Ultrafast laser bursts welding glass and metal with solder paste to create an ultra-large molten pool

A novel, to our knowledge, method is proposed for the welding of glass and metal with a large gap filled with solder paste using ultrafast laser bursts. The addition of solder paste enables a reliable glass–metal connection even at gaps of hundreds of microns, while the position of the glass can be flexibly adjusted. By ultrafast laser bursts, the volume of the molten pool increases significantly, and the height of the molten pool reaches approximately 350 µm, which is more than an order of magnitude higher than that of conventional ultrafast lasers (10–20 µm). Cross-sectional analysis of the welded region shows that extensive material mixing and element diffusion occur, and stable connections are achieved at multiple interfaces. An analysis of the interaction between the ultrafast laser bursts and the material, as well as the mixing of multiple materials during the welding process, leads to a clear welding mechanism.