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Sapphire is an important material for LED substrates. Because of its unique physical property, sapphire is strongly resistant to wet and dry chemical etching. Laser-based scribing techniques have a good prospect on sapphire scribing application. During the laser scribing, the assisting gas significantly affects the scribing depth, width and quality. A pulsed laser with a wavelength of 532 nm is used to scribe the sapphire substrate by twin assisting gas impinging both in co-axis and off-axis. This process is simulated by a computational fluid dynamics code, FLUENT. During the simulation, inlet pressure of co-axial nozzle and off-axial nozzle are varied at different intersection angle. By analyzing the static pressure and flow velocity at different inlet pressure and intersection angle, optimal laser processing parameters are obtained to improve the groove quality and reduce the groove width. Experiments are carried out to testify the simulation result. The result of both the simulation and experiment show that when laser pulse energy is 150μJ with co-axial inlet pressure 2 bar, offaxial inlet pressure 2~3 bar and intersection angle 70°, a better groove quality and an optimal groove size can be obtained.

Twin Gas Jet-assisted Pulsed Green Laser Scribing of Sapphire Substrate