Korean researchers have developed technology that can break down limits in electronic circuit integration. When the electronic device put into a circuit is reduced to the micro (μm, 1 μm = one millionth of a meter) level, the distance among devices becomes narrower when arranged on a circuit board, and it becomes difficult to connect and arrange electrodes to each other. The researchers have developed a “conductive adhesive” to address this problem.
The National Research Foundation of Korea announced on May 13 that Professor Kim Tae-il of the Chemical Engineering/Polymer Engineering Department at Sungkyunkwan University and Samsung Electronics' researchers have developed a conductive adhesive that can improve electronic circuit density by more than 20 times from the current level.
This adhesive is used when arranging tiny electronic devices on a circuit board. Through this, the researchers successfully put together thousands of 30 μm × 60μm micro light-emitting diodes (LEDs), which are thinner than a hair, onto a flexible board at a low temperature and under low pressure. By applying this technology, 600,000 micro LEDs can be arranged, 100 μm apart, on a substrate (5cm x 5cm) which is smaller than a credit card.
Unlike other current commercial adhesives, this conductive adhesive can be applied to flexible substrates that can be bent and unfolded. This means that the adhesive will pave the way for further miniaturizing biomedical devices such as wearable devices or micro-stimulators that must be flexibly attached to the human body.
The researchers were able to connect devices and devices, or devices and electrodes vertically, using polymer adhesives and conductive adhesives made of nano-metal particles. In this process, a relatively simple process such as spin coating or extreme ultraviolet (UV) exposure was used, and the temperature and pressure of the process were lowered below 100 degrees Celsius and 1 atmosphere to minimize the possibility of damage to the substrate. As a result, thousands of micro LEDs can be arranged over a large area while maintaining a high yield of over 99.9 percent. The stability of device bonding through a conductive adhesive was confirmed even in a high temperature and high humidity environment due to a rapid temperature change.
This R&D project was carried out with support from the Ministry of Science and ICT, the National Research Foundation of Korea and Samsung Electronics. The results of this study were published as the cover paper of the international academic journal Advanced Materials on May 16.