Flexible circuit board, manufacturing method therefor, and semiconductor package and electronic device including flexible circuit board

Abstract

Provided are: a flexible circuit board including a heat dissipation layer formed to fill a trench structure of a base film; a manufacturing method therefor; and a semiconductor package and an electronic device, each including the flexible circuit board. The flexible circuit board includes: a substrate layer; a wiring layer formed on a first surface of the substrate layer; and a heat dissipation layer formed on a second surface of the substrate layer, wherein the second surface of the substrate layer includes a plurality of grooves, and the heat dissipation layer includes the plurality of grooves to cover a portion of the second surface of the substrate layer.

Description

Flexible circuit board and method for manufacturing the same, and semiconductor package and electronic device including the flexible circuit board

[0001] The present invention relates to a flexible circuit board that can be provided as a chip-on-film (COF) package and a method for manufacturing the same. The present invention also relates to a semiconductor package that can be provided as a chip-on-film package (COF PKG) including a flexible circuit board, and an electronic device including the same.

[0002] Display driver ICs (DDIs) can be used to provide resolution in flat-panel display devices such as OLEDs and LCDs. DDIs can be connected to the display panel via a Chip-On-Film (COF) and serve as a signal conduit between the Application Processor (AP) and the display panel, driving the pixels within the display panel.

[0003] Due to the driving characteristics of flat panel displays, the signal power supplied from the display driver chip to the display panel is high. Consequently, the display driver chip can consume significant power and generate significant heat. To address this heat generation issue, methods such as improving the material of the bumps connecting the display driver chip and the chip-on-film (COP) have been proposed. However, these methods have limitations in improving heat dissipation efficiency in high-resolution display devices.

[0004] The technical problem to be solved by the present invention is to provide a flexible circuit board including a heat dissipation layer formed to fill a trench structure of a base film, a method for manufacturing the same, and a semiconductor package and electronic device including the flexible circuit board.

[0005] The technical problems of the present invention are not limited to the technical problems mentioned above, and other technical problems not mentioned will be clearly understood by those skilled in the art from the description below.

[0006] One aspect of the flexible circuit board of the present invention for achieving the above technical task includes a substrate layer; a wiring layer formed on a first surface of the substrate layer; and a heat dissipation layer formed on a second surface of the substrate layer, wherein the second surface of the substrate layer includes a plurality of grooves, and the heat dissipation layer covers a portion of the second surface of the substrate layer by including the plurality of grooves.

[0007] One aspect of a method for manufacturing a flexible circuit board of the present invention for achieving the above technical task includes the steps of forming a wiring layer on a first surface of a substrate layer; forming a plurality of grooves on a second surface of the substrate layer; and forming a heat dissipation layer to cover a portion of the second surface of the substrate layer including the plurality of grooves.

[0008] One aspect of a semiconductor package of the present invention for achieving the above technical task includes a flexible circuit board; and a semiconductor chip mounted on the flexible circuit board, wherein the flexible circuit board includes a substrate layer; a wiring layer formed on a first surface of the substrate layer; and a heat dissipation layer formed on a second surface of the substrate layer, wherein the second surface of the substrate layer includes a plurality of grooves, and the heat dissipation layer covers a portion of the second surface of the substrate layer by including the plurality of grooves.

[0009] One aspect of an electronic device of the present invention for achieving the above technical task includes a flexible circuit board, and a semiconductor package including a semiconductor chip mounted on the flexible circuit board; and an external device electrically connected to the semiconductor package, wherein the flexible circuit board includes a substrate layer; a wiring layer formed on a first surface of the substrate layer; and a heat dissipation layer formed on a second surface of the substrate layer, wherein the second surface of the substrate layer includes a plurality of grooves, and the heat dissipation layer covers a portion of the second surface of the substrate layer including the plurality of grooves.

[0010] Specific details of other embodiments are included in the detailed description and drawings.

[0011] According to the present invention, the following effects can be obtained.

[0012] First, by forming a heat dissipation layer to fill the trench structure of the base film, the heat dissipation efficiency of the flexible circuit board can be improved. When the heat dissipation layer is formed to fill the trench structure of the base film, the cross-sectional area and volume can be significantly increased even when the heat dissipation layer is formed with the same area in plan view as when it is formed with a flat structure on one side of the base film. Accordingly, thermal conductivity can be increased, and as a result, the heat dissipation efficiency of the flexible circuit board can be significantly improved.

[0013] Second, it can be universally applied to circuit boards that require high heat dissipation efficiency.

[0014] The effects of the present invention are not limited to those mentioned above, and other effects not mentioned will be clearly understood by those skilled in the art from the description below.

[0015] Figure 1 is a first example drawing showing the internal structure of a flexible circuit board including a heat dissipation layer in cross-section.

[0016] Figure 2 is an exemplary cross-sectional view showing the internal structure of a semiconductor package including a flexible circuit board.

[0017] Figure 3 is an exemplary diagram schematically showing the structure of an electronic device including a semiconductor package.

[0018] Figure 4 is an exemplary diagram for explaining the trench structure of the substrate layer constituting the flexible circuit board.

[0019] Figure 5 is a partial enlarged view of part M of Figure 1.

[0020] Figure 6 is a first example diagram for explaining the positional characteristics of a heat dissipation layer constituting a flexible circuit board.

[0021] Figure 7 is a second example diagram for explaining the positional characteristics of a heat dissipation layer constituting a flexible circuit board.

[0022] Figure 8 is a third example diagram for explaining the positional characteristics of a heat dissipation layer constituting a flexible circuit board.

[0023] Figure 9 is a fourth exemplary drawing for explaining the positional characteristics of a heat dissipation layer constituting a flexible circuit board.

