Flexible printed circuit board, COF module comprising flexible printed circuit board and electronic equipment

Abstract

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

Description

Technical Field

[0001] The embodiment relates to a flexible circuit board, a COF module and an electronic device including the flexible circuit board. The flexible circuit board may be a flexible circuit board for COF. Background Art

[0002] Recently, various electronic products have become thinner, smaller, and lighter. Therefore, various studies are being conducted to mount semiconductor chips at high density in narrow areas of electronic products.

[0003] COF (Chip On Film) uses a flexible substrate. Therefore, COF is applied to flexible displays. That is, the COF method is applied to various wearable electronic devices. In addition, COF can achieve fine pitch. Therefore, COF can be applied to high-resolution displays.

[0004] The COF is formed by mounting a semiconductor chip on a flexible circuit board in the form of a thin film. For example, the semiconductor chip may include an integrated circuit (IC) chip or a large-scale integrated circuit (LSI) chip.

[0005] On the other hand, the chip is connected to the external printed circuit board and the display panel through the circuit pattern. For example, the pad portion is respectively arranged at one end and the other end of the circuit pattern. In addition, one pad portion is electrically connected to the terminal of the chip. In addition, the other pad portion is connected to the terminal of the printed circuit board and the terminal of the display panel. Therefore, the chip, the printed circuit board and the display panel are electrically connected through the COF. In addition, the signal is transmitted to the display panel through the circuit pattern.

[0006] COF (Chip On Film) type flexible circuit boards are used in flexible displays. Accordingly, the flexible circuit boards are bent in one direction.

[0007] When the flexible circuit board is bent, cracks may be generated in the circuit pattern located in the bent area, and thus, the electrical characteristics of the flexible circuit board may be degraded.

[0008] Therefore, a flexible circuit board with a new structure that can solve the above problems is needed. Summary of the invention

[0009] Technical issues

[0010] The embodiment provides a flexible circuit board having improved reliability.

[0011] Technical Solution

[0012] A flexible circuit board according to an embodiment includes: a substrate, the substrate including a first surface and a second surface opposite to the first surface; a circuit pattern, the circuit pattern is arranged on the first surface of the substrate; and a protective layer, the protective layer is located 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 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, wherein the second circuit pattern includes a third pad portion configured to be electrically connected to the 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, wherein the first surface of the substrate includes a first bonding area and a second bonding area, the second pad portion is arranged on the first bonding area, and the fourth pad portion is arranged on the second bonding area, and wherein the dummy pattern is arranged on the second surface of the substrate corresponding to the second bonding area.

[0013] Beneficial Effects

[0014] The flexible circuit board according to the embodiment includes a dummy pattern.

[0015] In detail, the flexible circuit board according to the embodiment includes a circuit pattern disposed on a first surface and a dummy pattern disposed on a second surface.

[0016] The dummy pattern is partially disposed on the second surface. The dummy pattern is disposed in a region that completely or partially corresponds to a pad portion connected to the display panel.

[0017] The flexible circuit board forms a COF module by mounting a chip. In addition, the flexible circuit board is bent in one direction. Therefore, stress may be generated in the flexible circuit board. The stress may be transmitted in a direction toward the pad portion.

[0018] Therefore, when the pad portion and the terminal portion of the display panel are bonded, the anti-corrosion layer for preventing the pad portion from corroding may be peeled off. In addition, cracks may be generated in the pad portion exposed by the peeling of the anti-corrosion layer due to stress.

[0019] The flexible circuit board according to the embodiment includes a dummy pattern arranged on the second surface corresponding to the pad part or the pad part and the wiring part. The dummy pattern can prevent the peeling of the anti-corrosion layer. In addition, the dummy pattern can prevent the pad part from breaking.

[0020] Therefore, the flexible circuit board according to the embodiment may have improved bending characteristics and reliability. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 is a top view of a flexible circuit board according to an embodiment.

[0022] Figure 2 and Figure 3 is along Figure 1 A cross-sectional view taken at area AA'.

[0023] Figure 4 is along Figure 1 A cross-sectional view taken at area BB'.

[0024] Figure 5 is along Figure 1 A cross-sectional view taken at area CC'.

[0025] Figure 6 yes Figure 1 An enlarged view of the bottom view of the flexible circuit board in area D.

[0026] Figure 7 is along Figure 6 A cross-sectional view taken at area EE'.

[0027] Figure 8 yes Figure 1 Another enlarged view of the bottom view of the flexible circuit board in area D.

[0028] Fig. 9 is along Figure 8 A cross-sectional view taken at area FF'.

[0029] Fig.10 yes Figure 1 Another enlarged view of the bottom view of the flexible circuit board in area D.

[0030] Fig.11 is along Fig.10 A cross-sectional view taken at area G-G'.

[0031] Figure 12 to Figure 14 yes Figure 1 Another enlarged view of the bottom view of the flexible printed circuit board in area D.

[0032] Fig.15 is a top view of a COF module according to an embodiment.

[0033] Fig.16 is a cross-sectional view illustrating a connection relationship of a COF module including a flexible printed circuit board according to an embodiment.

