Method of making a metal mesh without a substrate

Abstract

The application provides a method for manufacturing a metal mesh without a substrate, comprising the following steps: sputtering a metal seed layer on a substrate; covering the metal seed layer with a photoresist layer; forming a plurality of opening regions exposing part of the metal seed layer in the photoresist layer by using a photolithography technology; oxidizing the exposed metal seed layer through the opening regions; forming a metal circuit layer by electroplating in the opening regions; and removing the photoresist layer by a stripping process, and stripping the metal circuit layer from the metal seed layer to form a metal mesh without a substrate. The application can greatly simplify the complexity of the process, reduce the waste liquid generated by using chemical liquid, and reduce the cost of waste liquid treatment and environmental pollution.

Description

Technical Field

[0001] This application relates to the technical field of metal mesh, and in particular to a method for manufacturing a substrate-free metal mesh. Background Technology

[0002] To meet the growing demand for flexible touch panels, many alternative conductive materials to indium tin oxide (ITO) have emerged in recent years, offering good flexibility and excellent conductivity. Among them, copper metal mesh, with its excellent ductility and low impedance, is considered one of the alternative materials to ITO conductive films.

[0003] Please refer to Figures 1A to 1F The diagram illustrates the typical manufacturing process of a metal mesh. First, as shown... Figure 1A As shown, copper is sputtered onto the substrate 110 as a dielectric layer 120; as Figure 1B As shown, a photoresist layer 130 is then coated; then, as... Figure 1C As shown, using photolithography, the positions of the fine lines are defined by a high-precision mesh photomask, and an etching process is performed to remove the photoresist layer 130 from the required opening area 131; as Figure 1D As shown, a copper plating thickening process is then performed to form the copper circuit layer 140; subsequently, as... Figure 1E As shown, the photoresist layer 130 of the protected area is then stripped to obtain the electroplated copper circuit layer 140 and the sputtered copper dielectric layer 120; as Figure 1F As shown, the sputtered copper dielectric layer 120 is then removed using wet etching technology, thus obtaining the desired metal mesh 100 with ultra-fine lines. However, this method is complex, and the chemical solutions used cause serious environmental pollution. The etching bath solution and Cu used in the fabrication of metal meshes typically contain... 2+ The concentrations are shown in Table 1 below.

[0004] Table 1

[0005]

[0006] This demonstrates that the wastewater discharged from the metal mesh manufacturing process contains a considerably high level of copper. Irrigating farmland with this copper-containing wastewater leads to copper accumulation in the soil and crops, causing poor growth, especially in rice and barley, and contaminating the grains. The critical concentration of copper sulfate in irrigation water that is harmful to rice is 0.6 mg / L. Copper is highly toxic to aquatic organisms; there have been incidents in coastal areas and harbors where copper contamination has caused oyster meat to turn green. While copper is an essential trace element for life, excessive amounts are harmful to humans, animals, and plants.

[0007] Therefore, the industry urgently needs to find a method for manufacturing substrate-free metal meshes that can simplify the process and effectively reduce the use of chemical solutions, so as to solve the various difficulties and shortcomings encountered in the above process. Summary of the Invention

[0008] In view of this, the main objective of this application is to provide a method for fabricating a substrate-free metal mesh. By oxidizing the surface of the metal seed layer, not only can subsequent electroplating of the metal circuit layer be performed, but the electroplated metal circuit layer can also be easily separated from the metal seed layer, thus obtaining a substrate-free metal mesh. This application simplifies the complexity of the process and reduces the waste liquid generated by the use of chemical solutions, thereby reducing waste liquid treatment costs and environmental pollution.

[0009] To achieve the above objectives, this application provides a method for fabricating a substrate-free metal mesh, which includes the following steps:

[0010] S10. A metal seed layer is sputtered onto the substrate to form a metal seed layer;

[0011] S20. Cover the metal seed layer with a photoresist layer;

[0012] S30. Using photolithography, multiple opening areas are formed in the photoresist layer to expose part of the metal seed layer.

[0013] S40. Oxidize the exposed surface of the metal seed layer through the opening area;

[0014] S50, Electroplating to form a metal circuit layer in the opening area; and

[0015] S60. The photoresist layer is removed through a stripping process, and the metal circuit layer is peeled off from the metal seed layer to form a substrate-free metal mesh.

[0016] According to embodiments of this application, the aforementioned substrate is made of polyethylene terephthalate (PET), inorganic transparent polyimide (CPI), cyclic olefin polymer (COP), polyvinylidene chloride (HPVDF), cyclic block copolymer (CBC), polycarbonate (PC), or glass.

[0017] According to embodiments of this application, the aforementioned metal seed layer is made of silver, copper, or gold.

[0018] According to an embodiment of this application, the thickness of the aforementioned metal seed layer is 0.2 μm to 0.4 μm.

