Flexible circuit board

Abstract

A flexible circuit board is suitable for being electrically connected to a target substrate through an adhesive layer. The flexible circuit board comprises a base material and a plurality of joint pins. The substrate has a substrate edge. The plurality of bonding pins are arranged on the substrate along the arrangement direction and are adjacent to the edge of the substrate. The substrate is provided with at least one hole between any two adjacent bonding pins, and the at least one hole overlaps the bonding pins along the arrangement direction.

Description

Technical Field

[0001] The invention relates to a circuit board, and in particular to a flexible circuit board. Background Art

[0002] In order to increase the flexibility of electromagnetic wave signal transmission and reception, most mobile devices with communication capabilities will be equipped with multiple antenna modules on different mechanical surfaces, but this also limits the placement space of other components (such as GPS antennas, Bluetooth antennas, WiFi antennas, etc.) or modules (NFC and wireless charging modules). Therefore, an idea of ​​arranging the antenna substrate above the display panel and overlapping the display area was proposed.

[0003] Generally speaking, the antenna substrate is mostly electrically connected to the printed circuit board arranged behind the display panel via multiple flexible circuit boards. In order to meet the operational requirements of high-frequency communication, the substrate of the flexible circuit board is usually selected from a board with low loss characteristics under high-frequency operation. However, during the hot-press bonding process between this type of flexible circuit board and the antenna substrate, its substrate is easily deformed due to the high process temperature, which hinders the overflow of the bonding glue layer, resulting in poor bonding between the flexible circuit board and the antenna substrate and affecting electrical conduction. Summary of the invention

[0004] The invention provides a flexible circuit board with better bonding yield.

[0005] The flexible circuit board of the present invention is suitable for being electrically bonded to a target substrate via an adhesive layer. The flexible circuit board comprises a substrate and a plurality of bonding pins. The substrate has a substrate edge. The plurality of bonding pins are arranged on the substrate along an arrangement direction and are adjacent to the substrate edge. The substrate is provided with at least one hole between any two adjacent ones of the bonding pins, and the at least one hole overlaps the bonding pins along the arrangement direction.

[0006] Based on the above, in a flexible circuit board of an embodiment of the present invention, a hole is provided in the substrate between any two adjacent ones of the plurality of bonding pins. In the process of bonding the flexible circuit board to the target substrate via the adhesive layer, the hole can serve as an overflow space of the adhesive layer to avoid the adhesive layer between the bonding pin and the target substrate being too thick and affecting the conductivity between the two, which helps to improve the bonding yield between the flexible circuit board and the target substrate. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] Figure 1 It is a top view schematic diagram of a flexible printed circuit board and a target substrate when they are bonded according to the first embodiment of the present invention.

[0008] Figure 2A yes Figure 1 A schematic cross-sectional view of a flexible printed circuit board when it is bonded to a target substrate.

[0009] Figure 2Byes Figure 1 A schematic cross-sectional view of a flexible circuit board.

[0010] Figure 3 FIG. 4 is a schematic top view of a flexible printed circuit board according to a second embodiment of the present invention.

[0011] Figure 4 FIG. 4 is a schematic top view of a flexible printed circuit board according to a third embodiment of the present invention.

[0012] Figure 5 FIG. 4 is a schematic top view of a flexible printed circuit board according to a fourth embodiment of the present invention.

[0013] Figure 6 FIG. 5 is a cross-sectional view of a flexible printed circuit board and a target substrate when they are bonded together according to a fifth embodiment of the present invention.

[0014] Figure 7 FIG. 4 is a cross-sectional view of a flexible printed circuit board and a target substrate when the flexible printed circuit board is bonded to the target substrate according to the sixth embodiment of the present invention.

