JP2014033012A - Printed wiring board and method for manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a printed wiring board capable of suppressing occurrence of a disconnection failure of jumper wiring.SOLUTION: A printed wiring board 1 comprises: a first wiring pattern 20 provided on a base material 10; a resist layer 30 provided on the base material 10 so as to overlap with a part of the first wiring pattern 20; and a second wiring pattern 40 provided on the base material 10 so as to cross the first wiring pattern 20 via the resist layer 30. Height Hof an end of the resist layer 30 is the lowest height in the resist layer 30.

Description

  The present invention relates to a printed wiring board having jumper wiring and a manufacturing method thereof.

  A technique is known in which an insulator is formed on a first wiring layer formed on a substrate using a screen printing method, and a jumper wiring is further formed on the insulator (for example, Patent Document 1). (See paragraphs 0005-0008, FIG. 6)).

JP 2010-258377 A

  When the jumper wiring is formed by the gravure offset printing method instead of the screen printing method, the film thickness of the jumper wiring becomes thin, and there is a problem that the jumper wiring may be disconnected at the step of the end portion of the insulator.

  The problem to be solved by the present invention is to provide a printed wiring board capable of suppressing the occurrence of disconnection failure of jumper wiring and a method for manufacturing the same.

  [1] A printed wiring board according to the present invention includes a first wiring pattern provided on a base material, an insulating layer provided on the base material so as to overlap a part of the first wiring pattern, A second wiring pattern provided on the substrate so as to intersect the first wiring pattern via an insulating layer, and the height of the end of the insulating layer is within the insulating layer Characterized by the lowest.

  [2] In the above invention, the insulating layer has an inclined portion that gradually decreases toward an end portion of the insulating layer, and a height of a portion of the insulating layer that overlaps the first wiring pattern However, it may be the highest among the insulating layers.

  [3] In the above invention, the end of the insulating layer may be an end in the extending direction of the second wiring pattern on the insulating layer.

  [4] In the method for manufacturing a printed wiring board according to the present invention, the first step of forming the first wiring pattern on the substrate and the insulating layer so as to overlap a part of the first wiring pattern A second wiring pattern is formed on the substrate by a gravure offset printing method, and a second wiring pattern is formed on the substrate by a gravure offset printing method so as to intersect the first wiring pattern via the insulating layer. A third step, wherein the second step includes using a gravure plate having a recess having a shape corresponding to the insulating layer, and a plurality of protrusions are provided in the recess. The density of the protrusions is increased toward the end of the recess.

  [5] In the above invention, the interval between the protrusions may become narrower toward the end of the recess, and the plurality of protrusions may have substantially the same width.

  [6] In the above invention, the protrusion may include a wall shape or a column shape.

  [7] In the above invention, the third step includes using a second gravure plate having a second concave portion having a shape corresponding to the second wiring pattern, and on the insulating layer. The portion of the second recess corresponding to the extending portion of the second wiring pattern extends along the first direction in the second gravure plate, and the end of the recess is It may be an end portion in the first direction.

  According to the present invention, since the height of the end portion of the insulating layer is the lowest among the insulating layers, the step at the end portion of the insulating layer is reduced. For this reason, even if the second wiring pattern is thinned, occurrence of disconnection of the second wiring pattern can be suppressed.

  Further, according to the present invention, the plurality of protrusions are provided in the concave portion of the ink filling portion of the gravure plate, and the density of the protrusions increases toward the end portion of the concave portion. The height of the portion can be made the lowest among the insulating layers. For this reason, the level | step difference of the edge part of an insulating layer can be made small, and generation | occurrence | production of the disconnection of a 2nd wiring pattern can be suppressed.

FIG. 1 is a plan view showing a printed wiring board according to an embodiment of the present invention. FIG. 2 is a cross-sectional view taken along the line II-II in FIG. 3 is a cross-sectional view taken along line III-III in FIG. FIG. 4 is a schematic diagram illustrating an example of a gravure offset printing machine. FIG. 5 is a flowchart showing a method for manufacturing a printed wiring board according to an embodiment of the present invention. FIG. 6 is a plan view showing a concave portion of the gravure plate used in step S20 of FIG. 7 is a cross-sectional view taken along line VII-VII in FIG. FIG. 8 is a plan view showing a modification of the concave portion of the gravure plate used in step S20 of FIG.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  First, the configuration of the printed wiring board in the present embodiment will be described with reference to FIGS. 1-3 is a figure which shows the printed wiring board in this embodiment.

