Flexible printed circuit board, cof module and electronic device including the same

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 first circuit pattern, a second circuit pattern, and a metal pattern disposed on the first surface, in which the first circuit pattern includes a first pad portion, a second pad portion, and a first wiring portion connected to the first pad portion and the second pad portion, and the metal pattern includes a second wiring portion connected to the first pad portion and the second pad portion; the second circuit pattern includes a third pad portion, a fourth pad portion, and a second wiring portion connected to the third pad portion and the fourth pad portion, the second wiring portion includes 2-1 and 2-2 wiring portions extending in different directions, the 2-1 wiring portions are spaced apart by a first pitch, the 2-2 wiring portions are spaced apart by a second pitch, and the second wiring portions are spaced apart by a second pitch. The first pitch is larger than the second pitch, and the metal pattern is disposed between the 2-1-th wiring portions.

Description

Technical Field

[0001] Embodiments relate to a flexible circuit board, a COF module, and an electronic device including the COF module. 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] Among these studies, the COF (Chip-on-Film) method has been applied to flexible displays because it uses a flexible substrate. In other words, the COF method has attracted attention due to its applicability to various wearable electronic devices. Furthermore, the COF method can achieve fine pitches. Therefore, due to the increased number of pixels, it can be used to realize high-resolution displays.

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

[0005] The chip can be connected to an external circuit board and display panel via a circuit pattern. For example, a pad portion is provided at one end and the other end of the circuit pattern, with one pad portion electrically connected to a terminal of the chip. Alternatively, another pad portion can be connected to a terminal of the circuit board and display panel. Thus, the chip, circuit board, and display panel are electrically connected via the COF. This allows signals to be transmitted to the display panel via the circuit pattern.

[0006] The flexible circuit board can include multiple circuit patterns connected to the chip, circuit board, and display panel. Signals can be transmitted to the chip, circuit board, and display panel through the circuit patterns. Subsequently, the chip can be mounted on the flexible circuit board. The flexible circuit board can then be cut along the cutting lines. Thus, a COF module can be manufactured.

[0007] Flexible circuit boards can be bent in one direction. As a result, cracks may appear in the circuit pattern. As a result, the reliability of the COF module may be reduced.

[0008] Therefore, there is a need for a new structure of a flexible circuit board, a COF module, and an electronic device including the COF module that can solve the above problems.

[0009] As a patent related to a flexible circuit board, Korean Patent No. KR10-0618898 (2006.09.01) has been published. Summary of the Invention

[0010] Technical issues

[0011] The present disclosure provides a flexible circuit board with improved reliability.

[0012] Technical Solution

[0013] According to an embodiment, a flexible circuit board includes: a substrate, the substrate including a first surface and a second surface opposite to the first surface; a first circuit pattern, a second circuit pattern and a metal pattern, the first circuit pattern, the second circuit pattern and the metal pattern being arranged on the first surface; and a protective layer, the protective layer being arranged on the first circuit pattern, the second circuit pattern and the metal pattern, wherein the first circuit pattern includes a first pad portion, a second pad portion 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, a fourth pad portion and a second wiring portion connected to the third pad portion and the fourth pad portion, the second wiring portion includes a 2-1 wiring portion and a 2-2 wiring portion extending in different directions, the 2-1 wiring portions are spaced apart by a first spacing, the 2-2 wiring portions are spaced apart by a second spacing, the first spacing is greater than the second spacing, and the metal pattern is arranged between the 2-1 wiring portions.

[0014] Beneficial effects

[0015] The flexible circuit board according to the embodiment includes a metal pattern.

[0016] Flexible circuit boards can be bent in one direction. Therefore, stress may be transferred to the circuit pattern. This may cause cracks to form in the circuit pattern.

[0017] The stress may be proportional to the spacing between the circuit patterns. Therefore, the stress may be greater in areas where the spacing between the circuit patterns is greater.

[0018] The metal pattern is located in an area where the spacing between the circuit patterns is large, thereby preventing cracks from forming in the circuit patterns when the flexible circuit board is bent.

[0019] Therefore, the reliability of the flexible circuit board according to the embodiment is improved.

[0020] Furthermore, the metal patterns are provided in various lengths and positions.

[0021] The metal pattern is spaced apart from the cutting line. Specifically, the metal pattern is located inside the cutting line. Therefore, the flexible circuit board can be easily cut.

[0022] Furthermore, the protective layer is located on the metal pattern, thereby preventing corrosion of the metal pattern. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 is a top view of the flexible circuit board according to the first embodiment.

[0024] Figure 2 yes Figure 1 Magnified view of area A.

[0025] Figure 3 is a graph showing bending strength according to the pitch of the circuit pattern.

[0026] Figure 4 is a photograph showing cracks formed in a circuit pattern.

