Mechanistic optimization of wide-gap ultrafast laser quartz glass welding with plasma dynamics

Abstract

Ultrafast lasers have the advantages of high speed, small heat-affected zones, and non-contact processing. They can achieve fine welding in the field of microelectronic packaging, improve product quality, and reduce losses. However, ultrafast laser glass welding under wide-gap conditions faces challenges such as insufficient filling and an unstable molten pool, which limit its operability in practical applications. In this study the factors influencing welding strength are investigated by studying the interaction mechanism between the laser and glass, plasma density evolution, and temperature field analysis. First, the principle of irreversible expansion occurring in large gaps during welding was analyzed, and the welding results under different conditions were explained according to this principle. Avalanche ionization and photoionization are key mechanisms of plasma-induced irreversible expansion. Second, to obtain the optimal process parameters for use in the experiment, the plasma density and temperature field were numerically simulated, which reduced the experimental group and improved the experimental efficiency. Finally, the relationships between the process parameters, cavity shape, and welding strength were verified in an experiment involving ultrafast laser welding of quartz glass. The revealed plasma–cavity interaction mechanism and predictive modeling framework are applicable to a broad class of transparent dielectrics, offering a transferable scientific basis for precision laser joining. This work provides foundational insights into laser–matter interaction under wide-gap conditions and supports future extensions to heterogeneous material systems, complex interface geometries, and high-integration photonic manufacturing.