[0034] Figures 17 to 19 is a diagram of an electronic device including a flexible printed circuit board according to an embodiment. DETAILED DESCRIPTION

[0035] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, the spirit and scope of the present invention are not limited to a part of the described embodiments, and can be implemented in various other forms, and one or more elements of the embodiments can be selectively combined and rearranged within the spirit and scope of the present invention.

[0036] In addition, unless otherwise clearly defined and described, the terms (including technical terms and scientific terms) used in the embodiments of the present invention may be understood to have the same meaning as that generally understood by ordinary technicians in the field to which the present invention belongs, and terms (for example, terms defined in commonly used dictionaries) may be interpreted as having a meaning consistent with their meaning in the context of the relevant field.

[0037] In addition, the terms used in the embodiments of the present invention are used to describe the embodiments and are not intended to limit the present invention. In this specification, unless otherwise specified in the wording, a singular form may also include a plural form, and when described as "at least one (or more) of A (and), B and C", it may include at least one of all combinations that can be combined with A, B and C.

[0038] In addition, when describing the elements of the embodiments of the present invention, terms such as first, second, A, B, (a), and (b) may be used. These terms are only used to distinguish elements from other elements, and these terms are not limited to the nature, order, or sequence of the elements.

[0039] In addition, when an element is described as being “connected” or “coupled” to another element, it may include not only a case where the element is directly “connected” or “coupled” to the other element, but also a case where the element is “connected” or “coupled” to the other element through another element between the element and the other element.

[0040] In addition, when described as being formed or arranged "on" or "under" each element, "on" or "under" may include not only the case where two elements are directly connected to each other, but also the case where one or more other elements are formed or arranged between the two elements.

[0041] In addition, when expressed as “upper” or “lower”, not only an upper direction based on one element but also a lower direction based on one element may be included.

[0042] Hereinafter, a flexible circuit board, a COF module, and an electronic device including the same according to embodiments will be described with reference to the accompanying drawings.

[0043] Figure 1 is a top view of a flexible circuit board according to an embodiment.

[0044] Reference Figure 1, the flexible circuit board 1000 includes a substrate 100 and a circuit pattern 200 disposed on the substrate 100 .

[0045] The substrate 100 includes a first surface 1S and a second surface 2S opposite to the first surface 1S.

[0046] 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 thereto. The substrate 100 may include polyethylene terephthalate (PET) or polyethylene naphthalate (PEN). Therefore, the flexible circuit board can be used in various electronic devices. For example, the flexible circuit board has excellent flexibility. Therefore, the flexible circuit board can be applied to wearable electronic devices.

[0047] The substrate 100 may have a thickness of 20 μm to 100 μm. 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 μm to 40 μm. If the thickness of the substrate 100 exceeds 100 μm, the overall thickness of the flexible circuit board may increase. Therefore, the flexibility characteristics of the flexible circuit board are reduced. In addition, if the thickness of the substrate 100 is less than 20 μm, the rigidity of the substrate may be reduced. Therefore, when the chip is mounted on the substrate, the substrate 100 may be damaged by heat and pressure.

[0048] The substrate 100 includes an active area UA and a non-active area UA. The active area AA may be a central area of ​​the substrate 100. The non-active area UA may be an edge area of ​​the substrate 100. The non-active area UA may surround the active area AA.

[0049] The active area AA includes a chip mounting area CA. In detail, the chip mounting area CA is an area on which a chip (C) connected to a circuit pattern is mounted.

[0050] In addition, the circuit patterns 210 and 220 are disposed on the active area AA. In detail, the circuit pattern includes a plurality of circuit patterns. The plurality of circuit patterns extend in a plurality of directions. In addition, the plurality of circuit patterns are spaced apart from each other.

[0051] The active area AA is an area actually used in the flexible wiring board 1000 .

[0052] The circuit pattern is not provided in the unactive area UA. That is, the active area AA and the unactive area UA are distinguished by whether the circuit pattern is provided.

[0053] The unactive area UA includes a plurality of holes. In detail, the unactive area UA includes a plurality of sprocket holes H. The flexible circuit board is rolled or unrolled in a roll-to-roll manner through the sprocket holes.

[0054] The unactive area UA is an area that is not actually used in the flexible circuit board 1000. In detail, the unactive area UA is an area that is removed after manufacturing the COF module.

[0055] In detail, the boundary between the active area AA and the unactive area UA is defined by the cutting line CL. After the cutting line CL is cut, the flexible circuit board 1000 is processed into a COF module. Therefore, the flexible circuit board 1000 is applied to various electronic devices.

[0056] The circuit pattern includes a wiring portion and a pad portion. In addition, a plurality of circuit patterns are disposed in the active area AA. In detail, the first circuit pattern 210 and the second circuit pattern 220 are disposed in the active area AA. The first circuit pattern 210 and the second circuit pattern 220 are disposed on the first surface 1S.

[0057] Reference Figures 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 portion 211 is connected to the first pad portion 212a and the second pad portion 212b.

[0058] The first wiring portion 211 , the first pad portion 212 a , and the second pad portion 212 b may be integrally formed.

[0059] In addition, the first wiring portion 211 may extend in the first direction D1 based on the chip mounting area CA.

