CN112020207B

CN112020207B - Flexible printed circuit board and display device

Info

Publication number: CN112020207B
Application number: CN202011014246.6A
Authority: CN
Inventors: 黄祥; 徐宁; 余志华
Original assignee: Wuhan Tianma Microelectronics Co Ltd
Current assignee: Wuhan Tianma Microelectronics Co Ltd
Priority date: 2020-09-24
Filing date: 2020-09-24
Publication date: 2022-01-14
Anticipated expiration: 2040-09-24
Also published as: CN112020207A

Abstract

The invention provides a flexible printed circuit board and a display device, the flexible printed circuit board includes: a plurality of pads; the pad comprises a first branch part and a second branch part which are connected with each other; the second branch part comprises a first branch part and a second branch part, the first branch part is arranged close to the first branch part, and the second branch part is arranged far away from the first branch part; the first sub-branch part extends along the second direction, and the second sub-branch part extends along a third direction perpendicular to the first direction; the included angle between the first branch part and the second branch part is between 90 and 180 degrees, and end point values are not included; the first direction is an extending direction of a boundary line between the first sub-branch portion and the second sub-branch portion. This application sets up the second branch portion through the below at the first branch portion of pad, and the second branch portion includes two relative sub-branch portions of buckling the setting to the border line of buckling of position department is for counterpoint mark laminating protection film, has improved the laminating precision of protection film, has optimized the size of pad, has improved and has bound the effect.

Description

Flexible printed circuit board and display device

Technical Field

The invention relates to the field of display, in particular to a flexible printed circuit board and a display device.

Background

Among the prior art, no matter the pad of the flexible printed circuit board of display module assembly is vertical type or eight characters, all can't provide protection film laminating counterpoint mark in production, and the pad length fluctuation is great, influences conductive particle pressfitting quantity, can't guarantee to bind the effect. Two kinds of pads also can not directly judge whether the supplied materials are qualified through the outward appearance, all need judge through the measurement size, and detection efficiency is low.

Therefore, how to guarantee the binding effect of the flexible printed circuit board is becoming a big problem in the display field.

Disclosure of Invention

In view of this, the invention provides a flexible printed circuit board and a display device, in which two sub-branch portions are arranged below a bonding pad and bent oppositely, and a protective film is attached to the bonding pad by using a bent boundary line at a bent position as an alignment mark, so that the attachment accuracy of the protective film is improved, the size of the bonding pad is optimized, and the binding effect is improved.

In one aspect, an embodiment of the present application provides a flexible printed circuit board, including:

the circuit board comprises a substrate, a plurality of bonding pads and a plurality of control pads, wherein the bonding pads are arranged along a first direction;

the pad comprises a first branch part and a second branch part which are connected with each other;

the second branch part comprises a first branch part and a second branch part, the first branch part is arranged close to the first branch part, and the second branch part is arranged far away from the first branch part;

the first sub-branch portion extends along a second direction, and the second sub-branch portion extends along a third direction perpendicular to the first direction;

the included angle between the first branch part and the second branch part is between 90 and 180 degrees, and end point values are not included;

the first direction is an extending direction of a boundary line between the first sub-branch portion and the second sub-branch portion.

On the other hand, based on the same inventive concept, embodiments of the present application provide a display device including the above-described flexible printed circuit board.

According to the flexible printed circuit board and the display device, the second branch part is arranged below the first branch part of the bonding pad and comprises the two sub branch parts which are oppositely bent, and the protective film is attached by taking the bending boundary line at the bending position as the alignment mark, so that the attachment precision of the protective film is improved, the size of the bonding pad is optimized, and the binding effect is improved.

Drawings

Fig. 1 is a schematic structural diagram of a flexible printed circuit board provided in an embodiment of the present application;

FIG. 2 is a cross-sectional view taken along line A1-A2 of FIG. 1;

fig. 3a is a schematic view illustrating a bonding effect of a protective film according to an embodiment of the present disclosure;

fig. 3b is a schematic view illustrating a bonding effect of another protection film provided in the embodiment of the present application;

FIG. 4 is a schematic diagram of one configuration of the bonding pad 20 of FIG. 1;

fig. 5 is a comparative schematic diagram of different structures of the second sub-branch 2022 in fig. 1;

FIG. 6 is a schematic structural diagram of a further flexible printed circuit FZ 203166-ATL-coin cell FTO survey report V1-20200924 board provided by the embodiment of the present application;

FIG. 7 is a schematic view of another structure of the bonding pad 20 of FIG. 1;

FIG. 8 is a schematic view of another structure of the bonding pad 20 of FIG. 1;

FIG. 9 is a schematic view of another structure of the bonding pad 20 of FIG. 1;

fig. 10 is a schematic structural diagram of a display device according to an embodiment of the present application.