[0024] Figure 10 is a first exemplary diagram for explaining the structural characteristics of a heat dissipation layer constituting a flexible circuit board.

[0025] Figure 11 is a second exemplary diagram for explaining the structural characteristics of a heat dissipation layer constituting a flexible circuit board.

[0026] Figure 12 is a third exemplary diagram for explaining the structural characteristics of a heat dissipation layer constituting a flexible circuit board.

[0027] Figure 13 is a first example diagram for explaining various shapes of grooves formed in a substrate layer constituting a flexible circuit board.

[0028] Figure 14 is a second example diagram for explaining various shapes of grooves formed in a substrate layer constituting a flexible circuit board.

[0029] Figure 15 is a third example diagram for explaining various shapes of grooves formed in a substrate layer constituting a flexible circuit board.

[0030] Figure 16 is a fourth exemplary drawing for explaining various shapes of grooves formed in a substrate layer constituting a flexible circuit board.

[0031] Figure 17 is a fifth example diagram for explaining various shapes of grooves formed in a substrate layer constituting a flexible circuit board.

[0032] Figure 18 is a sixth exemplary drawing for explaining various shapes of grooves formed in a substrate layer constituting a flexible circuit board.

[0033] Figure 19 is a second example drawing showing the internal structure of a flexible circuit board including a heat dissipation layer in cross-section.

[0034] Figure 20 is a flowchart sequentially illustrating a method for manufacturing a flexible circuit board.

[0035] Figure 21 shows the results of a simulation analysis of the heat dissipation characteristics of a flexible circuit board.

[0036] Figures 22 and 23 are examples of simulation analysis of the heat dissipation performance of a flexible circuit board according to the width and depth of the groove.

[0037] Hereinafter, embodiments of the present invention will be described in detail with reference to the attached drawings. Identical components in the drawings are designated by the same reference numerals, and redundant descriptions thereof will be omitted.

[0038] The present invention provides a flexible circuit board, a semiconductor package including the flexible circuit board, and an electronic device including the semiconductor package. The flexible circuit board of the present invention can be formed as a chip-on-film (COF) and can be applied to a display device including a display driver IC (DDI). The flexible circuit board of the present invention can solve the problem of heat generation of the display driver IC by including a heat dissipation layer formed to fill a trench structure of a base film. Hereinafter, the present invention will be described in detail with reference to the drawings.

[0039] Fig. 1 is a first exemplary cross-sectional view showing the internal structure of a flexible circuit board including a heat dissipation layer. According to Fig. 1, the flexible circuit board (100) may be configured to include a substrate layer (110), a wiring layer (120), and a heat dissipation layer (130). The flexible circuit board (100) may be applied to a COF substrate made of 1-metal, 2-metal, etc., and is not limited thereto, and may of course be applied to various circuit boards having properties such as rigidity, rigid-flexibility, etc.

[0040] The substrate layer (110) may be formed of a base film having a certain thickness. For example, the substrate layer (110) may be formed of a base film having a thickness of 150 μm or less. Preferably, the substrate layer (110) may be formed of a base film having a thickness of 10 μm or more and 50 μm or less. The substrate layer (110) may be formed of a flexible film, but is not limited thereto, and may also be formed of a rigid flexible film or a rigid film.

[0041] The substrate layer (110) may be formed of an insulating resin. For example, the substrate layer (110) may include at least one polymer material selected from polyimide, polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polycarbonate, epoxy, and glass fiber. The polymer material forming the substrate layer (110) is not limited thereto, and any material may be used as long as it enables insulating performance within the flexible circuit board (100).

[0042] Although not shown in FIG. 1, a seed layer may be provided to increase bonding between the substrate layer (110) and the wiring layer (120). The seed layer may be provided as a conductive layer in the form of a thin film on the substrate layer (110). For example, the seed layer may be formed of any one metal selected from conductive metals such as nickel (Ni), chromium (Cr), copper (Cu), gold (Au), aluminum (Al), and palladium (Pd), or an alloy composed of multiple metals. The seed layer may be formed on the substrate layer (110) by a physical method such as deposition, adhesion, or plating, or by a chemical method.

[0043] An underlayer may be further provided on the seed layer. The underlayer may be formed of the same metal as the seed layer, but may also be formed of a different metal. The underlayer may have a thickness equivalent to that of the seed layer, but is not limited thereto, and may be formed to be thicker or thinner than the seed layer. It is also possible for only the underlayer to be formed on the substrate layer (110) without the seed layer being formed.

[0044] The wiring layer (120) may be formed on the substrate layer (110). The wiring layer (120) may be formed of an electrically conductive material. For example, the wiring layer (120) may be formed of any one metal selected from conductive metals such as nickel (Ni), chromium (Cr), copper (Cu), gold (Au), silver (Ag), platinum (Pt), aluminum (Al), palladium (Pd), titanium (Ti), and tin (Sn), or an alloy formed of multiple metals.

[0045] The wiring layer (120) can be formed on the substrate layer (110) using etching. In this case, a metal layer is formed on the substrate layer (110) and wiring is formed through photo etching, thereby providing the wiring layer (120) as a conductive layer on the substrate layer (110).

[0046] The wiring layer (120) may be formed on the substrate layer (110) using plating. In this case, after forming a metal layer on the substrate layer (110), wiring may be formed through an additive process, printing, coating, etc., so that the wiring layer (120) may be provided as a conductive layer on the substrate layer (110). The additive process refers to a method of forming a plating resist pattern on a metal layer and then forming wiring through a plating method. Printing refers to a method of printing a conductive paste on the substrate layer (110). Coating refers to a method of transferring a conductive paste onto the substrate layer (110). When plating is used, the wiring layer (120) may be formed on the substrate layer (110) using either an electrolytic plating method or an electroless plating method.

