Transparent circuit board

Abstract

A transparent circuit board includes a first layer, a second layer, and conductive pillars. The first layer includes a first metal line layer and a first electrochromic structure. The first electrochromic structure is located on the upper surface of the first metal line layer. The second layer includes a second metal line layer and a second electrochromic structure. The second electrochromic structure is located on the lower surface of the second metal line layer. The conductive pillars are located between the first layer and the second layer, connecting the first and second metal line layers, wherein the first electrochromic structure partially overlaps the conductive pillars perpendicularly along a via direction.

Description

[Technical Field]

[0001] This application relates to a transparent circuit board. [Previous Technology]

[0002] With the rapid development of electronic products, printed circuit boards (PCBs), which serve as component supports and carriers of electrical signals, should gradually move towards miniaturization, lightweighting, high density, and multifunctionality. Among these, transparent PCBs can be used in flexible screens, transparent televisions, wearable devices, and other fields. However, with the popularization of wearable devices, there are higher requirements for the manufacturing methods of printed transparent PCB circuits. [Summary of the Invention]

[0003] Some embodiments of this application provide a transparent circuit board. This transparent circuit board can change the color of the electrochromic layer on its vias and circuits by providing an electrochromic layer and electrodes, thereby preventing the vias and circuits from reflecting colored light. This transparent circuit board improves the visual effect of the transparent circuit board, making it difficult for the human eye to perceive the presence of circuits. Furthermore, this design allows for a multi-layered transparent circuit board design, making it difficult to detect structures such as circuits, interlayer conductive areas, and via rings. Moreover, the color of the electrochromic layer can be changed by controlling the voltage, allowing the transparent circuit board to be designed with various different colors. In addition, this transparent circuit board uses a transparent flexible conductive material, making the entire transparent circuit board bendable, thereby improving the user experience.

[0004] Some embodiments of this application disclose a transparent circuit board. This circuit board includes a first layer, a second layer, and conductive pillars. The first layer includes a first metal line layer and a first electrochromic structure. The first electrochromic structure is located on the upper surface of the first metal line layer. The second layer includes a second metal line layer and a second electrochromic structure. The second electrochromic structure is located on the lower surface of the second metal line layer. Conductive pillars are located between the first layer and the second layer, wherein the conductive pillars connect the first metal line layer and the second metal line layer, and the first electrochromic structure partially overlaps the conductive pillars perpendicularly along a via direction.

[0005] According to a partial embodiment of this application, the second electrochromic structure partially overlaps the conductive pillars vertically.

[0006] According to some embodiments of this application, a first transparent insulating layer is further included. The first transparent insulating layer surrounds the conductive pillar, wherein the first transparent insulating layer separates the first layer from the second layer.

[0007] According to some embodiments of this application, the upper surface of the first metal wire layer has a first convex surface, and the first electrochromic structure is located on the first convex surface of the upper surface of the first metal wire layer.

[0008] According to some embodiments of this application, the lower surface of the second metal wire layer has a second convex surface, and the second electrochromic structure is located on the second convex surface of the lower surface of the second metal wire layer.

[0009] According to some embodiments of this application, the first electrochromic structure includes a first electrochromic layer and a transparent conductive layer, wherein the first electrochromic layer is located between the transparent conductive layer and the first metal wire layer.

[0010] According to some embodiments of this application, the first metal wire layer includes a metal wire, the first electrochromic structure includes an electrochromic line, the metal wire and the electrochromic line form a wire stack, and the first layer includes a second transparent insulating layer stacked around the wire.

[0011] Some embodiments of this application disclose a transparent circuit board. This circuit board includes a first layer, a second layer, and conductive pillars. The first layer includes a first metal line layer, a first electrochromic structure, and a second electrochromic structure. The first electrochromic structure is located on the upper surface of the first metal line layer. The second electrochromic structure is located on the lower surface of the first metal line layer. The second layer includes a second metal line layer, a third electrochromic structure, and a fourth electrochromic structure. The third electrochromic structure is located on the lower surface of the second metal line layer. The fourth electrochromic structure is located on the upper surface of the second metal line layer. Conductive pillars are located between the first layer and the second layer, wherein the conductive pillars connect the first metal line layer and the second metal line layer, and the first electrochromic structure partially overlaps the conductive pillars perpendicularly along a via direction.

[0012] According to some embodiments of this application, the second electrochromic structure does not vertically overlap the conductive pillars.

[0013] According to some embodiments of this application, the length of the second electrochromic structure is less than the length of the first electrochromic structure.

[0014] According to some embodiments of this application, the fourth electrochromic structure does not vertically overlap the conductive pillars.

[0015] According to some embodiments of this application, the length of the fourth electrochromic structure is less than the length of the second electrochromic structure.

[0016] According to some embodiments of this application, the first layer further includes a first transparent insulating layer. The first transparent insulating layer surrounds the conductive pillar, wherein the first transparent insulating layer separates the first layer from the second layer.

[0017] According to some embodiments of this application, a first transparent insulating layer separates the second electrochromic structure from the conductive pillar.

[0018] According to some embodiments of this application, the first electrochromic structure includes a first electrochromic layer and a transparent conductive layer, wherein the first electrochromic layer is located between the transparent conductive layer and the first metal wire layer.

Implementation Method

[0020] The embodiments of this disclosure are discussed in detail below. However, it should be understood that the embodiments provide many applicable concepts that can be implemented in a wide variety of specific situations. The discussed and disclosed embodiments are for illustrative purposes only and are not intended to limit the scope of this disclosure. The terms "first," "second," etc., used herein do not specifically refer to any order or sequence, but are merely used to distinguish components or operations described using the same technical terms.

[0021] Additionally, for ease of description, spatial relative terms such as “below,” “under,” “lower,” “above,” “upper,” and similar terms may be used herein to describe the relationship between one element or feature and another element or feature illustrated in the figures. In addition to the orientations depicted in the figures, spatial relative terms are also intended to cover different orientations of the device in use or operation. The device may be oriented in other ways (rotated 90 degrees or in other orientations), and the spatial relative descriptive terms used herein shall be interpreted accordingly. As used herein, “approximately,” “about,” “closely,” or “substantially” generally refer to within 20%, 10%, or 5% of a given value or range. The numerical quantities given herein are approximate, meaning that the terms “approximately,” “about,” “closely,” or “substantially” may be speculative unless explicitly specified.