[0015] Description of reference numerals:

[0016] 10, 10A, 10B, 10C, 10D, 10E: Flexible circuit boards

[0017] 20: Target substrate

[0018] 100, 100A, 100B, 100C: Base material

[0019] 100e: substrate edge

[0020] 100h1, 100h2, 100Ah1, 100Ah2, 100Bh, 100Ch: Holes

[0021] 100p1, 100p2: Part

[0022] 100s1: First surface

[0023] 100s2: Second surface

[0024] 111: First copper layer

[0025] 112: Second copper layer

[0026] 120: Bonding pin

[0027] 131: First adhesive layer

[0028] 132: Second adhesive layer

[0029] 141, 142: Conductive pattern

[0030] 141e, 142e: Pattern edge

[0031] 151, 151A: First protective layer

[0032] 152, 152A: Second protective layer

[0033] 180: Counterpoint mark

[0034] 200: Substrate

[0035] 200e: substrate edge

[0036] 210: Antenna electrode

[0037] 215: Feed line

[0038] 220: Grounding electrode

[0039] 230: Virtual electrode

[0040] 250: glue layer

[0041] BA: Bendable Area

[0042] CP: Conductive particles

[0043] DA: Display Area

[0044] he, he1, he2: hole edges

[0045] ML1, ML2: Metal layer

[0046] S, Sa, Sb: Spacing

[0047] t, t1, t2: thickness

[0048] TH: Through Hole

[0049] W1, W2, Wa, Wb, Wo: Width

[0050] X, Y, Z: direction

[0051] A-A', B-B': section line DETAILED DESCRIPTION

[0052] As used herein, "about," "approximately," "substantially," or "substantially" include the stated value and the average value within an acceptable deviation range of the particular value determined by one of ordinary skill in the art, taking into account the measurement in question and the particular amount of error associated with the measurement (i.e., the limitations of the measurement system). For example, "about" can mean within one or more standard deviations of the stated value, or within, for example, ±30%, ±20%, ±15%, ±10%, ±5%. Furthermore, as used herein, "about," "approximately," "substantially," or "substantially" can select a more acceptable deviation range or standard deviation depending on the measured property, cutting property or other property, and can apply to all properties without one standard deviation.

[0053] In the accompanying drawings, for the sake of clarity, the thickness of layers, films, panels, regions, etc. is magnified. It should be understood that when an element such as a layer, film, region, or substrate is referred to as being "on" or "connected to" another element, it may be directly on or connected to another element, or an intermediate element may also exist. On the contrary, when an element is referred to as being "directly on" or "directly connected to" another element, there is no intermediate element. As used herein, "connection" may refer to physical and / or electrical connection. Furthermore, "electrical connection" may be the presence of other elements between two elements.

[0054] In addition, relative terms such as "lower" or "bottom" and "upper" or "top" may be used herein to describe the relationship of one element to another element, as shown in the figures. It should be understood that relative terms are intended to include different orientations of the device in addition to the orientation shown in the figures. For example, if the device in one figure is turned over, the element described as being on the "lower" side of the other elements will be oriented on the "upper" side of the other elements. Therefore, the exemplary term "lower" can include both "lower" and "upper" orientations, depending on the specific orientation of the figure. Similarly, if the device in one figure is turned over, the element described as being "below" or "below" other elements will be oriented as being "above" other elements. Therefore, the exemplary terms "above" or "below" can include both above and below orientations.

[0055] Exemplary embodiments are described herein with reference to cross-sectional views as schematic diagrams of idealized embodiments. Therefore, variations in the shapes of the illustrations as a result of, for example, manufacturing techniques and / or tolerances can be expected. Therefore, the embodiments described herein should not be construed as limited to the specific shapes of the regions as shown herein, but rather include shape deviations, for example, caused by manufacturing. For example, a region shown or described as flat may typically have rough and / or nonlinear features. In addition, the sharp angles shown may be rounded. Therefore, the regions shown in the figures are schematic in nature, and their shapes are not intended to illustrate the precise shapes of the regions and are not intended to limit the claims.

[0056] Reference will now be made in detail to exemplary embodiments of the present invention, examples of which are illustrated in the accompanying drawings. Whenever possible, the same reference numerals are used in the drawings and the description to refer to the same or like parts.

[0057] Figure 1 It is a schematic top view of a flexible printed circuit board and a target substrate when they are bonded according to the first embodiment of the present invention. Figure 2A yes Figure 1 A schematic cross-sectional view of a flexible printed circuit board when it is bonded to a target substrate. Figure 2B yes Figure 1 A schematic cross-sectional view of a flexible circuit board. Figure 2A Corresponds to Figure 1 At the section line A-A' in. Figure 2B Corresponds to Figure 1 At the section line B-B' in.

