Laser grooving of Al2O3 plate by a pulsed Nd:YAG laser: Characteristics and application to the manufacture of gas sensors array heater

Laser grooving on a 0.635 mm thick alumina ceramic plate was carried out by a 400 W pulsed Nd:YAG laser. The effects of the laser grooving parameters, such as laser pulse frequency, laser peak pulse energy, assisting gases (oxygen and nitrogen), laser beam diameter and grooving speed on the morphologies of grooves were investigated by using field-emission scanning electron microscopy (FE-SEM) and optical microscopy. Results show that the U-type groove with smooth inner surface was produced at a fixed pulse frequency of 40 Hz, a grooving speed of 4 mm s−1 and an assisting gas pressure of 3 bar. The depth of the U-type groove increased with an increase in laser pulse peak energy. The assisting gas type was found to influence the grooving mechanism, that is, nitrogen gas had a chemical reaction with alumina, and then changed the substrate surface absorptivity to laser beam. So the smaller heat-affected zone (HAZ) was obtained in the substrate than that of the oxygen assisting gas. In addition, the stable and reliable RuO2-buried heater was produced in the U-type groove with smooth inner surface, which reduced sensing element power consumption and improved the thermal response rate in a sensor array.