[0027] Figure 5 is a top view of a flexible circuit board according to a second embodiment.

[0028] Figure 6 and Figure 7 yes Figure 5 Magnified view of area B.

[0029] Figure 8 is a top view of a flexible circuit board according to a third embodiment.

[0030] Figure 9 and Figure 10 yes Figure 8 Magnified view of area C.

[0031] Figure 11 and Figure 12 It is along Figure 1 A cross-sectional view taken at area AA′.

[0032] Figure 13 is a diagram illustrating a COF module according to an embodiment.

[0033] Figures 14 to 16 is a diagram of an electronic device including a flexible circuit board according to an embodiment. DETAILED DESCRIPTION

[0034] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. However, the spirit and scope of the present disclosure are not limited to a portion of the described embodiments and can be implemented in various other forms. Within the spirit and scope of the present disclosure, one or more of the elements of the embodiments can be selectively combined and rearranged.

[0035] In addition, unless otherwise explicitly defined and described, the terms (including technical terms and scientific terms) used in the embodiments of the present disclosure may be interpreted as having the same meaning as that commonly understood by ordinary technicians in the field to which the present disclosure belongs, and those terms such as those defined in commonly used dictionaries may be interpreted as having a meaning consistent with their meaning in the context of the relevant field.

[0036] In addition, the terms used in the embodiments of the present disclosure are used to describe the embodiments and are not intended to limit the present disclosure. 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.

[0037] In addition, when describing the elements of the embodiments of the present disclosure, terms such as first, second, A, B, (a), and (b) may be used. These terms are only used to distinguish an element from other elements and are not limited to the nature, order, or sequence of the elements.

[0038] In addition, when an element is described as being “connected,” “combined” or “in contact with” another element, it may include not only the case where the element is directly “connected,” “combined” or “in contact with” the other element, but also the case where the element is “connected,” “combined” or “in contact with” the other element through another element between the element and the other element.

[0039] In addition, when described as being formed or arranged "on (above)" or "under (below)" each element, "on (above)" or "under (below)" may include not only a situation where two elements are directly connected to each other, but also a situation where one or more other elements are formed or arranged between the two elements.

[0040] Furthermore, when expressed as “on (above)” or “under (below)”, not only an upper direction based on one element but also a lower direction based on the one element may be included.

[0041] In the following description, a first direction 1D is defined as a lengthwise (longitudinal) direction of the flexible circuit board, and a second direction 2D is defined as a widthwise (horizontal) direction of the flexible circuit board.

[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] Reference Figure 1 and Figure 2 , the flexible circuit board 1000 according to the embodiment includes a substrate 100 , a circuit pattern, a protective layer 300 , and a metal pattern 400 .

[0044] The substrate 100 includes a first surface 1S and a second surface 2S opposite to the first surface 1S. A circuit pattern, a protective layer 300, and a metal pattern 400 are provided on the first surface 1S.

[0045] The substrate 100 includes cutting lines CL. The flexible circuit board 1000 is cut along the cutting lines CL. Specifically, after the circuit pattern, metal pattern, protective layer, and chip are provided on the substrate 100, the substrate 100 is cut along the cutting lines CL. Thus, the flexible circuit board 1000 is manufactured into the COF module 2000.

[0046] The substrate 100 includes an active area AA and a non-active area UA. Specifically, the first surface 1S includes the active area AA and the non-active area UA.

[0047] The active area AA and the unactive area UA are separated by the cutting line CL. Specifically, the active area AA is defined as the inner area of ​​the cutting line CL. In addition, the unactive area UA is defined as the outer area of ​​the cutting line CL.

[0048] The active area AA includes a circuit pattern, a protective layer, and a chip. Furthermore, the unactive area UA includes a dummy pattern and sprocket holes SH. The dummy pattern increases the strength of the substrate 100. Furthermore, the flexible circuit board 1000 is wound or unwound in a roll-to-roll manner through the sprocket holes SH.

[0049] The substrate 100 includes a chip mounting area CHA. The chip mounting area CHA is provided on the first surface 1S. The chip mounting area CHA is provided in the active area AA. A chip is provided in the chip mounting area CHA. In addition, a pad portion of a circuit pattern is provided within the chip mounting area CHA. In addition, a protective layer is not provided on the chip mounting area CHA.

[0050] The substrate 100 includes a flexible material. For example, the substrate 100 may include polyimide (PI). However, the embodiment is not limited thereto. The substrate 100 may include a polymer material such as polyethylene terephthalate (PET) or polyethylene naphthalate (PEN). Therefore, the flexible circuit board can be used in various electronic devices including curved display devices. For example, since the flexible circuit board has excellent flexibility, it can be used to mount a semiconductor chip of a wearable electronic device.