Detailed Description

In order to make the aforementioned objects, features and advantages of the present invention comprehensible, the present invention is further described with reference to the accompanying drawings and examples.

It should be noted that in the following description, specific details are set forth in order to provide a thorough understanding of the present invention. The invention can be implemented in a number of ways different from those described herein and similar generalizations can be made by those skilled in the art without departing from the spirit of the invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

The terminology used in the embodiments of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used in the examples of the present invention and the appended claims, the singular forms "a," "an," and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise.

It should be noted that the terms "upper", "lower", "left", "right", and the like used in the description of the embodiments of the present invention are used in the angle shown in the drawings, and should not be construed as limiting the embodiments of the present invention. In addition, in this context, it is also to be understood that when an element is referred to as being "on" or "under" another element, it can be directly formed on "or" under "the other element or be indirectly formed on" or "under" the other element through an intermediate element.

Fig. 1 is a schematic structural diagram of a flexible printed circuit board according to an embodiment of the present application. As shown in fig. 1, a flexible printed circuit board 1 includes: a substrate 10, a plurality of pads 20 disposed on the substrate 10, the plurality of pads being arranged along a first direction D1; the pad 20 includes a first branch 201 and a second branch 202 connected to each other; the second branch 202 includes a first sub-branch 2021 and a second sub-branch 2022. The first sub-branch portion 2021 is disposed near the first branch portion 201, and the second sub-branch portion 2022 is disposed far from the first branch portion 201.

With continued reference to fig. 1, the first sub-branch 2021 extends along the second direction D2, the second sub-branch 2022 extends along the third direction D3, and an included angle between the first sub-branch 2021 and the second sub-branch 2022 is between 90 ° and 180 °, excluding end points. That is, the second sub-branch portion 2022 is bent relative to the first sub-branch portion 2021, and forms an obtuse angle a.

Since the first sub-branch portion 2021 and the second sub-branch portion 2022 are bent relatively, there is a bending boundary line BL therebetween, wherein the extending direction of BL is the first direction D1.

Fig. 2 is a sectional view taken along line a1-a2 in fig. 1, and as shown in fig. 2, a protective film 30 is provided on a side away from the substrate 10, the protective film 30 covering the second branch portions 202 of the pads 20. The protective film 30 protects the second branch portion 202 of the pad from being exposed to the air, and prevents oxidation of the second branch portion 202.

Because of the relative bending arrangement of the first sub-branch 2021 and the second sub-branch 2022, a bending boundary line BL is generated at the bending position. Therefore, the fold boundary line BL can be used as the protective film 30 to attach the alignment mark. Meanwhile, the extending direction of the bending boundary line is consistent with the arrangement direction of the bonding pads. Therefore, the protective film can bond the pad with the bent boundary line BL as the alignment mark.

In this application, set up the second branch portion through the below at the first branch portion of pad, and the second branch portion includes two relative sub-branch portions of buckling the setting to the border line of buckling of position department is counterpoint mark laminating protection film, has improved the laminating precision of protection film, has optimized the size of pad, has improved and has bound the effect.

In order to increase the bonding strength between the flexible circuit board and the display screen, the inventor of the present application proposes that the extending direction of the first branch portion is the same as the extending direction of the first branch portion, that is, the first branch portion is a forward extending portion of the first branch portion. When the protective film is attached to the second branch part by taking the bending boundary line of the first branch part and the second branch part as the alignment mark, the protective film generates a compressive stress Fc to the first branch part, and the compressive stress Fc applied to the first branch part by the protective film is equivalent to the compressive stress Fc applied to the first branch part by the protective film because the first branch part is the extension part of the first branch part. Namely, the first branch part of the pad with the protective film has a pre-pressing stress, so that after the pad is attached to the display screen, the pre-pressing stress of the protective film on the first branch part can increase the peeling force of the first branch part, and the pad is prevented from being glued.

The tolerance of the lamination process of the protective film 30 is generally 0.2mm, referring to s1 and s3 in fig. 3a, when the side edge 301 of the protective film falls between the line s1 and the line s3, including the line s1 and the line s3, the lamination quality of the protective film is considered to be acceptable, as shown in fig. 3 a; when the side edge 301 of the protective film falls outside the line s3, the quality of the fit of the protective film is considered to be unacceptable, as shown in fig. 3 b.

