Photocleavable non-conductive adhesives based on o-nitrobenzyl ester epoxies for reworkable micro-LED packaging

초록

Micro-LED displays represent a significant advancement in display technology, offering enhanced efficiency, brightness, and durability compared to traditional LCD and OLED systems. However, their miniaturized scale and fine-pitch electrode designs pose considerable challenges in assembly and repair. In this study, we investigate the use of o-nitrobenzyl ester (NBE) epoxies as photocleavable components in non-conductive adhesives (NCAs) for micro-LED packaging—a system aligned with advanced organic coatings. Two NBE-based epoxies, NBE-a and NBE-b, differing in CH₂ linkage length, were synthesized and characterized. Notably, NBE-b achieved a higher yield (72 % vs. 42 %) and exhibited superior thermal stability, with a decomposition onset at 237 °C compared to 209 °C for NBE-a. Although NBE-a cured more rapidly at lower temperatures, NBE-b's slower curing profile was more compatible with high-temperature processing. Photodegradation studies revealed that NCAs incorporating NBE-b showed an 82 % reduction in adhesion strength under low-energy UV exposure, significantly enhancing repairability. Additionally, NBE-b's lower viscosity enabled more uniform application and improved reworkability, which are critical for precise micro-LED bonding. These findings position NBE-b as a promising candidate for reliable, reworkable adhesive systems in micro-LED packaging. © 2025 Elsevier B.V.

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