WO2024120485A1

WO2024120485A1 - Flexible circuit board, chip-on-film packaging structure, and display apparatus

Info

Publication number: WO2024120485A1
Application number: PCT/CN2023/137116
Authority: WO
Inventors: 蔡文娟
Original assignee: 颀中科技（苏州）有限公司; 合肥颀中科技股份有限公司
Priority date: 2022-12-09
Filing date: 2023-12-07
Publication date: 2024-06-13
Also published as: CN116095952A

Abstract

Disclosed in the present invention are a flexible circuit board, a chip-on-film packaging structure, and a display apparatus. The flexible circuit board comprises a chip bonding area, a first outer bonding area, a second outer bonding area, a second outer lead and a first outer lead, wherein the first outer bonding area is provided with a first edge and a second edge, the first outer lead comprises an upper outer pin extending in the first edge, and the second outer lead comprises a lower outer pin extending in the second edge. According to the present invention, more external pins can be arranged.

Description

Flexible circuit board, film-on-chip packaging structure and display device

Technical Field

The present invention relates to the technical field of semiconductor packaging, in particular to a flexible circuit board, a chip-on-film packaging structure and a display device.

Background technique

With the rapid development of electronic technology, all kinds of electronic products are developing towards miniaturization and thinness. At the same time, consumers have higher and higher demands on product performance, which requires the pins of the circuit board and the bumps on the surface of the chip to be set more closely. In comparison, the chip on film (COF) packaging structure uses a flexible circuit board as a chip carrier and bonds the bumps of the chip to the inner pins on the flexible circuit board. It has the characteristics of compact structure, high performance, and flexibility. It can better meet product design requirements and improve chip integration. In recent years, it has received more and more attention from the industry.

Most of the existing flexible circuit boards are arranged in a rectangular shape and include a flexible substrate and a circuit layer arranged on the flexible substrate. The flexible substrate is provided with a chip bonding area, an inner bonding area and an outer bonding area. The outer bonding area includes a first outer bonding area and a second outer bonding area arranged at two opposite edges of the flexible substrate. The chip bonding area is used to load the chip. The circuit layer includes a first outer lead extending between the chip bonding area and the first outer bonding area, and a second outer lead extending between the chip bonding area and the second outer bonding area. Part of the outer leads extend in the chip bonding area to form inner pins for bonding with the chip, and part of the outer leads extend in the first outer bonding area or the second outer bonding area to form outer pins. The outer pins are used to bond with external devices.

With the demand for high-definition screen display and high refresh rate, as well as the trend of chip miniaturization and high functional integration, the number of external pins on the flexible substrate has also increased significantly. Since the external bonding area of the flexible circuit board in the prior art is generally set at the edge of the long side of the rectangular flexible substrate, all the external pins are arranged in parallel along the long side of the flexible substrate. When the number of external pins increases, it is necessary to reduce the line spacing or increase the size of the flexible substrate. These methods not only increase the cost and difficulty of the flexible circuit board manufacturers, but also put forward higher space requirements for the structure design of the terminal panel factory.

In view of this, it is necessary to design a flexible circuit board that can accommodate more external pins.

Summary of the invention

The purpose of the present invention is to provide a flexible circuit board to solve the deficiencies in the prior art. It can form two rows of external pins in the area of the external bonding area, and can arrange more external pins, so that more pins can be accommodated without changing the pin thickness and the size of the flexible substrate, thereby improving the performance of the chip; in addition, it can increase the pin width and spacing without changing the number of external pins and the size of the flexible substrate, thereby reducing the process difficulty of the manufacturer of the flexible circuit board.

The present invention provides a flexible circuit board, comprising: a flexible substrate and a circuit layer arranged on the flexible substrate, wherein a chip bonding area, a first external bonding area and a second external bonding area are arranged on the flexible substrate; the circuit layer comprises a second external lead extending between the chip bonding area and the second external bonding area and a first external lead extending between the chip bonding area and the first external bonding area; the first external bonding area is arranged at a position inside the flexible substrate away from the edge of the flexible substrate;

The first external bonding area has a first edge and a second edge, and the first external leads include a plurality of upper external leads extending between the first edge and the chip bonding area and a plurality of lower external leads extending between the second edge and the chip bonding area;

The first external lead includes an upper external pin extending inside the first edge, and the second external lead includes a lower external pin extending inside the second edge.

