WO2024043595A1

WO2024043595A1 - Flexible circuit board, cof module, and electronic device including same

Info

Publication number: WO2024043595A1
Application number: PCT/KR2023/012057
Authority: WO
Inventors: 전세미나; 박지효; 채성민
Original assignee: 엘지이노텍 주식회사
Priority date: 2022-08-24
Filing date: 2023-08-14
Publication date: 2024-02-29
Also published as: KR20240028215A

Abstract

A flexible circuit board according to an embodiment comprises: a base material having a first surface and a second surface opposite the first surface; a circuit pattern disposed on the first surface of the base material; and a protective layer on the circuit pattern. The circuit pattern includes a first circuit pattern and a second circuit pattern. The first circuit pattern includes: a first pad portion configured to be electrically connected to a chip; a second pad portion configured to be electrically connected to a printed circuit board; and a first wiring portion connected to the first pad portion and the second pad portion. The second circuit pattern includes: a third pad portion configured to be electrically connected to a chip; a fourth pad portion configured to be electrically connected to a display panel; and a second wiring portion connected to the third pad portion and the fourth pad portion. The first surface of the base material includes: a first bonding region on which the second pad portion is disposed; and a second bonding region on which the fourth pad portion is disposed. A dummy pattern is disposed on the second surface, corresponding to the second bonding region, of the base material.

Description

Flexible circuit boards, COF modules, and electronic devices containing them

The embodiment relates to a flexible circuit board, a COF module, and an electronic device including the same. The flexible circuit board may be a COF flexible circuit board.

Recently, various electronic products are becoming thinner, smaller, and lighter. Accordingly, various researches are being conducted to mount semiconductor chips at high density in narrow areas of electronic products.

COF (Chip On Film) uses a flexible substrate. Accordingly, the COF is applied to flexible displays. That is, the COF method is applied to various wearable electronic devices. Additionally, the COF can implement fine pitch. Therefore, the COF can be applied to high-resolution displays.

The COF is formed by mounting a semiconductor chip on a thin film-shaped flexible circuit board. For example, the semiconductor chip may include an integrated circuit (IC) chip or a large scale integrated circuit (LSI) chip.

Meanwhile, the chip is connected to an external printed circuit board and display panel by a circuit pattern. For example, pad portions are disposed on one end and the other end of the circuit pattern, respectively. Additionally, one pad portion is electrically connected to a terminal of the chip. Additionally, the other pad portion is connected to a terminal of the printed circuit board and a terminal of the display panel. Accordingly, the chip, the printed circuit board, and the display panel are electrically connected through the COF. Additionally, signals are transmitted to the display panel by the circuit pattern.

The COF (Chip On Film) type flexible circuit board is applied to flexible displays. Accordingly, the flexible circuit board is bent in one direction.

When the flexible circuit board is bent, cracks may occur in the circuit pattern located in the bent area. Accordingly, the electrical properties of the flexible circuit board may be reduced.

Therefore, a flexible circuit board with a new structure that can solve the above problems is required.

Embodiments provide a flexible circuit board with improved reliability.

A flexible circuit board according to an embodiment includes a substrate including a first side and a second side opposite the first side; a circuit pattern disposed on the first side of the substrate; and a protective layer on the circuit pattern, wherein the circuit pattern includes a first circuit pattern and a second circuit pattern, wherein the first circuit pattern includes a first pad portion configured to be electrically connected to the chip, a printed circuit board, and A display comprising a second pad portion configured to be electrically connected and a first wiring portion connected to the first pad portion and the second pad portion, wherein the second circuit pattern is configured to be electrically connected to a chip, and a third pad portion configured to be electrically connected to the chip. It includes a fourth pad portion set to be electrically connected to the panel and a second wiring portion connected to the third pad portion and the fourth pad portion, and the first surface of the substrate is a first bonding portion on which the second pad portion is disposed. region and a second bonding area where the fourth pad portion is disposed, wherein the second bonding area

The flexible circuit board according to the embodiment includes a dummy pattern.

In detail, the flexible circuit board according to the embodiment has a circuit pattern disposed on the first side and the dummy pattern is disposed on the second side.

The dummy pattern is partially disposed on the second surface. The dummy pattern is disposed in an area that fully or partially corresponds to the pad portion connected to the display panel.

The flexible circuit board mounts chips to form a COF module. Additionally, the flexible circuit board is bent in one direction. As a result, stress may occur in the flexible circuit board. The stress may be transmitted in the direction of the pad portion.

Accordingly, when the pad portion and the terminal portion of the display panel are bonded, the anti-corrosion layer that prevents corrosion of the pad portion may be peeled off. Additionally, cracks may occur in the pad portion exposed by peeling of the corrosion prevention layer due to stress.

The flexible circuit board according to the embodiment has a dummy pattern disposed on the pad portion or the second surface corresponding to the pad portion and the wiring portion. The dummy pattern can prevent peeling of the corrosion prevention layer. Additionally, cracks in the pad portion can be prevented by the dummy pattern.

Therefore, the flexible circuit board according to the embodiment may have improved bending characteristics and reliability.

1 is a top view of a flexible circuit board according to an embodiment.

Figures 2 and 3 are cross-sectional views taken along area A-A' of Figure 1.

Figure 4 is a cross-sectional view taken along the line B-B' in Figure 1.

FIG. 5 is a cross-sectional view taken along region C-C' of FIG. 1.

FIG. 6 is an enlarged view of the bottom of the flexible circuit board in area D of FIG. 1.

Figure 7 is a cross-sectional view taken along the line E-E' of Figure 6.

FIG. 8 is another enlarged view of the bottom view of the flexible circuit board in area D of FIG. 1.

FIG. 9 is a cross-sectional view taken along area F-F' of FIG. 8.

FIG. 10 is another enlarged view of the bottom view of the flexible circuit board in area D of FIG. 1.

FIG. 11 is a cross-sectional view taken along the line G-G' of FIG. 10.

