KR20240028215A - Flexible printed circuit board, cof module and electronic device comprising the same - Google Patents

Abstract

A flexible printed 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 a semiconductor, a printed circuit board, and A display comprising a second pad part set to be electrically connected and a first wiring part connected to the first pad part and the second pad part, wherein the second circuit pattern is set to be electrically connected to a semiconductor, a display 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, and a dummy pattern is disposed on the second surface of the substrate corresponding to the second bonding area.

Description

Flexible printed circuit board, COF module, and electronic device including the same {FLEXIBLE PRINTED CIRCUIT BOARD, COF MODULE AND ELECTRONIC DEVICE COMPRISING THE SAME}

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

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.

Among them, the COF (Chip On Film) method can be applied to flexible displays because it uses a flexible substrate. In other words, the COF method is attracting attention because it can be applied to various wearable electronic devices. Additionally, because the COF method can implement a fine pitch, it can be used to implement a high-resolution display as the number of pixels increases.

COF (Chip On Film) is a method of mounting a semiconductor chip on a thin film-shaped flexible printed circuit board. For example, a semiconductor chip may be an integrated circuit (IC) chip or a large scale integrated circuit (LSI) chip.

Meanwhile, the chip can be connected to an external PCB and display panel through a circuit pattern. For example, pad portions may be disposed on one end and the other end of the circuit pattern, one pad portion may be electrically connected to a terminal of the chip, and the other pad portion may be connected to a terminal of the PCB and the display panel. Accordingly, the chip, PCB, and display panel are electrically connected through the COF, and signals can be transmitted to the display panel through the circuit pattern.

As explained earlier. Since the COF (Chip On Film) type flexible printed circuit board is applied to a flexible display, the flexible printed circuit board can be bent in one direction.

Therefore, when the flexible printed circuit board is bent, film removal cracks may occur in the circuit pattern located in the bent area, thereby deteriorating the electrical characteristics of the flexible printed circuit board.

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

As a patent related to the flexible printed circuit board, Korean registered patent KR10-0618898 (2006.09.01) is disclosed.

The embodiment seeks to provide a flexible printed circuit board with improved reliability.

A flexible printed 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 a semiconductor, 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 semiconductor, and a third pad portion configured to be electrically connected to the semiconductor. 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, and a dummy pattern is disposed on the second surface of the substrate corresponding to the second bonding area.

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

In detail, the flexible printed 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 a pad portion connected to the display panel among the circuit patterns of the flexible printed circuit board.

The flexible printed circuit board can form a COF module by mounting chips, and can be bent in one direction. As a result, stress may be generated in the flexible printed circuit board, and this stress may be transmitted toward 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 defilmed. In addition, cracks may occur in the pad portion exposed by defilming of the corrosion prevention layer due to stress.

The flexible printed circuit board according to the embodiment can solve the above problems by disposing a dummy pattern on the pad portion or the second surface corresponding to the pad portion and the wiring portion. In other words, the dummy pattern can prevent defilming of the corrosion inhibitor due to stress and prevent cracks in the pad portion.

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

1 is a top view of a flexible printed circuit board according to an embodiment.
Figures 2 and 3 are cross-sectional views taken along area AA' of Figure 1.
FIG. 4 is a cross-sectional view taken along area BB' of FIG. 1.
FIG. 5 is a cross-sectional view cut along area CC' of FIG. 1.
FIG. 6 is an enlarged view of the bottom view of the flexible printed circuit board in area D of FIG. 1.
FIG. 7 is a cross-sectional view taken along area EE' of FIG. 6.
FIG. 8 is another enlarged view of the bottom view of the flexible printed circuit board in area D of FIG. 1.
FIG. 9 is a cross-sectional view taken along area FF' of FIG. 8.
FIG. 10 is another enlarged view of the bottom view of the flexible printed circuit board in area D of FIG. 1.
FIG. 11 is a cross-sectional view taken along area GG' of FIG. 10.
FIGS. 12 to 14 are enlarged views of another bottom view of the flexible printed circuit board in area D of FIG. 1 to illustrate various shapes of dummy patterns.
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 printed 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 printed circuit board according to an embodiment.

