Microfabrication of notches for electric contacts in the conductive ceramic fiber by femtosecond pulses

Abstract

Nowadays, development of advanced devices or sensors often requires unique solutions that can be only solved with femtosecond laser micromachining. In this report we present the study of one of them: in order to create sensor for monitoring the health of metallic mould, conductive ceramic fiber ( Fig. 1-a) has be integrated into precut groove on the mould surface. Latter, the resistivity of the fiber has to be constantly monitored as it is directly linked to the wear level of the instrument [1]. Unfortunately, to get data about resistivity, electric wires should be attached to the ends of the ceramic fiber. This procedure is not straightforward: fiber has to be prepared in special way for sufficient and secure wire-to-fiber contact after the soldering. This preparation consists of creating micrometric notch in the fiber ( Fig. 1-b) for precise wire positioning and tight attachment.In this report we demonstrate that using femtosecond, high repetition rate Yb:KGW laser system it is possible to fulfil such task. Tested conductive ceramic samples had a diameter of ~250 μm [2]. We have used galvanometric scanners for beam deflection and long focusing f-theta lens together with various patterning algorithms in order to achieve required sizes of the notch. A simplified sketch of such processing is shown in Fig 1-c. For microfabrication of the notches we used following laser parameters: average power -2W at 1030 nm, pulse duration -300 fs and repetition rate -25 kHz. The cutting conditions for the good electric contact were selected and applied. In our experiments we achieved the steepness of the groove ~20°. We demonstrate that such microcutting procedure meets industrial requirements as it takes less than a second to process one ceramic fiber.Similar microcuting tests were also performed with picosecond laser pulses. We show that picosecond pulses can remelt conductive ceramics around processed region and amorphous slag appears that isolates ceramics from the conductive wire. Fig. 1 (a) Ceramic fibers and (b) the sketch of the notch made in fiber with targeted dimensions (units in micrometers).(c) Sketch of the notch cutting process at the both sides of the fiber with spiral algorithm.(d) Notch made in the ceramic fiber with patterning parameters.