In the present application, in order to easily determine whether or not the protective film is properly attached by visual inspection, as shown in fig. 4, the height H1 of the first sub-branch portion in the third direction is 0 < H1 < 0.2 mm. When H1 is smaller than 0.2mm, the second sub-branch 2022 is inevitably present between the line s1 and the line s3, and the bending boundary line between the second sub-branch 2022 and the first sub-branch 2021 is also inevitably present, so that when the side 301 of the passivation falls between the line s1 and the line s3, the bending boundary line between the second sub-branch 2022 and the first sub-branch 2021 is covered by the passivation; when the side edge 301 of the passivation falls outside the line s3, the bending boundary line between the second sub-branch 2022 and the first sub-branch 2021 is not shielded by the passivation, and the exposed bending position can be visually identified. Therefore, the present application can determine whether the flexible printed circuit board is qualified according to whether the bending boundary line between the second sub-branch portion 2022 and the first sub-branch portion 2021 is exposed.

In order to make the bending position between the second sub-branch 2022 and the first sub-branch 2021 more easily perceived by the viewer, the height H2 of the second sub-branch 2022 in the third direction is H2 ≧ 0.05 mm. If the height H2 of the second sub-branch portion in the third direction is too small, the bending formed between the second sub-branch portion 2022 and the first sub-branch portion 2021 has less obvious bending characteristics, and is not easily distinguished by human eyes. Fig. 5 shows (a) and (b) the bends formed between the second sub-branch 2022 and the first sub-branch 2021 at two different heights, respectively, and it is obvious that (a) the bend formed between the second sub-branch 2022 and the first sub-branch 2021 is more obvious in design.

In order to improve the binding bias to reduce the risk of shallow guiding, the first branch is arranged obliquely, and as shown in fig. 1, the included angle between the first branch and the first direction D1 is 0-90 ° (excluding end point values).

Optionally, the included angle between the first branch portion and the first direction D1 may be different for any two pads. The advantage of design like this lies in, when the fluctuation of pad interval size is great, can reciprocate through the board and compensate pad interval fluctuation to optimize and bind the effect and reduce and bind the off normal risk.

In order to realize module multiplexing in the design stage of the flexible circuit board so as to improve the design efficiency, the inventor of the application proposes that the shape of the second branch part is a regular pattern.

Fig. 6 explains how the flexible circuit board provided by the present application performs module multiplexing in the design stage. Referring to fig. 6, the flexible circuit board 10 further includes traces 40, and the traces 40 are connected to the second sub-branch portion 2022. The traces can be divided into different types according to different signal functions on the traces, such as GND traces and REF traces illustrated in fig. 6, where the same type of traces can be used for module multiplexing according to the design provided by the present application. Taking the design of the GND wiring as an example, in the design process of the flexible circuit board, after the pad is designed, the first GND wiring is designed, because the wiring is connected with the second sub-branch part, and the shape of the second sub-branch part is a regular pattern, therefore, the contact area of the wiring and the pad is a regular area, and the regular area can repeatedly appear on the second sub-branch parts with other shape rules, therefore, other GND wirings can be obtained by copying the existing GND wiring, and the design efficiency is greatly improved. Specifically, as shown in fig. 6, the pads include #1 to #12, where two sets of pads connected to GND are #1 to #2 and #5 to #6, respectively. After the design of the first GND trace connected to the pad groups #1 to #2 is determined, the second GND trace can be obtained by copying the first GND trace.

When the flexible circuit board in the prior art is adopted for design, the second sub-branch part with a regular shape does not exist in the bonding pad, and the included angle between the bonding pad and the first direction is different. Therefore, the contact areas of the traces and the pads are different, which results in different designs of the traces connected to different pads, and thus the design efficiency cannot be improved by the module multiplexing method.

In order to facilitate the connection with the trace, the second sub-branch portion has a perpendicular bisector extending along the third direction. That is to say, the second sub-branch portion has a first side parallel to the first direction, and the second sub-branch portion extends toward the trace in the third direction. The perpendicular bisector of the second sub-branch portion extends along the third direction, so that the geometric center of the second sub-branch portion can be ensured to be positioned on the central line of the wiring, and effective contact between the wiring and the second sub-branch portion is fully ensured.

