Flexible modulation of molten areas by fs-laser discrete scanning glass welding

Ultrafast laser glass welding is well suited for glass connection techniques, especially for the encapsulation of precision devices. The continuous scanning welding method (CSW) is the primary method for ultrafast laser glass welding. Laser irradiation and laser scanning are executed simultaneously, which results in the coupling relationship between the morphology and interval of molten areas. Thus, the uniformity and predictability of the welding are limited. In this paper, a discrete scanning welding (DSW) method is proposed, and laser irradiation and scanning are executed independently. The morphology and the interval (I) can be independently modulated, depending on the laser parameters and the spacing of the designed discrete points, respectively. Molten areas can be uniformly arranged according to designed parameters. When I is flexibly modulated to be comparable to the width of molten areas, a high number density of molten areas without cracks can be achieved leading to the maximum tensile strength. As the heat accumulation effect increases, the tensile strength decreases. At a molten area height of 260 μm, the tensile strength was maximum with the value of 8.9 MPa. Glass square cavities with a leakage rate of 1.0×10-12 Pa·m3/s and a gas pressure resistance of 0.32 MPa were fabricated. DSW is flexible and practical, and is a significant value for advancing the engineering application of laser welding glass.