WO2021127845A1

WO2021127845A1 - Flexible printed circuit board

Info

Publication number: WO2021127845A1
Application number: PCT/CN2019/127434
Authority: WO
Inventors: 马长进
Original assignee: 瑞声声学科技(深圳)有限公司; 瑞声科技(新加坡)有限公司
Priority date: 2019-12-23
Filing date: 2019-12-23
Publication date: 2021-07-01

Abstract

A flexible printed circuit board is divided into a bendable region (A) and a non-bendable region, and has a copper foil layer (13). The copper foil layer (13) comprises a first portion (131) corresponding to the bendable region (A) and a second portion (133) corresponding to the non-bendable region. A plurality of through-holes (135) forming a mesh structure pass through the first portion (131), and each through-hole (135) is provided with a hole wall (137) having a smooth transition. The bendable region (A) of the flexible printed circuit board is flexible, and stress on the bendable region (A) can be dispersed to a significant extent, thus improving bending performance and reliability.

Description

Flexible printed circuit board

Technical field

The invention relates to the field of design and manufacture of flexible printed circuit boards, in particular to a flexible printed circuit board.

Background technique

Flexible printed circuit board (Flexible Printed Circuit Board, referred to as FPC board) is made of flexible polyester film or polyphthalimide and other insulating substrates, combined with circuits formed by etching on copper foil. It has high reliability and insulation. Good flexibility. It can be bent, wound, and folded freely, can be arranged arbitrarily according to the space layout requirements, and can move and expand in three-dimensional space, so as to achieve the integration of component assembly and wire connection. The use of FPC boards can greatly reduce the volume of electronic products, and is suitable for the development of electronic products in the direction of high density, miniaturization and high reliability. Therefore, FPC boards have been widely used in aerospace, military, mobile communications, laptop computers, computer peripherals, handheld computers, digital cameras and other fields or products.

In general FPC production, some products need to be bent to meet the requirements of the assembly mechanism. In the related art, the structure of the bending zone and the non-bending zone of the FPC is the same. When bending, the bending zone is not soft enough and easy to break, and when the bending R angle is small, there is a shortage of local stress concentration.

Therefore, it is necessary to provide a new flexible printed circuit board to solve the above technical problems.

technical problem

The object of the present invention is to provide a flexible printed circuit board, which not only has soft bending area, but also can improve the deficiency of local stress concentration.

Technical solutions

In order to achieve the above object, the present invention provides a flexible printed circuit board, which is divided into a bending area and a non-bending area. The flexible printed circuit board has a copper foil layer, and the copper foil layer includes the same with the bending area. Corresponding to the first part and the second part corresponding to the non-bending area, the first part is provided with a plurality of through holes forming a mesh structure, the through holes are provided with a hole wall, and the hole wall is smooth transition.

Preferably, the hole wall is circular.

Preferably, a plurality of the through holes are staggered.

Preferably, the flexible printed circuit board includes a base layer and a cover film covering the base layer, the base layer includes a copper foil layer connected to the cover film, and the cover film corresponds to the area of the first part after being cut A window is formed that exposes the first part.

Preferably, the flexible printed circuit board further includes a flexible ink layer, and the flexible ink layer covers at least the surface of the first part facing the side of the covering film.

Preferably, the flexible ink layer extends to the surface of the second part facing the cover film.

Preferably, the flexural ink layer extends to the surface of the cover film on a side away from the copper foil layer.

Preferably, the thickness of the cover film is 1 mil to 5 mils.

Beneficial effect

Compared with the related art, the flexible printed circuit board of the present invention is provided with a plurality of through holes forming a mesh structure through the first portion of the copper foil layer corresponding to the bending area, and the through holes are provided with The hole wall has a smooth transition, so that the bending area of the flexible printed circuit board has sufficient flexibility, and when the flexible printed circuit board is bent, the stress in the bending area can be dispersed to the greatest extent, thereby improving the bending Reducing effect and reliability.

Description of the drawings

In order to explain the technical solutions in the embodiments of the present invention more clearly, the following will briefly introduce the drawings needed in the description of the embodiments. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative work, other drawings can be obtained based on these drawings, among which:

Figure 1 is a cross-sectional view of a preferred embodiment of a flexible printed circuit board of the present invention;

FIG. 2 is a schematic structural diagram of a part of the structure of the flexible printed circuit board shown in FIG. 1;

Fig. 3 is an enlarged view of the bending area in the partial structure shown in Fig. 2;

4 is a cross-sectional view of another embodiment of the flexible printed circuit board of the present invention.

Embodiments of the present invention

The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative work shall fall within the protection scope of the present invention.

Please refer to FIGS. 1 to 4 in combination, the flexible printed circuit board is divided into a bending area A and a non-bending area. The flexible printed circuit board has a copper foil layer 13. The copper foil layer 13 includes a first portion 131 corresponding to the bending area A and a second portion 133 corresponding to the non-bending area. A through hole 135 is provided with a hole wall 137, and the hole wall 137 has a smooth transition.

