Metallized ceramic substrate with mesa structure for voltage ramp-up of power modules

Abstract

As the available wide bandgap semiconductors continuingly increase their operating voltages, the electrical insulation used in their packaging is increasingly constrained. More precisely the ceramic substrate, used in demanding applications, represents a key multi-functional element is being in charge of the mechanical support of the metallic track that interconnects the semiconductor chips with the rest of the power system, as well as of electrical insulation and of thermal conduction. In this complex assembly, the electric field enhancement at the triple junction between the ceramic, the metallic track borders and the insulating environment is usually a critical point. When the electrical field at the triple point exceeds the critical value allowed by the insulation system, this hampers the device performance and limits the voltage rating for future systems. The solution proposed here is based on the shape modification of the ceramic substrate by creating a mesa structure (plateau) that holds the metallic tracks in the assembly. A numerical simulation approach is used to optimize the structure. After the elaboration of the structures by ultrasonic machining we observed a significant increase (30%) in the partial discharge detection voltages, at 10 pC sensitivity, in a substrate with a mesa structure when comparing to a conventional metallized ceramic substrate.

Insulation Materials and Systems for Power Electronics Modules: A Review Identifying Challenges and Future Research Needs

“…In the geometric technique proposed in [83,84], a gap between the top Cu electrodes was created to form a mesa structure, leading to significant electric field reduction as shown in Figure 14. This mesa structure was fabricated as shown in Figure 15 by an ultrasonic machining technique.…”

“…The geometry of (a) conventional structure and (b) mesa structure and the corresponding electric field distribution[83], © [2019] EPJ AP.…”

Innovative ceramic-matrix composite substrates with tunable electrical conductivity for high-power applications

“…Nevertheless, such PE technological breakthrough will be accompanied by the need to miniaturize electrical systems, which will not only make it more complicated to manage the power density and extract the heat dissipated by the chips, but will also markedly intensify undue stresses within the power module. Effectively, increasing the voltage level in the current power module results in heightening the electric field at the junction between the ceramic substrate ( Figure 1 ), the metallic track borders and the encapsulating polymer [ 13 ]. The induced electrical constraint at this triple point can dramatically impair the performances of the power module and, subsequently, reduce its lifespan, when it exceeds the critical one allowed by the dielectric strength of the insulating materials, thereby limiting the voltage ratings for future systems.…”

FEM simulation based study of electric field reduction by linear and nonlinear resistive solution for HV power module under switching operation

“…In this regard, the electric field control at TP in order to limit PD is needed for future high voltage power modules. Methods to control the electric field E and protect the device by ameliorating the geometrical designs [4,5] or adding some new parts in critical area [6,7,8] have been proposed. The use of a bridging resistive surface layer, which connects the high voltage electrode and the ground potential [9,10], is regarded as an effective field control method.…”