Process study of picosecond laser welding of soda-lime glass

• Appropriate laser power is the basis for forming a reliable connection. Low power will lead to insufficient energy to form a weld; high power will cause an increase in defects. • The scanning spacing and scanning times are too large or too small to have a negative effect on the strength of the weld. • The maximum breaking strength is obtained when the scanning direction is perpendicular to the force direction of the test. • Effective welds can be formed with focal points located up to 200 μm above and below the interface, with the greatest strength obtained at the interface. The various excellent properties of glass make it widely used in aerospace, solar cells and other fields, and its processing methods have also attracted much attention. Ultra-fast laser has the characteristics of high peak energy density and low heat impact, which has unique advantages in welding of transparent materials such as glass. At this stage, most of the ultra-fast laser welding is carried out for the glass with optical contact, and the harsh optical contact conditions hinder the further application of glass welding technology. In this paper, an attempt is made to weld non-optical contacted soda-lime glass using high repetition frequency infrared picosecond laser. The effects of laser power, scanning times, scanning spacing, scanning direction and focus position on weld morphology and breaking strength were systematically investigated. The results show that the scanning times and scanning spacing affect the volume of glass melt on one hand, and the stress magnitude during the welding process on the other hand, which have a greater impact on the overall weld strength. Under the optimal process parameters, an effective connection can be achieved within ± 200 μm of the defocusing amount, and the weld formed has a size of 10 mm × 5 mm. A strength of 24.85 MPa is obtained when the force direction is perpendicular to the scanning direction. The mechanism of glass welding was finally revealed, providing technical guidance for the practical application of ultrafast laser welding of glass.