12 to 14 are another enlarged bottom views of the flexible circuit board in area D of FIG. 1.

Figure 15 is a top view of a COF module according to an embodiment.

Figure 16 is a cross-sectional view showing the connection relationship of a COF module including a flexible printed circuit board according to an embodiment.

17 to 19 are diagrams of electronic devices including a flexible printed circuit board according to an embodiment.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the attached drawings. However, the technical idea of the present invention is not limited to some of the described embodiments, but may be implemented in various different forms, and as long as it is within the scope of the technical idea of the present invention, one or more of the components may be optionally used between the embodiments. It can be used by combining and replacing.

In addition, terms (including technical and scientific terms) used in the embodiments of the present invention, unless explicitly specifically defined and described, are generally understood by those skilled in the art to which the present invention pertains. It can be interpreted as meaning, and the meaning of commonly used terms, such as terms defined in a dictionary, can be interpreted by considering the contextual meaning of the related technology.

Additionally, the terms used in the embodiments of the present invention are for describing the embodiments and are not intended to limit the present invention. In this specification, the singular may also include the plural unless specifically stated in the phrase, and when described as “at least one (or more than one) of A, B, and C,” it can be combined with A, B, and C. It can contain one or more of all possible combinations.

Additionally, when describing the components of an embodiment of the present invention, terms such as first, second, A, B, (a), and (b) may be used. These terms are only used to distinguish the component from other components, and are not limited to the essence, sequence, or order of the component.

And, when a component is described as being 'connected', 'coupled' or 'connected' to another component, the component is not only directly connected, coupled or connected to the other component, but also is connected to the other component. It may also include cases where other components are 'connected', 'coupled', or 'connected' by another component between them.

Additionally, when described as being formed or disposed "above" or "below" each component, "above" or "below" refers not only to cases where two components are in direct contact with each other, but also to one This also includes cases where another component described above is formed or placed between two components.

Additionally, when expressed as “top (above) or bottom (bottom),” it can include the meaning of not only the upward direction but also the downward direction based on one component.

Hereinafter, a flexible circuit board, a COF module, and an electronic device including the same according to an embodiment will be described with reference to the drawings.

1 is a top view of a flexible circuit board according to an embodiment.

Referring to FIG. 1, the flexible circuit board 1000 includes a substrate 100 and a circuit pattern 200 disposed on the substrate 100.

The substrate 100 includes a first side 1S and a second side 2S opposite to the first side 1S.

The substrate 100 may include a flexible substrate. For example, the substrate 100 may be a polyimide (PI) substrate. However, the examples are not limited thereto. The substrate 100 may include polyethylene terephthalate (PET) or polyethylene naphthalate (PEN). Accordingly, the flexible circuit board can be used in various electronic devices. For example, the flexible circuit board has excellent flexibility characteristics. Therefore, the flexible circuit board can be applied to wearable electronic devices.

The substrate 100 may have a thickness of 20㎛ to 100㎛. For example, the substrate 100 may have a thickness of 25 μm to 50 μm. For example, the substrate 100 may have a thickness of 30㎛ to 40㎛. If the thickness of the substrate 100 exceeds 100㎛, the overall thickness of the flexible circuit board may increase. Accordingly, the flexible characteristics of the flexible circuit board are reduced. Additionally, if the thickness of the substrate 100 is less than 20㎛, the strength of the substrate may decrease. Accordingly,. When mounting a chip on the substrate, the substrate 100 may be damaged due to heat and pressure.

The substrate 100 includes an active area (UA) and an unactive area (UA). The effective area (AA) may be the central area of the substrate 100. The uneffective area (UA) may be an edge area of the substrate 100. The unactive area (UA) may surround the effective area (AA).

The effective area (AA) includes the chip mounting area (CA). In detail, the chip mounting area CA is an area where the chip C connected to the circuit pattern is mounted.

Additionally,

circuit patterns

210 and 220 are disposed on the effective area AA. In detail, the circuit pattern includes a plurality of circuit patterns. The plurality of circuit patterns extend in multiple directions. Additionally, the plurality of circuit patterns are spaced apart from each other.

The effective area AA is an area actually used in the flexible circuit board 1000.

The circuit pattern is not disposed in the unactive area (UA). That is, the effective area (AA) and the unactive area (UA) are distinguished by whether or not the circuit pattern is arranged.

The unavailable area (UA) includes a plurality of holes. In detail, the uneffective area (UA) includes a plurality of sprocket holes (H). The flexible circuit board is wound or unwound in a roll-to-roll manner by the sprocket hole.

The unavailable area (UA) is an area that is not actually used in the flexible circuit board 1000. That is, the unavailable area (UA) is an area that is removed after manufacturing the COF module.

In detail, the boundary between the effective area (AA) and the unavailable area (UA) is defined by a cutting line (CL). The flexible circuit board 1000 is processed into a COF module after cutting the cutting line CL. Accordingly, the flexible circuit board 1000 is applied to various electronic devices.

The circuit pattern includes a wiring portion and a pad portion. Additionally, a plurality of circuit patterns are disposed in the effective area AA. In detail, the first circuit pattern 210 and the second circuit pattern 220 are disposed in the effective area AA. The first circuit pattern 210 and the second circuit pattern 220 are disposed on the first surface 1S.

Referring to FIGS. 1 to 3 , the first circuit pattern 210 includes a first wiring portion 211, a first pad portion 212a, and a second pad portion 212b. The first pad portion 212a is disposed inside the chip mounting area CA. The second pad portion 212b is disposed outside the chip mounting area CA. The first wiring portion 211 is disposed between the first pad portion 212a and the second pad portion 212b. The first wiring part 211 is connected to the first pad part 212a and the second pad part 212b.

The first wiring portion 211, the first pad portion 212a, and the second pad portion 212b may be formed integrally.

Additionally, the first wiring unit 211 may extend in the first direction D1 based on the chip mounting area CA.