[0047] The wiring layer (120) may include an inner lead (121), an outer lead (122), and a wiring pattern (123). The inner lead (121), the outer lead (122), and the wiring pattern (123) may each be formed as a plurality of lines, and the width of each line may be formed to be 100 μm or less, and the pitch between each line may be formed to be 200 μm or less.

[0048] The inner lead (121) is a wiring formed within the inner lead area (IL) and can be connected to a wiring pattern (123) formed within the wiring area (WL). The inner lead (121) can be provided as a terminal portion of the wiring pattern (123). As will be described later, the outer lead (122) can also be provided as a terminal portion of the wiring pattern (123).

[0049] As previously described, the present invention can provide a semiconductor package (200) including a flexible circuit board (100). FIG. 2 is an exemplary cross-sectional view showing the internal structure of a semiconductor package including a flexible circuit board. The following description refers to FIGS. 1 and 2.

[0050] A semiconductor package (200) is a package in which a semiconductor chip (210) is mounted on a flexible circuit board (100), and may include not only the semiconductor chip (210) but also several individual components connected through a wiring layer (120). The semiconductor package (200) may be mounted on an electronic product (e.g., a smartphone, a digital camera, a display device, etc.) to function as a controller, and may also serve to control electronic components (e.g., a camera actuator). For example, the flexible circuit board (100) may be provided as a chip-on-film (COF), and the semiconductor package (200) may be provided as a chip-on-film package (COF PKG).

[0051] A semiconductor chip (210) may be placed within an inner lead region (IL). The semiconductor chip (210) may be connected to an inner lead (121) via a bump (220). The inner lead (121) may electrically connect the semiconductor chip (210) and a wiring pattern (123).

[0052] The outer lead (122) is a wiring formed within the outer lead area (OL) and, like the inner lead (121), can be connected to a wiring pattern (123) formed within the wiring area (WL). The inner lead (121) and the outer lead (122) can be electrically connected through the wiring pattern (123).

[0053] As previously described, the present invention can provide an electronic device (300) including a semiconductor package (200). FIG. 3 is an exemplary diagram schematically illustrating the structure of an electronic device including a semiconductor package. The following description refers to FIGS. 1 to 3.

[0054] The electronic device (300) may include a semiconductor package (200) and a plurality of external devices. For example, the electronic device (300) may include a semiconductor package (200), a first external device (310), and a second external device (320). However, the present invention is not limited thereto, and the electronic device (300) may also include a semiconductor package (200) and a single external device. For example, the electronic device (300) may include a semiconductor package (200) and a first external device (310). Alternatively, the electronic device (300) may include a semiconductor package (200) and a second external device (320).

[0055] The outer lead (122) can be connected to an external device. When the electronic device (300) includes a first external device (310) and a second external device (320), the outer lead (122) disposed on one side of the flexible circuit board (100) can be connected to the first external device (310), and the outer lead (122) disposed on the other side of the flexible circuit board (100) can be connected to the second external device (320). The inner lead (121) and the outer lead (122) can electrically connect the semiconductor chip (210) and the external devices (310, 320). For example, the semiconductor package (200) can be provided as a chip-on-film package (COF PKG) including a display driver chip (DDI), and the first external device (310) and the second external device (320) can be provided as a display panel and a PCB circuit board, respectively.

[0056] This is explained again with reference to Figure 1.

[0057] A heat dissipation layer (130) may be formed on the base layer (110). The heat dissipation layer (130) may include at least one material selected from the group consisting of a metal material, a ceramic material, an inorganic material, and a resin material including heat dissipation particles, all of which have thermal conductivity. For example, when the heat dissipation layer (130) includes a metal material, it may include a metal tape or a metal paste such as metal ink. In addition, when the heat dissipation layer (130) includes a ceramic material, it may include a ceramic tape. In addition, when the heat dissipation layer (130) includes an inorganic material, it may include a compound tape of a polymer material.

[0058] A semiconductor package (200) can be prepared by mounting a display driver chip (DDI) on a flexible circuit board (100) including a heat dissipation layer (130). When the semiconductor package (200) electrically connects a display panel and an application processor (AP), the heat dissipation layer (130) can be utilized to solve a heat generation issue of the display driver chip (DDI).

[0059] Recently, there has been a growing demand for display devices such as TVs to be lighter, smaller, higher resolution, and more functional. Consequently, the operating speed of display driver chips (DDIs) has increased significantly, and their deterioration has also accelerated rapidly due to rising operating temperatures. Therefore, there is a need to apply heat dissipation solutions for display driver chips (DDIs) not only to semiconductor packages (220) but also to flexible circuit boards (100).

[0060] In the present invention, the heat dissipation layer (130) may be formed to cover one surface of the substrate layer (110) including a trench structure formed in the substrate layer (110). This will be described in detail below.

[0061] The wiring layer (120) and the heat dissipation layer (130) may be formed on the substrate layer (110). When the wiring layer (120) is formed on the first surface (110a) of the substrate layer (110), the heat dissipation layer (130) may be formed on the second surface (110b) of the substrate layer (110). For example, the first surface (110a) of the substrate layer (110) may be the upper surface of the substrate layer (110), and the second surface (110b) of the substrate layer (110) may be the lower surface of the substrate layer (110).

