Recently, there have been many developments on power devices to improve their functions. Especially, the junction temperature of power modules that equip SiC (Silicon Carbide) chips will be higher than 200 °C as current densities are too high, and new electronic packaging technologies shall be developed to meet higher temperature and higher power cycle durability requirements. In order to meet these requirements, in the present study, we propose Cu wire, Cu ribbon and Cu connector between Cu wirings of the substrates and investigate their feasibilities, including electrical resistances, footprints of bonding area, and bonding reliability under accelerated stress test, respectively.

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Significant growth of the Electric Vehicle (EV) market i s making a valuable contribution to the efficient reduction of CO 2 emissions. Application of power semiconductors in EVs is attracting a lot of attention, since many silicon (Si) power semiconductor chips, packages and modules are implemented in the main traction inverter, electric power steering system (EPS) , battery management system, and other motor drivers that are key components for EVs. Recently, silicon Carbide (SiC) power devices are promising alternatives, and with a view to achieving the superior semiconductor performance, the transition from Si power devices to SiC devices is underway. The maximum operating temperature of Si power devices is around 175℃, that of SiC devices is expected to be as high as 250℃, taking advantage of their wide bandgap characteristics, which induces high thermal stress around a SiC chip owing to a Coefficient of Thermal Expansion (CTE) mismatch and deteriorates the power module reliability. Al wire bond interconnections damage rapidly due to a thermal strain between the SiC chip and the wire material, which accelerates failures near the interface of the wire bonds in the power module, due to the T j changes caused by higher current loads. In this study, Al-Clad Cu (AlCu) wire bonding structure on a thick ion-plated Cu over-pad metallization (OPM) layer is proposed. To demonstrate the power cycling durability, SiC-Schottky barrier diodes (SBD) with AlCu wire bonds on a 25 m-thick Cu-OPM layer were assembled into the test vehicles. Applying finite element method (FEM) analysis, the reliability of AlCu wire bonds on Cu-OPM was demonstrated.The lifetime during power cycling tests of AlCu wire bonds on a 25 m-thick Cu-OPM layer was 14-times longer than that of Al wire bonds on an Al pad at ΔT j = 75℃. In light of inelastic stress-strain analysis, the lifetimes of the AlCu wire bonds on a 100 μmthick and a 300 μm-thick Cu-OPM layer during power cycling tests were predicted to be 42-times and 1,600 times longer than that of Al wire bonds on an Al pad, respectively.

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