As shown in FIGS. 1 and 2, the non-bending area is divided by the bending area A into a first area B and a second area C arranged at intervals.

As shown in FIG. 3, the through hole 135 is circular.

As an embodiment of the present invention, preferably, a plurality of the through holes 135 are staggered. As shown in FIG. 3, the plurality of through holes 135 are arranged in multiple rows at intervals along the X-axis direction, and each row is provided with a plurality of through holes 135 at intervals along the Y-axis direction, and any one of the through holes 135 in each row The connection line between the axis of and the axis of any one of the through holes 135 in another adjacent column is neither perpendicular to the X-axis direction nor perpendicular to the Y-axis direction. Wherein, the first area B and the second area C are arranged at intervals along the Y-axis direction.

As shown in FIGS. 1 and 3, the flexible printed circuit board includes a base layer 1 and a cover film 3 covering the base layer 1.

The base layer 1 includes a base material layer 11 and a copper foil layer 13. The base material layer 11 is provided with the copper foil layer 13 on opposite sides thereof, and the cover film 3 covers the copper foil layer 13 away from the copper foil layer 13 The substrate layer 11 is on one side.

The cover film 3 is made of materials such as polyimide, polyester, etc., and is adhered to the copper foil layer 13 through an adhesive. The thickness of the cover film 3 is 1 mil-5 mil.

In this embodiment, the area of the cover film 3 corresponding to the first portion 131 is cut to form a window 31 that exposes the first portion 131. In other words, the first portion 131 is not covered with a cover film. Therefore, when the flexible printed circuit board is assembled, the bending area A is bent, and the phenomenon of rebound and warping of the cover film caused by the cover film provided on the first part 131 in the prior art will not occur.

It can be understood that, in other embodiments, the window 31 may be formed on only one of the cover films in the flexible printed circuit board.

In this embodiment, the flexible printed circuit board further includes a flexible ink layer 5 covering at least the surface of the first portion 131 facing the cover film 3. The flexible ink layer 5 is made of soft ink, which has extremely strong ductility. When the flexible printed circuit board is bent, it will expand along the curvature of the substrate without breaking or cutting. The wiring on the copper foil layer 13 can protect the first part 131 that is not covered by the cover film.

As shown in FIG. 1, the flexural ink layer 5 extends to the surface of the second portion 133 facing the cover film 3. As shown in FIG. 4, the flexural ink layer 3 extends to the surface of the cover film 3 away from the copper foil layer 131. That is to say, the area covered by the flexure ink layer 5 is larger than the bending area A. In addition to covering the bending area A, it also overlaps with the first area B and the second area C. . This can provide better protection when the flexible printed circuit board is bent.

Compared with the related art, the flexible printed circuit board of the present invention is provided with a plurality of through holes 135 forming a mesh structure through the first portion 131 of the copper foil layer 13 corresponding to the bending area B, and the The through hole 135 is provided with a hole wall 137, the hole wall 137 has a smooth transition, so that the bending area B has sufficient flexibility, and when the flexible printed circuit board is bent, the stress in the bending area B can be dispersed to the greatest extent , Thereby improving the bending effect and reliability.

The above are only the embodiments of the present invention. It should be pointed out here that for those of ordinary skill in the art, improvements can be made without departing from the inventive concept of the present invention, but these all belong to the present invention. The scope of protection.

Claims

A flexible printed circuit board is divided into a bending area and a non-bending area. The flexible printed circuit board has a copper foil layer, wherein the copper foil layer includes a first part corresponding to the bending area and A second part corresponding to the non-bending area is provided with a plurality of through holes forming a mesh structure through the first part, the through holes are provided with hole walls, and the hole walls are smoothly transitioned.
The flexible printed circuit board according to claim 1, wherein the hole wall is circular.
The flexible printed circuit board according to claim 1, wherein a plurality of the through holes are staggered.
The flexible printed circuit board according to claim 1 or 2, wherein the flexible printed circuit board includes a base layer and a cover film covering the base layer, and the base layer includes a copper foil connected to the cover film Layer, the cover film corresponding to the first part is cut to form a window that exposes the first part.
The flexible printed circuit board according to claim 4, wherein the flexible printed circuit board further comprises a flexible ink layer, the flexible ink layer covering at least the surface of the first part facing the cover film .
5. The flexible printed circuit board according to claim 5, wherein the flexural ink layer extends to a surface of the second part facing the cover film.
5. The flexible printed circuit board according to claim 5, wherein the flexural ink layer extends to the surface of the cover film on a side away from the copper foil layer.
The flexible printed circuit board according to claim 4, wherein the thickness of the cover film is 1 mil to 5 mils.