For example, as shown in fig. 1 to 6, the second sub-branch portion is rectangular, and the rectangle has two first sides parallel to the first direction, so that, as a perpendicular bisector of the first sides, it can be found that the perpendicular bisector of the first sides extends along the third direction. Because the second sub-branch portion has a perpendicular bisector along the third direction, and the routing also extends along the third direction, the design of the application can improve the effective contact area between the second sub-branch portion and the routing, and the electrical connectivity of the routing and the bonding pad is enhanced.

Alternatively, as shown in fig. 4, the length D of the first side is equal to the length C of the first leg in the first direction.

Alternatively, as shown in fig. 7, the second sub-branch portion is shaped as an isosceles triangle.

Alternatively, as shown in fig. 8, the second sub-branch portion is shaped as an isosceles trapezoid.

On the premise of ensuring a higher effective contact area, in order to avoid the influence of local tip static electricity on the pad and the trace, the shape of the second sub-branch portion may be designed to be an arc shape as shown in fig. 9. Arc ofRadius r of the shape is (4B)²+C²) and/8B, wherein B is the maximum height perpendicular to the first side edge on the second branch part, and C is the length of the first branch part along the first direction.

When the second branch portion is in an arc-shaped structure as shown in fig. 9, in order to make the bending position between the second branch portion 2022 and the first branch portion 2021 more easily perceived by an observer, the maximum height B of the second branch portion perpendicular to the first side is greater than or equal to 0.05 mm.

Fig. 10 is a schematic structural diagram of a display device provided in an embodiment of the present application, and the display device 001 includes the flexible printed circuit board 1 described above. The display device can be any electronic equipment with a display function, such as a mobile phone, a tablet computer, a notebook computer, an electronic paper book or a television.

Because the display device provided by the embodiment of the invention comprises the flexible printed circuit board, by adopting the display device, the second branch part is arranged below the first branch part of the bonding pad and comprises two sub-branch parts which are oppositely bent, and the protective film is attached by taking the bending boundary line at the bending position as the alignment mark, so that the attachment precision of the protective film is improved, the size of the bonding pad is optimized, and the binding effect is improved. Simultaneously, can directly judge whether qualified through the outward appearance display device, need not to judge through the measurement size, improve detection efficiency.

It should be noted that the number and size of the bonding pads shown in the drawings of the present application are only used for illustrating the inventive concept, and do not constitute a limitation on the actual number and size of the bonding pads; the proportional relationship between the first branch portion and the second branch portion shown in the drawings of the present application is only used for illustrating the invention point, and does not constitute a limitation on the actual proportional relationship between the first branch portion and the second branch portion. The foregoing is a more detailed description of the invention in connection with specific preferred embodiments and it is not intended that the invention be limited to these specific details. For those skilled in the art to which the invention pertains, several simple deductions or substitutions can be made without departing from the spirit of the invention, and all shall be considered as belonging to the protection scope of the invention.

Claims

1. A flexible printed circuit board, comprising:

2. The flexible printed circuit board according to claim 1, wherein the second direction is an extending direction of the first branch portion.

3. The flexible printed circuit board of claim 2, wherein the angle between the second direction and the first direction is between 0 ° and 90 °, inclusive.

4. The flexible printed circuit board of claim 1, wherein the second sub-branch is shaped in a regular pattern and has a perpendicular bisector extending along the third direction.

5. The flexible printed circuit board of claim 4, wherein the second sub-branch portion includes a first side extending along the first direction, and a length of the first side is equal to a length of the first branch portion in the first direction.

6. The flexible printed circuit board according to claim 5, wherein the second sub-branch portion has a shape of any one of a rectangle, an isosceles triangle, an isosceles trapezoid, and an arc.

7. The flexible printed circuit board of claim 6, wherein the radius r of the arc is (4B)²+C²) and/8B, wherein B is the maximum height perpendicular to the first side edge on the second branch part, and C is the length of the first branch part along the first direction.

8. The flexible printed circuit board of claim 1, wherein the first sub-branch has a height H1, 0 < H1 < 0.2mm in the third direction.

9. The flexible printed circuit board of claim 1, wherein the second sub-branch has a height H2 in the third direction, H2 ≧ 0.05 mm.

10. The flexible printed circuit board of claim 1, further comprising a protective film, a projection of the protective film in the substrate plane covering a projection of the second branch in the substrate plane.

11. A display device characterized by comprising the flexible printed circuit board according to any one of claims 1 to 10.