In-Situ Reduction Sintering of Micro-Copper Paste for High-Power Electronic Application

Developing new packaging materials with a high melting point was eternally desirable for better reliability at higher service temperature. A pre-oxidization strategy was proposed to develop a novel micron copper paste. With the pre-oxidization of micro-Cu. a layer of
$\text{Cu}_{2}\mathrm{O}$
nano-particles with a diameter of 15 nm was uniformly prepared on its surface.
$\text{Cu}_{2}\mathrm{O}$
nano-particles were then in-situ reduced by the selected reducing agent into nano-Cu particles to promote the sintering process. The sintering activity of the powder was increased with the excess surface energy of nano-Cu particles, making the transformation process of the sintering system from high-energy to low-energy easier to actuate. The sintered microstructure was denser compared with the microstructure obtained from the unoxidized Cu particles. At
$250^{\circ}\mathrm{C}$
, the optimal shear strength of the interconnect microstructure reached 50.7 MPa, which was sintered under 20 Mpa for 10 min. The designed reduction agent and the in-situ sintering process were beneficial to the power chip interconnection, which also provided an excellent strategy for reliable paste preparation at a low cost.