[0060] The first pad portion 212a is electrically connected to a chip disposed in a chip mounting region. In addition, the second pad portion 212b is electrically connected to a printed circuit board. In addition, the first wiring portion 211 transmits a signal between the chip and the printed circuit board.

[0061] The 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. In addition, the protective layer 300 is not disposed on the first pad portion 212a and the second pad portion 212b. Therefore, the first pad portion 212a and the second pad portion 212b are exposed to the outside.

[0062] In addition, refer to Figure 1 and Figure 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 arranged inside the chip mounting area CA. The fourth pad portion 222b is arranged outside the chip mounting area CA. The second wiring portion 221 is arranged between the third pad portion 222a and the fourth pad portion 222b. The second wiring portion 221 is connected to the third pad portion 222a and the fourth pad portion 222b.

[0063] The second wiring portion 221 , the third pad portion 222 a , and the fourth pad portion 222 b may be integrally formed.

[0064] In addition, 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 a direction opposite to the first direction D1.

[0065] The third pad portion 222a is electrically connected to a chip disposed in a chip mounting region. In addition, the fourth pad portion 222b is electrically connected to a display panel. In addition, the second wiring portion 221 transmits a signal between the chip and the display panel.

[0066] The 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. In addition, the protective layer 300 is not disposed on the third pad portion 222a and the fourth pad portion 222b. Therefore, the third pad portion 222a and the fourth pad portion 222b are exposed to the outside.

[0067] 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 may include at least one metal of copper (Cu), aluminum (Al), chromium (Cr), nickel (Ni), silver (Ag), molybdenum (Mo), gold (Au), titanium (Ti), and alloys thereof.

[0068] In the following, reference will be made to Figure 2 and Figure 3 Describes the layer structure of the circuit pattern. Figure 2 and Figure 3 , description will be made based on the first circuit pattern 210. However, the embodiment is not limited thereto. Figure 2 and Figure 3 The description described in can be equally applied to the second circuit pattern 220 .

[0069] Reference Figure 2The first circuit pattern 210 is formed in multiple layers. In detail, the first wiring portion 211 and the first pad portion 212a include a first metal layer 201 and a second metal layer 202. In addition, although not shown in the figure, the second pad portion 212b also includes a first metal layer 201 and a second metal layer 202.

[0070] 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 by electroless plating. The seed layer includes a metal material. For example, the seed layer may include copper.

[0071] In addition, the second metal layer 202 is a plated layer. In detail, the second metal layer 202 is a plated layer formed by electroplating using the first metal layer 201 as a seed layer.

[0072] The thickness of the first metal layer 201 is smaller than the thickness of the second metal layer 202 .

[0073] For example, the thickness of the first metal layer 201 may be 0.7 μm to 2 μm. In addition, the thickness of the second metal layer 202 may be 10 μm to 25 μm.

[0074] 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).

[0075] The bonding layer 203 may be disposed on the second metal layer 201. In detail, the bonding layer 203 is disposed on the side surface of the first metal layer 201, the side surface of the second metal layer 202, and the upper 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.

[0076] The bonding layer 203 includes a metal. For example, the bonding layer 203 may include tin (Sn).

[0077] The thickness of the bonding layer 203 may be 0.3 μm to 0.7 μm. The bonding layer 203 may increase the tin content as the bonding layer extends from the lower surface of the bonding layer to the upper surface of the bonding layer. The lower surface of the bonding layer 203 is the surface that the second metal layer 202 contacts.

[0078] Since the bonding layer 203 and the second metal layer 202 are in contact with each other, the tin content in the bonding layer 203 increases and the copper content decreases as the bonding layer extends from the lower surface of the bonding layer to the upper surface of the bonding layer.

[0079] Therefore, only pure tin may remain in a thickness range of 0.1 μm to 0.3 μm on the upper surface of the bonding layer 203 .

[0080] The terminals of the chip, the terminals of the printed circuit board, and the terminals of the display panel are easily bonded to the first pad portion and the second pad portion through the bonding layer 203. In detail, the terminals and the pad portion are bonded 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 bonded.

[0081] Therefore, the bonding layer 203 is not separated from the first pad portion 212 a but becomes a part of the first pad portion 212 a .

[0082] The first circuit pattern 210 may have a thickness of 2 μm to 25 μm. For example, the first circuit pattern 210 may have a thickness of 5 μm to 20 μm. For example, the first circuit pattern 210 may have a thickness of 7 μm to 15 μm.

[0083] 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 during the manufacturing process to separate the circuit pattern. Therefore, the first metal layer 201 is etched. Therefore, the thickness of the first circuit pattern 210 finally manufactured is less than the sum of the thicknesses of the first metal layer 201, the second metal layer 202, and the bonding layer 203.

[0084] If the thickness of the first and second circuit patterns 210 and 220 is less than 2 μm, the resistance of the first and second circuit patterns 210 and 220 increases. If the thickness of the first and second circuit patterns 210 and 220 exceeds 25 μm, it is difficult to form a fine pattern.

[0085] On the other hand, a buffer layer 205 may be further disposed between the substrate 100 and the first circuit pattern 210. The buffer layer 205 improves adhesion between the substrate 100 and the first circuit pattern 210.

