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This study reports a novel high-temperature and high-current wire interconnection by printing Ag sinter paste for WBG semiconductor power devices. The Ag sinter paste wire interconnection (APW) was successfully fabricated connecting two Cu electrodes coated by Ag. Both the high-temperature reliability and the high-current reliability of the APW were evaluated by aging test at 250 °C for 1000 h and by electro-migration (EM) test at 2.2 × 104 A/cm2 for 2000 h. In the aging, a resistivity of about 4.1 × 10−6 Ω cm was achieved, which further decreased to 3.4 × 10−6 Ω cm after aging for 1000 h. This reduction can be attributed to further sintering of the sintered Ag network. The initial shear strength was 17 MPa, which, while high enough, was maintained even after an aging test of 1000 h. In the EM test, the resistance of APW was not changed significantly up to 1000 h and then only slightly increased at 2000 h. This only slight change in resistance demonstrates greater stability than that of conventional wire interconnection material such as Al and Cu under high temperature and high current density. The influence of EM on the interface between APW and a Cu substrate was observed by scanning electron microscopy with EDX. The change of resistance of the APW was induced by the formation of Cu oxide at a cathode side, which leads to a crack extension along the interface between APW and a Cu substrate. Thus, the results obtained in the present work show the APW as a promising new alternative to wire bonding technology for WBG power electronic devices. [ABSTRACT FROM AUTHOR]

[Display omitted] • Fatigue characteristics of high-purity Cu films from RT to 200 °C were investigated. • TMF characteristics of high-purity Cu were systematically and numerically revealed. • The change in the grain of Cu at high temperatures leads to a reduced fatigue life. • Ʃ3 fraction decreases and the LAGB fraction increases as the temperature increases. • Fatigue life is significantly changed even below the recrystallization temperature. This study conducts stress-controlled cyclic tension-tension tests from room temperature (RT) to 200 °C, at 50 °C intervals, on high-purity Cu films to comprehensively understand the temperature-dependent fatigue life and the related microstructural and fracture characteristics. As evidenced by the electron backscattering diffraction analysis, the Ʃ3 boundary fraction decreases and the low-angle grain boundary fraction increases as the temperature increases. The significant change in the grain structure at high temperatures leads to a reduced fatigue life. The fatigue striations are closely spaced at RT and the fracture surface develops into the typical fatigue striation and the void zones. [ABSTRACT FROM AUTHOR]

Abstract Solid-state porous Ag was utilized to achieve interface bonding under low temperature and low-pressure for large area, high-reliability designs for high performance die-attach power modules in high temperature applications. In this process, solid-state porous Ag was first fabricated by sintering Ag particles onto both a Cu substrate and an Si die with different bonding areas. After polishing the surface of the solid-state porous Ag, the Ag-Ag interface was bonded together under low pressure (0.4 MPa) and low temperature (250 °C and 300 °C). The bonding strength was greater than 30 MPa for a 15 mm x 15 mm bonding area at a bonding temperature of 300 °C. The electrical resistivity of the solid-state porous Ag was about 7 µΩ cm, or half that of Pb-free alloy solder materials. The bonding mechanism of the Ag-Ag interface was analyzed by a transmission electron microscope. It was observed that Ag hillocks and nanoparticles had been generated and bridged the Ag-Ag interface. This resulted in a large interface connection ratio and a high bonding strength. In addition, it was observed that the shear strength of the solid-state porous Ag with a thick bonding layer decreased thermomechanical stress in the die-attached power module and thus improved structural reliability. This bonding process featuring solid-state porous Ag presents an attractive technology for the fabrication of large area bonding and high-reliability die-attached module structures for high temperature applications. [ABSTRACT FROM AUTHOR]