Flexible circuit board, thin film flip chip packaging structure and display device

Abstract

The application discloses a flexible circuit board, a film chip package structure and a display device. The flexible circuit board comprises a flexible substrate and a circuit layer arranged on the flexible substrate. The flexible substrate is provided with a chip bonding area, a first outer bonding area and a second outer bonding area. The circuit layer comprises a second outer lead wire extending between the chip bonding area and the second outer bonding area and a first outer lead wire extending between the chip bonding area and the first outer bonding area. The first outer bonding area is arranged inside the flexible substrate. The first outer bonding area has a first edge and a second edge. The first outer lead wire comprises an upper outer lead wire and a lower outer lead wire. The first outer lead wire comprises an upper outer lead pin extending in the first edge. The second outer lead wire comprises a lower outer lead pin extending in the second edge. The application can form two rows of outer lead pins in the area of the first outer bonding area, and more outer lead pins can be arranged.

Description

Technical Field

[0001] This invention relates to the field of semiconductor packaging technology, and in particular to flexible circuit boards, thin-film flip-chip packaging structures, and display devices. Background Technology

[0002] With the rapid development of electronic technology, various electronic products are trending towards miniaturization and thinner designs. Simultaneously, consumers are demanding increasingly higher product performance, requiring more compact pin configurations on circuit boards and on chip surfaces. In contrast, chip-on-film (COF) packaging uses a flexible circuit board as the chip carrier, bonding the chip's bumps to the internal pins on the flexible circuit board. It features a compact structure, high performance, and flexibility, better meeting product design requirements and improving chip integration, and has received increasing attention from the industry in recent years.

[0003] Most existing flexible circuit boards are rectangular in shape and include a flexible substrate and a circuit layer disposed on the flexible substrate. The flexible substrate has 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 disposed on two opposite edges of the flexible substrate. The chip bonding area is used to load a 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 lead extends into the chip bonding area to form an inner pin for bonding with the chip, and part of the outer lead extends into the first outer bonding area or the second outer bonding area to form an outer pin. The outer pin is used to bond with an external device.

[0004] With the increasing demand for high-definition displays and high refresh rates, as well as the trend towards chip miniaturization and high functional integration, the number of external pins on flexible circuit boards has also increased significantly. Since the external bonding area of ​​existing flexible circuit boards is generally located at the edge of the long side of a rectangular flexible circuit board, with all external pins arranged side-by-side along the long side, increasing the number of external pins requires either reducing the line spacing or increasing the size of the flexible circuit board. These methods not only increase the cost and difficulty for flexible circuit board manufacturers but also place higher space requirements on the structural design of terminal panel manufacturers.

[0005] Therefore, it is necessary to design a flexible circuit board that can accommodate more external pins. Summary of the Invention

[0006] The purpose of this invention is to provide a flexible circuit board that overcomes the shortcomings of the prior art. It enables the outer bonding area to form two rows of external pins, allowing for the arrangement of more external pins. This allows for the accommodation of more pins without changing the pin thickness or the size of the flexible substrate, thereby improving chip performance. Furthermore, it can increase the pin width and spacing without changing the number of external pins or the size of the flexible substrate, reducing the manufacturing difficulty for flexible circuit board manufacturers.

[0007] The present invention provides a flexible circuit board, comprising: a flexible substrate and a circuit layer disposed on the flexible substrate. The flexible substrate is provided with a chip bonding region, a first external bonding region and a second external bonding region. The circuit layer includes a second external lead extending between the chip bonding region and the second external bonding region and a first external lead extending between the chip bonding region and the first external bonding region. The first external bonding region is disposed inside the flexible substrate at a position away from the edge of the flexible substrate.

[0008] The first external bonding area has a first edge and a second edge, and the first external lead includes 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.

[0009] The first outer lead includes an upper outer pin extending within the first edge, and the second outer lead includes a lower outer pin extending within the second edge.

[0010] Furthermore, the first edge and the second edge are disposed on opposite sides of the first outer bonding area.

[0011] Furthermore, the first outer bonding area is rectangular and has a pair of long sides and a pair of short sides, with the first edge and the second edge positioned near the edge of the long side.

[0012] Furthermore, the flexible substrate is rectangular and has a length direction and a width direction, and the first outer bonding area extends along the length direction of the flexible substrate; in the length direction, the size of the first outer bonding area is smaller than the size of the flexible substrate, so as to form a wiring space between the first outer bonding area and the wide side of the flexible substrate.

[0013] Furthermore, the chip bonding area is also rectangular and extends along the length of the flexible substrate, and the chip bonding area is arranged parallel to the first outer bonding area.

