Electrical characterization of thick film materials

The thick-film technology is one of the fundamental technologies for the production of circuit carriers for electronic modules. It is mainly used in areas with harsh environmental conditions, such as sensor or automotive applications. Basis of the thick film technology are glass-based pastes, which are screen printed on ceramic substrates and fired in a high temperature process at (500…1000) ° C. Such thick film pastes are commercially available from various suppliers as elements of paste systems, which mainly include compatible isolation, resistance and conductive pastes. There are a number of requirements according the fired thick film characteristics, such as high breakdown voltage of isolation thick films or low noise performances of resistance thick films. However, the most requirements are concentrating on conductor thick films. They should guarantee excellent properties in terms of assembling (soldering, bonding) which are focused in a many publications. Simultaneously, they should also offer very good electrical characteristics that have not been completely investigated until today. At Fraunhofer IKTS different measurement methods are developed and adapted to characterize the electrical performance of thick film structures. Already well known is the short term overload (STOL) measurement of thick film resistances, which determining the maximum power dissipation of the thick film structure. The basic concept of this measurement is adapted on conductive thick film structures like conductive tracks or vias. The investigations show correlations between geometrical thick film properties and the resulting thermal characteristics of the thick film structure. Results can be used to improve screen-printing layouts in terms of cost reduction (paste consumption) and thermal management (track width, via diameter), but can also help to improve paste compositions itself. The paper will give an overview of the used electrical measurement methods and present exemplary results.