High yield direct fusion welding of glass and metal

Bonding components made from highly dissimilar materials is generally accomplished by the use of an interlayer such as an adhesive, solder or frit. However this form of indirect bonding exhibits issues with absolute accuracy of positioning, thermal conductivity, contamination and, critically, lifetime outgassing. A reliable technique to directly bond highly dissimilar materials would thus be highly attractive.
Microwelding using an ultrashort pulsed laser has been demonstrated to be such a method [1, 2]. Here the weld process is accomplished by tightly focussing an ultra-short laser through the glass and onto the metal surface. Careful control allows for simultaneous absorption in both the glass and the metal with the resulting plasma, mixing, cooling and forming a fusion weld.
Transferring this process from the lab to industry requires a high yield. In this presentation we report studies on the surface finish requirements in order to obtain this while maintaining bonding strength.

[1] R.M. Carter, J. Chen, J.D. Shephard, R.R. Thomson, D.P. Hand (2014) Picosecond laser welding of similar and dissimilar materials, Applied Optics, vol. 19, pp. 4233-4238.
[2] R.M. Carter, M. Troughton, J. Chen, I. Elder, R.R. Thomson, M. J. D. Esser, R. A. Lamb, and D. P. Hand, (2017) Towards industrial ultrafast laser microwelding: SiO2 and BK7 to aluminium alloy, Applied Optics, vol. 56, pp. 4873-4881.