[0014] Furthermore, in the length direction, both the chip bonding area and the first external bonding area are located at the center of the flexible substrate; 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.

[0015] Furthermore, the second outer bonding area is located at the edge near the long side of the flexible substrate, the chip bonding area is located between the first outer bonding area and the second outer bonding area, and the chip structure area is located relatively close to the first outer bonding area.

[0016] Furthermore, the second outer bonding area is disposed at the edge of the flexible substrate and located near the long side of the flexible substrate, and the second outer lead includes a second outer pin extending within the second outer bonding area, and a plurality of the second outer pins are arranged side by side on the flexible substrate.

[0017] Another embodiment of the present invention discloses a flip-chip package structure including the aforementioned flexible circuit board and chip, wherein the chip is disposed in the chip bonding area, and the side of the chip facing the flexible circuit board is provided with a plurality of metal bumps that engage with the second external lead and the first external lead.

[0018] Another embodiment of the present invention discloses a display device, including: a display screen and a thin-film flip-chip package structure, wherein the thin-film flip-chip package structure includes the aforementioned flexible circuit board and chip, the chip is disposed in the chip bonding area, and the chip has a plurality of metal bumps on the side facing the flexible circuit board that engage with the second external lead and the first external lead; the first external lead is electrically connected to the display screen.

[0019] Compared to existing technologies, this embodiment of the invention places the first external bonding area inside the flexible substrate, allowing external pins to be placed on multiple edges of the first external bonding area. Compared to existing technologies where the first external bonding area is located at the edge, placing it inside allows external pins to be placed on both opposite edges of the first external bonding area, resulting in two rows of external pins in the first external bonding area. This allows for the arrangement of more external pins, accommodating more pins without changing the pin thickness or the size of the flexible substrate, thus improving chip performance. This embodiment of the invention also increases the width and spacing of the external pins in the external bonding area, increasing pin width and spacing without changing the number of pins or the size of the flexible substrate, reducing the manufacturing difficulty for flexible circuit board manufacturers. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the structure of a flexible circuit board in the prior art;

[0021] Figure 2 This is a schematic diagram of a thin-film flip-chip packaging structure in the prior art;

[0022] Figure 3 This is a schematic diagram of the flexible circuit board structure disclosed in an embodiment of the present invention;

[0023] Figure 4 This is a schematic diagram of the thin-film flip-chip packaging structure disclosed in the embodiments of the present invention;

[0024] Explanation of reference numerals in the attached drawings: 1-Flexible substrate, 11-Chip bonding area, 12-Second outer bonding area, 13-First outer bonding area, 131-First edge, 132-Second edge, 2-Circuit layer, 21-Second outer lead, 211-Second outer pin, 22-First outer lead, 221-First outer pin, 222-First inner pin, 223-Upper outer lead, 224-Lower outer lead, 3-Protective layer, 100-Chip, 101-Metal bump. Detailed Implementation

[0025] The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0026] Embodiments of the present invention: such as Figure 1-2 As shown, a flexible circuit board is disclosed. This flexible circuit board, when combined with a chip, forms a thin-film flip-chip package structure. This thin-film flip-chip package structure can be used in display devices such as liquid crystal displays (LCDs) and organic light-emitting diodes (OLEDs). The flexible circuit board is provided with external pins for connection to the display device.

[0027] With the increasing demand for high-definition displays and high refresh rates, as well as the trend towards chip miniaturization and high functional integration, the performance requirements for chips will also increase. Consequently, the number of external pins on flexible substrates will also increase significantly.

[0028] Existing technologies such as Figure 1 As shown, a flexible circuit board 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 and is provided with a chip bonding region 11, a second external bonding region 12, and a first external bonding region 13. The second external bonding region 12 and the first external bonding region 13 are disposed opposite to each other on opposite sides of the flexible substrate 1, and are generally disposed along the long side of the rectangular flexible substrate 1. The circuit layer 2 includes a second external lead 21 extending between the second external bonding region 12 and the chip bonding region 11 and a second external lead 22 extending between the first external bonding region 13 and the chip bonding region 11. Multiple second external leads 21 and multiple first external leads 22 are provided.

[0029] The first external lead 22 extends into the first external bonding region 13 to form a first external pin 221, and the first external lead 22 extends into the chip bonding region 11 to form a first internal pin 222. Correspondingly, multiple first internal pins 222 and multiple first external pins 221 are also provided. In the prior art, several first external pins 221 are generally arranged side by side in the first external bonding region 13. Since the first external bonding region 13 is located at the edge of the flexible substrate 1, several first external pins 221 are actually arranged side by side at the edge of the flexible substrate 1.

