Current-Carrying Capacity of Thick-Film Metallization Paths

In this work the results of experimental results on measuring the current strength of thick-film metallization are described. The tests were performed for paths made of commercial thick film pastes based on silver, silver-palladium and copper. The layers were screen printed on Al2O3 and AlN ceramic substrates. Resistance changes were determined as function of current density through the paths and then the maximum current density at burnout was determined. The current density in the paths was limited by ability of heat carrying away from the layer through the substrate to a heatsink. The AlN based ceramic was expected to achieve much better critical values of the current density thanks to its better thermal conductivity than alumina substrates. However, higher thermal conductivity of the substrate has not always meant significantly higher maximum current density.