Referring to FIG. 1, a flexible printed circuit board 1000 according to an embodiment may include 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 embodiment is not limited to this, and the substrate 100 may include a polymer material such as polyethylene terephthalate (PET) or polyethylene naphthalate (PEN). Accordingly, the flexible printed circuit board including the substrate 100 can be used in various electronic devices equipped with a curved display device. For example, the flexible printed circuit board including the substrate 100 has excellent flexible characteristics and may be suitable for mounting semiconductor chips of 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 printed circuit board may increase, and as a result, the flexible characteristics may deteriorate. Additionally, if the thickness of the substrate 100 is less than 20㎛, it may be vulnerable to heat/pressure applied to the substrate 100 during the chip mounting process.

The substrate 100 may include an effective area (UA) and an unactive area (UA). For example, the effective area (AA) may be a central area of the substrate 100, and the unactive area (UA) may be an edge area of the substrate 100. That is, the unactive area (UA) may be arranged to surround the effective area (AA).

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

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

The effective area AA may be an area actually used in the flexible printed circuit board 1000. That is, when the flexible printed circuit board is in contact with another panel, etc., the effective area AA may be an area that is in contact with the flexible printed circuit board.

The circuit pattern may not be disposed in the unactive area (UA). That is, the active area (AA) and the unactive area (UA) can be distinguished depending on whether or not the circuit pattern is arranged.

The unactive area (UA) may include a plurality of holes. In detail, the unactive area (UA) may include a plurality of sprocket holes (H). The flexible printed circuit board can be wound or unwound by the sprocket hole (H) in a roll-to-roll manner.

The unavailable area (UA) may be an area that is not actually used in the flexible printed circuit board 1000. That is, the non-effective area (UA) may be an area that is removed when the flexible printed circuit board is in contact with another panel, etc.

In detail, the flexible printed circuit board 1000 is processed into a COF module after cutting a cutting line (CL) defined as the boundary between the unactive area (UA) where the sprocket hole (H) is formed and the effective area (AA). It can be mounted on various electronic devices.

The circuit pattern may include a wiring portion and a pad portion. Additionally, a plurality of circuit patterns may be disposed in the effective area AA. In detail, a first circuit pattern 210 and a second circuit pattern 220 may be disposed in the effective area AA. The first circuit pattern 210 and the second circuit pattern 220 are disposed on the first surface 1S of the substrate 100.

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

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 be arranged to extend in the first direction D1 based on the chip mounting area CA.

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

A protective layer 300 may be disposed on the first circuit pattern 210 . In detail, the protective layer 300 may be disposed on the first wiring portion 211. The protective layer 300 may be disposed surrounding the first wiring portion 211 . Additionally, the protective layer 300 may not be disposed on the first pad portion 212a and the second pad portion 212b.

That is, the first wiring portion 211 is disposed below the protective layer 300, and the protective layer 300 is not disposed on the first pad portion 212a and the second pad portion 212b. and may be exposed to the outside.

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

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

Additionally, the second wiring unit 221 may be arranged to extend in the second direction D2 based on the chip mounting area CA. In detail, the second wiring unit 221 may be arranged to extend in a second direction D2, which is opposite to the first direction D1.

The third pad portion 222a may be electrically connected to a semiconductor or chip disposed in the chip mounting area. Additionally, the fourth pad portion 222b may be electrically connected to the display panel. Additionally, the second wiring unit 221 may transmit 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 may be disposed on the second wiring portion 221. The protective layer 300 may be disposed surrounding the second wiring portion 221 . Additionally, the protective layer 300 may not be disposed on the third pad portion 222a and the fourth pad portion 222b.

That is, the second wiring portion 221 is disposed below the protective layer 300, and the protective layer 300 is not disposed on the third pad portion 222a and the fourth pad portion 222b. and may be exposed to the outside.

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

Hereinafter, with reference to FIGS. 2 and 3, the layer structure of the circuit pattern of the flexible printed circuit board according to the embodiment will be described. 2 and 3, the description is centered on the first circuit pattern 210, but the embodiment is not limited thereto, and the description of the layer structure described in FIGS. 2 and 3 is the same as that of the second circuit pattern 220. It can be applied easily.