[0030] As the demands on chip performance increase, the number of first external pins 221 required to improve transmission efficiency will continuously increase. Correspondingly, the number of first external leads 22 also increases. How to accommodate the increased number of first external pins 221 is a problem that needs to be solved. In existing technologies, the size of the first external pins 221 is generally reduced, thereby allowing more first external pins 221 to be placed while keeping the size of the flexible substrate 1 unchanged. Alternatively, the size of the flexible substrate 1 can be increased to accommodate more first external pins 221. Both of these methods increase the manufacturing difficulty for manufacturers, increase production costs, and also place higher space requirements on the structural design of terminal panel manufacturers.

[0031] In response, the flexible circuit board proposed in this invention, such as... Figure 3 As shown, the device includes a flexible substrate 1 and a circuit layer 2 disposed on the flexible substrate 1. The flexible substrate 1 is provided with a chip bonding region 11, a second external bonding region 12, and a first external bonding region 13 for loading chips. The circuit layer 2 includes a second external lead 21 extending between the chip bonding region 11 and the second external bonding region 12 and a first external lead 22 extending between the chip bonding region 11 and the first external bonding region 13. The chip bonding region 11 is used to load chips during thin-film flip-chip packaging, the first external bonding region 13 is used for electrical connection with customer products, and the second external bonding region 12 is used for connection with other devices.

[0032] In this embodiment, the first external bonding area 13 is located 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 located at the edge of the flexible substrate 1. In the scheme disclosed in this embodiment, the first external bonding area 13 is located in the middle of the interior of the flexible substrate 1, and the first external bonding area 13 is spaced apart from each edge of the flexible substrate 1.

[0033] The first outer bonding area 13 has a first edge 131 and a second edge 132. The first outer lead 22 includes a plurality of upper outer leads 223 extending between the first edge 131 and the chip bonding area 11 and a plurality of lower outer leads 224 extending between the second edge 132 and the chip bonding area 11.

[0034] The upper outer lead 223 includes an upper outer pin extending within the first edge 131, and the lower outer lead 224 includes a lower outer pin extending within the second edge 132. Since there are multiple upper outer leads 223 and multiple lower outer leads 224, there are correspondingly multiple upper and lower outer pins. Multiple upper outer pins are arranged side by side on the first edge 131, and multiple lower outer pins are arranged side by side on the second edge 132.

[0035] It should be noted that in this embodiment, the upper outer pin can be a part of the upper outer lead 223 itself, or it can be a conductive part disposed on the upper outer lead 223 and electrically connected to the upper outer lead 223. Correspondingly, the lower outer pin can also be a part of the lower outer lead 224 itself, or it can be a conductive part disposed on the lower outer lead 224 and electrically connected to the lower outer lead 224.

[0036] In this embodiment, placing the first external bonding area 13 inside the flexible substrate 1 allows external pins to be placed on multiple edges of the first external bonding area 13. Compared to the prior art where the first external bonding area 13 is placed on the edge, the corresponding external pins can only be arranged in a row side by side on the first external bonding area 13, limiting the number of external pins that can be placed. Placing the first external bonding area 13 inside allows external pins to be placed on both opposite edges of the first external bonding area 13, thus forming two rows of external pins in the area of ​​the first external bonding area 13. This allows for the arrangement of more external pins, accommodating more pins without changing the pin thickness and the size of the flexible substrate 1, thereby improving the chip performance.

[0037] Furthermore, since the first outer bonding area 13 is located inside the flexible substrate, its position away from the edge can completely avoid direct contact between the punching tool and the outer pin during the punching process of the terminal panel, reducing metal debris generated during punching, thereby reducing the risk of short circuits caused by metal debris in the panel.

[0038] It should be noted that, in this embodiment, since the arrangement of the pins on the first external bonding area 13 has been changed, the plug-in part that is electrically connected to the external pins of the first external bonding area 13 also needs to be modified accordingly.

[0039] Since the first external bonding area 13 is located inside the flexible substrate 1 near the center, there is space between the first external bonding area 13 and each edge of the flexible substrate 1. This space can be used to arrange the first external leads 22, allowing the first external leads 22 to be wound around each edge of the first external bonding area 13, thereby forming corresponding pins at each edge. This expands the position of the external pin arrangement, thereby increasing the number of external pins.

[0040] Therefore, this embodiment only defines the first edge 131 and the second edge 132. Of course, the first outer bonding area 13 may also have a third edge and a fourth edge. External pins are set on each edge, and only the corresponding first external leads need to be adjusted.