[0019] According to embodiments of this application, the aforementioned photoresist layer is a positive photoresist or a negative photoresist.

[0020] According to an embodiment of this application, the aforementioned step S40 is achieved by acid washing or placing the exposed metal seed layer in a humid environment to react with oxygen and water vapor.

[0021] According to embodiments of this application, the aforementioned metal circuit layer is made of silver, copper, or gold.

[0022] According to an embodiment of this application, the aforementioned step S60 is performed by either spraying a peeling agent or soaking in a peeling agent.

[0023] Compared with prior art, the technical solution of this application has the following advantages:

[0024] (1) The method for manufacturing substrate-free metal mesh provided in this application can overcome the problem that conventional technologies are complicated in process and cause environmental pollution by using chemical solutions, which leads to increased process costs.

[0025] (2) The method for manufacturing substrate-free metal mesh provided in this application can simplify the complexity of the process, reduce the use of chemical solutions, and reduce environmental pollution and waste liquid treatment costs.

[0026] (3) The method for producing substrate-free metal mesh provided in this application can successfully produce substrate-free metal mesh. The substrate-free metal mesh is not limited by the material of the substrate and the shape of the covered object. It can be arbitrarily transferred to the required place, and its thickness and line width can be increased or decreased arbitrarily according to the needs, which greatly improves the speed of productization.

[0027] (4) The substrate with a metal seed layer formed in the substrate-free metal mesh manufacturing method provided in this application can be recycled and reused multiple times, thereby reducing production costs.

[0028] The following detailed description through specific embodiments will make it easier to understand the purpose, technical content, features and effects achieved by this application. Attached Figure Description

[0029] Figures 1A to 1F This is a structural cross-sectional view comparing each step in the typical metal mesh fabrication method.

[0030] Figure 2 A flowchart illustrating a method for manufacturing a substrate-free metal mesh provided in an embodiment of this application.

[0031] Figures 3A to 3F The structural cross-sectional view of each step in the method for manufacturing a substrate-free metal mesh provided in the embodiments of this application.

[0032] Figure 3G This is a schematic diagram of a substrate-free metal mesh produced by the substrate-free metal mesh manufacturing method provided in the embodiments of this application.

[0033] Figure 4 This is an optical microscope image of the photoresist layer surface taken after the photolithography process was completed in an embodiment of this application.

[0034] Figure 5 This is an optical microscope image of the surface of the metal circuit layer taken after the electroplating process is completed in an embodiment of this application.

[0035] Explanation of icon numbers

[0036] 100: Metal mesh

[0037] 110: Substrate

[0038] 120: Dielectric layer

[0039] 130: Photoresist layer

[0040] 131: Opening area

[0041] 140: Copper circuit layer

[0042] 200: Substrate-free metal mesh

[0043] 210: Substrate

[0044] 220: Metal seed layer

[0045] 221: Metal oxide layer

[0046] 230: Photoresist layer

[0047] 231: Opening area

[0048] 240: Metallic circuit layer

[0049] S10~S60: Steps Detailed Implementation

[0050] The embodiments of this application will be further explained below with reference to the accompanying drawings. Wherever possible, the same reference numerals represent the same or similar components in the drawings and specification. In the drawings, shapes and thicknesses may be exaggerated for simplicity and convenience, and some details may not be fully drawn for the sake of brevity. It is understood that elements not specifically shown in the drawings or described in the specification are forms known to those skilled in the art. Those skilled in the art can make various changes and modifications based on the content of this application.

[0051] The technical solutions employed in the embodiments of this application are used to more clearly illustrate the technical solutions of this application, and are therefore only examples. Unless otherwise specified, they should not be used to limit the scope of protection of this application. In the description of the specification, many specific details are provided to give the reader a more complete understanding of this application; however, this application may still be implemented even if some or all of the specific details are omitted. Furthermore, well-known steps or elements are not described in the details to avoid unnecessarily limiting this application. Unless otherwise specified, the embodiments and features in the embodiments of this application can be arbitrarily combined with each other. It should be noted that, unless otherwise specified, all technical and scientific terms used in this application have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains.

[0052] No embodiment or claim of this application is required to achieve all the objectives, advantages, or features disclosed herein. Unless otherwise stated, certain conditional phrases or words, such as “may,” “possibly,” “perhaps,” or “may,” are generally intended to express that the embodiments of this application have features, elements, or steps that may not be necessary. In other embodiments, these features, elements, or steps may be unnecessary.

[0053] As described in previous art, the current methods for manufacturing conventional metal meshes are quite complex, and the chemical solutions used cause serious environmental pollution, leading to excessively high wastewater treatment costs. To address these technical problems, the basic idea of ​​this application is to provide a method for manufacturing substrate-free metal meshes. This method not only simplifies the complexity of the process but also effectively reduces the use of chemical solutions, thereby lowering wastewater treatment and production costs and promoting environmental sustainability.