  As shown in FIGS. 1 to 3, the printed wiring board 1 in this embodiment includes a base material 10, two wiring patterns 20 and 40, and a resist layer 30 interposed between the wiring patterns. Yes. Such a printed wiring board 1 is used for applications such as a touch panel and a touch pad, for example. Note that the resist layer 30 in the present embodiment corresponds to an example of an insulating layer in the present invention.

  The substrate 10 is a film having flexibility and electrical insulation. Examples of the material constituting the substrate 10 include polyethylene terephthalate (PET) and polyethylene naphthalate (PEN).

  The first wiring pattern 20 is provided on the surface of the substrate 10, and in this example, is formed linearly along the X-axis direction in FIG. The first wiring pattern 20 is formed by printing ink on the substrate 10 by a gravure (intaglio) offset printing method. Specific examples of the ink for forming the first wiring pattern 20 include a conductive paste containing a conductive material such as silver (Ag) or copper (Cu). Note that the first wiring pattern 20 may be formed by a printing method other than the gravure offset printing method (for example, a screen printing method, a letterpress printing method, a silk printing method, an on-demand printing method, or the like).

  The resist layer 30 is provided on the surface of the base material 10 so as to cover a part of the first wiring pattern 20, and in this example, has a substantially strip shape along the Y-axis direction of FIG. ing. Similar to the first wiring pattern 20, the resist layer 30 is formed by printing ink on the substrate 10 by a gravure offset printing method. Examples of the ink for forming the resist layer 30 include liquid resist inks based on urethane acrylate resin or the like.

  The second wiring pattern 40 is provided on the surface of the base material 10 so as to intersect the first wiring pattern 20 via the resist layer 30, and in this example, along the Y-axis direction of FIG. It is formed in a straight line. Similarly to the first wiring pattern 20, the second wiring pattern 40 is also formed by printing ink on the substrate 10 by a gravure offset printing method. As the ink for forming the second wiring pattern 40, for example, a conductive paste containing a conductive material such as silver (Ag) or copper (Cu) is exemplified as in the first wiring pattern 20 described above. be able to.

  Note that the shapes of the first and second wiring patterns 20 and 40 described above are merely examples, and if the two wiring patterns 20 and 40 intersect via the resist layer 30, the first and second wiring patterns are formed. The shape of the patterns 20 and 40 is not particularly limited. Similarly, the shape of the resist layer 30 described above is merely an example, and the shape of the resist layer 30 is not particularly limited as long as the resist layer 30 is interposed between the first wiring pattern 20 and the second wiring pattern 40.

  As shown in FIG. 3, the resist layer 30 in the present embodiment has a central portion 31, an end portion 32, and an inclined portion 33.

A central portion 31 of the resist layer 30 covers the first wiring pattern 20. The height H ₁ of the central portion 31 is the highest in the resist layer 30.

On the other hand, the end portions 32 of the resist layer 30 are both end portions in the extending direction (Y-axis direction in the drawing) of the second wiring pattern 40 on the resist layer 30. The height H ₂ of the end portion 32 is the lowest in the resist layer 30. Note that the height (including heights H ₁ and H ₂ ) of the resist layer 30 in this example is a height based on the surface of the substrate 10.

  The inclined portion 33 extends between both ends of the central portion 31 and the end portion 32 in the resist layer 30. The inclined portion 33 has an inclination that gradually decreases from the central portion 31 toward the end portion 32.

  As described above, in this embodiment, since the end portion 32 of the resist layer 30 is the lowest in the resist layer 30, the level difference caused by the end portion 32 of the resist layer 30 is reduced. For this reason, generation | occurrence | production of the disconnection of the 2nd wiring pattern 40 can be suppressed.

  Next, the configuration of a gravure offset type printing machine used when manufacturing a printed wiring board in the present embodiment will be outlined with reference to FIG. FIG. 4 is a schematic diagram showing an example of the configuration of the gravure offset printing machine 50.

  As shown in FIG. 4, in the gravure offset type printing machine 50, a gravure plate (intaglio) 51 wound around a plate cylinder 52 is immersed in an ink tank 53, and then excess ink is scraped off by a doctor blade 54. Only the concave portion (for example, the concave portion 511 shown in FIG. 6) of the gravure plate 51 is filled with ink. Next, the ink filled in the concave portion is received by the blanket 55, and the blanket 55 is rolled while being pressed against the base material 10 to transfer the ink held by the blanket 55 to the base material 10, Ink is printed on the substrate 10.

  In addition, the structure of the gravure offset printing machine which can be used by this embodiment is not specifically limited above. For example, in the gravure offset printing machine 50 shown in FIG. 4, the base material 10 that is the printing medium is held on the table 56, but the base material 10 passes through between the blanket 55 and the impression cylinder. A gravure offset printing machine may be used.