[0041] In order to better realize the arrangement of the first external pin 22, the first edge 131 and the second edge 132 are arranged on opposite sides of the first external bonding area 13, and the first edge 131 and the second edge 132 are arranged opposite to each other.

[0042] In this embodiment, the first outer bonding area 13 is rectangular with a pair of long sides and a pair of short sides. The first edge 131 and the second edge 132 are located near the edges of the long sides. Both the first edge 131 and the second edge 132 are located along the long sides of the rectangular first outer bonding area 13, which allows for better space utilization and the arrangement of more external pins. In this embodiment, the first edge 131 and the second edge 132 are actually two parallel areas. The external pins are arranged in two parallel rows after being placed in these two areas, thus widening the area for the external pins. Of course, in other embodiments, the first edge 131 and the second edge 132 can also be non-parallel, and the first outer bonding area 13 can also be configured with other irregular shapes.

[0043] That is, the first outer mating area 13 can also be other shapes, such as ellipse or circle, and the corresponding first edge and second edge can be two opposite edges of a circle or ellipse. It's just that the rectangular structure of the first outer mating area 13 is easier to design and manufacture.

[0044] In this embodiment, the flexible substrate 1 is rectangular and has a length direction and a width direction. The first outer bonding area 13 is also rectangular and extends along the length direction of the flexible substrate 1. In the length direction, the size of the first outer bonding area 13 is smaller than the size of the flexible substrate 1, so as to form a wiring space between the first outer bonding area 13 and the wide side of the flexible substrate 1. It is understood that in other embodiments, the shape of the flexible substrate 1 can also be other shapes and is not limited to a rectangle.

[0045] The extension direction of the first outer bonding area 13 is actually consistent with the extension direction of the flexible substrate 1. This structure can make better use of the space of the flexible substrate 1, thereby achieving a better arrangement of the first outer lead 22.

[0046] In other embodiments, the first outer bonding region 13 may also extend along the width direction of the flexible substrate 1, extending obliquely on the flexible substrate 1.

[0047] 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 routed through the wiring space to the side of the first external bonding area 13 away from the chip bonding area 11, so as to form an external pin on one edge of the first external bonding area 13 away from the chip bonding area 11.

[0048] In a specific embodiment, the first edge 131 is located away from the chip bonding area 11 in the first outer bonding area 13, and the second edge 132 is located at the edge of the first outer bonding area 13 close to the chip bonding area 11. Therefore, the upper external lead 223 comes out from the chip bonding area 11 and is arranged in the wiring space, and then winds around the first edge 131 through the wiring space to form the upper external pin.

[0049] Furthermore, the chip bonding area 11 is also rectangular and extends along the length direction of the flexible substrate 1, and the chip bonding area 11 is arranged parallel to the first outer bonding area 13.

[0050] The parallel arrangement of the chip bonding area 11 and the first outer bonding area 13 enables the second edge 132 to be better connected to the chip bonding area 11 through the lower outer lead 224. The lower outer lead 224 can be connected between the chip bonding area 11 and the first outer bonding area 13 with the shortest path, reducing the difficulty of arranging the lower outer lead 224.

[0051] In the length direction, the chip bonding area 11 and the first external bonding area 13 are both located 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.

[0052] By positioning the chip bonding area 11 and the first external bonding area 13 at the midpoint of the flexible substrate 1 along its length, the first external lead 22 connecting the first external bonding area 13 and the chip bonding area 11 can be symmetrically arranged during routing, resulting in neater wiring and reduced wiring difficulty. It is understood that both the first external bonding area 13 and the chip bonding area 11 can be positioned off-center.

[0053] The second outer bonding area 12 is located at the edge near the long side of the flexible substrate 1. The chip bonding area 11 is located between the first outer bonding area 13 and the second outer bonding area 12. The first outer bonding area 13 is located relatively close to the chip bonding area 11, and the chip bonding area 11 is relatively closer to the first outer bonding area 13.

[0054] Setting the first external bonding area 13 close to the chip bonding area 11 can effectively shorten the straight-line space between the first external bonding area 13 and the chip bonding area 11. During use, it can reduce the bending space reserved on the panel for the flexible circuit board, leaving space for other components of the panel.

[0055] The second outer bonding area 12 is disposed at the edge of the flexible substrate 1 and located near the long side of the flexible substrate 1. The second outer lead 21 includes a second outer pin 211 extending within the second outer bonding area 12. A plurality of the second outer pins 211 are arranged side by side on the flexible substrate 1.

