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US-12628269-B2 - Flexible printed board

US12628269B2US 12628269 B2US12628269 B2US 12628269B2US-12628269-B2

Abstract

A flexible printed board according to the present disclosure includes a first pattern layer including, at an end part thereof, a wiring end part to be connected to a substrate and a resist and a coverlay overlaid on the first pattern layer, wherein the coverlay covers an inside of the wiring end part of the first pattern layer in a planar view, and the resist is provided from a portion of the first pattern layer covered with the coverlay to a portion of the first pattern layer exposed from the coverlay, in a planar view.

Inventors

  • Takuro Shinada

Assignees

  • MITSUBISHI ELECTRIC CORPORATION

Dates

Publication Date
20260512
Application Date
20210609

Claims (9)

  1. 1 . A flexible printed board, comprising: a first pattern layer including, at an end part thereof, a wiring end part to be connected to a substrate; and a resist and a coverlay overlaid on the first pattern layer, wherein the coverlay covers an inside of the wiring end part of the first pattern layer in a planar view, the resist is provided from a portion of the first pattern layer covered with the coverlay to a portion of the first pattern layer exposed from the coverlay, in a planar view, an end part of the coverlay in a signal propagation direction has a wave shape in a planar view, a center portion of the first pattern layer in the signal propagation direction is exposed from the resist in a planar view, an end part of the resist on the center portion side has a wave shape in a planar view, and is provided along the end part of the coverlay, and the end part of the coverlay having the wave shape faces an opposite direction from the end part of the resist having the wave shape.
  2. 2 . The flexible printed board according to claim 1 , wherein the wiring end part includes a plurality of patterns, and the resist is provided between the plurality of patterns.
  3. 3 . The flexible printed board according to claim 2 , wherein the resist is thinner than the first pattern layer.
  4. 4 . The flexible printed board according to claim 1 , wherein an opening is provided at a portion other than the wiring end part of the first pattern layer.
  5. 5 . The flexible printed board according to claim 4 , further comprising: a base provided with the first pattern layer on a first surface; and a second pattern layer provided on a second surface on a side opposite to the first surface of the base, wherein the opening is provided while avoiding a portion of the first pattern layer overlapping with the second pattern layer in a planar view.
  6. 6 . The flexible printed board according to claim 1 , wherein an opening is provided at a portion other than the wiring end part of the first pattern layer, and the opening is provided along the end part of the coverlay and the end part of the resist in a planar view.
  7. 7 . A flexible printed board, comprising: a first pattern layer including, at an end part thereof, a wiring end part to be connected to a substrate; and a resist and a coverlay overlaid on the first pattern layer in a vertical direction, wherein the coverlay covers an inside of the wiring end part of the first pattern layer in a planar view, the resist is provided from a portion of the first pattern layer covered with the coverlay to a portion of the first pattern layer exposed from the coverlay, in a planar view, an opening is provided in the first pattern layer at a portion other than the wiring end part of the first pattern layer, the opening extending all the way through the first pattern layer in the vertical direction, and the opening has a wave shape in a planar view.
  8. 8 . A flexible printed board, comprising: a first pattern layer including, at an end part thereof, a wiring end part to be connected to a substrate; and a resist and a coverlay overlaid on the first pattern layer in a vertical direction, wherein the coverlay covers an inside of the wiring end part of the first pattern layer in a planar view, the resist is provided from a portion of the first pattern layer covered with the coverlay to a portion of the first pattern layer exposed from the coverlay, in a planar view, an end part of the coverlay in a signal propagation direction has a wave shape in a planar view, an opening is provided in the first pattern layer at a portion other than the wiring end part of the first pattern layer, the opening extending all the way through the first pattern layer in the vertical direction, and the opening is provided along the end part of the coverlay in a planar view.
  9. 9 . A flexible printed board, comprising: a first pattern layer including, at an end part thereof, a wiring end part to be connected to a substrate; and a resist and a coverlay overlaid on the first pattern layer in a vertical direction, wherein the coverlay covers an inside of the wiring end part of the first pattern layer in a planar view, the resist is provided from a portion of the first pattern layer covered with the coverlay to a portion of the first pattern layer exposed from the coverlay, in a planar view, a center portion of the first pattern layer in a signal propagation direction is exposed from the resist in a planar view, an end part of the resist on the center portion side has a wave shape in a planar view, an opening is provided in the first pattern layer at a portion other than the wiring end part of the first pattern layer, the opening extending all the way through the first pattern layer in the vertical direction, and the opening is provided along the end part of the resist in a planar view.