The first pad portion 212a is electrically connected to the chip disposed in the chip mounting area. Additionally, the second pad portion 212b is electrically connected to the printed circuit board. Additionally, the first wiring unit 211 transmits signals between the chip and the printed circuit board.

A protective layer 300 is disposed on the first circuit pattern 210. In detail, the protective layer 300 is disposed on the first wiring portion 211. The protective layer 300 surrounds the first wiring portion 211. Additionally, the protective layer 300 is not disposed on the first pad portion 212a and the second pad portion 212b. Accordingly, the first pad portion 212a and the second pad portion 212b are exposed to the outside.

Additionally, referring to FIGS. 1 and 4 , the second circuit pattern 220 includes a second wiring portion 221, a third pad portion 222a, and a fourth pad portion 222b. The third pad portion 222a is disposed inside the chip mounting area CA. The fourth pad portion 222b is disposed outside the chip mounting area CA. The second wiring portion 221 is disposed between the third pad portion 222a and the fourth pad portion 222b. The second wiring part 221 is connected to the third pad part 222a and the fourth pad part 222b.

The second wiring portion 221, the third pad portion 222a, and the fourth pad portion 222b may be formed integrally.

Additionally, the second wiring portion 221 may extend in the second direction D2 based on the chip mounting area CA. In detail, the second direction 2D is opposite to the first direction D1.

The third pad portion 222a is electrically connected to the chip disposed in the chip mounting area. Additionally, the fourth pad portion 222b is electrically connected to the display panel. Additionally, the second wiring unit 221 transmits signals between the chip and the display panel.

A protective layer 300 may be disposed on the second circuit pattern 220. In detail, the protective layer 300 is disposed on the second wiring portion 221. The protective layer 300 surrounds the second wiring portion 221. Additionally, the protective layer 300 is not disposed on the third pad portion 222a and the fourth pad portion 222b. Accordingly, the third pad portion 222a and the fourth pad portion 222b are exposed to the outside.

The first circuit pattern 210 and the second circuit pattern 220 may include a metal material. In detail, the first circuit pattern 210 and the second circuit pattern 220 may include copper (Cu). However, the embodiment is not limited thereto. The first circuit pattern 210 and the second circuit pattern 220 are copper (Cu), aluminum (Al), chromium (Cr), nickel (Ni), silver (Ag), and molybdenum (Mo). It may include at least one metal selected from gold (Au), titanium (Ti), and alloys thereof.

Below, the layer structure of the circuit pattern will be described with reference to FIGS. 2 and 3. In FIGS. 2 and 3 , the description will focus on the first circuit pattern 210. However, the embodiment is not limited thereto. Descriptions described in FIGS. 2 and 3 may be equally applied to the second circuit pattern 220 .

Referring to FIG. 2, the first circuit pattern 210 is formed in multiple layers. In detail, the first wiring part 211 and the first pad part 212a include a first metal layer 201 and a second metal layer 202. Also, although not shown in the drawing. The second pad portion 212b also includes the first metal layer 201 and the second metal layer 202.

The first metal layer 201 is a seed layer of the first circuit pattern 210. In detail, the first metal layer 201 is a seed layer formed through electroless plating. The seed layer includes a metal material. For example, the seed layer may include copper.

Additionally, the second metal layer 202 is a plating layer. In detail, the second metal layer 202 is a plating layer formed by electroplating using the first metal layer 201 as a seed layer.

The thickness of the first metal layer 201 is smaller than the thickness of the second metal layer 202.

For example, the thickness of the first metal layer 201 may be 0.7 μm to 2 μm. Additionally, the thickness of the second metal layer 202 may be 10 μm to 25 μm.

The first metal layer 201 and the second metal layer 202 may include the same metal material. For example, the first metal layer 201 and the second metal layer 202 may include copper (Cu).

A bonding layer 203 may be disposed on the second metal layer 201. In detail, the bonding layer 203 is disposed on the side of the first metal layer 201, the side of the second metal layer 202, and the top surface of the second metal layer 202. That is, the bonding layer 203 surrounds the first metal layer 201 and the second metal layer 202.

The bonding layer 203 includes metal. For example, the bonding layer 203 may include tin (Sn).

The thickness of the bonding layer 203 may be 0.3 ㎛ to 0.7 ㎛. As the bonding layer 203 extends from the lower surface to the upper surface, the tin content may increase. The lower surface of the bonding layer 203 is the surface that the second metal layer 202 contacts.

Since the bonding layer 203 and the second metal layer 202 are in contact, the bonding layer 203 extends from the lower surface toward the upper surface, and the tin content increases and the copper content decreases.

Accordingly, only pure tin may remain in the bonding layer 203 in a thickness range of 0.1 ㎛ to 0.3 ㎛ on the upper surface.

By the bonding layer 203, the chip terminal, the printed circuit board terminal, and the display panel terminal are easily bonded to the first pad portion and the second pad portion. In detail, the terminals and the pad portion are joined by heat and pressure. That is, when heat and pressure are applied to the first pad portion and the second pad portion, the upper surface of the bonding layer where pure tin remains is melted. As a result, the terminals and the pad portion are easily joined.

Accordingly, the bonding layer 203 is not separated from the first pad portion 212a, but becomes a part of the first pad portion 212a.

The thickness of the first circuit pattern 210 may be 2㎛ to 25㎛. For example, the thickness of the first circuit pattern 210 may be 5㎛ to 20㎛. For example, the thickness of the first circuit pattern 210 may be 7㎛ to 15㎛.

The thickness of the first circuit pattern 210 may be different from the sum of the thicknesses of the first metal layer 201, the second metal layer 202, and the bonding layer 203. In detail, a flash etching process is performed to separate circuit patterns during the manufacturing process. Accordingly, the first metal layer 201 is etched. Accordingly, the thickness of the finally manufactured first circuit pattern 210 is smaller than the sum of the thicknesses of the first metal layer 201, the second metal layer 202, and the bonding layer 203.

