A double-sided ITO etching process

Abstract

The present application relates to the technical field of etching, and specifically discloses a double-sided ITO etching process, comprising the following steps: back side covering protective layer - front side coating photosensitive glue - first exposure - first development - front side etching - first cleaning - front side covering protective layer - back side coating photosensitive glue - second exposure - second development - back side etching - second cleaning. The double-sided ITO etching process of the present application, by covering the protective layer on the other side of the substrate before the exposure and development of the photosensitive glue coated on one side of the substrate, not only avoids the contamination caused by the contact between the second coating photosensitive glue and the exposure / development pattern, and thus causes the line defect in the subsequent etching, but also reduces the strict requirement of the previous ITO etching process for the cleanliness of the workbench, thereby effectively improving the production efficiency and greatly improving the yield.

Description

Technical Field

[0001] This invention relates to the field of etching technology, and specifically discloses a double-sided ITO etching process. Background Technology

[0002] In the process of fabricating character patterns on transparent conductive glass, ITO etching technology plays a crucial role. ITO, or indium tin oxide, is a transparent conductive material widely used in the thin film and semiconductor industries. Electrode photolithography, as a comprehensive precision surface processing technology combining pattern copying and chemical etching, is essential for the production of liquid crystal displays (LCDs). Its core purpose is to coat a layer of photosensitive adhesive onto a conductive glass substrate according to product design requirements, perform precise exposure, and then, with the protection of the photoresist, selectively chemically etch the ITO conductive layer to form a pattern on the ITO conductive glass that is completely identical to the photomask. This process not only requires extremely high precision but also needs to ensure the clarity and consistency of the pattern to meet the ever-increasing demands of display technology.

[0003] ITO etching technology is divided into single-sided ITO etching and double-sided ITO etching. Single-sided ITO etching is mainly used for applications that only need to form conductive patterns on one side of the conductive glass, while double-sided ITO etching is used for complex applications that require forming conductive patterns on both sides of the conductive glass, such as the production of capacitive touch screens. See [link to related information]. Figure 1 The existing double-sided ITO etching process is as follows: First application of photosensitive emulsion to the front side --- exposure --- development --- First application of photosensitive emulsion to the back side --- front side etching --- removal of emulsion --- Second application of photosensitive emulsion to the back side --- exposure --- development --- Second application of photosensitive emulsion to the front side --- back side etching --- removal of emulsion.

[0004] However, existing processes are not only time-consuming, but also prone to contaminating the existing photosensitive emulsion pattern on the front side during the first application of photosensitive emulsion to the back side; similarly, the second application of photosensitive emulsion to the front side can also contaminate the photosensitive emulsion pattern on the back side. Existing double-sided ITO etching requires high precision from operators. Furthermore, the current process demands strict cleanliness of the workbench; it must be cleaned after each operation, otherwise contamination of the photosensitive emulsion or ITO pattern can occur, negatively impacting yield. Therefore, existing processes not only reduce production efficiency but also struggle to lower the scrap rate, severely affecting production costs and product quality. Thus, developing a more efficient and cleaner double-sided ITO etching process is crucial for improving the production efficiency and reducing the cost of LCD displays. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide a double-sided ITO etching process.

[0006] This invention discloses a double-sided ITO etching process, employing the following technical solution:

[0007] A double-sided ITO etching process includes the following steps:

[0008] S1. Backside protective layer: A protective layer is coated on the back side of the substrate with ITO layers on both sides;

[0009] S2. Apply photosensitive emulsion to the front side: Place the side of the substrate with the protective layer on the worktable and apply photosensitive emulsion to the front side of the substrate.

[0010] S3, First Exposure: Move the substrate coated with photosensitive emulsion into the exposure machine with the front side facing up, and expose the photosensitive emulsion on the front side of the substrate using a mask and ultraviolet light;

[0011] S4. First development: The substrate is placed in the developing solution for development. The photosensitive emulsion exposed on the front side of the substrate is dissolved by the developing solution, leaving the unexposed photosensitive emulsion to cover part of the ITO on the substrate. The ITO part not covered by the photosensitive emulsion will be exposed, thus forming the preset pattern on the front side.

[0012] S5. Front etching: The substrate is immersed in the etching solution for etching. The ITO part on the front side of the substrate that is not covered by photosensitive adhesive is etched away, thereby forming the required ITO pattern on the front side.