[0058] Please refer to Figure 1 and Figure 2A , the flexible circuit board 10 is suitable for being electrically bonded to the target substrate 20 via the glue layer 250. The target substrate 20 is, for example, an antenna substrate provided with a plurality of antenna units. The antenna substrate is suitable for being arranged on one side of the display surface of the display panel (not shown), and overlapping the display area DA of the display panel. For example, the antenna substrate may include a substrate 200, an antenna electrode 210, a feeding line 215 and a ground electrode 220. The material of the substrate 200 includes, for example, glass or a light-transmitting polymer material (such as polymethyl methacrylate (PMMA), polycarbonate (PC), polyimide (PI), etc.). In this embodiment, the number of antenna electrodes 210 and feeding lines 215 included in the antenna substrate may be multiple, respectively, and these antenna electrodes 210 may be arranged into an antenna array (for example: a one-dimensional antenna array arranged along the direction X), and adjacent to the substrate edge 200e of the substrate 200.

[0059] It is particularly noted that these antenna electrodes 210 can be arranged in the display area DA of the display panel, and a plurality of feeding lines 215 extend from an edge area of ​​one side of the substrate 200 into the display area DA, and are respectively electrically connected to the plurality of antenna electrodes 210. A plurality of ground electrodes 220 are arranged between these feeding lines 215. For example, the feeding line 215 and two adjacent ground electrodes 220 can form a coplanar waveguide and serve as a transmission structure for electromagnetic wave signals. More specifically, an antenna electrode 210 and a feeding line 215 connected to each other and two ground electrodes 220 adjacent to the feeding line 215 can constitute an antenna unit of the antenna substrate.

[0060] One end of the flexible circuit board 10 away from the target substrate 20 can be connected to a printed circuit board (not shown). The antenna substrate (i.e., the target substrate 20) can transmit an electromagnetic wave receiving signal to the printed circuit board or receive an electromagnetic wave sending signal from the printed circuit board via the flexible circuit board 10, wherein the printed circuit board is provided with a plurality of radio frequency (RF) antenna control chips, for example.

[0061] In order to reduce the visibility of the antenna electrode 210 in the display area DA, a dummy electrode 230 may be further provided on the substrate 200 of the target substrate 20 and overlapped with the display area DA along the direction Z. The dummy electrode 230 is provided around the antenna electrode 210 and is electrically separated from the antenna electrode 210. More specifically, the dummy electrode 230 is provided in the area in the display area DA where the antenna electrode 210 is not provided to increase the concealment of the antenna electrode 210. In order to increase the radiation efficiency of these antenna electrodes 210, the dummy electrode 230 may have a floating potential, that is, the dummy electrode 230 is electrically independent of any power supply or any conductor with a fixed potential.

[0062] Further, the flexible circuit board 10 includes a substrate 100 and a plurality of bonding pins 120. In order to meet the low loss requirement of the flexible circuit board 10 during high-frequency signal transmission, the substrate 100 may be a liquid crystal polymer (LCP) having a low dielectric constant (Dk) and a low loss factor (Df), but is not limited thereto. The thickness t of the substrate 100 is, for example, 25 microns, 50 microns, or 75 microns. Preferably, the thickness t of the substrate 100 may be greater than or equal to 75 microns.

[0063] A plurality of bonding pins 120 are arranged on the substrate 100 along an arrangement direction (e.g., direction X) and adjacent to the substrate edge 100e of the substrate 100. In the present embodiment, the flexible circuit board 10 may further include a plurality of conductive patterns 141 and a plurality of conductive patterns 142, and each bonding pin 120 is respectively adjacent to a conductive pattern 141 and a conductive pattern 142 on opposite sides along the direction X. These conductive patterns are electrically independent of these bonding pins 120 and have a ground potential. Preferably, the conductive pattern 141 and the conductive pattern 142 have a width Wa and a width Wb respectively along the direction X, and the width Wa and the width Wb may each be greater than or equal to 1000 microns.

