Printed Electronic Materials

Printed electronic technology is the next generation semiconductor manufacturing technology. Compared with traditional manufacturing methods, printed electronic technology has the advantages of reliable connection between electronic circuits and components, flexible, suitable for various shape requirements, and environmentally friendly. All or parts of electronic products can be prepared by printed electronic technology. The products have the characteristics of large area, flexibility, thin film and light quality. Printed electronic technology can be used in silk-screen printing, inkjet printing, gravure flexible printing. The performance of printed electronic products greatly depends on the development of printed electronic materials.

Figure 1 The printing mechanism of silk-screen printing, inkjet printing and gravure flexible printing.

Applications:

• Semiconductor device: Compared with traditional silicon-based materials, printed electronic materials are light in weight, small in size, suitable for flexion, low-temperature assembly, and low in cost. They have been used in semiconductor equipment such as thin film transistor (TFT), RFID system, logic circuit and memory devices.

Figure 2 Schematic diagram of flexible organic transistor that made by printed electronic technology.

• Display field: Using printed electronic materials can strengthen flat-panel displays, and can be designed as new products for crimping, which is suitable for high-efficiency roll-up production. This technology already used in organic photoelectric display tube (OLED), organic photoelectric advertising screen, electronic paper, electrophoresis display, electrochromic display, field luminescence display and thermal display.

Figure 3 An example of flexible screen.

• Lighting field: Printed electronic materials have the advantages of low power consumption, dispersible, crimped lighting, low cost and high production efficiency, which can meet the requirements of the new generation lighting equipment.

Figure 4 An example of light emitting diode (LED).

• Sensor: Electronic materials can be used to prepare contact pressure sensors, photoelectric sensors and temperature sensors, which are widely applied in biological products.

Classification:

• Substrate: Printed electronic substrates can be divided into two categories: rigid substrate and flexible substrate. Rigid substrates mainly refer to metal substrates, ceramic substrates and glass substrates. Flexible substrates include paper, fiber fabric, plastic film, metal foil and others. The choice of substrate mainly depends on the design of the product and the production process. The following factors are usually taken into account: physical and mechanical strength, thermal stability, climate resistance, chemical stability, optical properties, surface roughness, wettability and cost. Typically, the most used flexible printed substrates are PET, PEN and PI films.
• Conductive ink: Conductive ink is a solution or suspension that includes electric conductor, binding agent, solvent and additives. Conductive ink needs to possess specified dispersion, viscosity, surface tension, solid content and other physical and chemical properties to meet the requirements of printing or coating process. In sintering curing process, with the volatile solvent volatilization and volume shrinkage, filler particles and binding agent will tightly link together, and spacing between particles becomes smaller. Therefore, under the action of an external electric field a current can form, and achieve the conductive function. According to the conductive properties, conductive ink can be divided into inorganic systems, organic systems and carbon materials.

Reference:

1. Mi-Young Lee, Myung-Won Lee, Ji-Eun Park, A printing technology combining screen-printing with a wet-etching process for the gate electrodes of organic thin film transistors on a plastic substrate[J], Microelectronic Engineering 87, (2010) 1922-1926.