[0054] Please refer to Figure 2 This is a flowchart illustrating the method for fabricating a substrate-free metal mesh according to an embodiment of this application. Please also refer to... Figures 3A to 3G ; Figures 3A to 3F The following are structural cross-sectional views comparing each step of the method for manufacturing a substrate-free metal mesh provided in the embodiments of this application. Figure 3A This is a schematic diagram of a substrate-free metal mesh produced by the method for manufacturing a substrate-free metal mesh provided in an embodiment of this application. Additionally, Figure 4 This is an optical microscope image of the photoresist layer surface taken after the photolithography process was completed in an embodiment of this application; Figure 5 These are optical microscope images taken of the surface of the metal circuit layer after the electroplating process is completed in the embodiments of this application. All optical microscope images have been digitally processed to increase contrast and to convert them from color to grayscale. The various steps in the method for fabricating a substrate-free metal mesh according to this embodiment are described in detail below.

[0055] First, see step S10, as follows Figure 3A As shown, a metal seed layer 220 is sputtered onto a substrate 210. In embodiments of this application, the substrate 210 is made of materials including, but not limited to, polyethylene terephthalate (PET), inorganic transparent polyimide (CPI), cyclic olefin polymer (COP), polyvinylidene chloride (HPVDF), cyclic block copolymer (CBC), polycarbonate (PC), and glass; the metal seed layer 220 is made of materials including, but not limited to, silver, copper, and gold. In embodiments of this application, the thickness of the metal seed layer 220 is preferably 0.2 to 0.4 μm. If the metal seed layer 220 is too thin, especially if its thickness is less than 0.2 μm, subsequent electroplating processes may cause the metal seed layer 220 to peel off from the substrate 210.

[0056] Next, see step S20, as follows Figure 3B As shown, a photoresist layer 230 is coated on the metal seed layer 220. In embodiments of this application, the photoresist layer 230 can be formed by coating with a positive or negative photoresist. Specifically, in embodiments of this application, a positive photoresist is used, and the coating is performed at a rate of 2 m / min and at 110°C to form the photoresist layer 230.

[0057] Then, see step S30, as follows Figure 3C As shown, using photolithography, multiple opening regions 231 are formed in the photoresist layer 230, exposing portions of the metal seed layer 220. In embodiments of this application, the photolithography process includes using an exposure energy of 110 mJ / cm². 2 The photoresist layer 230 is exposed, and then developed with a developer containing approximately 0.5-1.0% potassium carbonate. In this embodiment, the photoresist layer 230 with a positive photoresist coating, after exposure, is not covered by the photomask. After UV irradiation, the photoresist layer 230 can be easily removed by the developer, forming an opening region 231. Conversely, if a negative photoresist layer 230 is used, the developer cannot remove it after UV irradiation. The result of this embodiment after photolithography is as follows... Figure 4 As shown.

[0058] See step S40, such as Figure 3DAs shown, through the opening region 231, the exposed metal seed layer 220 surface is oxidized to form a metal oxide layer 221. In the embodiments of this application, the exposed metal seed layer 220 must not be covered with the photoresist layer 230 for chemical reaction to achieve oxidation of the metal seed layer 220. In the embodiments of this application, the oxidation method in step S40 includes using acid washing to achieve rapid oxidation, or placing it in a humid environment to allow the exposed metal seed layer 220 to react with oxygen and water vapor in the atmosphere to achieve uniform oxidation. For example, if the metal seed layer 220 is made of copper, copper will form cuprous oxide after reacting with oxygen and water vapor.

[0059] Then, see step S50, as follows Figure 3E As shown, a metal circuit layer 240 is electroplated within the opening region 231. This metal circuit layer 240 covers the metal oxide layer 221. In the embodiments of this application, the metal circuit layer 240 is made of silver, copper, or gold, and the thickness of the metal circuit layer 240 is not limited, as long as it is designed according to the required thickness. The result after the electroplating operation in this embodiment is as follows. Figure 5 As shown.

[0060] Then, see step S60, as follows Figure 3F As shown, the photoresist layer 230 is removed via a stripping process, and the metal circuit layer 240 is peeled off from the metal seed layer 220, as follows. Figure 3G As shown, the substrate-free metal mesh 200 of this application is finally obtained. In the embodiments of this application, the stripping method in step S60 is performed by either spraying a stripping agent or immersing the stripping agent. For example, in the embodiments of this application, a stripping agent with an ethanolamine content of about 3.0~5.0% is used. The stripping agent can be heated to a temperature of 40°C first, and then the electroplated workpiece can be immersed in the stripping solution for about 90~120 seconds to effectively strip the metal circuit layer 240.