  Next, the manufacturing method of the printed wiring board 1 in this embodiment is demonstrated, referring FIGS.

  FIG. 5 is a flowchart showing a method for manufacturing a printed wiring board according to the present embodiment, FIG. 6 is a plan view showing a concave portion of a gravure plate used in step S20 of FIG. 5, and FIG. 7 is a cross section corresponding to the plan view of FIG. FIG. 8 is a plan view showing a modification of the concave portion of the gravure plate.

  First, in step S <b> 10 of FIG. 5, the first wiring pattern 20 is formed on the base material 10. Specifically, in Step S10, the conductive paste is printed on the substrate 10 using the gravure offset printing machine 50 shown in FIG. 4, and then the conductive paste is dried using an infrared heating furnace or the like. Then, the first wiring pattern 20 is formed by curing.

  Note that the first wiring pattern 20 may be formed by, for example, screen printing instead of gravure offset printing.

  Next, in step S <b> 20 of FIG. 5, a resist layer 30 is formed on the substrate 10 so as to cover a part of the first wiring pattern 20. Specifically, in step S20, a resist ink is printed on the substrate 10 using the gravure offset printing machine 50 shown in FIG. Form.

  At this time, in this embodiment, printing is performed using a gravure plate 51A having a recess 511 as shown in FIGS. The concave portion 511 of the gravure plate 51 </ b> A has an outer shape corresponding to the contour of the resist layer 30, and a plurality of protrusions 513 are provided in the concave portion 511. 6 and 7 show the gravure plate 51 removed from the plate cylinder 52 and developed. In FIG. 6, the outer edge of the recess 511 is indicated by a one-dot chain line.

  Each protrusion 513 has a wall shape that is erected on the bottom surface of the recess 511 and extends along the X-axis direction in the drawing. The protrusion 513 is disposed only in the vicinity of the end portion 512 in the Y-axis direction of the concave portion 511, and the central portion of the concave portion 511 in the Y-axis direction is not provided with the protrusion 513 and is simply recessed. Yes. Therefore, the concave portion 511 is partitioned into a plurality of portions in the Y-axis direction in the vicinity of the end portion 512 of the concave portion 511 by the projection 513. As a result, a groove is formed between the adjacent projections 513. It has a shape.

The intervals S ₁ , S ₂ , S ₃ of the protrusions 513 are narrower toward both ends 512 in the Y-axis direction of the recess 511 (S ₁ <S ₂ <S ₃ ). The density increases as it goes toward both ends 512 of the recess 511. Specific examples of the interval between the protrusions 513 include, for example, S ₁ = 30 [μm], S ₂ = 60 [μm], and S ₃ = 150 [μm].

The number of protrusions 513 is not particularly limited to the number shown in FIGS. In the example shown in the figure, three types of intervals S ₁ , S ₂ , and S ₃ are set, but the type of the interval between the protrusions 513 is not particularly limited to this. In the example shown in the figure, the three types of intervals S ₁ , S ₂ , and S ₃ are repeated three times each, but the present invention is not limited to this. For example, all the intervals of the recesses 511 along the Y-axis direction may be varied.

On the other hand, the width W ₁ along the Y-axis direction of the projection 513 are all the same. The width W _{1 of the} protrusion 513 is preferably 60 [μm] or less, and more preferably 50 [μm] or less.

When the resist ink is printed on the substrate 10 using the gravure plate 51A having such a recess 511, the resist ink filled in the recess 511 is received by the blanket 55 and then transferred to the substrate 10. At this time, the resist ink is received by the blanket 55 in a state where a space is formed in a portion corresponding to the protrusion 513, but the blanket 55 strongly presses the substrate 10 during transfer from the blanket 55 to the substrate 10. The resist ink is crushed and flows into the space. Therefore, the end portion 32 of the resist layer 30 the density of the protrusions 513 corresponding to the high part, while height H ₂ of the resist layer 30 is lowered, the central portion 31 projecting 513 is not formed, the height _{H 1} of the resist layer 30 is increased.

Moreover, the intervals S ₁ , S ₂ , S ₃ of the projections 513 of the gravure plate 51 are set so as to become gradually narrower toward the end portion 512 of the recess 511 (that is, the space density becomes higher). Therefore (S ₁ <S ₂ <S ₃ ), the inclined portion 33 is formed between the central portion 31 and the end portion 32 of the resist layer 30.

