Abstract :
[en] The main technique used in microelectronics to realize passive components of hybrid circuits, combines screen-printing and furnace firing. The main disadvantage of this approach is to require numerous successive heat treatments to fire all the components of the circuits in suitable conditions. Using laser for local heat treatments offers numerous advantages: the treatments can be optimized for each material, the energy consumption is minimized and the whole processing time can be significantly reduced.
The topic of our research is the understanding of microstructural and dimensional modifications generated by selective laser treatments (melting, sintering, and crystallization) on thick coatings of material usually encountered in passive components of hybrid circuits. Our final goal is to develop an innovating process to realize bi-dimensional or three-dimensional components by coupling ink-jet printing and selective laser treatments in substitution respectively to screen-printing and to heat treatment furnace. Problems to be solved are: i)- the control of the consolidation, densification, microstructure and crystallization of the coatings and ii)- the bond between the coated material and the substrate or between the different layers in the case of multilayer coatings.
This article is about the melting and the crystallization of a piezoelectric glass ceramic and is linked to two others talking about: i). Part I - Silver conductor fabrication on glass and alumina substrates and ii). Part II - The sintering of BaTiO3 by SLS.
The piezoelectric glass ceramic investigated contains fresnoite crystals in a glass matrix and is obtained by crystallization of a parent glass of the SrO-SiO2-B2O3-K2O-TiO2 system [1]. Fresnoite is a pyroelectric non-ferroelectric material that requires a suitable crystallographic texture to exhibit macroscopically piezoelectric properties [2]. In the present work, thick coatings were realized by serigraphy of a parent glass ink on alumina substrates. The coating were then heat treated by a YAG-laser with a maximal powder of 10W and a spot size of 40 µm. Scanning parameters (Power %, scan speed and vectorization step) were then investigated. The objective was in a first stage to melt a uniform and homogeneous glass surface and then, by mean of a second treatment, to crystallize the glass.
The next steps will be to control the crystallization of fresnoite in order to obtain the suitable crystallographic preferential orientation and then to characterize the piezoelectric property of the coatings.
[1] N. Maury, M. Gonon, J.P. Erauw, J. Simons, F. Cambier, 10th European Inter-regional Conference on Ceramics (Swansea), September 3-6, 2006
[2] N. Maury, J. Delvallée, M. Gonon, J. Simons, F. Cambier, 10th International Conference and Exhibition of the European Ceramic Society (Berlin), June 17 - 21, 2007
Acknowledgement:
This research is part of the LASESURF project funded by the EU and the Walloon Region.
