High electric field strengths at the edge of the metallization of insulated gate bipolar transistor (IGBT) power modules are, besides defects in the substrate or the potting gel, the main reason for partial discharge. These critical electric field strengths occur at the energized contact where it is bordered by the insulating ceramic and the cover (mostly silicone gel). The reduction of high electric field strengths for increasing the threshold voltage for partial discharge has been studied in several publications based on experiments as well as on simulations. Simulations allow the localization of the critical spots and the quantification of the maximum electric field strength. However, a systematic study of the singularities of the electric field strength at the sharp edges is lacking. Such singularities are investigated in this article. The calculation of an absolute electric field strength value is only possible for finite edge radii. For sharp edges, however, the maximum electric field strength returned by simulation depends on the grid size: Through the finite grid size a virtual edge radius is induced that suppresses the singularity at the edge. To get around this problem, a mesh-independent evaluation procedure is introduced. With this procedure it is possible to quantitatively evaluate the electric field strength in the vicinity of the sharp edge. As an example, the influence of the offset between the top and bottom metallization layer on the maximum electric field strength is studied. Moreover, the influence of the thickness of the involved layers and of the shape of the electrodes is discussed. Also, the impact of the material properties of the involved dielectrics is examined. In addition to electrostatic simulations we have carried out electric transient simulations, which show that the ratio of the conductivities of the involved dielectric materials plays a major role for determining the maximum electric field strength

High voltages and the edges of the metallization on ceramic substrates (AMB, DBA, DBC, HTCC, LTCC) lead to high electric field strengths. In the vicinity of the metal edges these high electric field strengths induce partial discharges in the ceramic insulation and in the potting and thereby represent one key degradation mechanism of power modules. In this work the correlation of the simulated electric field strength with phase resolved partial discharge (PRPD) measurements has been investigated. For the simulation of the electric field strength a new method was used to bypass numerical artifacts. The simulated values show that it is possible to reduce the electric field strength by an adaption of the metallization structure. There the distance of the upper and the lower metallization to the rim of the ceramic was changed relative to each other. Due to this variation a reduction of the electric field strength of about 30% can be reached by choosing the optimum distance compared to state of the art design. In PRPD measurements for insulating ceramic substrates (AlN/Al 2 O 3 by DCB) we examined whether the electric field strength reduction leads to higher partial discharge inception voltages (PDIV). The measurements were executed on layouts with different dimensions of the upper and lower metallization relative to each other as well as for 3 different thicknesses of the ceramic insulation layer. An increase from 20% to 35% of the PDIV was measured for layouts designed according to the findings from the simulation with respect to electric field strength reduction. Finally, the calculated electric field strength and the measured PDIV were correlated.

High voltages and the edges of the metallization on ceramic substrates (AMB, DBA, DBC, HTCC, LTCC) lead to high electric field strengths. In the vicinity of the metal edges these high electric field strengths induce partial discharges in the ceramic insulation and in the covering synthetics and thereby represent one key degradation mechanism of power modules. In this work the correlation of the simulated electric field strength with phase resolved partial discharge (PRPD) measurements has been investigated. For the simulation of the electric field strength a new method was used to bypass numerical artifacts. The simulated values showed that it is possible to reduce the electric field strength by an adaption of the metallization structure. There the distance of the upper and the lower metallization to the rim of the ceramic was changed relative to each other. Due to this variation a reduction of the electric field strength by about 30 % can be reached by choosing the optimum distance compared to state of the art modules. In PRPD measurements for ceramic substrates (AlN/Al2O3 by DCB) we examined whether the field reduction leads to higher partial discharge inception voltages (PDIV). The measurements were executed on layouts with different dimensions of the upper and lower metallization relative to each other as well as for 3 different thicknesses of the ceramic insulation (1 mm and 0.63 mm AlN DBC, 0.63 mm and 0.38 mm Al2O3 DBC) layer. An increase from 20 % to 35 % of the PDIV was measured for layouts which were designed according to the findings from the simulation with respect to field strength reduction. Finally, the calculated electric field strength and the measured PDIV were correlated

Due to the ongoing development of high-blocking semiconductors the installed ceramic circuit boards in power modules, such as DBC (Direct Bond Copper) or AMB (Active Metal Brazed) substrates, will have to isolate high voltages (HV) beyond 6.5 kV in the near future with high lifetime and reliability. Such high blocking voltages and the correlating increased electrical field strengths induce partial discharges (PD) in the ceramic substrate as well in the encapsulating organic materials, which represent a key degradation mechanism of HV power modules. In this work a promising novel coating technology for ceramic substrate trenches, significantly enhancing the partial inception voltage (PDIV) of these substrates, is presented. The coating works as a refractive field control and reduces the field strengths in the most critical section for PD - the so-called triple point - between ceramic, encapsulate and copper metallization