Referring to FIG. 2, the first circuit pattern 210 may be formed in multiple layers. In detail, the first wiring part 211 and the first pad part 212a may include a first metal layer 201 and a second metal layer 202. Also, although not shown in Figure 3. The second pad portion 212b may also include the first metal layer 201 and the second metal layer 202.

The first metal layer 201 may be a seed layer of the first circuit pattern 210. In detail, the first metal layer 201 may be a seed layer formed on the substrate 100 through electroless plating using a metal material such as copper (Cu).

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

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

For example, the first metal layer 201 may have a thickness of 0.7 μm to 2 μm, and the second metal layer 202 may have a thickness of 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).

Additionally, a bonding layer 203 may be disposed on the second metal layer 201. In detail, the bonding layer 203 may be disposed on the sides of the first metal layer 201 and the second metal layer 202, and on the top surface of the second metal layer 202. That is, the bonding layer 203 may be disposed surrounding the first metal layer 201 and the second metal layer 202.

The bonding layer 203 may include metal. In detail, the bonding layer 203 may include tin (Sn).

The bonding layer 203 may be formed to have a thickness of 0.3 ㎛ to 0.7 ㎛. The bonding layer 203 may have an increased tin content as it extends from the lower surface where the bonding layer 203 and the second metal layer 202 are in contact with the upper surface.

That is, since the bonding layer 203 is disposed in contact with the second metal layer 202, the tin content may increase and the copper content may decrease as it moves from the lower surface to the upper surface of the bonding layer 203. .

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

The bonding layer 203 can easily bond the terminals of the chip, the printed circuit board, and the display panel to the first and second pad portions through heat and pressure. That is, when heat and pressure are applied to the first pad portion and the second pad portion, the upper surface where pure tin remains in the bonding layer is melted and easily connected to the terminals of the chip, the printed circuit board, and the display panel. It can be easily glued.

Accordingly, the bonding layer 203 is not separated from the first pad portion 212a and can become a part of the first pad portion 212a.

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

Since the first circuit pattern 210 undergoes a process of etching the first metal layer 201 by flash etching, which is performed to separate the circuit patterns during the manufacturing process, the first circuit that is finally manufactured is The pattern 211 and the second circuit pattern 220 may be smaller than the sum of the thicknesses of the first metal layer 201, the second metal layer 202, and the bonding layer 203 formed during the manufacturing process.

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 may increase. If the thickness of the first circuit pattern 210 and the second circuit pattern 220 exceeds 25㎛, it may be difficult to implement a fine pattern.

Meanwhile, a buffer layer 205 may be further disposed between the substrate 100 and the first and second circuit patterns 210 and 220 . The buffer layer 205 can improve adhesion between the substrate 100, which is a dissimilar material, and the first circuit pattern 210 and the second circuit pattern 220.

The buffer layer 205 may be formed of multiple layers. In detail, a first buffer layer 205a and a second buffer layer 205b on the first buffer layer 205a may be disposed on the substrate 100. Accordingly, the first buffer layer 205a may be disposed in contact with the substrate 100, and the second buffer layer 205b may be disposed 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 including the first buffer layer 205a and the second buffer layer 205b may have a thin film thickness in nanometer units. For example, the buffer layer 205 may have a thickness of 20 nm or less.

The buffer layer 205 can improve adhesion between the substrate 100, which is a dissimilar material, and the first circuit pattern 210, thereby preventing delamination of the first circuit pattern 201.

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 first wiring portion 211, the first pad portion 212a, and the second pad portion 212b may have different layer structures due to 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 be disposed at different thicknesses. In detail, 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 μm to 0.06 μm, and the second bonding layer 203b may have a thickness of 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 printed circuit board is bent. Accordingly, the first bonding layer 231 between the protective layer 300 and the first wiring portion 211 is formed to have a thin film thickness, thereby preventing cracks from occurring when bending the flexible printed circuit board. there is.

Additionally, the tin content of the second bonding layer 203b may increase as it extends from the lower surface where the second bonding layer 203b and the first bonding layer 203a contact the upper surface.

That is, the tin content of the second bonding layer 203b may increase and the copper content may decrease as it moves from the lower surface to the upper surface of the second bonding layer 203b.

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.