[0064] It is particularly noted that the bonding pin 120 on the flexible circuit board 10 is electrically bonded to the feed line 215 on the target substrate 20 via the adhesive layer 250, and the conductive pattern 141 and the conductive pattern 142 on the flexible circuit board 10 are electrically bonded to two ground electrodes 220 on the target substrate 20 and adjacent to the feed line 215 via the adhesive layer. In other words, one bonding pin 120 on the flexible circuit board 10 and the conductive pattern 141 and the conductive pattern 142 adjacent to the bonding pin 120 on opposite sides can constitute a bonding structure corresponding to one antenna unit on the target substrate 20.

[0065] In this embodiment, the adhesive layer 250 is, for example, an anisotropic conductive film (ACF). In order to allow the adhesive material to have suitable fluidity during the thermal compression bonding process, the adhesive layer 250 may use an anisotropic conductive film including an epoxy resin adhesive. It is particularly noted that since the fluidity of acrylic adhesive is worse than that of epoxy adhesive, it is less recommended to use it as the material for the adhesive layer 250. In detail, the anisotropic conductive film (i.e., the adhesive layer 250) may also include a plurality of conductive particles CP dispersed in the epoxy resin adhesive.

[0066] During the thermocompression bonding process between the flexible circuit board 10 and the target substrate 20, the matrix (e.g., epoxy resin glue) of the glue layer 250 is squeezed by an external force (e.g., the downward pressure generated by the thermocompression head of the bonding equipment) and overflows along the bonding surface of the bonding pin or the conductive pattern. When the material of the substrate 100 is a liquid crystal polymer (LCP), it is easy to deform and embed into the gap between two adjacent conductive patterns 141 and 142 and the gap between the bonding pin 120 and the conductive pattern 141 (or the conductive pattern 142) during the thermocompression bonding process because the process temperature is higher than the glass transition temperature (Tg) of the liquid crystal polymer, resulting in the matrix of the glue layer 250 being difficult to overflow and discharge from between the conductive pattern and the ground electrode 220 (or between the feeding line 215 and the bonding pin 120). This will cause the adhesive layer 250 to be too thick after lamination, for example, the distance between the conductive pattern and the ground electrode 220 (or the distance between the feed-in line 215 and the bonding pin 120) is greater than the particle size of the conductive particles CP, causing electrical conduction failure between the flexible circuit board and the target substrate.

[0067] In order to solve the above-mentioned problem, in the flexible circuit board 10 of the present embodiment, the substrate 100 is provided with a hole between any two adjacent bonding pins 120. More specifically, the hole overlaps these bonding pins 120 along the arrangement direction of the plurality of bonding pins 120 (e.g., direction X). For example, the substrate 100 of the present embodiment may be provided with two holes 100h1 and 100h2 spaced apart from each other between any two adjacent bonding pins 120. It is particularly noted that, in order to ensure the debonding effect of the hole, the hole edge he1 of the hole 100h1 is aligned with the pattern edge 141e of the conductive pattern 141, and the hole edge he2 of the hole 100h2 is aligned with the pattern edge 142e of the conductive pattern 142. The hole 100h1 and the hole 100h2 have a width W1 and a width W2 respectively along the direction X. Preferably, the width W1 and the width W2 may each be greater than or equal to 500 microns.

[0068] The hole can be used as an overflow space for the glue layer 250 during the thermocompression bonding process to prevent the glue layer 250 between the bonding pin 120 and the feeding line 215 and the glue layer 250 between the conductive pattern 141 (or the conductive pattern 142) and the ground electrode 220 from being too thick and affecting the electrical conduction between the two, which helps to improve the bonding yield of the flexible circuit board 10 and the target substrate 20. In other words, during the thermocompression bonding process, the glue layer 250 can overflow into the hole, so that its film thickness can be smaller than the particle size of the conductive particles CP, so that the conductive pattern and the ground electrode 220 (or the bonding pin 120 and the feeding line 215) squeeze the conductive particles CP in the glue layer 250 and are electrically connected to each other.

[0069] In the present embodiment, the top view profile of each of the hole 100h1 and the hole 100h2 in the direction Z is, for example, a rectangle, but not limited thereto. It is particularly noted that each of the hole 100h1 and the hole 100h2 is separated from the substrate edge 100e of the substrate 100. In other words, the substrate 100 still retains a portion that defines both the hole and the substrate edge 100, which can increase the stiffness of the substrate 100 to reduce the risk of warping of the flexible circuit board 10 during the thermal compression bonding process.