Incidentally, when the width W ₁ of the protrusion 513 is greater than 60 [[mu] m] is too space is broadened formed by the projection 513, there is a possibility that the ink resulting in pin holes are generated in the not flow sufficiently .

  As shown in FIG. 8, the protrusion 513B may have a prismatic shape, or the protrusion 513B may have a cylindrical shape although not particularly illustrated. In this case, the interval between the protrusions 513B in the X-axis direction in the drawing may be narrowed toward the Y-axis direction in the drawing.

  Next, in step S <b> 30 of FIG. 5, the second wiring pattern 40 is formed on the substrate 10 so as to intersect the first wiring pattern 20 via the resist layer 30. Specifically, in this step S30, the conductive paste is printed on the base material 10 using the gravure offset printing machine 50 shown in FIG. 4, and the conductive paste is dried using an infrared heating furnace or the like. The second wiring pattern 40 is formed by curing.

  In steps S10 and S30, unlike the gravure plate 51A used in step S20 described above, a conventional gravure plate in which no protrusion 513 is formed in the concave portion is used. Although not shown in particular, the gravure plate used in step S30 includes a recess having a shape corresponding to the second wiring pattern 40, and the Y direction in FIG. 6 corresponds to the extending direction of the recess. doing.

  As described above, in the present embodiment, the plurality of projections 513 are provided in the concave portion 511 of the gravure plate 51A for forming the resist layer 30, and the density of the projections 513 is directed toward the end portion 512 of the concave portion 511. According to the higher. For this reason, since the end portion 32 of the resist layer 30 can be made the lowest in the resist layer 30, the level difference caused by the end portion 32 of the resist layer 30 can be reduced, and the second wiring pattern 40 The occurrence of disconnection can be suppressed.

  The embodiment described above is described for facilitating the understanding of the present invention, and is not described for limiting the present invention. Therefore, each element disclosed in the above embodiment is intended to include all design changes and equivalents belonging to the technical scope of the present invention.

  Below, the effect of the present invention was confirmed by examples and comparative examples that further embody the present invention. The following examples and comparative examples are for confirming the effect of suppressing disconnection occurrence in the above-described embodiment.

<Example 1>
In Example 1, a sample was produced as follows. First, after a silver paste is printed on a PET film using a gravure offset printing machine, the silver paste is dried in an infrared drying furnace, whereby a width of 50 [μm] and a thickness of 2.2 [μm] are obtained. 1 wiring pattern was formed.

  This silver paste is a mixture of silver powder (S-603 manufactured by Daiken Chemical Industry Co., Ltd.), a binder (Byron (registered trademark) 300 manufactured by Toyobo Co., Ltd.), and a solvent (carbitol acetate). is there. The mixing ratio of the silver powder as the solid content was 85% by weight, the mixing ratio of the binder as the solid content was 15% by weight, and 20% by weight of the solvent was mixed with the solid content. Further, the silver paste was dried at 150 ° C. for 4 minutes in an infrared drying oven.

Next, using the gravure plate having the configuration described with reference to FIGS. 6 and 7, a resist ink is printed on the PET film on which the first wiring pattern is formed, and then 600 [mJ / cm ² ] is applied to the resist ink. A resist layer having a length of 1 [mm] and a width of 100 [μm] was formed.

This resist ink is a mixture of a resin (UV-7510B manufactured by Nippon Synthetic Chemical Industry Co., Ltd.) and a polymerization initiator (Irgacure 184 manufactured by Ciba Specialty Chemicals Co., Ltd.). The mixing ratio of the resin was 90% by weight, and the mixing ratio of the polymerization initiator was 10% by weight. Further, the width W ₁ of all the projections in the gravure plate was set to 50 [μm], and the intervals S ₁ , S ₂ and S ₃ of the projections were set to 30 [μm], 60 [μm] and 150 [μm], respectively.

The thickness of the thus formed resist layer, 2.2 [[mu] m] at the portion corresponding to the spacing S ₁ of the protrusion, 4.4 [[mu] m] at the portion corresponding to the spacing S ₂ of the projection, the projection distance 8.2 [[mu] m] at the portion corresponding to S _3, was 10.2 [[mu] m] in the solid portion of the central protrusion is not formed.

  Next, after printing the silver paste on the PET film on which the first wiring pattern and the resist layer are formed, the silver paste is dried in an infrared drying furnace, so that the width is 50 [μm] and the thickness is 2.2. A second wiring pattern of [μm] was formed.