Furthermore, the first edge and the second edge are arranged on opposite sides of the first outer bonding area.

Furthermore, the first outer bonding area is rectangular and has a pair of long sides and a pair of short sides, and the first edge and the second edge are arranged at edge positions close to the long sides.

Furthermore, the flexible substrate is rectangular and has a length direction and a width direction, and the first external bonding area is extended along the length direction of the flexible substrate; in the length direction, the size of the first external bonding area is smaller than the size of the flexible substrate to form a wiring space between the first external bonding area and the wide side of the flexible substrate.

Furthermore, the chip bonding area is also rectangular and is extended along the length direction of the flexible substrate, and the chip bonding area is arranged in parallel with the first external bonding area.

Furthermore, in the length direction, the chip bonding area and the first external bonding area are both arranged at the center of the flexible substrate; and two wiring spaces formed between the first external bonding area and the two wide sides of the flexible substrate are symmetrically arranged on both sides of the first external bonding area.

Furthermore, the second external bonding area is arranged at an edge position close to the long side of the flexible substrate, the chip bonding area is located between the first external bonding area and the second external bonding area, and the chip bonding area is arranged at a position relatively close to the first external bonding area.

Furthermore, the second external bonding area is arranged at the edge of the flexible substrate and is located near the edge of the long side of the flexible substrate. The second external lead includes a second external pin extending in the second external bonding area. A plurality of the second external pins are arranged in parallel on the flexible substrate.

Another embodiment of the present invention further discloses a flip chip packaging structure including the flexible circuit board and a chip, wherein the chip is arranged in the chip bonding area, and a side of the chip facing the flexible circuit board is provided with a plurality of metal bumps connected with the second external lead and the first external lead.

Another embodiment of the present invention further discloses a display device, comprising: a display screen and a film-on-chip packaging structure, wherein the film-on-chip packaging structure comprises the flexible circuit board and the chip, wherein the chip is arranged in the chip bonding area, and a plurality of metal bumps engaged with the second external lead and the first external lead are provided on the side of the chip facing the flexible circuit board; the upper external pin and the lower external pin are electrically connected to the display screen.

Compared with the prior art, the first external bonding area is arranged inside the flexible substrate in this embodiment of the present invention, so that multiple edges of the first external bonding area can be provided with external pins. Compared with the prior art in which the first external bonding area is arranged at the edge, the first external bonding area is arranged inside so that the edges on both sides of the first external bonding area can be provided with external pins, so that the area of the first external bonding area is formed with two rows of external pins, and more external pins can be arranged, so that more pins can be accommodated without changing the pin thickness and the size of the flexible substrate, thereby improving the performance of the chip. The embodiment of the present invention can increase the width and spacing of the external pins in the area of the external bonding area, so that the pin width and spacing can be increased without changing the number of pins and the size of the flexible substrate, thereby reducing the process difficulty of the manufacturer of the flexible circuit board; in addition, since the first external bonding area is arranged inside the flexible substrate, away from the edge of the flexible substrate, it can avoid direct contact between the punching tool and the external pins in the punching process, thereby reducing the metal debris generated by punching, and further reducing the risk of short circuit of the substrate caused by metal debris.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG1 is a schematic diagram of the structure of a flexible circuit board in the prior art;

FIG2 is a schematic diagram of a structure of a chip-on-film packaging structure in the prior art;

FIG3 is a schematic diagram of the structure of a flexible circuit board disclosed in an embodiment of the present invention;

FIG4 is a schematic structural diagram of a chip-on-film packaging structure disclosed in an embodiment of the present invention;

Explanation of the accompanying drawings: 1-flexible substrate, 11-chip bonding area, 12-second external bonding area, 13-first external bonding area, 131-first edge, 132-second edge, 2-circuit layer, 21-second external lead, 211-second external pin, 22-first external lead, 221-first external pin, 222-first inner pin, 223-upper external lead, 224-lower external lead, 3-protective layer, 100-chip, 101-metal bump.