[0022] FIG1 is a top view of a transparent circuit board 100 according to a partial embodiment of the present application. FIG2A is a cross-sectional view of a transparent circuit board 100 according to an embodiment of the present application along line A-A' in FIG1. ​​FIG2B is a cross-sectional view of a transparent circuit board 100 according to an embodiment of the present application along line B-B' in FIG1. ​​Please refer to FIG1, FIG2A and FIG2B simultaneously.

[0023] In some embodiments, the transparent circuit board 100 includes a first layer 120, a second layer 140, conductive pillars 160, and a transparent insulating layer 180.

[0024] In some embodiments, the first layer 120 includes a metal wire layer 122, an electrochromic structure 124, and a transparent insulating layer 126. The metal wire layer 122 includes metal wires 122L and portions 1222 of vertically overlapping conductive pillars 160. The electrochromic structure 124 includes electrochromic lines 124L and portions 124P of vertically overlapping conductive pillars 160 along a via direction VD. The second layer 140 is similar to the first layer 120, and the second layer 140 and the first layer 120 are mirror images of each other and aligned. The second layer 140 may include a metal wire layer 142, an electrochromic structure 144, and a transparent insulating layer 146. The metal wire layer 142 includes a metal wire 142L and a portion 1422 of vertically overlapping conductive pillars 160. The electrochromic structure 144 is located on surface 142A of the metal wire layer 142 and includes an electrochromic line 144L and a portion 144P of vertically overlapping conductive pillars 160 along a via direction VD. The metal wire 122L, the electrochromic lines 124L, and 144L form a line stack LS, and the transparent insulating layers 126, 180, and 146 are stacked around this line stack LS. Furthermore, portions 124P of the electrochromic structure 124, 144P of the electrochromic structure 144, portions 1222 and 1422 of the metal wire layer 122, and the conductive pillars 160 form an interlayer conductive area ID.

[0025] The metal wire layer 122 may be made of materials including nickel, nickel alloys, copper, platinum, similar materials, or combinations thereof. However, it should be noted that the metal wire layer 122 may be made of any suitable material, and is not limited thereto. The width W1 of the metal wire layer 122 may be varied according to functional requirements. For example, in some embodiments, the width W1 of the metal wire layer 122 is 30µm or less than 25µm, wherein the width W1 of the metal wire layer 122 is preferably 15µm. A wider metal wire layer 122 can increase adhesion to the transparent insulating layers 180 and 126, causing reflected light to diffuse, thus making the metal wire layer 122 less noticeable to the human eye. This improves the visual transparency of the transparent circuit board 100.

[0026] In some embodiments, the electrochromic structure 124 is located on the surface 122A of the metal wire layer 122, and may include a transparent conductive layer 1242, an electrochromic layer 1244, an electrolyte layer 1246, and an ion storage layer 1248, wherein the ion storage layer 1248 is in contact with the metal wire layer 122, the electrochromic layer 1244 is in contact with the transparent conductive layer 1242, and the electrolyte layer 1246 is formed between the ion storage layer 1248 and the electrochromic layer 1244.

[0027] The transparent conductive layer 1242 may be a transparent flexible conductive polymer material. For example, in some embodiments, the transparent conductive layer 1242 may be a graphene composite transparent conductive flexible film composed of graphene sheets and conductive polymer materials. In another embodiment, the transparent conductive layer 1242 may be a surface-coated nano-metal, such as nano-silver. In another embodiment, the transparent conductive layer 1242 may be a poly(ethylenedioxythiophene) / poly(styrenesulfonate) (PEDOT / PSS), a polymeric conductive material, antimony tin oxide (ATO), or similar or combined materials.

[0028] The electrochromic layer 1244 may include a material having a low oxidation potential and high coulombic efficiency. A material with a low oxidation potential can remain stable in the dyed state. A material with high coulombic efficiency can minimize side reactions, wherein when the coulombic efficiency approaches 100%, almost no side reactions occur, resulting in a longer-lifetime component. For example, in some embodiments, the electrochromic layer 1244 may be a polypyrrole (PPY), polyaniline (PANI), polyazulene, polythiophene (PT), polyindole, polycarbazole, or similar or combinations thereof. In this embodiment, PPY is a preferred material for the electrochromic layer 1244 because it is black when fully oxidized and has a long repetition life. This design enhances the visual contrast of the transparent circuit board 100, thereby increasing the transparency of the transparent circuit board 100.

[0029] The electrolyte layer 1246 may provide electrolyte ions that participate in the electrochromic reaction to the electrochromic layer 1244. For example, the electrolyte layer 1246 may be a channel for transferring electrolyte ions from the ion storage layer 1248 to the electrochromic layer 1244. For example, the electrolyte layer 1246 may comprise a liquid electrolyte, a gel polymer electrolyte, an inorganic solid electrolyte, or similar or combined materials. However, it should be noted that the electrolyte layer 1246 may be made of any suitable material, and is not limited thereto.

[0030] The ion storage layer 1248 may be an oxide or hydroxide for storing and providing electrolyte ions for the electrochromic reaction. For example, in some embodiments, the ion storage layer 1248 may include an oxide or hydroxide selected from Ni, Co, Mn, W, V, and Ti, or similar or combinations thereof. However, it should be noted that the ion storage layer 1248 may be made of any suitable material, and is not limited thereto.

[0031] The transparent insulating layer 126 may be a polyester polymer compound. For example, in some embodiments, the transparent insulating layer 126 may be a transparent polyethylene terephthalate (PET), polyimide (PI), polyethylene naphthalate (PEN), or similar or combined materials.

[0032] Furthermore, in actual operation, the electrochromic structure 124 can cause the electrochromic material in the electrochromic layer 1244 to produce a stable and reversible color change when the voltage changes between the metal wire layer 122 and the transparent conductive layer 1242. The ion storage layer 1248 in the electrochromic structure 124 is used to store ions (e.g., hydrogen ions or monovalent cations), and the electrolyte layer 1246 is used to provide ion transport channels.

