Low pressure Cu-Cu bonding using MOD ink-modified Cu particle paste for die-attachment of power semiconductors

Cu-Cu bonding is always conducted at high temperature and high pressure in reductive atmosphere to eliminate the influence caused by oxidation. Herein, a novel low-pressure sinterable Cu nanoparticle (Cu-NPs) paste was developed using Cu Metal Organic Decomposition (MOD) ink as solvent and surface modifier. The Cu MOD ink in paste introduced in Cu nanoparticle paste not only eliminated the surface oxidation of Cu-NPs, but also modified Cu-NPs with Cu atoms due to the thermal decomposition during sintering process. As a result, robust Cu sinter joints for die-attachment could be realized at a low pressure of 0.4 MPa in non-reductive nitrogen atmosphere. Using the paste with 20 wt.% Cuf addition in solvent, a relative high shear strength of 17.1 MPa could be achieved at 300 °C, which is about 3.8 times higher than that sintered without MOD ink (4.5 MPa). When bonding temperature rose to 350 °C, even higher shear strength over 20 MPa was obtained. The bonding strength was comparable to the traditional Pb-5Sn solder alloy, promising its industrial potential.