Reconstructing more sinterable surfaces for copper nanoparticles to form high-strength Cu-Cu joints in air atmosphere

Abstract

Low temperature sintering Cu nanoparticle (NP) paste is a promising solution to fulfill the harsh requirements of Wide band gap (WBG) power device packaging. However, spontaneous oxidation of the Cu NPs is one of the great challenges in their practical application. In this work, a facile surface treatment method that first removing surface oxides by acid and then forming a protective layer by a short-chain amine molecules was used to reconstruct the surface chemical environment of commercial Cu NPs and improve their resistance to oxidation and sintering performance. The reconstructed Cu NPs were mixed with suitable solvents to prepare Cu NP paste. To figure out the sintering performance and resistance to oxidation of the reconstructed Cu NPs, the Cu NP paste was sintered in air at various temperatures with 10 MPa. The shear test results revealed that the shear strength of reconstructed Cu NP paste after sintering was far higher than that of sintered original Cu NP paste. Especially, when the sintering temperature was 250 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">o</sup> C, the shear strength of reconstructed Cu NP paste after sintering was over 4 times than that of sintered original Cu NP paste. This means that the reconstruction of Cu NPs improves their sintering performance and resistance to oxidation efficiently, which may facilitate the practical application of Cu NP paste in the WBG power device packaging.