Inhibiting effects of the Ni barrier layer on the growth of porous Cu3Sn in 10-μm microbumps

With the shrinkage of size, porous Cu3Sn has become a new potential threat of the reliability in Cu pillar microbump. The formation of porous Cu3Sn is caused by the decomposition of Cu6Sn5 after Sn atoms in solder depletion. Besides, the stress introduced by the phase transition from eta-Cu6Sn5 to eta '-Cu6Sn5 will promote the formation of porous Cu3Sn. In this paper, uniform CYRILLIC CAPITAL LETTER EF10 mu m Cu/Sn and Cu/Ni (similar to 0.6 mu m)/Sn microbumps have been fabricated by multilayer electrodeposition and the effect of the Ni layer on the growth behavior of porous Cu3Sn was investigated by comparing IMCs' (Intermetallic Compound) evolution in Cu/Sn and Cu/Ni/Sn bumps aged at 170 degrees C and 200 degrees C. The similar to 0.6 mu m Ni barrier layer can effectively retard the Cu atoms diffusion, which can hinder IMC from overgrowth. Moreover, the results of X-ray diffraction indicate that the ability of the Ni layer can stabilize Cu6Sn5 phase and weakens the tendency of the porous Cu3Sn formation. Under the conjoint action of retarding the growth of IMC and stabilizing Cu6Sn5 phase, the Ni layer can inhibit the formation of porous Cu3Sn efficaciously.

Automated summary

The study shows that the Ni layer can effectively hinder the diffusion of Cu atoms, thereby preventing excessive growth of IMC, stabilize the Cu6Sn5 phase, and weaken the formation tendency of porous Cu3Sn, effectively inhibiting the formation of porous Cu3Sn.