[0013] S6. First cleaning: Remove the residual photosensitive adhesive on the front of the substrate and the protective layer on the back, clean it thoroughly and dry it for later use.

[0014] S7, Front Cover Protective Layer: Cover the front of the substrate with the ITO pattern already formed on it.

[0015] S8. Apply photosensitive emulsion to the back side: Place the side of the substrate with the protective layer on the worktable and apply photosensitive emulsion to the back side of the substrate.

[0016] S9. Second exposure: The substrate coated with photosensitive emulsion is moved into the exposure machine with the back side facing up. The photosensitive emulsion on the back side of the substrate is exposed using a mask and ultraviolet light.

[0017] S10, Second Development: The substrate is placed in the developing solution for development. The photosensitive emulsion on the back of the substrate that has been exposed is dissolved by the developing solution, leaving the unexposed photosensitive emulsion to cover part of the ITO on the substrate. The ITO part that is not covered by the photosensitive emulsion will be exposed, thereby forming the preset pattern on the back.

[0018] S11, Backside etching: The substrate is immersed in an etching solution for etching. The ITO portion on the backside of the substrate that is not covered by photosensitive adhesive is etched away, thereby forming the required ITO pattern on the backside.

[0019] S12. Second cleaning: Remove the residual photosensitive adhesive on the back of the substrate and the protective layer on the front, clean it thoroughly and dry it for later use.

[0020] Preferably, the protective layer in steps S1 and S7 is a PVC protective adhesive formed by printing.

[0021] Preferably, in steps S6 and S12, the residual photosensitive adhesive is first removed using an alkaline solution, and then the protective adhesive is peeled off using tape.

[0022] Preferably, in steps S6 and S12, the concentration of the degumming alkaline solution is 3±0.1%, the soaking temperature is 45±3℃, and the soaking time is 2 to 5 minutes.

[0023] Preferably, the protective layer in steps S1 and S7 is formed by screen printing the protective adhesive onto the substrate and then heating and curing it. The printing thickness of the protective adhesive is 10-30 μm; preferably 25 μm.

[0024] Preferably, in steps S2 and S8, the thickness of the photosensitive adhesive is 1.2–2.0 μm; more preferably, it is 1.4 μm.

[0025] Preferably, in steps S3 and S9, the light intensity of the exposure is 19–25 mW / cm². 2 Exposure time: 3–5 seconds; preferred light intensity: 22 mW / cm² 2 Exposure time: 3.5 seconds.

[0026] Preferably, in steps S4 and S10, the developing solution is an alkaline solution with a concentration of 0.6±0.1%, and the developing time is 1 to 2 minutes; more preferably, the developing time is 1.5 minutes.

[0027] Preferably, in steps S5 and S11, aqua regia at 35±3°C is used for etching, and the etching time is 1 to 5 minutes.

[0028] Compared with the prior art, the present invention has at least the following beneficial effects:

[0029] The double-sided ITO etching process of this invention involves covering the other side of the substrate with a protective layer before applying photosensitive emulsion to one side for exposure and development. This not only protects the side that does not require etching, eliminating the need for subsequent double-sided photosensitive emulsion application and preventing contamination caused by contact with the pattern formed during exposure / development during the second application of photosensitive emulsion, thus avoiding circuit defects during subsequent etching, but also, because the bottom of the substrate is covered with a protective layer first, even if the worktable is contaminated with photosensitive emulsion or other solvents, it will not affect the ITO pattern. This reduces the stringent requirements for worktable cleanliness in previous ITO etching processes, effectively improving production efficiency and significantly increasing the yield rate. Attached Figure Description

[0030] Figure 1 This refers to the existing double-sided ITO etching process steps;

[0031] Figure 2 This is a structural diagram of a glass plate with ITO layers on both sides of the substrate.

[0032] Figure 3 This is a structural diagram of the glass plate after step S1 of the double-sided ITO etching process of the present invention.

[0033] Figure 4 This is a structural diagram of the glass plate after step S2 of the double-sided ITO etching process of the present invention.

[0034] Figure 5 This is a structural diagram of the glass plate after step S3 of the double-sided ITO etching process of the present invention.

[0035] Figure 6 This is a structural diagram of the glass plate after step S4 of the double-sided ITO etching process of the present invention.