[0033] In some embodiments, the electrochromic structure 144 is located on the surface 142A of the metal wire layer 142. The electrochromic structure 144 includes a transparent conductive layer 1242, an electrochromic layer 1244, an electrolyte layer 1246, and an ion storage layer 1248 stacked in sequence.

[0034] In some embodiments, the conductive post 160 is located between the first layer 120 and the second layer 140, wherein the conductive post 160 connects the metal wire layer 122 and the metal wire layer 142, and the electrochromic structures 124 and 144 partially overlap the conductive post 160 perpendicularly along a via direction VD. Specifically, the conductive post 160 can be a conductive paste, and can be made of materials including copper paste, solder paste, silver paste, similar materials, or combinations thereof. However, it should be noted that the conductive post 160 can be made of any suitable material, and is not limited thereto. The length L1 of the conductive post 160 can be varied according to functional requirements. For example, in this embodiment, the length L1 of the conductive post 160 is within 80µm, wherein a preferred length of the conductive post 160 is within 40µm. The length L2 of the interlayer conductive area ID can be varied according to functional requirements, only needing to be greater than the length L1 of the conductive post 160. For example, in some embodiments, the length L2 can be within 100µm. The width W3 of the interlayer conductive area ID can be changed according to functional requirements. For example, in this embodiment, the width W3 of the interlayer conductive area ID needs to be greater than the width W2 of the conductive post 160. In this way, portions 124P and 144P of the electrochromic structures 124 and 144 and portions 1222 and 1422 of the metal wire layers 122 and 142 can cover the conductive post 160, preventing metal reflection and thus improving the visual transparency of the transparent circuit board 100. Furthermore, the electrochromic structures 124 and 144 make it difficult for users to see the circuitry of the transparent circuit board 100 when looking from top to bottom or bottom to top, thereby increasing the transparency of the transparent circuit board 100.

[0035] In some embodiments, a transparent insulating layer 180 surrounds the conductive pillar 160. The material of the transparent insulating layer 180 is similar to that of the transparent insulating layers 126 and 146. In some embodiments, the transparent insulating layer 180 separates the first layer 120 from the second layer 140.

[0036] Figures 3A to 3I are schematic diagrams of a transparent circuit board 100 according to an embodiment of this application at various stages of the manufacturing process. This description is illustrative only and is not intended to further limit the content contained in the subsequent patent application. It should be understood that additional steps may be added before, during, and after Figures 3A to 3I, and for another part of the implementation of Figures 3A to 3I, some of the steps mentioned below may be replaced or eliminated. The order of steps / procedures may be changed.

[0037] Referring to Figures 3A, 3B, and 3C, a transparent insulating layer 180 is provided. An opening OP is then formed in the transparent insulating layer 180. For example, a drilling process is performed on the middle portion of the transparent insulating layer 180 to form the opening OP, wherein the opening OP penetrates the transparent insulating layer 180. A conductive post 160 is then provided in the opening OP to form an interlayer conductive electrical connection.

[0038] Referring to Figure 3D, a photoresist layer PR1 is disposed on the transparent insulating layer 180 and the conductive pillar 160. For example, in this embodiment, the photoresist layer PR1 can be formed by a lamination process. However, it should be noted that the photoresist layer PR1 can be formed using any suitable process, and is not limited thereto. Next, the photoresist layer PR1 is subjected to an exposure and development process to form an opening OP2 above the conductive pillar 160 and expose the surface 160A of the conductive pillar 160. The exposure and development process may include exposure, development, baking, or similar or combined steps. Furthermore, the width difference between the width W2 of the conductive pillar 160 and the width W4 of the opening OP2 can be changed according to functional requirements. For example, in this embodiment, the width difference between the width W2 of the conductive pillar 160 and the width W4 of the opening OP2 is within 20µm, with a preferred width difference being within 10µm. This not only facilitates alignment during manufacturing, but also ensures that the width W3 of the subsequently formed interlayer conductive area ID is greater than the width W2 of the conductive pillar 160 (see Figure 3I), thereby shielding the conductive pillar 160, preventing metal reflection, and achieving the transparent visual effect of the transparent circuit board 100.

[0039] Referring to Figures 3E, 3F, and 3G, a metal wire layer 122 is provided in the opening OP2. For example, in this embodiment, the metal wire layer 122 may be formed in the opening OP2 and on the surface 160A of the conductive pillar 160 through an electroplating process or the like. Next, the photoresist layer PR1 is removed. For example, in some embodiments, the photoresist layer PR1 may be removed by means of a chemical agent or the like. Next, a photoresist layer PR2 is provided on the transparent insulating layer 180 and the metal wire layer 122, wherein the thickness of the photoresist layer PR2 is greater than the thickness of the photoresist layer PR1. For example, in this embodiment, the photoresist layer PR2 may be formed through a lamination process. Next, the photoresist layer PR2 is subjected to an exposure and development process to form an opening OP3 above the metal wire layer 122 and expose the surface 122A of the metal wire layer 122. The width W5 of the opening OP3 is the same as the width W1 of the metal wire layer 122 and the width W3 of the subsequently formed interlayer conductive area ID (see Figure 3I). Next, the ion storage layer 1248, electrolyte layer 1246, electrochromic layer 1244, and transparent conductive layer 1242 of the electrochromic structure 124 are sequentially formed on the surface 122A of the metal wire layer 122, wherein each layer of the electrochromic structure 124 is baked. For example, in this embodiment, the electrochromic structure 124 can be formed on the metal wire layer 122 by a spray coating process, an inkjet process, or a similar or combined process.

[0040] Referring to Figures 3H and 3I, the photoresist layer PR2 is removed. For example, in some embodiments, the photoresist layer PR2 can be removed by means of a reagent or the like. Next, a transparent insulating layer 126 is disposed on the transparent insulating layer 180 and the electrochromic structure 124, wherein the transparent insulating layer 126 surrounds the electrochromic structure 124 and the metal wire layer 122. For example, in this embodiment, the transparent insulating layer 126 can be formed by a lamination and curing process. In this way, a first layer 120 can be formed on the transparent insulating layer 180 and the conductive pillar 160, wherein a portion 124P of the electrochromic structure 124 and a portion 1222 of the metal wire layer 122 of the first layer 120 form an interlayer conductive area ID with the conductive pillar 160.

