Composition-dependent low-temperature bonding reactivity in multicomponent silicate glasses

• Low-temperature direct bonding of multicomponent silicate glasses achieved. • NH 3 plasma forms reactive Si–NH 2 groups to improve fracture energy. • Reaction efficiency of Si–NH 2 groups governed by surface glass composition. • Acid leaching boosts Si–OH density and bonding reactivity. • Strong bonding of aluminosilicate glass at 150 °C via acid leaching + NH 3 plasma. Direct glass bonding is essential for developing multifunctional optical and electronic devices. Differences in glass composition significantly affect its thermal expansion coefficient, necessitating low-temperature direct bonding techniques for diverse glass types. Alkali‑free aluminosilicate glass is a promising material for advanced packaging technology; however, its low‑temperature bonding is challenging. Addressing this issue requires understanding the fundamental relationship between glass surface composition and bonding reactivity. In this study, we developed an ammonia gas plasma treatment that enables direct bonding of various multicomponent silicate glasses at 200 °C. The treatment improved the fracture energy, which depended on the surface Si–NH 2 group density. Comparing the consumption of Si–NH 2 groups during annealing across different glass types—including silica, borosilicate, and alkali-free aluminosilicate—revealed that the acidity of the surface hydroxyl groups is the key factor governing the propensity of the surface Si–NH 2 groups to undergo condensation reactions. Based on these insights, we developed a novel activation method combining acid leaching and ammonia gas plasma treatment, resulting in an improved fracture energy of alkali-free aluminosilicate glass at an annealing temperature as low as 150 °C. These findings provide valuable insights into the fundamental chemistry of glass bonding and direct bonding techniques for various industrial applications.