  This silver paste is composed of silver powder (S-603, manufactured by Daiken Chemical Co., Ltd.) and a binder (Byron (registered trademark) 300, manufactured by Toyobo Co., Ltd.) in the same manner as the silver paste constituting the first wiring pattern. ) And a solvent (carbitol acetate). The mixing ratio of the silver powder as the solid content was 85% by weight, the mixing ratio of the binder as the solid content was 15% by weight, and 20% by weight of the solvent was mixed with the solid content. Further, the silver paste was dried at 150 ° C. for 4 minutes in an infrared drying oven.

  About 30 samples produced as mentioned above, the resistance value of a 2nd wiring pattern was measured, and the presence or absence of generation | occurrence | production of the disconnection of a 2nd wiring pattern was determined. In Example 1, no disconnection of the second wiring pattern occurred in 30 samples (disconnection occurrence rate: 0.0%).

<Comparative Example 1>
In Comparative Example 1, a sample was prepared in the same manner as in Example 1 except that a conventional gravure plate in which no protrusion was provided in the recess was used as the gravure plate for forming the resist layer. When the thickness of the resist layer of the sample in Comparative Example 1 was measured in the same manner as in Example 1, it was a substantially uniform thickness of 10 [μm].

  About the 30 samples produced as mentioned above, the presence or absence of occurrence of disconnection of the second wiring pattern was determined in the same manner as in Example 1. In Comparative Example 1, disconnection of the second wiring pattern occurred in 4 samples out of 30 samples (disconnection occurrence rate of 13.3%).

<Comparative example 2>
In Comparative Example 2, a sample was prepared in the same manner as in Example 1 except that the resist layer was formed by screen printing instead of gravure offset printing. When the thickness of the resist layer of the sample in Comparative Example 2 was measured in the same manner as in Example 1, it was a substantially uniform thickness of 20 [μm].

  About the 30 samples produced as mentioned above, the presence or absence of disconnection of the second wiring pattern was determined in the same manner as in Example 1. In Comparative Example 2, disconnection of the second wiring pattern occurred in 8 samples out of 30 samples (disconnection rate: 26.7%).

  As described above, by comparing Example 1 with Comparative Examples 1 and 2, a plurality of projections are provided in the recesses of the gravure plate, and the intervals between the projections are narrowed toward the end portions of the recesses, thereby providing a resist. It was confirmed that the step at the end of the layer was reduced.

  In addition, by comparing Example 1 with Comparative Examples 1 and 2, it was confirmed that the occurrence of disconnection of the second wiring pattern was suppressed by reducing the step at the end of the resist layer.

DESCRIPTION OF SYMBOLS 1 ... Printed wiring board 10 ... Base material 20 ... 1st wiring pattern 30 ... Resist layer 31 ... Center part 32 ... End part 33 ... Inclined part 40 ... 2nd wiring pattern 50 ... Gravure offset printing machine 51, 51A ... Gravure Plate 511 ... Concave portion 512 ... End portion 513 ... Protrusion 52 ... Plate cylinder 53 ... Ink tank 54 ... Doctor blade 55 ... Blanket 56 ... Table H ₁ ... Height H ₂ at the center portion ... Height W ₁ at the end portion ... Width S _{1 to} S ₃ ... spacing between protrusions

Claims (5)

A first wiring pattern provided on the substrate;
An insulating layer provided on the base material so as to overlap a part of the first wiring pattern;
A second wiring pattern provided on the base material so as to intersect the first wiring pattern via the insulating layer,
The printed wiring board characterized in that the end portion of the insulating layer has the lowest height among the insulating layers. The printed wiring board according to claim 1,
The insulating layer has an inclined portion that gradually decreases toward an end of the insulating layer;
The printed wiring board, wherein a height of a portion of the insulating layer overlapping the first wiring pattern is the highest among the insulating layers. A first step of forming a first wiring pattern on a substrate;
A second step of forming an insulating layer on the substrate by a gravure offset printing method so as to overlap a part of the first wiring pattern;
A third step of forming a second wiring pattern on the base material by a gravure offset printing method so as to intersect the first wiring pattern via the insulating layer,
The second step includes using a gravure plate having a recess having a shape corresponding to the insulating layer;
A plurality of protrusions are provided in the recess,
The method of manufacturing a printed wiring board, wherein the density of the protrusions increases toward the end of the recess. It is a manufacturing method of the printed wiring board according to claim 3,
The interval between the protrusions becomes narrower toward the end of the recess,
A method for manufacturing a printed wiring board, wherein the plurality of protrusions have substantially the same width. A method for producing a printed wiring board according to claim 3 or 4,
The method of manufacturing a printed wiring board, wherein the protrusion includes a wall shape or a column shape.

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