[0036] Figure 7 This is a structural diagram of the glass plate after step S5 of the double-sided ITO etching process of the present invention.

[0037] Figure 8 This is a structural diagram of the glass plate after step S6 of the double-sided ITO etching process of the present invention.

[0038] Figure 9 This is a structural diagram of the glass plate after step S7 of the double-sided ITO etching process of the present invention.

[0039] Figure 10 This is a structural diagram of the glass plate after step S8 of the double-sided ITO etching process of the present invention.

[0040] Figure 11 This is a structural diagram of the glass plate after step S9 of the double-sided ITO etching process of the present invention.

[0041] Figure 12 This is a structural diagram of the glass plate after step S10 of the double-sided ITO etching process of the present invention.

[0042] Figure 13 This is a structural diagram of the glass plate after step S11 of the double-sided ITO etching process of the present invention.

[0043] Figure 14 This is a structural diagram of the glass plate after step S12 of the double-sided ITO etching process of the present invention.

[0044] Figure 15 This is a quality inspection diagram of a product manufactured using traditional processes that exhibits point-like connection defects in its wiring.

[0045] Explanation of icon numbers:

[0046] 1. Substrate; 2. ITO; 3. Protective layer; 4. Photosensitive emulsion; 5. Mask. Detailed Implementation

[0047] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0048] like Figure 2-14 As shown, a double-sided ITO etching process includes the following steps:

[0049] S1. Backside protective layer: A protective layer is applied to the backside of the substrate with ITO layers on both sides. The protective layer is a modified PVC protective adhesive, which is printed onto the substrate using screen printing and then cured by heating at 150°C for 30 minutes. The printing thickness of the protective adhesive is 10-30 μm.

[0050] S2. Front-side photosensitive adhesive coating: Place the side of the substrate with the protective layer on the coating machine worktable, and uniformly coat the front side of the substrate with photosensitive adhesive using coating rollers, and perform hard film treatment. The thickness of the photosensitive adhesive is 1.2 to 2.0 μm.

[0051] S3. First Exposure: Transfer the substrate coated with photosensitive emulsion to the exposure machine, front side up. Expose the photosensitive emulsion on the front side of the substrate using a mask and ultraviolet light. The light intensity of the exposure is 19-25 mW / cm². 2 Exposure time: 3-5 seconds;

[0052] S4. First development: The substrate is placed in the developing solution for development. The developing solution is an alkaline solution with a concentration of 0.6±0.1%. The development time is 1 to 2 minutes. The photosensitive emulsion exposed on the front side of the substrate is dissolved by the developing solution, leaving the unexposed photosensitive emulsion to cover part of the ITO on the substrate. The ITO part not covered by the photosensitive emulsion will be exposed, thus forming the preset pattern on the front side.

[0053] S5. Front etching: The substrate is immersed in the etching solution for etching. Aqua regia at 35±3℃ is used for etching. The etching time is 1 to 5 minutes. The etching time is adjusted according to the ITO resistance of different products. The ITO part on the front of the substrate that is not covered by photosensitive adhesive is etched away, thereby forming the required ITO pattern on the front.

[0054] S6. First cleaning: First, use alkaline solution to remove residual photosensitive adhesive on the front side of the substrate. The concentration of the alkaline solution is 3±0.1%, the soaking temperature is 45±3℃, and the soaking time is 2 to 5 minutes. Then, peel off the protective adhesive with tape. Finally, use deionized water to clean the substrate surface and dry it for later use.

[0055] S7, Front Cover Protective Layer: Cover the front of the substrate with the ITO pattern formed with a protective layer;

[0056] S8. Apply photosensitive emulsion to the back side: Place the side of the substrate with the protective layer on the worktable, apply photosensitive emulsion evenly to the front side of the substrate using an emulsion roller, and perform hard film treatment. The thickness of the photosensitive emulsion is 1.5μm.

[0057] S9. Second exposure: Move the substrate coated with photosensitive emulsion into the exposure machine with the back side facing up. Use a mask and ultraviolet light to expose the photosensitive emulsion on the back side of the substrate, which is the same as the operation in S3.

[0058] S10, Second Development: The substrate is placed in the developing solution for development, which is the same as the operation in S4. The photosensitive emulsion exposed on the back of the substrate is dissolved by the developing solution, leaving the unexposed photosensitive emulsion to cover part of the ITO on the substrate, while the ITO part not covered by the photosensitive emulsion will be exposed, thus forming the preset pattern on the back.