[0051] The thickness of substrate 100 may be 20 μm to 100 μm. For example, the thickness of substrate 100 may be 25 μm to 50 μm. For example, the thickness of substrate 100 may be 30 μm to 40 μm. If the thickness of substrate 100 exceeds 100 μm, the overall thickness of the flexible circuit board increases, which may reduce the flexibility of the flexible circuit board. Furthermore, if the thickness of substrate 100 is less than 20 μm, the substrate 100 may be damaged due to the heat and pressure applied to the substrate when the chip is mounted on the flexible circuit board.

[0052] The circuit pattern, the metal pattern 400 and the protective layer 300 are provided on the substrate 100. Specifically, the circuit pattern, the metal pattern 400 and the protective layer 300 are provided on the first surface 1S. Specifically, the circuit pattern, the metal pattern 400 and the protective layer 300 are provided on at least one of the active area AA and the unactive area UA.

[0053] The circuit patterns include a first circuit pattern 210 , a second circuit pattern 220 , and a third circuit pattern 230 .

[0054] Reference Figure 1 The first circuit pattern 210 includes a first wiring portion 211, a first pad portion 212a, and a second pad portion 212b. The first wiring portion 211, the first pad portion 212a, and the second pad portion 212b may be made of the same material. Alternatively, the first wiring portion 211, the first pad portion 212a, and the second pad portion 212b may be integrally formed.

[0055] The first pad portion 212a is provided inside the chip mounting area CHA. Therefore, the first pad portion 212a can be connected to a terminal of the chip. Therefore, the first circuit pattern 210 can be connected to the chip.

[0056] In addition, the second pad portion 212b is located outside the chip mounting area CHA. The second pad portion 212b can be connected to a terminal of an external circuit board. Therefore, the first circuit pattern 210 can be connected to the circuit board.

[0057] Furthermore, the first wiring portion 211 is located between the first pad portion 212a and the second pad portion 212b. That is, the first wiring portion 211 connects the first pad portion 212a and the second pad portion 212b. Thus, the chip is connected to the circuit board. Therefore, signals generated by the chip are transmitted to the circuit board.

[0058] The first circuit pattern 210 may further include a test pad portion. Specifically, a first test pad portion TP1 is provided in the unactive area UA. The first wiring portion 211, the first pad portion 212a, the second pad portion 212b, and the first test pad portion TP1 may be integrally formed.

[0059] The first circuit pattern 210 may be tested before connecting the circuit board to the second pad portion 212b. For example, the first test pad portion TP1 may be used to check whether the first circuit pattern is open or short.

[0060] The second circuit pattern 220 includes a second wiring portion 221, a third pad portion 222a, and a fourth pad portion 222b. The second wiring portion 221, the third pad portion 222a, and the fourth pad portion 222b may be made of the same material. In addition, the second wiring portion 221, the third pad portion 222a, and the fourth pad portion 222b may be formed integrally.

[0061] The third pad portion 222a is provided inside the chip mounting area CHA. Therefore, the third pad portion 222a can be connected to a terminal of the chip. Therefore, the second circuit pattern 220 can be connected to the chip.

[0062] In addition, the fourth pad portion 222b is located outside the chip mounting area CHA. The fourth pad portion 222b can be connected to a terminal of an external display panel. Therefore, the second circuit pattern 220 can be connected to the display panel.

[0063] In addition, the second wiring portion 221 is located between the third pad portion 222a and the fourth pad portion 222b. In other words, the second wiring portion 221 connects the third pad portion 222a and the fourth pad portion 222b. Therefore, the chip is connected to the display panel. Therefore, the signal generated by the chip is transmitted to the display panel.

[0064] The second circuit pattern 220 may further include a test pad portion. Specifically, the second test pad portion TP2 is located in the unactive area UA. The second wiring portion 221, the third pad portion 222a, the fourth pad portion 222b, and the second test pad portion TP2 may be integrally formed.

[0065] The second circuit pattern 220 may be tested before connecting the display panel to the fourth pad portion 222b. For example, the second test pad portion TP2 may be used to check for open circuits and short circuits in the second circuit pattern.

[0066] The third circuit pattern 230 includes a third wiring portion 231, a fifth pad portion 232a, and a sixth pad portion 232b. The third wiring portion 231, the fifth pad portion 232a, and the sixth pad portion 232b may be made of the same material. Alternatively, the third wiring portion 231, the fifth pad portion 232a, and the sixth pad portion 232b may be integrally formed.

[0067] The fifth and sixth pad portions 232a and 232b are disposed outside the chip mounting area CHA. The fifth pad portion 232a may be connected to a terminal of an external circuit board. In addition, the sixth pad portion 232b may be connected to a terminal of an external display panel.