[0056] 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 metallic copper or copper alloy, and can be obtained by wet etching or electroplating using predetermined chemical agents. A protective layer 3 is also provided outside the circuit layer 2, and the circuit layer 2 is disposed between the protective layer 3 and the flexible substrate 1.

[0057] The protective layer 3 is generally made of a moisture-proof paint with good waterproof and corrosion-resistant properties 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.

[0058] like Figure 4 As shown, another embodiment of the present invention also discloses a flip-chip package structure, including the flexible circuit board and the chip 100, wherein the chip 100 is disposed in the chip bonding area 11, and the chip 100 is provided with a plurality of metal bumps 101 on the side facing the flexible circuit board, which are engaged with the second external lead 21 and the first external lead 22.

[0059] Another embodiment of the present invention discloses a display device, including: a display screen and a flip-chip package structure, the flip-chip package structure including the aforementioned flexible circuit board and chip 100, the chip 100 being disposed in the chip bonding area 11, and the chip 100 having a plurality of metal bumps 101 on the side facing the flexible circuit board, which engage with the second external lead 21 and the first external lead 22; the first external lead 221 being electrically connected to the display screen.

[0060] The above description, based on the embodiments shown in the figures, details the structure, features, and effects of the present invention. The above description is only a preferred embodiment of the present invention, but the present invention is not limited to the scope of implementation shown in the figures. Any changes made in accordance with the concept of the present invention, or equivalent embodiments modified to have equivalent changes, that do not exceed the spirit covered by the specification and figures, should be within the protection scope of the present invention.

Claims

1. A flexible circuit board, characterized in that, include: A flexible substrate and a circuit layer disposed on the flexible substrate. The flexible substrate has a chip bonding area, a first external bonding area and a second external bonding area. The circuit layer includes 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 disposed inside the flexible substrate at a position away from the edge of the flexible substrate, and there is space between the first external bonding area and each edge of the flexible substrate for arranging the first external lead. The first external bonding area has a first edge and a second edge. The first edge is disposed on the side of the first external bonding area away from the chip bonding area. The first external lead includes 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 upper outer lead includes an upper outer pin extending within the first edge, and the lower outer lead includes a lower outer pin extending within the second edge; The flexible substrate is rectangular and has a length direction and a width direction. The first outer bonding area extends along the length direction of the flexible substrate. In the length direction, the size of the first outer bonding area is smaller than the size of the flexible substrate, so as to form a wiring space between the first outer bonding area and the wide side of the flexible substrate and on the side of the first outer bonding area away from the chip bonding area. The upper outer lead is wound through the wiring space to the side of the first outer bonding area away from the chip bonding area to form the upper outer pin on the first edge.

2. The flexible circuit board according to claim 1, characterized in that: The first edge and the second edge are disposed on opposite sides of the first outer bonding area.

3. The flexible circuit board according to claim 2, characterized in that: The first outer bonding area is rectangular and has a pair of long sides and a pair of short sides, with the first edge and the second edge located near the edge of the long side.

4. The flexible circuit board according to claim 3, characterized in that: The chip bonding area is also rectangular and extends along the length of the flexible substrate, and the chip bonding area is arranged parallel to the first outer bonding area.

5. The flexible circuit board according to claim 4, characterized in that: In the length direction, both the chip bonding area and the first external bonding area are located at the center of the flexible substrate; 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.

6. The flexible circuit board according to claim 5, characterized in that: The second outer bonding area is located at the edge near the long side of the flexible substrate, and the chip bonding area is located between the first outer bonding area and the second outer bonding area, and the chip bonding area is located relatively close to the first outer bonding area.

7. The flexible circuit board according to claim 1, characterized in that: The second outer bonding area is disposed at the edge of the flexible substrate and located near the long side of the flexible substrate. The second outer lead includes a second outer pin extending within the second outer bonding area. A plurality of the second outer pins are arranged side by side on the flexible substrate.

8. A thin-film flip-chip packaging structure, characterized in that: The invention includes a flexible circuit board and a chip as described in any one of claims 1 to 7, wherein the chip is disposed in the chip bonding area, and the chip has a plurality of metal bumps on the side facing the flexible circuit board that engage with the second external lead and the first external lead.

9. A display device, characterized in that, include: The display screen and the thin-film flip-chip package structure include a flexible circuit board and a chip as described in any one of claims 1 to 7, the chip being disposed in the chip bonding area, and the chip having a plurality of metal bumps on the side facing the flexible circuit board that engage with the second external lead and the first external lead; the upper external lead and the lower external lead are electrically connected to the display screen.

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