Laser welded-and-cut glass support pillars for vacuum insulated glazing

Vacuum insulated glazing (VIG) consists of two panes of window glass separated by a small gap that has been evacuated to create a vacuum and hence minimises heat transfer to improve thermal efficiency of buildings [1]. An array of support pillars is required to separate the two glass panes to prevent collapse due to the external atmospheric pressure [2-4]. Currently, miniature metal pillars are used but, due to their high thermal conductivity, reduce the effectiveness of the glazing[1, 3] and as they are opaque, they have some negative visual impact. A good alternative solution would be to replace the metal pillars with glass; however, a suitably high speed and hence low-cost fabrication process is key for this consumer application.
Our solution is to exploit the ultra-short laser welding process to bond thin flex glass to one of the glass panes, followed by a laser driven cutting/separation process to cut around each small weld region leaving an array of support pillars. As a proof of concept, soda-lime coverslip glass is directly bonded to a soda-lime microscope slide by laser welding with 5ps pulses. Here, the weld takes the form of a 1 mm outer diameter Archimedean spiral. The pillar is formed by creating a circular cut of 1.2 mm diameter around the weld using the same laser source but with a pulse duration of 260 fs, without inducing damage in the microscope slide. Surface profilometer measurements confirm a flat surface and clean edges which prevents points of stress when in contact with the other glass pane.
We will also present results from the coaxial ring bending and the compression testing that further assesses the suitability in VIG applications.