[0068] In addition, the third wiring portion 231 is provided between the fifth pad portion 232a and the sixth pad portion 232b. That is, the third wiring portion 231 connects the fifth pad portion 232a and the sixth pad portion 232b. Thus, the circuit board is connected to the display panel.

[0069] The third circuit pattern 230 may be a bypass circuit. For example, the third circuit pattern 230 may be a power supply pattern. Therefore, the circuit board and the display panel may receive power from the third circuit pattern 230.

[0070] The third circuit pattern 230 may include a plurality of third circuit patterns spaced apart in the second direction 2D. The line width and spacing of the third circuit pattern 230 may be greater than the line width and spacing of the first circuit pattern 210. In addition, the line width and spacing of the third circuit pattern 230 may be greater than the line width and spacing of the second circuit pattern 220.

[0071] The protective layer 300 is provided on the first surface 1S. Therefore, the protective layer 300 is provided on the first circuit pattern 210, the second circuit pattern 220, and the third circuit pattern 230. The protective layer 300 is provided on the area other than the area where the first pad portion 212a, the second pad portion 212b, the third pad portion 222a, the fourth pad portion 222b, the fifth pad portion 232a, and the sixth pad portion 232b are provided.

[0072] The flexible circuit board 1000 can be bent in one direction. For example, the flexible circuit board 1000 can be bent in one direction in the area between the chip mounting area CHA and the third pad portion 222b. Therefore, a bending area BA can be formed in the flexible circuit board 1000.

[0073] Stress may occur in the bending area BA. For example, compressive stress or tensile stress may occur in the bending area BA. The second circuit pattern 220 may overlap with the bending area BA. Specifically, a portion of the second circuit pattern 220 may overlap with the bending area BA. As a result, stress may be transmitted to the second circuit pattern 200. Consequently, cracks may form in the second circuit pattern 200 due to the stress. This may reduce the reliability of the flexible circuit board.

[0074] The flexible circuit board according to the embodiment includes the metal pattern 400. This can solve the above-mentioned problem.

[0075] Reference Figures 1 to 4 , the flexible circuit board 1000 according to the first embodiment includes the metal pattern 400 .

[0076] The metal pattern 400 is disposed adjacent to the second circuit pattern 220. For example, the metal pattern 400 is disposed adjacent to the second wiring portion 221.

[0077] The second wiring portion 221 may extend in multiple directions. For example, the second wiring portion 221 may include a 2-1 wiring portion 221a and a 2-2 wiring portion 221b. The 2-1 wiring portion 221a and the 2-2 wiring portion 221b may extend in different directions. The 2-1 wiring portion 221a may extend in one direction. Alternatively, the 2-2 wiring portion 221b may extend in another direction.

[0078] The 2-1st wiring portion 221a is in contact with the fourth pad portion 222b.

[0079] The 2-1 wiring portions 221a are spaced apart by a first spacing S1. Furthermore, the 2-2 wiring portions 221b are spaced apart by a second spacing S2. The first spacing S1 and the second spacing S2 may be 8 μm or less. The first spacing S1 and the second spacing S2 may be different from each other. For example, the first spacing S1 may be greater than the second spacing S2.

[0080] The second circuit pattern includes a plurality of circuit patterns. A first interval S1 and a second interval S2 are defined as intervals between adjacent second circuit patterns.

[0081] The metal pattern 400 is located at the first interval S1. That is, the metal pattern 400 is located between wiring portions having a larger interval. That is, the metal pattern 400 is located between the 2-1st wiring portions 221a.

[0082] The stress generated when bending a flexible printed circuit board is related to the spacing between the circuit patterns. For example, the stress is proportional to the spacing between the wiring sections. Therefore, the stress transmitted to the 2-1 wiring section 221a may be greater than the stress transmitted to the 2-2 wiring section 221b.

[0083] Figure 3 is a graph showing bending strength according to the interval between wiring portions. Figure 4 is a photograph showing cracks formed in the wiring portion. Figure 3 The graph shows the experimental results of forming circuit patterns of the same pitch at different intervals. Specifically, when bending the circuit pattern 90 degrees back and forth is defined as one cycle, the number of cracks occurring in the bent circuit pattern is tested.

[0084] Reference Figure 3 The bending strength varies according to the spacing between the wiring parts. That is, when the spacing between the wiring parts is large, the bending strength is low.

[0085] The process of reducing the spacing between circuit patterns may be difficult. Specifically, if the spacing between circuit patterns becomes smaller, process defects may occur. Alternatively, if the spacing between circuit patterns becomes smaller, a short circuit may occur between adjacent circuit patterns.

[0086] In addition, the process of increasing the line width of the circuit pattern may be difficult. Specifically, if the line width of the circuit pattern is increased, the size of the flexible circuit board may increase. In addition, if the line width of the circuit pattern is increased, the spacing between the circuit patterns may be reduced.

