Laser-Grown Bumps on Window Glass

The process of forming bumps on window glass with an ultra-violet nanosecond laser is described. Bump growth is caused by heating the glass to temperatures above the softening point, inducing directional flow towards the surface, forming a swelling, and finally freezing the swelling to a bump. The shape of the bump is mostly determined by the surface tension of the molten glass. We show that the height of the bumps, which are typically about 180 um, can be controlled within sub-micrometer accuracy and the shape can be altered from semi-spherical to flat-top. The time required for growing a bump is on the order of a second or less. These bumps may be an alternative to the posts in the incumbent vacuum-insulated glazing designs. Advantages include: ease of placement, transparency, low thermal conductivity, and mechanical strength.