The soldering process, essential for electrical and mechanical connections in the microelectronics industry, is crucial for IGBT die attachment as well. This paper investigates the impact of the vacuum reflow process on IGBT assembly using fluxless solder paste activated by formic acid. The paste demonstrates excellent print quality, formability, and consistent solder joint formation. Achieving satisfactory wetting, it compares favorably to traditional solder materials. Key optimized parameters include reflow temperature profiles, activation, and vacuum conditions, such as preheat time, time above liquid (TAL), peak temperature, formic acid concentration, and vacuum ratio. Crucially, formic acid's concentration and activation duration play significant roles in reducing void percentages, effectively decreasing voids from 7.5% to as low as 1%. Vacuum pressure also critically influences void behavior, with reductions in pressure resulting in increased void percentages from 1% to a high of 30%. This study underscores the potential of fluxless solder methodology as a sustainable and economic advancement in the power electronics industry.

IGBT device is developed from silicon to wide bandgap semiconductor materials, and its working temperature has reached to 300 °C, so the encapsulation is particularly important. NanoCu paste is investigated under H2 at 300°C. A chip is linked to DBC substrate by nanoCu paste under air with different temperature. Results shows the increase of sintered time temperature effectively reduce the porosity of sintered layer and enhance the strength.