[0087] Therefore, the flexible circuit board according to the embodiment includes the metal pattern 400. Specifically, the metal pattern 400 is located at a larger interval among the intervals between the wiring portions. Therefore, cracks can be prevented from occurring in the circuit pattern when the flexible circuit board 1000 is bent.

[0088] The metal pattern 400 is spaced apart from the second wiring portion 221. For example, the metal pattern 400 is spaced apart from the 2-1 wiring portion 221a. Specifically, the metal pattern 400 is spaced apart from the 2-1 wiring portion 221a by a third distance S3. Furthermore, the metal pattern 400 is spaced apart from the cutting line CL. For example, the metal pattern 400 is spaced apart from the cutting line CL by a fourth distance S4.

[0089] The metal pattern 400 may have a set line width. Specifically, the line width W2 of the metal pattern 400 may be different from the line width W1 of the second wiring portion 221. For example, the line width W2 of the metal pattern 400 may be less than or equal to the line width W1 of the second wiring portion 221.

[0090] In addition, the line width W2 of the metal pattern 400 may be different from the third spacing S3. In addition, the line width W2 of the metal pattern 400 may be different from the fourth spacing S4. For example, the line width W2 of the metal pattern may be smaller than the third spacing S3, and the line width W2 of the metal pattern may be larger than the fourth spacing S4.

[0091] For example, the line width W1 of the second wiring portion 221 may be greater than or equal to 8 μm. For example, the line width W1 of the second wiring portion 221 may be between 8 μm and 15 μm.

[0092] For example, the line width W2 of the metal pattern 400 may be greater than or equal to 8 μm. For example, the line width W2 of the metal pattern 400 may be between 8 μm and 11 μm or between 9 μm and 10 μm.

[0093] The metal pattern 400 is disposed away from the cutting line CL. Therefore, when the flexible circuit board 1000 is cut, the metal pattern 400 does not need to be cut. Therefore, the flexible circuit board 1000 can be easily cut. In addition, the fragments formed when the flexible circuit board 1000 is cut can be reduced.

[0094] Furthermore, since the circuit pattern and the metal pattern 400 have different lengths, the circuit pattern and the metal pattern 400 can be easily distinguished.

[0095] Furthermore, the metal pattern 400 does not overlap with the second test pad portion TP2 , making it easier to test the flexible circuit board. Specifically, interference with the metal pattern 400 is prevented, thereby reducing test errors.

[0096] The metal pattern 400 is spaced apart from the end E1 of the protective layer 300. Therefore, the protective layer 300 may be disposed around the metal pattern 400. Therefore, corrosion of the metal pattern 400 may be prevented. In addition, the metal pattern 400 and the fourth pad portion 222b may be distinguished.

[0097] In the following, reference will be made to Figures 5 to 7 A flexible circuit board 1000 according to a second embodiment will be described.

[0098] The flexible circuit board 1000 according to the second embodiment includes a metal pattern 400 .

[0099] The metal pattern 400 may overlap the fourth pad portion 222b. For example, the metal pattern 400 may overlap the fourth pad portion 222b in the second direction 2D.

[0100] Reference Figure 6 , the metal pattern 400 extends to a region between the end E1 of the protection layer 300 and the cutting line CL. Therefore, the fourth pad portion 222 b may partially overlap with the metal pattern 400 .

[0101] For example, the distance between the metal pattern 400 and the cutting line CL may be less than 200 μm. In detail, the distance between the metal pattern 400 and the cutting line CL may be 50 μm to 200 μm or 100 μm to 150 μm.

[0102] Therefore, when cutting along the cutting line CL, damage to the metal pattern can be prevented.

[0103] Reference Figure 7 , the metal pattern 400 extends to the cutting line CL. Therefore, the fourth pad portion 222b may overlap the metal pattern 400 in two horizontal directions. That is, the fourth pad portion 222b may overlap the metal pattern 400 in the second direction as a whole.

[0104] The flexible circuit board according to the second embodiment is arranged so that the metal pattern 400 horizontally overlaps the pad portion. This prevents stress from being transferred to the pad portion when the flexible circuit board is bent. This facilitates connection between the flexible circuit board and the display panel. In other words, the flexible circuit board can prevent the pad portion from cracking. This improves the connection characteristics between the flexible circuit board and the display panel.

[0105] In the following, reference will be made to Figures 8 to 10 A flexible circuit board 1000 according to a third embodiment is described.

[0106] The flexible circuit board 1000 according to the third embodiment includes a metal pattern 400 .

[0107] Reference Figure 9 and Figure 10 , the metal pattern 400 may also be located outside the cutting line CL. Specifically, the metal pattern 400 may be located in both the active area AA and the unactive area UA.