[0041] In some embodiments, the second layer 140 may be formed using steps similar to those used for the first layer 120, which will not be described in detail here. Thus, the first layer 120 and the second layer 140 may be formed simultaneously on and below the transparent insulating layer 180 and the conductive pillar 160, respectively. In another embodiment, the first layer 120 may be formed first on the transparent insulating layer 180 and the conductive pillar 160, and then the second layer 140 may be formed on the transparent insulating layer 180 and the conductive pillar 160. In yet another embodiment, the second layer 140 may be formed first below the transparent insulating layer 180 and the conductive pillar 160, and then the first layer 120 may be formed on the transparent insulating layer 180 and the conductive pillar 160.

[0042] FIG4A is a cross-sectional view of a transparent circuit board 100 according to an embodiment of the present application along line A-A' in FIG1. ​​FIG4B is a cross-sectional view of a transparent circuit board 100 according to an embodiment of the present application along line B-B' in FIG1. ​​Please refer to FIG4A and FIG4B simultaneously. FIG4A and FIG4B are similar to FIG2A and FIG2B, wherein the difference between FIG4A and FIG4B and FIG2A and FIG2B is that the portions 124P, 144P, 1222 and 1422 that form the interlayer conductive part ID with the conductive pillar 160 are convex structures. The surface 122A of the metal line layer 122 has a convex surface, and the electrochromic structure 124 is located on the convex surface of the surface 122A of the metal line layer 122, wherein the metal line layer 142 has a convex surface similar to the metal line layer 122, and the electrochromic structure 144 is located on the convex surface of the metal line layer 142. In detail, the shapes of portions 124P, 144P, 1222, and 1422 can be changed according to functional requirements. For example, in some embodiments, portions 124P, 144P, 1222, and 1422 are arc-shaped, trapezoidal, semi-circular, or similar or combined shapes. This increases the surface area of ​​portions 124P, 144P, 1222, and 1422, thereby improving the adhesion between portions 124P, 144P, 1222, and 1422 and their surface coating.

[0043] Figures 5A to 5I are schematic diagrams of a transparent circuit board 100 according to an embodiment of the present application at various stages of the manufacturing process. Figures 5A to 5I are similar to Figures 3A to 3I. The difference between Figures 5A to 5I and Figures 3A to 3I is that: referring to Figure 5A, after the photoresist layer PR2 is disposed on the transparent insulating layer 180 and the metal line layer 122, the photoresist layer PR2 is subjected to an exposure and development process to form an opening OP4 above the metal line layer 122 to expose a portion of the surface 122A of the metal line layer 122.

[0044] Referring to FIG5B, a seed layer 200 is formed on the photoresist layer PR2 and the metal line layer 122. For example, in some embodiments, the seed layer 200 may include Ni metal. In some embodiments, the seed layer 200 may be formed in the opening OP4, on the photoresist layer PR2, and on the exposed portion of the surface 122A of the metal line layer 122 by means of sputtering or deposition, so as to facilitate differentiated etching in subsequent processes.

[0045] Referring to FIG5C, remove the photoresist layer PR2 (referring to FIG5B). In detail, since the opening OP4 (referring to FIG5B) of the photoresist layer PR2 is small, when removing the photoresist layer PR2 (referring to FIG5B), the seed layer 200 located on the metal line layer 122 can be retained, and only the seed layer 200 located on the photoresist layer PR2 (referring to FIG5B) is removed.

[0046] Referring to FIG5D, an etching process is performed on the metal line layer 122. An etchant with different etching rates for the metal line layer 122 and the seed layer 200 can be selected. For example, in this embodiment, an etchant with an etching rate for the metal line layer 122 that is more than 10 times the etching rate for the seed layer 200 can be selected to form a convex surface on the metal line layer 122.

[0047] Referring to FIG5E, the seed layer 200 (refer to FIG5D) can be selectively removed and the metal line layer 122 etched to give the metal line layer 122 a better convex curvature and surface shape. For example, in this embodiment, the seed layer 200 (refer to FIG5D) can be removed by etching or other suitable processes.

[0048] Referring to FIG5F, a photoresist layer PR3 is disposed on the transparent insulating layer 180 and the metal line layer 122. For example, in this embodiment, the photoresist layer PR3 can be formed by a lamination process. Next, the photoresist layer PR2 is subjected to an exposure and development process to form an opening OP5 above the metal line layer 122, and to expose the surface 122A of the metal line layer 122 and the surface 180A of a portion of the transparent insulating layer 180.

[0049] Referring to FIG5G, the ion storage layer 1248', electrolyte layer 1246', electrochromic layer 1244', and transparent conductive layer 1242' of the electrochromic structure 124' are sequentially formed on the surface 122A of the metal wire layer 122 and the surface 180A of the transparent insulating layer 180, wherein each layer of the electrochromic structure 124' is baked. For example, in this embodiment, the electrochromic structure 124 can be formed on the surface 180A of the metal wire layer 122 and the transparent insulating layer 180 by a spray coating process, an inkjet process, or a similar or combined process. Furthermore, by using a dam structure (i.e., photoresist layer PR3 and opening OP5) above the transparent insulating layer 180, excessive residual electrochromic structure 124' on the surface 180A of the transparent insulating layer 180 can be avoided when coating the electrochromic structure 124'. Furthermore, since the surface 122A of the metal wire layer 122 is convex, the electrochromic structure 124' located on the surface 122A can also form a convex structure.

