Development of Organic and Printed Electronics manufacturing technology for high volume production
Currently, inorganic silicon and metals have been the mainstay of the semiconductor and electronics industry. However, there has been a growing interest in using organic electronics to replace them. Low-cost, large area printing process using organic electronic materials makes the production of thin, lightweight, flexible and low-cost electronics products feasible. In 2007, the market for organic electronics is about USD 1.18 billion and it is likely to exceed $300 billion and in coming years becoming a huge business. Examples of the applications are printed RFID, power source, sensors, photovoltaic cells and displays. Although the technology has a huge potential, and market forecasts are bright; materials, equipment, processes and applications still need much further development. There are no single off-the-shelf standard processes for organic electronics in existence today. This project is therefore launched to develop this technology.
This project emphasizes on the development of a manufacturing platform to fabricate organic electronics. This is an approach to transfer the conventional media printing techniques to fabricate organic electronics products. The project consists of three main investigation sections to develop this technology and the research findings will be consolidated into a guideline for the manufacturing of organic electronics products.
1. Study of functional inks
The main part of a typical printing process flow involves printing functional inks onto substrates and then baked or cured or sintered for test and inspection. The functional inks provide electrical, thermal, chemical or optical properties, which is a function of various factors such as formulation of functional ink, thickness of printed structures and curing conditions. In this section, these three factors affecting the functional properties of printed structures will be investigated. The effect of different printing techniques on the thickness of printed structure and the interaction relationship between the formulation of functional inks and the curing condition will be studied.
2. Surface treatment technology
Most substrates such as polymer are chemically inert with low surface tensions, which results in poor bonding with printing inks. To cope with this, surface treatment is needed to promote adhesion for printing. In this section, a number of surface treatment techniques will be developed and their effectiveness will be compared.
3. Processing guideline for organic and printed electronics
The finding in this research project will be summarized in a processing guideline for each specific application of organic electronics products.
The objectives of this project are:
- To develop printing techniques to be used in high volume production of organic electronics devices;
- To establish a processing guideline for organic electronics products.
- Develop a processing technology in organic and printed electronics manufacturing;
- Develop a database for selection criteria of ink and printing platforms, printing process parameters, and surface treatment techniques of organic and printed electronics for local manufacturer access;
- Promote and transfer the know-how and technology for organic and printed electronics manufacturing;
- Guidelines of manufacturing technology of organic and printed electronics for local manufacturers.
The manufacturing techniques for gravure and ink-jet printing of conductors are presented. Guidelines for gravure and ink-jet printings are developed for reference, and both can be used in producing printed and organic electronics.
Factors, such as ink viscosity and printing parameters, affecting printing quality were investigated. Major types of defects associated with improper gravure printing were determined. The effect of the conductor width on the resistivity and the distortion of the gravure printing were also studied. 50 micron conductors were printed by using high ink viscosity, low angle of doctor blade, high pressure of impression roll, and high printing speed, in order to balance the printing defects associated of each individual parameter to produce good and fine printed conductors. Changing of any setting may require other parameters to be adjusted. For instance if low viscosity ink is preferred, then a higher doctor blade pressure may be required to have clean wiping. Other parameters may also need to be tuned in order to maintain the same conductor width.
The chemical reduction method to fabricate silver nanoparticles was presented, and the effect of chemicals on the size of silver nanoparticles was investigated. Suitable ink for ink-jet printing was formulated, and conductors were successfully printed. The size effect of silver nanoparticles on the curing temperature requirement was discussed. Two curing methods, including baking and flashing, were studied. The new flashing approach was found to perform better than the conventional baking method for higher throughput without compromising curing quality, particularly resistivity.
Each printing technology has its advantages and limitations. For instance, the printing speed of ink-jet printing is slow, and the printed conductor resistivity is low for both printing methods, in particular fine conductors, compared to bulk conductors. Therefore, both methods require further study and development in order to improve their capability in meeting the needs for low-cost large area production on a mass-scale.
Project Commencement Date:
Project Completion Date:
October 31, 2009
Dr. Winco K.C. Yung
Tel (852) 2766-6599
Project Team Member:
1. Dr. Winco K.C. Yung
2. Prof. T.M. Yue
3. Mr. James Tam
4. Mr. C.P. Lee
5. Ms. Cindy Chak
6. Mr. S.K. Chan
7. Ms. Joanne Wong