Multichip-to-Wafer Mini-LED Bonding Technology for Photobiomodulation Sheet Devices Using Flexible FOWLP

This paper focuses on flexible hybrid electronics (FHE) fabrication with small dies embedded in a hydrogel flexible substrate based on a redistribution layer (RDL)-first fan-out wafer-level packaging (FOWLP) methodology for low-power light therapy called photobiomodulation (PBM). The near-infrared (NIR) mini-LEDs integrated with the hydrogel substrate irradiate tissues with NIR light, promoting chemical reactions within cells and producing analgesic, anti-inflammatory., and tissue regeneration effects. The focus of this study is to lower the bonding temperature and improve the bonding yield of the NIR mini-LEDs in the chip-to-wafer bonding process. Cu/Sn microbumps and a unique ACF (anisotropic conductive film) were employed to enhance the low-temperature repetitive bondabilities.