[0062] The second surface (110b) of the substrate layer (110) may have a trench structure. Referring to FIG. 4, a plurality of grooves (410a, 410b, …, 410k, …, 410n) may be formed on the second surface (110b) of the substrate layer (110) toward the surface of the substrate layer (110). The plurality of grooves (410a, 410b, …, 410k, …, 410n) may be formed at a certain interval. The heat dissipation layer (130) may cover the second surface (110b) of the substrate layer (110) by including the plurality of grooves (410a, 410b, …, 410k, …, 410n) formed on the second surface (110b) of the substrate layer (110). Figure 4 is an exemplary diagram for explaining the trench structure of the substrate layer constituting the flexible circuit board.

[0063] Fig. 5 is a partial enlarged view of part M of Fig. 1. The following description refers to Figs. 1, 4, and 5. A plurality of grooves (410a, 410b, …, 410k, …, 410n) constituting the trench structure can be formed under the same conditions. Hereinafter, the kth groove (410k) will be described as a representative thereof.

[0064] The heat dissipation effect can be improved as the surface area of ​​the heat-absorbing or heat-emitting portion increases. In the present invention, in order to secure the surface area of ​​the heat-absorbing portion, a plurality of grooves (410a, 410b, …, 410k, …, 410n) can be formed on the second surface (110b) of the base layer (110) to have a constant width and depth.

[0065] The depth (a) of the k-th groove (410k) can be determined by considering the thickness (d) of the substrate layer (110) and the fluidity of the processing process. The depth (a) of the k-th groove (410k) can be formed to be 5 μm or more. The depth (a) of the k-th groove (410k) can be formed to be 50% or less of the thickness (d) of the substrate layer (110). For example, when the thickness (d) of the substrate layer (110) is 150 μm, the depth (a) of the k-th groove (410k) can be formed to be 75 μm or less.

[0066] The width (b) of the k-th groove (410k) can be determined by considering the surface area of ​​the heat dissipation layer (130) corresponding to the surface area of ​​the trench structure and the filling property of the heat dissipation material filling the inside of the k-th groove (410k). The heat dissipation layer (130) can be formed by applying a paste containing the heat dissipation material to the second surface (110b) of the base layer (110). In order to secure the filling property of the inside of the k-th groove (410k), the width (b) of the k-th groove (410k) is preferably equal to or larger than the particle size of the heat dissipation material. Typically, the particle size of the heat dissipation material is 2 μm or less, and considering this particle size of the heat dissipation material, the width (b) of the k-th groove (410k) is preferably formed to be 5 μm or more.

[0067] The width (b) of the k-th groove (410k) may be formed to be 50% or less of the thickness (d) of the substrate layer (110), similar to the depth (a) of the k-th groove (410k). However, if the width (b) of the k-th groove (410k) is greater than the depth (a) of the k-th groove (410k), the surface area of ​​the heat dissipation layer (130) may decrease, and thus the heat dissipation efficiency in the flexible circuit board (100) may deteriorate. Therefore, the width (b) of the k-th groove (410k) may be formed to be less than or equal to the depth (a) of the k-th groove (410k). Preferably, the width (b) of the k-th groove (410k) may be formed to be 5 µm or more and 50 µm or less in consideration of the particle size of the heat dissipating material, the relationship with the depth (a) of the k-th groove (410k), etc.

[0068] As previously explained, if the ratio (b) of the width of the k-th groove (410k) to the depth (a) of the k-th groove (410k), i.e., b / a, is greater than 1.0, the surface area of ​​the heat dissipation layer (130) may decrease, and the heat dissipation efficiency in the flexible circuit board (100) may deteriorate. In addition, if b / a is less than 0.05, the width (b) of the k-th groove (410k) may become smaller than the particle size of the heat dissipation material, and in this case, it is difficult to secure the filling property inside the k-th groove (410k). Therefore, in the present invention, b / a may have a range of 0.05 to 1.0.

[0069] Meanwhile, the k-th groove (410k) may be formed at a constant interval from other adjacent grooves. The interval between the k-th groove (410k) and other adjacent grooves may be proportional to the width of the groove. The interval between the k-th groove (410k) and other adjacent grooves may be 0.1 to 0.6 times the width of the groove.

[0070] A protrusion surface may be arranged between two different grooves formed on the second surface (110b) of the substrate layer (110). For example, a protrusion surface (420) may be arranged between the j-th groove (410j) and the k-th groove (410k). However, if the width (c) of the protrusion surface (420) is larger than the width (b) of the k-th groove (410k), the distance between the heat dissipation layer filled in the j-th groove (410j) and the heat dissipation layer filled in the k-th groove (410k) increases, which may lower the heat dissipation efficiency in the flexible circuit board (100). Therefore, in the present invention, the width (c) of the protrusion surface (420) may be formed to be equal to or less than the width (b) of the k-th groove (410k).

[0071] The heat dissipation layer (130) may be formed in a portion of the second surface (110b) of the substrate layer (110). The heat dissipation layer (130) may be formed at a position corresponding to the area including the inner lead area (IL) and the wiring area (WL). The heat dissipation layer (130) may be formed with an area equal to or larger than the size of the inner lead area (IL), or may be formed with an area equal to or smaller than the size of the area including the inner lead area (IL) and the wiring area (WL).

[0072] Referring to Fig. 6, the heat dissipation layer (130) may be formed at a position corresponding to an area including an inner lead region (IL). The heat dissipation layer (130) may be formed on the second surface (110b) of the substrate layer (110) with a minimum area corresponding to the size of the inner lead region (IL). Fig. 6 is a first exemplary diagram for explaining the positional characteristics of the heat dissipation layer constituting the flexible circuit board.