When the thickness of the first circuit pattern 210 and the second circuit pattern 220 is less than 2㎛, the resistance of the first circuit pattern 210 and the second circuit pattern 220 increases. If the thickness of the first circuit pattern 210 and the second circuit pattern 220 exceeds 25㎛, it is difficult to form a fine pattern.

Meanwhile, a buffer layer 205 may be further disposed between the substrate 100 and the first circuit pattern 210. Adhesion between the substrate 100 and the first circuit pattern 210 is improved by the buffer layer 205.

The buffer layer 205 may be formed of multiple layers. In detail, the buffer layer 205 includes a first buffer layer 205a and a second buffer layer 205b on the first buffer layer 205a. Accordingly, the first buffer layer 205a contacts the substrate 100. Additionally, the second buffer layer 205b is in contact with the first circuit pattern 201.

The first buffer layer 205a may include a material that has good adhesion to the substrate 100. For example, the first buffer layer 205a may include nickel (Ni). Additionally, the second buffer layer 205b may include a material that has good adhesion to the first circuit pattern 210. For example, the second buffer layer 205b may include chromium (Cr).

The buffer layer 205 may have a thin film thickness in nanometer units. For example, the thickness of the buffer layer 205 may be 20 nm or less.

Adhesion between the substrate 100 and the first circuit pattern 210 is improved by the buffer layer 205. Accordingly, peeling of the first circuit pattern 201 is prevented.

Meanwhile, referring to FIG. 3, the bonding layer 203 may include a first bonding layer 203a and a second bonding layer 203b.

In detail, the first bonding layer 203a may be disposed on the first wiring portion 211 and the first pad portion 212a. Additionally, although not shown in the drawing, the first bonding layer 203a may also be disposed on the second pad portion 212b. That is, the first bonding layer 203a may be disposed on the first circuit pattern 210.

Additionally, the second bonding layer 203b may be disposed only on the first pad portion 212a and the second pad portion 212b. That is, the layer structure of the first wiring portion 211 and the layer structures of the first pad portion 212a and the second pad portion 212b are changed by the second bonding layer 203b.

The first bonding layer 203a and the second bonding layer 203b may include metal. In detail, the first bonding layer 203a and the second bonding layer 203b may include tin (Sn).

The first bonding layer 203a and the second bonding layer 203b may have different thicknesses. In detail, the thickness of the second bonding layer 203b may be greater than the thickness of the first bonding layer 203a.

For example, the first bonding layer 203a may have a thin film thickness of 0.02 ㎛ to 0.06 ㎛. also. The thickness of the second bonding layer 203b may be 0.2 μm to 0.6 μm.

If the bonding layer is thickly disposed between the protective layer 300 and the first wiring portion 211, cracks may occur when the flexible circuit board is bent. Accordingly, the first bonding layer 231 between the protective layer 300 and the first wiring portion 211 is formed with a thin film thickness. Therefore, it is possible to prevent cracks from occurring when the flexible circuit board is bent.

Additionally, the tin content of the second bonding layer 203b may increase as it extends from the lower surface to the upper surface. The lower surface is a surface in contact with the first bonding layer 203a.

As the second bonding layer 203b extends from the lower surface to the upper surface, the tin content may increase and the copper content may decrease. Accordingly, only pure tin may remain in the upper surface of the second bonding layer 203b in a thickness range of 0.1 μm to 0.3 μm.

The terminals of the chip, the printed circuit board, and the display panel are easily bonded to the first and second pad portions by the second bonding layer 203b. In detail, the terminals and the pad portion are joined by heat and pressure. That is, when heat and pressure are applied to the first pad portion and the second pad portion, the upper surface of the bonding layer where pure tin remains is melted. As a result, the terminals and the pad portion are easily joined.

Accordingly, the first bonding layer 203a and the second bonding layer 203b are not separated from the first pad portion 212a and become a part of the first pad portion.

Meanwhile, the protective layer 300 is disposed on the wiring portion of the first circuit pattern 210 and the wiring portion of the second circuit pattern 220. In detail, the protective layer 300 surrounds the first wiring portion 211 and the second wiring portion 221. That is, the protective layer 300 is disposed on the first circuit pattern 210 and the second circuit pattern 220 excluding the first pad portion, second pad portion, third pad portion, and fourth pad portion. It can be.

The protective layer 300 may include solder paste. For example, the solder paste may include a thermosetting resin, a thermoplastic resin, a filler, a curing agent, or a curing accelerator.

Meanwhile, in the previous description, it was described that the first circuit pattern 210 and the second circuit pattern 220 are disposed on the same surface of the substrate 100, but the embodiment is not limited thereto.

In detail, the first circuit pattern 210 and the second circuit pattern 220 may be disposed on different sides of the substrate 100. For example, the first circuit pattern 210 may be disposed on one side of the substrate 100, and the second circuit pattern 220 may be disposed on the other side opposite to one side of the substrate 100. there is.

Accordingly, the display panel is connected to the chip on one surface of the substrate 100. Additionally, the printed circuit board is connected to the chip on the other side of the substrate 100.

Referring to FIG. 1, the flexible circuit board 1000 includes a first bonding area BA1 and a second bonding area BA2.

The second pad portion 212b is disposed on the first bonding area BA1. Additionally, the fourth pad portion 222b is disposed on the second bonding area BA2. That is, the protective layer 300 is not disposed on the first bonding area BA1 and the second bonding area BA2.

The printed circuit board and the display panel are bonded in the first bonding area BA1 and the second bonding area BA2. In detail, the first bonding area BA1 is bonded to the terminal portion of the printed circuit board through a conductive adhesive. Additionally, the second bonding area BA2 is bonded to the terminal portion of the display panel through a conductive adhesive. At this time, a corrosion prevention layer may be additionally disposed in the area of the second pad part 212b and the fourth pad part 222b in the bonding area where the conductive adhesive is not disposed. The corrosion prevention layer prevents corrosion of the pad part. do.