[0070] From another point of view, in order to set the hole 100h1 and the hole 100h2, the spacing S between the adjacent conductive patterns 141 and the conductive patterns 142 along the direction X may be greater than or equal to 3000 microns. In particular, in order to avoid signal coupling between two adjacent antenna units, no dummy conductive pattern other than the conductive pattern 141 and the conductive pattern 142 can be set between the corresponding two bonding pins 120.

[0071] Considering the insulation capability of the anisotropic conductive film in the direction X and the manufacturing tolerance of the flexible circuit board 10 , the spacing Sa between the conductive pattern 141 and the adjacent bonding pin 120 in the direction X and the spacing Sb between the conductive pattern 142 and the adjacent bonding pin 120 in the direction X may each be greater than or equal to 50 μm.

[0072] Furthermore, the flexible circuit board 10 may further include a first copper layer 111, a second copper layer 112, a first protective layer 151, and a second protective layer 152. The first copper layer 111 and the second copper layer 112 are respectively disposed on a first surface 100s1 and a second surface 100s2 of the substrate 100 that are opposite to each other, and are electrically connected to each other via the through hole TH of the substrate 100. More specifically, the flexible circuit board 10 of the present embodiment may be a double copper layer circuit board, but is not limited thereto.

[0073] The first protective layer 151 is attached to the first copper layer 111 via the first adhesive layer 131. The second protective layer 152 is attached to the second copper layer 112 via the second adhesive layer 132. In the present embodiment, the first copper layer 111 and the second copper layer 112 are, for example, a combination of a treated rolled and annealed (RA) copper foil and an electroplated copper layer, wherein the thickness of the treated rolled copper foil is, for example, 12 microns, and the thickness of the electroplated copper layer may be in the range of 6 microns to 9 microns, but not limited thereto. In other embodiments, the first copper layer 111 and the second copper layer 112 may be a high temperature elution (HTE) copper foil, and its thickness may be, for example, 12 microns or 18 microns. The materials of the first protective layer 151 and the second protective layer 152 include, for example, polyimide (PI), and their respective film thicknesses may be, for example, 12.5 microns, but not limited thereto.

[0074] In the present embodiment, the material of the bonding pin 120, the conductive pattern 141 and the conductive pattern 142 may include electroless nickel immersion gold (ENIG), and its structure may be a stacked structure of a metal layer ML1 (e.g., a nickel layer) and a metal layer ML2 (e.g., a gold layer) sequentially formed on the first copper layer 111. The thickness of the metal layer ML1 may be in the range of 1 micron to 4 microns. The thickness of the metal layer ML2 may be in the range of 0.03 microns to 0.1 microns. However, the present invention is not limited thereto. In other embodiments, the material of the bonding pin 120, the conductive pattern 141 and the conductive pattern 142 may include electroplated nickel gold, and the thickness of the electroplated nickel layer (i.e., the metal layer ML1) may be in the range of 2 microns to 6 microns, and the thickness of the electroplated gold layer (i.e., the metal layer ML2) may be in the range of 0.03 microns to 0.19 microns.

[0075] Please refer to Figure 1 and Figure 2B The flexible circuit board 10 may further include an alignment mark 180 disposed on the first surface 100s1 of the substrate 100. In this embodiment, the alignment mark 180, the bonding pin 120, the conductive pattern 141 and the conductive pattern 142 may be the same film layer. That is, the structure of the alignment mark 180 may be a stacked structure of the metal layer ML1 and the metal layer ML2 sequentially formed on the first copper layer 111, but is not limited thereto.

[0076] It is particularly noted that the flexible circuit board 10 must be aligned with the target substrate 20 before the thermocompression bonding. For example, during the alignment process, the process equipment uses the alignment mark 180 on the flexible circuit board 10 and the alignment mark (not shown) on the target substrate 20 to perform optical alignment from the side of the second surface 100s2 of the substrate 100. Since the substrate 100 made of liquid crystal polymer (LCP) has a low transmittance in the visible light band, it is difficult for the camera element (such as a charge coupled device CCD) on the process equipment (not shown) to clearly capture the alignment mark 180 on the first surface 100s1 of the substrate 100.