[0073] Referring to Fig. 7, the heat dissipation layer (130) can be formed at a position corresponding to an area including an inner lead area (IL), a wiring area (WL), and an outer lead area (OL). The heat dissipation layer (130) can be formed on the second surface (110b) of the substrate layer (110) with a maximum area corresponding to the size of the area including the inner lead area (IL), the wiring area (WL), and the outer lead area (OL). Fig. 7 is a second exemplary diagram for explaining the positional characteristics of a heat dissipation layer constituting a flexible circuit board.

[0074] Hereinafter, a heat dissipation layer (130) formed at a position corresponding to an area including part or all of an inner lead area (IL) and a wiring area (WL) is defined as a first heat dissipation layer, a heat dissipation layer (130) formed at a position corresponding to an area including part or all of an inner lead area (IL) is defined as a second heat dissipation layer, and a heat dissipation layer (130) formed at a position corresponding to an area including part or all of an inner lead area (IL), a wiring area (WL), and an outer lead area (OL) is defined as a third heat dissipation layer.

[0075] Meanwhile, the number of grooves corresponding to the heat dissipation layer (130) may be proportional to the area size of the heat dissipation layer (130), but is not limited thereto, and may be formed in various ways regardless of the area of ​​the heat dissipation layer (130).

[0076] Referring to FIGS. 1, 5, and 8, the first heat dissipation layer can fill the same number of grooves as the second heat dissipation layer. In this case, the width (b) of the grooves filled by the first heat dissipation layer may be greater than the width (b1) of the grooves filled by the second heat dissipation layer (b > b1). Similarly, referring to FIGS. 1, 5, and 9, the first heat dissipation layer can fill the same number of grooves as the third heat dissipation layer. In this case, the width (b) of the grooves filled by the first heat dissipation layer may be less than the width (b2) of the grooves filled by the third heat dissipation layer (b < b2). In summary, the width of the grooves that the heat dissipation layer (130) can fill may vary depending on whether the heat dissipation layer (130) is formed at a position corresponding to the wiring area (WL) and the outer lead area (OL), and if it is formed at a position corresponding to the wiring area (WL) and the outer lead area (OL), the area ratio thereof. Fig. 8 is a third exemplary diagram for explaining the positional characteristics of a heat dissipation layer constituting a flexible circuit board. And, Fig. 9 is a fourth exemplary diagram for explaining the positional characteristics of a heat dissipation layer constituting a flexible circuit board.

[0077] This is explained again with reference to Figure 5.

[0078] The heat dissipation layer (130) may be formed on the second surface (110b) of the substrate layer (110) to include a predetermined thickness (e). The distance (e) from the surface of the second surface (110b) of the substrate layer (110) to the surface of the heat dissipation layer (130) may be determined in consideration of heat dissipation and processing fluidity. Preferably, the distance (e) from the surface of the second surface (110b) of the substrate layer (110) to the surface of the heat dissipation layer (130) may be 5 µm or more, and may be less than or equal to the thickness (d) of the substrate layer (110).

[0079] The shapes of one side and the other side of the heat dissipation layer (130) may be different. Referring to Fig. 10, the first side (130a) of the heat dissipation layer (130) may be formed along the profile of the trench structure formed in the substrate layer (110), and the second side (130b) of the heat dissipation layer (130) may be formed flat. That is, the first side (130a) of the heat dissipation layer (30) corresponds to the trench structure of the substrate layer (110), and the second side (130b) of the heat dissipation layer (30) may be flat. Fig. 10 is a first exemplary diagram for explaining the structural characteristics of the heat dissipation layer constituting the flexible circuit board.

[0080] The plurality of protrusions (430a, 430b, …, 430k, …, 430n) formed on the first surface (130a) of the heat dissipation layer (130) may have a rectangular cross-sectional shape in the vertical direction (third direction (D3)). However, the present invention is not limited thereto, and the plurality of protrusions (430a, 430b, …, 430k, …, 430n) may have a circular or oval cross-sectional shape in the vertical direction (D3). Alternatively, the plurality of protrusions (430a, 430b, …, 430k, …, 430n) may also have a polygonal cross-sectional shape such as a triangle or a pentagon in the vertical direction (D3).

[0081] The plurality of protrusions (430a, 430b, …, 430k, …, 430n) may have the same upper width (W1) and lower width (W2) (W1 = W2). However, the present invention is not limited thereto, and the plurality of protrusions (430a, 430b, …, 430k, …, 430n) may have different upper widths (W1) and lower widths (W2) depending on the cross-sectional shape in the vertical direction (D3) (W1 ≠ W2). For example, referring to FIG. 11, the plurality of protrusions (430a, 430b, …, 430k, …, 430n) may have a narrower upper width (W1) than a lower width (W2) (W1 < W2). Alternatively, referring to FIG. 12, the plurality of protrusions (430a, 430b, …, 430k, …, 430n) may have a width (W1) of their upper portions wider than a width (W2) of their lower portions (W1 > W2). FIG. 11 is a second exemplary drawing for explaining the structural characteristics of a heat dissipation layer constituting a flexible circuit board. And, FIG. 12 is a third exemplary drawing for explaining the structural characteristics of a heat dissipation layer constituting a flexible circuit board.

[0082] The second surface (110b) of the substrate layer (110) and the first surface (130a) of the heat dissipation layer (130) may be in contact with each other. A plurality of grooves (410a, 410b, …, 410k, …, 410n) may be formed on the second surface (110b) of the substrate layer (110). A plurality of protrusions (430a, 430b, …, 430k, …, 430n) may be formed on the first surface (130a) of the heat dissipation layer (130). The plurality of protrusions (430a, 430b, …, 430k, …, 430n) may be formed to fill the plurality of grooves (410a, 410b, …, 410k, …, 410n).

