32. Therefore, compared with the case where the silver paste is applied to the stepped portion, the change in the film thickness of the silver paste is reduced, and the film thickness variation is also reduced. Therefore, it is possible to set a wide margin for processing conditions such as irradiation energy when performing laser processing.

  Note that a covering portion may be formed by various resists, coverlays, or the like which are not shown, and laser processing may be performed in a state where the covering portion is formed. Through the steps as described above, a flexible printed board 10A as shown in FIGS. 1 to 3 can be formed.

(Second Embodiment)
Next, a flexible printed circuit board 10B according to the second embodiment of the present invention will be described. In the following description, the description of the portions common to the flexible printed circuit board 10A in the first embodiment described above may be omitted.

<About Configuration of Flexible Printed Circuit Board 10B>
FIG. 8 is a plan view showing a configuration of a flexible printed board 10B according to the second embodiment. FIG. 9 is a partial cross-sectional view of the flexible printed circuit board 10B according to the second embodiment, and shows a state cut along the line EE in FIG.

  In the configuration shown in FIGS. 8 and 9, a configuration in which only one copper wiring 31 exists on the back surface side of the base material 20 is shown. However, a plurality of copper wirings 31 may exist on the back side of the base material 20. Similarly, a plurality of silver paste wirings 41 may exist on the back side of the base material 20, or may be provided so as to be connected to other copper wirings 31 and silver paste wirings 41.

  The flexible printed circuit board 10B according to the present embodiment is configured as follows. That is, in the flexible printed circuit board 10 </ b> A according to the first embodiment, the copper pattern portion 30 is provided only on one side of the base material 20. However, in the flexible printed circuit board 10B according to the second embodiment, the copper pattern portions 30 are provided on both sides of the base material 20.

  Further, as shown in FIG. 9, the base material 20 is provided with a through hole 21. The opening portion of the through hole 21 is located in the space 50 on the surface side of the base material 20 (the surface side on the Z1 side). However, on the back surface side (the Z2 side surface side) of the base material 20, the opening portion of the through hole 21 is configured to be blocked by the copper wiring 31 of the copper pattern portion 30 located on the back side of the base material 20. .

  However, a configuration in which both the opening portion on the front surface side and the opening portion on the back surface side of the base material 20 in the through hole 21 are not blocked by the copper wiring 31 may be adopted. Further, at least one of the through holes 21 may exist in the space 50 between the copper wirings 31, but both the opening portion on the front surface side and the opening portion on the back surface side do not exist in the space 50. Also good. For example, the through hole 21 may be formed in the copper wiring 31.

  In addition, an interlayer connection portion 45 constituting the paste pattern portion 40 enters the through hole 21. The interlayer connection portion 45 is continuous with the above-described overlapped portion 43 and is electrically connected to the copper wiring 31 provided on the back surface on the opposite side of the base material 20 by entering the through hole 21. In addition, when the thickness of the base material 20 is thick, the part which the interlayer connection part 45 does not become continuous, but interrupts may be formed. However, when the thickness of the base material 20 is not so different from the thickness of the interlayer connection portion 45, the interlayer connection portion 45 is continuously provided.

  The other configuration of the flexible printed circuit board 10B according to the second embodiment is the same as that of the flexible printed circuit board 10A of the configuration example according to the first embodiment described above.

<About manufacturing method of flexible printed circuit board 10B>
Next, a method for manufacturing the flexible printed circuit board 10B will be described below. In the following description, the fourth to seventh steps are sequentially described, but it is needless to say that various other steps may exist in the method for manufacturing the flexible printed circuit board 10B.