[0050] Referring to FIG5H, the electrochromic structure 124' on the surface 180A of the transparent insulating layer 180 is removed (see FIG5G). For example, in this embodiment, the electrochromic structure 124' on the surface 180A of the transparent insulating layer 180 (see FIG5G) can be formed by laser ablation. Next, the photoresist layer PR3 is removed. Next, referring to FIG5I, a transparent insulating layer 126 is provided on the transparent insulating layer 180 and the electrochromic structure 124, wherein the transparent insulating layer 126 surrounds the electrochromic structure 124 and the metal wire layer 122. For example, in this embodiment, the transparent insulating layer 126 can be formed by a lamination and curing process. In this way, by means of the steps in Figures 5A to 5I, the first layer 120 can be formed on the transparent insulating layer 180 and the conductive pillar 160, wherein the portion 124P of the electrochromic structure 124 of the first layer 120 and the portion 1222 of the metal wire layer 122 form an interlayer conductive area ID with the conductive pillar 160.

[0051] FIG6A is a cross-sectional view of a transparent circuit board 100 according to an embodiment of the present application along line A-A' in FIG1. ​​FIG6B is a cross-sectional view of a transparent circuit board 100 according to an embodiment of the present application along line B-B' in FIG1. ​​Please refer to FIG6A and FIG6B simultaneously. FIG6A and FIG6B are similar to FIG4A and FIG4B, wherein the difference between FIG6A and FIG6B and FIG4A and FIG4B is that the transparent insulating layer 126 has a groove TH. The groove TH can further improve the adhesion of the transparent insulating layer 126 and the coating bonding reliability.

[0052] Figures 7A to 7L are schematic diagrams of a transparent circuit board 100 according to an embodiment of this application at various stages of the manufacturing process. Figures 7A to 7L are similar to Figures 5A to 5I. The difference between Figures 7A to 7L and Figures 5A to 5I is that, referring to Figure 7A, a metal line layer 122 is formed on the conductive pillar 160, and after the metal line layer 122 is formed, a transparent insulating layer 126 is disposed on the transparent insulating layer 180 and the metal line layer 122. For example, in this embodiment, the transparent insulating layer 126 can be formed through a lamination and curing process. The height H1 of the transparent insulating layer 126 can be changed according to functional requirements. For example, in this embodiment, the height H1 of the transparent insulating layer 126 is more than 10µm higher than the height H2 of the metal line layer 122, so that the electrochromic structure 124 is entirely located within the groove TH (refer to Figure 7J).

[0053] Referring to FIG7B, after the photoresist layer PR4 is disposed on the transparent insulating layers 180 and 126, the photoresist layer PR4 is subjected to an exposure and development process to form an opening OP6 in the photoresist layer PR4. Subsequently, the transparent insulating layer 126 is etched through the opening OP6, so that the opening OP6 penetrates the photoresist layer PR4 and the transparent insulating layer 126, thereby exposing a portion of the surface 122A of the metal line layer 122. The width W7 of the opening OP6 is smaller than the width W2 of the conductive pillar 160 to facilitate the etching of the transparent insulating layer 126 in subsequent processes, wherein the width W3 of the subsequently formed interlayer conductive area ID (refer to FIG7L) is larger than the width W7 of the opening OP6.

[0054] Referring to FIG7C, a seed layer 200 is formed on the photoresist layer PR4 and the metal line layer 122. For example, in some embodiments, the seed layer 200 may include Ni metal. In some embodiments, the seed layer 200 may be formed on the exposed portion of the surface 122A of the photoresist layer PR4 and the metal line layer 122 by sputtering or deposition, etc., to facilitate differentiated etching in subsequent processes.

[0055] Referring to Figure 7D, remove the photoresist layer PR4 (referring to Figure 7C). In detail, since the opening OP6 of the photoresist layer PR4 (referring to Figure 7C) is small, when removing the photoresist layer PR4 (referring to Figure 7C), the seed layer 200 located on the metal line layer 122 can be retained, and only the seed layer 200 located on the photoresist layer PR4 is removed.

[0056] Referring to FIG7E, a photoresist layer PR5 is formed on the transparent insulating layer 126 and the seed layer 200. For example, in this embodiment, the photoresist layer PR5 can be formed by a lamination process.

[0057] Referring to FIG7F, an opening process is performed on the photoresist layer PR5 and the transparent insulating layer 126, and then the transparent insulating layer 126 below is etched through the opening of the photoresist layer PR5 to form a groove TH. In this way, the width W8 of the groove TH can be made larger than the width W1 of the metal line layer 122, thereby exposing the surface 122B of the metal line layer 122.

[0058] Referring to FIG7G, an etching process is performed on the metal line layer 122. An etchant with different etching rates for the metal line layer 122 and the seed layer 200 can be selected. For example, in this embodiment, an etchant with an etching rate for the metal line layer 122 that is more than 10 times the etching rate for the seed layer 200 can be selected to form a convex surface on the metal line layer 122.

[0059] Referring to FIG7H, the seed layer 200 (refer to FIG7G) can be selectively removed and the metal line layer 122 etched to give the metal line layer 122 a better convex curvature and surface shape. For example, in this embodiment, the seed layer 200 (refer to FIG7G) can be removed by etching or other suitable processes.

[0060] Referring to FIG7I, an ion storage layer 1248', an electrolyte layer 1246', an electrochromic layer 1244', and a transparent conductive layer 1242' are sequentially formed on the surface 122A of the metal wire layer 122 and the surface 180A of the transparent insulating layer 180 in the electrochromic structure 124', wherein each layer in the electrochromic structure 124' is baked. For example, in this embodiment, the electrochromic structure 124 can be formed on the surface 180A of the metal wire layer 122 and the transparent insulating layer 180 by a spray coating process, an inkjet process, or a similar or combined process, wherein the electrochromic structure 124' is not higher than the transparent insulating layer 126. Furthermore, since the surface 122A of the metal wire layer 122 is convex, the electrochromic structure 124' located on the surface 122A can also form a convex structure.

[0061] Referring to Figures 7J, 7K, and 7L, the electrochromic structure 124' on the surface 180A of the transparent insulating layer 180 is removed. For example, in this embodiment, the electrochromic structure 124' on the surface 180A of the transparent insulating layer 180 can be formed by laser ablation. Next, the photoresist layer PR5 is removed. Next, a transparent insulating layer 300 is disposed in the groove TH, wherein the transparent insulating layer 300 surrounds the electrochromic structure 124 and the metal wire layer 122. For example, in this embodiment, the transparent insulating layer 300 can be formed by a lamination process. In this way, by means of the steps in Figures 7A to 7K, the first layer 120 can be formed on the transparent insulating layer 180 and the conductive pillar 160, wherein the portion 124P of the electrochromic structure 124 of the first layer 120 and the portion 1222 of the metal wire layer 122 form an interlayer conductive area ID with the conductive pillar 160.