[0083] A plurality of grooves (410) may be formed in various shapes on the second surface (110b) of the substrate layer (110). The plurality of grooves (410) may be formed in parallel and side by side on the second surface (110b) of the substrate layer (110). Referring to FIG. 13, the plurality of grooves (410) may be formed as vertical comb-shaped grooves on the second surface (110b) of the substrate layer (110). FIG. 13 is a first exemplary drawing for explaining various shapes of grooves formed on the substrate layer constituting the flexible circuit board. Alternatively, referring to FIG. 14, the plurality of grooves (410) may be formed as horizontal comb-shaped grooves on the second surface (110b) of the substrate layer (110). FIG. 14 is a second exemplary drawing for explaining various shapes of grooves formed on the substrate layer constituting the flexible circuit board.

[0084] A plurality of grooves (410) may be formed as donut-shaped grooves on the second surface (110b) of the substrate layer (110), as illustrated in FIG. 15. The donut-shaped grooves may be formed in a rectangular structure, but are not limited thereto, and may also be formed in a circular structure or an oval structure. Alternatively, the donut-shaped grooves may be formed in a polygonal structure, such as a triangular structure or a pentagonal structure. FIG. 15 is a third exemplary diagram illustrating various shapes of grooves formed on the substrate layer constituting the flexible circuit board.

[0085] The plurality of grooves (410) may be formed as wavy grooves on the second surface (110b) of the substrate layer (110), as illustrated in FIG. 16. Although not illustrated in the drawing, the plurality of grooves (410) may also be formed as uneven grooves with different depths in the vertical direction (D3). Alternatively, the plurality of grooves (410) may also be formed as zigzag grooves. FIG. 16 is a fourth exemplary diagram illustrating various shapes of grooves formed on the substrate layer constituting the flexible circuit board.

[0086] The plurality of grooves (410) may be formed in a grid shape or a honeycomb shape. Referring to Fig. 17, the plurality of grooves (410) may be formed as grid-shaped grooves on the second surface (110b) of the substrate layer (110). Fig. 17 is a fifth exemplary drawing for explaining various shapes of grooves formed on the substrate layer constituting the flexible circuit board. Alternatively, referring to Fig. 18, the plurality of grooves (410) may be formed as honeycomb-shaped grooves on the second surface (110b) of the substrate layer (110). Fig. 18 is a sixth exemplary drawing for explaining various shapes of grooves formed on the substrate layer constituting the flexible circuit board.

[0087] The flexible circuit board (100) may further include a protective layer covering each of the wiring layer (120) and the heat dissipation layer (130). Fig. 19 is a second exemplary diagram showing a cross-sectional view of the internal structure of a flexible circuit board including a heat dissipation layer. According to Fig. 19, the flexible circuit board (100) may include a substrate layer (110), a wiring layer (120), a heat dissipation layer (130), a first protective layer (140), and a second protective layer (150).

[0088] A first protective layer (140) may be formed on the wiring layer (120) to protect the wiring layer (120). And, a second protective layer (150) may be formed on the heat dissipation layer (130) to protect the heat dissipation layer (130).

[0089] The first protective layer (140) and the second protective layer (150) may be formed as an insulating resin layer including a solder resist. The first protective layer (140) and the second protective layer (150) may be formed using various methods such as printing, bonding, coating, and photolithography. In the case of printing or coating, the first protective layer (140) and the second protective layer (150) may be formed by printing or coating a liquid solder resist. In the case of bonding, the first protective layer (140) and the second protective layer (150) may be formed by bonding a coverlay film in a laminated manner.

[0090] The first protective layer (140) may not be formed to cover the entire wiring layer (120). The first protective layer (140) may be formed to cover only the wiring pattern (123). That is, the first protective layer (140) may be formed so as not to cover the inner lead (121) and the outer lead (122). The first protective layer (140) may be formed to cover the upper surface of the wiring pattern (123), and the inner lead (121) and the outer lead (122) may be exposed to the outside.

[0091] The second protective layer (150) may be formed to cover the heat dissipation layer (130) to prevent peeling or scratching of the heat dissipation layer (130). The second protective layer (150) may be formed to cover both the upper surface and the side surfaces of the heat dissipation layer (130). However, the present invention is not limited thereto, and the second protective layer (150) may also be formed to cover only the upper surface of the heat dissipation layer (130).

[0092] Next, a method for manufacturing a flexible circuit board (100) including a heat dissipation layer (130) is described. Fig. 20 is a flowchart sequentially illustrating a method for manufacturing a flexible circuit board. The following description refers to Fig. 20.

[0093] First, a wiring layer (120) is formed on the first surface (110a) of the substrate layer (110) (S510). The wiring layer (120) may include an inner lead (121), an outer lead (122), and a wiring pattern (123).

[0094] Thereafter, a plurality of grooves (410a, 410b, …, 410k, …, 410n) are formed on the second surface (110b) of the substrate layer (110) (S520). Accordingly, the substrate layer (110) may include a trench structure on the second surface (110b). The plurality of grooves (410a, 410b, …, 410k, …, 410n) may be formed through laser processing or etching processing using a laser beam. The plurality of grooves (410a, 410b, …, 410k, …, 410n) may be formed at regular intervals on the second surface (110b) in a trench shape having a predetermined width and depth.

[0095] The plurality of grooves (410a, 410b, …, 410k, …, 410n) may be formed to overlap with the inner lead region (IL) and the wiring region (WL). However, the present invention is not limited thereto, and the plurality of grooves (410a, 410b, …, 410k, …, 410n) may be formed to overlap with the inner lead region (IL). Alternatively, the plurality of grooves (410a, 410b, …, 410k, …, 410n) may be formed to overlap with the inner lead region (IL), the wiring region (WL), and the outer lead region (OL).

