Formation of near-surface melt films on glass ceramics due to ultrashort laser pulses
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REVIEW
Formation of near‑surface melt films on glass ceramics due to ultrashort laser pulses Maria Friedrich1 · Martin Kahle1 · Jens Bliedtner2 · Jean Pierre Bergmann3 Received: 31 July 2020 / Accepted: 15 September 2020 © Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract Glass ceramics are highly specialized composite materials, which have a partly polycrystalline and a partly glassy state. Due to their special properties such as good mechanical strength, low thermal expansion, and excellent thermal shock resistance, they are especially well known for their use in consumer goods industry. But also in the high-tech sector, like optics or microsystems technology, the applications for glass ceramics are constantly growing. Simultaneously, the continuing miniaturization of microelectronic components requires precise, high-resolution processing methods. While mechanical processing is limited due to the brittle-hard properties of the material, ultrashort pulse lasers can serve as an ideal tool for this purpose. The pulse durations in the pico- and femtosecond range are known to enable a highly precise and gentle processing with very small thermal load for the workpiece. Therefore, the process is often referred to as cold ablation. It has been known for some time, however, that if pulse energies and repetition rates are sufficiently high, heat accumulation effects can occur. In this article, we report on surface modifications on glass ceramics arising during femtosecond ablation. Using Low Temperature Co-fired Ceramics (LTCC) as an example, we show that even at low repetition rates of 100 kHz and moderate average laser power below 3 W several micrometer thick molten patterns can emerge. Another peculiarity of the observed phenomenon lies in the increase of the vitreous layer with decreasing pulse duration. The dependence of the effect on the material structure is investigated by means of X-ray diffraction (XRD) measurements. Keywords Ultrashort pulse ablation · Glass ceramics · LTCC · Surface modifications · Heat accumulation · Melt film
1 Introduction LTCC technology, which is based on the co- and postfiring of glass ceramic tapes and varying functional materials, enables the fabrication of multilayer substrates with integrated electronic components [1]. Due to their flexible design and good mechanical and electrical properties, LTCC can be used for numerous applications, for example to set up precise, complex microsystems [2], and sensors such as pressure, force, or flow sensors [3]. The patterning and * Maria Friedrich mfriedrich@ifw‑jena.de 1
Günter Köhler Institute for Joining Technology and Materials Testing, Otto‑Schott‑Straße 13, 07745 Jena, Germany
2
Ernst Abbe University of Applied Sciences, Carl‑Zeiss‑Promenade 2, 07745 Jena, Germany
3
Technische Universität Ilmenau, Gustav‑Kirchhoff‑Platz 2, 98693 Ilmenau, Germany
structuring of the single tapes in their green state as well as of the sintered multilayer substrate represent the most important technological steps, which d
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