(4) Fourth Step: Formation of Copper Pattern Part 30 FIG. 10 is a plan view showing the intermediate product C4 in a state where the copper pattern part 30 is formed on both surfaces of the base material 20. FIG. 11 is a partial cross-sectional view showing a state in which the intermediate product C4 shown in FIG. 10 is cut along the line FF. As shown in FIGS. 10 and 11, a single-sided copper-clad laminate having a base copper foil layer having a thickness of 35 μm, for example, is prepared on both sides of a base material 20 made of a polyimide film having a thickness of 12.5 μm, for example. To do. Then, for this base copper foil layer, as in the case of the first embodiment described above, the copper pattern portion 30 having the copper wiring 31 is used by using a normal photofabrication technique such as etching. Form.

  In the fourth step, as in the case of the copper wiring 31 formed in the first step, the inclined surface 32 having the inclination angle θ is formed. Note that the product formed in the fourth step is referred to as an intermediate product C4.

(5) Fifth Step: Formation of Through Hole 21 FIG. 12 is a partial cross-sectional view showing a state in which the through hole 21 is formed with respect to the intermediate product C4 shown in FIGS. As shown in FIG. 12, the through hole 21 is formed by irradiating the base material 20 with a laser beam capable of laser processing even on a transparent body such as polyimide. An example of such laser light is a carbon dioxide laser having a wavelength of 10600 nm. However, the through hole 21 may be formed by drilling using, for example, an NC device, instead of drilling using laser light. And the desmear process which removes the resin smear which exists after a drilling process is performed. This desmear process may be performed using a desmear process liquid, and may be performed by a plasma process. The intermediate product formed in the fifth step is referred to as intermediate product C5.

(6) Sixth Step: Silver Paste Screen Printing FIG. 13 is a plan view showing a state where the silver paste is screen-printed on the intermediate product C5. As shown in FIG. 13, a portion of the intermediate product C5 formed in the fifth step described above is overlapped with the copper wiring 31 by using a silver paste capable of laser processing using a technique such as screen printing. Print in the ready state. Thereby, the paste printing part 44 is formed. At this time, the silver paste also enters the through hole 21.

  Here, when printing is performed using a screen plate or a metal plate as described in the first embodiment, a vacuum printing method may be used. When such a vacuum printing method is used, printing can be reliably performed in a state where no void or the like is formed inside the through hole 21.

  The sixth step is different in that the silver paste enters the through hole 21, but the other points are the same as those in the second step in the first embodiment described above. Therefore, the details of screen printing and the like are not described here. The intermediate product formed in the sixth step is referred to as intermediate product C6.

(7) Seventh Step: Formation of Silver Paste Wiring 41 Next, unnecessary portions are removed from the paste printing unit 44 after printing with respect to the intermediate product C6 formed in the sixth step, and the silver paste wiring 41 is formed. Form. Then, a flexible printed circuit board 10B as shown in FIGS. 8 and 9 is formed.

  In addition, about the printed silver paste, the detail which removes an unnecessary part is the same as that of the 3rd process in 1st Embodiment mentioned above. Therefore, the details of the removal of unnecessary parts are omitted.

<About effect>
According to the manufacturing method of flexible printed circuit boards 10A and 10B and flexible printed circuit boards 10A and 10B configured as described above, the following effects are produced.

  That is, the flexible printed circuit boards 10 </ b> A and 10 </ b> B include inclined surfaces 32 in which the side walls of the respective copper wirings 31 are inclined with respect to the base material 20, and include the copper pattern portions 30 stacked on the base material 20. . The flexible printed boards 10A and 10B also include a paste pattern portion 40. The paste pattern portion 40 includes a plurality of silver paste wirings 41 (conductive paste wirings) obtained by curing a conductive paste, is provided so as to at least partially overlap the copper wiring 31, and is thicker than the copper wiring 31. And the minimum width between the silver paste wirings 41 is narrower than the minimum width between the copper wirings 31.

  For this reason, a sufficient current capacity can be ensured by the copper pattern portion 30 having the plurality of copper wirings 31, and a portion to be a fine wiring can be formed in the paste pattern portion 40 having the plurality of silver paste wirings 41. Can be formed. That is, a thick copper wiring 31 is disposed in a portion where current capacity is required, and a silver paste wiring 41 is disposed in a portion such as a terminal or a routing portion to realize a fine wiring. Therefore, such a flexible printed circuit board 10A, 10B can meet such a demand for securing current capacity and miniaturization.