[0077] In order to make the alignment mark 180 easier to be read by the camera element on the process equipment, the thickness t2 of the portion 100p2 of the substrate 100 provided with the alignment mark 180 may be less than the thickness t1 of the portion 100p1 of the substrate 100 provided with the bonding pin 120. In the present embodiment, the thickness t1 of the portion 100p1 of the substrate 100 may be greater than or equal to 75 microns, and the thickness t2 of the other portion 100p2 of the substrate 100 may be in the range of 20 microns to 50 microns. The aforementioned thickness is, for example, defined by the normal direction (e.g., direction Z) of the first surface 100s1 or the second surface 100s2.

[0078] Other embodiments will be listed below to illustrate the present disclosure in detail, wherein the same components will be marked with the same symbols, and the description of the same technical content will be omitted. For the omitted parts, please refer to the aforementioned embodiments, which will not be repeated below.

[0079] Figure 3 is a top view schematic diagram of a flexible circuit board according to a second embodiment of the present invention. Figure 3 The flexible circuit board 10A of this embodiment is Figure 1The difference between the flexible circuit board 10 and the flexible circuit board 10A is that the top view profile of the hole of the substrate is different. Specifically, in the present embodiment, the top view profiles of the holes 100Ah1 and 100Ah2 of the substrate 100A of the flexible circuit board 10A in the direction Z are, for example, elliptical. It is particularly noted that, although the hole profiles of the present embodiment are elliptical, the hole edges thereof still maintain the pattern edge setting that is aligned with the conductive pattern. For example, the hole edge he1 of the hole 100Ah1 is aligned with the pattern edge 141e of the conductive pattern 141, and the hole edge he2 of the hole 100Ah2 is aligned with the pattern edge 142e of the conductive pattern 142.

[0080] Figure 4 FIG. 4 is a schematic top view of a flexible printed circuit board according to a third embodiment of the present invention. Figure 5 FIG. 1 is a top view of a flexible printed circuit board according to a fourth embodiment of the present invention. Figure 4 The flexible circuit board 10B of this embodiment is Figure 1 The difference between the flexible circuit board 10 and the flexible circuit board 10 is that the arrangement of the holes of the substrate is different. Specifically, in the present embodiment, the substrate 100B has only one hole 100Bh between any two adjacent bonding pins 120, and the hole 100Bh extends from the pattern edge 141e of the conductive pattern 141 to the pattern edge 142e of the conductive pattern 142 in the direction X. In other words, the hole edge he of the hole 100Bh of the present embodiment is aligned with the pattern edge 141e of the conductive pattern 141 and the pattern edge 142e of the conductive pattern 142 at the same time.

[0081] However, the present invention is not limited thereto. Figure 5 In another variant embodiment, the hole 100Ch between any two adjacent bonding pins 120 of the substrate 100C of the flexible circuit board 10C may extend to the substrate edge 100e.

[0082] Figure 6 FIG. 5 is a cross-sectional view of a flexible printed circuit board and a target substrate according to a fifth embodiment of the present invention when they are bonded. Figure 6 The difference between the flexible circuit board 10D of this embodiment and the flexible circuit board 10 of FIG. 2 lies in that the number of copper layers is different and the configuration of the second protection layer is different.

[0083] For example, in the flexible circuit board 10D of the present embodiment, the second copper layer 112 as shown in FIG. 2 is not provided on the second surface 100s2 of the substrate 100. That is, the flexible circuit board 10D of the present embodiment may be a single copper layer circuit board. Therefore, in the present embodiment, the first copper layer 111 may be only formed of rolled copper foil, and its thickness is, for example, 18 microns, but not limited thereto. Since the second copper layer 112 is not provided on the second surface 100s2 of the substrate 100, the second protective layer 152A may be provided in a manner of partially covering the second surface 100s2.

