In the production process of modern capacitive touch screen, lithography technology is a crucial process link. It directly affects the performance, accuracy and durability of the touch screen. Yellow light process and ultraviolet lithography (UV lithography) are two common lithography techniques, and although they have similarities, there are significant differences in application and characteristics.
1. Overview of lithography technology
Lithography, an integral part of microelectronics manufacturing, uses a light source to illuminate light-sensitive materials to create tiny patterns or lines on a surface. In the manufacturing of capacitive touch screens, lithography techniques are used to form circuit patterns, especially in the processing of thin film capacitive sensors and ITO (indium tin oxide) layers.
In general, lithography can be divided into two main categories: yellow light process and ultraviolet lithography. Both processes involve the selection of light source, the coating of photoresist, exposure, development and other steps, and finally the formation of accurate circuit patterns on the substrate.
2. Yellow Light process (Yellow light lithography)
The yellow light process, as the name suggests, uses yellow light as an exposure source. Yellow light is visible light in the wavelength range of 430-550 nanometers. The technology is widely used in the manufacturing process of semiconductors and display panels.
The basic flow of yellow light process
Light source selection: Yellow light usually refers to ultraviolet light with a wavelength of about 435-450 nanometers (shorter wavelength), and this type of light source is used to irradiate substrates coated with sensitive materials. It can expose certain areas of the photoresist to form the desired circuit pattern.
Exposure process: In yellow lithography, the light source shines on the photoresist through a mask to transfer the circuit pattern to the surface. Photoresist is a photosensitive material, the part exposed to the light source will undergo a chemical reaction, and the exposed area can be removed during the development process.
Development process: The photoresist area exposed to the light source is removed after development, leaving behind the desired pattern.
The advantages of yellow light process
Mature technology: Huang Guang lithography technology has been developed for many years, with mature process flow and equipment, widely used in various fields, especially in low and medium precision circuit process.
High luminous flux: The luminous flux of yellow light is relatively large, which helps to improve production efficiency.
Low cost: Due to the maturity of equipment and technology, the cost of the yellow light process is usually lower than that of ultraviolet lithography, which is suitable for mass production.
Limitations of the yellow light process
Low resolution: Due to the limitation of light wavelength, the resolution of the yellow light process is limited, which is suitable for large-size circuit pattern processing, but it is difficult to deal with fine circuits at the nano level.
Not suitable for fine patterns: In applications that require fine patterns and high density circuits, the capabilities of Huangguang photolithography are limited.
3. Ultraviolet lithography (UV lithography)
Ultraviolet lithography is a process that uses ultraviolet light (UV light) as an exposure source, usually in the wavelength range of 10-400 nanometers. Compared with the yellow process, ultraviolet lithography can provide higher resolution and is suitable for making finer circuit patterns.
The basic process of ultraviolet lithography
Light source selection: Ultraviolet lithography uses ultraviolet light sources with shorter wavelengths, including mercury lamps (Hg), xenon chloride lamps (XeCl), nitrogen chloride lamps, etc. Shorter wavelengths can provide finer lithographic patterns.
Exposure process: ultraviolet lithography irradiates the photoresist through an ultraviolet light source, and the photosensitive area reacts and is removed to form a circuit pattern. Ultraviolet lithography usually has a higher resolution than yellow lithography and can handle finer circuit structures.
Development process: Similar to the yellow light process, the development process needs to be carried out after ultraviolet lithography to remove the unexposed part of the photoresist, leaving the circuit pattern.
Advantages of ultraviolet lithography
High resolution: Ultraviolet light has a shorter wavelength than yellow light, so ultraviolet lithography can achieve higher resolution and make more accurate circuit patterns. It can provide better support for capacitive touch screens that require fine-grained circuits and high-density configurations.
Suitable for high-precision manufacturing: UV lithography is often used for the production of more delicate electronic components, suitable for high-precision equipment, such as high-resolution displays, smartphone screens, etc.
Detailed pattern production: Ultraviolet lithography can effectively produce circuit patterns at the nanoscale, so it is particularly important in miniaturized products.
Limitations of ultraviolet lithography
High cost: Due to the need to use special ultraviolet light sources and more complex equipment, the cost of ultraviolet lithography is relatively high, suitable for the manufacture of high-end products.
Equipment complexity: UV lithography equipment is relatively complex, requiring higher technical support and precision calibration, so the operation is difficult and the maintenance cost is high.
4. Applications in capacitive touch screen manufacturing
In the manufacture of capacitive touch screen, yellow light process and ultraviolet lithography each undertake different tasks. The yellow light process is usually used for the production of touch screens with lower precision requirements, especially in mass production, which can achieve higher production efficiency and lower costs. Ultraviolet lithography plays an important role in the production of fine touch circuits, especially in high-end touch screens, and ultraviolet lithography technology can provide higher accuracy to ensure the sensitivity and stability of touch functions.
With the development of capacitive touch screens in the direction of high resolution and refinement, the application of ultraviolet lithography will be more and more extensive, especially in high-end display devices that require small circuits and high sensitivity touch. However, the yellow light process still occupies an important position in the low-end market, especially in the production of equipment in large demand, the high efficiency and low cost advantages of the yellow light process are still its irreplaceable competitiveness.
Conclusion
Yellow light process and ultraviolet lithography technology have their own characteristics in the production of capacitive touch screen, and with the continuous development of touch screen technology and the progress of manufacturing process, the two technologies will play their respective advantages according to different needs and application scenarios in the future. The yellow light process will continue to provide efficient, low-cost solutions for low-end products, while ultraviolet lithography is taking an increasingly important position in the high-end touch screen market, driving the development of touch technology in the direction of higher precision and higher performance.