Detailed ways

The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, but should not be construed as limiting the present invention.

Embodiments of the present invention: As shown in FIG1-2, a flexible circuit board is disclosed, which forms a chip-on-film packaging structure after being combined with a chip. The formed chip-on-film packaging structure can be used in display devices such as liquid crystal display (LCD) and organic light-emitting diode (OLED). The flexible circuit board is provided with external pins for connecting to the display device.

With the demand for high-definition screen display and high refresh rate, and the trend of chip miniaturization and high functional integration, the performance requirements for chips will also increase, and accordingly, the number of external pins on the flexible substrate will also increase significantly.

As shown in FIG. 1 , the prior art generally includes a flexible substrate 1 and a circuit layer 2 disposed on the flexible substrate 1. The flexible substrate 1 has a rectangular structure. The flexible substrate 1 is provided with a chip bonding area 11, a second external bonding area 12 and a first external bonding area 13. The second external bonding area 12 and the first external bonding area 13 are relatively disposed on opposite sides of the flexible substrate 1. The second external bonding area 12 and the first external bonding area 13 are generally disposed along the long side direction of the rectangular flexible substrate 1. The circuit layer 2 includes a second external lead 21 extending between the second external bonding area 12 and the chip bonding area 11 and a first external lead 22 extending between the first external bonding area 13 and the chip bonding area 11. A plurality of the second external lead 21 and the first external lead 22 are provided.

The first external lead 22 extends to the first external bonding area 13 to form a first external pin 221, and the first external lead 22 extends to the chip bonding area 11 to form a first internal pin 222. Accordingly, there are multiple first internal pins 222, and there are multiple first external pins 221. In the prior art, a plurality of first external pins 221 are generally arranged in parallel in the first external bonding area 13. Since the first external bonding area 13 is arranged at the edge of the flexible substrate 1, the plurality of first external pins 221 are actually also arranged in parallel at the edge of the flexible substrate 1.

As the requirements for chip performance increase, the number of first external pins 221 that need to improve transmission efficiency will continue to increase. Correspondingly, the number of first external leads 22 also increases accordingly. How to accommodate the increased number of first external pins 221 is a problem that needs to be solved. In the prior art, the size of the first external pins 221 is generally chosen to be thinner, so that more first external pins 221 can be placed while the size of the flexible substrate 1 remains unchanged. In addition, the size of the flexible substrate 1 can be increased to achieve the arrangement of more first external pins 221. Both of the above methods increase the manufacturing difficulty of manufacturers and also increase production costs. At the same time, they also put forward higher space requirements for the mechanism design of the terminal panel factory.

In this regard, the flexible circuit board proposed in the present invention is shown in Figure 3, including a flexible substrate 1 and a circuit layer 2 arranged on the flexible substrate 1, the flexible substrate 1 is provided with a chip bonding area 11, a second external bonding area 12 and a first external bonding area 13 for loading the chip, and the circuit layer 2 includes a second external lead 21 extending between the chip bonding area 11 and the second external bonding area 12 and a first external lead 22 extending between the chip bonding area 11 and the first external bonding area 13; the position of the chip bonding area 11 is used to load the chip during the thin film flip chip packaging, the first external bonding area 13 is used to electrically connect with the customer product, and the second external bonding area 12 is used to connect with other devices.

In this embodiment, the first external bonding area 13 is arranged inside the flexible substrate 1 at a position away from the edge of the flexible substrate 1; in the prior art, the first external bonding area 13 is generally arranged at the edge of the flexible substrate 1, and the first external bonding area 13 of the scheme disclosed in this embodiment is arranged in the middle of the inside of the flexible substrate 1, and the first external bonding area 13 is spaced a certain distance from each edge of the flexible substrate 1.