[0059] S11, Backside Etching: The substrate is immersed in the etching solution for etching, which is the same as the operation in S5. The ITO part on the back of the substrate that is not covered by photosensitive adhesive is etched away, thereby forming the required ITO pattern on the backside.

[0060] S12, Second cleaning: Remove the residual photosensitive adhesive on the back of the substrate and the protective layer on the front, in the same way as S6. After cleaning, a product with double-sided ITO pattern is obtained.

[0061] The PVC protective film used in this solution is Paloma 1314F, which is used to temporarily protect the ITO film. It provides temporary protection and can be easily peeled off with tape after the process is completed, without leaving any residue on the surface.

[0062] The protective colloid thickness, photosensitive emulsion thickness, exposure parameters, and development parameters in this process are interconnected. If the protective colloid is too thin, it is prone to wrinkling during acid and alkali soaking and drying, and it is also prone to tearing when peeling off; if it is too thick, it will affect the thickness and effect of the photosensitive emulsion coating. If the photosensitive emulsion is too thick, the exposure time will be longer, and the resolution will be reduced (fine lines will show a large difference from the design value after exposure); if the photosensitive emulsion is too thin, it is prone to over-exposure and over-development (lines will be much thinner than the design after exposure and development), or the photosensitive emulsion may peel off during development. Excessively high developer concentration will also lead to over-development of the photosensitive emulsion, or even peeling off. Actual production verification shows that the PVC protective colloid printing thickness in steps S1 and S7 is 25μm; the photosensitive emulsion thickness in steps S2 and S8 is 1.4μm; and the exposure light intensity in steps S3 and S9 is 22mW / cm². 2 The exposure time is 3.5s; in steps S4 and S10, the developer is an alkaline solution with a concentration of 0.6±0.1%, and the development time is 1.5min; by designing the process parameters to be in combination with the above specific values, the yield of double-sided ITO products can reach the highest level.

[0063] This process achieves a higher yield rate in actual production compared to the traditional process. In the original process, because the front side already has a pattern formed by exposure / development when the photosensitive emulsion is applied to the back side, contact between the front side and the emulsion roller easily leads to contamination, which in turn causes circuit defects during subsequent etching. The actual production yield rates of products manufactured using the old and new processes are as follows:

[0064] Product size: 10 inches

[0065] / old techniques New process Yield 70％ 90％

[0066] Currently, there are three main types of product defects: dirt, trace spotting, and broken silver paste lines. Dirt is primarily caused by insufficient cleanliness in the operating environment; trace spotting is mainly due to poor control during exposure, development, or etching; and broken silver paste lines are mainly caused by problems with the silver paste printing process or the quality of the silver paste itself. Larger product sizes have a greater impact on yield. Statistics from actual 10-inch product production show that the main defects of the old process were dirt and trace spotting. Figure 15 .

[0067] Compared to the old process, the new process in this solution has the following advantages:

[0068] 1. The production process of the yellow room is more streamlined. After exposure and development, there is no need to apply photosensitive emulsion a second time before etching. Instead, exposure-development-etching-removal are carried out in sequence, which improves production efficiency.

[0069] 2. The protective adhesive is printed first, which will not contaminate the photosensitive adhesive pattern, thus eliminating the problem of dotted lines connecting the product lines.

[0070] 3. The protective adhesive always isolates the bottom of the product from the workbench, preventing the ITO or substrate from being contaminated due to a decrease in the cleanliness of the workbench, thus better preventing defective products caused by dirt.

[0071] 4. In the old process, during the development and exposure process on the top of the substrate, ultraviolet light would irradiate the photosensitive adhesive at the bottom edge of the substrate, causing the photosensitive adhesive at the bottom edge to dissolve during development, leaving the exposed ITO without corrosion protection. In contrast, the new process uses a protective adhesive that will not dissolve after exposure and development, thus ensuring that the pattern edges are not corroded, improving the yield. The only defect type in the new process is a small number of silver paste breaks, and the yield is about 20% higher than that of the old process.

