Laser welding of sapphire wafers using a thin-film fresnoite glass solder

Abstract

Two sapphire substrates are tightly bonded through a fresnoite-glass thin film, by irradiation with a 1,064 nm nanosecond laser. The composition of the glass solder at the bond interface changes, due to incorporation of Al from the upper substrate. The oxidic solder remains amorphous after laser irradiation, but after annealing (850 A degrees C for 1 h) crystalline structures are observed in different morphologies, which are attributed not only to fresnoite, but also to Ba-Ti-Al-O phases, which lead to a strong luminescence of the laser irradiated region under UV excitation

Laser-Welded Steel Foils with Sapphire Substrates

“…The steel foil presents bumps in those positions which were irradiated, with the hillock pointing in the direction of the laser entry (from sapphire side). Similar bumps were also observed in our previous works, in which the sapphire substrates were laser-welded through different glass thin-film solders [16,18]. In these works, the upper sapphire substrate was ablated because of laser irradiation and molten solder material filled the ablated region, forming similar bumps and leading to a solder material containing material from the upper substrate.…”

“…Sapphire has been bonded to other materials like metals [13], including gold and silver [14], and alloys Inconel Ò through a Cu/Ni interlayer [12]. In our previous works, two sapphire substrates were laser-welded through a 50-nm titanium thin film [15], as well as through glass thin films [16][17][18].…”

Processing technologies for sealing glasses and glass‐ceramics

“…Thus, the laser beam goes through it and efficiently deposits thermal energy in the BTS.xSiO 2 (x = 2, 3) interface (Figure A). In comparison with previous works on BTS‐glass thin film sealant, the enrichment in SiO 2 was performed to better fit the CTE requirements. The difference in CTEs of silica glass and sapphire is one order of magnitude, being 0.55.10 −6 and 6.10 −6 K −1 , respectively.…”

“…For acoustic coupling, the samples were submerged in de‐ionized and degassed water at 21°C. The employed set‐up and analysis parameters are similar to our previous works …”

“…In our previous works, different combinations of transparent materials and BTS‐based thin films acting as sealants were investigated ).…”