For example, referring to FIG. 5 , the second bonding area BA2 may include a 2-1 bonding area BA2-1 and a 2-2 bonding area BA2-2. Different materials may be disposed in the 2-1 bonding area BA2-1 and the 2-2 bonding area BA2-2.

The 2-1 bonding area BA2-1 is an area where the conductive adhesive is disposed. Additionally, the 2-2 bonding area BA2-2 is an area where the corrosion prevention layer is disposed. In detail, when connecting the fourth pad portion 222b and the terminal of the display panel, the conductive adhesive is disposed only in a partial area of the fourth pad portion 222b. Accordingly, an area where the fourth pad portion 222b is exposed is generated. The exposed area is defined as the 2-2 bonding area (BA2-2). Accordingly, a corrosion prevention layer is disposed on the 2-2 bonding area BA2-2. Thereby, corrosion of the 2-2 bonding area BA2-2 is prevented.

Meanwhile, the flexible circuit board 1000 is bent in one direction. In detail, the flexible circuit board 1000 is bent in one direction with the folding axis FAX as an axis. Accordingly, the stress generated by the bending is transmitted to the second bonding area. The corrosion prevention layer disposed in the 2-2 bonding area BA2-2 may be peeled off due to the stress. That is, the corrosion prevention layer has a lower adhesive force than the conductive adhesive. Therefore, it may be peeled off from the pad portion due to the stress.

Accordingly, stress is transmitted from the boundary area of the 2-1 bonding area BA2-1 and the 2-2 bonding area BA2-2 to the fourth pad portion. Additionally, cracks may occur in the fourth pad portion corresponding to the boundary area. Accordingly, the reliability of the flexible circuit board may decrease.

Accordingly, the flexible circuit board according to the embodiment solves the above problems by additionally arranging a dummy pattern.

Additionally, the dummy pattern prevents the corrosion prevention layer on the 2-2 bonding area from peeling off.

Referring to FIGS. 6 and 7 , a dummy pattern 400 is disposed on the second surface 2S. The dummy pattern 400 is disposed at a position overlapping with the fourth pad portion 222b. In detail, the dummy pattern 400 partially overlaps the fourth pad portion 222b. The dummy pattern 400 is located in the second bonding area BA2 where the fourth pad portion 222b is disposed. It is placed smaller than the area. For example, the width W1 of the dummy pattern 400 is 50% or more of the width W2 of the two bonding areas BA2. It may be 60% or more or 70% or more. For example, the width W1 of the dummy pattern 400 may be less than 50% to 90% of the width W2 of the second bonding area BA2.

Additionally, the area of the dummy pattern 400 is 50% or more of the area of the second bonding area BA2 or the fourth pad portion 222b. It may be 60% or more or 70% or more. For example, the area of the dummy pattern 400 may be less than 50% to 90% of the area of the second bonding area BA2 or the fourth pad portion 222b.

The total area of the dummy pattern in the second bonding area may be larger than the total area of the fourth pad portion. The fourth pad portion includes a plurality of fourth pad portions spaced apart from each other. The plurality of fourth pad parts are each electrically connected to a terminal part of the display panel. However, the dummy pattern is disposed to prevent cracks in the fourth pad portion. Therefore, even if the spacing between the plurality of dummy patterns is small, the characteristics do not decrease. Additionally, the characteristics do not decrease even when multiple dummy patterns are connected. Alternatively, the dummy pattern may be formed on the entire surface of the second bonding area.

The dummy pattern 400 is arranged to be smaller than the area of the second bonding area BA2 or the fourth pad portion 222b. Accordingly, the difference in intensity between the boundary area of the 2-1 bonding area BA2-1 and the 2-2 bonding area BA2-2 and the 2-1 bonding area BA2-1 is reduced. Additionally, the difference in intensity between the boundary area of the 2-1 bonding area BA2-1 and the 2-2 bonding area BA2-2 and the 2-2 bonding area BA2-2 is reduced. Accordingly, it is possible to prevent the flexible printed circuit board from bending due to the dummy pattern 400.

The dummy pattern 400 is disposed at a position overlapping the 2-1 bonding area BA2-1 and the 2-2 bonding area BA2-2. Additionally, the dummy pattern 400 is disposed on the boundary area BAA of the 2-1 bonding area BA2-1 and the 2-2 bonding area BA2-2.

The adhesion of the conductive adhesive and the corrosion prevention layer disposed on the fourth pad portion 222b can be improved by the dummy pattern 400. That is, since the dummy pattern 400 is disposed in the boundary area (BAA) of the 2-1 bonding area (BA2-1) and the 2-2 bonding area (BA2-2), cracks occur in the fourth pad portion. You can prevent this from happening. Additionally, it is possible to prevent the conductive adhesive and anti-corrosion layer disposed in the 2-1 bonding area (BA2-1) and the 2-2 bonding area (BA2-2) from peeling off. especially. The anti-corrosion layer with low adhesive force can be prevented from peeling off from the pad portion.

The dummy pattern 400 serves to support the boundary area between the conductive adhesive and the anti-corrosion layer. Accordingly, the corrosion prevention layer can be prevented from peeling off in the boundary area when the flexible circuit board is bent. Accordingly, the fourth pad portion can be prevented from being exposed to the outside due to peeling of the corrosion prevention layer. Additionally, it is possible to prevent cracks from occurring in the fourth pad portion due to the stress.

The dummy pattern 400 may include copper (Cu). However, the embodiment is not limited thereto. The dummy pattern 400 includes copper (Cu), aluminum (Al), chromium (Cr), nickel (Ni), silver (Ag), and molybdenum (Mo). It may include at least one metal selected from gold (Au), titanium (Ti), and alloys thereof.

The dummy pattern 400 is not connected to the chip C. That is, the signal does not move through the dummy pattern 400.

The embodiment has a layer structure similar to a double-sided flexible circuit board in which circuit patterns are formed on both sides of the substrate. However, through holes and through electrodes are not formed separately in the substrate. Therefore, manufacturing costs and defects are reduced, thereby improving process efficiency.

