Micro LED mass transfer achieves a new milestone: researchers at Fuzhou University (China) and Chalmers University of Technology (Sweden) report a polymer-residue-free, laser-induced transfer (LIT) method that delivered 100% transfer yield under specific conditions (30 × 38 μm spot; 1200–1500 mJ/cm²) and scales to TFT backplanes for AR/VR microdisplays.
The research team successfully developed a polymer-residue-free, ultra–high-yield laser-based mass transfer method for Micro LEDs. This achievement is expected to significantly accelerate the commercialization of Micro LED in cutting-edge display applications such as AR/VR, wearables, and smart glasses.
The team adopted a Laser-Induced Transfer (LIT) scheme, combined with big-data grouping analysis and empirical mathematical models, effectively improving the accuracy and yield of chip transfer. By controlling the laser delamination energy within 1200–1500 mJ/cm², the method achieved a very high chip retention rate; in the subsequent secondary transfer stage, when the laser energy density and chip sinking depth satisfied a specific relationship, and the laser spot size was 30 × 38 μm, the transfer yield reached 100%.
According to the team, traditional mass transfer technologies such as electrostatic transfer, micro-stamps, or roller stamps face numerous limitations in large-scale applications. For example, electrostatic transfer may damage chips due to charge accumulation, micro-stamps are constrained by photolithography precision, and roller stamps struggle to achieve the required alignment accuracy. In contrast, the proposed laser transfer technology not only enables precise control of the laser focal depth but also avoids chip surface damage and transfer misalignment, offering excellent stability and flexibility.
The study also found that during transfer to the second temporary carrier, polymers such as PDMS (polydimethylsiloxane) can adversely affect final alignment accuracy. To address this, the team established a mathematical relationship between chip sinking depth and optimal laser energy, effectively compensating for instabilities caused by sapphire warpage and bonding non-uniformity, and achieving—for the first time—precise transfer with no polymer residue and uniform sinking.
More importantly, this technology is applicable to a variety of Micro LED chip sizes and types, demonstrating strong scalability and compatibility. This lays a solid foundation for transferring Micro LED chips onto TFT (thin-film transistor) backplanes.
Looking ahead, the team plans to further expand the application potential of this technology in full-color Micro LED, flexible displays, and micro-projection.
Notably, Fuzhou University serves as a National New Display Technology Innovation Center and a Micro LED Display Innovation Platform, with strong technological leadership and applied experience in basic research; common key technologies and process equipment; technology verification and industrial demonstration; patents and standards; and discipline development and talent training.
At present, Fuzhou University has achieved a series of research results in μLED emissive chip fabrication, mass transfer of chips and micro-scale chips (MicroIC), and chip-to-substrate bonding.
In recent years, Fuzhou University has continued to collaborate with enterprises and domestic and international universities on Micro LED research. In terms of industry collaboration, last July Fuzhou University, Mindu Laboratory, and Fuzhou Jiaxin Chuanghui Mechatronics Co., Ltd. formed a partnership with Hymson, focusing on iterative upgrades of key processes in the new display field and the exploration of next-generation disruptive technologies.
Just this May, Hymson announced that, in collaboration with Fuzhou University, it had successfully developed China’s first wafer-level Micro LED chip non-contact electroluminescence inspection engineering prototype, FED-NCEL, enabling non-contact electroluminescence inspection of red, green, and blue Micro LED epitaxial wafers, wafers, and temporary-carrier chips.
In terms of university collaboration, last year Fuzhou University worked with the Fujian Institute of Research on the Structure of Matter (FJIRSM), Wenzhou University of Technology, Shenzhen University, and others to achieve multiple Micro LED–related research outcomes, including high-efficiency near-infrared quantum-dot phosphors, performance improvements in QLED devices, and enhancements in new color-conversion display performance, thereby continuously advancing Micro LED technology.