[0086] The buffer layer 205 may be formed as a multilayer. In detail, the buffer layer 205 includes a first buffer layer 205a and a second buffer layer 205b located on the first buffer layer 205a. Therefore, the first buffer layer 205a contacts the substrate 100. In addition, the second buffer layer 205b contacts the first circuit pattern 201.

[0087] The first buffer layer 205a may include a material having good adhesion to the substrate 100. For example, the first buffer layer 205a may include nickel (Ni). In addition, the second buffer layer 205b may include a material having good adhesion to the first circuit pattern 210. For example, the second buffer layer 205b may include chromium (Cr).

[0088] The buffer layer 205 may have a film thickness in nanometers, for example, the thickness of the buffer layer 205 may be less than 20 nm.

[0089] The adhesion between the substrate 100 and the first circuit pattern 210 is improved by the buffer layer 205. Therefore, peeling of the first circuit pattern 201 is prevented.

[0090] On the other hand, referring to Figure 3 , the bonding layer 203 may include a first bonding layer 203 a and a second bonding layer 203 b .

[0091] In detail, the first bonding layer 203a may be disposed on the first wiring portion 211 and the first pad portion 212a. In addition, although not shown in the figure, 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.

[0092] In addition, the second bonding layer 203b may be provided only on the first and second pad portions 212a and 212b. That is, the layer structure of the first wiring portion 211 and the layer structure of the first and second pad portions 212a and 212b are changed by the second bonding layer 203b.

[0093] The first bonding layer 203a and the second bonding layer 203b may include a metal. In detail, the first bonding layer 203a and the second bonding layer 203b may contain tin (Sn).

[0094] 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.

[0095] For example, the first bonding layer 203a may have a film thickness of 0.02 μm to 0.06 μm. In addition, the second bonding layer 203b may have a thickness of 0.2 μm to 0.6 μm.

[0096] If the bonding layer is thickly disposed between the protective layer 300 and the first wiring portion 211, cracks may be generated when the flexible circuit board is bent. Therefore, the first bonding layer 231 between the protective layer 300 and the first wiring portion 211 is formed to a thin film thickness. Therefore, cracks can be prevented from being generated when the flexible circuit board is bent.

[0097] In addition, the second bonding layer 203b may have a high tin content as extending from the lower surface to the upper surface. The lower surface is a surface with which the first bonding layer 203a makes contact.

[0098] The second bonding layer 203b may have a higher tin content and a lower copper content as it extends from the lower surface to the upper surface. Therefore, only pure tin may remain in a thickness range of 0.1 μm to 0.3 μm on the upper surface of the second bonding layer 203b.

[0099] Through the second bonding layer 203b, the terminals of the chip, the terminals of the printed circuit board, and the terminals of the display panel are easily bonded to the first pad portion and the second pad portion. In detail, the terminal and the pad portion are bonded 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 terminal and the pad portion are easily bonded.

[0100] Therefore, the first bonding layer 203 a and the second bonding layer 203 b are not separated from the first pad portion 212 a but become a part of the first pad portion.

[0101] On the other hand, 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 may be disposed on the first circuit pattern 210 and the second circuit pattern 220 except for the first pad portion, the second pad portion, the third pad portion, and the fourth pad portion.

[0102] The protective layer 300 may contain solder paste. For example, the solder paste may include a thermosetting resin, a thermoplastic resin, a filler, a curing agent, or a curing accelerator.

[0103] On the other hand, in the above description, the first circuit pattern 210 and the second circuit pattern 220 are described as being disposed on the same surface of the substrate 100 , but the embodiment is not limited thereto.

[0104] 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 surface of the substrate 100, and the second circuit pattern 220 may be disposed on another surface of the substrate 100 opposite to the one surface.

[0105] Therefore, the display panel is connected to the chip on one surface of the substrate 100. In addition, the printed circuit board is connected to the chip on the other surface of the substrate 100.

[0106] Reference Figure 1 , the flexible circuit board 1000 includes a first bonding area BA1 and a second bonding area BA2.

[0107] The second pad portion 212b is disposed on the first bonding area BA1. In addition, 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.

[0108] The printed circuit board and the display panel are joined at the first joining area BA1 and the second joining area BA2. In detail, the first joining area BA1 is joined to the terminal portion of the printed circuit board by a conductive adhesive. In addition, the second joining area BA2 is joined to the terminal portion of the display panel by a conductive adhesive. At this time, an anti-corrosion layer may be additionally provided in the region of the second pad portion 212b and the fourth pad portion 222b where the conductive adhesive is not provided in the joining area. The anti-corrosion layer prevents corrosion of the pad portion.

[0109] For example, refer to Figure 5 The second bonding area BA2 may include a 2-1st bonding area BA2-1 and a 2-2nd bonding area BA2-2. Different materials may be provided in the 2-1st bonding area BA2-1 and the 2-2nd bonding area BA2-2.

