We’re pleased to feature ETRI, Korea's national research institute conducting advanced R&D across ICT, semiconductors, AI, and digital technologies, in our latest MicroLED Industry Association spotlight series.
Among its diverse research areas, ETRI is advancing microLED displays through SITRAB (Simultaneous Transfer and Bonding), a laser-assisted technology enabling high-throughput, precise, and scalable MicroLED integration.
We spoke with Dr. Kwang-Seong Choi, Assistant Vice President and principal researcher at ETRI.
Can you introduce your institute and technology?
ETRI is a government-funded research institute in Korea focused on advanced semiconductor and display technologies.
In microLED, we have developed the full transfer and integration flow—from 1st transfer (laser release), 2nd transfer (intermediate transfer), and 3rd transfer (SITRAB bonding and underfill), to repair.
All technologies, including materials and processes, were developed in-house. To the best of our knowledge, ETRI is the only organization that has completed the entire chain and demonstrated it through working prototypes.
A key enabler is our Laser-Assisted Bonding (LAB) materials, developed over more than 20 years. These materials make ultra-fine-pitch bonding practical. It has already been transferred to industry, establishing a commercial supply chain.
Our focus is clear: solving the key bottlenecks for MicroLED commercialization.
Can you say why you joined the MicroLED Association and what you hope to achieve?
We joined the MicroLED Association to connect with the global ecosystem and accelerate commercialization.
Our goal is simple—move from technology to real products through collaboration.
What is your biggest challenge, and success to date in the microLED industry?
The biggest challenge is achieving high yield at ultra-fine pitch with reasonable cost.
Our approach is to make the technology practical, not just feasible.
We adopted industry-standard laser release for the 1st transfer and developed the required materials. The 2nd transfer can be implemented by modifying existing equipment, along with our interposer materials. For the 3rd transfer, compatible equipment is already deployed in OSAT lines.
Even repair is designed for low-cost implementation, using modified equipment without additional material processes.
This is how we address scalability and cost together.
Can you detail your latest prototype or demonstration?
We demonstrated a 4,000 ppi monochrome MicroLED display using SITRAB bonding.
The device uses ~1.5 µm solder bumps at 4 µm pitch on a silicon backplane.
We also completed the full transfer process using ~20 µm × 35 µm MicroLED chips, achieving functional emission with 100% yield at laboratory level.
This confirms that ultra-fine-pitch integration can be achieved with a scalable, solder-based approach.
Complete MicroLED transfer chain demonstrated by ETRI, from wafer to bonded Si backplane
How do you see microLEDs changing the display industry in the next 5–10 years?
MicroLED will move from niche to mainstream as manufacturing becomes scalable.
Beyond displays, we already see expansion into optical interconnect, with future opportunities in bio-related applications.
To enable this transition, ecosystem collaboration is critical—and the MicroLED Association plays an important role in making that happen.