[0108] The metal pattern 400 and the circuit pattern may extend to an end portion E2 of the substrate 100 .

[0109] Therefore, one end of the metal pattern 400 can correspond to one end of the circuit pattern. For example, one end of the second circuit pattern 220 can correspond to one end of the metal pattern 400. Therefore, the metal pattern 400 and the circuit pattern can be easily formed. In other words, a separate process for separating the metal pattern 400 from the cutting line CL can be omitted.

[0110] Reference Figure 10 The metal pattern 400 may have different line widths at different locations. For example, the metal pattern 400 may include a first metal portion 410 located between the end E1 of the protective layer and the end E2 of the substrate, and a second metal portion 420 located outside the end E1 of the protective layer.

[0111] The line width of the first metal portion 410 may be different from the line width of the second metal portion 420. Specifically, the minimum line width W2-1 of the first metal portion 410 may be different from the minimum line width W2-2 of the second metal portion. Specifically, the minimum line width W2-1 of the first metal portion 410 may be smaller than the minimum line width W2-2 of the second metal portion.

[0112] The first metal portion 410 overlaps the cutting line CL. Therefore, if the line width of the first metal portion 410 is large, cutting may be difficult. Furthermore, debris may increase during the cutting process. Therefore, the line width of the first metal portion 410 can be made smaller. This makes it easier to cut the flexible circuit board.

[0113] The flexible circuit board according to the embodiment includes a metal pattern.

[0114] Flexible circuit boards can be bent in one direction. Therefore, stress may be transferred to the circuit pattern. This may cause cracks to form in the circuit pattern.

[0115] The stress may be proportional to the spacing between the circuit patterns. Therefore, the stress may be greater in areas where the spacing between the circuit patterns is greater.

[0116] The metal pattern is located in an area where the spacing between the circuit patterns is large, thereby preventing cracks from forming in the circuit patterns when the flexible circuit board is bent.

[0117] Therefore, the reliability of the flexible circuit board according to the embodiment is improved.

[0118] Furthermore, the metal patterns are provided in various lengths and positions.

[0119] The metal pattern is spaced apart from the cutting line. Specifically, the metal pattern is located inside the cutting line. Therefore, the flexible circuit board can be easily cut.

[0120] Furthermore, the protective layer is located on the metal pattern, thereby preventing corrosion of the metal pattern.

[0121] In the following, reference will be made to Figure 11 and Figure 12 The layer structures of the first circuit pattern, the second circuit pattern, and the third circuit pattern are described below. For ease of explanation, the following description focuses on the first circuit pattern. The following description applies to both the second circuit pattern and the third circuit pattern.

[0122] Reference Figure 11 , the first circuit pattern may be formed as a multilayer. Specifically, the first wiring portion 211 and the first pad portion 212a may include a first metal layer 201 and a second metal layer 202. In addition, although Figure 11 Although not shown in the figure, the second pad portion 212 b may also include the first metal layer 201 and the second metal layer 202 .

[0123] The first metal layer 201 may be a seed layer of the first circuit pattern. For example, the first metal layer 201 may be a seed layer formed on the substrate 100 by chemical plating using a metal material such as copper (Cu).

[0124] In addition, the second metal layer 202 may be a plated layer. For example, the second metal layer 202 may be a plated layer formed by electroplating using the first metal layer 201 as a seed layer.

[0125] The thickness of the first metal layer 201 may be smaller than the thickness of the second metal layer 202 .

[0126] 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.

[0127] 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).

[0128] In addition, a bonding layer 203 may be provided on the second metal layer 201. Specifically, the bonding layer 203 may be provided on the side surfaces of the first metal layer 201 and the second metal layer 202 and on the upper surface of the second metal layer 202. In other words, the bonding layer 203 may be provided to surround the first metal layer 201 and the second metal layer 202.

[0129] The bonding layer 203 may include a metal. Specifically, the bonding layer 203 may include tin (Sn).

[0130] The bonding layer 203 may be formed to have a thickness of 0.3 μm to 0.7 μm. The tin content of the bonding layer 203 may increase as it extends from the lower surface toward the upper surface.

[0131] That is, the bonding layer 203 is provided in contact with the second metal layer 202. Therefore, the tin content of the bonding layer 203 may increase as it extends from the lower surface toward the upper surface, and the copper content of the bonding layer 203 may decrease as it extends from the lower surface toward the upper surface.

[0132] Therefore, pure tin may remain only within a thickness range of 0.1 μm to 0.3 μm on the upper surface of the bonding layer 203 .

