Improvement of ampacity of LTCC conductors

Abstract

Improvement of the current load-carrying capacity can be achieved by combining different technologies in Low Temperature Cofired Ceramics (LTCC). Screen and stencil printing, full tape thickness features (FTTF) and embossing in LTCC were investigated. Silver paste conductors with 80 – 200 μm line width are included in the study. The structures on the test substrates are fed with an increasing current until the surface reaches an equilibrium temperature of 100°C measured by an infrared camera. 200 μm lines created by screen printing and stencil printing are able to bear 4.3 A and 14 A, respectively. For the FTTF conductor with a thickness of 190 μm the estimated maximum current is about 30 A and for the embossed conductor (thickness approx. 125μm) about 20 A. FTTF allowed the highest current without strong LTCC heating. However, such conductors are relatively difficult to process by laser and to fill with paste. Therefore the line resolution cannot be much smaller than 200 μm. Furthermore, spiral structures are not compatible to this technology. Hot embossing supports both structural resolution and a high current load-carrying capacity but requires additional tooling. Embossing can be used for the production of curved conductors and coils. With the laser cut stencil, structures with small line width and considerable line thickness can be achieved. Screen printing gives a good possibility to produce small conductors, complex structures and coils.