The research team led by Professor Kim Tae-il of the Department of Chemical Engineering LED intensity limit exceeded
- 공과대학
- Hit5049
- 2020-06-12
The research team led by Professor Kim Tae-il of the Department of Chemical Engineering
Ultra-small micro LED intensity limit exceeded
- Development of conductive adhesive obtained from lotus flowers
- Application to high density aggregation of flexible electronic devices
- Show potential commercialization of next-generation display micro-LED
A research team led by Professor Kim Tae-il of the Department of Chemical Engineering/High-molecular Engineering (Dr. Lee Joo-seung, 1st author) announced that it has developed conductive adhesives for high density aggregation of ultra-small (electrode 15 μm) electronic devices with Samsung Electronics researchers.
When the element becomes a micro unit, the distance between the element becomes narrower and the electrode becomes smaller, making the arrangement of the element or connection with the electrode more difficult. The patterning method using metal wire or conductive film is mainly used to integrate components (LED, transistor, resistance, etc.) of devices into substrates.
However, this method is difficult to apply to flexible substrates that can be modified at high temperature and high pressure. There was a limit to using it for wearable devices that needed flexibility or biomedical devices such as ultra-small neurostimulator.
Research team succeeded in integrating thousands of micro LEDs (30μm×60μm) smaller than the thickness of hair onto flexible substrates by using conductive adhesive at low temperature and low pressure. This is a level that allows 600,000 microLEDs to be arranged at intervals of 100 간격으로m on substrates (5 cm x 5 cm) that are numerically smaller than credit cards, and can increase the aggregation by more than 20 times compared to conventional commercialized technologies.
The secret is to connect the element and the element or the element and electrode vertically using a polymer adhesive and conductive adhesive made from nanotallic particles. In addition to using relatively simple processes such as spin coating and UV exposure, the temperature and pressure of the process could be reduced below 100°C and 1 atmosphere to reduce the physical impact on the substrate.
As a result, thousands of ultra-small micro-LEDs were able to be killed on a large scale, maintaining a high rate of 99.9 percent or more. Furthermore, the stability of coupling was confirmed by testing the reliability in thermal shock or high temperature and humidity environment due to rapid temperature changes.
The research team took a hint from the phenomenon of water splashing off the surface of lotus flowers and focused on the ability to control wetness of the adhesive surface. The stability of the flexible thin adhesive film covering the substrate depends on the thickness of the film, the element, and the surface characteristics of the electrode, so that it can come into contact with each other or fall off.
Specifically, conductive adhesives, which are transparent viscous polymeric materials, are coated on flexible substrates with metal circuits, and combine elements and substrates through a transcription process. Meanwhile, metal nanoparticles play a role in controlling the stability and wetness of polymer adhesives, helping the electrical connection and high density aggregation of ultra-small electronic devices.
This research was conducted by the Ministry of Science and ICT and the Korea Research Foundation with the support of the Brain Science Source Technology Development Project and Samsung Electronics' Samsung Future Development Project, and the results of the research were published as a cover paper on April 16 (Thursday) in the international journal Advanced Materials in the field of materials.