Experimental investigation of the reliability of Printed Circuit Board (PCB)-embedded power dies with pressed contact made of metal foam

Abstract

A Printed Circuit Board (PCB)-embedding process using pressed metal foam to connect the top-side pads of power dies is considered. The manufacturing process, simple and highly cost-effective, is described in detail; samples are manufactured and their reliability and robustness are characterised. It is shown that thermally cycled prototypes exhibit reliability close to that of Direct Bounded Copper (DBC) substrates. Samples submitted to 150 A-surges have highly scattered reliability. SiC MOSFETs submitted to destructive current limiting tests and repetitive short-circuit tests performed similarly to dies reported in TO247 packages. A discussion on the development of reliability-assessment-methods, especially suited for PCB-embedding processes, is proposed.

Thermal simulations of SiC MOSFETs under short-circuit conditions: influence of various simulation parameters

“…(1) Were 2 and 3 are the Electric field (E-field) and the current density. 3 was obtained from current measurements (detailed in [18]) normalized by the die active area. As for the E-field, it is assumed that the transistor drift layer is homogenously doped and thick enough so that the E-filed in the crystal is triangular.…”

“…It was, in particular, developed in order to study the robustness of a new die topside connection technic [17]. Its mains point was to estimate, through simulation, the robustness of a PCB embedded power die having its top-side connected to the circuit using a pressed piece of nickel foam [18].…”

A Double-Side Cooled SiC MOSFET Power Module With Sintered-Silver Interposers: I-Design, Simulation, Fabrication, and Performance Characterization

“…And to reduce the thermomechanical stresses, it would be desirable that the interposer is made of a material or structures having low CTE or low elastic modulus or both. Deformable Ag tubing [30] and metal foams [45], [46] have been explored as interposers to achieve adjustable height, but the tradeoff is large thermal resistance through the top terminals because of the small heat conduction area.…”