Protruding Ceramic Substrates for High-Voltage Packaging of Wide-Bandgap Semiconductors

With the development of wide bandgap semiconductors, voltage ratings of 10kV and more become realistic. As a consequence, it is now mandatory to propose a suitable packaging. Ceramic-metal substrates are an established technology for voltages up to 3.3kV, but they exhibit some weaknesses for higher voltages. Due to their manufacturing process (especially the etching of the copper layers), the metallization profile is sharp and induces electric field reinforcements at the so-called triple point (junction between ceramic, conductor and encapsulant).

Even when this field reinforcement is not sufficient to induce a dielectric breakdown, it can lead to Partial Discharges (PD) which cause a progressive degradation of the substrate. Intuitively, a solution would be to resort to thicker ceramic layers, but this degrades the thermal performances. In this paper, we propose a new substrate structure in which the triple point is located in a low-electric field area, with smoother surfaces.