  In each of the above-described embodiments, the copper pattern portion 30 having the copper wiring 31 can be formed by a photofabrication technique such as an etching process, so that the inclined surface 32 having the inclination angle θ is formed. can do. Therefore, it is possible to prevent the copper wiring 31 from forming a portion that is not continuous but is interrupted.

  Moreover, in each embodiment mentioned above, the copper wiring 31 side is provided so that it may become 45 degree | times among the inclination angles which the inclined surface 32 makes with respect to the base material 20. FIG. Therefore, the silver paste can be suitably printed by screen printing or the like. Further, in the copper wiring 31, the line width / space width need not be excessively increased.

  Furthermore, in each of the above-described embodiments, the silver paste wiring 41 can have a portion of the copper wiring 31 that reaches the upper surface 31 a continuous with the inclined surface 32. When configured in this manner, the connection between the copper wiring 31 and the silver paste wiring 41 can be ensured. For example, even when some positional deviation occurs in screen printing, it is possible to reliably realize the connection between the copper wiring 31 and the silver paste wiring 41 while absorbing such positional deviation.

  In the second embodiment described above, the copper pattern portion 30 including the copper wiring 31 is provided on both surfaces of the base material 20, and the base material 20 is provided with a through hole 21 penetrating in the thickness direction. It has been. The through-hole 21 is provided with an interlayer connection portion 45 made of the silver paste wiring 41 and for ensuring conductivity on the front surface side and the back surface side of the base material 20. For this reason, since the copper pattern part 30 with which current capacity was ensured can be formed in both surfaces of the base material 20, one more current capacity can be ensured.

  Further, in each of the above-described embodiments, the copper pattern portion 30 is formed in the first step or the fourth step, but the copper pattern portion 30 is formed by a photofabrication technique such as an etching process. can do. Therefore, the inclined surface 32 can be formed relatively easily. Furthermore, the paste pattern portion 40 can be formed by a printing method such as screen printing in the second step or the fifth step. Therefore, it is possible to print on the minimum necessary part at the time of printing. In the third step or the seventh step, after forming the paste printing portion 44, scanning is performed while irradiating a laser beam, and unnecessary portions are removed from the paste printing portion to provide a paste pattern including a plurality of silver paste wirings 41. Part 40 is formed. By using these first step or fourth step, second step or fifth step, third step or seventh step, the flexible printed boards 10A and 10B can be formed in a relatively simple process. Manufacturing efficiency can be improved and cost can be reduced.

  Further, in the formation of the paste pattern portion 40, unnecessary portions of the silver paste application portion are removed by laser light irradiation, and the space 51 is formed. In this way, by irradiating the laser beam and removing unnecessary portions, the minimum width between the adjacent silver paste wirings 41 can be made narrower than the minimum width between the copper wirings 31.

  In the second embodiment described above, the through hole 21 is formed in the base material 20 in the fifth step, and in the subsequent sixth step, a part of at least one copper wiring 31 is covered and the through hole is formed. The silver paste is printed so as to cover 21, and the printed portion is dried to form a paste printing portion 44 having a thickness smaller than that of the copper pattern portion 30. In the seventh step, a paste pattern portion 40 having a plurality of silver paste wirings 41 is formed by irradiating laser light. Therefore, in the configuration including the copper pattern portions 30 on both surfaces, it is possible to realize a state in which the copper pattern portions 30 on both surfaces are electrically connected by the interlayer connection portion 45.

<Modification>
As mentioned above, although each embodiment of this invention was described, this invention can be variously deformed besides this. This will be described below.

  In the above-described embodiment, the silver paste wiring 41 is described as the conductive paste wiring. However, the conductive paste wiring is not limited to the silver paste wiring 41. The conductive paste wiring may be formed from a conductive paste containing a conductive material such as carbon or aluminum.