[0110] The 2-1st bonding area BA2-1 is an area where a conductive adhesive is provided. In addition, the 2-2nd bonding area BA2-2 is an area where an anti-corrosion layer is provided. In detail, when the fourth pad portion 222b is connected to the terminal of the display panel, the conductive adhesive is only provided on a portion of the fourth pad portion 222b. Therefore, an area where the fourth pad portion 222b is exposed appears. The exposed area is defined as the 2-2nd bonding area BA2-2. Therefore, an anti-corrosion layer is provided on the 2-2nd bonding area BA2-2. Therefore, corrosion of the 2-2nd bonding area BA2-2 is prevented.

[0111] On the other hand, 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 the axis. Therefore, the stress generated by the bending is transmitted to the second bonding area. The anti-corrosion layer provided in the 2-2 bonding area BA2-2 may be peeled off due to the stress. That is, the anti-corrosion layer has a lower adhesive strength than the conductive adhesive. Therefore, it may be peeled off from the pad portion due to the stress.

[0112] Therefore, stress is transmitted from the boundary region between the 2-1st bonding area BA2-1 and the 2-2nd bonding area BA2-2 to the fourth pad portion. In addition, cracks may be generated in the fourth pad portion corresponding to the boundary region. Therefore, the reliability of the flexible circuit board may be reduced.

[0113] Therefore, the flexible circuit board according to the embodiment solves the above-mentioned problem by additionally arranging a dummy pattern.

[0114] In addition, the dummy pattern prevents the anticorrosion layer on the 2-2 bonding region from being peeled off.

[0115] Reference Figure 6 and Figure 7 , a dummy pattern 400 is provided on the second surface 2S. The dummy pattern 400 is provided at a position overlapping with the fourth pad portion 222b. In detail, the dummy pattern 400 partially overlaps with the fourth pad portion 222b. The dummy pattern 400 is provided to be smaller than the area of ​​the second bonding area BA2 where the fourth pad portion 222b is provided. For example, the width W1 of the dummy pattern 400 may be more than 50%, more than 60%, or more than 70% of the width W2 of the second bonding area BA2. For example, the width W1 of the dummy pattern 400 may be 50% to less than 90% of the width W2 of the second bonding area BA2.

[0116] In addition, the area of ​​the dummy pattern 400 may be greater than 50%, greater than 60%, or greater than 70% of the area of ​​the second bonding area BA2 or the fourth pad portion 222b. For example, the area of ​​the dummy pattern 400 may be 50% to less than 90% of the area of ​​the second bonding area BA2 or the fourth pad portion 222b.

[0117] The total area of ​​the dummy pattern in the second bonding area can be greater 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 portions are electrically connected to the terminal portion of the display panel, respectively. However, the dummy pattern is arranged to prevent cracks in the fourth pad portion. Therefore, even if the intervals between the plurality of dummy patterns are small, the characteristics will not be reduced. In addition, even if the plurality of dummy patterns are connected, the characteristics will not be reduced. Alternatively, the dummy pattern can be formed on the entire surface of the second bonding area.

[0118] The dummy pattern 400 is set to be smaller than the area of ​​the second bonding area BA2 or the fourth pad portion 222b. Therefore, the strength difference between the boundary area of ​​the 2-1st bonding area BA2-1 and the 2-2nd bonding area BA2-2 and the 2-1st bonding area BA2-1 is reduced. In addition, the strength difference between the boundary area of ​​the 2-1st bonding area BA2-1 and the 2-2nd bonding area BA2-2 and the 2-2nd bonding area BA2-2 is reduced. Therefore, the flexible printed circuit board can be prevented from bending by the dummy pattern 400.

[0119] The dummy pattern 400 is disposed at a position overlapping the 2-1st bonding area BA2-1 and the 2-2nd bonding area BA2-2. In addition, the dummy pattern 400 is disposed on a boundary area BAA between the 2-1st bonding area BA2-1 and the 2-2nd bonding area BA2-2.

[0120] The adhesion of 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 on the boundary area BAA of the 2-1st bonding area BA2-1 and the 2-2nd bonding area BA2-2, cracks can be prevented from being generated in the fourth pad portion. In addition, the conductive adhesive and the anti-corrosion layer disposed in the 2-1st bonding area BA2-1 and the 2-2nd bonding area BA2-2 can be prevented from being peeled off. In particular, the anti-corrosion layer having a low adhesion strength can be prevented from being peeled off from the pad portion.

[0121] The dummy pattern 400 is used to support the boundary area of ​​the conductive adhesive and the anti-corrosion layer. Therefore, when the flexible circuit board is bent, the anti-corrosion layer can be prevented from being peeled off at the boundary area. Therefore, the fourth pad portion can be prevented from being exposed to the outside due to the peeling of the anti-corrosion layer. In addition, the fourth pad portion can be prevented from being broken due to stress.

[0122] The dummy pattern 400 may include copper (Cu). However, the embodiment is not limited thereto. The dummy pattern 400 may include at least one metal of copper (Cu), aluminum (Al), chromium (Cr), nickel (Ni), silver (Ag), molybdenum (Mo), gold (Au), titanium (Ti), and alloys thereof.

[0123] The dummy pattern 400 is not connected to the chip (C). That is, a signal does not move through the dummy pattern 400.

[0124] The embodiment has a layer structure similar to that of a double-sided flexible circuit board in which circuit patterns are formed on both sides of a substrate. However, through holes and through electrodes are not separately formed in the substrate. Therefore, manufacturing costs and defects are reduced, thereby improving process efficiency.