[0133] The bonding layer 203 can be used to easily bond the chip terminals, circuit board terminals, display panel terminals, and pad portions using heat and pressure. Specifically, when heat and pressure are applied to the pad portion, the upper surface of the bonding layer, where pure tin remains, melts. Therefore, the chip terminals, circuit board terminals, and display panel terminals can be easily bonded.

[0134] Therefore, the bonding layer 203 may be a portion of the first pad portion 212 a and the second pad portion 222 b .

[0135] The first circuit pattern may have a thickness of 2 μm to 25 μm. For example, the first circuit pattern may have a thickness of 5 μm to 20 μm. For example, the first circuit pattern may have a thickness of 7 μm to 15 μm.

[0136] The process of forming the first circuit pattern includes a rapid etching process to separate the circuit patterns. Thus, the first metal layer 201 is etched. Therefore, the thickness of the first circuit pattern finally produced may be less than the sum of the thicknesses of the first metal layer 201, the second metal layer 202, and the bonding layer 203 formed during this process.

[0137] If the thickness of the first circuit pattern is less than 2 μm, the resistance of the second circuit pattern may increase. If the thickness of the first circuit pattern exceeds 25 μm, it may be difficult to achieve a fine pattern.

[0138] On the other hand, a buffer layer 205 may be further provided between the substrate 100 and the first circuit pattern. The buffer layer 205 may improve the adhesive force between the substrate 100 and the first circuit pattern.

[0139] The buffer layer 205 may be formed in multiple layers. Specifically, a first buffer layer 205a and a second buffer layer 205b may be provided on the substrate 100. Thus, the first buffer layer 205a may be in contact with the substrate 100. In addition, the second buffer layer 205b may be in contact with the first circuit pattern 210.

[0140] 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 second circuit pattern. For example, the second buffer layer 205b may include chromium (Cr).

[0141] The buffer layer 205 may have a film thickness in the nanometer range. For example, the thickness of the buffer layer 205 may be 20 nm or less.

[0142] The buffer layer 205 can enhance the adhesion between the substrate 100 and the first circuit pattern, thereby preventing the first circuit pattern from being peeled off.

[0143] Reference Figure 12 The bonding layer 203 may include a plurality of bonding layers. For example, the bonding layer 203 may include a first bonding layer 203a and a second bonding layer 203b.

[0144] In detail, the first bonding layer 203 a may be disposed on the first wiring portion 211 , the first pad portion 212 a , and the second pad portion 212 b .

[0145] In addition, the second bonding layer 203b may be provided only on the first and second pad portions 212a and 212b. That is, the first wiring portion 211, the first and second pad portions 212a and 212b may have different layer structures due to the second bonding layer 203b.

[0146] The first bonding layer 203a and the second bonding layer 203b may include metal. Specifically, the first bonding layer 203a and the second bonding layer 203b may include tin (Sn).

[0147] The first bonding layer 203a and the second bonding layer 203b may be provided with different thicknesses. Specifically, the thickness of the second bonding layer 203b may be greater than the thickness of the first bonding layer 203a.

[0148] For example, the thickness of the first bonding layer 203 a may be 0.02 μm to 0.06 μm. In addition, the thickness of the second bonding layer 203 b may be 0.2 μm to 0.6 μm.

[0149] If the bonding layer between the protective layer 300 and the first wiring portion 211 is thick, cracks may occur when the flexible circuit board is bent. Therefore, the first bonding layer 203a between the protective layer 300 and the first wiring portion 211 can be formed to a thin film thickness. This prevents cracks from occurring when the flexible circuit board is bent.

[0150] In addition, the tin content of the second bonding layer 203 b may increase as it extends from the lower surface toward the upper surface.

[0151] That is, the tin content of the second bonding layer 203 b may increase as it extends from the lower surface toward the upper surface, and the copper content of the second bonding layer 203 b may decrease as it extends from the lower surface toward the upper surface.

[0152] Therefore, pure tin may remain only on the upper surface of the second bonding layer 203 b within a thickness range of 0.1 μm to 0.3 μm.

[0153] The second bonding layer 203b allows for easy bonding of the chip terminals, circuit board terminals, display panel terminals, and pad portions using heat and pressure. In other words, when heat and pressure are applied to the pad portions, the upper surface of the bonding layer, which retains pure tin, melts. Thus, the chip terminals, circuit board terminals, and display panel terminals can be easily bonded.

[0154] According to an embodiment, a flexible circuit board may be formed by mounting a chip CH on a chip mounting area CHA, and cutting along cutting lines CL to form a COF module.

[0155] The COF module 2000 may be located between the display panel 4000 and the circuit board 3000 to connect electrical signals.