Additionally, the embodiment has a layer structure similar to a flexible circuit board in which a circuit is formed on one side of the substrate and a heat dissipation pattern is formed on the other side. However, the heat dissipation pattern is formed in an area corresponding to the chip mounting area. However, the dummy pattern in the embodiment is formed in the second bonding area that contacts the display. In detail, the dummy pattern is formed between the bending area of the flexible printed circuit board and the second bonding area, and therefore does not affect bending characteristics when bending the flexible printed circuit board. Accordingly, design reliability and display reliability can be improved. Additionally, in the embodiment, a separate heat dissipation pattern different from the dummy pattern may be additionally disposed in an area corresponding to the chip mounting area.

The dummy pattern may overlap the fourth pad portion 222b, and the heat dissipation pattern may be formed on a second surface that overlaps the chip mounting area. Additionally, the dummy pattern and the heat dissipation pattern may be disposed in an area that does not correspond to the folding axis FAX. If the dummy pattern or the heat dissipation pattern is formed in an area corresponding to the folding axis FAX, cracks may occur in the dummy pattern or the heat dissipation pattern when the flexible circuit board and the display are combined and then bent. Accordingly, the reliability of the flexible circuit board may decrease.

The dummy pattern 400 may include the same material as at least one of the first circuit pattern 210 and the second circuit pattern 220 . Accordingly, the difference in thermal expansion coefficient between the first surface 1S and the second surface 2S of the substrate 100 may be reduced.

The dummy pattern 400 and the fourth pad portion 222b may have the same thickness. Alternatively, the thickness of the dummy pattern 400 and the fourth pad portion 222b may be different. For example, the thickness T1 of the dummy pattern 400 may be smaller than the thickness T2 of the fourth pad portion 222b. The dummy pattern 400 may not form the bonding layer 203 of the fourth pad portion. Accordingly, the manufacturing cost of the flexible circuit board can be reduced. For example, the thickness T1 of the dummy pattern 400 may be greater than the thickness T2 of the fourth pad portion 222b. Accordingly, the dummy pattern 400 can stably support the fourth pad portion 222b on the second surface 2S. Therefore, concentration of stress can be prevented.

Referring to FIGS. 8 and 9 , the dummy pattern 400 may be disposed at a position that both overlaps the fourth pad portion 222b. In detail, the area of the dummy pattern 400 may be the same or similar to the area of the second bonding area BA2. For example, the width W1 of the dummy pattern 400 may be 90% or more, 93% or more, or 95% or more of the width W2 of the second bonding area BA2. In detail, the width W1 of the dummy pattern 400 may be 90% to 110% of the width W2 of the second bonding area BA2.

Additionally, the area of the dummy pattern 400 may be 90% or more, 93% or more, or 95% or more of the area of the second bonding area BA2 or the fourth pad portion 222b. The area of the dummy pattern 400 may be 110% or less, 107% or less, or 105% or less of the area of the second bonding area BA2 or the fourth pad portion 222b. In detail, the area of the dummy pattern 400 may be 90% to 110% of the area of the second bonding area BA2 or the fourth pad portion 222b.

The dummy pattern 400 is arranged to be substantially equal to the area of the second bonding area BA2 or the fourth pad portion 222b. Accordingly, the dummy pattern 400 can stably support the second bonding area BA2. That is, the dummy pattern 400 is disposed on almost the entire area of the second bonding area BA2. Accordingly, it is possible to prevent cracks and peeling of the anti-corrosion layer of the fourth pad portion due to stress occurring in the second bonding area.

Referring to FIGS. 10 and 11 , the dummy pattern 400 may be disposed in a position that overlaps the fourth pad portion 222b. In detail, the area of the dummy pattern 400 may be larger than the area of the second bonding area BA2 or the fourth pad portion 222b. That is, the dummy pattern 400 may be disposed at a position overlapping the fourth pad portion 222b and the second wiring portion 221. In detail, the dummy pattern 400 completely overlaps the second bonding area BA2 where the fourth pad portion 222b is disposed. Additionally, the dummy pattern 400 partially overlaps the area where the second wiring unit 221 is disposed. One side of the dummy pattern 400 may be formed equal to or close to the cutting line CL. Additionally, the other side of the dummy pattern 400 may be disposed closer to the fourth pad portion 222b than the folding axis FAX.

The dummy pattern 400 overlaps the second wiring portion 221 between the folding axis FAX and the fourth pad portion 222b. Additionally, the dummy pattern 400 is not formed in an area corresponding to the folding axis FAX. Therefore, when the flexible circuit board is combined with the display and bent, cracks are prevented from occurring in the dummy pattern 400 due to tension generated in the area of the second surface corresponding to the folding axis (FAX). You can. Accordingly, the reliability of the display can be improved.

The dummy pattern 400 is larger than the area of the second bonding area BA2. Accordingly, the difference in intensity between the boundary area between the fourth pad portion 222b and the second wiring portion 221 may be reduced. Additionally, the difference in intensity between the boundary area between the fourth pad portion 222b and the protective layer may be reduced. That is, the dummy pattern 400 is also disposed in an area that overlaps the second wiring portion. Accordingly, it is possible to prevent an intensity difference from occurring in the boundary area between the fourth pad part 222b and the second wiring part 221 and the boundary area between the fourth pad part 222b and the protective layer. Accordingly, it is possible to prevent cracks from occurring in the wiring portion due to bending of the flexible circuit board at the boundary area between the pad portion and the wiring portion. Additionally, peeling of the protective layer and anti-corrosion layer can be prevented.

Meanwhile, FIGS. 6 to 11 show that only the dummy pattern 400 is disposed on the second surface 2S. However, the embodiment is not limited thereto. In detail, an additional protective layer may be disposed on the dummy pattern 400. For example, the additional protective layer may surround the dummy pattern 400. Accordingly, corrosion of the dummy pattern 400 can be prevented.