[0062] Furthermore, between Figures 7J and 7K, additional steps may be performed on the transparent insulating layer 126. For example, in some embodiments, an additional spray coating process may be performed on the transparent insulating layer 126. This improves the reliability of the transparent insulating layer 300, preventing air bubbles or misalignment from occurring at the corners of the groove TH when the transparent insulating layer 300 is pressed together.

[0063] FIG8A is a top view of a transparent circuit board 100 according to a partial embodiment of the present application. FIG8B is a bottom view of the first layer 120 in FIG8A. FIG8C is a cross-sectional view along line C-C' in FIG8A. Please refer to FIG8A, FIG8B and FIG8C simultaneously. FIG8A, FIG8B and FIG8C are similar to FIG1 and FIG2A. The difference between FIG8A, FIG8B and FIG8C and FIG1 and FIG2A is that the first layer 120 further includes an electrochromic structure 128, and the second layer 140 further includes an electrochromic structure 148.

[0064] The electrochromic structure 128 may include a transparent conductive layer 1282, an electrochromic layer 1284, an electrolyte layer 1286, and an ion storage layer 1288, wherein the ion storage layer 1288 is in contact with the metal wire layer 122, the electrochromic layer 1284 is in contact with the transparent conductive layer 1282, and the electrolyte layer 1286 is formed between the ion storage layer 1288 and the electrochromic layer 1284.

[0065] The transparent conductive layer 1282 may be a transparent flexible conductive polymer material. For example, in some embodiments, the transparent conductive layer 1282 may be a graphene composite transparent conductive flexible film composed of graphene sheets and conductive polymer materials. In another embodiment, the transparent conductive layer 1282 may be a surface-coated nano-metal, such as nano-silver. In yet another embodiment, the transparent conductive layer 1282 may be a poly(ethylenedioxythiophene) / poly(styrenesulfonate) (PEDOT / PSS), a polymeric conductive material, antimony tin oxide (ATO), or similar or combined materials.

[0066] The electrochromic layer 1284 may include a material having a low oxidation potential and high coulombic efficiency. A material with a low oxidation potential can remain stable in the dyed state. A material with high coulombic efficiency can minimize side reactions, wherein when the coulombic efficiency approaches 100%, almost no side reactions occur, resulting in a longer-lifetime component. For example, in some embodiments, the electrochromic layer 1284 may be a polypyrrole (PPY), polyaniline (PANI), polyazulene, polythiophene (PT), polyindole, polycarbazole, or similar or combinations thereof. In this embodiment, PPY is a preferred material for the electrochromic layer 1284 because it is black when fully oxidized and has a long repetition life. This design enhances the visual contrast of the transparent circuit board 100, thereby increasing the transparency of the transparent circuit board 100.

[0067] The electrolyte layer 1286 may provide electrolyte ions that participate in the electrochromic reaction to the electrochromic layer 1284. For example, the electrolyte layer 1286 may be a channel for transferring electrolyte ions from the ion storage layer 1288 to the electrochromic layer 1284. For example, the electrolyte layer 1286 may comprise a liquid electrolyte, a gel polymer electrolyte, an inorganic solid electrolyte, or similar or combined materials. However, it should be noted that the electrolyte layer 1286 may be made of any suitable material, and is not limited thereto.

[0068] The ion storage layer 1288 may be an oxide or hydroxide for storing and providing electrolyte ions for the electrochromic reaction. For example, in some embodiments, the ion storage layer 1288 may include an oxide or hydroxide selected from Ni, Co, Mn, W, V, and Ti, or similar or combinations thereof. However, it should be noted that the ion storage layer 1288 may be made of any suitable material, and is not limited thereto.

[0069] Furthermore, in actual operation, the electrochromic structure 124 can cause the electrochromic material in the electrochromic layer 1284 to produce a stable and reversible color change when the voltage changes between the metal wire layer 122 and the transparent conductive layer 1282. The ion storage layer 1288 in the electrochromic structure 128 is used to store ions (e.g., hydrogen ions or monovalent cations), and the electrolyte layer 1286 is used to provide ion transport channels.

[0070] The electrochromic structure 128 may be located on the surface 122C of the metal wire layer 122 and does not perpendicularly overlap the conductive pillar 160. For example, in this embodiment, the length of the electrochromic structure 128 is less than the length of the electrochromic structure 124, wherein the transparent insulating layer 126 separates the electrochromic structure 128 from the conductive pillar 160 and separates the first layer 120 from the second layer 140. The electrochromic structure 148 is similar to the electrochromic structure 128. The electrochromic structure 148 is located on the surface 142B of the metal wire layer 142 and does not perpendicularly overlap the conductive pillar 160. For example, in this embodiment, the length of the electrochromic structure 148 is less than a certain length of the electrochromic structure 144, wherein the transparent insulating layer 146 separates the electrochromic structure 148 from the conductive pillar 160 and separates the first layer 120 from the second layer 140.

[0071] Figures 9A to 9P are schematic diagrams of a transparent circuit board 100 according to an embodiment of this application at various stages of the manufacturing process. This description is illustrative only and is not intended to further limit the content contained in subsequent patent applications. It should be understood that additional steps may be added before, during, and after Figures 9A to 9P, and for another part of the implementation of Figures 9A to 9P, some of the steps mentioned below may be replaced or omitted. The order of steps / procedures may be changed.

[0072] Referring to Figures 9A, 9B, 9C, and 9D, a transparent insulating layer 180 is provided. Next, a photoresist layer PR6 is disposed on surfaces 180A and 180B of the transparent insulating layer 180. Next, an opening OP8 is formed. For example, in this embodiment, a laser process is performed on the middle portion of the photoresist layer PR6 to ablate and form the opening OP8, wherein the opening OP8 penetrates both the photoresist layer PR6 and the transparent insulating layer 180. Next, a conductive post 160 is disposed in the opening OP, wherein the height H3 of the conductive post 160 is greater than the height H4 of the transparent insulating layer 180. Next, the photoresist layer PR6 is removed. In this way, an interlayer conductive electrical connection hole can be formed in the transparent circuit board 100.

