Thermal and electrical properties of lasermodified ceramics

S. Schreck / R. Heidinger / M. Rohde / J. Schneider / K.-H. Zum Gahr

Forschungszentrum Karlsruhe, Institut für Materialforschung I and

Universität Karlsruhe (TH), Institut für Werkstoffkunde II

D-76021 Karlsruhe

The laser induced surface modification process can be used to increase thermal and electrical conductivity of a ceramic locally. A material with high thermal and electrical conductivity can be added by powder injection into the laser induced melt pool or by local remelting of a precoated ceramic substrate. After solidification a composite is developed, which shows different properties than the ceramic itself. In comparison to the established thick-film technology where conducting lines are generated by lithographical methods, the laser process offers the advantage of direct structuring and good bonding to the substrate.

In the present study paths with increased thermal and electrical conductivity were generated into a cordierite ceramic. This material was selected because of its properties like low density, low thermal expansion and especially low dielectric permittivity, which makes it to a promising substrate material for high frequency applications in microelectronics.

The experiments were carried out with a CO2-laser and tungsten was used as additive. The obtained conducting lines were characterised in respect to their microstructure and electrical resistance. An enhancement of thermal conductivity, which is restricted to the laser treated area could be established by measurements of thermal conductivity with spatial resolution using the photothermal method. In addition test structures were generated, which allow local heating of the ceramic by applying a voltage to the conducting structure.

Further work is orientated towards transferring of the process to other ceramic materials like alumina or PZT-ceramics.