By using the second bonding layer 203b, the terminals of the chip, the printed circuit board, and the display panel can be easily bonded to the first and second pad portions through heat and pressure. That is, when heat and pressure are applied to the first pad portion and the second pad portion, the upper surface where pure tin remains in the bonding layer is melted and easily connected to the terminals of the chip, the printed circuit board, and the display panel. It can be easily glued.

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

Meanwhile, the protective layer 300 may be disposed on the wiring portions of the first circuit pattern 210 and the second circuit pattern 220. In detail, the protective layer 300 may be arranged to surround 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 protective layer 300 may include a solder paste containing 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 surfaces 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 may be connected to the chip on one side of the substrate 100, and the printed circuit board may be connected to the chip on the other side of the substrate 100.

Referring to FIG. 1, the flexible printed circuit board 1000 may include 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 may be bonded in the first bonding area BA1 and the second bonding area BA2. In detail, the first bonding area BA1 may be bonded to the terminal portion of the printed circuit board using a conductive adhesive, such as an anisotropic conductive adhesive (ACF). Additionally, the second bonding area BA2 may be bonded to the terminal portion of the display panel using a conductive adhesive, such as an anisotropic conductive adhesive (ACF). At this time, a corrosion prevention layer to prevent corrosion of the pad portion may be additionally disposed in the area of the second pad portion 212b and the fourth pad portion 222b in the bonding area where the conductive adhesive is not disposed.

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 defined as an area where the conductive adhesive is disposed. Additionally, the 2-2 bonding area BA2-2 is defined as 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 with a conductive adhesive, 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 as is is created. This exposed area is defined as the 2-2 bonding area (BA2-2). Accordingly, in order to prevent corrosion from occurring in the 2-2 bonding area (BA2-2), a corrosion prevention layer is disposed on the 2-2 bonding area (BA2-2).

Meanwhile, the flexible printed circuit board 1000 is bent in one direction. In detail, the flexible printed circuit board 1000 is bent in one direction around the folding axis (FAX). Accordingly, stress generated by bending of the flexible printed circuit board 1000 is transmitted to the second bonding area. Accordingly, the corrosion prevention layer disposed in the 2-2 bonding area BA2-2 may be defilmed due to this stress. That is, since the corrosion prevention layer has a lower adhesive force than the conductive adhesive, it may be delaminated from the pad portion while lifting occurs due to stress.

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

Accordingly, the flexible printed circuit board according to the embodiment has a dummy pattern to prevent the stress generated by bending of the flexible printed circuit board 1000 from being transferred to the second bonding area and concentrating the stress on the fourth pad portion. The above problems are solved by additionally arranging .

In addition, the dummy pattern also prevents defilming of the corrosion prevention layer disposed in the 2-2 bonding area.

Referring to FIGS. 6 and 7 , a dummy pattern 400 is disposed on the second surface 2S of the substrate 100. The dummy pattern 400 is disposed at a position overlapping with the fourth pad portion 222b. In detail, the dummy pattern 400 is disposed to partially overlap the fourth pad portion 222b. The dummy pattern 400 is disposed in the second bonding area BA2 where the fourth pad portion 222b is disposed. ) is placed smaller than the area of . For example, the width W1 of the dummy pattern 400 is 50% of the width W2 of the two bonding areas BA2. It may be 60% 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% of the area of the second bonding area BA2 or the fourth pad portion 222b. It may be 60% 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. In the case of the fourth pad portion, a plurality of pad portions are formed and spaced apart from each other to be electrically connected to the terminal portion of the display panel, but the dummy pattern serves to prevent cracks in the fourth pad portion, so a plurality of dummy patterns are formed. Even if the space between them is small, it is okay to connect them. Additionally, one dummy pattern may be formed over the entire second bonding area.

Since the dummy pattern 400 is disposed smaller than the area of the second bonding area BA2 or the fourth pad portion 222b, the 2-1 bonding area BA2-1 and the 2-2 bonding area The intensity difference between the boundary area of the area BA2-2 and the 2-1 bonding area BA2-1 and the 2-2 bonding area BA2-2 can be reduced. Accordingly, the arrangement of the dummy pattern 400 can prevent the flexible printed circuit board from bending in one direction.