[0125] In addition, the embodiment has a layer structure similar to that of 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 of the embodiment is formed in the second bonding area in contact with the display. In detail, the dummy pattern is formed between the bending area and the second bonding area of ​​the flexible circuit board, so that the bending characteristics are not affected when the flexible circuit board is bent. Therefore, the design reliability and the reliability of the display can be improved. In addition, the embodiment can also arrange a separate heat dissipation pattern different from the dummy pattern in the area corresponding to the chip mounting area.

[0126] The dummy pattern may overlap with the fourth pad portion 222b, and the heat dissipation pattern may be formed on the second surface overlapping with the chip mounting area. In addition, the dummy pattern and the heat dissipation pattern may be provided in an area not corresponding 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, when the flexible circuit board and the display are combined and bent, the dummy pattern or the heat dissipation pattern may generate cracks. Therefore, the reliability of the flexible circuit board may be reduced.

[0127] 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. Therefore, a difference in thermal expansion coefficient between the first surface 1S and the second surface 2S of the substrate 100 may be reduced.

[0128] The thickness of the dummy pattern 400 and the fourth pad portion 222b may be the same. 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 less 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. Therefore, 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. Therefore, the dummy pattern 400 can stably support the fourth pad portion 222b on the second surface 2S. Therefore, stress concentration can be prevented.

[0129] Reference Figure 8 and Fig. 9 , the dummy pattern 400 may be located at a position overlapping with the fourth pad portion 222b. In detail, the area of ​​the dummy pattern 400 may be the same as or similar to the area of ​​the second bonding area BA2. For example, the width W1 of the dummy pattern 400 may be more than 90%, more than 93%, or more than 95% 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.

[0130] In addition, 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.

[0131] The dummy pattern 400 is set to be almost the same as the area of ​​the second bonding area BA2 or the fourth pad portion 222b. Therefore, the dummy pattern 400 can stably support the second bonding area BA2. That is, the dummy pattern 400 is set on almost the entire area of ​​the second bonding area BA2. Therefore, cracks in the fourth pad portion and peeling of the anti-corrosion layer caused by the stress generated in the second bonding area can be prevented.

[0132] Reference Fig.10 and Fig.11 , the dummy pattern 400 may be arranged at a position overlapping with the fourth pad portion 222b. In detail, the area of ​​the dummy pattern 400 may be greater than the area of ​​the second bonding area BA2 or the fourth pad portion 222b. That is, the dummy pattern 400 may be arranged at a position overlapping with the fourth pad portion 222b and the second wiring portion 221. In detail, the dummy pattern 400 completely overlaps with the second bonding area BA2 provided with the fourth pad portion 222b. In addition, the dummy pattern 400 partially overlaps with the area provided with the second wiring portion 221. One side of the dummy pattern 400 may be formed identically or closely to the cutting line CL. In addition, the other side of the dummy pattern 400 may be arranged closer to the fourth pad portion 222b than the folding axis FAX.

[0133] The dummy pattern 400 overlaps the second wiring portion 221 between the folding axis FAX and the fourth pad portion 222b. In addition, the dummy pattern 400 is not formed in the region corresponding to the folding axis FAX. Therefore, when the flexible circuit board is combined with the display and bent, cracks can be prevented from being generated in the dummy pattern 400 due to tension occurring in the region corresponding to the folding axis FAX of the second surface. Therefore, the reliability of the display can be improved.

[0134] The dummy pattern 400 is larger than the area of ​​the second bonding area BA2. Therefore, the strength difference between the boundary area of ​​the fourth pad portion 222b and the second wiring portion 221 can be reduced. In addition, the strength difference between the boundary area of ​​the fourth pad portion 222b and the protective layer can be reduced. That is, the dummy pattern 400 is also arranged in the area overlapping with the second wiring portion. Therefore, it is possible to prevent the strength difference from occurring in the boundary area between the fourth pad portion 222b and the second wiring portion 221 and in the boundary area between the fourth pad portion 222b and the protective layer. Therefore, it is possible to prevent cracks from occurring in the wiring portion due to the bending of the flexible circuit board at the boundary area between the pad portion and the wiring portion. In addition, it is possible to prevent the peeling of the protective layer and the anti-corrosion layer.

[0135] On the other hand, Figures 6 to 11, it is shown 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. Therefore, corrosion of the dummy pattern 400 may be prevented.

[0136] 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 anti-corrosion layer from being peeled off. In addition, cracks can be prevented from being generated in the pad portion.

[0137] In addition, the width of the dummy pattern may be less 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 flexibility of the flexible circuit board. Therefore, the bending characteristics of the flexible circuit board are reduced. Therefore, the thickness of the display panel may increase. Alternatively, as the dummy patterns formed on the second surface increase, additional cracks may be generated. Therefore, the reliability of the flexible circuit board may be reduced.

[0138] On the other hand, the dummy pattern may be formed into patterns of various shapes.

[0139] Reference Figure 12 to Figure 14 , the dummy pattern 400 may include a plurality of patterns spaced apart from each other.

