Abstract
In this study, the feasibility of low-cost Cu-sintering technology for power electronics packaging and the effect of sintering conditions on the bonding strength of the Cu-sintered joint have been evaluated. A Cu paste with nano-sized Cu powders and a metal content of ~78% as a high-temperature bonding material was fabricated. The sinter-bonding reactions and mechanical strengths of Cu-sintered joints were evaluated at different sinter bonding pressures, temperatures, and durations during the sintering process. The shear strength of the Cu-sintered joints increased with increasing sintering pressure. Good interfacial uniformity and stable metallurgical microstructures were observed in the Cu joints sintered at a high sintering pressure of 10 MPa, irrespective of the sintering time. It was confirmed that a high-pressure-assisted sintering process could create relatively dense sintered layers and good interfacial uniformity in the Cu-sintered joints, regardless of the sintering temperatures being in the range of 225–300 °C. The influence of the sinter bonding pressure on the shear strengths of the Cu-sintered joints was more significant compared to that of the sintering temperature. Durations of 10 min (at 300 °C) and 60 min (at 225 and 250 °C) are sufficient for complete sintering reactions between the Si chip and the direct bond copper (DBC) substrate. Relatively good metallic bonding and dense sintered microstructures created by a high sintering pressure of 10 MPa resulted in high shear strength in excess of 40 MPa of the Cu-sintered joints.
Highlights
Of late, there has been considerable interest in improving technology for electric vehicles (EV)and hybrid EVs (HEV) due to global environmental issues
In order to evaluate oxidation degree of Cu nano powders, the Cu powders were analyzed by XRD
Some relatively weak intensity Cu2 O peaks were observed, we tried to fabricate Cu paste, because the nano-sized Cu weak intensity Cu2O peaks were observed, we tried to fabricate Cu paste, because the nano-sized powders are oxidized in air
Summary
There has been considerable interest in improving technology for electric vehicles (EV)and hybrid EVs (HEV) due to global environmental issues. A main component of any power electronic system in EV/HEV is the inverter power module, which contains power semiconductor devices, die-attached materials, ceramic substrate or lead-frame, and bonding/interconnection materials [1,2]. Die-attachment or chip bonding plays an important role in current power electronic systems because the chip bonding material directly interfaces with the semiconductor chips and ceramic substrates. The maximum temperature of the chip is extremely high during operation of the power electronic systems, e.g., modules in EV/HEV. The high-temperature endurable reliability levels for such power modules are required, and new die-attach bonding materials and technologies should be used to meet the demands of power modules.
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