[0061] According to the substrate-free metal mesh fabrication method provided in this application, in step S40, the surface of the metal seed layer 220 is oxidized to form a metal oxide layer 221. This metal oxide layer 221 can facilitate the subsequent electroplating process of the metal circuit layer 240 in step S50. At the same time, the metal oxide layer 221 on the surface of the metal seed layer 220 will make the adhesion between the metal circuit layer 240 and the metal seed layer 220 poor, which can facilitate the easy separation during the subsequent stripping process in step S60, and thus successfully complete the stripping.

[0062] The method for fabricating a substrate-free metal mesh provided in this application can be applied to form metal circuit layers of any electroplating thickness, and its line width and line spacing can also be changed with the change of the photomask. In the embodiments of this application, metal circuit layers 204 with an electroplating thickness of 53μm and a line width of 20μm, an electroplating thickness of 53μm and a line width of 15μm, an electroplating thickness of 11μm and a line width of 20μm, and an electroplating thickness of 11μm and a line width of 15μm were tested. After the stripping process, the stripping was successfully completed. The test results confirm that the method for fabricating a substrate-free metal mesh provided in this application can successfully obtain the desired substrate-free metal mesh.

[0063] On the other hand, the typical fabrication process for metal meshes involves complex procedures such as inner layer etching, black / brown oxidation, through-hole plating, full-area copper plating, circuit copper plating, tin-lead micro-etching, and outer layer etching, and uses etching baths with a relatively high total copper content (see Table 1). In contrast, the substrate-free metal mesh fabrication method provided in this application only involves an inner layer etching step, and the composition of the etching bath used for the inner layer etching and the Cu content are significantly different. 2+ The concentrations are shown in Table 2 below. It can be clearly seen that the method for fabricating the substrate-free metal mesh provided in this application can significantly reduce the copper content of the discharged wastewater. Since wastewater treatment is quite expensive, this application can reduce wastewater treatment costs, thereby reducing environmental pollution and lowering production costs.

[0064] Table 2

[0065]

[0066] In summary, the method for fabricating a substrate-free metal mesh disclosed in this application utilizes the generation of a metal oxide layer on the surface of a metal seed layer. This not only facilitates subsequent electroplating of the metal circuit layer but also reduces the adhesion between the metal circuit layer and the metal seed layer, making them easy to separate. Only a stripping process is required to obtain the substrate-free metal mesh. This application simplifies the process and reduces wastewater pollution from the use of chemical solutions, thereby lowering environmental pollution and wastewater treatment costs. Furthermore, the substrate-free metal mesh produced by this application is not limited by the substrate material or the shape of the coated object; it can be arbitrarily applied to any desired location, and its thickness and linewidth can be adjusted as needed, significantly accelerating productization. Additionally, the substrate with the metal seed layer formed during the fabrication process of this application can be recycled and reused multiple times, reducing production costs.

[0067] The above description is merely a preferred embodiment of this application and is not intended to limit the scope of this application. Therefore, all equivalent variations or modifications made in accordance with the features and spirit described in the claims of this application should be included within the scope of this application.

Claims

1. A method for manufacturing a substrate-free metal mesh, characterized in that, Includes the following steps: S10. A metal seed layer is sputtered onto the substrate to form a metal seed layer; S20. Cover the metal seed layer with a photoresist layer; S30. Using photolithography, multiple opening regions are formed in the photoresist layer to expose a portion of the metal seed layer. S40. Oxidize the exposed surface of the metal seed layer through the plurality of opening regions; S50. Electroplating is performed in the plurality of opening areas to form a metal circuit layer; as well as S60. The photoresist layer is removed via a stripping process, and the metal circuit layer is peeled off from the metal seed layer to form the substrate-free metal mesh.

2. The method for fabricating a substrate-free metal mesh according to claim 1, characterized in that, The substrate is made of polyethylene terephthalate, inorganic transparent polyimide, cyclic olefin polymer, polyvinylidene chloride, cyclic block copolymer, polycarbonate, or glass.

3. The method for fabricating a substrate-free metal mesh according to claim 1, characterized in that, The metal seed layer is made of silver, copper, or gold.

4. The method for fabricating a substrate-free metal mesh according to claim 1, characterized in that, The thickness of the metal seed layer is 0.2 μm to 0.4 μm.

5. The method for fabricating a substrate-free metal mesh according to claim 1, characterized in that, The photoresist layer is either a positive photoresist or a negative photoresist.

6. The method for fabricating a substrate-free metal mesh according to claim 1, characterized in that, Step S40 is achieved by acid washing or placing the exposed metal seed layer in a humid environment to react with oxygen and water vapor.

7. The method for fabricating a substrate-free metal mesh according to claim 1, characterized in that, The metal circuit layer is made of silver, copper, or gold.

8. The method for fabricating a substrate-free metal mesh according to claim 1, characterized in that, Step S60 is performed by either spraying or soaking the film-removing agent.

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