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.

Adhesion between the conductive adhesive and the anti-corrosion 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. can be prevented, and the conductive adhesive and corrosion prevention layer disposed in the 2-1 bonding area (BA2-1) and the 2-2 bonding area (BA2-2) can be prevented from being defilmed. especially. The corrosion prevention layer, which has a small adhesive force, can be prevented from being defilmed from the pad portion.

Therefore, the dummy pattern 400 serves to support the boundary area between the conductive adhesive and the corrosion prevention layer, thereby preventing the corrosion prevention layer from being defilmed at the boundary area when the flexible printed circuit board is bent. Accordingly, it is possible to prevent the fourth pad portion from being exposed to the outside by defilming of the corrosion prevention layer and cracks from occurring in the fourth pad portion due to transmitted stress.

The dummy pattern 400 may include copper (Cu). However, the embodiment is not limited to this, and the dummy pattern 400 includes copper (Cu), aluminum (Al), chromium (Cr), nickel (Ni), silver (Ag), and molybdenum (Mo). Of course, 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, no signal is transmitted through the dummy pattern 400.

Through this, it has a layer structure similar to a double-sided flexible circuit board with circuit patterns formed on both sides of the substrate, but there is no need to separately form through holes and through electrodes on the substrate, thereby increasing production efficiency, such as reducing manufacturing costs and defects.

In addition, it 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, but the heat dissipation pattern must be formed in an area corresponding to the chip mounting area. However, the present invention provides a second substrate in contact with the display. There is a difference formed in the bonding area. This is formed between the bending area where the flexible circuit board is bent when combined with the display and the second bonding area in contact with the display, so it can be manufactured in a design that does not affect the bending characteristics when bending, thereby improving design reliability and display reliability. It can be improved. A separate heat dissipation pattern different from the dummy pattern of the present invention may be additionally formed in the area corresponding to the chip mounting area.

At this time, the dummy pattern is preferably formed to overlap the fourth pad portion 222b, and the heat dissipation pattern is preferably formed on the second side of the substrate to overlap the chip mounting area. In addition, it is better to form the dummy pattern and heat dissipation pattern avoiding the folding axis (FAX). When the dummy pattern or heat dissipation pattern is formed in an area corresponding to the folding axis (FAX) of the second side of the substrate, when the flexible circuit board is coupled to the display, it corresponds to the folding axis (FAX) of the second side of the substrate. Cracks may occur in the dummy pattern or heat dissipation pattern formed in the area where the flexible circuit board is bent, resulting in poor reliability of the flexible circuit board.

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 can 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 saved. 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 of the substrate 100 and prevent stress from being concentrated.

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 dummy pattern 400 may be arranged with an area that is the same as or similar to that of the second bonding area BA2. For example, the width W1 of the dummy pattern 400 may be 90%, 93%, 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%, 93%, 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 less than 110%, 107%, or 105% 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.

Since the dummy pattern 400 is disposed to be almost the same as the area of the second bonding area BA2 or the fourth pad portion 222b, the dummy pattern 400 stabilizes the second bonding area BA2. can be supported. That is, since the dummy pattern 400 is disposed on almost the entire area of the second bonding area BA2, it effectively prevents cracking and delamination of the corrosion prevention layer of the fourth pad portion due to stress occurring in the second bonding area. can do.

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 dummy pattern 400 may be arranged to have an area 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, and partially overlaps the area where the second wiring portion 221 is disposed. It can be. One side of the dummy pattern 400 may be formed identical to or close to the cutting line CL, and the other side may be disposed closer to the fourth pad portion 222b than the folding axis FAX. The dummy pattern 400 is arranged to overlap the second wiring part 221 between the folding axis (FAX) and the fourth pad part 222b, and is formed in an area corresponding to the folding axis (FAX). Otherwise, when the flexible circuit board is combined with the display and bent, additional cracks are prevented from occurring due to tension in the dummy pattern 400 in the area corresponding to the folding axis (FAX) on the second side of the substrate. can do.

This can further increase the reliability of the display. Therefore, it is desirable that the overlapping area between the dummy pattern 400 and the second wiring portion does not exceed the folding axis FAX.