The flexible circuit board according to the embodiment includes a dummy pattern. The reliability of the flexible circuit board is improved by the dummy pattern. When the flexible circuit board is bent, stress is transmitted to the fourth pad portion. The dummy pattern can prevent the corrosion prevention layer from peeling off. Additionally, it is possible to prevent cracks from occurring in the pad portion.

Additionally, the width of the dummy pattern may be smaller than the minimum length of the second circuit pattern. If the width of the dummy pattern is greater than the minimum length of the second circuit pattern, the dummy pattern is formed on most of the lower surface of the substrate, thereby reducing the ductility of the flexible circuit board. Accordingly, the bending characteristics of the flexible circuit board are reduced. . Accordingly, the thickness of the display panel may be increased. Alternatively, additional cracks may occur as the dummy pattern formed on the second surface increases. Accordingly, the reliability of the flexible circuit board may decrease.

Meanwhile, the dummy pattern may be formed into patterns of various shapes.

Referring to FIGS. 12 to 14 , the dummy pattern 400 may include a plurality of patterns spaced apart from each other.

Referring to FIG. 12, the dummy pattern 400 may overlap the fourth pad portion 222b. In detail, the dummy pattern 400 and the fourth pad portion 222b may overlap in the thickness direction of the substrate 100. In detail, the dummy pattern 400 and the fourth pad portion 222b may completely or partially overlap in the thickness direction of the substrate 100.

For example, the dummy pattern 400 may be disposed in an area on the second surface 2S corresponding to the fourth pad portion 222b on the first surface 1S.

Alternatively, referring to FIG. 13, the dummy pattern 400 may be arranged to be staggered with the fourth pad portion 222b. In detail, the dummy pattern 400 may be disposed on the second surface 2S corresponding to the spaced area between the fourth pad portions 222b. That is, the dummy pattern 400 and the fourth pad portion 222b do not overlap in the thickness direction of the substrate 100.

In the second bonding area BA2, the dummy pattern 400 and the fourth pad portion 222b are arranged to be staggered. Accordingly, it is possible to prevent waviness from occurring in areas where the copper pattern is not disposed on the first surface 1S and the second surface 2S of the second bonding area.

That is, since the dummy pattern 400 and the fourth pad portion 222b are arranged to be staggered in the second bonding area BA2, a copper pattern is disposed on almost the entire area of the second bonding area BA2. Accordingly, the occurrence of waviness in areas where the copper pattern is not disposed can be reduced.

Referring to FIG. 14, the dummy pattern 400 may extend in a direction different from the fourth pad portion 222b. That is, the longitudinal direction of the dummy pattern 400 may be different from the longitudinal direction of the fourth pad portion 222b. For example, the dummy pattern 400 may extend in a diagonal direction forming a predetermined angle with the fourth pad on the second surface.

Accordingly, the dummy pattern 400 may partially overlap the fourth pad portion 222b. Additionally, the dummy pattern 400 may be disposed while covering the width direction of the spaced area of the fourth pad portion 222b.

For example, the dummy pattern and the fourth pad portion may overlap in the vertical direction at the boundary area between the 2-1 bonding area and the 2-2 bonding area. Through this, it is possible to prevent stress from being concentrated in the boundary area. In addition, the width direction of the spaced areas of the four pad parts can be covered together.

Since the dummy pattern 400 is arranged diagonally, the dummy pattern 400 is arranged while covering the width direction of the spaced area of the fourth pad portion 222b. Accordingly, the dummy pattern 400 can support the fourth pad portion 222b over a wider area.

Hereinafter, the present invention will be described in more detail through the bending characteristics of the flexible circuit board according to examples and comparative examples. These embodiments are merely provided as examples to explain the present invention in more detail. Therefore, the present invention is not limited to these embodiments.

Example 1

A flexible circuit board is manufactured by forming the previously described first circuit pattern, second circuit pattern, and protective layer on the first side of a polyimide (PI) substrate.

Next, a dummy pattern is formed on the second surface corresponding to the second bonding area of the second circuit pattern. At this time, the dummy pattern is placed on the area corresponding to the fourth pad portion as shown in FIG. 12.

Next, the bending characteristics of the flexible circuit board are measured. The bending characteristic measures the number of bending times at which cracks occur in the second pad portion when the flexible circuit board is bent.

Example 2

A flexible circuit board was manufactured in the same manner as in Example 1, except that the dummy pattern was arranged alternately with the fourth pad portion as shown in FIG. 13, and the bending characteristics of the flexible circuit board were measured.

Example 3

A flexible circuit board was manufactured in the same manner as Example 1, except that the dummy patterns were all placed on the area corresponding to the second bonding area as shown in FIG. 8, and the bending characteristics of the flexible circuit board were measured.

Example 4

A flexible circuit board was manufactured in the same manner as Example 1, except that the dummy pattern was arranged in a diagonal pattern on the area corresponding to the second bonding area as shown in FIG. 14, and the bending characteristics of the flexible circuit board were measured. .

Comparative example

A flexible circuit board was manufactured in the same manner as in Example 1, except that the dummy pattern was not arranged, and the bending characteristics of the flexible circuit board were measured.

	실시예1Example 1	실시예2Example 2	실시예3Example 3	실시예4Example 4	비교예Comparative example
벤딩특성 (크랙이 발생하는 벤딩횟수)Bending characteristics (Number of bending times where cracks occur)	9393	9191	108108	9393	7575

Referring to Table 1, the flexible circuit boards of Examples 1 to 4 have improved bending characteristics than the flexible circuit boards of the Comparative Example. That is, the flexible circuit boards of Examples 1 to 4 include dummy patterns. The dummy pattern can prevent cracks in the second pad portion due to stress during bending. Accordingly, damage to the second pad portion due to the stress may be reduced by the dummy pattern. Therefore, the flexible circuit board according to the embodiment may have improved reliability.

Figure 15 is a top view of a COF module according to an embodiment.