Description

FIELD The present disclosure relates to a flexible printed board. BACKGROUND PTL 1 discloses a flexible printed circuit board. The flexible printed circuit board includes a substrate having a first edge and a second edge. A first wiring pattern and a second wiring pattern are disposed on the substrate. A first brazing material pattern is disposed on a lead connection portion of the first wiring pattern positioned at a side of the first edge of the substrate. A second brazing material pattern that extends longer than the first brazing material pattern is disposed on a lead connection portion of the second wiring pattern positioned at a side of the first edge of the substrate. As a result, when the flexible printed circuit board is bent, stress is distributed. This makes it possible to prevent disconnection of the wiring patterns. CITATION LIST Patent Literature [PTL 1] JP 2011-238883 A SUMMARY Technical Problem When a flexible printed board is bent, stress is generally likely to concentrate on a root portion of the flexible printed board. Therefore, disconnection may occur. In PTL 1, stress is distributed by providing the long second brazing material pattern at the edge. However, providing the long second brazing material pattern may inhibit reduction in length of the flexible printed board. An object of the present disclosure is to provide a flexible printed board that can be reduced in length while preventing disconnection. Solution to Problem A flexible printed board according to the present disclosure includes a first pattern layer including, at an end part thereof, a wiring end part to be connected to a substrate and a resist and a coverlay overlaid on the first pattern layer, wherein the coverlay covers an inside of the wiring end part of the first pattern layer in a planar view, and the resist is provided from a portion of the first pattern layer covered with the coverlay to a portion of the first pattern layer exposed from the coverlay, in a planar view. Advantageous Effects of Invention In the flexible printed board according to the present disclosure, the resist is provided at the portion of the first pattern layer corresponding to the end part of the coverlay where stress is likely to concentrate. This makes it possible to prevent disconnection. Further, it is unnecessary to provide a long pattern at the end part of the substrate in order to distribute stress. Accordingly, the flexible printed board can be reduced in length. BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is a diagram to explain a structure of a flexible printed board according to Embodiment 1. FIG. 2 is a plan view of the flexible printed board according to Embodiment 1. FIG. 3 is a bottom view of the flexible printed board according to Embodiment 1. FIG. 4 is a cross-sectional view of the flexible printed board according to Embodiment 1. FIG. 5 is a diagram illustrating a state where the flexible printed board according to Embodiment 1 is connected to the substrate. FIG. 6 is a diagram illustrating a state where the flexible printed board according to Embodiment 1 is connected to a transmission substrate. FIG. 7 is a diagram illustrating a state where the flexible printed board according to Embodiment 1 is connected to an LD module. FIG. 8 is a diagram illustrating a state where the flexible printed board according to Embodiment 1 is connected to a PD module. FIG. 9 is a diagram illustrating a state where the flexible printed board according to Embodiment 1 is bent. FIG. 10 is a diagram to explain a structure of a flexible printed board according to Embodiment 2. FIG. 11 is a plan view of the flexible printed board according to Embodiment 2. FIG. 12 is a bottom view of the flexible printed board according to Embodiment 2. FIG. 13 is a cross-sectional view of the flexible printed board according to Embodiment 2. FIG. 14 is a diagram to explain portions as boundaries of the members of the flexible printed board according to embodiment 1. FIG. 15 is a diagram to explain portions as boundaries of the members of the flexible printed board according to Embodiment 2. FIG. 16 is a diagram to explain a structure of a flexible printed board according to Embodiment 3. FIG. 17 is a plan view of the flexible printed board according to Embodiment 3. FIG. 18 is a bottom view of the flexible printed board according to Embodiment 3. FIG. 19 is a cross-sectional view of the flexible printed board according to Embodiment 3. FIG. 20 is a diagram to explain a structure of a flexible printed board according to Embodiment 4. FIG. 21 is a plan view of the flexible printed board according to Embodiment 4. FIG. 22 is a bottom view of the flexible printed board according to Embodiment 4. FIG. 23 is a cross-sectional view of the flexible printed board according to Embodiment 4. FIG. 24 is a diagram to explain a portion where a cross-sectional area is changed in the pattern layer according to Embodiment 3. FIG. 25 is a diagram to explain a portion where a cross-sectio