The first external bonding area 13 has a first edge 131 and a second edge 132, and the first external leads 22 include a plurality of upper external leads 223 extending between the first edge 131 and the chip bonding area 11 and a plurality of lower external leads 224 extending between the second edge 132 and the chip bonding area 11;

The upper external lead 223 includes an upper external pin extending in the first edge 131, and the lower external lead 224 includes a lower external pin extending in the second edge 132. Since there are multiple upper external leads 223, there are also multiple lower external leads 224, and there are multiple upper external pins and multiple lower external pins, multiple upper external pins are arranged in parallel on the first edge 131, and multiple lower external pins are arranged in parallel on the second edge 132.

It should be noted that in this embodiment, the upper external pin may be a part of the upper external lead 223 itself, or a conductive part disposed on the upper external lead 223 and electrically connected to the upper external lead 223. Correspondingly, the lower external pin may be a part of the lower external lead 224 itself, or a conductive part disposed on the lower external lead 224 and electrically connected to the lower external lead 224.

In this embodiment, the first external bonding area 13 is arranged inside the flexible substrate 1, so that multiple edges of the first external bonding area 13 can be provided with external pins. Compared with the prior art in which the first external bonding area 13 is arranged at the edge, the corresponding external pins can only be arranged in a row on the first external bonding area 13, and the number of external pins is limited. The first external bonding area 13 is arranged inside so that the edges on both sides of the first external bonding area 13 are provided with external pins, so that the area of the first external bonding area 13 is formed with two rows of external pins, and more external pins can be arranged, so that more pins can be accommodated without changing the pin thickness and the size of the flexible substrate 1, thereby improving the performance of the chip.

In addition, since the first external bonding area 13 is arranged inside the flexible substrate, the position away from the edge can completely avoid direct contact between the punching tool and the external pins during the terminal panel punching process, reduce metal debris generated by punching, and thus reduce the risk of short circuit caused by metal debris on the panel.

It should be noted that, in this embodiment, since the arrangement of the pins on the first external bonding area 13 is changed, the plug-in portion electrically connected to the external pins of the first external bonding area 13 also needs to be modified accordingly.

Since the first external bonding area 13 is arranged near the center of the flexible substrate 1, there is space between the first external bonding area 13 and each edge of the flexible substrate 1, and these spaces can be used to arrange the first external leads 22, so that the first external leads 22 can be arranged around each edge of the first external bonding area 13, thereby forming corresponding pins at each edge. The position where the external pins are arranged can be widened, thereby increasing the number of external pins arranged.

Therefore, in this embodiment, only the first edge 131 and the second edge 132 are defined. Of course, the first external bonding area 13 can also have a third edge and a fourth edge. External leads are set on each edge, and only the corresponding first external leads need to be adjusted.

In order to better arrange the first external pins 22 , the first edge 131 and the second edge 132 are disposed on opposite sides of the first external bonding area 13 , and the first edge 131 and the second edge 132 are disposed opposite to each other.

In the present embodiment, the first external bonding area 13 is rectangular and has a pair of long sides and a pair of short sides, and the first edge 131 and the second edge 132 are arranged at edge positions close to the long sides. The first edge 131 and the second edge 132 are both located at the long side positions of the rectangular first external bonding area 13, so that the space can be better utilized, thereby arranging more external pins. In the present embodiment, the first edge 131 and the second edge 132 are actually two areas arranged in parallel, and the external pins are arranged in two rows in parallel after these two areas are arranged, thereby widening the arrangement area of the external pins. Of course, in other embodiments, the first edge 131 and the second edge 132 can also be arranged to be non-parallel, and the first external bonding area 13 can also be arranged to other irregular shapes.

That is, the first outer bonding area 13 can also be in other shapes such as oval or circular, and the corresponding first edge and second edge can be two opposite edge positions of the circular or oval shape. However, the first outer bonding area 13 of rectangular structure can be more convenient to design and manufacture.

In this embodiment, the flexible substrate 1 is rectangular and has a length direction and a width direction, the first external bonding area 13 is also rectangular, and the first external bonding area 13 is extended along the length direction of the flexible substrate 1; in the length direction, the size of the first external bonding area 13 is smaller than the size of the flexible substrate 1, so as to form a wiring space between the first external bonding area 13 and the wide side of the flexible substrate 1. It can be understood that in other embodiments, the shape of the flexible substrate 1 can also be other shapes and is not limited to a rectangle.