[0084] For example, the second protective layer 152A may partially overlap the first protective layer 151, and the overlapping area of ​​the first protective layer 151 and the second protective layer 152A may serve as the bendable area BA of the flexible circuit board 10D. By partially overlapping the first protective layer 151 and the second protective layer 152A, it is possible to prevent the stress generated when the flexible circuit board 10D is bent from being excessively concentrated on the cross section of a specific film layer. Preferably, the width Wo of the bendable area BA along the direction Y may be greater than or equal to 0.5 mm.

[0085] Figure 7 FIG. 6 is a cross-sectional view of a flexible printed circuit board and a target substrate according to a sixth embodiment of the present invention. Figure 7 , the difference between the flexible circuit board 10E of this embodiment and the flexible circuit board 10 of FIG. 2 is that the composition of the first protective layer is different. For example, in this embodiment, the first protective layer 151A of the flexible circuit board 10E can be a screen printing ink (SR) layer with a thickness of 15 microns, a developer ink (PSR) layer with a thickness of 20 microns, or a developer cover film (PIC) with a thickness of 20 microns, but is not limited thereto. That is, the first protective layer 151A of this embodiment can be directly formed on the first copper layer 111 by coating or printing. Therefore, the flexible circuit board 10E is not provided with the first adhesive layer 131 in FIG. 2.

[0086] In summary, in a flexible circuit board of an embodiment of the present invention, a hole is provided in the substrate between any two adjacent ones of the plurality of bonding pins. In the process of bonding the flexible circuit board to the target substrate via the adhesive layer, the hole can serve as an overflow space of the adhesive layer to avoid the adhesive layer between the bonding pin and the target substrate being too thick and affecting the conductivity between the two, which helps to improve the bonding yield of the flexible circuit board and the target substrate.

Claims

1. A flexible circuit board, adapted to be electrically bonded to a target substrate via an adhesive layer, the flexible circuit board comprising: a substrate having a substrate edge; as well as A plurality of bonding pins are arranged on the substrate along an arrangement direction and adjacent to the substrate edge of the substrate, wherein the substrate is provided with at least one hole between any two adjacent bonding pins, and the at least one hole overlaps the bonding pins along the arrangement direction.

2. The flexible circuit board according to claim 1, further comprising: A plurality of conductive patterns are electrically independent from the bonding pins and have a ground potential, wherein each side of each bonding pin arranged along the arrangement direction is adjacent to a conductive pattern. 3 . The flexible printed circuit board as claimed in claim 2 , wherein two of the conductive patterns are disposed between any two adjacent ones of the bonding pins, and the two conductive patterns are spaced apart from each other along the arrangement direction. 4 . The flexible printed circuit board as claimed in claim 2 , wherein two of the conductive patterns are disposed between any two adjacent ones of the bonding pins, and the at least one hole is disposed between the two conductive patterns. 5 . The flexible printed circuit board as claimed in claim 4 , wherein each of the two conductive patterns has a pattern edge facing the at least one hole, and a hole edge of any one of the at least one hole is aligned with the pattern edge of one of the two conductive patterns. 6 . The flexible printed circuit board as claimed in claim 4 , wherein each of the two conductive patterns has a pattern edge facing the at least one hole, the at least one hole is a hole, and a hole edge of the hole is aligned with the pattern edge of each of the two conductive patterns.

7. The flexible circuit board as described in claim 5, wherein the at least one hole includes a first hole and a second hole separated from each other, the hole edge of the first hole is aligned with the pattern edge of one of the two conductive patterns, and the hole edge of the second hole is aligned with the pattern edge of the other of the two conductive patterns. 8 . The flexible printed circuit board as claimed in claim 1 , wherein the at least one hole is spaced apart from an edge of the substrate. 9 . The flexible printed circuit board as claimed in claim 1 , wherein the at least one hole extends to an edge of the substrate. 10 . The flexible printed circuit board as claimed in claim 1 , wherein the adhesive layer is an anisotropic conductive film, and the material of the anisotropic conductive film comprises epoxy resin adhesive.

11. The flexible circuit board according to claim 1, further comprising: An alignment mark is arranged on the substrate, wherein the substrate includes a first part and a second part, the bonding pins are arranged on the first part, the alignment mark is arranged on the second part, and the thickness of the second part of the substrate is less than the thickness of the first part.

12. The flexible circuit board as claimed in claim 1, wherein a material of the base material comprises a liquid crystal polymer.

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