[0073] Referring to FIG9E, a substrate 400 is provided, and metal line layers 122' and 142' are respectively disposed on surfaces 400A and 400B of the substrate 400. The lengths L4 and L5 of the metal line layers 122' and 142' can be changed according to functional requirements. For example, in this embodiment, the lengths L4 and L5 of the metal line layers 122' and 142' are the same as the length L3 of the substrate 400.

[0074] Referring to FIG9F, metal line layers 122' and 142' are patterned (refer to FIG9E) to form metal line layers 122 and 142. For example, in this embodiment, a photoresist layer (not shown) is disposed on metal line layers 122' and 142' (refer to FIG9E). Next, an exposure and development process is performed on the photoresist layer, wherein the exposure and development process may include exposure, development, baking, or similar or combined steps. Next, through the photoresist layer, metal line layers 122' and 142' (refer to FIG9E) are etched to form metal line layers 122 and 142. After the etching process, the photoresist layer (not shown) can be removed.

[0075] Referring to FIG9G, a photoresist layer PR7 is disposed on substrate 400, metal line layers 122 and 142, wherein the photoresist layer PR7 covers surfaces 400A and 400B of substrate 400, and metal line layers 122 and 142. For example, in this embodiment, the photoresist layer PR7 can be formed by a lamination process. However, it should be noted that the photoresist layer PR7 can be formed using any suitable process, and is not limited thereto. Next, an exposure and development process is performed on the photoresist layer PR7. Next, a portion of the photoresist layer PR7 is removed to expose surface 122A of metal line layer 122 and surface 142A of metal line layer 142.

[0076] Referring to FIG9H, the ion storage layer 1248, electrolyte layer 1246, electrochromic layer 1244, and transparent conductive layer 1242 of the electrochromic structure 124 are sequentially formed on the surface 122A of the metal line layer 122 on the surface 400A of the substrate 400, and the ion storage layer 1448, electrolyte layer 1446, electrochromic layer 1444, and transparent conductive layer 1442 of the electrochromic structure 144 are sequentially formed on the surface 142A of the metal line layer 142 on the surface 400B of the substrate 400, wherein each layer of the electrochromic structures 124 and 144 is baked. For example, in this embodiment, the electrochromic structures 124 and 144 can be formed on the metal line layers 122 and 142 by a spray coating process, an inkjet process, or a similar or combined process.

[0077] Please refer to FIG9I. First, remove the photoresist layer PR7 (refer to FIG9H). For example, in some embodiments, the photoresist layer PR7 (refer to FIG9H) can be removed by means of a reagent or the like. Next, a transparent insulating layer 500 is formed on the substrate 400, the electrochromic structures 124 and 144 to form layers 600 and 700, wherein the transparent insulating layer 500 surrounds the electrochromic structures 124, 144, and the metal wire layers 122 and 142. For example, in this embodiment, the transparent insulating layer 126 can be formed by a lamination and curing process. Next, referring to FIG9J, remove the substrate 400 to separate layers 600 and 700. In some embodiments, layer 700 can be fabricated simultaneously with layer 600 using the same steps as layer 600. In another embodiment, layer 700 can be fabricated separately from layer 600 using the same steps as layer 600.

[0078] Referring to FIG9K, a photoresist layer PR8 is disposed on the surface 500A of the transparent insulating layer 500 and the surface 122C of the metal line layer 122 of the layer body 600. For example, in this embodiment, the photoresist layer PR8 can be formed by a lamination process. However, it should be noted that the photoresist layer PR8 can be formed by any suitable process, and is not limited thereto. Next, the photoresist layer PR8 is subjected to an exposure and development process to expose the surface 122C of the metal line layer 122.

[0079] Referring to FIG9L, on the surface 122C of the metal wire layer 122, an ion storage layer 1288', an electrolyte layer 1286', an electrochromic layer 1284', and a transparent conductive layer 1282' are sequentially formed in the electrochromic structure 128', wherein each layer in the electrochromic structure 128' is baked. For example, in this embodiment, the electrochromic structure 128' can be formed on the surface 122C of the metal wire layer 122 by a spray coating process, an inkjet process, or a similar or combined process.

[0080] Referring to Figure 9M, remove the photoresist layer PR8. For example, in some embodiments, the photoresist layer PR8 can be removed by means of a reagent or the like. Next, a transparent insulating layer 800 is disposed on the transparent insulating layer 500 and the electrochromic structure 128', wherein the transparent insulating layer 800 surrounds the electrochromic structure 128'. For example, in this embodiment, the transparent insulating layer 800 can be formed by a lamination and curing process.

[0081] Referring to Figure 9N, a portion of the electrochromic structure 128' and a portion of the transparent insulating layer 800 are removed. For example, in this embodiment, a laser ablation process can be used to remove a portion of the electrochromic structure 128' and a portion of the transparent insulating layer 800 to form an opening OP9, thereby forming the electrochromic structure 128. This prevents a short circuit between the electrochromic structure 128 and the conductive post 160. The length L6 of the opening OP9 can be changed according to functional requirements. For example, in this embodiment, the length L6 of the opening OP9 can be greater than 20µm.

[0082] Please refer to Figures 90 and 9P for the bonding layer 600, conductive pillar 160, and layer 700. For example, in this embodiment, layer 600, conductive pillar 160, and layer 700 can be bonded through a lamination process. During the lamination of layer 600, conductive pillar 160, and layer 700, transparent insulating material flows into openings OP9 and OP10 to form transparent insulating layers 126 and 146 with transparent insulating layers 800 and 900, respectively. In this way, a first layer 120 and a second layer 140 with non-parallel alignment of metal line layers 122 and 142 can be formed to improve the transparency of the transparent circuit board 100.