[0156] Reference Figure 13 , one end of the COF module 2000 according to the embodiment may be connected to the display panel 4000, and the other end opposite to the one end may be connected to the circuit board 3000. For example, the display panel 4000 may be provided on one surface of the COF module 2000, and the circuit board 3000 may be provided on the other surface opposite to the one surface of the COF module 2000. However, the embodiment is not limited thereto, and the display panel 4000 and the circuit board 3000 may be provided on the same surface of the COF module 2000.

[0157] Since the COF module 2000 includes a flexible substrate, it may have a rigid form and a bent form between the display panel 3000 and the circuit board 4000. That is, the COF module 2000 may include a bending area BA.

[0158] Because the COF module 2000 can connect the display panel 4000 and the circuit board 3000, which are arranged facing each other, in a bent configuration, the thickness of the electronic device can be reduced. Furthermore, design freedom can be increased. Furthermore, even when the COF module 2000, which includes a flexible substrate, is bent, the wiring portion does not crack. Consequently, the reliability of the electronic device incorporating the COF module can be improved.

[0159] In addition, the COF module 2000 includes the metal pattern 400. Therefore, the strength of the wiring portion can be improved. Therefore, when the COF module is bent, cracks in the wiring portion can be prevented.

[0160] The COF module is flexible, and thus, the COF module can be used in various electronic devices.

[0161] For example, refer to Figure 14 The COF module can be applied to a flexible touch window. Therefore, the user can bend the touch device with his hand.

[0162] Reference Figure 15 The COF module can be applied to wearable touch devices including curved displays. Therefore, electronic devices including the COF module can be made thinner or lighter.

[0163] Reference Figure 16 The COF module can be applied to electronic devices with a display portion, such as a television, a monitor, or a notebook computer. In addition, the COF module can also be applied to electronic devices with a curved display portion.

[0164] The characteristics, structures, and effects described in the above embodiments are included in at least one embodiment, but are not limited to one embodiment. In addition, those skilled in the art can even combine or modify the characteristics, structures, and effects shown in each embodiment for other embodiments. Therefore, it should be understood that the contents related to such combinations and such modifications are included in the scope of the embodiments.

[0165] The description focuses on the embodiments, but this is illustrative only and does not limit the embodiments. Those skilled in the art will appreciate that various modifications and applications not shown above can be made without departing from the essential features of the embodiments. For example, various components specifically shown in the embodiments can be modified and implemented. Furthermore, it should be understood that differences related to such modifications and applications are included within the scope of the embodiments defined in the appended claims.

Claims

1. A flexible circuit board, comprising: a substrate comprising a first surface and a second surface opposite to the first surface; a first circuit pattern, a second circuit pattern, and a metal pattern, the first circuit pattern, the second circuit pattern, and the metal pattern being disposed on the first surface; and a protective layer disposed on the first circuit pattern, the second circuit pattern, and the metal pattern, The first circuit pattern includes a first pad portion, a second pad portion, 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, a fourth pad portion, and a second wiring portion connected to the third pad portion and the fourth pad portion. The second wiring portion includes a 2-1 wiring portion and a 2-2 wiring portion extending in different directions. The 2-1 wiring portions are spaced apart by a first interval. The 2-2 wiring portions are spaced apart by a second interval. wherein the first spacing is greater than the second spacing, and Wherein, the metal pattern is arranged between the 2-1 wiring parts.

2. The flexible circuit board according to claim 1, wherein: The substrate includes a cutting line, The metal pattern and the 2-1 wiring portion are spaced apart by a third distance. wherein the metal pattern is spaced apart from the cutting line, Wherein, the line width of the metal pattern is smaller than the third spacing, and Wherein, the line width of the metal pattern is greater than the fourth interval.

3. The flexible circuit board according to claim 2, wherein: The line width of the metal pattern is 8 μm to 11 μm.

4. The flexible circuit board according to claim 1, wherein The line width of the metal pattern is smaller than or equal to the line width of the 2-1 wiring portion.

5. The flexible circuit board according to claim 1, wherein The metal pattern is spaced apart from an end portion of the protection layer.

6. The flexible circuit board according to claim 1, wherein The substrate includes cutting lines, and The metal pattern extends to a region between an end portion of the protection layer and the cutting line.

7. The flexible circuit board according to claim 1, wherein: The substrate includes a cutting line, wherein the metal pattern extends to the cutting line, and The fourth pad portion entirely overlaps the metal pattern in a horizontal direction.

8. A COF module, comprising: The flexible circuit board according to any one of claims 1 to 7; as well as A chip is arranged in a chip mounting area of ​​the flexible circuit board.

9. The COF module according to claim 8, wherein The flexible circuit board includes a bending area formed between the chip mounting area and the fourth pad portion, and Wherein, the metal pattern overlaps with the bending area.

10. An electronic device comprising: The COF module according to claim 8; a circuit board connected to the first circuit pattern; as well as A display panel is connected to the second circuit pattern.

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