Effect of Metallization Corner Radius on Electric Field Distribution, Partial Discharges and Breakdown Voltage

Abstract

Sharp edges and corners of conductive patterns on dielectric substrates locally intensify the electric field, which is a primary source of partial discharges (PD) in high-voltage electronics. This study investigates the in-plane edge radius of a conductive path as a critical design parameter governing PD inception. Stencil-printed silver electrodes on an alumina substrate act as a representative test structure. Six geometries with edge radii from 0 to 2 mm were analysed using a 2D finite-element model in the substrate plane, with the electric field evaluated at a $\mathbf{1 0} \boldsymbol{\mu} \mathbf{m}$ offset from the electrode edge. The samples were experimentally characterised by measuring PD inception voltage (PDIV) according to IEC 60270 and performing breakdown voltage tests, both without encapsulation (in air) and potted in silicone gel. The measured experimental trends are consistent with the simulated reduction in electric-field, and the locations of observed breakdown traces coincides with the simulated field maxima. These results demonstrate that the in-plane corner radius is an important design parameter governing PD inception and breakdown behavior.