Korea's ETRI demonstrated a 4,000 PPI 720x540 monochrome microLED display, produced using its proprietary SITRAB bonding technology. The researchers at ETRI says that this demonstration showcases a scalable alternative to hybrid bonding for ultra-high-resolution integration.
1 µm Solder Bumps at 4 µm Pitch, enabling a 4000 PPI microLEDF
The device was fabricated by bonding microLED chips to a silicon backplane using a Cu pillar / Sn solder cap structure with approximately 1 µm bump diameter and 4 µm bump pitch.
The researchers say that a SITRAB adhesive layer was first applied to the silicon backplane, followed by the SITRAB bonding process. Achieving a 4 µm pitch with solder-based interconnects is particularly significant, as hybrid bonding is generally considered necessary at this scale. SITRAB leverages the mature solder ecosystem, offering a potentially more cost-effective and production-friendly solution.
The SITRAB adhesive is already commercially available through a Korean materials supplier, and compatible bonding equipment is currently deployed in OSAT mass-production lines. This demonstrates that the manufacturing ecosystem for SITRAB-based microLED integration is already forming in Korea. This achievement highlights a practical pathway toward scalable, ultra-high-resolution microLED displays.
ETRI has recently joined the MicroLED Industry Association, and is commercializing its novel SITRAB microLED bonding technology.