[0083] Some embodiments of this application provide a transparent circuit board. This transparent circuit board can change the color of the electrochromic layer on its vias and circuits by providing an electrochromic layer and electrodes, thereby preventing the vias and circuits from reflecting colored light. This transparent circuit board improves the visual effect of the transparent circuit board, making it difficult for the human eye to perceive the presence of circuits. Furthermore, this design allows for a multi-layered transparent circuit board design, making it difficult to detect structures such as circuits, interlayer conductive areas, and via rings. Moreover, the color of the electrochromic layer can be changed by controlling the voltage, allowing the transparent circuit board to be designed with various different colors. In addition, this transparent circuit board uses a transparent flexible conductive material, making the entire transparent circuit board bendable, thereby improving the user experience.

[0084] The foregoing summary outlines features of several embodiments, enabling those skilled in the art to better understand the various aspects of this application. Those skilled in the art should understand that they can readily use this application as a basis for designing or modifying other processes and structures to achieve the same purposes and / or advantages of the embodiments introduced herein. Those skilled in the art should also recognize that such equivalent constructions do not depart from the spirit and scope of this application, and various changes, substitutions, and modifications can be made herein without departing from the spirit and scope of this application. [Simplified Explanation of the Diagram]

[0019] FIG1 is a top view of a transparent circuit board according to a partial embodiment of the present application. FIG2A is a cross-sectional view of a transparent circuit board according to an embodiment of the present application along line A-A' in FIG1. ​​FIG2B is a cross-sectional view of a transparent circuit board according to an embodiment of the present application along line B-B' in FIG1. ​​FIG3A to FIG3I are schematic diagrams of a transparent circuit board according to an embodiment of the present application at various stages of the manufacturing process. FIG4A is a cross-sectional view of a transparent circuit board according to an embodiment of the present application along line A-A' in FIG1. ​​FIG4B is a cross-sectional view of a transparent circuit board according to an embodiment of the present application along line B-B' in FIG1. ​​FIG5A to FIG5I are schematic diagrams of a transparent circuit board according to an embodiment of the present application at various stages of the manufacturing process. FIG6A is a cross-sectional view of a transparent circuit board according to an embodiment of the present application along line A-A' in FIG1. ​​FIG6B is a cross-sectional view of a transparent circuit board according to an embodiment of the present application along line B-B' in FIG1. ​​FIG7A to FIG7L are schematic diagrams of a transparent circuit board according to an embodiment of the present application at various stages of the manufacturing process. Figure 8A is a top view of a transparent circuit board according to a partial embodiment of this application. Figure 8B is a bottom view of the first layer in Figure 8A. Figure 8C is a cross-sectional view along line C-C' in Figure 8A. Figures 9A to 9P are schematic diagrams of the transparent circuit board according to an embodiment of this application at various stages of the manufacturing process. [Biomaterial Storage]

[0086] Domestic storage information (please note in order of storage institution, date, and number): None. International storage information (please note in order of storage country, institution, date, and number): None.

Claims

1. A transparent circuit board, comprising: A first layer comprising: a first metal wire layer; a first electrochromic structure located on an upper surface of the first metal wire layer, wherein the first metal wire layer includes a metal wire, and the first electrochromic structure includes an electrochromic line; and a second transparent insulating layer stacked around a line formed by the metal wire and the electrochromic line; a second layer comprising: a second metal wire layer; and a second electrochromic structure located on a lower surface of the second metal wire layer; and a conductive post located between the first layer and the second layer, wherein the conductive post connects the first metal wire layer and the second metal wire layer, and wherein the first electrochromic structure partially overlaps the conductive post perpendicularly along a via direction.

2. The transparent circuit board as described in claim 1, wherein the second electrochromic structure portion perpendicularly overlaps the conductive pillar.

3. The transparent circuit board as claimed in claim 1 further comprises: a first transparent insulating layer surrounding the conductive pillar, wherein the first transparent insulating layer separates the first layer from the second layer.

4. The transparent circuit board as claimed in claim 1, wherein the upper surface of the first metal line layer has a first convex surface, and the first electrochromic structure is located on the first convex surface of the upper surface of the first metal line layer.

5. The transparent circuit board as claimed in claim 1, wherein the lower surface of the second metal line layer has a second convex surface, and the second electrochromic structure is located on the second convex surface of the lower surface of the second metal line layer.

6. The transparent circuit board as claimed in claim 1, wherein the first electrochromic structure includes a first electrochromic layer and a transparent conductive layer, the first electrochromic layer being located between the transparent conductive layer and the first metal wire layer.

7. A transparent circuit board, comprising: A first layer includes: a first metal wire layer; a first electrochromic structure located on an upper surface of the first metal wire layer; and a second electrochromic structure located on a lower surface of the first metal wire layer; a second layer includes: a second metal wire layer; a third electrochromic structure located on a lower surface of the second metal wire layer; and a fourth electrochromic structure located on an upper surface of the second metal wire layer; and a conductive post located between the first layer and the second layer, wherein the conductive post connects the first metal wire layer and the second metal wire layer, and wherein the first electrochromic structure partially overlaps the conductive post perpendicularly along a via direction.

8. The transparent circuit board as described in claim 7, wherein the second electrochromic structure does not perpendicularly overlap the conductive pillar.

9. The transparent circuit board as claimed in claim 7, wherein a length of the second electrochromic structure is less than a length of the first electrochromic structure.

10. The transparent circuit board as claimed in claim 7, wherein the fourth electrochromic structure does not perpendicularly overlap the conductive pillar.

11. The transparent circuit board as claimed in claim 7, wherein a length of the fourth electrochromic structure is less than a length of the second electrochromic structure.

12. The transparent circuit board as claimed in claim 7, wherein the first layer further includes a first transparent insulating layer surrounding the conductive pillar, wherein the first transparent insulating layer separates the first layer from the second layer.

13. The transparent circuit board as claimed in claim 12, wherein the first transparent insulating layer separates the second electrochromic structure from the conductive pillar.

14. The transparent circuit board as claimed in claim 7, wherein the first electrochromic structure includes a first electrochromic layer and a transparent conductive layer, the first electrochromic layer being located between the transparent conductive layer and the first metal wire layer.

Images