Since the dummy pattern 400 is disposed to be larger than the area of the second bonding area BA2, the intensity difference between the fourth pad part 222b and the second wiring part 221 can be reduced. , the intensity difference at the boundary area between the fourth pad portion 222b and the protective layer can also be reduced. That is, since the dummy pattern 400 is also disposed in an area overlapping with the second wiring part, the boundary area between the fourth pad part 222b and the second wiring part 221 and the second wiring part 221 are formed by the dummy pattern. 4 It is possible to prevent an intensity difference from occurring in the boundary area between the pad portion 222b and the protective layer. Therefore, it is possible to prevent cracks in the wiring portion and defilming of the protective layer and anti-corrosion layer due to bending of the flexible printed circuit board at the boundary area between the pad portion and the wiring portion.

Meanwhile, FIGS. 6 to 11 illustrate that only the dummy pattern 400 is disposed on the second surface 2S of the substrate, but 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 be disposed while surrounding the dummy pattern 400. Accordingly, the dummy pattern 400 can be prevented from corroding.

The reliability of the flexible printed circuit board according to the embodiment can be improved by the dummy pattern. That is, the dummy pattern can prevent the corrosion prevention layer from being defilmed due to stress transmitted to the fourth pad portion when the flexible printed circuit board is bent. Additionally, it is possible to prevent cracks from occurring in the pad portion.

Additionally, the width W1 of the dummy pattern may be smaller than the minimum length of the second circuit pattern. When the width (W1) of the dummy pattern is greater than the minimum length of the second circuit pattern, a dummy pattern is formed on most of the lower surface of the substrate, thereby lowering the ductility of the flexible printed circuit board and causing the flexible printed circuit board to be tilted in one direction. Banding can be reduced. This causes the problem of increasing the thickness of the display panel, or when the flexible circuit board is bent and coupled to the display panel, the dummy pattern formed on the second side of the substrate is stretched and additional cracks are generated, thereby damaging the flexible printed circuit. Board defects may occur.

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

For example, the dummy pattern 400 may be disposed on the second surface 2S of the substrate 100 in an area 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 of the substrate 100 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.

Since the dummy pattern 400 and the fourth pad portion 222b are arranged alternately in the second bonding area BA2, copper is formed on the first surface 1S and the second surface 2S of the second bonding area BA2. It is possible to reduce waviness in areas where patterns are not placed.

That is, since the dummy pattern 400 and the fourth pad portion 222b are disposed alternately in the second bonding area BA2, a copper pattern is disposed over almost the entire area of the second bonding area BA2, As a result, the occurrence of waviness in areas where copper patterns are 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 be disposed to 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 be formed to 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 and also cover the width direction of the spaced area of the four pad parts.

Since the dummy pattern 400 is disposed in a diagonal direction, the dummy pattern 400 is disposed 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 printed 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 printed circuit board was 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 was formed on the second surface corresponding to the second bonding area of the second circuit pattern. At this time, the dummy pattern was placed on the area corresponding to the fourth pad portion as shown in FIG. 12.

Next, the bending characteristics of the flexible printed circuit board were measured. The bending characteristics were measured by measuring the number of bending times at which cracks occurred in the second pad portion when bending the flexible printed circuit board.

Example 2

A flexible printed 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 printed circuit board were measured.

Example 3

A flexible printed 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 printed circuit board were measured. .

Example 4

A flexible printed 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 printed circuit board were measured. did.

Comparative example

A flexible printed 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 printed circuit board were measured.

Example 1 Example 2 Example 3 Example 4 Comparative example Bending characteristics
(Number of bending times where cracks occur) 93 91 108 93 75

Referring to Table 1, the flexible printed circuit boards of Examples 1 to 4 including dummy patterns have improved bending characteristics than the flexible printed circuit boards of the comparative example. That is, the flexible printed circuit boards of Examples 1 to 4 include a dummy pattern that can prevent cracks in the second pad portion due to stress during bending. Accordingly, damage to the second pad portion caused by stress caused by bending of the flexible printed circuit board can be reduced by the dummy pattern. Therefore, the flexible printed 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 according to the embodiment includes the flexible printed circuit board described above, and may include a chip C disposed in the chip mounting area CA of the flexible printed circuit board 1000. .