[0140] Reference Fig.12 , the dummy pattern 400 may overlap with 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 overlap completely or partially in the thickness direction of the substrate 100.

[0141] For example, the dummy pattern 400 may be disposed on the second surface 2S in a region corresponding to the fourth pad portion 222 b on the first surface 1S.

[0142] Alternatively, refer to Fig.13 , the dummy pattern 400 may be arranged alternately with the fourth pad portion 222b. In detail, the dummy pattern 400 may be arranged on the second surface 2S corresponding to the separation 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.

[0143] In the second bonding area BA2, the dummy patterns 400 and the fourth land portions 222b are arranged in an alternating manner. Therefore, it is possible to prevent ripples from being generated in areas where the copper pattern is not arranged in the first and second surfaces 1S and 2S of the second bonding area.

[0144] That is, since the dummy patterns 400 and the fourth pad parts 222b are alternately disposed in the second bonding area BA2, the copper pattern is disposed in almost the entire area of ​​the second bonding area BA2. Therefore, generation of ripples in an area where the copper pattern is not disposed can be reduced.

[0145] Reference Fig.14 , the dummy pattern 400 may extend in a direction different from the fourth pad portion 222b. That is, the length direction of the dummy pattern 400 may be different from the length direction of the fourth pad portion 222b. For example, the dummy pattern 400 may extend in a diagonal direction forming a specific angle with the fourth pad on the second surface.

[0146] Therefore, the dummy pattern 400 may partially overlap the fourth pad portion 222b. In addition, the dummy pattern 400 may be disposed to cover the width direction of the separation region of the fourth pad portion 222b.

[0147] For example, the dummy pattern and the fourth pad portion may overlap vertically at the boundary region between the 2-1st bonding region and the 2-2nd bonding region. This can prevent stress from concentrating at the boundary region. In addition, the width direction of the separation region of the fourth pad portion may be covered together.

[0148] Since the dummy pattern 400 is disposed in the diagonal direction, the dummy pattern 400 is disposed to cover the width direction of the separation region of the fourth pad portion 222b. Therefore, the dummy pattern 400 can support the fourth pad portion 222b in a wider region.

[0149] Hereinafter, the present invention will be described in more detail by the bending characteristics of the flexible circuit board according to the embodiments and the comparative examples. These embodiments are presented only as examples to describe the present invention in more detail. Therefore, the present invention is not limited to these embodiments.

[0150] Example 1

[0151] The flexible circuit board is manufactured by forming the above-mentioned first circuit pattern, second circuit pattern and protective layer on a first surface of a polyimide (PI) substrate.

[0152] Next, a dummy pattern is formed on the second surface corresponding to the second bonding area of ​​the second circuit pattern. Fig.12 As shown, the dummy pattern is disposed on a region corresponding to the fourth pad portion.

[0153] Next, the bending characteristics of the flexible circuit board were measured. The bending characteristics measured the number of bends at which cracks were generated in the second pad portion when the flexible circuit board was bent.

[0154] Example 2

[0155] A flexible circuit board was manufactured in the same manner as in Example 1, except that Fig.13 As shown, the dummy patterns and the fourth pad portions are alternately arranged, and the bending characteristics of the flexible circuit board are measured.

[0156] Example 3

[0157] A flexible circuit board was manufactured in the same manner as in Example 1, except that Figure 8 As shown, the dummy patterns are all arranged on the area corresponding to the second bonding area, and the bending characteristics of the flexible circuit board are measured.

[0158] Example 4

[0159] A flexible circuit board was manufactured in the same manner as in Example 1, except that Fig.14 As shown, the dummy pattern is disposed in a diagonal pattern on an area corresponding to the second bonding area, and the bending characteristics of the flexible circuit board are measured.

[0160] Comparative Example

[0161] A flexible circuit board was manufactured in the same manner as in Example 1 except that the dummy pattern was not provided, and the bending characteristics of the flexible circuit board were measured.

[0162] [Table 1]

[0163]

[0164] Referring to Table 1, the flexible circuit boards of Examples 1 to 4 have improved bending characteristics compared to the flexible circuit board of the comparative example. That is, the flexible circuit boards of Examples 1 to 4 include dummy patterns. The dummy patterns can prevent the second pad portion from being broken due to stress during bending. Therefore, damage to the second pad portion due to stress can be reduced by the dummy patterns. Therefore, the flexible circuit board according to the embodiment can have improved reliability.

[0165] Fig.15 is a diagram showing a top view of a COF module according to an embodiment.

[0166] Reference Fig.15 The COF module includes the above-mentioned flexible circuit board. In addition, it may include a chip (C) disposed in a chip mounting area CA.

[0167] In addition, the flexible circuit board 1000 may include the above-mentioned protection layer 300 .

[0168] On the other hand, the COF module 2000 is manufactured by cutting the flexible circuit board 1000 and then mounting the chip (C). Figure 1 After the cutting lines CL are cut, a driving chip electrically connected to the first circuit pattern and the second circuit pattern is mounted in the chip mounting region.

[0169] The COF module is located between the display panel and the substrate and is capable of transmitting electrical signals.

[0170] 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.