[0072] The technical solution provided by the present invention has been described in detail above. Specific examples have been used to illustrate the principle and implementation of the present invention. The description of the above embodiments is only for the purpose of helping to understand the method and core idea of ​​the present invention. At the same time, for those skilled in the art, there will be changes in the specific implementation and application scope based on the idea of ​​the present invention. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A double-sided ITO etching method, characterized in that, Includes the following steps: S1. Backside protective layer: A protective layer is coated on the back side of the substrate with ITO layers on both sides; S2. Apply photosensitive emulsion to the front side: Place the side of the substrate with the protective layer on the worktable and apply photosensitive emulsion to the front side of the substrate. S3, First Exposure: Move the substrate coated with photosensitive emulsion into the exposure machine with the front side facing up, and expose the photosensitive emulsion on the front side of the substrate using a mask and ultraviolet light; S4. First development: The substrate is placed in the developing solution for development. The photosensitive emulsion exposed on the front side of the substrate is dissolved by the developing solution, leaving the unexposed photosensitive emulsion to cover part of the ITO on the substrate. The ITO part not covered by the photosensitive emulsion will be exposed, thus forming the preset pattern on the front side. S5. Front etching: The substrate is immersed in the etching solution for etching. The ITO part on the front side of the substrate that is not covered by photosensitive adhesive is etched away, thereby forming the required ITO pattern on the front side. S6. First cleaning: Remove the residual photosensitive adhesive on the front of the substrate and the protective layer on the back, clean it thoroughly and dry it for later use. S7, Front Cover Protective Layer: Cover the front of the substrate with the ITO pattern already formed on it. S8. Apply photosensitive emulsion to the back side: Place the side of the substrate with the protective layer on the worktable and apply photosensitive emulsion to the back side of the substrate. S9. Second exposure: The substrate coated with photosensitive emulsion is moved into the exposure machine with the back side facing up. The photosensitive emulsion on the back side of the substrate is exposed using a mask and ultraviolet light. S10, Second Development: The substrate is placed in the developing solution for development. The photosensitive emulsion on the back of the substrate that has been exposed is dissolved by the developing solution, leaving the unexposed photosensitive emulsion to cover part of the ITO on the substrate. The ITO part that is not covered by the photosensitive emulsion will be exposed, thereby forming the preset pattern on the back. S11, Backside etching: The substrate is immersed in an etching solution for etching. The ITO portion on the backside of the substrate that is not covered by photosensitive adhesive is etched away, thereby forming the required ITO pattern on the backside. S12. Second cleaning: Remove the residual photosensitive adhesive on the back of the substrate and the protective layer on the front, clean it thoroughly and dry it for later use. The protective layer in steps S1 and S7 is formed by printing the protective adhesive onto the substrate using screen printing and then curing it by heating. The printing thickness of the protective adhesive is 10~30μm. In steps S6 and S12, the residual photosensitive adhesive is first removed using an alkaline solution, and then the protective adhesive is peeled off using tape.

2. The double-sided ITO etching method according to claim 1, characterized in that, In steps S6 and S12, the concentration of the degumming alkaline solution is 3±0.1%, the soaking temperature is 45±3℃, and the soaking time is 2~5min.

3. The double-sided ITO etching method according to claim 1, characterized in that, In steps S2 and S8, the thickness of the photosensitive adhesive is 1.2~2.0μm.

4. The double-sided ITO etching method according to claim 1, characterized in that, In steps S3 and S9, the light intensity of the exposure is 19~25mW / cm². 2 Exposure time is 3-5 seconds.

5. The double-sided ITO etching method according to claim 1, characterized in that, In steps S4 and S10, the developing solution is an alkaline solution with a concentration of 0.6±0.1%, and the developing time is 1~2 min.

6. The double-sided ITO etching method according to claim 1, characterized in that, In steps S5 and S11, aqua regia at 35±3℃ is used for etching, and the etching time is 1~5 minutes.

7. The double-sided ITO etching method according to claim 4, characterized in that, The protective layers in steps S1 and S7 are formed by printing the protective adhesive onto the substrate using screen printing and then curing it by heating. The printing thickness of the protective adhesive is 25 μm. In steps S2 and S8, the thickness of the photosensitive adhesive is 1.4 μm. In steps S3 and S9, the light intensity of the exposure is 22 mW / cm². 2 Exposure time: 3.5 seconds; In steps S4 and S10, the developing solution is an alkaline solution with a concentration of 0.6 ± 0.1%, and the developing time is 1.5 min.

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