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

Meanwhile, the COF module can be manufactured by cutting the flexible printed circuit board 1000 and then mounting the chip (C). In detail, after cutting along the cutting line CL in FIG. 1, the driving chip electrically connected to the first circuit pattern and the second circuit pattern is placed in the chip mounting area of the flexible printed circuit board and the driving chip is mounted. COF module 2000 may be manufactured.

For example, after testing the driving characteristics of the flexible printed circuit board through wiring and pad portions disposed outside the cutting line (CL) of the flexible printed circuit board, the flexible printed circuit board is cut along the cutting line (CL). can do.

At this time, an identification pattern is punched out to form a pattern hole on the flexible printed circuit board that is determined to be a defective product, and the driving chip is not mounted. Additionally, a driving chip is mounted on a flexible printed circuit board that is determined to be a normal product without punching an identification pattern.

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

That is, the pad portions of the first and second circuit patterns that are exposed without the protective layer 300 may be connected to the display panel, the printed circuit board, and the chip in the chip mounting area.

Referring to FIG. 16, one end of the COF module 2000 including a flexible printed circuit board according to the embodiment is connected to the display panel 3000, and the other end opposite to the one end is connected to the printed circuit board 4000. can be connected

For example, one end of the COF module 2000 including a flexible printed circuit board according to the embodiment is electrically connected by contacting the display panel 3000, and the other end opposite to the one end is connected to the printed circuit board ( 4000) can be electrically connected. Here, contact may mean direct contact. Alternatively, it may mean contact with an anisotropic conductive film (ACF) in between.

Additionally, the COF module 2000 may be bonded to the terminal 3100 of the display panel 3000 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 through the conductive adhesive 510. The COF module 2000 and the display panel 3000 can be adhered and electrically connected at the same time using the conductive adhesive. The conductive adhesive may be a resin in which conductive particles are dispersed. Accordingly, the electrical signal connected by the display panel 3000 can be transmitted to the COF module 2000 through the conductive particles included in the conductive adhesive.

Subsequently, the corrosion prevention layer 520 is disposed on the 2-2 bonding area BA2-2 to prevent corrosion of the exposed area of the fourth pad portion 222b.

In addition, since the dummy pattern 400 is disposed on the substrate 100, when the COF module 2000 is bent, the corrosion prevention layer 520 is defilmed and cracks occur in the fourth pad portion 222b. can be prevented.

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

The COF module 2000 can connect the display panel 3000 and the printed circuit board 4000, which are disposed opposite each other, in a curved form, thereby reducing the thickness of the electronic device and improving design freedom. You can do it. In addition, the COF module 2000 including the flexible substrate may not have broken wires even in a bent shape, thereby improving the reliability of an electronic device including the COF module.

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

For example, referring to FIG. 17, the COF module may be included in a bendable flexible touch window. Accordingly, a touch device including this may be a flexible touch device. Therefore, the user can bend or bend it by hand. These flexible touch windows can be applied to wearable touches, etc.

Referring to FIG. 18, the COF module may be included in various wearable touch devices including curved displays. Accordingly, the electronic device including the COF module can be slimmed or lightened.

Referring to FIG. 19, the COF module can be used in various electronic devices having a display portion, such as TVs, monitors, and laptops. At this time, the COF module can also be used in an electronic device having a curved display portion.

However, the embodiment is not limited to this, and of course, the COF flexible printed circuit board and the COF module processed therefrom 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 (10)

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 a semiconductor, a second pad portion electrically connected to a 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 semiconductor, 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 printed 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 printed 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 printed circuit board wherein the width of the dummy pattern is smaller than the width of the two bonding regions. According to clause 1,
A flexible printed circuit board wherein the dummy pattern has a width greater than the width of the two bonding regions. According to clause 1,
The dummy pattern is a flexible printed circuit board including the same material as the circuit pattern. According to clause 1,
The dummy pattern is a flexible printed circuit board arranged to overlap the fourth pad portion in the thickness direction of the substrate. According to clause 1,
A flexible printed 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 a flexible printed circuit board arranged in a diagonal pattern forming a predetermined angle with the fourth pad on a second surface corresponding to the second bonding area. A flexible printed 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.

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