To a new, facility-free manufacturing process for electronic devices

Dr. Tomoji Ohishi, professor of Department of Applied Chemistry, has developed a new way to draw circuits on a surface coated in a specific type of copper complex solution with laser beams. Dr. Ohishi’s new method will not only simplify the manufacturing process of electronic devices, it will enable handling of copper, which is easily oxidized, without a vacuum setting. The method can form electronic circuits as small as 10-200μm wide.

In recent years, circuit- and device-making techniques using printing technology (printed electronics) have been in the limelight. Copper is frequently used for making wiring materials for its low cost and high conductivity.
However, due to copper’s vulnerability to oxidization, the current manufacturing methods require a complex and a tightly controlled vacuum environment, costing money and time for manufacturers.
Dr. Ohishi’s method is expected to significantly reduce time and cost in manufacturing digital displays and smartphones.

Drawing a circuit using a laser beam

<Background>

Traditionally electronic circuits were made with high-performance but expensive metals such as gold and silver. Today many manufacturers favor the more economical and equally efficient copper for circuit board production. However, copper’s vulnerability to oxidization forced manufacturers to spend large amounts of time and money in securing a vacuum environment to work with the fragile metal.


<The Experiment>

Dr. Ohishi succeeded in fixing copper on a glass circuit board which was coated in thermally decomposable copper complex solution beforehand. Laser beams on the solution-coated glass cause chemical reactions so that solid copper lines form. The experiment confirmed the feasibility of rapid production of small-scale copper circuits (between 10-200μm).
Since the rest of the chemicals (such as carbon dioxide) except for copper will be released into the air as gases, there will be no need for complicated disposable processes, making this method a very cost-efficient and sustainable one.

First, the glass panel is coated with copper complex solution (left). Lines are drawn by using laser beams then the glass panel is heated to reveal the circuit lines after the liquid evaporates (right)
First, the glass panel is coated with copper complex solution (left). Lines are drawn by using laser beams then the glass panel is heated to reveal the circuit lines after the liquid evaporates (right)

<Future Developments>

Striving for development of more flexible electronic devices
Striving for development of more flexible electronic devices

This technique likely impacts on the development of printed electronics such technology as many tablets and digital signage.
Dr. Ohishi is also leading a research project to develop lightweight flexible displays with organic-inorganic hybrid resin for everyday use. Dr. Ohishi plans to team up with companies to make further improvements on his discoveries.