The extension direction of the first external bonding area 13 is actually consistent with the extension direction of the flexible substrate 1 . Such a structural arrangement can better utilize the space of the flexible substrate 1 , thereby achieving a better arrangement of the first external leads 22 .

In other embodiments, the first external bonding area 13 may also be extended along the width direction of the flexible substrate 1 , extending obliquely on the flexible substrate 1 .

The wiring space is actually the area between the wide side of the first external bonding area 13 and the wide side of the flexible substrate 1. This area is used for the arrangement of the first external lead 22. The first external lead 22 is arranged through the wiring space to the side of the first external bonding area 13 away from the chip bonding area 11 to form an external pin on an edge of the first external bonding area 13 away from the chip bonding area 11.

In a specific embodiment, the first edge 131 is disposed at a position of the first external bonding area 13 away from the chip bonding area 11, and the second edge 132 is disposed at an edge of the first external bonding area 13 close to the chip bonding area 11. Therefore, the upper external lead 223 is arranged in the wiring space from the chip bonding area 11, and then is wound through the wiring space to the first edge 131 to form an upper external pin.

Furthermore, the chip bonding area 11 is also rectangular and is extended along the length direction of the flexible substrate 1 . The chip bonding area 11 is arranged parallel to the first external bonding area 13 .

The parallel arrangement of the chip bonding area 11 and the first external bonding area 13 enables the second edge 132 to be better connected to the chip bonding area 11 through the lower external lead 224. The lower external lead 224 can be connected between the chip bonding area 11 and the first external bonding area 13 via the shortest path, reducing the difficulty of arranging the lower external lead 224.

In the length direction, the chip bonding area 11 and the first external bonding area 13 are both arranged at the center of the flexible substrate 1; the two wiring spaces formed between the first external bonding area 13 and the two wide sides of the flexible substrate 1 are symmetrically arranged on both sides of the first external bonding area 13.

The chip bonding area 11 and the first external bonding area 13 are arranged in the middle position in the length direction of the flexible substrate 1, so that the first external lead 22 connected between the first external bonding area 13 and the chip bonding area 11 can be arranged symmetrically, thereby making the wiring more neat and reducing the difficulty of wiring. It is understandable that the first external bonding area 13 and the chip bonding area 11 can be arranged at a position deviated from the middle.

The second external bonding area 12 is arranged at an edge position close to the long side of the flexible substrate 1, the chip bonding area 11 is located between the first external bonding area 13 and the second external bonding area 12, and the first external bonding area 13 is arranged at a position relatively close to the chip bonding area 11, and the chip bonding area 11 is relatively closer to the first external bonding area 13.

Setting the first external bonding area 13 near the chip bonding area 11 can effectively shorten the linear space between the first external bonding area 13 and the chip bonding area 11, and can reduce the bending space reserved for the flexible circuit board on the panel during use, leaving space for other components of the panel.

The second external bonding area 12 is arranged at the edge of the flexible substrate 1 and is located near the edge of the long side of the flexible substrate 1. The second external lead 21 includes a second external pin 211 extending into the second external bonding area 12. A plurality of the second external pins 211 are arranged in parallel on the flexible substrate 1.

It should be noted that in this embodiment, the flexible substrate 1 is configured as a flexible insulating film, such as a polyimide (PI) film; the circuit layer 2 is mainly made of metal copper or copper alloy, and can be obtained by wet etching or electroplating with a predetermined chemical agent. A protective layer 3 is also provided outside the circuit layer 2, and the circuit layer 2 is provided between the protective layer 3 and the flexible substrate 1.

The protective layer 3 is generally made of moisture-proof paint with good waterproofness and corrosion resistance to protect the circuit layer 2 and improve the reliability and electrical stability of the flexible circuit board. The color of the moisture-proof paint can be selected according to different product specifications.

As shown in FIG. 4 , another embodiment of the present invention further discloses a flip chip packaging structure, including the flexible circuit board and the chip 100, wherein the chip 100 is arranged in the chip bonding area 11, and a plurality of metal bumps 101 connected with the second external lead 21 and the first external lead 22 are provided on the side of the chip 100 facing the flexible circuit board.