[0171] Reference Fig.16 , one end of the COF module 2000 is connected to the display panel 3000 . In addition, the other end of the COF module 2000 is connected to the printed circuit board 4000 .

[0172] In addition, the COF module 2000 and the terminal 3100 of the display panel 3000 may be bonded via the conductive adhesive 510 and the anti-corrosion layer 520. Specifically, the 2-1st bonding area BA2-1 of the COF module and the terminal 3100 of the display panel 3000 are bonded via the conductive adhesive 510.

[0173] The COF module 2000 and the display panel 3000 may be electrically connected via a conductive adhesive. The conductive adhesive is a resin in which conductive particles are dispersed. Therefore, the signal of the display panel 3000 may be transmitted to the COF module 2000 via the conductive particles.

[0174] Next, the anticorrosion layer 520 is provided on the 2-2 bonding area BA2-2, thereby preventing corrosion of the exposed area of ​​the fourth pad portion 222b.

[0175] In addition, the dummy pattern 400 is disposed on the substrate 100. Therefore, when the COF module 2000 is bent, the anti-corrosion layer 520 may be peeled off, and cracks may be prevented from being generated in the fourth pad part 222b.

[0176] The COF module 1000 includes a flexible substrate, and thus, can have a rigid form or a bent form between the display panel 3000 and the printed circuit board 4000 .

[0177] The COF module 2000 can connect the display panel 3000 and the printed circuit board 4000, which are arranged facing each other, into a bent state. Therefore, the thickness of the electronic device is reduced and the degree of freedom of design is improved. In addition, even if the COF module 2000 is in a bent state, the wire will not break. Therefore, the reliability of the electronic device is improved.

[0178] Since the COF module is flexible, it can be used in various electronic devices.

[0179] For example, refer to Fig.17 , COF modules can be applied to curved flexible touch windows. Flexible touch windows can be applied to wearable touch.

[0180] Reference Fig.18 , the COF module can be applied to a wearable touch device including a curved display. Therefore, the electronic device including the COF module can be thinned or lightweight.

[0181] Reference Fig.19 , the COF module can be applied to various electronic devices having displays such as TVs, monitors, and notebook computers.

[0182] However, the embodiment is not limited thereto. The COF flexible circuit board and the COF module may be used in various electronic devices.

[0183] The characteristics, structures, effects, etc. described in the above embodiments are included in at least one embodiment of the present invention, but are not limited to only one embodiment. In addition, those skilled in the art can combine or modify the characteristics, structures, and effects shown in each embodiment for other embodiments. Therefore, it should be understood that such combinations and modifications are included within the scope of the present invention.

[0184] In addition, the above mainly describes the embodiments, but these embodiments are only examples and do not limit the present invention, and those skilled in the art will understand that, without departing from the essential features of the embodiments, several modifications and applications not presented above can be made. For example, each component specifically represented in the embodiment can be changed. In addition, it should be understood that the differences related to such modifications and such applications are included in the scope of the present invention defined in the appended claims.

Claims

1. A flexible circuit board, include: a substrate comprising a first surface and a second surface opposite to the first surface; a circuit pattern disposed on the first surface of the substrate; and a protective layer, the protective layer being located on the circuit pattern, Wherein, 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 the chip, a fourth pad portion configured to be electrically connected to the display panel, and a second wiring portion connected to the third pad portion and the fourth pad portion. The first surface of the substrate includes a first bonding area and a second bonding area, the second pad portion is arranged on the first bonding area, the fourth pad portion is arranged on the second bonding area, and Wherein, a dummy pattern is arranged on the second surface of the substrate corresponding to the second bonding area.

2. The flexible circuit board according to claim 1, in, The second bonding region includes a 2-1 bonding region configured to be provided with a conductive adhesive and a 2-2 bonding region configured to be provided with an anti-corrosion layer, and Wherein, the dummy pattern is arranged on a boundary area between the 2-1st bonding area and the 2-2nd bonding area.

3. The flexible circuit board according to claim 1, in, A width of the dummy pattern is smaller than a width of the second bonding region.

4. The flexible circuit board according to claim 1, in, The width of the dummy pattern is set to be greater than the width of the second bonding region.

5. The flexible circuit board according to claim 1, in, The dummy pattern includes the same material as the circuit pattern.

6. The flexible circuit board according to claim 1, in, The dummy pattern is disposed to overlap the fourth pad portion in a thickness direction of the substrate.

7. The flexible circuit board according to claim 1, in, The thickness of the dummy pattern is different from the thickness of the fourth pad portion.

8. The flexible circuit board according to claim 1, in, The dummy pattern is disposed on the second surface corresponding to the second bonding area in an inclined pattern forming a certain angle with the fourth pad.

9. A COF module, include: The flexible circuit board according to any one of claims 1 to 8; as well as A chip is disposed in the chip mounting area.

10. An electronic device, include: The COF module according to claim 9; a printed circuit board connected to the first circuit pattern; as well as a display panel connected to the second circuit pattern, The second bonding region includes a 2-1 bonding region and a 2-2 bonding region. A conductive adhesive for bonding the display panel is formed in the 2-1 bonding region, and Wherein, the 2-2 bonding region includes an anti-corrosion layer formed on the fourth pad portion.

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