US-20260129751-A1 - PRINTED CIRCUIT BOARD

Abstract

A printed circuit board includes a bendable portion. The bendable portion is bendable in a bending direction in plan view and has a first dielectric layer, a signal pattern, a second dielectric layer, a cloth, and a ground pattern. The first dielectric layer has a first main surface. The signal pattern is arranged on the first main surface. The second dielectric layer has a second main surface and a third main surface opposite to the second main surface, and the second main surface is arranged to face the first main surface. The cloth includes a plurality of first reinforced fibers extending in a first direction in plan view and a plurality of second reinforced fibers extending in a second direction inclined with respect to the first direction in plan view, the plurality of first reinforced fibers and the plurality of second reinforced fibers being knitted together in a cloth form.

Inventors

• Katsuya MORIZANE
• Takuto NISHI
• Yukinori NISHIMURA

Assignees

• SUMITOMO ELECTRIC PRINTED CIRCUITS, INC.

Dates

Publication Date

20260507

Application Date

20251104

Priority Date

20241106

Claims (9)

1. 1 . A printed circuit board comprising: a bendable portion, wherein the bendable portion is bendable in a bending direction in plan view and has a first dielectric layer, a signal pattern, a second dielectric layer, a first cloth, and a ground pattern, wherein the first dielectric layer has a first main surface, wherein the signal pattern is arranged on the first main surface, wherein the second dielectric layer has a second main surface and a third main surface opposite to the second main surface, and the second main surface is arranged to face the first main surface, wherein the first cloth includes a plurality of first reinforced fibers extending in a first direction in plan view and a plurality of second reinforced fibers extending in a second direction inclined with respect to the first direction in plan view, the plurality of first reinforced fibers and the plurality of second reinforced fibers being knitted together in a cloth form, wherein the first cloth is arranged inside the second dielectric layer, wherein the ground pattern is arranged on the third main surface, and wherein each of the first direction and the second direction is inclined with respect to the bending direction.
2. 2 . The printed circuit board according to claim 1 , wherein the first direction is perpendicular to the second direction.
3. 3 . The printed circuit board according to claim 2 , wherein an angle formed by the first direction and the bending direction in plan view is 30° or more.
4. 4 . The printed circuit board according to claim 2 , wherein an angle formed by the first direction and the bending direction in plan view is 40° or more.
5. 5 . The printed circuit board according to claim 1 , wherein the plurality of first reinforced fibers and the plurality of second reinforced fibers are made of glass.
6. 6 . The printed circuit board according to claim 1 , wherein the second dielectric layer is made of a fluororesin.
7. 7 . The printed circuit board according to claim 1 , further comprising: an adhesion layer arranged between the first main surface and the second main surface to cover the signal pattern.
8. 8 . The printed circuit board according to claim 1 , further comprising: a second cloth arranged inside the first dielectric layer, wherein the second cloth includes a plurality of third reinforced fibers extending in a third direction in plan view and a plurality of fourth reinforced fibers extending in a fourth direction inclined with respect to the third direction in plan view, the plurality of third reinforced fibers and the plurality of fourth reinforced fibers being knitted together in a cloth form, and wherein each of the third direction and the fourth direction is inclined with respect to the bending direction.
9. 9 . The printed circuit board according to claim 1 , wherein the bendable portion is bendable such that the second dielectric layer is compressed.

Description

CROSS REFERENCE TO RELATED APPLICATIONS This application claims priority based on Japanese Patent Application No. 2024-194532 filed on November 6, 2024, and the entire contents of the Japanese patent application are incorporated herein by reference. TECHNICAL FIELD The present disclosure relates to a printed circuit board. BACKGROUND Japanese Unexamined Patent Application Publication No. 2011-54919 (Patent literature 1) describes a printed circuit board. The printed circuit board described in Patent Literature 1 includes a first dielectric layer, a signal pattern disposed on the first dielectric layer, an adhesion layer disposed on the first dielectric layer so as to cover the signal pattern, a second dielectric layer disposed on the adhesion layer, and a ground pattern disposed on the second dielectric layer. SUMMARY A printed circuit board of the present disclosure includes a bendable portion. The bendable portion is bendable in a bending direction in plan view and has a first dielectric layer, a signal pattern, a second dielectric layer, a cloth, and a ground pattern. The first dielectric layer has a first main surface. The signal pattern is arranged on the first main surface. The second dielectric layer has a second main surface and a third main surface opposite to the second main surface, and the second main surface is arranged to face the first main surface. The cloth includes a plurality of first reinforced fibers extending in a first direction in plan view and a plurality of second reinforced fibers extending in a second direction inclined with respect to the first direction in plan view, the plurality of first reinforced fibers and the plurality of second reinforced fibers being knitted together in a cloth form. The cloth is arranged inside the second dielectric layer. The ground pattern is arranged on the third main surface. Each of the first direction and the second direction is inclined with respect to the bending direction. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic side view of a printed circuit board 100. FIG. 2 is a plan view of the printed circuit board 100. FIG. 3 is a cross-sectional view taken along line III-III in FIG. 2. FIG. 4 is a schematic view showing the orientations of a reinforced fiber 51a and a reinforced fiber 51b in a cloth 51 arranged inside a dielectric layer 50 in a bendable portion 10 of the printed circuit board 100. FIG. 5 is a cross-sectional view of the printed circuit board 100 according to a modification 1. FIG. 6 is a cross-sectional view of the printed circuit board 100 according to a modification 2. FIG. 7 is a manufacturing process diagram of the printed circuit board 100. FIG. 8 is a first cross-sectional view for explaining a preparation step S1. FIG. 9 is a second explanatory view for explaining the preparation step S1. FIG. 10 is a cross-sectional view for explaining a patterning step S2. FIG. 11 is a schematic view showing the orientations of the reinforced fiber 51a and the reinforced fiber 51b in the cloth 51 arranged inside the dielectric layer 50 in the bendable portion 10 of a printed circuit board 200. FIG. 12 shows load-strain curves for samples when changing an angle formed by the longitudinal direction and a first direction DR1. FIG. 13 is a graph showing a relationship between an angle formed by the longitudinal direction of each sample and a first direction DR1 and a breaking strain. DETAILED DESCRIPTION When the printed circuit board described in Patent Literature 1 is bent such that the second dielectric layer is located on the inner side of the bend compared to the first dielectric layer, compressive stress acts on the second dielectric layer. When the second dielectric layer buckles due to the compressive stress, the distance between the signal pattern and the ground pattern changes, and thus the impedance of the signal pattern changes. As a result, transmission characteristics of a high frequency signal in the signal pattern deteriorate. The present disclosure provides a printed circuit board capable of improving transmission characteristics of a high frequency signal in a signal pattern. Description of Embodiments of Present Disclosure First, embodiments of the present disclosure will be listed and described. (1) A printed circuit board according to an embodiment includes a bendable portion. The bendable portion is bendable in a bending direction in plan view and has a first dielectric layer, a signal pattern, a second dielectric layer, a cloth, and a ground pattern. The first dielectric layer has a first main surface. The signal pattern is arranged on the first main surface. The second dielectric layer has a second main surface and a third main surface opposite to the second main surface, and the second main surface is arranged to face the first main surface. The cloth includes a plurality of first reinforced fibers extending in a first direction in plan view and a plurality of second reinforced fibers extending in a second d