[0096] Thereafter, a heat dissipation layer (130) is formed on the second surface (110b) of the substrate layer (110) (S530). The heat dissipation layer (130) may include a plurality of grooves (410a, 410b, …, 410k, …, 410n) and cover the second surface (110b) of the substrate layer (110). The heat dissipation layer (130) may cover a portion of the second surface (110b) of the substrate layer (110).

[0097] The heat dissipation layer (130) can be formed on the second surface (110b) of the substrate layer (110) by printing or coating. For example, the heat dissipation layer (130) can be formed by applying a heat dissipation paste containing a heat dissipation material (e.g., a metal paste such as metal ink) to the second surface (110b) of the substrate layer (110). However, the present invention is not limited thereto, and the heat dissipation layer (130) can also be formed on the second surface (110b) of the substrate layer (110) by laminating. For example, the heat dissipation layer (130) can be formed by laminating or bonding a heat dissipation film to the second surface (110b) of the substrate layer (110).

[0098] Thereafter, a first protective layer (140) and a second protective layer (150) are formed on the wiring layer (120) and the heat dissipation layer (130) (S540). The first protective layer (140) and the second protective layer (150) can be formed by printing or coating an insulating material such as solder resist. The second protective layer (150) may not be formed on the heat dissipation layer (130) depending on the metal paste material.

[0099] The first protective layer (140) and the second protective layer (150) may be formed simultaneously, but this is not limited to the case, and either the first protective layer (140) or the second protective layer (150) may be formed first. For example, the first protective layer (140) may be formed first. The first protective layer (140) may be formed to cover the wiring layer (120) before forming the plurality of grooves (410a, 410b, ..., 410k, ..., 410n) on the second surface (110b) of the substrate layer (110). The first protective layer (140) may be formed between steps S510 and S520.

[0100] Meanwhile, it is also possible to form a heat dissipation layer (130) on the second surface (110b) of the base layer (110) by applying a heat dissipation paste, and then harden the heat dissipation layer (130) through heat treatment. This process can be performed before forming the second protective layer (150) on the heat dissipation layer (130).

[0101] Fig. 21 is a result of analyzing the heat dissipation characteristics of a flexible circuit board through simulation. The comparative example of Fig. 21 shows the heat dissipation characteristics of the circuit board when a heat dissipation layer (130) having a flat structure is formed on the second surface (110b) of the substrate layer (110) without forming a plurality of grooves (410a, 410b, …, 410k, …, 410n) on the second surface (110b) of the substrate layer (110). And, the embodiment of FIG. 21 shows the heat dissipation characteristics of the circuit board when a plurality of grooves (410a, 410b, …, 410k, …, 410n) are formed on the second surface (110b) of the substrate layer (110) and a heat dissipation layer (130) is formed on the second surface (110b) of the substrate layer (110) to fill the plurality of grooves (410a, 410b, …, 410k, …, 410n).

[0102] The simulation conditions are as follows. A hot plate is heated to a constant temperature (e.g., 125°C) and maintained for 30 minutes. Then, the circuit board to be evaluated is placed on the hot plate. Thereafter, the temperature of the heat dissipation layer (130) within the circuit board is measured using a thermal imaging camera.

[0103] Referring to the simulation results of Fig. 21, it can be confirmed that the heat dissipation efficiency of the circuit board according to the present embodiment is superior to the heat dissipation efficiency of the circuit board according to the comparative example. In the case of the circuit board according to the comparative example, the distance from the surface of the substrate layer (110) to the surface of the heat dissipation layer (130), that is, the thickness of the heat dissipation layer (130), is 30 μm. On the other hand, in the case of the circuit board according to the present embodiment, the depth of the groove (410k) formed in the substrate layer (110), that is, a (8 μm) in Fig. 5, and the distance from the surface of the substrate layer (110) to the surface of the heat dissipation layer (130), that is, the sum of e (8 μm) in Fig. 5, that is, the thickness of the heat dissipation layer (130) is 16 μm. In the case of the flexible circuit board (100) according to the present embodiment, it can be confirmed that although the thickness of the heat dissipation layer (130) is formed thinner, the heat dissipation effect is superior.

[0104] Figures 22 and 23 show simulation results showing the ratio of the heat generation reduction temperature for each condition according to the width ratio (b:c) between the plurality of grooves (410a, 410b, …, 410k, …, 410n) and the width (c) of the protrusion (420) according to an embodiment of the present invention, and the depth (a) and width (b) of the plurality of grooves (410a, 410b, …, 410k, …, 410n), and the reduction temperature of a flexible circuit board (comparative example) including a conventional heat sink. In Figures 22 and 23, the units of depth and width are ㎛.

[0105] In this experimental example, a simulation was conducted under the condition that the width ratios (b:c) of the groove (410) and the protrusion (420) were 1:0.3, 1:0.6, and 1:0.9. The depth (a) of the groove (410) was 5 µm, 10 µm, 15 µm, 20 µm, 25 µm, and 30 µm, respectively, and the width (b) of the groove (410) was 3 µm, 5 µm, 10 µm, 20 µm, and 30 µm, respectively. The thickness of the heat sink applied to this experimental example, that is, the thickness (e) from the second surface (110b) of the substrate layer (110) to the surface of the heat sink layer (130), was 10 µm, and the size of the heat sink was a rectangular shape with a length x width of 36 mm x 18 mm.