  Further, in each of the above-described embodiments, the copper wiring 31 may have any form and arrangement. Similarly, the silver paste wiring 41 may have any form and arrangement. For example, the copper wiring 31 and the silver paste wiring 41 may have a curved portion or a bent portion in addition to the linear portion.

  In the second embodiment described above, the paste pattern portion 40 is formed by screen-printing silver paste on the surface side of the base material 20. However, silver paste may be screen-printed on the back side of the base material 20 and the paste pattern portion 40 may be formed on the back side.

DESCRIPTION OF SYMBOLS 10A, 10B ... Flexible printed circuit board, 20 ... Base material, 21 ... Through-hole, 30 ... Copper pattern part, 31a ... Upper surface, 31 ... Copper wiring, 32 ... Inclined surface, 40 ... Paste pattern part, 41 ... Silver paste wiring ( Corresponding to conductive paste wiring), 42 ... connection part, 43 ... overlapping part, 44 ... paste printing part, 45 ... interlayer connection part, 50, 51 ... space, C1, C2, C4 to C6 ... intermediate product

Claims (5)

A base material made of a sheet-like member having electrical insulation;
A plurality of copper wirings, and a side wall of each copper wiring has an inclined surface that is inclined with respect to the base material, and a copper pattern portion laminated on the base material;
A plurality of conductive paste wirings obtained by curing a conductive paste, provided so as to at least partially overlap the copper wiring, and are provided with a thickness smaller than the copper wiring, and between the conductive paste wirings Paste pattern portion provided with a minimum width smaller than the minimum width between the copper wirings,
Equipped with a,
The copper pattern part is provided on both surfaces of the base material,
The base material is provided with a through-hole penetrating in the thickness direction,
The through-hole is provided with an interlayer connection portion for securing conductivity between the surface side and the back side of the base material and the conductive paste as a material,
On the surface side of the base material, the opening part of the through hole is located outside the adjacent copper wiring and exposed to the outside,
On the back side of the base material, the opening portion of the through hole is blocked by the copper wiring,
A flexible printed circuit board characterized by that. The flexible printed circuit board according to claim 1,
Of the inclination angle formed by the inclined surface with respect to the base material, the copper wiring side is provided to be 45 degrees.
A flexible printed circuit board characterized by that. A flexible printed circuit board according to claim 1 or 2,
In the conductive paste wiring, there is a portion reaching the upper surface continuous to the inclined surface of the copper wiring,
A flexible printed circuit board characterized by that. Provided with a plurality of copper wirings on both sides of a double-sided copper-clad laminate in which a base copper foil layer is laminated on both sides of a base material made of a sheet-like member having electrical insulation, A fourth step of forming a copper pattern portion having an inclined surface in which a side wall of the copper wiring is inclined with respect to the base material;
A fifth step of forming a through-hole penetrating the base material at a desired position of the base material;
Print the at least one of the conductive paste for ensuring conductivity between the front surface and the rear surface of the base material in the through hole also covering Ukoto with a portion of the copper wiring to cover, dried the print site A sixth step of forming a paste printing portion having a thickness smaller than that of the copper pattern portion;
The paste printing unit is scanned while irradiating laser light, and unnecessary portions are removed from the paste printing unit to form a paste pattern unit having a plurality of conductive paste wirings, and the paste pattern unit is formed. A seventh step in which a minimum width between the conductive paste wirings is narrower than a minimum width between the copper wirings;
Equipped with a,
The opening portion of the through hole formed in the fifth step is exposed to the outside in the space existing between the adjacent copper wirings on the surface side of the base material. On the back side, the opening of the through hole is blocked by the copper wiring.
A method for producing a flexible printed circuit board. It is a manufacturing method of the flexible printed circuit board according to claim 4 ,
In the fourth step , the copper wiring side of the inclined angle formed by the inclined surface with respect to the base material is 45 degrees.
A method for producing a flexible printed circuit board.