Referring to FIG. 15, the COF module includes the flexible circuit board described above. Additionally, it may include a chip (C) disposed in the chip mounting area (CA).

Additionally, the flexible circuit board 1000 may include the protective layer 300 described above.

Meanwhile, the COF module 2000 is manufactured by cutting the flexible circuit board 1000 and mounting the chip C. In detail, after cutting along the cutting line CL of FIG. 1, a driving chip electrically connected to the first circuit pattern and the second circuit pattern is mounted on the chip mounting area.

The COF module is located between the display panel and the substrate and can transmit electrical signals.

That is, the pad portions of the first circuit pattern and the second circuit pattern may be connected to the display panel, the printed circuit board, and the chip.

Referring to FIG. 16, one end of the COF module 2000 is connected to the display panel 3000. Additionally, the other end of the COF module 2000 is connected to the printed circuit board 4000.

Additionally, the COF module 2000 and the terminal 3100 of the display panel 3000 may be bonded using a conductive adhesive 510 and an anti-corrosion layer 520. In detail, the 2-1 bonding area BA2-1 of the COF module and the terminal 3100 of the display panel 3000 are bonded by the conductive adhesive 510.

The COF module 2000 and the display panel 3000 may be electrically connected by the conductive adhesive. The conductive adhesive is a resin in which conductive particles are dispersed. Accordingly, the signal of the display panel 3000 may be transmitted to the COF module 2000 by the conductive particles.

Next, a corrosion prevention layer 520 is disposed on the 2-2 bonding area BA2-2. As a result, corrosion of the exposed area of the fourth pad portion 222b can be prevented.

Additionally, a dummy pattern 400 is disposed on the substrate 100. Accordingly, when the COF module 2000 is bent, the corrosion prevention layer 520 is peeled off and cracks are prevented from occurring in the fourth pad portion 222b.

The COF module 1000 includes a flexible substrate. Accordingly, the space between the display panel 3000 and the printed circuit board 4000 may have a rigid or bent shape.

The COF module 2000 may be connected in a curved form between the display panel 3000 and the printed circuit board 4000, which are disposed opposite each other. Accordingly, the thickness of the electronic device is reduced and design freedom is improved. Additionally, the wiring of the COF module 2000 is not broken even when it is bent. Accordingly, the reliability of the electronic device is improved.

Because the COF module is flexible, it can be used in various electronic devices.

For example, referring to FIG. 17, the COF module can be applied to a bendable flexible touch window. The flexible touch window can be applied to wearable touch.

Referring to FIG. 18, the COF module can be applied to a wearable touch device including a curved display. Accordingly, the electronic device including the COF module can be slimmed or lightweight.

Referring to FIG. 19, the COF module can be applied to various electronic devices with displays such as TVs, monitors, and laptops.

However, the embodiment is not limited to this. The COF flexible circuit board and the COF module can be used in various electronic devices.

The features, structures, effects, etc. described in the above-described embodiments are included in at least one embodiment of the present invention and are not necessarily limited to only one embodiment. Furthermore, the features, structures, effects, etc. illustrated in each embodiment can be combined or modified and implemented in other embodiments by a person with ordinary knowledge in the field to which the embodiments belong. Therefore, contents related to such combinations and modifications should be construed as being included in the scope of the present invention.

In addition, although the description has been made focusing on the embodiments above, this is only an example and does not limit the present invention, and those skilled in the art will understand the above examples without departing from the essential characteristics of the present embodiments. You will be able to see that various modifications and applications are possible. For example, each component specifically shown in the embodiments can be modified and implemented. And these variations and differences in application should be construed as being included in the scope of the present invention as defined in the attached claims.

Claims

A substrate comprising a first side and a second side opposite the first side;

a circuit pattern disposed on the first side of the substrate; and

Includes a protective layer on the circuit pattern,

The circuit pattern includes a first circuit pattern and a second circuit pattern,

The first circuit pattern includes a first pad portion electrically connected to the chip, a second pad portion electrically connected to the printed circuit board, and a first wiring portion connected to the first pad portion and the second pad portion. Contains,

The second circuit pattern includes a third pad portion electrically connected to the chip, a fourth pad portion electrically connected to the display panel, and a second wiring portion connected to the third pad portion and the fourth pad portion. do,

The first surface of the substrate includes a first bonding area where the second pad unit is disposed and a second bonding area where the fourth pad unit is disposed,

A flexible circuit board wherein a dummy pattern is disposed on a second surface of the substrate corresponding to the second bonding area.
According to clause 1,

The second bonding region includes a 2-1 bonding region in which a conductive adhesive is disposed and a 2-2 bonding region in which a corrosion prevention layer is disposed,

The dummy pattern is a flexible circuit board disposed on a boundary area between the 2-1 bonding area and the 2-2 bonding area.
According to clause 1,

A flexible circuit board in which the width of the dummy pattern is smaller than the width of the two bonding regions.
According to clause 1,

A flexible circuit board in which the width of the dummy pattern is larger than the width of the two bonding regions.
According to clause 1,

A flexible circuit board wherein the dummy pattern includes the same material as the circuit pattern.
According to clause 1,

A flexible circuit board wherein the dummy pattern overlaps the fourth pad portion and the base material in a thickness direction.
According to clause 1,

A flexible circuit board wherein the thickness of the dummy pattern and the thickness of the fourth pad portion are different.
According to clause 1,

The dummy pattern is disposed in a diagonal pattern forming a predetermined angle with the fourth pad on a second surface corresponding to the second bonding area.
A flexible circuit board according to any one of claims 1 to 8; and

A COF module including a chip disposed in the chip mounting area.
COF module according to claim 9;

a printed circuit board connected to the first circuit pattern; and

It includes a display panel connected to the second circuit pattern,

The second bonding area includes a 2-1 bonding area and a 2-2 bonding area,

A conductive adhesive for adhering the display panel is formed in the 2-1 bonding area,

An electronic device comprising a corrosion prevention layer formed on the fourth pad in the 2-2 bonding area.