[0106] For example, as an example of experimental conditions, when the width (b) of the groove (410) is 10 ㎛, the width (c) of the protrusion is 3 ㎛, the width ratio (b:c) is 1:0.3, and the depth (a) of the groove (410) is 5 ㎛, the temperature change is 118.09 ℃, which is lower than the heating temperature of 125 ℃ when there is no heat dissipation layer, and a temperature reduction effect of 6.91 ℃ is shown.

[0107] The comparative example is a heat sink in the shape of a rectangular plate formed on a flat surface without a groove on the back surface of the substrate layer. The thickness of the heat sink applied to the comparative example is 25㎛, and the size of the heat sink is 36mm x 18mm in length x width, which is the same as that of the present experimental example. The temperature change due to the heat sink of the comparative example was 118.46℃, which was lower than the heat generation temperature of 125℃ when there was no heat sink, and there was a temperature reduction effect of 6.54℃. In other words, the heat dissipation effect of the condition example of the present invention was improved by 105.6% compared to the heat dissipation effect of the comparative example.

[0108] Referring to Fig. 22, the deeper the depth (a) of the groove (410) and the narrower the width (c) of the protrusion surface, the higher the results. When the depth (a) of the groove (410) is 5 ㎛ under the condition of a width ratio of 1:0.9, the heat dissipation efficiency was lower at 96.3% compared to the comparative example.

[0109] Although embodiments of the present invention have been described with reference to the attached drawings, the present invention is not limited to the above embodiments, but can be manufactured in various different forms. Those skilled in the art to which the present invention pertains will understand that the present invention can be implemented in other specific forms without changing the technical spirit or essential characteristics of the present invention. Therefore, it should be understood that the embodiments described above are exemplary in all respects and not restrictive.

[0110] The flexible circuit board of the present invention can be provided as a chip-on-film (COF). The flexible circuit board of the present invention can be utilized in manufacturing a display device including a display driver chip (DDI).

Claims

1. Base layer; A wiring layer formed on the first surface of the above substrate layer; and Includes a heat dissipation layer formed on the second surface of the above-mentioned substrate layer, The second surface of the above substrate layer includes a plurality of grooves, A flexible circuit board in which the heat dissipation layer covers a portion of the second surface of the substrate layer, including the plurality of grooves.

2. In paragraph 1, The above plurality of grooves are trench structures, A flexible circuit board in which the heat dissipation layer covers a portion of the second surface of the substrate layer while filling the groove.

3. In paragraph 1, A flexible circuit board wherein the spacing between the grooves is 0.1 to 0.6 times the width of the grooves.

4. In paragraph 1, A flexible circuit board having a depth of the groove of 5㎛ or more and 50% or less of the height of the substrate layer.

5. In paragraph 1, A flexible circuit board in which the width of the protrusion formed between two different grooves is equal to or smaller than the width of the grooves.

6. In paragraph 1, A flexible circuit board wherein the depth of the above groove is less than 50% of the thickness of the above substrate layer.

7. In paragraph 1, A flexible circuit board in which the heat dissipation layer is formed at a position corresponding to the inner lead area of ​​the wiring layer.

8. In paragraph 7, A flexible circuit board in which the heat dissipation layer has a size equal to or larger than the size of the inner lead area.

9. In paragraph 1, A flexible circuit board in which the distance from the surface of the second side of the substrate layer to the surface of the heat dissipation layer is 5 ㎛ or more and less than the thickness of the substrate layer.

10. In paragraph 1, A flexible circuit board in which the plurality of grooves are formed in at least one shape among a comb-shaped groove, a donut-shaped groove, a zigzag-shaped groove, a recessed groove, a grid-shaped groove, and a honeycomb-shaped groove.

11. In paragraph 1, A first protective layer covering the wiring layer; and A flexible circuit board comprising a second protective layer covering the heat dissipation layer.

12. In paragraph 11, A flexible circuit board in which the first protective layer covers a portion of the wiring layer or covers an upper surface of the wiring layer.

13. In paragraph 11, The second protective layer is a flexible circuit board covering the upper surface and side surfaces of the heat dissipation layer.

14. Step of forming a wiring layer on the first surface of the substrate layer; A step of forming a plurality of grooves on the second surface of the above-mentioned substrate layer; and A method for manufacturing a flexible circuit board, comprising the step of forming a heat dissipation layer to cover a portion of the second surface of the substrate layer, including the plurality of grooves.

15. In paragraph 14, A method for manufacturing a flexible circuit board, wherein the step of forming the plurality of grooves uses any one of laser processing and etching to form the plurality of grooves.

16. In paragraph 14, A method for manufacturing a flexible circuit board, wherein the step of forming the heat dissipation layer uses any one of printing, coating, and laminating methods.

17. In paragraph 14, A method for manufacturing a flexible circuit board, further comprising a step of hardening the heat dissipation layer by heat treatment.

18. Flexible circuit board; and It includes a semiconductor chip mounted on the above flexible circuit board, The above flexible circuit board is, substrate layer; A wiring layer formed on the first surface of the above substrate layer; and Includes a heat dissipation layer formed on the second surface of the above-mentioned substrate layer, The second surface of the above substrate layer includes a plurality of grooves, A semiconductor package in which the heat dissipation layer covers a portion of the second surface of the substrate layer, including the plurality of grooves.

19. A semiconductor package including a flexible circuit board and a semiconductor chip mounted on the flexible circuit board; and Includes an external device electrically connected to the above semiconductor package, The above flexible circuit board is, substrate layer; A wiring layer formed on the first surface of the above substrate layer; and Includes a heat dissipation layer formed on the second surface of the above-mentioned substrate layer, The second surface of the above substrate layer includes a plurality of grooves, An electronic device in which the heat dissipation layer covers a portion of the second surface of the substrate layer, including the plurality of grooves.

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