Stacked substrates for high voltage applications

A new way of insulation high voltages in modules is described, solving the problem of high electric fields at sharp corners with multilayer structures. Today, modules with a blocking voltage above 1700V are based on Si3N4 or AlN substrates. Special effort is required to manage the high electric fields that occur at the sharp edges of the metal layers on both sides of the ceramic layer. Simulations show that stacking substrates can significantly reduce the peak electric fields that are generated. This allows cheaper isolation solutions such as partial discharge Al2O3 ceramics can be used to replace the more expensive AlN or Si3N4 ceramic. The Influence of ceramic and metallization thickness as well as the layout design have been discussed. The simulations have been confirmed by measurements. Finally limitations of the stacked structures are highlighted and suggestions are made for practical use in modules.