Another embodiment of the present invention further discloses a display device, comprising: a display screen and a flip-chip packaging structure, wherein the flip-chip packaging structure comprises the flexible circuit board and the chip 100, wherein the chip 100 is arranged in the chip bonding area 11, and a plurality of metal bumps 101 engaged with the second external leads 21 and the first external leads 22 are provided on the side of the chip 100 facing the flexible circuit board; the upper external pins and the lower external pins are electrically connected to the display screen respectively.

The above describes in detail the structure, features and effects of the present invention based on the embodiments shown in the drawings. The above is only a preferred embodiment of the present invention, but the present invention is not limited to the scope of implementation shown in the drawings. Any changes made according to the concept of the present invention, or modified into equivalent embodiments with equivalent changes, which still do not exceed the spirit covered by the description and the drawings, should be within the protection scope of the present invention.

Claims

A flexible circuit board, characterized in that it comprises: a flexible substrate and a circuit layer arranged on the flexible substrate, wherein a chip bonding area, a first external bonding area and a second external bonding area are arranged on the flexible substrate; the circuit layer comprises a second external lead extending between the chip bonding area and the second external bonding area and a first external lead extending between the chip bonding area and the first external bonding area; the first external bonding area is arranged at a position inside the flexible substrate away from the edge of the flexible substrate;

The first external bonding area has a first edge and a second edge, and the first external leads include a plurality of upper external leads extending between the first edge and the chip bonding area and a plurality of lower external leads extending between the second edge and the chip bonding area;

The first external lead includes an upper external pin extending inside the first edge, and the second external lead includes a lower external pin extending inside the second edge.
The flexible circuit board according to claim 1, wherein the first edge and the second edge are arranged on opposite sides of the first outer bonding area.
The flexible circuit board according to claim 2, characterized in that: the first external bonding area is rectangular and has a pair of long sides and a pair of short sides, and the first edge and the second edge are arranged at edge positions close to the long sides.
The flexible circuit board according to claim 3 is characterized in that: the flexible substrate is rectangular and has a length direction and a width direction, and the first external bonding area is extended along the length direction of the flexible substrate; in the length direction, the size of the first external bonding area is smaller than the size of the flexible substrate to form a wiring space between the first external bonding area and the wide side of the flexible substrate.
The flexible circuit board according to claim 4 is characterized in that: the chip bonding area is also rectangular and extends along the length direction of the flexible substrate, and the chip bonding area is arranged parallel to the first external bonding area.
The flexible circuit board according to claim 5 is characterized in that: in the length direction, the chip bonding area and the first external bonding area are both arranged at the center position of the flexible substrate; and the two wiring spaces formed between the first external bonding area and the two wide sides of the flexible substrate are symmetrically arranged on both sides of the first external bonding area.
The flexible circuit board according to claim 6 is characterized in that: the second external bonding area is arranged at an edge position close to the long side of the flexible substrate, the chip bonding area is located between the first external bonding area and the second external bonding area, and the chip bonding area is arranged at a position relatively close to the first external bonding area.
The flexible circuit board according to claim 1 is characterized in that: the second external bonding area is arranged at the edge of the flexible substrate and is located near the edge of the long side of the flexible substrate, the second external lead includes a second external pin extending in the second external bonding area, and a plurality of the second external pins are arranged in parallel on the flexible substrate.
A film flip chip packaging structure, characterized in that it includes the flexible circuit board and chip as described in claim 1, the chip is arranged in the chip bonding area, and the side of the chip facing the flexible circuit board is provided with a plurality of metal bumps connected with the second external lead and the first external lead.
A display device, characterized in that it comprises: a display screen and a film chip packaging structure, the film chip packaging structure comprises the flexible circuit board and the chip as described in claim 1, the chip is arranged in the chip bonding area, and the side of the chip facing the flexible circuit board is provided with a plurality of metal bumps connected with the second external lead and the first external lead; the upper external pin and the lower external pin are electrically connected to the display screen respectively.